Incheon, South Korea
Incheon, South Korea

Inha University ) is a private research university located in Incheon, South Korea.Known traditionally for research and education in the engineering and physical science, the University was established by the first president of South Korea, Syngman Rhee. It is a Korean-American collaboration school, even in its name: the Morpheme "In" comes from the city of Incheon and "Ha" comes from Hawaii, USA. At first time, it started as a technical college, named Inha Institute of Technology .Currently, Inha is ranked 10th nationwide, and especially 4th in Engineering and Science, by JoongAng Ilbo's annual ranking of South Korean universities. Inha is a member of GU8. Wikipedia.

Time filter

Source Type

Yu S.-L.,Inha University | Lee S.-K.,Inha University
Molecular and Cellular Toxicology | Year: 2017

Ultraviolet (UV) radiation is one of the most common environmental health hazards that cause highly toxic effects in most living organisms. UV irradiation leads to harmful effects including skin aging, eye damage, and skin cancer because of increased production of cellular reactive oxygen species and by direct DNA damage. Damaged DNA, if not properly repaired, is a source of mutation, and interferes with many cellular mechanisms such as replication, transcription, and the cell cycle. Because most UV damaged DNA is efficiently repaired by nucleotide excision repair (NER), which is a specialized UV-induced DNA damage repair system, many UV-induced symptoms are closely related to NER. Therefore, understanding the function of NER genes will elucidate the cause of different UV-induced symptoms. Furthermore, a multidisciplinary understanding of damaged DNA repair systems and other cellular mechanisms affected by unrepaired DNA damage would lead to an improved understanding of UV-induced symptoms and toward developing various preventive and therapeutic methods against UV damage. For this purpose, in this review we discuss two NER-related human genetic disorders, xeroderma pigmentosum (XP) and Cockayne syndrome (CS), the cellular mechanisms that are impaired by defective NER genes, and the functions of RAD2/XPG in relation to the cause of various UV damage-induced symptoms. © 2017, The Korean Society of Toxicogenomics and Toxicoproteomics and Springer Science+Business Media Dordrecht.

Han Y.-J.,Inha University | Park S.-J.,Inha University
Applied Surface Science | Year: 2016

In this study, multiwalled carbon nanotube (CNT)-nickel hybrid materials were prepared from CNTs by the impregnation of nickel at various CNT/nickel mass ratios. The presence of nickel nanoparticles on CNTs influences the spillover effect on hydrogen storage capacity. A thermal reduction method was employed to increase the contacts between the nickel metal particles and the carbon support, thus facilitating hydrogen spillover. The as-obtained nickel-decorated CNTs exhibited a high hydrogen storage capacity of 0.87. wt.% at 298. K and 100. bar, resulting in an enhancement factor of 2.5 relative to the untreated CNTs. These experimental results demonstrate that the presence of nickel creates hydrogen-favorable sites that can lead to improved hydrogen storage capacities based on the spillover effect. © 2016 Elsevier B.V.

Lee S.,Inha University
International Journal of Marine and Coastal Law | Year: 2017

On 16 April 2014, the Sewol Ferry sank off the coast of Jindo, Korea, resulting in the deaths of 304 passengers. The Korean government enacted the 'Sewol Ferry Special Act' to provide special forms of compensation to victims by the State. It permits the Korean government to subrogate the claims of the victims and to take action against the private persons and public agencies at fault for the sinking of the Sewol. But problems have arisen because of the complexities of insurance law and the difficulties of identifying the respective degrees of fault between the responsible parties. © 2017 Koninklijke Brill NV, Leiden, The Netherlands.

Lee J.,Inha University | Song M.,Inha University
Proceedings - 2016 IEEE International Symposium on Multimedia, ISM 2016 | Year: 2016

The combination of cost and performance offered by solid-state disks (SSDs) makes them potentially suitable for caching in video servers. However, it is necessary to determine which video segments should be cached on SSD, and how to combine DRAM and SSD caching. We introduce a dynamic programming algorithm that allows for segment popularity in determining which videos will have their initial segments (prefixes) stored on SSD; and another algorithm that determines the intervals between pairs of consecutive requests for segments, and hence which segments should be stored on DRAM. Simulations of combined caching show that prefix caching saves appreciable disk bandwidth between 17% and 60%, and that DRAM and SSD caching can be combined effectively. © 2016 IEEE.

Shim H.S.,Inha University | Kim K.Y.,Inha University
IOP Conference Series: Earth and Environmental Science | Year: 2016

Severe radial thrust under off-design operating conditions can be harmful factor for centrifugal pumps. In the present work, effects of geometry of a double volute casing on the hydrodynamic performance of a centrifugal pump have been investigated focusing on off-design conditions. Three-dimensional steady Reynolds-averaged Navier-Stokes analysis was carried out by using shear stress transport turbulence model. Numerical results for the hydrodynamic performance of the centrifugal pump were validated compared with experimental data. The hydraulic efficiency and radial thrust coefficient were used as performance parameters to evaluate the hydrodynamic characteristics of the centrifugal pump. The cross-sectional area ratio of the volute casing, the expansion coefficient of the rib structure, distance between the rib starting point and volute entrance, and radius of the volute entrance, were selected as geometric parameters. The results of parametric study show that performance parameters are significantly affected by both the geometric variables and operating conditions. Some configurations of the double volute casing showed outstanding performance in terms of the efficiency and radial thrust coefficient.

Liu H.,Shandong Jiaotong University | Kwak K.S.,Inha University
2016 International Conference on Information and Communication Technology Convergence, ICTC 2016 | Year: 2016

Considering a decode-And-forward relay network with multiple source-destination pairs, this paper proposes a two-phase relaying protocol, which enables the massive multiple-input multiple-output (MIMO) relay to simultaneously harvest wireless energy from multiple sources' information signals and multiple destinations' energy flows (EFs). Asymptotic expression of the harvested energy is derived when a power splitting relay node employs an unlimited number of antennas. The analysis reveals that the asymptotic harvested energy is independent of the fast fading effect of the wireless channel, meanwhile the transmit powers of each source and each destination can be scaled down inversely proportional to the number of relay antennas. To significantly reduce the energy leakage interference (ELI) and multipair interference (MI), the maximum-ratio combing/maximum-ratio transmission (MRC/MRT) techniques have been employed at the relay node. The exact achievable sum rate and the optimal destination transmit power that maximizes the achievable sum rate are derived in closed-form, respectively. Moreover, the fundamental trade-off between the harvested energy and the achievable sum rate is quantified. It has shown that the destination-Aided EFs are beneficial for both the energy harvesting at the relay and the quality improvement of the second-hop link. Meanwhile, the detrimental impact of ELI and MI for signal decoding can be cancelled completely by using MRC/MRT when the number of relay antennas grows without bound. © 2016 IEEE.

Kim T.-W.,Inha University | Park S.-J.,Inha University
Journal of Colloid and Interface Science | Year: 2017

Reduced graphene oxide (rGO)/thorn-like TiO2 nanofiber (TTF) aerogels, or GTTF aerogels, with different TTF weight ratios were successfully prepared by electrospinning, silica etching and hydrothermal combination method. During the hydrothermal reaction, the rGO nanosheets and TTF self-assembled into three-dimensional (3D) interconnected networks, in which the TTF is loaded onto the rGO nanosheets. The electrochemical performance of the GTTF aerogels was assessed using cyclic voltammetry and galvanostatic charge–discharge measurements in a 1 M aqueous Na2SO4 electrolyte. The TTF-to-rGO ratio of the aerogel material significantly affected the electrochemical performance of the aerogel electrodes, and the GTTF aerogels prepared with 20 wt% TTF (denoted GTTF-20) exhibited excellent electrochemical performance. The maximum specific capacitance of this aerogel electrode was 178 F/g at a current density of 1 A/g. The GTTF-20 aerogel also exhibited good electrochemical stability with a capacitance degradation of less than 10% after 3000 cycles. We can deduce that the electrochemical performance of the as-prepared aerogels may be enhanced by increasing the chemical interactions between rGO and TiO2. The results indicate that the GTTF aerogels show enormous potential for application in energy storage devices. © 2016 Elsevier Inc.

Kim M.-Y.,Inha University | Park E.-J.,Yonsei University | Shin J.,Yonsei University
Computers and Mathematics with Applications | Year: 2017

In this work, we present novel high-order discontinuous Galerkin methods with Lagrange multiplier (DGLM) for hyperbolic systems of conservation laws. Lagrange multipliers are introduced on the inter-element boundaries via the concept of weak divergence. Static condensation on element unknowns considerably reduces globally coupled degrees of freedom, resulting in the stiffness equations in the Lagrange multipliers only. We first establish stability results and provide conditions on the stabilization parameter, which plays an important role in resolving discontinuities as well. Accuracy tests are then performed, which shows optimal convergence in the L2 norm. Extensive numerical results indicate that the DGLM has potentials in delivering high order accurate information for various problems in hyperbolic conservation laws. Numerical examples include inviscid Burgers' equations, shallow water equations (subcritical flow and supercritical upstream, subcritical downstream flow, and 2D circular dam break), and compressible Euler equations (Intersection of Mach 3 and Sod's shock tube). © 2017 Elsevier Ltd.

Deep eutectic solvents (DESs) are potential ecofriendly surfactants for the preparation of various materials. In this study, molecularly imprinted polymers (MIPs) were modified by betaine-based DESs. These materials were characterized by field emission scanning electron microscope and Fourier transform infrared spectroscopy. The molecular recognition capability for antibiotics of materials was evaluated by static absorption and dynamic adsorption curves. Five materials were used as solid phase extraction (SPE) adsorbents for the rapid purification of levofloxacin and tetracycline from the millet extract. The DES-based materials showed more selective adsorption than the conventional MIPs. The adsorption curves of DES-MIP showed superior molecular recognition ability and binding capability for antibiotics than the other materials. The limit of detection and the limit of quantitation of the method for levofloxacin were 0.01 μg mL−1 and 0.03 μg mL−1, respectively. The method recoveries ranged from 97.2-100.2% for levofloxacin with DES-LMIP and 95.7-99.2% for tetracycline with DES-TMIP. DES-LMIP and DES-TMIP showed the highest selectivity recovery for levofloxacin (94.5%) and tetracycline (93.3%) from millet extract with mixture antibiotics, and could remove the interferent effectively. © The Royal Society of Chemistry.

Abideen Z.U.,Inha University | Kim J.-H.,Inha University | Kim S.S.,Inha University
Sensors and Actuators, B: Chemical | Year: 2017

SnO2 nanowires (NWs) functionalized with Ag nanoparticles (NPs) were tested for NO2 gas sensing ability; the results revealed a bell-shaped curve as a function of the surface coverage of Ag NPs. A model that can explain these experimental observations regarding the functionalization of metal NPs on oxide NWs, which is the most widely used approach for improving the sensing capabilities of NWs, was proposed and validated. Based on the electronic and chemical sensitizations of metal NPs, a mathematical equation was formulated to predict the optimal surface coverage of metal NPs on the NWs to obtain maximum sensing performance. This study may provide new insight and guidelines for the development of highly sensitive NW-based gas sensors. © 2016 Elsevier B.V.

Choi M.,Inha University | Son J.,Pohang University of Science and Technology
Current Applied Physics | Year: 2017

We propose the novel strategy for indirect-to-direct band gap transition of gallium oxide-based semiconductors for ultraviolet lighting device through first-principles calculations using a screened hybrid functional. Our calculations show that the tuning of electronic band gap of α-Ga2O3 is straightforward by adding dopants, which mimics alloy-like system. In order to put the band gap in the energy range of ultraviolet light, Group-III (In, Tl) at the Ga site and Group-V (N, P) or Group-VI (S, Se) at the O site are examined. We find that the most of doped Ga2O3 possess direct or nearly direct band gaps lying in the ultraviolet energy that is essential for optoelectronic devices. © 2017 Elsevier B.V.

Park D.,Inha University
2016 International Conference on Information and Communication Technology Convergence, ICTC 2016 | Year: 2016

We investigate the optimal power allocation that maximizes the sum throughput in two-user interference channel under individual power constraints. The optimal power allocation depends not only on the peak power level, but also on the cross channel coefficient. The derived optimal power allocation scheme is to allocate full power to both users in the case of low peak power level. However, if the peak power level is above some threshold, then it is optimal that only one user transmits at full power while the other user remains silent. © 2016 IEEE.

Ahmad I.,Inha University | Chang K.,Inha University
2016 International Conference on Information and Communication Technology Convergence, ICTC 2016 | Year: 2016

The development on the underwater communication network for sea observation is on the rise due to increasing importance of its applications such as oceanography, marine commercial operation and military surveillance. In this paper, we design the system-level simulator (SLS) architecture for the underwater acoustic communications which can be the basis for the design model of future application-specific underwater network deployment. © 2016 IEEE.

You R.,Inha University | Kwon J.-W.,Inha University
ACM International Conference Proceeding Series | Year: 2016

This paper presents a novel convolution neural network for classifying the orientation (or viewpoint) of a vehicle in a given image. Current equipping sensors in self-driving car is able to produce bounding box of vehicles in the proximity, but it does not recognize the viewpoint of them. Analyzing surrounding cars' direction in very complex environment has a significant role for autonomous driving. Utilizing nothing but a captured image, the purpose of this research is to classify viewpoint of vehicle: (1) front; (2) rear; (3) side; (4) front-side; and (5) rear-side. Deep convolutional neural network is used as the tool in performing classification task. The approach involves examining different CNN architectures using a large scale car dataset. In addition to that, the goal of the model is to be small and fast enough for limited hardware resource. We are able to achieve 95% accuracy, 57ms inference time on NVIDIA GRID K520 GPU, and 1.6 MB Caffe model size. © 2016 ACM.

Lee J.W.,Inha University | Nobi A.,Noakhali Science and Technology University
Computational Economics | Year: 2017

We consider the effects of the 2008 global financial crisis on the global stock market before, during, and after the crisis. We generate complex networks from a cross-correlation matrix such as the threshold network (TN) and the minimal spanning tree (MST). In the threshold network, we assign a threshold value by using the mean and standard deviation of cross-correlation coefficients. When the threshold is equal to the mean of these coefficients, we observe a giant cluster composed of three economic zones in all three periods. We find that during the crisis, the countries in the Asian zone were weakly connected and those in the American zone were tightly linked to the countries in the European zone. At a large threshold, the three economic zones were fragmented. The European countries connected tightly, but the Asian countries bound weakly. The MST constructed from the distance matrix. In the MST, France remained a hub node in all three periods. The size of the MST shrank slightly during the crisis. We observe a scaling relation between the network distance of nodes from the central hub (France) and the geometrical distance. We observe the topological change of the financial network structure during the global financial crisis. The TN and MST are complementary roles to understand the connecting structure of financial complex networks. The TN reveals to observe the clustering effects and robustness of the cluster during the financial crisis. The MST shows the central hub and connecting node among the economic zones. © 2017 Springer Science+Business Media New York

Huh J.,Inha University | Lee S.,Inha University
30th Congress of the International Council of the Aeronautical Sciences, ICAS 2016 | Year: 2016

Lateral jets used in hit-to-kill vehicles induce complex jet interactions with external supersoni c flows. It is of paramount importance to analyze these jet interactions accurately in order to predict the missile performance. In this paper, we numerically analyzed the jet interaction on a supersonic generic missile by using an in-house CFD solver, MSAPv. Various numerical flux schemes were used to examine the complex flow field. The results at three conditions were computed and compared to the experimental results as well as each other. In addition, the complexity of the interacting flow was investigated using the behavior of vortical flow structure around the lateral jet.

Kim J.,Inha University
TAPPI International Conference on Nanotechnology for Renewable Materials 2015 | Year: 2015

□ Sustainable materials are abundant, environmentally friendly, non-toxic. □ Extraction technologies have con and pro so as to compete each other. □ Applications of sustainable materials are huge: High strength composites, lightweight vehicles, airplanes, flexible display, sensors, paint/coatings/additives and medicine. □ Market of renewable materials will be $600 Billion (2020), growing rapidly. □ Smart optics is a fascinating application of sustainable materials. □ Flexible and reconfigurable smart optics devices made with sustainable materials will bring ultimate technological impact in the future.

Shrestha R.,Inha University | Kim J.M.,Inha University
International Conference on ICT Convergence | Year: 2012

Recently the demand for high data rate has been increasing along with the need to connect many users to an access point (AP) or a base station (BS). In this paper, we propose a bit-interleaved coded multi-user multilevel modulation (MU-MLM) for orthogonal frequency division multiple access (OFDMA) systems. MU-MLM is multilevel modulation (MLM) incorporating multiple users at each modulated symbol. This allows each channel resource of OFDM system to be optimized with higher order modulation (HOM) as well as carry data to multiple users. At the receive side, the received signal is MMSE equalized and successive decoding is done until the level of MLM that is assigned to respective user is decoupled. The equalization at the receiver for the proposed system is far less complex as the same signal is transmitted to all the users. Simulation results show that the proposed system has better BER performance compared to conventional M-ary Quadrature amplitude modulation (M-QAM). The performance is further improved for HOM like 1024-QAM. © 2012 IEEE.

Noh J.H.,Inha University | Hwang B.B.,Inha University
International Journal of Precision Engineering and Manufacturing | Year: 2017

A double cup extrusion process (DCEP) has been analyzed numerically to investigate the characteristics of energy consumptions for a selected model material, AA 2024 aluminum alloy. The forming energy in a double cup extrusion process was analyzed in terms of ideal, redundant and frictional energy or work, which constitute of a total forming energy in metal forming process. Ideal and theoretical forming or deformation efficiencies were also examined for various process parameters chosen for analysis. The objective of this study is to investigate the influence of geometrical process parameters in DCEP on the characteristics of energy consumption or dissipation. It was revealed from this study that frictional energy was expected to be more dissipated for high reductions and low thickness ratios. It was also found that the theoretical work efficiency would decrease as the thickness ratio increases and the reduction decreases. © 2017, Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

Nguyen T.T.B.,Inha University | Lee H.,Inha University
Journal of Semiconductor Technology and Science | Year: 2017

This paper presents a high-throughput low-complexity 512-point eight-parallel mixed-radix multipath delay feedback (MDF) fast Fourier transform (FFT) processor architecture for orthogonal frequency division multiplexing (OFDM) applications. To decrease the number of twiddle factor (TF) multiplications, a mixed-radix 24/23 FFT algorithm is adopted. Moreover, a dual-path shared canonical signed digit (CSD) complex constant multiplier using a multi-layer scheme is proposed for reducing the hardware complexity of the TF multiplication. The proposed FFT processor is implemented using TSMC 90-nm CMOS technology. The synthesis results demonstrate that the proposed FFT processor can lead to a 16% reduction in hardware complexity and higher throughput compared to conventional architectures. © 2017, Institute of Electronics Engineers of Korea. All rights reserved.

Ansari D.,Inha University | Kim K.-Y.,Inha University
Micromachines | Year: 2017

Performance analysis of double-layer microchannel heat sinks was performed under non-uniform heating conditions having randomly distributed hotspots. Two parallel-channel (parallel-flow and counter-flow) and one cross-channel (transverse-flow) designs of double-layer heat sink were evaluated with three sets of heating schemes. Each set of heating scheme consisted of eleven randomly distributed hotspots generated by Latin hypercube sampling. The heat flux, area, and location of the hotspots were selected as the design parameters. Conjugate heat transfer analysis of the heat sinks was performed by solving three-dimensional Navier-Stokes and energy equations. Water with temperature-dependent properties was selected as the coolant. The thermal resistance, pressure drop, maximum temperature rise, and temperature variation among hotspots were evaluated for all the heat sinks. The transverse-flow microchannel heat sink exhibited the lowest thermal resistance, temperature rise and temperature variation among the hotspots throughout the specified range of flow rate. The lowest pressure drop was exhibited by the counter-flow heat sink. © 2017 by the authors.

Yun D.-U.,Inha University | Lee S.-K.,Inha University
Journal of Sound and Vibration | Year: 2017

In this paper, we present a novel method for an objective evaluation of knocking noise emitted by diesel engines based on the temporal and frequency masking theory. The knocking sound of a diesel engine is a vibro-acoustic sound correlated with the high-frequency resonances of the engine structure and a periodic impulsive sound with amplitude modulation. Its period is related to the engine speed and includes specific frequency bands related to the resonances of the engine structure. A knocking sound with the characteristics of a high-frequency impulsive wave can be masked by low-frequency sounds correlated with the harmonics of the firing frequency and broadband noise. The degree of modulation of the knocking sound signal was used for such objective evaluations in previous studies, without considering the masking effect. However, the frequency masking effect must be considered for the objective evaluation of the knocking sound. In addition to the frequency masking effect, the temporal masking effect occurs because the period of the knocking sound changes according to the engine speed. Therefore, an evaluation method considering the temporal and frequency masking effect is required to analyze the knocking sound objectively. In this study, an objective evaluation method considering the masking effect was developed based on the masking theory of sound and signal processing techniques. The method was applied successfully for the objective evaluation of the knocking sound of a diesel engine. © 2017 Elsevier Ltd

Jin S.,Inha University | Lee S.-K.,Inha University
Journal of Mechanical Science and Technology | Year: 2017

Vibration signals measured from a mechanical system are useful to detect system faults. Signal processing has been used to extract fault information in bearing systems. However, a wide vibration signal frequency band often affects the ability to obtain the effective fault features. In addition, a few oscillation components are not useful at the entire frequency band in a vibration signal. By contrast, useful fatigue information can be embedded in the noise oscillation components. Thus, a method to estimate which frequency band contains fault information utilizing group delay was proposed in this paper. Group delay as a measure of phase distortion can indicate the phase structure relationship in the frequency domain between original (with noise) and denoising signals. We used the empirical mode decomposition of a Hilbert-Huang transform to sift the useful intrinsic mode functions based on the results of group delay after determining the valuable frequency band. Finally, envelope analysis and the energy distribution after the Hilbert transform were used to complete the fault diagnosis. The practical bearing fault data, which were divided into inner and outer race faults, were used to verify the efficiency and quality of the proposed method. © 2017, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Park I.,Inha University | Lee U.,Inha University
Composite Structures | Year: 2017

Various solution techniques have been developed in the last decades for accurate prediction of the dynamic responses of a laminated composite structure. The spectral element method (SEM) is well known as an exact solution method that provides extremely accurate dynamic responses even in the high-frequency region. In this study, we develop a spectral element model for a rectangular finite composite plate element. The present spectral element model is developed by modifying the boundary splitting method introduced in the previous studies of the authors. As a result, the four corner nodes of the rectangular finite composite plate element, which were inactive (fixed) in the previous studies, become active. Thus, the present spectral element model can be used as a generic type of finite element, which can be applied to any laminated composite plates with arbitrary boundary conditions. The accuracy and efficiency of the present spectral element model are evaluated by comparing its results with exact solutions and solutions using the commercial finite element analysis package, ANSYS. In addition, the vibration and wave characteristics are numerically investigated by varying the lay-ups of some examples of laminated composite plates with various geometries and boundary conditions. © 2017 Elsevier Ltd

Piao S.H.,Inha University | Choi H.J.,Inha University
Procedia Engineering | Year: 2017

Compared to graphene, the functional groups of graphene oxide (GO) widen its application along with its GO-based composites in various engineering areas. Here, we briefly review their relatively new applications to the areas of both electrorheological (ER) and magnetorheological (MR) fluids under external electric or magnetic fields, respectively when they are dispersed in electrically or magnetically inert medium fluids. All the GO composites are found to exhibit improved ER characteristics compared to that of pure GO, while the GO can be adopted as either a coating layer or an additive in the carbonyl iron based MR fluids.

Hyun C.H.,Daegu University | Kim H.-C.,Inha University | Kim H.-C.,Korea Institute for Advanced Study KIAS | Lee H.-J.,Chungbuk National University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2017

We investigate the parity-violating pion–nucleon–nucleon coupling constant hπNN 1, based on the chiral quark-soliton model. We employ an effective weak Hamiltonian that takes into account the next-to-leading order corrections from QCD to the weak interactions at the quark level. Using the gradient expansion, we derive the leading-order effective weak chiral Lagrangian with the low-energy constants determined. The effective weak chiral Lagrangian is incorporated in the chiral quark-soliton model to calculate the parity-violating πNN constant hπNN 1. We obtain a value of about 10−7 at the leading order. The corrections from the next-to-leading order reduce the leading order result by about 20%. © 2017 The Author(s)

Choi S.-B.,Inha University | Kim G.-W.,Inha University
Journal of Physics D: Applied Physics | Year: 2017

This study presents an investigation on the measurement of flexoelectric response in β-phase polyvinylidene fluoride (PVDF) films attached on cantilever beam-based flexible piezoelectric vibration energy harvesters (PVEHs). The flexoelectric response associated with negative strain gradients was simulated through harmonic response analysis by using the finite element method (FEM). The polarization frequency response functions (FRFs) modified by direct flexoelectric effect of PVDF films was experimentally validated by multi-mode FRFs. From quantitative comparisons between experimental observations and simulated estimation of FRFs, it is demonstrated that the direct flexoelectric response can be observed in PVDF films attached on PVEHs. © 2017 IOP Publishing Ltd.

Moon Y.-A.,Inha University
Endocrinology and Metabolism | Year: 2017

Nonalcoholic fatty liver disease (NAFLD) is strongly associated with insulin resistance, obesity, and dyslipidemia. NAFLD encompasses a wide range of states from the simple accumulation of triglycerides in the hepatocytes to serious states accompanied by inflammation and fibrosis in the liver. De novo lipogenesis has been shown to be a significant factor in the development of hepatic steatosis in insulin-resistant states. Sterol regulatory element binding protein-1c (SREBP-1c) is the main transcription factor that mediates the activation of lipogenesis, and SREBP cleavage activating protein (SCAP) is required for the activation of SREBPs. Here, recent animal studies that suggest SCAP as a therapeutic target for hepatic steatosis and hypertriglyceridemia are discussed. © 2017 Korean Endocrine Society.

The effect of 75% ethanol extract of daraesoon and samnamul (200 mg/kg) on the lipid oxidation of soybean oil-in-water (4:6, w/w) emulsion containing iron (5 mg/kg) in dark conditions at 25°C was studied by determining headspace oxygen and hydroperoxide contents. Polyphenol, carotenoid, and chlorophyll contents were also evaluated using spectrophotometry. The headspace oxygen contents were higher and hydroperoxide contents were lower (p<0.05) in the emulsions with added daraesoon and samnamul extracts compared with the control emulsion without the extract. The antioxidant activity of the daraesoon and samnamul extracts in the lipid oxidation of the emulsions was comparable to that of dibutylhydroxytoluene at 200mg/kg. Polyphenols, carotenoids, and chlorophylls were degraded during oxidation of the emulsions, possibly due to a role of the antioxidants. The results suggest that contribution to the improved lipid oxidative stability of the emulsion with added samnamul and daraesoon would be due to polyphenols and pigments, respectively. © 2017, The Korean Society of Food Science and Technology and Springer Science+Business Media Dordrecht.

The innovation literature often argues that major inventions arise through the cumulative synthesis of existing components and principles. An important economic phenomenon associated with this argument is the knowledge spillover. Although increasing attention has been paid to knowledge spillovers as a means to grasp innovation, little is known about its structural characteristics. This study examines the structural patterns of knowledge flow evidenced in patent citations by focusing on two aspects: the reciprocity of citations between technology sectors and the concentration of citing and cited sectors. The results indicate that the knowledge flow tends to be highly reciprocal within pairs of technology sectors instead of having a clear direction and that there are relatively low inflow and outflow concentrations in most sectors, although there are some exceptions. These results suggest that most technological sectors become both a knowledge provider and a knowledge consumer at the same time and they coevolve with reciprocal knowledge exchanges with each other. © 2017 Akadémiai Kiadó, Budapest, Hungary

Song J.,Jeju National University | Oh D.-H.,Inha University | Kang J.,Jeju National University
Computational Statistics and Data Analysis | Year: 2017

This study proposes a robust estimator for stochastic frontier models by integrating the idea of Basu et al. (1998) into such models. It is shown that the suggested estimator is strongly consistent and asymptotic normal under regularity conditions. The robust properties of the proposed approach are also investigated. A simulation study demonstrates that the estimator has strong robust properties with little loss in asymptotic efficiency relative to the maximum likelihood estimator. Finally, a real data analysis is performed to illustrate the use of the estimator. © 2016 Elsevier B.V.

Kim T.,Korea University | Choi R.,Inha University | Jeon S.,Korea University
IEEE Electron Device Letters | Year: 2017

Amorphous InHfZnO (a-IHZO) thin-film devices have attracted considerable attention owing to their high mobility. However, the mobility of a-IHZO thin-film transistors has not been correctly determined, because it is affected by fast charging. In this letter, we investigated the effect of transient charging on the mobility. On the basis of the pulse IDS VGS method, we present an approach to estimate a correction factor for the measured apparent mobility, which was extracted from pulse amplitude versus threshold voltage shift. © 1980-2012 IEEE.

Park J.-H.,Inha University
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2017

Computer generated holography plays a main role in the contents generation for holographic displays and digital archiving of three-dimensional objects. The fully analytic mesh based computer generated holography finds exact complex optical field for each triangular mesh of the three-dimensional objects for given sampling interval in the hologram plane without any approximation, enhancing the quality of the reconstruction. The mesh based processing rather than conventional point based one makes it compatible with most computer graphics techniques and efficient especially for large objects. In this paper, we present a few recent progress on fully analytic mesh based computer generated holography techniques including the dark line artifact removal, continuous shading of each mesh surface, the implementation of the angular reflectance distribution of the object surface and application of the texture map. © 2016 SPIE.

Garrisi D.,Inha University
Indagationes Mathematicae | Year: 2016

We characterize the projectors P on a Banach space E having the property of being connected to all the other projectors obtained as a conjugation of P. Using this characterization we show an example of Banach space where the conjugacy class of a projector splits into several path-connected components, and describe the conjugacy classes of projectors onto subspaces of ℓp⊕ℓq with p≠q. © 2016 Royal Dutch Mathematical Society (KWG).

Jeong K.M.,Inha University | Song B.C.,Inha University
2016 IEEE International Conference on Consumer Electronics-Asia, ICCE-Asia 2016 | Year: 2016

Conventional vehicle detection algorithms with rearlamp mostly utilize color data. However, due to the specification of night-Time environment with low-light, the color data often has not fully information. To resolve that problem, this paper contains vehicle detection algorithm using only gray value of rear-lamp in night-Time. Unlike implement binarization with the color data and gray value, this paper implement tone-mapping process with only intensity of illumination to preserve the shape of rear-lamp. Misdetection rate increases because of using only gray value, but this can be solved by applying condition of rearlamp characteristic to proposed algorithm. In addition, misdetection is removed through the tracking algorithm. This process can be utilized in automatic driving system, diriving assistance system and so on that recently has been issued because the proposed algorithm works in real-Time. © 2016 IEEE.

Han T.Y.,Inha University | Song B.C.,Inha University
2016 IEEE International Conference on Consumer Electronics-Asia, ICCE-Asia 2016 | Year: 2016

Performance of computer vision algorithm for pedestrian detection decrease in case of night vision system. Since intensity of luminance at night is extremely low compare to daytime, even human visibility cannot recognize object properly at night. Most recent generation of night vision system have researched using near infrared camera to settle the problem, but it still have poor visibility and application. This paper describes a night vision pedestrian detection for AEB (Automatic Emergency Braking) system using near infrared camera. ACF (Aggregated Channel Features) and AdaBoost algorithm are employed to discriminate pedestrians reflected by infrared. Most significant contribution of this paper is adaptive preprocessing to enhance contrast of pedestrians. Implementation have been done on both desktop and embedded board. With improved pedestrian detection performance, our approach allow drivers to avoid potential collisions effectively. © 2016 IEEE.

Helsing J.,Lund University | Kang H.,Inha University | Lim M.,Korea Advanced Institute of Science and Technology
Annales de l'Institut Henri Poincare (C) Analyse Non Lineaire | Year: 2016

We study spectral properties of the Neumann-Poincaré operator on planar domains with corners with particular emphasis on existence of continuous spectrum and pure point spectrum. We show that the rate of resonance at continuous spectrum is different from that at eigenvalues, and then derive a method to distinguish continuous spectrum from eigenvalues. We perform computational experiments using the method to see whether continuous spectrum and pure point spectrum appear on domains with corners. For the computations we use a modification of the Nyström method which makes it possible to construct high-order convergent discretizations of the Neumann-Poincaré operator on domains with corners. The results of experiments show that all three possible spectra, absolutely continuous spectrum, singularly continuous spectrum, and pure point spectrum, may appear depending on domains. We also prove rigorously two properties of spectrum which are suggested by numerical experiments: symmetry of spectrum (including continuous spectrum), and existence of eigenvalues on rectangles of high aspect ratio. © 2016 Elsevier Masson SAS.

Kim H.S.,Inha University | Asmis R.,University of Texas Health Science Center at San Antonio
Free Radical Biology and Medicine | Year: 2017

MAPK pathways play a critical role in the activation of monocytes and macrophages by pathogens, signaling molecules and environmental cues and in the regulation of macrophage function and plasticity. MAPK phosphatase 1 (MKP-1) has emerged as the main counter-regulator of MAPK signaling in monocytes and macrophages. Loss of MKP-1 in monocytes and macrophages in response to metabolic stress leads to dysregulation of monocyte adhesion and migration, and gives rise to dysfunctional, proatherogenic monocyte-derived macrophages. Here we review the properties of this redox-regulated dual-specificity MAPK phosphatase and the role of MKP-1 in monocyte and macrophage biology and cardiovascular diseases. © 2017 Elsevier Inc.

Chang C.-K.,Hannam University | Woo S.,Inha University
KSCE Journal of Civil Engineering | Year: 2017

Timely completion has been one of the most important concern due to its impact on both owner and contractor. When schedule is behind, one of most widely used schedule acceleration methods is working longer time: overtime. Overtime practice is one of key management decision because it may have a negative impact on labor productivity. Since overtime is the most widely used and numerous studies concluded that excessive amounts of overtime work could serious negative impact on labor productivity, quantification of the effect of overtime on labor productivity has been discussed in a number of papers. However, it was found that most studies reviewed in this paper have pitfalls. Most of them are out of date, based on a small sample size, and largely developed from questionable or unknown sources. Very little is known about how and from where the data were collected. Where the data source is known, little is known about other pertinent information, such as the characteristics of the project, work environments, quality of management and supervision, type of work, and trades involved. These information should be clearly provided to the users, who considers overtime to speed up the work, to see whether the result of the previous studies can be applied to the work he/she is currently doing. At the same time, for the researcher, this study will be able to guide what characteristics should be considered when he/she want to quantify the effect of overtime on construction labor productivity so that practitioners will not misuse the result of studies. © 2017 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg

Thi H.P.,Inha University | Lee H.,Inha University
2016 IEEE Asia Pacific Conference on Circuits and Systems, APCCAS 2016 | Year: 2016

This paper proposes a novel forward-backward four-way merger min-max algorithm and low latency check node unit (CNU) architecture for check node processing of nonbinary low-density parity check (NB-LDPC) codes. This algorithm derives simultaneously two output vectors for forward and backward processing in each step. A parallel switch network and parallel-serial elementary computation unit are proposed. Then, the CNU architecture corresponding to the algorithm is designed. The analysis and synthesis results show that the proposed CNU architecture obtains a latency reduction of 82.58% and 49.75% for any code rate without any loss performance, compared to previous works. © 2016 IEEE.

Afdhal N.H.,Beth Israel Deaconess Medical Center | Giannini E.G.,University of Genoa | Tayyab G.,Lahore General Hospital | Mohsin A.,Services Hospital Lahore | And 10 more authors.
New England Journal of Medicine | Year: 2012

BACKGROUND: Eltrombopag is an oral thrombopoietin-receptor agonist. This study evaluated the efficacy of eltrombopag for increasing platelet counts and reducing the need for platelet transfusions in patients with thrombocytopenia and chronic liver disease who are undergoing an elective invasive procedure. METHODS: We randomly assigned 292 patients with chronic liver disease of diverse causes and platelet counts of less than 50,000 per cubic millimeter to receive eltrombopag, at a dose of 75 mg daily, or placebo for 14 days before a planned elective invasive procedure that was performed within 5 days after the last dose. The primary end point was the avoidance of a platelet transfusion before, during, and up to 7 days after the procedure. A key secondary end point was the occurrence of bleeding (World Health Organization [WHO] grade 2 or higher) during this period. RESULTS: A platelet transfusion was avoided in 104 of 145 patients who received eltrombopag (72%) and in 28 of 147 who received placebo (19%) (P<0.001). No significant difference between the eltrombopag and placebo groups was observed in bleeding episodes of WHO grade 2 or higher, which were reported in 17% and 23% of patients, respectively. Thrombotic events of the portal venous system were observed in 6 patients who received eltrombopag, as compared with 1 who received placebo, resulting in the early termination of the study. The incidence and severity of other adverse events were similar in the eltrombopag and placebo groups. CONCLUSIONS: Eltrombopag reduced the need for platelet transfusions in patients with chronic liver disease who were undergoing elective invasive procedures, but it was associated with an increased incidence of portal-vein thrombosis, as compared with placebo. (Funded by GlaxoSmithKline; ELEVATE number, NCT00678587.) Copyright © 2012 Massachusetts Medical Society.

Jung M.H.,Sogang University | Park S.,Korea Basic Science Institute | You C.-Y.,Inha University | Yuasa S.,Japan National Institute of Advanced Industrial Science and Technology
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We investigate the bias dependences of in-plane and out-of-plane spin-transfer torque by employing magnetic noise measurement in symmetric MgO-based magnetic tunneling junction devices. The measured power spectra densities of magnetic noise are successfully analyzed by the fluctuation-dissipation theorem with an imaginary part of transverse susceptibility including spin-transfer torque contributions. We find that the in-plane component has a linear dependence of the bias voltage, while the out-of-plane component has a quadratic dependence. These results are well consistent with the noise amplitude analysis, neglecting the Joule heating effect with small bias voltage. © 2010 The American Physical Society.

You C.-Y.,Inha University | Jung M.-H.,Sogang University
Journal of Applied Physics | Year: 2013

We investigate the dependence of switching current density on the junction sizes in the in-plane spin transfer torque nanopillar structures by using micromagnetic simulations. While the macrospin model predicts weak dependence of switching current density on the junction sizes, we find that the switching current density is a sensitive function of the junction sizes. It can be explained with the complicated spin configurations and dynamics during the switching process. The detail spin configurations and dynamics are determined by spin wave excitation with the finite wave vector, which is related with the exchange coupling energy and junction shape. © 2013 American Institute of Physics.

Chung K.-Y.,Sangji University | Na Y.-J.,Inha University | Lee J.-H.,Inha University
Wireless Personal Communications | Year: 2013

Analysis of a customer's sensibility preferences is an important strategy in a market that is becoming increasingly more customer-oriented. In this paper, the interactive design recommendation using the sensor based smart wear and the weather WebBot (DRS-WB) is proposed. The proposed method is increasing the efficiency of merchandising for human-oriented sensibility product designs. Development of the DRS-WB included a user interface and collaborative filtering of textile and fashion designs to satisfy the user's needs. Collaborative filtering is used to recommend designs of interest for users based on predictive relationships discovered between the current user and other previous users. Current weather information is simultaneously acquired from the sensor based smart wear and the weather WebBot. The sensor based smart wear is fabricated as a way of non-tight and comfortable style fitting for the curves of the human body based on clothes to wear in daily life. The design sample of the smart wear uses basic stretch materials and is designed to sustain its wearable property. The weather WebBot uses a database of weather forecast information extracted from the Web pages and RSS (Really Simple Syndication) feed of the Korea Meteorological Administration and collects information from the various links off the main URL. Information is stored in a database using XML query for collecting effective weather data and processed as a form of XML through extracting and exchanging the information. These signals are then transmitted to the connected DRS-WB. This information can be easily monitored in real time. Textile designs and fashion designs were incorporated into the survey. Pictures of fashion design details such as collar type, sleeve type, skirt type, skirt length, and color tone were evaluated in terms of sensibility. Finally, this paper suggests empirical applications to verify the adequacy and validity of this system. © 2013 Springer Science+Business Media New York.

Lee Y.-R.,Inha University | Chung Y.-M.,Kunsan National University | Ahn W.-S.,Inha University
RSC Advances | Year: 2014

A highly porous and stable acid-base bifunctional metal-organic framework, MIL-101-NH2-SO3H, was prepared by direct solvothermal synthesis using two mixed (-NO2, -SO3H) terephthalate linkers followed by post-synthesis reduction to the NH2 form, which showed excellent performance for a one-pot tandem deacetalization-nitroaldol reaction. © 2014 the Partner Organisations.

Kim E.,Korea Institute of Science and Technology | Kim E.,Inha University | Kim W.,Sogang University | Lee K.H.,Inha University | And 2 more authors.
Advanced Functional Materials | Year: 2014

Achieving sub-10 nm high-aspect-ratio patterns from diblock copolymer self-assembly requires both a high interaction parameter (χ, which is determined by the incompatibility between the two blocks) and a perpendicular orientation of microdomains. However, these two conditions are extremely difficult to achieve simultaneously because the blocks in a high-χ copolymer typically have very different surface energies, favoring in-plane microdomain orientations. A fully perpendicular orientation of a high-χ block copolymer, poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) is realized here using partially hydrolyzed polyvinyl alcohol (PVA) top coats with a solvent annealing process, despite the large surface energy differences between PS and PDMS. The PVA top coat on the block copolymer films under a solvent vapor atmosphere significantly reduces the interfacial energy difference between two blocks at the top surface and provides sufficient solvent concentration gradient in the through-thickness direction and appropriate solvent evaporation rates within the film to promote a perpendicular microdomain orientation. The effects of interfacial energy differences and the swellability of PVA top coats controlled by the degree of hydrolysis on the orientation of microdomains are examined. The thickness of the BCP film and top coats also affects the orientation of the BCP film. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Xue N.,University of Texas at Dallas | Chang S.-P.,Inha University | Lee J.-B.,University of Texas at Dallas
Journal of Microelectromechanical Systems | Year: 2012

With the growing demand in noncontact detection of human diseases, this paper presents an implantable passive wireless pressure sensor using an inductively coupled wireless sensing technique, particularly designed to monitor the intraocular pressure (IOP) of glaucoma patients. The microfabricated IOP sensor consists of a planar spiral gold coil inductor, a two-parallel-gold-plate (metal-insulator-metal) capacitor, and a SU-8 pressure-sensitive diaphragm. The IOP sensor is fully encapsulated inside biocompatible SU-8 stacking layers to isolate the IOP sensor from the biological tissue medium environment. By measuring the impedance phase dip frequency shift from the external coil, the IOP signal can be obtained through the implanted IOP sensor. The optimized size of the manually wound external coil was investigated. The readout distance is up to 6 mm from the implanted sensor. Characterization results show that the microfabricated IOP sensor has relatively high sensitivities7035 ppm/mmHg in air and 3770 ppm/mmHg in saline mediumwith pressure resolution lower than 1 mmHg, which is adequate for IOP monitoring application. © 2012 IEEE.

Pan J.H.,National University of Singapore | Zhao X.S.,National University of Singapore | Lee W.I.,Inha University
Chemical Engineering Journal | Year: 2011

Over the last decade, mesoporous TiO2 nanocrystalline films have been intensively investigated not only for fundamental research interest but also for technological applications. This critical review summarizes recent progress of the block copolymer-templated highly organized mesoporous TiO2-based films prepared via an evaporation-induced self-assembly (EISA) process and their photoelectrochemical applications. With a brief introduction to the principle of block copolymer self-assembly and EISA process, control of the cooperative self-assembly between Ti species and block copolymer in the sol solution as well as in the deposited films, aging under a controlled humid environment, and subsequent thermal treatment is described. Key experimental parameters for the preparation of highly organized mesoporous TiO2 films are analyzed. Applications of mesoporous TiO2-based films in photocatalytic reactions, catalytic chemical synthesis, dye-sensitized solar cells, and electrochromic and photochromic devices are discussed. The synthesis-component-structure-property relationship in mesoporous TiO2-based films is highlighted, and the perspectives in this rapidly developing field are suggested. © 2010 Elsevier B.V.

Fan J.,Nanjing Forestry University | Li F.,Nanjing University | Nakamura G.,Inha University
Zeitschrift fur Angewandte Mathematik und Physik | Year: 2015

We prove the global-in-time and uniform-in-(ϵ1,ϵ2) of strong solutions to the isentropic Navier–Stokes–Maxwell system in a bounded domain, when ϵ1 is the Mach number, and ϵ2 is the dielectric constant. Consequently, we obtain the convergences of compressible Navier–Stokes–Maxwell system to the incompressible Navier–Stokes–Maxwell system (Formula Presented.), the compressible magnetohydrodynamic equations (Formula Presented.) or the incompressible magnetohydrodynamic equations (Formula Presented.) for well-prepared data. © 2014, Springer Basel.

Shi L.,University of California at Davis | Mukherjee B.,University of California at Davis | Lee S.-S.,Inha University | Lee S.-S.,Electronics and Telecommunications Research Institute | Lee S.-S.,Korean University of Science and Technology
IEEE Network | Year: 2012

Energy usage in our networks is increasing rapidly; and to conserve energy, progress has been made in designing energy-efficient passive optical networks, which are being widely deployed for broadband access. Among the various energy-saving techniques, enabling sleep mode in optical network units is a very promising approach. However, the slow transition of power from active mode to sleep mode in an optical network unit, and the relatively large recovery and synchronization time needed during the wakeup process are challenges that need to be addressed. In this regard, we propose a service-level-agreement-based scheduling scheme for passive optical networks in which the optical line terminal can adjust the sleep time and the optical network unit can quit sleep mode for sending high-priority packets. The trade-off in energy savings vs. delay performance is evaluated using simulations under practical power consumption settings. © 2012 IEEE.

Jee S.C.,Inha University | Lee H.J.,Inha University | Joo Y.H.,Kunsan National University
Nonlinear Dynamics | Year: 2012

This paper addresses sensor fault detection observer design problems for discrete- and continuous-time nonlinear systems in Takagi-Sugeno's (T-S) form. It is desired that the fault detection observer is as sensitive to fault and robust against disturbance as possible. To this end, sufficient conditions for stable T-S fuzzy model-based observer design with ℋ -/ ℋ ∞ performance are derived in terms of linear matrix inequalities in both cases. An example on the backing-up problem of a truck-trailer is provided to illustrate the effectiveness of the proposed methodology. © 2011 Springer Science+Business Media B.V.

Kang S.-K.,Inha University | Chung K.-Y.,Sangji University | Lee J.-H.,Inha University
Personal and Ubiquitous Computing | Year: 2014

This paper proposes a technique for the detection of head nod and shake gestures based on eye tracking and head motion decision. The eye tracking step is divided into face detection and eye location. Here, we apply a motion segmentation algorithm that examines differences in moving people's faces. This system utilizes a Hidden Markov Model-based head detection module that carries out complete detection in the input images, followed by the eye tracking module that refines the search based on a candidate list provided by the preprocessing module. The novelty of this paper is derived from differences in real-time input images, preprocessing to remove noises (morphological operators and so on), detecting edge lines and restoration, finding the face area, and cutting the head candidate. Moreover, we adopt a K-means algorithm for finding the head region. Real-time eye tracking extracts the location of eyes from the detected face region and is performed at close to a pair of eyes. After eye tracking, the coordinates of the detected eyes are transformed into a normalized vector of x-coordinate and y-coordinate. Head nod and shake detector uses three hidden Markov models (HMMs). HMM representation of the head detection can estimate the underlying HMM states from a sequence of face images. Head nod and shake can be detected by three HMMs that are adapted by a directional vector. The directional vector represents the direction of the head movement. The vector is HMMs for determining neutral as well as head nod and shake. These techniques are implemented on images, and notable success is notified. © 2013 Springer-Verlag London.

Kim G.-S.,Yeungjin College | Lee S.-H.,Inha University
IEEE Transactions on Plasma Science | Year: 2010

As the temperature of the panel increases in AC-PDPs, the minimum driving voltage increases. Thus, the driving voltage margin is not sufficient at high temperature. In this paper, we have investigated the mechanism of a misdischarge which is generated due to the decrement of the driving voltage margin at high temperature. The main factor of the high-temperature misdischarge is the increased electron emission ability from the MgO surface. We have confirmed that the wall charge loss in the address period is the largest among the driving periods. We have verified that the wall charge loss at high temperature depends on not only the voltage difference but also the time when the voltage difference is applied. Therefore, the wall charge loss is influenced by the number of sustain discharges in the previous subfield and address load. Finally, we have improved the driving voltage margin at high temperature using a narrow scan time and a high scan voltage in a 50-in panel with HD resolution. © 2006 IEEE.

Lee J.O.,Korea Atomic Energy Research Institute | Lim J.G.,Korea Atomic Energy Research Institute | Kang I.M.,Korea Institute of Geoscience and Mineral Resources | Kwon S.,Inha University
Engineering Geology | Year: 2012

One of the major functions of a bentonite buffer for a HLW repository is to provide the buffer with a self-sealing capacity through its ability to swell on contact with free water. Swelling pressure measurements were carried out to investigate the swelling behavior of Ca-bentonite. Experimental results showed that the swelling pressure increased with an increase in dry density, and its dependence on dry density increased at higher dry densities beyond 1.6Mg/m 3. The effect of salinity on the swelling pressure for the Ca-bentonite was different from that for Na-bentonite. The swelling pressure of the Ca-bentonite was higher in a diluted concentration of NaCl solution (0.04M) compared with de-mineralized water, and it then decreased with an increase in the concentration of the NaCl solution beyond 0.04M. Such a swelling behavior of the Ca-bentonite was explained by the ion-exchange of Ca 2+ for Na + from the solution followed by hydration with water molecules and osmosis due to the differences in concentrations of the NaCl solutions. © 2012 Elsevier B.V..

Kang D.W.,Inha University | Kim T.S.,Inha University | Hur K.B.,Korea Electric Power Research Institute | Park J.K.,Korea Electric Power Research Institute
Applied Energy | Year: 2012

We investigated the influence of firing biogas on the performance and operating characteristics of gas turbines. Combined heat and power systems based on two different gas turbines (simple and recuperative cycle engines) in a similar power class were simulated. A full off-design analysis was performed to predict the variations in operations due to firing biogas instead of natural gas. A wide range of biogas compositions differing in CH4 content was simulated. Without consideration of operating restrictions on the compressor and turbine, using biogas was predicted to augment the power output in both engines. Power output increased as CH4 content decreased. The main reason is the increase in turbine power due to increased fuel flow. Gas turbine efficiency increased with decreasing CH4 content in the simple cycle engine, but decreased in the recuperative cycle engine. Net efficiency including the fuel compression power consumption decreased with decreasing CH4 content even in the simple cycle engine. The heat recovery also increased by firing biogas. However, the increased turbine flow was accompanied by a surge margin reduction of the compressor and overheating of the turbine blade. These two problems were more severe in simple cycle gas turbines and as the ambient temperature increased. The turbine blade temperature and the compressor surge margin could be recovered to the reference values by either under-firing or compressor air bleeding, which are effective for blade temperature control and surge margin control, respectively. However, satisfaction of both restrictions by a single modulation caused excessive power and efficiency losses. An optimal combination between under-firing and air bleeding would minimize the performance penalty. © 2011 Elsevier Ltd.

Kim J.,Inha University | Kim S.-N.,Inha University | Jang H.-G.,Chonnam National University | Seo G.,Chonnam National University | Ahn W.-S.,Inha University
Applied Catalysis A: General | Year: 2013

Metal organic framework (MOF) structures of UIO-66, UIO-66-NH2, Mg-MOF-74, MIL-101, CuBTC, ZIF-8, IRMOF-3, and MOF-5 having different acid/base properties were prepared and tested for their catalytic activity in the CO 2 cycloaddition to styrene epoxide using a high-pressure batch reactor. The high crystallinity and excellent textural properties of the prepared MOF materials were confirmed by XRD and the N2 adsorption-desorption isotherms at 77 K. Their catalytic cycloaddition activities were found to be well correlated with the Lewis acid/base distributions of the materials examined by NH3- and CO 2-TPD, respectively, such that the concurrent presence of Lewis acid and base sites were desirable for high catalytic activity. For a given catalyst weight, UIO-66-NH2 showed the best catalytic performance among the MOF samples tested with close to 100% selectivity to carbonate in chlorobenzene under relatively mild reaction conditions (2.0 MPa, 373 K). UIO-66-NH 2 could be reused 3 times without losing catalytic activity in a truly heterogeneous mode without structural deterioration, and it also exhibited excellent cycloaddition activities for different epoxide substrates as well. © 2012 Elsevier B.V.

Zhao C.,Inha University | Zhao C.,Beijing University of Posts and Telecommunications | Kwak K.,Inha University
IEEE Communications Letters | Year: 2010

The jointly optimal allocation of sensing time and power for a two-user amplify-and-forward overlay cognitive network is developed by maximizing the averaged aggregate throughput of the secondary network. In particular, observing that the sensing duration lies within a strict interval, the jointly optimal strategy of sensing time and power allocation is proved to be tractable by sequential optimization. © 2010 IEEE.

Kim G.-W.,Kyungpook National University | Kim J.,Inha University
Smart Materials and Structures | Year: 2013

This paper presents a bio-inspired mechanism for the performance enhancement of piezoelectric power generation in vibration energy harvesting. A compliant bistable mechanism for vibration energy harvesting was explored based on the negative stiffness inspired by the auditory hair bundle structures. The proposed mechanism consists of a compliant, four-bar linkage system to mimic the hair bundle structure inside an inner ear. Our initial prototype energy harvester demonstrates that the compliant bistable mechanism featuring negative stiffness outperforms the conventional vibration energy harvester in the infra-low frequency range (1-10 Hz). © 2013 IOP Publishing Ltd.

Kim S.-Y.,Korea University of Technology and Education | Kim J.,Inha University | Kim K.-B.,Inha University
Smart Materials and Structures | Year: 2014

The most important factor in haptic interaction with hand-held devices is to develop a thin film type actuator which can be easily inserted into the devices and create vibrotactile signals with wide frequency bandwidth. This paper reports a film type vibrotactile actuator which is tiny enough to be embedded into small hand-held devices. The vibration mechanism and experiment results for the suggested vibrotactile actuator are explained. The aim of the actuator is to convey a vibrotactile force greater than a human's vibrotactile threshold with broad frequency bandwidth to users. To achieve the requirement, we fabricate a film type vibrotactile actuator with cellulose acetate. When an AC voltage is applied to the actuator, the cellulose acetate film gets charged and then generates vibration. The suggested vibrotactile actuator is fabricated in two sizes: 50 mm × 25 mm and 25 mm × 25 mm. For each size of actuator, three kinds of actuator are fabricated with different pillar materials to support the cellulose acetate films. An experiment for measuring vibrational amplitude is conducted over a wide frequency range of actuation voltage. It is known that the proposed film type actuator is feasible for haptic application in the small hand-held devices. © 2014 IOP Publishing Ltd.

Hong S.-H.,Inha University | Jang M.-S.,Inha University | Cho S.J.,Chonnam National University | Ahn W.-S.,Inha University
Chemical Communications | Year: 2014

Mesoporous chabazite ion-exchanged with Ca2+ was effective for CO2 capture at 20 bar and 473 K, whereas 13X as a support material enabled recyclable carbonation of ca. 8 wt% Mg(OH)2 approaching the theoretical maximum for CO2 capture with 10% H2O. © 2014 the Partner Organisations.

Lee H.,Seoul National University | Kumar Kundu J.,Keimyung University | Cha Y.,Inha University | Surh Y.,Seoul National University | Surh Y.,Seoul National University of Science and Technology
Journal of Cell Science | Year: 2013

Phagocytosis of apoptotic neutrophils, termed efferocytosis, is essential for the resolution of inflammation as it prevents the tissues surrounding the inflamed site from being exposed to the toxic contents of lytic cells. Resolvin D1 (RvD1), endogenously generated from docosahexaenoic acid during resolution of inflammation, is known to stimulate efferocytosis. However, the molecular mechanism underlying RvD1-mediated enhancement of efferocytosis remains largely unresolved. In the present study, murine macrophage-like RAW264.7 cells treated with lipopolysaccharide (LPS) exhibited markedly reduced efferocytic activity, but this was restored by coincubation with RvD1. RvD1-induced restoration of the efferocytic activity appears to be mediated by downregulation of LPS-induced TNF-α expression. The inhibitory effect of RvD1 on LPS-induced TNF-α expression was associated with enhanced nuclear localization of p50/p50 homodimer and concomitant reduction of p65/p50 heterodimer accumulation in the nucleus. RvD1 triggered phosphorylation and proteasomal degradation of nuclear factor κB1 (NF-κB1) p105 to generate p50, which was subsequently translocated to the nucleus as a p50/p50 homodimer. Knockdown of NF-κB p50 abolished the ability of RvD1 to suppress TNF-α expression and also to restore efferocytosis, suggesting that the replacement of p65/p50 with p50/p50 homodimer in the nucleus is crucial for RvD1-mediated stimulation of efferocytosis. In a murine peritonitis model, intraperitoneal administration of RvD1 abolished the zymosan-A-induced TNF-α production, thereby stimulating efferocytosis. Taken together, these findings indicate that RvD1 expedites resolution of inflammation through induction of efferocytosis by p50/p50-homodimer-mediated repression of TNF-α production. © 2013. Published by The Company of Biologists Ltd.

Premaratne P.,University of Wollongong | Ajaz S.,Inha University | Premaratne M.,Monash University
Neurocomputing | Year: 2013

Dynamic hand gesture tracking and recognition system can simplify the way humans interact with computers and many other non-critical consumer electronic equipments. This system is based on the well-known "Wave Controller" technology developed at the University of Wollongong [1-3] and certainly a step forward in video gaming and consumer electronics control interfaces. Currently, computer interfacing mainly involves keyboard, mouse, joystick or gaming wheels and occasionally voice recognition for user input. These modes of interaction have constrained the artistic ability of many users, as they are required to respond to the computer through pressing buttons or moving other apparatus. Voice recognition is seen as unreliable and impractical in areas where more than one user is present. All these drawbacks can be tackled by using a reliable hand gesture tracking and recognition system based on both Lucas-Kanade and Moment Invariants approaches. This will facilitate interaction between users and computers and other consumer electronic equipments in real time. This will further enhance the user experience as users are no longer have any physical connection to the equipment being controlled. In this research, we have compared our proposed moment invariant based algorithm with template based and Fourier descriptor based methods to highlight the advantages and limitations of the proposed system. © 2012 Elsevier B.V.

Na K.,Center for Functional Nanomaterials | Na K.,KAIST | Jo C.,Center for Functional Nanomaterials | Jo C.,KAIST | And 4 more authors.
ACS Catalysis | Year: 2011

Titanosilicate MFI (a three-letter structural code among ∼200 zeolite framework codes) nanosheets of single-unit-cell thickness were synthesized with a diquaternary ammonium surfactant as the zeolite structure-directing agent, that is, C16H33-N+(CH3) 2-C6H12-N+(CH3) 2-C6H13. The resultant titanosilicate nanosheet possessed a large intersheet mesopore volume with high surface area due to the nanomorphic crystalline architecture as well as the isomorphically incorporated titanium species. Thus, it exhibited notable catalytic activities with high epoxide selectivity for bulky molecular epoxidation reactions using H 2O2 or t-butyl hydroperoxide as an oxidant. In addition, the catalytic performance could be enhanced via postsynthetic fluoride treatment with NH4F that can reduce the surface silanol groups and, hence, increase the surface hydrophobicity. © 2011 American Chemical Society.

Zhao C.,Beijing University of Posts and Telecommunications | Zhao C.,Inha University | Kwak K.,Inha University
IEEE Transactions on Vehicular Technology | Year: 2010

Conflict-free power allocation for secondary users (SUs) in cognitive networks is a challenging problem because the accessible spectrum of the SUs is shared with the primary users (PUs). The problem becomes particularly difficult when the objective is to achieve maximum network capacity considering the mutual interference between the PUs and the SUs. In this paper, we specify the case with a single SU and multiple PUs, where both the SU and the PUs are orthogonal frequency-division multiplexing (OFDM) modulated. The power allocation for the subcarriers of the SU is modeled into a constrained optimization problem, where the mutual interference between the SU and the PUs is comprehensively formulated as restrictions on the SU's transmission power. As a result, the proposed modeling scheme restrains the interference to the PUs, as well as maximizing the capacity of the SU. A novel iterative power-loading algorithm with low computational complexity is proposed to realize the power loading. On this basis, a suboptimal integral-bit-loading algorithm is further presented. In a simplified scenario, simulation results are exhibited to confirm the efficiency of the proposed power and bit-loading algorithms. Finally, the influence of the mutual interference on the SU's power/bit loading and the system capacity is illustrated. © 2006 IEEE.

Jeong S.-H.,Inha University | Mwafy A.M.,United Arab Emirates University | Elnashai A.S.,University of Illinois at Urbana - Champaign
Engineering Structures | Year: 2012

Fragility analyses are conducted in this study to evaluate the relative seismic safety margins of seismic code-designed multi-story reinforced concrete (RC) buildings with varying input motion intensity, ductility level and configuration. Structural variations are accounted for by using twelve buildings [13] with diverse structural systems, heights and ductile detailing. The design peak ground acceleration (PGA) is also varied. The reference structures also include regular and irregular buildings in order to cover a wide spectrum of contemporary mid-rise buildings. Incremental dynamic analyses (IDAs) are deployed using the twelve inelastic fiber-based simulation models of the reference structures and sixty natural ground motions recorded on different soil conditions with a wide range of spectral amplifications. The regression analyses of the selected response quantities show that the soil condition has a marginal effect on the demand-ground motion intensity relationships when adopting spectral acceleration to characterize the ground shaking intensity. The damage state probabilities of wall-frame structures designed to high PGA and ductility levels do not satisfactorily achieve the most favorable safety objectives. Fragilities are reduced by decreasing the design PGA due to the higher contribution of gravity loads to the details of the building design. Using extensive results from twelve buildings subjected to sixty ground motions, a relationship is proposed to enable the quantifying of the Life Safety limit state probabilities of code-compliant mid-rise RC buildings. © 2011 Elsevier Ltd.

Cho W.Y.,Soonchunhyang University | Jang J.Y.,Kyung Hee University | Lee D.H.,Inha University
Clinical Endoscopy | Year: 2011

The desire to better recognized such malignancies, which may be difficult to distinguish from inflammation or trauma, has accelerated the development of endoscopy with new optical technologies. Narrow-band imaging is a novel endoscopic technique that may enhance the accuracy of diagnosis using narrow-bandwidth filters in a red-green-blue sequential illumination system. Autofluorescence imaging is based on the detection of natural tissue fluorescence emitted by endogenous molecules. I-scan technology using a digital filter that modifies normal images through software functions, is the newly developed image-enhanced endoscopic technology from PENTAX. Flexible spectral imaging color enhancement enhances the visualization of mucosal structure and microcirculation by the selection of spectral transmittance with a dedicated wavelength. Confocal laser endomicroscopy images were collected with an argon beam with a scanning depth of 0 (epithelium) to 250 μm (lamina propria) and analyzed using the reflected light. © 2011 The Korean Society of Gastrointestinal Endoscopy.

Oh M.,Pusan National University | Park S.-J.,Inha University | Jung Y.,Korea University of Technology and Education | Kim S.,Pusan National University
Synthetic Metals | Year: 2012

Polyaniline (PANI)/titanium dioxide (TiO 2) composites were prepared by a chemical oxidation polymerization. The composites were prepared with various amount of TiO 2 to find a relation between electrochemical properties of composites and compositions of TiO 2 and PANI in the composites. PANI/TiO 2 composites which had PANI as a shell and TiO 2 as a core part of the composites were successfully synthesized. Fiber-like PANI was also observed within the composites. The synthesis was explained as two stages of polymerization. First stage is a polymerization reaction occurred by a strong oxidative potential of TiO 2. Second stage is started by adding ammonium peroxydisulfate in reaction solution. Diameters of aggregations of the composites increased with the added amounts of TiO 2. The composite prepared with 10 wt.% of TiO 2 per aniline monomer weight showed the highest capacitance of 784 F g -1 among the prepared composites. But the composites prepared with excess amounts of TiO 2 showed lower capacitance than the highest one. The lower capacitances of the composites prepared with excess amounts of TiO 2 was considered as related with the diameters of the aggregations. The composites prepared with excess amounts of TiO 2 had large diameters for the aggregations. The TiO 2 particles in the core of composites that had large diameter are hard to participate in electrochemical reaction due to a long pathway from electrolyte to TiO 2 core and a blocking effect by outer TiO 2 particles. © 2012 Elsevier B.V. All rights reserved.

Oh C.H.,Guro Teun Teun Hospital | Yoon S.H.,Inha University
Keio Journal of Medicine | Year: 2013

Cervical arthroplasty was developed in an attempt to maintain cervical motion and potentially to avoid or minimize adjacent-segment degeneration. If cervical arthroplasty is successful, the long-term results of surgery for cervical disc disease should improve. However, problems associated with cervical arthroplasty have been reported: these include kyphosis, heterotopic ossification-induced motion limitation, no motion preservation even at the index level, and a higher revision rate in a limited number of cases compared with anterior cervical discectomy and fusion (ACDF). In addition, for degenerative cervical disc disorders, the risk of developing adjacent segment degeneration more than 2 years after surgery is reportedly similar for ACDF and cervical arthroplasty. Cervical disc arthroplasty is an emerging motion-sparing technology and is currently undergoing evaluation in many countries as an alternative to arthrodesis for the treatment of cervical radiculopathy and myelopathy. The decision whether to use arthrodesis or arthroplasty is a difficult one. The achievement of good prosthetic performance demands exacting implantation techniques to ensure correct placement. This fact underlines the increasing importance of special instrumentation and surgical skills that involve an understanding of prosthetic lubrication, wear, and biologic effects and familiarity with currently available information regarding kinematics, basic science, testing, and early clinical results. Fortunately, a number of devices are at the late preclinical study stage or at the early clinical trial stage, and results in many cases are promising. In the near future, it is likely that new designs will be produced to replace spinal discs totally or partially in a pathologic entity-specific manner. © 2013 by The Keio Journal of Medicine.

Ledwig T.,University Mainz | Silva A.,University of Porto | Kim H.-C.,Inha University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider 1/Nc rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: κTu=3.56 and κTd=1.83, respectively. The strange anomalous tensor magnetic moment is yielded to be κTs=0.2∼-0.2, that is compatible with zero. We also calculate the corresponding form factors κTq(Q2) up to a momentum transfer Q2≤1GeV2 at a renormalization scale of 0.36GeV2. © 2010 The American Physical Society.

Kim H.-C.,Inha University | Kim H.-C.,University of Connecticut | Kim H.-C.,Korea Institute for Advanced Study | Schweitzer P.,University of Connecticut | Yakhshiev U.,Inha University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

The nucleon form factors of the energy-momentum tensor are studied in nuclear medium in the framework of the in-medium modified Skyrme model. We obtain a negative D-term, in agreement with results from other approaches, and find that medium effects make the value of d 1 more negative. © 2012 Elsevier B.V.

Guo X.-F.,Inha University | Kim J.-H.,Chonnam National University | Kim G.-J.,Inha University
Catalysis Today | Year: 2011

Multi-walled carbon nanotubes were synthesized by chemical vapor deposition method using SBA-15 as a template under methane and carbon dioxide as carbon sources. As-synthesized multi-walled carbon nanotubes were treated by NaOH at 80 °C to remove the template and retain the Ni and Co metals. The multi-walled carbon nanotubes supported (Co and Ni) were used as catalysts. The catalysts were characterized by SEM, TEM, XRD, Raman and SEM-EDX. The catalytic activity was investigated for the dehydrogenation of ethylbenzene at different oxidants and temperatures. CNTs-Co-10 showed the highest styrene selectivity (92.3%) at 450 °C and ethylbenzene conversion (93.5%) at 700 °C with a higher styrene yield (80.6). The catalyst also showed a high thermal stability. © 2010 Elsevier B.V. All rights reserved.

Choi M.-J.,Keimyung University | Chang K.J.,Inha University
Advances in Experimental Medicine and Biology | Year: 2013

The purpose of this study was to determine the effect of arginine or taurine alone and taurine plus arginine on bone mineral density (BMD) and markers of bone formation and bone resorption in growing female rats. Forty female SD rats (75 ± 5 g) were randomly divided into four groups (control, taurine, arginine, taurine + arginine group) and treatment lasted for 9 weeks. All rats were fed on a diet and deionized water. BMD and bone mineral content (BMC) were measured using PIXImus (GE Lunar Co, Wisconsin, USA) in spine and femur. The serum and urine concentrations of calcium and phosphorus were determined. Bone formation was measured by serum osteocalcin and alkaline phosphatase concentrations, and the bone resorption rate was measured by deoxypyridinoline cross-links. Femur BMD was significantly increased in the group with taurine supplementation and femur BMC/weight was significantly increased in the group with arginine + taurine supplementation. Rats fed an arginine or taurine supplemental diet increased femur BMD or femur BMC, but a taurine + arginine-supplemented diet does not have a better effect than arginine or taurine alone in the spine BMD. The femur BMC, expressed per body weight, was higher in arginine + taurine group than in the taurine or arginine group. The results of this study suggest that taurine + arginine supplementation may be beneficial on femur BMC in growing female rats. Additional work is needed to clarify the interactive effects between the taurine and arginine to determine whether dietary intakes of arginine and taurine affect bone quality in growing rats. © Springer Science+Business Media New York 2013.

Park H.-Y.,Korea Advanced Institute of Science and Technology | Yang H.,Inha University | Choi S.-K.,Korea Advanced Institute of Science and Technology | Jang S.-Y.,Kookmin University
ACS Applied Materials and Interfaces | Year: 2012

Polymer-based field-effect transistors are fabricated using the gas-assisted spray technique, and their performance is considerably improved when a solvent-assisted post-treatment method, solvent sprayed overlayer (SSO), is used. The SSO method is a unique treatment that can facilitate chain packing to increase crystallinity within the sprayed polymer layers, which inherently have a kinetically trapped amorphous chain morphology with lack of crystallinity due to rapid solvent evaporation. The device performance was drastically improved after SSO relative to conventional post-treatment, thermal annealing (TA). This occurred because SSO can rearrange the polymer chains into a dominantly edge-on crystal orientation, which is preferential for charge transport, whereas TA increases the crystallinity without rearrangement of the crystal orientation resulting in a complex of edge-on and face-on. The development of edge-on crystal domains after SSO within the active layers was responsible for the significant improvement in performance. The SSO is a simple and effective post-treatment method that validates the use of spray process and holds promise for use in other high-throughput processes for OFETs fabrication. © 2011 American Chemical Society.

Jeong S.-H.,Inha University | Elnashai A.S.,University of Illinois at Urbana - Champaign
Structure and Infrastructure Engineering | Year: 2012

It is desirable to use probabilistic performance targets for decision-making as it relates to intervention methods, because of high uncertainties of structure responses under earthquake loadings. This is based on the probabilistic performance assessment of structures with various retrofit options. Extensive computer simulations to account for the randomness in both input motion and response characteristics have been a serious obstacle to the adoption of the probabilistic performance assessment in the decision of seismic intervention schemes. This study presents an approach whereby a fragility assessment result with known reliability is derived based on the fundamental response quantities of stiffness, strength and ductility. An exact solution for a generalised single-degree-of-freedom system is employed to construct a response database of maximum responses. Once the fundamental response quantities of a wide range of structural systems are defined, the fragility assessment for various limit states can be constructed without recourse to further simulation. By virtue of its instantaneous nature, the proposed method is especially useful for practical application of the analytical fragility assessment that includes the planning of seismic rehabilitation and regional earthquake mitigation, where fast estimation of probabilities of reaching damage states for a large number of structural configurations and different mitigation measures is required. For cases of selection between different retrofitting options, the proposed approach gives rapid estimates of probabilities of various damage levels inflicted on the structures under consideration, given only the stiffness, strength and ductility for each alternative retrofitting scheme. The presented fragility contour and constant fragility spectra enable the engineer to use visualised data sets to practically and conveniently investigate the probabilistic performance of every retrofit option. © 2012 Copyright Taylor and Francis Group, LLC.

Yun S.W.,Seoul National University | Kim J.H.,Seoul National University | Shin S.,Seoul National University | Yang H.,Inha University | And 3 more authors.
Advanced Materials | Year: 2012

Novel π-conjugated cyanostilbene-based semiconductors (Hex-3,5-TFPTA and Hex-4-TFPTA) with tight molecular stacking and optimized energy levels are synthesized. Hex-4-TFPTA exhibits high-performance n-type organic field-effect transistor (OFET) properties with electron mobilities as high as 2.14 cm 2 V-1s-1 and on-off current ratios >10 6. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Airbus Group and the Global Engineering Deans Council (GEDC), have named Dr Yacob Astatke, from Morgan State University in the USA, as the recipient of the 2016 GEDC Airbus Diversity Award for his work in engineering education. The Award ceremony took place during the GEDC and World Engineering Education Forum (WEEF) conference in Seoul, South Korea. The Award is designed to promote a more diverse engineering workforce globally. It recognises grass roots initiatives and the people behind them which enable students from all backgrounds and profiles to study and succeed in the field of engineering. Out of a total of 40 candidates from 17 countries, Dr Yacob Astatke was selected as the award recipient for his impressive introduction of technology and training initiatives across universities in Ethiopia to improve the delivery of engineering education in Africa. For the past 13 years, he conducted graduate courses, sharing best practice and delivering training. He led the implementation of Mobile Studio Technology and pedagogy in five universities in Ethiopia and has been instrumental in facilitating the donation of equipment and other resources. In addition to the global visibility which the award offers, Dr Astatke has received a significant financial contribution to support and develop his work. Along with two other remarkable finalists, Dr Astatke presented his project to a distinguished international Jury led by Charles Champion, Airbus' Executive Vice President Engineering and Peter Kilpatrick, Chairperson of the GEDC and Dean of Engineering at the University of Notre Dame, US. "At Airbus diversity is in our DNA. Our future success will continue to draw on the diversity of our workforce because innovation, creativity and performance are driven by this diversity," said Charles Champion. "The achievement of our 2016 award recipient is testimony to their hard work and commitment in this field. We hope that engineering leaders from around the world will be inspired to follow this example, and replicate these initiatives in order to build a more diverse global community of engineers." Airbus Group and the GEDC are united in their belief that both industry and academia need to actively encourage more diverse students to study and pursue a career in engineering. The finalists' presentations were evaluated by the Jury based on their ability to channel a desire for more diversity in engineering into real, measurable change through an initiative that has the potential to be replicated elsewhere. "Our three finalists have taken up the vital challenge of encouraging more young people to become engineers in order to solve some of the biggest challenges we face in the 21st century," said Peter Kilpatrick of the GEDC. "The message is that together, looking to the work of our finalists for inspiration and as great examples for success, the work we do can and will make a difference." The Jury also included: Doctor Sirin Tekinay, President, Rector of ISIKUN University and a GEDC leader; Professor Qidi Wu, Director at Tsinghua University, Chairperson of the CEEAA, Director of the International Centre for Engineering Education under the Auspices of UNESCO (ICEE) and Director of the Department of Management Sciences of NSFC; and Professor Soonja Choe, President of Inha University (part of KAL group), South Korea. More information can be found at

Airbus Group and the Global Engineering Deans Council (GEDC), have named Dr Yacob Astatke, from Morgan State University in the USA, as the recipient of the 2016 GEDC Airbus Diversity Award for his work in engineering education. The Award ceremony took place during the GEDC and World Engineering Education Forum (WEEF) conference in Seoul, South Korea. The Award is designed to promote a more diverse engineering workforce globally. It recognises grass roots initiatives and the people behind them which enable students from all backgrounds and profiles to study and succeed in the field of engineering. Out of a total of 40 candidates from 17 countries, Dr Yacob Astatke was selected as the award recipient for his impressive introduction of technology and training initiatives across universities in Ethiopia to improve the delivery of engineering education in Africa. For the past 13 years, he conducted graduate courses, sharing best practice and delivering training. He led the implementation of Mobile Studio Technology and pedagogy in five universities in Ethiopia and has been instrumental in facilitating the donation of equipment and other resources. In addition to the global visibility which the award offers, Dr Astatke has received a significant financial contribution to support and develop his work. Along with two other remarkable finalists, Dr Astatke presented his project to a distinguished international Jury led by Charles Champion, Airbus' Executive Vice President Engineering and Peter Kilpatrick, Chairperson of the GEDC and Dean of Engineering at the University of Notre Dame, US. "At Airbus diversity is in our DNA. Our future success will continue to draw on the diversity of our workforce because innovation, creativity and performance are driven by this diversity," said Charles Champion. "The achievement of our 2016 award recipient is testimony to their hard work and commitment in this field. We hope that engineering leaders from around the world will be inspired to follow this example, and replicate these initiatives in order to build a more diverse global community of engineers." Airbus Group and the GEDC are united in their belief that both industry and academia need to actively encourage more diverse students to study and pursue a career in engineering. The finalists' presentations were evaluated by the Jury based on their ability to channel a desire for more diversity in engineering into real, measurable change through an initiative that has the potential to be replicated elsewhere. "Our three finalists have taken up the vital challenge of encouraging more young people to become engineers in order to solve some of the biggest challenges we face in the 21st century," said Peter Kilpatrick of the GEDC. "The message is that together, looking to the work of our finalists for inspiration and as great examples for success, the work we do can and will make a difference." The Jury also included: Doctor Sirin Tekinay, President, Rector of ISIKUN University and a GEDC leader; Professor Qidi Wu, Director at Tsinghua University, Chairperson of the CEEAA, Director of the International Centre for Engineering Education under the Auspices of UNESCO (ICEE) and Director of the Department of Management Sciences of NSFC; and Professor Soonja Choe, President of Inha University (part of KAL group), South Korea. More information can be found at

Kim S.H.,Pohang University of Science and Technology | Jang M.,Inha University | Yang H.,Inha University | Anthony J.E.,University of Kentucky | Park C.E.,Pohang University of Science and Technology
Advanced Functional Materials | Year: 2011

A chemically coupled polymer layer is introduced onto inorganic oxide dielectrics from a dilute chlorosilane-terminated polystyrene (PS) solution. As a result of this surface modification, hydrophilic-oxide dielectrics gain hydrophobic, physicochemically stable properties. On such PS-coupled SiO 2 or AlOx dielectrics, various vacuum- and solution-processable organic semiconductors can develop highly ordered crystalline structures that provide higher field-effect mobilities (μFETs) than other surface-modified systems, and negligible hysteresis in organic field-effect transistors (OFETs). In particular, the use of PS-coupled AlOx nanodielectrics enables a solution-processable triethylsilylethynyl anthradithiophene OFET to operate with μFET ∼ 1.26 cm2 V-1 s-1 at a gate voltage below -1 V. In addition, a complementary metal-oxide semiconductor-like organic inverter with a high voltage gain of approximately 32 was successfully fabricated on a PS-coupled SiO2 dielectric. Ultrathin polymer layers were chemically coupled on oxide dielectrics with chlorosilane-terminated polystyrene (PS). The PS-brush layer was physicochemically stable and provided a smooth, hydrophobic surface to induce highly ordered crystalline structures of vacuum- and solution-processable organic semiconductors. In particular, PS-coupled AlOx nanodielectrics allowed solution-processable organic field-effect transistors to operate at a gate voltage of approximately -1 V, with a field-effect mobility of ∼1.26 cm2 V-1 s -1. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kang S.M.,KAIST | Park S.,Inha University | Kim D.,KAIST | Park S.Y.,Korea University | And 2 more authors.
Advanced Functional Materials | Year: 2011

This study presents a method of simultaneous reduction and surface functionalization of graphene oxide by a one-step poly(norepinephrine) functionalization. The pH-induced aqueous functionalization of graphene oxide by poly(norepinephrine), a catecholamine polymer inspired by the robust adhesion of marine mussels, chemically reduced and functionalized graphene oxide. Moreover, the polymerized norepinephrine (pNor) layer provided multifunctionality on the reduced graphene oxide that includes surface-initiated polymerization and spontaneous metallic nanoparticle formation. This facile surface modification strategy can be a useful platform for graphene-based nano-composites. Simultaneous reduction and surface functionalization of graphene oxide were achieved via a simple one-step procedure under mild conditions. An aqueous mixture of graphene oxide and a norepinephrine, a molecule inspired by the chemical composition of mussel adhesive proteins, resulted in a robust modification of graphene oxide surfaces. The poly(norepinephrine) modification exhibited simultaneous reduction of graphene oxide and became a platform of surface-initiated polymerization and metallic nanoparticle formation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ha S.H.,Hannam University | Koo Y.-M.,Inha University
Korean Journal of Chemical Engineering | Year: 2011

Ionic liquids (ILs) having unique properties such as no measurable vapor pressure, nonflammability and a wide temperature range of liquid phase have been recognized as potential green solvents. As a result, ILs have been extensively explored as reaction media for various biocatalytic reactions over a decade. Enzyme activities in ILs are generally comparable with or higher than those observed in conventional organic solvents. Furthermore, enhanced thermal and operational stabilities and regio- or enantioselectivities have been observed in many cases. Thus, ILs offer new possibilities for the application of solvent engineering to biocatalytic reactions. This review discusses the effect of physicochemical properties of ILs on biocatalysis with respect to enzyme activity, stability and selectivity by systematizing literature data on enzyme-catalyzed reaction in ILs. © 2011 Korean Institute of Chemical Engineers, Seoul, Korea.

Kang J.-H.,University of Pennsylvania | Kang J.-H.,Inha University | Vanderstichele H.,ADx Neurosciences | Trojanowski J.Q.,University of Pennsylvania | Shaw L.M.,University of Pennsylvania
Methods | Year: 2012

The xMAP-Luminex multiplex platform for measurement of Alzheimer's disease (AD) cerebrospinal fluid (CSF) biomarkers using Innogenetics AlzBio3 immunoassay reagents that are for research use only has been shown to be an effective tool for early detection of an AD-like biomarker signature based on concentrations of CSF Aβ 1-42, t-tau and p-tau 181. Among the several advantages of the xMAP-Luminex platform for AD CSF biomarkers are: a wide dynamic range of ready-to-use calibrators, time savings for the simultaneous analyses of three biomarkers in one analytical run, reduction of human error, potential of reduced cost of reagents, and a modest reduction of sample volume as compared to conventional enzyme-linked immunosorbant assay (ELISA) methodology. Recent clinical studies support the use of CSF Aβ 1-42, t-tau and p-tau 181 measurement using the xMAP-Luminex platform for the early detection of AD pathology in cognitively normal individuals, and for prediction of progression to AD dementia in subjects with mild cognitive impairment (MCI). Studies that have shown the prediction of risk for progression to AD dementia by MCI patients provide the basis for the use of CSF Aβ 1-42, t-tau and p-tau 181 testing to assign risk for progression in patients enrolled in therapeutic trials. Furthermore emerging study data suggest that these pathologic changes occur in cognitively normal subjects 20 or more years before the onset of clinically detectable memory changes thus providing an objective measurement for use in the assessment of treatment effects in primary treatment trials. However, numerous previous ELISA and Luminex-based multiplex studies reported a wide range of absolute values of CSF Aβ 1-42, t-tau and p-tau 181 indicative of substantial inter-laboratory variability as well as varying degrees of intra-laboratory imprecision. In order to address these issues a recent inter-laboratory investigation that included a common set of CSF pool aliquots from controls as well as AD patients over a range of normal and pathological Aβ 1-42, t-tau and p-tau 181 values as well as agreed-on standard operating procedures (SOPs) assessed the reproducibility of the multiplex methodology and Innogenetics AlzBio3 immunoassay reagents. This study showed within-center precision values of 5% to a little more than 10% and good inter-laboratory %CV values (10-20%). There are several likely factors influencing the variability of CSF Aβ 1-42, t-tau and p-tau 181 measurements. In this review, we describe the pre-analytical, analytical and post-analytical sources of variability including sources inherent to kits, and describe procedures to decrease the variability. A CSF AD biomarker Quality Control program has been established and funded by the Alzheimer Association, and global efforts are underway to further define optimal pre-analytical SOPs and best practices for the methodologies available or in development including plans for production of a standard reference material that could provide for a common standard against which manufacturers of immunoassay kits would assign calibration standard values. © 2012 Elsevier Inc.

Kim K.J.,Inha University | Tsiftsis T.A.,Technological Educational Institute of Lamia | Schober R.,University of British Columbia
IEEE Transactions on Vehicular Technology | Year: 2011

In this paper, a semiblind iterative receiver is proposed for coded multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. A novel iterative extended soft-recursive least square (IES-RLS) estimator for joint channel and frequency offset estimation is introduced. Extrinsic bit information obtained from the channel decoder and expected symbol decisions obtained from the demodulator are simultaneously exploited by the IES-RLS. The proposed receiver combines the MIMO data demodulator, the proposed channel estimator, and the channel decoder in an iterative manner to yield an improved bit error rate (BER) performance. To arrive at a feasible algorithm, the first-order linearization of the received vector signal with respect to the frequency offset is used in the IES-RLS channel estimator. The BER performance, a constellation-constrained mutual information analysis, and an EXIT chart analysis are used to verify the effectiveness of the proposed receiver. Simulation results show the superiority of the proposed semiblind receiver, compared with conventional semiblind receivers. © 2010 IEEE.

Kim S.H.,Pohang University of Science and Technology | Jang M.,Inha University | Yang H.,Inha University | Park C.E.,Pohang University of Science and Technology
Journal of Materials Chemistry | Year: 2010

Organic field-effect transistors (OFETs) are fabricated by depositing a thin film of semiconductor on the functionalized surface of a SiO2 dielectric. The chemical and morphological structures of the interface between the semiconductor and the functionalized dielectric are critical for OFET performance. We have characterized the effect of the affinity between semiconductor and functionalized dielectric on the properties of the semiconductor-dielectric interface. The crystalline microstructure/nanostructure of the pentacene semiconductor layers, grown on a dielectric substrate that had been functionalized with either poly(4-vinyl pyridine) or polystyrene (to control hydrophobicity), and grown under a series of substrate temperatures and deposition rates, were characterized by X-ray diffraction, photoemission spectroscopy, and atomic force microscopy. By comparing the morphological features of the semiconductor thin films with the device characteristics (field-effect mobility, threshold voltage, and hysteresis) of the OFET devices, the effect of affinity-driven properties on charge modulation, charge trapping, and charge carrier transport could be described. © The Royal Society of Chemistry 2010.

Kang J.-H.,University of Pennsylvania | Kang J.-H.,Inha University | Korecka M.,University of Pennsylvania | Toledo J.B.,University of Pennsylvania | And 2 more authors.
Clinical Chemistry | Year: 2013

BACKGROUND: Over the past 2 decades, clinical studies have provided evidence that cerebrospinal fluid (CSF) amyloid β1-42 (Aβ1-42), total τ (t-τ), and τ phosphorylated at Thr181 (p-τ181) are reliable biochemical markers of Alzheimer disease (AD) neuropathology. CONTENT: In this review, we summarize the clinical performance and describe the major challenges for the analytical performance of the most widely used immunoassay platforms [based on ELISA or microbead-based multianalyte profiling (xMAP) technology] for the measurement of CSF AD biomarkers (Aβ1-42, t-τ, and p-τ181). With foundational immunoassay data providing the diagnostic and prognostic values of CSF AD biomarkers, the newly revised criteria for the diagnosis of AD include CSF AD biomarkers for use in research settings. In addition, it has been suggested that the selection of AD patients at the predementia stage by use of CSF AD biomarkers can improve the statistical power of clinical trial design. Owing to the lack of a replenishable and commutable human CSF-based standardized reference material (SRM) and significant differences across different immunoassay platforms, the diagnostic-prognostic cutpoints of CSF AD biomarker concentrations are not universal at this time. These challenges can be effectively met in the future, however, through collaborative ongoing standardization efforts to minimize the sources of analytical variability and to develop reference methods and SRMs. SUMMARY: Measurements of CSF Aβ1-42, t-τ, and p-τ181 with analytically qualified immunoassays reliably reflect the neuropathologic hallmarks of AD in patients at the early predementia stage of the disease and even in presymptomatic patients. Thus these CSF biomarker tests are useful for early diagnosis of AD, prediction of disease progression, and efficient design of drug intervention clinical trials. © 2013 American Association for Clinical Chemistry.

Shin H.-J.,Research Institute and Hospital | Rho S.B.,Research Institute and Hospital | Jung D.C.,Research Institute and Hospital | Han I.-O.,Inha University | And 2 more authors.
Journal of Cell Science | Year: 2011

Expression of carbonic anhydrase IX (CA9) was shown to be strongly involved in high incidences of metastasis and poor prognosis in various human tumors. In this study, we investigated the possible role for CA9 in tumor metastases in vitro, using a gene transfection tool in the human cervical carcinoma cell line C33A. Gene expression profiling of CA9-transfected cells (C33A/CA9) and vectortransfected cells (C33A/Mock) was investigated by DNA microarray. The biological functions of differentially expressed genes between the C33A/CA9 and C33A/Mock cells included cell growth, regulation of cell-cell and cell-extracellular matrix adhesion and cytoskeletal organization. Immunofluorescent stain and Matrigel culture showed cytoskeletal remodeling, disassembled focal adhesion, weakened cell-cell adhesion and increased motility in C33A/CA9 cells. These invasive and metastatic phenotypes were associated with Rho-GTPase-related epithelial-mesenchymal transition. Inhibition of the Rho/Rho kinase pathway by a ROCK inhibitor (Y27632) and si-Rho (short interference RNA against RhoA) showed that Rho-GTPase signaling was involved in cellular morphologic and migratory changes. The effect of CA9 on Rho-GTPase signaling was also confirmed by silencing CA9 expression. Our results suggest that CA9 overexpression induces weakening of cell adhesions and augmented cell motility by aberrant Rho-GTPase signal transduction. Our study shows an underlying mechanism of CA9-related enhanced metastatic potential of tumor cells. © 2011. Published by The Company of Biologists Ltd.

Kim K.J.,Inha University | Tsiftsis T.A.,Technological Educational Institute of Lamia
IEEE Transactions on Vehicular Technology | Year: 2011

The maximum average achievable rate and the outage probability of the opportunistic scheduling over the cyclically prefixed (CP) single-carrier (SC) downlink transmissions are analyzed. In the user terminal, the QR-decomposition (QRD)-based receiver is employed to maintain the multipath diversity gain. Based on the proposed receiver, closed-form expressions for the maximum average achievable rate and the outage probability can be derived using the property of the circulant matrix. In addition, the outage diversity gain is obtained at high average signal-to-noise ratio (SNR). Simulations verified the derived analysis. © 2010 IEEE.

Nakamura G.,Inha University | Wang H.,Nanjing Southeast University
Inverse Problems | Year: 2013

We are concerned with the reconstruction of unknown inclusions inside a heat conductor from boundary measurements, which is modeled as an inverse boundary value problem for a parabolic equation. Taking the Neumann-to-Dirichlet map as measured data, we establish a linear sampling-type method to identify the inclusions. As in inverse scattering problems, the so-called forward interior transmission problem naturally arises in the linear sampling method for identifying inclusions. The unique solvability of the forward interior transmission problem for parabolic equations is also investigated. © 2013 IOP Publishing Ltd.

Min S.-Y.,Pohang University of Science and Technology | Kim T.-S.,Pohang University of Science and Technology | Kim B.J.,Sungkyunkwan University | Cho H.,Pohang University of Science and Technology | And 4 more authors.
Nature Communications | Year: 2013

Controlled alignment and patterning of individual semiconducting nanowires at a desired position in a large area is a key requirement for electronic device applications. High-speed, large-area printing of highly aligned individual nanowires that allows control of the exact numbers of wires, and their orientations and dimensions is a significant challenge for practical electronics applications. Here we use a high-speed electrohydrodynamic organic nanowire printer to print large-area organic semiconducting nanowire arrays directly on device substrates in a precisely, individually controlled manner; this method also enables sophisticated large-area nanowire lithography for nano-electronics. We achieve a maximum field-effect mobility up to 9.7 cm2 V -1 s-1 with extremely low contact resistance (<5.53 Ω cm), even in nano-channel transistors based on single-stranded semiconducting nanowires. We also demonstrate complementary inverter circuit arrays comprising well-aligned p-type and n-type organic semiconducting nanowires. Extremely fast nanolithography using printed semiconducting nanowire arrays provide a simple, reliable method of fabricating large-area and flexible nano-electronics. © 2013 Macmillan Publishers Limited. All rights reserved.

Kim K.J.,Inha University | Tsiftsis T.A.,Technological Educational Institute of Lamia | Poor H.V.,Princeton University
IEEE Transactions on Wireless Communications | Year: 2011

To address the issues of high peak-to-average power ratio and high power backing-off in orthogonal frequency-division multiplexing (OFDM) relaying systems, a cyclic prefixed single-carrier (CP-SC) relaying system employing best terminal selection (BTS) is considered in this paper. Under a system power constraint, the problem of joint optimal power allocation to the source and relay is investigated. For a two-hop amplify-and-forward (AF) relaying protocol, the optimal power allocation is first obtained by maximizing the achievable spectral efficiency. After applying the obtained optimal power allocations to the source and relay, a destination terminal that has the best effective end-to-end signal-to-noise ratio is selected. With the help of the statistical properties of circulant channel matrices in the relay links, closed-form bounds for the maximum achievable spectral efficiency, outage probability, and average symbol error rate (ASER) are derived. Further, an asymptotic analysis of the outage probability and ASER is conducted and it is shown that both the number of terminals in the system and the number of channel taps being supported by the CP length play key roles in determining the overall diversity gain. Monte Carlo simulation results verify the derived closed-form analytical expressions. © 2011 IEEE.

Sridhar V.,KAIST | Kim H.-J.,KAIST | Jung J.-H.,KAIST | Lee C.,Sungkyunkwan University | And 2 more authors.
ACS Nano | Year: 2012

The development of three-dimensional carbon-based nanostructures is the next step forward for boosting industrial applications of carbon nanomaterials such as graphenes and carbon nanotubes. Some defects, which have been considered as detrimental factors for maintaining exceptional materials properties of two-dimensional graphene, can be actively used to synthesize three-dimensional graphene-based carbon nanostructures. Here we describe a fast and heretofore unreported defect-engineered method to synthesize three-dimensional carbon nanohybrid structures with strong bonding between graphene nanoplatelets and carbon nanotubes using simple microwave irradiation and an ionic liquid. Our one-pot method utilizes defect-engineered sequential processes: microwave-based defect generation on graphene nanoplatelets, anchoring of palladium nanoparticles on these defects, and subsequent growth of carbon nanotubes by use of an ionic liquid. The unique three-dimensional nanostructures showed an ultrahigh redox capacitance due to high porosity, a high surface-to-volume ratio from the spacer role of vertically standing one-dimensional carbon nanotubes on graphene sheets, and capacitance-like redox response of the palladium nanoparticles. The proposed defect-engineered method could lead to novel routes to synthesizing three-dimensional graphene-based nanostructures with exceptionally high performance in energy storage systems. © 2012 American Chemical Society.

Choung J.,Inha University | Nam J.-M.,Inha University | Ha T.-B.,Research and Development Center
Marine Structures | Year: 2012

This paper provides two convergence criteria to find translational and rotational locations of the neutral axis plane (NAP) for intact and damaged vessels. Definition of three types of asymmetries of a ship section is proposed: material-, load-, and geometry-induced asymmetries. Concept of moment plane (MP) is introduced to define the heeling angle of ship section. It is suggested that force equilibrium and force vector equilibrium criteria are simultaneously necessary to determine new position of NAP due to both translational and rotational shifts. In order to verify the applicability of the convergence criteria, midship section of a VLCC is selected with two types of asymmetries: one is due to heeling of a section and the other due to hull damages. 0° and 30° heeling conditions and collision-induced and grounding-induced damage extents based on ABS Guides and DNV Ship Rules are taken into account. The various section properties are compared according to the area reduction ratios for each heeling and damage cases. It is shown that ultimate hull girder capacities are closely related to the area reduction due to the damages. Using new convergence criterion, mobility of NAPs and force centroids in elastic and inelastic regimes are visually provided. © 2011 Elsevier Ltd.

Lee J.W.,Hyundai E and C Co. | Jung H.J.,KAIST | Park J.Y.,Inha University | Lee J.B.,POSCO | Yoon Y.,KAIST
Renewable Energy | Year: 2013

This paper presents and optimizes the annual heating, cooling and lighting energy consumption associated with applying different types and properties of window systems in a building envelope. Through using building simulation modeling, various window properties such as U-value, solar heat gain coefficient (SHGC), and visible transmittance (Tvis) are evaluated with different window wall ratios (WWRs) and orientations in five typical Asian climates: Manila, Taipei, Shanghai, Seoul and Sapporo. By means of a regression analysis, simple charts for the relationship between window properties and building energy performance are presented as a function of U-value, SHGC, Tvis, WWR, solar aperture, effective aperture, and orientation. As a design guideline in selecting energy saving windows, an optimized window system for each climate is plotted in detailed charts and tables. © 2012 Elsevier Ltd.

Faustini M.,Pohang University of Science and Technology | Kim J.,Inha University | Jeong G.-Y.,Pohang University of Science and Technology | Kim J.Y.,Ulsan National Institute of Science and Technology | And 3 more authors.
Journal of the American Chemical Society | Year: 2013

Herein, we report a novel nanoliter droplet-based microfluidic strategy for continuous and ultrafast synthesis of metal-organic framework (MOF) crystals and MOF heterostructures. Representative MOF structures, such as HKUST-1, MOF-5, IRMOF-3, and UiO-66, were synthesized within a few minutes via solvothermal reactions with substantially faster kinetics in comparison to the conventional batch processes. The approach was successfully extended to the preparation of a demanding Ru3BTC2 structure that requires high-pressure hydrothermal synthesis conditions. Finally, three different types of core-shell MOF composites, i.e., Co3BTC2@Ni3BTC 2, MOF-5@diCH3-MOF-5, and Fe3O 4@ZIF-8, were synthesized by exploiting a unique two-step integrated microfluidic synthesis scheme in a continuous-flow mode. The synthesized MOF crystals were characterized by X-ray diffraction, scanning electron microscopy, and BET surface area measurements. In comparison with bare MOF-5, MOF-5@diCH3-MOF-5 showed enhanced structural stability in the presence of moisture, and the catalytic performance of Fe3O 4@ZIF-8 was examined using Knoevenagel condensation as a probe reaction. The microfluidic strategy allowed continuous fabrication of high-quality MOF crystals and composites exhibiting distinct morphological characteristics in a time-efficient manner and represents a viable alternative to the time-consuming and multistep MOF synthesis processes. © 2013 American Chemical Society.

An N.B.,Institute of Physics | Kim J.,Korea Institute for Advanced Study | Kim K.,Inha University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We derive exact time evolution of three two-level atoms coupled to a common environment. The environment is structured and is modeled by a leaky cavity with Lorentzian spectral density. The atoms are initially prepared in a generalized W state and later on experience pairwise dipole-dipole interactions and couplings to the cavity. We study tripartite disentangling and entangling dynamics as well as protecting bipartite entanglement with both atom-atom interactions and atom-cavity couplings taken simultaneously into account. © 2011 American Physical Society.

Chen H.-Y.,University of California at Los Angeles | Hou J.,University of California at Los Angeles | Hayden A.E.,University of California at Los Angeles | Yang H.,University of California at Los Angeles | And 2 more authors.
Advanced Materials | Year: 2010

(Figure Presented)A new silole-containing low-bandgap polymer is synthesized by replacing the 5-position carbon of PCPDTBT with a silicon atom (PSBTBT; see figure). Through experiments and computational calculations, we show that the material properties, particular the packing of polymer chains, can be altered significantly. As a result, the polymer changes from amorphous to highly crystalline with the replacement of the silicon atom. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA.

Yang S.Y.,Cornell University | Kim B.N.,Cornell University | Zakhidov A.A.,Cornell University | Taylor P.G.,Cornell University | And 4 more authors.
Advanced Materials | Year: 2011

Microelectrodes based on poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) are able to record the oxidation of catecholamines released from chromaffin cells during exocytosis with a high signal-to-noise ratio. This result represents a new capability for organic electronics that could lead to devices that interface with the nervous system in novel ways. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Newby C.,Cornell University | Lee J.-K.,Inha University | Ober C.K.,Cornell University
Journal of Materials Chemistry C | Year: 2013

With the rise of functional printing there is a need to understand the inkjet printability of a greater range of materials. Fluorinated materials and solvents have some unusual properties but this study finds them to be reliably inkjet printable. The fluorinated ink used has Reynolds and Weber numbers of 9.2 ± 1.8 and 20.3 ± 3.0, respectively. Printed line widths on silicon can be varied from 45 μm to 90 μm by adjusting printing parameters. A key advantage of printing from fluorinated solvents is that they can be printed on other organic layers without damaging or dissolving the underlayer. Test patterns are demonstrated on PMMA, P3HT, pentacene and F8BT. This naturally suggests their application to patterning organic semiconductors by selectively protecting some areas. The utility of this technique is demonstrated in the fabrication of an array of P3HT transistors with 2 μm channel lengths in which the active area is patterned using an inkjet printed single-drop fluoropolymer etch mask. This journal is © 2013 The Royal Society of Chemistry.

Choi B.G.,Korea Advanced Institute of Science and Technology | Huh Y.S.,Inha University | Hong W.H.,Korea Advanced Institute of Science and Technology | Erickson D.,Cornell University | Park H.S.,Kyung Hee University
Nanoscale | Year: 2013

Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g-1, three-fold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features. © 2013 The Royal Society of Chemistry.

Fang F.F.,Inha University | Choi H.J.,Inha University | Choi W.S.,Hoseo University
Colloid and Polymer Science | Year: 2010

Magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids generally posses serious dispersion defects due to the large density mismatch between the CI particles and continuous oil medium, which restricts further MR applications. Polymer coating technology has been introduced in an attempt to reduce the density or prevent CI particle aggregation. In this study, a unique functional coating composed of a polyaniline layer and multiwalled carbon nanotube nest was fabricated on the surface of CI particles using a dispersion polymerization and solvent casting method to improve the sedimentation problem of CI-based MR fluids when dispersed in medium oil. The coating morphology was analyzed by scanning electron microscopy. The effect of the functional coating on the MR performance along with the sedimentation observations was investigated using a rotational rheometer. The results showed that the sedimentation of dispersed particles was improved considerably by the reduced density and rough morphology © Springer-Verlag 2009.

An N.B.,Institute of Physics | Kim J.,Korea Institute for Advanced Study | Kim K.,Inha University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We study exact entanglement dynamics of three-qubit W-class states in a common structured cavity at zero temperature in both Markovian and non-Markovian regimes using the concept of lower bound of concurrence. We also propose three methods to control the qubits' entanglement evolution and establish monogamy equalities relevant to the class of states under consideration. © 2010 The American Physical Society.

Bialek B.,Inha University | Lee J.I.,Inha University | Kim M.,Sookmyung Womens University
Computational Materials Science | Year: 2014

The electronic and the magnetic properties of the (0 0 1) surfaces of GeKCa and SnKCa with half-Heusler structure are studied with the use of a full-potential linearized augmented plane wave method. It is shown that although the two compounds are half-metals in their bulk structures, only the surfaces terminated with a carbon group atom retain the half-metallic properties. The magnetic properties of the surfaces terminated with layers containing group 14 atoms are enhanced compared with the properties of the bulk. The calculated magnetic moments on the Ge atom in GeKCa are 0.38μB in the bulk and 0.97μB at the (0 0 1) surface. In the SnKCa surface, the value of the magnetic moment on the Sn atom increases from 0.28μB in the bulk to 0.75μB at the surface. In the Ge (Sn) terminated Ge(Sn)KCa surfaces, the metal atoms are also polarized. In addition to destroyed half-metallicity at the surfaces terminated with metal atoms we also find a strong demagnetization of the systems. © 2013 Elsevier B.V. All rights reserved.

Zhang K.,Harbin Institute of Technology | Choi H.J.,Inha University
Materials | Year: 2014

This review article summarizes the preparation of polymer/carbon nanotube (CNT) nanocomposites and their applications as electrorheological (ER) fluids. These ER fluids exhibited a controllable electro-response under an applied electric field due to the presence of well-dispersed CNTs. The background, morphology, preparations, and characteristics of these materials are discussed, specifically focusing on the various approaches in the preparation of polymer/CNT nanocomposites, morphology, and their effects on the ER characteristics. © 2014 by the authors.

Park S.-J.,Inha University | Kim B.-J.,Korea Institute of Carbon Convergence Technology
Springer Series in Materials Science | Year: 2015

Traditionally, the application of carbon fibers has been limited to very special fields such as aerospace and military because of their high cost. However, various techniques for low-cost carbon fibers are under development in terms of using low-cost precursors, low-cost manufacturing processes, and even functional coating methods. Moreover, future applications of carbon fibers can widen not only as structural reinforcements but also in information technology-based applications such as housings for electric devices, smart cloths, and healthcare items. In this chapter, we will cover the carbon fibers and their composites in recent various applications. In particular, there are classified as a low-cost production technique of carbon fibers for general industries, thin carbon fibers for extreme industries, and functional carbon fibers for smart composites. © Springer Science+Business Media Dordrecht 2015.

Son M.,Chungnam National University | Lee G.-H.,Inha University
Water Resources Research | Year: 2013

To investigate the effects of wave shape on cohesive sediment flux in shallow water environments, a one-dimensional vertical (1DV) model for cohesive sediment transport previously validated with field measurement is applied to conditions of skewed and asymmetric oscillatory flows. Cohesive sediments usually portray behaviors different from those of noncohesive sediments. This is mainly due to the flocculation process through which the density and the size of cohesive sediment change continuously. Therefore, a robust flocculation model is incorporated with a 1DV model in this study. Under the condition of skewed oscillatory flow (second-order Stokes wave-type oscillatory flow), the flux of cohesive sediment is significantly affected by the change of flow skewness, whereas the flux of noncohesive sediment of which size is 100 μm does not show a clear relationship with skewness. Under the condition of forward-leaning asymmetric oscillatory flow (saw-tooth wave-type oscillatory flow), the direction of cohesive sediment flux is negative, whereas the flux of noncohesive sediment shows the positive direction. The phase-lag effect is considered as the main mechanism of these behaviors. The interactional relationship between the settling velocity, the variation of concentration profile, and hydrodynamics of carrier fluid enhances the phase-lag effect and causes different behaviors in cohesive sediment compared to the flux of fine noncohesive sediment. ©2013. American Geophysical Union. All Rights Reserved.

Atta A.K.,Inha University | Kim S.-B.,Inha University | Heo J.,Chungnam National University | Cho D.-G.,Inha University
Organic Letters | Year: 2013

The Hg(II)-specific intramolecular cyclization reaction of ethynyl phenols was carried out for the first time in semiaqueous media at ambient temperature. The reaction unit (ethynyl phenol) was coupled with a malononitrile derivative (signal unit), which afforded the chromogenic Hg(II) indicator 7. The reaction of the chromogenic Hg(II) indicator 7 was further optimized in DMSO/water (3:7, v/v) (10 mM PBS buffer, pH = 7.0). Compound 7 displays a color change from blue to pale yellow in the presence of Hg(II). © 2013 American Chemical Society.

Kim H.S.,Dongguk University | Kim J.-H.,Chosun University | Kim J.,Inha University
International Journal of Precision Engineering and Manufacturing | Year: 2011

This paper reviews energy harvesting technology from mechanical vibration. Recent advances on ultralow power portable electronic devices and wireless sensor network require limitless battery life for better performance. People searched for permanent portable power sources for advanced electronic devices. Energy is everywhere around us and the most important part in energy harvesting is energy transducer. Piezoelectric materials have high energy conversion ability from mechanical vibration. A great amount of researches have been conducted to develop simple and efficient energy harvesting devices from vibration by using piezoelectric materials. Representative piezoelectric materials can be categorized into piezoceramics and piezopolymers. This paper reviews key ideas and performances of the reported piezoelectric energy harvesting from vibration. Various types of vibration devices, piezoelectric materials and mathematical modeling of vibrational energy harvestings are reviewed. © KSPE and Springer 2011.

Hwang K.,Center for Advanced Medical Education by 21 Project | Kim D.H.,Inha University
Journal of Craniofacial Surgery | Year: 2010

The aim of this study was to elucidate the supporting strength of the curved poly-l-lactic acid (PLLA) sheet and porous polyethylene (Medpor) for reconstruction of orbital floor fractures.For one-half and two-thirds orbital floor fractures, reconstruction was performed using the PLLA sheet and Medpor. The PLLA sheet was molded to fit the orbital floor (concavity). The anterior portion (1 cm) was curved to fit the inferior orbital rim and fixed with a screw. Medpor was designed to fit the orbital floor. A screw was fixed 6 mm away from the anterior border of the orbital floor. Each implant was hung by wire, and the degree of sagging of the implant was measured using micrometers by the power of a force gauge. For one-half orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 2.46 (SD, 0.14) N, and that of Medpor was 0.59 (SD, 0.04) N. The power of the PLLA sheet to sag 10 mm was 6.9 (SD, 0.14) N, and that of Medpor was 1.52 (SD, 0.16) N. For two-thirds orbital floor fractures, the power of the PLLA sheet to sag 5 mm was 1.79 (SD, 0.24) N, and that of Medpor was 0.39 (SD, 0.04) N. For 10 mm of sagging, the power of the PLLA sheet was 5.61 (SD, 0.29) N, and that of Medpor was 0.94 (SD, 0.09) N. For sagging of 15 mm, the power of the PLLA sheet was 8.99 (SD, 0.16) N, and that of Medpor was 2.98 (SD, 0.24) N. The PLLA sheet was irreversibly bent when the force reached ̃8 to 9 N. For Medpor, the degree of sagging during the early stage was larger than at the later stage. In all situations, the supporting power of the PLLA sheet was greater than that of Medpor. The differences were significant in all situations (P = 0.000). The degree of sagging in one-half orbital floor fractures was 2.87 mm for the PLLA sheet and 7.96 mm for Medpor. There was an increased orbital volume of 0.4 mL with the PLLA sheet and 1.19 mL for Medpor. The predicted enophthalmos was 0.41 mm with the PLLA sheet and 1.07 mm with Medpor. The degree of sagging for the two-thirds orbital floor fractures was 4.28 mm for the PLLA sheet and 11.47 mm for Medpor. The increased orbital volume was 0.78 mL for the PLLA sheet and 2.22 mL for Medpor. The predicted enophthalmos was 0.73 mm with the PLLA sheet and 1.93 mm with Medpor. The predicted enophthalmos was below 2 mm with both the PLLA sheet and Medpor for reconstruction of orbital floor fractures; however, it was near 2 mm with Medpor in reconstruction of two-thirds orbital floor fractures.The results of this study show that the PLLA sheet and Medpor were sufficient for reconstruction of one-half and two-thirds orbital floor fractures with a defective posterior part. However, the supporting power of the PLLA sheet was stronger than that of Medpor. Copyright © 2010 by Mutaz B. Habal, MD.

Sohn J.W.,Inha University | Choi S.-B.,Inha University | Kim H.S.,Dongguk University
International Journal of Mechanical Sciences | Year: 2011

Active vibration control to suppress structural vibration of the smart hull structure was investigated based on optimized actuator configurations. Advanced anisotropic piezoelectric composite actuator, Macro-Fiber Composite (MFC), was used for the vibration control. Governing equations of motion of the smart hull structure including MFC actuators were obtained using the DonnellMushtari shell theory and Lagranges equation. The RayleighRitz method was used to obtain the dynamic characteristics of the smart hull structure. Experimental modal tests were conducted to verify the proposed mathematical model. In order to achieve high control performance, optimal locations and directions of the MFC actuators were determined by genetic algorithm. Optimal control algorithm was then synthesized to suppress structural vibration of the proposed smart hull structure and experimentally implemented to the system. Active vibration control performances were evaluated under various modes excitations. Vibration tests revealed that optimal configurations of MFC actuators improved the control performance of the smart hull structure in case of the limited number of actuators available. © 2011 Elsevier Ltd.

Jiang W.,Jilin Institute of Chemical Technology | Jin F.-L.,Jilin Institute of Chemical Technology | Park S.-J.,Inha University
Journal of Industrial and Engineering Chemistry | Year: 2012

This study examined the thermo-mechanical behavior of epoxy resins/nano-Al 2O 3 composites including the curing behavior, thermal stability, dynamic mechanical properties and thermal mechanical properties. The DSC curve peak temperature of the composites was decreased by the addition of nano-Al 2O 3. The thermal stability of the composites was similar to that of the neat epoxy resins. Dynamic mechanical analysis (DMA) indicated the glass transition temperature of the composites to be approximately 11°C higher than that of the neat epoxy resins. The coefficient of thermal expansion (CTE) of the composites decreased with increasing nano-Al 2O 3 content. © 2011 The Korean Society of Industrial and Engineering Chemistry.

Joo J.M.,Sungkyunkwan University | Lee S.,Inha University | Kwon O.C.,Sungkyunkwan University
International Journal of Hydrogen Energy | Year: 2012

The combustion stability limits and nitrogen oxide (NOx) emissions of burner-stabilized premixed flames of ammonia (NH 3)-substituted hydrogen (H2)-air mixtures at normal temperature and pressure are studied to evaluate the potential of partial NH3 substitution to improve the safety of H2 use. The effects of NH3 substitution, nitrogen (N2) coflow and mixture injection velocity on the stability limits and NOx emissions of NH3-H2-air flames are experimentally determined. Results show a reduction of stability limits with NH3 substitution and coflow, supporting the potential of NH3 as a carbon-free, green additive in H2-air flames and indicating a different tendency from that for no coflow condition. The NOx emission index is almost constant even with enhanced NH3 substitution, though the absolute value of NOx emissions increases in general. At fuel-rich conditions, the NOx emission index decreases with increasing mixture injection velocity and the existence of coflow. The thermal deNOx process in the post-flame region is involved in reducing NOx emissions for the fuel-rich flames. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights.

Matos J.,Venezuelan Institute for Scientific Research | Garcia A.,Venezuelan Institute for Scientific Research | Park S.-E.,Inha University
Applied Catalysis A: General | Year: 2011

Photodegradation of methylene blue (MB) on Ti-containing mesoporous silica prepared by microwave-assisted irradiation as a function of Si/Ti molar ratio was studied. The materials were characterized by N2 adsorption, XRD, UV-vis/DR, and TEM. All solids showed mesoporous textures with high surface areas, relatively small pore size diameters and large pore volume. XRD showed that framework of solids consists of amorphous silica. It was found that the lower the Si/Ti ratio the higher the photocatalytic activity. Under irradiation with a lamp with more photons from visible light the sample with a Si/Ti ratio equal to 10 showed a higher photoactivity than that of a commercial TiO 2 photocatalyst. This result was in agreement with the UV-vis/DR spectra which showed that material with a Si/Ti = 10 has slightly higher energy band gap than that of commercial TiO2 suggesting that these materials behave as a photoactive semiconductor. © 2010 Elsevier B.V. All rights reserved.

Kim K.J.,Samsung | Kwak K.S.,Inha University | Choi B.D.,Sungkyunkwan University
Journal of Communications and Networks | Year: 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the singlechannel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution. We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay. © 2013 KICS.

Seo J.H.,ETH Zurich | Seo J.H.,Inha University | Heinrich C.A.,ETH Zurich | Heinrich C.A.,University of Zürich
Geochimica et Cosmochimica Acta | Year: 2013

Recent experimental studies have raised concerns that Cu concentrations in quartz-hosted fluid inclusions from magmatic-hydrothermal ore deposits do not represent pristine concentrations in the trapped fluids, but are modified by post-entrapment diffusional exchange through the host quartz. New microanalyses of fluid inclusions hosted in topaz show significantly lower Cu concentrations in vapor inclusions, compared to otherwise identical inclusions hosted by coexisting quartz, whereas coeval brine (hypersaline liquid) inclusions are very similar independent of host mineral in one sample. Sulfur is present as a major component in all vapor inclusions, as in most porphyry-related vapor inclusions, and Cu never exceeds S, but commonly matches the S content at a molar ratio of Cu:S. ≤. 2 in vapor inclusions hosted by quartz.Univalent ions with a radius smaller than ~1Å are known to diffuse rapidly through the channels of the quartz structure, parallel to its crystallographic c axis. Since only Cu concentrations differ between topaz- and quartz-hosted inclusions, we hypothesize that Cu+ and H+ re-equilibrate by diffusional ion exchange through these channels, while all other element concentrations remain essentially unchanged. A thermodynamic model considering charge-balanced Cu+H+ exchange and diffusive H2 re-equilibration of an initially Cu-poor but S-rich vapor inclusion with a typical rock-buffered fluid environment outside the host crystal demonstrates a strong chemical driving force for Cu+ to migrate from the surrounding rock into the fluid inclusion during cooling of the system. The driving force for Cu diffusion, against the gradient in total Cu concentration, is the abundant H+ liberated inside the inclusion by dissociation of HCl and particularly by the precipitation of CuFeS2 by reaction with the initially trapped H2S and/or SO2. Gold is not only a much larger ion, but is subject to an opposing driving force, suggesting that high concentrations of this larger ion analyzed in vapor inclusions probably represent true gold concentrations in magmatic-hydrothermal vapor.These findings imply that brine-vapor separation in porphyry deposits does not cause selective Cu transfer to the vapor, but is more likely to destabilize Cu complexes and promote copper ore deposition during decompression and unmixing of the two fluid phases. By contrast, Au may be selectively transferred into the vapor phase, allowing its transport through the deeper porphyry copper deposits to form epithermal gold deposits closer to the earth's surface. © 2013 Elsevier Ltd.

Kwon M.-J.,Ewha Womans University | Jang B.,Ewha Womans University | Yi J.Y.,Korea Institute of Radiological and Medical Sciences | Han I.-O.,Inha University | Oh E.S.,Ewha Womans University
FEBS Letters | Year: 2012

Syndecan are a family of cell surface heparan sulfate proteoglycans that act as cell surface receptors. Most cell surface receptors have a limited number and type of ligand interactions, responding only to the binding of (a) specific ligand(s). In contrast, syndecans can interact with various numbers and types of ligands, and thus play more diverse roles than others. Various syndecan functions have not yet been fully classified and categorized, but we herein review previous studies suggesting that syndecans play dual function as cell surface receptors by acting as both adhesion receptors and docking receptors. Through this dual regulatory function, syndecans are capable of regulating both intra- and extracellular activities, potentially altering a variety of cell behaviors. Crown Copyright © 2012 Published by Elsevier B.V. on behalf of Federation of European Biochemical society. All rights reserved.

Sotto A.,Rey Juan Carlos University | Boromand A.,Catholic University of Leuven | Balta S.,Catholic University of Leuven | Balta S.,University of Galati | And 2 more authors.
Journal of Materials Chemistry | Year: 2011

Doping of nanofiltration membranes with TiO2 nanoparticles was studied in the ultralow concentration range, in the absence of photocatalysis. Blended polyethersulfone/TiO2 flat-sheet membranes were manufactured and investigated in terms of pure water flux, permeability, fouling resistance and solute rejection. The membranes were synthesized at four different polymer concentrations by the phase inversion method, using 1-methyl-2-pyrrolidone (NMP) and deionized water as solvent and coagulant, respectively. The influence of TiO2 addition was investigated in an unusually low concentration interval (0.035-0.375 wt%). The membrane morphology was studied by determining particle size distributions of TiO2 to explore the effect of nanoparticle aggregation. Furthermore, membranes were characterized by hydrophilicity (contact angle), morphology (SEM), porosity, mechanical strength (bursting pressure) and thermal analysis (TGA). Membrane fouling was studied with humic acids as model organic foulants. Overall, a remarkable improvement in the permeability was observed with the addition of ultralow amounts of nanoparticles to the polymer. The optimum permeability was found to be as low as 0.085 wt%, using a constant rejection of dyes as the boundary condition. It was shown that rejection of solutes is not negatively influenced by the increase in permeability. In addition, the resistance against membrane fouling was found to be above 12% for the TiO2 blended membranes. © 2011 The Royal Society of Chemistry.

Jin F.-L.,Jilin Institute of Chemical Technology | Yop Rhee K.,Kyung Hee University | Park S.-J.,Inha University
Journal of Solid State Chemistry | Year: 2011

In this study, covalent functionalization of carbon nanotubes (CNTs) was accomplished by surface-initiated epoxide ring-opening polymerization. FT-IR spectra showed that polyether and epoxide group covalently attached to the sidewalls of CNTs. TGA results indicated that the polyether was successfully grown from the CNT surface, with the final products having a polymer weight percentage of ca. 1474 wt%. The O/C ratio of CNTs increased significantly from 5.1% to 29.8% after surface functionalization of CNTs. SEM and TEM images of functionalized CNTs exhibited that the tubes were enwrapped by polymer chains with thickness of several nanometers, forming coreshell structures with CNTs at the center. © 2011 Elsevier Inc. All rights reserved.

Ha C.-W.,Sungkyunkwan University | Noh M.J.,TissueGene Inc. | Choi K.B.,Kolon Life Science Inc. | Lee K.H.,TissueGene Inc. | Lee K.H.,Inha University
Cytotherapy | Year: 2012

Background aims. TissueGene-C (TG-C) represents a cell-mediated gene therapy for localized delivery of allogeneic chondrocytes expressing transforming growth factor (TGF)-β1 directly to the damaged knee joint. Untransduced human chondrocytes (hChonJ cells) have also been incorporated into the TG-C product at a 3:1 ratio with TGF-β1-expressing chondrocytes (hChonJb#7) in order to help fill in the defect and as target cells for the actions of the expressed TGF-β1. Methods. A phase I dose-escalating clinical trial was performed to evaluate the safety and biologic activity of TG-C in patients with advanced osteoarthritis of the knee joint (full thickness cartilage defect) that was refractory to existing non-operative therapies. Following a single intra-articular injection into the joint space of the damaged knee, patients were monitored for safety, and an evaluation was performed to assess the pharmacokinetics and biologic activity of TG-C. Results. There were no treatment-related serious adverse events. Swelling, effusion and minor localized reactions such as warming sensation or itching were observed in a dose-dependent manner at the injection site. Knee evaluation scores seemed to indicate a dose-dependent trend toward efficacy; however, patient numbers were not sufficient to determine statistical significance. Conclusions. Overall, there were no significant safety issues related to the administration of TG-C, with only some minor injection site reactions observed. Additionally, knee scoring analyzes indicated a possibility that TG-C may contribute to improvement of arthritic symptoms. More study is warranted to evaluate further the safety and determine the potential efficacy of TG-C. © 2012 Informa Healthcare.

Lee S.,Inha University | Kwon O.C.,Sungkyunkwan University
International Journal of Hydrogen Energy | Year: 2011

The potential of partial ammonia substitution to improve the safety of hydrogen use was evaluated computationally, using counterflow nonpremixed ammonia/hydrogen/air flames at normal temperature and pressure. The ammonia-substituted hydrogen/air flames were considered using a recent kinetic mechanism and a statistical narrow-band radiation model for a wide range of flame strain rates and the extent of ammonia substitution. The effects of ammonia substitution on the extinction limits and structure, including nitrogen oxide (NOx) and nitrous oxide (N2O) emissions, of nonpremixed hydrogen/air flames were investigated. Results show reduction of the high-stretch extinction (i.e.; blow-off) limits, the maximum flame temperature and the concentration of light radicals (e.g.; H and OH) with ammonia substitution in hydrogen/air flames, supporting the potential of ammonia as a carbon-free, clean additive for improving the safety of hydrogen use in nonpremixed hydrogen/air flames. For high-stretched flames, however, NO x and N2O emissions substantially increase with ammonia substitution even though ammonia substitution reduces flame temperature, implying that chemical effects (rather than thermal effects) of ammonia substitution on flame structure are dominant. Radiation effects on the extinction limits and flame structure are not remarkable particularly for high-stretched flames. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Jhon M.S.,Carnegie Mellon University | Jhon M.S.,Sungkyunkwan University | Choi H.J.,Inha University
Polymer | Year: 2010

The novelty lies on the molecular level investigation of the end group functionality on rheological properties of fractionated, monodisperse oligomeric perfluoropolyethers (PFPEs) with various molecular weights and chain-end functionalities in this study. A sharp transition observed in the slope of the shear viscosity at a critical molecular weight for PFPEs was interpreted based on temporal tube mechanism caused by end group agglomeration of strong functional polar end groups. The temperature dependence of the shear viscosity was found to yield an Arrhenius form, determining the flow activation energy and hydrodynamic volume. The flow activation energy was also compared to the activation energy for surface diffusion to examine the role of end group-solid surface interaction. Modified Cole-Cole plots for storage and loss moduli along with polymer relaxation show the microstructural changes due to the interaction of PFPE end-group, which alters effective molecular weights. © 2010 Elsevier Ltd. All rights reserved.

Jun Y.C.,Sandia National Laboratories | Jun Y.C.,Inha University | Reno J.,Sandia National Laboratories | Ribaudo T.,Sandia National Laboratories | And 6 more authors.
Nano Letters | Year: 2013

We present a new type of electrically tunable strong coupling between planar metamaterials and epsilon-near-zero modes that exist in a doped semiconductor nanolayer. The use of doped semiconductors makes this strong coupling tunable over a wide range of wavelengths through the use of different doping densities. We also modulate this coupling by depleting the doped semiconductor layer electrically. Our hybrid approach incorporates strong optical interactions into a highly tunable, integrated device platform. © 2013 American Chemical Society.

Han D.,Hebei University | Tang B.,Inha University | Ri Lee Y.,Inha University | Ho Row K.,Inha University
Journal of Separation Science | Year: 2012

Ionic liquids (ILs) are novel nonmolecular solvents. Their unique properties, such as high thermal stability, tunable viscosity, negligible vapor pressure, nonflammability, and good solubility for inorganic and organic compounds, make them excellent candidates as extraction media for a range of microextraction techniques. Many physical properties of ILs can be varied, and the structural design can be tuned to impart the desired functionality and enhance the analyte extraction selectivity, efficiency, and sensitivity. This paper provides an overview of the applications of ILs in liquid phase microextraction technology, such as single-drop microextraction, hollow fiber based liquid phase microextraction, and dispersive liquid-liquid microextraction. The sensitivity, linear calibration range, and detection limits for a range of target analytes in the methods were analyzed to determine the advantages of ILs in liquid phase microextraction. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lohani C.R.,Inha University | Kim J.-M.,Inha University | Chung S.-Y.,Ewha Womans University | Yoon J.,Ewha Womans University | Lee K.-H.,Inha University
Analyst | Year: 2010

We developed a simple dual signal (color and 'Off-On' fluorescent change) ensemble system based on the complex between a rhodamine derivative 1 and Al3+ for the detection of pyrophosphate (PPi) in 100% aqueous solutions. The complex between the rhodamine compound and Al3+ was utilized as a chemosensing ensemble for the first time. The ensemble showed highly sensitive and selective fluorescent and colorimetric response to pyrophosphate among the anions in 100% aqueous solutions and no interference of the potent biological competitors including ATP, ADP, and phosphate for the detection of PPi in 100% aqueous solutions at pH 7.4. © 2010 The Royal Society of Chemistry.

Jin F.-L.,Jilin Institute of Chemical Technology | Park S.-J.,Inha University
Polymer Degradation and Stability | Year: 2012

Epoxy resin/filler hybrid composites were prepared by the melt blending of diglycidylether of bisphenol- A (DGEBA), as the epoxy resin, with nano-Al 2O3 or nano-SiC particles, as the nanoscaled fillers. The thermal properties, such as the curing behavior, thermal stability, dynamic mechanical properties, and thermal mechanical properties of the DGEBA/nano-Al2O3 and DGEBA/nano-SiC composites were examined using a range of techniques. As a result, the DSC curve peak temperature of both composites decreased with increasing filler content. The integral procedure decomposition temperature increased from 630 °C to 853 °C for DGEBA/nano-Al2O3 composite and 858 °C for DGEBA/nano-SiC composite. The char yield at 800 °C increased from 14.3% to 26.2-26.6% for both composites. Both composites had a 10 °C higher glass transition temperature than the neat epoxy resin. The coefficient of thermal expansion of both composites at the glassy and rubbery regions decreased with increasing filler content. © 2012 Elsevier Ltd. All rights reserved.

Lee H.-I.,Inha University | Mok J.,Sun Moon University
Physics of Plasmas | Year: 2010

Electromagnetic waves are considered for periodic structures consisting of lossy plasmonic components and dielectric host media. For the plasmonic components, not only low-loss metals but also high-loss gas plasmas are taken into consideration. For small filling fractions of the plasmonic components, the intercell interactions are kept to a minimum. In this way, the zero-order solution to the dispersion relation is solved by focusing on its cubic nonlinearity in frequency. Analysis shows that there are two types of solutions: propagating waves and stationary states, depending on the magnitudes of the temporal attenuation rates. Depending on the relative strengths of the material loss of the plasmonic component and its filling fraction, several key critical parameters for the transitions between these two solution types are thus identified. In the following companion paper of Paper II, the cubic nonlinearities in frequency of the dispersion relations stem from different origins. Notwithstanding, they lead to strikingly similar features such as the transitions in wave types and Hopf bifurcations. © 2010 American Institute of Physics.

Kim K.J.,Seoul National University | Kim J.,Seoul National University | Yu W.-R.,Seoul National University | Youk J.H.,Inha University | Lee J.,Agency for Defense Development
Carbon | Year: 2013

We demonstrate that the tensile strength of carbon fibers (CFs) can be increased by more than 14% by the catalytic growth of carbon nanotubes (CNTs) onto their surface. Repair to some of the damage incurred during the formation of catalyst nanoparticles, an increase in the carbon crystal size, and the formation of crosslinks of neighboring crystals by CNTs all occur during the chemical vapor deposition process, and are the main reasons for the improvement. The interfacial shear strength of the CFs is also shown to be significantly improved due to the CNTs grown on the CF surface. © 2012 Elsevier Ltd. All rights reserved.

Lee W.,Inha University | Loh W.-K.,Sungkyul University | Sohn M.M.,Sungkyunkwan University
Computers and Industrial Engineering | Year: 2012

The enormous growth in information technology has revolutionized the way people can access information sources. Web search engines have played an important role to support what the user wants precisely and efficiently from the vast web database. Different from conventional search engine approaches, searching the structure of the web, where the answer comprises more than a single page connected by hyperlinks, needs to be meritoriously developed. We propose Linear Programming models in order to generate the optimal structured web objects searching for relevant web graphs. In the model, the web objects with node and edge weights that represent the ranking measures for Webpages and hyperlinks are devised to rank the relevance in terms of keyword vectors. We also developed a tree-filtering algorithm and top-k Steiner tree algorithm that is used to provide the search recommendations in practical applications. With real web databases, the experimental study shows that the LP approach outperforms the conventional search engines with respect to execution time and quality of results. © 2011 Elsevier Ltd. All rights reserved.

Kim K.J.,Seoul National University | Yu W.-R.,Seoul National University | Youk J.H.,Inha University | Lee J.,Agency for Defense Development
ACS Applied Materials and Interfaces | Year: 2012

This study reports on the main cause of the reduced tensile strength of carbon fibers (CFs) by investigating the microstructural changes in the CFs that are undergoing mainly two processes: catalyst nanoparticle formation and chemical vapor deposition (CVD). Interestingly, the two processes oppositely influenced the tensile strength of the CFs: the former negatively and the latter positively. The catalysts coating and nanoparticle formation degraded the CF surface by inducing amorphous carbons and severing graphitic layers, while those defects were healed by both the injected carbons and interfaced CNTs during the CVD process. The revealed degradation and healing mechanisms can serve as a fundamental engineering basis for exploring optimized processes in the manufacturing of hierarchical reinforcements without sacrificing the tensile strength of the substrate CFs. © 2012 American Chemical Society.

Yim J.,Gachon University | Hwang S.-S.,Inha University | Yoo K.-Y.,Seoul National University | Kim C.-Y.,Seoul National University
Journal of Epidemiology and Community Health | Year: 2012

Objectives: To examine differences in the survival rates of cancer patients according to socioeconomic status, focusing on the role of the degree of healthcare utilisation by the patient. Methods: An observational follow-up study was done for 261 lung cancer, 259 liver cancer, 268 stomach cancer and 270 colon cancer patients, diagnosed during 1999-2002. Income status and healthcare utilisation were assessed with National Health Insurance (NHI) data; survival during 1999-2002 was identified by death certificate. HRs and 95% CI were derived from Cox proportional hazards regression. Results and Conclusions: The HRs for low income status are larger for colon cancer (2.37, 95% CI 1.17 to 4.80), followed by stomach (1.67, 95% CI 1.01 to 2.78), liver (1.57, 95% CI 1.03 to 2.39) and lung cancers (1.46, 95% CI 0.99 to 2.14). In the model including the variable of healthcare utilisation, colon and stomach cancers exhibited a lower HR in the moderate healthcare utilisation groups (0.40, 95% CI 0.21 to 0.76 in colon; 0.59, 95% CI 0.37 to 0.96 in stomach), whereas for liver cancer, the high utilisation group exhibited a higher hazard (1.72, 95% CI 1.07 to 2.75). A lower income status is independently related to a shorter survival time in cancer patients, especially in less fatal cancers. Healthcare utilisation independently affects the likelihood of survival from colon and stomach cancers, implying that a moderate degree of healthcare utilisation contributes to a longer survival time.

Ryu H.-Y.,Inha University | Lee J.-M.,Electronics and Telecommunications Research Institute
Applied Physics Letters | Year: 2013

A light-emitting diode (LED) structure containing p-type GaN layers with two-step Mg doping profiles is proposed to achieve high-efficiency performance in InGaN-based blue LEDs without any AlGaN electron-blocking-layer structures. Photoluminescence and electroluminescence (EL) measurement results show that, as the hole concentration in the p-GaN interlayer between active region and the p-GaN layer increases, defect-related nonradiative recombination increases, while the electron current leakage decreases. Under a certain hole-concentration condition in the p-GaN interlayer, the electron leakage and active region degradation are optimized so that high EL efficiency can be achieved. The measured efficiency characteristics are analyzed and interpreted using numerical simulations. © 2013 AIP Publishing LLC.

Kim J.,Seoul National University of Science and Technology | Cha Y.-N.,Inha University | Surh Y.-J.,Seoul National University of Science and Technology | Surh Y.-J.,Seoul National University
Mutation Research - Fundamental and Molecular Mechanisms of Mutagenesis | Year: 2010

Nuclear factor-erythroid 2-related factor-2 (Nrf2) is a key transcription factor that plays a central role in cellular defense against oxidative and electrophilic insults by timely induction of antioxidative and phase-2 detoxifying enzymes and related stress-response proteins. The 5'-flanking regions of genes encoding these cytoprotective proteins contain a specific consensus sequence termed antioxidant response element (ARE) to which Nrf2 binds. Recent studies have demonstrated that Nrf2-ARE signaling is also involved in attenuating inflammation-associated pathogenesis, such as autoimmune diseases, rheumatoid arthritis, asthma, emphysema, gastritis, colitis and atherosclerosis. Thus, disruption or loss of Nrf2 signaling causes enhanced susceptibility not only to oxidative and electrophilic stresses but also to inflammatory tissue injuries. During the early-phase of inflammation-mediated tissue damage, activation of Nrf2-ARE might inhibit the production or expression of pro-inflammatory mediators including cytokines, chemokines, cell adhesion molecules, matrix metalloproteinases, cyclooxygenase-2 and inducible nitric oxide synthase. It is likely that the cytoprotective function of genes targeted by Nrf2 may cooperatively regulate the innate immune response and also repress the induction of pro-inflammatory genes. This review highlights the protective role of Nrf2 in inflammation-mediated disorders with special focus on the inflammatory signaling modulated by this redox-regulated transcription factor. © 2009 Elsevier B.V.

Park C.-S.,Inha University | Bochner B.S.,Johns Hopkins University
International Neurourology Journal | Year: 2011

Mast cell increases and activation are detected in the chronic inflammatory bladder disease interstitial cystitis (IC), and their proinflammatory mediators are felt to contribute to regional pelvic pain and inflammatory pathophysiology. The immunoreceptor tyrosine-based inhibition motif-containing sialic acid-binding immunoglobulin-like lectins (Siglecs) expressed in mast cells could be evaluated as in vivo signaling regulators capable of inhibiting IC-related mast cell activation. © 2011 Korean Continence Society.

Kim H.N.,Seoul National University | Hong Y.,Seoul National University | Kim M.S.,Seoul National University | Kim S.M.,Inha University | Suh K.-Y.,Seoul National University
Biomaterials | Year: 2012

We report on the effect of synthetic extracellular matrix (ECM) scaffold in the form of uniformly-spaced nanogrooved surfaces in dermal wound healing. The rate of wound coverage was measured on various nanotopographical densities with vertical or parallel orientation using nanogrooves of 550 nm width with three different gaps of 550, 1100, and 2750 nm (spacing ratio: 1:1, 1:2 and 1:5). Guided by the nanotopographical cues in the absence of growth factors in wound healing process, the cultured NIH-3T3 cells demonstrated distinctly different migration speed, cell division, and ECM production as dictated by the topographical density and orientation, whereas the proliferation rate turned out to be nearly the same. Based on our experimental results, the nanopattern of 1:2 spacing ratio yielded the best wound healing performance in terms of migration speed, which seems similar to the natural organization of collagen fibers. © 2012.

Aim of the study: The appropriate duration of cardiopulmonary resuscitation (CPR) for patients who experience out-of-hospital cardiac arrest (OHCA) remains unknown. This study aimed to evaluate the duration of CPR in emergency departments (EDs) and to determine whether the institutions' median duration of CPR was associated with survival-to-discharge rate. Methods: A cohort of adult patients from a nationwide OHCA registry was retrospectively evaluated. The main variable was the median duration of CPR for each ED (institutional duration), and the main outcome was survival to discharge. Multivariable logistic regression analysis was performed to adjust for individual and aggregated confounders. Results: Among the 107,736 patients who experienced OHCA between 2006 and 2010, 30,716 (28.5%) were selected for analysis. The median age was 65 years, and 67.1% were men. The median duration of CPR for all EDs was 28. min, ranging from 11 to 45. min. EDs were categorized into 3 groups according to their institutional duration of CPR: groups A (<20. min), B (20-29. min), C (≥30. min). The observed survival rates of the 3 groups were 2.11%, 5.20%, and 5.62%, respectively. Compared with group B, the adjusted difference (95% confidence interval) for survival to discharge was 3.01% (1.90-4.11, P<. 0.001) for group A, and 0.33% (-0.64 to 1.30, P= 0.51) for group C. Conclusion: The duration of CPR varied widely among hospitals. The institutional duration of CPR less than 20. min was significantly associated with lower survival-to-discharge rate. © 2015 Elsevier Ireland Ltd.

Cho I.,Inha University | Park H.-A.,Seoul National University | Chung E.,Seoul National University
International Journal of Medical Informatics | Year: 2011

Objective: The aims of this study were to explore pressure ulcer incidences and practice variations in the nursing intervention provided for preventive pressure-ulcer care to patients either with pressure ulcers or at risk of pressure ulcers, and to examine them in relation to the patients' medical problems and the characteristics of the nurses who cared for them. Methods: The narrative nursing notes of 427 intensive-care patients who were discharged in 2007 that were documented at the point-of-care using standardized nursing statements were extracted from a clinical data repository at a teaching hospital in Korea and analyzed. The frequencies of five nursing interventions for pressure-ulcer prevention were compared between pressure-ulcer and pressure-ulcer risk groups, as were the characteristics of the nurses who were treating the patients in these two groups. Nursing interventions for pressure-ulcer prevention were also assessed relative to the patients' medical problems. Results: The overall incidence of pressure ulcers was 15.0%. Position change was the most popular nursing intervention provided for pressure-ulcer prevention in both the pressure-ulcer and at-risk groups, followed by skin care. There was a statistically significant tendency toward a greater frequency of providing skin care and nutritional care in the at-risk group than in the pressure-ulcer group. There was no statistically significant difference in the mean frequencies of nursing interventions relative to the patients' medical problems in the pressure-ulcer group. However, frequencies of nursing interventions did differ significantly between patients with neurological problems and those with other medical problems in the at-risk group. Analysis of the nurses' characteristics revealed that more nursing interventions were documented by those who were younger, less experienced, and more educated. Conclusion: A standardized nursing-terminology-based electronic nursing record system allowed us to monitor the variations in nursing practice with regard to preventive pressure-ulcer care in intensive-care patients with and at risk of pressure ulcers. We found that pressure-ulcer prevention care was provided at frequencies much lower than the recommended guidelines. Further studies on identifying the factors affecting pressure-ulcer prevention care and ways to improve the quality of that care are needed. © 2010 Elsevier Ireland Ltd.

Hwang S.,Seoul National University | Lee D.-S.,Inha University | Kahng B.,Seoul National University
Physical Review Letters | Year: 2012

The first passage time (FPT) for random walks is a key indicator of how fast information diffuses in a given system. Despite the role of FPT as a fundamental feature in transport phenomena, its behavior, particularly in heterogeneous networks, is not yet fully understood. Here, we study, both analytically and numerically, the scaling behavior of the FPT distribution to a given target node, averaged over all starting nodes. We find that random walks arrive quickly at a local hub, and therefore, the FPT distribution shows a crossover with respect to time from fast decay behavior (induced from the attractive effect to the hub) to slow decay behavior (caused by the exploring of the entire system). Moreover, the mean FPT is independent of the degree of the target node in the case of compact exploration. These theoretical results justify the necessity of using a random jump protocol (empirically used in search engines) and provide guidelines for designing an effective network to make information quickly accessible. © 2012 American Physical Society.

Jang S.,Inha University | Thirupathi P.,Inha University | Neupane L.N.,Inha University | Seong J.,Seoul National University | And 3 more authors.
Organic Letters | Year: 2012

A pyrene derivative chemosensor (Pyr-WH) based on a dipeptide shows a highly sensitive ratiometric response to Ag(I) as well as silver nanoparticles in aqueous solution at physiological pH. Pyr-WH penetrated live HeLa cells and exhibits a ratiometric response to intracellular Ag(I). The binding mode of Pyr-WH with Ag(I) was characterized based on fluorescence changes in different pH, NMR, and ESI mass spectrometer experiments. © 2012 American Chemical Society.

Kim J.,Seoul National University | Lee I.,Inha University | Tak Y.,Inha University | Cho B.H.,Seoul National University
Renewable Energy | Year: 2013

This work deals with a diagnosis of cathode flooding and membrane drying associated with a low frequency ripple current of a polymer electrolyte membrane fuel cell (PEMFC) based on impedance measurement on 12 single cells using electrochemical impedance spectroscopy (EIS). Average values of the identified model parameters obtained from direct measurement of the impedance curves of 12 single cells obtained after cycling for hours at variable frequencies, it has been found that impedance magnitude of a fuel cell injecting a low frequency ripple current (100 Hz) increased when compared with those injecting high frequency ripple currents (1 kHz and 10 kHz). Based on these investigations, additional impedance measurements are directly conducted to gain insight into cathode flooding and membrane drying concerning a low frequency ripple current. Regardless of operating frequency of ripple current, two PEMFC failures lead to an increase in the impedance magnitude in comparison with that of a fresh cell. Specifically, it is shown that a low frequency ripple current more accelerates the PEMFC degradation associated with two PEMFC failures. © 2012 Elsevier Ltd.

Park S.K.,Inha University | Kim T.S.,Inha University | Sohn J.L.,Seoul National University | Lee Y.D.,Korea Institute of Machinery and Materials
Applied Energy | Year: 2011

An integrated power generation system combining solid oxide fuel cell (SOFC) and oxy-fuel combustion technology is proposed. The system is revised from a pressurized SOFC-gas turbine hybrid system to capture CO2 almost completely while maintaining high efficiency. The system consists of SOFC, gas turbine, oxy-combustion bottoming cycle, and CO2 capture and compression process. An ion transport membrane (ITM) is used to separate oxygen from the cathode exit air. The fuel cell operates at an elevated pressure to facilitate the use of the ITM, which requires high pressure and temperature. The remaining fuel at the SOFC anode exit is completely burned with oxygen at the oxy-combustor. Almost all of the CO2 generated during the reforming process of the SOFC and at the oxy-fuel combustor is extracted from the condenser of the oxy-combustion cycle. The oxygen-depleted high pressure air from the SOFC cathode expands at the gas turbine. Therefore, the expander of the oxy-combustion cycle and the gas turbine provides additional power output. The two major design variables (steam expander inlet temperature and condenser pressure) of the oxy-fuel combustion system are determined through parametric analysis. There exists an optimal condenser pressure (below atmospheric pressure) in terms of global energy efficiency considering both the system power output and CO2 compression power consumption. It was shown that the integrated system can be designed to have almost equivalent system efficiency as the simple SOFC-gas turbine hybrid system. With the voltage of 0.752V at the SOFC operating at 900°C and 8bar, system efficiency over 69.2% is predicted. Efficiency penalty due to the CO2 capture and compression up to 150bar is around 6.1%. © 2010 Elsevier Ltd.

Kim S.,Seoul National University | Lee B.G.,Seoul National University | Park D.,Inha University
IEEE Transactions on Wireless Communications | Year: 2014

In this paper, we present an energy-per-bit minimized radio resource allocation scheme in heterogeneous networks equipped with multi-homing capability, simultaneously connecting to different wireless interfaces. Specifically, we formulate an optimization problem related to minimization of energy-per-bit which takes a form of nonlinear fractional programming. Then we derive a parametric optimization problem out of that fractional programming and solve the original problem by using a double-loop iteration method. In each iteration, we derive the optimal resource allocation policy by applying Lagrangian duality and an efficient dual update method. In addition, we present suboptimal resource allocation algorithms using the properties of the optimal resource allocation policy. Numerical results reveal that the optimal allocation algorithm improves energy efficiency significantly over the existing resource allocation algorithms designed for homogeneous networks and its performance is superior to suboptimal algorithms in reducing energy consumption as well as in enhancing network energy efficiency. © 2002-2012 IEEE.

Jang M.J.,Inha University | Baek S.H.,Seoul National University | Kim J.H.,Inha University
Cancer Letters | Year: 2011

Ubiquitin C-terminal hydrolse-L1 (UCH-L1) is a deubiquitinating enzyme (DUB) that cleaves the ubiquitin (ub) moiety from ub precursors or protein substrates. The correlation between UCH-L1 and cancer has been reported in various tissues, but the role of UCH-L1 in prostate cancer has not been thoroughly researched. Here we found that UCH-L1 is specifically highly expressed in the metastatic DU145 prostate cancer cell line, but not in the benign or weakly metastatic prostate cancer cells. To determine the role of UCH-L1 in prostate cancer metastasis, we constructed UCH-L1-knockdown DU145 and UCH-L1 or the active site mutant form of UCH-L1 (UCH-L1 C90S) expressing RWPE1 stable cells. Notably, the expression of UCH-L1 in RWPE1 cells promotes epithelial-to-mesenchymal transition (EMT), and this is an important process for cancer cell invasion and metastasis. On the contrary, knockdown of UCH-L1 in DU145 cells induces MET, the reverse program of EMT. Furthermore, the change of EMT status caused by altering the UCH-L1 level affects the migration and invasiveness of prostate cancer cells. Our results indicate that UCH-L1 promotes prostate cancer metastasis through EMT induction and UCH-L1 could be a novel diagnostic and therapeutic target for prostate cancer treatment. © 2011 Elsevier Ireland Ltd.

Seo Y.P.,Seoul National University | Choi H.J.,Inha University | Seo Y.,Seoul National University
Polymer | Year: 2011

A new rheological model is applied to the analysis of the behavior of electrorheological (ER) fluids. A comparison of the model's predictions with experimental data shows that the proposed model correctly predicts the shear stress behavior both quantitatively and qualitatively. The shear stress data for the aligned particles' structure reformation can be fitted as a function of shear rate with the new model. Proposed model using less parameters than CCJ model affords good agreement with the experimental data and consistent parameter values through the whole shear rate range and different applied electric field strengths. Furthermore, the yield stress was found to be almost linearly dependent on the field strength, different from the predictions of the polarization model. © 2011 Elsevier Ltd. All rights reserved.

Hong J.-Y.,University of Suwon | Wie J.J.,Inha University | Xu Y.,University of Suwon | Park H.S.,University of Suwon
Physical Chemistry Chemical Physics | Year: 2015

Graphene aerogel is a relatively new type of aerogel that is ideal for energy storage applications because of its large surface area, high electrical conductivity and good chemical stability. Also, three dimensional interconnected macropores offer many advantages such as low density, fast ion and mass transfer, and easy access to storage sites. Such features allow graphene aerogels to be intensively applied for electrochemical capacitor applications. Despite the growing interest in graphene aerogel-based electrochemical capacitors, however, the graphene aerogels still suffer from their low capacitive performances and high fragility. Both relatively low capacitance and brittleness of physically crosslinked graphene aerogels remain a critical challenge. Until now, a number of alternative attempts have been devoted to overcome these shortcomings. In this perspective, we summarize the recent research progress towards the development of advanced graphene aerogel-based electrochemical capacitors according to the different approaches (e.g. porosity, composition and structure controls). Then, the recently proposed chemical strategies to improve the capacitive performances and mechanical durability of graphene aerogels for practical applications are highlighted. Finally, the current challenges and perspectives in this emerging material are also discussed. © 2015 the Owner Societies.

Hwang J.Y.,Electronics and Telecommunications Research Institute | Lee S.,Electronics and Telecommunications Research Institute | Chung B.-H.,Electronics and Telecommunications Research Institute | Cho H.S.,Electronics and Telecommunications Research Institute | Nyang D.,Inha University
Information Sciences | Year: 2013

In this paper we present a novel group signature scheme for dynamic membership which enables fine-grained control over the release of user information. This scheme could be widely used for various anonymity-based applications such as privacy-preserving data mining and customized anonymous authentication owing to a useful property called controllable linkability. A valid signer is able to create signatures that hide his or her identity as normal group signatures but can be anonymously linked regardless of changes to the membership status of the signer and without exposure of the history of the joining and revocation. From signatures, only linkage information can be disclosed, with a special linking key. Using this controllable linkability and the controllable anonymity of a group signature, anonymity may be flexibly or elaborately controlled according to a desired level. To begin construction of our scheme, we first introduce the Decision Linear Combination (DLC) assumption in a so-called gap Diffie-Hellman group where the DDH problem is tractable but the CDH problem is hard, and we prove that this assumption can be guaranteed in generic bilinear groups. To identify security requirements more precisely, we formally present definitions of anonymity, traceability, non-frameabilty, and linkability. We then prove that our scheme achieves all these security properties in the random oracle model. Our scheme supporting controllable linkability yields a short signature that is only 33.3% longer than the best-known normal group signature. Furthermore, we show that our scheme is comparable to the group signature scheme in terms of the amount of computation for basic operations such as signing, verification, and the key update caused by revocation. Finally, using the linkability for dynamic membership, computation overhead in opening signer's identity can be significantly reduced or minimized. © 2012 Elsevier Inc. All rights reserved.

Yun Y.S.,Inha University | Cho S.Y.,Inha University | Shim J.,Inha University | Kim B.H.,Incheon National University | And 7 more authors.
Advanced Materials | Year: 2013

Novel carbon-based microporous nanoplates containing numerous heteroatoms (H-CMNs) are fabricated from regenerated silk fibroin by the carbonization and activation of KOH. The H-CMNs exhibit superior electrochemical performance, displaying a specific capacitance of 264 F/g in aqueous electrolytes, a specific energy of 133 Wh/kg, a specific power of 217 kW/kg, and a stable cycle life over 10000 cycles. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyun S.,Seoul National University | Pyun S.,Inha University | Son W.,Seoul National University | Shin C.,Seoul National University
Geophysical Prospecting | Year: 2011

In this paper we propose a 3D acoustic full waveform inversion algorithm in the Laplace domain. The partial differential equation for the 3D acoustic wave equation in the Laplace domain is reformulated as a linear system of algebraic equations using the finite element method and the resulting linear system is solved by a preconditioned conjugate gradient method. The numerical solutions obtained by our modelling algorithm are verified through a comparison with the corresponding analytical solutions and the appropriate dispersion analysis. In the Laplace-domain waveform inversion, the logarithm of the Laplace transformed wavefields mainly contains long-wavelength information about the underlying velocity model. As a result, the algorithm smoothes a small-scale structure but roughly identifies large-scale features within a certain depth determined by the range of offsets and Laplace damping constants employed. Our algorithm thus provides a useful complementary process to time- or frequency-domain waveform inversion, which cannot recover a large-scale structure when low-frequency signals are weak or absent. The algorithm is demonstrated on a synthetic example: the SEG/EAGE 3D salt-dome model. The numerical test is limited to a Laplace-domain synthetic data set for the inversion. In order to verify the usefulness of the inverted velocity model, we perform the 3D reverse time migration. The migration results show that our inversion results can be used as an initial model for the subsequent high-resolution waveform inversion. Further studies are needed to perform the inversion using time-domain synthetic data with noise or real data, thereby investigating robustness to noise. © 2010 European Association of Geoscientists & Engineers.

Chung W.,Seoul National University | Shin C.,Seoul National University | Pyun S.,Inha University
Bulletin of the Seismological Society of America | Year: 2010

There are many obstacles to applying waveform inversion to seismic data. However, the most critical factor is the absence of the low-frequency components that are needed for constructing long-wavelength structure. This problem stems from the highly nonlinear property of waveform inversion, which causes the algorithm to be trapped in a local minimum. The waveform inversion in the Laplace domain, rather than the usual frequency domain, is capable of producing velocity models with longwavelength information. A study on this method was recently published, which was limited to the problem of acoustic media. In this paper, we extend Laplace-domain waveform inversion to elastic media. Unlike acoustic inversion, elastic inversion requires sophisticated manipulation of the gradient direction. We suggest a method to modify pseudo-Hessian matrices by using a heuristic weighting function. We test our inversion algorithm on synthetic seismic data generated using the Society of Exploration Geophysicists/European Association of Geoscientists & Engineers (SEG/EAGE)salt-dome model and the Commission on Controlled-Source Seismology (CCSS) model. Inversion results using these data sets also produce the long-wavelength velocity model and demonstrate that Laplace-domain waveform inversion is robust to the initial velocity model. Furthermore, we provide an example showing that our inverted result is a suitable initial model for the frequency-domain waveform inversion.

Kim B.-S.,National Cancer Center | Bae J.N.,Inha University | Cho M.J.,Seoul National University
Journal of Affective Disorders | Year: 2010

Background: The association of hypotension with depression in the elderly is controversial. The aim of this study was to examine the relationship between hypotension and depression in the elderly, focusing on symptom manifestations of depression in the hypotensive group. Methods: This study was a community-based, cross-sectional study that included 962 elderly adults aged 65 years or older without cognitive impairment; analysis focused on subjects who were not taking antihypertensive drugs (n = 480). The Korean version of the Geriatric Depression Scale-Short Form (SGDS-K) was used for the evaluation of depression. Participants were classified into 10th percentile groups by blood pressure level. The risks of depression were evaluated by logistic regression in the various blood pressure groups and were compared using a reference group whose blood pressure was within the 40-59th percentile range. To explore symptomatology, logistic regression analyses were performed between the lowest 10th percentile blood pressure group and the reference group to obtain the odds ratio for each item on the SGDS-K. Results: Participants with systolic blood pressure in the lowest 10th percentile range were at increased odds of depression when compared with the reference group after adjustment for possible confounders (adjusted odds ratio 3.33, 95% confidence interval 1.47-7.84). Of the depressive symptoms, significant differences were found between the systolic hypotension group and the reference group for the depression items of 'satisfied with life', 'feel life is empty', 'in good spirits', 'wonderful to be alive' and 'full of energy'. Conclusions: Hypotension was related to depression, specifically to low positive affect in the elderly. Aged people with hypotension and depressed mood should be monitored carefully. © 2010 Elsevier B.V. All rights reserved.

Kim J.,Seoul National University | Lee I.,Inha University | Tak Y.,Inha University | Cho B.H.,Seoul National University
International Journal of Hydrogen Energy | Year: 2012

This work investigates a pattern recognition-based diagnosis approach as an application of the Hamming neural network to the identification of suitable fuel cell model parameters, which aim to diagnose state-of-health (SOH) for a polymer electrolyte membrane (PEM) fuel cell. The fuel cell output voltage (FCOV) patterns of the 20 PEM fuel cells were measured, together with the model parameters, as representative patterns. Through statistical analysis of the FCOV patterns for 20 single cells, the Hamming neural network is applied for identification of the representative FCOV pattern that matches most closely of the pattern of the arbitrary cell to be measured. Considering the equivalent circuit fuel cell model, the purpose is to select a representative loss ΔRd, defined as the sum of two losses (activation and concentration losses). Consequently, the selected cell's ΔRd is properly applied to diagnose SOH of an arbitrary cell through the comparison with those of fully fresh and aged cells with the minimum and maximum of the ΔRd in experimental cell group, respectively. This avoids the need for repeated parameter measurement. Therefore, these results could lead to interesting perspectives for diagnostic fuel cell SOH. Copyright © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Kang B.-W.,Samsung | Kim J.,Inha University
IEEE/ASME Transactions on Mechatronics | Year: 2013

This paper deals with the newly developed piezoelectric stepper motors that generate the precise stepping motion using a piezoelectric torsional actuator and a pair of one-way roller clutches. The torsional actuator consists of piezoelectric segments that produce the angular motion associated with its shear mode of piezoelectric ceramics, d15. A pair of one-way roller clutches converts the angular motion of the torsional actuator into continuous stepping rotation with a driving shaft. Because the piezoelectric torsional actuator functions as the driving source at high frequency, a precise step motion can be produced without any conversion mechanism of stepping rotation. In this paper, two types of torsional stepper motors are designed and fabricated. In the design stage, the shear resonance mode of the piezoelectric actuator is analyzed by using a finite-element analysis, and rotation speed and torque measurement are performed. Also, possibility of achieving higher rotation speed using a torsion bar is addressed. Once the proposed piezoelectric stepping motor is miniaturized, it can be used for many compact and precision motion applications. © 2013 IEEE.

Rawal S.B.,Inha University | Bera S.,Inha University | Lee D.,Seoul National University | Jang D.-J.,Seoul National University | Lee W.I.,Inha University
Catalysis Science and Technology | Year: 2013

According to relative energy band positions between TiO2 and visible-light-absorbing semiconductors, three different types of heterojunction were designed, and their visible-light photocatalytic efficiencies were analyzed. In Type-A heterojunction, the conduction band (CB) level of sensitizer is positioned at a more negative side than that of TiO2, whereas in Type-B system its valence band (VB) level is more positive than that of TiO 2 and in Type-C system the sensitizer energy level is located between the CB and VB of TiO2. In evolving CO2 from gaseous 2-propanol (IP) under visible-light irradiation, the Type-B systems such as FeTiO3/TiO2, Ag3PO4/TiO2, W18O49/TiO2, and Sb-doped SnO2 (ATO)/TiO2 demonstrated noticeably higher photocatalytic efficiency than the Type-A such as CdS/TiO2 and CdSe/TiO2, while the Type-C such as NiTiO3/TiO2, CoTiO3/TiO 2, and Fe2O3/TiO2 did not show any appreciable improvement. Remarkably high visible-light photocatalytic activity of Type-B heterojunction structures could be explained by inter-semiconductor hole-transfer mechanism between the VB of the sensitizer and that of TiO 2. The evidence for the hole-transport between sensitizer and TiO2 was also obtained by monitoring the hole-scavenging reactions with iodide (I-) and 1,4-terephthalic acid (TA). © 2013 The Royal Society of Chemistry.

Suh M.,Inha University | Choi-Kwon S.,Seoul National University | Kim J.S.,University of Ulsan
Journal of Stroke and Cerebrovascular Diseases | Year: 2014

Background Poststroke sleep disturbances (PSSDs) are frequent and reported to be associated with unfavorable clinical outcomes. PSSDs appear to be related to a multitude of factors including lesion location and environmental causes. Moreover, depression and fatigue, which frequently develop in stroke patients may also contribute to PSSD development. The purpose of this study was to evaluate the prevalence and characteristics of PSSDs and factors related to PSSDs including depression and fatigue in hospitalized stroke patients. Methods Patients who were hospitalized with acute stroke at the Asan Medical Center were evaluated. The quality (Verran-Snyder-Halpern [VSH] Sleep Scale score), duration and latency of night-time sleep, the frequency of waking after sleep onset, and daytime sleepiness were evaluated during the hospitalization period. To validate the self-reported night-time sleep, an actigraphy was performed in a subset of patients. The location, circulation, and laterality of each lesion were determined from brain magnetic resonance images obtained within 7 days of stroke onset. Depression and fatigue were assessed using the Beck Depression Inventory and the Fatigue Severity Scale, respectively. For environmental factors, the duration of hospitalization and the number of other patients in the same room were recorded. Univariate, multiple regression, and multiple logistic regression analyses were used to evaluate predictors of PSSD development. Results A total of 282 patients completed the study. The mean age of the patients was 62.3 (±12.76) years and 58.9% of them were male. Sixty patients (21.3%) reported sleep duration less than 6 hours/night and 110 (39.0%) reported more daytime sleepiness than before the stroke. In 54 patients who agreed to wear an actigraph, self-reported sleep duration was significantly correlated with time in bed measured with an actigraph (r =.407, P =.002) and, VSH Sleep Scale score and sleep efficiency in actigraphy were also significantly correlated (r =.305, P =.026). Quality of night-time sleep was independently related to cortical lesion location (P =.002), diabetes mellitus (P =.020), and depression (P <.001), whereas increased daytime sleepiness was independently associated with subcortical lesion location (P =.031), fatigue (P =.001), and quality of night-time sleep (P =.001). Conclusions PSSDs are common in hospitalized stroke patients. The most powerful factor predicting night-time sleep disturbances in stroke patients was depression. Cortical brain lesion and diabetes mellitus were also associated with night-time sleep disturbances. On the other hand, although poststroke daytime sleepiness is in part caused by night-time sleep disturbance, it is more closely associated with fatigue and subcortical lesion location. © 2014 by National Stroke Association.

Chung S.-Y.,Inha University | Chung S.-Y.,Nalphates LLC | Kim Y.-M.,Korea Basic Science Institute | Choi S.-Y.,Korea Institute of Materials Science
Advanced Functional Materials | Year: 2010

The control of unexpectedly rapid Li intercalation reactions without structural instability in olivine-type LiFePO4 nanocrystals is one of the notable scientific advances and new findings attained in materials physics and chemistry during the past decade. A variety of scientific studies and technological investigations have been carried out with LiFePO4 to elucidate the origins of many peculiar physical aspects as well as to develop more effective synthetic processing techniques for better electrochemical performances. Among the several features of LiFePO4 that have attracted much interest, in this article we address four important issues-regarding doping of aliovalent cations, distribution of Fe-rich secondary metallic phases, nanoparticle formation during crystallization, and antisite Li/Fe partitioning-by means of straightforward atomic-scale imaging and chemical probing. The direct observations in the present study provide significant insight into alternative efficient approaches to obtain conductive LiFePO 4 nanocrystals with controlled defect structures. Olivine-type ordered LiFePO4 (see picture) has been studied during the past decade to elucidate the origins of its many peculiar physical aspects for achieving better electrochemical performance. Based on straightforward atomic-scale imaging and chemical probing, four different issues regarding LiFePO4 are discussed in this article, giving a brief overview on the valuable experimental demonstrations made to date. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chung S.-Y.,Inha University | Chung S.-Y.,Nalphates LLC | Kim J.-G.,Korea Basic Science Institute | Kim Y.-M.,Korea Basic Science Institute | Lee Y.-B.,Korea Basic Science Institute
Advanced Materials | Year: 2011

The three-dimensionally isolated morphology of secondary iron phosphide phases in a polycrystalline LiFePO4 matrix is determined using a combination of electron tomography in high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDS), and electron energy-loss spectroscopy (EELS). The present evidence shows that the enhanced bulk electronic conductivity in LiFePO 4 has no relation to secondary metallic phases at the grain boundaries. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kim Y.J.,Inha University | Liu Y.D.,Inha University | Liu Y.D.,Yanshan University | Seo Y.,Seoul National University | Choi H.J.,Inha University
Langmuir | Year: 2013

Core-shell-structured magnetic polystyrene (PS)/inorganic particles were fabricated by Pickering emulsion polymerization using nanosized Fe 2O3 particles as a solid stabilizer. Scanning electron microscopy and transmission electron microscopy confirmed the synthesized PS/Fe2O3 particles to be comprised of a PS surface coated with Fe2O3 nanoparticles. The chemical structure of the composite nanospheres was characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The thermal properties of composite nanospheres and corresponding pure polymer were examined by thermogravimetric analysis. The rheological properties of the core-shell-structured magnetic PS/inorganic particles dispersed in silicone oil were investigated under an external magnetic field strength using a rotational rheometer. The particles with extremely lower density than common magnetic particles exhibited solid-like magnetorheological phase characteristics, and the flow curves were fitted to the Cho-Choi-Jhon model of the rheological equation of state. © 2013 American Chemical Society.

Fang F.F.,Inha University | Choi H.J.,Inha University | Seo Y.,Seoul National University
ACS Applied Materials and Interfaces | Year: 2010

A two-step process for the sequential coating of magnetic carbonyliron (CI) particles with polystyrene (PS) and multiwalled carbon nanotubes (MWCNTs) was used to improve the sedimentation stability of micrometer-sized magnetic CI particles for magnetorheological (MR) applications under an applied magnetic field. The CI particles were initially coated with nanosized PS beads using an in situ dispersion polymerization method and then wrapped with a dense MWCNT nest through a solvent-casting method in a water/oil emulsion system. The morphology, MR performance, and sedimentation stability of the synthesized magnetic composite particles were examined. The composite particles showed enhanced MR characteristics and dispersion stability. © 2010 American Chemical Society.

Hong S.J.,Seoul National University | Yu W.-R.,Seoul National University | Youk J.H.,Inha University
Smart Materials and Structures | Year: 2010

Thermo-responsive shape memory polyurethane (SMPU) is a smart material that can respond to external heat by changing its macroscopic shape from a temporary configuration to a memorized permanent one. The temporary shape can be processed using mechanical forces above a certain temperature (the transition temperature) and can be maintained until the material acquires a certain thermal energy. Thereafter, the material will recover its memorized permanent shape. However, it is unclear what will occur if the thermal energy is then dissipated, i.e., the material temperature decreases. There are two possibilities: the material will respond to the dissipated energy, resulting in another macroscopic shape change; or nothing will happen beyond the thermal contraction. The former is called two-way shape memory (TWSM) behavior and the latter is called one-way shape memory behavior. This paper reports novel findings showing that TWSM behavior can be imparted to SMPUs using a thermo-mechanical treatment, i.e., imposing a constant stress on them after their temporary shaping. A series of experiments were carried out to characterize the TWSM behavior of SMPUs and to explain its mechanism. © 2010 IOP Publishing Ltd.

Zhang W.L.,Inha University | Choi H.J.,Inha University | Seo Y.,Seoul National University
Macromolecular Chemistry and Physics | Year: 2013

This paper reports a facile approach for fabricating core-shell structured graphene oxide (GO)-wrapped amine-modified poly(glycidyl methacrylate) (ami-PGMA) microspheres. The resulting core-shell structure is confirmed by scanning electron micsroscopy (SEM) and transmission electron microscopy (TEM), whereas the coexistence of GO and PGMA is confirmed by FTIR spectroscopy. The thermal stability of the ami-PGMA/GO microspheres is enhanced compared with that of pure PGMA microspheres. The novel ami-PGMA/GO composite microsphere-based electrorheological (ER) fluid shows typical ER characterization, using a rotational rheometer under an applied electric field. The dielectric analysis results along with the relaxation time and achievable polarizability of the fluid are correlated with the ER performance using a LCR meter. Core-shell structured graphene oxide-wrapped amine-modified poly(glycidyl methacrylate) composite microspheres are fabricated through an amine-epoxide/carboxyl chemical reaction and then dispersed in silicone oil for an electrorheological fluid. When an electric field is applied, the dispersed particles form chains over the electrode, resulting in a solid-like behavior with a yield stress. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Kang J.,Inha University | Nyang D.,Inha University | Lee K.,University of Suwon
Information Sciences | Year: 2014

Although authentication using biometric techniques is convenient, security issues such as the loss of personal bio-information are serious problems. However, the development of a secure biometrics scheme poses considerable challenges because users' bio-information is not precisely the same for each authentication attempt. This uncertainty during the authentication process obstructs direct application of cryptographic one-way functions in the authentication system. In this paper, we suggest a two-factor face authentication scheme using matrix transformations and a user password. Our scheme is designed with a secure cancellation feature, in that templates composed of permutation and feature vectors can be freely changed. Through experimental scenarios and results, we introduce the notable features of our scheme. Furthermore, we consider possible attacks on the proposed scheme and suggest security enhancement methods. © 2014 Elsevier Inc. All rights reserved.

Hwang S.,Seoul National University | Lee D.-S.,Inha University | Kahng B.,Seoul National University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

Exploring the World Wide Web has become one of the key issues in information science, specifically in view of its application to the PageRank-like algorithms used in search engines. The random walk approach has been employed to study such a problem. The probability of return to the origin (RTO) of random walks is inversely related to how information can be accessed during random surfing. We find analytically that the RTO probability for a given starting node shows a crossover from a slow to a fast decay behavior with time and the crossover time increases with the degree of the starting node. We remark that the RTO probability becomes almost constant in the early-time regime as the degree exponent approaches two. This result indicates that a random surfer can be effectively trapped at the hub and supports the necessity of the random jump strategy empirically used in the Google's search engine. © 2012 American Physical Society.

Kim S.,University of Minnesota | Sobelman G.E.,University of Minnesota | Lee H.,Inha University
IEEE Transactions on Very Large Scale Integration (VLSI) Systems | Year: 2011

A reduced-complexity low density parity check (LDPC) layered decoding architecture is proposed using an offset permutation scheme in the switch networks. This method requires only one shuffle network, rather than the two shuffle networks which are used in conventional designs. In addition, we use a block parallel decoding scheme by suitably mapping between required memory banks and processing units in order to increase the decoding throughput. The proposed architecture is realized for a 672-bit, rate-1/2 irregular LDPC code on a Xilinx Virtex-4 FPGA device. The design achieves an information throughput of 822 Mb/s at a clock speed of 335 MHz with a maximum of 8 iterations. © 2010 IEEE.

Kim D.-H.,Inha University | Seong J.,Seoul National University | Lee H.,Seoul National University | Lee K.-H.,Inha University
Sensors and Actuators, B: Chemical | Year: 2014

A fluorescent chemosensor (Pyr-Tyr) based on tyrosine showed highly selective and sensitive ratiometric response to Hg(II) among 14 metal ions in buffered aqueous solutions. The emission intensity ratio at 480 and 383 nm increased significantly from 0 to about 1.5 with the increase of Hg(II) concentrations (0-1 equiv.) and the ratiometric response to Hg(II) was not interfered by other metal ions such as Cu(II), Cd(II), and Ag(I). The detection limit of the chemosensor for Hg(II) was calculated to be 12 ± 1 nM (2.4 ppb). Pyr-Tyr exhibited ratiometric responses to Hg(II) in a wide range of pH values (pH 4.5-11.5) and the chemosensor was demonstrated to detect intracellular Hg(II) in HeLa cells. The binding mode of the chemosensor with Hg(II) was investigated by 1H NMR titration and pH titration experiments, and ESI mass spectrometry. © 2014 Elsevier B.V. All rights reserved.

Kwon Y.-M.,SamYook Medical Center | Oh S.-W.,Seoul National University | Hwang S.-S.,Inha University | Lee C.,Seoul National University | And 2 more authors.
American Journal of Gastroenterology | Year: 2012

Objectives: Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease, and its prevalence is much higher in obese individuals. NAFLD is closely related to metabolic syndrome (MetS); however, most concepts about the relationship between NAFLD and MetS have emphasized obesity, although NAFLD is not a rare disease in the non-obese population. In the present study, we aim to determine the association between NAFLD and MetS and to compare this association between non-obese and obese individuals.METHODS: A total of 29,994 adults who underwent routine comprehensive health evaluations, including abdominal ultrasonography, were selected. We calculated the adjusted prevalence ratios (PRs) for components of MetS (high blood pressure (BP), impaired fasting glucose, low high-density lipoprotein cholesterol (HDL-C), and high triglycerides (TG)) according to NAFLD in non-obese and obese patients.Results: NAFLD was found in 12.6% of non-obese subjects and 50.1% of obese subjects. NAFLD was associated with most components of MetS in both obese and non-obese subjects. However, non-obese NAFLD patients had significantly higher PRs for certain components of MetS than did obese patients, especially among women. Adjusted PRs (95% confidence interval) for components of MetS in non-obese women vs. obese women were as follows: (1) high BP: 1.41 (1.31-1.51) vs. 1.05 (0.89-1.22) (2) impaired fasting glucose: 2.04 (1.95-2.75) vs. 1.37 (1.21-1.53) (3) low HDL-C: 2.00 (1.92-2.08) vs. 1.40 (1.26-1.55), and (4) high TG: 3.36 (3.24-3.47) vs. 1.97 (1.76-2.17).CONCLUSIONS:NAFLD was associated with risk for components of MetS, and the association was stronger in non-obese than in obese individuals, especially in women. Therefore, NAFLD should be considered a meaningful predictor of metabolic diseases in the non-obese population. © 2012 by the American College of Gastroenterology.

Lee J.-H.,Seoul National University | Um S.,Seoul National University | Jang J.-H.,Inha University | Seo B.M.,Seoul National University
Cell and Tissue Research | Year: 2012

Human periodontal ligament stem cells (PDLSCs) from extracted third molar teeth are a type of adult stem cell originating from dental tissue. PDLSCs are known to have a self-renewal capacity and multi-lineage differentiation potential. Vascular endothelial growth factor (VEGF), an angiogenic/ vasculogenic factor, has been shown to stimulate endothelial cell mitogenesis and cell migration. Another growth factor, fibroblast growth factor-2 (FGF-2), a mitogenic factor, enhances osteogenesis in mesenchymal stem cells (MSCs). This study examines the effects of VEGF and FGF-2 on PDLSCs in vitro and in vivo compared with those on bone marrow stem cells (BMSCs) as a positive control. Treatment of PDLSCs with VEGF increases the accumulation of calcium nodules, alkaline phosphatase (ALP) activity and the formation of hard tissue and upregulates the mRNA level of runt-related transcription factor 2 (Runx2). In contrast, FGF-2 enhances the proliferation of PDLSCs in vitro in cell culture, where it significantly decreases calcium accumulation and ALP activity and down-regulates the expression of osteogenic gene markers (i.e., Runx2, ALP, type I collagen) involved in osteogenic induction. We have also transplanted PDLSCs with hydroxyapatite/ tricalcium phosphate particles (HA/TCP) as carriers for each factor (VEGF, FGF-2) into nude mice and, after 8 weeks, observed the in vivo formation of hard tissue at the dorsal surface. Based on our results, we suggest that VEGF has positive effects on odonto-/osteogenic differentiation in vitro and on the formation of mineralized structure in vivo. FGF-2 might be a powerful promoter of the proliferation of progenitor cells in hard tissue regeneration but exogenous FGF-2 might inhibit terminal differentiation. © Springer-Verlag 2012.

Kim Y.,Inha University | Kim J.,Seoul National University | Kang S.,Seoul National University
Journal of Materials Chemistry C | Year: 2013

Thermodynamic stabilities of the phases of Sr-Si-N-O system were evaluated by simulating phase diagrams at various conditions based on first-principles density functional theory calculations. Synthesis conditions and stability of the compounds belonging to the system, in which oxidation and nitridation reactions are involved complicatedly, could be interpreted through this first systematic investigation on the two-gas system. Practical synthetic methods of nitrides, such as hydrogen-reduction and nitridation or carbothermal reduction and nitridation reactions, were studied with special attention. This study enabled us to calculate proper conditions for synthesis of the Sr 2Si5N8 phase, which is drawing attention as a new phosphor material for light emitting diodes. The types of impurities appearing with deviation from the proper synthetic conditions were also investigated, which may provide information about optimizing synthesis conditions. Synthesis of Sr2Si5N8:Eu phosphor using SiO2, instead of conventionally used Si3N 4, was predicted by first-principles calculations, and we succeeded in synthesizing Sr2Si5N8:Eu phosphor for the first time using all oxide raw materials under normal pressure on this basis. The results of this study are expected to provide useful guidelines for synthesis of nitrides and the established simulation method may effectively be applied to other multi-gas systems. © 2013 The Royal Society of Chemistry.

Song B.C.,Inha University | Song B.C.,Samsung | Jeong S.-C.,Inha University | Choi Y.,Inha University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2011

This paper presents a video super-resolution algorithm to interpolate an arbitrary frame in a low resolution video sequence from sparsely existing high resolution key-frames. First, a hierarchical block-based motion estimation is performed between an input and low resolution key-frames. If the motion-compensated error is small, then an input low resolution patch is temporally super-resolved via bi-directional overlapped block motion compensation. Otherwise, the input patch is spatially super-resolved using the dictionary that has been already learned from the low resolution and its corresponding high resolution key-frame pair. Finally, possible blocking artifacts between temporally super-resolved patches and spatially super-resolved patches are concealed using a specific de-blocking filter. The experimental results show that the proposed algorithm provides significantly better subjective visual quality as well as higher peak-to-peak signal-to-noise ratio than those by previous interpolation algorithms. © 2006 IEEE.

Kim S.,Dongyang University | Singh V.P.,Texas A&M University | Seo Y.,Dongyang University | Kim H.S.,Inha University
Water Resources Management | Year: 2014

The objective of this study is to develop soft computing and data reconstruction techniques for modeling monthly California Irrigation Management Information System (CIMIS) evapotranspiration (ETo) at two stations, U.C. Riverside and Durham, in California. The nonlinear dynamics of monthly CIMIS ETo is examined using autocorrelation function, phase space reconstruction, and close returns plot. The generalized regression neural networks and genetic algorithm (GRNN-GA) conjunction model is developed for modeling monthly CIMIS ETo. Among different input variables considered, solar radiation (RAD) is found to be the most effective variable for modeling monthly CIMIS ETo using GRNN-GA for both stations. Adding other input variables to the best 1-input combination improves the model performance. The generalized regression neural networks and backpropagation algorithm (GRNN-BP) conjunction model is compared with the results of GRNN-GA for modeling monthly CIMIS ETo. Two bootstrap resampling methods are implemented to reconstruct the training data. Method 1 (1-BGRNN-GA) employs simple extensions of training data using the bootstrap resampling method. For each training data, method 2 (2-BGRNN-GA) uses individual bootstrap resampling of original training data. Results indicate that Method 2 (2-BGRNN-GA) improves modeling of monthly CIMIS ETo and is more stable and reliable than are GRNN-GA, GRNN-BP, and Method 1 (1-BGRNN-GA). © 2013 Springer Science+Business Media Dordrecht.

Fang F.F.,Inha University | Liu Y.D.,Inha University | Choi H.J.,Inha University | Seo Y.,Seoul National University
ACS Applied Materials and Interfaces | Year: 2011

The dispersion stability of soft magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids was improved by applying a unique functional coating composed of a conducting polyaniline layer and a multiwalled carbon nanotube nest to the surfaces of the CI particles via conventional dispersion polymerization, followed by facile solvent casting. The coating morphology and thickness were analyzed by SEM and TEM imaging. Chemical composition of the polyaniline layer was detected by Raman spectroscope, which also confirmed the coating performance successfully. The influence of the functional coating on the magnetic properties was investigated by measuring the MR performance and sedimentation properties using a vibrating sample magnetometer, rotational rheometer, and Turbiscan apparatus. Improved dispersion characteristics of the MR fluid were observed. © 2011 American Chemical Society.

Lee K.P.,Seoul National University | Kim J.-S.,Inha University | Min K.-J.,Inha University
Animal Behaviour | Year: 2013

Mating elicits dramatic changes in behaviour and physiology related to reproduction in female Drosophila melanogaster, but little is known about how mating affects nutrient intake and preferences in this model organism. Postmating switches in reproductive activity and feeding are likely to alter life span because both reproduction and nutrition are closely linked to survival. To explore these possibilities, we compared the intake patterns of protein (P) and carbohydrate (C) preferred by male, mated female and virgin female adults of D. melanogaster and their life span responses under varying dietary P:C balances (0:1, 1:1 and 4:1). Despite sex differences, the patterns of both macronutrient intake and life span were remarkably similar between males and virgin females. Compared to unmated virgins, mated females consumed ca. 2.7 times more nutrients and preferred a diet that was significantly more protein-rich (mated versus virgin females: P:C 1:1.5 versus 1:4). Surprisingly, females that had experienced mating in early adulthood lived longer than those that remained virgin, and this life span-extending effect of mating in females was most profound on a diet that was equally balanced (P:C 1:1). Our results indicate that mating is an important modulator that regulates sex-specific nutrient preference, which in turn alters longevity in D. melanogaster. © 2013 The Association for the Study of Animal Behaviour.

Lee J.,Seoul National University | Kim J.,Korea Atomic Energy Research Institute | Choi H.,Seoul National University | Yang K.-S.,Inha University
Journal of Computational Physics | Year: 2011

When a discrete-forcing immersed boundary method is applied to moving-body problems, it produces spurious force oscillations on a solid body. In the present study, we identify two sources of these force oscillations. One source is from the spatial discontinuity in the pressure across the immersed boundary when a grid point located inside a solid body becomes that of fluid with a body motion. The addition of mass source/sink together with momentum forcing proposed by Kim et al. [J. Kim, D. Kim, H. Choi, An immersed-boundary finite volume method for simulations of flow in complex geometries, Journal of Computational Physics 171 (2001) 132-150] reduces the spurious force oscillations by alleviating this pressure discontinuity. The other source is from the temporal discontinuity in the velocity at the grid points where fluid becomes solid with a body motion. The magnitude of velocity discontinuity decreases with decreasing the grid spacing near the immersed boundary. Four moving-body problems are simulated by varying the grid spacing at a fixed computational time step and at a constant CFL number, respectively. It is found that the spurious force oscillations decrease with decreasing the grid spacing and increasing the computational time step size, but they depend more on the grid spacing than on the computational time step size. © 2011 Elsevier Inc.

Shin J.W.,Seoul National University | Chang J.-H.,Inha University | Kim N.S.,Seoul National University
Computer Speech and Language | Year: 2010

The voice activity detectors (VADs) based on statistical models have shown impressive performances especially when fairly precise statistical models are employed. Moreover, the accuracy of the VAD utilizing statistical models can be significantly improved when machine-learning techniques are adopted to provide prior knowledge for speech characteristics. In the first part of this paper, we introduce a more accurate and flexible statistical model, the generalized gamma distribution (GΓD) as a new model in the VAD based on the likelihood ratio test. In practice, parameter estimation algorithm based on maximum likelihood principle is also presented. Experimental results show that the VAD algorithm implemented based on GΓD outperform those adopting the conventional Laplacian and Gamma distributions. In the second part of this paper, we introduce machine learning techniques such as a minimum classification error (MCE) and support vector machine (SVM) to exploit automatically prior knowledge obtained from the speech database, which can enhance the performance of the VAD. Firstly, we present a discriminative weight training method based on the MCE criterion. In this approach, the VAD decision rule becomes the geometric mean of optimally weighted likelihood ratios. Secondly, the SVM-based approach is introduced to assist the VAD based on statistical models. In this algorithm, the SVM efficiently classifies the input signal into two classes which are voice active and voice inactive regions with nonlinear boundary. Experimental results show that these training-based approaches can effectively enhance the performance of the VAD. Crown Copyright © 2009.

Seo Y.P.,Seoul National University | Choi H.J.,Inha University | Seo Y.,Seoul National University
Soft Matter | Year: 2012

A new rheological model was applied to the analysis of the electrorheological behavior of a fluid containing silica nanoparticle-decorated polyaniline nanofibers. The model's predictions were compared with the experimental data, revealing that the proposed model correctly predicted the shear stress behavior both quantitatively and qualitatively. The shear stress data of the electrorheological fluid showing aligned fibers' structural reformation as a function of the shear rate agreed well with the new model which required fewer parameters than the CCJ (Cho-Choi-Jhon) model. The static yield stress was found to be quadratically dependent on the field strength, in agreement with the predictions of the polarization model. A scaling function was used to model the yield stress behavior of the electrorheological fluid over a range of electric fields, and it correctly predicted the static yield stress behavior both quantitatively and qualitatively. © 2012 The Royal Society of Chemistry.

Yi H.,Seoul National University | Cho J.-C.,Inha University | Chun J.,Seoul National University
International Journal of Systematic and Evolutionary Microbiology | Year: 2012

Two yellow, rod-shaped, Gram-reaction-negative, strictly aerobic bacterial strains, designated JC2682T and JC2681T, were isolated from a seawater sample of Jeju Island, Korea. The isolates required sea salts for growth and showed gliding motility. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strains JC2682T and JC2681T shared 96.9% similarity and formed a robust monophyletic group within the radiation encompassing the family Flavobacteriaceae. This distinct clade, which had varying branch positions depending on the treemaking algorithm used, represents a new genus within the family Flavobacteriaceae. The predominant isoprenoid quinone (menaquinone 6, MK-6) and DNA G+C content (27-33 mol%) were consistent with its assignment to the family Flavobacteriaceae, but the polar lipid profile, fatty acid composition and overall phenotypic traits demonstrated that the test strains were not closely affiliated to any recognized genera. Based on data from the present polyphasic taxonomic study, strains JC2682T and JC2681T are considered to represent two novel species of a new genus in the family Flavobacteriaceae, for which the names Flavivirga jejuensis gen. nov., sp. nov. and Flavivirga amylovorans sp. nov. are proposed, respectively. The type strain of Flavivirga jejuensis is JC2682T (=KACC 14158T =JCM 17113T). The type strain of Flavivirga amylovorans is JC2681T (=KACC 14157T =JCM 17112T). Amended descriptions of the genera Psychroserpens and Lacinutrix are provided. © 2012 IUMS.

Xue P.,Samsung | Gong P.,Beijing Institute of Technology | Park J.H.,Inha University | Park D.,Inha University | Kim D.K.,Inha University
IEEE Transactions on Wireless Communications | Year: 2012

We study the radio resource management (RRM) in orthogonal frequency division multiple access (OFDMA) involved heterogeneous networks, to maximize the system sum-rate under the proportional user rate constraint. An analytical model which reflects the network access features is presented. Allowing multi-homing access and resource element sharing, the RRM problem can be formulated as a linear programming (LP) problem, and the optimal solution provides upper-bound performance. In order to analyze the network selection criterion, we consider an approximated RRM problem with average resource allocations. Two different multi-homing formulations are used, and both are proven to have the same solution, where the network selection is related to the users' rate ratios between different networks. Then, we propose a low complexity suboptimal RRM algorithm, which is composed of a basic part without multi-homing access and a supplementary part with multi-homing support. The basic part makes single network selection and resource allocations. The network selection algorithm is designed based on the criterion found in the approximated problem. After network selection, an efficient resource allocation algorithm is utilized in the OFDMA network, which can employ the multi-user time and frequency diversity well. If multi-homing is allowed, the supplementary part selects the multi-homing users and reallocates partial resources to further improve the performance. Our simulation results show that the proposed suboptimal algorithm can achieve considerable gains over the previous schemes with minor performance degradation compared with the optimal solution. © 2011 IEEE.

Lee S.-M.,Inha University | Kim K.-Y.,Inha University | Kim S.-W.,Korea University
Applied Thermal Engineering | Year: 2013

The zigzag flow channels in a printed circuit heat exchanger (PCHE) of the double-faced type have been optimized to enhance heat transfer performance and reduce friction loss by using three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis and a multi-objective evolutionary algorithm. The response surface approximation (RSA) model was applied in light of the surrogate fidelity of the approximate analysis. A shear stress transport turbulence model and high-resolution scheme were used for numerical analysis. The effectiveness and non-dimensional pressure drop of zigzag channels were employed as the two objective functions of the optimization, and three nondimensional variables, i.e., the ratios of the fillet radius, wavelength, and wave height to the hydraulic diameter of the channels, were selected as the design variables. The design points within the design space were selected using Latin hypercube sampling. Two objective functions were calculated at each design point through RANS analysis to construct RSA models. A Pareto-optimal front was obtained with the multi-objective evolutionary algorithm, and four optimal designs were selected on the Pareto-optimal front by using K-means clustering. The thermal and hydraulic characteristics of these designs were compared with those of a conventionally designed PCHE. An exergy analysis showed that both designs located at opposite extremes of the Pareto-optimal front have an energy savings advantage over the reference design. © 2013 Elsevier Ltd. All rights reserved.

Hye Kim J.,Yonsei University | Gyu Park S.,Korea University | Gyu Park S.,Ajou University | Kim W.-K.,Yonsei University | And 2 more authors.
Stem Cells | Year: 2015

Platelet-derived growth factor-D (PDGF-D) was recently identified, and acts as potent mitogen for mesenchymal cells. PDGF-D also induces cellular transformation and promotes tumor growth. However, the functional role of PDGF-D in adipose-derived stem cells (ASCs) has not been identified. Therefore, we primarily investigated the autocrine and paracrine roles of PDGF-D in this study. Furthermore, we identified the signaling pathways and the molecular mechanisms involved in PDGF-D-induced stimulation of ASCs. It is of interest that PDGF-B is not expressed, but PDGF-D and PDGF receptor-β are expressed in ASCs. PDGF-D showed the strongest mitogenic effect on ASCs, and PDGF-D regulates the proliferation and migration of ASCs through the PI3K/Akt pathways. PDGF-D also increases the proliferation and migration of ASCs through generation of mitochondrial reactive oxygen species (mtROS) and mitochondrial fission. mtROS generation and fission were mediated by p66Shc phosphorylation, and BCL2-related protein A1 and Serpine peptidase inhibitor, clade E, member 1 mediated the proliferation and migration of ASCs. In addition, PDGF-D upregulated the mRNA expression of diverse growth factors such as vascular endothelial growth factor A, fibroblast growth factor 1 (FGF1), FGF5, leukemia inhibitory factor, inhibin, beta A, interleukin 11, and heparin-binding EGF-like growth factor. Therefore, the preconditioning of PDGF-D enhanced the hair-regenerative potential of ASCs. PDGF-D-induced growth factor expression was attenuated by a pharmacological inhibitor of mitogen-activated protein kinase pathway. In summary, PDGF-D is highly expressed by ASCs, where it acts as a potent mitogenic factor. PDGF-D also upregulates growth factor expression in ASCs. Therefore, PDGF-D can be considered a novel ASC stimulator, and used as a preconditioning agent before ASC transplantation. © 2014 AlphaMed Press.

Yi Y.,TissueGene Inc. | Noh M.J.,Inha University | Lee K.H.,TissueGene Inc. | Lee K.H.,Inha University
Current Gene Therapy | Year: 2011

There have been major changes since the incidents of leukemia development in X-SCID patients after the treatments using retroviral gene therapy. Due to the risk of oncogenesis caused by retroviral insertional activation of host genes, most of the efforts focused on the lentiviral therapies. However, a relative clonal dominance was detected in a patient with β-thalassemia Major, two years after the subject received genetically modified hematopoietic stem cells using lentiviral vectors. This disappointing result of the recent clinical trial using lentiviral vector tells us that the current and most advanced vector systems does not have enough safety. In this review, various safety features that have been tried for the retroviral gene therapy are introduced and the possible new ways of improvements are discussed. Additional feature of chromatin insulators, co-transduction of a suicidal gene under the control of an inducible promoter, conditional expression of the transgene only in appropriate target cells, targeted transduction, cell type-specific expression, targeted local administration, splitting of the viral genome, and site specific insertion of retroviral vector are discussed here. © 2011 Bentham Science Publishers Ltd.

Meng L.-Y.,Inha University | Meng L.-Y.,Yanbian University | Park S.-J.,Inha University
Materials Chemistry and Physics | Year: 2014

A one-pot synthetic method was used for the preparation of nanoporous carbon containing nitrogen from polypyrrole (PPY) using NaOH as the activated agent. The activation process was carried out under set conditions (NaOH/PPY = 2 and NaOH/PPY = 4) at different temperatures in 600-900 C for 2 h. The effect of the activation conditions on the pore structure, surface functional groups and CO2 adsorption capacities of the prepared N-doped activated carbons was examined. The carbon was analyzed by X-ray photoelectron spectroscopy (XPS), N2/77 K full isotherms, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The CO2 adsorption capacity of the N-doped activated carbon was measured at 298 K and 1 bar. By dissolving the activation agents, the N-doped activated carbon exhibited high specific surface areas (755-2169 m2 g-1) and high pore volumes (0.394-1.591 cm3 g-1). In addition, the N-doped activated carbons contained a high N content at lower activation temperatures (7.05 wt.%). The N-doped activated carbons showed a very high CO2 adsorption capacity of 177 mg g-1 at 298 K and 1 bar. The CO2 adsorption capacity was found to be dependent on the microporosity and N contents. © 2013 Elsevier B.V. All rights reserved.

Kim M.-Y.,Inha University | Wheeler M.F.,University of Texas at Austin
Computers and Mathematics with Applications | Year: 2014

We investigate DG-DG domain decomposition coupling using mortar finite elements to approximate the solution to general second-order partial differential equations. We weakly impose an inflow boundary condition on the inflow part of the interface and the Dirichlet boundary condition on the elliptic part of the interface via Lagrange multipliers. We obtain the matching condition by imposing the continuity of the total flux through the interface and the continuity of the solution on the elliptic parts of the interface. The diffusion coefficient is allowed to be degenerate and the mortar interface couples efficiently the multiphysics problems. The (discrete) problem is solvable in each subdomain in terms of Lagrange multipliers and the resulting algorithm is easily parallelizable. The subdomain grids need not match and the mortar grid may be much coarser, giving a two-scale method. Convergence results in terms of the fine subdomain scale h and the coarse mortar scale H are then established. A non-overlapping parallelizable domain decomposition algorithm (Arbogast et al., 2007) reduces the coupled system to an interface mortar problem. The properties of the interface operator are discussed. © 2013 Elsevier Ltd. All rights reserved.

Ashrafuzzaman K.,Chittagong University | Kwak K.S.,Inha University
IEEE Communications Letters | Year: 2011

Employing relatively simple constructs, this letter presents an analytical model for the slotted CSMA/CA algorithm adopted in the contention access period of the beacon-enabled mode MAC in IEEE 802.15.4. The analysis is validated against simulation vis-a-vis another related model. © 2011 IEEE.

Yi C.-S.,Inha University | Lee J.-H.,Korea Environment Institute | Shim M.-P.,Inha University
Renewable Energy | Year: 2010

Recently, the necessity for developing small hydropower (SHP) plants has emerged due to the increase in environmental concerns. Although there remains an abundant of potential sites for SHP plants in Korea, SHP development has scarcely been performed since the 1990s due to the absence of a suitable approach and economic feasibility. Such a situation encourages decision makers to develop a systematic approach for SHP development. The purpose of this study is to propose a new location analysis methodology to search for potential SHP sites using GSIS (Geo-Spatial Information System). The location analysis in this study focuses on establishing the criteria and methodology for searching for alternative locations rather than selecting the most suitable site among the alternatives. By applying the newly developed methodology, a large area can be precisely surveyed within a short period of time and we expect to be able to use the method in policy making for SHP development by improving the convenience for the user. The newly developed methodology was applied to the upper part of Geum River Basin, in Korea, and found six potential SHP sites. As a fundamental work, this study will be beneficial to the future activation of SHP development. © 2009 Elsevier Ltd. All rights reserved.

Park S.,University of Texas at Austin | Park S.,Inha University | An J.,University of Texas at Austin | Potts J.R.,University of Texas at Austin | And 3 more authors.
Carbon | Year: 2011

We prepared hydrazine-reduced materials from both graphite oxide (GO) particles, which were not exfoliated, and completely exfoliated individual graphene oxide platelets, and then analyzed their chemical and structural properties by elemental analysis, XPS, TGA, XRD, and SEM. Both reduced materials showed distinctly different chemical and structural properties from one another. While hydrazine reduction of graphene oxide platelets produced agglomerates of exfoliated platelets, the reduction of GO particles produced particles that were not exfoliated. The degree of chemical reduction of reduced GO particles was lower than that of reduced graphene oxide and the BET surface area of reduced GO was much lower than that of reduced graphene oxide. © 2011 Elsevier Ltd. All rights reserved.

Choung J.,Inha University | Cho S.-R.,University of Ulsan | Kim K.S.,Inha University
Ocean Engineering | Year: 2010

This paper first reviews the physical meanings and the expressions of two representative strain rate models: CSM (Cowper-Symonds model) and JCM (Johnson-Cook model). Since it is known that the CSM and JCM are suitable for low-intermediate and intermediate-high rate ranges, many studies regarding marine accidents such as ship-to-ship collisions, ship-to-rock groundings, and explosions in FPSO have employed the former in particular. A formula to predict the material constant of the CSM is introduced from a literature survey. The validity of the formula is proved by comparing with strain rate test results of high strength marine structural steels of DH-36. Numerical simulations with two different material constitutive equations, the classical metal plasticity model based on the von Mises yield function and the micromechanical porous plasticity model based on the Gurson yield function, have been carried out for stiffened plates under impact loading. It is concluded that the porous plasticity model with the porosity fracture criterion can quantitatively predict plastic deformation process and final fracture under impact loading if the material constants are properly chosen. Crown Copyright © 2010.

Lee H.J.,Inha University | Kim D.W.,Hanbat National University
Information Sciences | Year: 2016

Performance-recoverable intelligent digital redesign (IDR) in a fast sampling limit is proposed for fuzzy tracking controllers with time-varying references. IDR uses a delta operator and a piecewise linear - rather than constant - approximation of the reference improve the state-matching performance for both an extremely small and a large sampling period T∈R>0, respectively. It is proved that the analog control performance is recovered by the proposed intelligently digitally redesigned sampled-data controller in three perspectives - controller gain, stability, and closed-loop trajectory - when T goes to zero. © 2015 Elsevier Inc. All rights reserved.

Lee H.-H.,Inha University | Hill J.T.,University of Texas at Austin
International Journal of Mobile Communications | Year: 2013

This study investigates the utilitarian and hedonic consumer value perceptions of mobile marketing based on the short message service (SMS) and examines the moderating effect of situational involvement. The study uses service-dominant logic as the conceptual framework and employs a 2 (controllability) 2 (message type) 2 (situational involvement) between-subjects factorial design. The findings indicate significant main effects of controllability on both utilitarian and hedonic perceptions and the type of message only on utilitarian perceptions. Situational involvement had a significant. Moreover, the results show significant moderating role of situational involvement with controllability and a three-way effect of factors on both perceived utilitarian and hedonic perceptions. Copyright © 2013 Inderscience Enterprises Ltd.

Kim M.-Y.,Inha University | Wheeler M.F.,University of Texas at Austin
Computers and Mathematics with Applications | Year: 2014

We provide a general framework of multiscale discontinuous Galerkin methods developed in Buffa et al. (2006), Hughes et al. (2006) for general second-order partial differential equations. We establish stability of the method and prove the error estimates. © 2014 Elsevier Ltd. All rights reserved.

Kim D.W.,Hanbat National University | Lee H.J.,Inha University
Fuzzy Sets and Systems | Year: 2012

This paper presents a new direct discrete-time design methodology of a sampled-data observer-based output-feedback fuzzy controller for a class of nonlinear system that is exactly modeled in Takagi-Sugenos form at least locally. A fundamental yet challenging issue in this direction is the unavailability of the exact discrete-time model of the nonlinear plant in a closed form. In contrast to the earlier works that are based on an approximate discrete-time model thus the stability obtained in the design step is not preserved in the implementation step, we employ an exact discrete-time fuzzy model in an integral form. Sufficient asymptotic stabilization conditions are investigated in the discrete-time Lyapunov sense. We then show that the resulting sampled-data controller indeed asymptotically stabilizes the nonlinear plant. An example is provided to illustrate the effectiveness of the proposed methodology. © 2012 Elsevier B.V. All rights reserved.

Han J.,Inha University | Zhang L.L.,University of Texas at Austin | Lee S.,Inha University | Oh J.,Inha University | And 6 more authors.
ACS Nano | Year: 2013

Chemically modified graphene (CMG) nanoplatelets have shown great promise in various applications due to their electrical properties and high surface area. Chemical doping is one of the most effective methods to tune the electronic properties of graphene materials. In this work, novel B-doped nanoplatelets (borane-reduced graphene oxide, B-rG-O) were produced on a large scale via the reduction of graphene oxide by a borane-tetrahydrofuran adduct under reflux, and their use for supercapacitor electrodes was studied. This is the first report on the production of B-doped graphene nanoplatelets from a solution process and on the use of B-doped graphene materials in supercapacitors. The B-rG-O had a high specific surface area of 466 m 2/g and showed excellent supercapacitor performance including a high specific capacitance of 200 F/g in aqueous electrolyte as well as superior surface area-normalized capacitance to typical carbon-based supercapacitor materials and good stability after 4500 cycles. Two- and three-electrode cell measurements showed that energy storage in the B-rG-O supercapacitors was contributed by ion adsorption on the surface of the nanoplatelets in addition to electrochemical redox reactions. © 2012 American Chemical Society.

Kim D.W.,Hanbat National University | Lee H.J.,Inha University
International Journal of Control | Year: 2010

This article develops a digital redesign (DR) technique for sampled-data observer-based output-feedback control of a continuous-time linear system with nonlinear perturbation. It is assumed that the nonlinear perturbation is a locally Lipschitz function. To deal with the discrete-time modelling error in nonlinear systems, as opposed to the previous approach, the DR problem is configured as a stabilisation one for error dynamics between the closed-loop system of nominal linear model under an analogue state-feedback controller and that of the linear system with the nonlinear perturbation under a sampled-data output-feedback controller. A constructive DR condition is formulated in the format of linear matrix inequalities. The stability of the actual sampled-data control system is guaranteed within the DR procedure. The effectiveness of the proposed DR methodology is demonstrated through a numerical simulation. © 2010 Taylor & Francis.

Kim B.-J.,Jeonju Institute of Machinery and Carbon Composites | Cho K.-S.,Korea University | Park S.-J.,Inha University
Journal of Colloid and Interface Science | Year: 2010

Copper oxide-loaded porous carbons (PCs) for high efficient carbon dioxide capture were prepared. Copper oxides were loaded onto porous carbons by a postoxidation method involving copper electroplated PCs at 300 °C in an air stream. Additionally, porous carbons were prepared from ion-exchangeable polymeric resin by a chemical activation method. The microstructure of the copper oxide/PCs was characterized by XRD, and the formation of copper oxides after the postoxidation process was confirmed by XPS. The carbon dioxide adsorption behaviors were evaluated by a PCT (pressure-composition-temperature) apparatus at 298 K and 1.0 atm. It was found that the presence of copper oxides significantly led to an increase in the carbon dioxide adsorption capacity of the carbons. Copper oxide nanoparticles have electron-donor features, resulting in the enhancement of adsorption capacity of carbon dioxide molecules, which have an electron acceptor feature. © 2009.

Oh E.-O.,Inha University | Whang C.-M.,Inha University | Lee Y.-R.,Korea University | Park S.-Y.,Korea Institute of Science and Technology | And 5 more authors.
Advanced Materials | Year: 2012

An extremely thin bilayer electrolyte consisting of yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (GDC) is successfully fabricated on a sintered NiO-YSZ substrate (see figure). Major processing flaws are effectively eliminated by applying local constraints to YSZ nanoparticles, and excellent open circuit voltage and cell performance are demonstrated in a solid oxide fuel cell (SOFC) at intermediate operating temperatures. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ma Y.J.,Illinois State University | Lee H.-H.,Inha University
International Journal of Consumer Studies | Year: 2012

Using the Schwartz value system, this study explored the personal values of consumers related to fair trade product consumption. This study further investigated how the values determine beliefs, attitudes and purchase intentions associated with fair trade non-food products. Data were collected using an online survey from a random sample of 1824 nationwide consumers. The results of this study revealed that fair trade purchasers show a higher level of self-transcendence (universalism, benevolence) and openness to change values (self-direction, stimulation) than non-purchasers. These values also have positive effects on the formation of beliefs, attitudes and purchase intentions pertaining to fair trade non-food products. Fair trade purchasers were also found to possess distinctive socio-demographic characteristics concerning age, education and income. Findings can offer marketers specific information regarding consumers' motivations to purchase fair trade goods, which can improve targeting of products and ultimately increase the business and benefits of fair trade. © 2011 Blackwell Publishing Ltd.

Choung J.,Inha University | Nam W.,Inha University | Lee J.-Y.,Steel Structure Research Laboratory
Marine Structures | Year: 2013

This paper presents a new formula for prediction of the dynamic hardening effect for various marine structural steels, considering dependencies on the strain rates and temperatures. Dynamic tensile tests are carried out for three kinds of marine steels, 2W50, EH36, and DH36, changing the steel layer in the thickness direction, the strain rates, and temperatures. Considering two thickness layers at the middle and surface, five strain rate levels of 0.001/s, 1/s, 10/s, 100/s, and 200/s, three temperature levels of LT (-40°C), RT, and HT (200°C), and two repetitions, the total number of tests is 180. Dynamic hardening is clearly seen at LT and RT regardless of the material type, while dynamic strain aging occurs at HT, leads to negative strain rate sensitivity, and thus elevates the quasi-static flow stress above the dynamic flow stress to a certain strain rate. Dynamic hardening factors (DHFs) are derived as a function of the proof strains of 0.05, 0.10, and 0.15 according to each material type and temperature level. A new formula to determine the material constant D of Cowper-Symonds constitutive equation is developed. The correctness of the proposed formula is verified through comparison with test flow stress curves and reference test data in large plastic strain and high strain rate ranges. © 2013 Elsevier Ltd.

Choi C.,Inha University | Choi C.,Building and Tunnel Technologies Inc. BNTTEK | Yang K.,Inha University
Physics of Fluids | Year: 2013

The onset of the three-dimensional (3D) instability in the flow past two side-by-side square cylinders has been studied via Floquet stability analysis. The gap between the two cylinders is the key parameter that alters flow topology, leading to change of stability characteristics. Depending on the gap, four distinct flow patterns have been identified for base flow. For each pattern of base flow, distinctive Floquet modes of 3D instability have been found. The spatial and temporal characteristics of the Floquet modes are similar to those of mode A or mode B of the single square cylinder case, namely, odd or even Reflection-Translation symmetries. Six distinct Floquet modes have been identified in total, and the spatial and temporal characteristics of each mode are described in detail. The criticality of Floquet modes, including their critical Reynolds number and the associated dominant spanwise wave number, is presented for each gap considered in the current study. For a small gap, the flow past the two cylinders resembles that of a single object, resulting in an approximately doubled characteristic length. Consequently, the critical Reynolds number becomes low with a small gap between the two cylinders. When the two cylinders are moderately apart, the interaction between the two wakes diminishes, and the criticality of 3D instabilities approaches that of the single cylinder case. Coexisting 3D instabilities for a specific base-flow topology are also noticed with a moderate gap. Neutral stability curves are computed and presented for some selected values of the gap. © 2013 AIP Publishing LLC.

Lim H.S.,Massachusetts Institute of Technology | Baek J.H.,Soongsil University | Park K.,Soongsil University | Shin H.S.,Inha University | And 2 more authors.
Advanced Materials | Year: 2010

(Figure Presented) Thermally stable superhydrophobic fabrics with multifunctionality were fabricated through the combination of sol-gel chemistry and electrospinning. MTES sols were electrospun into fibers, in which fiber morphology was controlled by the gelation time. The resulting superhydrophobic fabrics are not only very stable and heat-resistant but perform with high filtration efficiency, enabling emerging applications for smart materials and devices. © 2010 WILEY-VCH Verlag GmbH & CO. KGaA,.

We determined the complete mitochondrial genome sequences for Bursaphelenchus mucronatus, one species of pinewood nematode. The genome is a circular-DNA molecule of 14,583. bp (195. bp smaller than its congener Bursaphelenchus xylophilus) and contains 12 protein-coding genes (lacking atp8), 22 tRNA genes, and 2 rRNA genes encoded in the same direction, consistent with most other nematodes. Based on sequence comparison of mtDNA genomes, we developed a PCR-based molecular assay to differentiate B. xylophilus (highly pathogenic) and B. mucronatus (relatively less virulent) using species-specific primers. The molecular identification system employs multiplex-PCR and is very effective and reliable for discriminating these Bursaphelenchus species, which are economically important, but difficult to distinguish based on morphology. The comparison of the mitochondrial genomes and molecular identification system of the two species of Bursaphelenchus spp. should provide a rich source of genetic information to support the effective control and management (quarantine) of the pine wilt disease caused by pinewood nematodes. © 2013 Elsevier B.V.

Choi S.-W.,Inha University | Katoch A.,Inha University | Sun G.-J.,Inha University | Wu P.,Singapore University of Technology and Design | Kim S.S.,Inha University
Journal of Materials Chemistry C | Year: 2013

Highly sensitive and selective NO2 sensing performances were realized with the networked SnO2 microrods functionalized with Ag nanoparticles by applying γ-ray radiolysis. The Ag nanoparticles were transformed into nanoparticles of the Ag/Ag2O phase by thermal heating. The NO2 sensing characteristics of the Ag-functionalized SnO2 microrods were compared with those of bare SnO2 microrods. The cross-sensibility of the Ag-functionalized SnO2 microrods to other gases was tested for O2, SO2, CO, C6H6 and C7H8. The sensing results demonstrated not only that γ-ray radiolysis was an effective means of functionalizing the surface of oxide microrods with catalytic Ag nanoparticles, but also that the Ag functionalization greatly enhanced the SnO2 microrods' capability of detecting NO2 in light of response and selectivity. The special energy band structure built on the surface of SnO 2 microrods associated with Ag nanoparticles leads to a superior response to oxidizing gases than reducing gases. Being combined with this, easy dissociation of NO2 into more active chemical species by the unique catalytic role of Ag is likely to be responsible for the selective, sensitive NO2 sensing performances of the Ag-functionalized SnO2 microrods. © 2013 The Royal Society of Chemistry.

Sun G.-J.,Inha University | Choi S.-W.,Inha University | Katoch A.,Inha University | Wu P.,Singapore University of Technology and Design | Kim S.S.,Inha University
Journal of Materials Chemistry C | Year: 2013

In this study, a bi-functional mechanism is proposed and validated, which may be used to explain all of the reported experimental observations and to predict new sensing control parameters. Fast response and recovery in H 2S sensing was then realized by using bi-functional SnO2 nanowires which have been radially modulated with CuO. Firstly, Cu metal nanoparticles were synthesized by applying γ-ray radiolysis. The Cu nanoparticles (attached to the surface of the SnO2 nanowires) were oxidized to the CuO phase by a thermal treatment at 500°C in air. The H 2S sensing characteristics of the CuO-functionalized SnO2 nanowires were compared with those of bare SnO2 nanowires. The results demonstrated that γ-ray radiolysis is an effective means of functionalizing the surface of oxide nanowires with CuO nanoparticles, and CuO functionalization greatly enhanced the ability of the SnO2 nanowires to detect H2S in terms of the response and recovery times. In addition, two control parameters, a 0.5 CuO to SnO2 surface ratio and a sensing temperature range of 80-220°C, are predicted. The radially modulated nanostructures achieve two functions: (1) the formation and break-away of p-n (CuO-SnO2) junctions, and (2) the formation and dissolution of CuS using CuO-SnO2 solid solutions. This journal is © The Royal Society of Chemistry 2013.

Amarnath M.,Indian Institute of Information Technology, Design and Manufacturing | Lee S.-K.,Inha University
Measurement: Journal of the International Measurement Confederation | Year: 2015

Gears are one of the most common mechanisms for transmitting power and motion and their usage can be found in numerous applications. Studies on gear teeth contacts have been considered as one of the most complicated applications in tribology. The changes in operating conditions such as increase in temperature, load, reduction in viscosity result decrease in lubricant film thickness and degradation of lubricating oil thereby triggering several types of failures on tooth surfaces viz. pitting, scuffing, micro pitting, scoring, and spalling, these faults influence changes in vibration signals. This paper presents the results of experimental investigations carried out to assess wear in spur gears of single stage spur gear box under fatigue test conditions. The studies considered the lubricant film thickness analysis, wear mechanism studies on gear tooth surfaces, oil degradation analysis using Fourier transform infrared radiation (FTIR) method along with vibration signal analysis. The results provide a good understanding of tribological and vibration parameters as measures for effective assessment of wear in spur gears. © 2015 Elsevier Ltd. All rights reserved.

Lee J.-H.,Gachon University | Park D.,Inha University
IEEE Communications Letters | Year: 2012

In this letter, we propose a transmit antenna selection and unitary precoding strategy for maximum-likelihood (ML) detector in interference-aligned multiple input multiple output (MIMO) networks. The proposed transmit antenna selection for ML receiver is to maximize the minimum among all receivers' minimum distances. In order to achieve further performance enhancement, we also propose an unitary precoding strategy for ML detector associated with the antenna selection. Numerical results show that the proposed scheme provides enhanced performance compared with the conventional algorithms. © 1997-2012 IEEE.

News Article | November 17, 2016

One of the impediments to developing miniaturized, ‘squishy’ robots is the need for an internal power source that overcomes the power-to-weight ratio for efficient movement. An international group of researchers from the University of Pittsburgh, the US Air Force Research Laboratory and Inha University in South Korea has now identified new materials that can directly convert ultraviolet (UV) light into motion without the need for electronics or other traditional methods. The research is described in a paper in Nature Communications. The group includes M. Ravi Shankar, co-author and professor of industrial engineering at Pitt's Swanson School of Engineering; the lead author is Jeong Jae Wie, assistant professor of polymer science and engineering at Inha University. The experiments were conducted at the Air Force Research Laboratory (AFRL)'s Materials & Manufacturing Directorate at Wright-Patterson Air Force Base, Ohio, under the direction of Timothy White. Other research groups have proposed using ambient energy sources such as magnetic fields, acoustics, heat and other temperature variations to avoid adding structures to induce locomotion. Shankar explains that light is more appealing than these other sources because of its speed, temporal control and ability to target the mechanical response effectively. For their light-responsive material, the group zeroed in on monolithic polymer films prepared from a form of liquid crystalline polymer. "Our initial research indicated that these flexible polymers could be triggered to move by different forms of light," Shankar explained. "However, a robot or similar device isn't effective unless you can tightly control its motions. Thanks to the work of Dr White and his team at AFRL, we were able to demonstrate directional control, as well as climbing motions." According to Wie, the ‘photomotility’ of these specific polymers is the result of their spontaneous formation into spirals when exposed to UV light. By controlling this exposure, the researchers can induce motion without the use of external power sources attached directly to the polymer itself. "Complex robotic designs result in additional weight in the form of batteries, limb-like structures or wheels, which are incompatible with the notion of a soft or squishy robot," Wie said. "In our design, the material itself is the machine, without the need for any additional moving parts or mechanisms that would increase the weight and thereby limit motility and effectiveness." In addition to simple forward movement, the researchers were able to make the polymers climb a glass slide placed at a 15° angle. Although the flat polymer strips are small – approximately 15mm long and 1.25mm wide – they can move at several millimeters per second when propelled by light. This movement persists for as long as the material remains illuminated. "The ability for these flexible polymers to move when exposed to light opens up a new ground game in the quest for soft robots," Shankar said. "By eliminating the additional mass of batteries, moving parts and other cumbersome devices, we can potentially create a robot that would be beneficial where excess weight and size is a negative, such as in space exploration or other extreme environments." This story is adapted from material from the University of Pittsburgh, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

News Article | November 10, 2016

PITTSBURGH (Nov. 10, 2016) ... One of the impediments to developing miniaturized, "squishy" robots is the need for an internal power source that overcomes the power-to-weight ratio for efficient movement. An international group involving Inha University, University of Pittsburgh and the Air Force Research Laboratory has built upon their previous research and identified new materials that directly convert ultraviolet light into motion without the need for electronics or other traditional methods. The research, "Photomotility of Polymers," was published today in the journal Nature Communications (DOI: 10.1038/ncomms13260). The group includes M. Ravi Shankar, co-author and professor of industrial engineering at Pitt's Swanson School of Engineering. Lead author is Jeong Jae Wie, assistant professor of polymer science and engineering at Inha University, South Korea. The experiments were conducted at the Air Force Research Laboratory's (AFRL)Materials & Manufacturing Directorate at Wright-Patterson Air Force Base, Ohio, under the direction of Timothy J. White. Other investigations have proposed the use of ambient energy resources such as magnetic fields, acoustics, heat and other temperature variations to avoid adding structures to induce locomotion. However, Dr. Shankar explains that light is more appealing because of its speed, temporal control and the ability to effectively target the mechanical response. For the material, the group zeroed in on monolithic polymer films prepared from a form of liquid crystalline polymer. "Our initial research indicated that these flexible polymers could be triggered to move by different forms of light," Dr. Shankar explained. "However, a robot or similar device isn't effective unless you can tightly control its motions. Thanks to the work of Dr. White and his team at AFRL, we were able to demonstrate directional control, as well as climbing motions." According to Dr. Wie, the "photomotility" of these specific polymers is the result of their spontaneous formation into spirals when exposed to UV light. Controlling the exposure enables a corresponding motion without the use of external power sources attached directly to the polymer itself. "Complex robotic designs result in additional weight in the form of batteries, limb-like structures or wheels, which are incompatible with the notion of a soft or squishy robot," Dr. Wie said. "In our design, the material itself is the machine, without the need for any additional moving parts or mechanisms that would increase the weight and thereby limit motility and effectiveness." In addition to simple forward movement, Dr. White and the collaborative team were able to make the polymers climb a glass slide at a 15-degree angle. While the flat polymer strips are small - approximately 15mm long and 1.25mm wide - they can move at several millimeters per second propelled by light. The movement can be perpetual, as long as the material remains illuminated. "The ability for these flexible polymers to move when exposed to light opens up a new ground game in the quest for soft robots," Dr. Shankar said. "By eliminating the additional mass of batteries, moving parts and other cumbersome devices, we can potentially create a robot that would be beneficial where excess weight and size is a negative, such as in space exploration or other extreme environments."

News Article | November 11, 2016

One of the impediments to developing miniaturized, "squishy" robots is the need for an internal power source that overcomes the power-to-weight ratio for efficient movement. An international group involving Inha University, University of Pittsburgh and the Air Force Research Laboratory has built upon their previous research and identified new materials that directly convert ultraviolet light into motion without the need for electronics or other traditional methods. The research, "Photomotility of Polymers," was published in the journal Nature Communications. The group includes M. Ravi Shankar, co-author and professor of industrial engineering at Pitt's Swanson School of Engineering. Lead author is Jeong Jae Wie, assistant professor of polymer science and engineering at Inha University, South Korea. The experiments were conducted at the Air Force Research Laboratory's (AFRL)Materials & Manufacturing Directorate at Wright-Patterson Air Force Base, Ohio, under the direction of Timothy J. White. Other investigations have proposed the use of ambient energy resources such as magnetic fields, acoustics, heat and other temperature variations to avoid adding structures to induce locomotion. However, Dr. Shankar explains that light is more appealing because of its speed, temporal control and the ability to effectively target the mechanical response. For the material, the group zeroed in on monolithic polymer films prepared from a form of liquid crystalline polymer. "Our initial research indicated that these flexible polymers could be triggered to move by different forms of light," Dr. Shankar explained. "However, a robot or similar device isn't effective unless you can tightly control its motions. Thanks to the work of Dr. White and his team at AFRL, we were able to demonstrate directional control, as well as climbing motions." According to Dr. Wie, the "photomotility" of these specific polymers is the result of their spontaneous formation into spirals when exposed to UV light. Controlling the exposure enables a corresponding motion without the use of external power sources attached directly to the polymer itself. "Complex robotic designs result in additional weight in the form of batteries, limb-like structures or wheels, which are incompatible with the notion of a soft or squishy robot," Dr. Wie said. "In our design, the material itself is the machine, without the need for any additional moving parts or mechanisms that would increase the weight and thereby limit motility and effectiveness." In addition to simple forward movement, Dr. White and the collaborative team were able to make the polymers climb a glass slide at a 15-degree angle. While the flat polymer strips are small -- approximately 15mm long and 1.25mm wide -- they can move at several millimeters per second propelled by light. The movement can be perpetual, as long as the material remains illuminated. "The ability for these flexible polymers to move when exposed to light opens up a new ground game in the quest for soft robots," Dr. Shankar said. "By eliminating the additional mass of batteries, moving parts and other cumbersome devices, we can potentially create a robot that would be beneficial where excess weight and size is a negative, such as in space exploration or other extreme environments."

News Article | November 10, 2016

An animated gif of an azobenzene-functionalized liquid crystalline polymer moving when exposed to broadband ultraviolet-visible light. Credit: Jeong Jae Wie, Inha University/AFRL One of the impediments to developing miniaturized, "squishy" robots is the need for an internal power source that overcomes the power-to-weight ratio for efficient movement. An international group involving Inha University, University of Pittsburgh and the Air Force Research Laboratory has built upon their previous research and identified new materials that directly convert ultraviolet light into motion without the need for electronics or other traditional methods. The research, "Photomotility of Polymers," was published today in the journal Nature Communications. The group includes M. Ravi Shankar, co-author and professor of industrial engineering at Pitt's Swanson School of Engineering. Lead author is Jeong Jae Wie, assistant professor of polymer science and engineering at Inha University, South Korea. The experiments were conducted at the Air Force Research Laboratory's (AFRL)Materials & Manufacturing Directorate at Wright-Patterson Air Force Base, Ohio, under the direction of Timothy J. White. Other investigations have proposed the use of ambient energy resources such as magnetic fields, acoustics, heat and other temperature variations to avoid adding structures to induce locomotion. However, Dr. Shankar explains that light is more appealing because of its speed, temporal control and the ability to effectively target the mechanical response. For the material, the group zeroed in on monolithic polymer films prepared from a form of liquid crystalline polymer. "Our initial research indicated that these flexible polymers could be triggered to move by different forms of light," Dr. Shankar explained. "However, a robot or similar device isn't effective unless you can tightly control its motions. Thanks to the work of Dr. White and his team at AFRL, we were able to demonstrate directional control, as well as climbing motions." According to Dr. Wie, the "photomotility" of these specific polymers is the result of their spontaneous formation into spirals when exposed to UV light. Controlling the exposure enables a corresponding motion without the use of external power sources attached directly to the polymer itself. "Complex robotic designs result in additional weight in the form of batteries, limb-like structures or wheels, which are incompatible with the notion of a soft or squishy robot," Dr. Wie said. "In our design, the material itself is the machine, without the need for any additional moving parts or mechanisms that would increase the weight and thereby limit motility and effectiveness." In addition to simple forward movement, Dr. White and the collaborative team were able to make the polymers climb a glass slide at a 15-degree angle. While the flat polymer strips are small - approximately 15mm long and 1.25mm wide - they can move at several millimeters per second propelled by light. The movement can be perpetual, as long as the material remains illuminated. "The ability for these flexible polymers to move when exposed to light opens up a new ground game in the quest for soft robots," Dr. Shankar said. "By eliminating the additional mass of batteries, moving parts and other cumbersome devices, we can potentially create a robot that would be beneficial where excess weight and size is a negative, such as in space exploration or other extreme environments." Explore further: Snap to attention: Polymers that react and move to light More information: Jeong Jae Wie et al, Photomotility of polymers, Nature Communications (2016). DOI: 10.1038/ncomms13260

Zhang N.,Jiangxi University of Finance and Economics | Choi Y.,Inha University
Renewable and Sustainable Energy Reviews | Year: 2014

Recently, a relatively new methodology named directional distance function (DDF) has been attracting positive attention in the field of energy and environmental (E&E) modeling. However, there is still no literature review on the application of DDF in E&E studies. This paper is intended to fill this gap. First, the most widely used DDF techniques and its extensions are briefly introduced. Second, this article attempts a classification of typical publications in this field. The main issues raised by the previous studies are discussed. Some guidelines for model selection and future directions are proposed for DDF related research in E&E studies. © 2014 Elsevier Ltd.

Zhang N.,Jiangxi University of Finance and Economics | Zhang N.,New York University | Choi Y.,Inha University
Energy Policy | Year: 2013

This paper aims to conduct a comparative study of the changes in CO2 emission performance of state-owned fossil fuel power plants between China and Korea. For this purpose, we combine the concept of the metafrontier Malmquist productivity index and the non-radial directional distance function to develop a new index called the non-radial metafrontier Malmquist CO2 emission performance index (NMMCPI). This new methodology allows for the incorporation of technological heterogeneities and slack variables into the previously introduced Malmquist CO2 emission performance index (MCPI). The NMMCPI can be derived by solving several non-radial data envelopment analysis (DEA) models. The NMMCPI can be decomposed into an efficiency change (EC) index, a best-practice gap change (BPC) index, and a technology gap change (TGC) index. By fixing the non-energy inputs, we measure the pure CO2 emission performance change. Based on the proposed indices, the comparative study between Chinese and Korean fossil fuel power industries is conducted for the 2005-2010 period. Empirical results indicate significant differences in terms of various decomposed CO2 emission performance changes between China and Korea. Korean power plants demonstrate improvements in innovation, while Chinese power plants demonstrate a higher ability for technological leadership. Some related policy implications are also proposed based on the empirical results. © 2013 Elsevier Ltd.

Zhang N.,Jiangxi University of Finance and Economics | Choi Y.,Inha University
Energy Economics | Year: 2013

This paper proposes the metafrontier non-radial Malmquist CO2 emission performance index (MNMCPI) for measuring dynamic changes in total-factor CO2 emission performance over time. The MNMCPI method allows for the incorporation of group heterogeneity and non-radial slack into the previously introduced Malmquist CO2 emission performance index (MCPI). We derive the MNMCPI by solving several non-radial data envelopment analysis (DEA) models. We decompose the MNMCPI into an efficiency change (EC) index, a best-practice gap change (BPC) index, and a technology gap change (TGC) index, and based on the proposed indices, we examine the dynamic changes in CO2 emission performance and its decomposition of fossil fuel power plants in China for the 2005-2010 period. The empirical results show a 0.38% increase in total-factor CO2 emission performance as a whole and a U-shaped MNMCPI curve for the sample period. Because companies owned by the central government lack innovation and technological leadership, the results suggest a missing link in the role of the central government in promoting CO2 emission performance. © 2013 Elsevier B.V.

Choi S.,Jeju National University | Kim M.K.,Inha University | Kim G.M.,Jeju National University | Roh Y.-H.,Jeju National University | And 2 more authors.
Journal of Shoulder and Elbow Surgery | Year: 2014

Background: This study was conducted to evaluate clinical outcomes, maintenance of repair integrity, and retear rate after arthroscopic rotator cuff repair by a suture bridge technique among patients with medium, large, and massive rotator cuff tears. Methods: We evaluated 147 patients who had undergone arthroscopic rotator cuff repair. Clinical and functional evaluations were performed with the Constant and University of California-Los Angeles scores. All patients were confirmed to have magnetic resonance imaging evidence of tendon healing at least 12months postoperatively. Results: The average postoperative time to follow-up magnetic resonance imaging was 23.4months (range, 12-48months). A total of 25 (17.0%) retears were observed. All clinical outcome scores were improved significantly at follow-up. Larger intraoperative tear sizes were correlated with higher retear rates. The incidence of retear was also higher in cases in which the preoperative fatty degeneration grade was higher. The incidence of retear increased with age and in the heavy worker group (e.g., farmers, carriers, car mechanics) but was not statistically significant. Conclusions: Arthroscopic rotator cuff repair by a suture bridge technique yields improvements in clinical outcome measures and a relatively high degree of patient satisfaction despite the fact that repair integrity is not maintained in many cases. © 2014 Journal of Shoulder and Elbow Surgery Board of Trustees.

Ammari H.,Ecole Normale Superieure de Paris | Ciraolo G.,University of Palermo | Kang H.,Inha University | Lee H.,Inha University | Yun K.,Hankuk University of foreign Studies
Archive for Rational Mechanics and Analysis | Year: 2013

When holes or hard elastic inclusions are closely located, stress which is the gradient of the solution to the anti-plane elasticity equation can be arbitrarily large as the distance between two inclusions tends to zero. It is important to precisely characterize the blow-up of the gradient of such an equation. In this paper we show that the blow-up of the gradient can be characterized by a singular function defined by the single layer potential of an eigenfunction corresponding to the eigenvalue 1/2 of a Neumann-Poincaré type operator defined on the boundaries of the inclusions. By comparing the singular function with the one corresponding to two disks osculating to the inclusions, we quantitatively characterize the blow-up of the gradient in terms of explicit functions. In electrostatics, our results apply to the electric field, which is the gradient of the solution to the conductivity equation, in the case where perfectly conducting or insulating inclusions are closely located. © 2012 Springer-Verlag Berlin Heidelberg.

Ammari H.,Ecole Normale Superieure de Paris | Ciraolo G.,University of Palermo | Kang H.,Inha University | Lee H.,Inha University | Milton G.W.,University of Utah
Archive for Rational Mechanics and Analysis | Year: 2013

The aim of this paper is to give a mathematical justification of cloaking due to anomalous localized resonance (CALR). We consider the dielectric problem with a source term in a structure with a layer of plasmonic material. Using layer potentials and symmetrization techniques, we give a necessary and sufficient condition on the fixed source term for electromagnetic power dissipation to blow up as the loss parameter of the plasmonic material goes to zero. This condition is written in terms of the Newtonian potential of the source term. In the case of concentric disks, we make the condition even more explicit. Using the condition, we are able to show that for any source supported outside a critical radius, CALR does not take place, and for sources located inside the critical radius satisfying certain conditions, CALR does take place as the loss parameter goes to zero. © 2013 Springer-Verlag Berlin Heidelberg.

Shin K.,Smart Game Research Team | Kim J.,Inha University | Choi S.B.,Inha University
IEEE Communications Letters | Year: 2011

In the wireless network, if the TCP cannot identify the wireless error, it overly reduces the transmission rate by unnecessarily cutting the congestion window down. Therefore, to improve TCP goodput by accurately detecting wireless loss, we propose the MAC MIB based loss recovery scheme that can differentiate between congestion loss and wireless loss without intervention of any intermediate node. The simulation results show that the goodput is substantially enhanced compared to existing schemes in the wireless access network environment, where errors tend to occur in burst due to the intrinsic wireless link characteristics. © 2006 IEEE.

Zhang N.,Jiangxi University of Finance and Economics | Kong F.,Jiangxi University of Finance and Economics | Choi Y.,Inha University | Zhou P.,Nanjing University of Aeronautics and Astronautics
Energy Policy | Year: 2014

This paper examines the effect of size control policy on the energy and carbon efficiency for Chinese fossil fuel power industry. For this purpose, we propose two non-radial directional distance functions for energy/carbon efficiency analysis of fossil fuel electricity generation. One is named a total-factor directional distance function that incorporates the inefficiency of all input and output factors to measure the unified (operational and environmental) efficiency of fossil fuel power plants, and the other is called an energy-environmental directional distance function that can be used to measure the energy-environmental performance of fossil fuel electric power plants. Several standardized indicators for measuring unified efficiency and energy-environmental performance are derived from the two directional distance functions. An empirical study of 252 fossil fuel power plants in China is conducted by using the proposed approach. Our empirical results show that there exists a significant positive relationship between the plant size and unified efficiency, the five state-owned companies show lower unified efficiency and energy-environmental performance than other companies. It is suggested that Chinese government might need to consider private incentives and deregulation for its state-owned enterprises to improve their performance proactively. © 2014 Elsevier Ltd.

Lee S.,Inha Technical College | Lim J.-S.,Inha University | Baik S.J.,Korea Advanced Institute of Science and Technology
Journal of the Electrochemical Society | Year: 2011

We report the latest works on via interconnects of future memory or LSI devices, where multi-wall carbon nanotubes (MWCNTs) are used instead of conventional metals. MWCNTs are grown vertically in 80 nm via holes using plasma-enhanced chemical vapor deposition. The carbon nanotube (CNT) via interconnects are integrated into an 8-inch Si wafer in full compatibility with conventional semiconductor processes. We have used buried catalyst method for the catalyst layer deposition, two-step etch method for achieving via etch stop on the thin catalyst layer (ca. 3 nm), and the chemical mechanical polishing (CMP) process for cutting CNT. The two-step etch method is composed of two consecutive etch steps: the first step is a conventional oxide etch while the second step chemically etches the silicon nitride layer to relieve the damage of the catalyst layer. After a full integration, a resistance of 293 ∼ 493 and a CNT density of about 4 1011cm2 have been achieved for the 80 nm via. These results show that the 2-step etch scheme is a promising candidate for the realization of CNT interconnects in conventional semiconductor devices. © 2011 The Electrochemical Society.

Kang C.,Inha University | Yang K.-S.,Inha University
International Journal of Heat and Fluid Flow | Year: 2012

Flow instability in baffled channel flow, where thin baffles are mounted on both channel walls periodically in the direction of the main flow, has been numerically investigated. The geometry considered here can be regarded as a simple model for finned heat exchangers. The aim of this investigation is to understand how baffle interval (L) and Reynolds number (Re) influence the flow instability. With a fixed baffle length of one quarter of channel height (H), ratios of baffle interval to channel height (RB=L/H) between 1 and 4 are considered. The critical Reynolds number of the primary instability, a Hopf bifurcation from steady flow to time-periodic flow, turned out to be minimum when RB=3.08. The friction factor (f) is strongly correlated with the critical Reynolds number for RB. 2.5. For the particular cases of RB=1.456 and RB=1.0, we performed Floquet stability analysis in order to study the secondary instability through which time-periodic two-dimensional flow bifurcates into three-dimensional flow. The results obtained in this investigation are in good agreement with those computed from full simulations, and shed light on understanding and controlling flow characteristics in a finned heat exchanger, quite beneficial to its design. © 2012 Elsevier Inc.

Meng L.-Y.,Korea Institute of Energy Research | Meng L.-Y.,Inha University | Park S.-J.,Korea Institute of Energy Research | Park S.-J.,Inha University
Journal of Colloid and Interface Science | Year: 2012

Thermally exfoliated graphene nanoplates were found to be a novel high efficiency sorbent for the capture of CO 2. The exfoliated graphene nanoplates were expanded successfully from graphite oxide by a low-heat treatment at temperatures ranging from 150 to 400°C under vacuum conditions. The texture was analyzed by N 2 full isotherms and XRD. The CO 2 capture characteristics of the graphene nanoplates at 25°C and 30bar were examined using a pressure-composition-temperature apparatus. The inter-layer spacing of the graphene layers and pore structure on the CO 2 capture capacities were studied as a function of the processing conditions. The prepared graphene nanoplates exhibited high capture capacities, up to 248wt.%, at 25°C and 30bar. The improved CO 2 capture capacity of the graphene nanoplates was attributed to the larger inter-layer spacing and higher interior void volume. © 2012.

Rawal S.B.,Inha University | Kim H.J.,Inha University | Lee W.I.,Inha University
Applied Catalysis B: Environmental | Year: 2013

Monodispersed 250nm-sized TiO2 sphere (TiO2 SP) with large internal surface area was successfully employed in fabricating the Fe3+-grafted nitrogen-doped TiO2 (Fe3+/N-TiO2), exhibiting ultra-high visible-light photocatalytic efficiency. In evolving CO2 from the gaseous 2-propanol (IP) and acetaldehyde, the prepared Fe3+/N-TiO2 SP demonstrated twice of catalytic activity, comparing with the nanoparticle (NP)-based Fe3+/N-TiO2. Consequently, the optimized Fe3+/N-TiO2 SP exhibited 5.0-7.3 times higher efficiency than the bare N-TiO2 NP. The instability of photocatalytic activity is a well-known drawback of the Fe3+/N-TiO2 system, caused by the inherent weakness of Fe3+ ions from the chemical attacks. Herein, however, it was found that SP system with large internal surface is remarkably advantageous for protecting the grafted Fe3+ ions. With mixing of 20wt% silica binder, which is regarded to be a typical dosage for application, photocatalytic efficiency of the Fe3+/N-TiO2 SP was decreased by only 21-25%, whereas that of the NP-based sample was reduced by 73-80%. © 2013 Elsevier B.V.

Heo G.-Y.,Inha University | Park S.-J.,Inha University
Powder Technology | Year: 2012

In this study, the different silane coupling agents were added to epoxy/silica systems. The effects of the type of silane coupling agent in the epoxy/silica compounds on the thermal, flow and adhesion properties were investigated. The curing behavior was examined by differential scanning calorimetry (DSC), and the flow properties of the epoxy compounds were evaluated from penetration rate measurements. The adhesion strength as a mechanical property was determined by die shear strength testing. The silane coupling agent type had a significant effect on the thermal, flow and adhesion properties. The coefficients of thermal expansion (CTE) and adhesion of the DGEBF epoxy/SiO 2 systems could be enhanced by the addition of silane coupling agents. In addition, the penetration rate was increased by the addition of a coupling agent except for the CA-A coupling agent. This was interpreted in terms of the reactive functional groups and dispersion forces resulting in coupling agents on the interfaces between the DGEBF epoxy resin and silica. © 2012 Elsevier B.V..

Mujtaba G.,Myongji University | Choi W.,Myongji University | Lee C.-G.,Inha University | Lee K.,Myongji University
Bioresource Technology | Year: 2012

A two-stage process, composed of growth under nutrient-rich conditions followed by cultivation under nitrogen starvation and controlled conditions of phosphate, light intensity, aeration, and carbon sources was applied for lipid production by the green alga Chlorella vulgaris. Using conditions without addition of nitrogen, 2mg/L PO4-P, light intensity of 100μmol/m2/s and 0.25vvm of air, about 43% of dry cell weight accumulated as lipids after 12h, which equates to a lipid productivity of 77.8mg/L/d. In a medium containing 5mg/L NO3-N and 2mg/L PO4-P, and at a light intensity of 100μmol/m2/s and 0.25vvm of 2% CO2, about 53% of dry cell weight consisted of lipids after 24h, representing a lipid productivity of 77.1mg/L/d. The low amount of nutrients, moderate aeration and light intensity were helpful for increasing lipid productivity. © 2012 Elsevier Ltd.

Zhang W.L.,Inha University | Piao S.H.,Inha University | Choi H.J.,Inha University
Journal of Colloid and Interface Science | Year: 2013

Electro-responsive core-shell structured particles were fabricated in two steps. In the first step, a spherical and monodisperse poly(glycidyl methacrylate) (PGMA) core was prepared by dispersion polymerization with an epoxy group, which was then functionalized with an amine functional group (ami-PGMA) via an epoxide-amine reaction with ethylenediamine. In the second step, a conducting polyaniline (PANI) shell was grafted onto the ami-PGMA surface via the in situ polymerization of an aniline monomer with a uniform thickness. The epoxy group on the PGMA microspheres provided a simple and fast way to react with amine functional groups without the need for a further swelling or grafting process. The morphology of the core-shell structure was confirmed by scanning election microscopy and transmission electron microscopy. The electrorheological properties of the PGMA/PANI particles-based suspension were examined using a Couette-type rotational rheometer under an applied electric field. The shear stress curves were fitted to the Cho-Choi-Jhon (CCJ) model of the rheological equation of state. © 2013 Elsevier Inc.

Fang F.F.,Inha University | Liu Y.D.,Inha University | Choi H.J.,Inha University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

In order to improve not only the magnetorheological (MR) properties of soft magnetic carbonyl iron (CI) but also its dispersion stability, we fabricated a dense network of multi-walled carbon nanotubes (MWCNTs) on the surface of CI particles by using 4-aminobenzoic acid as a grafting agent through a two-step method: ultrasonication and solvent casting, based on the self-assembly of MWCNTs which have a similar density to the polymer but better magnetic properties due to the iron catalyst located in the MWCNT. The influence of coating layers on magnetic properties along with MR performance such as yield stress behavior and shear viscosity were investigated by a vibrating sample magnetometer and rotational rheometer. The suspension stability was found to be improved from a Turbiscan test. © 2012 Elsevier B.V.

Lee M.-J.,Incheon Christian Hospital | Kim C.-E.,Inha University
Journal of Korean Medical Science | Year: 2010

This report describes the efficacy of combined use of aripiprazole in the treatment of a patient with clozapine induced enuresis. Aripiprazole acts as a potential dopamine partial agonist and the dopamine blockade in the basal ganglia might be one of the causes of urinary incontinence and enuresis. We speculate that aripiprazole functioned as a D2 agonist in hypodopaminergic state of basal ganglia caused by clozapine and maintained dopamine level that would improve enuresis ultimately. © 2010 The Korean Academy of Medical Sciences.

Ansari M.B.,Inha University | Jin H.,Inha University | Park S.-E.,Inha University
Catalysis Science and Technology | Year: 2013

The catalytic oxidation of primary/secondary alcohols with molecular O 2 to the corresponding carbonyl compounds and acids was studied over mesoporous carbon nitride (MCN) as a metal free catalyst. The aromatic alcohols showed conversions between 34-63% with O2 whereas in the co-presence of CO2 augmented conversions (54-91%) with higher selectivities for acids were observed. The quantification of the promotional effect of the synergism in the co-presence of CO2 was found to be 18-21%. The catalyst and the gaseous mixture were analysed after the reaction with IR spectroscopy, which revealed the formation of surface carbamate and the existence of CO in the gaseous mixture. The kinetic studies revealed that the first order rate constants are higher in the co-presence of CO2 and that the kinetic ρ, obtained from the Hammett plot, indicated the development of a positive charge on the substrates during the rate determining step. © 2013 The Royal Society of Chemistry.

Liu Y.D.,Inha University | Choi H.J.,Inha University | Choi S.-B.,Inha University
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2012

Silica encapsulated core-shell structured carbonyl iron (CI) magnetic particles (CI@SiO 2) were successfully prepared via a facile sol-gel method based on the silane grafted CI particles in two steps, and then confirmed by scanning electron microscopy and X-ray energy dispersive spectra. Anti-corrosion property of the as-fabricated CI@SiO 2 particles was examined under conditions of being both heated in the air environment and sustained in an acid solution. Magnetorheological (MR) performance of the CI@SiO 2 based MR fluid dispersed in silicone oil, including complex viscosity, storage and loss modulus as well as the related loss factor and relaxation modulus, was investigated and compared with that of the CI based MR fluid by using a rotational rheometer equipped with a magnetic device, showing enhanced property of heat-induced oxidation resistance with decreased particle density. © 2012 Elsevier B.V.

Hong H.,Inha University | Park I.K.,Inha University
Optical Engineering | Year: 2010

We present a novel algorithm to remove motion blur from a single blurred image. To estimate the unknown motion blur kernel as accurately as possible, we propose an adaptive algorithm using anisotropic regularization. The proposed algorithm preserves the point spread function (PSF) path while keeping the properties of the motion PSF when solving for the blur kernel. Adaptive anisotropic regularization and refinement of the blur kernels are incorporated into an iterative process to improve the precision of the blur kernel. Maximum likelihood (ML) estimation deblurring based on edge-preserving regularization is derived to reduce artifacts while avoiding oversmoothing of the details. By using the estimated blur kernel and the proposed ML estimation deblurring, the motion blur can be removed effectively. The experimental results for real motion blurred images show that the proposed algorithm can removes motion blur effectively for a variety of real scenes. © 2010 SPIE.

Jin C.,Inha University | Kim H.,Inha University
Pattern Recognition | Year: 2010

Singular point, as a global feature, plays an important role in fingerprint recognition. Inconsistent detection of singular points apparently gives an affect to fingerprint alignment, classification, and verification accuracy. This paper proposes a novel approach to pixel-level singular point detection from the orientation field obtained by multi-scale Gaussian filters. Initially, a robust pixel-level orientation field is estimated by a multi-scale averaging framework. Then, candidate singular points in pixel-level are extracted from the complex angular gradient plane derived directly from the pixel-level orientation field. The candidate singular points are finally validated via a cascade framework comprised of nested Poincare indices and local feature-based classification. Experimental results over the FVC 2000 DB2 confirm that the proposed method achieves robust and accurate orientation field estimation and consistent pixel-level singular point detection. The experimental results exhibit a low computational cost with better performance. Thus, the proposed method can be employed in real-time fingerprint recognition. © 2010 Elsevier Ltd. All rights reserved.

Lee S.-M.,Inha University | Kim K.-Y.,Inha University
Journal of Nuclear Science and Technology | Year: 2012

Printed circuit heat exchanger (PCHE) is recently considered as a recuperator for the high-temperature gas cooled reactor. In this study, shape optimization of zigzag flow channels in a PCHE has been performed to enhance heat transfer performance and reduce the friction loss based on three-dimensional Reynolds-averaged Navier-Stokes analysis with the Shear Stress Transport Turbulence model. A multiobjective genetic algorithm is used for the multi-objective optimization. Two non-dimensional objective functions related to heat transfer performance and friction loss are employed. The shape of a flow channel is defined by two geometric design variables, viz. the cold channel angle and the ellipse aspect ratio of the cold channel. The experimental points within the design space are selected using Latin hypercube sampling as the design of the experiment. The response surface approximation model is used to approximate the Pareto-optimal front. Five optimal designs on the Pareto-optimal front have been selected using k-means clustering. The flow and heat transfer characteristics, as well as the objective function values, of these designs have been compared with those of the reference design. © 2012 Atomic Energy Society of Japan. All rights reserved.

Kim E.H.,Inha University | Lee T.Y.,Inha University | Chung C.W.,Inha University
Journal of the Electrochemical Society | Year: 2012

Etch characteristics of magnetic tunnel junction (MTJ) stacks masked with WTiN films were investigated using an inductively coupled plasma reactive ion etching in a CH 3OHAr gas. The effect of CH 3OH concentration on the etch rate, etch selectivity and etch profile of MTJ stacks was examined. The high degree of anisotropy of etched MTJ stacks at high CH 3OH concentrations resulted from the high etch selectivity of MTJ stacks to hard mask which was closely related with the high ratio of HAr peaks obtained by optical emission spectroscopy. The evolution of etch profile of MTJ stacks was examined to elucidate the etch mechanism in a CH 3OHAr gas. Transmission electron microscopy of the etched MTJ stacks revealed the redeposition on the sidewall of MTJ stacks occurred during the early stage of etching and the gradual sputtering-off of the redeposited materials during further etching, resulting in a high degree of anisotropy. In addition, the redeposited materials turn out to be mainly Pt and Mn with low levels of Co and Fe by using energy dispersive X-ray spectroscopy © 2011 The Electrochemical Society.

Lee S.-Y.,Korea Institute of Energy Research | Lee S.-Y.,Inha University | Park S.-J.,Korea Institute of Energy Research | Park S.-J.,Inha University
Journal of Colloid and Interface Science | Year: 2013

Commercially available activated carbon fibers (ACFs) were modified further by a chemical activation method to obtain superior CO 2 adsorption capacity. The relationship between the pore structure of the modified ACF and the CO 2 adsorption behaviors was investigated. Chemical activation (with KOH at a fixed activation temperature of 900°C for 1h and various KOH/ACF weight ratios ranging from 1 to 4) of ACF increased the total pore volume and specific surface area to 1.124cm 3g -1 (KOH/ACF weight ratio of 2) and 2318m 2g -1 (KOH/ACF weight ratio of 4), respectively. Compared to ACF, the total pore volume and specific surface area were improved by factors of 2.5 and 2.3, respectively. Interestingly, the highest CO 2 adsorption capacity of 250mgg -1 at 298K and 1bar was observed at a KOH/ACF weight ratio of 3. The modified ACF had the narrowest microporosity ranging from 0.5 to 0.7nm. Therefore, the increase in CO 2 adsorption capacity after chemical activation is closely related to the narrower pore size distribution rather than the total or micropore volume and specific surface area. © 2012 Elsevier Inc.

Kim J.-Y.,Inha University | Kim E.-K.,Inha University | Kim E.-K.,Korea Institute of Science and Technology | Kim S.S.,Inha University
Journal of Colloid and Interface Science | Year: 2013

This paper reports the preparation of superhydrophobic SiO2 layers with a micro-nano hierarchical surface structure. SiO2 layers, which were rough on the microscale, were prepared using an electrospraying method combined with a sol-gel chemical route. To create a nanoscale structure, the surface of the SiO2 layers was coated with Au nanoparticles using an ultraviolet-enhanced chemical reduction process, resulting in a micro-nano hierarchical surface structure. A subsequent fluorination treatment with a solution containing trichloro(1H,1H,2H,2H-perfluorooctyl)silane resulted in fluorination of the micro-nano hierarchical SiO2 layers. The resulting SiO2 layers showed outstanding repellency toward a range of liquid droplets, for example, a water-repellency of 170°. The surface fraction and work of adhesion of the fluorinated, micro-nano hierarchical SiO2 layers were estimated using the Cassie-Baxter and Young-Dupre equations, respectively. The long-term durability and ultraviolet resistance of the superhydrophobic SiO2 layers prepared in this study highlight their potential in a range of practical applications. © 2012 Elsevier Inc.

The time series of the dynamic response of a slender marine structure was predicted in approximate sense using a truncated quadratic Volterra series. The wave-structure interaction system was identified using the NARX (Nonlinear Autoregressive with Exogenous Input) technique, and the network parameters were determined through supervised training using prepared datasets. The dataset used for network training was obtained by nonlinear finite element analysis of the slender marine structure under random ocean waves of white noise. The nonlinearities involved in the analysis were both large deformation of the structure under consideration and the quadratic term of the relative velocity between the water particle and structure in the Morison formula. The linear and quadratic frequency response functions of the given system were extracted using the multi-tone harmonic probing method and the time series of the response of the structure was predicted using the quadratic Volterra series. To check the applicability of the method, the response of a slender marine structure under a realistic ocean wave environment with a given significant wave height and modal period was predicted and compared with the nonlinear time domain simulation results. The predicted time series of the response of structure with quadratic Volterra series successfully captured the slowly varying response with reasonably good accuracy. This method can be used to predict the response of the slender offshore structure exposed to a Morison type load without relying on the computationally expensive time domain analysis, especially for screening purposes. © 2014 Elsevier Ltd.

Xu H.,Inha University | Lu Y.,Hanyang University | Lee Y.P.,Hanyang University | Ham B.S.,Inha University
Optics Express | Year: 2010

We have studied electromagnetically induced transparency (EIT) in metamaterials for various schemes corresponding to those in an atomic medium. We numerically calculate a symmetric dolmen scheme of metamaterials corresponding to a tripod model of EIT-based optical switching and illustrate plasmonic double dark resonances. Our study provides a fundamental understanding and useful guidelines in using metamaterials for plasmonic-based all-optical information processing. © 2010 Optical Society of America.

Lengthening of photon storage time has been an important issue in quantum memories for long distance quantum communications utilizing quantum repeaters. Atom population transfer into an auxiliary spin state has been adapted to increase photon storage time of photon echoes. In this population transfer process phase shift to the collective atoms is inevitable, where the phase recovery condition must be multiple of 2π to satisfy rephasing mechanism. Recent adaptation of the population transfer method to atomic frequency comb (AFC) echoes [Afzelius et al., Phys. Rev. Lett. 104, 040503 (2010)], where the population transfer method is originated in a controlled reversible inhomogeneous broadening technique [Moiseev and Kroll, Phys. Rev. Lett. 87, 173601 (2001)], however, shows contradictory phenomenon violating the phase recovery condition. This contradiction in AFC is reviewed as a general case of optical locking applied to a dilute medium for an optical depth-dependent coherence leakage resulting in partial retrieval efficiency. © 2010 Optical Society of America.

Jo T.,Inha University
Soft Computing | Year: 2014

This research is concerned with the improved version of table-based matching algorithm as the approach to text categorization tasks. It is intended to tackle the three problems in encoding texts into numerical vectors and the unstable performance by the fluctuations from text lengths in the previous version. In this research, we encode texts into tables rather than into numerical vectors, define the similarity measure between two tables which is always as a normalized value between zero and one, and apply it to the tasks of text categorization. As the benefits from this research, we expect better performance by solving the three problems resulting from encoding texts into numerical vectors, and more stable performance by improving the previous version. Therefore, we empirically validate the proposed approach through the four sets of experiments, with respect to both performance and stability. © 2014 Springer-Verlag Berlin Heidelberg.

Ham B.S.,Inha University
Optics Express | Year: 2010

A photon echo storage-time extension protocol is presented by using a phase locking method in a three-level backward propagation scheme, where phase locking serves as a conditional stopper of the rephasing process in conventional two-pulse photon echoes. The backward propagation scheme solves the critical problems of extremely low retrieval efficiency and π rephasing pulse-caused spontaneous emission noise in photon echo based quantum memories. The physics of the storage time extension lies in the imminent population transfer from the excited state to an auxiliary spin state by a phase locking control pulse. We numerically demonstrate that the storage time is lengthened by spin dephasing time. © 2010 Optical Society of America.

Choi W.J.,Yonsei University | Kim B.S.,Inha University | Lee J.W.,Yonsei University
American Journal of Sports Medicine | Year: 2012

Background: Several studies have addressed the issue of the feasibility of arthroscopic surgery in older patients, usually by choosing an arbitrary age limit.Hypothesis: Patient age is not associated with poor clinical outcome after arthroscopic surgery for osteochondral lesion of the talus (OLT), and other patient variables are the major determinants of clinical success/failure.Study Design: Cohort study; Level of evidence, 3.Methods: Between 2001 and 2008, 173 ankles underwent arthroscopic marrow stimulation treatment for OLT and were stratified into 6 age groups (<20, 20-29, 30-39, 40-49, 50-59, and ≥60 years). Bivariate and multivariate analyses were performed to determine the effect of age on clinical outcome.Results: There were no significant differences among the 6 age groups in the preoperative and postoperative visual analog scale (VAS) for pain or the American Orthopaedic Foot and Ankle Society (AOFAS) score. There was a significant increase in the duration of symptoms (P <.001) and a significant decrease in the incidence of trauma (P =.01) in the older group. Both the size of the osteochondral defect and the number of associated intra-articular lesions independently predicted a poor clinical outcome (P <.001).Conclusion: In contrast to some of the previous studies on this topic, we found that increased age was not an independent risk factor for poor clinical outcome after arthroscopic treatment for OLT. We did find that older patients were less likely to have a history of trauma and had a longer duration of symptoms, had smaller osteochondral defects, and had more associated intra-articular lesions. © 2012 American Orthopaedic Society for Sports Medicine.

Riazul Islam S.M.,Inha University | Kwak K.S.,Inha University
International Journal of Digital Content Technology and its Applications | Year: 2010

New channel estimation technique is proposed for multiband orthogonal frequecny division multiplexing (MB-OFDM) ultra wideband (UWB) systems in multipath time varying wireless channels. Two-stages approch has been used to achieve this purpose. In first stage, Winner-Hopf filtration has been employed for the interpolation of unknown channel state information (CSI) using comb-type known pilots. In second stage, interpolated channel statistics are then modeled as autoregressive (AR) process and fed into kalman filter. Moreover, inorder to suppress intercarrier interference (ICI), an ICI mitigation filter does joinly work with kalman filter. A mathematical framework is given for the ralization of our proposed system. Link level simulation (LLS) urgs that this new tecnique shows exact channel tarcking and provides better symbol error rate (SER) performance.

Ha S.H.,Inha University | Mai N.L.,Inha University | Koo Y.-M.,Inha University
Journal of Chromatography A | Year: 2010

Microwave-assisted separation has been applied to recover ionic liquid (IL) from its aqueous solution as an efficient method with respect to time and energy compared to the conventional vacuum distillation. Hydrophilic ILs such as 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([Bmim][TfO]) and 1-ethyl-3-methylimidazolium methylsulfate ([Emim][MS]) could be recovered in 6min from the mixture of ILs and water (1:1, w/w) under microwave irradiation at constant power of 10W while it took at least 240min to obtain ILs containing same water content (less than 0.5wt%) by conventional vacuum oven at 363.15K with 90kPa of vacuum pressure. Energy consumptions per gram of evaporated water from the homogeneous mixture of hydrophilic ILs and water (1:1, w/w) by microwave-assisted separation were at least 52 times more efficient than those in conventional vacuum oven. It demonstrated that microwave-assisted separation could be used for complete recovery of ILs in sense of time and energy as well as relevant purity. © 2010 Elsevier B.V.

Woo S.B.,Inha University | Yoon B.I.,Inha University
Journal of Coastal Research | Year: 2011

The barotropic tidal characteristics of Gyeong-Gi Bay (west coast of Korea) were studied with using observed tidal elevation data and numerical model. The estuary consists of 3 main tidal channels and freshwater discharges by three rivers through which major tidal flow and river discharge meet each other. It was found that the type of this estuary can be characterized by different tidal propagation pattern along those three main channels. Although three major channels show a hyper-synchronous type in general, the maximum tidal amplitude were observed at different channel. Numerical model study was performed to find out major physical factors that influence channel-dependent tidal propagation. Model results showed that the important factor for the change of tidal amplitude and phase along each channel were bottom friction, river discharge and tidal flat existences. On the other hand the river discharge modifies phase lag at high and low tide. Model experiment showed that the topographical characteristic was the most important factor for the generation of hyper-synchronous pattern in Gyeong-Gi Bay (GGB). The quantitative method shows that classification of the type. At Yeumha channel is more frictional than Seokmo channel.

Hong J.I.,Inha University | Huh C.S.,Inha University
Progress in Electromagnetics Research | Year: 2010

Reverberation chambers are widely used in electromagnetic compatibility test facilities because they provide a large working volume and are cheaper than other types of test facilities. In addition, they provide a statistically uniform field and generate a high maximum electric field within a relatively large volume. The volume of the cavity, the structure of the stirrer, and high tested frequency must be used in the reverberation chamber appropriately. Changing a volume of cavity dimensions and test frequency can be difficult in the reverberation chamber because they were determined already in the design process. In these cases, the stirrer should be changed. We investigated of the effects of various stirrer angles and heights on a reverberation chamber. The optimization of the stirrer with respect to various stirrer parameters was investigated; these parameters are related to field uniformity, the quality factor, stirred efficiency, and electric field polarity. Our results suggest that a reverberation chamber can be successfully operated if careful decisions are made regarding the stirrer design.

Choochottiros C.,Inha University | Park E.,Inha University | Chin I.-J.,Inha University
Journal of Industrial and Engineering Chemistry | Year: 2012

Block copolymers of polylactide (PLA) and poly(methyl methacrylate) (PLA-PMMA) were synthesized by the combination of ring-opening polymerization (ROP) and activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP), where PLA was prepared as macroinitiator with active bromo end group (PLA-Br). Tin octoate (Sn(oct) 2) and benzyl alcohol were applied as the initiation system for ROP of lactide. During AGET ATRP, copper (II) chloride (CuCl 2) with N, N, N', N', N'-pentamethyl-diethylenetriamine (PMDETA) was used as the catalyst system including Sn(oct) 2 as reducing agent. At the feed ratio [PLA-Br]/[CuCl 2]/[PMDETA]/[Sn(oct) 2]/[MMA] of 1/1/9.6/0.45/100, the mole fraction of the PMMA block was 0.6 as determined by 1H NMR. Thermal stability of PLA was enhanced by incorporating of PMMA as block copolymers. In addition, blend between of PLA and PLA-PMMA copolymer was investigated and 5phr of PLA-PMMA showed optimum condition to decrease in Young's modulus and increase in impact strength. © 2012 The Korean Society of Industrial and Engineering Chemistry.

Lee S.-K.,Inha University | Kim H.-W.,Inha University | Na E.-W.,Inha University
Journal of Sound and Vibration | Year: 2010

A new sound metric for impact sound is developed based on the continuous wavelet transform (CWT), a useful tool for the analysis of non-stationary signals such as impact noise. Together with new metric, two other conventional sound metrics related to sound modulation and fluctuation are also considered. In all, three sound metrics are employed to develop impact sound quality indexes for several specific impact courses on the road. Impact sounds are evaluated subjectively by 25 jurors. The indexes are verified by comparing the correlation between the index output and results of a subjective evaluation based on a jury test. These indexes are successfully applied to an objective evaluation for improvement of the impact sound quality for cases where some parts of the suspension system of the test car are modified. © 2010 Elsevier Ltd. All rights reserved.

Shin C.,Inha University | Bae J.,Inha University | McCarty P.L.,Inha University | McCarty P.L.,Stanford University
Bioresource Technology | Year: 2012

A general concern that anaerobic treatment of dilute wastewaters is limited by the inability of methanogenic and related syntrophic organisms to reduce substrate concentrations adequately was evaluated using a 35°C granular activated carbon-containing laboratory-scale fluidized bed reactor fed an acetate-propionate equal chemical oxygen demand (COD) mixture synthetic wastewater. Contrary to general expectations, effluent acetate and propionate concentrations remained near or below their detection limits of 0.4mg COD/L with influent COD of 200mg/L, 17min hydraulic retention time, and organic loading as high as 17kg COD/m 3d, or with influent COD values ranging from 45 to 2010mg COD/L and organic loadings of 4.2-4.5kg COD/m 3d. The effluent acetate concentrations in these well-fed systems were at or much below reported threshold limits for starving non-fed cultures, suggesting that a better understanding of threshold values and factors affecting treatment efficiency with anaerobic treatment of dilute wastewaters is needed. © 2012 Elsevier Ltd.

Ryu H.-Y.,Inha University | Shim J.-I.,Hanyang University
IEEE Journal of Quantum Electronics | Year: 2010

Light extraction efficiency (LEE) in thin-film InGaN vertical light-emitting diode (LED) structures with photonic crystal patterns is studied using the three-dimensional finite-difference time-domain simulation. We systematically investigate the dependence of LEE on various structural parameters of photonic crystal vertical LEDs such as the thickness of the p-GaN and n-GaN layers, and air-hole depth and size. It is found that high LEE of >80% is obtainable from unencapsulated photonic crystal LEDs for a wide range of structural parameters. In particular, higher LEE is observed for the structures with relatively long-period photonic crystal patterns and possible mechanisms for the large enhancement of LEE are discussed. © 2009 IEEE.

Yadav M.,Kyung Hee University | Rhee K.Y.,Kyung Hee University | Park S.J.,Inha University
Carbohydrate Polymers | Year: 2014

In this work, graphene oxide/carboxymethylcellulose/alginate (GO/CMC/Alg) composite blends were prepared by a simple solution mixing-evaporation method. The resulting structure, thermal stability, and mechanical properties of the blends were investigated by wide-angle X-ray diffractometry, Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis, and mechanical testing. The obtained findings revealed that CMC, Alg, and graphene oxide were able to form a homogeneous mixture. When compared to a CMC/Alg blend, the incorporation of 1 wt% graphene oxide improved the tensile strength and Young's modulus by 40% and 1128%, respectively. In addition, the GO/CMC/Alg composite blend film showed a higher storage modulus than the CMC/Alg blend. © 2014 Elsevier Ltd.

Cheong W.J.,Inha University
Journal of Separation Science | Year: 2014

It is surprising that there has been no devoted review article for frits and relevant studies so far despite the long history of packed columns and the use of frits in them. This review was activated for such a reason. Both separate frits and in situ permanent frits have been covered since the appearance of primitive frits. The in situ fritting methods such as the formation of organic monoliths, sol-gel technology, sintering, fritless techniques such as tapered tip and capillary restrictors, and miscellaneous fritting techniques including magnetically trapped frits and single particle frits are introduced and discussed. In addition, frit-related studies and patents are also introduced. Finally, some conclusive comments on the choice of fritting technique in different situations and future perspectives are given. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Of all the intracellular organelles, secretory granules contain by far the highest calcium concentration; secretory granules of typical neuroendocrine chromaffin cells contain ∼40 mM Ca2+ and occupy ∼20% cell volume, accounting for >60% of total cellular calcium. They also contain the majority of cellular inositol 1,4,5-trisphosphate receptors (IP3Rs) in addition to the presence of >2 mM of chromogranins A and B that function as high-capacity, low-affinity Ca2+ storage proteins. Chromogranins A and B also interact with the IP3Rs and activate the IP 3R/Ca2+ channels. In experiments with both neuroendocrine PC12 and nonneuroendocrine NIH3T3 cells, in which the number of secretory granules present was changed by either suppression or induction of secretory granule formation, secretory granules were demonstrated to account for >70% of the IP3-induced Ca2+ releases in the cytoplasm. Moreover, the IP3 sensitivity of secretory granule IP3R/Ca 2+ channels is at least ∼6- to 7-fold more sensitive than those of the endoplasmic reticulum, thus enabling secretory granules to release Ca2+ ahead of the endoplasmic reticulum. Further, there is a direct correlation between the number of secretory granules and the IP3 sensitivity of cytoplasmic IP3R/Ca2+ channels and the increased ratio of IP3-induced cytoplasmic Ca2+ release, highlighting the importance of secretory granules in the IP3-dependent Ca2+ signaling. Given that secretory granules are present in all secretory cells, these results presage critical roles of secretory granules in the control of cytoplasmic Ca2+ concentrations in other secretory cells. - Yoo, S. H. Secretory granules in inositol 1,4,5-trisphosphatedependent Ca2+ signaling in the cytoplasm of neuroendocrine cells. © FASEB.

Woo M.S.,Inha University | Kang J.S.,Inha University | Moon K.H.,Inha University
Journal of Arthroplasty | Year: 2014

This study evaluated the result of total hip arthroplasty (THA) for avascular necrosis of the femur head (AVNFH) in systemic lupus erythematosus (SLE) patients. Nineteen THAs were performed on 13 patients with SLE. The results of these patients were compared with the results of the control group (19 patients) who had THR due to AVNFH with none-SLE conditions. The Harris hip score increased from a preoperative average of 65.3 points to 94.9 at the most recent follow-up. In the control group, the mean HHS was 67.2 preoperatively and 96.1 postoperatively at the last follow-up. No significant difference was found between SLE patients and non-SLE patients who underwent hip arthroplasty. In conclusion, THA is an acceptable treatment for achieving functional improvement in patients who had SLE and AVNFH. © 2014 Elsevier Inc.

Choe E.,Inha University
JAOCS, Journal of the American Oil Chemists' Society | Year: 2013

Light and temperature effects on tocopherols during the oxidation of sunflower oil were studied. The oxidation was performed at 40, 60, or 80 C for 30, 15, and 6 days, respectively, in the dark or under 1,700 lux light. Oil oxidation was analyzed with peroxide values and conjugated dienoic acid contents, and tocopherols in the oil were separated and quantified by HPLC. The oxidation of sunflower oil was increased with temperature increase, and the light decreased the temperature dependence of the oil oxidation. Sunflower oil before oxidation contained tocopherols with a total of 737.96 mg/kg, with α- and γ-tocopherol at 726.41 and 11.56 mg/kg, respectively, and the tocopherol contents decreased during the oil oxidation. Degradation of tocopherols increased with the temperature increase, and its dependence on the temperature was lower under light than in the dark. γ-Tocopherol showed higher stability than α-tocopherol during oxidation of the oil in the dark and under light. Residual amounts of tocopherols showed a relatively good correlation with the degree of oil oxidation, and the dependence of α-tocopherol degradation on the oil oxidation was higher than that of γ-tocopherol, and light decreased the dependence on the oil oxidation in both tocopherols. © 2013 AOCS.

Bi W.,Nanjing Normal University | Bi W.,Inha University | Row K.H.,Inha University
Journal of Separation Science | Year: 2013

This paper reports the application of a multiphase dispersive extraction method to the extraction, separation, and determination of the phenolic acids from Salicornia herbacea L. using silica-confined ionic liquids as sorbents. A suitable sorbent for phenolic acid extraction and separation was first identified based on the adsorption behavior of the phenolic acids on different silica-confined ionic liquids. The sample was then mixed with the optimized sorbent and solvent to achieve multiphase dispersive extraction. The sample/sorbent ratio was optimized using theoretical calculations from the adsorption isotherm and experiments. After transferring the supernatant to an empty cartridge, an SPE process was used to separate the three phenolic acids from the other interference. Through systematic optimization, the optimal conditions produced high recovery rates of protocatechuic acid (91.20%), caffeic acid (94.03%), and ferulic acid (91.33%). Overall, the proposed method is expected to have wide applicability. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Duong T.H.,Inha University | Jo G.S.,Inha University
Neurocomputing | Year: 2012

Previous work on ontology integration involves only blind or exhaustive matching among all the concepts in different ontologies. Therefore, the computational complexity rapidly increases in integrating large ontologies. In addition, semantic mismatches, logical inconsistencies, and conceptual conflicts in ontology integration have not yet become avoidable. The aim of this paper is to investigate a method to reduce the computational complexity and enhance accurate matching ontology. In this paper, a novel approach has been proposed using propagating Priorly Matchable Concepts (PMCs). The key idea of our approach is analyzing multiple contexts, including the role of "natural categories", relations, and constraints among concepts to provide additional suggestions for possible matching concepts. PMC is a collection of pairs of concepts across two different ontologies in the same Concept Types 11Concept Types are used to identify concepts playing a role of "natural categories" in an ontology. that are arranged in descending order of Concept Importance 22Concept Importance is an importance measurement of a concept that shows how a central and "richly" described concept is in the taxonomy of the ontology. distances for the pairs. PMC guides on how to priorly check the similarity between concepts. It is useful to avoid checking similarities among unmatchable concepts. In addition, dependency rules are applied to filter mismatches in PMC during the integration process. Our experiments compare the computational complexity and accurate matching to previous approaches. The use of PMC as a pre-process in the integration process enhances both complexity and accuracy compared to unused PMC. © 2012 Elsevier B.V.

Chen C.,Inha University | Chen C.,Xinyang Normal University | Kim J.,Inha University | Ahn W.-S.,Inha University
Korean Journal of Chemical Engineering | Year: 2014

Amine-functionalized nanoporous materials can be prepared by the incorporation of diverse organic amine moieties into the pore structures of a range of support materials, such as mesoporous silica and alumina, zeolite, carbon and metal organic frameworks (MOFs), either by direct functionalization or post-synthesis through physical impregnation or grafting. These hybrid materials have great potential for practical applications, such as dry adsorbents for post-combustion CO2capture, owing to their high CO2capture capacity, high capture selectivity towards CO2compared to other gases, and excellent stability. This paper summarizes the preparation methods and CO2capture performance based on the equilibrium CO2uptake of a range of amine-functionalized nanoporous materials. © 2014, Korean Institute of Chemical Engineers, Seoul, Korea.

Park I.,Inha University | Jun Y.,Inha University | Lee U.,Inha University
Wave Motion | Year: 2014

Lamb waves propagate over large distances in plate-like thin structures and they have received great attention in the structural health monitoring (SHM) field as an efficient means to inspect a large area of a structure by using only a small number of sensors. The times-of-flight of the Lamb wave modes are useful for detecting damage generated in a structure. However, due to the dispersive and multi-mode nature of Lamb waves, it is very challenging to decompose Lamb wave modes into symmetric and anti-symmetric modes for potential applications to structural health monitoring. Thus, we propose an efficient Lamb wave mode decomposition method based on two fundamental rules: the group velocity ratio rule and the mode amplitude ratio rule. The group velocity ratio rule means that the ratio of the group velocities of A0 and S0 modes must be constant. The mode amplitude ratio rule means that the ratio of the magnitudes of A0 and S0 modes in a measured response signal must be always greater than one once the center frequency of the input signal is determined, such that the magnitude of the A0 mode in the excited signal is larger than that of the S0 mode, and vice versa. The proposed method is verified through experiments conducted for a plate specimen. © 2013 Elsevier B.V.

Zhang W.L.,Inha University | Choi H.J.,Inha University
Polymers | Year: 2014

Electrorheological (ER) and magnetorheological (MR) suspensions undergo a reverse phase transition from a liquid-like to solid-like state in response to an external electric or magnetic field, respectively. This paper briefly reviews various types of electro- or magneto-responsive materials from either polymeric or inorganic and hybrid composite materials. The fabrication strategies for ER/MR candidates and their ER/MR characteristics (particularly for ER fluids) are also included. © 2014 by the authors.

Nguyen Q.H.,Ho Chi Minh University of Industry | Choi S.B.,Inha University
Smart Materials and Structures | Year: 2010

This paper presents an optimal design of a magnetorheological (MR) brake for a middle-sized passenger car which can replace a conventional hydraulic disc-type brake. In the optimization, the required braking torque, the temperature due to zero-field friction of MR fluid, the mass of the brake system and all significant geometric dimensions are considered. After describing the configuration, the braking torque of the proposed MR brake is derived on the basis of the field-dependent Bingham and Herschel-Bulkley rheological model of the MR fluid. The optimal design of the MR brake is then analyzed taking into account available space, mass, braking torque and steady heat generated by zero-field friction torque of the MR brake. The optimization procedure based on the finite element analysis integrated with an optimization tool is proposed to obtain optimal geometric dimensions of the MR brake. Based on the proposed procedure, optimal solutions of single and multiple disc-type MR brakes featuring different types of MR fluid are achieved. From the results, the most effective MR brake for the middle-sized passenger car is identified and some discussions on the performance improvement of the optimized MR brake are described. © 2010 IOP Publishing Ltd.

Gu J.Y.,California State University, Long Beach | Kusnadi J.,California State University, Long Beach | You C.-Y.,Inha University
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We investigate the proximity effect in a superconductor/ferromagnet (S/F) hybrid system with a noncollinear magnetic configuration. A new structure of an S/exchange-spring (ES) magnet is fabricated, where an ES magnet is employed as an F layer since the magnetization configuration is varied from a collinear state to a noncollinear state by a rotating external magnetic field in a well controllable way. We found that the resistance decreases and the superconducting transition temperature increases, as noncollinearity is introduced starting from a collinear state. We interpret that our experimental observation is due to the contribution of the odd-triplet superconducting condensate that survived in a noncollinear magnetization configuration in the ES magnet. © 2010 The American Physical Society.

Mahadeva S.K.,Inha University | Kim J.,Inha University
Journal of Physics D: Applied Physics | Year: 2010

This paper reports that nanocoating of polypyrrole (PPy) and ionic liquid (IL) on cellulose film improves the electromechanical performance and durability of a cellulose electro-active paper actuator. Cellulose-PPy-IL nanocomposites were fabricated by the polymerization-induced adsorption process of PPy followed by subsequent activation in IL solutions. X-ray photoelectron spectroscopy, transmission electron microscopy and secondary ion mass spectroscopy analyses validated the successful nanocoating of the PPy and IL layers on the cellulose. The results revealed that the cellulose-PPy-IL nanocomposites are suitable for durable bending actuators working under ambient conditions. Preparation, characterization and performance test of the nanocomposites are explained. © 2010 IOP Publishing Ltd.

Ham B.S.,Inha University
Journal of the Optical Society of America B: Optical Physics | Year: 2011

Optical locking applied to rephased atoms in photon echoes is analyzed for on-demand photon storage time extension, where the storage time extension is confined by the inverse of spin inhomogeneous broadening. Both optical locking and photon storage mechanisms in atomic frequency comb echoes are discussed and compared with those in two-pulse photon echo-based phase-locked echoes and three-pulse photon echoes. © 2011 Optical Society of America.

You C.-Y.,Inha University
Current Applied Physics | Year: 2010

Critical current density of composite free layer (CFL) in magnetic tunneling junction is investigated. CFL consists of two exchange coupled ferromagnetic layers, where the coupling is parallel or anti-parallel. Instability condition of the CFL under the spin transfer torque, which is related with critical current density, is obtained by analytic spin wave excitation model and confirmed by macro-spin Landau-Lifshitz-Gilbert equation. The critical current densities for the coupled two identical layers are investigated with various coupling strengths, and spin transfer torque efficiencies. © 2009 Elsevier B.V. All rights reserved.

Nam S.-I.,Korea Aerospace University | Kim H.-C.,Inha University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We investigate the spin structure of the pion within the framework of the nonlocal chiral quark model from the instanton vacuum. We first evaluate the tensor form factors of the pion for the first and second moment (n=1,2) and compare it with the lattice data. Combining the tensor form factor of the pion with the electromagnetic one, we determine the impact-parameter dependent probability density of transversely polarized quarks inside the pion. It turns out that the present numerical results for the tensor form factor as well as those for the probability density are in good agreement with the lattice data. We also discuss the distortion of the spatial distribution of the quarks in the transverse plane inside the pion. © 2011 Elsevier B.V.

Yun S.,Inha University | Kim J.,Inha University
Sensors and Actuators, B: Chemical | Year: 2010

This paper reports the multi-walled carbon nanotubes (MWCNTs)-cellulose paper as a chemical vapor sensor. Cellulose solution was prepared by dissolving cotton pulp in LiCl/N,N-dimethylacetamide solution. MWCNTs were covalently grafted to cellulose by reacting imidazolides-MWCNTs with cellulose solution. Using this product, the MWCNTs/cellulose (M/C) paper was fabricated, followed by mechanical stretching to align MWCNTs with cellulose chains. Characteristics of the M/C paper were analyzed in terms of scanning electron microscope images, Young's modulus and electrical resistance. The M/C paper was investigated as a chemical sensor that can detect vaporized analyte molecules, such as, methanol, ethanol, 1-butanol and 1-propanol. Their electrical responses on the sensor were evaluated by not only comparing their relative resistance response (A R) depending on the concentration, but also checking signal reversibility under cyclic exposure of each analyte. Due to sensitive and reversible expansion/contraction of the M/C paper in response to analytes, the M/C paper showed reversible and fast response with the following rank of A R: methanol < ethanol < 1-propanol < 1-butanol. Especially, the linear response to 1-propanol concentration proved that the M/C paper can be a qualified sensor for n-propanol. © 2010 Published by Elsevier B.V.

Ham B.S.,Inha University | Hahn J.,Inha University
New Journal of Physics | Year: 2011

Light control by another light has drawn much attention in nonlinear quantum optics. Achieving all-optical control of the refractive index has been a key issue in all-optical information processing. Ultraslow light has been a good candidate for this purpose, where a giant phase shift can be achieved. The recent presentation of stationary light utilizing ultraslow light is an advanced example of such research. The stationary light functions as cavity quantum electrodynamics, where no high-Q-factor mirror pair is needed. In this paper, we report on two-color halted light pulses inside a solid medium, where the trapping time is comparable with that of ultraslow light but is much longer than quantum mapping storage time. The observed two-color halted light is achieved by means of double Raman optical field-excited spin coherence gratings, where slow light enhanced backward nondegenerate four-wave mixing processes play a major role. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Lee H.-I.,Inha University
Journal of Lightwave Technology | Year: 2011

Wavenumber matching is crucial to proper designs of optical devices such as ring-bus waveguides or planar cavities. In particular, the range of in-plane wavenumbers needs to be adequately determined along the coupling direction. Oftentimes, numerically intensive search is necessary for its accurate determination for surface plasmon resonances in particular nanostructures. In this paper, a method based on contour integrals is employed in order to provide a rough idea on the coupling capability of participating optical components. An example is provided for a semi-infinite metal-dielectric periodic multilayer ounded by another semi-infinite medium. © 2011 IEEE.

Yakhshiev U.,Inha University | Kim H.-C.,Inha University
Physical Review C - Nuclear Physics | Year: 2011

We investigate the binding energy per nucleon and hadron properties in infinite and homogeneous nuclear matter within the framework of the in-medium modified Skyrme model. We first consider the medium modifications of the single hadron properties by introducing the optical potential for pion fields into the original Lagrangian of the Skyrme model. The parameters of the optical potential are well fitted to the low-energy phenomenology of pion-nucleus scattering. Furthermore, the Skyrme term is also modified in such a way that the model reproduces the bulk properties of nuclear matter, in particular, the binding energy per nucleon. © 2011 American Physical Society.

Seo M.-K.,Inha University | Park S.-J.,Inha University
Current Applied Physics | Year: 2010

Energy-storage composite electrodes were prepared by mixing activated carbons (ACs) modified with nanosize titanium oxide (TiO2) through ultrasonic vibration in ethanol solution for 30 min. We examined the cyclic voltammetry of the composite electrodes in an aqueous electrolyte, 1 M H2SO4. It was found that the specific capacitance of the composite electrodes measured in a range of 0-0.8 V was increased from 100 to 155 F/g compared electrodes comprised of ACs only. This was attributed to a reduction of polarization of the ACs modified by nanosized TiO2. © 2009 Elsevier B.V. All rights reserved.

Choi Y.,Inha University
Journal of biomedical materials research. Part B, Applied biomaterials | Year: 2012

Silk fibroin particles prepared by phase separation with polyethylene oxide were coated with calcium-deficient hydroxyapatite (CDHA) crystals under various pH conditions. For different pH values, the growth and the morphology of CDHA crystals on the surface of silk fibroin particles were investigated in detail by zeta potential analysis, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction techniques. Negative charges formed by deprotonation of the functional groups on the surface of silk fibroin particles at high pH lead to an increase of binding affinity between the calcium ions of the CDHA crystals and the functional groups of the silk fibroin particles. Consequently, the generation of many CDHA crystals was promoted to deposit on the surface of silk fibroin particles at a high pH value. Copyright © 2012 Wiley Periodicals, Inc.

Kweon M.,Inha University
Nuclear Physics A | Year: 2014

This article summarizes recent results on open heavy-flavour observables from selective experiments in relativistic nuclear collisions as presented during the Quark Matter 2014 conference. Commonalities and differences of their results are highlighted as a function of energy and relative to pp and pA collisions. © 2014 Elsevier B.V.

Jang T.Y.,Inha University | Kim Y.H.,Inha University
International Neurourology Journal | Year: 2015

Interleukin (IL) 33, a member of the IL-1 superfamily, is an "alarmin" protein and is secreted in its active form from damaged cells undergoing necrotic cell death. Mast cells are one of the main effector cell types in allergic disorders. They secrete a variety of mediators, including T helper 2 cytokines. As mast cells have high-affinity IgE receptors (FceRI) on their surface, they can capture circulating IgE. IgE-bound mast cells degranulate large amounts of histamine, heparin, and proteases when they encounter antigens. As IL-33 is an important mediator of innate immunity and mast cells play an important role in adaptive immune responses, interactions between the two could link innate and adaptive immunity. IL-33 promotes the adhesion of mast cells to laminin, fibronectin, and vitronectin. IL-33 increases the expression of adhesion molecules, such as intracellular adhesion molecule-1 and vascular cell adhesion molecule-1, in endothelial cells, thus enhancing mast cell adhesion to blood vessel walls. IL-33 stimulates mast cell proliferation by activating the ST2/Myd88 pathway; increases mast cell survival by the activation of survival proteins such as Bcl-XL; and promotes the growth, development, and maturation of mast cell progenitors. IL-33 is also involved in the activation of mature mast cells and production of different proinflammatory cytokines. The interaction of IL-33 and mast cells could have important clinical implications in the field of clinical urology. Epithelial dysfunction and mast cells could play an important role in the pathogenesis of interstitial cystitis. Urinary levels of IL-33 significantly increase in patients with interstitial cystitis. In addition, the number of mast cells significantly increase in the urinary bladders of patients with interstitial cystitis. Therefore, inhibition of mast cell activation and degranulation in response to increase in IL-33 is a potential therapeutic target in the treatment of interstitial cystitis. © 2015 Korean Continence Society.

Jo T.,Inha University
Proceedings - 2013 IEEE International Conference on Granular Computing, GrC 2013 | Year: 2013

This research is concerned with applying the table based approach to text categorization in the bio-medical domain. The popularity and interests in the bio-medical domain are increasing recently with respect to the text processing. In this research, we encode texts in the domain into tables, define the similarity measure between tables representing the texts, and apply it to categorizations of the bio-medical texts. We may expect better performance and stability of the proposed approach as well as in other domains. Thus, we will use the collection of medical documents, called Oshumed, as the test data for evaluating the proposed approach. © 2013 IEEE.

Kim Y.H.,Inha University | Jang T.Y.,Inha University
American Journal of Rhinology and Allergy | Year: 2010

Background: Many researchers have focused on the definition and pathophysiology of localized mucosal allergy. However, there are few studies on its clinical characteristics and therapeutic outcomes. The goal of this study was to analyze the prevalence, epidemiology, clinical characteristics, and response to antiallergic medication of localized mucosal allergy patients compared with those in patients with allergic rhinitis. Methods: Among 836 patients suspected to have rhinitis, 29 patients with localized mucosal allergy (group A) and 29 patients with allergic rhinitis (group B) were selected. Medical history, family history, symptoms, and their severity were obtained using a questionnaire. The change in minimal cross-sectional area (MCA) after provocation was measured by acoustic rhinometry. After 2 weeks of antihistamine medication, the changes in symptoms were compared between groups. Results: The prevalence of localized mucosal allergy was ∼3.5%. There were no differences in patient history, symptoms, or symptom severity. The decrease in MCA after provocation was not significantly different. After two weeks of oral antihistamine (ebastine 10 mg once daily), group A reported significantly less symptom improvement than group B. Conclusion: Because patient or family history and clinical picture are very similar in localized mucosal allergy and allergic rhinitis, clinicians should take more care in differentiating them. Based on the reduced effectiveness of an oral antihistamine alone, a combined regimen of oral and topical antihistamine or anti-inflammatory medication is recommended for patients with localized mucosal allergy. Copyright © 2010, OceanSide Publications, Inc.

Yoo I.,Inha University | Lee S.,Inha University
AIAA Journal | Year: 2012

Realistic computations of flows induced by synthetic jets in multiple flow conditions are studied with an unsteady preconditioned Reynolds-averaged Navier-Stokes solver with deforming meshes. Deforming meshes suitable for structured grid systems are used to simulate the motion of diaphragms driven at a given frequency. With deforming meshes, a boundary-condition model is not necessary for synthetic jet calculations. To obtain time-accurate solutions with a grid system under deformation, the geometric conservation law is employed. Numerical calculations of three cases of the Langley Research Center Workshop Computational Fluid Dynamics Validation of Synthetic Jets and Turbulent Separation Control workshop are carried out, and the computational results are compared with the experimental data. The results indicate the effectiveness of the current method in synthetic jet flow computations. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

The author theoretically investigates the effects of internal polarization fields on the efficiency of InGaN/GaN multiple-quantum-well (MQW) blue light-emitting diodes (LEDs) based on numerical simulations. Internal quantum efficiency (IQE), current leakage, and carrier distributions are calculated with varying the strength of polarization fields to study the role of the polarization fields on the efficiency characteristics. Simulation results show that, as the strength of the polarization fields increases, electron current leakage from active layers to the p-GaN layer increases and hole concentration distribution at MQWs becomes more inhomogeneous. It is found that these two effects by the internal polarization fields lead to significant decrease in the IQE of InGaN blue LEDs. © 2012 The Japan Society of Applied Physics.

Mai N.L.,Inha University | Koo Y.-M.,Inha University
Enzyme and Microbial Technology | Year: 2014

Enzymatic hydrolysis of penicillin G to produce 6-aminopenicillanic acid, key intermediate for the production of semisynthetic β-lactam antibiotics, is one of the most relevant example of industrial implementation of biocatalysts. The hydrolysis reaction is traditionally carried out in aqueous buffer at pH 7.5-8. However, the aqueous rout exhibits several drawbacks in enzyme stability and product recovery. In this study, several ionic liquids (ILs) have been used as media for enzymatic hydrolysis of penicillin G. The results indicated that hydrophobic ILs/water two-phase system were good media for the reaction. In addition, a novel aqueous two-phase system based on the lower critical solution temperature type phase changes of amino acid based ILs/water mixture was developed for in situ penicillin G hydrolysis and product separation. For instance, hydrolysis yield of 87.13% was obtained in system containing 30. wt% [TBP][Tf-ILe] with pH control (pH 7.6). Since the phase-separation of this medium system can be reversible switched from single to two phases by slightly changing the solution temperature, enzymatic hydrolytic reaction and product recovery were more efficient than those of aqueous system. In addition, the ILs could be reused for at least 5 cycles without significant loss in hydrolysis efficiency. © 2014 Elsevier Inc.

Liu Y.D.,Inha University | Fang F.F.,Inha University | Choi H.J.,Inha University
Materials Letters | Year: 2010

Polyaniline (PANI) fibers as well as silica nanoparticle decorated PANI (silica-PANI) fibers were successfully synthesized as a dispersed phase of an electrorheological (ER) fluid. The fibers obtained through interfacial polymerization were about 300-400 nm in diameter and 2-5 μm long. Then the fibers were redispersed in ethanol containing tetraethyl orthosilicate (TEOS), and silica nanoparticles were formed on the surface of the fibers through a modified Stöber method. The ER characteristics of the ER fluids based on pure PANI fibers and silica-PANI fibers were examined under various electric field strengths using a rotational rheometer, demonstrating slight different flow curves for the silica-based ER fluid. © 2009 Elsevier B.V. All rights reserved.

Lohani C.R.,Inha University | Lee K.-H.,Inha University
Sensors and Actuators, B: Chemical | Year: 2010

We investigated the effect of ferric ion absorbance on the detection of Fe3+ by fluorescent sensors. The presence of Fe3+ ion resulted in a decrease of emission intensity of fluorophores (naphthalene, dansyl chloride, and anthracene) excited with UV light. Absorbance spectrum and reversibility studies revealed that the decrease in emission intensity of the fluorophores without a receptor moiety was mainly due to the absorbance of ferric ion. We synthesized fluorescent chemical sensors consisting of the receptor for Fe3+ and naphthyl fluorophore or dansyl fluorophore, respectively. The sensors detected Fe3+ by a fluorescent quenching effect of Fe3+, as well as by the absorbance effect of Fe3+. The absorbance of Fe3+ has a considerable interference effect on the excitation of the fluorophore with a short excitation wavelength range in UV light. Hence, fluorophores with longer excitation wavelength are highly recommended in the synthesis of fluorescent sensors for Fe3+. © 2009 Elsevier B.V. All rights reserved.

Kim K.-S.,Inha University | Park S.-J.,Inha University
Synthetic Metals | Year: 2010

The transmittance and electrical properties of conductive multi-walled carbon nanotubes (MWCNTs)/poly(methyl methacrylate) (PMMA) films were investigated as a function of MWCNT content. The effect of silver doped MWCNTs (Ag-MWCNTs) on the surface resistance of the films was also determined. The surface characteristics of acid-treated MWCNTs were confirmed using FT-Raman. The dispersion and formation of a conductive network of MWCNTs in PMMA were observed by SEM and AFM analyses. The transmittance of the films observed by UV-vis-NIR was decreased from 89% to 64%, and the surface resistance of the films was decreased from 392 MΩ/sq to 293 kΩ/sq while increasing the MWCNT content due to the increase of the electron conductive pathway. The Ag-MWCNTs/PMMA films showed a lower surface resistance about 2-4 times than that of MWCNTs/PMMA films. This was probably due to the synergic effect induced between MWCNTs and Ag. © 2009 Elsevier B.V. All rights reserved.

Singh P.,Inha University | Jung J.H.,Inha University
Physica B: Condensed Matter | Year: 2010

We investigate the effect of oxygen annealing on magnetic, electric and magnetodielectric properties of Ba-doped BiFeO3, Bi0.75Ba0.25FeO3 (BBFO) bulk. Magnetization, resistivity, polarization and magnetodielectric measurements reveal that as-grown BBFO shows weak ferromagnetism, leaky dielectric behavior with activation energy of 0.40 eV and 0.06% change of dielectric constant at 60 kOe. However, oxygen-annealed BBFO at 850 °C shows antiferromagnetism, leaky dielectric behavior with activation energy of 0.73 eV and 0.04% change of dielectric constant at 60 kOe. These differences are discussed by the formation of Fe3+ valence with oxygen vacancy in as-grown BBFO, and the formation of mixed Fe3+ and Fe4+ valences without oxygen vacancy for oxygen-annealed BBFO. © 2009 Elsevier B.V. All rights reserved.

Park J.Y.,Inha University | Choi S.-W.,Inha University | Kim S.S.,Inha University
Nanoscale Research Letters | Year: 2010

We report a novel method for fabricating a highly sensitive chemical sensor based on a ZnO nanorod array that is epitaxially grown on a Pt-coated Si substrate, with a top-top electrode configuration. To practically test the device, its O 2 and NO 2 sensing properties were investigated. The gas sensing properties of this type of device suggest that the approach is promising for the fabrication of sensitive and reliable nanorod chemical sensors. © 2009 to the authors.

Seo M.-K.,Inha University | Park S.-J.,Inha University
Current Applied Physics | Year: 2010

In this work, air-oxidized multi-walled carbon nanotube (MWCNT) electrodes have been prepared from catalytically grown MWCNTs of high purity and narrow diameter distribution. The experimental results show that air-oxidation modifies the intrinsic structure of individual MWCNTs and a little improves the dispersity of the MWCNTs. The specific capacitances of the electrodes in electric double layer capacitors (EDLCs) based on oxidized MWCNTs are obviously improved through air-oxidation. The specific capacitance of 50 F/g is obtained in the air-oxidized MWCNTs at 600 °C on a single cell device with 35 wt% H2SO4 as an electrolyte. This is probably increased BET specific surface area and mesopore volume of the oxidized MWCNT electrode materials of EDLCs. These properties are, therefore highly desirable for the development of electrochemical capacitors with high power and long cycle life. © 2009 Elsevier B.V. All rights reserved.

Kim H.W.,Inha University | Kebede M.A.,Inha University | Kim H.S.,Inha University
Current Applied Physics | Year: 2010

Al-doped ZnO (AZO) shell layers were coated on core ZnO nanowires to fabricate ZnO/AZO core-shell nanowires. The energy-dispersive X-ray spectra confirmed the presence of Al element in the shell layers, and the lattice resolved transmission electron microscopy image revealed that these layers corresponded to the hexagonal ZnO structure. The X-ray diffraction pattern exhibited a shift of the ZnO peaks, suggesting the substitutive incorporation of Al into the ZnO lattice. The A1(LO) mode line in the Raman spectra was enhanced by the AZO coating. In the photoluminescence measurements, the AZO coating enhanced the intensity ratio of the UV to green emission. © 2009 Elsevier B.V. All rights reserved.

Kim K.-S.,Inha University | Kim I.-J.,Korea Electrotechnology Research Institute | Park S.-J.,Inha University
Synthetic Metals | Year: 2010

In this work, silver (Ag) nanoparticles were deposited on graphene sheets by chemical reduction and Ag-doped graphene (Ag-GR)/polypyrrole (PPy) nanocomposites were prepared by oxidation polymerization. The effect of the Ag-GR incorporation on the electrochemical properties of the PPy nanocomposites was investigated. It was found that highly dispersed Ag nanoparticles (2-5 nm) could be deposited onto the GR and that Ag-GR was successfully coated by PPy. From the cyclic voltammograms, Ag-GR showed higher electrocatalytic activity than that of pristine GR. Furthermore, the Ag-GR/PPy showed remarkably increased current density, quicker response, and better specific capacitance compared with GR/PPy. This indicates that, due to their high electrocatalytic activity, the Ag nanoparticles deposited onto the GR serve as an efficiency catalyst to improve electrochemical performance of the GR/PPy and that they resulted in the increase of the charge transfer between GR and PPy by bridge effect. © 2010 Elsevier B.V.

Hahn J.,Inha University | Ham B.S.,Inha University
New Journal of Physics | Year: 2011

Quantum coherence control of two-pulse photon echoes has been demonstrated for a rephasing halt, resulting in storage-time extension using atom phase-controlled optical deshelving (optical locking) in a backward propagation scheme for the additional benefit of echo intensity enhancement. Compared with conventional forward two-pulse photon echoes, the backward two-pulse photon echo efficiency is enhanced by 15-fold even in a dilute sample, and the storage time is lengthened by spin dephasing time accelerated by spin inhomogeneous broadening. The mechanism of delayed photon echoes via optical locking is due to the temporal hold of the rephasing process by coherent population transfer to a robust spin state. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Jeon H.-Y.,Inha University
Advanced Materials Research | Year: 2014

8 Geotextiles (; 4 woven and 4 nonwoven types), 4 geogrids and 2 geocomposites of [nonwoven/fibers/nonwoven] structure were used as raw materials and the different seaming methods were applied to compare the seam properties of 3 geosynthetics and transmissivity of geocomposites. Tensile strength retentions of these geosynthetics were evaluated as the degree of damage by chemical degradation. Woven geotextiles showed the higher seam strength in the order (SSd-1 < SSd-2) > (SSa-1 < SSa-2) > geospacer without regard to the design strength. For nonwoven geotextiles, the order of seam strength is geospacer > (SSa-1 < SSa-2). Geogrids showed the higher seam strength in the order of band > geospacers but reduction factors were increased in the order of band > geospacer without regard to the geogrid's compositions. Finally, geocomposites showed the higher seam strength in the order of geospacer > (SSa-1 < SSa-2) but showed the transmissivity in the order of geospacer > (SSa-1 > SSa-2) without regard to the kinds of filled fibers and weight of geocomposite. © (2014) Trans Tech Publications, Switzerland.

Zhang W.L.,Inha University | Liu Y.D.,Inha University | Choi H.J.,Inha University
Journal of Materials Chemistry | Year: 2011

Core-shell structured polystyrene (PS)-graphene oxide (GO) microspherical particles were synthesized by adsorbing the GO sheets on the PS surface through a strong π-π stacking interaction. As core materials, monodispersed PS microspheres were prepared using a dispersion polymerization, while the shell part of GO was synthesized by a modified Hummers method. Morphology of the composite particles was studied by both scanning electron microscopy and transmission electron microscopy, while their structure and chemical components were examined via X-ray diffraction and Fourier-transform infrared spectroscopy, respectively. All the data confirmed the coexistence of PS and GO with the expected core-shell s