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Korea University is a private research university located in Seoul, South Korea. It was established in 1905, making it one of the oldest institutions of higher education in South Korea.The student body consists of over 20,000 undergraduate students and over 10,000 graduate students. The university’s academic breadth is extensive with its 81 departments in 19 colleges and divisions, and 18 graduate schools and it has over 1,500 full-time faculty members with over 95% of them holding Ph.D. or equivalent qualification in their field. The Korea University Alumni Association consists of more than 280,000 university graduates.Korea University is a research institution consisting of sixteen undergraduate colleges and twenty graduate divisions.The university is notable in South Korean history for being the first educational institution to offer academic programs in various disciplines, such as law, economics, and journalism. Korea University is particularly well known for its College of Law, which is widely considered to be one of the most prestigious undergraduate law programs in South Korea. Korea University also has auxiliary educational facilities such as the Institute of Foreign Language Studies, the Institute for Continuing Education, the Institute of International Education, and the Center for Teaching and Learning. There are 115 research institutes, including the Battelle@KU Laboratory, the Ilmin International Relations Institute, and the Center for Information Security Technologies. Wikipedia.

Choi Y.K.,Korea University
Current topics in microbiology and immunology | Year: 2013

Swine influenza viruses (SIVs) are respiratory viral pathogens of pigs that are capable of causing serious global public health concerns in human. Because of their dual susceptibility to mammalian and avian influenza A viruses, pigs are the leading intermediate hosts for genetic reassortment and interspecies transmission and serve as reservoirs of antigenically divergent human viruses from which zoonotic stains with pandemic potential may arise. Pandemic influenza viruses emerging after the 1918 Spanish flu have originated in asia. Although distinct lineages of North American and European SIVs of the H1N1, H3N2, and HiN2 subtypes have been widely studied, less is known about the porcine viruses that are circulating among pig populations throughout Asia. The current review understanding of Contemporary viruses, human infection with SIVs, and the potential threat of novel pandemic strains are described, Furthermore, to best use the limited resources that are available for comprehensive genetic assessment of influenza, consensus efforts among Asian nations to increase epidemiosurveillance of swine herds is also strongly promoted.

Yoo Y.,Korea University
Korean Journal of Pediatrics | Year: 2013

Severe childhood asthma is a complicated and heterogeneous disorder with distinct phenotypes. Children with severe asthma have more persistent symptoms despite receiving treatment, more atopy, greater airway obstruction, and more air trapping than those with mild-to-moderate asthma. They also have higher morbidity and substantial airflow limitations that persist throughout adulthood. Identification of the phenotype clusters and endotypes of severe asthma can allow further modulation of the natural history of severe asthma and may provide the pathophysiologic rationale for appropriate management strategies. © 2013 by The Korean Pediatric Society.

Lee K.B.,Korea University | Wong V.,University of Sussex
Technovation | Year: 2011

Few studies have attempted to investigate the following: (1) whether the firms core capabilities or resources and routines (e.g., integration among functions) for product development, in the presence of environmental dynamics, become incumbent inertia or core rigidities? and (2) how environmental dynamics affect the influence of a project teams implementation capabilities in the new product development (NPD) process on new product launch performance? This study approaches these questions by addressing the three most indispensable NPD process components (i.e., marketing, technology, and organization) and incorporating new moderators, namely pace of technological change and competitive intensity, within a single study. It specifically examines the extent to which the latter two external environmental variables moderate the impact of NPD practices on new product launch outcome. Data obtained from a survey of NPD projects developed and launched by Korean manufacturers suggest that environmental dynamics would reduce the contribution of functional-specific sources of advantage (resources) and project-specific sources of advantage (e.g., integration among functions) to organizational implementation capabilities (i.e., a project teams proficiency in executing NPD activities). Moreover, the research also shows that market dynamics may increase the contribution of organizational implementation capabilities to NPD project performance. © 2011 Elsevier Ltd. All rights reserved.

Park C.-S.,Sangmyung University | Ko S.-J.,Korea University
IEEE Signal Processing Magazine | Year: 2014

The discrete Fourier transform (DFT) produces a Fourier representation for finite-duration data sequences. In addition to its theoretical importance, the DFT plays a key role in the implementation of a variety of digital signal-processing algorithms. Several algorithms including the fast Fourier transform (FFT) and the Goertzel algorithm have been introduced for the fast implementation of the DFT [1], [2]. © 1991-2012 IEEE.

Kim J.,Korea University
Computers and Education | Year: 2013

This study attempts to examine how students participate and interact in different discussion modules organized with different group size in an online environment. It adopts a case study methodology where full semester online course with two small-group and three class-wide discussion forums was examined. The researcher counted the number of messages and hits (i.e. the number of students' clicks on other messages) and analyzed that to classify the level of interactivity of every individual message into four categories, i.e. independent, quasi-interactive, interactive (elaborative) and interactive (negotiating). It found that the class guidelines and active encouragement by the instructor had contributed to the high number of total messages and hits representing students' overall participation in all discussion forums. However, large discussion forums in the course had their limitations in promoting higher level of interactivity among the students. On the other hand, two small-group discussion forums had a higher number (by 21%) of enhanced interactivity (elaborating and negotiating mode). The study then concludes that a high quality participation in a large online class could be effected through sub-grouping. It further alludes that other practices should be taken into consideration to promote interactivity in discussion. © 2012 Elsevier Ltd. All rights reserved.

Fahim M.,Korea University
Methods in molecular biology (Clifton, N.J.) | Year: 2013

RNA-mediated virus resistance is increasingly becoming a method of choice for antiviral defense in plants when effective natural resistance is unavailable. In this chapter we discuss the design principles of artificial micro RNA (amiRNA), in which a natural miRNA precursor gene is modified to target a different species of RNA, in particular viral RNA. In addition, we explore the advantages and effectiveness of multiple amiRNAs within one polycistronic amiRNA precursor against a virus, as illustrated with Wheat streak mosaic virus, WSMV. The judicious selection of amiRNAs, which are sequences of short length as compared to other related methodologies of RNA interference, greatly assists in avoiding unintended off-targets in the host plant. The viral sequences targeted can be genomic or replicative and should be derived from conserved regions of the published WSMV genome. In short, using published folding and miRNA selection rules and algorithms, candidate miRNA sequences are selected from conserved regions between a number of WSMV genomes, and are BLASTed against wheat TIGR ESTs. Five miRNAs are selected that are least likely to interfere with the expression of transcripts from the wheat host. Then, the natural miRNA in each of the five arms of the polycistronic rice miR395 is replaced in silico with the chosen artificial miRNAs. This artificial precursor is transformed into wheat behind a ubiquitin promoter, and its integration into transformed wheat plants is confirmed by PCR and Southern blot analysis. We have demonstrated the effectiveness of this methodology using an amiRNA precursor that we have termed Fanguard. The processing of amiRNAs in transgenic leaves is verified through splinted ligation assay, and the functionality of the transgene in preventing viral replication is verified by virus bioassay. Resistance is confirmed using mechanical virus inoculation over two subsequent generations. This example demonstrates the potential of polycistronic amiRNA to achieve stable immunity to economically important viruses.

Ahn C.K.,Korea University
International Journal of Electronics | Year: 2013

This article proves that there exists an l2-l∞ stability criterion for fixed-point state-space digital filters without overflow oscillations. By the l2-l∞ stability property, this new criterion guarantees asymptotic stability and attenuates the effect of external interference to a prescribed l2-l∞-induced norm bound. We represent this stability criterion as the form of linear matrix inequality, which can be solved easily using the existing numerical packages. Finally, we present an illustrative example, which shows the effectiveness of the proposed stability criterion. © 2013 Taylor and Francis Group, LLC.

This paper applies online analytic processing (OLAP), a widely accepted database analysis technique, to a product data management (PDM) database to evaluate the performance of in-progress product development. This paper introduces a set of processing key performance indicators (KPIs) that can measure ongoing product development. To convert and analyze operational data in a PDM database with interactive OLAP operations, this study proposes a multidimensional data model specified by product facts with associated dimensions. The model is implemented using a commercial OLAP engine, and applied to a database supported by a prototype PDM system. The OLAP engine allows analysts to interactively evaluate the performance of in-progress product development in a multidimensional data space. This is a far more flexible and efficient approach than other result-oriented static evaluation approaches. © 2014 Elsevier B.V.

In this paper, an input-to-state stability (ISS) approach is used to derive two new criteria for the realization of fixed-point state-space and direct-form digital filters with saturation overflow nonlinearity and external interference via augmented Lyapunov functions. The two proposed realization criteria ensure ISS for external interference. Moreover, these criteria guarantee asymptotic stability without external interference. They take the form of linear matrix inequality (LMI) and, hence, are computationally tractable. Illustrative examples demonstrate the effectiveness of the two proposed criteria. © 2013 Elsevier B.V. All rights reserved.

Ahn C.K.,Korea University
International Journal of Control | Year: 2014

In this paper, we use an induced l∞ approach to create a new filter with a finite impulse response (FIR) structure for state-space models with external disturbances. This filter is called an induced l ∞ FIR filter (ILIFF). The proposed ILIFFs gain matrix can be determined by solving a linear matrix inequality problem for a fixed positive scalar variable. An illustrative example is given to demonstrate the effectiveness of the ILIFF. © 2013 © 2013 Taylor & Francis.

Ahn C.K.,Korea University
IEEE Signal Processing Letters | Year: 2014

Recently, Ahn's criteria were proposed for dealing with deterministic external interference with finite energy in two-dimensional (2-D) digital filters. However, these criteria fail for cases where the 2-D filters have stochastic noise. In this letter, we propose a new criterion for overflow oscillation elimination of 2-D digital filters in the Roesser model with Wiener process noise. The criterion guarantees the asymptotic stability as well as a 2-D expected power bound. Thus, it can ascertain the attenuation of the effect of Wiener process noise to a prescribed level. This criterion is also expressed by linear matrix inequality (LMI). A numerical example is provided to show the usefulness of the proposed result. © 1994-2012 IEEE.

Song J.,Korea University
Advances in Mechanical Engineering | Year: 2013

Three active front-steering (AFS) controllers were developed to enhance the lateral stability of a vehicle. They were designed using proportional-integral- derivative (PID), fuzzy-logic, and sliding-mode control methods. The controllers were compared under several driving and road conditions with and without the application of braking force. A 14-degree-of-freedom vehicle model, a sliding-mode antilock brake system (ABS) controller, and a driver model were also employed to test the controllers. The results show that the three AFS controllers allowed the yaw rate to follow the reference yaw rate very well, and consequently the lateral stability improved. On a split- road, the controllers forced the vehicle to proceed straight ahead. The results also verify that the driver model can sufficiently control the vehicle to allow it to follow a desired path. © 2013 Jeonghoon Song.

Paik K.,Korea University
Environmental Modelling and Software | Year: 2012

The choice of a flow path extraction method is a key issue in numerical simulation of fluvial landscape evolution. Most whole landscape evolution models use the deterministic eight-neighbor flow direction retrieval method (D8), which generates angular uncertainty in determined flow paths. In the modeling of landscape evolution, the uncertainty generated at each local flow direction accumulates over both space and time. Recently, a new method which searches for flow paths over global scale, called global D8 or GD8, was proposed as an alternative to D8. GD8 relaxes uncertainty generated at a local level over an entire flow path while still defining specific flow paths without artificial dispersion. On the basis of these advantages of GD8 demonstrated for static landscapes, this paper presents the first landscape evolution model that uses GD8, i.e., a new Landscape Evolution model using Global Search (LEGS). Using LEGS, the difference between D8 and GD8 simulations is investigated with focus on both evolution rate and resulting topography. Theoretical landscapes simulated by LEGS are evaluated using typical characteristics of natural river networks such as concave profiles, Hack's law, the power-law exceedance probability distribution of contributing areas, and the power-law variogram. © 2012 Elsevier Ltd.

Stoeger J.A.,University of Minnesota | Choi J.,Korea University | Tsapatsis M.,University of Minnesota
Energy and Environmental Science | Year: 2011

Continuous MFI-type zeolite membranes were fabricated on porous stainless steel tube supports by secondary (seeded) growth. The physical attachment of zeolite seed particles was initiated through sonication assistance on unmodified supports. Despite a sparse seed layer, a single hydrothermal growth step reliably led to c-/h0h-out-of-plane-oriented pure-silica MFI membranes. Rapid thermal processing was applied to as-synthesized membranes, extending the findings of a previous report on controlling the density of grain boundary defects. The RTP-treated membranes showed an improved separation factor of 29 for p-/o-xylene with a maximum p-xylene permeance of 6.6 × 10 -8 mol m -2 s -1 Pa -1, while conventionally (slowly) calcined counterparts had a maximum separation factor and p-xylene permeance of 3-4 and 2.7-4.5 × 10 -8 mol m -2 s -1 Pa -1, respectively. The membranes also showed insensitivity to temperature for n-/i-butane separation performance (separation factor ca. 15 and n-butane permeance ca. 1.3 × 10 -7 mol m -2 s -1 Pa -1), while conventionally calcined ones exhibited a significant decrease in the separation factor with temperature. Pervaporation measurements from a dilute aqueous feed that exploited the hydrophobicity of RTP-treated membranes revealed their potential use in bioalcohol recovery processes from fermentation broths, specifically for ethanol (total flux and separation factor of 1.2 kg m -2 h -1 and 43, respectively) and n-butanol (total flux and separation factor of 0.11 kg m -2 h -1 and 21, respectively) extraction from the aqueous phase. © 2011 The Royal Society of Chemistry.

Lee S.,Korea University
Water International | Year: 2015

This study aims to evaluate the extent to which the cooperative relationship between China and the downstream countries in the Mekong River basin has evolved in relation to the various benefits shared between these riparian countries from the 1990s to the present. Benefit sharing is deployed as an analytical framework. Larger benefits obtained through cooperation have led China to become more cooperative with the downstream countries, as seen in the Greater Mekong Subregion programme. The establishment of a new form of cooperation in the river basin hinges upon the ability to share the socio-economic, political, and energy security benefits. © 2014, © 2014 International Water Resources Association.

Park S.C.,Kangwon National University | Chun H.J.,Korea University
Gut and Liver | Year: 2013

No standard adjuvant or palliative chemotherapy regimen has been internationally approved for patients with advanced gastric cancer. Adjuvant chemoradiotherapy is administered prior to surgery and is used in the Unitied States, and intensified chemotherapy is administered prior to and after surgery and is used in Europe. Limited D1 dissections are also frequently performed in the United States and Europe. In Korea, patients undergoing D2 resection appear to benefit from postoperative adjuvant chemotherapy using S-1 or capecitabine plus oxaliplatin. Fluoropyrimidine, platinum, taxane, epirubicin, and irinotecan may be employed alone or in combination as a first-line therapy in a palliative chemotherapy regimen. In Asia, an orally administered fluoropyrimidine, such as capecitabine or S-1, is favored over the continuous infusion of 5-fluorouracil because of its convenience. Trastuzumab has been integrated into the current standard chemotherapy for human epidermal growth factor receptor 2-overexpressing gastric cancers. There is currently no standard regimen for secondary palliative chemotherapy. Clinical studies of several targeted therapies are ongoing.

Song J.,Korea University
Journal of Mechanical Science and Technology | Year: 2013

In this study, four integrated dynamics control (IDC) systems abbreviated as IDCB, IDCS, IDCF, and IDCR are developed, evaluated and compared. IDC systems were integrated with brake and steer control systems to enhance lateral stability and handling performance. To construct the IDC systems, a vehicle model with fourteen degrees of freedom, a fuzzy logic controller, and a sliding mode ABS controller were used. They were tested with various steering inputs when excessive full brake pressure or no brake pressure was applied on dry asphalt, wet asphalt, a snow-covered paved road, and a split-μ road. The results showed that an IDC-equipped vehicle improved lateral stability and controllability in every driving condition compared to an ABS-equipped vehicle. Under all road conditions, IDC controllers enabled the yaw rate to follow the reference yaw rate almost perfectly and reduced the body slip angle. On a split-road, IDCB, IDCS, IDCF, and IDCR vehicles drove straight ahead with only very small deviations. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Lee Y.H.,Korea University
Annals of Laboratory Medicine | Year: 2015

The object of this review is to help readers to understand meta-analysis of genetic association study. Genetic association studies are a powerful approach to identify susceptibility genes for common diseases. However, the results of these studies are not consistently reproducible. In order to overcome the limitations of individual studies, larger sample sizes or meta-analysis is required. Meta-analysis is a statistical tool for combining results of different studies on the same topic, thus increasing statistical strength and precision. Meta-analysis of genetic association studies combines the results from independent studies, explores the sources of heterogeneity, and identifies subgroups associated with the factor of interest. Meta-analysis of genetic association studies is an effective tool for garnering a greater understanding of complex diseases and potentially provides new insights into gene-disease associations. © The Korean Society for Laboratory Medicine.

PURPOSE:: To evaluate the effect of photobleaching on fundus autofluorescence (FAF) images in acute central serous chorioretinopathy. METHODS:: We obtained prephotobleaching and postphotobleaching images using an Optomap 200Tx, and photobleaching was induced with a Heidelberg Retina Angiograph 2. Degrees of photobleaching were assessed as grayscale values in Optomap images. Concordances among the three kinds of images were analyzed. Hyper-AF lesions in prephotobleaching images were classified as Type 1 (changed to normal-AF after photobleaching) and Type 2 (unchanged after photobleaching). The FAF composite patterns of central serous chorioretinopathy lesions were classified as diffuse or mottled. Initial and final best-corrected visual acuity, central retinal thickness, and disease duration were compared according to fovea FAF type. RESULTS:: Forty-one eyes of 41 patients were analyzed. The lesion brightness of postphotobleaching Optomap FAF showed greater concordance with Heidelberg Retina Angiograph 2 FAF (94.74%) than the prephotobleaching Optomap FAF (80.49%). Eyes with Type 1 fovea had greater initial and final best-corrected visual acuity (20/23 vs. 20/41, 20/21 vs. 20/32, P < 0.0001, P = 0.001, respectively) and shorter disease duration (19.68 ± 12.98 vs. 51.55 ± 44.98 days, P = 0.043) than those with Type 2 fovea. However, eyes with diffuse Type 2 fovea had only lower initial and final best-corrected visual acuity (20/23 vs. 20/45, 20/21 vs. 20/36, P < 0.0001, P < 0.0001, respectively) than those with Type 1 fovea. CONCLUSION:: Understanding the photobleaching effect is necessary for the accurate interpretation of FAF images. Furthermore, comparing prephotobleaching and postphotobleaching FAF images may be helpful for estimation of lesion status in central serous chorioretinopathy. © 2016 by Ophthalmic Communications Society, Inc.

Sohn K.R.,Korea University
Sensors and Actuators, A: Physical | Year: 2010

All-fiber-optic liquid sensors were developed to detect liquid solutions and monitor the submersion. Their operating principle is based on Fresnel's laws of reflection at the end-face of silica fibers. Two types of sensing probes were fabricated using single-mode and multi-mode fibers. Their spectral responses were measured with respect to the intensity modulation caused by a change in the refractive index of the surrounding media. By comparing the optical output power of the sensor on exposing the probe to air and water, its potential as a sensitive submersion sensor was proved. The difference in the output power levels between exposure to air and water was 10 dB. Further, a fiber-Bragg grating (FBG) spliced to the sensor head was used for remote monitoring of whether the optical fiber or sensor head were damaged or not. The possibility of self-diagnosis of the sensor was demonstrated. © 2010 Elsevier B.V. All rights reserved.

Song G.G.,Korea University
International journal of rheumatic diseases | Year: 2013

The aim of this study was to analyze the results of interferon-gamma release assays (IGRAs) and tuberculin skin tests (TST) performed to detect latent tuberculosis infection (LTBI) in patients with rheumatoid arthritis (RA). Interferon-γ release assays and TST test results were summarized and systematically reviewed. Four hundred and five RA patients and 339 controls that underwent IGRA and/or TST were identified in seven studies. Five studies were case-control studies and two were cross-sectional studies. Among RA patients, the IGRA positivity rate was 31.6% (89/282; range 11.4%-44.6%), and the TST positivity rate was 23.0% (78/339; range from 14.60% to 45%). Concordance rates ranged from 40% to 76% and discordance rates from 24% to 29.7%. Agreement between IGRAs and TST in RA was poor (69.6%, k = 0.33, 95% CI 0.188-0.478). The IGRA positivity rate was 31.0% in RA and 40.0% in controls, which was not significant (relative risk [RR] 0.802, 95% CI 0.629-1.023, P = 0.075). The TST positivity rate was 24.7% in RA and 50.5% in controls, and this difference was not significant (RR 0.680, 95% CI 0.331-1.339, P = 0.295). Positivity rates of IGRA and TST were 31.6 and 23.0%, respectively, in RA patients. Agreement between IGRA and TST results in RA was poor. Our data suggest that both IGRA and TST are needed to detect LTBI in RA. © 2013 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

Liver fibrosis is characterized by accumulation of extracellular matrix, and activated hepatic stellate cells (HSCs) are the primary source of the fibrotic neomatrix and considered as therapeutic target cells. We previously showed that albumin in pancreatic stellate cells (PSCs), the key cell type for pancreatic fibrogenesis, is directly involved in the formation of vitamin A-containing lipid droplets, inhibiting PSC activation. In this study, we evaluated the anti-fibrotic activity of both albumin and retinol binding protein-albumin domain III fusion protein (R-III), designed for stellate cell-targeted delivery of albumin III, in rat primary HSCs and investigated the underlying mechanism. Forced expression of albumin or R-III in HSCs after passage 2 (activated HSCs) induced lipid droplet formation and deactivated HSCs, whereas point mutations in high-affinity fatty acid binding sites of albumin domain III abolished their activities. Exogenous R-III, but not albumin, was successfully internalized into and deactivated HSC-P2. When HSCs at day 3 after plating (pre-activated HSCs) were cultured in the presence of purified R-III, spontaneous activation of HSCs was inhibited even after passage 2, suggestive of a potential for preventive effect. Furthermore, treatment of HSCs-P2 with R-III led to a significant reduction in both cytoplasmic levels of all-trans retinoic acid and the subsequent retinoic acid signaling. Therefore, our data suggest that albumin deactivates HSCs with reduced retinoic acid levels and that R-III may have therapeutic and preventive potentials on liver fibrosis.

Kang E.-Y.,Korea University
Journal of the Korean Medical Association | Year: 2015

Lung cancer is the leading cause of cancer-related death worldwide. Most patients are diagnosed with advanced disease, resulting in a poor prognosis. Screening may induce the early detection of lung cancer and early detection of lung cancer may reduce lung cancer-related mortality. Recently, the National Lung Screening Trial has demonstrated that lung cancer screening with low-dose chest computed tomography (LDCT) showed a 20% reduction in lung cancer-related mortality and a 6.7% decrease in all-cause mortality in the US. Based on the results of National Lung Screening Trial, various lung cancer-related societies recommend lung cancer screening using LDCT in asymptomatic populations at high risk based on old age and a heavy smoking history. For effective and responsible lung cancer screening, LDCT should be performed at sites providing high-quality low-radiation exposure computed tomography (CT). LDCT must be performed with multidetector helical CT in a single breath-hold and use adequate technical parameters. CT is interpreted accurately by qualified physicians. And structured reporting and management system should be recommended for high quality reporting and medical outcomes monitoring. Adverse events associated with LDCT screening may include a high detection rate of lung nodules and high false positive results, overdiagnosis, and relatively high radiation exposure. However, lung cancer screening with LDCT can result in more benefits than harms when performed in settings with high quality screening programs. © Korean Medical Association.

Middle East respiratory syndrome (MERS) is an emerging zoonosis caused by the novel MERS corona virus isolated in 2012. Most MERS cases have been reported from Arab countries of the Middle East, including Saudi Arabia, United Arab Emirates, Qatar, and Jordan. There have been a few imported cases in many countries, but the exception is Korea, which reported 186 confirmed cases originating from one imported case in a two-month outbreak in 2015. There are many lessons to be learned from the MERS outbreak in Korea, among them, management of contacts. The definition of "close contact" used by the Korean Centers for Disease Control and Prevention (KCDC) for MERS response was not clear and not compatible with the definition of the World Health Organization. This incorrect definition allowed the KCDC make serious mistakes in contact tracing and management in the early epidemic stage of MERS. After the rapid expansion of the outbreak, the KCDC redefined a "close contact" according to the definition of the US CDC. The total number of close contacts was 16,693 in this outbreak, and they were all forced to conduct a self-quarantine for 14 days after the last contact with a MERS patient. It was not clear whether self-quarantine of close contacts was effective to control the outbreak. Given the lack of prepared guidelines or a social support system for them, these measures for the massive number of asymptomatic contacts caused a great deal of confusion in the field A clear response guideline is needed for contact management based on robust evidence from this MERS epidemic in Korea. © Korean Medical Association.

Hameed I.A.,Korea University
International Journal of Innovative Computing, Information and Control | Year: 2010

The efficiency of plant production in greenhouses relies on the measurements provided by several electronic sensors located inside and outside the greenhouse. Environmental conditions such as the direct exposure of sensors to sunlight and the deterioration of connections between sensors and the controllers could result in very noisy and incomplete measurements which may impair the greenhouse operation. It may also increase the number of false alarms received from fault detection and isolation (FDI) systems and reduce its detection capability which, in turn, may result in significant financial losses to the grower. The objective of this paper is to explore the ability of the Extended Kalman Filter (EKF) for improving the efficiency of the greenhouse climate controller by using the on-line estimated air temperature and humidity ratio inside the greenhouse as the controlled variables instead of the observed noisy states. The result suggests that the EKF is able to improve the efficiency of the greenhouse climate control and also increase the sensitivity of failure detectability. This approach is not limited to greenhouses but it is also applicable to any control system installed in a noisy environment. © ICIC International 2010.

Kim B.,Stanford University | Sung Y.S.,Korea University | McClure S.M.,Stanford University
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2012

People generally prefer to receive rewarding outcomes sooner rather than later. Such preferences result from delay discounting, or the process by which outcomes are devalued for the expected delay until their receipt. We investigated cultural differences in delay discounting by contrasting behaviour and brain activity in separate cohorts ofWestern (American) and Eastern (Korean) subjects. Consistent with previous reports, we find a dramatic difference in discounting behaviour, with Americans displaying much greater present bias and elevated discount rates. Recent neuroimaging findings suggest that differences in discounting may arise from differential involvement of either brain reward areas or regions in the prefrontal and parietal cortices associated with cognitive control. We find that the ventral striatum is more greatly recruited in Americans relative to Koreans when discounting future rewards, but there is no difference in prefrontal or parietal activity. This suggests that a cultural difference in emotional responsivity underlies the observed behavioural effect. We discuss the implications of this research for strategic interrelations between Easterners and Westerners. © 2012 The Royal Society.

Hwang Y.H.,Konyang University | Kim Y.Y.,Korea University | Kim H.K.,Konyang University | Sohn Y.H.,Konyang University
Ophthalmology | Year: 2013

Purpose: To investigate the ability of clock-hour, deviation, and thickness maps of Cirrus high-definition spectral-domain optical coherence tomography (HD-OCT) in detecting retinal nerve fiber layer (RNFL) defects identified in red-free fundus photographs in eyes with early glaucoma (mean deviation >-6.0 dB). Design: Cross-sectional study. Participants: Two hundred ninety-five eyes with glaucomatous RNFL defects with clear margins observed in red-free fundus photographs and 200 age-, sex-, and refractive error-matched healthy eyes were enrolled. Methods: The width and location of RNFL defects were evaluated by using the red-free fundus photograph. When a RNFL defect detected by red-free fundus photograph did not present as (1) yellow/red codes in the clock-hour map, (2) yellow/red pixels in the deviation map, or (3) blue/black areas in the thickness map, the event was classified as a misidentification of a photographic RNFL defect by Cirrus HD-OCT. In healthy eyes, the presence of false-positive RNFL color codes of Cirrus HD-OCT maps was investigated. Main Outcome Measures: The prevalence of and factors associated with the (1) misidentification of photographic RNFL defects by Cirrus HD-OCT in eyes with glaucoma and (2) false-positive RNFL color codes of Cirrus HD-OCT maps in healthy eyes were assessed. Results: Among the 295 red-free fundus photographic RNFL defects from 295 eyes with glaucoma, 83 (28.1%), 27 (9.2%), and 0 (0%) defects were misidentified in the clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively. Fifty-six defects (19.0%) were misidentified only in the clock-hour map and 27 (9.2%) in both the clock-hour and deviation maps. The misidentification of photographic RNFL defects by Cirrus HD-OCT was associated with a narrower width and a temporal location of RNFL defects (P<0.05). Among the 200 healthy eyes, 25 (12.5%), 30 (15.0%), and 12 (6.0%) eyes had false-positive RNFL color codes in clock-hour, deviation, and thickness maps of Cirrus HD-OCT, respectively. Conclusions: Among the clock-hour, deviation, and thickness maps obtained with Cirrus HD-OCT, the thickness map showed the best diagnostic ability in detecting photographic RNFL defects. The RNFL thickness map may be a useful tool for the detection of RNFL defects in eyes with early glaucoma. Financial Disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article. © 2013 American Academy of Ophthalmology.

Park Y.,Seoul National University | Min J.-K.,Korea University | Shim K.,Seoul National University
Proceedings of the VLDB Endowment | Year: 2013

The skyline operator and its variants such as dynamic skyline and reverse skyline operators have attracted considerable attention recently due to their broad applications. However, computations of such operators are challenging today since there is an increasing trend of applications to deal with big data. For such data-intensive applications, the MapReduce framework has been widely used recently. In this paper, we propose efficient parallel algorithms for processing the skyline and its variants using MapReduce. We first build histograms to effectively prune out non-skyline (non-reverse skyline) points in advance. We next partition data based on the regions divided by the histograms and compute candidate (reverse) skyline points for each region independently using MapReduce. Finally, we check whether each candidate point is actually a (reverse) skyline point in every region independently. Our performance study confirms the effectiveness and scalability of the proposed algorithms. © 2013 VLDB Endowment.

Suh S.J.,Korea University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2013

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in Korea. Curative treatment is only possible when the disease is diagnosed at the early stage. The prognosis of patients with HCC is even dismal in advanced stages. No systemic cytotoxic chemotherapy has proven to be beneficial in overall survival. Recently, the understanding of the molecular pathogenesis led to the development of new therapies. With the evidence of dysregulation of critical genes associated with cellular proliferation, growth factor signaling, cell cycling, apoptosis, and angiogenesis in HCC, a number of molecular target agents are under clinical trials. Sorafenib is the first systemic anticancer drug which has proven to gain survival benefit in the global as well as Asia-Pacific trials. However, the survival gain is still modest, and further efforts to improve outcomes in patients with HCC are necessary by developing novel drugs or combining other forms of therapies. This article will review signaling pathways in HCC and introduce molecular target agents under investigation currently.

Stability criteria have been proposed previously by Ahn for two-dimensional (2-D) digital filters described by the Roesser model with external interference. However, no stability criteria have yet been established for 2-D digital filters described by the Fornasini-Marchesini second model. In this paper, we propose a new realization criterion for 2-D digital filters in the Fornasini-Marchesini second model with saturation arithmetic and external interference. This new criterion guarantees that 2-D digital filters in this model are asymptotically stable with a guaranteed H∞ performance. The criterion is described by linear matrix inequalities (LMIs). Illustrative examples show the effectiveness of the proposed new criterion. © 2014 Elsevier B.V.

Kim H.M.,Ajou University | Cho B.R.,Korea University
Chemical Reviews | Year: 2015

The scientific review presents a condensed, all-inclusive evaluation of the design, synthesis, and biomedical application of the various small-molecule two-photon (TP) probes that have been published before December 2014. The review has focused on only the TP probes for which the properties have been clearly characterized and which produce high-quality two-photon microscopy (TPM) images in an effort to avoid an excessive number of references. The review starts by describing the fundamental concept of two-photon absorption (TPA), followed by a description of the organic solvent-based model studies that established the use of TPM in the biomedical field.

The effect on growth and body composition of various dietary additives with putative growth or health-enhancing properties were determined in juvenile olive flounder (25 g initial weight). Nine experimental diets were prepared to contain one of the following additives: control (Con) with no additive, Opuntia ficus-indica ver. saboten (OF), propolis (PP), lactic acid bacteria (LA), γ-poly-glutamic acid (PG), onion extract (OE), organic sulfur (OS), Biostone® (BS), and fig extract (FE). Fishmeal, dehulled soybean meal, and corn gluten were used as the protein source of the experimental diets. Wheat flour and soybean oil were used as the carbohydrate and lipid sources, respectively. Dietary additives were included in each experimental diet at 1% at the expense of wheat flour except for the FE (aqueous), which was substituted at 1% of the amount of water added to the diet. Fish were hand-fed to satiation twice a day for 6 d/wk for 6 wk. Weight gain of fish fed the OE diet was higher than that of fish fed with the PP diet. Chemical composition of fish was not different among the experimental diets. OE was the most effective dietary additive to improve performance of olive flounder among additives used in this study. © by the World Aquaculture Society 2011.

Chen G.,State University of New York at Buffalo | Chen G.,Harbin Institute of Technology | Agren H.,KTH Royal Institute of Technology | Ohulchanskyy T.Y.,State University of New York at Buffalo | And 2 more authors.
Chemical Society Reviews | Year: 2015

Light upconverting nanostructures employing lanthanide ions constitute an emerging research field recognized with wide ramifications and impact in many areas ranging from healthcare, to energy and, to security. The core-shell design of these nanostructures allows us to deliberately introduce a hierarchy of electronic energy states, thus providing unprecedented opportunities to manipulate the electronic excitation, energy transfer and upconverted emissions. The core-shell morphology also causes the suppression of quenching mechanisms to produce efficient upconversion emission for biophotonic and photonic applications. Using hierarchical architect, whereby each shell layer can be defined to have a specific feature, the electronic structure as well as the physiochemical structure of the upconverting nanomaterials can be tuned to couple other electronic states on the surface such as excitations of organic dye molecules or localized surface plasmons from metallic nanostructures, or to introduce a broad range of imaging or therapeutic modalities into a single conduct. In this review, we summarize the key aspects of nanophotonic control of the light upconverting nanoparticles through governed design and preparation of hierarchical shells in the core-shell nanostructures, and review their emerging applications in the biomedical field, solar energy conversion, as well as security encoding. This journal is © The Royal Society of Chemistry.

Nahm C.-W.,Korea University
Ceramics International | Year: 2011

The aging behavior against a pulse-current in the ZnO-Pr6O 11-CoO-Cr2O3-Dy2O3 varistor ceramics was investigated in accordance with sintering time. The varistors sintered for 1 h exhibited the best clamp characteristics; the clamping voltage ratio was in the range of 1.69-1.92 for the lower pulse-current region (5-50 A) and in the range of 2.0-2.98 for the higher pulse-current region (400-1800 A). The best electrical stability against a pulse-current was obtained by the varistor ceramics sintered for 3 h, with %ΔE1mA/cm 2=-7.2%, %Δα = -21.9%, and %ΔJL = 13.0% after applying the multi-pulse current of 1800 A. © 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The degradation behavior against impulse-current stress of the Co-Cr-Al-Y-doped ZnO-Pr6O11-based varistors was investigated in accordance with sintering temperature. The clamp voltage ratio (K) for impulse current increased in accordance with increasing sintering temperature. The varistors sintered at 1300 °C exhibited the best voltage clamp characteristics, which the clamping voltage ratio was in the range of 1.49-1.57 at a low impulse-current region (5-10 A) and was in the range of 1.70-2.44 at a high impulse-current region (400-1200 A). The best electrical stability against multi-impulse stress for continuously 3 times 1200 A was obtained at 1350 °C in sintering temperature, where %ΔE1mA/cm2=-5.0%, %Δα = -13.9%, and %ΔJL = -21.9%. © 2010 Elsevier Ltd and Techna Group S.r.l.

The microstructure, electrical properties, and aging behavior of the ZnO-Pr6O11-CoO-Cr2O3-Y 2O3-Er2O3 varistor ceramics were investigated for different contents of Er2O3. The microstructure consisted of ZnO grain and an intergranular layer (Pr, Y, and Er-rich phases) as a secondary phase. The increase of Er2O 3 content decreased the average grain size and increased the sintered density. As the Er2O3 content increased, the breakdown field increased from 4206 V/cm to 5857 V/cm and the nonlinear coefficient increased from 32.6 to 48.6. The varistor ceramics added with 1.0 mol% Er 2O3 exhibited excellent stability by exhibiting -0.2% in the variation rate of the breakdown field and -2.7% in the variation rate of the nonlinear coefficient for aging stress of 0.95 E1 mA/150 °C/24 h. © 2011 Elsevier Ltd and Techna Group S.r.l.

Johansson J.R.,RIKEN | Nation P.D.,Korea University | Nori F.,RIKEN | Nori F.,University of Michigan
Computer Physics Communications | Year: 2013

We present version 2 of QuTiP, the Quantum Toolbox in Python. Compared to the preceding version [J.R. Johansson, P.D. Nation, F. Nori, Comput. Phys. Commun. 183 (2012) 1760.], we have introduced numerous new features, enhanced performance, and made changes in the Application Programming Interface (API) for improved functionality and consistency within the package, as well as increased compatibility with existing conventions used in other scientific software packages for Python. The most significant new features include efficient solvers for arbitrary time-dependent Hamiltonians and collapse operators, support for the Floquet formalism, and new solvers for Bloch-Redfield and Floquet-Markov master equations. Here we introduce these new features, demonstrate their use, and give a summary of the important backward-incompatible API changes introduced in this version. © 2012 Elsevier B.V. All rights reserved.

Kim M.-J.,Korea University
Geochemistry: Exploration, Environment, Analysis | Year: 2010

In this study, the effects of pH, adsorbate/adsorbent ratio, temperature and ionic strength on the adsorption of arsenate, As(V) onto soil were investigated. Three soil samples, with negligible background levels of arsenic, were collected from the vicinity of the Jingok mine, an abandoned mine located in Bongwha, Korea. Results show that the adsorption of arsenate on soil strongly depends on pH, adsorbate/adsorbent ratio and temperature, but not on ionic strength; higher adsorption was found at lower pH, lower adsorbate/adsorbent ratio and/or higher temperature. It was observed that pH is a very strong factor in immobilization of arsenate onto soil by adsorption. Soil samples containing the highest concentrations of Fe and Al showed the greatest arsenate adsorption. Iron and aluminum (hydr)oxides are likely the main adsorbents, which are active under the natural conditions in the study area. The experimental data of isotherms at various pH values and temperatures from the three soil samples show good agreement with both Freundlich and Langmuir equations. © 2010 Geological Society of London.

Lee W.,University of Iowa | Reeve J.,Korea University
Social Cognitive and Affective Neuroscience | Year: 2013

Neuroscientific studies on agency focus rather exclusively on the notion of who initiates and regulates actions, not on the notion of why the person does. The present study focused on the latter to investigate two different reasons underlying personal agency. Using event-related functional magnetic resonance imaging, we scanned 16 healthy human subjects while they imagined the enactment of volitional, agentic behavior on the same task but either for a self-determined and intrinsically motivated reason or for a non-self-determined and extrinsically motivated reason. Results showed that the anterior insular cortex (AIC), known to be related to the sense of agency, was more activated during self-determined behavior while the angular gyrus, known to be related to the sense of loss of agency, was more activated during non-self-determined behavior. Furthermore, AIC activities during selfdetermined behavior correlated highly with participants' self-reported intrinsic satisfactions. We conclude that self-determined behavior is more agentic than is non-self-determined behavior and that personal agency arises only during self-determined, intrinsically motivated action. © The Author (2012).

Bunzli J.-C.G.,Ecole Polytechnique Federale de Lausanne | Bunzli J.-C.G.,Korea University
Chemical Reviews | Year: 2010

The problematic issues of lanthanide luminescent bioprobes (LLB) from the standpoint of their photophysical and biochemical properties are studied. Quenching of the lanthanide luminescence by high-energy vibrational overtones is a major concern in the design of luminescent probes. On the other hand, it allows one to assess the number of water molecules q interacting in the inner coordination sphere from lifetimes measured in water and deuterated water. Several phenomenological equations have been proposed, based on the assumptions that O-D oscillators contribute little to deactivation and that all the other deactivation paths are the same in water and in deuterated water. Efficient lanthanide luminescent bioprobes must meet several stringent requirements, chemical, photophysical, and biochemical. A growing number of bioanalyses require specific targeting of the analyte, and therefore the lanthanide luminescent probes have to be fitted with adequate functionalities able to couple with biological material.

Quang D.T.,Hue University | Kim J.S.,Korea University
Chemical Reviews | Year: 2010

Several researchers conducted studies to demonstrate the use of fluoro- and chromogenic chemodosimeters for heavy metal ion detection in solution and biospecimens. They demonstrated that fluorescent chemodosimeters had emerged as as a research area of significant importance due to their potential in detecting heavy metal ions in solution and biospecimens. Chemodosimeters were used to detect an analyte through a highly selective and irreversible chemical reaction between the dosimeter molecule and the target analyte. This led to an observable signal that had an accumulative effect and was directly related to the concentration of the analyte. The chemodosimeter also provided signaling changes in absorption wavelength and color that were widely used as detection events, as they required only the use of cost-effective equipment or no equipment in some cases.

Van Boxtel J.J.A.,California Institute of Technology | Tsuchiya N.,California Institute of Technology | Tsuchiya N.,Tamagawa University | Koch C.,California Institute of Technology | Koch C.,Korea University
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

The brain's ability to handle sensory information is influenced by both selective attention and consciousness. There is no consensus on the exact relationship between these two processes andwhether they are distinct. So far, no experiment has simultaneously manipulated both. We carried out a full factorial 2 x 2 study of the simultaneous influences of attention and consciousness (as assayed by visibility) on perception, correcting for possible concurrent changes in attention and consciousness. We investigated the duration of afterimages for all four combinations of high versus low attention and visible versus invisible. We show that selective attention and visual consciousness have opposite effects: paying attention to the gratingdecreases theduration of its afterimage,whereas consciously seeing the grating increases the afterimage duration. These findings provide clear evidence for distinctive influences of selective attention and consciousness on visual perception.

Lee Y.,Korea University
Mathematical Problems in Engineering | Year: 2015

This paper considers a discrete-time bulk-arrival bulk-service queueing system with variable service capacity, where the service capacity varies depending on the previous service time. Using the supplementary variable method and the generating function technique, we obtain the queue length distributions at arbitrary slot boundaries and service completion epochs. © 2015 Yutae Lee.

Eliseeva S.V.,Ecole Polytechnique Federale de Lausanne | Bunzli J.-C.G.,Ecole Polytechnique Federale de Lausanne | Bunzli J.-C.G.,Korea University
Chemical Society Reviews | Year: 2010

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) "soft" luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references). © 2010 The Royal Society of Chemistry.

HcEXLX2 is a bacterial expansin found in a marine bacterium, Hahella chejuensis. Previously, HcEXLX2 was reported to act synergistically with a commercial cellulase preparation on the cellulose hydrolysis. The aim of the present study was to investigate the possible synergistic activity of HcEXLX2 with an endo-type xylanase from Saccharophagus degradans 2-40(T) (Xyn10C) in the hydrolysis of xylan. When 160 μg of HcEXLX2 was incubated with 12 μg of Xyn10C, the yield of reducing sugar increased 3.1 times when compared to that without HcEXLX2. The optimal temperature and pH for the synergism of HcEXLX2 with Xyn10C were 30°C and pH 7, respectively. In addition, binding experiments revealed that HcEXLX2 binds to xylan more preferentially than to Avicel. These results imply that HcEXLX2 could be used as an accessory protein to boost the activity of xylanase if its synergistic effect is strengthened at lower dosages. Copyright © 2013 Elsevier Ltd. All rights reserved.

Rabczuk T.,University of Canterbury | Bordas S.,University of Glasgow | Zi G.,Korea University
Computers and Structures | Year: 2010

This paper reviews different crack tracking techniques in three-dimensions applicable in the context of partition of unity methods, especially meshfree methods. Issues such as describing and tracking the crack surface are addressed. A crack tracking procedure is proposed in detail and implemented in the context of the extended element-free Galerkin method (XEFG). Several three-dimensional cracking examples are compared to other results from the literature or the experimental data and show good agreement. © 2008 Elsevier Ltd. All rights reserved.

Koo S.H.,Korea University
Clinical and molecular hepatology | Year: 2013

Liver plays a central role in the biogenesis of major metabolites including glucose, fatty acids, and cholesterol. Increased incidence of obesity in the modern society promotes insulin resistance in the peripheral tissues in humans, and could cause severe metabolic disorders by inducing accumulation of lipid in the liver, resulting in the progression of non-alcoholic fatty liver disease (NAFLD). NAFLD, which is characterized by increased fat depots in the liver, could precede more severe diseases such as non-alcoholic steatohepatitis (NASH), cirrhosis, and in some cases hepatocellular carcinoma. Accumulation of lipid in the liver can be traced by increased uptake of free fatty acids into the liver, impaired fatty acid beta oxidation, or the increased incidence of de novo lipogenesis. In this review, I would like to focus on the roles of individual pathways that contribute to the hepatic steatosis as a precursor for the NAFLD.

Although much advancement has been achieved in the treatment of chronic hepatitis B, antiviral resistance is still a challenging issue. Previous generation antiviral agents have already developed resistance in a number of patients, and it is still being used especially in resource limited countries. Once antiviral resistance occurs, it predisposes to subsequent resistance, resulting in multidrug resistance. Therefore, prevention of initial antiviral resistance is the most important strategy, and appropriate choice and modification of therapy would be the cornerstone in avoiding treatment failures. Until now, management of antiviral resistance has been evolving from sequential therapy to combination therapy. In the era of tenofovir, the paradigm shifts again, and we have to decide when to switch and when to combine on the basis of newly emerging clinical data. We expect future eradication of chronic hepatitis B virus infection by proper prevention and optimal management of antiviral resistance.

Hyung S.W.,Korea University
Molecular & cellular proteomics : MCP | Year: 2011

Prediction of the responses to neoadjuvant chemotherapy (NACT) can improve the treatment of patients with advanced breast cancer. Genes and proteins predictive of chemoresistance have been extensively studied in breast cancer tissues. However, noninvasive serum biomarkers capable of such prediction have been rarely exploited. Here, we performed profiling of N-glycosylated proteins in serum from fifteen advanced breast cancer patients (ten patients sensitive to and five patients resistant to NACT) to discover serum biomarkers of chemoresistance using a label-free liquid chromatography-tandem MS method. By performing a series of statistical analyses of the proteomic data, we selected thirteen biomarker candidates and tested their differential serum levels by Western blotting in 13 independent samples (eight patients sensitive to and five patients resistant to NACT). Among the candidates, we then selected the final set of six potential serum biomarkers (AHSG, APOB, C3, C9, CP, and ORM1) whose differential expression was confirmed in the independent samples. Finally, we demonstrated that a multivariate classification model using the six proteins could predict responses to NACT and further predict relapse-free survival of patients. In summary, global N-glycoproteome profile in serum revealed a protein pattern predictive of the responses to NACT, which can be further validated in large clinical studies.

Background: The level of disability and endurance of back muscles have been investigated, but there is conflicting evidence following specific exercise interventions for participants with recurrent low back pain (LBP). The purpose of this study was to compare the level of disability and slope of median frequency (MF) of thoracic and lumbar erector spinae (ES) muscles following core stabilization exercise (CSE) and spinal flexibility exercise (SFE). Material/Methods: In total, 46 individuals participated in this study. There were 25 participants in the CSE intervention group (average age of 47.7±8.9 years) and 21 participants in the SFE group (average age of 53.1±9.0 years). Each group participated in the specific exercise intervention program for 4 weeks while maintaining their current activity and/or exercise levels. The Oswestry Disability Index (ODI) was used to measure the level of disability changes. The fatigability of the ES back muscles was measured by the slope of MF, using a modifed Sorensen test. Results: The disability level decreased significantly following CSE intervention (t=2.23, p<0.05). However, there was no significant diference in muscle fatigability changes in the 4-week intervention period for either group. Conclusions: The CSE intervention reduced disability level following the 4-week intervention period. Further studies are needed to investigate the effectiveness of specific back muscle exercises in longer intervention periods for back muscle fatigability.

Low back pain (LBP) is one of the most common symptoms reported in adults. However, the contribution of postural control on the lumbar spine and hips during squatting has not been carefully investigated in individuals with LBP. The aim of this study was to compare three-dimensional kinematic changes of the lumbar spine and hips between subjects with and without idiopathic chronic LBP during squatting activities. In total, 30 subjects enrolled in the study (15 control subjects and 15 subjects with idiopathic chronic LBP). All participants were asked to perform squatting activities five times repeatedly while holding a load of 2. kg in a basket. The outcome measures included the Oswestry Disability Index (ODI) and kinematic angular displacement for the hips and lumbar spine. The LBP group demonstrated increased range of motion (ROM) in flexion of the dominant (T= -2.14, p= 0.03) and non-dominant (T= -2.11, p= 0.03) hips during squatting. The lumbar spine flexion ROM significantly decreased (T= 2.20, p= 0.03). The kinematic changes demonstrated interactions with region × group (F= 5.56, p= 0.02), plane × group (F= 4.36, p= 0.04), and region × plane (F= 2292.47, p= 0.001). The ODI level demonstrated significant interaction on combined effects of body region and plane (F= 4.91, p= 0.03). Therefore, the LBP group utilized a compensation strategy to increase hip flexion with a stiffened lumbar spine in the sagittal plane during squatting. This compensatory kinematic strategy could apply to clinical management used to enhance lumbar spine flexibility in subjects with idiopathic chronic LBP. © 2013 Elsevier Ltd.

Han W.K.,Korea University
Journal of the Korean Physical Society | Year: 2011

We simulate the thermodynamic behaviors of Cu3au(100) and Ni3pt(100) surfaces, focusing on the segregation and ordering. Through Monte Carlo simulations of a short-range Ising model Hamiltonian, we develop a phase digram to distinguish surface behaviors. We can explain the bulk phase transition and surface segregation on a quantitative level in good agreement with previous experimental observations. Further, we reveal that Cu3au(100) shows a surface-induced disordering behavior, as suggested in previous works, but Ni3pt(100) shows a surface-induced ordering, which awaits further experimental testing.

Kim S.Y.,Korea University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2011

Helicobacter pylori (H. pylori) is known to be associated with many gastrointestinal diseases including peptic ulcer. In Korea, eradication of H. pylori is recommended for peptic ulcer disease, low grade gastric mucosa-associated lymphoid tissue lymphoma, and early gastric cancer. Standard triple therapy using proton pump inhibitor, clarithromycin, and amoxicillin and bismuth-containing quadruple therapy have been the main first-line and second-line therapy for H. pylori in Korea. Although eradication rate of second-line quadruple therapy remains similar to that of the past, the success rate of eradication with triple therapy has decreased with increasing antimicrobial resistance to H. pylori. There is no standard third-line therapy, and some regimens that incorporate levofloxacin, moxifloxacin, and rifabutin can be used. New regimens such as sequential or concomitant therapy are suggested as alternative treatment for H. pylori. We need more well designed randomized controlled studies to choose proper treatment for H. pylori infection.

Lee D.Y.,Korea University
The Angle orthodontist | Year: 2010

OBJECTIVE: To determine potential differences in treatment efficiencies of face mask therapy without rapid maxillary expansion (RME) at different early dental stages. MATERIALS AND METHODS: Forty-nine Class III children who were treated with a face mask without RME were divided into two groups according to their pretreatment dental stage. The primary dentition treatment group consisted of 26 subjects and the mixed dentition treatment group consisted of 23 subjects. Lateral cephalograms before treatment (T0), at the end of treatment (T1), and at least 1 year after the end of treatment (T2) were calculated and analyzed. Fourteen cephalometric variables were evaluated by t-test to identify any significant differences in skeletal changes between the two groups during T1-T0, T2-T1, and T2-T0. RESULTS: The primary dentition group showed not only a greater response to maxillary protraction without RME than did the mixed dentition group during T1-T0, but also a greater relapse tendency during T2-T1. As a result, no significant differences were noted between the two groups in the treatment effects of face masks without RME over the time period T2-T0. CONCLUSION: This study suggests that face mask therapy without RME may be postponed to the early to mid mixed dentition period because the therapy induces similar skeletal changes when initiated at primary or mixed dentition.

Yoon W.S.,Korea University
DNA and cell biology | Year: 2012

Atopic dermatitis (AD) is an inflammatory, chronically relapsing, puritic skin disorder. These syndromes result from multifactorial inheritance, with interaction between genetic and environmental factors. In particular, the macrophage-derived chemokine CCL22 is directly implicated in skin inflammatory reactions and its levels are significantly elevated in serum and correlated with disease severity in AD. We tested the suppression of the CCL22 gene by microRNA (miRNA) and observed the effects in mice with inflammation similar to AD. We used Salmonella as a vector to deliver miRNA. The recombinant strain of Salmonella typhimurium expressing CCL22 miRNA (ST-miRCCL22) was prepared for in vivo knockdown of CCL22. ST-miRCCL22 was orally inoculated into mice and the CCL22 gene suppressed with CCL22 miRNA in the activated lymphocytes. IgE and interleukin-4 were inhibited and interferon-γ was induced after treatments with ST-miRCCL22 and CCL22 was suppressed. Further, Th17 cells were suppressed in the atopic mice treated with ST-miRCCL22. These results suggested that suppression of the CCL22 gene using Salmonella induced anti-inflammatory effects.

Yong K.-T.,Nanyang Technological University | Law W.-C.,State University of New York at Buffalo | Hu R.,Nanyang Technological University | Ye L.,Chinese PLA General Hospital | And 4 more authors.
Chemical Society Reviews | Year: 2013

Tremendous research efforts have been devoted to fabricating high quality quantum dots (QDs) for applications in biology and medicine. Much of this research was pursued with an ultimate goal of using QDs in clinical applications. However, a great deal of concern has been voiced about the potential hazards of QDs due to their heavy-metal content. Many studies have demonstrated toxicity of various QDs in cell culture studies. However, in a smaller number of studies using small animal models (mice and rats), no abnormal behaviour or tissue damage was noticed over periods of months after the systemic administration of QDs. Nevertheless, the correlation of these results with the potential for negative effects of QD on humans remains unclear. Many urgent questions must be answered before the QDs community moves into the clinical research phase. This review provides an overview of the toxicity assessment of QDs, ranging from cell culture studies to animal models and discusses their findings. Guidelines for using various nonhuman primate models for QD toxicity studies are highlighted. This review article is intended to promote the awareness of current developments of QD applications in biology, the potential toxicity of QDs, and approaches to minimizing toxicity. © 2013 The Royal Society of Chemistry.

Lee S.,Korea University
Water Resources Management | Year: 2010

This study analyzes the transformation of urban water services in China since the late 1990s focusing on the interaction between the government and private players in the form of public private partnership projects. A lack of fund, outdated technologies and management skills, and underpriced water tariffs had deteriorated urban water services in China. Chinese authorities decided to adopt private sector participation in the urban water sector. The institutional reform has attracted private players to contribute to public private partnership projects. Water multinationals and Chinese companies have actively participated in such new development. But a myriad of risks are identified in the Chinese water market, including socio-political, institutional and regulatory, revenue and foreign exchange, and project construction and operation risks. The key to success of this policy shift depends on the extent to which Chinese authorities can provide an institutional platform for improvement of urban water services with the participation of private players. Also the changing role of the government from a service provider to a regulator is necessary. © 2009 Springer Science+Business Media B.V.

Nahm C.-W.,Korea University
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2010

Al doping effect on electrical and dielectric aging behavior against impulse surge in the ZPCCYA-based varistors was investigated. The clamp ratio (K) decreased in accordance with increasing Al2O3 content up to 0.005 mol%. A further increase in Al2O3 doping level caused K to increase. The K value at a surge current of 5 A and 10 A for the varistor doped with 0.005 mol% Al2O3 exhibited 1.49 and 1.57, respectively. Furthermore, the K value at a higher surge current of 1200 A was 2.44 for the varistors doped with 0.005 mol% and 0.01 mol% Al2O3. The best electrical and dielectric stability against impulse surge current of 1200 A was obtained at 0.01 mol% Al2O3, where %ΔE1 mA/cm2 = -1.0%, %Δα = 0%, %ΔJL = -3.9%, %Δε′APP = +1.4%, and %Δ tan δ = -10.5%. Conclusively, Al2O3 content was optimized at 0.01 mol% in terms of the surge absorption capability. © 2010 Elsevier B.V. All rights reserved.

The nonlinear electrical behavior against the impulse stress (400-1200 A) in the ZnO-Pr6O11-CoO-Cr2O3-Y 2O3 varistors has been investigated with sintering time. The sintering time did have a significant effect on the clamp ratio, which exhibits a surge protection capability. The varistors sintered for 1 h exhibited the best clamp characteristics, in which the clamp voltage ratio was in the range of K = 1.61-1.92 at a lower impulse current region (5-50 A) and was in the range of K = 2.06-2.55 at a higher single impulse current region (400-1200 A). The best electrical stability against the multi-impulse aging stress of 1200 A was also obtained from the varistors sintered for 2 h, where %ΔE 1 mA =-1.6%, %Δα =1.3%, and %ΔJL =-4.9%. © 2010 Elsevier B.V. All rights reserved.

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.

The Forkhead box O (FoxO) transcription factors, including FoxO1, FoxO3a, FoxO4, and FoxO6, are implicated in the regulation of cell apoptosis and survival. Here, we examined the role of FoxO transcription factors and the involvement of the PI3K/Akt and mitogen-activated protein kinase (MAPK) pathways in neuronal apoptosis in the brain of the silkworm Bombyx mori following starvation. Starvation inhibited cell proliferation and induced apoptosis through caspase-3 activation. The level of phosphorylated kinase Akt increased when the animals ceased feeding. Starvation conditions reduced extracellular-signal-regulated kinase phosphorylation but increased both c-Jun N-terminal kinase and p38 (MAPK) phosphorylation. FoxO1 and FoxO3a were simultaneously localized in the nuclei. These results provide new insights into the process of apoptosis of brain neurons through the involvement of FoxO transcription factors following starvation of insect species.

Rimberg A.J.,Dartmouth College | Blencowe M.P.,Dartmouth College | Armour A.D.,University of Nottingham | Nation P.D.,Korea University
New Journal of Physics | Year: 2014

We propose a scheme involving a Cooper pair transistor (CPT) embedded in a superconducting microwave cavity, where the CPT serves as a charge tunable quantum inductor to facilitate ultra-strong coupling between photons in the cavity and a nano- to meso-scale mechanical resonator. The mechanical resonator is capacitively coupled to the CPT, such that mechanical displacements of the resonator cause a shift in the CPT inductance and hence the cavity's resonant frequency. The amplification provided by the CPT is sufficient for the zero point motion of the mechanical resonator alone to cause a significant change in the cavity resonance. Conversely, a single photon in the cavity causes a shift in the mechanical resonator position on the order of its zero point motion. As a result, the cavity-Cooper pair transistor coupled to a mechanical resonator will be able to access a regime in which single photons can affect single phonons and vice versa. Realizing this ultra-strong coupling regime will facilitate the creation of non-classical states of the mechanical resonator, as well as the means to accurately characterize such states by measuring the cavity photon field. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Jo M.,Korea University
Journal of Physics G: Nuclear and Particle Physics | Year: 2011

Although the RHIC experiments have measured the inclusive J/ψ and open heavy-flavor productions at = 200 GeV, no data are available yet for the contribution of secondary J/ψ from the B-hadron decays in heavy-ion collisions. Since the B-hadron and the prompt J/ψ interact with the medium differently, subtracting the non-prompt J/ψ contribution is crucial for our understanding of modifications in the prompt J/ψ production in heavy-ion collisions. It should also be a measure of b-quark energy loss. CMS is able to separate the prompt and the non-prompt J/ψ in PbPb collisions performing an unbinned two-dimensional maximum-likelihood fit to the mass and pseudo-proper decay length distributions. In this paper, the first measurement of non-prompt J/ψ production in the dimuon channel, as a function of centrality in PbPb collisions at = 2.76 TeV, is presented. © CERN 2011.

Singh D.,Korea University
Proceedings of the 2013 International Conference on Advances in Computing, Communications and Informatics, ICACCI 2013 | Year: 2013

We are designing a novel architecture to support future internet services which is going to solve fundamental issues such as addressing, mobility, routing scalability challenges, security and control to support trillion of things to connect with internet. In this paper we have presented an efficient hierarchical identification mapping server (IMS) which uses separation mechanism of identification (ID) and location (LOC). IMS introduces huge amount of LOC independent globally unique Flat ID and Bloom Filter (BF) has been introduces the management of Flat IDs during the Lookup process into the IMS. Hence, we can state that hierarchical IMS architecture could be an alternative solution of current internet oriented innovations in a scalable manner. The aim of architecture is the coverage of Internet and sensors oriented smart objects. © 2013 IEEE.

Nahm C.-W.,Korea University
Journal of Materials Science: Materials in Electronics | Year: 2010

The microstructure, electrical properties, dielectric characteristics, and DC accelerated aging behavior of the MnCoDy modified Zn-V-based varistors were investigated for Nb amount of 0.0-0.25 mol% by sintering at 900 °C. The microstructure of the MnCoDy modified Zn-V-based varistors consisted of ZnO grain as a main phase and Zn 3(VO 4) 2, ZnV 2O 4, and DyVO 4 as the secondary phases. The Nb addition led to the increase of grain size, whereas it does not have an effect on the sintered density. The nonlinear coefficient improved with the increase of Nb amount up to 0.1 mol%, whereas the further Nb additions impaired it. A maximum of the nonlinear coefficient (35) was obtained at 0.1 mol% Nb. The Nb acted as a donor less than 0.1 mol% and an acceptor more than 0.25 mol%. The best stability of system against DC accelerated aging stress was obtained at 0.1 mol% Nb, in which %ΔE 1 mA = -0.24%, %Δα = -15.4%, %Δ ε' app = -1.4%, and %Δ tanδ = +12.5% for stress state of 0.85 E 1 MA/85 °C/24 h. © Springer Science+Business Media, LLC 2009.

Chung W.,Korea University
IEEE Photonics Technology Letters | Year: 2010

Maximum likelihood sequence detection (MLSD) is the most effective electrical domain equalization scheme for mitigating dispersive optical channel impairments such as chromatic dispersion or polarization-mode dispersion. Parameter estimation for MLSD is not straightforward in optical communication systems due to the square-law nature of photodiodes. We propose a simple and efficient channel parameter estimation scheme for MLSD based on Volterra kernel modeling of the nonlinear distortion of the electrical postdetection signals. © 2010 IEEE.

Chay J.,Korea University | Kim C.,Seoul National University of Science and Technology
Physical Review Letters | Year: 2013

A consistent factorization theorem is presented in the framework of effective field theories. Conventional factorization suffers from infrared divergences in the soft and collinear parts. We present a factorization theorem in which the infrared divergences appear only in the parton distribution functions by carefully reorganizing collinear and soft parts. The central idea is extracting the soft contributions from the collinear part to avoid double counting. Combining it with the original soft part, an infrared-finite kernel is obtained. This factorization procedure can be applied to various high-energy scattering processes. © 2013 American Physical Society.

Nahm C.-W.,Korea University
Journal of Alloys and Compounds | Year: 2013

This study focuses on that Gd2O3-modified ZnO-V 2O5-MnO2-Nb2O5 ceramics were sintered at temperature as low as 900 °C and very good varistor properties. Increasing amount of Gd2O3 decreased the sintered density in the range of 5.51-5.44 g/cm3 and it reduced the average grain size from 5.6 to 5.2 |j.m up to 0.1 mol%. The breakdown field increased from 4822 to 5365 V/cm up to 0.05 mol% with an increase in the amount of Gd2O3, whereas a further increase caused it to decrease. The ceramics modified with 0.05 mol% in the amount of Gd 2O3 exhibited an excellent nonlinear coefficient as high as 66. The donor concentration increased from 4.46 × 1017 to 7.38 × 1017 cm3 with an increase in the amount of Gd2O3 and the barrier height exhibited a maximum value (1.22 eV) at 0.05 mol% Gd2O3. © 2013 Elsevier B.V. All rights reserved.

Park C.,Korea University
Plastic and Reconstructive Surgery | Year: 2015

Background: Patients with solitary-type congenital tragal malformations accompanied by dystopic cartilage growth (accessory tragus) show not only a disfigured or absent tragus but also unnecessary tragal or pretragal lumps. Furthermore, an absent tragus causes a wholly exposed external auditory canal. Materials: Sixty-five ears (54 patients) showing congenital tragal malformations accompanied by dystopic cartilage growth were reconstructed from March of 1991 to February of 2014. Reconstructions were reviewed using medical records and photographs, surgical methods were analyzed, and postoperative outcomes were evaluated. Results: Six kinds of tragal framework fabrication methods were used in the reconstructions: free cartilage grafting (n = 7); cartilage transposition and anchoring (n = 7); cartilage folding and anchoring (n = 46); vascularized chondrocutaneous island flap (n = 4); and costal cartilage grafting (n = 1). Immediate postoperatively, four cases showed congestion of the covered skin. Forty-three patients (78 percent) were followed up for an average period of 15 months. The following were observed: larger tragus (n = 3); flat tragus without peak (n = 2); posterior protrusion of the tragal wall (n = 2); and hypertrophic scar (n = 1). All cases with a wholly exposed external auditory canal were corrected. The average score of the aesthetic outcomes, rated on a four-point Likert scale (1 = poor, 2 = fair, 3 = good, 4 = excellent), was 3.8 points. Conclusions: Cartilage and covered skin from the dystopic cartilage growth provided the best-available tissues for new tragal reconstructions. Different surgical techniques were used in accordance with the severity of the tragal malformation encountered. Most techniques provided aesthetically pleasing outcomes. © 2015 by the American Society of Plastic Surgeons.

In seeking aryl acylamidase (EC acting on an amide bond in p-acetaminophenol (Tylenol), we identified a novel gene encoding 496 residues of a protein. The gene revealed a conserved amidase signature region with a canonical catalytic triad. The gene was expressed in E. coli and characterized for its biochemical properties. The optimum pH and temperature for the activity on p-acetaminophenol were 10 and 37 degrees C, respectively. The half-life of enzyme activity at 37 degrees C was 192 h and 90% of its activity remained after 3 h incubation at 40 degrees C. Divalent metals was found to inhibit the activity of enzyme. The K (m) values for various aryl acylamides such as 4-nitroacetanilide, p-acetaminophenol, phenacetin, 4-chloroacetanilide and acetanilide were 0.10, 0.32, 0.83, 1.9 and 19 mM, respectively. The reverse reaction activity (amide synthesis) was also examined using various chain lengths (C(1) approximately C(4) and C(10)) of carboxylic donors and aniline as substrates. These kinetic parameters and substrate specificity in forward and reverse reaction indicated that the aryl acylamidase in this study has a preference for aryl substrate having polar functional groups and hydrophobic carboxylic donors.

The microstructure and electrical properties of ZnO-V 2O 5-MnO 2-Nb 2O 5-Er 2O 3 (ZVMNE) ceramics were investigated at different sintering temperatures (875-950°C). The average grain size increased from 4.3 to 9.2 μm with the increase of sintering temperature. The breakdown field decreased from 7095 to 1256 V/cm with the increase of sintering temperature. The ZVMNE ceramics sintered at 900°C exhibited a surprisingly high nonlinear coefficient (63). The donor concentration increased from 3.09 × 10 17 to 7.99 × 10 17 cm -3 with the increase of sintering temperature and the barrier height exhibited the maximum value (1.21 eV) at 900°C. © 2011 Elsevier Ltd and Techna Group S.r.l.

Lee H.-J.,Korea University | Kang S.-G.,Catholic University of Daegu
International Review of Neurobiology | Year: 2011

Tardive dyskinesia (TD) is one of the most serious adverse side effects of antipsychotic drugs and is an important topic of pharmacogenetic studies. Since there is a genetic susceptibility for developing this adverse reaction, and given that it is hard to predict its development prior to or during the early period of medication, the genetic study of TD is a promising research topic that has a direct clinical application. Moreover, such studies would improve our understanding of the genetic mechanism(s) underlying abnormal dyskinetic movement. A substantial number of case-control association studies of TD have been performed, with numbers of studies focusing on the genes involved in antipsychotic drug metabolism, such as those for cytochrome P450 (CYP) and oxidative stress related genes as well as various neurotransmitter related genes. These studies have produced relatively consistent though controversial findings for certain polymorphisms such as CYP2D6*10, DRD2 Taq1A, DRD3 Ser9Gly, HTR2A T102C, and MnSOD Ala9Val. Moreover, the application of the genome-wide association study (GWAS) to the susceptibility of TD has revealed certain associated genes that previously were never considered to be associated with TD. , such as the rs7669317 on 4q24, GLI2 gene, GABA pathway genes, and HSPG2 gene. Although a substantial number of genetic studies have investigated TD, many of the positive findings have not been replicated or are inconsistent, which could be due to differences in study design, sample size, and/or subject ethnicity. We expect that more refined research will be performed in the future to resolve these issues, which will then enable the genetic prediction of TD and clinical application thereof. © 2011 Elsevier Inc.

The degradation behavior against a surge-current in the ZPCCYE (ZnO-Pr 6O 11-CoO-Cr 2O 3-Y 2O 3-Er 2O 3) varistors was investigated for different amounts of Er 2O 3. The addition of Er 2O 3 has a significant effect on nonlinear electrical properties and surge degradation behavior of the ZPCCYE varistors. Increasing amount of Er 2O 3 improved the clamp characteristics, in which the clamping voltage (K) decreases at a surge-current of 1-40 A. The varistors added with 0.5 mol% Er 2O 3 exhibited the strongest electrical stability, with the variation rate of the breakdown field of -3.2%, the variation rate of the nonlinear coefficient of -20.9%, and the variation rate of the leakage current of -40.0% after applying 1000 times for a surge-current of 100 A/cm 2. Furthermore, the varistors added with 0.5 mol% Er 2O 3 exhibited the good surge withstand capability with the variation rate of the breakdown field of -7.9% after applying the surge-current of 400 A. On the contrary, the varistors added with 0.25 mol% were destroyed after applying the surge-current of 400 A and the varistors added with 1.0 mol% were destroyed after applying 55 times for a surge-current of 100 A/cm 2. © 2012 Elsevier Ltd and Techna Group S.r.l.

Nahm C.-W.,Korea University
Ceramics International | Year: 2013

The microstructure and electrical properties of the ZnO-V2O 5-MnO2-Nb2O5-Bi2O 3 varistor ceramics were systematically investigated at different sintering temperatures (875-950 °C). The average grain size increased remarkably in the range of 5.4 to 15.0 μm with an increase in the sintering temperature. The sintered density of pellets decreased from 5.50 to 5.34 g/cm3 as the sintering temperature increased. The breakdown field decreased noticeably from 5785 to 1181 V/cm with an increase in the sintering temperature. The varistor ceramics sintered at 900 °C exhibited excellent nonlinear properties, in which the nonlinear coefficient is 61.5 and the leakage current density is 14.1 μA/cm2. © 2012 Elsevier Ltd and Techna Group S.r.l.

Oh D.,Korea University
Yonsei Medical Journal | Year: 2011

The Korean venous thromboembolism (VTE) registry, which was initiated by the Working Parties of Korean Society on Thrombosis and Hemostasis, and the Korean Society of Hematology, is a web-based multi center registry (http://kdvt.chamc.co.kr) for recruiting consecutive VTE patients. The aim of the registry is to prospectively collect data on the epidemiology and clinical outcomes of VTE from a large, unselected cohort of patients, and to provide data on the true incidence and management of VTE in the real-world. By the end of 2007, the starting year of the registry, 840 patients were registered. By the end of 2008, 1,121 were registered, with 1,289 by the end of 2009, and 1,463 by April 2010 from 11 hospitals. The first report on the epidemiologic characteristics of 596 consecutive VTE patients was released in October 2007. © Yonsei University College of Medicine 2011.

Critical user interface design features of computer-assisted instruction programs in mathematics for students with learning disabilities and corresponding implementation guidelines were identified in this study. Based on the identified features and guidelines, a multimedia computer-assisted instruction program, 'Math Explorer', which delivers addition and subtraction word problem-solving instruction for students with learning disabilities at the early elementary level, was designed and developed. Lastly, usability testing was conducted to assess whether Math Explorer was well-designed in terms of the interface for students with learning disabilities. Given the results of the usability testing, this study corroborated the fact that the critical user interface design features and guidelines in mathematics computer-assisted instruction programs would be essential for facilitating the mathematical learning of students with learning disabilities. Implications for practice and future research were discussed. © 2010 Elsevier Ltd. All rights reserved.

Nahm C.-W.,Korea University
Journal of Alloys and Compounds | Year: 2011

The microstructure and electrical properties of quaternary ZnO-V 2O5-MnO2-Nb2O5 ceramics were investigated at different sintering temperature (875-950 °C). The average grain size increased from 4.4 μm to 9.6 μm with increasing sintering temperature. The breakdown field decreased from 6991 V/cm to 943 V/cm with increasing sintering temperature. Proper sintering for quaternary ZnO-V2O5-MnO2-Nb2O5 ceramics led to surprisingly high nonlinear coefficient (50). The donor concentration increased from 3.33 × 1017 cm-3 to 7.64 × 1017 cm-3 with increasing sintering temperature and the barrier height exhibited the maximum value (1.07 eV) at 900 °C. © 2011 Elsevier B.V. All rights reserved.

Kim J.K.,Korea University | Choi K.-J.,CHA Medical University | Lee M.,Hanyang University | Jo M.-H.,CHA Medical University | Kim S.,CHA Medical University
Biomaterials | Year: 2012

MicroRNAs (miRNA, miR) have been reported as cancer biomarkers that regulate tumor suppressor genes. Hence, simultaneous detecting and inhibiting of miRNA function will be useful as a cancer theragnostics probe to minimize side effects and invasiveness. In this study, we developed a cancer-targeting therangostics probe in a single system using an AS1411 aptamer - and miRNA-221 molecular beacon (miR-221 MB)-conjugated magnetic fluorescence (MF) nanoparticle (MFAS miR-221 MB) to simultaneously target to cancer tissue, image intracellularly expressed miRNA-221 and treat miRNA-221-involved carcinogenesis. AS1411 aptamer-conjugated MF (MFAS) nanoparticles displayed a great selectivity and delivery into various cancer cell lines. The miR-221 MB detached from the MFAS miR-221 MB in the cytoplasm of C6 cells clearly imaged miRNA-221 biogenesis and simultaneously resulted in antitumor therapeutic effects by inhibiting miRNA function, indicating a successful astrocytoma-targeting theragnostics. MFAS miRNA MB can be easily applied to other cancers by simply changing a targeted miRNA highly expressed in cancers. © 2011 Elsevier Ltd.

Jain A.K.,Michigan State University | Jain A.K.,Korea University
Pattern Recognition Letters | Year: 2010

Organizing data into sensible groupings is one of the most fundamental modes of understanding and learning. As an example, a common scheme of scientific classification puts organisms into a system of ranked taxa: domain, kingdom, phylum, class, etc. Cluster analysis is the formal study of methods and algorithms for grouping, or clustering, objects according to measured or perceived intrinsic characteristics or similarity. Cluster analysis does not use category labels that tag objects with prior identifiers, i.e., class labels. The absence of category information distinguishes data clustering (unsupervised learning) from classification or discriminant analysis (supervised learning). The aim of clustering is to find structure in data and is therefore exploratory in nature. Clustering has a long and rich history in a variety of scientific fields. One of the most popular and simple clustering algorithms, K-means, was first published in 1955. In spite of the fact that K-means was proposed over 50 years ago and thousands of clustering algorithms have been published since then, K-means is still widely used. This speaks to the difficulty in designing a general purpose clustering algorithm and the ill-posed problem of clustering. We provide a brief overview of clustering, summarize well known clustering methods, discuss the major challenges and key issues in designing clustering algorithms, and point out some of the emerging and useful research directions, including semi-supervised clustering, ensemble clustering, simultaneous feature selection during data clustering, and large scale data clustering. © 2009 Elsevier B.V. All rights reserved.

In the culture system using human feeder cells, the mechanism through which these cells support undifferentiated growth of embryonic stem cells (ESCs) has not been well investigated. Here, we explored the mechanisms of 3 kinds of human feeder cells, including human placental cells from the chorionic plate, human bone marrow stromal cells, and human foreskin fibroblasts. First, we determined that undifferentiated growth of 2 kinds each of human (H1 and HSF6) and mouse (D3 and CE3) ESCs was possible in all human feeder cell types tested (human placental cells, human bone marrow stromal cells, and human foreskin fibroblasts), without the need for exogenous cytokine supplementation including basic fibroblast growth factor (bFGF) and leukemia inhibitory factor. We then prepared their corresponding endogenous bFGF-knockout feeders using siRNA and tried to maintain human and mouse ESCs in their undifferentiated state; however, neither human nor mouse ESCs could be maintained in bFGF-knockout human feeder cells. The expressions of stemness markers such as Oct-4 and Nanog were significantly decreased in the bFGF-knockout group compared with those in the controls, and differentiation had already occurred, despite the undifferentiated morphologic appearance of the ESCs. In conclusion, human feeder cells are able to support the undifferentiated growth of human and mouse ESCs via bFGF synthesis. Further, a bFGF-dependent pathway might be crucial for maintaining the undifferentiated characteristics of mouse and human ESCs.

Lee S.,Korea University
Nuclear and Particle Physics Proceedings | Year: 2016

The mechanisms of charmonium production in the high-density medium created in heavy ion collisions are still not quantitatively understood. In order to disentangle among different mechanisms which changes the charmonium cross section, a multi-dimensional analysis is needed in a wide kinematic range and in various collision systems (pp, pA and AA). This paper will present the first measurement of the prompt and non-prompt J/ψ production with the CMS detector from the pPb collisions at √sNN=5.02 TeV with an integrated luminosity of 34.6 nb-1 in 2013. The ratio of the forward and backward production yields is measured in bins of pT and rapidity of J/ψ, as well as the event activity. © 2016 Elsevier B.V.

Chung W.,Korea University
IEEE Photonics Technology Letters | Year: 2010

This letter presents a computationally efficient scheme to mitigate the effect of phase noise, including intercarrier interference, in coherent optical orthogonal frequency-division-multiplexing systems. Utilizing the fact that phase noise in the time domain can be modeled as a circular convolution with a finite impulse response filter in the frequency domain, and its matched filter is the optimal solution to cancel the phase noise, semiblind adaptive channel equalization algorithms are applied to directly remove the effect of phase noise without the estimation process. Simulation results demonstrate substantial improvement in phase noise suppression using the proposed algorithm. © 2006 IEEE.

Min H.,Chung - Ang University | Yoon S.,Korea University
Experimental and Molecular Medicine | Year: 2010

MicroRNAs (miRNAs) are a class of small RNAs of 19-23 nucleotides that regulate gene expression through target mRNA degradation or translational gene silencing. The miRNAs are reported to be involved in many biological processes, and the discovery of miRNAs has been provided great impacts on computational biology as well as traditional biology. Most miRNA-associated computational methods comprise the prediction of miRNA genes and their targets, and increasing numbers of computational algorithms and web-based resources are being developed to fulfill the need of scientists performing miRNA research. Here we summarize the rules to predict miRNA targets and introduce some computational algorithms that have been developed for miRNA target prediction and the application of the methods. In addition, the issue of target gene validation in an experimental way will be discussed.

Chan J.,University of Minnesota | Ghose A.,New York University | Ghose A.,Korea University
MIS Quarterly: Management Information Systems | Year: 2014

Online platforms offer access to a larger social group than is generally available through offline contacts, making the Internet an emerging venue for seeking casual sex partners. The ease of seeking sex partners through classified ad sites may promote risky behaviors that increase the transmission of STDs. In this paper, using a natural experiment setup, we investigate whether the entry of a major online personals ad site, Craigslist, increases the prevalence of HIV over a 10 year period from 1999 to 2008 across 33 states in the United States. After controlling for extraneous factors, our results suggest that the entry of Craigslist is related to a 15.9 percent increase in HIV cases. Our analysis suggests that the site entry produces an average of 6,130 to 6,455 cases of HIV infection in the United States each year, mapping out to between $62 million and $65.3 million in annual treatment costs. In addition, the analyses reveal that nonmarket-related casual sex is the primary driver of the increase in HIV cases, in contrast to paid transactions solicited on the site (e.g., escort services and prostitution), which has a negative relationship with HIV trends. These findings are essential to understanding the social routes through which HIV transmission takes place and the extent to which site entry can influence HIV trends. Implications for healthcare practitioners and policy makers are discussed.

Alzheimer's disease (AD) brains demonstrate decreased levels of brain-derived neurotrophic factor (BDNF) and increased levels of β-amyloid peptide (Aβ), which is neurotoxic. The present study assessed the impact of BDNF on the toxic effects of Aβ25-35-induced apoptosis and the effects on BDNF-mediated signaling using the MTT assay, western blotting and reverse transcription quantitative polymerase chain reaction. Aβ25-35was found to induce an apoptosis, dose-dependent effect on SH-SY5Y neuroblastoma cells, which peaked at a concentration of 20 μM after 24 h. A combination of Aβ25-35and BDNF treatment increased the levels of Akt and decreased the level of glycogen synthase kinase-3β (GSK3β) in SH-SY5Y neuroblastoma cells. These findings indicated that BDNF administration exerted a neuroprotective effect against the toxicity of the Aβ25-35-induced apoptosis in these cells, which was accompanied by phosphoinositide 3-kinase/Akt activation and GSK3β phosphorylation. The mechanisms and signaling pathways underlying neuronal degeneration induced by the Aβ peptide remain to be further elucidated. © 2014, Spandidos Publications. All rights reserved.

The microstructure and electrical properties of ZnO-V2O5-MnO2-Co3O4-Dy2O3-Nb2O5 (ZVMCDN) ceramics were investigated in accordance with sintering temperature (850-950 °C). The microstructure of the samples consisted of mainly ZnO grain as a main phase, and Zn3(VO4)2, ZnV2O4, and DyVO4 as the minor secondary phases. The sintered density decreased from 5.69 to 5.52 g/cm3 due to the volatility of V2O5 in accordance with increasing sintering temperature. The maximum nonlinear coefficient (57) was obtained at 925 °C. The donor concentration increased from 1.15 × 1018/cm3 to 11.1 × 1018/cm3 in accordance with increasing sintering temperature and the barrier height exhibited the maximum value (1.03 eV) at 925 °C. © 2010 Elsevier B.V. All rights reserved.

Seo Y.,Korea University
Biotechnology and Bioprocess Engineering | Year: 2010

The scavenging activity of the flower buds of Magnolia denudata Desrousseaux on reactive oxygen species (ROS) was evaluated using 2',7'-dichlorofluorescin diacetate (DCFH-DA) in HT 1080 cells. Methanol (MeOH) and dichloromethane (CH2Cl2) extracts inhibited dosedependently generation of ROS in the cellular system. MeOH and CH 2Cl2 extracts were combined and fractionated with n-hexane, 85% aqueous MeOH, and n-butanol (n- BuOH). Both n-hexane-soluble and 85% aqueous-soluble fractions showing strong radical-scavenging activity in the cellular system were further separated by diverse chromatographic methods to give five known lignans (1-5). All these compounds exhibited significant radical-scavengingeffect on intracellular ROS in a dose-dependent manner.Their scavenging activity on various reactive oxygen species (ROS) was also evaluated using electron spin resonance (ESR) spin-trap techniques. © The Korean Society for Biotechnology and Bioengineering and Springer 2010.

Boo C.,Yale University | Elimelech M.,Yale University | Hong S.,Korea University
Journal of Membrane Science | Year: 2013

A hybrid system that combines forward osmosis with a reverse osmosis seawater desalination process could reduce both energy requirements and environmental impacts by osmotic dilution of the seawater and concentrated brine with an impaired low salinity stream, such as treated wastewater effluent. In this study, we investigate the membrane fouling behavior in forward osmosis under conditions simulating the osmotic dilution process and the use of hydrodynamic methods without the use of cleaning chemicals, to control membrane fouling. Fouling runs with seawater or SWRO brine draw solution and deionized (DI) water feed solution showed insignificant water flux decline, which implies negligible effect of particulate and organic matter in the seawater/brine on fouling of the FO membrane support layer. Fouling of the membrane active layer was evaluated by using an enriched synthetic wastewater effluent containing a mixture of inorganic and organic foulants, focusing on the impact of permeate drag force on fouling layer formation. Our results demonstrate that higher permeate water flux causes an increase in concentration build-up of foulants at the membrane surface, thereby forming a dense inorganic/organic combined fouling layer during FO fouling runs. We also examined three hydrodynamic methods for minimizing FO membrane fouling in the osmotic dilution process: (1) applying shear force on the membrane surface by increasing the cross-flow velocity, (2) using a feed-channel spacer to induce turbulence, and (3) employing pulsed flow to remove foulants from the membrane surface. Our results show that these hydrodynamic methods substantially reduce fouling and flux decline rate. © 2013 Elsevier B.V.

Kim C.-G.,Korea University
Technology and Health Care | Year: 2016

To minimize exposure dose during lateral spine X-Ray testing and obtain optimal image for diagnosis a water filter was made to measure and evaluate dose distribution. When applying the water filter, as thickness increased exposure dose decreased. When applying 2 cm of water filter, clarity of contrast and boundary was found to be 4.5 ± 0.5 and resolution was found to be 2.00 ± 0.5 Lp/mm which was almost identical image quality compared to not applying water filter which showed clarity of contrast and boundary of 5.0 ± 0.0, and resolution of 2.50 ± 0.0 Lp/mm, while reducing exposure dose by 55%. This result is expected to have many uses as important basic data to predict exposure dose of patients and to minimize medical exposure dose through applying water filters during lateral spine X-Ray testing. © 2016 - IOS Press and the authors. All rights reserved.

Zhu X.,University of North Carolina at Chapel Hill | Suk H.-I.,University of North Carolina at Chapel Hill | Shen D.,University of North Carolina at Chapel Hill | Shen D.,Korea University
NeuroImage | Year: 2014

Recent studies on AD/MCI diagnosis have shown that the tasks of identifying brain disease and predicting clinical scores are highly related to each other. Furthermore, it has been shown that feature selection with a manifold learning or a sparse model can handle the problems of high feature dimensionality and small sample size. However, the tasks of clinical score regression and clinical label classification were often conducted separately in the previous studies. Regarding the feature selection, to our best knowledge, most of the previous work considered a loss function defined as an element-wise difference between the target values and the predicted ones. In this paper, we consider the problems of joint regression and classification for AD/MCI diagnosis and propose a novel matrix-similarity based loss function that uses high-level information inherent in the target response matrix and imposes the information to be preserved in the predicted response matrix. The newly devised loss function is combined with a group lasso method for joint feature selection across tasks, i.e., predictions of clinical scores and a class label. In order to validate the effectiveness of the proposed method, we conducted experiments on the Alzheimer's Disease Neuroimaging Initiative (ADNI) dataset, and showed that the newly devised loss function helped enhance the performances of both clinical score prediction and disease status identification, outperforming the state-of-the-art methods. © 2014 Elsevier Inc.

Hou X.,California Institute of Technology | Harel J.,California Institute of Technology | Koch C.,California Institute of Technology | Koch C.,Korea University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

We introduce a simple image descriptor referred to as the image signature. We show, within the theoretical framework of sparse signal mixing, that this quantity spatially approximates the foreground of an image. We experimentally investigate whether this approximate foreground overlaps with visually conspicuous image locations by developing a saliency algorithm based on the image signature. This saliency algorithm predicts human fixation points best among competitors on the Bruce and Tsotsos [1] benchmark data set and does so in much shorter running time. In a related experiment, we demonstrate with a change blindness data set that the distance between images induced by the image signature is closer to human perceptual distance than can be achieved using other saliency algorithms, pixel-wise, or GIST [2] descriptor methods. © 2012 IEEE.

Ultraselective and sensitive detection of xylene and toluene with minimum interferences of other indoor air pollutants such as benzene, ethanol, and formaldehyde is achieved using NiO hierarchical nanostructures doped with Cr. Pure and 1.15-2.56 at% Cr-doped NiO flower-like hierarchical nanostructures assembled from nanosheets are prepared by a simple solvothermal reaction and their gas sensing characteristics toward o-xylene and toluene gases are investigated. The 1.15 at% Cr-doped NiO hierarchical nanostructures show high responses to 5 ppm of o-xylene and toluene (ratio of resistance to gas and air = 11.61 and 7.81, respectively) and negligible cross-responses to 5 ppm of benzene, formaldehyde, ethanol, hydrogen, and carbon monoxide. However, pure NiO nanostructures show low responses to 5 ppm of o-xylene and toluene (ratio of resistance to gas and air = 2.01 and 1.14, respectively) and no selectivity toward any specific gas is observed. Significant enhancement of the response and selectivity to o-xylene and toluene is attributed to the decrease in the hole concentration in NiO and the catalytic oxidation of methyl groups by Cr doping.

Molecular function of the expansin superfamily has been highlighted for cellulosic biomass conversion. In this report, we identified a new bacterial expansin subfamily by analysis of related bacterial sequences and biochemically examined a member of this new subfamily from Hahella chejuensis (HcEXLX2). Among the various complex polysaccharides tested, HcEXLX2 bound most efficiently to cellulose. The relative binding constant (K( r )) against Avicel was 2.1 L g(-1) at pH 6.0 and 4 degrees C. HcEXLX2 enhanced the activity of cellulase, producing about 4.6 times more hydrolysis product after a 36 h reaction relative to when only cellulase was used. The extension strength test on filter paper indicated that HcEXLX2 has a texture loosening effect on filter paper, which was 53% of that observed for 8 M urea treatment. These activities, compared with a cellulose binding domain from Clostridium thermocellum, implied that the synergistic effect of HcEXLX2 comes from not only binding to cellulose but also disrupting the hydrogen bonds in cellulose. Based on these results, we suggest that the new bacterial expansin subfamily functions by binding to cell wall polysaccharides and increasing the accessibility of cell wall degrading enzymes.

Jamali M.,National University of Singapore | Yang H.,National University of Singapore | Lee K.-J.,Korea University
Applied Physics Letters | Year: 2010

The interaction between the propagating spin waves and the current driven motion of a transverse domain wall in magnetic nanowires is studied by micromagnetic simulations. If the speed of domain walls due to current induced spin transfer torque is comparable to the velocity driven by spin waves, the speed of domain wall is improved by applying spin waves. The domain wall velocity can be manipulated by the frequency and amplitude of spin waves. The effect of spin waves is suppressed in the high current density regime in which the domain wall is mostly driven by current induced spin transfer torque. © 2010 American Institute of Physics.

To characterize the outcomes of initial and repeated office-based probing as a primary treatment for congenital nasolacrimal duct obstruction (CNLDO) in children. The medical records of patients who underwent nasolacrimal duct office-based probing for CNLDO between March 2004 and January 2008 were reviewed retrospectively. Nasolacrimal duct probing was performed on 244 eyes from 229 consecutive patients with CNLDO. Patients who were refractory to the first probing underwent a second probing 4 to 8 weeks later. Based on exclusion criteria, 244 eyes from 229 patients (117 males and 112 females), aged 6 to 71 months (mean, 12.4 ± 8.36) were included. The success rate of the initial probing was 80% (196 of 244) for all patients, 82% (111 of 136) in the 6 to 12 month age group, 79% (64 of 81) in the 13 to 18 months age group, and 78% (21 of 27) among individuals older than 19 months (p = 0.868, Pearson chi-square test). The success rate of the second probing was 61% (25 of 41) for all patients, 74% (17 of 23) in the 6 to 12 months age group, 58% (7 of 12) in the 13 to 18 months age group, and 17% (1 of 6) among individuals older than 19 months (p = 0.043, Fisher's exact test). While the success rate of initial nasolacrimal duct probing is not affected by age, the rate of success rate with a second probing was significantly lower in patients older than 19 months. Based on the results, authors recommend further surgical interventions, such as silicone tube intubation or balloon dacryocystoplasty, instead of repeated office probing for patients older than 19 months, if an initial office probing has failed.

Choi J.U.,Korea University
Advances and technical standards in neurosurgery | Year: 2012

Hypothalamic hamartoma (HH) is usually associated with refractory epilepsy, cognitive impairment, and behavioral disturbance. There is now increasing evidence that HH can be treated effectively with a variety of neurosurgical approaches. Treatment options for intractable gelastic seizure in HH patients include direct open surgery with craniotomy, endoscopic surgery, radiosurgery with gamma knife (GKS) and stereotactic radiofrequency thermocoagulation. Selection of treatment modalities depends on type and size of the HH and the surgeon's preference. Two surgical techniques, resection and disconnection, had been described with favorable outcomes. Pretreatment evaluation, patient selection, surgical techniques, complications, and possible selection of treatment are discussed in this chapter.

Woo S.,Broadcom Korea Research Ltd. | Kim H.,Korea University
IEEE/ACM Transactions on Networking | Year: 2013

In recent years, it has been widely believed in the community that the link reliability is strongly related to received signal strength indicator (RSSI) [or signal-to-interference-plus-noise ratio (SINR)] and external interference makes it unpredictable, which is different from the previous understanding that there is no tight relationship between the link reliability and RSSI (or SINR), but multipath fading causes the unpredictability. However, both cannot fully explain why the unpredictability appears in the link state. In this paper, we unravel the following questions: 1) What causes frame losses that are directly related to intermediate link states? 2) Is RSSI or SINR a right criterion to represent the link reliability? 3) Is there a better measure to assess the link reliability? We first configured a testbed for performing a real measurement study to identify the causes of frame losses, and observed that link reliability depends on an intraframe SINR distribution, not a single value of RSSI (or SINR). We also learned that an RSSI value is not always a good indicator to estimate the link state. We then conducted a further investigation on the intraframe SINR distribution and the relationship between the SINR and link reliability with the ns-2 simulator. Based on these results, we finally propose an interference modeling framework for estimating link states in the presence of wireless interferences. We envision that the framework can be used for developing link-aware protocols to achieve their optimal performance in a hostile wireless environment. © 1993-2012 IEEE.

Engels E.A.,U.S. National Cancer Institute | Cho E.R.,Korea University | Jee S.H.,Institute for Health Promotion
The Lancet Oncology | Year: 2010

Background: Hepatitis B virus (HBV) infection is common throughout Asia and Africa. Whether chronic HBV infection increases risk of non-Hodgkin lymphoma (NHL) is unclear. We aimed to assess the association between chronic HBV infection and subsequent development of NHL in a South Korean cohort. Methods: The Korean Cancer Prevention Study is a cohort study of South Korean workers and their dependants enrolled during 1992-95. From this cohort, we excluded individuals who died before Jan 1, 1993, who had cancer at or before the initial visit, who had missing information about weight, height, alanine aminotransferase or aspartate aminotransferase concentrations, or alcohol use, or who had evidence of HIV or HCV infection. Of 1 284 586 eligible participants, 603 585 had baseline data for serum hepatitis B surface antigen (HBsAg) status and were included in our study. We regarded HBsAg positivity at baseline as evidence of chronic HBV infection. Participants were followed up from baseline until Dec 31, 2006. We used national databases of inpatient and outpatient diagnoses and mortality records to ascertain occurrence of haematological malignancies. We assessed incidence of NHL overall and of NHL subtypes, malignant immunoproliferation, Hodgkin's lymphoma, multiple myeloma, and various leukaemias. We used Cox regression to evaluate associations with HBsAg status, adjusting for sex, age, and enrolment year. Findings: 53 045 (9%) of 603 585 participants tested positive for HBsAg at baseline. Subsequently, 133 HBsAg-positive and 905 HBsAg-negative individuals developed NHL. HBsAg-positive participants had an increased risk of NHL overall compared with those who were HBsAg-negative (incidence 19·4 vs 12·3 per 100 000 person-years; hazard ratio [HR] 1·74, 95% CI 1·45-2·09, adjusted for sex, age at baseline, and enrolment year). Among NHL subtypes, HBsAg positivity was associated with increased risk of diffuse large B-cell lymphoma (n=325, incidence 6·86 vs 3·79 per 100 000 person-years; adjusted HR 2·01, 1·48-2·75) and other or unknown subtypes (n=591, incidence 10·5 vs 7·07 per 100 000 person-years; adjusted HR 1·65, 1·29-2·11), compared with HBsAg negativity. Increased risk was also recorded for malignant immunoproliferation (n=14, incidence 0·44 vs 0·15 per 100 000 person-years; adjusted HR 3·79, 1·05-13·7). Risk of these malignancies was consistently raised in HBsAg-positive participants throughout 14 years of follow-up. HBsAg positivity was not associated with follicular or T-cell NHL, Hodgkin's lymphoma, multiple myeloma, or various leukaemias. Interpretation: During extended follow-up, HBsAg-positive individuals had an increased risk of NHL, suggesting that chronic HBV infection promotes lymphomagenesis. Funding: Korean Seoul City Research and the National Research and Development Program for Cancer Control, Ministry for Health, Welfare and Family Affairs, Republic of Korea; US National Cancer Institute. © 2010 Elsevier Ltd.

This study examined the effect of tongue strengthening training and long-term detraining on tongue tip pressure, tongue base pressure, and tongue pressure during effortful swallowing. Ten young healthy volunteers (21–35 years) were participated in this study. Participants received 8-week tongue strengthening exercise 3 days a week with each session lasting 30 min. Measurement of tongue pressure and tongue strengthening exercise were administrated using Iowa Oral Performance Instrument (IOPI). Training intensity was applied at 60 and 80 % of maximal tongue pressure for the first week and the remainder, respectively. Following completion of 8-week training, 28 weeks of detraining period was continued. Training increased tongue tip pressure, tongue base pressure, and tongue pressure during effortful swallowing above pre-training values (p < 0.05). After 28-week detraining, all tongue variables were significantly lower than after 8-week training (p < 0.05) but remained significantly higher than pre-training levels (p < 0.05). These findings demonstrate that high-intensity tongue strengthening exercise can improve tongue pressures. However, training effects were diminished gradually during detraining period. Thus, maintenance programs after strengthening exercise would be required for prolonging training effects. © 2015, Springer Science+Business Media New York.

Bunzli J.-C.G.,Korea University | Bunzli J.-C.G.,Ecole Polytechnique Federale de Lausanne | Eliseeva S.V.,CNRS Center for Molecular Biophysics | Eliseeva S.V.,Institute for Advanced Studies
Chemical Science | Year: 2013

The enthralling properties of lanthanide luminescence have propelled luminescent probes, tags and materials based on these elements to the forefront of science and technology. In this minireview, attention is focused on the latest innovations and on less-known aspects of this field. Exciting new developments in bioimaging, therapy, drug delivery, security tags, luminescent sensors, and solar energy conversion are highlighted. © 2013 The Royal Society of Chemistry.

Baik J.-H.,Korea University
Frontiers in Neural Circuits | Year: 2013

Dopamine (DA) regulates emotional and motivational behavior through the mesolimbic dopaminergic pathway. Changes in DA mesolimbic neurotransmission have been found to modify behavioral responses to various environmental stimuli associated with reward behaviors. Psychostimulants, drugs of abuse, and natural reward such as food can cause substantial synaptic modifications to the mesolimbic DA system. Recent studies using optogenetics and DREADDs, together with neuron-specific or circuit-specific genetic manipulations have improved our understanding of DA signaling in the reward circuit, and provided a means to identify the neural substrates of complex behaviors such as drug addiction and eating disorders. This review focuses on the role of the DA system in drug addiction and food motivation, with an overview of the role of D1 and D2 receptors in the control of reward-associated behaviors. © 2013 Baik.

Feng J.,Tsinghua University | Jain A.K.,Michigan State University | Jain A.K.,Korea University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

Fingerprint matching systems generally use four types of representation schemes: grayscale image, phase image, skeleton image, and minutiae, among which minutiae-based representation is the most widely adopted one. The compactness of minutiae representation has created an impression that the minutiae template does not contain sufficient information to allow the reconstruction of the original grayscale fingerprint image. This belief has now been shown to be false; several algorithms have been proposed that can reconstruct fingerprint images from minutiae templates. These techniques try to either reconstruct the skeleton image, which is then converted into the grayscale image, or reconstruct the grayscale image directly from the minutiae template. However, they have a common drawback: Many spurious minutiae not included in the original minutiae template are generated in the reconstructed image. Moreover, some of these reconstruction techniques can only generate a partial fingerprint. In this paper, a novel fingerprint reconstruction algorithm is proposed to reconstruct the phase image, which is then converted into the grayscale image. The proposed reconstruction algorithm not only gives the whole fingerprint, but the reconstructed fingerprint contains very few spurious minutiae. Specifically, a fingerprint image is represented as a phase image which consists of the continuous phase and the spiral phase (which corresponds to minutiae). An algorithm is proposed to reconstruct the continuous phase from minutiae. The proposed reconstruction algorithm has been evaluated with respect to the success rates of type-I attack (match the reconstructed fingerprint against the original fingerprint) and type-II attack (match the reconstructed fingerprint against different impressions of the original fingerprint) using a commercial fingerprint recognition system. Given the reconstructed image from our algorithm, we show that both types of attacks can be successfully launched against a fingerprint recognition system. © 2011 IEEE.

Fe3O4-decorated graphene balls were prepared by a spray pyrolysis process. Analysis by Raman spectroscopy and X-ray photoelectron spectroscopy indicated that the spray pyrolysis at 800 °C resulted in the complete reduction of graphene oxide sheets containing oxygen functional groups into graphene sheets, leading to the formation of Fe3O4-decorated graphene balls. The graphene content in the composite ball was 27 wt%. The Brunauer-Emmett-Teller surface area of the Fe3O4-decorated graphene balls was as high as 130 m2 g-1. The initial discharge and charge capacities of the Fe3O4-decorated graphene balls at a high current density of 7 A g-1 were 1210 and 843 mAh g-1, respectively, and the discharge capacity was as high as 690 mAh g-1 even after 1000 cycles. The stable reversible discharge capacities of the Fe3O4-decorated graphene balls decreased from 1040 to 540 mAh g-1 with the increase in current density from 1 to 30 A g-1. The Fe3O4-decorated graphene balls with a uniform distribution of ultrafine Fe3O4 nanocrystals below 15 nm showed superior electrochemical properties as anode materials for lithium ion batteries. The overall structure of the Fe3O4-decorated graphene balls was maintained even after long-term cycling. © 2014 Elsevier Ltd. All rights reserved.

Park D.S.,Korea University
Korean Journal of Urology | Year: 2012

Brachytherapy was developed to treat prostate cancer 50 years ago. Current advanced techniques using transrectal ultrasonography were established 25 years ago. Transrectal ultrasound (TRUS) has enabled the prostate to be viewed with improved resolution with the use of modern ultrasound machines. Moreover, the development of software that can provide images captured in real time has improved treatment outcomes. Other new radiologic imaging technologies or a combination of magnetic resonance and TRUS could be applied to brachytherapy in the future. The therapeutic value of brachytherapy for early-stage prostate cancer is comparable to that of radical prostatectomy in long-term follow-up. Nevertheless, widespread application of brachytherapy cannot be achieved for several reasons. The treatment outcome of brachytherapy varies according to the skill of the operator and differences in patient selection. Currently, only three radioactive isotopes are available for use in low dose rate prostate brachytherapy: I-125, Pd-103, and Cs-131; therefore, more isotopes should be developed. High dose rate brachytherapy using Ir-192 combined with external beam radiation, which is needed to verify the long-term effects, has been widely applied in high-risk patient groups. Recently, tumor-selective therapy or focal therapy using brachytherapy, which is not possible by surgical extraction, has been developed to maintain the quality of life in selected cases. However, this new application for prostate cancer treatment should be performed cautiously because we do not know the oncological outcome, and it would be an interim treatment method. This technique might evolve into a hybrid of whole-gland treatment and focal therapy. © The Korean Urological Association, 2012.

Yoo S.-H.,Hoseo University | Kwak S.-Y.,Korea University
Energy Policy | Year: 2010

This paper attempts to investigate the causal relationship between electricity consumption and economic growth among seven South American countries, namely Argentina, Brazil, Chile, Columbia, Ecuador, Peru, and Venezuela using widely accepted time-series techniques for the period 1975-2006. The results indicate that the causal nexus between electricity consumption and economic growth varies across countries. There is a unidirectional, short-run causality from electricity consumption to real GDP for Argentina, Brazil, Chile, Columbia, and Ecuador. This means that an increase in electricity consumption directly affects economic growth in those countries. In Venezuela, there is a bidirectional causality between electricity consumption and economic growth. This implies that an increase in electricity consumption directly affects economic growth and that economic growth also stimulates further electricity consumption in that country. However, no causal relationships exist in Peru. The documented evidence from seven South American countries can provide useful information for each government with regard to energy and growth policy. © 2009 Elsevier Ltd. All rights reserved.

In this paper, we propose a new linear matrix inequality criterion for suppression of limit cycles in state-space direct form digital filters with saturation arithmetic and external interference via a passivity approach. The passive approach is employed to reduce the effect of external interference on the digital filter. The criterion guarantees not only asymptotic stability but also passivity from the external interference to the output vector. This criterion is in the form of linear matrix inequality; hence, it is computationally tractable. An example shows the effectiveness of the proposed criterion. Copyright © 2013 John Wiley & Sons, Ltd.

Eom Y.,Korea University
Korean journal of ophthalmology : KJO | Year: 2012

To investigate systemic factors associated with central serous chorioretinopathy (CSC). We retrospectively reviewed the medical records of 113 Korean patients who were diagnosed with CSC and who underwent history taking with a specialized questionnaire for CSC. They were matched for age and gender at a ratio of 1 : 3 to 339 normal controls. Normal controls were consecutively selected from a database at the Health Promotion Center. General characteristics and medical histories were compared between the two groups. The statistical analyses used included independent t-test, Mann-Whitney test, Fisher's exact test, and multivariate logistic regression analysis. There were 90 men and 23 women in the CSC group, and the male-female ratio for both groups was 3.9 : 1. The mean age of the patients was 45.6 years. In multivariate analysis, hypertension (odds ratio [OR], 2.327; 95% confidence interval [CI], 1.349-4.013), use of medicinal plants (OR, 2.198; 95% CI, 1.193-4.049), sleep disturbances (OR, 1.732; 95% CI, 1.096-2.739), and snoring (OR, 1.727; 95% CI, 1.058-2.820) were strongly associated with CSC. Hypertension, sleep disturbance, snoring, and medicinal plant use were identified as factors associated with CSC. Expanded history taking, including systemic factors and culture-specific behavior related to stress or fatigue such as use of medicinal plants, will be helpful in identifying Korean patients at an increased risk for CSC.

Ku S.-J.,Korea University | Yoo S.-H.,Hoseo University
Renewable and Sustainable Energy Reviews | Year: 2010

Renewable energy sources are considered as alternatives for coping with the high price of oil and global warming. The Korean government has set a target that 11% of the total primary energy supply should be obtained through renewable energy sources until 2030. In order to develop proper policies for renewable energy investment, it is necessary to analyze the benefits of renewable energy investment based on households' willingness to pay. This study attempts to apply a choice experiment (CE) for assessing renewable energy investment in Korea. Moreover, we employ a multinomial probit (MNP) model to relax the assumption that all respondents have the same preferences for the attributes being valued, which is usually required in empirical CE studies. An MNP model allows the most flexible pattern of error correlation structure. The results reveal that the Korean public puts a value on the protection of wildlife, reduction of pollution, and increased employment opportunities. On the other hand, respondents do not derive significant values from the improvement of landscapes. This study is expected to provide policy-makers with useful information for evaluating and planning policies related to renewable energy investment. © 2010 Elsevier Ltd.

Kwon J.,Korea University
Korean journal of ophthalmology : KJO | Year: 2012

To analyze the postoperative strabismic angle for five years or more and to investigate when the angle stabilized in intermittent exotropia. We retrospectively reviewed the clinical records of 89 patients who had undergone surgery for intermittent exotropia. The postoperative strabismic angles measured were analyzed at one-year intervals up to five years postoperatively. We divided them into two groups according to their age at the time of surgery. Group 1 was less than 5 years of age, while Group 2 participants were 5 years of age or older. For our 89 total patients, average exo-angles were 7.8 ± 7.26, 7.9 ± 7.51, 9.5 ± 7.05, 10.1 ± 6.87, and 9.4 ± 6.90 prism diopters at one, two, three, four, and five years postoperatively, respectively. Average exo-angles between postoperative year one and year three, as well as between postoperative year two and year three, were statistically significant (p = 0.015, 0.022). However, the angles were not statistically significant between postoperative year three and year four or between years three and five, respectively (p = 0.707, p = 0.948). The stabilization characteristics of the angle were somewhat different according to age group. In Group 1, the average exo-angle in postoperative years one and three were statistically significant (p = 0.016), but the angle in the same period was not statistically significant in Group 2 (p = 0.203). There was no significant interval change after three years postoperatively in intermittent exotropia, but if the patient's age at surgery was 5 years or higher, no significant change of exo-angle was found following postoperative year one in this study.

Hewitt C.A.,Wake forest University | Kaiser A.B.,MacDiarmid Institute for Advanced Materials and Nanotechnology | Roth S.,Korea University | Craps M.,NanoTechLabs Inc. | And 2 more authors.
Nano Letters | Year: 2012

Thermoelectrics are materials capable of the solid-state conversion between thermal and electrical energy. Carbon nanotube/polymer composite thin films are known to exhibit thermoelectric effects, however, have a low figure of merit (ZT) of 0.02. In this work, we demonstrate individual composite films of multiwalled carbon nanotubes (MWNT)/polyvinylidene fluoride (PVDF) that are layered into multiple element modules that resemble a felt fabric. The thermoelectric voltage generated by these fabrics is the sum of contributions from each layer, resulting in increased power output. Since these fabrics have the potential to be cheaper, lighter, and more easily processed than the commonly used thermoelectric bismuth telluride, the overall performance of the fabric shows promise as a realistic alternative in a number of applications such as portable lightweight electronics. © 2012 American Chemical Society.

Choi J.S.,University of Rochester | Cho M.,Korea University | Cho M.,Korea Basic Science Institute
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

Recently, Tang and Cohen proposed and demonstrated the use of "superchiral" electromagnetic fields to enhance optical enantioselectivity. Their work generated much excitement as enantioselective signals are typically quite small, and it appeared that the enhancement factor could be extremely large. In this paper we explicitly show the limitations of such fields by including the magnetic susceptibility term. This term is small and is ignored in most cases compared to the electric polarizability term. However, for the fields used, the enhancement was obtained at the electric field energy node. Due to conservation of field energy, the magnetic field energy is then maximum, and the magnetic susceptibility contribution can no longer be ignored. This then is what limits the enhancement of the optical enantioselectivity. For a counterpropagating left- and right-circularly polarized light field, as used in the aforementioned experiment, we show that this fundamentally limits the enhancement to one or two orders of magnitude in general, determined by the ratio of the magnetic susceptibility to the electric polarizability of the material used. We also generalize the dissymmetry factor to include optical rotation effects present in chiral media, as opposed to fields being in vacuum. In the process, we generalize Lipkin's "Z000 zilch" (or "optical chirality") to that for a linear medium. This generalization shows that chirality of the material cannot be completely separated from chirality of the field and that opposite enantiomers are symmetric in terms of the dissymmetry factor enhancement. Finally, an analogy between ellipsometric chiroptical signal enhancement and enhanced optical enantioselectivity using a standing wave chiral field is discussed. Our analysis and generalization can be used as a guide for future searches of locally enhanced chiral fields. © 2012 American Physical Society.

Han J.-A.,Sangmyung University | Lim S.-T.,Korea University
Carbohydrate Polymers | Year: 2012

Octenylsuccinylated (OS) starches from waxy rice or high-amylose rice (28.1% amylose) (DS 0.023 and 0.025, respectively) were gamma-irradiated at 10, 30, or 50 kGy and their pasting and thermal properties, crystallinity, and emulsification property were examined. When the OS starches were irradiated, the degrees of substitution gradually decreased as irradiation dose increased. A significant decrease in pasting viscosity was observed with an increase in irradiation dose, indicating the presence of chain degradation induced by the radiation. The melting temperature and enthalpy determined by differential scanning calorimetry increased slightly by irradiating at 10 or 30 kGy. Little change in crystallinity was observed in the X-ray diffraction analysis for the OS high-amylose rice starch regardless of irradiation doses, whereas a decrease in crystallinity was observed with the OS waxy starch irradiated at 50 kGy. Chain degradation induced by irradiation occurred mainly in the amorphous regions, but some loss of crystallinity occurred when the irradiation was excessive. The OS starches showed greater emulsion capacity and stability than the native counterparts due to their amphipathic nature. The irradiation further improved the emulsification properties of OS starches. The irradiation at 10 kGy was optimal, and treating at higher doses decreased the emulsion capacity and stability of the OS starches. © 2012 Elsevier Ltd. All rights reserved.

Kim N.H.,Korea University
Diabetes and Metabolism Journal | Year: 2012

Obstructive sleep apnea (OSA) is a chronic disorder that is prevalent, especially in subjects with obesity or diabetes. OSA is related to several metabolic abnormalities, including diabetes, insulin resistance, hypertension, and cardiovascular diseases. Although Koreans are less obese than Caucasians, the prevalence of OSA is comparable in both groups. Thus, the impact of OSA on metabolism may be similar. Many epidemiologic and experimental studies have demonstrated that OSA is associated with glucose intolerance and insulin resistance via intermittent hypoxia, sleep fragmentation, and sleep deprivation. The effect of continuous positive airway pressure treatment on glucose metabolism is still controversial. Randomized controlled trials are needed to evaluate the ability of OSA treatment to reduce the risk of diabetes and insulin resistance in subjects without diabetes and to ameliorate glucose control in patients with diabetes. © 2012 Korean Diabetes Association.

Jung E.S.,Korea University | Im Y.,Korea Institute for Defense Analyses
International Journal of Industrial Ergonomics | Year: 2015

As the use of mobile touch devices continues to increase, distinctive user experiences can be provided through a direct manipulation. Therefore, the characteristics of touch interfaces should be considered regarding their controllability. This study aims to provide a design approach for touch-based user interfaces. A derivation procedure for the touchable area is proposed as a design guideline based on input behavior. To these ends, two empirical tests were conducted through a smart phone interface. Fifty-five participants were asked to perform a series of input tasks on a screen. As results, touchable area with a desirable hit rate of 90% could be yielded depending on the icon design. To improve the applicability of the touchable area, user error was analyzed based on omission-commission classification. The most suitable design had a hit rate of 95% compared to 90 and 99%. This study contributes practical implications for user interaction design with finger-based controls. Relevance to industry: This research describes a distinctive design approach that guarantees the desired touch accuracy for effective use of mobile touch devices. Therefore, the results will encourage interface designers to take into account the input behavior of fingers from a user-centered perspective. © 2015 Elsevier B.V.

Moon Y.J.,Korea University
European Journal of Mechanics, B/Fluids | Year: 2013

The sound of fluid at low Mach number is a special research area that poses diverse applications not only in aerodynamics but also in bio-medical or biological fluids. The related Mach numbers are in the order of O(10 -2) or even less and therefore the compressibility effects are substantially low but still play an important role in many aspects. A hybrid method of splitting the hydrodynamic field and the acoustic field is of our present interest and attention is given to the linearized perturbed compressible equations (LPCE). In this paper, the linearized perturbed compressible equations are reviewed with some discussion on the acoustic source term, -DP/Dt. A few selected applications of aerodynamic noise and bio-fluid sound are demonstrated by the present hybrid method. © 2013 Elsevier Masson SAS. All rights reserved.

Li C.-Z.,University of Washington | Yip H.-L.,University of Washington | Jen A.K.-Y.,University of Washington | Jen A.K.-Y.,Korea University
Journal of Materials Chemistry | Year: 2012

Tremendous progress has been made on the design and processing of new active and interfacial materials to enable organic photovoltaics to achieve high power conversion efficiencies of >10%. In this Feature Article the development of functional fullerenes as (1) acceptors, (2) electron selective layers, and (3) morphology stabilizers for bulk heterojunction polymer solar cells is reviewed. In addition to the standard PCBM based acceptors, a wide variety of newly developed fullerene-derived molecules have appeared in the past few years and started to show very encouraging photovoltaic performance when they were blended with low bandgap conjugated polymers. New fullerene derivatives with proper molecular design can also serve as electron selective interfacial materials and morphology stabilizers for the bulk heterojunction layer, which are essential to improve the interfacial property and long term stability of polymer solar cells. Although there still are many challenges ahead before practical polymer solar cells will arrive in the market place, the research in functional fullerenes deserves to have more attention in order to expedite this development process. © 2012 The Royal Society of Chemistry.

Chang M.,Korea University
Korean journal of ophthalmology : KJO | Year: 2012

To evaluate the accuracy of preoperative keratometers used in cataract surgery with toric intraocular lens (IOL). Twenty-five eyes received an AcrySof toric IOL implantation. Four different keratometric methods, a manual keratometer, an IOL master, a Pentacam and an auto keratometer, were performed preoperatively in order to evaluate preexisting corneal astigmatism. Differences between the true residual astigmatism and the anticipated residual astigmatism (keratometric error) were compared at one and three months after surgery by using a separate vector analysis to identify the keratometric method that provided the highest accuracy for astigmatism control. The mean keratomeric error was 0.52 diopters (0.17-1.17) for the manual keratometer, 0.62 (0-1.31) for the IOL master, 0.69 (0.08-1.92) for the Pentacam, and 0.59 (0.08-0.94) for the auto keratometer. The manual keratometer was the most accurate, although there was no significant difference between the keratometers (p > 0.05). All of the keratometers achieved an average keratometric error of less than one diopter. Manual keratometry was the most accurate of the four methods evaluated, although the other techniques were equally satisfactory in determining corneal astigmatism.

Nahm C.-W.,Korea University
Journal of Physics and Chemistry of Solids | Year: 2012

The effect of Ta 2O 5 addition on microstructure, electrical properties, and dielectric characteristics of the quaternary ZnO-V 2O 5-MnO 2 vaistor ceramics was investigated. Analysis of the microstructure indicated that the quaternary ZnO-V 2O 5-MnO 2-Ta 2O 5 ceramics consisted of mainly ZnO grain and minor secondary phases such as Zn 3(VO 4) 2, ZnV 2O 4, TaVO 5, and Ta 2O 5. As the amount of Ta 2O 5 increased, the sintered density increased from 94.8 to 97.2% of the theoretical density (5.78 g/cm 3 for ZnO), whereas the average grain size decreased from 7.7 to 6.0 μm. The ceramics added with 0.05 mol% Ta 2O 5 exhibited the highest breakdown field (2715 V/cm) and the highest nonlinear coefficient (20). However, further increase caused α to abruptly decrease. The Ta 2O 5 acted as a donor due to the increase of electron concentration in accordance with the amount of Ta 2O 5. The donor concentration increased from 1.97×10 18 to 3.04×10 18cm -3 with increasing the amount of Ta 2O 5 and the barrier height exhibited the maximum value (0.95 eV) at 0.05 mol% Ta 2O 5. © 2012 Elsevier Ltd.

Lloyd-Hughes J.,University of Oxford | Jeon T.-I.,Korea University
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2012

We review pioneering and recent studies of the conductivity of solid state systems at terahertz frequencies. A variety of theoretical formalisms that describe the terahertz conductivity of bulk, mesoscopic and nanoscale materials are outlined, and their validity and limitations are given. Experimental highlights are discussed from studies of inorganic semiconductors, organic materials (such as graphene, carbon nanotubes and polymers), metallic films and strongly correlated electron systems including superconductors. © Springer Science+Business Media, LLC 2012.

In this experiment, post-oxidizing treatments were implemented on AISI 316L stainless steel which was plasma nitrocarburized previously at various temperatures. Plasma nitrocarburizing was performed on AISI 316L stainless steel at various temperatures (400°C, 450°C, 500°C) with a gas mixture of H2, N2, and CH4 for 15 h. Additionally, the post oxidation treatment was carried out at 400°C for 1 h in a gas mixture of O2 and H2. After treatment, the behavior of the duplex layer was investigated by optical microscopy, X-ray diffraction, scanning electron microscopy and micro-hardness testing. A Potentiodynamic polarization test was also used to evaluate the corrosion resistance of the samples. The X-ray diffraction confirmed the development of a Cr2N, γn phase and magnetite (Fe3O4) phase under plasma nitrocarburizing and post-oxidizing processes. Additionally, it was found that the thickness and surface hardness increased with an increasing nitrocarburizing temperature. The experiment revealed that 316L stainless steel had better hardness and excellent corrosion resistance than the bare sample, when both the nitrocarburizing and oxidizing treatment temperatures were 400°C. Copyright © The Korean Institute of Metals and Materials.

Chay J.,Korea University | Kim C.,Seoul National University of Science and Technology
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We consider the structure of divergences in Drell-Yan process with small transverse momentum. The factorization proof is not trivial because various kinds of divergences are intertwined in the collinear and soft parts at high orders. We prescribe a method to disentangle the divergences in the framework of the soft-collinear effective theory. The rapidity divergence is handled by introducing the δ regulator in the collinear Wilson lines. The collinear part, which consists of the transverse-momentum-dependent parton distribution function, is free of the rapidity divergence after the soft zero-bin subtraction. There still remains the problem of mixing between the ultraviolet and infrared divergences, which forbids the renormalization group description. We show that the mixing is cancelled by the soft function. This suggests that the collinear and soft parts should be treated as a whole in constructing a consistent factorization theorem. The renormalization group behavior of the combined collinear and soft parts is presented explicitly at one loop. We also show that the integrated parton distribution function can be obtained by integrating the transverse-momentum-dependent parton distribution function over the transverse momentum. © 2012 American Physical Society.

Kwon S.-H.,Korea University
Applied Physics Express | Year: 2010

Gaussian-shaped far-field emission of low divergence, ±18.7°, was obtained in a two-dimensional photonic crystal coupled cavity mode. Breaking of the electric field balance by elongated air holes allowed linearly polarized, directional far-field emission. The divergence was further reduced to ±7.5° by increasing the size of the coupled cavity. Effects of the aspect ratio of elliptical air holes on quality factor and directionality are also discussed numerically. In addition, the coupling efficiency, 91%, of the proposed vertical emitter to the waveguide is obtained while quality factor is maintained as high as 1000. © 2010 The Japan Society of Applied Physics.

Nahm C.-W.,Korea University
Ceramics International | Year: 2013

The microstructure, electrical properties, and aging behavior of the ZnO-Pr 6O11-CoO-Cr2O3-Y2O 3 varistor ceramics modified with Tb4O7 were investigated. The microstructure consisted of ZnO grain and an intergranular layer (Pr-, Y-, and Er-rich phases) as a secondary phase. The increase in the amount of Tb4O7 decreased the average grain size from 8.0 to 4.6 μm and increased the sintered density from 5.72 to 5.82 g/cm 3. As the amount of Tb4O7 increased, the breakdown field increased significantly from 2886 to 6902 V/cm and the nonlinear coefficient increased from 32.5 to 40.3 at 0.75 mol%. The varistor ceramics added with 0.5 mol% Tb4O7 exhibited excellent stability by exhibiting -0.1% in the variation rate of the breakdown field and -0.3% in the variation rate of the nonlinear coefficient for aging stress state of 0.95 E1 mA/150 °C/24 h. © 2012 Elsevier Ltd and Techna Group S.r.l.

The clamping characteristics and pulse aging behavior of ZnO-V 2O5-Mn3O4 varistor ceramics modified with Nb2O5 were investigated at a specified pulse current. The varistor ceramics modified with 0.25 mol% Nb2O 5 exhibited the best clamp characteristics, in which the clamp voltage ratio is in the range of 1.83-2.57 at a pulse current in the range of 1-50 A. The varistor ceramics modified with 0.05 mol% Nb2O 5 exhibited the best electrical stability, where %ΔE1mA/ cm2=-2.2% and %Δα=-30.8% after applying the pulse current of 100 A. © 2012 Elsevier Ltd and Techna Group S.r.l.

Ahn C.K.,Korea University
Circuits, Systems, and Signal Processing | Year: 2013

In this paper, a new criterion for the absence of limit cycles in fixed-point state-space digital filters with saturation overflow arithmetic and external interference is proposed via an input/output-to-state stability (IOSS) approach. The criterion ensures not only the asymptotic stability, but also the reduction of the effect of the external interference. This criterion is represented by linear matrix inequality (LMI) and, hence, is computationally tractable. Via a numerical example, we demonstrate the effectiveness of the proposed IOSS criterion. © 2012 Springer Science+Business Media New York.

Nahm C.-W.,Korea University
Ceramics International | Year: 2012

The microstructure and electrical properties of ternary ZnO-V 2O 5-Mn 3O 4 varistor ceramics modified with Nb 2O 5 were systematically investigated for different amounts of Nb 2O 5. The average grain size for Nb 2O 5-doped ceramics was larger than Nb 2O 5-free ceramics and it was in the range of 6.64-7.27 μm. The sintered density of pellets increased from 5.50 to 5.54 g/cm 3 as the Nb 2O 5 amount increased. The breakdown field increased from 947 to 4521 V/cm with an increase in the amount of Nb 2O 5, whereas a further addition caused it to decrease up to 4374 V/cm at 0.25 mol%. The varistor ceramics doped with 0.05 mol% Nb 2O 5 exhibited the best nonlinear properties, in which the nonlinear coefficient is 47 and the leakage current density is 0.14 mA/cm 2. © 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Bstieler L.,University of New Hampshire | Hemmert M.,Korea University
Journal of Product Innovation Management | Year: 2010

Despite the growing popularity of new product development across organizational boundaries, the processes, mechanisms, or dynamics that leverage performance in interorganizational (I-O) product development teams are not well understood. Such teams are staffed with individuals drawn from the partnering firms and are relied on to develop successful new products while at the same time enhancing mutual learning and reducing development time. However, these collaborations can encounter difficulties when partners from different corporate cultures and thought worlds must coordinate and depend on one another and often lead to disappointing performance. To facilitate collaboration, the creation of a safe, supportive, challenging, and engaging environment is particularly important for enabling productive collaborative I-O teamwork and is essential for learning and time efficient product development. This research develops and tests a model of proposed factors to increase both learning and time efficiency on I-O new product teams. It is argued that specific behaviors (caring), beliefs (psychological safety), task-related processes (shared problem solving), and governance mechanisms (clear management direction) create a positive climate that increases learning and time efficiency on I-O teams. Results of an empirical study of 50 collaborative new product development projects indicate that (1) shared problem solving and caring behavior support both learning and time efficiency on I-O teams, (2) team psychological safety is positively related to learning, (3) management direction is positively associated with time efficiency, and (4) shared problem solving is more strongly related to both performance dimensions than are the other factors. The factors supporting time efficiency are slightly different from those that foster learning. The relative importance of these factors also differs considerably for both performance aspects. Overall, this study contributes to a better understanding of the factors that facilitate a favorable environment for productive collaboration on I-O teams, which go beyond contracts or top-management supervision. Establishing such an environment can help to balance management concerns and promote the success of I-O teams. The significance of the results is elevated by the fragility of collaborative ventures and their potential for failure, when firms with different organizational cultures, thought worlds, objectives, and intentions increasingly decide to work across organizational boundaries for the development of new products. © 2010 Product Development and Management Association.

Ahn C.K.,Korea University | Song M.K.,Wonkwang University
International Journal of Innovative Computing, Information and Control | Year: 2013

In this paper, we propose new sets of criteria for exponential robust stability of Takagi-Sugeno (T-S) fuzzy Hopfield neural networks. The L2-L∞ approach is applied to obtain new sets of stability criteria, under which T-S fuzzy Hopfield neural networks reduce the effect of external input to a prescribed level. These sets of criteria are presented based on the matrix norm and linear matrix inequality (LMI). The proposed sets of criteria also guarantee exponential stability for T-S fuzzy Hopfield neural networks without external input. © 2013 ICIC International.

Choi S.H.,Konkuk University | Lee J.-H.,Korea University | Kang Y.C.,Konkuk University
Nanoscale | Year: 2013

Core-shell structured NiO@TiO2 nanopowders for application as anode materials for lithium ion batteries are prepared by one-pot flame spray pyrolysis from aqueous spray solution containing Ni and Ti components. A new formation mechanism of the core-shell structured nanopowders in the flame spray pyrolysis is proposed. Composite nanopowders are first formed by surface growth and coagulation from NiO and TiO2 vapors. A small amount of TiO 2 in composite powders disturbs the crystallization of TiO 2. Therefore, the TiO2 component moves out to the surface of the powders forming an amorphous shell during the formation of single crystalline NiO. The initial discharge and charge capacities of the NiO@TiO 2 nanopowders at a current density of 300 mA g-1 are 1302 and 937 mA h g-1, respectively. The discharge capacities of the pure NiO and NiO@TiO2 nanopowders after 80 cycles are 542 and 970 mA h g-1, respectively. The capacity retentions of the pure NiO and NiO@TiO2 nanopowders after 80 cycles measured after the first cycles are 75 and 108%, respectively. © 2013 The Royal Society of Chemistry.

Singh D.,Korea University
Journal of Theoretical and Applied Information Technology | Year: 2014

The enhancement of existing electronics healthcare (e-health) has used internet-based embedded sensing biomedical devices. The biomedical devices are capable to interact with other mobile applications to deliver healthcare services on a global scale. The Internet Engineering Task Force (IETF) working group has introduced IPv6 over wireless personal area networks (6LoWPAN). The 6LoWPAN technology has capability to support Internet over wireless sensor networks (WSN). This paper has introduced the convergence of mobility and energy consumption mechanism to support global healthcare communications services with the use of 6LoWPAN based biomedical sensors. The energy management mechanism helps to increase the lifetime of IETF-6LoWPAN devices during the movement of patient's in personal area networks (PAN). In this system, several biomedical sensors fixed on the patient's body area networks with the association of 6LoWPAN technology to support global communication. We have presented a smart hospital scenario for global healthcare monitoring applications such as ECG, PPG, Blood-pressure, Temperature etc. © 2005 - 2014 JATIT & LLS. All rights reserved.

The aims of this study were (1) to identify the useful clinical parameters of noninvasive approach for distinguishing nonalcoholic steatohepatitis (NASH) from nonalcoholic fatty liver disease (NAFLD), and (2) to determine whether the levels of the identified parameters are correlated with the severity of liver injury in patients with NASH. One hundred and eight consecutive patients with biopsy-proven NAFLD (age, 39.8±13.5 years, mean±SD; males, 67.6%) were prospectively enrolled from 10 participating centers across Korea. According to the original criteria for NAFLD subtypes, 67 patients (62.0%) had NASH (defined as steatosis with hepatocellular ballooning and/or Mallory-Denk bodies or fibrosis ≥2). Among those with NAFLD subtype 3 or 4, none had an NAFLD histologic activity score (NAS) below 3 points, 40.3% had a score of 3 or 4 points, and 59.7% had a score >4 points. Fragmented cytokeratin-18 (CK-18) levels were positively correlated with NAS (r=0.401), as well as NAS components such as lobular inflammation (r=0.387) and ballooning (r=0.231). Fragmented CK-18 was also correlated with aspartate aminotransferase (r=0.609), alanine aminotransferase (r=0.588), serum ferritin (r=0.432), and the fibrosis stage (r=0.314). A fragmented CK-18 cutoff level of 235.5 U/L yielded sensitivity, specificity, and positive and negative predictive values of 69.0%, 64.9%, 75.5% (95% CI 62.4-85.1), and 57.1% (95% CI 42.2-70.9), respectively, for the diagnosis of NASH. Serum fragmented CK-18 levels can be used to distinguish between NASH and NAFL. Further evaluation is required to determine whether the combined measurement of serum CK-18 and ferritin levels improves the diagnostic performance of this distinction.

Kang Y.S.,Korea University
Electrolyte and Blood Pressure | Year: 2013

With excess nutrition, the burden of obesity is a growing problem worldwide. The imbalance between energy intake and expenditure leads to variable disorders as all major risk factors for cardiovascular disease. There are many hypothetical mechanisms to explain obesity-associated hypertension. Activation of the RAAS is a key contributing factor in obesity. Particularly, the RAAS in adipose tissue plays a crucial role in adipose tissue dysfunction and obesity-induced inflammation. The phenotypic changes of adipocytes occur into hypertrophy and an inflammatory response in an autocrine and paracrine manner to impair adipocyte function, including insulin signaling pathway. Adipose tissue produce and secretes several molecules such as leptin, resistin, adiponectin, and visfatin, as well as cytokines such as TNF-α, IL-6, MCP-1, and IL-1. These adipokines are stimulated via the intracellular signaling pathways that regulate inflammation of adipose tissue. Inflammation and oxidative stress in adipose tissue are important to interact with the microvascular endothelium in the mechanisms of obesity-associated hypertension. Increased microvascular resistance raises blood pressure. Therefore, a regulatory link between microvascular and perivascular adipose tissue inflammation and adipokine synthesis are provided to explain the mechanism of obesity-associated hypertension. Copyright © 2013 The Korean Society of Electrolyte Metabolism.

Lee K.,University of San Francisco | Nguyen V.,University of San Francisco | Lee K.-M.,Korea University | Kang S.-M.,University of San Francisco | Tang Q.,University of San Francisco
American Journal of Transplantation | Year: 2014

Regulatory T cells (Tregs) are essential for the establishment and maintenance of immune tolerance, suggesting a potential therapeutic role for Tregs in transplantation. However, Treg administration alone is insufficient in inducing long-term allograft survival in normal hosts, likely due to the high frequency of alloreactive T cells. We hypothesized that a targeted reduction of alloreactive T effector cells would allow a therapeutic window for Treg efficacy. Here we show that preconditioning recipient mice with donor-specific transfusion followed by cyclophosphamide treatment deleted 70-80% donor-reactive T cells, but failed to prolong islet allograft survival. However, infusion of either 5 × 106 Tregs with direct donor reactivity or 25 × 106 polyclonal Tregs led to indefinite survival of BALB/c islets in more than 70% of preconditioned C57BL/6 recipients. Notably, protection of C3H islets in autoimmune nonobese diabetic mice required islet autoantigen-specific Tregs together with polyclonal Tregs. Treg therapy led to significant reduction of CD8+ T cells and concomitant increase in endogenous Tregs among graft-infiltrating cells early after transplantation. Together, these results demonstrate that reduction of the donor-reactive T cells will be an important component of Treg-based therapies in transplantation. This study demonstrates that donor-reactive regulatory T cells are more potent than polyclonal regulatory T cells in preventing rejection; however, both types require depletion of donor-reactive T effector cells for optimal efficacy. See editorial by Bradley on page 5. © 2013 The American Society of Transplantation and the American Society of Transplant Surgeons.

Failure to establish agreed-upon criteria by which to measure and identify online video game addiction has resulted in a lack of reliable evidence of the actual percentage of individuals who are pathologically dependent. Building upon prior research, the present study sought to better determine the magnitude of pathological online video game play using a distinction between core and peripheral criteria for behavioral addiction. Preferences and perceptions towards online video games and addiction were also examined to better understand players' habits. A questionnaire was administered to 1332 South Korean students across 11 high schools and 1 middle school in an area surrounding the capital of Seoul. Using a monothetic and a polythetic classification system, findings showed rates ranging between 1.7% and 25.5%, with a 2.7% addiction rate when distinguishing core from peripheral criteria. These results may suggest that online video game addiction rates in intense gaming cultures such as South Korea are not as high as otherwise believed. The findings will be of assistance to educators, policymakers, clinicians, and researchers in understanding the challenges in deriving meaningful video game addiction prevalence rates, and thus being able to better separate reality from conjecture with regard to the notion of pathological game play. © 2012 Elsevier Ltd. All rights reserved.

Wallraven C.,Korea University
Psychonomic Bulletin and Review | Year: 2014

The idea that faces are represented within a structured face space (Valentine Quarterly Journal of Experimental Psychology 43: 161-204, 1991) has gained considerable experimental support, from both physiological and perceptual studies. Recent work has also shown that faces can even be recognized haptically-that is, from touch alone. Although some evidence favors congruent processing strategies in the visual and haptic processing of faces, the question of how similar the two modalities are in terms of face processing remains open. Here, this question was addressed by asking whether there is evidence for a haptic face space, and if so, how it compares to visual face space. For this, a physical face space was created, consisting of six laser-scanned individual faces, their morphed average, 50 %-morphs between two individual faces, as well as 50 %-morphs of the individual faces with the average, resulting in a set of 19 faces. Participants then rated either the visual or haptic pairwise similarity of the tangible 3-D face shapes. Multidimensional scaling analyses showed that both modalities extracted perceptual spaces that conformed to critical predictions of the face space framework, hence providing support for similar processing of complex face shapes in haptics and vision. Despite the overall similarities, however, systematic differences also emerged between the visual and haptic data. These differences are discussed in the context of face processing and complex-shape processing in vision and haptics. © 2014 Psychonomic Society, Inc.

Kim Y.,Korea University | Yokoyama W.H.,U.S. Department of Agriculture
Journal of Agricultural and Food Chemistry | Year: 2011

Hydroxypropyl methylcellulose (HPMC) is a substituted cellulose that reduces serum cholesterol at modest intake levels. HPMC has also been used for decades in gluten-free breads at a level to optimize loaf volume. Because consumers resist the consumption of whole wheat breads, the sensory and physical properties of all oat and barley breads incorporating HPMC were evaluated. Oat and barley also contain β-glucan, a glucose polymer similar to HPMC that also lowers cholesterol. The textural and sensory properties of the breads were determined by instrumental and chemical methods and sensory panels. HPMC increased the loaf volume of the breads by up to 2 times and decreased hardness immediately after baking and after up to 3 days of storage. Barley bread with HPMC was rated the highest in overall acceptability by sensory panelists compared to oat and wheat breads with or without HPMC. © 2010 American Chemical Society.

Yang J.H.,Korea University
Journal of orthopaedic surgery and research | Year: 2014

The sagittal alignment of the spine changes depending on body posture and degenerative changes. This study aimed to observe changes in sagittal alignment of the lumbar spine with different positions (standing, supine, and various sitting postures) and to verify the effect of aging on lumbar sagittal alignment. Whole-spine lateral radiographs were obtained for young volunteers (25.4 ± 2.3 years) and elderly volunteers (66.7 ± 1.7 years). Radiographs were obtained in standing, supine, and sitting (30°, 60°, and 90°) positions respectively. We compared the radiological changes in the lordotic and segmental angles in different body positions and at different ages. Upper and lower lumbar lordosis were defined according to differences in anatomical sagittal mobility and kinematic behavior. Lumbar lordosis was greater in a standing position (52.79° and 53.90° in young and old groups, respectively) and tended to decrease as position changed from supine to sitting. Compared with the younger group, the older group showed significantly more lumbar lordosis in supine and 60° and 90° sitting positions (P=0.043, 0.002, 0.011). Upper lumbar lordosis in the younger group changed dynamically in all changed positions compared with the old group (P=0.019). Lower lumbar lordosis showed a decreasing pattern in both age groups, significantly changing as position changed from 30° to 60° (P=0.007, 0.007). Lumbar lordosis decreases as position changes from standing to 90°sitting. The upper lumbar spine is more flexible in individuals in their twenties compared to those in their sixties. Changes in lumbar lordosis were concentrated in the lower lumbar region in the older group in sitting positions.

Lee H.J.,Korea University
The Korean journal of gastroenterology = Taehan Sohwagi Hakhoe chi | Year: 2014

We presented two interesting cases of gastrocolocutaneous fistula that occurred after percutaneous endoscopic gastrostomy (PEG) tube placement, and its management. This fistula is a rare complication that occurs after PEG insertion, which is an epithelial connection between mucosa of the stomach, colon, and skin. The management of the fistula is controversial, ranging from conservative to surgical intervention. Endoscopists should be aware of the possibility of gastrocolocutaneous fistula after PEG insertion, and should evaluate the risk factors that may contribute to the development of gastrocolocutaneous fistula before the procedure. We reviewed complications of gastrostomy tube insertion, symptoms of gastrocolocutaneous fistula, and its risk factors.

Lee J.-S.,Korea University
Nanotechnology Reviews | Year: 2014

Silver nanomaterials have attracted a lot of interest from researchers, mainly owing to their distinctive optical properties such as localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS). These properties are particularly interesting for the diagnostic applications when combined with target-recognition capabilities of surface ligands and target concentration-dependent quantitative aspects of the LSPR or SERS signal. This review covers these two main optical properties of silver nanomaterials with respect to their sensing applications for various chemical and biological targets. The LSPR-based colorimetric detection schemes are further divided into two categories based on what they depend on: (1) assembly and (2) deformation of the silver nanoparticle probes. Because the various shapes of the silver nanomaterials are highly associated with how to design and control the LSPR- and SERS-based detection schemes, the latest progress in the development of highly sensitive and selective detection strategies are discussed with respect to the morphological diversity of the silver nanomaterials.

Hwang M.,Korea University
PM & R : the journal of injury, function, and rehabilitation | Year: 2011

To evaluate the psychometric properties of the Care and Comfort Caregiver Questionnaire (CareQ), which was developed to measure the perceived effort of caregivers in providing care for children with moderate to severe cerebral palsy (CP). Cross-sectional data collection from a representative sample of a large racially/ethnically diverse geographic region. Outpatient CP clinics at a metropolitan rehabilitation institution. A total of 100 primary caregivers of children with CP whose Gross Motor Function Classification System (GMFCS) levels were III-V. The CareQ was administered to primary caregivers of children with CP. Internal consistency of the CareQ and its 3 domains (Personal Care, Positioning/Transfers, and Comfort) were evaluated with the Cronbach α. Construct validity of the CareQ was evaluated by its correlation with the Pediatric Functional Independence Measure (WeeFIM). Associations between CareQ scores and child and caregiver characteristics were assessed. Mean CareQ scores for children with GMFCS levels III, IV, and V were 30.6, 42.8, and 45.1, respectively (P < .01). The Cronbach α was 0.90 for total CareQ and 0.93, 0.80, and 0.82 for its Personal Care, Positioning/Transfers, and Comfort domains, respectively. Total CareQ and WeeFIM scores were negatively correlated (r = -.22; P = .03). Total CareQ scores were positively correlated with the child's age (r = .38; P < .01) and with body weight (r =.37; P < .01); however, no caregiver characteristics were associated with CareQ scores. The CareQ is a concise and internally consistent measure of difficulty of care as perceived by caregivers of children whose GMFCS levels were III-V. Further investigation should include assessment of responsiveness of the CareQ to changes in the child's functional status over time and/or with rehabilitation interventions. Copyright © 2011 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Shim J.O.,Korea University
Pediatric Gastroenterology, Hepatology and Nutrition | Year: 2013

The gut mucosal barrier plays an important role in maintaining a delicate immune homeostasis. The pathogenesis of inflammatory bowel disease (IBD) is considered to involve a defective mucosal immunity along with a genetic predisposition. Recent views have suggested an excessive response to components of the gut microbiota in IBD. A condition of "dysbiosis", with alterations of the gut microbial composition, has been observed in patients with IBD. In this article, the author review recent studies of gut microbiota in IBD, particularly the importance of the gut microbiota in the pathogenesis of pediatric IBD. © 2014 by The Korean Society of Pediatric Gastroenterology, Hepatology and Nutrition.

Ahn C.K.,Korea University
Information Sciences | Year: 2013

This paper proposes a new passive and exponential filter for Takagi-Sugeno fuzzy Hopfield neural networks, with time delay and external disturbance. Based on the Lyapunov-Krasovskii stability theory, Jensen's inequality, and linear matrix inequality (LMI), a new delay-dependent criterion is proposed such that the filtering error system becomes exponentially stable and passive from the external disturbance to the output error. The proposed filter can be obtained by solving the LMI, which can be easily facilitated using standard numerical packages. Two numerical examples are given to illustrate the effectiveness of the proposed filter. © 2013 Elsevier Inc.

Background Renal transplantation is the best treatment for patients with end-stage renal disease. Although there is significantly increased risk of malignancy after renal transplantation, carcinoma of the native kidney is very rare, and moreover, the risk of endocrinologic malignancy after renal transplantation is lower than in the general population and adrenal cortical carcinoma extremely rare. We report a case of incidental renal cell carcinoma originating from a native kidney after en-bloc resection for adrenal carcinoma in a kidney transplant recipient. Case Report A 57 year-old male patient had undergone living-donor kidney transplantation for chronic renal failure from hypertension 15 years earlier and had a right adrenal tumor diagnosed on surveillance abdomen-pelvis computerized tomography. Based on 24-hour catecholamine laboratory findings, nonfunctioning tumor was suspected. The planned en-bloc resection of right adrenal gland and right native kidney combining the perirenal tissue and Gerota fascia was performed, because the tumor was suspicious for malignancy and could possibly invade the perirenal tissue or right kidney. On the final pathology, combined adrenal cortical carcinoma and incidental renal cell carcinoma was confirmed. Renal cell carcinoma was papillary, type I, and stage T1N0M0. Adrenal cortical carcinoma was 7.6 × 6.5 cm in size, had marked nuclear atypia, and was grade IV/IV. Mitotic counts were >10 per high-power field, but it had no capsular invasion or vascular invasion, and free resection margin was confirmed. In the preoperative period, he had taken immunosuppressants FK506 and mycophenolate sodium, but after combined carcinomas were confirmed, the regimen of combination of immunosuppressants was changed to sirolimus with low-dose FK506 and half-dose mycophenolate sodium. © 2014 by Elsevier Inc. All rights reserved.

Jung W.-Y.,Gangneung - Wonju National University | Han S.-C.,Korea University
Composites Part B: Engineering | Year: 2014

In this paper, we investigate the vibration analysis of functionally graded material (FGM) and laminated composite structures, using a refined 8-node shell element that allows for the effects of transverse shear deformation and rotary inertia. The properties of FGM vary continuously through the thickness direction according to the volume fraction of constituents defined by sigmoid function, but in this method, their Poisson's ratios of the FGM plates and shells are assumed to be constant. The finite element, based on a first-order shear deformation theory, is further improved by the combined use of assumed natural strains and different sets of collocation points for interpolation the different strain components. We analyze the influence of the shell element with the various location and number of enhanced membrane and shear interpolation. Using the assumed natural strain method with proper interpolation functions the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. The natural frequencies of plates and shells are presented, and the forced vibration analysis of FGM and laminated composite plates and shells subjected to arbitrary loading is carried out. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. To validate and compare the finite element numerical solutions, the reference solutions of plates based on the Navier's method, the series solutions of sigmoid FGM (S-FGM) plates are obtained. Results of the present theory show good agreement with the reference solutions. In addition the effect of damping is investigated on the forced vibration analysis of FGM plates and shells. © 2013 Elsevier Ltd. All rights reserved.

Jung W.-Y.,Gangneung - Wonju National University | Han S.-C.,Korea University
Composite Structures | Year: 2014

In this study a numerical investigation is presented for initial buckling response of laminated composite plates and shells under the combined in-plane loading using a modified 8-ANS method. The finite element, based on a modified first-order shear deformation theory, is further improved by the combined use of assumed natural strain method. We analyze the influence of the shell element with the various location and number of enhanced membrane and shear interpolation. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. The effect of various types of lay-ups, materials and number of layers on initial buckling response is discussed. In addition, the effect of direction of shear load on the initial buckling response is studied. The interaction curves (between in-plane compression and shear for different parameters of the laminates) are presented. The numerical results obtained are in good agreement with those reported by other researchers. © 2013 Elsevier Ltd.

Ahn C.K.,Korea University
Digital Signal Processing: A Review Journal | Year: 2013

To the present time, stability criteria have been proposed for one-dimensional digital filters with external interference, but no stability criterion exists for cases where two-dimensional digital filters have external interference. In this paper, we propose a new criterion for the elimination of overflow oscillations in two-dimensional digital filters described by Roesser model with saturation arithmetic and external interference. This criterion ensures asymptotic stability with a guaranteed H∞ performance. The proposed criterion is represented in terms of linear matrix inequality (LMI); thus, it is computationally efficient. Illustrative examples are given to demonstrate the effectiveness of the proposed criterion. © 2013 Elsevier Inc. All rights reserved.

Ahn C.K.,Korea University
International Journal of General Systems | Year: 2013

This article presents a new design scheme for the state estimator for Takagi-Sugeno fuzzy delayed Hopfield neural networks that uses strict output passivation of the error system. Based on Lyapunov-Krasovskii functional, Jensens inequality, and linear matrix inequality (LMI) formulation, a new delay-dependent criterion is proposed such that makes the resulting estimation error system exponentially stable and passive from the input vector to the output error vector. The unknown gain matrix of the proposed state estimator can be obtained by solving the LMI, which can be facilitated using existing numerical packages. We verify the effectiveness of the proposed state estimation method through a numerical example. © 2013 Taylor and Francis Group, LLC.

Kim S.K.,Korea University
Numerical Heat Transfer, Part B: Fundamentals | Year: 2010

This work investigates overall performance of the modification techniques for resolving the singularity at the final time in the gradient method for the inverse heat conduction problem. Four representative methods are selected based on the literature and analyzed for the same case. They are the regularization term method, the differential equation method, the gradient integration method, and the sequential gradient method. All four methods are reproduced and tested for the same test case. Based on the test results, a two-step method that can both alleviate the systematic bias and at the same time resolve the singularity is proposed.

Ahn C.K.,Korea University
Nonlinear Analysis: Hybrid Systems | Year: 2013

In this article, we propose a new . H∞ synchronization method for chaotic systems with external disturbance based on the Takagi-Sugeno (T-S) fuzzy model and receding horizon control. This synchronization method is called a Takagi-Sugeno fuzzy receding horizon . H∞ synchronization (TSFRHHS) method. A new set of matrix inequality conditions on the terminal weighting matrix is proposed for T-S fuzzy chaotic systems wherein non-increasing monotonicity of the optimal cost is guaranteed. Under this set of terminal inequality conditions, the proposed TSFRHHS method guarantees the infinite horizon . H∞ performance for T-S fuzzy chaotic systems with external disturbance. As an application of the proposed synchronization method, the TSFRHHS problem for the Lorenz system is investigated. © 2013 Elsevier Ltd.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2011

The CoO-doping effect on impulse aging behavior of the Zn-Pr-Co-Cr-Dy varistors was investigated in the range of 0.5-2.0 mol%. The clamp voltage ratio (K) increased with increasing CoO content. The varistors doped with 0.5 mol% CoO exhibited the best clamping characteristics, which the K value is 2.05-2.53 at an impulse current of 400-1200 A. The best stability was obtained from the varistor doped with 1.0 mol% CoO, with, %δα=-4.4%, and %δJL=-2.3% after applying the impulse stress of 1200 A. © 2011 The American Ceramic Society.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2011

The effect of Nb2O5 addition on impulse aging behavior of ZnO-V2O5-MnO2-Co3O 4-Dy2O3-based varistors was investigated. The varistors doped with 0.25 mol% Nb2O5 exhibited the best clamp characteristics, in which the clamp voltage ratio was in the range of K=1.65-2.50 at an impulse current of 1-50 A. The varistors doped with 0.1 mol% Nb2O5 exhibited the best electrical stability by marking ΔE1 mA=-1.0%, Δα=-2.8%, and ΔJ L=31.5% after applying the impulse current of 100 A. © 2011 The American Ceramic Society.

Giesecke K.,Stanford University | Kim B.,Korea University
Operations Research | Year: 2011

Collateralized debt obligations, which are securities with payoffs that are tied to the cash flows in a portfolio of defaultable assets such as corporate bonds, play a significant role in the financial crisis that has spread throughout the world. Insufficient capital provisioning due to flawed and overly optimistic risk assessments is at the center of the problem. This paper develops stochastic methods to measure the risk of positions in collateralized debt obligations and related instruments tied to an underlying portfolio of defaultable assets. It proposes an adaptive point process model of portfolio default timing, a maximum likelihood method for estimating point process models that is based on an acceptance/rejection resampling scheme, and statistical tests for model validation. To illustrate these tools, they are used to estimate the distribution of the profit or loss generated by positions in multiple tranches of a collateralized debt obligation that references the CDX High Yield portfolio and the risk capital required to support these positions. © 2011 INFORMS.

Lee J.-N.,Korea University | Choi B.,Kookmin University
Information and Management | Year: 2011

Much has been written about the need for trust in outsourcing relationships, but the literature has produced only a few theoretical models that explain the process that helps it evolve. We proposed a theoretical model by distinguishing ongoing beliefs, such as ongoing trust and distrust, from initial perceptions, such as initial trust and distrust, in the context of IT outsourcing, and then explored empirically how these interacted with one another the knowledge sharing experience between the participants, thus leading to a successful experience from both the outsourcer and the service provider. The model and its hypotheses were tested using two-stage survey data collected from IT outsourcing projects. Our results showed that the ongoing trust and distrust between the receiver and provider were crucial in attaining benefits and that the outcome was also affected by the perceptions of the participants at the initial stage of the outsourcing process. We also found that knowledge-sharing experience between the parties moderated the impact of initial trust or distrust on the ongoing trust or distrust in different ways: the change in the service provider's initial perceptions were apparently more visible and positive than those of the service receiver's, although both initial perceptions tended to be cognitively consistent. These results helped us understand how trust evolves over time in an outsourcing relationship, and enabled us to explore the different viewpoints of the service provider and receiver. © 2011 Elsevier B.V. All rights reserved.

Several studies suggested that serum cystatin C (CysC) is more useful than serum creatinine (Cr) for the assessment of renal function in patients with liver cirrhosis. This study evaluated the clinical significance of CysC in patients with cirrhotic ascites and normal Cr level. We enrolled patients with cirrhotic ascites and a normal serum Cr level (<1.2 mg/dL). GFR was measured by (99m)Tc-DTPA renal scan. Serum Cr, CysC, and Cr clearance (CCr) were measured on the same day. Significant renal impairment and severe renal impairment were defined as GFR <60 mL/min and GFR <30 mL/min, respectively. Eighty-nine patients with cirrhotic ascites were enrolled in the study (63 men and 26 women; age, 55±11 years). Forty-seven (52.8%) and 42 (47.2%) patients were in Child-Pugh grade B and C, respectively. Serum Cr and CysC levels and GFR were 0.8±0.2 mg/dL, 1.1±0.3 mg/L, and 73.4±25.5 mL/min, respectively. Significant and severe renal impairment were noted in 28 (31.5%) and 2 (2.2%) patients, respectively. GFR was well correlated with serum Cr, CysC, and e-GFR(MDRD), while it was not correlated with e-GFR(C&G). In multivariate analysis, only CysC was significantly correlated with GFR (β, 45.620; 95% CI, 23.042-68.198; P<0.001). Serum CysC level was the only independent predictor for significant renal impairment. Significant renal dysfunction was not rare in patients with cirrhotic ascites, even their serum Cr level is normal. Serum CysC is a useful marker for detecting significant renal dysfunction in these patients.

Kim Y.,Korea University
Industrial Management and Data Systems | Year: 2013

Purpose - This paper aims to study the validity of potential factors that might affect US information and communication technology (ICT) holders' choice of foreign licensing partners. Design/methodology/approach - This study focuses on ICT industry. The sample firms for this study are drawn from the SDC by Thomson Financial and this sample was used to construct a data in which a unit of observation is the unique US licensor - foreign licensee pair, or a dyad. The hypotheses are tested using the random-effects logit model. Findings - The important explanatory factors relate to the knowledge appropriability and the level of economics freedom of a licensee's country, and familiarity between partners through prior licensing agreements. Market similarity between partners, however, appears to be an insignificant factor. Practical implications - The findings suggest that transaction cost, competition, and national absorb capacity considerations weigh in heavily in explaining firms' choice of foreign licensing partners. Originality/value - The paper makes an important contribution to licensing literature as the understanding of what drives partner choice is still sparse. Especially, the paper makes a uniqueness of dealing with international technology licensing. © Emerald Group Publishing Limited.

Kim H.J.,Korea University | Pedersen S.,Texas A&M University
Computers and Education | Year: 2011

Hypothesis development is a complex cognitive activity, but one that is critical as a means of reducing uncertainty during ill-structured problem solving. In this study, we examined the effect of metacognitive scaffolds in strengthening hypothesis development. We also examined the influence of hypothesis development on young adolescents' problem-solving performance. Data was collected from sixth-grade students (N = 172) using a computer-supported problem-based learning environment, Animal Investigator. The findings of the study indicated that participants using metacognitive scaffolds developed significantly better hypotheses and that hypothesis-development performance was predictive of solution-development performance. This article discusses further educational implications of the findings and future research. © 2010 Elsevier Ltd. All rights reserved.

Choi J.-S.,Korea University | Kim J.J.,University of Washington
Proceedings of the National Academy of Sciences of the United States of America | Year: 2010

In a natural environment, foragers constantly face the risk of encountering predators. Fear is a defensive mechanism evolved to protect animals from danger by balancing the animals' needs for primary resources with the risk of predation, and the amygdala is implicated in mediating fear responses. However, the functions of fear and amygdala in foraging behavior are not well characterized because of the technical difficulty in quantifying prey-predator interaction with real (unpredictable) predators. Thus, the present study investigated the rat's foraging behavior in a seminaturalistic environment when confronted with a predator-like robot programmed to surge toward the animal seeking food. Rats initially fled into the nest and froze (demonstrating fear) and then cautiously approached and seized the food as a function of decreasing nest-food and increasing food-robot distances. The likelihood of procuring food increased and decreased via lesioning/inactivating and disinhibiting the amygdala, respectively. These results indicate that the amygdala bidirectionally regulates risk behavior in rats foraging in a dynamic fear environment.

Nation P.D.,Korea University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Here we show that quantum states of a mechanical oscillator can be generated in an optomechanical analog of the micromaser in the absence of any atomlike subsystem, thus exhibiting single-atom masing effects in a system composed solely of oscillator components. In the regime where the single-photon coupling strength is on the order of the cavity decay rate, a cavity mode with at most a single-excitation present gives rise to sub-Poissonian oscillator limit-cycles that generate quantum features in the steady state just above the renormalized cavity resonance frequency and mechanical sidebands. The merger of multiple stable limit-cycles markedly reduces these nonclassical signatures. Varying the cavity-resonator coupling strength, corresponding to the micromaser pump parameter, reveals transitions for the oscillator phonon number that are the hallmark of a micromaser. The connection to the micromaser allows for a physical understanding of how nonclassical states arise in this system and how best to maximize these signatures for experimental observation. © 2013 American Physical Society.

Cho M.,Korea University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

It is shown that there is a direct connection between the enhancement effects of chiroptical spectroscopic signals using perpendicular-polarization detection method and the amplifications of various weak effects, known as weak-value measurements, in quantum optics. In addition, the acceptable range of chiroptical weak values is discussed. © 2013 American Physical Society.

Koo H.,Korea Institute of Science and Technology | Huh M.S.,Korea Institute of Science and Technology | Sun I.-C.,Korea Institute of Science and Technology | Yuk S.H.,Korea University | And 3 more authors.
Accounts of Chemical Research | Year: 2011

Therapy and diagnosis are two major categories in the clinical treatment of disease. Recently, the word "theranosis" has been created, combining the words to describe the implementation of these two distinct pursuits simultaneously. For successful theranosis, the efficient delivery of imaging agents and drugs is critical to provide sufficient imaging signal or drug concentration in the targeted disease site. To achieve this purpose, biomedical researchers have developed various nanoparticles composed of organic or inorganic materials. However, the targeted delivery of these nanoparticles in animal models and patients remains a difficult hurdle for many researchers, even if they show useful properties in cell culture condition.In this Account, we review our strategies for developing theranostic nanoparticles to accomplish in vivo targeted delivery of imaging agents and drugs. By applying these rational strategies, we achieved fine multimodal imaging and successful therapy. Our first strategy involves physicochemical optimization of nanoparticles for long circulation and an enhanced permeation and retention (EPR) effect. We accomplished this result by testing various materials in mouse models and optimizing the physical properties of the materials with imaging techniques. Through these experiments, we developed a glycol chitosan nanoparticle (CNP), which is suitable for angiogenic diseases, such as cancers, even without an additional targeting moiety. The in vivo mechanism of this particle was examined through rationally designed experiments. In addition, we evaluated and compared the biodistribution and target-site accumulation of bare and drug-loaded nanoparticles.We then focus on the targeting moieties that bind to cell surface receptors. Small peptides were selected as targeting moieties because of their stability, low cost, size, and activity per unit mass. Through phage display screening, the interleukin-4 receptor binding peptide was discovered, and we combined it with our nanoparticles. This product accumulated efficiently in atherosclerotic regions or tumors during both imaging and therapy. We also developed hyaluronic acid nanoparticles that can bind efficiently to the CD44 antigen receptors abundant in many tumor cells. Their delivery mechanism is based on both physicochemical optimization for the EPR effect and receptor-mediated endocytosis by their hyaluronic acid backbone.Finally, we introduce the stimuli-responsive system related to the chemical and biological changes in the target disease site. Considering the relatively low pH in tumors and ischemic sites, we applied pH-sensitive micelle to optical imaging, magnetic resonance imaging, anticancer drug delivery, and photodynamic therapy. In addition, we successfully evaluated the in vivo imaging of enzyme activity at the target site with an enzyme-specific peptide sequence and CNPs.On the basis of these strategies, we were able to develop self-assembled nanoparticles for in vivo targeted delivery, and successful results were obtained with them in animal models for both imaging and therapy. We anticipate that these rational strategies, as well as our nanoparticles, will be applied in both the diagnosis and therapy of many human diseases. These theranostic nanoparticles are expected to greatly contribute to optimized therapy for individual patients as personalized medicine, in the near future. © 2011 American Chemical Society.

Kim H.,Korea University
Disaster Prevention and Management | Year: 2013

Purpose: The main purpose of this paper is to explore the current practices of simulation exercises in Korea and to make desirable recommendations for the future of Korean simulations to increase their learning effectiveness. Design/methodology/approach: This paper employs a case study strategy, and the data collection methods include documentary research, qualitative interviews, and participation observation. Three representative simulation exercises were observed: the Keungogae Subway Counter Terrorism Exercise 2009, the Safe Korea 2010 Earthquake Exercise, and the Safe Korea 2010 Subway Fire Exercise. Findings: The current practices of simulation exercises in Korea can be categorised into four main themes: top-level commitment and support; repeating training through rehearsals; box seats, ill-structured scenario scripts, and a lack of adaptation; and podium and speech-based debriefing. Practical implications: Korean simulation exercises need to allow adaptation and diversion to take place, encouraging communication and discussion between exercise players. Furthermore, ensuing after-action reviews (debriefs) should be a discussion-orientated rather than evaluation-orientated to promote individual and organisational learning. The empirical findings and resulting recommendations of this paper can help Korean exercise planners to change their current flawed practices into evidence-based ones, setting a new direction for an effective simulation exercise model. Originality/value: This study is the first empirical research to investigate simulation exercises in Korea and to highlight their problems. © Emerald Group Publishing Limited.

We conducted a prospective cross-sectional study to examine the correlation between facial asymmetry, shoulder imbalance, and adolescent idiopathic scoliosis. Sixty-nine adolescent idiopathic scoliosis patients and 29 healthy volunteers were enrolled in this study. All patients underwent whole-spine standing anteroposterior radiographs and frontal cephalograms. Patients were divided into mild, moderate, and severe groups depending on Cobb angle (10°-25°, 25°-40°, and >40°, respectively). Facial measurements included maxilla height difference, ramus length difference, and anterior nasal spine-menton angle. Shoulder measurements included coracoid height difference, clavicular angle, clavicle-rib intersection difference, and radiographic shoulder height.The anterior nasal spine-menton angle in the severe group (>40°) was higher than in the other groups (P<.05), as was the clavicle-rib intersection difference (P<.05). In addition, the magnitude of the curve showed a possible correlation with the anterior nasal spine-menton angle and clavicle-rib intersection difference in scoliosis patients (r=0.433 and r=0.511, respectively). According to different curve patterns, the anterior nasal spine-menton angle and clavicle-rib intersection difference were significantly higher in the double thoracic group than in the other groups (P<.05). In the correlation analysis, the ramus length difference and anterior nasal spine-menton angle had a possible correlation with the coracoid height difference, clavicular angle, radiographic shoulder height, and clavicle-rib intersection difference (P<.05). Copyright 2011, SLACK Incorporated.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2011

The effect of sintering temperature on pulse aging behavior of ZnO-V 2O5-MnO2-Co3O4-Dy 2O3-Nb2O5 varistors was investigated. The sintering temperature did have a significant effect on clamp ratio, which exhibits a pulse-current handling capability. The varistors sintered at 900°C exhibited the best clamp characteristics, in which the clamp voltage ratio was in the range of K = 2.15-3.04 for the pulse-current region (5-50 A). The varistors sintered at 950°C in the sintering temperature exhibited excellent electrical stability against a pulse-current with %ΔE1mA/cm2 = 2.9%, %Δα = -19.6%, and %ΔJL = 49.4% after applying the multi-pulse-current of 100 A. © 2011 The American Ceramic Society.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2011

The microstructure and electrical properties of Er2O 3-doped ZnO-V2O5-MnO2-Nb 2O5 varistor ceramics were investigated with different contents of Er2O3. Increasing content of Er 2O3 increased the sintered density (5.51-5.61 g/cm 3 for Er2O3-doped samples) and reduced the average grain size (5.2-5.7 μm). With increasing content of Er 2O3, the breakdown field increased from 4800 to 5444 V/cm up to 0.05 mol%, whereas a further increase decreased it. The maximum nonlinear coefficient was 63, which was from the addition of 0.05 mol% Er 2O3. The donor concentration increased from 4.21 × 1017 to 1.04 × 1018cm-3 with increasing content of Er2O3 and the barrier height exhibited a maximum value (1.21 eV) at 0.05 mol% Er2O3. © 2011 The American Ceramic Society.

The aim of this study was to determine whether the functional integrin-α-M (ITGAM) rs1143679 polymorphism is associated with susceptibility to systemic lupus erythematosus (SLE), lupus nephritis (LN), and rheumatoid arthritis (RA). A series of meta-analyses were conducted to test for associations between the ITGAM rs1143679 polymorphism and SLE, LN, or RA. A total of 24 comparisons involving 7,738 patients and 8,309 controls for SLE, and 2,663 patients and 2,694 controls in RA were considered. Meta-analysis showed a significant association between the ITGAM rs1143679 A allele and SLE in all subjects (OR 1.773, 95 % CI 1.656, 1.901, p < 1.0 × 10−9). After stratification by ethnicity, the A allele was found to be significantly associated with SLE in European, Latin American, and Asian. A significant association was also found between the ITGAM A allele and lupus nephritis in Europeans (OR 2.131, 95 % CI 1.565, 2.903, p = 1.6 × 10−7). However, no association was found between RA and the ITGAM rs1143679 polymorphism. Our meta-analyses confirm that the ITGAM rs1143679 polymorphism is associated with SLE susceptibility in different ethnic groups and demonstrate that the polymorphism is associated with LN in European. © 2014, Springer-Verlag Berlin Heidelberg.

Kim S.-K.,Kyung Hee University | Park H.-G.,Korea University
Optics Express | Year: 2013

We propose a dielectric Bragg mirror that utilizes coherent coupling with multiple quantum wells (MQWs) to significantly enhance light extraction from GaN light-emitting diode (LED). Full vectorial electromagnetic simulation showed that, under constructive interference conditions, the Bragg mirror consisting of two dielectric (SiO2/TiO2) stacks and a silver layer led to >30% enhancement in light extraction, as compared to a single silver mirror. Such significant enhancement by a pre-designed Bragg/metal mirror was ascribed to the vertically oriented radiation pattern and reduced plasmonic metal loss. In addition, the gap distance between the MQWs and a Bragg mirror at which the constructive interference takes place could be controlled by modulating the thickness of the first lowrefractive- index layer. Moreover, a two-dimensional periodic pattern was incorporated into an upper GaN layer with the designed Bragg mirror and it was shown that a lattice constant of ~800 nm was optimal for light extraction. We believe that tailoring the radiation profile of light emitters by coherent coupling with designed high-reflectivity mirrors will be a promising route to overcome the efficiency limit of current semiconductor LED devices. © 2013 Optical Society of America.

Kim Z.H.,Korea University
Frontiers of Physics | Year: 2014

The single-molecule surface-enhanced Raman scattering (smSERS) has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application. © 2014 Higher Education Press and Springer-Verlag Berlin Heidelberg.

When loaded at cryogenic temperature under stresses below the global yield, an amorphous alloy revealed two clearly distinguishable exothermic events during heating in calorimetric experiments. These exotherms, commonly known as the α- and β-relaxations, were attributed to the annealing out of two different local structures with different structural stability, presumably free volume and shear transformation zone (STZ). In this study, we introduced a simple and reliable experimental technique, which enables the evaluation of the activation energy corresponding to the β-relaxation, Eβ. Based on experimental evidence and comparison with earlier studies, it is presumed that Eβ is directly related to the potential energy barrier to shear transformation. © 2013 Published by Elsevier Ltd.

Yi S.,Korea University
Mechatronics | Year: 2010

This paper proposes a gait planning and control algorithm for the quadruped robot pet commercialized by Dasarobot, Korea. Reliable motion and online characteristics are the key requisites for the motion planning algorithm of a commercialized robot. At joint control level of the proposed gait control, sample-based interpolation makes joint trajectory tractable for small motor and controller of the miniaturized robot. Centroid body sway ensures walking stability to achieve reliability of the proposed gaits at the motion planning level. By using ground coordinates representation, it is possible to integrate several online gaits and realize a compact and efficient gait planning algorithm. Experimental results are presented to verify the proposed gait planning and control algorithm. © 2010 Elsevier Ltd. All rights reserved.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2010

The sintering temperature dependence of varistor properties and aging behavior in ZnO-Pr6O11-CoO-Cr2O 3-Al2O3-Y2O3 ceramics were investigated at the sintering temperature of 1280°-1350°C. The sintered density was almost unaffected by the sintering temperature. The breakdown field decreased in the range of 4610-1513 V/cm with the increase of sintering temperature. The nonlinear coefficient decreased slightly from 47 to 44, whereas it is close to approximately 45 for all the samples. The highest stability of electrical and dielectric characteristics against DC-accelerated aging stress with sintering temperature was obtained for the sintering temperature of 1320°C, at which the %ΔEB=+0.3%, %Δα=7.3%, %Δε′APP=-5.6%, and %Δtan δ=+88.9%, respectively, for the stress state of 0.95 E B/150°C/24 h. © 2010 The American Ceramic Society.

Nahm C.-W.,Korea University
Journal of Alloys and Compounds | Year: 2010

The microstructure and electrical properties of MnTa-doped ZnO-V 2O5-ceramics with sintering was investigated. The microstructure consisted of a primary phase of ZnO grains and minor secondary phases such as Zn3(VO4)2, ZnV2O 4, and TaVO5, which act as liquid-phase sintering aids. The sintered density decreased from 5.69 g cm-3 to 5.52 g cm -3 due to the volatility of V2O5 in accordance with increasing sintering temperature. The maximum nonlinear coefficient (28) was obtained at 925 °C. The donor concentration increased from 1.07 × 1018 cm-3 to 3.56 × 1018 cm-3 in accordance with increasing sintering temperature and the barrier height exhibited the maximum value (1.25 eV) at 950 °C. © 2010 Elsevier B.V.All rights reserved.

Nahm C.-W.,Korea University
Journal of the American Ceramic Society | Year: 2010

The impulse aging behavior of the ZnO-Pr6O11-CoO- Cr2O3- Er2O3 varistor ceramics was investigated at the sintering temperature of 1335°-1345°C. Small change in the sintering temperature significantly affected the initial electric field-current density (E-J) characteristics, which decreased from 2878 to 1839 V/cm in the breakdown field and from 70.4 to 48.3 in the nonlinear coefficient. The clamp voltage ratio (V1200A/V1mA) for impulse current (1200 A) increased from 2.48 to 2.63 with the increasing sintering temperature. The varistors sintered at 1335°C exhibited the best clamp characteristics. The varistor sintered at 1345°C exhibited the best electrical stability, with %ΔEB=-2.7%, %Δα=-11.8%, and %ΔJ L=-6.7% after applying the multi-impulse stress of 1200 A. © 2010 The American Ceramic Society.

Jeon C.,Korea University
Korean Journal of Chemical Engineering | Year: 2011

Waste crab shell, which has some functional groups like -NHCO or NO2 groups, was used as an adsorbent to remove arsenate ions (As (V)). The functional groups in crab shells were confirmed by FT-IR analysis. Waste crab shell had a high uptake capacity of 35.92 mg/g-dry mass for arsenate ion at pH 4, and the regression curve using the Langmuir isotherm equation fit well with the experimental data. The effects of pH, loading of crab shells, and time on uptake capacity of arsenate ions were also investigated. The adsorption capacity of arsenate ions was increased as the pH value was increased because the amount of negative arsenic species increased as the pH value was increased. Waste crab shells could remove arsenate ions of about 45% with 0.5 g of loading amount, and adsorption of arsenate ions was almost completed in 30 min when initial concentration of arsenate ions was 100 and 9.3 mg/L, respectively. Considering recycling of crab shell, it could be an economical and promising adsorbent. © 2010 Korean Institute of Chemical Engineers, Seoul, Korea.

Truong P.L.,Sungkyunkwan University | Kim B.W.,Sungkyunkwan University | Sim S.J.,Korea University
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012

We report a simple, ultra-sensitive, and straightforward method for non-labeling detection of a cancer biomarker, using Rayleigh light scattering spectroscopy of the individual nanosensor based on antibody-antigen recognition and localized surface plasmon resonance (LSPR) λ max shifts. By experimentally measuring the refractive index sensitivity of Au nanorods, the Au nanorod with an aspect ratio of ∼3.5 was proven optimal for the LSPR sensing. To reduce the steric hindrance effect as well as to immobilize a large amount of ligand on the nanoparticle surface, various mixtures containing different molar ratios of HS(CH 2) 11(OCH 2CH 2) 6OCH 2COOH and HS(CH 2) 11(OCH 2CH 2) 3OH were applied to form different self-assembled monolayer surfaces. The results showed that the best molar ratio for antibody conjugation was 1:10. When using individual Au nanorod sensors for the detection of prostate specific antigen (PSA), the lowest concentration recorded was ∼1 aM (∼6 × 10 5 molecules), corresponding to LSPR λ max shifts of ∼4.2 nm. These results indicate that sensor miniaturization down to the nanoscale level, the reduction of steric hindrance, and optimization of size, shape, and aspect ratio of nanorods have led to a significant improvement in the detection limit of sensors. © 2012 The Royal Society of Chemistry.

Hong J.,Korea University
Journal of Product Innovation Management | Year: 2013

The purpose of this paper is to examine the relationship between strategic orientation and the performance of new products. In this paper, we develop a conceptual model that explores the roles of market orientation (MO) and entrepreneurship orientation (EO) on new product performance and seek to understand the mediating roles of process and product characteristics. Based on a survey of 471 small and medium-sized enterprises in Korea, we found that MO and EO positively affect new product performance. The main impact of MO is through new product development proficiency and product meaningfulness and that of EO is through proficient intellectual property management and product novelty. Academic and managerial implications are also discussed. © 2012 Product Development & Management Association.

Kim C.-Y.,Korea Institute of Ceramic Engineering And Technology | Riu D.-H.,Korea University
Thin Solid Films | Year: 2011

The texture control of transparent oxide thin film, the crystalline orientation, is very important, because it is related to the electrical resistivity and the optical transparency. It is known that the crystal orientation could be controlled by varying precursor source, gas flow rate, and deposition temperature. We deposited fluorine-doped tin oxide (FTO) thin film on aluminoborosilicate glass by spraying water-based solution and ethyl alcohol-added solution. We showed in this research that (200) and (301) preferential orientation of FTO thin film can be controlled by the addition of ethyl alcohol to FTO coating solution. (200) oriented FTO thin film deposited from ethyl alcohol-added solution comprises of pyramidal crystallites with {111} polar faces, which contain {101} contact twin planes. {101} contact twin planes forms salient reentrant angle which provides nucleating sites and makes crystallites grow abnormally. (301) orientation is thought through Periodic Bond Chains of tin hydroxide which forms prismatic long crystallites. Prismatic crystallites are comprised of {110} crystal faces which contain {101} repeated contact twin. It is very helpful to control (200) or (301) oriented crystal formation in transparent conducting oxide film, because the texture affects the electrical and optical properties of transparent conducting oxide film. We suggest that ethyl alcohol addition plays a role to form crystallites with {111} polar faces corresponding to (200) preferential orientation. The crystal morphologies are changed by doping elements, precursor sources, deposition conditions like flow rate and temperatures, and solvents. © 2010 Elsevier B.V. All rights Reserved.

Several noninvasive methods have recently been developed for the evaluation of liver fibrosis. The accuracy of transient elastography (TE), acoustic-radiation-force impulse (ARFI) elastography, and real-time elastography (RTE) in predicting liver fibrosis were evaluated. Seventy-four patients who had undergone a liver biopsy within the previous 6 months were submitted to evaluation with TE, ARFI, and RTE on the same day. THERE WERE SIGNIFICANT CORRELATIONS BETWEEN FIBROSIS STAGE AND LIVER STIFFNESS MEASUREMENT (LSM) USING THE THREE TESTED METHODS: TE, r(2)=0.272, P=0.0002; ARFI, r(2)=0.225, P=0.0017; and RTE, r(2)=0.228, P=0.0015. The areas under the receiver operating characteristic curves (AUROC) for the diagnosis of significant fibrosis (≥F2, Metavir stage) by TE, ARFI, RTE, TE/platelet count (PLT), velocity of shear wave (Vs)/PLT, and elasticity score (Es)/PLT were 0.727, 0.715, 0.507, 0.876, 0.874, and 0.811, respectively. The AUROC for the diagnosis of cirrhosis by TE, ARFI, RTE, TE/PLT, Vs/PLT, and Es/PLT were 0.786, 0.807, 0.767, 0.836, 0.819, and 0.838, respectively. Comparisons of AUROC between all LSMs for predicting significant fibrosis (≥F2) produced the following results: TE vs. RTE, P=0.0069; ARFI vs. RTE, P=0.0277; and TE vs. ARFI, P=0.8836. Applying PLT, the ability of each LSM to predict fibrosis stage significantly increased: TE/PLT vs. TE, P=0.0004; Vs/PLT vs. ARFI, P=0.0022; and Es/PLT vs. RTE, P<0.0001. However, the ability to predict cirrhosis was not enhanced, combining LSM and PLT. TE and ARFI may be better methods for predicting significant liver fibrosis than RTE. This predictive ability increased significantly when accounting for platelet count. However, all of the measures had comparable efficacies for predicting cirrhosis.

Nahm C.-W.,Korea University
Materials Science in Semiconductor Processing | Year: 2013

The effects of sintering temperature on the microstructure, electrical properties, and dielectric characteristics of ZnOV2O 5MnO2Nb2O5Er2O 3 semiconducting varistors have been studied. With increase in sintering temperature the average grain size increased (4.5-9.5 μm) and the density decreased (5.56-5.45 g/cm3). The breakdown field decreased with an increase in the sintering temperature (6214-982 V/cm). The samples sintered at 900 °C exhibited remarkably high nonlinear coefficient (50). The donor concentration increased with an increase in the sintering temperature (0.60×1018-1.04×1018 cm-3) and the barrier height exhibited the maximum value (1.15 eV) at 900 °C. As the sintering temperature increased, the apparent dielectric constant increased by more than four-fold. © 2013 Elsevier Ltd. All rights reserved.

Park S.W.,Korea University | Colvin C.R.,Northeastern University
Journal of Personality | Year: 2015

The relation between narcissism and other-derogation has been examined primarily in the context of ego threat. In three studies, we investigated whether narcissistic individuals derogate others in the absence of ego threat. In Study 1, 79 judges watched four videotaped dyadic interactions and rated the personality of the same four people. In Study 2, 66 judges rated the personality of a friend. In Study 3, 72 judges considered the average Northeastern University student and rated the personality of this hypothetical person. Across the three studies, targets' personality characteristics were described on the 100-item California Adult Q-Sort (CAQ; Block, 2008). Judges' ratings of targets were compared to a CAQ prototype of the optimally adjusted person to assess target-derogation. Judges' narcissism and other-derogation were positively related in Studies 1 and 2. Narcissism positively predicted and self-esteem negatively predicted target-derogation after controlling for each other in Study 3. Narcissistic individuals derogate others more than non-narcissistic individuals regardless of whether ego threat is present or absent. © 2014 Wiley Periodicals, Inc.

Kang H.M.,Yonsei University | Kwon H.J.,Korea University | Yi J.H.,Jeil Eye Clinic | Lee C.S.,Yonsei University | Lee S.C.,Yonsei University
American Journal of Ophthalmology | Year: 2014

Purpose To investigate the prognostic implication of subfoveal choroidal thickness on treatment outcome after intravitreal ranibizumab injections for typical exudative age-related macular degeneration (AMD). Design Retrospective study. Methods A total of 40 eyes of 37 patients who completed 6-month follow-up were analyzed. Patients' data were retrieved from medical records including best-corrected visual acuity (BCVA). Subfoveal choroidal thickness at baseline, 3 months, and 6 months was measured by enhanced depth imaging optical coherence tomography and adjusted for age and sex before statistical analysis. Treatment response was after 3 monthly intravitreal ranibizumab injections. Responders (responder group) were defined as a 100 μm or more decrease or complete resolution of subretinal fluid, whereas nonresponders (nonresponder group) were defined as changes less than 100 μm or more than 100 μm increase of subretinal fluid by optical coherence tomography. Results Mean age at diagnosis was 72.1 ± 8.1 years, and 22 eyes (55.0%) were responders. The responder group had thicker subfoveal choroid (257.2 ± 108.3 μm) and smaller lesions (1.3 ± 0.8 μm) at baseline than the nonresponder group (167.1 ± 62.4 μm, P =.003; and 2.0 ± 1.0 μm, P =.008). The responder group showed significantly better BCVA and thicker subfoveal choroid than the nonresponder group at 3 months (P =.002 and P =.023) and 6 months (P =.004 and P =.031). Stepwise and binary regression analysis demonstrated that subfoveal choroidal thickness was significantly correlated with visual outcome (B = -0.002, P =.003) and treatment response (B = 8.136, P =.018). Conclusion Subfoveal choroidal thickness may be a predictive factor for visual outcome and treatment response in typical exudative AMD after intravitreal ranibizumab injections. © 2014 by elsevier inc. all rights reserved.

The effects of di(2-ethylhexyl) phthalate (DEHP) on proteins secreted by HepG2 cells were studied using a proteomic approach. HepG2 cells were exposed to various concentrations of DEHP (0, 2.5, 5, 10, 25, 50, 100, and 250 microM) for 24 or 48 h. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) and comet assays were then conducted to determine the cytotoxicity and genotoxicity of DEHP, respectively. The MTT assay showed that 10 microM DEHP was the maximum concentration that did not cause cell death. In addition, the DNA damage in HepG2 cells exposed to DEHP was found to increase in a dose- and time-dependent fashion. Proteomic analysis using two different pI ranges (4-7 and 6-9) and large size 2-DE revealed the presence of 2776 protein spots. A total of 35 (19 up- and 16 down-regulated) proteins were identified as biomarkers of DEHP by ESI-MS/MS. Several differentiated protein groups were also found. Proteins involved in apoptosis, transportation, signaling, energy metabolism, and cell structure and motility were found to be up- or down-regulated. Among these, the identities of cystatin C, Rho GDP inhibitor, retinol binding protein 4, gelsolin, DEK protein, Raf kinase inhibitory protein, triose phosphate isomerase, cofilin-1, and haptoglobin-related protein were confirmed by Western blot assay. Therefore, these proteins could be used as potential biomarkers of DEHP and human disease associated with DEHP.

Kim H.-G.,Korea University
International Journal for Numerical Methods in Engineering | Year: 2010

This paper presents a new approach to simulate fluid-solid interaction (FSI) problems involving non-matching meshes. The coupling between the fluid and solid domains with dissimilar finite element meshes consisting of 4-node quadrilateral elements is achieved by using the interface element method. Continuity and compatibility conditions across the interface between fluid and solid meshes are satisfied exactly by introducing the interface elements defined on an interfacing region. Importantly, a consistent transfer of loads through the interface elements guarantees the present method to be an efficient approach of the solution strategy to FSI problems. An arbitrary Lagrangian-Eulerian description is adopted for the fluid domain, while for the solid domain an updated Lagrangian formulation is considered to accommodate finite deformations of an elastic structure. The fluid equations for velocity and pressure and the solid equations for velocity are strongly coupled in a single computational domain by means of the interface elements. Numerical results are presented for FSI problems involving non-matching meshes to demonstrate the effectiveness of the methodology. © 2009 John Wiley & Sons, Ltd.

Since the adoption of the 1969CLC and the 1971FC, the international oil-spill compensation regime has improved compensation for loss and damage caused by tanker oil spills. However, this regime has inherent limitations, such as protracted compensation payments and controversies over the scope and type of economic losses, including environmental damages, and the cost of environmental restoration. Therefore, given large oil-spill incidents, such as the Erika, Prestige, and Hebei Spirit, each government, respectively, has addressed compensation by enacting special laws or establishing domestic programs. This article contains a historical and legal analysis of the Hebei Spirit incident and discusses the limitations and necessary improvements to the international oil-spill compensation regime. © 2009 Elsevier Ltd. All rights reserved.

A maskless three-dimensional (3D) microfabrication method based on a digital micromirror device (DMD) is proposed for high lateral and vertical resolution. A substrate is scanned laterally under virtual masks of the DMD. The masks are allocated to a large number of virtual slices, all of which are projected in a single scan of the stage. A theoretical model for the cumulative dose distribution in a photoresist is derived and used to predict the resulting 3D profile. Experiments showed that the proposed method is promising for avoiding the stair-step problem and preventing misalignment errors. © 2011 Optical Society of America.

Northeast Asia is failing in its attempts to protect its regional seas from irreversible ecological damage and contamination. At the policy level, the regional architecture for marine protection has several glaring structural problems that need to be identified and resolved in an expeditious and politically sensitive manner. Although the UNDP/GEF Yellow Sea Large Marine Ecosystem Project (YS LME) and the Northwest Pacific Action Plan (NOWPAP) are the two most likely institutions from which to build the next phase of regional marine cooperation, synergies between the two institutions remain limited. Both institutions are endowed with unique opportunities, challenges and limitations that must be taken into full consideration when planning the next step of coordinated action for regional marine protection. For the purpose of developing a more effective phase of marine cooperation in Northeast Asia, this paper advocates the formation of a Marine Environmental Community based on an integrated approach towards Northeast Asia's regional marine programs. This will facilitate improvements in funding, policy coordination through high level policy dialogue, transparency and efficiency of information sharing systems and full participation of all the coastal states in the region. © 2009 Elsevier Ltd. All rights reserved.

Kim K.U.,Korea University
Cancer Nursing | Year: 2014

Background: Cancer is the leading cause of death in Korean adults. A good quality of life for patients at end life can control pain and symptoms and help maintain well-being. Objective: The aim of this study was to measure quality of life in end-stage cancer patients using the Korean version of the McMaster Quality of Life (K-MQOL). Methods: The K-MQOL was administered to adult end-stage cancer patients from 4 Korean university hospitals. We hypothesized quality-of-life differences between participants by daily activity level, number of symptoms, and participant status (alive or not) at end of study. Results: Participants' mean age was 49.2 years, and 74.5% were men. As hypothesized for discriminant validity, Pearson correlation coefficients among the K-MQOL were less than 0.4, with the exceptions of emotion (0.25-0.52) and cognition (0.33-0.51). A higher Eastern Cooperative Oncology Group Performance States Rating score was significantly associated with a lower quality of life (F = 2.840, P = 0.034). The mean score of those within 21 days of death was significantly lower than that of patients who were alive at the end of the study (t = -2.48, P = .04). Patients with a smaller number of symptoms other than pain had significantly higher quality-of-life scores than did those with more symptoms (F = 5.059, P = .004). Conclusions: The K-MQOL provided reliable and valid scores of quality of life in end-stage cancer patients. Implications for practice: Assessing end-stage cancer patients' quality of life helps to identify each patient's condition and aspects that could benefit from nursing care. We anticipate that the K-MQOL will be useful for patient assessment in clinical and community settings. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Shin H.-W.,Korea University
International Journal of Precision Engineering and Manufacturing | Year: 2012

Magnesium alloys as the substitution for heavy metals such as steel and aluminum alloys can substantially reduce weight at many structural parts with design changes. Magnesium alloys also have advantages in recycling, stiffness, NVH, and heat protection. Since magnesium alloy parts such as steering wheels, seat frames, and oil pans are mainly manufactured by die casting processes, their levels of productivity are not so high compared to sheet metal working. In this study, hood panels with magnesium sheets which have mechanical characteristics equivalent to steel sheets are designed and analyzed. By using finite element analysis, the thicknesses of the inner and outer panel under some design requirements are determined and the shape of the hood inner panel and hinge reinforcements were changed. Dent ability analysis on panel is performed to confirm the new magnesium hood panel by a nonlinear FEM package. Analysis results show that hood panels of magnesium sheets have higher performance in dent ability compared with those of steel sheets. © 2012 Korean Society for Precision Engineering and Springer-Verlag Berlin Heidelberg.

Song J.,Korea University
International Journal of Automotive Technology | Year: 2012

This study introduces an integrated dynamic control with steering (IDCS) system to improve vehicle handling and stability under severe driving conditions. It integrates an active rear-wheel steering control system and a direct yawmoment control system with fuzzy logic. Direct yaw-moment control is achieved by modifying the optimal slip of the front outer wheel. An 8-degree-of-freedom vehicle model was used to evaluate the proposed IDCS for various road conditions and driving inputs. The results show that the yaw rate tracked the reference yaw rate and that the body slip angle was reduced when the IDCS was employed, thereby increasing the controllability and stability of the vehicle on slippery roads. The IDCS system reduced the deviation from the center line for a vehicle running on a split m road. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg.

The nonspecific clinical presentation of acute hepatitis A (AHA) mandates the detection of anti-hepatitis A virus IgM antibodies (IgM anti-HAV) in the serum for obtaining a definitive diagnosis. However, IgM anti-HAV might not be present during the early phase of the disease. The aim of this study was to determine the optimal time for repeating the IgM anti-HAV test (HAV test) in AHA patients with a negative initial test. In total, 261 patients hospitalized with AHA were enrolled for this retrospective study. AHA was diagnosed when the test for IgM anti-HAV was positive and the serum alanine aminotransferase (ALT) level was ≥400 IU/L. Repeat HAV test was conducted after 1-2 weeks if the initial HAV test was negative but AHA was still clinically suspected. The results of the initial HAV test were negative in 28 (10.7%) patients. The intervals from symptom onset to the initial-HAV-test day and from the peak-ALT day to the initial-HAV-test day were significantly shorter in the negative-initial-HAV-test group, but on multivariate analysis only the latter was significantly associated with negative results for the initial HAV test (β=-0.978; odds ratio [95% confidence interval]=0.376 [0.189-0.747]; P=0.005). The HAV test was positive in all patients when it was performed at least 2 days after the peak-ALT day. The results of HAV tests were significantly associated with the interval from the peak-ALT day to the HAV-test day. The optimal time for repeating the HAV test in clinically suspicious AHA patients with a negative initial HAV test appears to be at least 2 days after the peak-ALT day.

Han J.-H.,Korea University | Kang J.U.,Johns Hopkins University
Applied Physics B: Lasers and Optics | Year: 2012

The effect of higher-order modes in fiber bundle imager-based optical coherence tomography (OCT) has been theoretically modeled using coupled fiber mode analysis ignoring the polarization and core size variation in order to visualize the pure effect of multimodal coupling of the imaging bundle. In this model, the optical imaging fiber couples several higher-order modes in addition to the fundamental one due to its high numerical aperture for achieving light confinement to the single core pixel. Those modes become evident in a distance domain using A-mode (depth) OCT based on a mirror sample experiment where multiple peaks are generated by the spatial convolution and coherence function of the light source. The distance between the peaks corresponding to each mode can be estimated by considering the effective indices of coupled (guided) modes obtained from numerically solving the fiber mode characteristics equations and the fiber length. The results have been compared for various types (fiber dimensions and wavelengths) and lengths of fibers, which have mode separation of 715 μm (1404 μm) and 764 μm (1527 μm) for the measurement and analysis, respectively in a 152.5 mm (305 mm)-long imaging fiber. © Springer-Verlag 2011.

Lee J.-H.,Korea University
Journal of Product Innovation Management | Year: 2013

The convergent product is an increasingly important phenomenon in the marketplace. The convergent product allows the developer to include more and more diverse functionalities into their products, which can satisfy a broad range of consumer needs. However, failures of convergent products arouse the need to understand its functionalities, and the optimal combination of functionalities and their relationships to attitude and purchase intention. In addition, because convergent product has the potential to offer more diverse functionality, we consider if this will have impacts on instrumental and emotional needs fulfillment and attitude and purchase intention. Additionally, consumer innovativeness was examined to ascertain if there were differences among consumers on their classification of the functionalities, or if it will moderate functional diversity, needs fulfillment, and product attitude. Using the Kano model, this study examined the nature of these relationships by examining the functionalities of a smartphone. Overall, our results show that the convergent products that include functionalities from two of the three categories of the Kano model, must-have and attractive, were rated more positively. Consumer innovativeness differences were found. Consumers with high innovativeness considered must-have and one-dimensional functionalities the most important, and consumers with low innovativeness considered all three important, although one-dimensional functionalities were considered significantly less important. Although increasing functional diversity positively raises product attitude and purchase intention, it tends to raise emotional needs fulfillment only once instrumental needs have been met, especially for respondents showing low innovativeness. The findings should arouse interest about factors that should not be overlooked when developing new convergent products. © 2012 Product Development & Management Association.

Kral C.,Austrian Institute of Technology GmbH | Haumer A.,Technical Consulting and Electrical Engineering | Lee S.B.,Korea University
IEEE Transactions on Power Electronics | Year: 2014

A thermal model for the determination of the temperatures of interior permanent magnets and stator windings is presented in this paper. The innovation of the model relies on one temperature sensor being located in the stator core of the machine. Such sensor is simple to implement in many applications such as traction or EV, where reliability is critical. The estimated stator winding and permanent magnet temperatures are determined by a simplified thermal lumped element network model with only two time constants. It is shown that the proposed thermal model is very robust due to the structure of the model and the measured stator core temperature. The distortion of the temperature estimates caused by the cooling circuit is inherently accounted for such that the model can be used for robust online prediction of temperatures. Experimental results based on a forced water-cooled interior permanent magnet synchronous machine setup are presented to validate the effectiveness of the presented model. © 1986-2012 IEEE.

Choi H.-S.,Samsung | Jeon S.,Korea University
Applied Physics Letters | Year: 2014

Persistent photoconductivity (PPC) in nanocrystalline InZnO thin-film transistors (TFTs) was studied using carrier fluctuation measurements and transient analysis. Low-frequency noise measurements and decay kinetics indicate that the band bending by the external field together with the ionized oxygen vacancy (Vo++) generated during the light exposure is the main cause of the PPC phenomenon. Based on these observations, a field-induced macroscopic barrier model is proposed as the origin of PPC for InZnO TFTs. In particular, this model explains that the carrier separation between e and V o++ is induced by the external field applied to the three electrodes inside the transistor. © 2014 AIP Publishing LLC.

Song J.O.,LG Innotek | Ha J.-S.,University of California at Santa Barbara | Seong T.-Y.,Korea University
IEEE Transactions on Electron Devices | Year: 2010

GaN-based semiconductors are of great technological importance for the fabrication of optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes. The further improvement of LED performance can be achieved through the enhancement of external quantum efficiency. In this regard, highquality p-type ohmic electrodes having low contact resistance and high transmittance (or reflectivity), along with thermal stability, must be developed because p-type ohmic contacts play a key role in the performance of LEDs. In this paper, we review recent advances in p-type ohmic-contact technology for GaN-based LEDs. A variety of methods for forming transparent and reflective ohmic contacts are introduced. © 2009 IEEE.

Chen G.,Harbin Institute of Technology | Chen G.,State University of New York at Buffalo | Seo J.,State University of New York at Buffalo | Seo J.,Seoul National University | And 3 more authors.
Chemical Society Reviews | Year: 2013

Nanochemistry and nanomaterials provide numerous opportunities for a new generation of photovoltaics with high solar energy conversion efficiencies at low fabrication cost. Quantum-confined nanomaterials and polymer-inorganic nanocomposites can be tailored to harvest sun light over a broad range of the spectrum, while plasmonic structures offer effective ways to reduce the thickness of light-absorbing layers. Multiple exciton generation, singlet exciton fission, photon down-conversion, and photon up-conversion realized in nanostructures, create significant interest for harvesting underutilized ultraviolet and currently unutilized infrared photons. Nanochemical interface engineering of nanoparticle surfaces and junction-interfaces enable enhanced charge separation and collection. In this review, we survey these recent advances employed to introduce new concepts for improving the solar energy conversion efficiency, and reduce the device fabrication cost in photovoltaic technologies. The review concludes with a summary of contributions already made by nanochemistry. It then describes the challenges and opportunities in photovoltaics where the chemical community can play a vital role. This journal is © The Royal Society of Chemistry 2013.

Oh S.C.,Korea University
Journal of Gastric Cancer | Year: 2012

Gastric cancer is the second cause of cancer that is related to death and the fourth most common cancer, worldwide. Complete resection of cancer is the only curative treatment for gastric cancer. However, even if complete resection is possible, recurrence is frequently observed in Gastric patients. Therefore, adjuvant treatment modality for resectable gastric cancer is needed to increase the survival of patients. This study wants to describe the role of adjuvant chemotherapy for resectable gastric cancer, with updated data of recent studies. Several meta-analysis studies demonstrated a benefit of adjuvant chemotherapy for resectable gastric cancer. Due to the heterogeneity of the population and regimens, there is no consensus regarding the adjuvant chemotherapy. Recently published, well designed phase III studies demonstrated the statistically significance of adjuvant chemotherapy for the resectable gastric cancer, with the extended lymph node dissection. Further phase III trials, to determine the best regimen and schedule of adjuvant chemotherapy, was suggested to use the fluoropyrimidine based regimen as control group. © 2012 by The Korean Gastric Cancer Association.

Shin W.S.,Korea University
Technology, Pedagogy and Education | Year: 2015

Until now, research on technology integration in K–12 settings focused on revealing factors that influence technology use in the classroom by teachers has not paid much attention to what teachers recognise and why they incorporate technology in the classroom. Thus, this study aims to investigate how teachers recognise important factors that influence quality technology integration and how teachers use technology in Korean schools, using closed- and open-ended items and verbatim quotes of teachers’ responses to a series of open-ended questions. The results indicate that teachers’ use of technology in practice is affected by the multidimensional characteristics of schools; hence, support of technology use therein should be improved. Teachers’ aptitude, disposition and attitudes toward technology are the most important factors for ICT-related instruction. Additionally, the answers given by the cohort to the open-ended questions help to explain the specific educational context in the Republic of Korea. Teachers report using technology largely because it provides personal convenience; additionally, the use of third-party content providers’ websites by teachers emerges as a substantial issue in the area of technology integration in the classroom. © 2014 Association for Information Technology in Teacher Education.

Acute hepatitis A is currently outbreaking in Korea. Although prognosis of acute hepatitis A is generally favorable, a minority of patients are accompanied by fatal complications. Severe cholestasis is one of the important causes of prolonged hospitalization in patients with acute hepatitis A. In such cases, higher chances of additional complications and increased medical costs are inevitable. We report three cases of severely cholestatic hepatitis A, who showed favorable responses to oral corticosteroids. Thirty milligram of prednisolone was initiated and tapered according to the responses. Rapid improvement was observed in all cases without side effects. We suggest that corticosteroid administration can be useful in hepatitis A patients with severe cholestasis who do not show improvement by conservative managements. Clinical trial will be needed to evaluate effectiveness of corticosteroids in these patients.

In this paper, we propose a new receding horizon disturbance attenuator (RHDA) for Takagi-Sugeno (T-S) fuzzy switched Hopfield neural networks with external disturbance. First, a new set of linear matrix inequality (LMI) conditions is proposed for the finite terminal weighting matrix of the receding horizon cost function with a cross term. Second, under this condition, we show that the proposed RHDA attenuates the effect of external disturbance on T-S fuzzy switched Hopfield neural networks with a guaranteed infinite horizon ℋ∞ performance. In addition, we prove that the proposed RHDA guarantees internal stability in closed-loop systems. A numerical example is presented to describe the effectiveness of the proposed RHDA scheme. © 2014 Elsevier Inc. All rights reserved.

Kay K.M.,Korea University
Korean journal of ophthalmology : KJO | Year: 2010

A 39-year-old man with poliosis of his lower eyelid lashes visited our clinic. He reported that his symptoms began with a few central lashes and then spread along the adjacent lashes during the ensuing 2 weeks. A pigmented nevus, approximately 4 mm in diameter, was identified just above the white lashes without surrounding skin depigmentation. No specific findings were identified with regard to the patient's general health or serologic and radiologic testing. Excisional biopsy of the pigmented nevus was performed. On histopathologic examination, infiltration of the dermis by numerous lymphocytes and melanophages was observed. The poliosis was ultimately diagnosed as a presenting sign of the halo phenomenon in the regressive stage of a melanocytic nevus.

Son J.-Y.,Yale University | Lee J.-T.,Korea University | Brooke Anderson G.,Yale University | Bell M.L.,Yale University
Environmental Health Perspectives | Year: 2012

Background: Understanding the health impacts of heat waves is important, especially given anticipated increases in the frequency, duration, and intensity of heat waves due to climate change. Objectives: We examined mortality from heat waves in seven major Korean cities for 2000 through 2007 and investigated effect modification by individual characteristics and heat wave characteristics (intensity, duration, and timing in season). Methods: Heat waves were defined as ≥ 2 consecutive days with daily mean temperature at or above the 98th percentile for the warm season in each city. We compared mortality during heat-wave days and non-heat-wave days using city-specific generalized linear models. We used Bayesian hierarchical models to estimate overall effects within and across all cities. In addition, we estimated effects of heat wave characteristics and effects according to cause of death and examined effect modification by individual characteristics for Seoul. Results: Overall, total mortality increased 4.1% [95% confidence interval (CI): -6.1%, 15.4%] during heat waves compared with non-heat-wave days, with an 8.4% increase (95% CI: 0.1%, 17.3%) estimated for Seoul. Estimated mortality was higher for heat waves that were more intense, longer, or earlier in summer, although effects were not statistically significant. Estimated risks were higher for women versus men, older versus younger residents, those with no education versus some education, and deaths that occurred out of hospitals in Seoul, although differences among strata of individual characteristics were not statistically significant. Conclusions: Our findings support evidence of mortality impacts from heat waves and have implications for efforts to reduce the public health burden of heat waves.

Sung Y.-M.,Korea University
Journal of Non-Crystalline Solids | Year: 2012

Oxyfluoride glasses containing different alkaline earth fluoride (CaF 2, SrF2, and BaF2) were prepared and their crystallization behavior was analyzed using non-isothermal kinetics based upon differential scanning calorimetry (DSC) scan results. The glass containing CaF2 showed the fastest kinetics for CaF2 crystallization, while that containing BaF2 showed the slowest kinetics for BaF 2 crystallization. On the other hand, all the oxyfluoride glasses showed very similar behavior in the crystallization of glass matrices. The difference in the crystallization behavior of the oxyfluoride glasses was discussed based upon the difference in the size of alkaline earth ions and the difference in the dissociation energy of alkaline earth-fluorine bonds. © 2011 Elsevier B.V. All rights reserved.

Klare B.F.,Noblis | Jain A.K.,Michigan State University | Jain A.K.,Korea University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

Heterogeneous face recognition (HFR) involves matching two face images from alternate imaging modalities, such as an infrared image to a photograph or a sketch to a photograph. Accurate HFR systems are of great value in various applications (e.g., forensics and surveillance), where the gallery databases are populated with photographs (e.g., mug shot or passport photographs) but the probe images are often limited to some alternate modality. A generic HFR framework is proposed in which both probe and gallery images are represented in terms of nonlinear similarities to a collection of prototype face images. The prototype subjects (i.e., the training set) have an image in each modality (probe and gallery), and the similarity of an image is measured against the prototype images from the corresponding modality. The accuracy of this nonlinear prototype representation is improved by projecting the features into a linear discriminant subspace. Random sampling is introduced into the HFR framework to better handle challenges arising from the small sample size problem. The merits of the proposed approach, called prototype random subspace (P-RS), are demonstrated on four different heterogeneous scenarios: 1) near infrared (NIR) to photograph, 2) thermal to photograph, 3) viewed sketch to photograph, and 4) forensic sketch to photograph. © 2013 IEEE.

Moon D.-O.,Jeju National University | Choi Y.H.,Korea University | Kim G.-Y.,Jeju National University
Cellular and Molecular Life Sciences | Year: 2011

The anti-cancer effect of the c-Jun N-terminal kinase (JNK) inhibitor SP600125 has been well evaluated in human cancer cells. However the role of p21 in SP600125-mediated G 2/M distribution is not fully understood. Our results showed that the transcriptional activation of p21 by SP600125 is mediated through the proximal regions of multiple Sp1 sites in the p21 promoter following ERK-dependent phosphorylation of Sp1. In this process, p21 induces endoreduplication through the inhibition of cyclin E/Cdk2 activity at 24 h but does not directly regulate cyclin B1/Cdc2 activity. Furthermore, SP600125 induces the phosphorylation of p21 at Thr 145 through the PI3K/Akt pathway. Akt-mediated phosphorylation of p21 and protection of apoptosis are completely abolished by inhibitors of PI3K and Akt. In summary using time points, we identified the dual functions of p21 as an inhibitor of cell-cycle progression at 24 h and as an anti-apoptotic factor at 48 h. © 2011 Springer Basel AG.

Paik K.,Korea University
IEEE Transactions on Evolutionary Computation | Year: 2011

This paper presents a unique optimization method developed for landscape evolution problems. An existing hypothesis of the optimal channel network states that fluvial landscape evolution can be characterized as the procedure that follows minimum total energy expenditure. Previous studies have tested this hypothesis by solving an optimization problem, i.e., finding landscapes that satisfy the minimum total energy expenditure criterion, and showed that such optimized landscapes are similar to natural landscapes in many respects. These studies have approximated a 3-D landscape as a 2-D river network. While this network-based approach has greatly simplified the formulation of the optimization problem, this approximation limits the investigation of features such as longitudinal profiles, since their representation requires the gravitational direction-wise dimension. Here, an alternative technique is devised to fully handle the optimization of 3-D landforms over time. The proposed idea is to break down the time domain and to apply an optimization algorithm sequentially for discrete time steps. For the optimization part, a heuristic algorithm motivated from adaptation strategies of natural systems (here landscape formation) is used. This method is applied to a theoretical landscape with the condition that the balance between tectonic uplift and sediment lost is satisfied. It is found that landscapes of minimum total energy expenditure exhibit the Hack's law and the power-law in the exceedance probability distribution of drainage area, which are the characteristics found in natural river networks. However, they demonstrate no systematic pattern in longitudinal profiles. © 2011 IEEE.

Kim M.,Korea University
Microwave and Optical Technology Letters | Year: 2012

A novel microstrip balun topology based on common-mode rejection is introduced. The balun is constructed with a short section of coupled line placed above a defected ground structure. Measurements on a PCB sample indicate a successful conversion from single end to differential mode showing 0.7 dB of insertion loss at 3 GHz along with 1-dB bandwidth that extends from 0.7 to 5.6 GHz. © 2012 Wiley Periodicals, Inc.

Sohn J.-I.,Korea University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2016

We study coarse-grained entropy production in an asymmetric random walk system on a periodic one-dimensional lattice. In coarse-grained systems, the original dynamics are unavoidably destroyed, but the coarse-grained entropy production is not hidden below the critical time-scale separation. The hidden entropy production is rapidly increasing near the critical time-scale separation. © 2016 American Physical Society.

The passivity concept plays an important role in circuit theory, signal processing, and control, but no criteria have yet been established for two-dimensional (2D) digital filters. In this article, we propose a new and first criterion for 2D digital filters in the Roesser form, to ensure passivity from the interference vector to the output vector with a certain storage function. The proposed criterion also guarantees the asymptotic stability of 2D digital filters in the Roesser form without interference. This criterion is described by linear matrix inequality, making it computationally attractive. A simulation example is presented, which demonstrates the usefulness of the 2D passivity criterion. © 2014, Springer Science+Business Media Dordrecht.

Ro K.-D.,Korea University
Journal of Mechanical Science and Technology | Year: 2014

The characteristics of the flow field of a square prism with detached splitter plate in its wake were investigated by measuring the fluid force on the prism and by visualizing the flow field through particle image velocimetry (PIV) with a high Reynolds number (Re = 10,000). The experimental parameters included the ratios of the splitter and prism widths (H/B = 0.5-1.5) as well as the gap ratios (G/B = 0-2) between the prism and the splitter plate at a high Reynolds number (Re = 10,000). The drag reduction rate of the square prism increased with increasing H/B for the same G/B; meanwhile, it increased and then decreased with increasing G/B for the same H/B. When the detached splitter place was installed, vortices rotating in opposite directions were generated on its upper and lower sides. Reverse flow was caused by the vortices in the wake region of the square prism, and the prism drag was decreased by the reverse flow. © 2014 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.

Nahm C.-W.,Korea University
Journal of Materials Science: Materials in Electronics | Year: 2012

The effect of sintering process on microstructure, electrical properties, and ageing behavior of ZnO-V 2O 5-MnO 2-Nb 2O 5 (ZVMN) varistor ceramics was investigated at 875-950 °C. The sintered density decreased from 5.52 to 5.44 g/cm 3 and the average grain size increased from 4.4 to 9.6 μm with the increase of sintering temperature. The breakdown field (E 1 mA) decreased from 6991 to 943 V/cm with the increase of sintering temperature. The ZVMN varistor ceramics sintered at 900 °C led to surprisingly high nonlinear coefficient (α = 50). The donor concentration (N d) increased from 3.33 × 10 17 cm -3 to 7.64 × 10 17 cm -3 with the increase of sintering temperature and the barrier height (Φ b) exhibited the maximum value (1.07 eV) at 900 °C. Concerning stability, the varistors sintered at 925 °C exhibited the most stable accelerated ageing characteristics, with %ΔE 1 mA = 1.5% and %Δα = 13.3% for DC accelerated ageing stress of 0.85 E 1 mA/85 °C/24 h. © 2011 Springer Science+Business Media, LLC.

Kim D.-R.,Korea University
Environment and Planning C: Government and Policy | Year: 2011

Scholars of environmental regulation have speculated that decentralization of policy authority may induce subnational governments to lower their regulatory stringency in pursuit of an economic advantage over other jurisdictions. I examine whether there is an environmental race to the bottom among local governments and to what extent local policy networks can offset this tendency in the nascent decentralized system of South Korea. The results of an empirical analysis of local enforcement activities show that, although positive regulatory gaps lack any significant influence, industrial decline leads local agencies to decrease their enforcement actions. Yet, I also find that local policy networks not only directly affect the regulatory behavior of local governments but also counterbalance the influence of industry, thereby mitigating the race to the bottom. Together, these findings suggest that decentralization may not always engender the interjurisdictional competition that leads to the suboptimal production of social policies. © 2011 Pion Ltd and its Licensors.

Hsu C.,National Taiwan University | Lee J.-N.,Korea University | Straub D.W.,Georgia State University
Information Systems Research | Year: 2012

This research investigates information security management as an administrative innovation. Although a number of institutional theories deal with information systems (IS) innovation in organizations, most of these institutional-centered frameworks overlook external economic efficiency and internal organizational capability in the presence of pressures of institutional conformity. Using Korea as the institutional setting, our research model posits that economic-based consideration will moderate the institutional conformity pressure on information security adoption while organization capability will influence the institutional confirmation of information security assimilation. The model is empirically tested using two-stage survey data from a field study of 140 organizations in Korea. The results indicate that in addition to institutional influences, our six proposed economic-based and organizational capability moderating variables all have significant influences on the degree of the adoption and assimilation of information security management. We conclude with implications for research in the area of organizational theory and the information security management literature, and for practices regarding how managers can factor into their information security planning the key implementation variables discovered in this study. The robust setting of the study in Korean firms allows us to generalize the theory to a new context and across cultures. © 2012 INFORMS.

Nahm C.-W.,Korea University
Journal of Rare Earths | Year: 2013

The effect of Tb4O7 on electrical behavior of the ZnO-Pr6O11-based varistor ceramics was investigated. Microstructural analysis indicated that the addition of Tb4O 7 decreased average grain size from 3.6 to 3.2 μm and increased the sintered density from 5.58 to 5.68 g/cm3. As the amount of Tb4O7 increased, the breakdown field increased from 9393 to 12437 V/cm and the nonlinear coefficient increased from 50 to 65. The varistor ceramics added with 0.5 mol.% in the amount of Tb4O 7 exhibited an excellent stability by exhibiting -0.1% in the variation rate of the breakdown field, 0% in the variation rate of the nonlinear coefficient, and 8.8% in the variation rate of the leakage current density for DC-accelerated aging stress of 0.85 E1 mA/115 °C/24 h. © 2013 The Chinese Society of Rare Earths.

Kim E.J.,Cardiovascular Center | Kim S.,Korea University | Kang D.O.,Cardiovascular Center | Seo H.S.,Cardiovascular Center
Circulation: Cardiovascular Imaging | Year: 2014

Background-Atherosclerosis is considered to be an infammatory disease associated with the activation of hematopoietic and immune-related organs such as the bone marrow (BM) and spleen. We evaluated the metabolic activity of those organs and of the carotid artery with 18F-fuorodeoxyglucose positron emission tomography in patients with coronary artery disease, including acute myocardial infarction. Methods and Results-Whole-body combined 18F-fuorodeoxyglucose positron emission tomography/computed tomography was performed in 32 patients with acute myocardial infarction, 33 patients with chronic stable angina, and 25 control subjects. The mean standard uptake value was calculated in the regions of interest in the spleen and the BM of lumbar vertebrae. The target-to-background ratio of the standard uptake values of the carotid artery and jugular vein was also calculated. In patients with acute myocardial infarction, the standard uptake values of the BM (1.67±0.16) and spleen (2.57±0.39), as well as the target-to-background ratio of the carotid artery (2.13±0.42), were signifcantly higher than the corresponding values of patients with angina (1.22±0.62; 2.03±0.35; 1.36±0.37; all P<0.001) and controls (0.80±0.44; 1.54±0.26; 1.22±0.22; all P<0.001), independent of traditional cardiovascular risk factors and high-sensitivity C-reactive protein. In all groups combined, the target-to-background ratio of the carotid artery was signifcantly associated with the standard uptake values of the BM (r=0.535; P<0.001), spleen (r=0.663; P<0.001), and high-sensitivity C-reactive protein (r=0.465; P<0.001). Conclusions-The metabolic activity of the BM and spleen, as well as of the carotid artery, was highest in patients with acute myocardial infarction, intermediate in patients with angina, and lowest in control subjects. The activation of the BM and spleen was signifcantly associated with infammatory activity of the carotid artery. © 2014 American Heart Association, Inc.

This study examined the effects of the immobilization of Arg-Gly-Asp (RGD) peptide (CAAALLLKERGDSK) on anodized titanium (Ti) via chemical grafting or physical adsorption methods on cell adhesion and osteoblast differentiation. The RGD peptide was immobilized on the anodized Ti surface by means of physical adsorption or chemical grafting. The chemical composition of each RGD-immobilized Ti substrate was examined by x-ray photoelectron spectroscopy. The level of cell proliferation was investigated via tetrazolium (XTT) assay. Alkaline phosphatase activity and calcium deposition were evaluated by alizarin red S staining, and mRNA expression of the differentiated osteoblast marker genes was analyzed by reverse-transcriptase polymerase chain reaction. Cell adhesion was enhanced on the RGD-immobilized Ti substrates compared to the anodized Ti surfaces. In addition, significantly increased cell spreading and proliferation were observed with the cells grown on the RGD-immobilized Ti (P < .05). Furthermore, the osteoblasts on the RGD-immobilized Ti showed significant increases in the integrin ?1 and type I collagen levels and small increases in osteonectin and osteocalcin levels (P < .05). Interestingly, the chemical grafting method resulted in significantly greater effects on adhesion and differentiation than the physical adsorption method (P < .05). RGD-immobilized Ti substrates might be effective in improving the osseointegration of dental implants. In particular, the chemical grafting method of RGD immobilization is more favorable and is expected to provide positive outcomes with future animal and clinical studies.

Do H.-L.,Korea University
IET Power Electronics | Year: 2011

The interleaved multi-channel converter is very popular these days because of its ability to reduce current ripples. In this study, an interleaved boost converter with a single magnetic component is proposed. Interleaving operation and a loosely coupled inductor significantly reduce the ripple component of the input current. Moreover, zero-voltage-switching characteristic of the proposed converter reduces the switching losses and raises the overall efficiency. Experimental results based on an 80 W (170 V/0.47 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter. © 2011 The Institution of Engineering and Technology.

Kim S.B.,Korea University | Rattakorn P.,University of Texas at Arlington
Expert Systems with Applications | Year: 2011

Feature selection has received considerable attention in various areas as a way to select informative features and to simplify the statistical model through dimensional reduction. One of the most widely used methods for dimensional reduction includes principal component analysis (PCA). Despite its popularity, PCA suffers from a lack of interpretability of the original feature because the reduced dimensions are linear combinations of a large number of original features. Traditionally, two or three dimensional loading plots provide information to identify important original features in the first few principal component dimensions. However, the interpretation of what constitutes a loading plot is frequently subjective, particularly when large numbers of features are involved. In this study, we propose an unsupervised feature selection method that combines weighted principal components (PCs) with a thresholding algorithm. The weighted PC is obtained by the weighted sum of the first k PCs of interest. Each of the k loading values in the weighted PC reflects the contribution of each individual feature. We also propose a thresholding algorithm that identifies the significant features. Our experimental results with both the simulated and real datasets demonstrated the effectiveness of the proposed unsupervised feature selection method. © 2010 Elsevier Ltd. All rights reserved.

Han J.-H.,Korea University
Electronics Letters | Year: 2011

An intra-cavity four-wave mixing (FWM) in a dual-wavelength erbium-doped fibre ring laser has been demonstrated where a 100m-long dispersion-shifted fibre has been introduced as a nonlinear medium to pronounce the FWM effect in a 1550nm window. The laser operates in the gain switched (pulse) mode for effectively achieving high power and increasing the intermodulation effect in the ring cavity. This scheme provides a simple and efficient way of archieving a dual-wavelength source for various optical systems. © 2011 The Institution of Engineering and Technology.

Jung J.,Korea University | Jackson S.R.,University of Nottingham | Parkinson A.,University of Nottingham | Jackson G.M.,University of Nottingham
Neuroscience and Biobehavioral Reviews | Year: 2013

Tourette syndrome [TS] is a neurodevelopmental disorder characterised by chronic vocal and motor tics. TS has been associated with dysfunctional cognitive (inhibitory) control of behaviour, however the evidence for this, beyond the occurrence of tics, is scant. Furthermore, in recent studies of uncomplicated TS, it has been shown that adolescents with TS exhibit paradoxically enhanced cognitive control of motor output, consistent with the typical developmental profile of increasing control of tics during adolescence. Here we present arguments, together with new data, that run counter to the widely held view that prefrontal cortex (PFC) is the source of inhibitory task-control signals. Instead, we argue that PFC should be viewed as a source of facilitatory signals that bias competition in brain areas more directly involved in motor execution. Importantly, we argue that in TS, over-activation of PFC may contribute to the hyper-excitability of motor regions and the occurrence of tics; and that compensatory changes, leading to enhanced cognitive control in TS, may primarily be implemented by distributed changes in local cortical excitability. © 2012 Elsevier Ltd.

Jacobs M.A.,University of Dayton | Swink M.,Texas Christian University | Swink M.,Korea University
Journal of Operations Management | Year: 2011

Managers struggle to cope with complexity in their product portfolios. However, research into diversification, product platforms, and other issues related to product portfolio complexity has often produced inconsistent guidance. This situation is at least partially attributable to an incomplete definition of portfolio complexity, and to corresponding limitations of theories applied to date. To address these limitations, we define product portfolio complexity as a design state manifested by the multiplicity, diversity, and interrelatedness of products within the portfolio. We conceptually establish the three-dimensional nature of complexity and present a model to provide insights into how each dimension impacts operational performance. As an extension to prior theoretical perspectives, the model explicitly addresses the roles of organizational learning and the character of fixed assets (utilization and flexibility) as mediator and moderator of product portfolio architectural complexity's effects, respectively. We also incorporate the principle of diminishing returns to address potential non-linearities in the proposed relationships. Prior theories and research studies have neglected these issues. We conclude by discussing useful perspectives with which to view the model, and by presenting measures of portfolio complexity and approaches for testing the propositions developed herein. © 2011 Elsevier B.V. All rights reserved.

Cho S.-H.,Hanseo University | Bae J.-S.,Korea University
Mathematical and Computer Modelling | Year: 2011

The aim of this paper is to give some new common fixed point theorems for mappings satisfying property (E.A) on cone metric spaces. And we prove the existence and uniqueness of solution for a ordinary differential equation with periodic boundary condition. © 2010 Elsevier Ltd.

The aim of this study is to evaluate the results of gradual ulnar correction and lengthening using the modified Ilizarov technique for the treatment of forearm deformities in patients with multiple cartilaginous exostoses. We retrospectively reviewed 23 forearms in 16 patients. Three different types of operative procedures were performed: (1) corrective osteotomy and gradual lengthening of the ulna, (2) corrective osteotomy of the radius, and (3) excision of exostoses. We evaluated the radiographs; range of motion of the wrist, forearm, and elbow; and functional status using a questionnaire before and after operation. During the clinical interview, post-operative functional status was significantly improved than pre-operative functional status, 12 patients stated that they had no difficulty in performing daily activities, 11 patients stated that they had no pain, and 11 patients stated that the post-operative appearance of the operated forearm was satisfactory. At time of final follow-up, the mean range of motion of the wrist in ulnar/radial deviation, forearm pronation/supination was significantly improved. Also, the radiographic parameters including radial articular angle, carpal slip, radial bowing, and ulnar variance were significantly improved at time of final follow-up. In conclusion, we achieved successful clinical and radiological outcomes in our patients with forearm deformities after treatment with the modified Ilizarov method. However, there could be a recurrence of ulnar shortening and deformity during growth periods in skeletally immature patients.

Lee J.-W.,Korea University
Asian Economic Policy Review | Year: 2011

Using both quantity- and price-based measures of financial integration, the paper shows an increasing degree of financial openness and integration in emerging Asia. Assessing the impact of a regional shock relative to a global shock on local equity and bond markets, the findings suggest that the region's equity markets are integrated more globally than regionally, although the degrees of both regional and global integration have increased significantly since the 1997/1998 Asian financial crisis. However, emerging Asia's local currency bond markets remain generally segmented, being neither regionally nor globally integrated. There are potential benefits from increased regional integration of financial markets. Financial integration at the regional level allows for the region's economies to benefit from allocation efficiency and risk diversification. Policymakers in the region must strike the right balance between maximizing the net benefits from regional and global financial openness, and minimizing the potential costs of financial contagion and crisis. © 2011 The Authors. Asian Economic Policy Review © 2011 Japan Center for Economic Research.

Park K.-S.,Korea University
International Journal of Stem Cells | Year: 2011

Ligands of transforming growth factor beta (TGF-β) family members have been implicated in the development and patho-physiological process of various organs. Embryonic stem cells (ESCs) are characterized by their ability to proliferate indefinitely and differentiated into all three germ layer cells, which are termed as pluripotency and self-renewal, respectively. For successful therapeutic application of ESCs, it is essential to understand the mechanisms underlying self-renewal and pluripotency, which involve complex networks among key factors including transcription factors, epigenetic control, microRNAs and signaling pathways. In this review, we discuss recent progress on the function of TGF beta family ligands and their canonical SMAD signaling in the maintenance of ESC's identity.

Sohn K.-R.,Korea University
Sensors and Actuators, A: Physical | Year: 2012

In this paper, a fiber Bragg grating (FBG) air flow sensor system using an all-fiber feedback laser is proposed. The operating principle of the feedback laser is based on the mode-locking mechanism between a Sagnac loop multi-grid filter and a tunable FBG single-wavelength filter. A shift in the lasing wavelength is attributed to the change in the heat energy of the coil heater. This is because the flow sensor depends on the variations in the heat energy of the coil heater surrounding the FBG, thereby causing a shift in the Bragg wavelength owing to a thermo-optic effect. In order to investigate the spectral response as a function of the flow speed of air, a simple and cost-effective intensity-based demodulation technique using a micro-optic band-pass filter is demonstrated. The flow sensitivity of the sensor system was 0.7 dB/(l/min) within a linear region. © 2012 Elsevier B.V. All rights reserved.

Shin M.W.,Yonsei University | Jang S.H.,Korea University
Solid-State Electronics | Year: 2012

In this paper we describe a novel thermal characterization method of GaN-based Light Emitting Diode (LED) package driven under the Alternating Current (AC) mode. The result was compared with the results from the thermal analysis for LED package operated under the Direct Current (DC) condition. Different from the DC condition, the junction temperature rise with the operation time of LED package was exhibited in a band formation. Finite Volume Method (FVM) was utilized to calculate the thermal performance of LED package under the AC condition using the input power extracted from the output current and voltage from the AC power supply. The experimental result was in a good agreement with the simulation data. © 2011 Elsevier Ltd. All rights reserved.

Ahn C.K.,Korea University
IEEE Transactions on Circuits and Systems II: Express Briefs | Year: 2014

Recently, Ahn proposed an l2-l stability criterion for interfered two-dimensional (2-D) digital filters described by the Roesser model. However, until now, no criteria for interfered 2-D digital filters in the Fornasini-Marchesini (FM) model have been studied. As a continuation of the results, this brief proposes a new criterion for the l2-l suppression of limit cycles in interfered 2-D digital filters in the FM model. The proposed criterion ensures the asymptotic stability and l2-l performance of 2-D digital filters. The effectiveness of the proposed criterion is demonstrated using numerical examples. The work in this brief and that of the Roesser model provide, as an integrity, systematic results on limit cycle suppression for 2-D digital filters in the l2-l sense. © 2014 IEEE.

Vogt-Koyanagi-Harada (VKH) disease is a multisystem syndrome characterized by ocular (uveitis and retinal detachment), neurological (headache, tinnitus, and meningitis), and integumentary (vitiligo, alopecia, and poliosis) involvement. Although the pathogenesis of VKH disease is not well understood, an autoimmune T-cell response to a melanocyte-associated antigen is considered to be a cause of VKH disease. The complex immunological response to interferon and ribavirin may induce or exacerbate the autoimmune condition; however, VKH disease is a very rare complication associated with interferon therapy in chronic hepatitis C. We report a case of VKH disease occurring during pegylated interferon-α2b and ribavirin combination therapy for chronic hepatitis C.

Kim H.M.,Ajou University | Cho B.R.,Korea University
Oxidative Medicine and Cellular Longevity | Year: 2013

Mitochondria provide the energy of the cells and are the primary site of oxygen consumption and the major source of reactive oxygen species. In mitochondria, metal ions and glutathione play vital roles in maintaining their structure and the redox environment. To understand their roles in mitochondria, it is crucial to monitor each of these chemical species in the mitochondria at the cell, tissue, and organism levels. An ideal tool for such purpose is the use of two-photon microscopy (TPM). Until recently, however, there has been no report on the two-photon (TP) probes suitable for such applications. In this paper, we summarize the mitochondria-targeted TP probes for Zn2+, H and thiols, as well as their bioimaging applications. © 2013 Hwan Myung Kim and Bong Rae Cho.

Do H.-L.,Korea University
IET Power Electronics | Year: 2011

An active-clamp soft-switching step-up converter with high-voltage gain is proposed. By utilising the active-clamp circuit, the voltages across the power switches in the proposed converter are clamped and the zero-voltage switching of the power switches is achieved. To increase the voltage gain, two voltage doubler rectifiers are connected serially and stacked on top of the clamp capacitor. Therefore high-voltage gain is obtained and soft-switching characteristic is achieved. Also, the voltage stresses of the power switches and the output diodes are effectively reduced. Theoretical analysis and performance of the proposed converter are verified on a 110 W experimental prototype operating at 110 kHz switching frequency. © 2011 The Institution of Engineering and Technology.

Park S.J.,Gachon University | Son W.S.,Korea University | Lee B.-J.,Seoul National University
Biochimica et Biophysica Acta - Proteins and Proteomics | Year: 2013

The bacterial toxin-antitoxin (TA) system is a module that may play a role in cell survival under stress conditions. Generally, toxin molecules act as negative regulators in cell survival and antitoxin molecules as positive regulators. Thus, the expression levels and interactions between toxins and antitoxins should be systematically harmonized so that bacteria can escape such harmful conditions. Since TA systems are able to control the fate of bacteria, they are considered potent targets for the development of new antimicrobial agents. TA systems are widely prevalent with a variety of systems existing in bacteria: There are three types of bacterial TA systems depending on the property of the antitoxin which binds either the protein toxin or mRNA coding the toxin protein. Moreover, the multiplicity of TA genes has been observed even in species of bacteria. Therefore, knowledge on TA systems such as the individual characteristics of TA systems, integrative working mechanisms of various TA systems in bacteria, interactions between toxin molecules and cellular targets, and so on is currently limited due to their complexity. In this regard, it would be helpful to know the structural characteristics of TA modules for understanding TA systems in bacteria. Until now, 85 out of the total structures deposited in PDB have been bacterial TA system proteins including TA complexes or isolated toxins/antitoxins. Here, we summarized the structural information of TA systems and analyzed the structural characteristics of known TA modules from several bacteria, especially focusing on the TA modules of several infectious bacteria. © 2013 Elsevier B.V.

Nahm C.-W.,Korea University
Journal of Alloys and Compounds | Year: 2010

The effect of Nb2O5 doping on microstructure and the electrical properties of ZnO-V2O5-MnO2-Co3O4-Dy2O3-Nb2O5-based varistors was investigated. The microstructure of all the samples consisted of a primary phase of ZnO grains and minor secondary phases such as Zn3(VO4)2, ZnVO4, and DyVO4, which act as liquid-phase sintering aids. The Nb2O5 doping did not have a significant effect on the density reached after sintering. However it increased the average grain sizes (d = 5.62-7.49 μm) compared with the Nb2O5-undoped sample. With increasing Nb2O5 doping level up to 0.1 mol%, the breakdown field (E1 mA) decreased from 7015 V cm-1 to 3358 V cm-1, and the nonlinear coefficient (α) increased from 26 to 37. However, further increase in doping level caused α to decrease. The highest value of the donor concentration and barrier height was obtained at 0.1 mol% Nb2O5, 5.9 × 1017 cm-3 and 1.20 eV, respectively. © 2009 Elsevier B.V. All rights reserved.

A second staged operation using temporary bridging external fixation (TBEF) has been widely used in patients with periarticular complex fracture, yet few papers have been published on the related complications. The purpose of this study was to report the complication rate and pitfalls directly related to TBEF through a retrospective study and to suggest some solutions. Fifty-nine cases that were treated by using TBEF were studied among 195 periarticular complex fractures. We retrospectively collected the clinical and radiological data and then the study data was evaluated for 1) cases with unsatisfactory restoration of length, 2) cases with deep infection caused by half pins invading the zone of definitive fixation, and 3) neurovascular injuries related to half pins. Complications were observed in 7/59 cases (11%). Problems related to the achievement of length were observed in one case of distal tibia fracture and 2 cases of distal femur fracture. Half pin related infection was observed in 2 cases of distal femur fracture. Neurovascular injury (medial calcaneal nerve injury in a distal tibia fracture) was observed in 2 cases. Among 7 complications, four were related to using TBEF in distal femur fracture. This is because the abundant leg muscles have strong deforming force and infection might be increased due to frequent irritation by the half pins. TBEF is a simple procedure with several advantages. However, complications might be observed if certain principles are not followed. It is thought that many complications due to TBEF can be reduced if the half pins are not inserted in the zone of injury, restoration of length is fully achieved and the neurovascular characteristics are carefully considered. In particular, much more caution is needed in the distal femur, which has abundant muscles surrounding it.

Han J.-H.,Korea University | Yoon S.M.,Japan National Institute of Advanced Industrial Science and Technology
Optics Letters | Year: 2011

We present an iterative method of eliminating pixelation artifacts from an endoscopic image acquired from a coherent fiber bundle imager. Our proposed approach for decoupling the honeycomb effect from the obtained sample image was formulated by using the prior probability for an approximate Bayesian framework in which the ideal complete image can be estimated by maximizing the posterior probability from the observed image. The maximization of the posterior probability from the original mask image (the mirrored fiber bundle imager structure) and the observed image (the sample image of the United States Air Force chart) has been performed by learning the image priors in the space of Markov random fields. By iteratively estimating the probability distribution, we reduced the noise effects from the mask image and recovered the ideal shape of the image. This method was efficient for automatically learning the sliding patch from the combination of projected kernels. The mask and observed images were obtained from en face images of the Fourier domain optical coherence tomography based on a common path interferometry scheme. © 2011 Optical Society of America.

Roh H.,Korea University | Reinhorn A.M.,State University of New York at Buffalo
Engineering Structures | Year: 2010

The maximum acceleration response of a simple yielding structure is proportional to its structural strength. Therefore, in order to reduce accelerations, the overall strength of the structure should be decreased while controlling possible resulting increases of displacements with supplemental damping. The use of "rocking columns", a type of double hinged gravity column, is suggested to reduce the strength of part of the lateral resisting system. A simplified analytical model of the columns represented by a moment-curvature relationship and a stiffness matrix, verified through experiments, is developed and implemented in the structural analysis program IDARC2D. The experimental study done on rocking concrete columns is briefly presented to show their global behavior and adjust the simplified model. For dynamic analysis, nonlinear stress zone approach and hysteretic models are also developed. A numerical study is conducted to demonstrate that story acceleration responses can be reduced compared to conventional structures, while the increased displacements are controlled using supplemental viscous dampers. A 1/3 scaled model structure, previously tested at the University at Buffalo, is used to evaluate the global seismic behavior of weakening alternatives modified using rocking columns and added viscous dampers. © 2010 Elsevier Ltd.

Shim W.J.,Korea University
Journal of Cardiovascular Ultrasound | Year: 2014

The widespread use of echocardiography has contributed to the early recognition of several distinct cardiac diseases in women. During pregnancy, safe monitoring of the disease process, as well as a better understanding of hemodynamics, is possible. During the use of potentially cardiotoxic drugs for breast cancer chemotherapy, echocardiographic patient monitoring is vital. Compared to men, the addition of an imaging modality to routine electrocardiogram monitoring during stress testing is more informative for diagnosing coronary disease in women. This review briefly discusses the role of echocardiography in the management of several women-specific cardiac diseases where echocardiography plays a pivotal role in disease management. © 2014 Korean Society of Echocardiography.

We investigated the durability of the biochemical and virologic responses after adefovir (ADV) discontinuation in lamivudine-resistant (LMV-R) chronic hepatitis B (CHB) patients, and the outcomes of ADV discontinuation compared to that of ADV maintenance. The indication for ADV treatment cessation was an undetectable level of hepatitis B virus (HBV) DNA documented on two occasions at least 6 months apart. All patients received additional ADV for at least 12 months after the confirmation of undetectable HBV DNA (Cobas TaqMan PCR assay, <70 copies/mL). Of 36 patients who had a sufficient ADV therapeutic effect, 19 discontinued ADV treatment, while the others maintained it. A virologic rebound was arbitrarily defined as the redetection of HBV DNA at a level higher than 10(5) copies/mL. In the ADV discontinuation group, ADV treatment and additional therapy were administered for medians of 33 months (range, 12-47 months) and 18 months, respectively. The patients were followed for a median of 12 months (range, 3-30 months) after ADV cessation. During that period, 18 of 19 patients (95%) experienced viral relapse. Viral rebound was observed in six patients (32%). However, 12 of 18 patients (67%) exhibited serum HBV DNA levels of less than (5) copies/mL. Biochemical relapses were observed in four of the six patients with viral rebound. In the ADV maintenance group, patients were treated for a median of 53 months (range, 31-85 months), and 9 patients (53%) experienced viral breakthrough. During short-term follow-up after ADV discontinuation, most patients (95%) exhibited viral relapse, whereas and viral breakthrough occurred in about half of patients (53%) maintained on ADV therapy. Therefore, the durability of virologic response after ADV discontinuation in LMV-R patients was unsatisfactory. In addition, and viral breakthrough was not infrequent in the ADV continuation group.

Choi J.W.,Qualcomm | Shim B.,Korea University | Singer A.C.,University of Illinois at Urbana - Champaign
IEEE Transactions on Information Theory | Year: 2012

Tree detection techniques are often used to reduce the complexity of a posteriori probability (APP) detection in multiantenna wireless communication systems. In this paper, we introduce an efficient soft-input soft-output tree detection algorithm that employs a new type of look-ahead path metric in the process of branch pruning (or sorting). While conventional path metrics depend only on symbols on a visited path, the new path metric accounts for unvisited parts of the tree in advance through an unconstrained linear estimator and adds a bias term that reflects the contribution of as-yet undecided symbols. By applying the linear estimate-based look-ahead path metric to an M-algorithm that selects the best M paths for each level of the tree, we develop a new soft-input soft-output tree detector, called an improved soft-input soft-output M-algorithm (ISS-MA). Based on an analysis of the probability of correct path loss, we show that the improved path metric offers substantial performance gain over the conventional path metric. We also demonstrate through simulations that the proposed ISS-MA can be a promising candidate for soft-input soft-output detection in high-dimensional systems. © 2012 IEEE.

To understand the first purchase mechanism in online shopping, this study established an integrated model of initial trust and TAM. According to the analysis results, initial trust beliefs were significantly influenced by initial trust bases such as company reputation, structural assurance, and trusting stance, and initial trust beliefs indirectly influenced the first purchase intention through consumer attitude. In TAM constructs, only perceived usefulness directly influenced the usage attitude of online shopping systems, then indirectly influenced the first purchase intention. These results imply that online consumers consider perceived ease of use as a basic requirement for system design. It was also found that there is a time cushion between the time of first purchase and the time of belief formation. On the whole, these results reinforced the theory that a relationship between belief (trust and perceived usefulness) and intention was better explained when it was mediated by attitude. © 2012 Springer Science+Business Media, LLC.

Kim J.-O.,Korea University
IEEE Transactions on Consumer Electronics | Year: 2010

It is expected that a number of heterogeneous radio access technologies will be available simultaneously at a single wireless terminal in next generation wireless networks. This paper addresses the challenge of link aggregation in a wireless terminal with multi-radio devices. A major issue in multi-path transmission is how to reduce the additional reordering delay at the receiver, which is mainly caused by the difference between link delays. This is particularly critical in wireless environments due to dynamics in link quality. Motivated by this observation, we propose a feedback-based technique to determine split ratios adaptively, based on measurements at the receiver. The link-level packet delay is measured on a periodic basis. The measurement is conveyed to the sender, and is used for split ratio calculation. The proposed technique has been implemented into an actual test-bed network which includes WiMAX and WiFi systems, and its potential usefulness is extensively evaluated. It was experimentally verified that for given radio link conditions, the traffic split ratio between WiMAX and WiFi links is optimally converged © 2006 IEEE.

Shim J.O.,Korea University
Pediatric Gastroenterology, Hepatology and Nutrition | Year: 2014

Clostridium difficile infection has been increasing since 2000 in children and in adults. Frequent antibiotics use, comorbidity, and the development of hypervirulent strains have increased the risk of infection. Despite the high carriage rates of C. difficile, infants rarely develop clinical infection. Discontinuing antibiotics and supportive management usually leads to resolution of disease. Antibiotics use should be stratified depending on the patient's age and severity of the disease. © 2014 by The Korean Society of Pediatric Gastroenterology, Hepatology and Nutrition.