Baek W.M.,Kongju National University |
Yoon J.H.,Korean Minjok Leadership Academy |
Kim C.,Sangji University
Scientific World Journal | Year: 2014
Many strategies have been proposed to reduce the mobility management cost in mobile communication networks. This paper studies the zone-based registration methods that have been adopted by most mobile communication networks. We focus on two special zone-based registration methods, called two-zone registration (2Z) and two-zone registration with implicit registration by outgoing calls (2Zi). We provide a new mathematical model to analyze the exact performance of 2Z and 2Zi. We also present various numerical results, to compare the performance of 2Zi with those of 2Z and one-zone registration (1Z), and show that 2Zi is superior to 2Z as well as 1Z in most cases. © 2014 Woon Min Baek et al.
Youm K.S.,Infra Structure Team |
Jeong Y.J.,Yonsei University |
Han E.S.H.,Korean Minjok Leadership Academy |
Yun T.S.,Yonsei University
Construction and Building Materials | Year: 2014
This study presents the compiled experimental data of compressive strength and the modulus of elasticity for five different lightweight concretes cured up to 365 days and compares them with those for a normalweight concrete. Mechanical properties sharply increased during early stage approaching asymptotic values, depending on design strength codes. Various empirical relationships approximately represent the experimental data, with the different types of concrete exhibiting discrepancies within acceptable bounds. Results highlight that the time-dependent mechanical properties of concretes containing lightweight aggregates can be reasonably estimated using conventional empirical models, provided that values at 28 days of curing are accurately known. Relationship between measured strength and modulus provides the first approximations, corroborated by coinciding values from nondestructive testing. The evolution of density and the effect of curing conditions are also discussed. These experimental results demonstrate that the type of lightweight aggregate strongly influences the mechanical properties of concretes. © 2014 Elsevier Ltd. All rights reserved.
Kim Y.,Korean Minjok Leadership Academy |
Park S.-H.,Kookmin University
Sensors | Year: 2011
Underwater sensor networks are emerging as a promising distributed data management system for various applications in underwater environments, despite their limited accessibility and restricted energy capacity. With the aid of recent developments in ubiquitous data computing, an increasing number of users are expected to overcome low accessibility by applying queries to underwater sensor networks. However, when multiple users send queries to an underwater sensor network in a disorganized manner, it may incur lethal energy waste and problematic network traffic. The current query management mechanisms cannot effectively deal with this matter due to their limited applicability and unrealistic assumptions. In this paper, a novel query management scheme involving query result merging is proposed for underwater sensor networks. The mechanism is based on a relational database model and is adjusted to the practical restrictions affecting underwater communication environments. Network simulations will prove that the scheme becomes more efficient with a greater number of queries and a smaller period range. © 2011 by the authors; licensee MDPI, Basel, Switzerland.
Kim M.,University of Pennsylvania |
Park K.,University of Oxford |
Kim J.M.,Korean Minjok Leadership Academy
Chemical Engineering Research and Design | Year: 2016
The key parts of this study included the fabrication of self-organized cylindrical nanotubes on the surface of iron (Fe) foil through anodization and the experimental evaluation of the adsorption and desorption performance of iron oxide nanotubes (INTs) for phosphate recovery with synthetic wastewater and raw livestock wastewater. Nanostructured INTs were achieved more than 95% of phosphate adsorption and desorption from synthetic wastewater in 30 min whereas pure Fe foil showed only less than 40% of phosphate adsorption in 60 min. Also, the INTs maintained the high efficiency of adsorption and desorption through three cycles of consecutive adsorption and desorption with the same INTs. In the case of raw livestock wastewater, the INTs adsorbed 43% of phosphate in 60 min in a continuous column experiment. The Freundlich isotherm model was more suitable than the Langmuir model for describing phosphate isotherms on INTs. Based on results of point of zero charge, the adsorption of phosphate was more effective in the acidic range of pH. For phosphate recovery using INTs, an additional recovery step to separate iron particles from treated wastewater is not necessary, which indicates that this method has great advantages for saving the operating cost in actual application. © 2016
Yu J.-Y.,Chonbuk National University |
Zheng Z.-H.,Chonbuk National University |
Son Y.-O.,University of Kentucky |
Shi X.,University of Kentucky |
And 2 more authors.
Toxicology in Vitro | Year: 2011
Zearalenone (ZEN) is commonly found in many food commodities and is known to cause reproductive disorders and genotoxic effects. However, the mode of ZEN-induced cell death of macrophages and the mechanisms by which ZEN causes cytotoxicity remain unclear. The present study shows that ZEN treatment reduces viability of RAW264.7 cells in a dose-dependent manner. ZEN causes predominantly necrotic and late apoptotic cell death. ZEN treatment also results in the loss of mitochondrial membrane potential (MMP), mitochondrial changes in Bcl-2 and Bax proteins, and cytoplasmic release of cytochrome c and apoptosis-inducing factor (AIF). Pre-treatment of the cells with either z-VAD-fmk or z-IETD-fmk does not attenuate ZEN-mediated cell death, whereas catalase suppresses the ZEN-induced decrease in viability in RAW264.7 cells. Treating the cells with c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), or p53 inhibitor prevented ZEN-mediated changes, such as MMP loss, cellular reactive oxygen species (ROS) increase, and cell death. JNK or p38 MAPK inhibitor inhibited mitochondrial alterations of Bcl-2 and Bax proteins with attendant decreases in cellular ROS levels. Knockdown of AIF via siRNA transfection also diminished ZEN-induced cell death. Further, adenosine triphosphate was markedly depleted in the ZEN-exposed cells. Collectively, these results suggest that ZEN induces cytotoxicity in RAW264.7 cells via AIF- and ROS-mediated signaling, in which the activations of p53 and JNK/p38 play a key role. © 2011 Elsevier Ltd.
So M.W.,University of Ulsan |
Lee E.-J.,Asan Institute for Life Science |
Lee H.S.,Korean Minjok Leadership Academy |
Koo B.S.,University of Ulsan |
And 3 more authors.
Modern Rheumatology | Year: 2013
Objectives: To explore whether Rg3, a major and especially potent ginsenoside, modulates human osteoarthritic (OA) chondrocyte senescence. Methods: Isolated chondrocytes were cultured in medium containing interleukin-1 beta (IL-1β) with or without Rg3. The expression levels of mRNAs encoding aggrecan (ACAN), a major structural proteoglycan, type II collagen (COL2A1), and metalloproteinases (MMP) -1, -3, and -13, respectively, were determined using real-time PCR. Cellular senescence was detected by measuring senescence-associated β-galactosidase (SA-β-Gal) activity. Chondrocyte telomerase activity also served as a senescence marker. Results: Chondrocytes stimulated by IL-1β showed increased MMP-1, MMP-3, and MMP-13 levels, whereas the expression of COL2A1 and ACAN decreased. However, in cells co-treated with IL-1β and Rg3, the levels of MMP-1 and MMP-13 were lower than in cells treated with IL-1β alone, and COL2A1 and ACAN expression levels recovered from the low values seen when cultured only in the presence of IL-1β. Also, compared to vehicle-treated controls, IL-1β stimulation alone resulted in an increased number of SA-β-Gal-positive cells, while co-incubation with IL-1β and Rg3 significantly suppressed the expression of this senescence marker. Chondrocytes cultured with Rg3 showed significantly higher proliferative and telomerase activities than did control cells. Conclusions: These findings indicate that Rg3 protects the cell against the development of chondrocyte senescence in osteoarthritis. © 2012 Japan College of Rheumatology.
Ju J.W.,Korean Minjok Leadership Academy
Applied Mechanics and Materials | Year: 2014
Sunlight generation in the schoolyard and geothermal generation are typical examples. However, from someday, sunlight generation is not doing its function enough. Many schools are trying to utilize renewable energy. But, in most of the cases, unlike preliminary plans, schools are not substantially utilizing renewable energy efficiently. In order to maximize the energy efficiency of school’s renewable energy, multiple renewable energy needs to be comprehensively combined and applied. The current method of solar energy is used in the rooftops of schools. Geothermal energy is installed using the large area of the schoolyard. Acupressure energy device using piezoelectric element is installed in the school gate, the 1st floor stairway, and the school building’s main entrance. Also, in the school’s streetlamps, noiseless, small wind energy generator is installed to generate wind energy. In conclusion, efficiently applying solar energy, geothermal energy, acupressure energy, wind energy will increase the school’s renewable energy effect. © (2014) Trans Tech Publications, Switzerland.
Lee S.,Korean Minjok Leadership Academy
World Academy of Science, Engineering and Technology | Year: 2011
Since the advent of the information era, the Internet has brought various positive effects in everyday life. Nevertheless, recently, problems and side-effects have been noted. Internet witch-trials and spread of pornography are only a few of these problems.In this study, problems and causes of malicious replies on internet boards were analyzed, using the key ideas of game theory. The study provides a mathematical model for the internet reply game to devise three possible plans that could efficiently counteract malicious replies. Furthermore, seven specific measures that comply with one of the three plans were proposed and evaluated according to the importance and utility of each measure using the orthogonal array survey and SPSS conjoint analysis.The conclusion was that the most effective measure would be forbidding unsigned user access to malicious replies. Also notable was that some analytically proposed measures, when implemented, could backfire and encourage malicious replies.
Eom D.,Kangwon National University |
Park S.,Kangwon National University |
Park Y.,Kangwon National University |
Lee K.,Kangwon National University |
And 2 more authors.
European Journal of Organic Chemistry | Year: 2013
Trifluoromethanesulfonic acid catalyzed intramolecular hydroarylation of alkynyl selenides and tellurides is developed for the preparation of cycloalkenyl selenide and telluride derivatives through a selective 6- and 7-endo mode. The cycloalkenyl selenides and tellurides can be easily converted into a wide range of other valuable functionalities, including cyclic olefins, allylic alcohols, enynes, 1,3-dienes, and α,β-unsaturated aldehydes. Trifluoromethanesulfonic acid catalyzed intramolecular hydroarylation of alkynyl selenides and tellurides is developed for the preparation of cycloalkenyl selenide and telluride derivatives through a selective 6- and 7-endo mode. The cycloalkenyl selenides and tellurides can be easily converted into a variety of valuable functionalities, including cyclic olefins, allylic alcohols, enynes, 1,3-dienes, and α,β-unsaturated aldehydes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Lee G.N.,Korean Minjok Leadership Academy |
Na J.,Korean Minjok Leadership Academy
ACS Synthetic Biology | Year: 2013
Synthetic biology has recently been at the center of the world's attention as a new scientific and engineering discipline. It allows us to design and construct finely controllable metabolic and regulatory pathways, circuits, and networks, as well as create new enzymes, pathways, and even whole cells. With this great power of synthetic biology, we can develop new organisms that can efficiently produce new drugs to benefit human healthcare and superperforming microorganisms capable of producing chemicals, fuels, and materials from renewable biomass, without the use of fossil oil. Based on several successful examples reported, this commentary aims at peeking into the potential of synthetic biology. © 2013 American Chemical Society.