• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.3
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• pp.263-268
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• 2012

It is important to know the mechanism of cell membrane fluctuation because it can be readout for the nanomechanical interaction between cytoskeleton and plasma membrane. Traditional techniques, however, have drawbacks such as probe contact with the cell surface, complicate analysis, and limit spatial and temporal resolution. In this study, we developed a new system for non-contact measurement of nano-scale localized-cell surface dynamics using modified-scanning ion-conductance microscopy. With 2 nm resolution, we determined that endothelial cells have local membrane fluctuations of ~20 nm, actin depolymerization causes increase in fluctuation amplitude, and ATP depletion abolishes all membrane fluctuations.

• Journal of Information Processing Systems
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• v.3 no.2
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• pp.43-53
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• 2007

The use of agent paradigm in today's applications is hampered by the security concerns of agents and hosts alike. The agents require the presence of a secure and trusted execution environment; while hosts aim at preventing the execution of potentially malicious code. In general, hosts support the migration of agents through the provision of an agent server and managing the activities of arriving agents on the host. Numerous studies have been conducted to address the security concerns present in the mobile agent paradigm with a strong focus on the theoretical aspect of the problem. Various proposals in Intrusion Detection Systems aim at securing hosts in traditional client-server execution environments. The use of such proposals to address the security of agent hosts is not desirable since migrating agents typically execute on hosts as a separate thread of the agent server process. Agent servers are open to the execution of virtually any migrating agent; thus the intent or tasks of such agents cannot be known a priori. It is also conceivable that migrating agents may wish to hide their intentions from agent servers. In light of these observations, this work attempts to bridge the gap from theory to practice by analyzing the security mechanisms available in Aglet. We lay the foundation for implementation of application specific protocols dotted with access control, secured communication and ability to detect tampering of agent data. As agents exists in a distributed environment, our proposal also introduces a novel security framework to address the security concerns of hosts through collaboration and pattern matching even in the presence of differing views of the system. The introduced framework has been implemented on the Aglet platform and evaluated in terms of accuracy, false positive, and false negative rates along with its performance strain on the system.

• Korean Journal of Health Education and Promotion
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• v.14 no.1
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• pp.47-62
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• 1997

본 연구는 한국 보건전문가들의 보건행동을 조사하고, 보건행동간의 상호 관련 요인과 보건행동에 영향을 미치는 인구학적 요인을 분석하는데 그 목적이 있다. 본 연구 대상으로는 한국보건협회 산하의 8개의 보건 관련 학회 중에서 보건교육과 가장 관련이 있는 한국보건교육학회(212명)와 한국보건 간호학회 (124명) 회원 336명이 선정되었다. 본 연구의 도구는 미국에서 이미 실시된 여러 보건행동 연구를 기초로 하여 focus group discussion, back-translation, 전문가들의 panel discussion, 그리고 pilot test(사전조사)를 통하여 한국인의 보건행동 연구를 위해 타당하게 개발되었다. 본 연구를 위하여 1995년 약 두달동안(11월, 12월), 3차에 걸친 우편설문조사를 실시하여 64.3%의 응답회수율을 보였고, 응답자들의 보건행동을 분석하기 위해서 factor analysis(요인분석)와 ANOVA (변량분석) 방법을 사용하였다. 본 연구의 결과는 다음과 같다. 1. 조사응답자의 분포는 남자가 33.8%, 여자가 66.2%였고, 응답자의 80.3%가 석사 이상의 학위를 소유하고 있었다. 응답자들의 전공분야는 다양하였고, 그들 중에서 36.3%가 간호학, 24.4%가 공중보건학을 전공하였다. 응답자 중 과반수 이상이 학교에 근무하였고, 서울에 거주하였으며, 응답자의 평균 직장 근무연수는 14년 이였다. 2. 응답자들의 보건행동에 대한 요인분석 적용의 적합성을 사전검증하기 위하여 Bartlett’s Test of Sphericity (630.37, p〈.00)를 실시하였다. 응답자들의 보건행동을 요인분석한 결과, 17개의 보건행동으로 구성된 네가지 보건행동요인들이 추출되었다. 응답자들의 네가지 보건행동요인들은 다음과 같다: (1) 규칙적인 식사 및 과일 섭취 (2) 음주 및 흡연 (3) 외식,간식 및 카페인 음료 섭취 (4) 운동 및 휴식 3. 응답자들의 인구학적 요인과 네가지 보건행동요인들과의 관계를 분석한 결과, 성별(F=69.59, df=1,203, p〈.05), 교육정도(F=3.48, df=3,199, p〈.05) 그리고 직장(F=4.04, df=3,201, p〈.05)에 따라 음주 및 흡연 행동에 커다란 차이를 보였다. 또한 응답자의 직장 근무연수(F=2.39, df=5,185, p〈.05)에 따라 운동 및 휴식 행동에 커다란 차이를 보였다.

• Ocean and Polar Research
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• v.27 no.2
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• pp.189-195
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• 2005

Several models predict large and potentially abrupt ocean circulation changes due to anthropogenic greenhouse-gas emissions. These circulation changes drive-in the models-considerable oceanic oxygen trend. A sound estimate of the observed oxygen trends can hence be a powerful tool to constrain predictions of future changes in oceanic deepwater formation, heat and carbon dioxide uptake. Estimating decadal scale oxygen trends is, however, a nontrivial task and previous studies have come to contradicting conclusions. One key potential problem is that changes in the historical observation network might introduce considerable errors. Here we estimate the likely magnitude of these errors for a subset of the available observations in the Southern Ocean. We test three common data analysis methods south of Australia and focus on the decadal-scale trends between the 1970's and the 1990's. Specifically, we estimate errors due to sparsely sampled observations using a known signal (the time invariant, temporally averaged, World Ocean Atlas 2001) as a negative control. The crossover analysis and the objective analysis methods are for less prone to spatial sampling location biases than the area averaging method. Subject to numerous caveats, we find that errors due to sparse sampling for the area averaging method are on the order of several micro-moles $kg^{-1}$. for the crossover and the objective analysis method, these errors are much smaller. For the analyzed example, the biases due to changes in the spatial design of the historical observation network are relatively small compared to the tends predicted by many model simulations. This raises the possibility to use historic oxygen trends to constrain model simulations, even in sparsely sampled ocean basins.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.6
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• pp.445-454
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• 1998

In order to establish a technical concept for the detection of defects in weldments in thin steel plate, an experimental and theoretical investigation was carried out for artificial defects in a steel plate having a thickness of 2.4mm by using the guided wave technique. In particular the goal was to find the most effective testing parameters paying attention to the relationship between the excitation frequency by a tone burst system and various incident angles. It was found that the test conditions that worked best was for a frequency of 840kHz and an incident angle of 30 or 85 degrees, most of the defects were detected with these conditions. Also, it was clear that a guided wave mode generated under an incident angle of 30 degrees was a symmetric mode, So, and that of 85 degrees corresponded to an antisymmetric mode, Ao. By using the two modes, most of all of the defects could be detected. Furthermore, it was shown that the antisymmetric mode was more sensitive to defects near the surface than the symmetric mode. Theoretical predictions confirmed this sensitivity improvement with Ao for surface defects because of wave structure variation and energy concentration near the surface.

• Nutrition Research and Practice
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• v.15 no.sup1
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• pp.22-31
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• 2021

Coronavirus disease 2019 (COVID-19) is a new type of respiratory disease that has been announced as a pandemic. The COVID-19 outbreak has changed the way we live. It has also changed the food service industry. This study aimed to identify trends in the food and food service industry after the COVID-19 outbreak and suggest research themes induced by industry trends. This study investigated the industry and academic information on the food and food service industry and societal trends resulting from the COVID-19 outbreak. The most noticeable changes in the food industry include the explosive increase in home meal replacement, meal-kit consumption, online orders, take-out, and drive-through. The adoption of technologies, including robots and artificial intelligence, has also been noted. Such industry trends are discussed in this paper from a research perspective, including consumer, employee, and organizational strategy perspectives. This study reviews the changes in the food service industry after COVID-19 and the implications that these changes have rendered to academia. The paper concludes with future expectations that would come in the era of COVID-19.

• Molecules and Cells
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• v.26 no.2
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• pp.193-199
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• 2008

The pro-apoptotic Bcl-2 family member Bim acts as a sensor for apoptotic stimuli and initiates apoptosis through the mitochondrial pathway. To identify novel regulators of Bim, we employed the yeast two-hybrid system and isolated the human gene encoding macrophage migration inhibitory factor (MIF), a ubiquitously expressed proinflammatory mediator that has also been implicated in cell proliferation, the cell cycle and carcinogenesis. The interaction between MIF and Bim was confirmed by both in vitro and in vivo protein interaction assays. Intriguingly, protein complexes between MIF and the three major Bim isoforms (BimEL/BimL/BimS) could be detected in HEK293 and K562 cells, especially in cells undergoing apoptosis. Moreover, exogenous expression of MIF partially inhibited Bim-induced apoptosis in HEK293 cells. SiRNA-mediated knockdown of MIF increased apoptosis in K562 cells exposed to the chemical oxidant diamide. Endogenous MIF may regulate the pro-apoptotic activity of Bim and inhibit the release of cytochrome c from mitochondria.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.419-439
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• 2018

Piezoelectric materials are essential parts of the electronics and electrical equipment used for consumer and industrial applications, such as ultrasonic piezoelectric transducers, sensors, actuators, transformers, and resonators. In this review, the development of piezoelectric materials and the figures of merit for various electromechanical applications are surveyed, focusing on piezoelectric crystals, i.e., the high-performance relaxor-$PbTiO_3$-based perovskite ferroelectric crystals and nonferroelectric high-temperature piezoelectric crystals. The uniqueness of these crystals is discussed with respect to different usages. Finally, the existing challenges and perspective for the piezoelectric crystals are discussed, with an emphasis on the temperature-dependent properties, from cryogenic temperatures up to the ultrahigh-temperature usage range.

• International Journal of Concrete Structures and Materials
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• v.9 no.4
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• pp.453-462
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• 2015

A critical review on existing creep theories in calcium-silicate-hydrate (C-S-H) is presented with an emphasis on several fundamental questions (e.g. the roles of water, relative humidity, temperature, atomic ordering of C-S-H). A consensus on the rearrangement of nanostructures of C-S-H as a main consequence of creep, has almost been achieved. However, main disagreement still exists on two basic aspects regarding creep mechanisms: (1) at which site the creep occurs, like at interlayer, intergranular, or regions where C-S-H has a relatively higher solubility; (2) how the structural rearrangement evolutes, like in a manner of interlayer sliding, intra-transfer of water at various scales, recrystallization of gelled-like particles, or dissolution-diffusion-reprecipitation at inter-particle boundary. The further understanding of creep behavior of C-S-H relies heavily on the appropriate characterization of its nanostructure.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.185-199
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• 2014

As the national transportation infrastructure ages and deteriorates, many existing bridges require frequent and costly maintenance and repairs. The objective of this work was to synthesize new and existing types of beam end coatings and treatments that have been proven to extend the life of new and existing concrete and steel bridge beams. A comprehensive literature review, along with online surveys and phone interviews of State department of transportations (DOTs) and coating manufacturers was conducted to gather information about existing and recently developed technologies. The study revealed that while many promising coatings and treatments are offered on the market, there is a lack of readily available laboratory results that would enable direct comparison of the available methods. This finding applies in terms of the coatings' durability and the potential for extending the service life of existing bridges. Most of the interviewed State DOTs' personnel assessed the products listed in respective DOT's Qualified Products Lists as performing 'well'. However, there was significant variability between states in the type of the products used. Among the agencies contacted, none was able to suggest the most promising or advanced products, either for concrete or steel bridge beam end treatments. This suggests that comprehensive laboratory evaluation would be necessary for selecting the best available beam end treatments and coatings.