• 한국환경성돌연변이발암원학회지
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• 제23권2호
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• pp.56-62
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• 2003

The liver progenitor cells could form a potential target cell population fore both tumor-initiating and -promoting chemicals. Induction of drug-metabolizing and antioxidant enzymes, including AhR-dependent CYP1A1, NQO-1 and AKR1C9, was detected in the rat liver epithelial WB-F344 "stem-like" cells. Additionally, WB-F344 cells express a functional, wild-type form of p53 protein, a biomarker of genotoxic events, and connexin 43, a basic structural unit of gap junctions forming an important type of intercellular communication. In this cellular model, two complementary assays have been established for detection of the modes of action associated with tumor promotion: inhibition of gap junctional intercellular communication (GJIC) and proliferative activity in confluent cells. We found that the PAHs and PCBs, which are AhR agonists, released WB-F344 cells from contact inhibition, increasing both DNA synthesis and cell numbers. Genotoxic effects of some PAHs that lead to apoptosis and cell cycle delay might interfere with the proliferative activity of PAHs. Contrary to that, the nongenotoxic low-molecular-weight PAHs and non-dioxin-like PCB congeners, abundant in the environment, did not significantly affect cell cycle and cell proliferation; however both groups of compounds inhibited GJIC in WB-F344 cells. The release from contact inhibiton by a mechanism that possibly involves the AhR activation, inhibition of GJIC and genotoxic events induced by environmental contaminants are three important modes of action that could play an important role in carcinogenic effects of toxic compounds. The relative potencies to inhibit GJIC, to induce AhR-mediated activity, and to release cells from contact inhibition were determined for a large series of PAHs and PCBs and their metabolites. In vitro bioassays based on detection of events on cellular level (deregulation of GJIC and/or proliferation) or determination of receptor-mediated activities in both ?$stem-like^{\circ}{\times}$ and hepatocyte-like liver cellular models are valuable tools for detection of modes of action of polyaromatic hydrocarbons. They may serve, together with concentration data, as a first step in their risk assessment.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2000년도 춘계수산관련학회 공동학술대회발표요지집
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• pp.530-530
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• 2000

The host defense system or immune system of all modern animals has their roots in very ancient organisms. After analyzing literature data concerning properties of invertebrates and vertebrates lectins we suggest that mechanism of mannans recognition may exist in marine invertebrates, as a universal mechanism for homeostasis maintenance and host defense, and mannan-binding lectins family of vertebrates has ancient precursor, as was shown for another S-type lectins family. We carried out the screening of mannan-binding type lectin among different species of echinoderms inhabiting in Piter the Grate Bay, the sea of Japan. As a result, the C-type lectins (SJL-32) specific for high mannose glycans was isolated from the coelomic plasma of the sea cucumbers Stichopus japonicus by ion-exchange chromatography on a DEAE-Toyopearl 650M, affinity chromatography on a mannan-Sepharose 6B and gel filtration on a Sephacryl S-200. SJL-32 is homodimer with molecular mass about 32 kDa on SDS-PAGE under non-reducing conditions. Protein part of the lectin has high conteins Asn, Glu, Ser. Hemagglutination of trypsin-treated O blood group human erythrocytes by SJL-32 was competitively inhibited by high-branched -D-mannan composed of -1,2 and -1,6 linked D-mannopyranose residues. In contrast, a variety of mono-, oligo-, and polysaccharides composed of residues of galactose and fucose showed absence or little inhibitory activities. The lectin activity strong depends on Ca2+ concentration, temperature and pH. Monospecific polyclonal antibodies were obtained to the lectin. As was shown by ELISA assay, antibodies to SJL-32 cross-reacted with human serum mannan-binding lectin. This data allows making conclusion about common antigenic determinants and structural homology of both lectins. In our opinion, SJL-32 belongs to evolutionary high conservative mannan-binding lectins (MBLs) family and takes part in the host defense against pathogenic microorganisms.

• 한국동물번식학회:학술대회논문집
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• 한국동물번식학회 2001년도 춘계학술발표대회
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• pp.86-86
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• 2001

The aims of this work were to determine the acrosin activity and to evaluate the structural and functional integrity of AS boar spermatozoa. The acrosin activity of spermatozoa were 5.40, 4.10 and 3.40 mIU/10$^{6}$ sperm in raw, extended and frozen semen respectively , which differed significantly each other (P<0.05). After the raw and extended semen were exposured to cold and thermal shock, the acrosin activities of spermatozoa in the raw semen were 5.39, 5.21 and 5.29 mIU/10$^{6}$ sperm for control (non-shock), cold shock and thermal shock, and those of extended semen were 4.21, 3.98 and 4.00 mIU/10$^{6}$ sperm. This value among treatments did not differ significantly. The acrosin activities of spermatozoa in the extended and stored semen were 3.27, 3.52, 3.46 and 3.23 mIU/10/suup 6/ sperm, while hypo-osmotic test(HOST) values were 56.5%, 64.7%, 66.0% and 56.0%, following 4 days storage at 4$^{\circ}C$, 17$^{\circ}C$ , $25^{\circ}C$ and 37$^{\circ}C$, respectively. The results at 17$^{\circ}C$ and $25^{\circ}C$ appeared to be best compared with the other storage temperatures.

• Earthquakes and Structures
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• 제24권4호
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• pp.303-316
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• 2023

Rapid post-earthquake damage estimation of subway stations is particularly necessary to improve short-term crisis management and safety measures of urban subway systems after a destructive earthquake. The conventional Performance-Based Earthquake Engineering (PBEE) framework with constant earthquake occurrence rate is invalid to estimate the aftershock risk because of the time-varying rate of aftershocks and the uncertainty of mainshock-damaged state before the occurrence of aftershocks. This study presents a time-varying probabilistic seismic risk assessment framework for underground structures considering mainshock and aftershock hazards. A discrete non-omogeneous Markov process is adopted to quantify the time-varying nature of aftershock hazard and the uncertainties of structural damage states following mainshock. The time-varying seismic risk of a typical rectangular frame subway station is assessed under mainshock-only (MS) hazard and mainshock-aftershock (MSAS) hazard. The results show that the probabilities of exceeding same limit states over the service life under MSAS hazard are larger than the values under MS hazard. For the same probability of exceedance, the higher response demands are found when aftershocks are considered. As the severity of damage state for the station structure increases, the difference of the probability of exceedance increases when aftershocks are considered. PSDR=1.0% is used as the collapse prevention performance criteria for the subway station is reasonable for both the MS hazard and MSAS hazard. However, if the effect of aftershock hazard is neglected, it can significantly underestimate the response demands and the uncertainties of potential damage states for the subway station over the service life.

• 한국공간구조학회논문집
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• 제23권3호
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• pp.95-103
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• 2023

With the increasing number of aging buildings across Korea, emerging maintenance technologies have surged. One such technology is the non-contact detection of concrete cracks via thermal images. This study aims to develop a technique that can accurately predict the depth of a crack by analyzing the temperature difference between the crack part and the normal part in the thermal image of the concrete. The research obtained temperature data through thermal imaging experiments and constructed a big data set including outdoor variables such as air temperature, illumination, and humidity that can influence temperature differences. Based on the collected data, the team designed an algorithm for learning and predicting the crack depth using machine learning. Initially, standardized crack specimens were used in experiments, and the big data was updated by specimens similar to actual cracks. Finally, a crack depth prediction technology was implemented using five regression analysis algorithms for approximately 24,000 data points. To confirm the practicality of the development technique, crack simulators with various shapes were added to the study.

• 정보교육학회논문지
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• 제26권6호
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• pp.533-541
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• 2022

코로나19로 인해 교육 현장에서는 비대면 수업이 정착되었다. 이에 온라인 수업, 블렌디드 러닝 등의 방법이 도입 되었으며, 학습자와 교수자, 학습자와 학습자 간 상호작용을 촉진하는 메타버스가 주목받기 시작했다. 메타버스는 비대면 방식에서 나타난 물리적 환경에서 오는 교육의 한계를 극복할 수 있어 초등교육 학습자들에게 보다 적합한 교육 방안이 될 수 있다. 메타버스를 교육 현장에 활용하기 위해서는 예비교사들의 사용의도가 중요하다. 본 연구에서는 기술수용모델에 기반하여 예비교사의 교육역량과 메타버스 사용의도 간의 구조적 관계를 분석하여, 새로운 테크놀로지에 대한 유연성, 교수효능감, 테크놀로지 내용교수지식(TPACK)의 영향 요인을 살펴보았다. 예비교사 240명을 대상으로 하였고, 최종 수집된 183명의 자료를 분석에 사용하였다. 연구 결과 예비교사의 메타버스 교육역량 중 유연성과 TPACK은 인지된 용이성을 매개하여 메타버스의 사용의도에 영향을 미치는 경로는 유의하였다. 이와 관련 논의와 예비교사들의 메타버스 사용의도에 도움을 줄 수 있는 이론적, 실천적 시사점을 제시하였다.

• Structural Engineering and Mechanics
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• 제86권1호
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• pp.1-16
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• 2023

The free vibration of temperature-dependent functionally graded plates (FGPs) resting on a viscoelastic foundation is investigated in this paper using a newly developed simple first-order shear deformation theory (FSDT). Unlike other first order shear deformation (FSDT) theories, the proposed model contains only four variables' unknowns in which the transverse shear stress and strain follow a parabolic distribution along the plates' thickness, and they vanish at the top and bottom surfaces of the plate by considering a new shape function. For this reason, the present theory requires no shear correction factor. Linear steady-state thermal loads and power-law material properties are supposed to be graded across the plate's thickness. Uniform, linear, non-linear, and sinusoidal thermal rises are applied at the two surfaces for simply supported FGP. Hamilton's principle and Navier's approach are utilized to develop motion equations and analytical solutions. The developed theory shows progress in predicting the frequencies of temperature-dependent FGP. Numerical research is conducted to explain the effect of the power law index, temperature fields, and damping coefficient on the dynamic behavior of temperature-dependent FGPs. It can be concluded that the equation and transformation of the proposed model are as simple as the FSDT.

• Composites Research
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• 제22권2호
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• pp.30-36
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• 2009

본 논문에서는 헬리콥터 착륙장치를 위한 복합재료 토크링크를 개발하기 위한 설계 기법을 제시하였다. 복합재 토크링크는 헬리콥터 착륙장치의 충격흡수부의 정렬을 위해 장착되는 장치로서 가벼우면서도 강성이 커서 외부하중에 대해 최소의 변형량을 가져야 한다. 또 가격적인 측면을 고려한 복합재 구조물 제조 공정(RTM: 수지충전공정)이 반영되어 대량생산이 가능한 구조 및 형태를 가져야 한다. 본 논문에서는 복합재 구조물 제조 공정과 동일한 공정으로 시편을 제작하여 설계에 필요한 기계적 특성을 얻었으며, 유한요소해석을 통하여 복합재 토크링크에 대한 최적 형상설계를 수행하였다. Lug 형태를 가지는 두꺼운 복합재료 구조물인 복합재료 토크링크의 설계를 위해서는 ABAQUS의 3D Layered Solid 요소로 구성된 유한요소모델을 활용하여 복합재료의 두께방향을 포함한 강도해석을 수행하였으며, Rigid-Deform 구속조건의 접촉문제를 고려한 비선형 정적 해석을 반복적으로 수행하여 주어진 정강도 요구조건을 만족시키는 복합재 토크링크를 설계하였다.

• 한국전자통신학회논문지
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• 제17권2호
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• pp.375-386
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• 2022

정보자산 보호가 조직의 중요한 관리 요인으로 인식되면서, 조직들은 정보보안 정책 및 기술 도입을 위한 투자를 높이고 있다. 하지만, 엄격한 정보보안의 적용은 조직원에게 스트레스를 통해 미준수 행동을 일으킬 수 있다. 본 연구의 목적은 정보보안 역할 강화로 인해 형성된 조직원의 스트레스가 자기결정성을 통해 준수 의도에 미치는 매커니즘을 제시하고, 개인조직 적합성을 통해 준수 의도 강화 방안을 제시하는 것이다. 연구는 정보보안 정책을 도입한 기업에 근무하는 조직원을 대상으로 온라인 설문을 하였으며, 475개의 표본을 활용하여 가설검증을 하였다. 첫째, 구조방정식 모형을 적용한 주효과 분석 결과는 역할 스트레스가 자기결정성을 감소하여 준수 의도에 영향을 미쳤다. 둘째, Process 3.1을 적용한 조절 효과 분석 결과는 개인조직 적합성이 자율성, 관계성이 준수 의도에 미치는 영향을 강화하였다. 연구는 조직원의 정보보안 스트레스, 행동 동기의 영향을 확인함으로써, 조직 내부의 정보보안 목표달성 방향을 제언한 측면에서 시사점을 가진다.

• 한국프랜차이즈경영연구
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• 제9권4호
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• pp.33-43
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• 2018

Purpose - In hotel industry, quality of leader-member exchange(LMX) relationship is very critical, because it impacts on the employee's work attitude and behaviors. Thus, this research examines the effect of LMX on employee loyalty in the context of hotel business and identifies mediating roles of work stressors, work role performance in the relationship between LMX and employee loyalty. This research suggests the guidelines for how hotel leaders should manage their employees and build employee loyalty that improve management and business performance. Research design, data, and methodology - This study tests the structural relationship between LMX, work stressors, work role performance, and employee loyalty. Work role performance divide into three sub-dimensions such as individual task proficiency, individual task adaptivity, and individual task proactivity. In order to examine the purposes of this research, research model and hypotheses were developed. All constructs were measured with multiple items developed and tested in the previous studies. The data were collected from 113 franchise hotel employees and were analyzed using SPSS 22.0 and SmartPLS 3 program. Result - The findings of this research are as follows. First, leader-member exchange(LMX) have significant positive impacts on work stressors, work role performance, and employee loyalty. Second, work stressors have significant negative impacts on work role performance and employee loyalty. Third, work role performance has significant positive impact on employee loyalty. Conclusions - The outcomes of this research indicate that hotel leaders should focus on the dyadic relationship with their employees how to improve employee productivity through LMX relationship. In turn, the quality of this relationship influences employees's work attitudes and behaviors. As a result of increasing job demands in hotel business which relies heavily on human resources, the hotel leader must find ways to prevent or reduce stressors and associated strains. If hotel employees perceive the high quality of LMX relationship, they improve their work role performance which influences loyalty. Therefore, the hotel leaders should develop monetary or non-monetary reward system for the employees and, make an efforts to have unique social exchange relationships with employees.