• 한국강구조학회 논문집
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• 제12권4호통권47호
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• pp.351-362
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• 2000

이 논문은 반복하중을 받는 관통형 고력볼트를 사용한 엔드플레이트형식 콘크리트 충전 각형강관 기둥-H형강 보 접합부의 거동에 관한 연구이다. 주요변수는 엔드플레이트의 두께(16mm, 22mm, 25mm)와 기둥의 두께(9mm, 12mm)이다. 각 변수에 대해 실험결과와 비교 분석한다. 보-기둥 접합부의 에너지 흡수능력을 구하고, 접합부 패널의 전단내력을 분석한다. 접합부 패널의 전단 내력은 von Mises 항복조건에 의한 강재의 내력과 콘크리트 충전효과를 고려한 Strut 모델을 사용한 콘크리트의 내력을 단순누가해서 구한다.

• 한국강구조학회 논문집
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• 제26권4호
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• pp.311-322
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• 2014

콘크리트 충전강관 기둥에 모멘트 접합부를 만들기 위해서는 추가적인 다이아프램 설치가 필요하다. 그 중 내측 다이아프램과 관통 다이아프램을 용접하기 위해서는 기둥강관에 특수한 용접기술이 필요하다. 하지만 이런 기술은 제작업체의 특수장비 보유에 따라서 제작성 저하와 생산단가 상승 유도 등의 문제를 갖고 있다. 따라서 본 연구에서는 외다이아프램을 갖는 실대형 기둥-보 접합부를 제작하였고, 반복가력 실험을 수행하였다. 다이아프램의 용접 유무와 콘크리트 충전 여부, 형상에 따른 총 6개의 T자형 접합부 실험을 통해 내진성능을 평가하였다. 또한 외다이아프램 내력식에 대한 분석이 이뤄졌다. 본 실험에서 나온 결과를 인장내력식의 적절성을 검토 하였다.

• 한국수소및신에너지학회논문집
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• 제28권5호
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• pp.471-480
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• 2017

A proton exchange membrane fuel cell (PEMFC) operated at $150^{\circ}C$ was evaluated by a controlling different amount of phosphoric acid (PA) to a membrane-electrode assembly (MEA) without humidification of the cells. The effects on MEA performance of the amount of PA in the cathode are investigated. The PA content in the cathodes was optimized for higher catalyst utilization. The highest value of the active electrochemical area is achieved with the optimum amount of PA in the cathode confirmed by in-situ cyclic voltammetry. The current density-voltage experiments (I-V curve) also shows a transient response of cell voltage affected by the amount of PA in the electrodes. Furthermore, this information was compared with the production variables such as hot pressing and vacuum drying to investigate those effect to the electrochemical performances.

• 전기화학회지
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• 제23권3호
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• pp.73-80
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• 2020

과산화수소를 이용한 펜톤(Fenton)산화법은 수처리 및 토양 복원분야에서 활용되는 친환경 산화방법이다. 이 방법으로 오염물질을 제거할 때, 오염물의 농도에 따라 과산화수소의 농도를 적절하게 조절하는 것이 상당히 중요하다. 이에 본 연구에서는 HRP (horseradish peroxidase) 효소를 이용한 전기화학적 바이오센서를 제조하고 효소의 활성과 과산화수소의 검출 특성에 대한 연구를 수행하였다. SPCE (Screen Printed Carbon Electrode)의 작업 전극 표면에 키토산과 AuNP를 이용하여 HRP를 전착하였다. 이 후, 전위주사법(CV)과 전기화학적 임피던스 분광법(EIS)을 이용하여 효소의 고정화를 확인하였다. 또한 시간대전류법(CA)과 UV 분광법으로부터 HRP 효소의 활성을 확인하였다. 본 연구에서 제조한 바이오센서를 PBS 전해질에 담그고 과산화수소를 적정하여 CA 분석으로부터 전극에서 발생하는 전류를 측정하였다. 발생 전류는 과산화수소의 농도에 대하여 선형적으로 증가하였으며, 전류로부터 과산화수소의 농도를 예측할 수 있는 검정곡선을 도출하였다.

• Bulletin of the Korean Chemical Society
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• 제35권1호
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• pp.177-181
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the reactions of Y-substituted-phenyl benzoates (5a-j) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. [EtOK] curve upward regardless of the electronic nature of the substituent Y in the leaving group. Dissection of $k_{obsd}$ into the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOK (i.e., $k_{EtO^-}$ and $k_{EtOK}$, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The Br${\phi}$nsted-type plots for the reactions with the dissociated $EtO^-$ and ion-paired EtOK exhibit highly scattered points with ${\beta}_{lg}$ = -$0.5{\pm}0.1$. The Hammett plots correlated with ${\sigma}^o$ constants result in excellent linear correlations, indicating that no negative charge develops on the O atom of the leaving Y-substituted-phenoxide ion in transition state. Thus, it has been concluded that the reactions with the dissociated $EtO^-$ and ion-paired EtOK proceed through a stepwise mechanism, in which departure of the leaving group occurs after the RDS, and that $K^+$ ion catalyzes the reactions by increasing the electrophilicity of the reaction center through a four-membered cyclic TS structure.

• Bulletin of the Korean Chemical Society
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• 제34권5호
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• pp.1525-1529
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• 2013

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the nucleophilic substitution reactions of 2-pyridyl thionobenzoate (5b) with alkali-metal ethoxides (EtOM, $M^+=Li^+$, $Na^+$, $K^+$, and 18-crown-6-ether complexed $K^+$) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plots of $k_{obsd}$ vs. $[EtOM]_o$ curve upward regardless of the nature of the $M^+$ ions, while those of $k_{obsd}/[EtO^-]_{eq}$ vs. $[EtO^-]_{eq}$ are linear with a positive intercept. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOM}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ and ion-paired EtOM, respectively) has revealed that the ion-paired EtOM is more reactive than the dissociated $EtO^-$, and $M^+$ ions catalyze the reactions in the order $K^+$ < $Na^+$ < $Li^+$ < 18C6-complexed $K^+$. The plot of log $k_{EtOM}$ vs. $1/r_{Stokes}$ results in an excellent linear correlation, indicating that the reactions are catalyzed by the solvated $M^+$ ions but not by the bare $M^+$ ions. The reactions of 5b with EtOM have been concluded to proceed through a six-membered cyclic TS, in which the solvated $M^+$ ions increase the electrophilicity of the reaction center and the nucleofugality of the leaving group.

• 유통과학연구
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• 제13권1호
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• pp.7-18
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• 2015

Purpose - This study integrates a corporate competition system with a bird predation system to examine how organizational strategic adjustment capacity influences firm performance. By proving the prominent effects on performance, a financial vector is constructed to represent corporate strategic adjustment results, and an operation capacity vector is constructed, which can be categorized as a parameter for locating birds. All these works help us to propose a new method of investment, the portfolio decision model based on the strategic adjustment capacity. Research design, data, and methodology - Strategic adjustment capacity can be decomposed into three aspects: the organizational learning capacity from the top firms, the extent to which firms maintainor rely on the best operational capacity vector in history, and the ability to eliminate the disadvantages or retain the advantages of the operation capacity vector from the previous year. The method of solving cyclic equations is designed to evaluate strategic adjustment. Firms manufacturing specialized equipment are chosen to test the effects of the strategic adjustment capacity on three aspects of firm performance. Results - There is a positive correlation between the capacity to learn from the best firms and performance improvement. The relationship between the dependence or maintenance of a firm's advantages and performance improvement is a U-shape curve, and there is no significant effect of inertial control on performance improvement. Conclusions - A firm's competition system is a sophisticated adaptation, and competitive advantage and performance can be investigated based on the principles of competition in nature.

• Structural Engineering and Mechanics
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• 제72권2호
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• pp.245-256
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• 2019

The experimentally determined mechanical behavior of the material under the prescribed service conditions is the basis of advanced engineering optimum design. To allow experimental data on the behavior of the material considered, uniaxial stress tests were made. The aforementioned tests have enabled the determination of mechanical properties of material at different temperatures, then, the material's resistance to creep at various temperatures and stress levels, and finally, insight into the uniaxial high cyclic fatigue of the material under different applied stresses for prescribed stress ratio. Based on fatigue tests, using modified staircase method, fatigue limit was determined. All these data contributes the reliability of the use of material in mechanical structures. Data representing mechanical properties are shown in the form of engineering stress-strain diagrams; creep behavior is displayed in the form of creep curves while fatigue of the material is presented in the form of S-N (maximum applied stress versus number of the cycles to failure) curve. Material under consideration was 18CrNi8 (1.5920) steel. Ultimate tensile strength and yield strength at room temperature and at temperature of $600^{\circ}C$: [${\sigma}_{m,20/600}=(613/156)MPa$; ${\sigma}_{0.2,20/600}=(458/141)MPa$], as well as endurance (fatigue) limit at room temperature and stress ratio of R = -1 : (${\sigma}_{f,20,R=-1}=285.1MPa$).

• 대한건축학회논문집:구조계
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• 제34권4호
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• pp.25-33
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• 2018

In regard to modular systems, new methods, as well as middle and high-story unit design ideas, are currently being studied. These studies need to focus on the enhanced stiffness and seismic performance of these connections, and see that the development of fully restrained moment connections can improve the seismic performance. For this reason, this study evaluates the performance of the connections of the ceiling bracket-typed modular system through repeated loading tests and analyses. In order to compare them with these modular units, new unit specimens with the bracket connection being different from that of the traditional modular unit specimens were designed, and the results of repeated loading tests were analyzed. In the traditional units, the structural performances of both welding connection and bolt connection were evaluated. In regard to the testing results, the initial stiffness of the hysteresis curve was compared with the theoretical initial stiffness, and the features of all specimens were also analyzed with regard to the maximum moment. In addition, the test results were examined with regard to the connection flexural strength of the steel special moment frame specified under the construction criteria KBC2016. The connections, which were proposed in the test results, were found to be fully restrained moment connections for designing strong column-weak beams and meeting the requirements of seismic performance of special moment frames.

• Computers and Concrete
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• 제26권6호
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• pp.547-563
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• 2020

In this paper, the influence of axial compression ratio on the mechanical properties of new type joints of side span of rectangular concrete-filled steel tubular column-H-type steel beam is studied. Two new types of side-span joints of rectangular concrete-filled steel tubular column-H-type steel beam are designed and quasi-static tests of five new type joints with 1:2 scale reduction ratios are performed. The axial compression ratio of joint JD1 is 0.3, 0.4 and 0.5, and the axial compression ratio of joint JD2 is 0.3 and 0.5. In the joint test, different axial forces were applied to the top of the column according to different axial compression ratios, and low-cyclic reciprocating load was applied on the beam. The stress and strain distribution, beam and column deformation, limit state, failure process, failure mechanism, stiffness degradation, ductile deformation and energy dissipation capacity of the joint were measured and analyzed. The results show that: with the increase of axial compression ratio, the ultimate bearing capacity of the joint decreases slightly, the plastic deformation decreases, and the stiffness and ductility decrease. According to the energy dissipation curve of the specimen, the equivalent damping coefficient also increases with the increase of axial compression ratio in a certain range, indicating that the increase of axial compression ratio can improve the seismic performance of the joint to a certain extent. The finite element method is used to simulate the joint test, and the test results are in good agreement with the simulation results.