• Journal of the Korean Operations Research and Management Science Society
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• v.41 no.1
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• pp.113-126
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• 2016

This study investigates the effect of power dynamics on R&D and market performances. Various types of relationships in a supply chain are considered. An R&D company offering new technology for product quality and a manufacturer responsible for both production and sales are utilized as subjects. The company with bargaining power differs with respect to the supply chain situation in practice, and no fixed single relationship and supply chain structure exist. However, only a few studies have considered the various relationships among players in a supply chain and their effects on performance. Therefore, we propose three models with different supply chain structures and power dynamics among players. This study contributes to the academia and supply chain practice by revealing the different characteristics of supply chain models.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.322-325
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• 1997

Concerns for wind energy as alternative energy have been highly increased. In this paper, the mechanism between mechanical wind turbine and power generating system is presented to specify the relationship of the energy transfer. Grid-connected DFIG could achieve unity leading power factor, in addition to variable speed operation at the wide sub-synchronous and super-synchronous shaft speed range and also its independent control of torque and reactive power is possible.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.222-228
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• 2015

Power MOSFETs (metal oxide semiconductor field effect transistor) operate as energy control semiconductor switches. In order to reduce energy loss of the device, it is essential to increase its conductance. However, a trade-off relationship between the breakdown voltage and conductance of the device have been the critical difficulty to improve. In this paper, theoretical analysis of electrical benefits on single floating island power MOSFET is proposed. By the method, the optimization point has set defining the doping limit under single floating island structure. The numerical multiple 2.22 was obtained which indicates the doping limit of the original device, improving its ON state voltage drop by 45%.

• Nuclear Engineering and Technology
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• v.36 no.1
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• pp.64-72
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• 2004

The purpose of this study is to develop a system dynamics model for the assessment of the organizational and human factors in a nuclear power plant which contribute to nuclear safety. Previous studies can be classified into two major approaches. One is the engineering approach using tools such as ergonomics and Probability Safety Assessment (PSA). The other is the socio-psychology approach. Both have contributed to find organizational and human factors and to present guidelines to lessen human error in plants. However, since these approaches assume that the relationship among factors is independent they do not explain the interactions among the factors or variables in Nuclear Power Plants. To overcome these restrictions, a system dynamics model, which can show cause and effect relationships among factors and quantify the organizational and human factors, has been developed. Handling variables such as the degree of leadership, the number of employees, and workload in each department, users can simulate various situations in nuclear power plant organization. Through simulation, users can get insights to improve safety in plants and to find managerial tools in both organizational and human factors.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1987-1989
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• 2001

전력선 통신은 디지털 변복조 통신 기술의 발달에 힘입어 높은 신뢰성과 고속의 데이터 전송 속도를 제공하게 됨에 따라 차세대 통신 기술로 기대되고 있다. 아울러 배전 계통에서의 원격 검침은 단순히 검침 비용의 절감 차원이 아닌 수용가 정보 취득 및 수요관리 등의 기능을 함께 수용할 수 있어 보다 효율적인 에너지 사용관리 및 감시가 가능한 배전 계통 구축이 가능하다. 아울러 구성된 통신망을 이용하여 제공되는 다양한 부가서비스를 통하여 CRM(Customer Relationship Management)의 차원을 한 단계 높일 수 있는 방안의 하나로서 인식되어 선진국 전력회사들간에 지대한 관심의 대상이 되고 있다. 본 논문에서는 전력선 통신을 이용하여 저압 수용가의 원격 검침 시스템의 구축 방안을 소개하며, 시스템 구축 상에 관련된 기술적 사항과 효과적인 네트웍 구축을 위한 프로토콜 등을 다루었다.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1480-1489
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• 2017

In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

• Korean Journal of Human Ecology
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• v.18 no.1
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• pp.65-74
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• 2009

The study was conducted by regression analysis based on a survey with the subjects of 107 daycare teachers working at 120 daycare facilities located in Gyeonggi-do, so as to investigate the influence of daycare teachers' 'job stress' and 'job satisfaction' on their 'psychological happiness'. The results are: first, there was significant difference in job stress(F(3,103)=2.85, p<.05), job satisfaction(F(3,103)=5.88, p<.05) and psychological happiness(F(3,103)=3.52, p<.05) accordant to the kind of work facilities among social demographic variables. In the correlation between 'job stress' and 'job satisfaction', there was negative correlation(r= .-56, p<.(01). Second, in the correlation between 'job stress' and 'psychological happiness', there was negative correlation(r= .-41, p<.001). Third, in the correlation between 'job satisfaction' and 'psychological happiness', there was positive correlation(r= .54, p<.001). In the relationship between 'job satisfaction' and 'job stress', job stress had influence on job satisfaction($R^2$= .43, F=79.42, p<.001). The explanatory power of it was 43%. In the relationship between 'job stress' and 'psychological happiness', 'job stress' had influence on 'psychological happiness'($R^2$= .41, F=21.46, p<.001). The explanatory power of it was 17%. In the relationship between 'job satisfaction' and 'psychological happiness', 'job satisfaction' had influence on 'psychological happiness'($R^2$= 59, F=5457, p<.001). The explanatory power of it was 34%.

• Journal of Navigation and Port Research
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• v.46 no.3
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• pp.259-268
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• 2022

Unlike the general buyer-supplier relationship, there are cases wherein the bargaining power of suppliers is greater than that of buyers. This relationship can be found especially in the shipbuilding industry. Thus, this paper focused on strategic items presented in Kraljic's study. The purpose of this study was to examine factors influencing buyers' purchase of strategic items in a market wherein the bargaining power of suppliers is superior. Results show that the path coefficient between environment factor and satisfaction factor was the highest. Additionally, the path coefficient between environment factor and reliability factor was the next highest. Also, as a result of analyzing if there is a difference in perception according to the superiority and inferiority of bargaining power perceived by buyers, significant results were found in some path coefficients.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.621-629
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• 2019

In this study we attempted to screen bacteria and fungi that generate electricity while treating wastewater using optimized double-chamber microbial fuel cell (MFC) system parameters. Optimization was carried out for five best exoelectrogenic isolates (two bacteria and three fungi) at pH values of 6.0, 7.5, 8.5, and 9.5, and temperatures of 30, 35, 40, and 45℃; the generated power densities were measured using a digital multimeter (DT9205A). The isolates were identified using molecular characterization, followed by the phylogenetic analysis of isolates with known exoelectrogenic microorganisms. The bacterium, Proteus species, N6 (KX548358.1) and fungus, Candida parapsilosis, S10 (KX548360) produced the highest power densities of 1.59 and 1.55 W/m² (at a pH of 8.5 and temperatures of 35 and 40℃) within 24 h, respectively. Other fungi-Clavispora lusitaniae, S9 (KX548359.1) at 40℃, Clavispora lusitaniae, S14 (KX548361.1) at 35℃-and bacterium-Providencia species, N4 (KX548357.1) at 40℃-produced power densities of 1.51, 1.46, and 1.44 W/m², respectively within 24 h. The MFCs achieved higher power densities at a pH of 8.5, temperature of 40℃ within 24 h. The bacterial isolates have a close evolutionary relationship with other known exoelectrogenic microorganisms. These findings helped us determine the optimal pH, temperature, evolutionary relationship, and exoelectrogenic fungal species other than bacteria that enhance MFC performance.

• Geophysics and Geophysical Exploration
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• v.7 no.1
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• pp.62-69
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• 2004

The objective of this study is to estimate the distribution of a zone disturbed by excavation (EDZ) around tunnels that have been excavated at about 500 m depth in pre-Tertiary hard sedimentary rock. One of the most important tasks is to evaluate changes in the dynamic stability and permeability of the rock around the tunnels, by investigating the properties of the rock after the excavation. We performed resistivity and acoustic tomography using two boreholes, 5 m in length, drilled horizontally from the wall of a tunnel in pre-Tertiary hard conglomerate. By these methods, we detected a low-resistivity and low-velocity zone 1 m in thickness around the wall of the tunnel. The resulting profiles were verified by permeability and evaporation tests performed at the same boreholes. This anomalous zone matched a high-permeability zone caused by open fractures. Next, we performed resistivity monitoring along annular survey lines in a tunnel excavated in pre-Tertiary hard shale by a tunnel-boring machine (TBM). We detected anomalous zones in 2D resistivity profiles surrounding the tunnel. A low-resistivity zone 1 m in thickness was detected around the tunnel when one year had passed after the excavation. However, two years later, the resistivity around the tunnel had increased in a portion, about 30 cm in thickness, of this zone. To investigate this change, we studied the relationship between groundwater flow from the surroundings and evaporation from the wall around the tunnel. These features were verified by the relationship between the resistivity and porosity of rocks obtained by laboratory tests on core samples. Furthermore, the profiles matched well with highly permeable zones detected by permeability and evaporation tests at a horizontal borehole drilled near the survey line. We conclude that the anomalous zones in these profiles indicate the EDZ around the tunnel.