• Proceedings of the KIEE Conference
• /
• 2006.04b
• /
• pp.261-263
• /
• 2006

A new soft switched active snubber circuit is proposed to achieve zero voltage and zero current switching for all the switching devices in PWM DC-DC converters. The unique location of the snubber and inductor ensures low current/voltage stresses and commutation losses. With a saturable reactor, the conduction loss of auxiliary switch could be further minimized. A boost converter adopting this technique is presented as an example, to illuminate its operation principles and derive the design procedures. Simulation and hardware implementation have been made to validate its performance. Some other basic PWM DC-DC topologies using the proposed snubber have also been given.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1993.10a
• /
• pp.63-68
• /
• 1993

Soil nailing is a method of reinforcing natural deposits of soil with passive inclusions, called nails, of steel or other materials. Its purpose is mainly to increase the tensile and shear strength of the soil mass. This method has been widely used during the last two decades to stabilize steep slopes in several countries (France, Germany, USA, Japan, etc.). The design methods that have been mostly used are Davis method, German method, and French method which are based on limit equilibrium approaches, and Juran method which utilizes the kinematical limit equilibrium design concept. This paper is focussed on the evaluation of the available design methods(especially, the France, Davis and German design methods) through comparison with each different assumption for the failure surface, the concept of failure mechanism and the definition of safety factor. The parametric study to identify the effects of design parameters on the overall factor of safety has also been conducted. By considering the results along with the associated assumptions which have been postulated in the several methods, the applicability of the method for a given soil and nail conditions has been evaluated.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.103-108
• /
• 1999

This paper describes development of a new automated real-time system which preforms measurement data reduction and management, geotechnical backanalysis, and feedback design for embankment construction on soft ground. Such a system can be an effective, useful and economical tool for managing a large site development on soft ground. The system consists of data base system to characterize soil properties and identify instrumentation, analysis system for ground behavior and stability coupled with automatic monitoring system, and feedback design system which is a new technique to reflect the analysis of measured ground behavior against original design.

• Journal of Environmental Impact Assessment
• /
• v.14 no.6
• /
• pp.415-425
• /
• 2005

To examine the geochemical behavior and pollution of soils in Gwangju City, an analysis was carried out for pH, on the contents of metals, and organic carbon. Soil samples were taken from environs areas, industrial areas and downtown areas. The major factor controlling the behavior of metallic elements in the soil was chemical weathering of clay mineral in the environs areas, industrialization, and urbanization. Heavy metals including Cu, Pb and Zn were highly enriched for the samples from central part of downtown area. This indicated that the urbanization and the industrialization affected soil pollution. The results show that soil pollution in a metropolitan city which is caused by harmful heavy metals is severest in the center of the city. In consequence, it is inevitable that practical measures should be taken to prevent soil pollution expansion.

• Textile Coloration and Finishing
• /
• v.22 no.2
• /
• pp.123-131
• /
• 2010

Shape and size controlled synthesis of gold particles has been studied by using wet-chemical method. When ${AuCl_4}^-$ in aqueous $HAuCl_4$ precursor was reduced using $Na_2SO_3$ as a reducing agent, mixtures of spherical, triangular and hexagonal particles were prepared in a few minutes. It was found that the shape selective oxidative etching by ${AuCl_4}^-\;+\;Cl^-$ anions and crystal growth took place simultaneously. As the ${AuCl_4}^-$ and $Cl^-$ concentration increased, yields of large triangular and hexagonal plate type particles increased, while the spherical particles decreased in most cases. Possible etching and growth mechanisms are discussed.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.366-367
• /
• 2011

The DC distribution system iis a new promising topologies in a field of future smart distribution system. This system has high efficiency and reliability. So it is expected that there would be an increase in the installation of DC distribution systems. In this paper, the parameter of the DC/DC converter impact on customer's the power quailty in the DC distribution system when the fault occurred. For the analysis, DC network to be modeled using PSCAD/EMTDC. The fault is occurred at phase A in secondary side of MTR which is AC system. Then compared voltage and power at the customer side by varying the capacity of capcitor in the DC/DC converter.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 2004.05a
• /
• pp.19-22
• /
• 2004

한정된 자원과 환경보존에 대한 중요성으로 인해 회수물류에 대한 관심이 점차 증가하고 있다. 본 논문에서는 역 물류의 다양한 형태 중 부품을 재활용하는 재생산과 원자재의 재활용 프로세스가 포함된 역 물류 네트워크를 제안한다. 제안된 역 물류 네트워크에서 수명이 다한 제품은 제조업자에 의해 수거되어 분해 된다. 분해 된 부품들 중 재사용이 가능한 일부는 재생산 프로세스에 투입되고 나머지 부품들은 재활용 프로세스를 거쳐 원재료 공급업자에게 역으로 판매되거나 폐기된다. 재생산프로세스에서는 분해 후 가공된 부품과 공급업자로부터 구매한 새 부품을 조립하여 제품을 생산한다. 본 논문에서는 제시된 역 물류 네트워크상에서 수거, 저장, 분해, 폐기, 재 가공 프로세스 비용을 산출하여 역 물류의 총 비용을 최소화 하는 부품의 재 사용량 결정 모델을 제시한다. 마지막으로 수치실험을 통해 제안된 모델의 적합성과 실용성을 검증한다

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2003.05a
• /
• pp.19-22
• /
• 2003

경사의 사선방향으로 절단하여 봉제된 바이어 컷 직물로 제조된 의류는 일반 의류와 달리 우아한 외관을 타나낸다. 이 직물의 단점은 형태안정성이 나빠서 완전제품의 형태가 패턴의 형의 형태와 다른 모양을 나타내는 경우가 많으며, 특히 밑단 부분이 불균일하게 쳐지므로, 가지런히 절단하는 트리밍공정을 부가적으로 거치게 된다. 현재의 봉제 공정에서는 트리밍 단계를 모두 숙련공들의 수작업에 의존한 평면 커팅 방법으로 수행하기 때문에 작업자의 피로도에 따라 불량품이 양산되고 그에 따른 소비자들의 불만 요인도 높아지므로, 본 연구에서는 치수 조절 마네킹을 제조하여 실제 의복 착용 상태를 그대로 재현 한 후, 회전시키면서 스스로 회전하는 자동 커터에 의해서 공간상에서 트리밍 하는 3-D 입체 시스템을 개발하였다. 이 시스템에 의하여 제조된 의류는 트리밍 라인이 균일하고 매끄러우며, 안감이 밖으로 밀려나오는 경우가 없어 외관상 품위가 있는 외관을 나타내었다. 또한 수작업에 비하여 제조 속도가 훨씬 빠르므로 봉제 후공정에서의 의류 제조 시간을 획기적으로 단축하는 신속 생산 시스템의 요소로서 충분히 사용될 수 있는 가능성을 나타낸다.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2003.05a
• /
• pp.5-7
• /
• 2003

의류용 섬유제품의 쾌적성을 객관적으로 측정하려는 시도가 계속되고 있지만, 아직 소비자의 미묘한 차이를 검출하는 능력을 재현하기에는 거리가 있어 보인다. 객관적 측정법들은 재현성과 신뢰성 면에서 제각기 자신들의 우수한 성능을 자랑하지만, 검출능력의 민감성은 주관적 평가에 훨씬 못 미치고 있기 때문에 비현실적인 경우가 많다. 본 연구의 목적은 주관적 평가의 신뢰성을 높이고 통계적인 추론이 가능한 보다 진보된 형식의 주관적 평가법을 개발하고 의류용 직물의 촉감평가에 응용하는 것이다. 국내에서 생산되는 여름용 캐쥬얼 웨어를 대상으로 여러 형태의 주관적 평가법을 적용하여 그 촉감을 평가하였다. 평정척도법, 표준 비교법, 순위법, Thurstone일대 비교법, Quad 분석법 등을 순차적으로 적용하여 평가자 판단의 일관성 여부, 평가자간의 일치성 여부, 재현성 및 논리성 여부를 통계적으로 평가한 후 이를 통과한 평가자들을 대상으로 실험을 반복한 후, 직물 촉감과 관련된 물리적 속성들과의 관련성을 고찰하였다.

• Proceedings of the KIEE Conference
• /
• 2003.04a
• /
• pp.266-269
• /
• 2003

A sterilizer equipment by using electrical energy has merits that no process of chemical and no second environmental pollution. Also, the power conversion circuit for sterilizer equipment has merits that are reducing switching loss for soft switching topology by using zero current and zero voltage switching, and miniaturizing size of equipment. Thus, it is expected that the cost of sterilization process, when quality of the device is measured by power consumption, will be reduced. Therefore, the purpose of this research is to solve the sterilization problems of existing powder with plasma sterilization device, to find more economical and effective way, and to suggest more improved sterilizer.