• 조명전기설비학회논문지
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• 제23권1호
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• pp.141-149
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• 2009

본 논문에서는 준정적 FDTD 기법을 FORTRAN 프로그래밍을 통해 직접 구현하고 이를 이용해 중간주파수 대역의 인체유도전류 분포를 해석하였다. 제작된 프로그램의 타당성을 검증하기 위하여 기존 FDTD 기법을 적용하기 어려운 테스트 모델에 대한 계산결과를 이론적 해와 비교하고, 타임스텝이 크게($5.68{\times}10^6$배) 단축되는 것을 확인하였다. 검증된 수치해석 기법을 이용하여 20[kHz] 자기장과 1[MHz] 전기장에 노출된 3차원 고해상도 인체모델에 유기되는 유도전류의 분포를 계산하고, 양 발의 접지조건이 유도전류의 분포와 크기에 미치는 영향을 분석하였다. 본 연구는 인체유도전류의 안전성 평가, 생체전기 응용 진단장치 개발 등을 포함한 다양한 분야에서 활용될 것으로 기대된다.

• Composites Research
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• 제14권5호
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• pp.1-11
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• 2001

본 논문은 금속복합재료를 반용융상태로 재가열하여 Thixoforming을 하는데 필요한 소재를 제공하기 위한 장비 설계와 제조방법 등에 관한 내용을 소개하고 있다. 장비 설계에서 기지재내에 강화재가 균일하게 분산되도록 하기 위하여 강화재의 연속주입 방법과 강화재의 온도를 제어하는 방법을 소개하고 있다. 일정한 양의 강화재를 기지재료 내에 분산시키는 것은 균일 혼합을 위하여 필요한 기술이다. 또한 분산시 강화재의 수분제거를 위하여 강화재의 온도를 제어하면서 연속적으로 강제분산시키는 것은 균일분산을 위하여 필요하다. 기지재의 초정 $\alpha$의 크기가 강화재의 분산성에 크게 영향을 미치기 때문에 기지재의 초기 온도가 초정$\alpha$의 크기에 미치는 영향 등을 검토하여 복합재료 빌렛트의 제조조건에 이용하였다.

• 한국수소및신에너지학회논문집
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• 제23권1호
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• pp.100-109
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• 2012

In this paper, some ideas are proposed to establish the infrastructure of all-electric houses which are able to reduce primary energy consumption and $CO_2$ emission by adopting heat pump systems and induction heating cookers excluding the use of fossil fuel energy. This electrification concept is based on the consumption of only one type of energy which means electricity as secondary energy and the conventional fossil fuel energy is just consumed to generate electricity as primary energy. All-electric house is laid on the extension of the hydrogen economy in a long-term viewpoint so that the effectiveness of this new conceptual house is estimated analyzing the reduction of $CO_2$ emission. In this analysis, the balance of electricity supply and demand is considered including the construction of new power plants by renewable energy such as nuclear, IGCC and fuel cell because decarbonization is an essential element of hydrogen technology and economy and this action is accomplished in both supply and demand side of electricity. The results are able to contribute to develop various useful hydrogen policies and strategies and some detail researches are required previously to make the best application of this new conceptual house.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제28권4호
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• pp.264-273
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• 2002

Pulsed electromagnetic field (PEMF) was used first to induce osteogenesis in 1974. The appliance which was consisted of the Helmholtz coil configuration have used to osteogensis. The objective of this study was to determine whether PEMF, a frequency of 100 Hz and magnetic field strength of 38 gauss applied to the calvarial defect in rabbit, could affect the induction of osteogenesis and the healing of the graft bone. This field should not produce excitation of nerve or muscle and heating the tissue. To evaluate the effect of PEMF on osteogenesis, 16 rabbit under the same condition was divided into 8 experimental groups and 8 control groups. 10 mm calvarial bone defects were formed around sagittal suture. The defect of left side was left without graft while the defect of right side was grafted by bone harvested from left side. A pulsed electromagnetic field was applied for 8 hours per day. Each group was sacrificed after 1 week, 2 weeks, 4 weeks, 8 weeks. Microscopic specimens were obtained from the calvarial bone defects and surrounding tissue using Hematoxylin-Eosin staining method. The results were as follows. 1. In the group which pulsed electromagnetic field was applied, new bone formation filled up the defect was observed after 4 and 8 weeks effectively. 2. There are no difference in the healing period for the fusion between the bone and graft bone. According to the result, the PEMF with 38 Gauss, 100 Hz was very effective in the healing of bone defect and new bone formation. So The PEMF will be useful in clinical aspect for oseteogenesis.

• 소성∙가공
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• 제6권3호
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• pp.239-249
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• 1997

The behaviour of alloys in the semi-solid state strongly depends on the imposed stress state and on the morphology of the phase which can vary from dendritic to globular. To optimal net shape forging of semi-solid materials, it is important to investigate for filling phenomena in forging process of arbitrarily shaped dies. To produce a automotive part which has good mechanical property, the filling pattern according to die velocity and solid fraction distribution has to be estimated for arbitrarily shaped dies. Therefore, the estimation of filling characteristic in the forging simulation with arbitrarily shaped dies of semi-solid materials are calculated by finite element method with proposed algorithm. The proposed theoretical model and a various boundary conditions for arbitrarily shaped dies is investigated with the coupling calculation between the liquid phase flow and the solid phase deformation. The simulation process with arbitrarily shaped dies is performed to the isothermal conditions of two dimensional problems. To analysis of forging process by using semi-solid materials, a new stress-strain relationship is described, and forging analysis is performed by viscoelastic model for the solid phase and the Darcy's law for the liquid flow. The calculated results for forging force and filling limitations will be compared to experimental data. The filling simulation of simple products performed with the uniform billet temperature(584$^{\circ}C$) from the induction heating by the commercial package MAGMAsoft. The initial step of computation is the touching of semi-solid material with the end of die gate and the initial concept of proposed system just fit with the capability of MAGMAsoft.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.84-92
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• 2010

현재 가동 중인 몇몇 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부는 일차수응력부식균열(PWSCC : Primary Stress Corrosion Cracking) 발생의 세가지 조건(민감 재질, 부식 환경, 인장응력)을 동시에 충족하고 있다. 즉, 이종금속 용접부는 PWSCC에 민감한 재질인 Alloy 600 계열 합금으로 제작 또는 용접되어 있으며 고온 수화학 부식 환경 하에 놓여있다. 아울러 오스테나이트 스테인리스 강의 예민화 예방을 위한 용접 후열처리 미실시로 높은 인장 용접 잔류응력이 작용하고 있다. 이러한 이종금속 용접부의 특성상 PWSCC가 발생할 잠재성이 있을 뿐만 아니라 국내외적으로 Alloy 600 계열 합금으로 제작 및 용접된 가압 경수로 원전 안전 1등급 설비의 이종금속 용접부에 실제 PWSCC가 발생된 사례들이 다수 보고되고 있다. 운전 환경 및 재질 변화 없이 PWSCC 발생을 예방하기 위해서는 인장 잔류응력을 이완시켜 낮은 인장 또는 압축 응력화하여야 한다. 이러한 인장 잔류응력 이완방법들로는 PWOL(Pre-emptive Weld Overlay), 레이저 피닝(Laser Peening), MSIP(Mechanical Stress Improvement Process), 워터 제트 피닝(Water Jet Peening), IHSI(Induction Heating Stress Improvement) 방법들이 있는데 공정 시간이 짧고 열 에너지 원이 필요 없으며 전체적인 소성 변형을 야기시키지 않는 레이저 피닝을 본 연구의 대상 방법으로 한다. 본 연구에서는 동적 유한요소 해석을 통해 용접 잔류응력을 이완시키는 레이저 피닝의 효과를 검증하고 용접 잔류응력에 미치는 레이저 피닝 변수의 영향을 고찰하고자 한다. 내부 보수용접이 수행된 경수로 원전 가압기 노즐 이종금속 용접부에 레이저 피닝을 적용한 경우에 대해 상용 유한요소 해석 프로그램인 ABAQUS를 이용하여 동적 유한요소해석을 수행한 결과, 고온 수화학 일차수와 접하는 Alloy 600 계열 합금 내면에서의 인장 잔류응력이 상당히 이완됨을 확인하였다. 또한, 최대충격 압력이 증가할수록, 충격압력 지속시간이 증가할수록, 레이저 스팟 직경이 증가할수록 내표면 인장 잔류응력 이완 정도는 감소하나 이완되는 영역의 깊이는 증가함을 알 수 있다. 또한, 레이저 피닝 방향이 잔류응력 이완에 미치는 영향은 미미함을 알 수 있다.

• 대한간호학회지
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• 제37권7호
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• pp.1061-1072
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• 2007

Purpose: The purpose of this study was to compare the effects of intravenous fluid warming and skin surface warming on peri-operative body temperature and acid base balance of abdominal surgical patients under general anesthesia. Method: Data collection was performed from January 4th, to May 31, 2004. The intravenous fluid warming(IFW) group(30 elderly patients) was warmed through an IV line by an Animec set to $37^{\circ}C$. The skin surface warming(SSW) group(30 elderly patients) was warmed by a circulating-water blanket set to $38^{\circ}C$ under the back and a 60W heating lamp 40 cm above the chest. The warming continued from induction of general anesthesia to two hours after completion of surgery. Collected data was analyzed using Repeated Measures ANOVA, and Bonferroni methods. Results: SSW was more effective than IFW in preventing hypothermia(p= .043), preventing a decrease of $HCO_3{^-}$(p= .000) and preventing base excess(p= .000) respectively. However, there was no difference in pH between the SSW and IFW(p= .401) groups. Conclusion: We conclude that skin surface warming is more effective in preventing hypothermia, and $HCO_3{^-}$ and base excess during general anesthesia, and returning to normal body temperature after surgery than intravenous fluid warming; however, skin surface warming wasn't able to sustain a normal body temperature in elderly patients undergoing abdominal surgery under general anesthesia.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.203-205
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• 2006

This paper presents a novel soft-switching PWM utility frequency AC to high frequency AC power conversion circuit incorporating boost-half-bridge inverter topology, which is more suitable and acceptable for cost effective consumer induction heating applications. The operating principle and the operation modes are presented using the switching mode and the operating voltage and current waveforms. The performances of this high-frequency inverter using the latest IGBTs are illustrated, which includes high frequency power regulation and actual efficiency characteristics based on zero voltage soft switching (ZVS) operation ranges and the power dissipation as compared with those of the previously developed high-frequency inverter. In addition, a dual mode control scheme of this high frequency inverter based on asymmetrical pulse width modulation (PWM) and pulse density modulation (PDM) control scheme is discussed in this paper in order to extend the soft switching operation ranges and to improve the power conversion efficiency at the low power settings. The power converter practical effectiveness is substantially proved based on experimental results from practical design example.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.18-19
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• 2005

EDDC(Evaporation using Drum in Dual Chamber) deposition system was manufactured for 100m long superconducting coated conductor. It is composed of reaction chamber, evaporation chamber and differential chamber. The drum is located across the differential and exposed to both of the evaporation chamber and the reaction chamber, and the tape is wound on the drum. The elements of superconducting material are co-evaporated from respective element boats in the evaporation chamber and deposited on the drum and reacted with oxygen in the reaction chamber. This process repeats by rotating the drum. When the total pressure of the reaction chamber was 5 mTorr, that of the evaporation chamber was $5{\sim}10^{-5}$Torr. This atmosphere can be achieved by means of differential pumping. There are four evaporator in the evaporation chamber. One is the radiation heating evaporator and the others are the high frequency induction evaporator. EDDC is one of promising methods for commercialization of superconducting coated conductor.

• Archives of Pharmacal Research
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• 제21권1호
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• pp.46-53
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• 1998

When NIH3T3 cells were exposed to mild heat and recovered at $37^{\circ}C$ for various time intervals, they were thermotolerant and resistant to subsequent stresses including heat, oxidative stresses, and antitumor drug methotrexate which are apoptotic inducers. The induction kinetics of apoptosis by stresses were determined by DNA fragmentation and protein synthesis using $[35^S]$methionine pulse labeling. We investigated the hypothesis that thermotolerant cells were resistant to apoptotic cell death compared to control cells when both cells were exposed to various stresses inducing apoptosis. The cellular changes in thermotolerant cells were examined to determine which components are involved in this resistance. At first, the degree of resistance correlates with the extent of heat shock protein synthesis which were varied depending on the heating times at $45^{\circ}C$ and recovery times at $37^{\circ}C$after heat shock. Secondly, membrane permeability change was observed in thermotolerant cells. When cells prelabeled with $[^{3}H]$thymidine were exposed to various amounts of heat and recovered at $37^{\circ}C$ for 1/2 to 24 h, the permeability of cytosolic $[^{3}H]$thymidine in thermotolerant cells was 4 fold higher than that in control cells. Thirdly, the protein synthesis rates in thermotolerant and control cells were measured after exposing the cells to the same extent of stress. It turned out that thermotolerant cells were less damaged to same amount of stress than control cells, although the recovery rates are very similar to each other. These results demonstrate that an increase of heat shock proteins and membrane changes in thermotolerant cells may protect the cells from the stresses and increase the resistance to apoptotic cell death, even though the exact mechanism should be further studied.