• 전기학회논문지
• /
• 제62권8호
• /
• pp.1101-1107
• /
• 2013

A light emitting diodes(LED) lighting has been increasingly used due to its low power consumption, long life time, high efficiency, and environment friendly characteristics. Also various power converters has been applied to drive these LED lighting. Among many power converters, a LLC resonant converter could be applied for LED lighting because of its high efficiency and high power density. Furthermore, the function of power factor correction(PFC) might be added. In this paper, 1-stage asymmetrical LLC resonant converter is proposed. The proposed converter performs both input-current harmonics reduction and PFC using the discontinuous conduction mode(DCM). The proposed 1-stage LLC resonant converter approach has the lower voltage stress across switching devices and achieve the zero voltage switching(ZVS) in switching devices. To verify the performance of the proposed converter, simulation and experimental results from a 300[W] prototype are provided.

• 동력기계공학회지
• /
• 제5권4호
• /
• pp.67-73
• /
• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of two-stage shot peening iud single-stage shot peening for two kinds of spring steel(SUP7, SAE9254). This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from decreasing the surface roughness unchanging the surface hardness increasing the compressive residual stress. Results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• 한국작물학회지
• /
• 제51권4호
• /
• pp.310-317
• /
• 2006

This study was conducted to investigate the influence of drought stress during the pod developing and seed filling stage on source-sink relationships of soybean (Glycine max). Drought treatments were imposed by withholding water at the full-pod stage, 19 days after flowering, and then limited watering was relieved at 15 days after the initiation of drought treatment. Soybean seed yield was reduced by 39% mainly due to decreased pod number under drought stress, but the 100-seed weight was relatively less reduced. In spite of the 15-day drought during the full-pod stage, soybean produced good seeds showing similar l00-seed weight, protein, starch and soluble sugar content to those from the well-watered. Although drought during the full-pod stage caused source limitations; i.e. accelerated leaf senescence and reduced leaf soluble sugars, it did not cause limitations of other source characteristics such as SGR and leaf starch level. This is because the reduction in size of sinks, such as pod and seed abortions compensated for source limitations, resulting in balanced source-sink as expressed by LAR and the ratio of leaf area to seed dry weight. Drought stress during the pod developing and seed filling stage did not disrupt the source-sink balance

• 대한간호학회지
• /
• 제33권5호
• /
• pp.538-543
• /
• 2003

Purpose: The purpose of this study was to identify the stress and the coping methodes in the cancer patients and their caregivers. Method: The stress method was measured by V AS(Visual Analogue Scale). The coping methodes was measured using the modified Ways of Coping Questionnaire. The phases of patient illness consisted of Ist(initial) stage, and 2nd(recurred) stage and 3rd(terminal) stage based on Lewandowski & Jones(1988) method. The data were collected by a survey of convenience sampling of 257 cancer patients and 196 of their caregivers from two hospitals in Seoul. The data were analyzed using paired t-test, unpaired t-test. Result: The stress level of cancer patients was lower than their caregivers. The cancer patients used emotion-focused coping mode than problem-focused coping mode. The caregivers problem-focused coping mode over emotion-focused coping mode. In the problem-focused coping mode, the caregivers significantly used two coping strategies that were ‘positve cope’, ‘information seeking’ more than patients. In emotion-focused coping mode, the caregivers significantly used one coping strategies that was ‘wish’ more than patients. The patients tended to used two coping strategies that were ‘blame’ and ‘emotion expression’ more than the caregivers. Conclusion: Further study needs to be done to positively identify these coping methods and develop interventions to assist patients and their caregivers.

• 한국작물학회지
• /
• 제49권4호
• /
• pp.289-294
• /
• 2004

This study was carried out to investigate the antioxidative enzymes and isozymes between chilling-tolerant and -susceptible varieties at the booting stage under cold water stress $(13^{\circ}C)$ in japonica rice. Total SOD, CAT, POX, and GR activities on the basis of protein were found to be important factors to defend cold water stress. Especially, SOD and CAT activities showed distinctive differences between chilling-tolerant and -susceptible varieties. Chilling-tolerant varieties were higher than chilling-susceptible varieties for SOD and CAT activities. One of eight isozyme bands for SOD was a inducible isoform. Three isozymes for CAT and one isozyme for POX were closely correlated with defense to cold water stress. Total GR activities except Stejaree 45 on the basis fresh weight and POX were increased by cold water stress, but there was no difference between chilling-tolerant and -sus­ceptible varieties.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2002년도 춘계학술대회 논문집
• /
• pp.348-352
• /
• 2002

a basis such as IT(Information Technology), NT(Nano Technology) and BT(Bio Technology). Recently, NT is applied to various fields that are composed of science, industry, media and semiconductor-micro technology. It has need of IT that is ultra-precision positioning technology with strokes of many hundreds mm and maintenance of nm precision in fields of ultra micro process, ultra precision measurement, photo communication part and photo magnetic memory. This thesis represents optimal design on ultra-precision positioning with single plane X-Y stage and development of artificial control system for adequacy of industrial demand. Also, dynamic simulation on global stage is performed by using ADAMS (Automated Dynamic Analysis of Mechanical System) for the purpose of grasping dynamic characteristic on user designed X-Y global stage. The error between displacements from micro stage and from FEM(Finite Element Method) is 3.53% by verifications of stability on micro stage and control performance. As maximum Von-mises stress on hinge of micro stage is 5.981kg/mm$^2$ that is 1.5% of yield stress, stability on hinge is secured. Preparing previous results, optimal design of micro stage can be possible, and reliance of results with FEM can be secured.

• 한국융합학회논문지
• /
• 제11권3호
• /
• pp.301-310
• /
• 2020

본 연구는 스트레스가 자살생각에 미치는 영향과 우울의 매개효과를 확인하기 위해 시도된 융합연구이다. 연구 대상은 G시 65세 이상 노인 166명, 연구기간은 2018년 8월 29일부터 9월 9일까지 진행하였다. 자료분석은 빈도와 백분율, t-test, ANOVA, Scheffe test, Pearson correlation coefficient, multiple regression 및 Sobel test로 분석하였다. 연구결과, 1단계에서 스트레스가 우울에 유의한 영향을 주었고 (β=0.533, p<.001), 2단계에서는 스트레스가 자살생각에 유의한 영향을 주었으며(β=0.497, p<.001), 3단계에서는 스트레스(β=0.389, p<.001)와 매개변수 우울(β=0.203, p=.011)이 유의한 예측 요인이었다. 변수의 설명력은 스트레스만 있는 경우 24.3%였고, 스트레스에 우울 동반 시 26.8%로 나타나, 스트레스가 자살생각에 미치는 영향에서 우울이 부분매개효과가 있는 것으로 확인되었다(p=.014). 본 연구결과를 토대로 노인의 자살생각 감소를 위한 기초자료로 활용될 수 있을 것으로 사료되며, 추후 자살 예방 프로그램 개발을 위한 후속 연구가 요구된다.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2008년도 하계학술대회 논문집
• /
• pp.535-537
• /
• 2008

This paper proposes a modularized two-stage charge equalization converter for a series-connected lithium-ion battery string. In this paper, the series-connected battery sting is modularized into M modules, and each module has K cells in series. With this modularization, low voltage stress on the electronic devices can be achieved. A two-stage dc-dc converter with cell selection switches is employed. The first stage dc-dc converter steps down the high bus voltage to about 10 V. The second stage dc-dc converter integrated with selection switches equalizes the cell voltages. A prototype for 88 lithium-ion battery cells is optimally designed and implemented. Experimental results verify that the proposed equalization method has good cell balancing performance showing low voltage stress, small size, and low cost.

• Journal of Advanced Marine Engineering and Technology
• /
• 제22권1호
• /
• pp.42-51
• /
• 1998

A 150 m$\^$3//hr, 30 kg/cm$\^$2/, air-cooled 3-stage reciprocating air compressor is designed to be used in starting large diesel engines of ships. A basic design procedure is presented to meet the targeted pressure and flow rate, and especially a volumetric efficiency of 80%. Temperature and stress analysis of the 1st stage cylinder are performed using axisymmetric FEM modelings. The dynamics of valve system is analyzed and stress at the 1st stage valve seat caused by valve impact is evaluated. To reduce friction loss and wear at the compressor engine system tribological design issues are reviewed and good design practices are suggested. Finally, forced-air pin-type interstage coolers are designed to dissipate generated compression heat at each stage.

• 한국작물학회지
• /
• 제28권4호
• /
• pp.451-457
• /
• 1983

영업생장말기, 수잉기, 출수개화기, 그리고 등숙초기의 네가지 주요한 생육기에 처리한 수분부족이 상위 3엽의 엽록소, 단백질유리 Proline과 상대팽압도의 변화와 몇가지 수량구성요소에 미치는 영향을 구명하기 위하여 과맥품종인 백동을 공시 수행하여 얻어진 결과를 요약하면 다음과 같다. 1. 수분부족처리에서 엽위별로 보면 지엽하위 1엽이 가장 높은 상대팽압도를 유지하여 엽록소와 단백질이 함량이 많았고, 유리Proline의 축적은 가장 적었다. 또한 생육기별로 보면 엽록소는 출수개화기에, 단백질은 수일기의 처리에서 가장 높았으며, 유리Proline은 수잉기의 처리에서 그 축적이 가장 낮았다. 2. 간장, 수장, 수당입수는 수잉기의 수분부족처리에서 감소영향이 가장 컸으며 천립중은 등숙초기에서, 그리고 종실의 크기는 수잉기와 그 이후 처리에서 가장 많이 감소되었다. 3. 종실의 단백질함량은 수분부족에 의해서 유의한 변화를 나타내지 않았으나 등숙초기에서 약간 감소한 경향이었다. 4. 불임율은 또한 수잉기와 출수개화기의 수분부족에서 심한 증가현상을 나타냈다. 5. 전반적으로 볼 때 생육단계별로는 수잉기에서, 그리고 엽위별로는 지엽 > 지엽하위 1엽 > 지엽하위 2엽의 순으로 수분부족의 영향이 컸다.