• Wind and Structures
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• 제20권6호
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• pp.793-810
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• 2015

Tests were conducted at the Florida International University (FIU) Wall of Wind (WOW) to investigate the susceptibility of Variable Message Signs (VMS) to wind induced vibrations due to vortex shedding and galloping instability. Large scale VMS models were tested in turbulence representative of the high frequency end of the spectrum in a simulated suburban atmospheric boundary layer. Data was measured for the $0^{\circ}$ and $45^{\circ}$ horizontal wind approach directions and vertical attack angles ranging from $-4.5^{\circ}$ to $+4.5^{\circ}$. Analysis of the power spectrum of the fluctuating lift indicated that vertical vortex oscillations could be significant for VMS with a large depth ratio attached to a structure with a low natural frequency. Analysis of the galloping test data indicated that VMS with large depth ratios, greater than about 0.5, and low natural frequency could also be subject to galloping instability.

• KSBB Journal
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• 제5권4호
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• pp.403-410
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• 1990

Application of the Rheocatch Hotwire Monitoring System for food biotechnology process was evaluated. The growth of microogranism, E coli (JM 83 and Sigma) and Corynesccfertun glutamicum, were monitored. in the fermentor. The cell growth could not be detected the temperature differences between the hotwire and samples($\Delta$T) as indicated by the monitoring system during the fermentation processes. The cell concentration of less than 2g/dl was not sufficient to generate the measurable temperature difference in the fermentor. In order to calibrate the Rheocatch Monitoring System, the temperature difference as a function of solute concentration (microbial cells, sodium cholide, sucrose and dextran) was studied. The relationship between $\Delta$T and the concentration of microbial cells, sucrose and dextran can be expressed in a power series. Further studied with dextran indicated that viscosity and/or kinematic viscosity increase exponentially with an increase in $\Delta$T This is regardless of the concentration and molecular weight of dextran. $\Delta$T linearly increases with the logarithm of molecular weight, while the logarithm of viscosity and the logarithm of kinematic viscosity increase with the logarithm of molecular weight.

• 한국축산식품학회지
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• 제26권2호
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• pp.223-228
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• 2006

This study was carried out to investigate the effects of ohmic power intensity on the physico-chemical properties of hamburger patties. Six different ohmic power intensities (0, 10, 20, 30, 40, and 50V) were delivered by controlling the power with the sine wave at 50Hz. The ohmic power intensity influenced the thawing rate, and increasing ohmic power intensity increased the thawing rate. The faster thawing rate was obtained at higher ohmic power intensity (50V) with 0.5% NaCl added meat patties in comparison to no NaCl added hamburger patties. The pH values of all patties were not significantly different with increasing ohmic power intensity (p<0.05). Increasing thawing rate did not tend to improve the water holding capacity (WHC) of all patties by ohmic thawing. Cooking losses were almost the same regardless of increasing ohmic power intensity. Increasing ohmic power intensity tended to increase the thiobarbituric acid reactive substance (TBARS) levels. TBARS levels of all hamburger patties without NaCl were significantly higher than that of 0.5% NaCl added hamburger patties (p<0.05) at higher ohmic intensity (50V). In conclusion, these results indicated that a higher ohmic power intensity at 50 V induced the lipid oxidation of all patties.

• 전기학회논문지
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• 제63권10호
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• pp.1328-1336
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• 2014

This paper proposes Power System Health Index(PSHI) newly. The paper describes several kind of power system health indices based on two main categories, which are adequacy and security. In adequacy, four kinds of health indices of Frequency, Voltage, Reserve(Operating Reserve Power and Frequency Regulation Reserve Power) and Overload of lines and transformers are proposed. In security, four kinds of health indices of Voltage(154kV, 345kV and 765kV), Overload of lines and transformers, Power flow constraint among areas and SPS are proposed. All indices are mapped with three domains, which are indicated as Health, Margin and Risk, defined with expert interview. While domains of health, margin and risk is defined similar with the conventional well being analysis of power system. The criterion of the domains is proposed using an interview with expert operators and practical reliability codes in Korea. The several kinds of health index functions, which are linear ratio, piecewise linear ration and reverse ratio function etc. are developed in this paper. It will be expected that the developed health indices can help operators to control power system more successfully and also prevent power system from accident as like as black out in future because operator can make a decision immediately based on more easily visual information of system conditions from too much indices acquisition of complex power system.

• Journal of Animal Science and Technology
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• 제55권2호
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• pp.103-107
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• 2013

A crucial first step in the planning of any scientific experiment is to evaluate an appropriate sample size to permit sufficient statistical power to detect the desired effect. In this study, we investigated the optimal sample size of quantitative trait locus (QTL) linkage analysis for simple random sibship samples in pedigreed chicken populations, under the variance component framework implemented in the genetic power calculator program. Using the program, we could compute the statistical power required to achieve given sample sizes in variance component linkage analysis in random sibship data. For simplicity, an additive model was taken into account. Power calculations were performed to relate sample size to heritability attributable to a QTL. Under the various assumptions, comparative power curves indicated that the power to detect QTL with the variance component method is highly affected by a function of the effect size of QTL. Hence, more power can be achievable for QTL with a larger effect. In addition, a marked improvement in power could be obtained by increasing the sibship size. Thus, the use of chickens is advantageous regarding the sampling unit issue, since desirable sibship size can be easily obtained compared with other domestic species.

• 한국전기전자재료학회논문지
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• 제16권12호
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• pp.1142-1149
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• 2003

The strength and characteristics of the soldering interface of the power semiconductor chip in a power module has been firstly surveyed by the peel strength measurement method. A power module is combined with several power chips which generally has 30∼400$\textrm{mm}^2$ chip area to allow several tens or bigger amps in current rating, so that the traditional methods for interface characterization like shear test could not be applied to high power module. In this study power diode modules were fabricated by using lead-tin solder with 10${\times}$10$\textrm{mm}^2$ or 7${\times}$7$\textrm{mm}^2$ soldering interface. The peel strengths of soldered interfaces were measured and then the microscopic investigation on the fractured surfaces were followed. The peel test indicated that the crack propagated either through the bulk of the soft lead-tin solder which has 55-60 kgf/cm peel strength or along the interface between the solder and the plated nickel layer which has much lower 22 kgf/cm strength. This study showed that the peel test would be a useful method to quantify the solderability as well as to recognize which is the worst interface or the softest material in a power module with a large soldering area.

• 대한토목학회논문집
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• 제43권1호
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• pp.33-41
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• 2023

최근 지구온난화로 인해 기후변화가 가속화되고, 극한 기상현상으로 인한 기상재해의 발생빈도와 강도 또한 증가하여, 날씨에 민감한 신재생에너지의 전력 생산에 대한 불확실성이 커지고 있다. 실제로 댐을 이용하는 수력발전소에서도 최근 기상재해로 인한 수력발전 피해가 다수 보고되고 있다. 본 연구에서는 충주댐 수력발전 실적 자료와 충주 기상관측소, 충주댐의 운영 자료를 바탕으로 기상재해의 월별 발생 횟수와 강도를 산정하여 구조방정식모형을 통해 가뭄과 홍수가 수력발전을 통한 전력 생산에 미치는 영향을 파악하였다. 이를 위해서는 충주댐 수력발전소 발전 실적 자료를 수집하고, 기상재해 관련 자료를 수집하였으며, 구조방정식모형을 통해 수력발전에 대한 기상재해의 영향을 분석하였다. 그 결과 가뭄 발생의 증가는 수력발전을 통한 전력 생산의 감소에 38.3 %의 영향이 있지만, 홍수 발생의 증가는 수력발전을 통한 전력 생산의 증가를 설명할 수 없었다. 미래에 가뭄 발생이 증가한다면 수력발전을 통한 전력 생산에 대한 영향 또한 커질 것이다.

• 복식
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• 제58권1호
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• pp.90-103
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• 2008

This study aims to examine the current state of wearing working clothes for the workers who work in Electric Technology Division, Korea Railroad Corporation, to identify inconveniences and problems in relation to the working clothes, and based on the examination, to find a way to improve them, creating a design of summer working clothes that will have more advanced functionalities including activity adaptability and comfort. Survey was conducted through direct observation and interview for Electric Railway Power Team. A total of 352 copies were collected and analyzed. Based on the results of questionnaire, an experimental clothes, the functionality of which has improved in terms of design, material, and patterns, was created. The followings are the results of the study. Easy activity, design, and comfort are required as functions of working clothes. In design related questions, the survey shows high dissatisfaction in the color of existing working clothes, and preferred colors are dark blue and gray. With regard to the method of zipping up the front side, zippers are preferred. Although many pockets on the existing working clothes have high satisfaction, dissatisfaction to pocket format is high. In material related questions, lower dissatisfaction is indicated for the sense of touch, ventilation and sweat absorption. It is shown that the areas frequently polluted include the lower part of pocket, the edges of sleeves and elbow areas on the jacket. The frequently polluted area of the trousers include knee areas, the edges of pants and buttocks. With regard to the areas where the workers felt discomfort when motion, discomfort is highly indicated with armpits and back on the jacket. Also discomfort is highly indicated with crotch, buttocks and knee areas on the trousers. In material related questions, lower dissatisfaction is indicated for the sense of touch, ventilation, sweat absorption.

• Human Ecology Research
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• 제53권4호
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• pp.391-404
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• 2015

This study examined job satisfaction and relevant variables for multi-cultural family home-visiting educators. The selected study subjects were 192 home-visiting educators who work at Multi-Cultural Family Support Centers in the Seoul, Gyeonggi-do, and Chungcheongnam-do areas. Data analysis was conducted using SPSS ver. 18.0. The main results were as follows. First, the job satisfaction level in multi-cultural family visiting educators stood at 3.29 points, subjects' age, averagely monthly income, marital status, and activity career were shown to influence generally upon job satisfaction, self-efficacy, job stress, and cultural competency. Job satisfaction was high in groups with: a high age, small career, low averagely monthly income, and married. Second, self-efficacy and job stress were big in the job satisfaction of multi-cultural family visiting educators. The same outcome as the existing prior research was indicated. Cultural competency was not significant. Third, an examination of relative influence upon job satisfaction in home visiting educators indicated that the explanation power was 29.0%. Significant influential variables included academic background, marital status, self-regulation, and role ambiguity. Self-regulation was greater for those with lower academic backgrounds and unmarried. Job satisfaction was higher in the lower role ambiguity. Thus, the same outcome as the existing prior research was indicated. Cultural competency wasn't indicated to be significant. This has significance in having shown characteristics of job satisfaction in multi-cultural family visiting educators.

• 동력기계공학회지
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• 제16권3호
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• pp.10-15
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• 2012

Recently we have a growing interest in environmental pollution and alternative energy. Diesel engine is generally used to produce the power on the ground and the sea. However, the combustion characteristics are changed on account of the wear of fuel system and the altered ambient condition of the combustion chamber by the increment of the engine operation hour. Therefore combustion characteristics on fuel injection timing are experimentally investigated to find out the optimum fuel injection timing in the case of the aged diesel engine using biodiesel blend oil. Cylinder pressure, rate of pressure rise, rate of heat release and combustion gas temperature are risen by the advancing fuel injection timing, while the exhaust gas temperature and soot emission level are decreased by the advancing of fuel injection timing. The least specific fuel oil consumption is indicated at BTDC $26^{\circ}$ CA on the 75%load and at 1800rpm.