• Journal of Biosystems Engineering
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• 제24권1호
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• pp.31-40
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• 1999

The objective of this study were to develop a cooling simulation model for fixed-bed of rough rice and to analyze the factors affecting cooling time of rough rice. A computer simulation model based on equilibrium conditions between grain and air was developed to predict temperature and moisture content changes during cooling of rough rice. the result of t-test showed that there were no significant differences between predicted and measured temperature changes on significance model agreed well with measured values. This cooling simulation model was applied to analyze the effect of some factors, such as air flow rate, cooling air temperature and humidity, initial grain temperature and moisture content, and bed depth, on cooling time of rough rice. Cooling rate increased with increase of air flow rate and bed depth whereas it decreased with increase of cooling air temperature and humidity and initial grain temperature. Among these factors, the most important factor was air flow rate. Specific air flow rate of 0.35㎥/min㎥ was required for cooling rough rice in 24 hours.

• 대한기계학회논문집B
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• 제28권4호
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• pp.449-455
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• 2004

The objective of this study is to obtain the correlation between the spray characteristics and the etching characteristics for the optimization of etching system in the micro fabrication industry. The etching characteristics such as etching rate were measured under different conditions. The single spray characteristics such as droplet size and velocity were measured by PDA system. These were compared to the etching characteristics. The twin spray characteristics in the overlap region were analyzed to predict the effect of them on the etching characteristics with the pitch and also were compared to the single spray. The etching rate was increased in case of high spray pressure and in the region of spray center. It was found that the etching characteristics could be correlated with the single spray characteristics and the twin spray characteristics were correlated with the etching characteristics.

• 동력기계공학회지
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• 제4권1호
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• pp.20-25
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• 2000

In this study, methods for the characteristics measurement of pneumatic elements using isothermal chamber, the methods for the flow rate and dynamic characteristic measurement of pneumatic control valve, are proposed. An isothermal chamber is a chamber in which the steel wool is stuffed and isothermal condition can almost be realized. Therefore, the instantaneous flow rate could be measured only from the pressure response using the state equation of gas. Effectiveness and simplicity of the proposed method are confirmed by comparing the measured results obtained by proposed methods with the methods defined JIS and the ISO standards.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.602-608
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• 2016

Because of the random characteristics of lightning, the Monte Carlo method is applied to estimate the flashover rate due to lightning, however, the simulations using previous methods are difficult to both beginner and expert in power corporations. Therefore, this paper proposes the new and easy method to simulate the flashover rate by connection of electromagnetic transients program (EMTP) and MATLAB. The magnitude of a lightning strike is based on a curve measured in the field, while the classification of direct and indirect lightning depends on the striking distance. In a Korean distribution system, the flashover rate induced by lightning is simulated using proposed method. Simulations of the footing resistance according to the existence of an overhead ground wire (OHGW) are performed and the simulation results are discussed. The simulation results are compared with findings obtained with the IEEE Flash 2.0 program.

• 한국항공우주학회지
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• 제47권2호
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• pp.161-168
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• 2019

본 논문에서는 소형 무인기 데이터 링크 시스템에 적용이 가능한 전송률 가변 비대칭 TDD(Time Division Duplex) 방식에 대해 다루었다. 긴 복호 시간이 필요한 터보 복호기를 비대칭 TDD 방식에 적용하기 위하여 이중 버퍼 제어기 구조의 터보 복호기를 제안하였다. 제안 방법은 전송률 가변과 동일 송수신 시간에 최대의 데이터 전송이 가능하다. 제안 방식을 적용한 데이터 링크 시스템을 제작하여 성능을 확인하였다. 측정 결과, 대칭 TDD 방식에 비해 전송률은 최대 약 1.8배 증가하였다. PER(Packet Error Rate) 성능은 동일하며, 전송률 가변이 가능함을 확인하였다.

• Journal of Biosystems Engineering
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• 제23권5호
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• pp.481-490
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• 1998

A computer vision system to measure low flow rate of solid particles was developed and tested to examine its performance with various sized 7 kinds of seeds, perilla, mung bean, paddy, small red bean, black soybean, Cuba bean and small potato tuber. The test was performed for two types of particle flow, continuous and discontinuous. For the continuous flow tested with perilla, mung bean and paddy, the tests resulted correlation coefficients for the flow rates measured by the computer vision and direct method about 0.98. Average errors of the computer vision measurement were in a range of 6∼9%. For the discontinuous flow tested with small red bean, black soybean, Cuba bean and small potato tuber, the tests resulted correlation coefficients for the flow rates measured by the computer vision and direct method 0.98∼0.99. Average errors of the computer vision measurement were in a range of 5∼10%. Performance of the computer vision system was compared with that of the conventional optical sensor to count particles in discontinuous flow. The comparison was done with black soybean, Cuba bean and small potato tuber, and resulted that the computer vision has much better performance than the optical sensor in a sense of precision of the measurement.

• 대한한방내과학회지
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• 제33권2호
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• pp.209-221
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• 2012

Objectives : The aim of this study was to investigate the relationship between the autonomic nervous system and the cold-heat pattern in patients with chronic constipation. Methods : Subjects with chronic constipation (n=30) and without chronic constipation (n=20) were recruited, interviewed and measured for heart rate variability (HRV). Chronic constipation was defined as functional constipation and Irritable Bowel Syndrome (IBS) with constipation based on Rome III criteria. We surveyed patients' general characteristics, categorized by cold-heat pattern, and took measurement of HRV for 5 minutes. Analysis was conducted among these three indices. Results : Women accounted for most of the subjects with chronic constipation (96.7%). In groups with or without constipation, the number of cold patterns was more than of heat patterns. The mean heart rate of subjects without chronic constipation was significantly higher than that of subjects with chronic constipation. No other statistical significance was noted among indices of HRV and cold-heat pattern. Conclusions : Through this study, there were few relationships between autonomic nervous system measured by HRV and cold-heat pattern in chronic constipation.

• 동력기계공학회지
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• 제13권5호
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• pp.59-66
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• 2009

High temperature and pressure valves in power plant have been used for fluid flowing and leakage occurred owing to valve internal damage such as disc wear, crack and inserting of foreign objects etc. in these valves. Recently, multi-measuring technique applied both ultrasonic and acoustic method have been used for evaluation of valve internal leakage in order to raise measurement reliability. Therefore, we have performed various leakage tests using ultrasonic and acoustic measuring system and acquired leakage data for the various leakage conditions. In this study, we developed the estimation method of regression model through leakage data, and expectation method for valve opening ratio, which is directly proportion to leakage rate, using the established estimation model from the measured data, valve size and fluid pressure so as to enhance data reliability. As a result of this study, it was founded that expectation method of leakage rate by statistical analysis method is appropriate to valve leakage evaluation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.468-472
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• 2003

The lifting technique is a standard control procedure that is commonly applied to dual-rate systems, where a critical difficulty is that care must be taken so that the resulting equivalent system preserves the causality constraint between the control signal and the measured output. To overcome this difficulty, the most attractive result has been suggested by defining control time sequences as the union of sample and hold time sequences. However, the sacrifice of regular control period scheme results in some serious disadvantages; restrictions on the implementation to hardware and the corresponding inefficient control scheme. On the contrary, this paper proposes a novel dual-rate control technique, which redescribes the system as a control-rate-based system having regular control period and designs the controller, with no causality constraint, through Linear Matrix Inequality (LMI) formulation.

• 대한기계학회논문집
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• 제11권5호
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• pp.846-855
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• 1987

본 연구에서는 실용적 설계및 이론해석에 필요한 동적 거동에 관한 현상규명 및 기초자료를 제공하기위해, 기하학적 형상변화에 따른 맥동연소의 안정성 및 흡입공 기량의 측정을 통한당량비의 범위를 관찰하고, 연소실과 배기관, 공기유입관, 연료노 즐실에서의 압력을 각각 동시측정해서 동적거동에 관해 고찰하고, 작동주파수에 관한 간단한 실험식의 확립과 추력성능에 관한 실험을 행했다.