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최종근,강윤구,이재종 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.2
This research suggests a cutting force model for the ball end milling processes. This model includes the effect of tool run out and tool deflection. In the proposed model, the flutes of ball end mills are considered as series of infinitesimal elements and each cutting edge is assumed to be straight for the analysis of the oblique cutting process, in which the small cutting edge element as been analyzed as an orthogonal cutting process in the plane including the cutting velocity and the chip-flow vector. Therefore, the cutting forces can be calculated through the model using the orthogonal cutting data obtained from the orthogonal cutting test. In order to enhance the performance of the model, the flutes of ball end mill are defined to keep geometric consistency at the peak of the ball part and the junction with he end mill part. The divided infinitesimal cutting edges are regulated to be even lengths. Some experiments show the validity of the developed model in the various cutting conditions.
( Youn Ku Kang ),( Young Sun Ryou ),( Jae Kyung Jang ),( Young Hwa Kim ) 한국농업기계학회 2014 바이오시스템공학 Vol.39 No.2
Purpose: This paper is aimed at analyzing the heating performance of the vertical closed loop type Geothermal Heat PumpSystem (GHPS) distributing the farm site and providing basic data of the GHPS. Method: Seedling greenhouse heating wasmade from October 2012 to May 2013. The seedling greenhouse was divided into 4 sectors (A, B, C and D zone, total 3,300m2) with different temperatures. It was heated from 5PM to 8AM, and during the night the greenhouse was covered bynon-woven fabric thermal curtains along the upper 2m of the greenhouse for temperature maintenance. In order to analyzethe heating performance of the GHPS, power consumption and operating time of the GHPS, inlet and outlet watertemperature of the condenser, temperatures of each zone of the greenhouse, and ambient temperature were measured. Results: When operating only one heat pump unit, heat generated in the condenser decreased as the experiment progressedand power consumption increased correspondingly. However, the heating coefficient of performance decreased from 3.3 to2.0 rapidly. Also, when operating two heat pump units, heat generated in the condenser decreased and power consumptionincreased. Heating coefficient of performance decreased from 4.5 to 3.7 rapidly. When the set temperature of thegreenhouse was 13.7~20.1°C and minimum ambient temperature was -20.8~4.8°C, the annually accumulated heat andpower consumption were 520,623 kW, 142,304 kW, respectively. Conclusion: When the set temperature of the greenhousewas 13.7~20.1°C and the minimum ambient temperature was 20.8~4.8°C, the annually accumulated heat and powerconsumption were 520,623 kW, 142,304 kW, respectively. When operating only one heat pump unit, the heating COP was2.0~3.3, and when operating 2 heat pump units, it was 3.7~4.5. If several heat pumps are installed in one GHPS, it issuggested that all heat pumps be operated except in special cases. Because the scale of the water pumps are set to the scaleof when all heat pump units are operating, if even one unit is not operating, the power consumption will increase. Thatbecomes the cause of COP decrease.
Kang, Youn Ku,Ryou, Young Sun,Jang, Jae Kyung,Kim, Young Hwa,Kim, Jong Goo,Kang, Geum Chun Korean Society for Agricultural Machinery 2014 바이오시스템공학 Vol.39 No.1
Purpose: In this study, the performance of cooling system with the water-water heat pump system of 100kW scale made for cooling agricultural facilities, especially for horticultural facilities, was analyzed. It was intended to suggest performance criteria and performance improvement for the effective cooling system. Methods: The measuring instruments consisted of two flow meters, a power meter and thermocouples. An ultrasonic and a magnetic flow meter measured the flow rate of the water, which was equivalent to heat transfer fluid. The power meter measured electric power in kW consumed by the heat pump system. T-type thermocouples measured the temperature of each part of the heat pump system. All of measuring instruments were connected to the recorder to store all the data. Results: When the water temperature supplied into the evaporator of the heat pump system was over $20^{\circ}C$, the cooling Coefficient Of Performance(COP) of the system was higher than 3.0. As the water temperature supplied into the evaporator, gradually, lowered, the cooling COP, also, decreased, linearly. Especially, when the water temperature supplied into the evaporator was lower than $15^{\circ}C$, the cooling COP was lower below 2.5. Conclusions: In order to maintain the cooling COP higher than 3.0, we suggest that the water temperature supplied into evaporator from the thermal storage tank should be maintained above $20^{\circ}C$. Also, stratification in the thermal storage tank should be formed well and the circulating pumps and the pipe lines should be arranged in order for the relative low-temperature water to be stored in the lower part of the thermal storage tank.
( Youn Ku Kang ),( Young Sun Ryou ),( Jae Kyung Jang ),( Young Hwa Kim ),( Jong Goo Kim ),( Gem Chun Kang ) 한국농업기계학회 2014 바이오시스템공학 Vol.39 No.1
Purpose : In this study, the performance of cooling system with the water-water heat pump system of 100kW scale made for cooling agricultural facilities, especially for horticultural facilities, was analyzed. It was intended to suggest performance criteria and performance improvement for the effective cooling system. Methods: The measuring instruments consisted of two flow meters, a power meter and thermocouples. An ultrasonic and a magnetic flow meter measured the flow rate of the water, which was equivalent to heat transfer fluid. The power meter measured electric power in kW consumed by the heat pump system. T-type thermocouples measured the temperature of each part of the heat pump system. All of measuring instruments were connected to the recorder to store all the data. Results: When the water temperature supplied into the evaporator of the heat pump system was over 20°C, the cooling Coefficient Of Performance(COP) of the system was higher than 3.0. As the water temperature supplied into the evaporator, gradually, lowered, the cooling COP, also, decreased, linearly. Especially, when the water temperature supplied into the evaporator was lower than 15°C, the cooling COP was lower below 2.5. Conclusions: In order to maintain the cooling COP higher than 3.0, we suggest that the water temperature supplied into evaporator from the thermal storage tank should be maintained above 20°C. Also, stratification in the thermal storage tank should be formed well and the circulating pumps and the pipe lines should be arranged in order for the relative low-temperature water to be stored in the lower part of the thermal storage tank.
Analysis on Heating Effects of the Vertical Type Geothermal Heat Pump System
Kang, Youn Ku,Ryou, Young Sun,Jang, Jae Kyung,Kim, Young Hwa Korean Society for Agricultural Machinery 2014 바이오시스템공학 Vol.39 No.2
Purpose: This paper is aimed at analyzing the heating performance of the vertical closed loop type Geothermal Heat Pump System (GHPS) distributing the farm site and providing basic data of the GHPS. Method: Seedling greenhouse heating was made from October 2012 to May 2013. The seedling greenhouse was divided into 4 sectors (A, B, C and D zone, total $3,300m^2$) with different temperatures. It was heated from 5PM to 8AM, and during the night the greenhouse was covered by non-woven fabric thermal curtains along the upper 2m of the greenhouse for temperature maintenance. In order to analyze the heating performance of the GHPS, power consumption and operating time of the GHPS, inlet and outlet water temperature of the condenser, temperatures of each zone of the greenhouse, and ambient temperature were measured. Results: When operating only one heat pump unit, heat generated in the condenser decreased as the experiment progressed and power consumption increased correspondingly. However, the heating coefficient of performance decreased from 3.3 to 2.0 rapidly. Also, when operating two heat pump units, heat generated in the condenser decreased and power consumption increased. Heating coefficient of performance decreased from 4.5 to 3.7 rapidly. When the set temperature of the greenhouse was $13.7{\sim}20.1^{\circ}C$ and minimum ambient temperature was $-20.8{\sim}4.8^{\circ}C$, the annually accumulated heat and power consumption were 520,623 kW, 142,304 kW, respectively. Conclusion: When the set temperature of the greenhouse was $13.7{\sim}20.1^{\circ}C$ and the minimum ambient temperature was $20.8{\sim}4.8^{\circ}C$, the annually accumulated heat and power consumption were 520,623 kW, 142,304 kW, respectively. When operating only one heat pump unit, the heating COP was 2.0~3.3, and when operating 2 heat pump units, it was 3.7~4.5. If several heat pumps are installed in one GHPS, it is suggested that all heat pumps be operated except in special cases. Because the scale of the water pumps are set to the scale of when all heat pump units are operating, if even one unit is not operating, the power consumption will increase. That becomes the cause of COP decrease.
Ku, Jeonghun,Lee, Jang Han,Han, Kiwan,Kim, Sun I.,Kang, Youn Joo,Park, Eun Sook Wolters Kluwer Health, Inc. All rights reserved. 2009 AMERICAN JOURNAL OF PHYSICAL MEDICINE & REHABILITA Vol.88 No.9
Ku J, Lee JH, Han K, Kim SI, Kang YJ, Park ES: Validity and reliability of cognitive assessment using virtual environment technology in patients with stroke. OBJECTIVES:: We assessed the validity and reliability of a virtual environment technology (VET)-based cognitive assessment program that was developed as a measurement tool of cognitive abilities in patients after a stroke. DESIGN:: Twenty participants diagnosed with stroke caused by unilateral brain lesions were enrolled to assess the VET program’s validity and test-retest reliability. Participants underwent evaluation by paper-based neuropsychological tests including the Korean Mini-Mental Status Examination, the Korean-Wechsler Adult Intelligence Scale, the Motor Free Visual Perception Test, Rey-Kim Memory Test, and Kim’s Frontal-Executive Neuropsychologic Test as well as the VET-based cognitive assessment. Major variables and indices of the VET program were calculated. The VET program validity was evaluated using a simple correlation analysis between variables from the VET program and conventional paper-based neuropsychological measurements, and the reliability was evaluated by investigating the test-retest correlation coefficients. RESULTS:: Major variables and indices of the VET program in patients with stroke correlated significantly with the related scores of paper-based neuropsychological tests. In addition, the test-retest reliability analysis revealed that the correlation coefficients ranged from 0.528 to 0.926. CONCLUSION:: The VET-based cognitive assessment program showed adequate reliability and validity as a method of cognitive assessment in patients after stroke.