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DSP를 利用한 Phase-shifted PWM 直列共振型 DC-DC 컨버터
김현준,김학성,김세찬,유동욱,원충연 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.2
This paper deals with a phase-shifted PWM high-frequency series resonant DC-DC converter using IGBTs. The converter output voltage regulation is digitally controlled using DSP(TMS320C31) for a fast rising time and low ripple output voltage. A PID controller and feed-forward controller is adopted as a controller and implemented on software. Simulation technique are employed to describe resonant converter behavior, which can present system output exactly and calculate in short time, by applying numerical method to the state equation of each equivalent circuit. And the simulation results are verified as compared with experimental results.
김종중,문정석,정주현 順天鄕大學校 1980 의대논문집 Vol.5 No.-
Authors took an abnormal spleen from a korean male adult cadava aged about 52 years in the Anatomy department of medical College, Chosun University. After dissection, we report views on autopsy and discussion on references. Particular matters were as follows 1. Spleen weight : 3,760gm; Speen length: 32,50cm ; Spleen width : 17,25cm, Spleen thickness : 11,50cm. 2. Spleen type : tetraheadral type.
X-ray용 고주파 공진형 고전압 발생장치에 관한 연구
김학성,유동욱,김현준,원충연 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.1
This paper is concerned with High Frequency, High Voltage Generator for X-ray using zerovoltage soft-switching PWM DC-DC power converter by resonant method, which makes the most of the parastic IBC parameters of high-voltage transformer link, for diagonostic X-ray power generator. The converter circuit basically utilizes phase-shift pulse width modulated series resonant full-bridge PWM DC-DC high-power converter operating at a constant frequency;25kHz. The high-frequency switching operation of the inverter has some effective advantages with consist in the physical reduction in size and weight and lowered acoustic noise. The converter output regulation is digitally controlled using DSP(Digital Signal Processor) for obtaining a fast rising time and adjust output voltage within a wide load range. This converter characteristics are evaluated in terms of computer-aided analytical and experimental results.
Comparison of pore shapes and water retention curves between anthropogenic and natural paddy fields
Hyen Chung Chun(전현정),Ki-Yuol Jung(정기열),YoungDae Choi(최영대),Su-min Jo(조수민),Sanghun Lee(이상훈),Byung-Keun Hyun(현병근),kook-sik Shin(신국식),Yeon-kyu Sonn(손연규),Hang-Won Kang(강항원) 한국토양비료학회 2015 한국토양비료학회 학술발표회 초록집 Vol.2015 No.12
Three Dimensional Measurements of Pore Morphological and Hydraulic Properties
Hyen-Chung Chun(전현정),Daniel Gimenez,Sung-Won Yoon(윤성원),Richard Heck,Laise Ziska,Kate Geaorge,Yeon-Kyu Sonn(손연규),Sang-Keun Ha(하상건),Tom Elliot 한국토양비료학회 2010 한국토양비료학회지 Vol.43 No.4
포어 네트웍 모델들 (Pore network model)은 토양 공극의 구조를 조사할 때 유용한 도구들이다. 이런 모델들은 삼차원 이미지들에서 공극의 구조와 관련된 양적 정보를 제공한다. 이 연구는 포어 네트웍 모델을 이용하여 공극의 구조와 수리학적 특성들을 양적으로 측정하였다. 연구목표는 큰 크기의 이미지에서 공극의 구조에 관한 양적 정보를얻기 위해 포어 네트웍 모델을 적용하고, 토양수분특성과 수리 전도도를 삼차원 이미지로부터 계산하고 이 값들은 실험을 통해 얻어진 실험값들과 결합하여 토양의 수리적 특성을 분석하는 것이었다. 토양 시료들은 발티모아 도시 중심에 있는발티모어 과학센터에 위치한 실험부지에서 채취되었다. 불교란 원주형 시료들이 채취되었고, 22 μm 의 해상도로 x선 단층 촬영되었다. 포어 네트웍은 중심축 변형에 의해 공극에서 축출되었고 이를 바탕으로 공극 구조가 계산되었다. 토양수분특성과 불포화 수리 전도도 값들은 토양 이미지에서 계산 되었다. 토양 밀도, 토양수분특성과 불포화 수리 전도도들은 3 토양 시료들로부터 실험을 통해 구하였다. 삼차원 이미지 분석은 토양 공극의 특성들을, 예를 들어 공극 부피, 길이, 굴곡도, 가장 정확히 분석하였다. 이런 정확한 분석은 토양 내 수문학적 정보를 정확히 산출할 수 있게 하였다. 계산된 값과 실험을 통한 실험치의 결합은 공극에 대한 더 광범한 범위를 분석할 수 있게 하였다. 이 연구를 통해 이미지에서 계산되고 측정된 수문학적 자료들은 토양내 대기공과 소기공을 모두 다 설명해 줄 수 있는 방법이라는 것이 밝혀졌다. Pore network models are useful tools to investigate soil pore geometry. These models provide quantitative information of pore geometry from 3D images. This study presents a pore network model to quantify pore structure and hydraulic characteristics. The objectives of this work were to apply the pore network model to characterize pore structure from large images to quantify pore structure, calculate water retention and hydraulic conductivity properties from a three dimensional soil image, and to combine measured hydraulic properties from experiments with calculated hydraulic properties from image. Soil samples were taken from a site located at the Baltimore science center, which is located inside of the city. Undisturbed columns were taken from the site and scanned with a computer tomographer at resolutions of 22 μm. Pore networks were extracted by medial-axis transformation and were used to measure pore geometry from one of the scanned samples. Water retention and unsaturated hydraulic conductivity values were calculated from the soil image. Properties of soil bulk density, water retention and unsaturated hydraulic conductivity were measured from three replicates of scanned soil samples. 3D image analysis provided accurate detailed pore properties such as individual pore volumes, pore length, and tortuosity of all pores. These data made possible to calculate accurate estimations of water retention and hydraulic conductivity. Combination of the calculated and measured hydraulic properties gave more accurate information on pore sizes over wider range than measured or calculated data alone. We could conclude that the hydraulic property computed from soil images and laboratory measurements can describe a full structure of intra- and inter-aggregate pores in soil.
Yearly Characterization of Soil Properties from Soybean Cultivation at Paddy Fields
Hyen Chung Chun(전현정),Sanghun Lee(이상훈),Hyeok Gong(공동혁),Ki Youl Jung(정기열) 한국토양비료학회 2021 한국토양비료학회 학술발표회 초록집 Vol.2021 No.11
Soybean(Glycine max (L) Merr.) cultivation from paddy fields has many benefits such as increase in yields, etc. However there have been found problems such as increase in desease and decrease in yields from contiguous soybean cultivation at paddy fields. This study investigated soil physical and chemical properties from paddy field soils by different soybean cultivation years; 1~3 year, 4~6 year and over 10 year. Ten sites from each year category were selected in Andong, Kyeongbuk and Gimje, Jeonbuk area in Korea. Soybean is only crop cultivated in all 30 sites and standard chemical fertilizer and manure were applied every year. Soil samples were taken during Mach and April before soybean planting in 2021. All samples were analyzed for physical properties such as soil texture, bulk density and soil moisture content and chemical properties such as pH, CEC, Available P₂O<SUB>5</SUB>, NO₃, etc. Statistical analyses were performed in SPSS(Statistical Package for the Social Science) at 95% siginificant level. Results of physical analyses did not show significant different as cultivation period increase, however chemical properties showed difference across different cultivation period. Values of NH₄ and NO₃ from over 10 year sites were significantly smaller than ones from less than 6 year sites. On the other hand, phosphate related properties, such as available P₂O<SUB>5</SUB> and organophosphoric acid, increased as soybean cultivation period increased. Paddy fields converted to soybean cultivation from rice under 3 years showed relatively great nitrogen and small phosphate values. These results may related to rice cultivation condition such as flooded condition. Nitrogen contents tend to decrease and phosphate contents to increase as soybean cultivation continues. This may be resulted in continuous application of fertilizer and manure to soil. Thsese results indicated that continuous cultivation of soybean in paddy fields may benefit for yield increase, but this benefit decrease under increase of cultivation period without manage chemical properties in soils.
Hyen Chung Chun,Ki-Yuol Jung,Young Dae Choi,Su-min Jo,Sanghun Lee,Byung-Keun Hyun,Kooksik Shin,Yeonkyu Sonn,Hang-Won Kang 한국토양비료학회 2015 한국토양비료학회지 Vol.48 No.5
Human influence on soil formation has dramatically increased with human civilization and industry development. Increase of anthropogenic soils induced researches on the anthropogenic soils; classification, chemical and physical characteristics of anthropogenic soils and plant growth from anthropogenic soils. However there have been no comprehensive analyses on soil pore or physical properties of anthropogenic soils from 3 dimensional images in Korea. The objectives of this study were to characterize physical properties of anthropogenic paddy field soils by depth and to find differences between natural and anthropogenic paddy field soils. Soil samples were taken from two anthropogenic and natural paddy field soils; anthropogenic (A_c) and natural (N_c) paddy soils with topsoil of coarse texture and anthropogenic (A_f) and natural (N_f) paddy soils with topsoil of fine texture. The anthropogenic paddy fields were reestablished during the Arable Land Remodeling Project from 2011 to 2012 and continued rice farming after the project. Natural paddy fields had no artificial changes or disturbance in soil layers up to 1m depth. Samples were taken at three different depths and analyzed for routine physical properties (texture, bulk density, etc.) and pore properties with computer tomography (CT) scans. The CT scan provided 3 dimensional images at resolution of 0.01 mm to calculate pore radius size, length, and tortuosity of soil pores. Fractal and configuration entropy analyses were applied to quantify pore structure and analyze spatial distribution of pores within soil images. The results of measured physical properties showed no clear trend or significant differences across depths or sites from all samples, except the properties from topsoils. The results of pore morphology and spatial distribution analyses provided detailed information of pores affected by human influences. Pore length and size showed significant decrease in anthropogenic soils. Especially, pores of A_c had great decrease in length compared to N_c. Fractal and entropy analyses showed clear changes of pore distributions across sites. The topsoil layer of A_c showed more degradation of pore structure than that of N_c, while pores of A_f topsoil did not show significant degradation compared with those of N_f. These results concluded that anthropogenic soils with coarse texture may have more effects on pore properties than ones with fine texture. The reestablished paddy fields may need more fundamental remediation to improve physical conditions.
Hyen Chung Chun,Suk Young Hong,Kwan Cheol Song,Yihyun Kim, Byung,Keun Hyun,Budiman Minasny 한국토양비료학회 2012 한국토양비료학회지 Vol.45 No.4
This study investigates the prediction of soil OM on Korean soils using the Visible-Near Infrared (Vis-NIR) spectroscopy. The ASD Field Spec Pro was used to acquire the reflectance of soil samples to visible to near-infrared radiation (350 to 2500 ㎚). A total of 503 soil samples from 61 Korean soil series were scanned using the instrument and OM was measured using the Walkley and Black method. For data analysis, the spectra were resampled from 500-2450 nm with 4 nm spacing and converted to the 1<SUP>st</SUP> derivative of absorbance (log (1/R)). Partial least squares regression (PLSR) and regression rules model (Cubist) were applied to predict soil OM. Regression rules model estimates the target value by building conditional rules, and each rule contains a linear expression predicting OM from selected absorbance values. The regression rules model was shown to give a better prediction compared to PLSR. Although the prediction for Andisols had a larger error, soil order was not found to be useful in stratifying the prediction model. The stratification used by Cubist was mainly based on absorbance at wavelengths of 850 and 2320 ㎚, which corresponds to the organic absorption bands. These results showed that there could be more information on soil properties useful to classify or group OM data from Korean soils. In conclusion, this study shows it is possible to develop good prediction model of OM from Korean soils and provide data to reexamine the existing prediction models for more accurate prediction.
Hyen Chung Chun,Ki Yuol Jung,Young Dae Choi,Sanghun Lee,Hang Won Kang 한국토양비료학회 2018 한국토양비료학회지 Vol.51 No.4
In Korea, the largest agricultural lands are paddy fields which have poor infiltration and drainage properties. Recently, Korean government pursuits cultivating upland crops in paddy fields to reduce overproduced rice in Korea. In order to succeed this policy, it is critical to understand topographic information of paddy fields and its effects on upland crops cultivating in paddy field soils. The objectives of this study were characterizing growth properties of soybean and adzuki bean from paddy fields with three soil topographic features and soil water effects which were induced by topographic features on sesame and perilla. The crops were planted in paddy fields located in Miryang, Gyeongnam with different topographies; mountain foot slope, local valley and alluvial plain. Soil water contents and groundwater levels were measured every hour during growing season. The paddy field of mountain foot slope was significantly effective to alleviate wet injury for soybean and adzuki bean in paddy fields. The paddy field of mountain foot slope decreased average soil water content and groundwater level during cultivation. Stress day index (SDI) from the alluvial plain paddy field had the greatest values from both crops and the smallest from ones of mountain foot slope. This result meant that soybean and adzuki bean had the smallest stress of soil water from the paddy field of mountain foot slope and the greatest from one of alluvial plain. It is important to consider topography of paddy fields to reduction of wet injury and to increase in yields.