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.

韓國人 成人 男子에 나타난 非 正常的인 脾臟의 1例

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.

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.

Difference in Biochemical Properties of Soils with Different Periods of Agricultural Practice after Conversion from Paddies to Uplands

Hyen Chung Chun,Sanghun Lee,Dong Hyeok Gong,Ki Youl Jung,Ju Young Cho,Young-Nam Kim,Yong Bok Lee 한국토양비료학회 2021 한국토양비료학회지 Vol.54 No.4

The intrinsic characteristics of soil can be altered by purpose of land use and its history, which would determine the quality and health of the soil. In South Korea, along with the trend of decreasing agricultural land area, land use conversion from paddies to uplands is being promoted to alleviate the oversupply of rice and to improve the self-sufficiency rate of field crops. So far, in order to increase the productivity of crops after land use conversion, various types of soil management have been applied, focusing mostly on chemical properties related to soil fertility rather than biological properties related to soil health. This study was conducted to compare the difference in soil biochemistry of uplands with different periods of land use conversion from paddies, and to investigate the interrelationship between these soil characteristics. In general, there were significant differences in chemical parameters of soils according to the period of soybean cultivation (2, 4, and 10 years) after land use conversion of paddy fields. In Andong region, soil pH, organic matter (OM), total nitrogen (T-N), available phosphate (Av. P), and exchangeable potassium (Ex. K) increased with increase in the period of the land use conversion. Similarly, pH, Av. P, Ex. K, Ex. Ca, Ex. Mg and Org. P were the highest in the 10-year soybean growing uplands. Like the soil chemistry, soil microbial enzyme activities including dehydrogenase (DHA), β-glucosidase (BG), alkaline phosphatase (ALP), and arylsulfatase (AS) differed by the period of agricultural practices since the land use conversion but varying with study areas. Principle component analysis (PCA) showed clear separations of the upland soils with different periods of farming since land use conversion that is highly influenced by soil OM and pH as well as BG and ALP in both areas. With comprehensive interpretation of all results in this study, we predicted that, in both areas, applications of inorganic and organic fertilizers have been continuously performed, thereby improving the soil productivity of uplands converted from paddies following the land use conversion. As such, improved quality of the soils by the land managements could result in a positive effect on the soil health, by enhancing the overall microbial abundance as well as stimulating their functions such as nutrient cycling.

Characterizations of Growth, Yield and Water Use Efficiency of Adzuki Bean as Affected by Drought Stress

Hyen Chung Chun,Sanghun Lee,Dong Hyeok Gong,Young Dae Choi,Ki Yuol Jung 한국토양비료학회 2020 한국토양비료학회지 Vol.53 No.4

Accurate and optimal water supply to crop is critical in growing stalks and producing maximum yields. Adzuki bean is one of the representative legume crops and known as a vulnerable crop to water stress. This study investigated drought effect on adzuki bean at various growth stages and water use efficiency (WUE) with different soil moisture contents in order to evaluate response of adzuki bean to drought. The experiment was performed at National Institute of Crop Science in Miryang. Adzuki beans were planted in a Wagner pot filled with 50% of silt loam soil and 50% of bed soil. Drought treatment was applied at six growth stages: V1, V3, V5, R1, R3, R5. Another pot experiment was performed in a stainless steel pot with an automated irrigation system in order to maintain targeted soil moisture content (40, 60 and 80% of field capacity). Growth and yield characteristics of adzuki bean were measured from all pots. Crop susceptibility (CS) was calculated from the Wagner pots to quantify drought effect at each growth stage and WUE was measured from the stainless pots to determine the least water requirement to prevent drought damage. Drought effect was the greatest in growth reduction at V1 and yield reduction at R3. CS value was the smallest value at V3 and the greatest at R3. Growth, yield and WUE data of adzuki bean were not different between soil moisture 60% of field capacity and 80%, while ones from 40% soil moisture content were smaller than others. Adzuki bean exhibited great vulnerability to drought stress at reproductive stage and it required at least soil moisture 60% of field capacity to prevent drought damage. These results will be useful to water management of adzuki bean and prevent drought damage in adzuki bean cultivation.

Differences in Soil Chemistry and Microbial Community between the Upland Converted from Paddy and the Existing Soybean Upland

Hyen Chung Chun,Sanghun Lee,Dong Hyeok Gong,Ki Youl Jung,Hyoen Ji Choe,Young-Nam Kim,Yong Bok Lee 한국토양비료학회 2021 한국토양비료학회지 Vol.54 No.4

Change in land use can alter soil chemical properties and microbial community composition that are greatly associated with the soil quality and health. In South Korea, large numbers of paddy areas have recently converted to upland fields, and various types of land management are conducting to improve the soil fertility and productivity. However, lack of studies have been reported to seek out proper soil management in uplands converted from paddies so far, and also there are few studies about soil microbial community and its relationship with soil properties in the agricultural lands. This study aimed to investigate differences in soil chemistry and microbial community structure between upland converted from paddy and existing soybean upland and to evaluate their changes according to the cultivation periods following the land use conversion. As a result, the soil chemistry and microbial community composition varied significantly with various fertilizer treatments including non-fertilizer (NF), inorganic fertilizer (NPK), and a mixture of NPK and compost (NPKC). Additionally, variations in the chemical and biological parameters were influenced by the period of farming practices following the land use conversion. Overall, the major soil factors related to the change in soil chemistry by different fertilizer treatments; in particular, organic matter (OM), available phosphate (Av. P2O5), and exchangeable K (Ex. K). It is likely that such differences in the chemical parameters were closely linked to the change in soil redox condition after the conversion to uplands. This may affect the formation of soil microbial community structure, directly or indirectly, throughout the whole treatments of this study. The indices of abundance/richness including abundance-based coverage estimator (ACE) and Chao and alpha diversity including Shannon and non-parametric Shannon (Np-Shannon) were in the order NPCK > NPK > NF, consistently. Also, the microbial community structure at phylum level was observed in the order of Proteobacteria > Acidobacteria > Actinobacteria > Chloroflexi > Verrucomicrobia > Planctomycetes > Firmicutes in the soils of this study. Among the bacterial phyla, Acidobacteria and Bacteroidetes that are aerobic and play a key role in nutrient cycling were found to increase their population as the cultivation period increased after the conversion of land use. However, despite the increase in such beneficial bacteria abundance related to nutrient cycling through the soil management for 3 years, it seems that the low availability of P in soils of all treatments and severe climatic conditions adversely affected the soybean yield. Therefore, in order to maximize the soil fertility and productivity after conversion from paddies to uplands, it is important to find out proper soil management approaches for each cropland. Also, such land management should be continuously implemented by identifying environmental factors and microbial community structures that are largely related to soil quality and health improvement.

Morphological and Fractal Characteristics of Sesame (Sesamum indicum L.) Roots from Various Soil Moisture Contents

Hyen Chung Chun,Amar Margaux,Romain Michel Gloaguen,Yu-Chien Tseng,Sanghun Lee,Ki-Yuol Jung,YoungDae Choi,Diane Rowland 한국토양비료학회 2018 한국토양비료학회지 Vol.51 No.3

Recently Korea has severe drought during sowing and early vegetative period of sesame cultivation. Sesame is an important oilseed crop in Korea, so it is important to understand adaptation of sesame to water stress. This study investigated changes of morphological properties and spatial distribution of sesame roots under different soil moisture contents. The experiment was performed at University of Florida in Gainsville, USA. Two sesame cultivars (Bene and Indie) were planted in a test tube with 35 in length, 21 in width, and 4 cm in depth and grew for 23 days. The tubes were filled with turface soil with four soil moisture treatments (40, 50, 75 and 100%). The root images were obtained every 2 days using a scanner. Root properties from the images were characterized by root length, surface area, volume, number of roots and fractal parameters (fractal dimension and lacunarity). The results of this study showed that the all of root properties had no significant difference between cultures, but there was difference across soil moisture contents. The total length, surface area, volumes and number of roots increased as soil moisture increased from both cultivars. The values of fractal dimension increased as soil moisture increased, while the ones of lacunarity decreased. These results indicated that greater soil moisture induced more abundant and heterogeneous root structure. Correlation analysis among morphological properties and fractal parameters resulted in that the fractal dimension had the greatest correlation with number of roots. This result indicates that fractal dimension is strongly related to branching of roots. Sesame roots from soil moisture of 40 and 50% did not develop enough to have fractal root structure. Sesame roots are sensitive to soil moisture content in germination and early vegetative stage and they require soil moisture close to 100% to develop full root structure. These results would be useful to understand sesame responses to water stress and to manage irrigation amounts in sesame cultivation.

Computer Tomography as a Tool for Physical Analysis in an Anthropogenic Soil

Hyen Chung Chun,Chan Won Park,Yeon Kyu Sonn,Hyun Joon Cho,Byung Keun Hyun,Kwan Cheol Song,Yong Seon Zhang 한국토양비료학회 2013 한국토양비료학회지 Vol.46 No.6

Human influence on soil formation has dramatically increased as the development of human civilization and industry. Increase of anthropogenic soils induced research of those soils; classification, chemical and physical characteristics and plant growth of anthropogenic soils. However there have been no reports on soil pore properties from the anthropogenic soils so far. Therefore the objectives of this study were to test computer tomography (CT) to characterize physical properties of an anthropogenic paddy field soil and to find differences between natural and anthropogenic paddy field soils. Soil samples of a natural paddy field were taken from Ansung, Gyeonggi-do (Ansung site), and samples of an anthropogenic paddy field were from Gumi in Gyeongsangnam-do (Gasan) where paddy fields were remodeled in 2011-2012. Samples were taken at three different depths and analyzed for routine physical properties and CT scans. CT scan provided 3 dimensional images to calculate pore size, length and tortuosity of soil pores. Fractal analysis was applied to quantify pore structure within soil images. The results of measured physical properties (bulk density, porosity) did not show differences across depths and sites, but hardness and water content had differences. These differences repeated within the results of pore morphology. Top soil samples from both sites had greater pore numbers and sizes than others. Fractal analyses showed that top soils had more heterogeneous pore structures than others. The bottom layer of the Gasan site showed more degradation of pore properties than ploughpan and bottom layers from the Ansung site. These results concluded that anthropogenic soils may have more degraded pore properties as depth increases. The remodeled paddy fields may need more fundamental remediation to improve physical conditions. This study suggests that pore analyses using CT can provide important information of physical conditions from anthropogenic soils.

Characterizations of Yields and Seed Components of Sesame (Sesamum indicum L.) as Affected by Soil Moisture from Paddy Field Cultivation

Hyen Chung Chun,Ki Yuol Jung,Young Dae Choi,Sanghun Lee,Sung-Up Kim,Eunyoung Oh 한국토양비료학회 2017 한국토양비료학회지 Vol.50 No.5

Accurate and optimal water supply to cereal crop is critical in growing stalks and producing maximum yields. Recently, upland crops are cultivated in paddy field soils to reduce overproduced rice in Korea. In order to increase productivity of cereal crops in paddy fields which have poor percolation and drainage properties, it is necessary to fully understand crop response to excessive soil water condition and management of soil drainage system in paddy field. The objectives of this study were to investigate effects of excessive soil water to sesame growth and to quantify stress response using groundwater levels. Two cultivars of sesame were selected to investigate; Gunbak and Areum. These sesames were planted in paddy fields located in Miryang, Gyeongnam with different soil drainage levels and drainage systems. The experiment site was divided into two plots by drainage class; very poorly and somewhat poorly drained. Two different drainage systems were applied to alleviate excessive soil water in each plot: open ditch and pipe drainage system. Soil water contents and groundwater levels were measured every hour during growing season. Pipe drainage system was significantly effective to alleviate wet injury for sesame in paddy fields. Pipe drainage system decreased average soil moisture content and groundwater level during sesame cultivation. This resulted in greater yield and lignan contetns in sesame seeds than ones from open ditch system. Comparison between two cultivars, Gunbak had greater decrease in growth and yield by excessive soil water and high groundwater level than Areum. Seed components (lignan) showed decrease in seeds as soil water increased. When soil moisture content was greater than 40%, lignan content tended to decrease than ones from less soil moisture content. Based on these results, pipe drainage system would be more effective to reduce wet injury to sesame and increase lignan component in paddy field cultivation.