• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.97-103
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• 2002

This paper deals with a PWM(Pulse Width Modulation) current amplifier using digital controller in order to generate a gradient magnetic field far the MRI(Magnetic Resonance Image) system. Because of tolerance of discrete devices, it is difficult to set accurate values of the control parameters and to make an analog-controlling circuit. However, using digital controller, it is possible to set exact control parameters and to adopt a modern control techniques. It is shown that the digital controller will highly enhance the output current response and it will improve the quality of the MRI.

• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.126-134
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• 2008

As many systems depend on electronics, concern for fault tolerance is growing rapidly. For example, a car with its steering controlled by electronics and no mechanical linkage from steering wheel to front tires (steer-by-wire) should be fault tolerant because a failure can come without any warning and its effect is devastating. In order to make system fault tolerant, there has been a body of research mainly from aerospace field. This paper presents the structure of predictive hybrid redundancy that can remove most erroneous values. In addition, several numerical simulation results are given where the predictive hybrid redundancy outperforms wellknown average and median voters.

• East Asian mathematical journal
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• v.32 no.1
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• pp.129-138
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• 2016

In this paper, we propose an efficient regularization technique (The Method of Regularized Ratios) for the reconstruction of the shape of a rigid elastic scatterer from far field measurements. The approach used is based on the factorization method and creates via Picard's condition ratios, baptized Regularized Ratios, that serve to effectively remove unwanted singular values that may lead to poor reconstructions. This is achieved through the use of a sophisticated algorithm that progressively adjusts an initially set moderate tolerance. In comparison with the well established Tikhonov-Morozov regularization techniques our new algorithm appears to be more computationally efficient as it doesn't require computation of the regularization parameter for each point in the grid.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.86-91
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• 2002

Glass/phenolic composite laminates have been used in the field of non-flammable light rail transit and their applications have expanded more widely. Low velocity impact tests have been used to evalute the effect of temperature and acceleration aging on low velocity impact response of phenolic matrix composites reinforced with woven E-glass fabric. The damage of matrix cracking and delamination are suddenly reduced the compressive strength after impact. The damage area increases with increasing temperature and impact energy. UT C-scan is used to determine damage areas by impact loading. Therefore, all this observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

• Journal of the Korean Institute of Landscape Architecture
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• v.22 no.1
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• pp.101-110
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• 1994

A field study was carried out to investigate the visual injury of zoysiagrass and creeping bentgrass by the application of various herbicides the result were as follows. 1. Trifluralin + benefin and dithiopyr did not injure creeping bentgrass and zoysiagrass. 2. Creeping bentgrass was safe while zoysiagrass was slightly injured within acceptable level with benefin. 3. Oryzalin caused injury both on creeping bentgrass and zoysiagrass. However, the injury of zoysigrass was within acceptable level while the injury of creeping bentgrass increased without acceptable level when applied at>5kg/ha. 4. Creeping bentgrass was tolerant to pendimethalin only when treated at<3.4kg/ha whereas zoysiagrass was tolerant regardless of rate. 5. Creeping bentgrass treated with fenoxaprop, oxadiazon, and bensulide were severely injured. However, turfgrasses treated with bensulide recovered rapidly when compared with fenoxaprop and oxadiazon. 6. Zoysiagrass treated with 2,4-D, dicambe, bentazon was safe when applied at mid summer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.274-275
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• 2005

The tensile strain dependency of critical current in YBCO coated conductors was examined at 77K and in the self magnetic field. A commercially available YBCO sample with Cu stabilizer layer was supplied. There existed a peak in the relation between the Ie and tensile strain, and the reversible variation of $I_c$ with applied tensile strain was found. In the neutral axis Ni alloy RABiTS-$Y_2O_3$/YSZ/$CeO_2$ buffered YBCO tape, the $I_c$ recovered reversibly until the applied strain reached to about 0.5%, representing that a significant residual compressive strain induced during cooling to 77 K influenced the axial strain tolerance of YBCO conductors. To investigate the strain and stress influence on the $I_c$, the stress-strain characteristics of YBCO conductors measured at 77 K were discussed.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1171-1181
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• 2019

Modular Multilevel Converter (MMC)-based HVDC power transmission using a real-time simulator is one of the key technologies in power electronics research. This paper introduces the design methodology of a physical MMC-HVDC control system based on a Field-Programmable Gate Array (FPGA), which has the advantage of high-speed parallel operation, and validates the accuracy of MMC-HVDC control when operated with a Real-Time Digital Simulator (RTDS). Finally, this paper compares and analyzes the characteristics of capacitor voltage balancing methods such as Nearest Level Control (NLC), NLC with a reduced switching frequency, and tolerance band modulation implemented on physical control system.

• Current Optics and Photonics
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• v.3 no.3
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• pp.227-235
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• 2019

With slimmer, lighter and all-reflective imaging systems in high demand for consumer and military applications, coaxially folded optical image systems are widely considered because they can extend focal length and reduce track length. Most of these systems consist of multiple surfaces, and these surfaces are machined on one element or grouping processing on two elements. In this paper, we report and first experimentally demonstrate an all-aluminum all-reflective optical system which consists of two optical elements, with two high order aspherical surfaces in each element. The coaxially folded system is designed with Seidel aberration theory and advanced optimization with Zemax. The system is made of all-aluminum material processing by single point diamond turning (SPDT). On this basis, we completed the system integration and performed an imaging experiment. The final system has the advantages of short track length and long focal length and broad application prospects in the micro-unmanned aerial vehicle field.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1566-1582
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• 2019

Silent Data Corruptions (SDCs) is a serious reliability issue in many domains of computer system. The identification and protection of the program instructions that cause SDCs is one of the research hotspots in computer reliability field at present. A lot of solutions have already been proposed to solve this problem. However, many of them are hard to be applied widely due to time-consuming and expensive costs. This paper proposes an intelligent approach named SDCPredictor to identify the instructions that cause SDCs. SDCPredictor identifies SDC-causing Instructions depending on analyzing the static and dynamic features of instructions rather than fault injections. The experimental results demonstrate that SDCPredictor is highly accurate in predicting the SDCs proneness. It can achieve higher fault coverage than previous similar techniques in a moderate time cost.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.337-337
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• 2017

Accurate and optimal water supply to cereal crop is critical in growing stalks and producing maximum yields. Excessive soil moisture may cause nutrient deficiencies and oxygen deficiency. Excessive soil water during crop growth stages results in decrease of yields. In Korea, the largest agricultural lands are paddy fields. Recently, upland crops are cultivated in paddy field soils to reduce overproduced rice in Korea. In order to success this policy, it is necessary to fully understand crop response to excessive soil moisture condition from paddy field soils. Adzuki bean is one of major legumes which provide protein in daily diet. Adzuki bean has been well know its weakness to excessive soil moisture condition, In order to obtain optimal yields of adzuki bean from paddy field cultivation, it is necessary to understand response of adzuki bean under different soil moisture conditions. This study investigated characteristics of growths, yields and response degree of water stress from adzuki bean. Three cultivars were selected for this study; Chungju, Hongeon, and Arari. All adzuki beans were cultivated in a paddy field which was divided into three sections with different soil moistures. The paddy field was located in Milyang, Gyeongsangnam during 2016. One section of the paddy field had the greatest average soil moisture content as 35.1% during adzuki bean cultivation (very poor). The second greatest soil moisture section had 32.6% (somewhat poor) and the smallest soil moisture section had 28.9% of soil moisture (somewhat well). During cultivation of three cultivar adzuki beans, soil moisture contents and groundwater levels were monitored. All the characteristics of growth and yield components were measured; height, thickness, 100 seed weights etc. Stress index values were calculated by Stress Day Index (SDI). All cultivars had the greatest yields from somewhat well section. Chungju had the greatest yields throughout all three sections compared to other cultivars. Chungju had 81% greater yield than Hongeon which had the smallest yield from somewhat well section. Arari set in middle from all sections. However there was no significant differences yields from very poor and somewhat poor sections. Leaf SPAD values tended to decrease and stable carbon isotope values increased as soil moisture increased. However, Chungju had no difference across different soil moistures in SPAD and stable carbon isotope values, while Hongeon had the greatest differences across sections. These trends followed by SDI values. Chungju had the smallest SDI values compared to other cultivars, which meant that Chungju was the strongest tolerance against excessive soil moisture than other cultivars. All three cultivars showed severe decrease of yields from very poor and somewhat poor sections. Arari and Hongeon showed great decrease from somewhat well section compared to yields from upland soil. These two cultivars may not be proper cultivating in paddy fields. In conclusion, adzuki bean is very sensitive to soil moisture condition and detailed soil managements are required to obtain optimal yields of adzuki bean from paddy field cultivation.