• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.193-196
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• 2001

This paper describes an improved short-circuit protection for a multilevel ac/dc power converter The output do power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. Once the fault has been cleared the dc power is reapplied to the load. The rising time of the do load voltage is as small as several hundred microseconds, and there is no overshoot of the dc voltage because the do output capacitors hold undischarged state. Therefore, the proposed converter can be used for a power supply, which requires a rapid disconnection of the load from the power supply in the case of a short circuit, as well as a rapid connection the load to the power supply after the clearance of the short circuit condition.

• Journal of Soil and Groundwater Environment
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• v.27 no.2
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• pp.36-40
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• 2022

To respond to rapidly changing water circumstances such as climate change, drought, etc., the korean government (MOE) established four advanced strategies for integrated groundwater management. The first strategy is watershed-based management of groundwater. The second strategy is total quantity management of groundwater including improvement of groundwater preservation area policy and procedure of investigation for groundwater influence area, additional construction of groundwater dam, installation of large-scale public wells, extention of spilled groundwater use. The third strategy is prevention of groundwater contamination including expansion of monitoring wells, introducing declaration of groundwater contamination. The last strategy is advancement of groundwater information management including integrated management of data, setting up a big-data based open platform. The above-mentioned four strategies will be reflected in the 4th National Groundwater Management Plan to secure implementation power, and it is expected to laid the foundation for advanced and rational groundwater management system.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.451-451
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• 2021

인간활동으로 인해 서식처의 변화, 서식처의 파편화를 비롯하여 기후변화, 토지이용의 변화 등으로 생태계 생물 다양성은 빠르게 손실되고있는 상황이다. 특히 생물 다양성은 생태계 복원력에 중요한 인자로서 유역의 건전성 회복을 위해 생물 다양성을 중요한 인자로 고려하려는 경향이 커지고 있다. 유역 건전성은 주로 큰 하천에서의 친수성, 서식처, 유량 및 수질 등에 적용되어왔고 국내에서는 최근 들어 유역 건전성을 확보하기 위해 수량 및 수질관리, 환경문제 등의 해결을 위해 유역관리 차원에서 접근하려는 시도가 시작되었으나 어떠한 수단을 통해 생물다양성과 서식처 관리를 접근할 수 있는지에 대한 연구는 아직 부족한 실정이다. 이에 본 연구에서는 최근 20년 동안 도시화, 댐 건설 등 토지이용변화가 크게 발생한 금강유역(9,865 km²)을 대상으로 InVest 모델 중 서식처 가치평가 모델 (Habitat Quality Model)을 이용하여 유역의 서식처 가치를 평가하고 이를 수생태계 건강성 모니터링 자료와 비교하여 모형의 적용성을 평가하고자 한다.

• Asia Marketing Journal
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• v.1 no.2
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• pp.1-18
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• 1999

본 연구의 목적은 국내의 마케팅의사결정지원시스템의 채택의도를 증가시키는 요소와 실제 시스템의 사용 만족도를 증가시키는 요소를 발견하여 이러한 요소들 사이의 관계를 규명하는데 그 목적이 있다. 이를 위해 기초적인 문헌조사와 심층 면접의 예비 조사를 통해 설문지를 구성하고 기업의사결정자를 대상으로 설문지를 통한 본 조사를 실시하였다. 본 논문의 연구결과는 다음과 같이 세가지로 요약될 수 있다. 첫째로 마케팅의사결정지원시스템의 채택의도에 영향을 미치는 요소들은 고객, 제품 경쟁자 등의 의사결정환경의 역동성으로 대표되는 환경요인, 조직규모, 최고경영자의 지원, 인센티브 도입정도 등으로 대표되는 조직요인, 마케팅부서의 독립성, 장기적 마케팅 전략수립정도, 마케팅 스탭수 등으로 대표되는 직무요인으로 나타났다. 둘째, 마케팅의사결정지원시스템의 사용자 만족에 영향을 미치는 요소들은 하부시스템의 개발정도, 개발형태, 개발참여로 대표되는 실행요인과 사용정보의 양, 고려하는 차원의 수, 정보시스템의 관여도 등으로 대표되는 사용자 행위요인과 시스템의 정교함과 유연성으로 대표되는 시스템만족요인으로 나타났다. 마지막으로 마케팅의사결정지원시스템의 채택의도에 영향을 미치는 요소와 마케팅의사결정지원시스템의 사용자들의 만족에 영향을 미치는 요소는 본질적으로 다른 것으로 밝혀졌다. 이는 채택의도와 사용자 만족에 영향을 미치는 요소들 중에서 실행요인이나, 시스템만족요인, 사용자 행위요인의 매개적인 역할이 채택의도와 사용자 만족에 각각 다른 영향을 미치고 있기 때문인 것으로 밝혀졌다.

• Journal of the Korean GEO-environmental Society
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• v.19 no.10
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• pp.21-26
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• 2018

Soil-water characteristic curve, which is called soil retention curve, is required to explore water flows in unsaturated soils, relative permeability of water in multi-phase fluids flow, and change to stiffness and volume of soils. Thus, the understanding of soil-water characteristic curves of soils help us explore the behavior of soils inclduing fluids. Biopolymers are environmental-friendly materials, which can be completely degraded by microbes and have been believed not to affect the nature. Thus, various biopolymers such as deacetylated power, polyethylene oxide, xanthan gum, alginic acid sodium salt, and polyacrylic acid have been studies for the application to soil remediation, soil improvement, and enhanced oil recovery. PAA (polyacrylic acid) is one of biopolymers, which have shown a great effect in enhanced oil recovery as well as soil remediation because of the improvement of water-flood performance by mobility control. The study on soil-water characteristic curves of sandy soils containing PAA (polyacrylic acid) has been conducted through experimentations and theoretical models. The results show that both capillary entry pressure and residual water saturation dramatically increase according to the increased concentration of PAA (polyacrylic acid). Also, soil-water characteristic curves by theoretical models are quite well consistent with the results by experimental studies. Thus, soil-water characteristic curves of sandy soils containing biopolymers such as PAA (polyacrylic acid) can be estimated using fitting parameters for the theoretical model.

• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.391-401
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• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and the results are compared to the existing experimental data. Steady two-dimensional flow in a collapsible channel with initial tension is also simulated and the results are compared with numerical solutions from the literature. Computational results show that as cross-sectional area decreases with the reduction in downstream pressure, flow rate increases and reaches the maximum when the speed index (mean velocity divided by wave speed) is near the unity at the point of minimum cross-section area, indicating the flow limitation or choking (flow speed equals wave speed) in one-dimensional studies. for further reductions in downstream pressure, flow rate decreases. The flow limitation or choking consist of the main reasons of waterfall effect which occurs in the airways, capillaries of lung, and other veins. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is 2, the area throat is located near the downstream end. As this ratio is increased to 3, the constriction moves to the upstream end of the tube.

• Journal of Fashion Business
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• v.10 no.2
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• pp.83-98
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• 2006

With the subjects of male consumers in their 20s to 40s living in the Ningbo area in Zhejiang Province, this study aims to investigate into the reality of their purchase attitude and size fitness of ready-made suits. The results are as follows; Looking into their demographic characteristics, 70.6% of the subjects were twenties, 60.6% were single, and educational career stood in the order of college, middle school, and high school graduation. They were largely absorbed in free trade, followed by teaching, commerce and service industry. 59.6% of them were Zhejiang Province belongs. One to two thousand yuan was the greatest portion of their monthly income. As for their purchase attitude of ready-made suits, they thought higher of material, quality, activity, and solidity than of design. They preferred to buy clothes at a department store. There was significant difference between purchase frequency and purchase price according to monthly income and jobs. Concerning brand recognition, the Chinese subjects favored "Youngor." Though Korea's brands were very lowly recognized, Korean products received really high recognition. Compared with China's brands, they found foreign brands excellent in design, followed by material/matter, wear, and sewing. As to their physical satisfaction and the size fitness of clothes, most subjects felt happy with their sizes. Trousers and jackets were among the unfitting suit items, while the girth of waist was the least satisfactory size. Therefore, in order to raise the market occupation rate of Korean suit goods in China, more aggressive marketing strategies are required to utilize the current Korean-style entertainment and maximize concerning brand images. In particular, outstanding products in consideration of prices should be made through the proper patternmaking to reflect the body types of the Chinese.

• Computational Structural Engineering
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• v.2 no.1
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• pp.65-70
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• 1989

An analytical study was conducted using the Galerkin technique to determine behaviour of thin fibrereinforced and laminated composite pipes under soil pressure. Geometric nonlinearity and material linearity have been assumed. It is assumed that vertical and lateral soil pressure are proportional to the depth and lateral displacement of the pipe respectively. It is also assumed that radial shear stress is negligible because the ratio of thickness to the radius of pipe is very small. The above results are verified by the finite element analysis.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.135-142
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• 2020

In the case of a concrete structure, vibration problems occur under various conditions because of its low damping performance. To solve this problem, a study on the high damping performance of the polymer concrete with hybrid damper has recently been increased. Since water is not used in polymer concrete, the curing time is short. Also, the physical properties and dynamic properties of polymer concrete are quite excellent. So polymer concrete is widely expected to be used for structural materials. The hybrid damper is the structural system that consists of steel balls and viscous fluid inside the pipe which is embedded in polymer concrete. It can reduce the structural vibrations through the energy dissipation mechanism of viscous fluid and steel balls. In this study, the physical and dynamic properties of polymer concrete with hybrid damper were compared with ordinary concrete. As a result, the elasticity coefficient and the strength of the polymer concrete with hybrid damper were so much excellent. In particular, the tensile strength was 6.5 to 10 times higher than ordinary concrete. The frequency response function and damping ratio were also compared. As a result, the dynamic Stiffness of the polymer concrete was 25% greater than that of ordinary concrete. The damping ratio of the polymer concrete was approximately 3 times higher than that of ordinary concrete. Although the dynamic stiffness of the hybrid damper showed similar tendency, the damping ratio was 3.5 times higher than that of ordinary concrete. Therefore, the polymer concrete with hybrid damper was superior to ordinary concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.1
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• pp.39-45
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• 2024

Seismic safety of expansion joints for piping systems has been underscored by water pipe ruptures and leaks resulting from the Gyeongju and Pohang earthquakes. Metal bellows in piping systems are applied to prevent damage from earthquakes and road subsidence in soft ground. Designed with a series of corrugated segments called convolutions, metal bellows exhibit flexibility to accommodate displacements. Several studies have examined variations in convolution shapes and layers based on the intended performance to be evaluated. Nonetheless, the research on the seismic performance of complex bellows having multiple corrugation heights is limited. In this study, monotonic loading tests, cyclic loading tests, and fatigue tests were conducted to evaluate the shear performance in seismic conditions, of metal bellows with variable convolution heights. Single- and triple-layer bellows were considered for the experimentation. The results reveal that triple-layer bellows exhibit larger maximum deformation and fatigue life than single-layer bellows. However, the high stiffness of triple-layer bellows in resisting internal pressure poses certain disadvantages. The convolutions are less flexible at lower displacements and experience leakage at a rate related to the variable height of the convolutions in certain conditions. At lower deformation rates, the fatigue life is rated higher as the number of layers increase. It converges to a similar fatigue life at higher deformation rates.