• 한국물환경학회지
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• 제29권6호
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• pp.808-812
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• 2013

A new type of microbial fuel cell (MFC) with anaerobic membrane filter was designed to produce bioelectricity and to treat domestic sewage at relatively high organic loading rate (OLR) of $6.25kgCOD/m^3/day$ and short hydraulic retention time (HRT) of 1.9 h. A following aeration system was applied to ensure effluent water quality in continuous operation. Glucose was supplemented to increase the influent concentration of domestic sewage. Influent substrate of 95% was removed via the MFC and following aeration system and the corresponding maximum power density was $25.6mW/m^3$. External resistor of $200{\Omega}$ and air-cathode system contributed better MFC performance comparing to $2000{\Omega}$ and dissolved oxygen as a catholyte.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.1180-1183
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• 1997

This paper addresses the issues of the external system modeling and power system state estimation with the external model. A set of significant measurements is identified in the external system based on their sensitivities on the tie-lines. These measurement data are transferred to internal system and updated in real-time. The state estimator is run for different loading conditions by using the actual values for the internal system and selected significant external system measurements while keeping the rest of the external system measurements at their base case values. Simulation results are presented using the IEEE 118 bus system as an example.

• 한국지반신소재학회논문집
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• 제2권2호
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• pp.13-24
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• 2003

본 논문에서는 유한요소해석을 통해 기초지반의 강성과 상재하중이 블록식 보강토 옹벽에 미치는 영향을 고찰한 내용을 다루었다. 이를 위해 기초지반의 강성과 상재하중의 위치를 변화시키며 매개변수 연구를 수행하였으며 해석결과에서는 벽체의 변위와 보강재의 유발인장력은 기초지반의 강성이 감소함에 따라 증가하는 것으로 나타났다. 한편, 해석결과에 따르면 현재 설계기준에서 적용되고 있는 상재하중 처리 방법은 경우에 따라서 상재하중의 영향을 지나치게 과대평가 하는 것으로 나타났으며 상재하중이 보강영역에 근접하여 작용할 경우 외적안정성 검토시 주의를 요하는 것으로 나타났다. 본 논문에서는 본 연구를 통해 얻어진 결과가 실무적 측면에서 의미하는 바를 심도 있게 고찰하였다.

• Wind and Structures
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• 제29권4호
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• pp.235-246
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• 2019

Wind loading is one of important loadings that should be considered in the design of large hyperbolic natural-draught cooling towers. Both external and internal surfaces of cooling tower are under the action of wind loading for cooling circulating water. In the previous studies, the wind loads on the external surface attracted concernedly attention, while the study on the internal surface was relatively ware. In the present study, the wind pressure on the internal surface of a 220 m high cooling tower is measured through wind tunnel testing, and the effect of ventilation rate of the packing layer on internal pressure is a major concern. The characteristics of internal wind pressure distribution and its effect on wind-induced responses calculated by finite element method are investigated. The results indicate that the wind loading on internal surface of the cooling tower behaves remarkable three-dimensional effect, and the pressure coefficient varies along both of height and circumferential directions. The non-uniformity is particularly strong during the construction stage. Analysis results of the effect of internal pressure on wind-induced responses show that the size and distribution characteristics of internal pressure will have some influence on wind-induced response, however, the outer pressure plays a dominant role in the wind-induced response of cooling tower, and the contribution of internal pressure to the response is small.

• KCI Concrete Journal
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• 제12권2호
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• pp.45-54
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• 2000

Precast R.C. slabs are being used widely for the construction of bridge structures due to their simplicity in construction processes. However, one of the disadvantages in precast R.C. slabs is the existence of transverse joints between two precast slabs. The transverse joints are structurally fragile and the task of strengthening the joints is difficult one due to their structural discontinuity. The aim of this study was to improve the behavior of transverse joints between precast R.C. slabs by introducing prestress with external cables. Three steel-concrete composite bridge specimens, which were prestressed with the external cables anchored on steel girders, were fabricated in the laboratory. Both pretension and post-tension methods were applied to introduce prestressing on the concrete slab with a straight tendon arrangement. Static tests were conducted at service load and ultimate load test was performed to evaluate punching shear capacity of the transverse joint. In this paper, two prestressing methods were tested and their effects were evaluated with respect to the elastic behavior and ultimate loading capacity of the transverse joints.

• Geomechanics and Engineering
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• 제16권2호
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• pp.113-124
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• 2018

Under repeated loading, the residual stresses within the subgrade and subsoil can accelerate the deformation of the road structures. In this paper, a series of laboratory cyclic loading model tests and small-scale model tests were conducted to investigate the dynamic stress response within soils under different loading conditions. The experimental results showed that a dynamic stress accumulation effect occurred if the soil showed cumulative deformation: (1) the residual stress increased and accumulated with an increasing number of loading cycles, and (2) the residual stress was superimposed on the stress response of the subsequent loading cycles, inducing a greater peak stress response. There are two conditions that must be met for the dynamic stress accumulation effect to occur. A threshold state exists only if the external load exceeds the cyclic threshold stress. Then, the stress accumulation effect occurs. A higher loading frequency results in a higher rate of increase for the residual stress. In addition to the superposition of the increasing residual stress, soil densification might contribute to the increasing peak stress during cyclic loading. An increase in soil stiffness and a decrease in dissipative energy induce a greater stress transmission within the material.

• 한국지반환경공학회 논문집
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• 제9권6호
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• pp.71-79
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• 2008

다양한 환경의 지반 속에 매설되어 있는 지하 매설관은 지반과 외부 하중의 종류 뿐만 아니라 하중 작용시간, 작용조건 등에 따라 다양한 거동특성을 보인다. 또한 같은 지역 내에서도 환경조건이 다르기 때문에 현재의 이론적 해석방법으로는 매설관의 응력상태나 거동상태를 정확히 예측하는 데는 현실적으로 많은 어려움이 따른다. 특히 예측치 않은 하중발생 상황이나 차량 및 열차 하중에 대한 매설관의 영향 평가는 국내의 경우 아직 미진한 상황이다. 이에 본 연구에서는 대형토조실험과 수치해석을 통하여 매설깊이에 대한 영향 평가, 지반 교란의 영향 평가를 실시하였다. 또한 열차하중과 같은 동적하중에 대한 매설관의 영향 평가를 위하여 수치해석을 통해 열차이동하중에 대한 영향 평가를 수행하였다.

• 한국항공우주학회지
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• 제40권10호
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• pp.910-915
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• 2012

본 논문에서는 탐색개발중인 전투기에 탑재할 EOTS의 운용유지 소요기술 개발비용에 대한 기술적 특성을 평가 분석하여 탑재방식을 연구하였다. 15개 항의 운용성 측면의 평가 결과, 내장형은 스텔스 기능의 장점이 있으며, 외장형은 장 탈착성, 접근성, 현 운용 항공기와의 호환 활용성 및 무장 교체 가능성 등의 장점이 있다고 평가되었다. 17개 항의 기술 및 개발 비용 평가 결과, 소형 경량화 및 소모 전력에서는 내장형 탑재 방식이 유리하지만, 국내 기술의 적용에 의한 비용 절감과 성능 달성을 위한 기술 안정성 측면에서는 외장형 탑재방식이 우수하다고 평가되었다.

• Journal of Biosystems Engineering
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• 제30권5호
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• pp.274-279
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• 2005

Impact is one of the major cause of damage to fruits druing varios processes from the production on the farm to the consumer. The tissue of fruits are ruptured in a very short period time less than 10ms by impact loading. Mechanical behavior of fruits under impact loading can be analyzed better with high speed sampling data acquisition system and one of them is a digital storage oscilloscope. A impact test system was developed to test the physical properties of fruits including apple, pear, and peach which may lead to a better understanding of the physical laws. The test system consisted of a digital storage oscilloscope and simple mechanism which can apply impact force to fresh produce. Rupture force, energy, and deffrmation were measured at the five levels of drop heights from 4 to 24cm fur each internal and external tissues. Rupture forces for apple and pear were in the range of 72.9 to 87.7 N and 70.8 to 84.1 N for external and internal tissues, respectively. Rupture forces far peach external tissues were in the range of 43.4 to 65.0 N.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.779-782
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• 1999

This study was carried out to estimate the effects of the loading conditions on the corrosion of reinforcing bars and permeation of chloride ion. The permeation of chlorides depends not only on the transfer properties in concrete but also on the load applied in the case of reinforced concrete structures. Recent studies reported that the loading conditions affected the corrosion rate of the reinforcing bars under existence of an external current supply. But it was not reported that loading conditions affected corrosion of reinforcing bar caused by the characteristics of permeation and the process of cracking. In this experiment, it was shown that the corrosion of reinforcing bars and the characteristics of permeating were greatly affected by the loading conditions.