• Computers and Concrete
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• 제10권5호
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• pp.469-487
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• 2012

This paper presents a study on the behaviour of the joints of segmental concrete bridges with external prestressing, focusing on the structural response of dry non-epoxied joints with shear keys. A Finite Element joint model to study such structures is validated modelling eight concrete panel tests. The most important feature of this model is that it has been validated with experimental tests on concrete panels which were specifically designed to fail in shear. Interface elements are used to reproduce the non linear behaviour of the joint and parameters deduced from the tests are used to define the constitutive law of these elements. This joint model is of great importance because it will permit the development of a structural model that faithfully reproduces the behaviour of these structures under combined flexure and shear and the study of its global behaviour after the opening of the joints. Interesting conclusions about the behaviour of the dry joints, about the contribution of the different mechanisms transferring shear (friction and cohesion) and about the shear stress distribution in the joint have been reached.

• 동력기계공학회지
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• 제19권3호
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• pp.36-41
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• 2015

The true north-finding equipment utilizing gyro sensor is used for INS(Inertial Navigation System) and has an increasing preference for gyro compass system due to compact size, lightening, low power and price. The purpose of this experiment is to research gyro compass system providing high performance in the field of manned or unmanned gyro compass system which proposes the accuracy of 1% utilizing experimented equipment at true north of the earth. Unlike the conventional system, the proposed gyro sensor system indicates to be applied in the various and specific equipment using multiple technique and method.

• 한국물환경학회지
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• 제22권6호
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• pp.1130-1136
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• 2006

This work elucidates the effects of pretreatment of the sewage sludge from wastewater treatment plant by microwave irradiation on elutriated acid fermentation. These experiments typically fell into two process; pretreatment as microwave irradiation and elutriated acid fermentation for hydrolysis and acidification as main process of primary sludge. The results of maximum solubilization rate of B, D primary and secondary sludge were 0.042, 0.086 and 0.15 gSCODprod./gICODin and the optimum irradiation time of microwave on 2,450 MHz and 900 W were 5 min. for primary sludge and 7 min. for secondary sludge. From batch tests on elutriated acid fermentation that was used the pretreated primary sludge as microwave, the optimum pH and HRT (hydraulic retention time) were 7 and 5 days at $35^{\circ}C$ condition.

• 한국태양에너지학회 논문집
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• 제32권spc3호
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• pp.275-281
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• 2012

Proton Exchange Membrane Fuel Cells (PEMFC) are the most appropriate for energy source of small robot applications. PEMFC has superior in power density and thermodynamic efficiency as compared with the Direct Methaol Fuel Cell (DMFC). Furthermore, PEMFC has lighter weight and smaller size than DMFC which are very important factors as small robot power system. The most significant factor of mobile robots is weight which relates closely with energy consumption and robot operation. This research tried to find optimum specifications in terms of type, number of cell, active area, cooling method, weight, and size. In order to find optimum 500W PEMFC, six options are designed in this paper and studied to reduce total stack weight by applying new materials and design innovations. However, still remaining problems are thermal management, robot space for energy sources, and soon. For a thermal management, design options need to analysis of Computational Fluid Dynamics (CFD) for determining which option has the improved performance and durability.

• 공업화학
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• 제10권3호
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• pp.415-418
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• 1999

튜브식 양극판과 겔전해액을 사용한 VRLA (valve regulated Iead-acid) 전지에 있어서 양극 활물질 (active material)의 충전 밀도에 따른 충 방전 싸이클 특성을 고찰하였다. VRLA전지에 사용된 양극 활물질의 밀도는 각각 3.2g/mL, 3.4g/mL 및 3.6g/ml 이었다. VRLA전지는 IU 방식 ($I_{max}=0.2C_{10}/10$, 상한 전압 2.40 v/cell)의 충전과, D.O.D 100%/C5의 방전 방법으로 충 방전 싸이클 수명 시험을 실시하였다. 시험은 $25{\pm}1^{\circ}C$의 항온항습기에서 실행하였다. 시험 결과 활물질 밀도별 VRLA전지의 초기 용량은 밀도와 무관하였다. 즉 3.4g/mL에서 가장 우수하였고, 3.6g/mL에서 가장 낮았다. 충 방전 싸이클에서의 특성은 3.6g/mL인 전지는 3.4g/mL와 거의 유사하였고, 3.2g/mL보다는 크게 우수하였다. 또한 VRLA 전지의 수분고갈 및 열화는 양극 활물질의 충전 밀도가 높을수록 적었다. 이상으로 충 방전 싸이클용 VRLA전지의 양극 활물질의 밀도는 3.4~3.6g/mL이 적절한 것으로 판단되었다.

• 센서학회지
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• 제3권1호
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• pp.12-18
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• 1994

본 연구에서는, calorimetric 형 흐름센서 소자를 미세가공된 실리콘 구조상에 제작하고 그 특성을 평가하였다. 기체의 흐름을 통한 냉각효과 및 가열효과를 가열저항을 중심으로 양측에 배열된 두개의 온도센서로 측정하였으며 절연박막 다이아프램을 기판으로 사용하여 열적절연효과를 향상시켰다. 제작된 흐름센서는 $0{\sim}0.25grs/min$의 질소가스의 흐름 범위 내에서, 10V의 브릿지 인가전압에 대해 $0{\sim}378.4mV$의 출력전압을 발생하였으며, 센서가 동작 영역에 이르는 시간은 10초 내외로 나타났다.

• 열처리공학회지
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• 제13권5호
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• pp.330-336
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• 2000

This study deals with the characteristic of refrigerant for heat-treatment deformation control of SM45C steel. The control of heat-treatment deformation must need the progress of production parts for a landing gear. Most of the deformation is occurred on unequal cooling. The unequal cooling is occurred by a property of quenching refrigeration. When a heated metal is deposited in the refrigeration, the cooling speed is so slow in early period of cooling because of occurring a steam-curtain. After more cooling, the steam-curtain is destroyed. In this progress, the cooling speed is very fast. The object of this study is to control the deformation of heat-treatment for landing gear by improving the conditions of quenching. The cooling curves and cooling rates of water, oil and polymer solution are obtained and illustrated. From the characteristics of the quenching refrigerant, the effects of heat-treatments on thermal deformation and fatigue strength are also investigated.

• 대한의용생체공학회:의공학회지
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• 제36권1호
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• pp.1-6
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• 2015

This study aims to design a monolayer cell adsorption apparatus that would help to produce high-quality slides for Liquid-Based Cytology (LBC) of an early cancer diagnosis for human bodies. The LBC collects exfoliated cells of human bodies and spreads the cells on the slides. Through processes of dyeing and cytological examination, the LBC screens for cancers in early stage. In this study, both of a cell suction module and a cell adsorption module, which are the key elements of the monolayer cell adsorption apparatus, were developed, and using those modules, the study set, first, conditions to help both GYN and NON-GYN apply principal cells without de-endothelialization before conducting its own analysis on the utility. As a results, for GYN, apparatus was determined to be able to produce high-quality slides under the condition of 4 and for NON-GYN, the apparatus would come up with other slides of high-quality under the condition of 2. The study carried out a repetitive test on selected conditions and proved 96% of the repetitive success rate. By the results of what has been learned so far, the study presents that the apparatus has a possibility to replace device from South Korea as one of those other currently-applied systems to run the LBC and that the system will also present a new paradigm for cancer diagnosis as it makes a contribution to the improvement in the LBC.

• Journal of Biosystems Engineering
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• 제29권2호
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• pp.131-140
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• 2004

본 연구에서는 배아미, 현미, 가능성쌀들 및 진공을 요하는 식품의 품질을 보존하기 위해서 연속식 자동진공포장기를 국내 최초로 개발하였다. 배아미의 진공포장 성공률은 92.6%이었고, 실패율 7.4%에서 진공포장기 자체에서 불완전 테이핑의 밀봉작업으로 진공이 서서히 풀리는 경우가 5.5%, 그리고 진공하기 전 자동비닐포장기에서 포장시 봉지 윗부분 밀봉이 불완전해 1.9%가 진공이 풀렸다. 이에 개발한 자동진공포장기의 진공포장성공률은 약 94.5%수준이었다. 진공포장기로 진공시간에 따른 진공압력을 측정하였고, 배아미 2, 3, 5 kg를 진공포장하는데 소요되는 시간은 각각 6, 8, 11초이었다. 진공포장으로 처리한 배아미와 진공포장 처리하지 않은 배아미를 각각 3재월간 저장실험하여 백도, 함수율, 과산화물가, 산가를 저장기간별로 분석하였다. 그 결과, 백도는 진공처리가 2 감소, 비처리가 4 감소하였고, 함수율은 진공처리가 0.8%감소, 비처리가 1.3%감소, 과산화물가는 진공처리가 최대 1.89 meq/kg까지 서서히 증가하였고, 비처리가 3.45 meq/kg까지 급속히 증가하였다가 서서히 감소하였다. 산가 역시 진공처리가 최대 0.71 mg/g까지 서서히 증가하였고, 비처리의 경우는 0.98 mg/g까지 급속히 증가하였다. 그리고 현미의 진공포장에서도 산가 및 과산화물가 변화가 배아미 경우와 비슷하였다. 또한 진공포장 제품에 인위적으로 쌀벌레들을 넣은 경우 15일 지나면 산소부족으로 모두 사멸하였다. 따라서 개발한 진공포장기로 진공포장한 경우 배아미 및 현미의 품질을 잘 보존할 수 있었다.

• 한국자기학회지
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• 제5권5호
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• pp.519-523
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• 1995

The Fe-TM-C-N nanocrystalline films (TM : Hf, Zr and Nb) are investigated to examine the relation between microstructure and soft magnetic properties. In these films, as the atomic radius of TM element increases, $P_{N2}$ which was added to get good soft magnetic properties was decreased and the maximum value of the permeability shifted to the high Fe range in the composition diagram. The best soft magnetic properties achieved in these films are : Hc of 0.15 Oe, $\mu_{eff}$ of 7800 (1MHz) and $4{\pi}M_{s}$ of 17.5 kG in Fe-Hf-C-N film ; Hc of 0.06 Oe, $\mu_{eff}$ of 2750 (1MHz) and $4{\pi}M_{s}$ of 16.8 kG in Fe-Zr-C-N film and Hc of 0.31 Oe; $\mu_{eff}$ of 2100 (1MHz) and $4{\pi}M_{s}$ of 15.5 kG in Fe-Nb-C-N film. It was considered that the stronger the bonding force between TM and C(N), the finer TM(C,N) phase is precipitated and therefore, the finer $\alpha$-Fe grains are formed. The effective permeability of the Fe-Zr-C-N films and Fe-Nb-C-N films remains nearly constant up to 10 MHz.