• 전기학회논문지
• /
• 제63권7호
• /
• pp.916-923
• /
• 2014

This paper proposes a low-cost switched-mode rectifier (SMR) for a small-scale wind turbine with a permanent magnet synchronous generator (PMSG) system. Also, a sensorless Fuzzy MPPT control is realized by the proposed system. In the PMSG system with the SMR, the synchronous impedance can be replaced as the input inductor of a boost converter. Moreover, the sensorless MPPT control using the Fuzzy technique is carried out by the duty-ratio regulation of the SMR. The relation between the generating power and the duty-ratio is ruled by the chain rule. The wind turbine model is implemented by the squirrel cage induction motor and generated the variable torque when the generator speed is varied. To verify the performance of the proposed system, simulation and experimental results are executed.

• 대한기계학회논문집B
• /
• 제30권3호
• /
• pp.246-254
• /
• 2006

The present study shows the experimental and modeling results of the cooling system using nanofludic loop thermosyphon. the experimental results show that nanofluid is not effective for small scale cooling system. The heat transfer performance is not much improved with the current small scale loop system comparing with the convectional water based loop system. In this study, various effects of nanofluids such as the concentration, the md of particle, host fluid, and heat capacity and so on were investigated. With nanofluid as the working fluid, the flow instability was improved at a certain concentration.

• 한국재난정보학회 논문집
• /
• 제18권2호
• /
• pp.395-404
• /
• 2022

연구목적:소규모 건축현장은 체계적인 안전관리활동이 미흡하고 건설현장의 특성상 외부환경의 요인으로 생산구조가 복합적이고 건설장비의 위험성 등으로 인해 산업재해의 가능성이 매우 높은 실정이다. 소규모 건설현장의 재해예방을 위한 위험요인을 도출하고 재해를 줄일 수 있는 실무적인 위험성평가의 기법 중 체크리스트 방법을 제안하고자 한다. 연구방법: 문헌조사와 재해사례를 분석하여 위험요인을 도출하여 위험요인 항목을 중심으로 소규모 건설현장에 적합하고 효율적인 위험성평가의 체크리스트를 위한 세부작업을 분류하였다. 연구결과:위험요인을 6개의 대분류로 구분하고 실질적인 작업공종을 중심으로 29개의 세부공종을 분류 하였으며 이에 따른 세부작업을 80개로 구분하였다. 결론:소규모 건축현장에 적합한 위험요인을 분류체계에 따라 정리함으로써 건설현장에 부족한 전문성을 보완할 수 있고 보다 쉽게 위험요인을 도출하여 안전대책수립을 통한 재해감소를 기대할 수 있을 것으로 보인다.

• 정보교육학회논문지
• /
• 제6권2호
• /
• pp.154-162
• /
• 2002

소인수학급에서는 교육과정의 획일적인 운영으로 인하여 아동들은 점점 학습에 흥미를 잃어가고, 학습활동에도 소극적인 태도로 임하는 문제점이 있다. 협동수업에 관한 WBI 모형들이 많이 연구되고 설계되었지만, 소인수학급의 특성에 맞는 WBI 협동수업 모델에 대한 연구는 미흡한 실정이다. 본 연구에서는 소인수 학급간의 연계를 통해 교사가 수업에 참여하며, 장기적으로 학생들의 학습태도에 변화를 줄 수 있는 WWW를 기반으로 한 협동수업 모델인 WIEZ를 설계하여 구현하였다. 현재 WIEZ는 경남지역의 3개 학교를 대상으로 교사들이 이 시스템 내에서 수업을 설계하고 학생들이 모둠을 나누어 참여하는 형식으로 시험 운영 중에 있다.

• 한국전산구조공학회논문집
• /
• 제19권3호
• /
• pp.233-238
• /
• 2006

이 논문에서는 소형 다층 구조물의 진동제어에 적용하기 위한 복합모드의 자기유변유체(MR) 감쇠기를 개발하였다. 우선, 도식적으로 전단, 유동, 복합모드 MR감쇠기의 형태를 설계조건과 함께 표현하였고, 각각의 모드에 대하여 자기장에 따른 감쇠력을 예측하기 위한 해석모델을 유도하였다. 다음으로 적당한 크기의 복합모드 MR감쇠기를 제작하고 자기장에 따른 감쇠특성을 시간영역에서 평가하였다. 마지막으로 지진하중을 받는 소형구조물에 제작된 MR감쇠기가 준능동 제어기로 제어하였을 때의 성능을 수치적으로 평가하였다.

• 한국압력기기공학회 논문집
• /
• 제7권2호
• /
• pp.1-6
• /
• 2011

PHE(Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR(Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established a small-scale gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype made of Hastelloy-X to be tested in the small-scale gas loop. Results from the elastic structural analysis on the PHE prototype were reported in the previous article. In order to investigate the macroscopic structural characteristics and behavior of the PHE prototype under the test condition of the small-scale gas loop far more in detail, elastic-plastic high-temperature structural-analysis of the PHE prototype was carried out in this study.

• Journal of Biosystems Engineering
• /
• 제23권3호
• /
• pp.245-252
• /
• 1998

The structural characteristics of a small scale rice polisher was analyzed to improve its performance. Spraying characteristic of nozzles used for rice polishing was also analyzed by a machine vision system. The internal pressure of the polishing chamber was measured according to outlet resistance, water spraying, and roller shaft speed. In addition, the performance of the rice polisher was evaluated to improve it in the basis of internal pressure in polishing chamber, whiteness, and broken rice ratio of clean rice according to the operating conditions. Actual nozzle discharge rate and drop size were 125 cc/min and 86~97 ${\mu}{\textrm}{m}$, respectively. In the case of water spraying on rices, the internal pressure showed 4.9~9.8N/$\textrm{cm}^2$ increase. broken rice ratio decreased, and there was no difference in whiteness. The internal pressure inueased up to two times with the increase of the outlet resistance. Also, the pressure at the upper part of screen was one and half times as high as the pressure at the lower part. In the case of water spraying rate of 150 cc/min, the roller shaft speed of 850 rpm resulted in no difference in whiteness and decrease of 0.3% in broken rice ratio, comparing to the roller shaft speed of 950 rpm.

• 한국농업기계학회:학술대회논문집
• /
• 한국농업기계학회 1998년도 하계 학술대회 논문집
• /
• pp.206-216
• /
• 1998

The structural characteristics of small scale rice polisher was analyzed to improve its performance. Spraying characteristic of nozzles used for rice polishing was also analyzed by a machine vision system. The internal pressure of the polishing chamber was measured according to outlet resistance, water spraying , and roller shaft speed. In addition , the performance of the rice polisher was evaluated to improve it in the basis of internal pressure in polishing chamber, whiteness , and broken rice ratio of clean rice according to the operating conditions. Actual nozzle discharge rate and drop size were 125cc/min and 86.97㎛, respectively. In the case of water spraying on rices, the internal pressure showed 4.9-9.8N/㎠ increase, broken rice ration decreased , and there was no difference in whiteness . The internal pressure increased up to two time with the increase of the outlet resistance. Also, the pressure at the upper part of screen was one and half times as high as the pressure at the lower part. In the case of water spraying rate of 150 cc/min, the roller shaft speed of 850 rpm resulted in no difference in whiteness and decrease of 0.3%in broken rice ratio, comparing to the roller shaft speed of 950 rpm.

• Fisheries and Aquatic Sciences
• /
• 제18권2호
• /
• pp.221-227
• /
• 2015

We analyzed the small-scale purse-seine gear that is used along the North Coast of Java, Indonesia, using computer-aided tools to modify the gear. Data from the middle position of the leadline showed that the maximum depth reached by the net was 30 m. A similar result was also calculated. According to the calculated result, the mean sinking speed of the current gear at the middle position of the leadline was 0.13 m/s, and the maximum tension during pursing was 1,794 kgf. The best sinking performance was found in modified gear that used a 30.3 mm mesh knotless polyester net. The maximum depth reached by the net was 38 m, and mean sinking speed was 0.16 m/s at the middle position of the leadline. The maximum tension during pursing was 1,044 kgf. Independent sample t-test results show that the mean sinking depth and sinking speed in the simulated and measured results did not differ (P > 0.05). These results are expected to improve the efficiency and selectivity of small-scale purse seine gear.

• Advances in nano research
• /
• 제13권4호
• /
• pp.393-406
• /
• 2022

In the present article, functionally graded small-scaled plates based on modified strain gradient theory (MSGT) are studied for analyzing the nonlinear bending and post-buckling responses. Von-Karman's assumptions are applied to incorporate geometric nonlinearity and the first-order shear deformation theory is used to model the plates. Modified strain gradient theory includes three length scale parameters and is reduced to the modified couple stress theory (MCST) and the classical theory (CT) if two or all three length scale parameters become zero, respectively. The Ritz method with Legendre polynomials are used to approximate the unknown displacement fields. The solution is found by the minimization of the total potential energy and the well-known Newton-Raphson technique is used to solve the nonlinear system of equations. In addition, numerical results for the functionally graded small-scaled plates are obtained and the effects of different boundary conditions, material gradient index, thickness to length scale parameter and length to thickness ratio of the plates on nonlinear bending and post-buckling responses are investigated and discussed.