• 한국콘텐츠학회논문지
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• 제9권1호
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• pp.89-97
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• 2009

어플리케이션의 데이터베이스 시스템 사용이 날로 증가하면서, 사용자 급증에 따른 데이터베이스 시스템에 동시접속 하는 커넥션 처리 방법에 있어 중요성이 부각되고 있다. 이러한 데이터베이스의 커넥션을 효과적으로 처리하기 위해 데이터베이스 커넥션 풀이 도입되었으나, 동시접속 사용자가 증가하는 형태에 따른 커넥션 처리는 미비한 실정이다. 본 논문에서는 기존의 커넥션 풀 아키텍처를 개선하기 위하여 주 커넥션 풀 이외에 보조 커넥션 풀을 추가하였다. 또한 두 커넥션 풀의 연결을 관리하기 위하여 커넥션 풀 브로커를 정의하였다. 커넥션 풀 브로커는 주 커넥션 풀이 한계에 도달하였을 때 보조커넥션 풀로 연결을 제어한다. 실험을 통하여 동시접속 사용자가 급격히 증가하는 형태의 요청처리에 있어, 기존 데이터베이스 커넥션 풀 구조와 비교해서 응답시간의 향상된 결과를 확인하였다.

• 한국환경복원기술학회지
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• 제17권2호
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• pp.61-71
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• 2014

A river fishway is a hydraulic structure enabling fish to overcome stream obstructions such as dams and weirs. The main aim of this paper is to investigate the collectibility of upstream-migrating fishes and hydraulic problems in pool-and-weir type fishway which has been established for upstream-migration at Namgang weir in the downstream of Namgang dam, and to grope for improvement measures which pool-and-weir type fishway can be switched to pool-and-partial weir type fishway through hydraulic field experiment. Exsisting fishway had problems which upstream-migrating fishes can not take a rest due to the seiche and vortex phenomena in pools and migrate to upstream because of height difference in entrance pool. In order to prevent hydraulically the seiche and vortex phenomena and establish rest area for fishes in each pool, we carried out hydraulic field experiments. In the fishway, it was to improve pool-and-weir into pool-and-partil weir, to decrease the height difference in entrance pool, and to reduce oriffice velocity of each pool. Also, we investigated fishes collectibility of after improving fishway for 6 days in September 2013. To resolve chronic problems(seiche-vortex phenomena and rest area for fishes), as weirs were remodeled into partial weir only which central part of weirs was part of non-overflow weir, we confirmed results that pool-and-weir type fishway could be switched to efficient pool-and-partial weir type fishway with relatively simple construction and low cost. Type-B which has the closed oriffices and the parts of non-overflow has the ideal conditions, but this conditions are limited to fishway of Namgang weir used in this study. Representative Ice-habor type fishway is pool-and-partial weir type fishway which has together parts of overflow and oriffices, and has excellent ability of upstream-migration. To switch from pool-and-weir type fishway to pool-and-partial weir type fishway, the size of oriffice has to be regulated by the discharge of fishway and the dimension on parts of non-overflow and overflow in weirs. Entrance pool is important facility which upstream-migrating fishes have to not only be collect but also charge with energy. In this study, entrance-pool is temporary and roughly-built, but fishes gather together more than the case of no entrance-pool. In the case of fishway which was protruded to downstream, as entrance of fishway turns toward or parallels to weir, the collectibility of fishway was excellent by attraction water.

• 한국유체기계학회 논문집
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• 제2권4호
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• pp.40-47
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• 1999

A hot water layer (HWL hereinafter) was installed at the depth of 1.2 m from the pool surface to reduce the radiation level at the pool top. After the HWL system was improved by the replacement of the filter with the Ion Exchanger to capture the Na-24, to purify the pool water of HWL and finally to reduce the radiation at the pool top. It was confirmed by the performance test of the pump and the measurement of the pressure difference through the Ion Exchanger and the strainer, that the flow characteristics of HWL system was not adversely affected after the system modification. Also the flow analysis using the pressure loss coefficients of the Ion Exchanger and strainer, calculated by the Darcy formula, could predict the flow variations by pressure changes within $10\%$ error in comparison with the field test results. It was also confirmed that HWL was maintained with the depth of 1.2 m from the pool surface because each electric water heater was electrically and thermodynamically maintained at 30 kW and the temperature of HWL was maintained with $5^{\circ}C$ higher temperature than that of pool water. Finally, it was confirmed that the pool top radiation was saturated and stabilized below 10000 nG/hr within 24 hours as the ion exchanger captured the main nucleus, Na-24 and purified the pool water of HWL.

• 한국재난정보학회 논문집
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• 제11권1호
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• pp.55-62
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• 2015

본 연구에서는 풍수해보험요율 산정을 위한 전국단위의 내수침수해석 방안을 제시하였다. 제시된 수정 Level-Pool침수해석은 실제 침수피해지역을 반영하고 내수침수 발생 범위를 한정하기 위해 도시계획 용도지역을 고려하였다. 수정 Level-Pool침수해석에 의한 내수침수지역과 풍수해저감종합계획의 내수재해위험지구와 비교를 통해 적용성을 검토한 결과 기존 Level-Pool침수해석과 비교하여 내수침수지역이 내수재해위험지구를 더 정확하게 재현하는 것으로 나타났다. 따라서 전국단위의 내수침수위험지역을 해석함에 있어서는 본 연구에서 제안한 수정 Level-Pool침수해석이 활용 가능할 것으로 판단된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.531-536
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• 1992

In GMA welding processes, monitoring and control of weld quality are extremely difficult problems. This paper describes a neural network-based method for monitoring and control of weld pool sizes. First, weld pool sizes are estimated via a neural estimator using multi-point surface temperatures, which are strongly related to the formation of weld pool, and then controlled using the estimated pool sizes. Two types of controllers using the pool size estimator are designed and tested. To evaluate the performance of the designed controllers, a series of simulation studies was performed.

• 한국화재소방학회논문지
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• 제11권1호
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• pp.55-64
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• 1997

Pool fire는 본격적인 화재연구의 시작과 더불어 그 구조 및 특성에 대한 연구가 지속적으로 수행되어 왔다. Pool fire는 복잡하고 취급하기 어려운 화재의 제문제들을 비교적 간단하게 다룰수 있게 하면서도 현실과 괴리되지 않는 형태를 가지는 가장 기본적인 형태의 화재로, 학문적 측면뿐 아니라 응용측면에서도 매우 유용한 결과 및 단서를 제공하여 왔다. 따라서, 본고에서는 pool fire의 특성을 화염기저(flame base)부근과 플륨(plume)부근으로 나누어 그 동안 발표되었던 연구결과를 정리하고, 화재 시뮬레이션을 위한 zone 모델기법의 가장 중요한 부분의 하나인 연기량 산정과 플륨해석이 어떤 형태로 연결되는 지를 설명하고자 한다.

• 대한기계학회논문집B
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• 제28권10호
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• pp.1202-1209
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• 2004

In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge and descends at the center of the weld pool if d$\sigma$/dT is dominantly negative. It is shown that the predicted weld pool width and depth with moving free surface are a little greater than those with flat weld pool surface. It is also believed that the weld pool surface oscillation during the melting process augments convective heat transfer rate in the weld pool. The present analysis with moving free surface should be considered when We number is very small compared to 1.0 since the deformation of the weld pool surface is noticeable as We number decreases.

• Nuclear Engineering and Technology
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• 제48권4호
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• pp.1015-1021
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• 2016

Structures, systems, and components (SSCs) important to safety of nuclear facilities shall be designed, fabricated, erected, and tested to quality standards commensurate with the importance of the safety functions. Although SSC classification guidelines for nuclear power plants have been well established and applied, those for research reactors have been only recently established by the International Atomic Energy Agency (IAEA). Korea has operated a pool-type research reactor (the High Flux Advanced Neutron Application Reactor) and has recently exported another pool-type reactor (Jordan Research and Training Reactor), which is being built in Jordan. Korea also has a plan to build one more pool-type reactor, the Kijang Research Reactor, in Kijang, Busan. The safety classification of SSCs for pool-type research reactors is proposed in this paper based on the IAEA methodology. The proposal recommends that the SSCs of pool-type research reactors be categorized and classified on basis of their safety functions and safety significance. Because the SSCs in pool-type research reactors are not the pressure-retaining components, codes and standards for design of the SSCs following the safety classification can be selected in a graded approach.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.307-313
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• 2002

This paper describes a weld pool monitoring technique, which is based on the weld pool image analysis. The proposed image analysis algorithm uses machine vision techniques to extract geometrical information from the weld pool image such as maximum weld pool width, gap width and misalignment between the joint longitudinal axis and the welding wire. These can be related to the welding parameters (welding voltage and current, wire feed speed and standoff) to produce control actions necessary to ensure that the required weld quality will be achieved. The experiments have shown that the algorithm is able to produce good estimates of the weld pool geometry; however, the adjustment of the camera parameters affects the image quality and, consequently, has a great influence over the estimation.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2204-2220
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• 2020

An open-pool type research reactor is designed and operated considering the accessibility around the pool top area to enhance the reactor utilization. The reactor structure assembly is placed at the bottom of the pool and filled with water as a primary coolant for the core cooling and radiation shielding. Most radioactive materials are generated from the fuel assemblies in the reactor core and circulated with the primary coolant. If the primary coolant goes up to the pool surface, the radiation level increases around the working area near the top of the pool. Hence, the hot water layer is designed and formed at the upper part of the pool to suppress the rising of the primary coolant to the pool surface. The temperature gradient is established from the hot water layer to the primary coolant. As this temperature gradient suppresses the circulation of the primary coolant at the upper region of the pool, the radioactive primary coolant rising up directly to the pool surface is minimized. Water mixing between these layers is reduced because the hot water layer is formed above the primary coolant with a higher temperature. The radiation level above the pool surface area is maintained as low as reasonably achievable since the radioactive materials in the primary coolant are trapped under the hot water layer. The key to maintaining the stable hot water layer and keeping the radiation level low on the pool surface is to have a stable flow of the primary coolant. In the research reactor with a downward core flow, the primary coolant is dumped into the reactor pool and goes to the reactor core through the flow guide structure. Flow fields of the primary coolant at the lower region of the reactor pool are largely affected by the dumped primary coolant. Simple, circular, and duct type discharge headers are designed to control the flow fields and make the primary coolant flow stable in the reactor pool. In this research, flow fields of the primary coolant and hot water layer are numerically simulated in the reactor pool. The heat transfer rate, temperature, and velocity fields are taken into consideration to determine the formation of the stable hot water layer and primary coolant flow. The bulk Richardson number is used to evaluate the stability of the flow field. A duct type discharge header is finally chosen to dump the primary coolant into the reactor pool. The bulk Richardson number should be higher than 2.7 and the temperature of the hot water layer should be 1 ℃ higher than the temperature of the primary coolant to maintain the stability of the stratified thermal layer.