• 한국수소및신에너지학회논문집
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• 제27권1호
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• pp.121-126
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• 2016

Hydraulic performance of a micro-bubble pump has been analyzed by numerical simulation and experimental measurements. Flow recirculation apparatus between the pump inlet and outlet reserviors has been adopted to measure pump performance according to flow conditions sequentially. To analyze three-dimensional flow field in the micro-bubble pump, general analysis code, CFX, is employed. SST turbulence model is employed to estimate the eddy viscosity and compared the pump performance to k-${\varepsilon}$ model. Unstructured grids are used to represent a composite grid system including blade, casing and inlet casing. It is found that the numerical model used in the present study is effective to evaluate the pump performance. From the numerical simulation, low velocity region due to pressure loss is decreased where pump efficiency has maximum value. Detailed flow field inside the micro-bubble pump is also analyzed and compared.

• Computers and Concrete
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• 제11권4호
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• pp.271-289
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• 2013

In this research, a developed microstructural model of cement particles was presented to describe the cement hydration procedure. To simplify the hydration process, the whole hydration was analyzed in a series of sub-steps. In each step, the hydration degree, as well as the microstructural size of the hydration cell, was calculated as a function of the radius of the unreacted cement particles. With the consideration of the water consumption and the reduction of the interfacial area between water and hydration products, the micro-level expressions of the cement hydration kinetics were established. Then the heat released and temperature history of the concrete was carried out with the hydration degree obtained from each sub-steps. The equivalent age method based on the Arrhenius law was introduced in this research. Based on the equivalent age method, a maturity model was applied to describe the evolution of the mechanical properties of the material during the hydration process. The finite element program ANSYS was used to analyze the temperature field in concrete structures. Then thermal stress field was calculated using the elasticity modulus obtained from code formulate. And the risk of thermal cracking was estimated by the comparison of thermal stress and concrete tensile strength.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2885-2890
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• 2011

본 연구에서는 최근 증가하고 있는 대심도역사의 화재위치에 따른 연기확산영향에 대하여 분석하였다. 시뮬레이션모델은 신금호 역사(5호선, 깊이 46m)를 대상으로 하였으며, 화재위치에 따른 연기확산 영향을 분석 하였다. 현장조사 및 실측을 통하여 계측된 실제 역사의 제연팬에 관한 데이터를 화재시뮬레이션 조건으로 적용하였다. 역사전체를 해석 대상으로 하여 총 400만개의 격자를 사용하였으며, 화재위치에 따른 연기확산 영향 비교를 위하여 화재 시나리오를 작성하여 Case별로 화재해석을 수행하였다. 계산 효율을 높이기 위하여 MPI병렬처리기법을 사용하였으며 해석코드는 LES(large eddy simulation) 기법을 주로 사용하는 FDS5 code를 사용하였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4477-4490
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• 2023

Fuel locking mechanisms (FLMs) are essential in upward-flow research reactors to prevent accidental fuel separation from the core during reactor operation. This study presents a novel design concept for a remotely controlled plate-type nuclear fuel locking mechanism. By employing electromagnetic field analysis, we optimized the design of the electromagnet for fuel unlocking, allowing the FLM to adapt to various research reactor core designs, minimizing installation space, and reducing maintenance efforts. Computational flow analysis quantified the drag acting on the fuel assembly caused by coolant upflow. Subsequently, we performed finite element analysis and evaluated the structural integrity of the FLM based on the ASME boiler and pressure vessel (B&PV) code, considering design loads such as dead weight and flow drag. Our findings confirm that the new FLM design provides sufficient margins to withstand the specified loads. We fabricated a prototype comprising the driving part, a simplified moving part, and a dummy fuel assembly. Through basic operational tests on the assembled components, we verified that the manufactured products meet the performance requirements. This remote-controlled micro locking mechanism holds promise in enhancing the safety and efficiency of plate-type nuclear fuel operation in upflow research reactors.

• 한국전산구조공학회논문집
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• 제20권2호
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• pp.95-103
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• 2007

본 논문에서는 포화된 다공성매체에서 파동의 전파속도와 감쇠를 구할 수 있는 해석적 이론해를 유도하여 제시하였다. 이론해의 유도를 위하여 압축성의 고체입자와 간극수를 고려하는 완전 연계 Field모델을 사용하였다. 완전 포화된 다공성 매체의 해석을 위한 공학적인 접근방법이 채택되었으며, 균질 영역에서 1차원 파동의 전파를 위한 이론해가 유도되었다. 본 논문에서 유도한 이론해는 고체입자의 압축성, 간극수의 압축성, 다공성입자의 변형, 공간의 감쇠(Spatial damping) 등을 고려할 수 있어 매우 다양하게 사용될 수 있다. 또한 다양한 지반체에서 두 가지 종류의 파속(Wavespeed)과 감쇠계수를 계산하는데 이용 가능하다. 본 논문에서 제시한 이론해를 전산코드화하여 파동의 전파속도와 감쇠에 대한 파라미터연구를 수행한 결과는 본 연구의 II부에 제시할 예정이다.

• 한국콘텐츠학회논문지
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• 제7권6호
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• pp.185-194
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• 2007

현재 전세계적으로 EPC(Electronic Product Code)의 표준 제정되면서 산업 전반에 영향을 미칠 것으로 기대되는 기술인 RFID(Radio Frequency Identification)기술에 이목이 집중되고 있다. 특히, RFID기술이 지닌 장점을 충분히 활용할 수 있는 분야가 물류분야이다. 때문에 SCM(Supply Chain Management)에서 RFE기술이 적용되면 현재 SCM에서 발생하고 있는 문제해결과 타 경쟁사들과의 차별화를 통해 많은 편익을 조직에게 줄 것이라고 전문가들은 예측하고 있다. 하지만, 새로운 기술에 수용에 대한 조직내부의 반발, 기술에 대한 신뢰 부족, 비용 편익에 대한 실증 분석 부재 등으로 인해 각 조직들은 시험적 도입을 꺼려하고 있다. 따라서 본 연구는 Rogers[32]의 혁신 확산이론을 토대로 선행 연구를 통해 새로운 기술이 조직 내 수용 시 영향을 주는 요인들을 찾아내고 이를 계층분석 방법을 이용하여 각 요인별 가중치를 분석하려 한다. 이를 통해 SCM에서 RFID기술을 도입하려는 조직에 의사결정에 도움을 주고자 한다.

• 한국항해항만학회지
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• 제41권4호
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• pp.173-180
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• 2017

수중음향통신은 다중경로로 인한 신호간의 간섭으로 성능이 열악하므로 채널 부호화의 적용은 필수적이다. 수중 통신에서 데이터를 전송하기 위한 패킷의 구조는 동기 획득을 위해 데이터 전송 전에 PN 시퀀스를 데이터의 헤드 부분에 첨가하여 전송한다. PN 시퀀스는 송 수신 간에 서로 알고 있는 데이터를 이용하여 동기를 획득하는 기능을 하고 있으므로 PN 시퀀스는 채널 부호화를 하지 않고 전송된다. 이러한 비부호화 된 PN 시퀀스는 대부분의 연구에서는 동기 획득을 위해 활용되지만 본 논문에서는 동기 획득 뿐 아니라 PN 시퀀스의 성능을 이용하여 데이터 필드의 성능 또한 예측할 수 있어 데이터 필드의 복호부에 정보를 제공할 수 있다. 본 논문에서는 다중 경로 전달 환경인 수중음향통신에서 원활한 통신과 함께 수신 신호의 성능을 향상시키기 위하여 낮은 SNR에서도 우수한 성능을 보이는 컨볼루션 부호화 기법과 BCJR 복호 방식을 이용하여 다양한 부호화 율에서 비 부호화 된 PN 시퀀스의 오류율과 부호화 된 데이터 필드의 오류율의 상관관계를 시뮬레이션 및 실제 수중 실험을 통해 분석하여 효율적인 수신 구조를 제시하였다.

• 한국지역사회생활과학회지
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• 제26권4호
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• pp.647-659
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• 2015

This study analyzes current technologies in personal protective equipment (PPE) and mechanisms that can be used in the agricultural field to provide data for research and development on PPE for farmers. There is growing awareness of the importance of PPE as part of efforts to reduce agricultural accidents, but data remain rare for developing PPE tailored to the farm work environment. In this regard, patent data on PPE can provide useful insights for facilitating relevant technologies and research. This study examines patents and utility models classified under the IPC code in Korea and other countries to analyze patented technologies and recent trends for the period from January 2003 to October 2014. Here Korea, the U.S., Japan, and Europe were considered. The results show that the number of patent applications for PPE remained steady without any sharp fluctuations. KIPO applications accounted for 43.5% of all cases, reflecting the highest proportion among the countries considered. Domestic applicants accounted for 94% of all cases. In Korea, patent applications were concentrated in safety gear for the face and eyes, indicating a high level of technology. The highest level of competition was observed for safety goggles in all countries. Some PPE technologies were dominated by a particular manufacturer. The analysis results for farming-related technologies show the current state of technologies and areas lacking technological development. This study analyzes patented technologies for PPE in Korea and other countries and recent research trends as part of the effort to develop PPE for workers in the farming and livestock industry. This study represents an early-stage effort to develop PPE for workers in the farming and livestock industry, and the results are expected to be useful for tailoring PPE to Korea's farming and livestock environment.

• 대한한방내과학회지
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• 제36권4호
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• pp.561-569
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• 2015

Objectives The purpose of this study was to improve the knowledge of the low-level laser therapy (LLLT) field and to review research reports on LLLT to understand the current situation with respect to the clinical indication and current research trends.Methods A survey was carried out on the subject of low-level laser therapy to September 2012, using the PubMed search engine. Selected literature was checked by two reviewers and was classified according to the International Classification of Diseases 10th (ICD-10) over 10 years.Results We selected 469 studies in total, of which 142 were case reports, 118 were case-controlled trials, and 209 were randomized controlled trials of LLLT. According to the ICD-10 classification of diseases, the K code and M code being the most common, 399 studies have been published in the last 10 years. This shows that the study and clinical indications of low-level laser therapy have rapidly increased over the past 10 years.Conclusions Low-level laser therapy has been used most frequently with respect to dentistry and pain and musculoskeletal disorders. Recently, interest in and research into LLLT has increased for various diseases. With the establishment of standard conditions for low-level laser therapy, supported by aggressive clinical utilization and systematic clinical research, LLLT will be a very useful treatment and a useful alternative method in many medical fields.

• Geomechanics and Engineering
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• 제28권6호
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• pp.637-644
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• 2022

Loess soils are unsaturated and widely distributed in the northwest zone in China. Many steep slope of unsaturated are observed are observed to be naturally stable. However, a low factor of safety (FoS) for these slopes would be computed from the slope stability analysis following local code practices. It seems that the analyzed results following the local code practices do not agree with the real condition as observed in the field. It is commonly known that soil suction plays an important role in slope stability due to a higher shear strength of the unsaturated soil as compared with that of the saturated soil. In this paper, it is observed that the computed FoS can also be affected by unsaturated unit weight of the soil. However, the effect of unsaturated unit weight of the soil on the slope stability is commonly ignored in engineering practice. Therefore, both the effects of shear strength and unit weight of the unsaturated soil on the computed FoS of unsaturated soil slope are investigated in this study. It is observed that the unsaturated unit weight of soil on the computed FoS increases with increase in slope angle. It is also observed that the effects of the unsaturated shear strength and unsaturated unit weight on the computed FoS are more significant than the effect of 3D analyses compared to the 2D analyses on the FoS.