• 한국유체기계학회 논문집
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• 제10권5호
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• pp.9-19
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• 2007

Fluid temperature fluctuations in a mixing tee pipe were numerically analyzed by LES model in order to clarify internal turbulent flows and to develope an evaluation method for high-cycle thermal fatigue. Hot and cold water with an temperature difference $40^{\circ}C$ were supplied to the mixing tee. Fluid temperature fluctuations in a mixing tee pipe is analysed by using the computational fluid dynamics code, FLUENT, Temperature fluctuations of the fluid and pipe wall measured as the velocity ratio of the flow in the branch pipe to that in the main pipe was varied from 0.05 to 5.0. The power spectrum method was used to evaluate the heat transfer coefficient. The fluid temperature characteristics were dependent on the velocity ratio, rather than the absolute value of the flow velocity. Large fluid temperature fluctuations were occurred near the mixing tee, and the fluctuation temperature frequency was random. The ratios of the measured heat transfer coefficient to that evaluated by Dittus-Boelter's empirical equation were independent of the velocity ratio, The multiplier ratios were about from 4 to 6.

• 한국양식학회지
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• 제16권1호
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• pp.51-58
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• 2003

The first Indian transgenic fish was generated in 1991 using borrowed constructs from foreign sources. To construct transformation vectors for the indigenous fishes, growth hormone genes of rohu (r-CH), Labeo rohita and catfish, Heteropneustes fossilis were isolated, cloned and sequenced; their fidelity was confirmed in prokaryotic and eukaryotic systems. A vector was constructed with grass carp b-actin promoter driving the expression of r-GH. Rohu eggs are large. fragile and swell 2~3 times. when fertilized. Hence they were amenable only for electroporated sperm-mediated gene transfer. Accordingly, the sperm electroporation technique was standardized to ensure 25% hatchling survival and 37% Presumptive transgenics without suffering any deformity. Southern analysis confirmed genomic integration in 15% of the tested individuals (Ti) belonging to family lines 2 and 3: another 25% of the Juveniles (Te) were also proved transgenic but with the transgene persisting extrachromosomally for longer than 1 to 2 years. perhaps due to the presence of replicon in the vector. Transgenics belonging to different family lines grew 6~8 times faster than the respective controls. Difference in growth trends of Ti and Te within a family line was not significant. In the Ti family 3 remarkable growth acceleration was sustained for a period longer than 36 weeks but in those of family 2, it gradually decreased. All transgenic fishes including the rohu converted the food at a significantly higher efficiency. Barring the transgenic mudloach, all the other transgenic fishes consumed food at significantly reduced rate.

• 한국자동차공학회논문집
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• 제12권6호
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• pp.46-53
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• 2004

Heat release analysis is a very important method for understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the measured cylinder pressures of a HSDI(high speed direct injection) and IDI(indirect injection) diesel engines, Those have benefits of simple equation, fast speed, reliability. The objective of the study is to compare the combustion characteristics between a HSDI and an IDI. The result shoes that the maximum heat release rate of a HSDI is higher than that of an IDI because of long ignition delay period. The heat release curve of an IDI is more linear than that of a HSDI, thus is similiar to that of a SI engine. The combustion efficiency of a HSDI is higher than that of an IDI because of the smaller heat transfer loss of a HSDI. There is a suggestion here that an IDI engine has broad heat transfer area which include two combustion chambers, the connection passage of combustion chambers, etc.

• 한국정보과학회논문지:시스템및이론
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• 제28권12호
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• pp.632-641
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• 2001

본 논문에서는 병렬컴퓨터의 하이퍼큐브, 메쉬, 트리 위상에서 부하를 재분배할 때 소요되는 계산비용을 줄이기 위한 기법을 제안하였다. 기본 개념은 두가지이다. 첫 번째는 부하를 재분배할 때 각단계마다 발생하는 idle한 링크를 겹쳐서 사용하여 전송하는 방법이며, 두 번째는 이전의 방법에 파이프라인 형태로 부하의 이동을 수행하여 링크를 최대한 사용함으로써 보다 효과적으로 계산비용을 줄이는 방법이다. 즉, idle한 링크가 가능한 발생하지 못하게 부하의 전송에 링크가 적극 참여하도록 함으로써 계산비용을 은닉하는 방법이다. 실험을 통하여 병렬컴퓨터의 위상(하이퍼큐브, 메쉬, 트리)에 따라 기존의 기법들에 두 방법을 적용한 결과, 기존의 기법보다 최소 20%에서 최대 50%의 계산비용이 감소됨을 알 수 있었다.

• 한국자동차공학회논문집
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• 제13권6호
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• pp.21-30
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• 2005

Heat release analysis is a very importent method in understanding the combustion phenomena inside an engine cylinder. In this study, one-zone heat release analysis was used with the mesured cylinder pressures of an IDI(indirect injection), a HSDI(high speed direct injection) and a SI(spark ignition) engine. It has benefits of simple equation, fast speed, reliability. The object of the study is to compare the combustion characteristics among an IDI, a HSDI and SI engine. Result of analysis, the maximum heat release rate of a HSDI is higher than an IDI because of long ignition delay period. The heat release curve of a IDI is more linear than an HSDI, so the combustion characteristics of a IDI is similiar to that of an SI engine. There is a suggestion here that the combustion efficiency of a HSDI is highest of that of all engines because of the smallest heat transfer loss of all engines.

• 한국전자통신학회논문지
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• 제13권4호
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• pp.881-886
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• 2018

지난 수십 년간, 컴퓨터 기술의 발전은 응용연구의 데이터집약형 연구라는 새로운 패러다임으로 변화를 가져왔다. 지리적으로 떨어진 연구자들에게 대용량 실험 데이터를 저장, 공유, 분석하는 환경이 요구되고, 우리나라는 연구 경쟁력 강화를 위해 국가과학기술연구망(KREONET)과 대용량데이터센터 등 국가 차원의 인프라를 서비스하고 있다. 특히, KREONET는 2016년부터 세계 주요 연구지까지 최대 100Gbps의 속도로 연결하는 네트워크를 제공하고 있다. 본 논문에서는 국제간 협업을 지원하는 초고속 장거리 전송의 연구 환경으로서, 고성능 전송 노드와 계산 자원을 고속의 네트워크에 연동한 대용량 데이터전용의 전송플랫폼 시연 결과를 소개하고자 한다.

• 조명전기설비학회논문지
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• 제21권2호
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• pp.86-93
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• 2007

본 논문은 가용송전용량(ATC)를 계산하기 위한 두 가지 빠른 계산 기법을 제안한다. 이 방법들은 선로의 열적용량한계(Thermal ATC)와 전압 안정도한계(Voltage ATC)를 제약조건으로 ATC를 계산한다. 먼저 선로의 열적용량을 고려한 방법에서는 모선의 전력 변화에 대한 선로의 조류 감도인 PTDF와 n-1 상정사고를 고려한 LODF를 이용하였으며, 전압안정도를 고려한 방법에서는 2모선 등가 시스템을 이용하여 최대 전력을 구하는 방법을 이용하였다. 제안된 방법은 IEEE 30모선 계통에 적용하였으며 그 결과를 다른 방법과 비교하여 제안된 방법의 타당성을 입증하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.317-317
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• 2010

This paper reports syntheses of $TiO_2$ nanocubes and theirs application to DSSC. We synthesized $TiO_2$ nanocubes via solvothermal method using titanium isopropoxide (TTIP) and tetramethylammoiumhydroxide (TMAH). By adding longer alkyl chain ammonium hydroxide that slowed down the growth rate of the crystal, $TiO_2$ nanocubes were obtained with average particle size in the range of 40 nm to 70 nm. By TEM investigation, each particle was found to be single crystal of anatase having six-faces of (001) and {100} crystallographic planes truncated by {101} series of planes, which are clearly distinguishable from spherical nanoparticles. Among various application, utilizing nanocubes as photo-electrode in dye-sensitized solar cell, we investigated photo-electron conversion performances in comparison with spherical shaped $TiO_2$ nanoparticles by I-V characteristics and IPCE measurements, etc.. Photocurrent-transient analysis revealed that $TiO_2$ nanocubes have a higher transient electron transfer rate by more than 10 times compared with spherical particles of similar size. Fast electron transport along the cube edges having small curvature was suggested as a plausible origin of high diffusion coefficient of electron in nanocube $TiO_2$.

• 한국재료학회지
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• 제29권11호
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• pp.657-663
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• 2019

In this work, we study physical and mechanical properties of oxide films formed on AZ91D magnesium alloy by plasma anodization at different temperatures. It is found that the higher the electrolyte temperature, the lower is the breakdown voltage of oxide layer. This is probably because films formed at higher temperatures are thinner and denser. Moreover, electrolyte temperature plays an important role in the physical properties of the films. As the electrolyte temperature increases from 20 to $50^{\circ}C$, the hardness of the oxide layer increases. Friction test against steel balls indicates that wear scars become narrower for films formed at higher temperatures because the films are harder, as indicated by the Vickers hardness. The thinner and denser nature of the oxide film formed at $50^{\circ}C$ is also advantageous for heat transfer when film is used as a heat sink. Laser flash test results show very fast heat transfer for AZ91D with plasma anodized oxide layer formed at higher temperatures.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1429-1435
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• 2021

The temperature distribution of an electromagnetic pump was analyzed with a flow rate of 1380 L/min and a pressure of 4 bar designed for the sodium thermo-hydraulic test in the Sodium Test Loop for Safety Simulation and Assessment-Phase 1 (STELLA-1). The electromagnetic pump was used for the circulation of the liquid sodium coolant in the Intermediate Heat Transport System (IHTS) of the Prototype Gen-IV Sodium-cooled Fast Reactor (PGSFR) with an electric power of 150 MWe. The temperature distribution of the components of the electromagnetic pump was numerically analyzed to prevent functional degradation in the high temperature environment during pump operation. The heat transfer was numerically calculated using ANSYS Fluent for prediction of the temperature distribution in the excited coils, the electromagnet core, and the liquid sodium flow channel of the electromagnetic pump. The temperature distribution of operating electromagnetic pump was compared with cooling of natural and forced air circulation. The temperature in the coil, the core and the flow gap in the two conditions, natural circulation and forced circulation, were compared. The electromagnetic pump with cooling of forced circulation had better efficiency than natural circulation even considering consumption of the input power for the air blower. Accordingly, this study judged that forced cooling is good for both maintenance and efficiency of the electromagnetic pump.