• 수산경영론집
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• 제41권1호
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• pp.113-128
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• 2010

This study is aimed to analyze the economic feasibility of the selective breeding program on the Oliver flounder aquaculture. First of all, in order to evaluate this program, we review the concept and research trend on the selective breeding. The objective of this research is the selective breeding program on the Oliver flounder aquaculture in the Genetics and Breeding Research Center, NFRDI. It was conducted to investigated economic effects of three factors of the selective breeding program on the Oliver flounder aquaculture such as fast growth, disease resistance and increase exports. The results of economic analysis of the selective breeding program on the Oliver flounder aquaculture are as follows; First, there were the significant meaning of the economic effects on the technology of the selective breeding program by fast growth, disease resistance and increase exports. Second, we analyzed in the economic feasibility of the selective breeding program on the Oliver flounder aquaculture from 2004 to 2020, internal rate of return(IRR) was 419%, a benefit-cost ratio was shown to be 24.92, net present value(NPV) was 989,942,464 thousand won, which indicates the economic feasibility of the selective breeding program is very high. Finally, in order to improve the economic feasibility, there is need to be focused on the efficient the selective breeding program on the Oliver flounder aquaculture.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.961-963
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• 2002

When high temperature superconducting(HTS) tapes are wound on former for HTS cable application, their critical characteristics are likely to be degraded seriously because of mechanical stress. In this study, prior to fabricate prototype HTS cables, we investigated the variation of critical characteristics of HTS tapes according to their pitch angles. For this work, we prepared the samples of HTS tapes on the former of which diameter is 3cm. Pitch angles of HTS tapes are $0^{\circ}$, $00^{\circ}$, $20^{\circ}$, $30^{\circ}$, $40^{\circ}$, respectively. We applied current up to 160 $A_{rms}$ to HTS tapes and investigated E-I characteristics. The critical current of HTS tapes was decreased as pitch angle increased. In addition, when the applied current was beyond their critical current, the rate of resistance increase of HTS tapes was in proportion to their critical current. Finally, We concluded that the pitch angles affected resistance increase of HTS tapes as well as critical current.

• Journal of Mechanical Science and Technology
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• 제16권10호
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• pp.1246-1252
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• 2002

Ultrafine grained (UFG) low carbon (0.15 wt.% C) steel produced by equal channel angula. pressing (ECAP) was tested for investigating the effect of load ratio on the fatigue crack growth rate. Fatigue crack growth resistance and threshold of UFG steel were lower than that of asreceived coarse grained steel. It was attributed to the less tortuous crack path. The UFG steel exhibited slightly higher crack growth rates and a lower △Kth with an increase of R ratio. The R ratio effect on crack growth rates and △Kth was basically indistinguishable at lower load ratio (R >0.3), compared to other alloys, which indicates that contribution of the crack closure vanishes. The crack growth rate curve for UFG steel exhibited a longer linear extension to the lower growth rate regime than that for the coarse grained as-received steel.

• 멤브레인
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• 제14권1호
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• pp.66-74
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• 2004

합성 하수 및 실제 하수를 이용한 금속 막의 정밀 여과 공정에서 분리 막의 전체 저항의 증가는 입자의 막 표면 축적에 의한 케이크 층의 저항 ($R_c$)에 가장 큰 영향을 받았다. 막 오염 저감을 위한 방법으로 오존 가스를 이용한 간헐적 역세정은 공기에 의한 경우보다 막 오염 저감에 훨씬 더 효과적인 것으로 나타났다. 운전 인자에 대한 영향으로 동일한 오존 주입량에서는 주입시간을 길게 하기보다는 주입 가스 유량을 크게 할수록 더 높은 막 투과 유속의 회복을 보였다. 여과시간이 길수록 오존가스를 이용한 막 오염 저감효과가 감소하는 것으로 나타나 부착층 및 막 내부에서 파울링 물질에 의한 비가역적인 막 오염이 발생하기 전에 막 세정을 실시하는 것이 바람직한 것으로 판단된다.

• 한국초전도ㆍ저온공학회논문지
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• 제17권3호
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• pp.9-12
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• 2015

NbN thin films were deposited on thermally oxidized Si substrate at room temperature by using reactive magnetron sputtering in an $Ar-N_2$ gas mixture. Total sputtering gas pressure was fixed while varying $N_2$ flow rate from 1.4 sccm to 2.9 sccm. X-ray diffraction pattern analysis revealed dominant NbN(200) orientation in the low $N_2$ flow rate but emerging of (111) orientation with diminishing (200) orientation at higher flow rate. The dependences of the superconducting properties on the $N_2$ gas flow rate were investigated. All the NbN thin films showed a small negative temperature coefficient of resistance with resistivity ratio between 300 K and 20 K in the range from 0.98 to 0.89 as the $N_2$ flow rate is increased. Transition temperature showed non-monotonic dependence on $N_2$ flow rate reaching as high as 11.12 K determined by the mid-point temperature of the transition with transition width of 0.3 K. On the other hand, the upper critical field showed roughly linear increase with $N_2$ flow rate up to 2.7 sccm. The highest upper critical field extrapolated to 0 K was 17.4 T with corresponding coherence length of 4.3 nm. Our results are discussed with the granular nature of NbN thin films.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권11호
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• pp.737-741
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• 2000

We fabricated resistive superconducting fault current limiters (SFCL) based on YBCO thin films grown on 2-inch diameter $Al_2O_3$ substrates. Two SFCLs with nearly identical properties were connected in series to investigate simultaneous quench. There was a slight difference in the rate of voltage increase between two SFCL units when they were operated independently. This difference resulted in significantly imbalanced power dissipation between the units. This imbalance was removed by connecting a shunt resister to an SFCL in parallel. The appropriate values of shunt resistance were 80 ${\Omega}$ at 75 $V_rms$ and 110 ${\Omega}$ at 120 $V_rms$, respectively. Increased power input at high voltages also reduced the initial imbalance in power dissipation, but with increase in film temperature to higher than 200 K.

• 펄프종이기술
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• 제47권5호
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• pp.112-119
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• 2015

The pulp mold attract the increasing concern as recyclable, biodegradable, and eco-friendly packaging materials. In order to broaden the applicability of the pulp mold as substitutes of the expanded styrofoam, the properties of various raw materials for the pulp mold were evaluated and the way for improving water resistance properties of the pulp mold were also tested by applying some additives. The higher value in the fines contents and in the water retention value were shown for the TMP (thermomechanical pulp), which resulted in the bulkier pulp mold with the higher moisture absorption property. In case of water resistance properties, the pulp mold made of white ledger stock showed the higher value in water contact angle and very slow water absorption rate. The addition of oil palm EFB fiber showed the improvement in the water resistance of the pulp mold made of UBKP. The effects of various additives on the improvement in the water resistance properties of the pulp mold were tested by using AKD, PVAm, epoxy resin. The application of AKD leaded to the higher increase in the water resistance. The results in this study showed the effects of AKD for the pulp mold could be improved and optimized by the application with fixing agent and by the ageing treatment after production.

• Journal of Mechanical Science and Technology
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• 제19권5호
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• pp.1158-1168
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• 2005

A shunt from the left ventricle to the left anterior descending artery is being developed for coronary artery occlusive disease, in which the shunt or conduit connects the the left ventricle (LV) with the diseased artery directly at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Computational fluid dynamic analysis for the shunt hemodynamics was also done using a commercial finite element package. Simulation results indicate that in complete left anterior descending artery (LAD) occlusion, flow can be returned to approximately 65% of normal, if the conduit resistance is equal for forward and reverse flow. The net coronary flow can increase to 80% when the backflow resistance is infinite. The increases in flow rate produced by asymmetric flow resistance are enhanced considerably for a partial LAD obstruction, since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but considerably augments it when the resistance is asymmetric. The computational results suggest that an LV-LAD conduit will be beneficial when the resistance due to artery stenosis exceeds 27 PRU, if the resistance is symmetric. Fluid dynamic simulations for the shunt flow show that a recirculating region generated near the junction of the coronary artery with the bypass shunt. The secondary flow is induced at the cutting plane perpendicular to the axis direction and it is in the attenuated of coronary artery.

• 한국기계가공학회지
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• 제20권11호
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• pp.121-126
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• 2021

In this study, the effect of thermal contact resistance between pin-channel tubes on the heat transfer characteristics was analytically examined around the channel tubes with the pins attached to two consecutive arranged channel pipes. The numerical results showed that the heat transfer coefficient decreased geometrically as the thermal contact resistance increased, and the corresponding temperature change on the contact surface increased as the thermal contact resistance increased. The thinner the pin, the more pronounced the geometric drop in the heat transfer coefficient. It was confirmed that the higher the height of the pin, the higher was the heat transfer coefficient, however, the greater the size of the thermal contact resistance, the smaller was the heat transfer coefficient. It was found that the temperature change in the inner wall of the channel tube did not significantly affect the heat transfer characteristics owing to the thermal contact resistance. Furthermore, the velocity of air at the entrance of the channel tube was proportional to the heat transfer coefficient due to a decrease in the convective heat resistance corresponding to an increase in the flow rate.

• 한국주조공학회지
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• 제17권3호
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• pp.302-308
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• 1997

In spite of the fact that magnesium has low density and good machinability, its applications are restricted as a structural engineering material because of the poor strength, ductility, and corrosion resistance of the conventional ingot metallurgy alloys. Such properties can be improved by microstructural refinement via rapid solidification processing. In this study, Mg-5wt%Zn alloys have been produced as continuous strips by the melt overflow technique. In order to evaluate the influence of the cooling rate on the grain refinement and mechanical properties, seven different thickness strips were produced by means of controlling the speed of the cooling wheel. Then the microstructual observations were undertaken with the objective of evaluating the grain refinement as function of the cooling rate. The tremendous increase in hardness of Mg-Zn alloy was mainly due to the refinement of the grain structure by the effect of rapid solidification. The formation of intermetallic phases on the grain boundaries may have a positive effect on the corroion resistance. Therefore, despite competition from many other developments, the rapid solidification process emerges as a valuable method to develop superior and commercially acceptable magnesium alloys.