• Progress in Superconductivity and Cryogenics
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• v.12 no.3
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• pp.29-33
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• 2010

For last 10 years, there are big progress and many efforts in the development of HTS power equipments by some country including South Korea. Especially HTS cable system is the strongest candidate among them from the viewpoint of applying to real grid, because of the feature of it, compact and large capacity. In South Korea, transmission level 154kV, the world top voltage class, HTS cable system was installed and has been tested in KEPCO Gochang Underground Cable Test Field since the early of 2010 in order to meet test requirements made by KEPCO, the only grid company in South Korea. The type test of it will be completed by October 2010 and subsequently long-term load cycle test will be performed during 6 months. Also in the near future, KEPCO has a plan to demonstrate transmission level HTS cable system in real grid, in order to meet practical requirements and confirm the feasibility of it. This paper says the test plan of transmission level 154kV HTS cable system and the way how to test it.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.417-422
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• 2010

Low temperature diesel combustion was achieved via a combination of late injection timing ($8.5^{\circ}$ CA BTDC to $0.5^{\circ}$ CA BTDC) and heavy exhaust gas recirculation (37% to 48%) with ultra low sulfur Swedish diesel fuel in a 1.7L common rail direct injection diesel engine. When injection timing is retarded at a certain exhaust gas recirculation rate, the particulate matter and nitrogen oxides decease simultaneously, while the hydrocarbon and carbon monoxide increase. Hydrocarbon speciation by gas chromatography using a flame ionization detector reveals that the ratio of partially burned hydrocarbon, i.e., mainly alkenes increase as the injection timing is retarded and exhaust gas recirculation is increased. The two most abundant hydrocarbon species are ethene which is a representative species of partially burned hydrocarbons, and n-undecane, which is a representative species of unburned hydrocarbons. They may be used as surrogate hydrocarbon species for performing a bench flow reactor test for catalyst development.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.109.1-109.1
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• 2016

진공산업 분야에서 OLED 디스플레이가 큰 시장으로 성장하며 크라이오 펌프가운데서 특별히 수분만 집중적으로 배기할 수 있는 워터펌프(CWP or cold trap)가 각광받고 있다. 이에 현민지브이티(Genesis)는 중소기업청 중소기업개발지원사업의 일환으로 진행된 2014년도 구매조건부 신제품 개발사업에 선정되어 '극저온 G-M냉동기를 이용한 대용량 Cold Trap개발'과제를 수행하면서 32인치 급으로 수분에 대해서 30,000[L/s] 이상의 배기속도를 가지는 대형 CWP를 개발하고 있다. 그 일환으로 본 CWP에 장착할 80K에서 200W급 단단 G-M 냉동기를 2015년 국내 최초로 개발하였다. 본 HPS80200(200W @80K) 단단 G-M냉동기에 대한 성능시험을 수행하던 중 기존 평가방식에 보완할 부분이 있음을 확인하였다. 통상적으로 G-M냉동기의 냉동능력은 저온 스테이지 상단에 온도센서와 히터가 설치된 히터 블럭을 장착한 후 일정한 열부하를 인가하면서 77K 또는 80K에서의 냉동능력을 측정한다. 문제는 여기에 설치하는 온도센서의 장착 위치의 중요성이다. 즉, 어느 부위의 온도를 냉동기의 대표 온도로 정하느냐에 따라 냉동기의 성능 값에 큰 차이를 나타내기 때문이다. 실제 확인 결과, 온도는 히터블럭 내의 위치뿐 아니라 저온 스테이지 부위별로도 크게 차이를 보였다. 따라서 본 연구에서는 보다 합리적이고 정확한 냉동 능력 측정을 위해 77K 에서 냉동기의 질소 액화 능력으로 냉동능력을 평가하고자 하였다. 이를 통해 개발된 HPS80200냉동기의 보다 정확한 냉동능력(77K에서 200W 이상임을 확인함)을 측정할 수 있었고 냉동기의 저온 스테이지에서 대표온도로 설정할 수 있는 위치도 확인할 수 있었다.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.225-233
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• 2011

The volume change in concrete takes place with changes in temperature and water content immediately after concrete casting. In the early age stage, the thermal and drying shrinkages can cause cracks that are very crucial to the durability of concrete. It was reported that when the cement with lightly-burnt MgO powder was used, the shrinkage of concrete can be reduced. This study investigates fundamental properties of cement composites with lightly burnt MgO powder by performing various experiments. The stability test results verified that MgO powder in cement composites does not cause any abnormal expansion. Also, the hydrate product analysis results obtained from MgO cement paste showed that MgO powder reduces the shrinkage at the longterm ages. In addition, the cement composites containing the proper amount of MgO powder could improve compressive strength. Finally, the shrinkage reduction from using MgO powder can be optimized by increasing MgO replacement level and curing temperature.

• Journal of Energy Engineering
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• v.10 no.4
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• pp.318-326
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• 2001

To enhance thermal efficiency of thermal facility through recovery of low and medium temperature waste heat, 1 MW organic Rankine cycle system was designed and developed. The exhaust gases of 175$^{\circ}C$ at two 100 MW power plants in pohang steel works were selected as the representative of low and medium temperature waste heat in industrial process for the heat source of the organic Rankine cycle system. HCFC-123, a kind of harmless refrigerant, was chosen as the working fluid for Rankine cycle. The organic Rankine cycle system with selected exhaust gases and working fluid was designed and constructed. From the operation, it was confirmed that the organic Rankine cycle system is available for low and medium temperature waste heat recovery in industrial process. The optimum operating manuals, such as heat-up of hot water, turbine start-up, and the process of electric power generation, were derived. However, electric power generated was not 1 MW as designed but only 670 kW. It is due to deficiency of pump capacity for supply of HCFC-123. So it is necessary to increase the pump capacity or to decrease the pressure loss in pipe for more improved HCFC-123 supply.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.352-361
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• 2001

Mode I fracture toughness ( $K_{IC}$) of the frozen rocks and that of the frozen-thawed rocks were obtained by using BDT and CCNBD specimens. The test temperatures ranged from +$25^{\circ}C$ to -16$0^{\circ}C$. Wet and air-dry specimens of granite and sandstone were used in order to investigate the effect of water and porosity on fracture toughness. The SEM images of the frozen-thawed rocks were also analysed to check the density of thermal cracks. The $K_{IC}$ of the frozen rocks increased as the test temperature went down. The rate of increase was higher in wet condition than in dry condition and the rate of increase for wet granite was higher than that for wet sandstone. The $K_{IC}$ of the frozen-thawed rocks varied within 15% from the $K_{IC}$ of the rocks at room temperature. After one freeze-thaw process, thermal crack occurred in granite but no thermal cracks occurred in sandstone. And the crack density was increased as the temperature went down.n.

• Composites Research
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• v.17 no.6
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• pp.52-57
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• 2004

In this study, mechanical tensile properties of carbon fiber reinforced polymeric (CFRP) composite cycled with thermo-mechanical loading under cryogenic temperature (CT) were measured using cryogenic environmental chamber. Thermo-mechanical tensile cyclic loading (up to 10 times) was applied to graphite/epoxy unidirectional laminate composites far room temperature (RT) to $-50^{\circ}C$, RT to $-100^{\circ}C$ and RT to $-150^{\circ}C$. Results showed that tensile stiffness obviously increased as temperature decreased while the thermo-mechanical cycling has little influence on it. Tensile strength, however, decreased as temperature down to CT while the reduction of strength showed little after CT-cycling. For the analysis of the test results, coefficient of thermal expansion (CTE) of laminate composite specimen at both RT and CT were measured and the interface between fiber and matrix was observed using SEM images.

• Horticultural Science & Technology
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• v.18 no.3
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• pp.387-390
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• 2000

The experiment was conducted to investigate the effects of vine management and yield on fruit quality and bud burst of 'Campbell Early' grapevines in Hwaseong and Suwon area. The extreme value of minimum temperature of Hwaseong area, frequently causing cold damage, was lower than that of Suwon area in winter. Narrow spacing, overbearing, and poor vine management were observed in Hwaseong area, where the harvest time was delayed by 7 days compared with that of Suwon area. Total carbohydrate content of bearing mother branches was lower with 1.2~1.7%, and the percentage of bud burst was extremely lower at $-15^{\circ}C$. In Suwon area, there were no differences in cluster and berry size, but soluble solids content was lower and skin coloration was poorer when yield was high. Total carbohydrate content was lower when yield was high. The percentage of bud burst was lower at cold treatments below $-20^{\circ}C$. The results suggest that appropriate yield based on fruit quality is 2.3~2.6 MT/10a.

• Special Issue of the Society of Naval Architects of Korea
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• 2007.09a
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• pp.118-127
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• 2007

SAW(Submerged Arc Welding) process is generally applied to a wide range of welding area in the fabrication of steel structure. This process has a good characteristic properties such as the high quality of welds and the high deposition rates, but in case of welding on a thick steel plate, it also has higher cold crack susceptibility than that of a thin steel plate. The purpose of this research is to find the main factor of crack generation and clarify the countermeasure for crack prevention, and then establish the optimum welding condition in a heavy thick steel plate. The results of this study are as follows, 1. The cause of crack generation is found the diffusible hydrogen penetrated into weld metal by decomposition of the remained moisture in SAW flux during welding. 2. For the removal of diffusible hydrogen, the raw materials of SAW flux are to be dehydrated at the high temperature in the initial manufacturing stage. 3. Mechanical properties of weld metal welded with the dehydrated SAW flux were evaluated very excellent, furthermore the weld metal has been proved to have low diffusible hydrogen content with 3.1ml /100g. 4. The weldability and quality welded with thick steel plates were improved by establishing the new optimum welding condition.

• Korean Journal of Soil Science and Fertilizer
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• v.17 no.1
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• pp.39-45
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• 1984

The effects of foliar application of phosphate was investigated in the light of plant physiological point of view. The phosphate applied on the foliar both in meiosis and heading time was penetrated considerably into the rice. The amount of P absorbed by foliar application at high temperature was higher than that at low temperature but still considerable amount of P was absorbed at low temperature. The phosphate applied on younger flag leaf was absorbed more vigorously than the second and third leaves. The absorbed P on leaf was translocated to the panicle, especially on the brown rice starch, then moved to another panicle wherever the phosphate was needed. The major fraction of absorbed P under high temperature condition was T.C.A. soluble-Ba insoluble phosphate of mainly phytic form but Ba soluble-EtOH insoluble fraction, sugar phosphate ester, was identified as dominant P under low temperature condition.