• 기술사
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• 제16권2호
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• pp.1-11
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• 1983

The resistance property of a high speed passenger craft (: "DOL-PIN HO" designed by the author in 1972) is investigated as follows; -. The Resistance property of the craft is determined by savitsky′s method and blount-Fox′s method. The theoretical results are also compared with the full scale data. The comparison reveals that the result when using blount/fox′s method are in much closer agreement with the full scale data than savitsky′s. -. The effects of ship speed on the positions of the center of pressure and of the longitudinal center of gravity (L.C.G.) are investigated. The investigation shows that the position of L.C.G. of the craft is almost constant although the ship speed is changed. -. The effect of transom flap on the Resistance property of the craft is studied using savitsky/brown′s method. From the study it is found that the resistance of the craft is decreased and hence speed gain (about 3% of the service speed) can be obtained, when using transom flap for the craft.

• 콘크리트학회논문집
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• 제13권3호
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• pp.285-293
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• 2001

본 연구는 기존 경량기포콘크리트의 문제점 및 역학적 성질의 개선을 위하여 산업폐기물인 폐스티로폼을 사용하여 경량기포콘크리트를 제조하고, 그 역학적 성질을 조사 분석하기 위한 것으로, 현장에서 주로 사용하는 배합을 기초로 하여 폐스티로폼의 혼입율을 최대 40%까지 단계별로 혼입하여 실험을 진행하였다. 또한 배합조건에 따른 경량기포콘크리트의 역학적 특성에 관한 상관관계를 분석하고자 하였다. 실험결과 폐스티로폼의 혼입율이 증가할수록 압축강도 증진에 효과적인 것으로 나타났으며, 현저한 흡수율 개선의 효과를 확인하였다. 그러나 플로우값의 경우 혼입율이 증가하면서 감소하여 해결해야 할 과제로 나타났다. 또한 단위시멘트량의 증가에 따라 압축강도도 증가하는 경향을 보였으며, 물시멘트비의 변화에 따른 압축강도의 변화는 미미한 것으로 나타났다. 또한 재령별 압축강도에 있어서는 초기의 압축강도 확보 및 장기강도의 증진을 위한 연구가 지속되어야 할 것으로 나타났다. 결과적으로 폐스티로폼을 사용하여 경량기포콘크리트를 제조할 경우, 산업폐기물의 재활용이라는 측면 뿐만 아니라, 경제적이고 안정된 품질의 경량기포콘크리트를 생산할 수 있음을 확인하였다.

• 소성∙가공
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• 제8권3호
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• pp.283-283
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• 1999

In the present study, the effect of microporosity on the tensile properties of as-cast AZ91D magnesium alloy was investigated through experimental observation and numerical prediction. The test specimens were fabricated by die-casting and gravity-casting. For gravity-casting, the inoculation and use of various metallic moulds were applied to obtain a wide range of microporosity. The deficiency of the interdendritic feeding of the liquid phase acted as d dominant mechanism on the formation of the micropores in the Mg-Al-alloys, rather than the evolution of hydrogen gas. Although tensile strength and elongation has a nonlinear and very intensive dependence upon microporosity, the yield strength appeared to have a linear relationship with microporosity. However, it was possible to quantitatively estimate the linear contribution of microporosity on the individual tensile property far a range of microporosity, which was below about B %. The numerical prediction suggests that the effect of microporosity on fractured strength and elongation decreased as the strain hardening exponent increased. Furthermore. the shape and distribution of micropores may play a more dominant role than local plastic deformation on the tensile behavior of AZ9lD alloy.

• Structural Engineering and Mechanics
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• 제78권1호
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• pp.53-66
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• 2021

The determination of the damage index to reveal the performance level of a structure can constitute the seismic risk generalization approach based on the parametric analysis. This study implemented this concept to one kind of civil engineering structure that is the concrete gravity dam. Different cases of the structure exhibit their individual responses, which constitute different considerations. Therefore, this approach allows the parametric study of concrete as well as soil for evaluating the seismic nature in the generalized case. To ensure that the target algorithm applicable to most of the concrete gravity dams, a very simple procedure has been considered. In order to develop a correlated algorithm (by response surface methodology; RSM) between the ground motion and the structural property, randomized sampling was adopted through a stochastic method called half-fractional central composite design. The responses in the case of fluid-foundation-dam interaction (FFDI) make it more reliable by introducing the foundation as being bounded by infinite elements. To evaluate the seismic generalization of FFDI models, incremental dynamic analysis (IDA) was carried out under the impacts of various earthquake records, which have been selected from the Pacific Earthquake Engineering Research Center data. Here, the displacement-based damage indexed fragility curves have been generated to show the variation in the seismic pattern of the dam. The responses to the sensitivity analysis of the various parameters presented here are the most effective controlling factors for the concrete gravity dam. Finally, to establish the accuracy of the proposed approach, reliable verification was adopted in this study.

• 한국군사과학기술학회지
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• 제14권2호
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• pp.264-270
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• 2011

This paper focuses on possibility to design and fabrication new combination of bullet core to substitute current toxic material of heavy metal such as lead by environment-friendly ones. The core is designed as dual structure to manipulate the core center of gravity easily by combining materials, which of basis is tungsten of low cost and easily acquired. Those combinations are W-M series such as W-Cu, W-Sn, W-Cu-Sn, and W-Cu-Ni to target the density of lead, $11.34g/cm^3$ through powder-metallurgy. Out of four, combination of W-Cu-Ni shows the highest compression density of 96% and is confirmed as the most suitable substitution for lead due to the excellent property of matter and sintering. All combination samples is simulated on the PRODAS software for designing and structure analysis by adjusting the center of gravity of dual core samples forward and backward. The simulations confirm the similarity of current bullet core with respect to properties of mass, aero dynamics, and flying stability.

• 접착 및 계면
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• 제15권1호
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• pp.9-13
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• 2014

본 연구는 폴리프로필렌/마이카 복합재료의 고상압출에 의한 배향에 따른 기계적 물성의 변화에 관한 연구이다. 마이카 함량이 증가할수록 복합재료의 비중이 증가하였다. 하지만 고상압출에 따른 배향에 의해 복합재료의 비중은 미세공극의 발생으로 말미암아 비중은 배향 전에 비해 현저히 감소하는 것으로 나타났다. 이러한 미세공극의 존재는 복합재료의 인장 및 굴곡물성에 큰 영향을 미치는 것으로 나타났다. 고상압출 여부에 관계없이 마이카 함량이 10 wt%일 때 최대 굴곡 물성이 관찰되었다.

• 한국결정성장학회지
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• 제22권5호
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• pp.254-259
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• 2012

순환유동층 연소방식의 화력발전소에서 석탄을 연소시킨 후 발생하는 석탄재 중 탄산화 반응 인자인 Ca 성분을 다량 포함한 비산회를 시멘트에 일정량 치환하여 제조한 인공경량 경화체를 초임계상태에서 이산화탄소($CO_2$)를 고정화하여 골재의 기계적 물성향상을 도모하였다. 초임계 분위기 $40^{\circ}C$ 조건에서 비산회의 치환량을 변화시켜 재령일수별 탄산화를 시행하였다. 비산회 치환량에 따른 탄산화 반응시킨 인공경량골재 경화체의 무게변화율, TG/DTA 분석, 1 % 페놀프탈레인 알칼리성 측정을 통하여 탄산화 진행여부를 확인하였으며 28일까지의 재령 이후 경화체의 압축강도 측정과 비중측정을 통하여 골재의 기계적 물성향상과 인공경량골재의 기준 비중치인 2.0 이하의 비중값을 갖는 탄소고정 인공경량골재 경화체를 얻는 것이 가능할 것으로 판단되었다.

• 동력기계공학회지
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• 제22권6호
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• pp.51-57
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• 2018

In Korea, the Air Quality Conservation Act and the Petroleum and Petroleum Substitute Fuel Business Act stipulate certain quality standards for fuels distributed in Korea, thereby striving to reduce vehicle performance and emissions. Domestic petroleum products import and produce all the crude oil from each oil refiner so that the quality of the petroleum product is different according to the characteristics of the crude oil. As a result, vehicles have been improved by using the physical properties calculated through the physical property measurement that has tried to improve the accuracy of the measurement of the energy consumption efficiency of the automobile by using standard fuel from abroad. In this study, the same test procedure and method as the test method of domestic gasoline vehicle emission are applied using four samples of gasoline and the latest gasoline vehicle which are actually distributed, and the performance evaluation is performed. The purpose of this study is to contribute to improvement of vehicle technology and fuel quality by collecting necessary basic data and obtaining data on the effect of differences in gasoline property on vehicle emissions. The results of the test showed that the emission of gases (NMOG, CO) from gasoline vehicles was the most influenced by the sulfur content, unlike the previous studies that the vehicles emission had the greatest influence on the distillation characteristics and the specific gravity of aromatic compounds. The catalytic reaction such as the poisoning action of the three-way catalyst which is the abatement device was interfered and the emission was increased. The distillation characteristics and specific gravity of aromatic compounds were found to affect the emission of vehicles. According to the physical properties of the fuel, the emission difference was 28.0% in the urban mode and 17.6 % in the highway mode.

• 한국조리학회지
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• 제22권1호
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• pp.42-51
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• 2016

This study investigated the quality characteristics of sponge cake added with pine leaf powder. The pine leaf powder sponge cake was prepared with different ration of pine leaf powder(0, 10, 20, 30, 40%). The specific gravity, baking loss rate and cake weight increased significantly with increasing the levels of pine leaf powder. In terms of color, lightness and yellowness increased with increasing levels of pine leaf powder. The sponge cake added with ratio of 40% pine leaf powder appeared to be the highest. In terms of textual property evaluation, sponge cake were increased by the level of pine leaf powder. The substance's level of springiness, and cohesiveness decreased by increasing of the level of pine leaf powder. In sensory evaluation, 10% pine leaf e sponge cake was better on taste, overall acceptability, and flavor. The results showed that sponge cake quality with 10% pine leaf powder was considered the best.

• 한국식품저장유통학회지
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• 제6권1호
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• pp.7-10
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• 1999

Physicochemical properties of Satsuma mandarin(Citrus unshiu Marc. var. miyagawa) harvested in middle of November according to production areas of Cheju were investigated. Peel thickness of citrus fruits was ranged from 2.54mm to 3.13mm, and it was lower on fruits harvested in western areas than those of other areas in Cheju. Soluble solids were ranged from 10.1 to 12.0$^{\circ}$Brix, and it was lower on fruits harvested in southern areas. Acid contents of citrus juice were ranged from 1.28% to 1.42%, it was higher on fruits harvested in eastern areas, specific gravity of citrus fruits was ranged between 0.86 and 0.88. Flesh ratio was ranged from 75.1% to 77.6%, it was lower on fruits harvested in southern areas. Soluble solids, acid content and specific gravity harvested in southern areas of below 100m and over 150m sea level altitude were 11.8 and 11.2, 1.43% and 1.40%, 0.87 and 0.9, respectively. Fruits quality harvested in southern areas was better, compared to other harvest areas of Cheju.