• 한국해양공학회지
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• 제15권4호
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• pp.14-19
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• 2001

In this paper, the wave and current forces acting on cylinders are investigated by theoretical and experimental methods. The models used are one-cylinder, four-cylinder and semi-submersible types. The theoretical investigations are carried out by the Morison equation and three dimensional source distribution method to calculate exciting forces in waves with and without currents. The experimental investigations are carried out in the wave tank which can generate currents in both directions. In these tests, the models have been exposed to the regular waves with and without currents. It is shown that the exciting forces acting on the one-cylinder or four-cylinders can be approximately estimated by the Morison equation and also by the diffraction theory. However, the Morison equation seems to be not appropriate to estimate the exciting forces on the present type of semi-submersible.

• 대한기계학회논문집
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• 제18권5호
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• pp.1347-1354
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• 1994

This paper deals with the experimental research, including measurement and analysis and field survey, on the causes of occurring noise defective gear boxes in hoist production plant in order to reduce the fraction of their occurrence. In this reserch following investigations are performed : measurement and gear-boxes, examination of each machining process of production, measurement and analysis of dimensional accuracy of each part, comparative vibration test with exchanging inaccurate parts. From these investigations, it is found that the machining accuracy of pinion gear tooth thickness is the most sensitive factor of noise problem. By maintaining the tooth thickness error within 0.05 mm tolerance in the gear cutting process, the fraction of noise defective gear-boxes are greatly reduced to less than 2%, where the usual rate of it has been 20-50%.

• Journal of Advanced Marine Engineering and Technology
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• 제24권2호
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• pp.17-23
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• 2000

Experimental investigations were conducted to study the forced convection of fully-developed turbulent flow in horizontal equilateral duct fabricated with the same length and equivalent diameter, but different surface roughness pitch ratio(P/e) of 4, 8 and 16 on the one side wall only. The experiments were performed with the hydraulic diameter based Reynolds number ranged from 70,000 to 10,000. The entire bottom wall of the duct was heated uniformly and the other surfaces were thermally insulated. To understand the mechanisms of the heat transfer enhancement, measurements of the heat transfer were done to investigate the contributive factor of heat transfer promotion, namely, the fin effect. And the results were compared with those of previous investigations for similarly configured channels, at which they were roughened by regularly spaced transverse ribs in the rectangular and circular channels.

• 한국분말재료학회지
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• 제22권5호
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• pp.337-343
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• 2015

Powder compaction is a continually and rapidly evolving technology where it is a highly developed method of manufacturing reliable components. To understand existing mechanisms for compaction, parameter investigation is required. Experimental investigations on powder compaction process, followed by numerical modeling of compaction are presented in this paper. The experimental work explores compression characteristics of soft and hard ductile powder materials. In order to account for deformation, fracture and movement of the particles, a discrete-finite element analysis model is defined to reflect the experimental data and to enable investigations on mechanisms present at the particle level. Effects of important simulation factors and process parameters, such as particle count, time step, particle discretization, and particle size on the powder compaction procedure have been explored.

• Advances in aircraft and spacecraft science
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• 제1권1호
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• pp.15-25
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• 2014

The developed concept of smart flow control based on turbulence scale modification was applied to control a flow around a circular cylinder. The concept was realized using arrays of vortex-generators regularly spaced along a cylinder generatrix with a given step. Mechanical and thermal vortex-generators were tested, the latter having been based on the localized surface heating or plasma discharges initiated with microwave radiation near the surface. Thus depending on a particular engineering solution, flow transport properties could be modified in passive or active ways. Matched numerical and experimental investigations showed a possibility to delay flow separation and, accordingly, to improve the aerodynamic performance of blunt bodies.

• 한국주조공학회지
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• 제1권3호
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• pp.19-29
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• 1981

An emphasis has been placed on the importance of selecting a sand for furan sand process, which ie affected by the properties of sand. Investigations have been carried out to use the domestic artificial sands for the furan sand process. For laboratory investigations, the sands have been prepared and tested for chemical analysis, loss on ignition, sieve analysis, AFS grain fineness number, grain shape, PH value, acid demand, surface shape, theoretical surface area, moisture absorption, crushing durability and compressive strength and S. S. I. of molding sands. Most commercial sands have been found to be able to be used. The main requirement of the sands has been shown to be that 3 or 4 screen sands, AFS no.40-70 (or 100), of low acid demand, good surface area and good grain shape require less resin and catalyst to give an adequate strength.

• 한국강구조학회 논문집
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• 제29권4호
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• pp.261-268
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• 2017

본 논문에서는 강관철탑의 3차원 비선형해석 및 비교 검증 실험을 통하여 보조재의 역할 및 결구 거동 특성을 파악하였다. 특히 기존 철탑의 삼각결구를 단순화한 사각결구의 거동특성을 살펴보기 위하여 외측결구와 내측결구의 형상을 달리하고 각 결구의 다양한 조합을 통하여 보조재가 철탑의 내력에 미치는 영향을 살펴보았다.

• Journal of Plant Biology
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• 제11권3호
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• pp.23-30
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• 1968

Using several varieties of Cymbidium, investigations were carried out to make clear how the protocormic tissue develops from the cultured explant. Explant to be cultured were prepared in several ways: exclusively apical meristem, apical meristem dissected out with the basal part attached, axillary bud primordia in their initial stage of development, or apical or axillary bud dissected out as a whole etc. It was observed that protocorms or protocormic tissues were developed from the explant's meristematic tissues regardless of where these tissues were located. Apical meristem, leaf primordia, leaf axil, or internodal part of young bud turned easily protocormic, while the scaly leaves of axillary bud or stem tissue of mother shoot turned quickly brwonish and died away. Both in axillary and apical bud explant alike, whether they were cultured whole or divided, some took quickly green color while others were slower, and some developed protocorms easily while others remained unchanged for months. Varietal difference as well as environmental factors seemed to be responsible for it. Further details should be clarified by histogenetical investigations.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 1998년도 공동 심포지엄 및 추계학술발표회
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• pp.32-37
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• 1998

In this paper, the role of intermediate cover soils with respect to the leachate and gas flow is investigated from various field investigations and the hydraulic conductivity of the disposed waste is obtained using pumping and slug tests. From the results of field investigations, it was found that the flow of leachate and gas is prevented by the buried cover soils. The hydraulic conductivities of field pumping test and slug tests are well matched and stayed in the range of hydraulic conductivities of well compacted wastes in the literature.

• 한국지구과학회지
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• 제23권2호
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• pp.140-146
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• 2002

We have studied 73 pre-service science teachers' conceptions about the nature of science (NOS) using 120 true-false test items based on AAAS Benchmarks statements. We have found that participants have inadequate understanding of the NOS, especially in understanding of five categories of conceptions; change and continuity in science, bias in scientific investigations, hypothesis in scientific investigations, things common in science, and science ethics. The result also indicates that there is a difference between primary pre-service teachers and secondary pre-service teachers. From the analysis of consistency, we also found that this inadequate understanding comes from confusion rather than misconception. All the results support that there is a need of intense pre-service teacher education concerning thenature of science.