• Korean Journal of Mathematics
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• 제22권1호
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• pp.57-69
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• 2014

We obtain a formula for the conditional Wiener integral of the first variation of functionals and establish several integration by parts formulas of conditional Wiener integrals of functionals on a function space. We then apply these results to obtain various integration by parts formulas involving conditional integral transforms and conditional convolution products on the function space.

• 한국가축번식학회지
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• 제3권2호
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• pp.24-31
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• 1979

The maturation changes in morphology were studied with the spermatozoa collected from the testis and three successive parts of the epididymis in Korean native Cattle. Acrosomal granules were observed in the testis. Avoiding the cap and acrosome phases, the tail base and the striated column of the neck were formed in spermatides. The volume of the acrosome was decreased during transit from the testis to the epididymis. The cell membranes were also separated from the acrosome or damage during the spermatozoan passage through successive parts of the reproductive tract. Cytoplasmic droplets were observed in the spermatozoa collected from various parts of the reproductive tract.

• 항공우주산업기술동향
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• 제7권2호
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• pp.106-114
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• 2009

그 동안 항공부품시장은 높은 신뢰성과 안전성을 요구하는 항공산업의 특성로 인해 OEM(Original Equipment Manufacturer) 부품이 주도하여 왔다. 그러나 제조기술의 발전, 경기침체, 유가상승 및 아시아-태평양 신흥 시장의 부각 등의 환경적 변화로 인해, 최근, 항공시장에서의 PMA 부품에 대한 관심이 지속적으로 증대되고 있다. 실제로 2006년 이후 FAA PMA 승인부품은 매년 40,000 개씩 증가하고 있으며, PMA 부품 보급률(아시아-태평양 시장)은 2007년 2.5%에서 2017년 8%까지 증대될 것으로 예상되고 있다. 따라서, 본 논문에서는 항공부품 승인제도에 대한 이해를 도모하고, 새로운 PMA 시장을 살펴보기 위해 FAA PMA/EASA EPA의 절차상 요건과 PMA 부품시장 현황을 소개하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.375-378
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• 2009

Hot press forming is a new forming process which also names as hot stamping. It can greatly enhance the formability of forming parts. This paper researches the formability of boron steel sheet in hot bending process which is a kind of hot press forming. In the text, the influence of hot press forming processing parameters, such as the heating temperature, blank holding force, punch speed and punch and die radius, on the mechanics properties and microstructure of the hot bending parts was analyzed by tension test and the metallographic observation on the parts with various processing parameters. The relationship between blank holding force and punch load was also presented.

• 소성∙가공
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• 제10권3호
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• pp.223-234
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• 2001

The characteristics of thixoforming process can decrease liquid segregation because of the improvement in fluidity in a globular microstructure state and utilizes flow without an air entrapment. Therefore, in order to obtain the sound parts of metal matrix composites by using thixoforming process which has co-existing solidus-liquidus phase, it is very important to design a die shape property and to obtain the fabrication conditions which affect the unifomity of the solid fraction on unfilling state and various defects throughout the fabricated parts. The die designs and fabrication conditions to obtain the good piston part are proposed for thixoforging process of metal matrix composites. When reheated metal matrix composites billets were transferred to the closed die gate, thixoforging were carried out under the various pressure(60, 80, 100MPa) with controled forging speed. The mechanical properties such as hardness and tensile strength for thixoforged parts have been investigated after T6 heat treatment.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 고액공존금속의 성형기술 심포지엄
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• pp.135-147
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• 1997

The production of light metal parts using aluminum is mainly performed by die casting and squeeze casting, which directly fabricate the required shape from the liquid state. However, die casting is subject to defects such as shrinkage porosity and air trapped when molten metal enters the cavity, whilst squeeze casting also has defects due to turbulent flow in the die cavity. Both diecasting and sqeeze casting have inhomogeneous mechanical property in terms of dendritic structure during solidification. Active research has been carried out on semi-solid processing, rather than on conventional process methods such as die casting, which involve various problems. Therefore in this paper, to introduce the fundamental technology for d e design, in die casting and forging process with semi-solid materials, relationship between stress and strain of semi-solid materials, and for producing parts die design has been proposed as parameters of globulization of the microstructure and gate shape. The prevention of various defects to produce sound parts are also introduced.

• 소성∙가공
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• 제20권8호
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• pp.575-580
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• 2011

Direct laser melting(DLM) is promising as a joining method for producing parts for automobiles, aerospace, marine and medical applications. An advantageous characteristic of DLM is that it affects the parent metal very little. The mechanical properties of parts made by DLM are strongly affected by the porosity and surface roughness of the laser melted beads. This is a systematic study of the effects of the porosity and surface roughness of laser melted beads using various processing parameters, such as laser power, scan rate and overlapping ratio of the fill spacing. The specimens were fabricated with 316L and 304L austenitic stainless steel powder. Dense parts with low porosity were obtained at low laser scan speed, as it increased the aspect ratio of the parental material and the depth of penetration. The variations of surface roughness were examined at various processing parameters such as overlapping ratio and laser power.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.143-148
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• 1995

A study on the generation of optimum tool path for machining the concave parts is discussed. Above all, the various cutting factors and their relationships are considered. Then optimum tool path for concave parts is generated on these cutting variables and their relationships. It is difficult for existing CAD/CAM systems tomachine the concave parts. For cutting the part even the experienced craft must give many attentions and muchtime since it needs consideration of various cutting conditions and geometric properties. The optimum tool path for the concave part is generated onnot only geometric properties byut also cutting conditions. We choose, as variables, feed and cutting direction for productivity, diameter of tool and constant(stable) cutting force for machining accuracy. The results are verified through simulation of the index of performance and cutting force.

• 산업경영시스템학회지
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• 제28권4호
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• pp.28-40
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• 2005

This paper focuses on a BOM(Bill of Materials) management problem for a small and medium manufacturing company that produce automobile parts. Automobile part's manufacturers produce various products due to various automobile characteristics such as types, colors, and the other options of car. These products are classified into product groups with common parts. And each product group is regarded as a product family. This paper proposes an efficient and effective EXCEL-based BOM management scheme using characteristics of the product family. And we have implemented the practical EXCEL-based BOM management system for real small and medium automobile part's manufacturing companies.

• 소성∙가공
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• 제11권4호
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• pp.323-331
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• 2002

The combination of rapid prototyping(RP) and rapid tooling(RT) has a potential for rapid manufacturing of three-dimensional parts. In the present study, a new RP system transfer type Variable Lamination Manufacturing using Expandable Polystyrene Foam (VLM-ST), is proposed to fabricate net shapes of three-dimensional prototypes. Various three-dimensional parts, such as a knob shape and a human head shape, are manufactured by the VLM-ST apparatus. In addition, a new rapid tooling technology, which utilizes a room temperature vulcanizing (RTV) molding technique and a triple reverse process technique, is proposed to manufacture net shapes of three-dimensional plastic parts using the prototypes of VLM-ST. A plastic part of the knob shape is produced by the proposed RT technology. The combination of the proposed RP and RT enables the manufacture of a plastic knob within two days.