• Korean Journal of Mathematics
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• v.22 no.1
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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.

• Korean Journal of Animal Reproduction
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• v.3 no.2
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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.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.2
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• pp.106-114
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• 2009

Until now, The Market of aviation parts had led by OEM(Original Equipment Manufacturer) parts because of aviation industry's nature required higher reliability and safety. But recently, The interest about PMA parts in aviation market is increasing continuously with various environmental changes, such as economic stagnation, oil price rise, development of the manufacture technique and newly rising market of Asia-Pacific region. Actually, after 2006, FAA PMA approval parts are increasing at a rate of around 40,000 parts per year and 2.5% of PMA parts penetration, in 2007, in Asia-Pacific market is forecast to enlarge up to 8% in 2017. So, this paper introduces the process requirements of FAA PMA / EASA EPA and the status of PMA market in order to enhance understanding for certification for aviation parts and to review a new PMA market.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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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.

• Transactions of Materials Processing
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• v.10 no.3
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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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.06a
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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.

• Transactions of Materials Processing
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• v.20 no.8
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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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04b
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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.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.28 no.4
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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.

• Transactions of Materials Processing
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• v.11 no.4
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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.