• 소성∙가공
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• 제17권8호
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• pp.600-606
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• 2008

In closed-die hot forging, a billet is formed in dies such that the flow of metal from the die cavity is restricted. Some parts can be forged in a single set of dies, whilst others, due to shape complexity and material flow limitations, must be shaped in multi sets of dies. The purpose of a performing operation is to distribute the volume of the parts such that material flow in the finisher dies will be sound. This study focused on the design of preforms, flash thickness and land width by theoretical calculation and finite element analysis, to manufacture the super hot forging product, 70MC type piston crown used in marine engine. The optimal design of preforms by the finite element analysis and the design experiment achieves adequate metal distribution without any defects and guarantees the minimum forming load and fully filling of the cavity of the die for producing the large piston crown. The maximum loads obtained by finite element analysis are compared with the results of experiments. The loads of the analysis have good agreements with those of the experiment. Results obtained using DEFORM-2D enable the designer and manufacturer of super hot forging dies to be more efficient in this field.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1997년도 추계학술대회논문집
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• pp.45-48
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• 1997

The kinematically admissible velocity field is developed for the eccentric extrusion of circular shaped products. The curving of product in extrusion is caused by the difference of the linearly distributed longitudinal velocity on the cross-section of the workpiece at the dies exit. The results of the eccentric extrusion by upper bound analysis show that the curvature of product increases with the increase in eccentricity of gravity center of the cross-section of workpiece at dies entrance from that of the corss-section at the dies exit end. By the DEFORMTM-3D analysis, the curving of circular shaped product in extrusion is changed by the eccentricity, die land length and the die length. The result of the analysis by DEFORMTM-3D software shows that the curvature of circular shaped product increases with the eccentricity. The two analysis and one experiment show the curving phenomenon in eccentric extrusion process.

• 한국잠사곤충학회지
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• 제14권1호
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• pp.1-7
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• 1972

최근 우리나라 각지의 신개간지상전에 원인불명의 지조고사현상이 발생하고 있어 그 원인을 구명하기 위하여 대표적인 피해상전을 택하여 토양의 물리성조사와 토양 및 식물체내의 붕소함량을 분석한바 다음과 같은 결과를 얻었다. 1. 피해증상의 특징은 발아도중 즉 탈포∼연구기까지 개엽하다가 갑자기 말라 죽는다. 2. 피해상전은 화강암모재에 사양토(암쇄토)로 되어 있으며 건전상전은 화강암모재에 양토로 되어 있었다. 3. 유효토심은 피해상전이 10∼20cm, 건전상전이 40∼50cm로서 유의있게 깊었다. 4. 표층토양의 토양반응과 유효붕소함량간에는 상관관계가 없었다. 5. 표토층의 유기물함량과 유효붕소함량간에는 유의한 회귀관계를 보였으며 고도로 유의한 정상관계수를 얻었다. 6. 토양중 유효붕소함량은 피해상전이 0.13∼0.20 ppm, 건전상전이 0.39∼0.49ppm으로서 피해상전보다 유의있게 많았다. 7. 토양중 아연함？은 피해상전이 0.95∼1.67ppm, 건전상전이 0.78∼1.23ppm으로 유의성이 없었다. 8. 피층내 붕소함량은 피해상전이 10.63∼12.99ppm, 건전상전이 18.42∼21.02 ppm으로 피해상전보다 유의있게 많았다. 9. 피층내 아연함량은 전자가 26.0∼33.8 ppm, 후자가 25.2∼30.7 ppm으로 유의성이 없었다.

• Design & Manufacturing
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• 제10권2호
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• pp.50-54
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• 2016

In the semiconductor industry the final products were checked for several environments before sell the products. The burning test of memory and chip was implemented in reliability for all of parts. The memory and chip were developed to high density memory and high performance chip, so circuit design was also high integrated and the test bed was needed to be thin and fine pitch socket. LGA(Land Grid Array) IC socket with thin wall thickness was designed to satisfy this requirement. The LGA IC socket plastic part was manufacture by injection molding process, it was needed accuracy, stiffness and suit resin with high flowability. In this study, injection molding process analysis was executed for 2 and 4 cavities moldings with runner, gate and sprue. The warpage analysis was also implemented for further gate removal process. Through the analyses the total deformations of the moldings were predicted within maximum 0.05mm deformation. Finally in consideration of these results, 2 and 4 cavities molds were designed and made and tested in injection molding process.

• 농촌지도와개발
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• 제3권1호
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• pp.55-66
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• 1996

Agricultural products are inferior in their competitiveness in the world market mainly due to die high production cost which could be attributed to the rising land and labor cost in Korea. The small scale farming system with the lower production infra structure requires relatively intensive input labor for the reduction of production cost of agricultural products and impediment in the mechanization of farming systems. There are limitations in the cultivation techniques that seek out other directions for the raising competitiveness in the world market of basic food crops. Future goals to raise competitiveness of basic food crops in Korea should include the following: 1. Fostering of the farmers organization by crop items. 2. Agribusiness should integrate management with priority given to farmers. 3. Raise competitiveness to find out the system of obtaining on from the consumers.

• Design & Manufacturing
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• 제15권2호
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• pp.49-55
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• 2021

In this study, CALPUFF, a three-dimensional atmospheric diffusion model, was used to predict the degree of influence of pollutants generated during clean center operation on surrounding areas. To drive the CALPUFF model, CALMET, a weather field calculation model, was used. Due to the influence of the wind field, air pollutants from the Clean Center diffused in the southeast direction, increasing the distribution area. SOx satisfies atmospheric environmental standards with an annual average value of 0.02 ppm or less NOx satisfies atmospheric environmental standards with an annual average value of 0.03 ppm or less. Dust (PM-10) satisfies atmospheric environmental standards with an annual average value of 50㎍/m³ or less and 24 hours average value of 100㎍/m³ or less. CO satisfies atmospheric environmental standards with an 8 hours average value of 9 ppm or less and an 1 hour average value of 25 ppm or less.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.332-337
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitative evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and friction condition on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the heights of the boss and rib. In addition, the effect of flow stress was also investigated on the deformation patterns through FE simulations.

• 소성∙가공
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• 제18권8호
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• pp.640-645
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• 2009

Recently, boss and rib test based on backward extrusion process was proposed to quantitatively evaluate the interfacial friction condition in bulk forming process. In this test, the tube-shaped punch with hole pressurizes the workpiece so that the boss and rib are formed along the hole and outer surface of the punch. It was experimentally and numerically revealed that the height of boss is higher than that of the rib under the severe friction condition. This work is focused on the effect of the punch design and flow stress on deformation pattern in boss and rib test. From the boss and rib test simulations, it was found that there is slight variation in both the heights of boss and rib according to the length of punch land, nose radius, and face angle. However the hole diameter of the punch and the clearance between the punch and die have a significant influence on the calibration curves showing the heights of the boss and rib. In addition, the effect of flow stress on the calibration curves was investigated through FE simulations. It was found that there is no effect of strength coefficient of the workpiece on the calibration curves for estimation of friction condition. On the other hand, the strain-hardening exponent of the workpiece has a significant influence on the calibration curve.

• 공학교육연구
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• 제14권3호
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• pp.3-8
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• 2011

Women in the predominantly male-oriented college of engineering which is afflicted by the high dropout rate and the low employment rate of coeds in their majoring fields because of the die-hard male dominant culture. In order to resolve the related problems, P University has been actively engaged in a movement called "Women into Engineering" (WIE) to raise the gender cognitive awareness and to train women engineers for highly qualified work force. As part of the movement, a subject called "Women in Engineering" that focuses on the gender cognitive perspective is effective to reduce the dropout rate and to land a job inside their fields by stimulating their interest in their specialty and masting soft/hard skills. The study was conducted a survey of the coeds who have completed the "Women in Engineering" course to evaluate the degree of satisfaction perceived, and a t-test through comparing the group of the coeds and a group of coeds who have not taken the course. The results showed statistically significant responses indicating that both groups of coeds would like to see WIE offer more basic engineering courses like "Women in Engineering". This may lay the foundation to offer other major engineering courses for juniors and seniors that emphasize the gender cognitive approach.

• 공학교육연구
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• 제17권5호
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• pp.8-12
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• 2014

Women in engineering subject were developed for women included engineering education in Korea. Women in the predominantly male-oriented college of engineering which is afflicted by the high dropout rate and the low employment rate of coeds in their majoring fields because of the die-hard male dominant culture. In order to resolve the related problems, Our University has been actively engaged in a movement called "Women into Engineering" (WIE) to raise the gender cognitive awareness and to train women engineers for highly qualified work force. As part of the movement, a subject called "Women in Engineering" that focuses on the gender cognitive perspective is effective to reduce the dropout rate and to land a job inside their fields by stimulating their interest in their specialty made soft/hard skills. The study was conducted a survey of the coeds who have completed the "Women in Engineering" course to evaluate the degree of satisfaction perceived, and a t-test through comparing the group of the coeds and a group of coeds who have not taken the course. The results showed statistically significant responses indicating that both groups of coeds would like to see WIE offer more basic engineering courses like "Women in Engineering." This may lay the foundation to offer other major engineering courses for juniors and seniors that emphasize the gender cognitive approach.