• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.365-372
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• 2004

The laser welding and its analysis were carried out using high power 6kW $CO_2$ laser for high strength steels such as DP, TRIP and conventional high strength steels. Bead on plate welding of thin sheet was examined to investigate the effect of weld variables of laser welding, and to obtain optimum welding condition. In order to investigate the formability of welded high strength steels, LDH test was added on this work. At high welding speed, the partial penetration was obtained by low heat input. Meanwhile, porosity was formed in the bead at low weld speed because of extremely higher heat input. The optimum welding condition of welding was derived from bead width, penetration and hardness property. It was shown that the DP steels had lower porosity level and smooth bead shape, therefore better laser weldability than TRIP steels and conventional high strength steels. In addition, LDH test shows that the welded DP steels have about $90\%$ formability value of base metal, although TRIP steel and conventional high strength steels have about $80\%$ formability value of its base metal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.5789-5794
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• 2015

Recently, thin and light-weight production technologies are needed in IT industry in accordance with increase of the smart phones and mobile PC products. In order to make light and high rigidity products, engineering plastic and aluminum materials are frequently used in products appearance and frame hat support structure. Especially aluminum extrusion and CNC Brick processes are widely used for high strength and high rigidity technology. But extrusion method has constraints to apply exterior design and CNC Brick process has relatively high production cost and low speed of manufacturing. In this research, a new process method is introduced in order to reduce material cost and to improve manufacturing speed dramatically. Plate forging process means basically that thickening of local wall area thickness after deform exterior shape by deep drawing and bending process. Therefore, it is possible to minimize the waste of material and the manufacturing time. In this study the process of plate forging is designed using finite element program AFDEX-2D and the thickness and the width of initial deformed blank. And it is verified as a sample which is a part of laptop developed through the proposed plate forging method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.2
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• pp.205-212
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• 1999

Recently, unexpected cracks in the concrete deck slab of composite steel bridges have been widely reported at an early age of concrete placing due to the concrete placing sequence and methods. Accordingly, the analytical research was carried out to verify the negative moment at an internal supports due to the several concrete pouring sequence and to determine the reasonable concrete placing method on the deck slab of composite steel bridge. The results show that the conventional concrete-placing method, which pours concrete first on the positive moment regions and then negative regions, leads to the minimum moment at an internal supports. However, the conventional method produces two impractical construction joints on every spans and makes field engineer to pour concrete continuously. In conclusion, this concrete-placing method was verified to be reasonable only when the construction joint was placed at the $\frac{5}{8}l{\sim}\frac{6}{8}l$ location of the middle span.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.247-247
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• 2010

본 연구는 주류 제조과정에서 발생하는 생전분발효 부산물을 펠릿(pellet)연료로 전환하는 과정에서 효율적인 방법에 대해 기술한다. 술을 정제하는 과정에서 발생하는 주박을 펠릿화하고 재생청정에너지인 폐자원의 효율성을 높이기 위한 방법을 제안한다. 술을 정제하고 남은 지게미를 주박(酒粕, 술지게미)이라 하고 흔히 부드러운 것을 단단하게 뭉친 알갱이를 펠릿이라 한다. 현재 펠릿화는 폐목재를 분쇄후 성형, 가공하여 목재펠릿을 만들어 상용화하고 있다. 목재펠릿은 성형, 가공하는데 비용이 주박보다 많이 들고 열량도 더 낮음을 확인하였다. 목재소에서 나온 나무(톱밥)와 주박을 열량측정기를 이용하여 측정한 결과로 나무는 약 1850 Kcal이고 주박은 약 1989 Kcal가 측정되었다. 나무는 일반 목재소 세 곳에서 채취한 것이고 주박은 막걸리, 약주 및 청주의 술지게미를 실험에 사용한다. 주류업체에서도 술을 정제하고 남은 주박을 처리하는데 많은 곤란과 비용이 든다. 또한 주박을 해양에 투척하여 처리해 왔으나 2012년부터 해양투기가 금지되어 더욱 처리에 곤란을 겪게 된다. 최근 주박을 토양개량제(비료)로 개발하여 사용하기도 하나 본 연구에서 제안하는 장점은 농산물을 재배해서 주류제조시 발생되는 주박을 펠릿화하여 연료로 사용하고 남은 재를 토양개량제로 사용하는 장점이 있다. 제품의 전체 라이프 사이클을 통해 환경으로 방출되는 모든 것을 가능한 한 0(zero)으로 하는 활동인 제로-이미션(zero-emision)이 된다. 이는 단순히 배출량만을 줄이는 것이 아니라 폐기물을 유용한 자원으로 활용한다는 측면이 가장 큰 이점이 된다. 주박의 효율성을 높이기 위해 주박을 종류별로 주박과 목재를 섞는 방법으로 열량을 측정하였다. 먼저 열량이 높은 순서로 막걸리 주박과 약주 주박의 비율을 1:1, 1:0.5, 1:0.2, 두 번째 막걸리 주박과 청주 주박의 비율을 1:1, 1:0.5, 1:0.2, 세 번째 막걸리 주박과 나무 톱밥의 비율을 1:1, 1:0.5, 1:0.2로 섞어서 열량을 측정하였다. 열량이 높은 순서는 세 번째(2015Kcal), 두 번째(1995Kcal), 첫 번째(1868Kcal)의 순이었다. 가장 열량이 높은 막걸리 주박과 나무 톱밥을 섞은 것이 가장 효율성이 높다. 주박 펠릿의 장점은 친환경적인 소재이고 지속적으로 재생이 가능한 에너지원이다. 더욱이 주박 펠릿은 발열량이 높고 다른 바이오매스 원료에 비해 청정하다는 큰 장점을 지니고 있다. 또한 사용에 소요되는 유지 관리비용을 최소화할 수 있고 자동화가 가능하여 사용에 편리하다. 가격면에서 화석연료에 비해 안정적이고 체적 또한 작아 이송의 큰 장점을 가지고 있다. 현재 펠릿의 경우는 목재펠릿이 제품화되어 있지만 주박을 이용하여 제품의 펠릿화를 통한 연료원으로 사용하는 경우는 전 세계 전무한 상태로 폐자원을 재사용하는 효율성이 제시된다. 향후 과제로 주박을 이용한 펠릿 연료원의 기술이 개발되고 기계적인 시스템을 개발하면 저탄소 녹색성장 신재생에너지 연료의 획기적인 미래형 에너지시스템이 될 것이다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.40 no.4
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• pp.328-336
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• 2004

This paper describes the effect of loading rate, specimen geometries and material properties for ModeⅠ and Mode Ⅱ interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) and end notched flexure (ENF) specimen. In the range of loading rate 0.2~20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (Gc).The value of Gc for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of Gc are highest with the increasing intial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.262-268
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• 2003

This paper describes the effect of loading rate, specimen geometries and material properties for Mode I interlaminar fracture toughness of hybrid composite by using double cantilever beam (DCB) specimen. In the range of loading rate 0.2-20mm/min, there is found to be no significant effect of loading rate with the value of critical energy release rate (G_IC). The value of $G_IC$ for variation of initial crack length are nearly similar values when material properties are CF/CF and GF/GF, however, the value of $G_IC/$ are highest with the increasing initial crack length at CF/GF. The SEM photographs show good fiber distribution and interfacial bonding of hybrid composites when the moulding is the CF/GF

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.802-807
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• 2012

Self-piercing rivet is sheet joining method. It is being used more to join aluminum alloy sheets. Self-piercing riveting is a large-deformation process that involves piercing. The self-piercing rivet, under the press from the punch, pierces the top sheet and forms a mechanical interlock with the bottom sheet. In this study, forging process was designed for manufacturing self-piercing rivet. The forging process has been simulated by using commercial FEM code DEFORM-2D. In simulation of forging process for manufacturing rivet, process sequence, formability, forging load, and distributions of stress and strain were investigated. The suitable forging process could be designed by comparisons of simulation results. The developed process consists of four stages: upsetting, first chamfering, back extrusion, and second chamfering. The simulated results for forging process were confirmed by experimental trials with the same conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1785-1796
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• 1998

This paper is concerned with the relationships between optimal number of wavelengths and tuning time in time division multiplexing(TDM) scheduling on wavelength division multiplexing(WDM) optical passive star networks. We assume that the traffic is nonuniform and each node has a tunable transmitter and a fixed receiver. Each node transmits spckets to all other nodes. Most of the earlier protocols on TDM based scheduling for WDM star networks [7, 8, etc.] use whold given wavelength chnnels. But in this paper, we investigate the optimal number of wavelengths that yidels minimum frame length when tuning time exists. It appears within the availble number of wavelengths that yields minimum frame length when tuning time exists. It appears within the available number of wavelengths. We analyze the relationships between optimal number of wavelengths and tuning time by experiments. We analyze the reationships between optimal number of wavelengths and tuning time by experiments. We also discuss on the possibility of reduction of frame length by increasing the number of nodes trans-mitters and receivers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.707-710
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• 2010

The most important things in the KSLV-I Kick Motor nozzle is a development of flexible seal that is utilized to drive a movable nozzle. Especially, a manufacturing technology of flexible seal is one of the key element in the Kick Motor nozzle development. The method used to produce flexible seal in the Kick Motor is injection method. Mold design technology, rubber injection technic and molding process through flexible seal manufacture has been established. After manufacturing, X-Ray inspection have been carried out to confirm a adhesive and internal array of flexible seal.

• The Korean Journal of Food And Nutrition
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• v.24 no.4
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• pp.528-534
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• 2011

This study was conducted to investigate the changes in saponin content and antioxidant activity of crude ginseng and extruded ginseng by using different solvent extraction methods. Each of the fractions was first extracted by 80% ethanol followed by ether treatment to remove the lipid components. Water soluble components were separated by ethylacetate and water saturated butanol. Four fraction, including 80% ethanol, ethylacetate, butanol and water were obtained from crude and extruded ginsengs to analyze saponin content and antioxidant activity. Saponin content and antioxidant capacity of each of the four fractions were measured by LC/MS analysis and ORAC(Oxygen Radical Absorbance Capacity) assay, respectively. It was found that a major portion of saponin was present in ethyl acetate and water saturated butanol fractions. When extracted by 80% ethanol, ginsenoside Rb1 and Rg1 were mostly found in crude ginseng, while ginsenoside Re and Rb1 were detected in extruded ginseng. Even though Rh1 and Rg3 were found in a very small quantity in crude ginseng, there was a significant quantity of both in extruded ginseng when extracted by 80% ethanol. Similar tendency was also observed in extruded ginseng fraction when extracted with ethyl acetate and butanol. In crude ginseng, the level of Rg1 was the highest among other ginsenosides upon extraction by ethyl acetate, while Rh1 and Rg3 were predominantly found by employing similar solvent extraction in the extruded ginseng. Also, Rg1, Re and Rb1 were also found in the extruded ginseng with small quantity. Rg1, Re and Rb1 were found in crude ginseng by butanol extraction, while Rb1 and Re were extracted from the extruded ginseng. Overall, there was no difference in the saponin content between crude ginseng and extruded ginseng when extracted by butanol and water, but twice as much of saponin was obtained by 80% ethanol extraction and 6 times more saponin were obtained in ethyl acetate fraction in the extruded ginseng. Antioxidant capacity of crude ginseng as determined by ORAC assay was higher in 80% ethanol(high in many different kinds of biological compounds) and water saturated butanol(high in polar saponin) fractions than the ethyl acetate and water fractions. No difference in antioxidant capacity was observed between crude and extruded ginseng. However, antioxidant capacity of ethyl acetate and water fractions in extruded ginseng was significantly higher than crude ginseng($P$ >0.05). All the fractions in both, crude and extruded ginseng possessed antioxidant capacity and even water fractions that contained almost no saponin had some antioxidant capacity. While determining correlation coefficient between fractions in extruded ginseng by Pearson correlation, it was observed that 80% ethanol fraction was in correlation with ethyl acetate($P$ >0.01) and ethanol($P$ >0.001) and in the case of ethylacetate, correlation was observed only with butanol fraction($P$ >0.05).