• Composites Research
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• v.34 no.4
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• pp.241-248
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• 2021

As the electric vehicle market grows, there is an issue of light weight vehicles to increase battery efficiency. Therefore, it is going to replace the battery module cover that protects the battery module of electric vehicles with high strength/high heat-resistant polymer composite material which has lighter weight from existing aluminum materials. It also aims to respond to the early electric vehicle market where technology changes quickly by combining 3D printing technology that is advantageous for small production of multiple varieties without restrictions on complex shapes. Based on the composite material mechanics, the critical length of glass fibers in short glass fiber (GF)/polycarbonate (PC) composite materials manufactured through extruder was derived as 453.87 ㎛, and the side feeding method was adopted to improve the residual fiber length from 365.87 ㎛ and to increase a dispersibility. Thus, the optimal properties of tensile strength 135 MPa and Young's modulus 7.8 MPa were implemented as GF/PC composite materials containing 30 wt% of GF. In addition, the filament extrusion conditions (temperature, extrusion speed) were optimized to meet the commercial filament specification of 1.75 mm thickness and 0.05 mm standard deviation. Through manufactured filaments, 3D printing process conditions (temperature, printing speed) were optimized by multi-optimization that minimize porosity, maximize tensile strength, and printing speed to increase the productivity. Through this procedure, tensile strength and elastic modulus were improved 11%, 56% respectively. Also, by post-processing, tensile strength and Young's modulus were improved 5%, 18% respectively. Lastly, using the FEA (finite element analysis) technique, the structure of the battery module cover was optimized to meet the mechanical shock test criteria of the electric vehicle battery module cover (ISO-12405), and it is satisfied the battery cover mechanical shock test while achieving 37% lighter weight compared to aluminum battery module cover. Based on this research, it is expected that 3D printing technology of polymer composite materials can be used in various fields in the future.

• Korean Journal of Veterinary Research
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• v.21 no.2
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• pp.123-133
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• 1981

진드기는 생물학적(生物學的) 여러 분야(分野)의 연구대상(硏究對象)으로 또는 진드기 매개전염병(媒介傳染病)의 역학(疫學)과 방제(防除)를 위(爲)한 연구재료(硏究材料)로 공시(供試)되는데, 이를 위(爲)하여는 실험작군(實驗作群)에 의(依)한 집단생산(集團生産)이 요구(要求)된다. 그러나 이러한 실험작군(實驗作群)에 있어서 동일(同一)한 가토(家兎)를 실험용(實驗用) 숙주(宿主)로 반복(反復)하여 사용(使用)했을 경우(境遇), 진드기의 흡혈성취도(吸血成就度)가 저하(低下)되는 현상(現象)을 경험(經驗)하게 된다. 이러한 현상(現象)에 흥미(興味)를 가지고, 이를 실험용(實驗用) 가토(家兎)에 대(對)한 Haemaphysalis longicornis 미포혈(未飽血) 자충(雌蟲)의 반복흡혈(反復吸血)에 있어서의 흡혈성취도(吸血成就度) 변화(變化)를 조사(調査)해 보고자 몇가지 실험(實驗)이 설계(設計) 진행(遂行)된 바, 결과(結果)는 다음과 같이 요약(要約)된다. 1. 최초(最初)(1차(一次)) 흡혈시도(吸血試圖)에 있어서 공시(供試)된 진드기의 흡혈성취도(吸血成就度)는 실험용(實驗用) 숙주(宿主)인 가토(家兎)의 월령별(月齡別) 비교군간(比較群間)에 유의성(有意性) 있는 차이(差異)가 인정(認定)되지 아니 하였다. 2. 성공적(成功的) 흡혈율(吸血率)은 최초(最初)(1차(一次)) 흡혈시도(吸血試圖)에서 82.29%를 보였으나, 반복흡혈시도(反復吸血試圖) 차수(次數)가 증가(增加)함에 따라, 76.04%(2차(二次)), 53.13%(3차(三次)), 50%(4차(四次)), 46.87%(5차(五次))로 점차적(漸次的)으로 저하(低下)되는 성적(成績)을 보였다. 3. 평균흡혈기간(平均吸血期間)은 최초(最初)(1차(一次))흡혈시도(吸血試圖)에서 9.34일(日)을 보였으나, 반복흡혈시도(反復吸血試圖) 차수(次數)가 증가(增加)함에 따라, 9.74일(日)(2차(二次)), 10.31(日)(3차(三次)), 10.42(日)(4차(四次)), 10.47(日)(5차(五次))로 점차(漸次) 지연(遲延) 되었으며, 평균흡혈속도(平均吸血速度)는 0.1070에서 0.1027, 0.0970, 0.0960, 0.0955로 점차(漸次) 감속화(減速化) 되었다. 4. 평균(平均) 흡혈체중(吸血體重)에 있어서는 최초(最初)(1차(一次)) 흡혈시도(吸血試圖)에서 253.3mg의 성적(成績)을 보였으나, 흡혈시도(吸血試圖)가 반복(反復)됨에 따라, 242.58mg(2차(二次)), 190.73mg(3차(三次)), 187.85mg(4차(四次)), 184.18mg(5차(五次))으로 점차(漸次) 경량화(輕量化)되는 경향(傾向)을 나타냈다. 5. 결론적(結論的)으로 실험용(實驗用) 가토(家兎)에 대(對)한 Haemaphysalis longicornis 진드기의 흡혈성취도(吸血成就度)는, 반복흡혈시도(反復吸血試圖) 차수(次數)가 증가(增加)함에 따라, 숙주체내(宿主體內)에 형성(形成) 누적(累積)되는 진드기에 대(對)한 획득면역(獲得免疫)의 영향(影響)을 받아 점차(漸次) 저하(低下)되며, 따라서 H. longicornis 진드기의 집단생산(集團生産)을 위(爲)한 실험작군(實驗作群)이나 혈류보존(血統保存)을 위(爲)한 계대흡혈(繼代吸血)에 있어서 동일(同一) 가토(家兎)를 2회이상(回以上) 반복사용(反復使用)하는 것은 바람직한 일이 아닌 것으로 사료(思料)된다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1345-1352
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• 2012

This paper aims to evaluate the low-velocity impact responses and mechanical properties of balsa-wood and urethane-foam core materials and their sandwich panels, which are applied as the impact limiter of a nuclear spent fuel shipping cask. For the urethane-foam core, which is isotropic, tensile, compressive, and shear mechanical tests were conducted. For the balsa-wood core, which is orthotropic and shows different material properties in different orthogonal directions, nine mechanical properties were determined. The impact test specimens for the core material and their sandwich panel were subjected to low-velocity impact loads using an instrumented testing machine at impact energy levels of 1, 3, and 5 J. The experimental results showed that both the urethane-foam and the balsa-wood core except in the growth direction (z-direction) had a similar impact response for the energy absorbing capacity, contact force, and indentation. Furthermore, it was found that the urethane-foam core was suitable as an impact limiter material owing to its resistance to fire and low cost, and the balsa-wood core could also be strongly considered as an impact limiter material for a lightweight nuclear spent fuel shipping cask.

• Economic and Environmental Geology
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• v.50 no.2
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• pp.145-157
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• 2017

Because of Recent intensive rainfall, nationally landslides and slope failure phenomenon has been frequently occur. Providing proposed-measures to the natural disasters that occur in these localities and the slope, must be derived ground of strength parameters(shear strength) as a design input data. However, it is such as extra deforestation and a lot of economic costs in order to make the access to the current area and the slopes ground survey is required. Thus, by small dynamic cone penetration test machine using the human to carry in the field, it is possible to easily measure the characteristics and strength constant of the ground of more than one region. In this study through researching analysis of the domestic and foreign small dynamic cone penetration test method, it has proposed a cone material and test methods suitable for the country. Cone penetration test Nc in the field has comparated with analysis of the value and the standard penetration test N value. And, in addition to this, direct shear test and borehole shear test were performed by depth, bedrock, and soil type and passing #200 and the correlation of the Nc value. In particular, in the present study, for the sandy soil that has distict distribute in mountain, it is proposed relation of shear strength corresponding to the Nc value (cohesion and internal friction angle) in order to calculate such effective ground shear strength.

• Journal of Biomedical Engineering Research
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• v.19 no.5
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• pp.519-530
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• 1998

In this paper, the basic study on the design of the flexible keel of the energy-storage prosthetic foot was performed in order to Improve the walking performance and Increase the activities of the below knee amputees. Based on the analysis of the anthropometric data and the normal gait on two dimensional sagittal plane available In the literature, we presented a model of the basic structure of the flexible keel of the prosthetic foot. The model of the basic structure was composed of the simple beams, and linear rotational spring and damper. Laminated carbon fiber-reinforced composites were selected as the material of the basic structure model of the flexible keel In order to apply the high strength and light weight materials to the basic structure of the flexible keel of the prosthetic foot. The recoverable strain energy In response to the change of beam shape was calculated bur the finite element analysis and it was suggested that the change of beam shape could be the design variable in flexible keel design. The simulation process was systematically designed by using orthogonal array table in order to design the flexible keel structure which could store the more recoverable strain energy. finite element analysis was carried but according to the design of simulations by using the finite element program ABAQUS and the flexible keel structure of the energy-storage prosthetic foot was obtained from the analysis of variance(ANOVA). The dynamic simulation model of the prosthetic walking using the flexible keel structure was made and the dynamic analysis was carried but during one walk cycle. Based on the above results, an effective design process was presented for the development of the prosthetic fool system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.452-459
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• 2017

In recent years, to reduce self-weight of structural elements, the use of SCP (Steel Concrete Plate) instead of prestressed concrete is increasing. Because SCP has a complicated sectional shape and includes a large number of studs, the use of high-fluidity concrete is required. Therefore, in this study, to prevent the restrained shrinkage behavior by the stud, the effects of using an expansive agent (EA) and shrinkage reducing agent (SRA) were investigated, and the optimal mixture proportions to maximize the filling capacity were determined based on the fine aggregate ratio. The test results indicated that the combined use of EA and SRA exhibited the smallest shrinkage. The ratio of the crushed sand and washed sea sand was determined to be 5:5, and the proper fine aggregate ratio was found to be 55.6%, because when the ratio was too high, a decrease in strength and an increase in shrinkage strain were expected. The high-fluidity concrete effectively filled the large-sized SCP module.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.27-27
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• 2009

드라이브 샤프트는 일반적으로 엔진에서 발생된 회전력을 바퀴에 직접 전달하는 동시에 조향기능을 수행하는 자동차 부품이다. 최근에 경량화를 통한 에너지 절감을 위하여 기존 스틸소재를 알루미늄으로 대체하는 방안에 대한 연구가 집중되고 있다. 그러나 알루미늄 단일소재로 드라이브 샤프트를 제조하는 것은 비경제적이며 또한 기 개발된 자동차 부품들과의 연결을 고려하여 알루미늄 튜브와 스틸 요크의 이종금속 접합기술이 요구된다. 전자기 펄스용접은 전자기력을 이용하여 용접대상물을 고속으로 충돌시켜 용접하는 기술로서 열 발생이 적어 재료의 특성차로 인한 결함 및 변형이 발생하지 않아, 이종금속간 고품질 용접이 가능하며, 전자기 펄스 용접부의 품질과 밀접한 관계를 갖는 공정변수 경우 모재와 접합재의 재질 따라 적정 공정변수 범위가 변화되므로 공정에 따른 데이터의 축적은 대단히 중요하다. 전자기 펄스 용접을 이용한 이종금속 접합시 접합부 품질에 영향을 미치는 공정변수는 충전전압, 모재와 접합재 사이의 간격 및 접합재의 직경과 두께의 비(D/T비)로서 보고되었으며, Al/Steel 이종 금속 접합시 이들 공정변수가 접합부에 미치는 영향 및 최적의 공정변수 도출을 위한 연구는 시도되지 않았다. 따라서 본 연구는 전자기 펄스 용접기술을 이용한 Al/Steel 이종금속 접합 실험을 통하여 전자기 펄스용접의 적정성과 최적의 충전전압, 모재와 접합재 사이의 간격, D/T비를 도출하고자 한다. 전자기 펄스 용접 장치는 한국생산기술연구원과 웰메이트(주)에서 공동으로 개발한 $120{\mu}F$의 캐패시터 6개로 구성된 'W-MPW36'을 사용하였으며 이 장치의 최대충전전압과 최대접합용량은 각각 10kV, 36kJ이다. 접합재는 전기 전도율의 높은 Al 1070 파이프를 사용하였으며 모재는 기존 스틸 요크재인 SM45C 환봉을 사용하였다. 기보고된 연구를 통하여 코일과 접합재 사이의 간격이 좁을수록 높은 전자기력이 접합재에 작용하는 것을 확인하였으나 코일내 접합재와 모재 삽입 편의를 위하여 1mm로 설정하였다. 접합부의 품질 평가를 위하여 수압시험을 실시하였으며, 시험 후 접합부 단면을 주사전자현미경(SEM)을 이용하여 관찰하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.699-705
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• 2015

Aircraft needs high lift-to-drag ratio and weight reduction of the structure for long endurance flight with a small power. Generally high aspect ratio wing is applied to HALE(High Altitude Long Endurance) aircraft. Also high modulus, and high strength CFRP(Carbon Fiber Reinforced Plastic) has been used in primary structures. and thin mylar(membrane material) film has been applied to skin of wing. As a result, wing is more flexible than the other structures. and the stiffness of thin mylar film has an affect on dynamic stability. In this study, the membrane characteristic of mylar film has been simulated using nonlinear gap elements. And equivalent modeling method using shell elements is presented using the nonlinear simulation result. The linear equivalent model has verified using the results of nonlinear membrane method. Proposed linear equivalent shell model has applied to mode analysis for estimate the effect of mylar mechanical properties on natural frequency.

• Journal of Adhesion and Interface
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• v.16 no.2
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• pp.69-75
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• 2015

Stone board for the rock bed was needed to reduce weight using thin thickness and reinforced materials. In this work, stone/wood board for rock bed was studied. Stone and wood were attached to reduce total weight of stone for rock bed. For reinforcing wood heat treatment method was used to change surface and mechanical properties. Mechanical strength of heat treated wood increased more than neat condition. The optimum heat treatment condition was set on $100^{\circ}C$ under tensile, flexural loads whereas surface energy was also obtained by contact angle measurement. Optimum adhesive condition was to get the maximum adhesion between stone and wood. Lap shear test was performed for stone/wood board with different adhesives such as amine type epoxy, polyurethane, chloro-rubber and vinyl chloride acetate type. Fracture surface of lap shear test was shown at wood fracture part on stone using amine type epoxy adhesive. It was found that for high adhesion between stone and wood the optimum adhesive was epoxy type for the rock bed.

• Journal of Convergence Society for SMB
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• v.3 no.2
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• pp.27-32
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• 2013

Wireless Body Area Networks (WBAN) have been made possible by the emergence of small and lightweight wireless systems such as Bluetooth, enabled devices and PDAs. Antennas are an essential part of any WBAN system and due to various technical requirements and physical constraints, careful consideration of their design and deployment is needed. This paper is proposing on the design of wearable antenna as parts of clothing to serve communications functions, such as tracking and navigation in health care applications. The substrates of the wearable antennas will be made from textile materials and since it is wearable, it should have a small size, be light weight, low maintenance, and unobtrusive. This proposed paper will also investigate the influence of different parameters for wearable antenna including types of textile/substrate to ensure that the antenna design satisfies WBAN requirements. The characteristics and behavior of the antenna need to adhere to specifications set by wireless standards and system technology requirements. This means that the transmitting and receiving frequency bands of the various units need to be chosen accordingly. Since there are restrictions on the level of power to which the human body can be exposed to, the antenna as well as other RF system components must be designed to meet these restrictions. Antenna gain, which directly affects power transmitted, is a critical parameter in ensuring power levels fall within the safety guidelines and so will be of primary importance in the design. The electromagnetic interaction between WBAN antennas and devices and the human body will also be explored.