• 한국강구조학회 논문집
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• 제23권1호
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• pp.125-135
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• 2011

최근 타워형 아파트구조에 많이 사용되고 있는 무량판 구조시스템을 대신해 층고절감 및 장스팬 구현 그리고 내화성능향상을 목적으로 GFRP를 이용한 경량합성바닥을 개발하였다. GFRP를 이용한 경량합성바닥은 웨브에 개구부를 가지는 비대칭 강재보 하부에 GFRP를 부착하고 슬래브에 경량체를 삽입한 중공합성바닥이다. 이에 개발된 합성바닥의 휨성능을 평가하기 위해 GFRP, 중공률, 웨브의 개구부 등을 변수로 실대 실험을 수행하였다. 그 결과 GFRP를 이용한 합성보 실험체는 기준 실험체에 비해 휨내력 및 강성 측면에서 10% 높은 성능을 나타냈으며, 구조물이 항복할 때까지 완전합성거동하였다. 항복 이후 웨브개구부 주변의 응력집중현상에 의해 연성이 감소하는 현상이 나타났으며, 최대내력점까지 미끄러짐의 발생은 미소하였다. 내력설계 측면에서는 안전율을 고려해 해석값의 85%를 설계내력으로 평가하는 것이 타당한 것으로 나타났다.

• 한국전자파학회논문지
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• 제19권1호
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• pp.61-70
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• 2008

본 논문에서는 멤스 기술의 하나인 연성 인쇄 회로 기판을 이용하여 임의의 형태로 변형이 가능한 초고주파 멤스 송신기를 제안하였다. 연성 인쇄 회로 기판은 그 무게가 가볍고 두께가 얇아 경량 소형화 모듈을 만드는데 유리한 장점이 있다. 또한, 연성 인쇄 회로 기판은 종이와 같이 유연한 특성을 가지고 있어 평면이 아닌 임의의 곡면 등에 실장할 수 있는 장정을 가지고 있다. 본 논문에서는 근거리 센서 네트워크 구성을 위한 직교 주파수 분할 다중 전송 방식을 위한 선형 무선 송신기를 설계 제작하였다. 송신 모듈의 능동 회로는 전력효율이 높고 선형성이 우수하여 전력 증폭기에 많이 사용되고 있는 InGaP/GaAs HBT 공정을 사용하여 설계 및 제작하였으며, 매칭 회로 및 필터 등의 수동 회로는 연성 인쇄 회로 기판에 직접 집적화 하여 제작하였다. 제작된 멤스 송신기는 EVM 특성을 통하여 시스템 성능을 분석하였다.

• 한국과학교육학회지
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• 제13권1호
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• pp.56-65
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• 1993

The purpose of this study is to analyze the inquiry activities of SCIIS and Korea primary school science curricular meterials and to make suggestions for the improvement of inquiry learning based on the analysis The Scientific Inquiry Evaluation Inventory (SIEI: Myung Hur, 1984) was used to evaluate the inquiry activity content of the primary school "Science, Level-6" and "SCIIS, Level-6" textbooks. The results are as follows: 1) The inquiry activities of Korean science textbooks are stressing on gathering and organizing data, but rarely require students to formulate a hypothesis, to design an experiment. 2) The SCIIS textbooks relatively tended to put more weight on interpreting/ analysing data and hypothesizing/ designing experiments. 3)The Korean science textbooks had little concern about establishing hypothesis and designing experiments, interpreting / analysing data. 4) The SCIIS textbooks require students to perform a variety of inquiry skills when compare to Korean science textbooks. 5) Competition / Cooperation Scale checks the level of competition and cooperation among student teams inherent in science curricular materials. The result from each team is incorporated into the formation of a class result. The communication is required to formulate a synthesized class response, enhances cooperation among teams. The SCIIS(84%) is the higher than Korea(50%) in cooperation scale. 6) Korean science textbooks rarely require students to discuss about experiment when compare to SCIIS textbooks. 7) Korean science textbooks provide students with both inquiry problems and experimental procedure, or including answers SCIIS textbooks provide students with both inquiry problems and experimental procedure, or problems only. 8) The Korean textbooks emphasize demonstrating or verifying of the text while the SCIlS emphasize extending the content of the text in inquiry scope scsle. The inquiry pyramid which helps analysis the inquiry activity curriculum as a whole is one of type 1- the course is centered on gathering and organizing data. The SCIIS are better than the Korean science textbook in the light of proportion of interpreting / analysing data and hypothesizing / designing experiments.

• 한국전산유체공학회지
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• 제20권4호
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• pp.63-69
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• 2015

The thermal balance test in vacuum chamber for satellite structures is an essential step in the process of satellite development. However, it is technically and economically difficult to fully replicate the space environment by using the vacuum chamber. To overcome these limitations, the thermal analysis through a computer simulation technique has been conducted. The CFRP composite material has attracted attention as satellite structures since it has advantages of excellent mechanical properties and light weight. However, the nonuniform nature of the thermal conductivity of the CFRP structure should be noted at the step of thermal analysis of the satellite. Two different approaches are studied for the thermal analyses; a detailed numerical modeling and a simplified model expressed by an effective thermal conductivity. In this paper, the effective thermal conductivities of the CFRP composite structures are extracted from the detailed numerical results to provide a practical thermal design data for the satellite fabricated with the CFRP composite structure. Calculation results of the surface temperature and the thermal conductivities along x, y, z directions show fairly good agreements between the detailed modeling and the simplified model for all the cases studied here.

• 한국전산유체공학회지
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• 제18권3호
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• pp.8-13
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• 2013

Drag reduction of a running vehicle is very important issue for the energy savings and emission reduction of its power train. Especially for a solar powered electric vehicle, the drag reduction and weight lightening are two serious problems to be solved to extend its driving distance under the given energy condition. In this study, the ground effect of an airfoil shaped road vehicle was studied for an optimum body design of an ultra-light solar powered electric vehicle. Clark-Y airfoil type was adopted to the body shape of the model vehicle to reduce aerodynamic drag. From the study, it was found that the drag of the model vehicle was reduced as the height(h) between ground and the lower surface of the model vehicle was decreased. It is due to the reduction of the down-wash decreasing the induced drag of the vehicle. The lift was also decreased as the height decreased. It is due to the turbulent boundary layer developed beneath the vehicle body. The drag is classified into two types; the form and friction drag. The fraction of form drag to friction one is 76 to 24 on the model vehicle. As the height(h) of the model vehicle from the ground surface increases the form drag also increases but the friction drag is in reverse.

• 한국의류산업학회지
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• 제16권3호
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• pp.446-455
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• 2014

This study revealed the results related to the functionality of outdoor wear required when man and women in their 30s to 50s engage in outdoor activities. Based on the results of the survey, we proposed composition draft for a smart outdoor jacket with main functions of GPS device and light-emitting device using solar cell and EL. Absorption and release of sweat, functionality regarding rain and wind, and lightweightness, etc. from material functionalities of outdoor wear were found to be important. From function required in clothing for outdoor activity, location tracking, night glow, and lighting functions were found to be most important. For results investigating the necessity of the jacket's location tracking function and lighting function using solar cell, high scores of 3.9~4.0 were given. Purchase intentions for smart outdoor jacket with location tracking and lighting functions devised by this study were fairly positive and most responses indicated that the appropriate purchase price was between 200,000 to 300,000 won while possible problems of this smart outdoor jacket were listed in the order of washing inconvenience, high price, device weight, and discomfort in movement. The draft proposal to integrate with wearable devices for smart outdoor jacket prototype is as follows: Solar cell has been attached to the upper arm but placed inside a transparent pocket which has been detachable for washing convenience while the solar cell and controller have been integrated into a single unit. Using frequent movement exhibited by the arms, EL has been attached along the center line of the raglan sleeve for easy spotting when used as an emergency signal or for night lighting function during outdoor activity. GPS has been attached on the left sleeve so that the person can bend the left arm inward and operate the GPS screen with the right hand while walking or running outdoors.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.62-67
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• 2005

Recently, polymer insulators that are used for high voltage applications have some advantages such as light weight, small size, vandalism resistance, hydrophobicity and easy making process. During outdoor service of polymer insulators, the surface of the insulating material is frequently subjected to moisture and contamination that lead to dry band arcing. Their tracking resistance, erosion resistance, end sealing and shed design are very important because dry band arcing causes degradation of polymer surface. Aging test to estimate life property of polymer insulator is executed through several international standard such as IEC 61109 and CEA tracking wheel test, but is not getting clear conclusion yet. There are two methods in the diagnosis method of polymer insulator such as off-line and on-line. The diagnosis methods in off-line are external condition analysis by the eye, contaminant analysis on surface, surface analysis, pollution withstand voltage test, power frequency flashover voltage test, lightning impulse flashover test, tensile fracture load test and flexural load test. Polymer material is also investigated it's tracking resistance by adding surface active agent in IEC 587. In this paper, the tracking performance of polymer insulator with salt solution which is added surface active agent. The diagnosis of insulator sample has been analyzed by leakage current and visual examination, STRI guide and thermal image camera.

• Composites Research
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• 제24권3호
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• pp.12-16
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• 2011

경량복합소재의 고속인장시험을 수행하여 변형률속도에 따른 강도변화를 측정하고자 한다. 준 정적 시험인 경우 섬유강화 복합소재의 인장시험은 ASTM D3039에 따른 시편 형상이 사용되지만 고속 인장시험인 경우 표준화된 시편 형상에 대한 연구가 진행되어 있지 않다. 본 연구에서는 ASTM D638에 나타난 시편 형상을 기본으로 몇 가지 변형된 형태의 시편을 가지고 고속인장 시험을 수행하여 변형률 속도에 따른 경량복합소재의 강도 변화를 측정하였다. 낙하방식의 고속인장 시험기를 제작하여 변형률 속도 15/s, 100/s에서 시편의 형상에 따른 섬유강화 복합소재의 인장거동을 측정하였으며 시편의 폭이 6mm, 8mm, 10mm인 경우에 대하여 시험을 수행하였다. 측정 결과 시편의 폭이 8mm인 경우 섬유강화 복합소재의 강도를 정확하게 평가할 수 있는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
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• 제9권3호
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• pp.376-380
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• 1999

Constructs, encoding a single-chain variable fragment of a catalytic antibody 4f4f (scFv-4f4f) with glycosidase activity, were made by combining the coding sequences for the heavy and light chain variable domains with a sequence encoding a linker (GGGGS). Using three different plasmid systems, single-chain antibodies were expressed separately in Escherichia coli, demonstrating significant differences in the expression level and amounts in soluble form of the recombinant protein. The protein expression from pET3a-scFv-4f4f was up to 20% of the total soluble proteins and, more importantly, the proteins were mostly found in a soluble form. An SDS-PAGE analysis of the purified single-chain proteins, yielding higher than 5mg from a 1-1 culture, showed a single band corresponding to its molecular weight of 29,100. A preliminary study shows that the expressed scFv-4f4f is catalytically active. The catalytic parameters for the hydrolysis of p-nitrophenyl-$\beta$-D-glucopyranoside by scFv-4f4f are being investigated.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.