• 마이크로전자및패키징학회지
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• 제10권4호
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• pp.1-8
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• 2003

고감도 모아레 간섭계를 이용하여 세라믹 ball grid array 패키지 결합체의 열-기계적 거동을 분석하였다. 한 온도 사이클의 선택된 몇 개의 온도 단계에서 모아레 간섭무늬를 기록하고 해석하였다. 패키지 결합체의 온도변화에 따른 전체적인 변형과 국부적인 변형거동을 정량적으로 나타내었고, 패키지의 굽힘변형과 맨 바깥쪽 솔더볼의 전단변형률에 대한 거동을 토의하였다. 높은 온도에서는 저온 융점 솔더의 응력완화로 인하여 심각한 비선형 거동이 발생되었으며. 솔더볼의 변형을 해석한 결과 높은 온도에서 저온용융 솔더부에 비탄성 변형이 축적되었음을 알 수 있었다.

• 대한기계학회논문집
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• 제15권1호
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• pp.190-200
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• 1991

본 연구에서는 고온에 노출되는 열-점소성 거동의 해석을 위해 소성유동, 크 리프, 응력풀림(stress relaxation)등의 거동을 동시에 다룰 수 있는 통일구성방정식 모델에 대해 논하고 적절한 모델을 선정한다. 이 모델은 미소변형이론에 근거한 것 이므로 구조물의 거동을 소변형률(small strain)과 소회전(small rotation)의 범위내 로 가정하여 해석한다.선정된 모델에 대해서 시간변화율 형태의 방정식으로부터 유 한요소법을 통한 수치화와 사용된 구성방정식을 효율적으로 처리할 수 있는 수치해석 법상의 알고리듬을 제안한다. 제안된 알고리즘을 사용하여 유한요소법 전산코드를 적상하고, 작성된 코드를 이용하여 고온에서 하중을 받는 단순보와 국부적으로 심한 가열을 받는 구조물에 적용하여 고전적인 구성방정식으로 복합적인 해석이 어려웠던 열-점소성 거동을 효과적으로 해석할 수 있음을 보인다. 본 논문은 응력해석에 주안 점을 두었으므로 열해석에 관한 상세한 논의는 가급적 생략하기로 한다.

• 한국식생활문화학회지
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• 제16권2호
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• pp.137-146
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• 2001

Purpose of this study was to investigate the health status and life style of middle-aged people in Daejon. The subjects expressed more fear for disease as getting older(p<0.01). Sixty six percent of the subjects have suffered in the past or suffer at present certain kinds of disease. The older they are, the more disease they have. The alimentary disease, neuralgia, and arthritis were the most popular disease. The eye strain and exhaustion of body were indicated more frequently in fifties than in thirties or forties(p<0.01). They considered excercise as the most important factor to maintain health status, and then moderation in diet, relaxation, rest, decrease of alcohol intake, no smoking. Forty three percent of them were non-drinker. The number of drinker was four times more in male than female and increased as getting younger(p<0.01). Only male revealed smoker and 29% of them smoked 10-20 cigarettes per day. The number of smoker decreased as getting older(p<0.01). Male played exercise more regularly than female and subjects have better exercise habit as getting older(p<0.01). This study suggests that practical programs for self-health control should be developed for playing exercise regularly for female and for considering nutrition, no smoking, and no drinking in the daily life for male.

• 세라미스트
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• 제23권1호
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• pp.16-26
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• 2020

Recently, polymer-metal composite (IPMC)-based ionic artificial muscle has been drawing a huge attention for its excellent soft actuator performance having outstanding soft actuator performance with efficient conversion of electrical energy to mechanical energy under low working voltage. In addition, light, flexible and soft nature of IPMC and high bending strain response enabled development of versatile sensor application in association with soft actuator. In this paper, current issues of IPMC were discussed including standardizing preparation steps, relaxation under DC bias, inhibiting solvent evaporation, and improving poor output force. Solutions for these drawbacks of IPMC have recently been suggested in recent studies. After following explanation of the IPMC working mechanism, we investigate the main factors that affect the operating performance of the IPMC. Then, we reviewed the optimized IPMC actuator fabrication conditions especially for the preparation process, additive selection for a thicker membrane, water content, solvent substitutes, encapsulation, etc. Lastly, we considered the pros and cons of IPMCs for sensor application in a theoretical and experimental point of view. The strategies discussed in this paper to overcome such deficiencies of IPMCs are highly expected to provide a scope for IPMC utilization in soft robotics application.

• 대한기계학회논문집
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• 제19권3호
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• pp.834-845
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• 1995

An experimental study is made in a nearly two-dimensional 90.deg. curved duct to investigate the effects of interaction between streamline curvature and mean strain on turbulence. The initial shear at the entrance to the curved duct is varied by an upstream shear generator to produce five different shear conditions ; a uniform flow (UF), a positive weak shear (PW), a positive strong shear(PS), a negative weak shear (NW) and a negative strong shear(NS). With the mean field data of the case UF, variations of the momentum thickness, the shape factor and the skin friction over the convex(inner) surface and the concave (outer) surface are scrutinized quantitatively in-depth. It is found that, while the pressure loss due to curvature is insensitive to the inlet shear rates, the distributions of wall static pressure along both convex and concave surfaces are much influenced by the inlet shear rates.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.73-76
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• 2001

We deposited epitaxial $Ba_{0.6}Sr_{0.4}TiO_{3}(BST)$ films having thickness of 400 nm on MgO(001) substrates, where a 10 nm thick $Ba_{1-x}Sr_{x}TiO_{3}$ (x = 0.1 - 0.7) interlayer was inserted between BST and MgO to manipulate the stress of the BST films. Since the main difference of those epitaxial BST films was the lattice constant of the interlayers, we were very successful in controlling the stress of the BST films. BST films under small tensile stress showed larger dielectric constant than that without stress as well as those under compressive stress. Stress relaxation was investigated using epitaxial BST films with various thicknesses grown on different interlayers. For BST films grown on $Ba_{0.7}Sr_{0.3}TiO_{3}$ interlayers, the critical thickness was about 600 nm. On the other hand, the critical thickness of single-layer BST film was less than 100 nm.

• The Journal of Korean Physical Therapy
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• 제14권4호
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• pp.423-440
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• 2002

The purpose of this study is to investigate the conception and developmental process of stretching in sports physical therapy. This study is to find conception of stretching, feature and effect, principles and fundamental rule, consideration of enforcement and developmental process in order to use the basic material which is very helpful in the every field and the scene of sports needing stretching. Flexibility is the ability to move muscles and joints through their full ranges of motion. Flexibility is developed by stretching. About player who insufficiency of flexibility, patient and disabled person who restrict of range of motion, older adult who reduce of flexibility, promote of flexibility for upgrading stability and efficiency of body on the based of scientific principles is completed by stretching. The method of stretching has been developed with passive stretching, CR, PNF stretching, PIC stretching, MET stretching in the order. The effects that we can get through stretching are as follows : 1. Enhance physical fitness. 2. Optimize learning, practice and performance of many types of skilled movement. 3. Increase mental and physical relaxation. 4. Promote development of body awareness. 5. Reduce risk of joint sprain or muscle strain. 6. Reduce risk of back problem. 7 Reduce muscular soreness. 8. Reduce the severity of painful menstruation for female athletes. 9. Reduce muscular tension. 10. Advance recognition of body.

• 전자공학회논문지A
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• 제32A권2호
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• pp.66-72
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• 1995

Using the Si/SiGe layer grown by solid source molecular beam epitaxy(SSMBE) on the LOCOS-patterned wafers, an emitter-base self-aligned hterojunction biplar transistor(HBT) with the polysilicon-emitter and the silicon germanium(SiGe) base has been fabricated. Trech isolation process, planarization process using a chemical-mechanical poliching, and the selectively implanted collector(SIC) process were performed. A titanium disilicide (TiSi$_{2}$), as a base electrode, was used to reduce an extrinsic base resistance. To prevent the strain relaxation of the SiGe epitaxial layer, low temperature (820${^\circ}C$) annealing process was applied for the emitter-base junction formation and the dopant activation in the arsenic-implanted polysilicon. For the self-aligned Si/SiGe HBT of 0.9${\times}3.8{\mu}m^{2}$ emitter size, a cut-off requency (f$_{T}$) of 17GHz, a maximum oscillation frequency (f$_{max}$) of 10GHz, a current gian (h$_{FE}$) of 140, and an emitter-collector breakdown voltage (BV$_{CEO}$) of 3.2V have been typically achieved.

• 한국표면공학회지
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• 제20권3호
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• pp.106-117
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• 1987

The microhardness and the structural characteristics of the chemically vapor deposited TiN film on the 430 stainless steel substrate have been investigated with various deposition parameters such as the deposition time, the total flow rate, the flow rate ratio $(H_2/N_2)$, and the deposition temperature. The most important factor to affect the microhardness of the TiN film in this study was the denseness of the structure in connection with the degree of the lattice strain. The relationship between the lattice parameter changes and the grain size variation under all deposition conditions generally followed the grain boundary relaxation model. The (111) preferred orientation prevailed in the early stage of the deposition conditions, however, the (200) preferred orientation was developed in the later stage. The surface morphology at optimum conditions displayed a dense diamond shaped structure and the microhardness of the films was high (1700-2400Hv) regardless of the type of the substrates used.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.183-194
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• 2002

A general procedure to evaluate the sensitivity of design variables to stresses and strains in PSC flexural members is proposed. To accomplish the purpose of this study, long-term losses including creep, shrinkage, and PS steel relaxation are formulated based on the equilibrium states of the deformed sectional geometry. Thereby, the formulation follows the basic steps which consider the fundamental formulas adopted by CEB-FIP, ACI, and KCI rather than the age adjusted effective modulus concept. Twenty-one design variable including the material and geometrical properties of concrete, nonprestressing steel and prestressing steel, and the geometry of the cross section are considered in the sensitivity analysis. The gradients of the stresses and strains needed for the sensitivity assessment are calculated in a closed format. The derived formulation is applied to the T-type section PSC beam with prestressing and nonprestressing steels for the sensitivity analysis. The analytically calculated sensitivity results are compared with those numerically calculated to ensure the validity of the proposed procedure.