• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.175-178
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• 1995

Distribution of relaxation time is presented in the Cole-Cole arc diagram with frequency parameter. In the case of estimation of activation energy for main chains, maximum loss frequencies of ${\alpha}$ peaks, f$\sub$m/(${\alpha}$) display curved change according to the WLF type with variations of temperature. Structural change by the filling of filler and degradation by the thermal aging can be estimated from the WLF factors, C$_1$and C$_2$in Log f$\sub$m/-1/T curves which reflect the variations of free volume and thermal expansivity of composites.

• 한국전기전자재료학회논문지
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• 제22권1호
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• pp.61-66
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• 2009

Characteristics of the photonic bandgaps (PEGs) in two-dimensional photonic crystals (2D PCs) with a square lattice have theoretically studied using a finite difference time domain (FDTD) simulation. In this paper, we propose a concept of optical coverage ratio (OCR) as a new structural parameter to determine the PEGs for E-polarized light. The OCR is an optically compensated filling factor. It is possible to normalize the PEGs of 2D PCs by introducing the OCR.

• 헤리티지:역사와 과학
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• 제54권1호
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• pp.220-237
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• 2021

국가민속문화재 전 순정효황후 주칠 나전가구(傳 純貞孝皇后 朱漆 螺鈿家具) 매트리스의 제작 기법 및 사용 재료의 특성을 확인한 후 보존처리를 진행하였으며, 창덕궁 대조전 매트리스와 비교하여 1920~30년대 국내에서 사용된 매트리스의 특징을 확인해보고자 하였다. 전 순정효황후 매트리스 분석 결과, 프레임은 소나무과 솔송이 사용되었으며, 구조부인 웨빙, 트와인은 마섬유로 확인되었다. 충전재인 버랩은 마섬유, 초석은 벼속, 그 외 충전재는 면섬유로 확인되었다. 커버 상단은 레이온, 하단은 면섬유가 사용되었다. 사용된 재료와 내부 구조를 확인한 결과, 서양 가구인 데이베드와 의자에서 주로 사용되는 업홀스터리로 제작되었다. 보존처리 과정에서는 분석 결과를 바탕으로 유사한 재료를 사용하였으며, 해체 → 세척 → 보수 및 보강 → 조립의 순으로 진행하였다. 해체 과정에서 상단의 커버가 새롭게 발견되었으며, 충전재인 버랩에서 요코하마, 고베, 조선의 단어가 발견되었다. 하지만 제작사나 제작 장소를 특정할 수 있는 추가적인 흔적은 발견되지 않았다. 구조부와 충전재, 커버는 건식 세척을 진행한 후 업홀스터리 구조에서 기존 재료는 제거하지 않고 유사한 재료를 사용하여 보수 및 보강을 진행하였다. 구조부 웨빙은 동종의 재료를 사용하여 보강하였으며, 스프링의 배열 및 고정은 트와인을 사용하여 목재 프레임에 고정하였다. 손상된 면천과 버랩은 유사한 소재의 보강재를 덧댄 후 바느질하였다. 상단 커버는 손상부에 보강 직물을 마름하여 안쪽에 넣고 바느질하였다. 조립은 해체의 역순으로 진행하였다. 스프링과 닿는 부분에 동일 소재의 버랩을 삽입하여 고정한 후 충전패드, 보강천, 초석, 면천, 솜포, 커버 보호용 광목천, 커버를 씌워 택으로 마무리하였다. 순정효황후가 사용한 2개의 매트리스는 제작 시기의 차이가 있을 뿐 프레임과 충전재, 커버로 구성된 서양의 업홀스터리로 제작되었다. 보존처리 과정에서 새로운 벨벳 커버가 발견되었고 이전 수리 흔적이 확인되었으며, 충전재로 초석, 가마니와 짚풀 등이 확인됨에 따라 제작 환경에 따른 사용 재료의 변화를 확인할 수 있었다. 향후 근대문화재 업홀스터리 의자 또는 소파의 보존처리에서 사용 재료 및 제작 방법의 변화를 살펴볼 수 있을 것으로 기대된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.435-438
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• 2001

Thin films of vanadium oxide(VO$\sub$x/) have been deposited by r.f. magnetron sputtering from V$_2$O$\sub$5/ target in gas mixture of argon and oxygen. The oxygen/(oxygen+argon) partial pressure ratio is changed from 0% to 8%. Crystal structure, chemical composition and bonding properties of films sputter-deposited under different oxygen gas pressures are characterized through XRO, XPS, RBS and FTIR measurements. All the films prepared below 8% O$_2$ are amorphous, and those prepared without oxygen are gray indicating the presence of V$_2$O$\sub$$_4$/ phase in the films. V$_2$O$\sub$5/ and lower oxides co-exist in sputter-deposited films and as the oxygen partial pressure is increased the films become more stoichiometric V$_2$O$\sub$5/. The increase of O/V ratio with increasing oxygen gas pressure is attributed to the partial filling of oxygen vacancies through diffusion. It is observed that the oxygen atoms. located on the V-O plane of V$_2$O$\sub$5/ layer participate more readily in the oxidation process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.456-459
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• 2000

Thin films of vanadium oxide(V$O_x$) have been deposited by r.f. magnetron sputtering from $V_2$$O_5$ prget in gas mixture of argon and oxygen. Crystal structure, surface morphology, chemical composition and bonding properties of films in-situ annealed in $O_2$ ambient with various heat-treatment conditions are characterized through XRD, SEM, AES, RBS and FTIR measurements. The filrns annealed below 200 $^{\circ}C$are amorphous, and those annealed above 30$0^{\circ}C$ are polycrystalline. The growth of grains and the transition of vanadium oxide into the higher oxide have been obsenred with increasing the annealing temperature and time. The increase of O/V ratio with increasing the annealing temperature and time is attributed to the diffusion of oxygen and the partial filling of oxygen vacancies. It is observed that the oxygen atoms located on the V-0 plane of $V_2$$O_5$ layer participate more readily in the oxidation process.

• Structural Engineering and Mechanics
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• 제76권6호
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• pp.765-779
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• 2020

This article presents a nonclassical size dependent model based on the modified couple stress theory to study and analyze the bending behavior of perforated microbeams under different loading patterns. Modified equivalent material and geometrical parameters for perforated beam are presented. The modified couple stress theory with one material length scale parameter is adopted to incorporate the microstructure effect into the governing equations of perforated beam structure. The governing equilibrium equations of the perforated Timoshenko as well as the perforated Euler Bernoulli are developed based on the potential energy minimization principle. The Poisson's effect is included in the governing equilibrium equations. Regular square perforation configuration is considered. Based on Fourier series expansion, closed forms for the bending deflection and the rotational displacements are obtained for simply supported perforated microbeams. The proposed methodology is validated and compared with the available results in the literature and an excellent agreement is detected. Numerical results demonstrated the applicability of the proposed methodology to investigate the bending behavior of regularly squared perforated beams incorporating microstructure effect under different excitation patterns. The obtained results are significantly important for the design and production of perforated microbeam structures.

• Structural Engineering and Mechanics
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• 제90권1호
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• pp.1-18
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• 2024

The present study conducts a thorough analysis of thermal vibrations in functionally graded porous nanocomposite beams within a thermal setting. Investigating the temperature-dependent material properties of these beams, which continuously vary across their thickness in accordance with a power-law function, a finite element approach is developed. This approach utilizes a nonlocal strain gradient theory and accounts for a linear temperature rise. The analysis employs four different patterns of porosity distribution to characterize the functionally graded porous materials. A novel two-variable shear deformation beam nonlocal strain gradient theory, based on trigonometric functions, is introduced to examine the combined effects of nonlocal stress and strain gradient on these beams. The derived governing equations are solved through a 3-nodes beam element. A comprehensive parametric study delves into the influence of structural parameters, such as thicknessratio, beam length, nonlocal scale parameter, and strain gradient parameter. Furthermore, the study explores the impact of thermal effects, porosity distribution forms, and material distribution profiles on the free vibration of temperature-dependent FG nanobeams. The results reveal the substantial influence of these effects on the vibration behavior of functionally graded nanobeams under thermal conditions. This research presents a finite element approach to examine the thermo-mechanical behavior of nonlocal temperature-dependent FG nanobeams, filling the gap where analytical results are unavailable.

• E2M - 전기 전자와 첨단 소재
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• 제14권12호
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• pp.3-6
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• 2001

In common globular proteins, the native form is n its most stable state. However, the native form of inhibitory serpins (serine protease inhibitors) and some viral membrane fusion proteins is in a metastable state. Metastability in these proteins is critical to their biological functions. Our previous studies revealed that unusual interactions, such as side-chain overpacking, buried polar groups, surface hydrophobic pockets, ad internal cavities are the structural basis of the native metastability. To understand the mechanism by which these structural defects regulate protein functions, cavity-filling mutations of $\alpha$1-antitrypsin, a prototype serpin, were characterized. Increasing conformational stability is correlated with decreasing inhibitory activity. Moreover, the activity loss appears to correlate with the decrease in the rate of the conformational switch during complex formation with a target protease. We also increased the stability of $\alpha$1-antitrypsin greatly via combining various stabilizing single amino acid substitutions that were distributed throughout the molecule. The results showed that a substantial increase of stability, over 13 kcal/mol, affected the inhibitory activity with a correlation of 11% activity loss per kcal/mol. The results strongly suggest that the native metastability of proteins is indeed a structural design that regulates protein functions and that the native strain of $\alpha$1-antitrypsin distributed throughout the molecule regulates the inhibitory function in a concerted manner.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.75-87
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• 2021

The present study pertains to the introduction of two new types of grip adaptor for universal testing machines, namely Polyvinyl Chloride (PVC) and Polyoxymethylene (POM) grip adaptors, and their application to tension testing of FRP bars with different fiber and surface finish types. The tabs are connected to the FRP bar sample with the help of mechanical anchors, i.e. bolts. These new adaptors offer vital superiorities over the existing end tab designs (anchors with filling material or mechanical anchorage), including the reduction in the time and labor for production, reusability and the mild nature, i.e. low hardness of the tab material, which retards and even prevents peeling and crushing in the gripping regions of an FRP sample. The methods were successfully applied to FRP bars with different types of fiber (CFRP, GFRP and BFRP) and different types of surface texture (ribbed, wrapped, sand-coated and wound). The test results indicated that the both types of end caps prevented slip of the bar, crushing and peeling in the gripping zone. The mechanical properties from the material tests with the new caps were in perfect agreement with the ones from the material tests with steel tubular caps.

• 한국구조물진단유지관리공학회 논문집
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• 제24권3호
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• pp.26-38
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• 2020

자기 충전형 콘크리트의 배합물 설계는 전형적인 다기준의사결정의 과정이다. 본 연구에서는 실험설계법과 반응표면법을 이용하여 SCC 배합물 전산 설계가 가능하도록 재료성능 및 비용모델을 생성하고, 요구조건을 반영한 여러 성능 사이의 상대적 중요도를 산정하여 가중 다목적 설계문제로 정식화하여 수치최적해를 계산함으로써 비용효율을 고려한 SCC최적설계를 수행하였다. 실험비용과 시간을 고려하여 SCC의 수많은 요구성능 중 압축강도, 철근충전성, 재료분리저항성, 비용정보 등을 다목적 최적화의 목적함수로 설정하였다. 재료경제성을 최적재료설계프로세스에 합리적으로 반영함으로써 경제적 콘크리트배합설계를 수행할 수 있었으며, 본 연구 결과 실험점 계획에서부터 최적해 산출에 이르는 과정을 객관적인 프로세스로 구성함으로써 콘크리트 범용 최적재료설계기술 및 전산화를 기대할 수 있다.