four kinds of models designed by the basis of British industrial standard and ISO international standard in this study. Energy release rates at mode 1 are investigated by the fatigue analysis of aluminum foam TDCB model bonded with adhesive. These analysis models are compared each other by classifying four models into m values with 2, 2.5, 3 and 3.5. The value of m as the gradient of model is represented with the function of crack length(a) and height of model(h). Through the correlation relation, the fracture behavior of bonded material is analyzed and these analysis results can be applied to composite structures of various areas. Mechanical property and fracture toughness of composite material are also analyzed in this study.

In the DBC (direct bonding of copper) process the oxygen partial pressure surrounding the AlN/Cu bonding pairs has been controlled by Ar gas mixed with oxygen. However, the direct bonding of Cu with sound interface and good adhesion strength is complicated process due to the difficulty in the exact control of oxygen partial pressure by using Ar gas. In this study, we have utilized the in-situ equilibrium established during the reaction of + 1/2 by placing powder bed of CuO or around the Cu/AlN bonding pair at . The adhesion strength was relatively better in case of using CuO powder than when powder was used. Microstructural analysis by optical microscopy and XRD revealed that the interface of bonding pair was composed of , Cu and small amount of CuO phase. Thus, it is explained that the good adhesion between Cu and AlN is attributed to the wetting of eutectic liquid formed by reaction of Cu and .

The ZnO thin films were grown on GaN template substrates by RF magnetron sputtering at different RF powers and n-ZnO/p-GaN heterojunction LEDs were fabricated to investigate the effect of the RF power on the characteristics of the n-ZnO/p-GaN LEDs. For the growth of the ZnO thin films, the substrate temperature was kept constant at 200˚C and the RF power was varied within the range of 200 to 500W at different growth times to deposit films of 100 nm thick. The electrical, optical and structural properties of ZnO thin films were investigated by ellipsometry, X-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and by assessing the Hall effect. The characteristics of the n-ZnO/p-GaN LEDs were evaluated by current-voltage (I-V) and electroluminescence (EL) measurements. ZnO thin films were grown with a preferred c-axis orientation along the (0002) plane. The XRD peaks shifted to low angles and the surface roughness became non-uniform with an increase in the RF power. Also, the PL emission peak was red-shifted. The carrier density and the mobility decreased with the RF power. For the n-ZnO/p-GaN LED, the forward current at 20 V decreased and the threshold voltage increased with the RF power. The EL emission peak was observed at approximately 435 nm and the luminescence intensity decreased. Consequently, the crystallinity of the ZnO thin films grown with RF sputtering powers were improved. However, excess Zn affected the structural, electrical and optical properties of the ZnO thin films when the optimal RF power was exceeded. This excess RF power will degrade the characteristics of light emitting devices.

Excellent electron transport properties with enhanced light scattering ability for light harvesting have made well-ordered one dimensional TiO2 nanotube(TNT) arrays an alternative candidate over TiO2 nanoparticles in the area of solar energy conversion applications. The principal drawback of TNT arrays being activated only by UV light has been addressed by coupling the TNT with secondary materials which are visible light-triggered. As well as extending the absorption region of sunlight, the introduction of these foreign components is also found to influence the charge separation and electron lifetime of TNT. In this study, a novel method to fabricate the TNT-based composite photoelectrodes employing visible responsive CuInS2 (CIS) nanoparticles is presented. The developed method is a square wave pulse-assisted electrochemical deposition approach to wrap the inner and outer walls of a TNT array with CIS nanoparticles. Instead of coating as a dense compact layer of CIS by a conventional non-pulsed-electrochemical deposition method, the nanoparticles pack relatively loosely to form a rough surface which increases the surface area of the composite and results in a higher degree of light scattering within the tubular channels and hence a greater chance of absorption. The excellence coverage of CIS on the tubular TiO2 allows the construction of an effective heterojunction that exhibits enhanced photoelectrochemical performance.

This study aims to analyze the structural behavior on TDCB models bonded adhesively with aluminum foam composite. These simulation models are designed on the basis of British industrial and ISO standards. The variable of configuration factor(m) is set up to investigate the fracture toughness of bonded joint due to the volume of material. Equivalent stress, deformation energy, pressure at bonded part, reaction force-crack length, energy release rate-crack length are obtained by this analysis. Through the data of this study, the fracture behavior can be analyzed by applying the practical composite structure bonded with aluminum foam and the mechanical property can be understood.

In this study, the influence on the surface passivation properties of crystalline silicon according to silicon wafer thickness, and the correlation with a-Si:H/c-Si heterojunction solar cell performances were investigated. The wafers passivated by p(n)-doped a-Si:H layers show poor passivation properties because of the doping elements, such as boron(B) and phosphorous(P), which result in a low minority carrier lifetime (MCLT). A decrease in open circuit voltage (Voc) was observed when the wafer thickness was thinned from 170μm to 50μm. On the other hand, wafers incorporating intrinsic (i) a-Si:H as a passivation layer showed high quality passivation of a-Si:H/c-Si. The implied Voc of the ITO/p a-Si:H/i a-Si:H/n c-Si wafer/i a-Si:H/n a-Si:H/ITO stacked layers was 0.715 V for 50μm c-Si substrate, and 0.704 V for 170μm c-Si. The Voc in the heterojunction solar cells increased with decreases in the substrate thickness. The high quality passivation property on the c-Si led to an increasing of Voc in the thinner wafer. Short circuit current decreased as the substrate became thinner because of the low optical absorption for long wavelength light. In this paper, we show that high quality passivation of c-Si plays a role in heterojunction solar cells and is important in the development of thinner wafer technology.

The concrete-filled tube (CFT) column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. Its Solution, 2 members of ㄷchennel in which Internal diaphragm is installed were welded beforehand and the method of making Rectangular Steel Tube was proposed. According to upside and downside junction shape, Internal diaphragm suggested as symmetric specimen and asymmetric specimen. The upper and lower diaphragm of the Symmetric specimen used the same horizontal and The upper diaphragm of the Asymmetric specimen used the horizontal plate and the lower diaphragm used the vertically plate. In this research, 4 T-shape column to beam steps connections were tested with cyclic loading experiment in order to evaluate the structural capability of the offered connection. Symmetric specimens be a failure in 0.03rad from beam flange. And Asymmetric specimens be a failure in 0.05rad from column interface. The comparison results of All specimens shown similar to energy absorption capacity in 0.02rad.

The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.

Welded Unreinforced Flange-Welded Web (WUF-W) connection is one of Special Moment Frame (SMF) specified in ANSI/AISC-358. From the experimental test of WUF-W connection specimens conducted by the previous study, fracture occurred in the beam flange before achieving total inter-story drift angle of 0.04radian required for Special Moment Frames (SMF) system even though the specimens satisfied the design and detailing requirement specified in ANSI/AISC-358. These results are estimated as problem of the access hole geometry. In this study, a full-scale WUF-W connection specimen was made with a modified access hole geometry, and tested with the same test setting and loading as the previous test. From test results, the deformation capacity of the tested WUF-W connection specimen exceeded 4%, which is required for connections in SMF system. Comparing with the WUF-W specimens of the previous study, the strain demand of the beam flange in the tested specimen was decreased and energy dissipation capacity of the specimen was improved.

Self-piercing riveting(SPR) is a sheet joining method that can be used for materials which are difficult or unsuitable to weld, such as aluminum alloy and different steel sheet metals. No pre-drilled hole is needed for SPR; the rivets are pushed directly into the sheets clamped together between a blank holder and a die in a press tool. In this paper, self-piercing rivet and anvil were designed for four joining conditions with dissimilar sheet metals. SPR was simulated by using commercial FEM code DEFORM-2D. In simulation of SPR process, various strengths of self-piercing rivet were considered. The mechanical properties could be determined by tensile test for quenched rivets and sheet metals. The designs of rivet and anvil were modified by comparisons of simulated results.

A capsule is the device for irradiation test of nuclear materials and fuels in HANARO. The instrumentation cables are sealed tightly by brazing at the top of the capsule. In this study, the integrities at the brazing of both Inconel 600 and STS 310 materials were confirmed by tensile test, survey of damage on coating, and measurement of insulation resistance. At tensile test, brazing areas were not damaged but the thermocouples themselves were broken on both the materials. At flame heat test, the coating of STS 310 material was maintained without damage but the brittle fracture on Inconel 600 material was observed. Insulation resistances were confirmed to be satisfactory in case of both the materials. In this analysis, the thermocouple was expanded by 0.81mm on the direction of y-axis and the tube was contracted by 0.57mm on the direction of x-axis. As the result, cracks might be occurred with thermal stresses. EDX spectrum analysis showed that the BAg-1 filler metal formed a thin reaction layer on the surface of brazed metal.

The Composite structures such as CFT(Concrete Filled Steel Tube) have many advantages compared to the H shape columns, concrete columns. But, CFT columns were reinforced difficult which was members with closed section. When beams size were different around the columns in buildings of various form, the construction was complex that diaphragm was overlapped or inclined. In this study, structural performance comparison of horizontal diaphragm and vertical plates was conducted.

In this paper, we present the results of experimental investigation pertaining to the structural behavior of Tee joint connection composed of pultruded I-shape FRP members. In this study, we focus on the evaluation of load carrying capacity of Tee joint which appeared frequently to fabricate framed structure composed of pultruded FRP members. Through the experimental investigation moment-rotation relationship is found and the result is used to estimate the rotaion stiffness.

본 연구는 개별적인 반·강접 복합접합부 구조물을 수치해석적인 방법을 통하여 거동성능을 조사하는 대 초점을 두고 있다. 강제 보와 콘크리트 충전기둥 (CFT) 사이에 저탄소 강 구속재와 초탄성 (Super-elastic) 형상기억합금 (SMA) 재료의 구속재를 이용하여 연결한 방식이 제안된 접합부 구조물의 가장 큰 특징이다. 이러한 설계는 초탄성 형상합금을 변형이 많이 일어나는 부분에 인장 바(Bar)로서 설치하여 복원현상을 기대할수 있다. 또한 저탄소 강재 바는 거동에 에너지 소산능력을 향상 시키는 대 기여한다. 반·강접 접합부는 단순한 핀이나 완전구속으로 모델 링이 불가능하므로 해석이나 설계가 실제로는 매우 복잡하다. 하지만 본 연구에서는 제안된 구조물의 장점과 특성 을 검증하기 위하여 정밀한 유한요소(Finite Element) 방법을 이용하여 접합부의 전반적인 거동을 재현하였다.

The microstructures and mechanical properties of friction stir welded lap joints of Inconel 600 and SS 400 were evaluated; friction stir welding was carried out at a tool rotation speed of 200 rpm and welding speed of 100 mm/min. Electron back-scattering diffraction and transmission electron microscopy were introduced to analyze the grain boundary characteristics and the precipitates, respectively. Application of friction stir welding was notably effective at reducing the grain size of the stir zone. As a result, the reduced average grain size of Inconel 600 ranged from 20μm in the base material to 8.5μm in the stir zone. The joint interface between Inconel 600 and SS 400 showed a sound weld without voids and cracks, and MC carbides with a size of around 50 nm were partially formed at the Inconel 600 area of lap joint interface. However, the intermetallic compounds that lead to mechanical property degradation of the welds were not formed at the joint interface. Also, a hook, along the Inconel 600 alloy from SS 400, was formed at the advancing side, which directly brought about an increase in the peel strength. In this study, we systematically discussed the evolution of microstructures and mechanical properties of the friction stir lap joint between Inconel 600 and SS 400.

The a-Si:H/c-Si hetero-junction (HJ) solar cells have a variety of advantages in efficiency and fabrication processes. It has already demonstrated about 23% in R&D scale and more than 20% in commercial production. In order to further reduce the fabrication cost of HJ solar cells, fabrication processes should be simplified more than conventional methods which accompany separate processes of front and rear sides of the cells. In this study, we propose a simultaneous deposition of intrinsic thin a-Si:H layers on both sides of a wafer by dual hot wire CVD (HWVCD). In this system, wafers are located between tantalum wires, and a-Si:H layers are simultaneously deposited on both sides of the wafer. By using this scheme, we can reduce the process steps and time and improve the efficiency of HJ solar cells by removing surface contamination of the wafers. We achieved about 16% efficiency in HJ solar cells incorporating intrinsic a-Si:H buffers by dual HWCVD and p/n layers by PECVD.

An ultrafine grained complex aluminum alloy was fabricated by an accumulative roll-bonding (ARB) process using dissimilar aluminum alloys of AA1050 and AA5052 and subsequently annealed. A two-layer stack ARB process was performed up to six cycles without lubricant at an ambient temperature. In the ARB process, the dissimilar aluminum alloys, AA1050 and AA5052, with the same dimensions were stacked on each other after surface treatment, rolled to the thickness reduction of 50%, and then cut in half length by a shearing machine. The same procedure was repeated up to six cycles. A sound complex aluminum alloy sheet was fabricated by the ARB process, and then subsequently annealed for 0.5h at various temperatures ranging from 100 to 350˚C. The tensile strength decreased largely with an increasing annealing temperature, especially at temperatures of 150 to 250˚C. However, above 250˚C it hardly decreased even when the annealing temperature was increased. On the other hand, the total elongation increased greatly above 250˚C. The hardness exhibited inhomogeneous distribution in the thickness direction of the specimens annealed at relatively low temperatures, however it had a homogeneous distribution in specimens annealed at high temperatures.

본 연구는 각 연결부에 대한 수치 해석을 통하여 강재-콘크리트 합성 프레임 구조물의 성능을 조사하였다. 본 연구 의 혁신적인 측면은 강재 보와 CFT 기둥의 연결부 사용과 저탄소강과 형상 기억 합금 구성요소의 조합을 활용하 는데 있다. 이러한 새로운 연결부의 목적은 지진 후 건물의 손상과 잔류 흐름을 줄이기 위해 고탄성 형상기억합금 인장부에서 발생하는 교정 작용과 저탄소강의 우수한 에너지 분산 능력을 활용하는 것이다. 연결부의 핀, 전체적인 고정 또는 부분 구속으로 모델링을 할 수 없기 때문에 이러한 구조물들의 해석과 설계는 복잡하여 PR-CFT 연결부 의 전체적인 거동을 알기 위한 수치해석을 위해 정교한 3차원 솔리드 요소로 구성된 유한해석 모델을 개발하였다. 이러한 유한요소 해석으로 얻은 결과를 바탕으로 스프링 요소를 이용하여 간단한 연결부 모델링을 공식화 시켰다. 반복 하중을 가하여 전체 프레임 구조물의 거동을 확인하였고 3D 유한요소 해석을 통하여 단순 거동을 비교하였 다.

Transparent conducting oxides (TCOs) used in the antireflection layer and current spreading layer of heterojunction solar cells should have excellent optical and electrical properties. Furthermore, TCOs need a high work function over 5.2 eV to prevent the effect of emitter band-bending caused by the difference in work function between emitter and TCOs. Sn-doped In2O3 (ITO) film is a highly promising material as a TCO due to its excellent optical and electrical properties. However, ITO films have a low work function of about 4.8 eV. This low work function of ITO films leads to deterioration of the conversion efficiency of solar cells. In this work, ITO films with various Zn contents of 0, 6.9, 12.7, 28.8, and 36.6 at.% were fabricated by a co-sputtering method using ITO and AZO targets at room temperature. The optical and electrical properties of Zn-doped ITO thin films were analyzed. Then, silicon heterojunction solar cells with these films were fabricated. The 12.7 at% Zn-doped ITO films show the highest hall mobility of 35.71 cm2/Vsec. With increasing Zn content over 12.7, the hall mobility decreases. Although a small addition of Zn content increased the work function, further addition of Zn content over 12.7 at.% led to decreasing electrical properties because of the decrease in the carrier concentration and hall mobility. Silicon heterojunction solar cells with 12.7 at% Zn-doped ITO thin films showed the highest conversion efficiency of 15.8%.