Recent research studies have confirmed that curved I-girders are capable of developing substantial shear postbuckling resistance due to tension field action and have demonstrated that the AASHTO LRFD equations for the tension field resistance in straight I-girders may be applied to curved I-girders within specific limits. However, the corresponding demands on intermediate transverse stiffeners in curved I-girders are still largely unknown. Furthermore, a number of prior research studies have demonstrated that transverse stiffeners in straight I-girders are loaded predominantly by bending induced by their restraint of web lateral deflections at the shear strength limit state, not by in-plane tension field forces. This is at odds with present Specification approaches for the design of transverse stiffeners, which are based on (1) providing sufficient stiffener bending rigidity only to develop the shear buckling strength of the web and (2) providing sufficient stiffener area to resist the in-plane tension field forces. In this research, the behavior of one- and two-sided intermediate transverse stiffeners in straight and horizontally curved steel I-girders is investigated by refined full nonlinear finite element analysis. Variations in stiffener rigidity, panel aspect ratio, panel slenderness, and stiffener type are considered. New recommendations for design of transverse stiffeners in straight and curved I-girder bridges are developed by combining the solutions from the above FEA studies with the results from prior research.

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In this thesis, the response of solder balls under high-speed impact was investigated. Five solder compositions, such as Sn/4.0Ag/0.5Cu,Sn/3.5Ag/0.75Cu,Sn/1.0Ag/1.0Cu, Sn/3.0Ag/0.5Cu and Sn/2.6Ag/0.6Cu with two pad surface finishes and ball impact test system were used to implement four kinds of experiments including different impact speeds, different hammers, different reflow times and different aging time in room temperature after reflow. From experiments, the variations of solder strength and mechanical properties were received and discussed. At the same time, failure modes and variations of solder structure after reflow were observed by using SEM and X-ray EDS. The experimental results show that maximum impact force on solder joints increases with the increasing of impact speed when it reaches a critical value. The impact force of Sn/2.6Ag/0.6Cu with Ni/Au pad finish is the maximum among all the solder compositions at varied impact speeds. Maximum impact force on solder joints will decrease with the increasing of mass of hammer. The strength of solder ball were reduced significantly after reflow, however, it makes no difference for solder strength to reflow twice. It was found that maximum impact force and impact energy of solder joints didn¡¦t change a lot, but the ductility and stiffness of them varied unstably under the condition of room temperature for seven days after reflow.

The research aims to design an experimental testing mechanism and process for measuring the scattering strength and the pattern induced by an underwater target. The experimental data are to compare with existing theoretical results to insure the integrity of experimental design. The experiment is conducted in a water tank of dimension 4m x 3.5 m x 2m. The main work is to measure the sound field scattered by a copper sphere of diameter 60mm. There are two types of sources employed in this analysis: one is omni-directional, 70kHz CTG-0708 transducer, and the other is directive, 192 kHz iTP-192k transducer. Both transducers transmit sine waves with the pulse lengths roughly equal to 0.143 msec (equivalent to 10 waves) and 0.333 msec (equivalent to 64 waves), respectively. The scattering field theory is based on the formulation developed by Hickling (JASA, 34, 1962, pp.1582-1592). The experimental process has demonstrated that it is more difficult to measure the forward scattering field than the backward scattering field, due to the fact that the forward scattering field is likely to be mingled with the direct waves. To deal with this problem, the treatment developed by L. Ding¡]JASA, 101,1997, pp.3398-3404¡^has been invoked, in that the direct waves may be filtered by phase shift. This procedure requires the special concern on synchronism of sound source in order to avoid the variation of scattering signals. The comparison between experimental and theoretical results shows that the discrepancy in the forward scattering sector is within 3 to 4 dB, while in the backscattering sector, it is within 1 to 2 dB; however, generally speaking, the variation of the curves show a good agreement. These results indicate that the design of this experiment is basically practicable, and with further improvements, it could be applied to measure other underwater targets. As a whole, the thesis is composed by basic theory deduction, experimental instrumentation, mechanism design, and experiment data analysis. The emphases place on the design and observation of the scattering experiment, data analysis, and further improvement.

The trend of electrical products is light, thin and minimized with the fast operation and multi functionality, which also drives assembly technology towards the same goal. In advanced assembly technology, flip-chip is the one that can achieve the purposes. The pitch and size of a bump, which is in charge of current transmit, are also getting small. The prohibition of using lead content material also stimulates the development of lead-free material in the related industries. The paper is focused on adopting lead free solder paste such as Sn/Ag1.0/Cu0.5 and Sn/Ag4.0/Cu0.5, together with Al/NiV/Cu UBM made by bumping technology. The empirical analysis is based the shear strength of three different bump heights. The result shows the higher the content of Ag, the higher of the initial shear strength. Moreover, the experiment also investigated two solder bump IMC conditions and shear strength by using multi-reflow. The result shows that the IMC of Sn/Ag4.0/Cu0.5 solder paste increases after times of multi-reflow, but the shear strength was sharply decreased. The reliability test was also performed, such as temperature cycling test, temperature and humidity test, highly accelerated temperature and humidity stress test, high temperature storage life test. It¡¦s found the Sn/Ag1.0/Cu0.5 solder bump could maintain the original ductility; while the Sn/Ag4.0/Cu0.5 solder bump was decreasing the ductility due to the generation of IMC. Keyword¡GShear Strength, Flip-chip, Bump, IMC

The purpose of thesis is aimed to predict the residual stiffness and residual strength of a composite laminate by adopting the method of cumulative damage theories numerically. In association with the experimental work the numerical result can be verified in comparison. The fatigue data in composites are well known more scattered than those in conventional metals, because the material properties are complicated due to nonhomogeneity and anisotropy. Until now there exists very few unified theories to model composite fatigue properties. Most of them are semi-empirical expressions fitted by selecting material characteristic values. This work tries to make a precise prediction with hopefully saving time, money and manpower in future experiments. On the aspect of numerical analysis, we employ finite element method incorporated with the software of ANSYS to generate 3-D finite element model and obtain the ultimate stress of cross-ply [0/90]4s and quasi-isotropic [0/+45/90/-45] laminates by Tsai-Wu failure criterion. It is assumed that the damage due to fatigue cycles is equal to the damage of stiffness and strength, in association with Miner¡¦s Rule and cumulative damage theories we obtain the residual stiffness and strength. The numerical result in comparison with the available empirical data is found acceptably well. Finally, this study can be concluded as follows. The error of ultimate stress is 3.84 % in cross-ply[0/90]4s , and 8.38 % in quasi-isotropic[0/45/90/-45]2s laminates. The error of ultimate stress in centrally notched cross-ply[0/90]4s is 0.4 %, and 22.4 % in centrally notched quasi-isotropic laminates. As the fatigue cycles increasing, the residual stiffness and residual strength of the laminates are all decreasing. The decreasing rate is very slight at first and intermediate stages, whilst it is much faster near the last stage. It is found that the prediction of residual strength is more accurate in the case of maximum stress of 60% ultimate stress than that of 80% ultimate stress.

Finland has made considerable advances in generating a coordinated national innovation system and building its national technology strengths. According to Castells (2000), Finland has established itself as the first true information society, with one website per person, internet access in 100 % of school, a computer literacy campaign for adults, the largest diffusion of computer power and mobile telephone in the world, and a globally competitive information technology industry, spearheaded by Nokia. The purpose of this thesis is to study and define the high frequency of consultation, deliberation and effective linkage creation between Finnish Government, education system, research institutes and industry. The process begins with the recognition that in the knowledge-based economy, knowledge can be fostered to produce economic benefits and national wealth. The result of the thesis found that not only basic components like government, education system, research institutes, and industry, but also outside components, like international cooperation, human resource and culture, play very important roles while investigating the factors which help to facilitate and enforce Finland to develop its information society and national technology strength.

There are two aspects in this study: cylinder penetrations and XBP (Expendable Bottom Penetrometer) interpretations. The cylinder studies firstly investigate the relationship between the soil resisting force and penetration depth by a series of rateindependent finite element analyses of pre-embedded penetration depths, and validate the results by upper and lower bound solutions from classical plasticity theory. Furthermore, strain rate effects are modeled by finite element simulations within a framework of rate-dependent plasticity. With all forces acting on the cylinder estimated, penetration depths are predicted from simple equations of motion for a single particle. Comparisons to experimental results show reasonable agreement between model predictions and measurements. The XBP studies follow the same methodology in investigating the soil shearing resistance as a function of penetration depth and velocity by finite element analyses. With the measurements of time decelerations during penetration of the XBP, sediment shear strength profile is inferred from a single particle kinetic model. The predictions compare favorably with experimental measurements by vane shear tests.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 277-283). Available also in a digital version from Dissertation Abstracts.