In the study, we confer with the effect of the circular cylinder for various flow fields, and investigate the phenomenon of the vortex shedding and fluid elastic instabilities. First, in the aspect of the vortex shedding, we observe the wake behind the cylinder after varying the locations of orifices on the cylinder and the forms of momentum addition, and the variation of the lift and drag coefficient can be obtained by using the commercial software STAR-CD. In the further study, we make the type of flow field to be a shear flow and build the database of the aerodynamic coefficients in different shear parameter and Reynolds numbers; furthermore, the database is an important basis for us to conjecture the surface force on the cylinder, and analyze the size of oscillations and the orbit that is caused by the shear parameter, mass ratio and damping factor respectively.

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

Vibrations of small cylinder in a jet flow are investigated experimentally. Because of the flow field in shear layers of jet flow is very complex and filled with vortex structures, so the flow induced vibration phenomena in jet flow is different from the flow induced vibration in uniform flow. The major subject in this experiment is to discuss the major cause of small cylinder vibrations, and the flow field influenced by the cylinder vibration. About flow measurement, velocity measurement by hot-wire is applied. As for the vibration measurement, by using the principle of electromagnetic, a new measurement technology was successfully developed. This new vibration measurement can measure the vibrations in two axial, so as to describe the orbit of vibrations. To find the interrelation of flow field and cylinder vibrations, flow measurement and vibration measurement was carry on at the same time. It is shown that when the jet velocity is increased constantly, small cylinder will vibration intensely. The fixed velocity is called critical velocity. If add a perturb, the vibration will occur in advance. The dominant frequency of cylinder vibration, fr, will be the same with it's nature frequency, fn, in the critical velocity, but when the flow velocity keep on increasing, the dominant frequency, fr, will also increase. Besides, the relation of reduced velocity and mass damping was found in this case. The orbits of vibrations are all like ellipse, and the orbit is different with different reduced velocity. The vibration amplitude be changed into three sections that have different reduced velocity, and different orbit. About the flow field, the velocity profile in potential core is not influenced by vibrations of small cylinder, but the velocity fluctuations in shear layer indeed be inflected. At the fixed velocity region, the dominant frequency of flow is the same with dominant frequency of vibrations when the flow at downstream of small cylinder in shear layer. This phenomena only exist when the vibration amplitude under the fixed range.

none

Triaxial extension experiments on Carrara Marble demonstrate that there is a continuous transition from extension to shear fracture on the basis of mechanical behavior, macroscopic fracture orientation and fracture morphology where hybrid fractures with extension and shear fracture characteristics are formed at the intermediate stress conditions. Extension fracture surfaces display discrete, highly reflective cleavage planes and shear fracture surfaces are covered with calcite gouge and display grooves and striations that are aligned parallel to slip. This study uses the fractured samples that were formed under triaxial extension experiments to characterize 1) microscopic surface features using scanning electron microscopy, 2) fracture surface morphology using laser profilometry, and 3) off-fracture damage using optical microscopy. These data are used to test the step-crack model of fracture development for the formation of hybrid fractures. Spectral analysis of the profiles demonstrates that microscopic roughness decreases gradually across the extension-to-shear fracture transition in both the orientations parallel and perpendicular to slip. However, macroscopic roughness gradually increases then decreases across the transition in the direction parallel to slip. The greatest macroscopic roughness occurs at the transition from extension fractures to tensile-hybrid fractures and is attributed to the presence of macroscopic steps in hybrid fractures surfaces. The treads of the steps in the hybrid fracture surfaces have characteristics of extension fracture surfaces and the risers have characteristics of shear fracture surfaces. The treads have a right-stepping left lateral geometry that is consistent with the step-crack model. Thin sections of hybrid fractures display systematically spaced, pinnate, microfractures that emanate from both sides of the macroscopic fracture surface. The pinnate fractures on both sides correlate across the macroscopic fracture, suggesting that they are precursory to the formation of the macroscopic fracture surface. The spacing to length ratio of the pinnate fractures and the macroscopic orientation of the fracture surface are also consistent the relationship dictated by the step-crack model of fault formation.

As the demand for oil and gas resources increases, the need to venture into more hostile environments becomes a dynamic focus in the petroleum industry. One problem associated with certain high risk formations is lost circulation. As a result, engineers have concentrated research efforts on developing novel Lost Circulation Materials (LCM’s) that will effectively treat thief zones. The most pioneering LCM’s require mixing energy to activate a reaction involving two or more chemicals. However, minimal research has been conducted to accurately predict downhole mixing capabilities. Therefore, this research focuses on developing a correlation between laboratory experiments and scaled model experiments for accurate prediction of downhole mixing energies in terms of flow rate for adequate mixing of lost circulation prevention fluids.

The study aims to explore flow-induced vibration of shear flow past a circular cylinder. The major parameters in the experiment are the natural frequency of the cylinder, and the velocity and velocity gradient of the shear flow approaching the cylinder. The vibration of the cylinder in a water tunnel were measured by two accelerometers to simultaneously obtain the vibration amplitudes in both the streamwise and cross-stream directions. The experimental results show that in the shear flow the cylinder tends of vibrate the orbits of the cylinder vibration become in the streamwise direction while in uniform flow the cylinder vibrates in all directions in the X-Y plane the tendency is obvious for the cylinder with high natural frequency (13Hz). The orbits of the cylinder with low natural frequency (9Hz) are basically similar in shear flow and in uniform flow.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 160-164).

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 363-370).

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xi, 126 p. : ill. Includes abstract. Includes bibliographical references (p. 123-126).