Lawrence Yao

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PURPOSE To investigate a tetrahedral diffusion gradient encoding scheme to measure the diffusion tensor in vivo for human calf muscle. MATERIALS AND METHODS The theoretical TE which maximizes the signal-to-noise ratio (SNR) of the diffusion images was derived for both the orthogonal and tetrahedral sampling strategies and the SNR advantage verified(More)
This paper investigates the condition of constant line energy, that is, the ratio of laser power to scanning velocity is kept constant. Under the condition, the effects of velocity change on temperature, net energy input, strain rate and material flow stress are studied. Their collective effects on dimension, residual stress, hardness and microstructure are(More)
To provide the best opportunities for life-saving interventions in the event of a radiological or nuclear threat, there is an urgent need to improve the speed and efficiency of biodosimetric assays for triage and therapy. A rapid automated biodosimetric system used to assess thousands of individual radiation exposure doses is helpful to curb mass panic, and(More)
The process of laser shock peening induces compressive residual stresses in a material to improve material fatigue life. For micron sized laser beams, the size of the laser-target interaction zone is of the same order of magnitude as the target material grains and thus the target material must be considered as being anisotropic and inhomogeneous. Single(More)
Experimental investigation and numerical simulation of the influence of the strain rate in laser forming are presented. To isolate and effectively study the strain rate effects, which are temperature dependent, a "constant peak temperature" method is developed with the aid of numerical modeling and solution. Under the condition of the constant peak(More)
The process of laser shock peening induces compressive residual stresses in a material to improve material fatigue life. For micron sized laser beams, the size of the laser-target interaction zone is of the same order of magnitude as the target material grains and, thus, the target material must be considered anisotropic and inhomogeneous. Single crystals(More)
This work focuses on application of the laser forming process to NiTi shape memory alloys. While all NiTi shape memory alloys exhibit both superlasticity and the shape memory effect, this study is restricted to a temperature range over which only the superelastic effect will be active. Specifically, this work addresses laser forming induced macroscopic(More)
Four laser scanning schemes for tube bending, including point-source circumferential scanning, pulsed line-source axial procession, and line-source axial scanning without and with water cooling are investigated in numerical simulation. The coupled thermo-mechanical model established using the finite element method is validated and applied to predict the(More)
Ankylosing Spondylitis is a disease characterized by abnormal bone structures (syndesmophytes) growing at intervertebral disk spaces. Because this growth is so slow as to be undetectable on plain radiographs taken over years, it is desirable to resort to computerized techniques to complement qualitative human judgment with precise quantitative measures. We(More)