Chinese alligator (Alligator sinensis) is one of the most critically endangered species among 23 extant crocodiles in the world. To prevent the extinction of the species, a captive propagation started at early 1980s, and the total number of alligator was brought up to 10 thousands from dozens of founder in 2000. But several genetic investigations showed those alligators were under an extremely low genetic diversity status with few detectible polymorphic loci. To get more insight into its genetic diversity for the management of captive Chinese alligator, AFLP was adopted to characterize variations in the population. Total of 347 bands were generated from 47 individuals using 3 primer combinations, of which 203 (58.50%) were polymorphic, and 35 AFLP phenotypes were revealed from those individuals. Comparing the results between RAPD and AFLP analysis on almost same sample set clearly indicated that AFLP is more efficient in revealing polymorphic loci, especially in those populations with extremely low genetic diversity. In present three assays, electrophoresis profile also displayed 3 individuals possessing very highly polymorphic AFLP phenotypes that were never been found by RAPD and mtDNA D-loop sequencing, implicating that we should offer these individuals more breeding opportunities to maintain the genetic diversity in the population and restrict those carrying few polymorphic loci from reproduction

I proposed a method of using full-custom design 32 × 32 multiplier to enhance performance, reduce the power consumption and the area of layout. I use improved Wallace tree structure for partial product compression, truncated beyond the 64 part of the plot and the look-ahead logarithmic adder using Radix-4 Kogge-Stone tree algorithm raise the multiplier performance. In the design of Booth2 encoding circuit and compression circuit, I use a transmission gate logic design with higher speed and smaller area. I also use Euler path method and heuristic Euler path method to reduce the layout area. The design use SMIC 0.18μm 1P4M CMOS process, with a layout area of 0.1684mm2. In a large number of test patterns, simulation results show that the computation time of a 32 × 32 multiplication is less than 3.107ns.

In order to simulate accurately the formation process of the keyhole in laser deep penetration welding. Multiple reflection and Fresnel absorption are implemented simultaneously with the ray tracing technique in the keyhole. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity.

In order to accurately simulate the process of laser deep penetration welding, a mathematical model to describe laser deep penetration welding was developed by using the heat source derived from the ray-tracing model, and taking account into the effect of keyhole on welding pool. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Numerical simulation was conducted by FLUENT 6.3 software package. The simulation results show that the formation of keyhole in the weld is caused by recoil pressure.

The elaborated model solves the coupled equations of a laminar fluid flow and heat transfer to predict the temperature distribution in the weld pool. The enthalpy-porosity technique was employed to account for the latent heat during melting and solidification. The coupled effects of buoyancy and Marangoni forces are considered in this model. The volume-of-fluid (VOF) method was employed to track free surfaces of weld pool. The molten temperature distribution, velocity field and molten shape were calculated using FLUENT software. The results clearly demonstrate Marangoni flow significantly alters the characteristics of the thawing and solidifying process, and makes the molten wider and shallower.