Stability Analysis of a Nonlinear Blister Test

The Griffith and stability criteria for the blister test have been derived from thermodynamic arguments. The Griffith criterion includes the stored energy in the blister as well as the interfacial energy change associated with debonding. Based on these criteria an analysis is given of a blister test with a neo-Hookian overlayer debonding from a rigid substrate. A closed analytic form for the strain energy release rate, G, is obtained valid for large elastic deformation of a thin circular film. The criteria derived indicate that quasi-static debonding of the blister is always stable, independent of the interfacial energies and the extent of blister deformation.     

Effects of Mg dopant on the degradation of InGaN multiple quantum wells in AlInGaN-based light emitting devices

We investigated the effects of Mg dopant on the degradation of AlInGaN-based light emitting diodes (LEDs) and laser diodes (LDs) with InGaN multi-quantum wells (MQWs). Photoluminescence (PL) intensity of InGaN MQWs was significantly decreased with increasing the Mg intentional doping process in InGaN active region, indicating that Mg dopant could degrade the optical quality of InGaN MQWs. From secondary ion mass spectroscopy (SIMS) analysis of AlInGaN-based LDs grown on GaN/sapphire and GaN substrate with different dislocation densities, we found that Mg concentration of LD on GaN/sapphire was higher than that of LD on GaN substrate at the InGaN MQWs regions. Additionally, we observed that Mg atoms were significantly diffused from p-type layer to InGaN MQWs region in the LD structure after aging evaluation. From these results, we could conclude that Mg diffusion along threading dislocations is one of the major gradual degradation mechanisms of AlInGaN-based LD/LEDs during the device operation under high voltage condition.     

Developing a custom DSP for vision based human computer interaction applications

Multimedia Tools and Applications - As the computing power of modern devices become greater, computer vision is increasingly adopted as the means of human-computer interaction. The industry is...     

Two versions of architectures for dynamic implied addressing mode

The complexity of today’s embedded applications increases with various requirements such as execution time, code size or power consumption. To satisfy these requirements for performance, efficient instruction set design is one of the important issues because an instruction customized for specific applications can make better performance than multiple instructions in aspect of fast execution time, decrease of code size, and low power consumption. Limited encoding space, however, does not allow adding application specific and complex instructions freely to the instruction set architecture. To resolve this problem, conventional architectures increases free space for encoding by trimming excessive bits required beyond the fixed word length. This approach however shows severe weakness in terms of the complexity of compiler, code size and execution time. In this paper, we propose a new instruction encoding scheme based on the dynamic implied addressing mode (DIAM) to resolve limited encoding space and side-effect by trimming. We report our two versions of architectures to support our DIAM-based approach. In the first version, we use a special on-chip memory to store extra encoding information. In the second version, we replace the memory by a small on-chip buffer along with a special instruction. We also suggest a code generation algorithm to fully utilize DIAM. In our experiment, the architecture augmented with DIAM shows about 8% code size reduction and 18% speed up on average, as compared to the basic architecture without DIAM.     

Efficient embedded code generation with multiple load/store instructions

In a recent study, we discovered that many single load/store operations in embedded applications can be parallelized and thus encoded simultaneously in a single‐instruction multiple‐data instruction, called the multiple load/store (MLS) instruction. In this work, we investigate the problem of utilizing MLS instructions to produce optimized machine code, and propose an effective approach to the problem. Specifically, we formalize the MLS problem, that is, the problem of maximizing the use of MLS instructions with an unlimited register file size. Based on this analysis, we show that we can solve the problem efficiently by translating it into a variant of the problem finding a maximum weighted path cover in a dynamic weighted graph. To handle a more realistic case of the finite size of the register file, our solution is then extended to take into account the constraints of register sequencing in MLS instructions and the limited register resource available in the target processor. We demonstrate the effectiveness of our approach experimentally by using a set of benchmark programs. In summary, our approach can reduce the number of loads/stores by 13.3% on average, compared with the code generated from existing compilers. The total code size reduction is 3.6%. This code size reduction comes at almost no cost because the overall increase in compilation time as a result of our technique remains quite minimal. Copyright © 2007 John Wiley & Sons, Ltd.     

Enhanced brightness and efficiency of organic light-emitting diodes with an LiF in the Alq/sub 3/

Highly efficient and bright organic light-emitting diodes have been realized by inserting a thin insulating lithium fluoride (LiF) layer in the tris-(8-hydroxyquinoline) aluminum (Alq/sub 3/) with conventional organic layers. By comparing the performances of newly devised devices as a function of the position of the LiF in the Alq/sub 3/ layer, the authors propose the optimal position of the LiF in the Alq/sub 3/ layer. Experimental results show that the efficiency and brightness of the newly devised device with LiF in the Alq/sub 3/ layer were seven times higher than that without LiF in the Alq/sub 3/ layer.