Comparison of Fatigue Strengths of Bulk Metallic Glasses Produced by Tilt Casting and High-Pressure Casting

High fatigue strength is one of the important factors that facilitates the industrial usage of bulk metallic glasses (BMGs). Fatigue data were analyzed using the Weibull probability models for BMGs produced with different casting processes in order to study the reliability of fatigue strengths of cast glassy alloys. The fatigue data of tilt-cast and high-pressure-cast BMGs can be explained by a three-parameter Weibull cumulative distribution function (cdf) and a mixture model of two-parameter Weibull cdfs, respectively. We conclude that the cast defects, which reduce fatigue strength, should be eliminated in order to realize a high reliability of fatigue strengths.     

A selectively deposited poly-gate ITLDD process with self-alignedLDD/channel implantation

An inverse-T lightly doped drain (ITLDD) CMOS process which features improved hot-carrier effects and self-aligned source/drain and channel implantation profiles is presented. Compensation effects by the heavy channel doping on the light N^-/P^- profile are minimized in this ITLDD structure, because the implants are self-aligned to the polysilicon-gate edge. In addition, because selective polysilicon deposition rather than an incomplete poly-gate etchback is used to define the ITLDD structure, a simpler, more manufacturable process is obtained due to improved control of the thin poly-gate shelf thickness     

Parallel pump-shared linear cavity laser array using 980-nm pumpreflectors or N pieces of gain fibers as self-equalizers

By using fiber gratings as pump reflectors with various reflectivities or N pieces of gain fibers with various lengths externally to linear cavity as self-equalizers, a parallel-type, pump-shared linear cavity laser array (LCLA) is proposed and numerically studied. The average output power is increased and the maximum power variation among channels is reduced from 7.2 to less than 0.1 dB when the reflectivity of each pump reflector or the length of each gain fiber is adjusted appropriately     

A fast VQ codebook generation algorithm using codeword displacement

In this paper, we present a fast codebook generation algorithm called CGAUCD (Codebook Generation Algorithm Using Codeword Displacement) by making use of the codeword displacement between successive partition processes. By implementing a fast search algorithm named MFAUPI (Modified Fast Algorithm Using Projection and Inequality) for VQ encoding in the partition step of CGAUCD, the codebook generation time can be further reduced significantly. Using MFAUPI, the computing time of CGAUCD can be reduced by a factor of 4.7–7.6. Compared to Generalized Lloyd Algorithm (GLA), our proposed method can reduce the codebook generation time by a factor of 35.9–121.2. Compared to the best codebook generation algorithm to our knowledge, our approach can further reduce the corresponding computing time by 26.0–32.8%. It is noted that our proposed algorithm can generate the same codebook as that produced by the GLA. The superiority of our method is more remarkable when a larger codebook is generated.     

A Novel Algorithm for Simple Hybrid of Adaptive Array and Equalizer

Adaptive array has been used for canceling the interference in communication. When the array cannot suppress all the interference, an equalizer following the array can add to further enhance the capability of canceling the inter-symbol interference (ISI). The adaptive array and equalizer (AE) will suffer the problems of insufficient degrees of freedom and main-beam multi-path ISI. The hybrid of adaptive array and equalizer (HAE) uses a modified training sequence to adjust the weights of adaptive array that leads the array to cancel only the co-channel interference (CCI). The ISI are removed by the equalizer following the array. Thus, the HAE can combat the above problems successfully. Though the HAE improves the performance of AE, a transversal filter is added to generate the modified training sequence. Besides, the weights of equalizer in the HAE, which adjust after the weights of adaptive array, will make the convergent rate slowly. A simple hybrid of adaptive array and equalizer (SHAE) utilizes the output signal of system to adjust the weights of both the adaptive array and equalizer simultaneously. Therefore, the convergent rate of the HAE can improve by the SHAE. Moreover, the ISI can be suppressed by the equalizer instead of the adaptive array in the SHAE that will improve the performance of AE without using the transversal filter. As the mutual coupling present, the convergent rate of the SHAE will slow down. In this paper, a least mean square error algorithm with mutual coupling present is proposed to improve the convergent rate of SHAE, also.     

Contact Friction Compensation for Robots Using Genetic Learning Algorithms

In this paper, the issues of contact friction compensation for constrained robots are presented. The proposed design consists of two loops. The inner loop is for the inverse dynamics control which linearizes the system by canceling nonlinear dynamics, while the outer loop is for friction compensation. Although various models of friction have been proposed in many engineering applications, frictional force can be modeled by the Coulomb friction plus the viscous force. Based on such a model, an on-line genetic algorithm is proposed to learn the friction coefficients for friction model. The friction compensation control input is also implemented in terms of the friction coefficients to cancel the effect of unknown friction. By the guidance of the fitness function, the genetic learning algorithm searches for the best-fit value in a way like the natural surviving laws. Simulation results demonstrate that the proposed on-line genetic algorithm can achieve good friction compensation even under the conditions of measurement noise and system uncertainty. Moreover, the proposed control scheme is also found to be feasible for friction compensation of friction model with Stribeck effect and position-dependent friction model.     

Drop-weight impact of plain-woven hybrid glass–graphite/toughened epoxy composites

The progressive damage behaviors of hybrid woven composite panels (101.6 mm × 101.6 mm) impacted by drop-weights at four different velocities were studied by a combined experimental and 3-D dynamic nonlinear finite element approach. The specimens tested were made of plain-weave hybrid S2 glass-IM7 graphite fibers/toughened epoxy (cured at 177 °C). The composite panels were damaged using a pressure-assisted Instron-Dynatup 8520 instrumented drop-weight impact tester. During these low-velocity simpact tests, the time-histories of impact-induced dynamic strains and impact forces were recorded. The damaged specimens were inspected visually and using ultrasonic C-Scan methods. The commercially available 3-D dynamic nonlinear finite element (FE) software, LS-DYNA, incorporated with a proposed user-defined damage-induced nonlinear orthotropic model, was then used to simulate the experimental results of drop-weight tests. Good agreement between experimental and FE results has been achieved when comparing dynamic force, strain histories and damage patterns from experimental measurements and FE simulations.     

Double noding technique for mixed mode crack propagation studies

A simple dynamic finite element algorithm for analysing a propagating mixed mode crack tip is presented. A double noding technique, which can be easily incorporated into existing dynamic finite element codes, is used together with a corrected ? integral to extract modes I and II dynamic stress intensity factors of a propagating crack. The utility of the procedure is demonstrated by analysing test problems involving a mode I central crack propagating in a plate subjected to uniaxial tension, a stationary slanted central crack in a plate subjected to uniaxial inpact loading and an extending slanted-edge crack in plate subjected to uniaxial tension.