Finite Time Fractional-order Adaptive Backstepping Fault Tolerant Control of Robotic Manipulator

In this paper, fractional calculus theory is employed to inspect a finite time fault tolerant controller for robotic manipulators in the presence of uncertainties, unknown external load disturbances, and actuator faults, using fractional-order adaptive backstepping approach in order to achieve, fast response and high-precision tracking performance. Knowing the advantages of adaptive controllers an adaptive form of the above controller is then established to deal with the overall uncertainties in the system. The most important property of the proposed controller is that we do not need to have knowledge about the actuator fault, external disturbances and system uncertainties exist in system. In this study two important achievements are made. The first one is that the finite time convergence of closed-loop system is ensured irrespective of initial states values. The second one is that the effects of the actuator faults and other uncertainties are attenuated by the suggested controller. The performance of the suggested controller is then tested for a PUMA560 robot in which the first three joints are used. The simulation results validate the usefulness of the suggested finite-time fractional-order adaptive backstepping fault-tolerant (FOAB-FTC) controller in terms of accuracy of tracking, and convergent speed.

     

Polypropylene/phosphazene nanotube nanocomposites: Thermal,mechanical, and flame retardation studies

In this study, flame retardant polypropylene (PP) nanocomposites with superior mechanical performance have been developed using amine-functionalized phosphazene nanotubes (APZS, 1–10 wt%) through melt-blending method. Polypropylene-graft-maleic anhydride was used as the compatibilizer to attain effective interaction between the nanofiller and the PP matrix. The characterization of amine-functionalized phosphazene nanotubes (APZS) using solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy, X-ray diffraction, fourier-transform infrared (FTIR), and transmission electron microscopy indicated successful amine functionalization, though structural changes were observed as compared to the unfunctionalized nanotubes. Owing to the covalent polymer-filler interfacial interactions and resulting in uniform filler dispersion, the nanocomposites exhibited significant enhancement in the tensile modulus up to 5 wt% APZS content (98% increment at 5 wt% content as compared to pure polymer). The addition of a small fraction of APZS (1 wt%) improved the impact strength of the nanocomposite by more than 180%. APZS acted as a weak nucleating agent for PP, thereby leading to enhanced degree of crystallinity (up to 5 wt% APZS content). The thermal stability of the nanocomposites was also enhanced with APZS content. The nanocomposites with 5 and 10 wt% APZS loading exhibited a V0 rating in UL-94 test, indicating that APZS introduced a robust flame retardancy behavior in the PP nanocomposites. The limiting oxygen index values also confirmed the findings from the UL-94 analysis. The developed nanocomposites exhibit high potential of use in a wide range of high temperature applications.     

Morphological,physicochemical, and pasting properties of modified water chestnut (Trapabispinosa) starch

Selected physicochemical properties of native and modified water chestnut starch (Trapabispinosa) were studied. Single- and dual-modifications were carried out by pregelatinization, acetylation and acid-thinning methods. Chemical modification created unevenness on the surface of starch granule. Swelling power, solubility, and water retention capacity were improved by all modification techniques used. The peak viscosity was reduced in all modified starches as compared to native water chestnut starch. The setback value which is an indication of retrogradation (re-association of starch molecules) tendency in the starch paste was reduced after pregelatinization and acid-thinning but increased by acetylation.     

Concept of double salt fortification; a tool to curtail micronutrient deficiencies and improve human health status

Fortification of food with micronutrients such as vitamins and minerals is one of the main strategies used to combat micronutrient deficiencies. Fortification in common salt is a fruitful strategy because of the daily consumption of 5–12 g salt per person globally. Therefore double fortification of salt with iodine and iron could be a reasonable approach to prevent both iodine and iron deficiencies. It is reckoned that about two billion people are iodine‐deficient worldwide. Iodine deficiency during pregnancy may affect the health status of both mother and fetus and increase infant mortality. Deficiencies of both these micronutrients during childhood affect somatic growth and cognitive and neurological function. Thyroid metabolism is negatively affected by iron deficiency and reduced effectiveness of iodine prophylaxis in areas of endemic goiter. High prevalence of iron deficiency among children may be reduced by the application of effective iodized salt programs. However, ensuring the stability and bioavailability of both iron and iodine as double‐fortified salt is difficult. Iodine present in iodide or iodate form in dual‐fortified salt is oxidized to free iodine in the presence of ferrous ions and oxygen and consequently loses its characteristics. Moreover, ferrous iron is more bioavailable but is readily oxidized to the less bioavailable ferric form. However, both forms of iron may lead to discoloration of the final product, which can be reduced by providing a physical barrier around the iron. Salt encapsulation is one of the best tools to provide a physical barrier for undesirable reactions and interactions during storage. In this review the concept of dual salt fortification, the impact of fortification on curing various life‐threatening maladies, latest assessments of mineral deficiencies and the choice of fortificants are discussed. © 2014 Society of Chemical Industry     

Optimization of operating parameters of video display units in text reading task: Luminance contrast,viewing distance,and character size

Abstract— The purpose of this study is to determine the reading performance of operators on a desktop computer. The effects of luminance contrast, viewing distance, and character size on the speed of reading were investigated. The luminance contrast between the background and character was varied while color contrast was held near‐constant. Stimuli with different levels of character size, viewing distance, and luminance contrast were considered while assessing the readability performance. The luminance contrast between the background and character (0.01, 0.15, and 1.00), character sizes (0.2, 1.5, and 4°), and viewing distance (40, 50, and 60 cm) were used, and the performance of the operators were recorded in terms of words per minutes (WPM). Standard workplace design recommendations to position the center of the visual display terminal (VDT) 15° and 40° below horizontal eye level were used for the visually intensive readability task. An orthogonal array, the signal‐to‐noise (S/N) ratio, and the analysis of variance (ANOVA) were employed to investigate the above‐mentioned operating parameters to determine the optimum readability performance. The results indicated that performance was better at a 15° viewing angle as compared to a 40° viewing angle.     

一种高效的指令缓存单元架构及其性能分析

为了提高高速DSP或通用处理器的程序执行速度,描述了一种指令缓存单元的有效架构,特别是实现细节和性能分析.因所提出的指令缓存单元是为一种高性能VLIW结构的DSP核而设计,使用了并行的标签比较逻辑和寄存器堆的结构,芯片面积、关键路径延迟、功耗都大大减小.该指令缓存单元使用高层次的RTL(使用Verilog)编码,并由Synopsys的Design Compiler综合,使用不同的StarCoreTM基准程序测试比较,并进行性能分析.比较结果表明,所提出的结构是有效的,适合用于任何高速的处理器核.     

Polyphenylene sulphide/carbon fiber composites: study on their thermal,mechanical and microscopic properties

The present study investigates the thermal, mechanical and microscopic properties of polyphenylene sulphide/carbon fiber (PPS/CF) composites by incremental number of fiber layers. The composites were prepared by hand lay-up technique followed by compression molding. A superior matrix-reinforcement adhesion was attained without the use of coupling agent and mechanical stability of the composites improved with increasing fiber layers. Transverse rupture strength and bending modulus were improved by 59.84 and 125.21 %, respectively, without loss in toughness. Impact strength and hardness values were enhanced while storage modulus, loss modulus and damping factor were dropped by increases in fiber layers. Thermogravimetric analysis (TGA) indicated a gradual rise in thermal stability (16.84 %) of the composite as compared to pure matrix. Surface morphology and crack propagation were studied by optical microscopy. It was found that crack was propagated in a linear plane by applying load. In addition, scanning electron microscopy (SEM) illustrated steady alignment of fibers and uniform distribution of the matrix around reinforcement. Based on the obtained results, fiber layers showed great potential for enhancement of thermal and mechanical properties of the composites.     

Interference Nomenclature in Wireless Mesh Networks

The Quality of Service of Multi-Channel Multi-Radio Wireless Mesh Networks is adversely affected by the complex behavior of interference patterns present between the sender and receiver of a link. This behavior is usually captured using wireless channel interference models. The accuracy of the interference model is highly dependent on the interaction of the Carrier Sense Multiple Access with Collision Avoidance Medium Access Control (CSMA/CA MAC) protocol based on the geometric location of the sender and receiver of the link. Therefore, this paper presents a nomenclature of interference modeling schemes available in Wireless Mesh Network (WMN) literature with respect to the geometric location of the sender and receiver of a link. The behavior and limitations of each model are analyzed with the help of empirical examples. The results indicate that Garetto’s model of interfering links is the best choice to model wireless channel interference in WMNs. In addition, this study provides an interference analysis of Garetto’s model for the two link case by computing the conditional packet loss probability of each class of interfering link. The probability analysis concluded that the links with disconnected senders are highly interfering compared to sender connected links. Further, the analysis will assist researchers and engineers in relay node placement, capacity analysis, channel assignment, and topology control schemes in the WMN.