Delta-doped tunnel FET (D-TFET) to improve current ratio ($$I_\mathrm{ON}/I_\mathrm{OFF}$$) and ON-current performance

A two dimensional (2D) analytical drain current model has been developed for a delta-doped tunnel field-effect transistor (D-TFET) that can address the ON-current issues of the conventional TFET. Insertion of a highly doped delta layer in the source region paves the way for improved tunneling volume and thus provides high drain current as compared with TFETs. The present model takes into account the effects of the distance between the delta-doping region and the source–channel interface on the subthreshold swing (SS), current ratio, and ON-current performance. The D-TFET is predicted to have a higher current ratio \(\left( {\frac{I_\mathrm{ON} }{I_\mathrm{OFF} }\cong 10^{11}} \right) \) compared with TFETs \(\left( {\frac{I_\mathrm{ON} }{I_\mathrm{OFF} }\cong 10^{10}} \right) \) with a reasonable SS \(\left( {{\sim }52\,\mathrm{mV/dec}} \right) \) and \(V_\mathrm{th}\) performance at an optimal position of 2 nm from the channel. The surface potential, electric field, and minimum tunneling distance have been derived using the solution of the 2D Poisson equation. The accuracy of the D-TFET model is validated using the technology computer aided design (TCAD) device simulator from Synopsys.     

Enhanced power quality based single phase photovoltaic distributed generation system

This article presents a novel control strategy for a 1-? 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.     

Silica encapsulated Ni nanoparticles: variation of optical and magnetic properties with particle size

Ni nanoparticles embedded in SiO2 matrix were prepared by sol-gel process. The molar percentages of Ni were varied from 2 to 20% of total SiO2 present in the matrix. Transmission electron microscope (TEM) images revealed that particle sizes varied from 8.0-15.7 nm at an annealing temperature of 773 K with variation of concentration. The optical absorption spectra revealed that the surface plasmon resonance (SPR) peak in the UV region of the spectrum shifted with the particle diameter (D) from that at 247.3 nm for D = 8.0 nm to 250.7 nm for D = 15.7 nm. In hysteresis loop measurements the magnetizations (M) of the nanocomposites also increased with higher Ni content in the matrix and did not saturate in the measuring limit of the magnetic filed (H) of 4 KOe. The anhysteric curves for different samples were analyzed with the law of approach to saturation (LAS). The zero field cooled (ZFC) and field cooled (FC) magnetization measurements at 50 Oe showed increasing broadening of the ZFC curve with the higher Ni content. To calculate the average blocking temperature ((T(B a distribution of the blocking temperatures (T(B)) was assumed to initiate theoretical fittings and it was found to be increasing with the Ni concentration in the matrix.     

Multiple multicast with minimized node contention on wormhole k-aryn-cube networks

This paper presents a new approach to minimize node contention while performing multiple multicast/broadcast on wormhole k-ary n-cube networks with overlapped destination sets. The existing multicast algorithms in the literature deliver poor performance under multiple multicast because these algorithms have been designed with only single multicast in mind. The new algorithms introduced in this paper do not use any global knowledge about the respective destination sets of the concurrent multicasts. Instead, only local information and a source-specific partitioning approach are used. For systems supporting unicast message-passing, a new SPUmesh (Source-Partitioned Umesh) algorithm is proposed and is shown to be superior than the conventional Umesh algorithm for multiple multicast. Two different algorithms, SQHL (Source-Quadrant Hierarchical Leader) and SCHL (Source-Centered Hierarchical Leader), are proposed for systems with multidestination message-passing and shown to be superior than the HL scheme. All of these algorithms perform 1) 5-10 times faster than the existing algorithms under multiple multicast and 2) as fast as existing algorithms under single multicast. Furthermore, the SCHL scheme demonstrates that the latency of multiple multicast can, in fact, be reduced as the degree of multicast increases beyond a certain number. Thus, these algorithms demonstrate significant potential to be used for designing fast and scalable collective communication libraries on current and future generation wormhole systems     

Stochastic Study of Windpumps with Reservoir in Southern High Plains

Hourly wind-speed data for 11 years (1983–1993), historical ground-water table data, and performance test results under varying conditions for two mechanical windpumps and one electrical windpump were used at Bushland, Tex., to evolve major recommendations pertaining to wind-powered irrigation management. Stochastic analysis of hourly wind-speed data showed that the average daily wind speed lies most frequently in the range of 5.5–6 m∕s, with the upper and lower limits being 16 and 4.5 m∕s, respectively. This is conducive to most of the wind energy conversion systems manufactured today. The discharge of the electrical windpump was more than four times higher than the mechanical windpumps at high wind speeds. The performance of the electrical windpump was also much better at a high operating head (60 m) than at low operating heads under high wind regimes, showing its suitability for ground-water pumping in the Southern High Plains. Stochastic estimation of daily windpump discharge revealed that pumping rates are high in the spring and autumn seasons, favoring irrigation of a winter wheat crop. The trend of variation in unit reservoir capacity, under different levels of daily demand and risk, shows that wind-powered irrigation systems with high risk can be adopted under higher economic return conditions. Though the results obtained in this study are applicable mainly to the Southern High Plains of the United States, the methodology developed will have general applicability.     

ARTIFICIAL NEURAL NETWORKS: PRINCIPLE AND APPLICATION TO MODEL BASED CONTROL OF DRYING SYSTEMS - A REVIEW

This paper reviews the developments in the model based control of drying systems using Artificial Neural Networks (ANNs). Survey of current research works reveals the growing interest in the application of ANN in modeling and control of non-linear, dynamic and time-variant systems. Over 115 articles published in this area are reviewed. All landmark papers are systematically classified in chronological order, in three distinct categories; namely, conventional feedback controllers, model based controllers using conventional methods and model based controllers using ANN for drying process. The principles of ANN are presented in detail. The problems and issues of the drying system and the features of various ANN models are dealt with upto-date. ANN based controllers lead to smoother controller outputs, which would increase actuator life. The paper concludes with suggestions for improving the existing modeling techniques as applied to predicting the performance characteristics of dryers. The hybridization techniques, namely, neural with fuzzy logic and genetic algorithms, presented, provide, directions for pursuing further research for the implementation of appropriate control strategies. The authors opine that the information presented here would be highly beneficial for pursuing research in modeling and control of drying process using ANN     

A novel technique for direct reuse of wastewater in combining scouring and bleaching of cotton fabric

Abstract

Wastewater generated from the conventional pretreatment process is having potential to reuse several times for pretreatment of subsequent batches without harming the fabric quality. As the major portion of water is used in textile pretreatment processes, in the present work a novel method was studied for direct reuse of wastewater in combining scouring and bleaching process. The wastewater generated by the conventional pretreatment was reused with and without mixing with freshwater. Simple technique like filtration with nylon mesh was also studied for its effects on efficiency of pretreatment. The pretreated fabrics were characterized using advanced techniques and further evaluated towards efficiency of scouring and bleaching. In order to evaluate the effect of novel pretreatment process involving reuse of wastewater on dyeability, the pretreated fabrics (using both conventional and novel methods) were further studied for dyeability using reactive dyes. The resulting wastewaters were characterized before reuse in novel method. The pretreated fabrics showed insignificant variations in strength and pretreatment efficiency. The dyeability of both fabrics towards reactive dyes was comparable. The volume of effluent generated was greatly reduced in novel method which showed a great promise to save 33% of water in pretreatment process of cotton fabric.     

Selectivity engineering in the nitration of chlorobenzene using eclectically engineered sulfated zirconia and carbon molecular sieve catalysts

Selective synthesis of the para‐nitro derivative from chlorobenzene by using nitric acid over an eclectically engineered sulfated zirconia carbon molecular sieve catalyst is reported. The p : o ratio in chlorobenzene nitration was found to be very high with eclectically engineered sulfated zirconia and carbon molecular sieve catalyst. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermal shock and thermal fatigue study of ceramic materials on a newly developed ascending thermal shock test equipment

A test equipment was designed to study thermal shock and thermal fatigue of ceramic materials subjected to fast heating (ascending). The equipment was designed to generate thermal stress in a test specimen by heating one surface of it by an oxy-hydrogen flame while cooling the opposite surface. The sample cracked when thermal stress exceeded its mechanical strength. The in situ crack formation was detected by an acoustic emission system coupled to the set up. The hot zone temperature was measured by an infra red pyrometer. The equipment was also designed to run thermal fatigue test cycles in automatic mode between two selected temperatures. The temperature and thermal stress distribution in the test specimen were modelled using finite element software. The effect of temperature distribution of the top and bottom surfaces on thermal stresses was studied. It was observed that the thermal stress is very sensitive to the temperature distribution on the top surface and maximum near the periphery of the top surface. This was in agreement with the experimental results in which the cracks were originated from the periphery of top surface. It was also observed that the failure temperature was higher for thicker samples.