Approximate dynamic programming solutions with a single network adaptive critic for a class of nonlinear systems

Approximate dynamic programming (ADP) formulation implemented with an adaptive critic (AC)-based neural network (NN) structure has evolved as a powerful technique for solving the Hamilton-Jacobi-Bellman (HJB) equations. As interest in ADP and the AC solutions are escalating with time, there is a dire need to consider possible enabling factors for their implementations. A typical AC structure consists of two interacting NNs, which is computationally expensive. In this paper, a new architecture, called the ‘cost-function-based single network adaptive critic (J-SNAC)’ is presented, which eliminates one of the networks in a typical AC structure. This approach is applicable to a wide class of nonlinear systems in engineering. In order to demonstrate the benefits and the control synthesis with the J-SNAC, two problems have been solved with the AC and the J-SNAC approaches. Results are presented, which show savings of about 50% of the computational costs by J-SNAC while having the same accuracy levels of the dual network structure in solving for optimal control. Furthermore, convergence of the J-SNAC iterations, which reduces to a least-squares problem, is discussed; for linear systems, the iterative process is shown to reduce to solving the familiar algebraic Ricatti equation.     

Switched-capacitor filters using unity-gain amplifiers

Switched-capacitor networks realizing second-order filter characteristics are presented. Realization is achieved with unity-gain amplifiers as buffers. The circuits have small sensitivities, good dynamic range and a reasonable spread of capacitor values. The filters can be used for high-Q realization and a relatively high frequency range.     

An adaptable problem-space-based search method for flexible flow line scheduling

Problem-space-based neighborhoods have been recently suggested in the literature for the approximate solution of scheduling problems. This paper explores how effectively these neighborhoods can be adapted to different regular measures of performance in the context of flexible flow line scheduling. Specifically, makespan and mean tardiness are used in the experiments. Near-optimal solutions and significant improvements in the performance of single-pass heuristics are found when searching these spaces with simple local search techniques for industrial and randomly generated problems.     

Effect of TiO2 nanotube length and lateral tubular spacing on photovoltaic properties of back illuminated dye sensitized solar cell

The main objective of this study is to show the effect of TiO₂ nanotube length, diameter and intertubular lateral spacings on the performance of back illuminated dye sensitized solar cells (DSSCs). The present study shows that processing short TiO₂ nanotubes with good lateral spacings could significantly improve the performance of back illuminated DSSCs. Vertically aligned, uniform sized diameter TiO₂ nanotube arrays of different tube lengths have been fabricated on Ti plates by a controlled anodization technique at different times of 24, 36, 48 and 72?h using ethylene glycol and ammonium fluoride as an electrolyte medium. Scanning electron microscopy (SEM) showed formation of nanotube arrays spread uniformly over a large area. X-ray diffraction (XRD) of TiO₂ nanotube layer revealed the presence of crystalline anatase phases. By employing the TiO₂ nanotube array anodized at 24?h showing a diameter ??80?nm and length ??1·5???m as the photo-anode for back illuminated DSSCs, a full-sun conversion efficiency (??) of 3·5 % was achieved, the highest value reported for this length of nanotubes.     

Technology of All Electroplated CdS:CuxS Solar Cells

Electrolytic deposition of CdS and Cu_xS for realizing solar cells holds considerable low cost potential. An electrodeposition technique from non-aqueous electrolytes is described and effect of important deposition variables on electrical and structural properties of films is discussed. Heterojunctions in frontwall configuration have been fabricated and the effect of Cu_xS bath composition on photovoltaic performance is evaluated. Voc = .412 V and Isc = 5.95 mA/sq cm have been achieved.     

Composite supercapacitor electrodes made of activated carbon/PEDOT:PSS and activated carbon/doped PEDOT

In this paper, we report on the high electrical storage capacity of composite electrodes made from nanoscale activated carbon combined with either poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) or PEDOT doped with multiple dopants such as ammonium persulfate (APS) and dimethyl sulfoxide (DMSO). The composites were fabricated by electropolymerization of the conducting polymers (PEDOT:PSS, doped PEDOT) onto the nanoscale activated carbon backbone, wherein the nanoscale activated carbon was produced by ball-milling followed by chemical and thermal treatments. Activated carbon/PEDOT:PSS yielded capacitance values of 640 F g^?1 and 26 mF cm^?2, while activated carbon/doped PEDOT yielded capacitances of 1183 F g^?1 and 42 mF cm^?2 at 10 mV s^?1. This is more than five times the storage capacity previously reported for activated carbon–PEDOT composites. Further, use of multiple dopants in PEDOT improved the storage performance of the composite electrode well over that of PEDOT:PSS. The composite electrodes were characterized for their electrochemical behaviour, structural and morphological details and electronic conductivity and showed promise as high-performance energy storage systems.     

Connected digit speech recognition system for Malayalam language

A connected digit speech recognition is important in many applications such as automated banking system, catalogue-dialing, automatic data entry, automated banking system, etc. This paper presents an optimum speaker-independent connected digit recognizer for Malayalam language. The system employs Perceptual Linear Predictive (PLP) cepstral coefficient for speech parameterization and continuous density Hidden Markov Model (HMM) in the recognition process. Viterbi algorithm is used for decoding. The training data base has the utterance of 21 speakers from the age group of 20 to 40 years and the sound is recorded in the normal office environment where each speaker is asked to read 20 set of continuous digits. The system obtained an accuracy of 99.5 % with the unseen data.     

焊接方法对Ti-6Al-4V合金接头微观组织及拉伸和冲击性能的影响

钛合金由于具有高比强度、优越的耐腐蚀性和出色的耐热性等优良特性,已成功应用于航空航天、造船和化学工业。尽管钛合金具有合适的可焊性特点,但焊接方法极大地影响焊接接头性能。焊接过程中热循环将会影响焊接金属凝固、相转变和微观组织。采用钨电极惰性气体保护焊接（GTAW）、激光束焊接（LBW）和电子束焊接（EBW）方法制备Ti-6Al-4V合金的焊接接头。EBW焊接接头的强度高于GTAW和LBW接头的强度,但GTAW接头较其它两种接头具有较高的断裂韧性。焊接接头的拉伸和冲击性能与焊接金属的微观组织有关。     

Effect of Hardfacing Consumables on Ballistic Performance of Q＆T Steel Joints

This study was canied out to evaluate the effect of hardfacing consmaaables on ballistic performance of armour grade quenched and tempered （Q＆T） steel welded joints. To evaluate the effect of harclfacilag constuaaables, j ohats were fabricated usilag 4 mm thick tungsten carbide （WC）/ chromium carbide （CrC） hardfaced middle layer; above and below which austenitic stahfless steel （SS） layers were deposited on both sides of the hardfaced interlayer. Shielded metal are weldhag （SMAW） process were used to deposite all （hardfaced layer and SS layers） layers. The fabricated j oints were evaluated for its ballistic peffomamace, and the results were compared with respect to depth of penetration （DOP） on weld metal and heat-affected zone （HAZ） locations. From the ballistic test results, it was observed that both the joints successfully stopped the bullet penen＇ation at weld center line. Of the two joints, the joilat made with CrC hardfaced ilaterlayer （CAHA） offered better ballistic resistmace at weld metal. This is because its harchaess is higher due to the presence of primary carbides of needle shape, polyhech＇al shape and eutectic matris contaillhag a mixture of γ ＋ M7C3 carbides in the CrC hardfaced interlayer. The scatterilag hardness level ha the WC interlayer, the matrix decomposition resulted lower harchaess and the co-existence of δ ferrite in the ilaterface between hardfacing and SS root/SS cap could be attributed to the lifferior ballistic resistmace of the joint made with WC hardfaced interlayer （WAHA joint）.