Structure and properties of diffusion bonded transition joints between commercially pure titanium and type 304 stainless steel using a nickel interlayer

The solid-state diffusion bonding was carried out between commercially pure titanium and Type 304 stainless steel using nickel as an interlayer in the temperature range of 800–900 °C for 9 ks under 3 MPa load in vacuum. The transition joints thus formed were characterized in the optical and scanning electron microscopes. The inter-diffusion of the chemical species across the diffusion interfaces were evaluated by electron probe microanalysis. TiNi₃, TiNi and Ti₂Ni are formed at the nickel–titanium (Ni–Ti) interface; however, the stainless steel–nickel (SS–Ni) diffusion interface is free from intermetallic compounds up to 850 °C temperature. At 900 °C, the Ni–Ti interface exhibits the presence of α-β Ti discrete islands in the matrix of Ti₂Ni and λ + χ + α-Fe, λ + FeTi and λ + FeTi + β-Ti phase mixtures occur at the SS–Ni interface. The occurrence of different intermetallics are confirmed by the x-ray diffraction technique. The maximum tensile strength of ∼276 MPa and shear strength of ∼209 MPa along with 7.3% elongation were obtained for the diffusion couple processed at 850 °C. At the 900 °C joining temperature, the formation of Fe–Ti base intermetallics reduces the bond strength. Evaluation of the fracture surfaces using scanning electron microscopy and energy dispersive spectroscopy demonstrates that failure takes place through Ni–Ti interface up to 850 °C and through the SS–Ni interface of the joint when processed at 900 °C.     

Wavelet Bootstrap Multiple Linear Regression Based Hybrid Modeling for Daily River Discharge Forecasting

A new hybrid model, the wavelet–bootstrap–multiple linear regression (WBMLR) is proposed to explore the potential of wavelet analysis and bootstrap resampling techniques for daily discharge forecasting. The performance of the developed WBMLR model is also compared with five more models: multiple linear regression (MLR), artificial neural network (ANN), wavelet-based MLR (WMLR), wavelet-based ANN (WANN) and wavelet–bootstrap–ANN (WBANN) models. Seven years of discharge data from seven gauging stations in the middle reaches of Mahanadi river basin in India are applied in this study. Significant input vectors are decomposed into discrete wavelet components (DWCs) using discrete wavelet transformation (DWT) to generate wavelet sub time series that are used as inputs to the MLR and ANN models to develop the WMLR and WANN models, respectively. Effective wavelets are selected by considering several types of wavelets with different vanishing moments. WBMLR and WBANN models are developed as ensemble of different WMLR and WANN models, respectively, developed using different realizations of the training dataset generated using bootstrap resampling technique. The results show that the wavelet bootstrap hybrid models (i.e. WBMLR and WBANN) produce significantly better results than the traditional MLR and ANN models. Hybrid models based on MLR (WMLR, WBMLR) perform better than the ANN based hybrid models (WBANN, WANN). The WBMLR and WMLR models simulate the peak discharges better than the WBANN, WANN, MLR and ANN models, whereas the overall performance of WBMLR model is found to be more accurate and reliable than the remaining five models.     

Three-Phase Induction Generators: A Discussion on Performance

Three-phase Induction Generators (IGs) are increasingly being used as smallscale energy producing devices in nonconventional energy conversion systems. Both squirrel-cage and wound rotor types of induction motors used as generators are popular in this regard. The aim of this paper is to discuss critically the important contributions of researchers on the applications in both grid-connected and isolated modes of operations and critical evaluation of performance of these generators under different operating conditions. The major focus has been on the evaluation performance of squirrel-cage induction motor used as Self-Excited Induction Generator (SEIG), and both experimental and theoretical results are provided to represent the important characteristics of this generator. Finally, the future trend of research in this field has been pointed out.     

Influence of process parameters on the formation of Silicalite-1 zeolite particles

Silicalite-1 particles with minimum twinning have been synthesized inside the polar core of non-ionic surfactant/co-surfactant-stabilized water-in-oil (w/o) type emulsions at 150° ± 1 °C within a short reaction time of 5 h. The non-ionic surfactants of varying hydrophilic–lipophilic balance (HLB) values, i.e. sorbitan monooleate (Span 80, HLB: 4.3), sorbitan monolaurate (Span 20, HLB: 8.6), polyoxyethylene (4) lauryl ether (Brij 30, HLB: 9.7) and polyoxyethylene sorbitan monooleate (Tween 80, HLB: 15), the cationic surfactant, i.e. cetyl trimethyl ammonium bromide (CTAB), surfactant concentration, co-surfactant, synthesis temperature and time have been found to play significant role in controlling size and characteristics of Silicalite-1. It has been observed that the crystallinity and size of Silicalite-1 can be tailored by adjusting the interactions between the polar surfactant head groups at the w/o interface and the growing crystallographic surfaces (or silicate/TPA ions) in the aqueous medium of the emulsion.     

Strategy logic

We introduce strategy logic, a logic that treats strategies in two-player games as explicit first-order objects. The explicit treatment of strategies allows us to specify properties of nonzero-sum games in a simple and natural way. We show that the one-alternation fragment of strategy logic is strong enough to express the existence of Nash equilibria and secure equilibria, and subsumes other logics that were introduced to reason about games, such as ATL, ATL¹, and game logic. We show that strategy logic is decidable, by constructing tree automata that recognize sets of strategies. While for the general logic, our decision procedure is nonelementary, for the simple fragment that is used above we show that the complexity is polynomial in the size of the game graph and optimal in the size of the formula (ranging from polynomial to 2EXPTIME depending on the form of the formula).     

System-Level Specification Testing Of Wireless Transceivers

This paper presents an efficient system-level manufacturing test methodology for wireless transceiver systems. Conventional system-level testing procedures incur large test times and require the use of multiple test hardware configurations for measuring frequency and modulation-domain performance specifications, e.g., system-gain, nonlinearity, noise-figure, channel power, adjacent-channel power-ratio, error vector magnitude, modulation signal-to-noise ratio and bit error rate. The proposed test methodology addresses these problems by simplifying the test stimulus application and test response capture/analysis procedures. In addition, the number of test hardware configurations needed to measure all the performance specifications is minimized and fewer as well as shorter tests are used to determine all the test specification values of interest. Test accuracy is achieved by optimizing the test stimulus so that the observed response has strong statistical correlation with the target test specification values. Experimental results show significant testing time reduction and was validated on 1.575 GHz and 900 MHz wireless transceiver prototypes.     

Codeposition of nanocrystalline aluminides on a copper substrate

The present study concerns codeposition of nanocrystalline aluminide particles (NbAl₃ and Cu₉Al₄) along with electrodeposition of Cu on a Cu substrate. It is shown that the success of codeposition primarily depends on the selection of an appropriate electrolyte. Following codeposition under an optimum deposition condition, the microstructure, phase identity and composition of the deposit layer have been studied. In addition, microhardness and electrical resistivity of the deposit have been determined. A suitable correlation of the microstructure and composition of the deposit with its properties suggests that codeposition of NbAl₃ is more effective in enhancing the hardness. However, codeposition beyond a limit adversely affects the electrical conductivity. The optimum conditions for codeposition to enhance hardness without adversely affecting conductivity have been determined. Finally, it is predicted codeposition could be a suitable technique for developing a surface composite microstructure with uniform distribution of nanocrystalline aluminide particles.     

Preparation of highly dispersed gold nanoparticles inside the porous support assisted by amphiphilic vinyl maleate copolymer

An amphiphilic copolymer composed of maleic acid and alkyl (C₁₈) vinyl monomer was encapsulated into the porous support. A series of colloidal gold nanoparticles of known size was substantially immobilized in the composite porous supports based on cross-linked polyacrylate ester and cross-linked polystyrene resin. Maleic acid moiety of the amphiphilic copolymer can act as a stabilizer for gold nanoparticles in analogy to citric acid, whereas alkyl chains play a role for the stable accommodation of the amphiphilic copolymer. Maleic acid stabilizes the gold nanoparticles by flexing the geometrical arrangement of the linear polymer. Presence of C₁₈ alkyl chain in the poly(C₁₈-vinyl maleate) is indispensable to act as spacing group that prevents mutual aggregation of gold nanoparticles. On the other hand, gold nanoparticles with average diameter of less than 8 nm were spontaneously formed by treatment of the composite resin beads with aqueous HAuCl₄ solution, subsequently dispersed inside the pores of resin beads as observed by TEM. We have also elucidated the catalytic activity of the material with the hydrogenation of cinnamaldehyde in supercritical carbon dioxide. Notably, apparent size effect of gold was observed in the selectivity of the reaction.