Enhancement in Physical Properties of Silver-Doped Fe–Ni Invar Nano-alloy Using Chemical Reduction Method

Journal of Superconductivity and Novel Magnetism - Silver-substituted Fe–Ni nano invar alloy is a new and innovative field of research due to their interesting invar, magnetic and electrical...     

Buckling of thin‐walled cylindrical shells under axial compression

Lightweight thin‐walled cylindrical shells subjected to external loads are prone to buckling rather than strength failure. The buckling of an axially compressed shell is studied using analytical, numerical and semi‐empirical models. An analytical model is developed using the classical shell small deflection theory. A semi‐empirical model is obtained by employing experimental correction factors based on the available test data in the theoretical model. Numerical model is built using ANSYS finite element analysis code for the same shell. The comparison reveals that the analytical and numerical linear model results match closely with each other but are higher than the empirical values. To investigate this discrepancy, non‐linear buckling analyses with large deflection effect and geometric imperfections are carried out. These analyses show that the effects of non‐linearity and geometric imperfections are responsible for the mismatch between theoretical and experimental results. The effect of shell thickness, radius and length variation on buckling load and buckling mode has also been studied. Copyright © 2009 John Wiley & Sons, Ltd.     

The coating of nickel compounds with copper compounds

Uniform fine particles of nickel basic carbonate were synthesized by heating, aqueous solution containing 0.08 mol dm⁻³ nickel sulfate and 0.8 mol dm⁻³ urea, at 85°C for various periods of time. These particles were then coated with copper compound by heating them in aqueous dispersion, containing urea and copper nitrate, at 85°C. The coating material was found to be amorphous and was composed of Cu₂(OH)₂CO₃. The coating mixture, when heated under similar conditions in the absence of the dispersed cores, produced greenish dispersion of the precipitated particles [coating precursor solids]. The later were also amorphous in nature and had the same chemical composition [Cu₂(OH)₂CO₃] as that of the coating material of the coated particles. Air-dried core, coated, and coating precursor materials were calcined at 700°C for 1 h at the heating rate of 5°C min⁻¹ in the air atmosphere, which converted them into NiO, NiO_[core]/CuO_[coating], and CuO, respectively. Scanning electron microscopic examination showed no sintering occurred in all these solids during the calcinations process and the particles retained their identities to a significant extent.     

Heterogeneous Wireless Networks: Configuration and Vertical Handoff Management

Vertical handoff is one of the most important issues for the next generation heterogeneous wireless networks. However, in many situations, unbeneficial vertical handoffs occur across intersystem heterogeneous networks cause network performance degradation. Therefore, we propose a novel configuration architecture that can be deployed in the next generation of wireless networks. Second, we propose a predictive and adaptive Vertical Handoff Decision Scheme that optimizes the handoff initiation time as well as selection of the most optimal network. The proposed vertical handoff decision algorithm considers the technology type as well as the Signal to Interference Ratio (SIR), the Mobile Station (MS) velocity, the user preferences, the applications requirements and the terminal capabilities as the most important factors to make vertical handoff decision. In order to minimize handoff costs, the proposed decision algorithm uses the dwell timer concept. The handoff costs are analyzed in terms of unnecessary and unbeneficial handoffs rate.The simulation results show that the reduction of unnecessary handoffs proposed in our vertical handoff decision scheme reduces the handoff blocking probability, the packets loss rate and the handoff overhead     

Preparation, Characterization, and Microwave Dielectric Properties of Sr2La3Nb1−x Ta x Ti4O17 (0 ≤ x ≤ 1) Ceramics

Sr₂La₃Nb_1?x Ta _x Ti₄O₁₇ (0 ≤ x ≤ 1) ceramics were processed via a solid-state mixed oxide route. Sr₂La₃Nb_1?x Ta _x Ti₄O₁₇ (0 ≤ x ≤ 1) solid solutions were single phase in the whole range of x values within the x-ray diffraction (XRD) detection limit. The microstructure comprised elongated and needle-shaped grains. The ceramics exhibit relative permittivity (ε _r) of 73 to 68.6, product of unloaded quality factor and resonant frequency (Q _u f ₀) of 7100 GHz to 9500 GHz, and temperature coefficient of resonant frequency (τ _f) of 78.6 ppm/°C to 56.6 ppm/°C.     

MIMO iterative receiver SNR estimation strategies for link to system interfacing

This paper presents link to system (L2S) interfacing technique for multiple input and multiple output (MIMO) iterative receivers. In L2S interfacing, usually the post detection signal to noise ratio (SNR)‐based frame error rate lookup tables (LUT) are used to predict the link level performance of receivers. While L2S interfacing for linear MIMO receivers can be conveniently implemented, it is more challenging for MIMO iterative receivers due to unavailability of the closed form SNR expressions. In this paper, we propose three methods for post detection SNR estimation for MIMO iterative receivers. The first is based on the QR decomposition of the channel matrix, the second relies on the residual noise calculation based on the soft symbols, and the third exploits the closed form SNR expressions for linear receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. It is shown that linear and residual noise‐based SNR approximations result in a very good prediction performance whereas the performance of QR decomposition‐based method degrades for higher order modulations and coding schemes. This paper presents link to system interfacing technique for MIMO iterative receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. Three post detection SNR evaluation schemes have been proposed for link to system interfacing all of which give good prediction performance especially at lower order modulation.     

Timely vs. delayed CEO turnover

This paper investigates changes in company performance following timely versus delayed CEO resignations due to financial wrongdoings. A timely resignation is proactively pushed by the company, and a delayed resignation is driven by investigations initiated by the SEC or other regulatory authorities. Our results show significant negative abnormal returns following the announcement of CEO resignations. In addition, compared with timely resignations, delayed resignations experience a larger and longer lasting negative stock market reaction. This suggests that CEO resignations due to financial wrongdoings are not perceived as good news by investors, and the delayed resignations could make investors lose more confidence, possibly because of worries about the ineffective corporate governance and supervision mechanism. We have found a significant negative relationship between CEO-chairman duality and the timeliness of CEO resignations. Our results have important implications for investors and policy makers.