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.     

Measurement and analysis of shocks to products packaged in pails in single parcel ground shipments

The objective of this study was to measure and analyse the shocks and impacts experienced by pails in the single parcel distribution environment, with and without a secondary corrugated shipper. The study was conducted in the FedEx Ground shipping environment in the USA. Instrumented 5 gal pails were shipped with and without an outer corrugated box, and with and without handling (precautionary warning) labels, from East Lansing, Michigan to destinations in California and New York. Data recorders were used to collect and analyse shock distribution data (drop heights, drop orientations and number of drops). The results showed that the precautionary labels had no effect in improving the handling or reducing the drop height levels for both corrugated boxes and pails in this environment. Pails without boxes experienced 10 drops per one‐way trip with an average drop height of 0.23 m (9 in). Pails with boxes experienced 18 drops per one‐way trip with a higher average drop height of 0.30 m (12 in), which amounted to 80% more drops at a 25% higher drop height level than pails without boxes. Impact orientations of pails without boxes showed that 60% of the drops occurred on the sides, and 40% on the bottom. Pails shipped in corrugated boxes showed 22% of the drops occurred on the bottoms, 34% on the side faces, 28% on edges and remaining 16% on the corners. The data collected was analysed to develop pre‐shipment package performance tests that can be conducted in a lab environment. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

Catalytic properties of dispersed iron oxides Fe2O3/MO2 (M = Zr,Ce, Ti and Si) for sulfuric acid decomposition reaction: Role of support

Supported iron oxides have been established as an important class of catalyst for high temperature sulfuric acid decomposition. With an objective to elucidate the role of support in modifying the overall catalytic properties of dispersed iron oxide catalysts, a series of supported iron oxide based catalysts, Fe₂O₃ (15 wt%)/MO₂ (M = Zr, Ce, Ti and Si), synthesized by adsorption-equilibrium method, is investigated for sulfuric acid decomposition reaction. The structure of dispersed iron oxide phases largely depended on the nature of the support oxide as revealed by the XRD and Mössbauer studies. α-Fe₂O₃ is found to be present as a major phase on ZrO₂ and CeO₂ support while ε-Fe₂O₃ was the major phase on silica supported iron oxide. On the other hand, presence of mixed oxide Fe₂TiO₅ was revealed over TiO₂ support. Strong dispersed metal oxide-support interactions inhibited the total reduction of the dispersed phase on SiO₂ and TiO₂ as compared to complete reduction of dispersed iron oxide on CeO₂ and ZrO₂ supports during temperature programmed reduction upto 1000 °C. The order of catalytic activity at a temperature of ～750 °C is observed as Fe₂O₃/SiO₂ > Fe₂TiO₅/TiO₂ > Fe₂O₃/ZrO₂ > Fe₂O₃/CeO₂, while at higher temperatures of ～900 °C the SO₂ yield is found to be comparable for all catalysts. A relationship between the rate of sulfate decomposition and catalytic activity is established through detailed TG-DTA investigations of sulfated catalyst and support. Considerable influence of the support oxide on the composition, structure, redox properties, morphology and catalytic activities of the active iron oxide dispersed phase has been observed. Thus, the support oxides operate as a critical component in the complex supported metal oxide catalysts and these findings might influence the design and development of future high temperature sulfuric acid decomposition catalysts.     

A novel image encryption scheme based on orthogonal matrix,skew tent map,and XOR operation

Neural Computing and Applications - Content protection is considered as an important issue in today’s world. Therefore, encryption of such contents is a challenging task for researchers. They...     

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.     

Ferromagnetic nano model study for the peristaltic flow in a plumb duct with permeable walls

Microsystem Technologies - The purpose of the present enquiry is to analyse the mechanics of an incompressible fluid, with water as base fluid, through a radially symmetric plumb duct with...     

Development of a crack created by hydraulic fracturing in a compressed block structure rock

The authors estimated trajectory of a created crack in a block-structured rock mass during hydraulic fracturing, and analyzed effect of the parameters of the block medium and two-axis compression field on the main crack trajectory and on the opening of lineal segments of the crack.