Magnetic Properties of Al‐doped B4C and SiC Ceramics

Al‐doped B₄C and Al‐doped SiC ceramic compounds were synthesized by high‐temperature solid‐state sintering. Ferromagnetic (FM) ordering was observed in the doped semiconducting ceramics. The changes in the FM ordering with doping level were different in the two doped systems although they were prepared by similar experimental condition. Our results indicated that some of the C in B₄C were replaced by the Al atoms, and these displaced C atoms existed in the form of graphite. The synthesized SiC samples, undoped or Al doped, were found to be a mixture consisting of the magnetic and nonmagnetic SiC polytypes. The mechanisms in the generation of the FM ordering due to the dopants in the two ceramics followed different routes.     

Oxidative ring‐opening of 2‐methylcyclohexanone catalysed by supported heteropolyacid catalysts for cetane number enhancement

Incipient wetness impregnation method was used to incorporate heteropolyacid H₆[PV₃Mo₉O₄₀]nH₂O (HPA) on SiO₂ at various HPA loadings (10, 20, 30, 40 wt.% HPA) and calcined temperatures. Catalytic activity of these synthesised catalysts were evaluated through oxidation of 2‐methylcyclohexanone to methyl 6‐oxoheptanoate which was a desired product. In the oxidative conditions the conversion and selectivity of the desired product methyl 6‐oxoheptanoate can reach as high as 97 and 94 wt.%, respectively. The results also suggested that the catalyst with 20 wt.% loading of HPA to be the best one. The catalysts were characterised using a variety of techniques including XRD, BET, FT‐IR and TGA‐DTA. The results indicated that HPA was well dispersed on the SiO₂ supporting material. An engine ignition test following ASTM D6890 standard indicated that the oxidative ring‐opening of cyclohydrocarbons can have a positive impact on the cetane numbers and ignition delay time of fuels. © 2012 Canadian Society for Chemical Engineering     

The Design and Construction of a Movable Image-Based Rendering System and Its Application to Multiview Conferencing

Image-based rendering (IBR) is an promising technology for rendering photo-realistic views of scenes from a collection of densely sampled images or videos. It provides a framework for developing revolutionary virtual reality and immersive viewing systems. While there has been considerable progress recently in the capturing, storage and transmission of image-based representations, most multiple camera systems are designed to be stationary and hence their ability to cope with moving objects and dynamic environment is somewhat limited. This paper studies the design and construction of a movable image-based rendering system based on a class of dynamic representations called plenoptic videos, its associated video processing algorithms and an application to multiview audio-visual conferencing. It is constructed by mounting a linear array of 8 video cameras on an electrically controllable wheel chair and its motion is controllable manually or remotely through wireless LAN by means of additional hardware circuitry. We also developed a real-time object tracking algorithm and utilize the motion information computed to adjust continuously the azimuth or rotation angle of the movable IBR system in order to cope with a given moving object in a large environment. Due to imperfection in tracking and mechanical vibration encountered in movable systems, the videos may appear very shaky and a new video stabilization technique is proposed to overcome this problem. The usefulness of the system is illustrated by means of a multiview conferencing application using a multiview TV display. Through this pilot study, we hope to disseminate useful experience for the design and construction of movable IBR systems with improved viewing freedom and ability to cope with moving object in a large environment.     

Transmission surveillance and self-restoration against fibre fault for time division multiplexing using passive optical network

This study proposes a practical transmission surveillance and self-protection scheme for time division multiplexing using passive optical network (TDM-PON) with centralised monitoring and self-restorable apparatus. Troubleshooting a TDM-PON involves locating and identifying the source of an optical problem in what may be a complex optical network topology that includes several optical line terminals (OLTs), optical splitters, fibres and optical network units (ONUs). Since most components in the network are passive, a large part of the issues are due to dirty/damaged/misaligned connectors or breaks/macrobends in optical fibre cables. These will affect one, some or all subscribers in the network, depending on the location of the problems. The proposed scheme is able to prevent and detect the occurrence of fibre faults in a network system through centralised monitoring and remotely operate from a central office via Ethernet connection. Even with fibre fault prevention mechanisms, failures will still occur. Therefore fibre fault detection is required in order to detect potential faults and precisely localise the exact failure location.Whenever any failure occurs on the primary entity, the proposed system can protect and switch the failure line to the protection line to ensure that traffic flows continuously. Meanwhile, the failure information will be delivered to field engineers for taking appropriate recovery action to treat the fibre fault and failure link. One suggestion in point-to-multipoint (P2PM) applications has been proposed with the experimental results as the feasibility approach. This approach has bright prospects for improving the survivability and reliability as well as increasing the efficiency and monitoring capabilities in TDM-PON.     

Synthesis of sub-micron nickel particles coated onto aluminum powders via a modified polyol process

Aluminum is commonly used as a fuel additive for propellants. The main limitations to its use lie in comparatively slow ignition and oxidation/combustion kinetics. Combustion performance of aluminized propellants can be improved through the use of Ni-coated Al particles. Sub-micron to nano-sized particles, with their increased reactivity, also improve combustion performance. Hence, in these contexts, fine Ni particles coated onto commercially available micron-sized Al powders using a modified polyol process were synthesized and evaluated. Ni-coated Al powders of various compositions produced by this method showed significant improvement in oxidation kinetics compared to untreated Al powders. The onset oxidation temperatures for the Ni-coated Al powders were found to be significantly reduced compared to pure untreated Al.     

Characterization of the in-situ non-linear shear response of laminated fiber-reinforced composites

A simple procedure to determine the non-linear in-plane lamina shear response of laminated composites is presented. Using the ±45° symmetric laminate tensile test results, in conjunction with computational micromechanics, a method was developed and validated to characterize the lamina shear response and the in-situ matrix shear response. Load, and axial and transverse strains measured in the tests were used to calculate the non-linear shear stress–shear strain response of the composite. From this result, the in-situ matrix equivalent stress–strain response was obtained, with some simplifying assumptions, and subsequently used in a micromechanics-based representative finite element (FE) model of the ±45° symmetric laminate tensile test to determine the accuracy of the non-linear response of the in-situ matrix. Results from the FE model of a representative cell (RC) that depicts fiber diameter, fiber volume fraction (V_f) and angled fiber packing of the ±45° symmetric laminate were found to match the tests result well. Thus, the procedure to extract the non-linear lamina shear response and the non-linear in-situ matrix response from the ±45° symmetric laminate tensile test was validated.     

A memory efficient testing scheme for combined field integral equation for solving scattering problems using adaptive integral method

A new memory efficient testing procedure for method of moment (MoM) has been proposed for solving combined field integral equation (CFIE) using adaptive integral method (AIM) for closed perfect electric conductor (PEC) scatterers. CFIE is a linear combination of electric field integral equation (EFIE) and magnetic field integral equation (MFIE) and hence the iterative solution for CFIE requires the simultaneous evaluation of both EFIE and MFIE. Using AIM, the MoM testing procedure is obtained by interpolating the grid potentials, computed using fast Fourier transform (FFT), onto the testing functions. For EFIE, the same set of multipole coefficients of the basis functions can be used as the testing functions, without the need to store additional interpolation coefficients. In this paper, we propose a similar simple but efficient and accurate method for the testing procedure for the MFIE using the same multipole coefficients for the basis functions. This enables CFIE to be solved using the same memory resources as EFIE. The accuracy of the radar cross section (RCS) computed for various geometries using CFIE with the proposed testing procedure is shown to be as accurate as the existing method. Copyright © 2005 John Wiley & Sons, Ltd.     

MOSFET drain/source charge partition under nonquasi-staticswitching

The channel charge partition of metal-oxide-semiconductor transistors in nonquasi-static switching has been studied. A new approach, with the help of a two-dimensional device simulator is used to separate the direct current and transient current component during device switching. Unlike the commonly accepted 40/60 drain/source channel charge partition ratio, our results show that it is closer to the 0/100 as long as the switch speed is higher than the channel charging time. The result is important for pass-gate type circuits to evaluate the amount of charge transferred to the source and drain nodes     

Reliability of Axially Loaded Driven Pile Groups

A method was presented to evaluate the reliability of axially loaded pile groups designed using the traditional concept of group efficiency along the lines of load and resistance factor design. Group effects and system effects were identified as the major causes that led to a significantly greater observed reliability of pile foundations than calculated reliability of single piles. Statistical analyses were conducted to evaluate these effects based on observed pile performance. A database of pile group load tests was collected and interpreted for this purpose. Subsequently, the reliability of pile groups associated with the allowable stress design practice was calculated using the suggested method. The calculated probability of failure of pile groups was found to be one to four orders of magnitude smaller than that of single piles, depending on the significance of group effects and system effects. Finally, values of the target reliability index βTS for single piles required to achieve a specified target reliability of pile group foundations were calculated for several design methods. Due to group effects and system effects, the values of βTS should be different for single piles, a pile group, and a pile system of several groups.     

Justice at the millennium: A meta-analytic review of 25 years of organizational justice research.

The field of organizational justice continues to he marked by several important research questions, including the size of relationships among justice dimensions, the relative importance of different justice criteria, and the unique effects of justice dimensions on key outcomes. To address such questions, the authors conducted a meta-analytic review of 183 justice studies. The results suggest that although different justice dimensions are moderately to highly related, they contribute incremental variance explained in fairness perceptions. The results also illustrate the overall and unique relationships among distributive, procedural, interpersonal, and informational justice and several organizational outcomes (e.g., job satisfaction, organizational commitment, evaluation of authority, organizational citizenship behavior, withdrawal, performance). These findings are reviewed in terms of their implications for future research on organizational justice. (PsycINFO Database Record (c) 2011 APA, all rights reserved)