Studies on the spin-state equilibria of cobalt ions in the system La1−x Na x Co1−x Nb x O3 (x⩽0·40)

The spin-state equilibria of cobalt ions in the system La_1−x Na _x Co_1−x Nb _x O₃ (x⩽0·40) has been studied by measuring its magnetic susceptibility as a function of temperature in the range 300–600 K. It is found that the behaviour of the samples withx⩽0·10 is similar to that of LaCoO₃, while compositions withx⩾0·20 behave quite differently, exhibiting simple paramagnetic behaviour.     

Modified staircase data broadcasting scheme for popular videos

In a broadcasting scheme, the user's latency is a very important parameter. The harmonic broadcasting scheme has been found to have the best performance for user's latency and staircase broadcasting scheme has been found to have the best performance for local storage as well as for disk transfer rates. In this paper a modified staircase scheme has been proposed which shows that if the video data is downloaded with lesser speed which would save the local storage and hence the disk transfer rate, the users still can be provided with the video in a continuous manner without any jerk or jitter. Further, if the downloading rate of the video is reduced after 3.25 channels, the users' services for viewing the videos does not get affected. In particular, for employing bandwidth of about 40 mbps, the modified staircase data scheme shows the performance for user latency about 29% better and the local storage is same but disk I/O transfer rates are slightly higher (4%) in comparison to staircase scheme. In comparison to harmonic scheme, user's latency is 24% higher but buffer storage and disk I/O transfer rates are about 35% and 30%, respectively, better for the same bandwidth. However the values of the performance parameters converge to those of harmonic scheme as the bandwidth is increased.     

Sintering of a Ceramic at Very Low Temperatures

Surface area, linear shrinkage, and compressive strength measurements show that, with the help of neutron irradiation, sintering of high-purity alumina can be initiated at temperatures lower than 150°C; such radiation sintering might be beneficial to many other ceramics.     

Use of the Finite-Difference Time-Domain Method in Calculating EM Absorption in Human Tissues

Although there are acceptable methods for calculating whole body electromagnetic absorption, no completely acceptable method for calculating the local specific absorption rate (SAR) at points within the body has been developed. Frequency domain methods, such as the method of moments (MoM) have achieved some success; however, MoM requires computer storage on the order of (3N) 2 and computation time on the order of (3N) 3 where N is the number of cells. The finite-difference time-domain (FDTD) method has been employed extensively in calculating the scattering of metallic objects, and recently is seeing some use in calculating the interaction of EM fields with complex, lossy dielectric bodies. Since the FDTD method has storage and time requirements proportional to N, it presents an attractive alternative to calculating SAR distribution in large bodies. This paper describes the FDTD method and evaluates it by comparing its results to analytic solutions in two and three dimensions. The utility of the FDTD method is demonstrated by a 3D scan of the human torso. The results obtained demonstrate that the FDTD method is capable of calculating internal SAR distribution with acceptable accuracy. With the availability of supercomputers, such as the CRAY II, the calculation of SAR distribution in a man model of 50 000 cells (1.27 cm per cell) appears to be feasible.     

C-HEAP: A Heterogeneous Multi-Processor Architecture Template and Scalable and Flexible Protocol for the Design of Embedded Signal Processing Systems

The key issue in the design of Systems-on-a-Chip (SoC) is to trade-off efficiency against flexibility, and time to market versus cost. Current deep submicron processing technologiesenable integration of multiple software programmable processors (e.g., CPUs,DSPs) and dedicated hardware components into a single cost-efficient IC. Ourtop-down design methodology with various abstraction levels helps designingthese ICs in a reasonable amount of time. This methodology starts with a high-levelexecutable specification, and converges towards a silicon implementation.A major task in the design process is to ensure that all components (hardwareand software) communicate with each other correctly. In this article, we tacklethis problem in the context of the signal processing domain in two ways: wepropose a modular, flexible, and scalable heterogeneous multi-processor architecturetemplate based on distributed shared memory, and we present an efficient andtransparent protocol for communication and (re)configuration. The protocolimplementations have been incorporated in libraries, which allows quick traversalof the various abstraction levels, so enabling incremental design. The designdecisions to be taken at each abstraction level are evaluated by means of(co-)simulation. Prototyping is used too, to verify the system's functionalcorrectness. The effectiveness of our approach is illustrated by a designcase of a multi-standard video and image codec.He currently works with Magma Design Automation. E-mail:     

Evidence of two ferroelectric PTCR components in valence-compensated ceramic system Ba1−x La x Ti1−x Co x O3

The electrical behaviour of valence-compensated ceramic system Ba_1−x La _x Ti_1−x Co _x O₃ has been studied as a function of temperature (300–600 K) and composition (x ⩽ 0·20), using the method of impedance spectroscopy. The necessary equivalent circuit models that represent the data best have been obtained using impedance and modulus formalisms and grain and grain boundary contributions have been separated out. The compositionsx = 0·20 and 0·10 show a negative temperature coefficient of resistance (NTCR) behaviour whereas a very small variation of the grain and grain boundary resistance with temperature is observed forx = 0·05. A positive temperature coefficient of resistance (PTCR) behaviour having two ferroelectric components is observed forx = 0·01. These results reveal limitations in current theories of the PTCR effect.     

On the frequency composition of inherent coolant boiling noise in BWRs

Frequency composition of inherent coolant boiling noise in BWRs is analysed using the equations governing the bubble formations and their detachment from the fuel-pin surface and a parametric study is conducted with respect to core cooling-channel parameters such as pressure, coolant flow velocity, cavity size and the contact angle. The results indicate that the frequency composition of inherent boiling noise in BWRs is not white but lies in the frequency range of 15–45 Hz.     

XPS and Mössbauer studies on BaSn1−xNbxO3 (x ≤ 0.100)

A few compositions of perovskite oxide BaSn_1?xNb_xO₃ (with x ≤ 0.10) system, prepared by solid state ceramic method, have been studied employing XPS and Mössbauer spectroscopy techniques. Mössbauer spectra of these compositions in the temperature range of 78–300 K reveal that the oxidation state of Sn is +4. In XPS measurements, compositions with x ≤ 0.010 show no evidence of Nb⁵⁺ signal whereas the compositions with x ≥ 0.050 show clear evidence of Nb⁵⁺ signals indicating some unreacted Nb₂O₅ component in the system. This confirms the earlier report where presence of small amount of unreacted Nb₂O₅ was predicted.     

Complex system reliability estimation methodology in the absence of failure data

This paper presents a comprehensive system reliability estimation methodology for cases when failure data are unavailable, at least initially. In this methodology, the laws of physics and thermal fundamentals are used to establish a mathematical model that relates the influential input operating characteristics, such as material properties and geometry, to system performance measures. Probability distributions for each influential operating characteristic, identified from the available manufacturing data, information found in instruction manuals and related technical journals, and expert knowledge, are used to simulate the system behavior with Monte Carlo simulation. An initial reliability estimate is obtained by comparing the simulated system performance with the permissible system performance. Fuzzy logic is used to incorporate the impact of environmental factors on the performance of the simulated system performance and hence the system reliability. Finally, with the use of Bayesian analysis, initial system reliability is updated to take into account the effect of environmental factors. The proposed methodology is applied to estimate the reliability of the hazardous gas detection system used in aerospace shuttles for the timely detection of explosive gases. Copyright © 2008 John Wiley & Sons, Ltd.