DEPOSITION AND RESTRUCTURING OF ADHESIVE PARTICLES IN UNIDIRECTIONAL FIELDS

The deposition of particles under the influence of gravity and adhesive interactions with the other deposited particles is examined using computer simulation. A parameter, s, that represents the probability of adhesion or sticking is used for studying the effects of variations in sticking on the resulting microstructure. A range of packing structures is generated between two limiting cases representing complete restructuring (s = 0) and no restructuring (s = 1). The bulk properties of the resulting structures, such as packing density, particle number density, and coordination number, are obtained. Structural correlations are examined through contact networks, radial and angular distribution functions, and diffraction patterns. The results show that local sticking rules have a significant influence on the long-range structure. Rhombic domains and significant long-range correlations are observed for the case of zero sticking probability. The range of correlations drops very sharply with increases in sticking probability, and large elongated voids, oriented in the direction of the external field, are formed with further increases in s. In the limit of perfect sticking, the deposit becomes columnar. The results have important implications to the structure of particle compacts and its influence on sintering of such compacts.     

DC to DC Converters with High-Frequency AC Link

The properties of a dual thyristor are advantageously used for the development of very high-efficiency dc-dc converters. A new device named ``dual thyristor' having static and dynamic characteristics dual to that of a thyristor has been recently reported. The development aspects of a dual thyristor based high-efficiency dc-dc converter with an intermediate ac link using a high-frequency inverter is described. The output voltage is regulated by varying the frequency of operation of the inverter. In spite of the relatively high-frequency operating range of this device between 30 kHz and 100 kHz, high efficiency of operation of the converter is obtained due to the use of lossless snubbers. Further, the selfprotective nature of the device against overcurrents enables a high reliability of operation of the dc-dc converter.     

Accidental acute fatal sodium nitrite poisoning

OBJECTIVES: To report two patients who developed reactive arthritis in association with Staphylococcus aureus infection. METHODS: A review of the case notes of two patients. RESULTS: Two adult female patients have developed sterile arthritis in association with Staph aureus infection. The first patient has had two episodes of arthritis; the first followed olecranon bursitis, the second followed infection of a central venous catheter used for dialysis. The second patient developed sterile arthritis while being treated for pyomyositis. Both patients had a self limited arthritis and were HLA-B27 negative. CONCLUSION: Reactive arthritis may rarely follow Staph aureus infection. HLA-B27 negativity may be associated with a self limited arthritis in these cases.     

Structural and metabolic relationship between the molybdenum cofactor and urothione

The molybdenum cofactor isolated from sulfite oxidase (sulfite: ferricytochrome c oxidoreductase, EC 1.8.2.1) and xanthine dehydrogenase (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) in the presence of iodine and KI (form A) has been shown to contain a pterin nucleus with an unidentified substituent in the 6 position [Johnson, J. L., Hainline, B. E. & Rajagopalan, K. V. (1980) J. Biol. Chem. 255, 1783-1786]. A second inactive form of the cofactor was isolated aerobically but in the absence of iodine and KI. The latter cofactor derivative (form B) is highly fluorescent, has a visible absorption band at 395 nm and, like form A, contains a phosphate group. Cleavage of the phosphate ester bond with alkaline phosphatase exposes a glycol function that is sensitive to periodate. Oxidation of form B with alkaline permanganate yields a highly polar compound with properties of a sulfonic acid, suggesting that the active molybdenum cofactor might contain sulfur. The sulfur-containing pterin urothione characterized by Goto et al. [Goto, M., Sakurai, A., Ohta, K. & Yamakami, H. (1969) J. Biochem. 65, 611-620] had been isolated from human urine. The permanganate oxidation product of urothione, characterized by Goto et al. as pterin-6-carboxylic-7-sulfonic acid, is identical to that obtained from form B. Because urothione also contains a periodate-sensitive glycol substituent, a structural relationship is suggested. The finding that urine samples from patients deficient in the molybdenum cofactor are devoid of urothione demonstrates a metabolic link between the two molecules.     

Superresolution of License Plates in Real Traffic Videos

In this paper, a novel method to enhance license plate numbers of moving vehicles in real traffic videos is proposed. A high-resolution image of the number plate is obtained by fusing the information derived from multiple, subpixel shifted, and noisy low-resolution observations. The image to be superresolved is modeled as a Markov random field and is estimated from the observations by a graduated nonconvexity optimization procedure. A discontinuity adaptive regularizer is used to preserve the edges in the reconstructed number plate for improved readability. Experimental results are given on several traffic sequences to demonstrate the robustness of the proposed method to potential errors in motion and blur estimates. The method is computationally efficient as all operations can be implemented locally in the image domain     

Synthesis and dielectric properties of MXTi<Subscript>7</Subscript>O<Subscript>16</Subscript> (M = Ba and Sr; X = Mg and Zn) hollandite ceramics

MXTi₇O₁₆ (M = Ba and Sr; X = Mg and Zn) ceramics have been synthesized by the conventional solid state ceramic route. The dielectric properties such as dielectric constant (ε_r), loss tangent (tan δ) and temperature variation of dielectric constant (τ_εr) of the sintered ceramic compacts are studied using an impedance analyser up to 13 MHz region. The strontium compounds have relatively high dielectric constant and low loss tangent compared to the barium analogue. The phase purity of these materials has been examined using X-ray diffraction studies and microstructure using SEM method.     

A learning aid for power electronics with knowledge basedcomponents

In this paper we have presented a self-study expert system based power electronics instruction aid for selection and analysis of suitable power electronic converter configurations. Converter input output specifications, analysis, and converter design methodologies are interactively pursued with extensive graphical aid to guide the user (student, engineers, etc.) in the study process. Furthermore, transient, steady-state, and harmonic analysis are possible with an integrated simulator within the instruction module. A fault diagnosis expert system based module for converter-fed motor-drives, which can be chained with the expert learning aid, has also been developed. This is in the process of development to diagnose faults on all converters available in the package     

An Economical Auxiliary Commutated Thyristor Three-Phase Inverter Suitable for Pulse Frequency Modulation

A new economical auxiliary impulse commutated thyristor inverter is described that is capable of providing a wide range of output ac voltage and output frequency which is useful in variable speed ac drive applications. Output voltage control is provided by a pulse frequency modulation technique, and input dc voltage to the inverter is constant and can be provided by a diode rectifier bridge. The parameters for the various circuit elements, such as commutating inductances and capacitances, di/dt limiting series thyristor inductances, and dv/dt limiting RC snubber circuits are all calculated from a dynamic simulation of a single-phase version of the inverter circuit using a software named ATOSEC I developed at the Universitédu Québec for a CDC 6400/IBM-370 computer. Experimental results obtained on a practical single-phase inverter are compared with those predicted from computer simulation and performance characteristics obtained in the case of a practical three-phase pulse frequency modulated inverter providing variable output voltage and variable output frequency are reported.     

A variational approach to recovering depth from defocused images

In this paper, we propose a regularized solution to the depth from defocus (DFD) problem using the space-frequency representation (SFR) framework. A smoothness constraint is imposed on the estimates of the blur parameter, and a variational approach to the DFD problem is developed. Among the numerous SFRs, we study the applicability of the complex spectrogram and the Wigner distribution, in particular, for depth recovery. The performance of the proposed variational method is tested on both synthetic and real images. The method yields good results, and the quality of the estimates is significantly better than that obtained without the smoothness constraint on the blur parameter