Improved modulation techniques for PWM-VSI drives

PWM-VSI based AC motor drives have two main problems. The inverter is nonlinear which causes instability problems in some specific working points of the AC machine and it emits acoustic noise due to the switching frequency. Nonlinearities like dead-time in the inverter, load dependent DC-link voltage ripple and the voltage drop across the switches are modeled and compensated by improved modulation techniques in order to obtain an almost ideal inverter. Different feedback and feedforward techniques are proposed. The acoustic noise is reduced by using a random modulation strategy. Measurements show a significant improvement by using feedforward and feedback techniques for linearizing the inverter. An improvement in reduction of the acoustic noise emission is also achieved by using random modulation. It is concluded that a combination of a random modulation strategy and feedforward/feedback techniques gives an almost ideal AC motor drive system     

New developments in CdTe and CdZnTe detectors for X and γ-ray applications

There has been considerable recent progress in II-VI semiconductor material and in methods for improving performance of the associated radiation detectors. New high resistivity CdZnTe material, new contact technologies, new detector structures, new electronic correction methods have opened the field of nuclear and x-ray imaging for industrial and medical applications. The purpose of this paper is to review new developments in several of these fields. In addition, we will present some recent results at LETI concerning first the CdTe 2-D imaging system (20 × 30 mm² with 400 × 600 pixels) for dental radiology and second the CdZnTe fast pulse correction method applied to a 5 × 5 × 5 mm³ CdZnTe detector (energy resolution = 5% for detection efficiency of 85% at 122 keV) for medical imaging.     

Microbiological safety of kinema, a fermented soya bean food

Kinema is a fermented soya bean food of Nepal and the hilly regions of North-eastern States of India. Generally, the fermentation is dominated by Bacillus spp. that often cause alkalinity and desirable stickiness in the product. The present study was undertaken in a limited number of commercial (market) kinema samples to test for the presence of foodborne pathogens and their properties. Bacillus cereus was present in numbers exceeding 10⁴ cfu/g product in five of the tested 15 market samples. Enterobacteriaceae and coliform bacteria exceeded 10⁵ cfu/g in 10 of the 15 samples. Escherichia coli exceeding 10⁵ cfu/g was found in two samples. Staphylococcus aureus was not detected in any of the tested samples. Of 31 isolated typical and atypical strains of B. cereus, 18 representative strains were tested qualitatively for the ability to produce diarrhoeal type enterotoxin (BCET) using an Oxoid BCET-RPLA test kit. Overall, BCET was formed by 12 strains in BHIG (brain heart infusion broth +1% glucose), by seven strains on sterilized cooked rice, and by five strains on sterilized cooked soya beans. Semi-quantitative tests on BCET revealed that levels exceeding 256 ng/g soya beans, produced by single pure culture inoculation with the isolated B. cereus strains, were reduced to ≤ 8 ng/g by frying kinema in oil, a common procedure when making kinema curry. It was also shown in a mixed pure culture experiment that a kinema strain B. Subtilis DK-W1, is able to suppress growth and BCET formation by a selected toxin producing strain (BC7-5) of B. cereus. It is concluded that the traditional way of making kinema and its culinary use in curries is safe. However, for novel applications of kinema, safety precautions are advisable.     

Reuse efficiency for non-uniform traffic distributions in CDMAsystems

An exact and simple method to evaluate the frequency reuse efficiency for the reverse link of cellular CDMA systems over a non-uniform traffic distribution is presented. This method is based on a traffic redistribution and decomposition process and on standard curves with which partial reuse efficiencies are obtained and conveniently added to give the final parameter     

Measurement of PLL phase error caused by power supply noise

The measurement of the accumulated phase error of phase-locked loops (PLLs) in microprocessor systems is discussed. A system which creates controlled power supply noise and measures the PLL response is described. Examples of the use of this technique are shown for a PLL used in a 400 MHz microprocessor     

Insertion/deletion polymorphism in the angiotensin-converting enzyme gene associated with macroangiopathy and blood pressure in patients with non-insulin-dependent diabetes mellitus

In the search for new risk factors for diabetic macroangiopathy the insertion/deletion (I/D) polymorphism in the angiotensin-converting enzyme gene was studied in 237 consecutive patients (125 men and 112 women) with non-insulin-dependent diabetes. The female population showed an excess of ischemic electrocardiographic changes or definite myocardial infarctions in the patients homozygous for the deletion [D/D; odds ratio (OR) 2.8; 95% confidence interval (CI) 1.4-5.3] and in the insertion/deletion heterozygotes (I/D; OR 1.8; CI 1.1-3.1) compared with the patients homozygous for the insertion (I/I). In the total series coronary heart disease, cerebrovascular disease, and claudication were more often observed in the patients with I/D (OR 1.5; CI 1.0-2.2) or the D/D genotype patients (OR 1.7; CI 1.1-2.6) than in those with the genotype I/I. The systolic blood pressure was lower in patients with genotype I/I (138 +/- 19 mmHg) than in those with the genotype I/D (149 +/- 22 mmHg) or D/D (150 +/- 21 mmHg; P < 0.02). The prevalence of hypertension and the median urinary albumin excretion rate also tended to be lowest in the I/I genotype patients. Multiple logistic analysis revealed that in women the angiotensin-converting enzyme D/D genotype is independently associated with coronary heart disease. Our findings suggest that variation at the angiotensin-converting enzyme gene locus is one of the factors involved in the predisposition of diabetic patients to the development of arterial disease and hypertension.     

Multilevel optimization applied to hull girder design using three panel forms

A multilevel design scheme for ship's hull girders (longitudinal members between two adjacent transverse frames) is presented in this paper. This design scheme handles, very conveniently, the complexity of using an optimization algorithm for such complex design problems having a large number of design variables, nonlinear constraints dealing with different failure modes and interactions among substructures, and nonlinear design objectives. The conventional multilevel design technique is modified by introducing an approach called constraint coordination to increase the probability of achieving the overall optimum very efficiently.The scheme is demonstrated by application to the structural design of hull girders with simple structural modelling to represent inland waterway ships on which there was a special emphasis in the original research project (Rahman 1991). Three possible panel (consisting of one stiffener and its attached plating) forms; tee stiffened, flat-bar stiffened and corrugated, are optimized to synthesize the hull girder in order to achieve the most efficient structure. The effect of price-structure (labour rate to material price ratio) on the design is also investigated.     

Staurosporine and its derivatives enhance f-Met-Leu-Phe-induced superoxide production via phospholipase D activation in human polymorphonuclear leukocytes

Staurosporine (STAR) is one of the most potent inhibitors of protein kinase C (PKC). It is known that in human polymorphonuclear leukocytes (PMNs), the phorbol ester-induced generation of superoxide anion (respiratory burst) is effectively inhibited by STAR in a dose-dependent manner, whereas superoxide generation induced by chemoattractants, e.g. n-formyl-methionyl-leucyl-phenylalanine (FMLP) or PAF, is regulated biphasically by STAR. We compared the effects of STAR and K252a on FMLP-induced superoxide production from PMNs and examined the effects of propranolol, a inhibitor of phosphatidic acid (PA) phosphohydrolase, on the potentiation of the production by STAR. We also examined the effects of some derivatives of STAR and K252a on the production and the alteration of the effects induced by propranolol pretreatment. When PMNs were stimulated with FMLP, STAR potentiated superoxide production by 240.5 +/- 30.9% at a low concentration (100 nmol/l). Propranolol pretreatment specifically inhibited the potentiation. When phorbol-12-myristate-13-acetate (PMA) was used as a stimulant, STAR inhibited superoxide production dose-dependently and did not enhance the production. K252a inhibited PMA or FMLP-induced superoxide production dose-dependently and did not enhance FMLP-induced superoxide production. STAR derivatives showed potentiation of FMLP-induced superoxide production similar to that of STAR at concentrations ranging from 10-100 nmol/l, and propranolol (200 mumol/l) effectively inhibited it. K252a derivative NA332 did not show any potentiative effect on the production. PMA-induced superoxide production was inhibited by all compounds dose-dependently.(ABSTRACT TRUNCATED AT 250 WORDS)