Three-phase switch mode rectifier with hysteresis current control

A three-phase configuration of a switch mode rectifier (SMR) that makes use of continuous conduction waveform of the input supply current is suggested. Continuous conduction is achieved by the hysteresis current control (HCC) technique. This three-phase SMR operates at close to unity power factor and has reduced current stresses on the switching devices because of the continuous nature of input current. The conduction period considered for the rectifier diodes is 180°. Digitally simulated performance results are provided. Selected experimental results demonstrating the SMR operation are also presented     

How multimedia workloads will change processor design

Workloads drive architecture design and will change in the next two decades. For high-performance, general-purpose processors, there is a consensus that multimedia will continue to grow in importance. The authors predict these processors will incorporate more media processing capabilities, eventually bringing about the demise of specialized media processors, except perhaps, in embedded applications. These enhanced general-purpose processor capabilities will arise from multimedia applications that require real-time response, continuous-media data types and significant fine-grained data parallelism     

Dynamic simulation model of indoor wideband directional channels

Culled from existing channel measurements, a dynamic indoor wideband directional-channel simulator is constructed by incorporating the spatial-temporal properties as well as the time-varying nature of propagation environments. A two-state semi-Markov model is used to account for the births and deaths of scattering clusters, which represents an improvement over the conventional Markov model where the duration in each state is forced to follow an exponential distribution. The spatial-temporal variations of clusters within their lifespan are modeled based on the real-life measurement results. The ranges of angle of arrival (AOA), angle of departure (AOD), and time of arrival (TOA) for each cluster are partitioned into finite number of intervals using the deterministic simulation methods. Subsequently, the cluster properties at different intervals can be derived from the empirical findings in previous channel-measurement campaigns. The efficacy of the proposed simulator is demonstrated by applying it to characterize a time-varying multiple-input multiple-output (MIMO) channel.     

Analysis of DC drive fed by single-phase half-controlled convertersin sequence control

Separately excited DC motors fed by multistage converters with sequence control are commonly used in mainline traction. The author describes the analysis and performance of a DC drive fed by a two-stage sequentially operated half-controlled converter. The modes of operation of the converter-motor system are identified and a method of performance calculation, taking these modes of operation into account, is presented. The nomograms, and the analytical method of calculating them, are presented for the calculation of an optimum value of filter inductance     

Design of saturistor for control of induction motor during starting

An interesting characteristic of a saturistor and a simple method of its design for low current starting of induction motor have been described.     

Synthesis and characterization of pH switching electrical conducting biopolymer hybrids for sensor applications

A novel electrically active, water soluble gum acacia-polyaniline (GA–PANI) hybrid was synthesized using ceric ammonium nitrate as initiator in acidic medium. The representative hybrid material was characterized using UV-visible, FTIR and SEM taking polyaniline as reference. The composition of aniline to gum acacia was tailored to optimize possible cross-linking in side the hybrid. The hybrid material exhibited pH switching electrical conductivity, which was decreased with increasing pH of the material. I-V characteristics and acid–base sensitivity of the hybrid material were extensively investigated in order to find out its electronic behavior during current flow.     

Antibody responses measured by various serologic tests in pigs orally inoculated with low numbers of Toxoplasma gondii oocysts

OBJECTIVE: To follow antibody responses measured by various serologic tests in pigs orally inoculated with low (< or = 10 oocysts) numbers of Toxoplasma gondii oocysts. ANIMALS: 24, 2- to 3-month-old pigs. PROCEDURE: Pigs (n = 42) were inoculated orally with 10 (14 pigs) or 1 (28 pigs) infective oocysts, and 6 pigs served as uninoculated controls. Blood (serum) samples were obtained at 1- to 3-week intervals until euthanasia. At necropsy, the brain, heart, and tongue of pigs were bioassayed in mice and cats for isolation of T gondii. Modified agglutination test (MAT), using whole, fixed tachyzoites and mercaptoethanol; latex agglutination test (LAT); indirect hemagglutination test (IHAT); Sabin-Feldman dye test (DT); and ELISA were used to evaluate serologic responses to T gondii. RESULTS: T gondii was isolated from tissues of 13 of 14 pigs each fed 10 oocysts, 17 of 28 pigs each fed 1 oocyst, and 0 of 6 control pigs. 29 of 30 T gondii-infected pigs developed antibodies when measured by MAT, DT, and ELISA; the 1 seronegative-infected pig had been fed 10 oocysts and was euthanatized 69 days after inoculation. LAT detected antibodies in 26 of 30 T gondii-infected pigs. IHAT detected antibodies in 11 T gondii-infected pigs. CONCLUSION: MAT, DT, and ELISA were more sensitive serologic assays than LAT and IHAT for detecting antibodies induced by low numbers of T gondii in pigs.     

Cedrus oil—A promising storage fungitoxicant

Seeds of two spices Coriandrum sativum and Foeniculum vulgare, were dressed separately with essential oil of Cedrus deodara as well as with five synthetic fungicides viz., phenylmercury acetate, 2-methoxyethyl mercury chloride, copper oxychloride, mancozeb and wettable sulphur. Treated seeds were stored in polythene bags for 12 months. On mycofloral analysis, the oil had checked the appearance of ten fungi, Absidia sp., Alternaria alternata, Aspergillus flavus, A. fumigatus, A. niger, A. ruber, A. versicolor, Cladosporium cladosporioides, Curvularia lunata, and Paecilomyces variotii on the seeds of C. sativum, and seven fungi, Absidia sp., A. flavus, A. fumigatus, A. niger, A. ruber, A. versicolor, and Rhizopus spp., on the seeds of F. vulgare. The oil proved to be more effective than the synthetic fungicides. Further, the oil did not show any adverse effect on seed germination and seedling growth of both spices.     

Study of recrystallization of SiC thin films

Thin films of SiC have been prepared by electron beam evaporation using 6H, 15R, 4H and other polytypes as starting materials. After pulse-annealing in electron microscope column, various complex structures of hexagonal and cubic phases are observed. The occurrence of 6H as single phase is rare.