A Step-Up Phenomenon of the Thyristor Control Circuit with Series RLC Elements

A circuit controlled by thyristors and having series RLC elements gives rise to a step-up phenomenon. The term step-up is defined with respect to the capacitance voltage on steady state operation, i.e., the ratio of the maximum peak value when controlled by thyristers to the peak amplitude when thyristors are short-circuited exceeds unity. The domain of possible step-up voltage is determined by the angle of displacement between current and voltage and damping factor. The step-up voltages appear across each element, i.e., not only across the capacitance, inductance, and resistance but also across the thyristors. The control characteristic has a distinctive hump phenomenon. The interrupted current results in waveform distortion, phase lag, and improved power factor. The difference of characteristics between the peak and rms values of voltages, particularly of inductance and thyristors, is large. The response time, which is evaluated by numbers of half cycles, is large when the step-up ratio becomes large. The output voltage when the circuit is used as a voltage source has a drooping characteristic.     

Radiotherapy for elderly patients

Fifty-seven revision total hip arthroplasties in fifty-six patients were performed with a Harris-Galante porous-coated acetabular component by one surgeon, and the patients were followed prospectively for a mean of seven years (range, five to twelve years). A trochanteric osteotomy was performed in forty hips, and a posterior approach with an extended anterior capsulectomy was used in the other seventeen. The acetabular defect was classified as segmental in seven hips, cavitary in twenty-three, and combined in twenty-one; six hips had no notable defect. A bulk allograft was used in eleven hips, and morseled cancellous-bone allograft or autogenous graft was used in thirty-four hips; twelve hips did not have bone-grafting. Both the femoral and the acetabular component were revised in forty-five hips, and only the acetabular component was revised in twelve. Thirty-nine hips (68 per cent) had a good or excellent clinical result according to the Harris hip score. The acetabular component was well fixed in the fourteen hips that had a fair result and the four hips that had a poor result. The acetabular component was considered to have migrated if there was a change in the angle of the cup of 5 degrees or more or a change in the horizontal or vertical position of the cup of more than three millimeters. Despite varying degrees of bone loss, no acetabular component had radiographic evidence of loosening at the latest follow-up examination. No component was revised and no revisions were scheduled. One hip was debrided for a late metastatic infection, but the component was well fixed and was not revised. There were no complications related to the use of screws for fixation. These mid-term results confirm the early success of acetabular revisions performed with fixation of a titanium fiber-metal-coated hemispherical component with multiple screws and no cement.     

Generalized Analytical Model for a Thyristor-Controlled Variable Inductor

A generalized analytical model is presented for thyristor- controlled variable inductors. The proposed model can represent the performance of various types of thyristor phase-controlled variable inductors (VI's), e. g., conventional, UM-concept, magnetically coupled reactor, and asymmetrically firing control types, by introducing two parameters: m and ?By means of numerical computation using this model, the characteristics of variable inductors can be clarified, and their characteristics can be compared with ease. This analytical model is very useful for deciding circuit configuration and design.     

Hemopoietic recovery in bone marrow of lethally irradiated rats following parabiosis. I. Granulopoiesis

Aplasia was induced in rats by total body irradiation. Three days later, the animal was conjugated by aortic anastomoses with a healthy untreated litter-mate. 6 h after parabiosis, the bone marrow of irradiated animals contained some granulocytes showing RNA synthesis. At 18 h, many myelocytes and promyelocytes were present but no myeloblast was encountered. These myeloid precursor cells showed active DNA synthesis but no mitoses, and no erythroblasts were observed at this time period. At 24 h, mitoses of myeloblasts were found. At 42--60 h, erythropoiesis was evident. Chromosome analysis and investigations of cells of irradiated parabionts conjugated with partners having labeled cells, revealed that these newly formed myeloid and erythroid cells originated from the untreated parabiont. The mechanism of triggering myelopoiesis in the aplastic bone marrow by parabiosis is discussed.     

Preparation and properties of electrodeposited Hg1-xCdxSe films

Hg_1-xCd_xSe (0.87 < x < 1) films were electrodeposited potentiostatically onto ITO glass substrates by varying the Hg content in the aqueous electrolyte with the pH adjusted to 1.5–2 at room temperature. The as-deposited and the as-grown and annealed films showed hexagonal structure with c-axes perpendicular to the substrate. The band gap (direct allowed transition) energies as determined from the optical absorption measurements, varied between 1.7 eV for x=1, and 1.2 eV for x=0.88. All of the samples showed n-type conductivity. The carrier concentration increased and the resistivity decreased with the increase of the Hg content in the solution. The resistivity activation energy of the sample, E, decreased with increasing mole fraction of Hg, and E became 0 at higher Hg concentrations (x < 0.88).     

A novel nanoscale catalyst system composed of nanosized Pd catalysts immobilized on Fe(3)O(4)@SiO(2)-PAMAM

This study reports the syntheses of Fe(3)O(4)@SiO(2)-Gn-PAMAM-Pd(0) composites and their applications as magnetically recoverable catalysts for the hydrogenation of allyl alcohol. The controlled growth of polyamidoamine (PAMAM) dendrimers with different generations on Fe(3)O(4)@SiO(2) surfaces was monitored by FT-IR spectra. Subsequently, Pd nanoparticles with diameters of about 2.5?nm were stabilized homogeneously on the surface of Fe(3)O(4)@SiO(2)-Gn-PAMAM (n = 1-4), investigated by thermogravimetry (TG) and transmission electron microscopy (TEM) measurements. The?Fe(3)O(4)@SiO(2)-Gn-PAMAM-Pd(0) have high catalytic activity for the hydrogenation of allyl alcohol and the rate of the reaction can be controlled by changing the generation of PAMAM. In particular, the composites made of superparamagnetic Fe(3)O(4) nanocrystals with diameters of about 10?nm are very suitable as catalyst supports for catalyst separation under a relatively low external magnetic field and catalyst re-dispersion after removing the external magnetic field.     

Applicability of Optical Scattering Model to β-Quartz Solid Solution Glass–Ceramics with Nanoscale Crystalline Phase

The applicability of Rayleigh-Gans and quasi-continuum scattering models to β-quartz solid solution (s.s.) glass–ceramics was studied. We evaluated the validity of these models using two specimens with different microstructures. The refractive indices of the crystalline and glass phases of the specimens were calculated by a method utilizing the transmittance change of the specimens due to structural relaxation. It was found that the quasi-continuum model is applicable to the glass–ceramics for estimating scattering intensity and its microstructure dependence. We demonstrated that the optical transmittance of the glass–ceramics can be simulated as a function of the microstructure on the basis of this model. The result of this study provides a quantitative approach for controlling the optical transmittance of β-quartz s.s. glass–ceramics.