Analysis and design-optimization of LCC resonant inverter forhigh-frequency AC distributed power system

The analysis and design of an LCC resonant inverter for a 20 kHz AC distributed power system are presented. Several resonant converter topologies are assessed to determine their suitability for high efficiency power conversion, under resistive and reactive loads. Two LCC-resonant inverter designs were implemented. One with all switches operating with zero voltage switching (ZVS), and another with two switches operating with ZVS and two switches with zero current switching (ZCS). The experimental results are presented along with a performance comparison of the two versions     

Transmission distance of in-line amplifier systems withgroup-velocity-dispersion compensation

Group-velocity dispersion (GVD) compensation in in-line amplifier systems is evaluated from the viewpoint of improving the transmission distance. The nonlinear Schrodinger equation, which simulates signal propagation in optical fibers, is numerically evaluated to clarify the optimum configuration for GVD compensation. It is shown that the optimum amount of GVD compensation is about 100% of the GVD experienced by the transmitted signal. The optimum compensation interval is found to be a function of the bit rate, signal power, and dispersion parameter. For dispersion parameter values ranging from about -0.1 ps/nm/km to -10 ps/nm/km, and an amplifier noise figure of about 6 dB, the optimum compensation configuration can eliminate the GVD from in-line amplifier systems, thus improving transmission distances to those limited by self-phase modulation and higher-order GVD     

Sensitivity of torsional stress predictions of diesel generatorsets to critical parameter values

In the present paper a new method is presented for the evaluation of torsional stressing of diesel-generator sets consisting of components with uncertain torsional characteristics. A frequency scanning technique is implemented for eigenvalue analysis of the elastic system. Due to the uncertainty of the values of stiffness and damping coefficients, a sensitivity analysis method is also presented, suitable for the evaluation of the range of the mechanical stresses. Special consideration is given to the correct simulation of the coupling to the electric network, including the influence of generator regulators and possible network interactions. An exact formula is extracted for the synchronizing and damping torque coefficients. The method presented was checked in a diesel power station of the autonomous electric system of a Greek island     

Trade-off between resolution and interactivity in spatial taskperformance

Virtual reality displays usually lag far behind classical computer graphics displays in static image quality parameters, such as resolution. Both the popular press and scientific papers often stress that resolution will have to increase greatly before users can experience virtual environments as “the real thing”. Nevertheless, it is already possible to do some useful work in VR environments. The point we experimentally demonstrate here is that resolution is much less important for interactive tasks that employ immersive VR, where users can explore the environment by moving their heads and bodies, than it is in classical computer graphics applications, where users can only explore by gazing at a single picture. In the context of unmanned aerial vehicles, frame rate (read: passive camera movement) is more important than resolution for target detection, recognition, designation, and tracking. In the experiments reported here, we investigated the relative importance of various image parameters like spatial resolution (number of pixels per video frame), intensity resolution (number of gray levels per pixel), and temporal resolution (number of frame updates per second). Most experimental data concerning these resolutions come from classical psychophysics. However, experimental conditions in classical psychophysics feature stationary observers looking at short-term, pointlike flashes on stationary displays, and are thus far more representative of human interaction with pictures and photographs than with highly interactive systems like those employed in virtual reality     

A capacitor-based device for the measurement of shaft torque

This paper describes a capacitor technique for the measurement of torque in a rotating shaft. The passive rotating part incorporates a capacitor bridge which is connected capacitively to the static part. This device is simple in operation and is relatively easy to manufacture     

Oblique flow impinging on a wall with suction or blowing

Summary The oblique flow of a viscous fluid impinging on a flat wall with suction or blowing is studied. It is found that when suction is applied the fluid penetrates the wall while blowing causes the shifting of the stagnation point. It is also found that this shifting depends upon the magnitude of the blowing.     

Effective scattering area of a three-faced corner cube reflector

Ray representations are used to refine a model for the equivalent aperture of a three-faced corner-cube reflector in which the faces are not perpendicular. This is used in calculating the actual value of the effective scattering area for such a reflector, which gives a correction factor to exclude the error component due to the nonperpendicularity. A table is given of calculated values for the correction factor together with experimental results. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 45–48, October, 1996.     

Optimization of a Reconstitutable Suspension of Rifampicin Using 24 Factorial Design

In this study 2⁴ factorial design associated with surface response methodology was used to develop and optimize a reconstitutable suspension of rifampicin. The study illustrated the effect of the percentage of each of sucrose, avicel RC-591, hydrophilic aerosil, and aerosol-OT on the flowability and the bulk density of the dry mixture as well as the viscosity, the sedimentation volume, and the redispersibility of the suspension. An empirical equation developed for each of the above responses was used with the aid of computer software to plot a contour map of the most significant effects and interactions. Five replicates at the center of the design were used to independently calculate the experimental error and to detect any curvature in the response surface. Three formulas which are not included in the design were prepared to check the validity of the model equation.