Response spectrum analysis of piping systems with elastic-plastic gap supports

A new seismic support device and its application in piping systems is described. The device, E-BAR (patented), can be cost effectively used for snubber replacement programs, mitigation of hydraulic transients, pipe whip and as a thermal stop. The device has pre-set gaps to allow free thermal movement. During a seismic or other dynamic load event, if the pipe movement exceeds the gap dimension, the device acts as an elastic or elastic-plastic restraint. The device also has a unique design feature for not exceeding the restraint force beyond a specified limit design value. To analyze piping systems with gap supports having elastic-plastic characteristics, modal analysis procedures for both response spectrum and time history methods are developed. The comparison of responses obtained from the procedures with nonlinear time history analysis and test results available in the literature shows excellent correlation. A pilot program conducted for snubber replacement with E-BARs demonstrates that the limit force feature of E-BAR makes them very attractive for snubber replacement. This is because a particular E-BAR with a specified limit design force can be selected, such that, the E-BAR replacing the snubber does not require any modifications be made to the existing support steel and hardware.     

Threshold voltage-minimum gate length trade-off in buried channelPMOS devices for scaled supply voltage CMOS technologies

The trade-off between threshold voltage (V_th) and the minimum gate length (L_min) is discussed for optimizing the performance of buried channel PMOS transistors for low voltage/low power high-speed digital CMOS circuits. In a low supply voltage CMOS technology it is desirable to scale V_th and L_min for improved circuit performance. However, these two parameters cannot be scaled independently due to the channel punch-through effect. Statistical process/device modeling, split lot experiments, circuit simulations, and measurements are performed to optimize the PMOS transistor current drive and CMOS circuit speed. We show that trading PMOS transistor V_th for a smaller L_min results in faster circuits for low supply voltage (3.3 to 1.8 V) n⁺-polysilicon gate CMOS technology, Circuit simulation and measurements are performed in this study. Approximate empirical expressions are given for the optimum buried channel PMOS transistor V _th for minimizing CMOS circuit speed for cases involving: (1) constant capacitive load and (2) load capacitance proportional to MOS gate capacitance. The results of the numerical exercise are applied to the centering of device parameters of a 0.5 μm 3.3 V CMOS technology that (a) matches the speed of our 0.5 μm 5 V CMOS technology, and (b) achieves good performance down to 1.8 V power supply. For this process the optimum PMOS transistor V_th (absolute value) is approximately 0.85-0.90 V     

Differential K+ channel clustering activity of PSD-95 and SAP97, two related membrane-associated putative guanylate kinases

The molecular mechanisms underlying the clustering and localization of K+ channels in specific microdomains on the neuronal surface are largely unknown. The Shaker subclass of voltage-gated K+ channel alpha-subunits interact through their cytoplasmic C-terminus with a family of membrane-associated putative guanylate kinases, including PSD-95 and SAP97. We show here that heterologous coexpression of either sap97 or PSD-95 with various Shaker-type subunits results in the coclustering of these proteins with the K+ channels. Mutation of the C-terminal sequence (-ETDV) of the Shaker subunit Kv1.4 abolishes its binding to, and prevents its clustering with, SAP97 and PSD-95. Whereas PSD-95 induces plaque-like clusters of K+ channels at the cell surface; however, SAP97 coexpression results in the formation of large round intracellular aggregates into which both SAP97 and the K+ channel proteins are colocalized. The efficiency of surface clustering by PSD-95 varies with different Shaker subunits: striking Kv1.4 clustering occurs in > 60% of cotransfected cells, whereas Kv1.1 and Kv1.2 form convincing clusters with PSD-95 only in approximately 10% of cells.     

Restoration of masonry facades, renders and final coats in a severe climate

The restoration of relatively old masonry buildings, 1870-1920, represents about 119930 flats and offices in the 4-5 largest cities in Norway. Driving rain and a severe climate are the key factors for deterioration. The paper describes a case study at the city campus of the University of Oslo.     

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