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[en] The most recent surge of innovations that have simplified and streamlined the process of determining macromolecular structures by crystallography owes much to the efforts of the structural genomics community. However, this was only the last step in a long evolution that saw the metamorphosis of crystallography from an heroic effort that involved years of dedication and skill into a straightforward measurement that is occasionally almost trivial. Many of the steps in this remarkable odyssey involved reducing the physical labor that is demanded of experimenters in the field. Other steps reduced the technical expertise required for conducting those experiments.
[en] This note describes a small spike filter used to remove SCR commutation spikes from the dc output voltage of magnet power supplies. Removal of these spikes reduces the noise problems in electronic detectors installed in the same area. The filter is small enough to be mounted inside a power supply
[en] Highlights: • Characteristics of countercurrent flow limitation (CCFL) in a pressurizer surge line were evaluated. • A correlation for CCFL at the sharp-edged upper end of vertical pipes (CCFL-U) was constructed. • It was found CCFL would take place at the sharp-edged upper end of the pressurizer surge line. • In the pressurizer surge line system, the falling liquid volumetric flux was smaller than that of CCFL-U. • From that, a CCFL correlation for the pressurizer surge line system was constracted. - Abstract: In order to clarify the characteristics of countercurrent flow limitation (CCFL) in a pressurizer surge line, CCFL in a vertical pipe with a large diameter was evaluated using previous experimental data and a one-region model with an existing correlation of interfacial shear stress. The CCFL is defined by the relationship between the gas and liquid volumetric fluxes under a quasi-steady state after onset of flooding. A correlation for CCFL at the sharp-edged upper end of vertical pipes was constructed and it was compared to CCFL in the slightly inclined pipe. The comparison indicated that the liquid volumetric flux at the sharp-edged upper end was lower than that in a slightly inclined pipe when they have a large diameter such for an actual-scale pressurizer surge line. However, it was found that the liquid volumetric flux in integral experiments (including a slightly inclined pipe, a vertical elbow, and a vertical pipe) was lower than that in slightly inclined pipes and vertical pipes. Considering system characteristics from experimental data for the pressurizer surge line, it was concluded that the Kutateladze parameter should be applied with the slope of m = 0.94 and the constant of CK = 1.24 ± 0.1 for the Wallis type CCFL correlation.
[en] A valve for damping out flow surges in a vacuum system is described. The surge-damping mechanism consists of a slotted, spring-loaded disk adjacent to the valve's vacuum port (the flow passage to the vacuum roughing pump). Under flow surge conditions, the differential pressure forces the disk into a sealing engagement with the vacuum port, thereby restricting the gas flow path to narrow slots in the disk's periphery. The increased flow damps out the flow surge. When pressure is equalized on both sides of the valve, the spring load moves the disk away from the port to restore full flow conductance through the valve
[en] Postpartum cerebral angiopathy (PCA) is an uncommon cause of ischemic and hemorrhagic stroke in young women. It is usually clinically benign and not relapsing. We describe a patient with non-hemorrhagic PCA who had an atypical progressive neurological deficit from bilateral hemisphere watershed ischemia despite treatment with aggressive medical therapy and intracranial balloon angioplasty. (orig.)
[en] A hollow cathode surge protective gap (HCSPG) was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter φ of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.
[en] The turbopump is a pressurizing system that supplies liquid propellants to the combustion chamber of a rocket engine at high pressure. As an integral component of a high-speed pumping system, the inducer used in a turbopump is forward-attached to an impeller to improve suction performance. This paper describes an experimental investigation on the flow instabilities of a two-bladed axial inducer due to cavitation. Cavitation development and its instabilities were analyzed. Asymmetric cavitation and cavitation surge were observed, and characterized by measuring the inlet pressure fluctuation for various cavitation numbers and flow coefficients. As flow coefficient decreases, the increased intensity of asymmetric cavitation was observed with an increased inception number of asymmetric cavitation. The frequency of the detected cavitation surge in the 4-10Hz range varied depending on the cavitation number. The instantaneous transition to cavitation surge appeared at the end of asymmetric cavitation as the cavitation number decreased. However, a further decrease in cavitation number resulted in the stable operation of the inducer with low values of pressure fluctuation. Finally, an intensive cavitation surge appeared after a significant amount of head loss
[en] Mathematical equations describing the dynamic behaviour of pressure, water mass, etc. in a steam drum are derived from basic principles. The resultant model includes such effects as steam superheating and water subcooling as well as spontaneous flashing of liquid and condensation of vapour. Experimental data from a pressurizer are adequately predicted by the model. The pressure rise following a turbine trip can be predicted by the isentropic-compression model but not by the thermodynamic-equilibrium model. The equations are individually linearized and implemented on an analog computer in such a way that their non-linear behaviour is retained for small-perturbation studies. (author)
[en] A unified model is developed for the propagation of the Westward Traveling Surge (WTS) which can explain the diversity in the observed surge characteristics. We start with the Inhester-Baumjohann model for the surge region which implicitly includes both the Hall and Pedersen currents. It is found that precipitating electrons at the conductivity gradient modify the gradient, causing it to propagate as a wave front. The velocity of propagation is directly dependent on the ionization efficiency of the precipitating electrons and, increases dramatically when they become more energetic during substorm onsets. The direction of the surge motion depends on the presence of polarization charges on the poleward surge boundary. This is related to the efficiency with which the poleward ionospheric currents are closed off into the magnetosphere by the field-aligned currents. Inclusion of the electron-ion recombination rate modifies the surge propagation velocity and leads to explicit expressions for the conductivity profile. Sufficient precipitation current is required to overcome electron-ion recombination in order for the surge to expand. Whem the precipitating current is less than this threshold the WTS retreats. Therefore, the model describes the ionospheric response to both the expansion and recovery phases of the magnetic substorm.(author)