Switching Phenomena between Laminar and Turbulent Flows of Superfluid 4He Generated by a Vibrating Wire

We have investigated the turbulence transition of the superfluid ⁴He flow generated by a vibrating wire. For a 1.2-kHz vibrating wire, we observed intermittent switchings between laminar and turbulent flows. The switching rate decreases with increasing temperature above 100 mK, until no occurrence of the switchings at 350 mK. For a 2.4-kHz vibrating wire, we find that the switching rate is much lower than that of the 1.2-kHz vibrating wire even at low temperatures. This result indicates that a mechanism causing the switchings is influenced by the temperature and the oscillation frequency of the superfluid flow.     

Ultrashort X-ray pulse generation using subpicosecond electron linac

As a promising tool for ultrafast material analyses, we propose to utilize the X-ray pulse which may be generated in a quite simple manner using subpicosecond electron linacs. The properties of the X-ray were numerically studied with the EGS4 code. Verification of the X-ray generation was also conducted at the Nuclear Engineering Research Laboratory (NERL) linac and clear diffraction patterns of characteristic X-ray were obtained for typical single crystals.     

Self-routing planar network for guided-wave optical switching systems

An N*N self-routing planar network suitable for fabricating optical space switches on lithium niobate substrate is presented. The network has O(N/sup 2/) cross points, good modularity and expandability. It also has no waveguide crossovers and no differential attenuation between any of the input and output pairs. A self-routing control can be applied to this network, which is indispensable for ATM switching systems.<>     

An efficient contention resolution algorithm for input queuing atm cross-connect switches

This paper describes an efficient contention resolution algorithm and its distributed implementation for large capacity input queuing cross-connect switches, which will establish virtual paths in future broadband ATM networks. The algorithm dynamically allocates sending time to cells held in input queues when no contention is indicated in the designated output ports. An expression for the mean delay and the cell loss probability for random traffic are derived through an approximate analysis. Input cells are served on a first-come, first-served basis as conventional contention resolution algorithms whose throughput saturates at 58 per cent because of head of line blocking in input queues. The proposed algorithm achieves a maximum throughput of 76 per cent.     

A High-Frequency Resonant Inverter Using Current-Vector Control Scheme and Its Performance Evaluations

The authors introduce a new configuration of resonant-type high-frequency inverter having inherent fast control response of the output power and variable-voltage variable-frequency (VVVF) capability. The circuit is composed of a parallel combination of two series-resonant inverters with common input and output terminals. Both inverter units are operated at synchronous frequency and with an adjustable phase difference from 0° to 180°, allowing control of the output power from full to null power, respectively. Operation of this inverter is explained and computer-simulated operating waveforms and characteristic curves are shown in terms of normalized control variables and circuit parameters. A prototype inverter using Power MOSFET modules has been originally tested with a high-frequency induction heating and melting load to demonstrate experimentally the proposed control principle and the steady-state inverter performances under parallel tuned load conditions.     

Polonium evaporation and adhesion experiments for the development of polonium filter in lead–bismuth cooled reactors

Fundamental experiments were performed to determine the adhesion characteristics of polonium to different metals and to develop a filter for polonium evaporated from neutron-irradiated LBE. The results of the first experiments suggested that adhesion characteristics are almost the same for stainless steel and nickel metal. The results of the preliminary experiments for a polonium filter suggested that stainless steel mesh with thin wires could effectively collect polonium evaporated from neutron-irradiated LBE. In the experiments, stainless steel wire mesh was used, but from the results of adhesion experiment, it is expected that the same effect can be obtained with wire mesh made of other kinds of metal.     

High performance liquid chromatographic separation of monoacylglycerol enantiomers on a chiral stationary phase

High performance liquid chromatographic separation of monoacylglycerol enantiomers as di-3,5-dinitrophenylurethane derivatives was carried out on a chiral stationary phase, N-(S)-2-(4-chlorophenyl)isovaleroyl-D-phenylglycine chemically bonded tov-aminopropyl silanized silica. Complete separation of the urethane derivatives of racemic monoacylglycerols with saturated acyl groups of C₁₂−C₁₈ was achieved using a stainless steel column (25 cm long) packed with the 5μ particles, an isocratic elution at ambient temperature with a mixture of hexane/ethylene dichloride/ethanol as a mobile phase, and a UV detector. Thesn-1 enantiomers were eluted ahead of the correspondingsn-3 enantiomers. Complete separation of thesn-2 isomers from the corresponding enantiomers and partial separation of the enantiomer homologues differing by two acyl carbons also were observed.     

Efficient parallel time-slot interchanger for high-performanceSDH/SONET digital crossconnect systems

A parallel design of time-slot interchangers is refined in order to scale the interchangers' capacity in an efficient manner. Performance analysis shows that this design scheme requires significantly less memory compared with a conventional parallel design because of newly implemented load-balancing switches, while keeping its switching control complexity to a minimum     

Processing of ethanol fermentation broths by Candida krusei to separate bioethanol by pervaporation using silicone rubber‐coated silicalite membranes

BACKGROUND: Pervaporation employing ethanol‐permselective silicalite membranes as an alternative to distillation is a promising approach for refining low‐concentration bioethanol solutions. However, to make the separation process practicable, it is extremely important to avoid the problems caused by the adsorption of succinate on the membrane during the separation process. In this work, the pervaporation of an ethanol fermentation broth without succinate was investigated, as well as the influence of several fermentation broth nutrient components. RESULTS: Candida krusei IA‐1 produces an extremely low level of succinate. The decrease in permeate ethanol concentration through a silicone rubber‐coated silicalite membrane during the separation of low‐succinate C. krusei IA‐1 fermentation broth was significantly improved when compared with that obtained using Saccharomyces cerevisiae broth. By treating the fermentation broth with activated carbon, bioethanol was concentrated as efficiently as with binary mixtures of ethanol/water. The total flux was improved upto 56% of that obtained from the separation of binary mixtures, compared with 43% before the addition of activated carbon. Nutrients such as peptone, yeast extract and corn steep liquor had a negative effect on pervaporation, but this response was distinct from that caused by succinate. CONCLUSION: For consistent separation of bioethanol from C. krusei IA‐1 fermentation broth by pervaporation, it is useful to treat the low nutrient broth with activated carbon. To further improve pervaporation performance, it will be necessary to suppress the accumulation of glycerol. Copyright © 2009 Society of Chemical Industry