[en] Ordered semiconductor In₂O₃ nanowire arrays are uniformly assembled into hexagonally ordered nanochannels of anodic alumina membranes (AAMs) by electrodeposition and oxidizing methods. Their microstructures were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. A blue-green photoluminescence (PL) band in the wavelength range of 300--650 nm was observed in the In₂O₃/AAM assembly system. The PL intensity and peak position depend on the annealing temperature, which is mainly attributed to the singly ionized oxygen vacancy in the In₂O₃ nanowire array system. Copyright 2001 American Institute of Physics

[en] We report optical investigations of the interaction of femtosecond Ti:sapphire laser pulses with underdense plasmas created from high density gas jet targets. Time-resolved shadowgraphy using a 2ω probe pulse and images of the transmitted radiation are presented for nitrogen and hydrogen. For the laser power available, the experimental results and their analysis based on a simple numerical Gaussian beam model show that ionization induced refraction dominates the interaction process for all gases except hydrogen. The numerical modeling also shows that for a given laser power there exists only a narrow density range in which self-focusing can be expected to occur. In the case of hydrogen for electron densities greater than ∼10²⁰ cm^-3, the onset of channeling expected at the critical power for relativistic self-focusing is experimentally observed

[en] A method to measure, resolve and filter the attitude of the three-freedom simulation platform is presented in this paper. The strapdown measurement system is composed of three single-axis angular speed gyros and three acceleration transducers. Kalman filtering algorithm and self-adaptive Kalman filtering algorithm are adopted to filter the signal. The strapdown measurement system's signal measurement, resolving and filtering are realized through LabVIEW, and the result shows that the measurement, resolving and filtering of the attitude are correctly done using this method, providing correct platform motion attitude signal

[en] A new digital signal processor based single path ultrasonic gas flowmeter is designed, constructed, and experimentally tested. To achieve high accuracy measurements, an optimized ultrasound driven method of incorporation of the amplitude modulation and the phase modulation of the transmit-receive technique is used to stimulate the transmitter. Based on the regularities among the received envelope zero-crossings, different received signal's signal-to-noise ratio situations are discriminated and optional time-of-flight algorithms are applied to take flow rate calculations. Experimental results from the dry calibration indicate that the designed flowmeter prototype can meet the zero-flow verification test requirements of the American Gas Association Report No. 9. Furthermore, the results derived from the flow calibration prove that the proposed flowmeter prototype can measure flow rate accurately in the practical experiments, and the nominal accuracies after FWME adjustment are lower than 0.8% throughout the calibration range.

[en] SnO₂ was successfully coated on the surface of alumina borate whiskers. The pure aluminum matrix composites reinforced with a SnO₂-coated alumina borate whisker were fabricated by squeeze casting. The effects of coating contents on the damping properties of the coated composites at various temperatures, frequencies, and strain amplitudes were examined. The microstructures of the coated composites were also investigated through transmission electron microscopy observations. These results indicate that the introduction of Sn at the interface between whisker and matrix in the coated composites during the squeeze casting process alters not only the interface structures but also the dislocation status of the matrices in the vicinity of the interface. The results of damping characterization indicate that the damping capacities of the coated composites strongly depend on the coating contents and strain amplitudes. A damping peak at low temperatures appeared not only in the coated composites but also in the noncoated one, which is related to dislocation motion and interfacial slip caused by Sn. A damping peak at high temperatures appeared only in the coated composites, and the damping mechanisms at high temperature change with the increase in strain amplitudes. Sn played an important role on the damping mechanisms of the coated composites all along.

[en] Francis turbine, as a widely used hydro turbine, is especially suited for the hydropower station with high hydraulic head and higher hydraulic head. For such turbine generator units all around the world, the crack streaks usually come out after a long time use and the resulted accidents may cause huge losses. Hence, it is meaningful to refine the design assuring the stability and safety of the Francis turbine. In this paper, the stiffness and strength as well as the fatigue life of the Francis turbine are studied. Concerning on the turbine of one certain hydropower station, the flow field inside the turbine are first simulated and the pressure distribution around the blades are derived. Meanwhile, the stress distributions of the blades are also obtained. Based on these, the fatigue analyses are applied on the turbine. According to the results of fatigue analyses, some optimal designs on the turbine are verified. The results show that with the optimal designs, the hydraulic performances of the turbine do not change too much while the maximum stress on the turbine decrease and the fatigue life increase as well.

[en] A suite of lacustrine mixed marlstone is developed in the lower third member of the Shahejie Formation (Es3^l) in the Shulu Sag, Bohai Bay Basin, and it is a tight oil reservoir which acts as both source bed and reservoir bed. According to the rock fabric characteristics, the marlstone in Es3^l can be divided into two types: lamellar marlstone (stratigraphically mixed) and massive marl (structurally mixed). Both of them contain minerals dominated by calcite, followed by dolomite, and minor quartz, feldspar and clay minerals. The marlstone in Es3l is a typical ultra-low porosity and ultra-low permeability tight reservoir. Its pore space is classified into two types and eight sub-types, and the matrix pores are mainly nano-scale pores. The lamellar marlstone reservoir shows better physical properties and pore structure than the massive marlstone reservoir. Both the chloroform asphalt “A” content and rock pyrolysis S0+S1 are high, and oil-bearing is universally observed. The development of “sweet spot” is jointly controlled by sedimentary facies, rock fabric, organic matter abundance and maturity, structural fractures. (paper)

[en] Information theory based Shannon entropy increment analysis of the differential pressure fluctuations was successfully developed to recognize dynamic behavior of gas-solid flow and different flow patterns. Experiments were carried out in a biomass fluidized bed with cross-section of 100 mmx30 mm and height of 500 mm was carried out. Cylinder-shaped biomass particles with the size of 2.6 mm in diameter and 6 mm in length were used to as bed materials. Pressure fluctuations and flow patterns were obtained by a multi-channel differential pressure sampling system and a high-resolution digital CCD camera, respectively. It was found that both Shannon entropy and the present developed Shannon entropy increment analyses were pronounced with the flow patterns and transitions. Besides, Shannon entropy increment analyses, i.e. Shannon entropy increment and Shannon entropy increment rate, are very helpful to obtain the chaotic nature especially the change of chaotic nature with operating condition in gas-solid flow.

[en] The superhyperfine parameters T_j (j = x, y, z) for Cu²⁺ in the square-planar K₂PdX₄ (X = Cl, Br) are theoretically studied from the perturbation formulas of these parameters for an octahedral 3d⁹ cluster, by considering both the contributions from the crystal-field and charge-transfer mechanisms. The related molecular orbital coefficients are determined from the cluster approach in a uniform way. Based on one adjustable proportional factor ρ for the orbital admixture coefficients, the calculated results of present work show reasonable agreement with the observed values.

[en] We report a double stage linearly polarized ytterbium-doped double clad fiber (YDCF) amplifier working at 1063.9 nm, which generates a diffraction-limited output with an average power of 102 W at a repetition rate of 100 kHz, a pulse duration of 14.9 ns, a peak power of 68 kW, a 3 dB spectral width of about 0.47 nm and a polarization extinction ratio (PER) of about 13 dB. The seed is modulated to work at a suitable Gaussian shape to restrain the pulse distortion in the fiber amplifier. To the best of our knowledge, this result represents the highest peak power with narrow line-width and excellent beam quality in linearly polarized YDCF. (paper)