Applied Mechanics and Materials Vols. 321-324

Abstract: Experimental investigations were made on the instability of supercritical kerosene flowing in active cooling channels. Two approaches were used to control the pressure in the channel. One is the back-pressure valve while the other is the venturi. In both conditions, a kind of low-frequency oscillation of pressure and temperature is observed. And the oscillation periods are calculated. By comparison with the flow time, it is concluded that the instability occurred in active cooling channels is probably one kind of density wave instability. And its period has no relationship with the cooling channel geometry, nor the pressure, but only depends on the flow time of kerosene in active cooling channels. When the mass flow rate, density and pressure drop couple with each other, the density wave instability will appear.

Abstract: The gas pipeline commissioning replacement is a vital section before the pipes being put into operation. It is related to the gas mixture length of segment regardless the replacement method, the gas mixing length theory formula is derived based on diffusion theory and convection diffusion equation. Taking the impact factors of gas movement into account, with software FLUENT, this paper simulated different flow regimes, pipe length, diameter, velocity, back pressure and temperature to influence the gas mixing length, the general influence law of various factors is identified. That is the gas mixing length increases with the increasing of pipe length, diameter, velocity, back pressure and temperature, the corresponding mixing length and displacement time are longer at laminar flow. The research results provide theoretical basis for the natural gas pipeline commissioning replacement to determine reasonable parameters.

Abstract: An approach by mixing laser and plasma to conduct nitriding treatment on the surface of titanium can improve the surface hardness, and the hardness of the surface in different nitriding depth is different. We wrote a program, by which we carried out Monte Carlo simulation calculation, in accordance with the model description by C language. In the calculation process, by changing laser power intensity, scanning velocity, nitrogen ion energy and angle of incidence, we got the distribution of nitrogen ions in iron under different conditions, and thus formed computer simulation diagram of titanium nitride process.

Abstract: In order to eliminate effects of soil bulk density variance and soil properties difference on soil water content forecast precision, a method was proposed to forecast soil volume water content based on near-infrared spectroscopy. This paper investigated relationship between volume water content and near infrared spectral reflectance characteristics in 900-2500nm band, used spectral parameters and support vector machine to built quantitative prediction model for three type variable bulk density soil volume water content, normalized signal characteristics by relative dry soil characteristic vector, putted forward three further processing methods. It was used support vector machine (SVM) method to establish spectral characteristics inverting soil volume water content model of undisturbed soil, and model parameters were optimized by genetic algorithm, through predict error comparison, the final determination was that relative characteristics variation of first-order derivative signal as model input characteristic vector, GA-SVM model prediction had best effect and its forecast error was 1.7866.

Abstract: The singlet potential surface of the OH + HN₂ reaction has been investigated at the B3LYP/6-311++G (3df, 3pd) level. The single-point energy calculations are performed at the high-level CCSD (T) / 6-311++G (3df, 3pd) for more accurate energy values. DFT calculations show that the most favorable association way starts with a barrierless addition of the OH to HN₂ leading to HNN-OH (im6). The adduct im6 goes through an H shift from N atom to O atom, forming the product of H₂O and N₂.

Abstract: Al₂O₃-13% TiO₂ based nanostructured ceramic coatings were prepared on the surface of NiCrAl alloy by Plasma Spraying technology. Compared to the micron ceramic coating (MCC), the average value of hardness of nanostructured ceramic coating (NCC) was much higher than that of MCC, and the NCC presents typical bi-modal distribution. The Weibull distribution of both coatings exhibited apparently dispersible, but NCCs was quite well-distributed. The relationship between microhardness and microstructure were analyzed through SEM, XRD and TEM. The results indicate that the microcracks of NCC are fine and the size of particles is small. The structure of NCC coatings contained more α-Al₂O₃ and TiO₂ and less γ-Al₂O₃ than that of MCC coatings. According to TEM analysis, it can be considered that the grain refinement, toughening of microcracks, and the dispersive refinement of Al₂O₃ nanoparticles on Al₂O₃-TiO₂ matrix are main mechanisms to improve the mechanical properties of NCC.

Abstract: Present work describes a piercing process in order to investigate the clearance of mold parameters and to obtain optimal clearance values for a given sheet material and thickness to be pierced, using the finite element method. The clearance was studied by simulating the piercing operation of a Q235-B sheet. The results of the present paper showed that clearance was the most influential factor for piercing, and numerical experiments was an effectiveness method to get optimal parameters of mold parameters, and the numerical experiment results showed that the best clearance could be got when the ratio of clearance and thickness of material was 0.11.

Abstract: A traveling wave matching (TWM) network is proposed for broadband variable gain amplifier design. The TWM network lessens input return loss and noise figure dependence on VGA’s gain, which is adjusted by biasing of the gain control circuit. A wide band (DC to 12 GHz) VGA with the novel TWM network as input matching is implemented in 2μm InGaP/GaAs HBT (fT of 29.5GHz) technology with die size of 1×2 mm2. As gain control voltage sweeps, the VGA shows a gain tuned from -15 dB to 15 dB and an average noise figure ranging from 8dB to 6.5dB, while S11 (lower than -20dB) and S22 (lower than -10dB) almost unchanged over the operation frequency band.

Abstract: This paper focuses on the design of the USB intelligent controller. The USB intelligent controller can be operated easily. It provides a variety of interfaces to connect MCU8032, MCU8051, Flash controller, Smart Media Controller, MMC controller.

Abstract: The application of soft-switching techniques is an important way to reduce switching losses of DC/DC converter. Aiming at the requirement of electric vehicles application, major soft-switching techniques for DC/DC converters are reviewed. Performance and design limitations are discussed. A comparison of soft-switching techniques used in high power converters of electric vehicles is presented. Through analyzing the state-of-art and existing deficiency of soft-switching techniques for DC/DC converters, it is concluded that power level upgrading, soft-switching range extending and auxiliary network simplification should be focused in the future.