Applied Mechanics and Materials Vols. 55-57

Abstract: In this paper, the control system for electric wheelchair is based on DSP.The motor drive by PWM DC/DC converter. In the speed feedback control system, the method to estimate the approximate motor speed by measuring the motor terminal voltage is established. The design and implementation for electric wheelchair control system will be depicted in this article.

Abstract: This paper discusses an embedded access platform which based on ARM and Linux operating system. Based on the character and advantage of GPRS, this article advances the solution scheme of the wireless sensor network gateway. Mainly analyzes the software design of the gateway, including the way to realize the connection of GPRS network. And this paper proposed a solution of Data loss which is caused by the different transmitting rates of different protocols. It also describes the structure of the hardware platform and running process, and analyzes the structure of the three layers software system, as well as PPP protocol’s characteristics and transplanting key point. As a result, the wireless data communication link between embedded gateway and GPRS network is set up, and the solution of keeping the gateway on line is proposed.

Abstract: The combustion characteristics of the mixtures, which are made from different proportions of paper mill sludge and coal, were studied by the thermogravimetric analysis (TG-DTG) at different heating rates. The results showed that there were obviously three temperature zones in the paper mill sludge combustion curves, which is respectively corresponding to two devolatilization stages and a fixed carbon combustion stage. In these stages, the weight of sludge was lost promptly. When the proportions of sludge – coal blends were rather different, ignition point obviously shifted to the larger proportions, and DTG curve was more closed to the larger proportions. During the combustion process of the mixture, the paper mill sludge and the coal had basically maintained their own devolatilisation characteristics. And the comprehensive combustion characteristic index S of sludge-coal blend declined, demonstrating that higher volatility had better combustion characteristics. As the heating rate and the proportions of coal increasing, total weight loss rate increased, while burnout index C_b raised.

Abstract: The rotary bending fatigue tests were to investigate the effect of the combined shot peening for surface nanocrystallization (CSPN) on the fatigue limit of titanium (TC4). CSPN formed nano-crystallization in surface layer of TC4, and may reduce and reducing the surface damage of TC4 by high energy shot peening. In the case of equiaxed microstructure, the fatigue limit of TC4 specimen treated by high-energy shot peening is increased by 13%, while the fatigue limit of TC4 specimen treated by the CSPN is increased by 34%. But in the case of lamellar microstructure, the fatigue limits of the specimens by either the surface treatment process both of the high energy shot peening and CSPN. The main reason of fatigue improvement change is due to that the effect of surface nanocrystallization and surface damage repairing by CSPN is changed between the different microstructure of TC4.

Abstract: During mixture of Nitrogen and spray water ejecting quenching under normal pressure and high velocity, the liquid film that is formed on the surface of specimen to reduce the heat transfer between specimen and quenching media is removed on the one hand; on the other hand, the heat transfer performance of the mixture exceeds that of pure Nitrogen. Because the surface heat transfer coefficient is difficult to measure, according the cooling curve of surface and centre of specimen measured experimentally, the law of surface heat transfer coefficient and specimen temperature is calculated by nonlinear estimate methods and finite difference method based on inverse heat transfer method. The results show that the cooling performance of mixture of Nitrogen and spray water is as well as that of water or oil. During quenching, the surface heat transfer coefficient increases rapidly at begin, and at temperature of 170 °C, the surface heat transfer coefficient decreases. During martensite phase transformation, the latent heat is used to increase drive force of phase transformation and to overcome resistance of phase transformation, thus the martensite phase transformation can fulfill.

Abstract: With the increase of voltage grade in power transmission system and the aggravation of industrial pollution, flashover of contaminated insulators in HV and UHV system is more and more serious, threatening the security of power transmission severely. The key of improving the security of system is exploring the methods of monitoring and recognizing states of insulator’s surface by some character values. In this paper, multi-characteristic Hidden Markov Model is founded with wavelet and chirplet fractal characteristics of leakage current(LC), through which the flashover patterns are recognized during the developing stages. The results show that fractal characteristics HMM recognized flashover pattern efficiently and successfully, and that is useful to help related stuff to make correct decision and ensure the security of power delivery.

Abstract: Molecular, dynamics simulation and the Boltzmann transport equation are used respectively to analyze the phonon transport in Si thin film. The MD result is in good agreement with the theoretical analysis values. The results show that the calculated thermal conductivity decreases almost linearly as the film thickness reduced and is almost independent of the temperature at the nanoscale. It was observed from the simulation results that there exists the obvious size effect on the thermal conductivity.

Abstract: Vehicle suspension system with hysteretic nonlinearity has obvious nonlinear characteristics, which directly cause the system to the possibility of existence of bifurcation and chaos. Two degrees of freedom for the 1/4 body suspension model is established and the behavior of the system under road multi-frequency excitations is analyzed. In the paper, it reveals the existence of chaos in the system with the Poincaré map, phase diagram, time history graph, and its chaotic behavior is controlled by nonlinear feedback. Numerical simulation shows the effectiveness and feasibility of the control method with improved ride comfort. The results may supply theoretical bases for the analysis and optimal design of the vehicle suspension system.

Abstract: Pure carbon, pure iron and single crystall silicon were firstly loaded into a pure graphite crucible to obtain a hypereutectic Fe-C melt by carburizing at high temperatures in this paper. The powder of oxide La₂O₃ and CeO₂ were added respectively to the melt under the same process conditions and cast iron samples were obtained. The graphite morphology of the samples was observed under optical microscope and SEM. Matrix of the samples were etched by electrolysis way. At last non-ferrous residue on the surface of cast iron samples was gathered, calcined,observed under SEI and BEI and analysed with EDS to find the trace of oxide La₂O₃ or CeO₂. The results showed that oxide La₂O₃ or CeO₂ was really added into the melt but the morphology of graphite did not change. The only effect of the oxides was making the amount of graphiteto increase slightly. All the results of this paper indicat that the oxide La₂O₃ or CeO₂ is possibly the base for graphite flake to precipitate but is not a sufficient condition for graphite to nodularize.

Abstract: Using Fourier transform infrared spectroscopy (FTIR), attenuated total reflection (ATR) technology and partial least square (PLS) method, the rapid quantification method of hemoglobin (HGB) in human soluble blood samples was established. Based on the distribution of samples’ HGB chemical value and absorbance on 1543 cm^-1 which had the highest signal to noise ratio for HGB, all samples were divided into calibration set and prediction set for 50 times. PLS models were established for all divisions, based on the average data RMSEP_Ave, the stable optimal model was selected, the corresponding PLS factor, RMSEP_Ave and R_P,Ave were 2, 6.81 g/L and 0.943 respectively.