Applied Mechanics and Materials Vols. 66-68

Abstract: A series of Pd/γ-Al₂O₃ catalysts with different additons of Pd were prepared by impregnation. The effect of calcination condition and Pd loading on catalytic performance of catalysts for one-step dimethyl ether synthesis has been investigated. The physic-chemical performance and structure of Pd/γ-Al₂O₃ catalysts were characterized by CO-TPD, TGA and nitrogen physisorption. The results show that the dispersion of Pd and the amount of adsorbration on the CO-bridge of Pd could be increased to by the moderate microwave heating on the catalysts, and the catalyst performance can be improved. But a large number of surface acidic sites of Pd/γ-Al₂O₃ are covered by highly fragmented Pd-grain, it causes DME selectivity reduced. And the excessive Pd can reduce the samples’ surface acid, decrease the dispersion of the metal Pd and block up the pore of γ-Al₂O₃. The CO conversion rate and DME space-time yield could reach 60.1% and 28.76 mmol·g^-1·h^-1 respectively at 2% Pd loading, at this time Pd/γ-Al₂O₃ has a high Pd activity surface and ideal acid sites.

Abstract: In this paper, a simple graphical method for the detection of delaminations in damaged composite laminates is introduced. By using this method, both delamination size and location can be predicted accurately. First, a frequency database for the damaged beams with a range of delamination sizes and locations is generated using a Finite Element (FE) model; then for each mode, a surface plot relating the delamination size, location and frequency shift is generated. The next step is to look up the actual frequency shift (either from numerical simulation or experiment) from surface plots relating to three or more modes to get the intersection curves, which show the possible combination of delamination size and location for each mode. Finally the intersection curves of different modes are plotted together and the intersection point of all the curves indicates the possible delamination size and location, where the frequency shifts for all the modes can be matched. We demonstrate that this method is able to predict both delamination size and location fairly accurately. This method can be expanded to detect the propagation of delaminations by only monitoring the shifts in natural frequencies. It has the potential to detect multiple delaminations through continuous monitoring, provided that they do not occur simultaneously. This method has promising applications in the Structure Health Monitoring (SHM) of composite structures.

Abstract: The use of composite materials in offshore engineering for deep sea oil production riser systems would lead to weight savings and improvement in fatigue and corrosion resistance. This paper examines the weight saving potentials offered by varying fibre orientations, stacking sequences, fibre matrix combinations and liner materials for deep sea riser tubulars. Four main load cases, recommended by design standards for the local design of composite offshore risers, are considered in the analysis using three-dimensional finite element modelling: maximum internal pressure, axial tension, top tension with external pressure and maximum external pressure.

Abstract: For optimal control of synchronous machine, chattering phenomenon will appear if traditional slider control is adopted because permanent magnet synchronous machine is a complex nonlinear time-dependent system with strong coupling of current and rotational speed to cause the deterioration of system control performance with load or load disturbance. In this article, based on the mathematical model of permanent magnet synchronous machine, a control system for it, which combines sliding mode control and active disturbance rejection control, is proposed to improve the dynamic performance and robustness of control system. In the control system, sliding mode control is adopted to control the inner current of machine and active disturbance rejection control is adopted to control the outer speed. The load disturbance of system is also estimated and offset. The results of matlab simulation show that the control system can eliminate serious chattering phenomenon existing in sliding mode control, improves the robustness of system for load and system parameter disturbance as well as has great dynamic and static performance.

Abstract: Energy partition of harmonic waves through a micro gap considering frictional contact was investigated. The incident waves were assumed to be strong enough to make the two solids come into contact. Using the Fourier analysis technique and corrective solution superposition method, the nonlinear boundary problem was reduced to a set of algebraic equations. Special examples for identical materials were discussed in detail. The locations and extents of the separation, slip and stick zones and the energy partition are displayed. Moreover, the effects of gap width, coefficients of friction and incident angle are discussed. These relations are quite effective on seismology and civil engineering.

Abstract: Underground mining causes the redistribution of surrounding rock stress. The value of rock stress is one of the important factors that should be considered when stope structure size is designed. E’xi iron ore body is gently declined in attitude, thin in thickness, and large in occurrence area. According to mining technological conditions and the selected mining method of E’xi iron mine, a typical section of the mine is selected, and it is abstracted into a plane strain problem. In terms of optional stope structure parameters, 9 calculation schemes are planed. Rock stress distributions of stope caused by mining are simulated by the Finite Element Method. Rational stope parameters are chosen by comparing stress distributions of all calculation schemes. Analysis result shows that 8m net distance between pillars, and 4m pillar width are the optimum stope parameters, which not only stabilize the stope but also improve mining efficiency. Choosing stope parameters based on rock stress distributions calculated with numerical simulations, is provided a scientific analysis method for determining rational mining parameters of underground mines.

Abstract: W-Cu precursor was prepared by chemical precipitation. Then the superfine W-Cu composite powder was prepared by roasting and hydrogen reduction process. The composite powder sample were characterized by SEM and XRD. The experimental results show that component uniform and stabilising ratio W-Cu precursor can be prepared by controlling pH of solution, then W-20%Cu uhrafine composite powder was prepared by hydrogen reduction proces ,The sizes of three compositions in the powder(Cu_0.4W_0.6, W and Cu)was to nanometer, in which the size of Cu_0.4W_0.6 and W was 40nm while the size of Cu was 70nm.

Abstract: The spectral responsivity of the filter radiometer（FR）is an essential parameter which needs to be measured accurately in the radiometric determination of the thermodynamic temperature. In this paper the facility of the spectral responsivity measurement and a 900 nm centered FR are studied. The influence issues of the facility and the FR, including the central region, wings and the wavelength step, are discussed. The measurement repeatability of the integration of spectral responsivity is estimated 0.03%, which is suitable for the requirement.

Abstract: The paper was to optimize the conditions of thermal and pressing dewatering of lignite based on four factors three levels of Orthogonal experiment and to study the effect of conditions on lignite burning characteristic. The results show that the importance to the dehydration rate of lignite is in turns, temperature, pressing time, pressure, particle size; and the optimizing condition is temperature 220°C, pressure 6MPa, pressing time 40min, and the particle size ratio 3 to 7. Thermo gravimetric analysis had been carried out to study the burning characteristic of the dewatered lignite. The results show that the burning characteristic temperatures: Preliminary release of volatile temperature, ignition point, point of maximum weightlessness rate, burnout temperature, are found to be an obvious rise, but the burnout temperature; and the four burning characteristic temperatures will be elevatory with the temperature elevated, pressing time extended and pressure increased.

Abstract: As of end of December 2010, Taiwan reports over 160 colleges and universities and is proclaimed as a country that reports highest college density. Therefore, a heavy impact and acute competition between colleges and universities has made the schools spare no effort to enhance quantity & quality of teaching and research related resources to stay competitive. However, a large improvement is required to the existing university e-libraries in terms of manpower allocation, budget amount, software & hardware facilities, quantity & quality of library collection and management philosophy deficiencies. Therefore, the management of various libraries needs to reinforce librarians’ capabilities in management and decision making to enhance overall library performance. The paper mainly follows various decision-making thinking, decision-making philosophy, decision-making mindset, decision-making methods and decision-making discipline ideas of Habitual Domains, with over 10 years personal experience of being a curator of university library considered to come up with strategies that are beneficial to the decision making thinking of university curators in Taiwan, so as to achieve the performance of library affairs and to expect to enable a new opportunity for the future development of university e-libraries in Taiwan.