Applied Mechanics and Materials Vols. 52-54

Abstract: The system is composed of Fire center console, wireless control board, wireless multifunctional fire detector and wireless PTZ camera control system. It is based on string-like network topology self-organizing wireless sensor networks, which adopts Simplici TI network protocol that can reduce power consumption of the system. The system uses BP algorithm program for judging whether there is a fire, uses Wireless PTZ camera control system, which is convenient to install, for real-time monitoring the detect area, uses voice module for fire automatic voice alarm to the fire department and uses Micro-Fire GIS to show the location of a fire. BP algorithm program is embedded in wireless multifunctional fire detector. The samples of BP algorithm were derived from the fire detection standard room of the State Key Laboratory of Fire Science of China. The system is low false alarm rate, low cost, fast response and convenient to install.

Abstract: In the traditional designs of milling cutter, we cannot get the required accuracy of machining as there may be local deformation on the edges, even more the cutter can break down. Aiming at this situation, a finite-element model of straight pin milling cutter with helical tooth are built using Marc, a nonlinear finite-element analysis software, the different cutting forces of the milling cutter during the cutting process are analyzed and the cutting forces of the milling cutter at different parameters are studied. We get the stress, the strain and the temperature distribution of the milling cutter in different situation. Our work offer a theoretical basis of improving stress of the cutter, designing the structure of cutters reasonably and analyzing the cutter failure as well as a new method of analysis and calculation of the cutter life and strength.

Abstract: Flooding and membrane dehydration are phenomena that must be avoided in a proton exchange membrane fuel cell (PEMFC) operation. It needs a sufficient knowledge about water transport behaviors. Electro-osmotic drag and back diffusion are the dominant water transport mechanisms through the membrane in PEMFC. In this study, the relative humidity (RH) profile along the channel at both anode and cathode sides have been recorded. The experiment was conducted in a single cell PEMFC with single serpentine flow field design. The water content profile was strongly influenced by RH profile thus in turn influenced the electro-osmotic drag coefficient, water diffusion coefficient and back diffusion flux. The operating temperatures of cell also influence those water transport behavior. The temperature was varied at 25, 40, 50 and 60 oC, while the pressure at the anode and the cathode was fixed at 1 bar. The higher the temperature, the smaller the water contents but with higher electro-osmotic drag coefficient, water diffusion coefficient and back diffusion flux. After all, the strategy of using saturated hydrogen and dry air in this study successfully prevents flooding and membrane dehydrating in the system – that are the major problems in PEMFC operation.

Abstract: The basic concepts and theories of Hilbert-Huang-Transformation (HHT) for signal analysis is introduced and its implementation procedure is programmed. For the collected three orthogonal directions wind speed signals at a measuring point at Sutong Bridge site, Empirical Mode Decomposition (EMD) is conducted to extract the Intrinsic Mode Functions (IMFs). Hilbert transformation is performed on IMFs and its marginal amplitude spectra and amplitude spectra are achieved. The orthogonal exponential matrix that reflects the orthogonalities between the IMFs is obtained, and eigenvalue decomposition is carried out. The results show that the measured wind speed appears non-stationary nature, even for the same measuring point, for the wind speed at different directions, the dominant frequencies are distinct.

Abstract: The results of unsteady Reynolds averaged Navier-Stokes (URANS) simulations of flow around a square cylinder using two-dimensional hybrid meshes were presented in this paper. The first part examined the accuracy of various RANS turbulence models, i.e. the standard model, RNG model, realizable model, standard model, SST model, and RSM, by comparing their results with available experimental data. Despite the limits imposed by the RANS approach and the relatively inexpensive two-dimensional computations, the main features of this complex flow can be predicted reasonably well. Among the computations using various RANS models compared here, the SST model shows the best agreement with the experiment. The second part investigated the effects of corner cutoffs on unsteady flow characteristics around a square cylinder by using the SST model. Especially the detailed near-surface flow structure around the cylinder was focused on, aiming at giving an explanation for the drastic modification of the aerodynamic characteristics as the corner shape is slightly changed.

Abstract: The semiconductor industry deals with the production at a scale of nanometer, thus resulting in the process control with little margin of error. Timely detection of faults during the manufacturing process is critical to the improvement in product yields. Difficulty of detecting accurately faulty processes and products is due to the abundant of data obtained from hundreds of tool-state and process-state sensors. We thus analyze this problem through the computational intelligence techniques. The analysis results reveal the minimal set of features for fault detection as well as the high precision classification model of faults.

Abstract: A recently reported promising new perovskite oxide cathode material, Ba0.2Sr0.8Co0.8Fe0.2O3−δ, (BSCF) (with x = 0.2 and y = 0.8) of high purity for intermediate-temperature solid oxide fuel cells (IT-SOFCs) was synthesised in the current work by using the co-precipitation method. The result indicated a precursor with a well-defined composition of fine particle size, high homogeneity, and high reactivity. After calcining has been developed at 900°C, the individual oxides from ammonium oxalate were alloyed into nanostructured perovskite (with x = 0.2 and y = 0.8) Ba0.2Sr0.8Co0.8Fe0.2O3 of high purity. The thermal properties, phase constituents, surface area and microstructure of the samples were characterised by TGA, XRD, BET, SEM and EDX techniques respectively. The results show that the BSCF powders have cubic perovskite-type structure with fine particle size, high surface area and high homogeneity. The current method employed is found to be very reliable for the synthesis of BSCF.

Abstract: Unlike ordinary plate air preheater, the new dual-plate air preheater can generate temperature gradient through adding another plate in cold side to maintain certain space. And it can decrease the temperature of hot fluid in the outlet while increasing the temperature of plate surface to achieve the purpose of anti-corrosion.

Abstract: As one of the main reason of fatigue failure, vibration has received more attention in reliability and comfort research on vehicles. The shock from bumpy roads has a great impact to the fatigue of vehicle parts and components. The method of survey user conditions is described for the road test in the article, and three accelerating data of X, Y, Z directions of a vehicle left shaft position have been obtained with the typical user condition. Through studied the data, we have obtained the load spectrum and the power spectral density data of one car. The obtained quantitative results from the analysis can be used for evaluating the comfort of using vehicle.

Abstract: The purpose of this paper is to build knowledge description model for complex product design. In order to uniform the semantic of glossary in design process, an extensive glossary semantic tree is built up and the corresponding semantic similarity calculation algorithm is proposed. The complex design knowledge can be divided into instance pattern, chart pattern, formula pattern and rule pattern. The knowledge models are proposed for these four pattern knowledge models. At last, a design knowledge modeling and reusing system for complex product is achieved, and the design knowledge can be inherited by it.