Advanced Materials Research Vols. 328-330

Abstract: Microstructure changes brought by the addition of La element to AZ91 magnesium alloy are studied, also, the precipitating phases were identified and their influence on the mechanical properties of alloys was investigated. Results show La makes refinement of microstructure of the AZ91 alloy, and decrease the size of Mg₁₇Al₁₂ phase. La element takes a priority to react with Al element over Mg, forming binary phase Al₁₁La₃ with high melting point. Certain amount of La increases tensile strength, yield strength and elongation. With more addition, La would combine more Al in matrix and decrease strengthening effect, because Al₁₁La₃ phase would become coarsening. The mechanical poroerties tests indicate that AZ91+0.16%La alloy has the best properties. Maximum tensile strength, maximum yield strength and elongation are 245MPa, 178MPa and 14.5% respective, increased by 21%, 19% and 48% respectively. The mechanism of La strenthing mechanical properties is proposed that Al11La3 phase enriched on solid-liquid interface, increased the degree of supercooling, refined the grain size and changed the crystal style.

Abstract: In the present work, Al–TiC composites were synthesized by Flux Assisted Synthesis (FAS) route. In this in situ method the TiC particles are generated from the reaction between the mixture of K₂TiF₆ salt and graphite in the molten aluminium. The XRD peaks have confirmed the presence of the TiC and no other undesirable intermetallics have formed after reaction. After casting the composites were extruded and then aged. All the cast, extruded and aged composites samples have exhibited significant improvement in mechanical properties in comparison with the monolithic alloy. The erosion corrosion test have been performed and found that wear resistance of the composites have significantly improved by the presence of TiC particles. Optical and Scanning electron microscopy were used for microstructural analysis and XRD was used for phase analysis. Mechanical testes were performed as per the ASTM standards.

Abstract: This paper introduces a design of ASIC with the advantages of high performance, low power, low cost and short development cycle, which is especially suitable for the middle and small scale production of complicated large programmable ASIC. Through introducing the performance and latest development of HardCopy series devices and Stratix FPGA series devices, and based on the development platform of Quartus II and Nios II system, this paper analyzes the complete development process of Stratix FPGA and HardCopy ASIC based on SOPC. This paper concludes the seamless transplant from Stratix FPGA to HardCopy ASIC based on the SOPC with IP multiplexing, which is the most promising development direction of producing large programmable ASIC with high performance and low cost in the future.

Abstract: The permanent magnet synchronous motor (PMSM) with its high efficiency, high power factor, small volume and advantage of saving electricity in many areas, has been widely used. The paper mainly analyses PMSM direct torque control (DTC) system, and estimates the speed based on speed sensorless control system, which based on the angle of speed estimation method of the motor rotor flux vector. Use Simulink tool in MATLAB to design and realize the control system simulation, and the simulation results are analyzed. Simulation results show the correctness and feasibility of the speed observation algorithm.

Abstract: Using unified model and theory of rock pressure, the problems, such as caving of stope roof with large mining height and destruction of support, strata movement and surface subsidence, are unified analyzed and researched. The results show that: pressure shell is dynamic shell, which moves forward with the propulsion of working face; with the increase of mining height on the face, the height of fracture zone in coal seam increases, not continuously, but jumpily; with the increase of mining height, support load rises, but the degree of this rise decreases gradually, increased degree of immediate roof weight should be greater than that of given deformation pressure. The results provide necessary basis for reliability of hydraulic support on the working face with large mining height and safety work in the underground.

Abstract: This paper presents a self motion and rotation video nodes coverage algorithm. Through software simulation and calculation, building hardware experiment platform, the block field and the overlapped field avoid experiments, It shows that the algorithm can makes the node identify and avoid the block field itself, avoid block and towards the angle of rotation, and reduce the neighbor node area of ​​the overlapped field, and obtain better coverage rate and monitoring results. It enhanced the underlying control techniques for the wireless sensor networks and self-organizing ability, so as to make the wireless sensor network more suitable for the battlefield environment.

Abstract: For the vibration noise problem of strap-down inertial navigation system in the vehicle, a better vibration damping system was designed. Based on the vibration characters of the vehicle environment, a vibration damping model fitted the SINS in the vehicle was presented; and then the mechanism of vibration damping system was designed especially; and then the design of vibration damping system was verified by using of the dynamic characteristic analysis, On the basis of the above analysis, the overall structure of actual vibration isolation system was built, and then the test for the vibration isolation system was made, the results show that the micro-isolation system for the SINS system vibration and noise has a better inhibition effect, and the applicability and the dependability of the vibration damping system is verified by the test results, which provides reference basis for the design of the strap-down inertial navigation damping system in the land vehicle and provides techniques for the better application of SINS in other fields.

Abstract: Multiple antennas at the transmitter and receiver have the potential to either increase data through spatial multiplexing or enhance the quality of transmission through exploitation of diversity. In this paper, based on studying proceeding of MIMO system, we propose a multi-service preceding algorithm. It makes sure different kinds of service have different SINR due to power allocation. The complex problem is decomposed into two separate steps. First, we achieve transmit vector for each user according SLNR to suppress CCI and noise. Then, we allocate the transmit power for users to satisfy SINR at receive end. Numerical simulation illustrates the effectiveness and support the use of multiple services in maximizing data rate and fairness among users.

Abstract: Firstly, the thesis analyzes the basic concepts and features of X3D virtual reality modeling language (VRML), X3D is 3D graphic criterion that is follow on, extensible. Secondly, the thesis presents the application frame of VRML in B2C Electronic Commerce systems. By using the technology of VRML, such as the 3D modeling technology, interactive technology and database access technology combined with ASP, the E-commerce system can connect business and customer. The B2C E-commerce platform based on X3D/VRML technology has the trait of instant, 3d, interactive and verisimilitude, provide enhanced receptivity and interactivity for E-commerce. With the organic integration of E-commerce system and VRML technology, the competitiveness of E-commerce will be improved. Virtual 3D B2C E-commerce system will be the platform for enterprise informatization.

Abstract: Based on the theory of direct torque control, the simulation model of asynchronous motor is designed to solve two problems. The one is that asynchronous motor in high speed, if a single circular flux control method used, its switching losses will be great; the other one is that asynchronous motor in low speed, if a single hexagonal flux control method used, it will make a large harmonic current. So double modes are used in solve problems together in this paper. That is when asynchronous motor runs at low speed circular flux control strategy is adopted, and when it runs at high speed hexagon flux control strategy is adopted. Auto-switch between circular flux control strategy and hexagon flux control strategy is achieved. Simulation results show that not only the harmonic current can be reduced, and the switching losses are reduced effectively by smooth switching the two control strategies.