Advanced Materials Research Vols. 430-432

Abstract: Since the classification of finite simple groups completed last century, the applications of group theory are more and more widely. We first introduce the connection of groups and symmetry. And then we respectively introduce the applications of group theory in polynomial equation, algebraic topology, algebraic geometry , cryptography, algebraic number theory, physics and chemistry.

Abstract: In order to improve surface characteristics of carbon fibers, using nickel granules as catalysts, nano carbon with different morphologies was deposited in-situ on the surface of carbon fibers by the method of Chemical Vapor Deposition (CVD). The observations by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) indicated that keeping the excellent performance of plating nickels catalyst and a suitable deposition rate of Pyrogenation Carbon (PyC) are the key factors for getting Carbon Nanotube and Carbon Nanofiber (CNT/CNF). In this experiment, the optimum operation conditions are: plating time at 5min, deposition temperature at 1173K, deposition time at 2 hours, flow of C3H6, H2 and N2 at 30, 200 and 400ml/min respectively, deposition pressure at 700-1000Pa. Evolution rules of nano carbon are explained in growth mechanism of Catalytic Chemical Vapor Deposition (CCVD).

Abstract: Z-source inverter main-line voltage has a fluctuation and its frequency is same with the second harmonic of output sine wave, it will increase the second harmonic content of output which affecting the performance of the inverter. Introduced the topology and control method of Z-source inverter. By modeling the Z-source inverter, analyzed the reason of DC voltage fluctuation. Proposed the method to weak the fluctuation based on circuit design. By Comparing the simulation results of main-line voltage under various circuit parameters, verified the effectiveness of this method.

Abstract: Upon the traditional wind-solar hybrid distributed generation system,a single-phase microgrid experimental system platform has been built based on the DC bus,Z topology was used to increase the energy utilization ratio. On the basic of realizing the maximum power point tracker of the new energy, different microgrid controlling strategy has been designed to apply to the island and grid connected operation mode: in the cases of island running, master slave control mode will be utilized in the system and the battery will be used as the main control unit to provide the reference voltage; on the other hand, a control method which can merge the generation into the grid as much as possible will be adopted in the case of grid connected. By the use of system model, the simulation of the two operation mode switch state and power flow has been done and the feasibility and effectiveness of the control strategy can be guaranteed,it also has been verified by the microgrid experimental platform.

Abstract: At present the mostly used land alteration survey method of direct field surveying investigation has the shortcoming of the separation of internal and external operations. This paper puts forward an internal and external integration of land alteration survey modes of PDA + GPS + ArcPAD. On the basis of demand analysis and logical structure design, the paper puts forward a land alteration data structure for the storage of PDA, studies a development method for system implementation, and further explores the solution to the problem of coordinate conversion in the GPS collection. This study is helpful for the changing of the current alteration survey mode, improving work efficiency, and reducing the error caused by the separation of internal and external operations, etc.

Abstract: The main defect of shrink flanging wing rib is wrinkling in rubber bladder hydroforming. In the aeronautical field, the side blank holder is usually used to avoid wrinkling. In order to obtain appropriate parameters of side blank holder, it be carried out that the simulation analysis for the process of the high hydraulic press rubber forming processes of high shrink flanging with side blank holder by the ABAQUS finite element software. Besides, the corresponding experiments verified also be implemented. The research results show that the sheet metal tends to wrinkle along with decrease of the blank lap width and increase of these parameters such as the distance between side blank holder and die, the dip angle and fillet radius of the side blank holder.

Abstract: In order to fully utilize the spectrum resource, dynamic spectrum access becomes a promising approach to increase the opportunity of spectrum access with the rapid development of cognitive radio. However the performance of cognitive radio networks (CRN) is considerably constrained by its limited power, memory and computing ability. Fortunately cloud computing, which is the highlight of current research, has the potential to make up for the disadvantages because of its vast storage and computing capacity. In this paper we will discuss the convergence of spectrum sharing and cloud computing from several aspects including model, advantages and challenges. A spectrum sharing model based on cloud computing (SSC) will be introduced.

Abstract: The flow stress behavior of nanometric Al₂O₃ particulate reinforced Al alloy composites were investigated using thermal simulation machine Gleeble-1500. Microsturctural analysis were carried out on optical microscopy. The results showed that the flow stress increased with increasing strain rate and decreased with decreasing temperature. Dynamic recovery and dynamic recrystallization occurred during hot compression of the Al composites. The grain size increased with increasing temperature (590k-710k) and decreased at 750k due to dynamic recrystallization. The grain size decreased with increasing strain rates at 750k.

Abstract: Most existing real-time data compressing algorithms are focused on dynamic and inconstancy of the process data, but a basic observation is ignored with some unexpectedness: on condition that sampling interval is not large, difference between amplitudes of real-time process data from two neighboring samples is relatively small, and most of data amplitudes are in the same range. In this paper we propose a compression algorithm based on the observation and experimentally evaluate the proposed approach and demonstrate that our algorithm is promising and efficient.

Abstract: The deep drawing process is one of the important sheet-metal forming processes. Using this operation, many parts are manufactured in various industries. With this regard, the numerical simulations of a kind of coated sheet deep-drawing process were conducted using LS-DYNA in this paper. The model takes into account the coating/substrate composite may delaminate or crack during drawing, the combination of coating and substrate was defined as tied with failure contact. The results of the simulations revealed that the substrate (steel sheet) and the nickel coating did not delaminate at the interface. Furthermore, it was found that the punch-nose radius is the danger zone for the break and at this zone, the thickness of the coating was thinner than the substrate, some experiments were done to validate the simulated results. At last, the influences of friction coefficients were analyzed and the result that greater friction coefficients will lead to increase the tendency of crack was attained.