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4H-SiC substrates and homo-epitaxial layers were obtained using the traditional methods of physical vapor transport and chemical vapor deposition. Defect morphology has been studied using both Synchrotron White Beam X-ray Topography and Monochromatic Beam X-ray Topography. Molten KOH etching method was adopted to further investigate the dislocation behavior mechanisms. Deflected dislocations were observed at the periphery regions in both substrate and epitaxial wafers. 3C polytypes and half loop arrays were observed in the 4H-SiC epitaxial wafer. It is also found that the majority of basal plane dislocations are converted to threading edge dislocations in the epitaxial wafer samples. The proportion of BPD to TED conversion depends on the surface step morphology and growth mode in epitaxial growth which in turn depends on the C/Si ratio. By the optimization of etching time prior to epitaxy and C/Si ratio, high-quality epitaxial wafers with extremely low basal plane dislocations densities (＜0.1 cm-2) was obtained.

The course of electromagnetic fields and waves has properties of abstract concept, strong theory and complex calculation, thus this course is difficult to study and understand, and then is also difficult to teach. In order to make the understanding of the course easier, MATLAB software is used as a platform in classroom teaching of electromagnetic fields and waves. This paper mainly discusses the electrical field intensity distribution of media sphere materials and the properties of electromagnetic wave propagation with MATLAB software. The optical properties of dielectric-metal core-shell multi-layered nano-shell are also studied with Laplace's equation. To enrich the teaching content and improve a better teaching effect, the optical property of nano-materials and electromagnetic wave propagation are visualized with MATLAB software, which makes the properties of nano-materials and electromagnetic wave propagation understand easily.

Recently, there has been an increased interest in optimizing horizontal multi-frac completion technologies used to complete offshore low permeability reservoirs in Western South China Sea, but the high-risk and high operating costs are the key problems to hold back the application of this technology, so the impact of economic factors should be taken into full account before fracturing design. This paper shows an new optimization approach of fracturing design by considering the relationship between economic aspects, reservoir size and fracturing treatment size, each fracturing stage of horizontal well is approximated by a rectangular drainage areas and the unified fracture design method is used to calculate the dimensionless productivity index, and an Optimal Proppant Index Function is established with maximization of economic profit as the objective function, while the Optimal Proppant Index Function is determined, the optimal fracture volume and parameters would be obtained.

In this paper, a camera ranging method for agricultural robot localization in arable farming is described. Three calibration objects in different directions in the field are set. The distances between the robot are calculated, and the calibration objects are used the camera to obtain the robot position. The benchmarking procedure in Matlab includes image binarization of the calibration object and the curve fitting method was used to establish the relationship between the pixels number of the calibration object and the actual distance. The verification results show that the relative error of ranging is less than 1.5%. Furthermore, the camera ranging method for agricultural robot localization is proved to be easy and feasible.

Considering the variable-permeability effect of non-Darcy flow in low-permeability reservoirs, this work set up a two-dimensional model with boundaries. The implicit finite difference algorithm was employed to solve the well test model, and typical curves in log-log scale by considering the effects of variable-permeability and non-Darcy flow were obtained. The results show that, in reservoirs with impermeable boundary, the upturned part of the pressure derivative curve caused by boundary effect will be covered by that of non-Darcy effect, indicating boundary effect is postponed to appear. The more of the non-Darcy effects result in less obvious upturn of the typical curves. The upturn of typical curves and the effect of boundary are enhanced by increasing the numbers of impermeable boundaries or by decreasing the distance from the well to the boundary.

The spring is a high incidence of dust-haze season especially in some mega-cities like Beijing. A complete dust-haze has happened from 19th to 24th April, 2013. Based on 3456 copies of PM2.5 concentration data in Beijing’s 24 monitoring points during the whole dust-haze period, and the weather information over the same period, and the correlation analysis on the dust-haze’s formation, continuous and dissipation process, we point out that PM2.5 concentration distribution has the following features in a spring dust-haze weather in Beijing: (1) dust-haze can be happened in strong wind; (2) PM2.5 concentration has a highest or lowest value during the dust-haze process at some monitoring sites (3) the monitoring sites’ PM2.5 concentration difference is bigger, the biggest can reach more than eight times.

Due to the uncertainty of the factors that influence the network service time and other characters of college student, Bayesian Network is used to model this kind of system. Different algorithms are used for learning Bayesian Networks in order to compare several models. It is suggested that researchers can use Bayesian Networks to explore the potential relationship between variables of complex social problems. The result indicates that learning target and family closeness degree are the key variables which influenced college students network service time. Origin of student and family economy didnt influence college students network service time directly. Schools and community should strengthen the education of college students life planning and communication with parents.

Continuous seasonal drought in past 3 years greatly affects rice production of Yunnan, China. Because upland rice has stronger performance than paddy rice for mountain farming, to develop mechanized production of upland rice is more beneficial to ensure food security of mountainous area. In this study, we investigate and survey traditional upland rice cultivation of peasant household in mountainous rural area of Lancang county, and use Cobb-Douglas production function to analyze the relationship between mechanized and non-mechanized upland rice cultivation. The results show that mechanized upland rice cultivation not only can increase the yield, but also is superior to non-mechanized system in techno-economics. Rational utilizing farm machinery is feasible to upland rice cultivation and will promote the development of the rice production of Yunnan Province.

The article proposed that the green seeing ratio should be introduced in high density planning and design of residential area in China, pointing out that the green seeing ratio is a clear, effective index of strong operational in visual ecological design. It is necessary and feasible that the green seeing ratio as a evaluation index in the planning and construction of high density urban residential area in China. Advocates to take a combination of centralized and decentralized groups-residential areas and other ways of planning that by reducing the area of road, natural green details, take the tortuous roads and other methods can effectively improve the green seeing ratio. Some guidelines being followed in the building layout, open space design, road shape, plant greening in the detail design can effectively improve the green seeing ratio of high density residential area.

A design of mechanical arm for laser weeding robot is described. The long term objective of the project is the replacement of chemical weeding by laser weeding. The distinguishing feature of this design is the use of a mechanical arm, which is equipped with a laser generator and a control center consisted of a single chip microcomputer and two driver hybrid ICs. The mechanical arm comprises two stepping motors vertically linked together. The robot moves ahead one step, the working area of laser generator is divided into 10×10 grids. Through the inverse operation of mechanical arm, the motor displacement angle of each grid is calculated. Mechanical arm turns to designated position if single chip gets weeds position information. The result of the design is a key executive mechanism of laser weeding. The operation error of mechanical arm is analyzed. The arm can point the laser beam towards the target weeds with small error. After the order of the execution areas is optimized, the length of arm moving path is shorter. Analysis of the running track shows that the sequence of execution area is feasible and reasonable.

The dust haze has posed a serious threat to residents physical and psychological health in China. PM2.5 is the main cause of dust haze. Recent studies on the distribution of PM2.5 points out that the uneven distribution of PM2.5 in city small scale landscape like residential area prevails. The landscape pattern, the maldistribution of pollution sources like motorways, architectural layouts, greening rate, plant community are considered to be the major causes. If residential areas site selection and landscape pattern are optimized, combining road network layout, form design, greening rate and building height are planned following design guidelines, the environment quality can be bettered and the exposure to PM2.5 can be reduced.

Direct feedback linearization control was applied to permanent magnet synchronous generator (PMSG) wind energy conversion system (WECS), which was to reduce the cost of wind energy conversion system and improve its performance. The PMSG-based wind energy conversion system was constructed with mathematical models of aerodynamics subsystem, drive train subsystem and simplified electromagnetic subsystem. With feedback linearization control theory based on differential geometry, the coordinated transformation and nonlinear state feedback were obtained and PMSG wind energy conversion system was linearized. With MATLAB/Simulink platform, the model and control strategy was established and the simulation result shows this control system with feasible speed tracking performance, which can effectively implement maximum energy capture.

An automatic watering controller with AT89S52 single-chip microcomputer was developed. According to the moisture condition detected by soil moisture sensor, the system could control the watering quantity by using fuzzy control rules to limit opening and closing time of electromagnetic valve of the irrigation system. Mamdani inference algorithm was employed as fuzzy control model for this closed-loop control system. Soil moisture sensor was put into the substrate for roots growth to obtain moisture information and used as the input. By comparing the water needed for plant growth, water demand and the electromagnetic valve opening and closing time was determined by the single-chip microcomputer program. Centroid method of defuzzification was used to determine the quantitative level of watering quantity. This fuzzy controller was designed by MATLAB fuzzy logic toolbox. The control system was simulated by Simulink. Simulation results show that this control method has good stability.

The ramp B of one overpass was designed as curved steel orthotropic box girder, whose deck was welded with open shaped bulb ribs in the range of driveways. Then, one detailed finite element model was built to simulate the structure. For the two arrangements of bulb towards and back to web in the cantilever, the tangential stresses of diaphragm cutout were compared under the action of vehicle load. In accordance with above research, it can be concluded that the stress will be more reasonable with the bulb back to web. After altering the transverse position of the vehicle load and calculating the tangential stress along the edge of diaphragm cutout, based on further analysis, it’s generally believed that the following two reasons made the arrangement of bulb back to web more appropriate at least. First of all, the diaphragm connected with the rib adjacent to the web could share part of vertical load. What's more, it could increase the distance from the edge of the cutout to the web center. What come next was to change the diaphragm cutout size, and that parameter optimization was carried out. The results show that a radius of 40-50mm is more applicable for the arc on the bottom of the diaphragm cutout.

The key problem to prepare carbon nanotubes (CNTs) reinforced ceramic matrix composites is how to break up massive agglomerates of CNTs and disperse uniformly CNTs. We obtain the CNTs-Al2O3composite powder by shear treatment on melted CNTs-Al2O3-agents mixture. Microstructure observations of CNTs-Al2O3composite powder show that CNTs can be dispersed uniformly by shearing process. The rheological results also affirm the conclusion. According to the rheological theory, we build the ideal dispersion model of CNTs-Al2O3suspension system and discuss the dispersion mechanism.

How to uniformly disperse carbon nanotubes (CNTs) and densely sinter green body are the key issues to prepare carbon nanotubes reinforced alumina (Al2O3) composite. We prepare CNTs-Al2O3 powder by shearing extruding dispersion method, and then obtain CNTs-Al2O3 composite by hydrogen atmosphere pressureless sintering. 93% of the relative increased fracture toughness can be achieved, when the CNTs content of composite is 1%. Because of Absorbing energy by pulling CNTs out from alumina matrix and refining grain by CNTs bundles sitting along alumina grain, the fracture toughness is improved obviously. By XRD and SEM analysis, the residual tensile stress which is caused by embedding CNTs into alumina matrix also plays an important role for the increase of fracture toughness.

In this paper, based on virtual prototype Collaborative Development Platform for Hydraulic support, a new technology way to the design and study of the mining hydraulic support is provided.The function constitute of the platform which can support the whole multi-disciplinary collaborative development procedure of Hydraulic support are given. The Development of Hydraulic support based on virtual prototype Collaborative Development Platform is given, which includes the following key steps: Team member management modeling, Process management modeling and Co-simulation. The development of hydraulic support shows the effectiveness of the virtual prototype collaborative development for hydraulic support.