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Background Blumeria graminis f. sp. tritici (Bgt), the causal agent of wheat powdery mildew severely affects yield security wheat production in China. Understanding the virulence structure and genetic variations of this pathogen is important for breeding wheat lines resistant to wheat powdery mildew. However, information related to genes controlling resistance remains elusive. This study analyzes the virulence structure and the genetic diversity of pathogenic Bgt populations isolated from northeastern (Liaoning, Heilongjiang) and northwestern (Gansu) China, two representative wheat producing areas, on 37 wheat cultivars each carrying a known powdery mildew resistance (Pm) gene. Results Bgt isolates from northeastern China show higher frequencies of virulence genes than populations from Gansu Province. Many of the known Pm genes failed to provide resistance in this study. However, Pm21 provided 100% resistance to all isolates from all three provinces, obtained during two consecutive years, while Pm13 provided 100% resistance in Gansu. Pm13, Pm16, Pm18, and Pm22 also showed partial resistance in northeastern China, while Pm16, Pm18, Pm22, Pm5 + 6 and Pm2 + 6 +? maintained some resistance in Gansu. Genetic diversity among populations in different regions was detected by cluster analyses using expressed sequence tag-simple sequence repeat (EST-SSR). When the genetic similarity coefficient is relatively high, populations from the same regional origin are mostly clustered into one group while populations from different regions exhibit large genetic differences. Conclusion Pm21 remains the best choice for breeding programs to maintain resistance to Bgt. Only 58% of the isolates tested show a clear correlation between EST-SSR genetic polymorphisms and frequency of virulence gene data.

The effect of the sintering temperature, quartz and sodium phosphate content on the core strength,shrinking percentage and solubility of alumina matrix ceramic cores was investigated．The results show that：the more the quartz is, the higher of the bending, tensile strength at room temperature of core are;It has the extreme point when quartz is 10wt%, then decreases slightly.The shrinkage rate and the room temperature strength of core increases with the rising of sintering temperature,but decreases with the increasing of content of sodium phosphate. Furthermore, the effect of the sintering temperature,quartz powder and sodium phosphate content on solubility of core was discussed.

According to the energy constraints characteristics of Wireless Sensor Networks, how to optimize clustering, reduce the node energy consumption and balance the network energy dissipation is an main target, we proposes an Energy Efficient Clustering protocol based on Niching Particle Swarm Optimization (NPSO-EEC), the algorithm considers the factors such as the nodes residual energy and neighbor nodes status, etc. The simulation results show that the proposed protocol can balance the nodes energy consumption effectively, reduce the sensor nodes death rate, and prolong the network lifetime.

We analyze the solar-powered wireless sensor network's energy gathering techniques, aiming to prolong the lifetime of wireless sensor network. We summarize wireless sensor network node's energy autonomy system, its characteristics in detail and new technology adopts, provides some suggestions and new ideas in the design and research of solar-powered wireless sensor networks.

Based on the summary of Wireless Sensor Networks' characteristics, we analyze the Wireless Sensor Networks' applications and its development trends, and put forward the factors that restrict the development of Wireless Sensor Networks. In this paper, we analyze the Wireless Sensor Networks development opportunities and challenges in the future, and provide some new ideas and enlightenment for the comprehensive development and widely used.

The undercooling behaviour of the superalloys IN 939 and CMSX-6 during the isothermal heating and cooling processes was investigated. Under the same process conditions, the undercoolability of CMSX-6 was measured to be 50.4 K while that of IN 939 was only 10.1 K. This great difference can be attributed to the amount of alloying elements. During Bridgman directional solidification using the same process parameters, the used alloys exhibited a very different tendency to form structure defects. While the CMSX-6 components were nearly defect-free, the IN 939 samples of the same geometry were very prone to stray grain formation. This difference can be attributed to the different undercoolability of the investigated superalloys. Therefore, the undercoolability is an important factor of castability and the cast quality of single crystal components can be effectively improved by increasing the undercoolability of the superalloys.

In locally long fiber reinforced aluminum parts two types residual stresses exist. They are the microscopic residual stress between fiber and matrix and the macroscopic residual stress between reinforced and unreinforced zones. The residual stresses between fiber and matrix in γ-Al2O3 long fiber reinforced aluminum alloy Al-6-1-1 were measured with X-ray Diffraction process as well as simulated with FEM method. The results indicated that the residual stresses in both fiber and matrix were distributed very unequally. The maximum tensile residual stress occurred at the boundary in the matrix and the maximum compressive residual stresses occurred near the boundary in the fiber. The macroscopic residual stresses between the reinforced and unreinforced zones were also measured with borehole method as well as simulated with FEM. It was found that the macroscopic residual stresses at most locations in both the reinforced and unreinforced zones were not harmfully high. However in both reinforced and unreinforced zones there were small sub-zones of very large tensile residual stresses.

During single crystal (SC) solidification in turbine blades of superalloys, grain defects often form in the platform region with abrupt variation in cross-section. In order to reduce grain defects induced by component geometries, a Heat Conductor (HC) technique was developed and applied to the production of SC turbine blades. The corresponding ceramic shell moulds were produced by a modified investment casting procedure. The heat conductors with excellent heat conductivity were inserted close to the inner corners of the platform, to effectively extract the local heat during directional solidification. Both computer simulation and temperature measurements have shown that this technique is able to produce a clear improvement of the thermal condition in the critical region of the components. The SC growth in the blade body can spread into the platform more quickly before the melt at the extremity becomes deeply undercooled. Microstructure investigations reveal a remarkable reduction in grain defect formation, providing confirmation of the effectiveness of the HC technique in improving the casting quality of SC components.

Freckle occurrence is known to be dependent on the casting size and the superalloy components with large cross section are more prone to freckle formation. In our directional solidification experiment of superalloys freckles are observed in some thin samples, while some significantly thicker samples in the same shell mould cluster remain freckle free. The EBSD analysis shows that the samples with freckles have a good axial orientation, while in freckle free samples the primary dendrite stems diverge from the sample axis. In an analogue system the flow behaviour through a mushy zone was simulated, in which the dendrite network was placed in different orientation. The dendrite array shows the lowest resistance to the vertical melt flow. As the dendrite alignment diverges from orientation, the flow speed slows down and reaches the minimum at the orientation. This orientation effect of the interdendritic permeability explains well why the crystal orientation plays such an important role in the occurrence of freckles in superalloy castings.

In the present work the influence of process parameters on freckle formation in superalloy CMSX-4 is demonstrated. A series of experiments were carried out using a laboratory furnace of Bridgman-type in which the temperature gradient G and solidification velocity V can be precisely controlled and individually varied over a wide range. On the etched surface and longitudinal sections of the quenched samples the formation and evolution of freckles were investigated. The initiation position of the freckles within the mushy zone was then determined. Based on the experimental observations a complete diagram was plotted to indicate the probability of freckle occurrence which is related to solidification parameters G and V. In this freckling map the freckle region is delimited by different criteria. Freckles arise only within a certain G/V-range for columnar dendrite growth; otherwise the solidification structure changes into cellular or equiaxed structure, depending on whether G/V-value increases or decreases. In comparison with the well-known freckling map of Copley et al., some new freckle-free regions are proposed. It is interesting to note that the freckle formation is also suppressed at very low cooling rates. In addition, the initiation position of the freckle formation in the mushy region was determined to be less than 2 mm below the dendrite tip of the solidification front.