Advanced Materials Research Vols. 217-218

Abstract: It is significant to scientifically evaluate the thermal insulation solutions used in building envelope. Considering four solutions, a regional suitability evaluation model is established by analyzing some factors such as technology, construction and economy. The evaluation model is based on the analytic hierarchy process, and the weights of performance indices are acquired from Delphi techniques. Combining the qualitative and quantitative analysis, some problems can be found out in the practical application of the solutions. The proposed suitability evaluation model can give scientific evaluation for the application and development of the energy-saving wall materials in hot summer and cold winter zone in China.

Abstract: As Chinese socialist market economy gradually has been improved, there is a lag in the agricultural production.It is a very possible research for the agricultural sector to make agricultural production policies to develop appropriate based on the government control means, consumer behavior, agricultural supply and demand balance, the outside weather conditions and other factors. In this paper, we proposed agricultural early warning system structure and function modules. It is based on the external conditions for agricultural production, agricultural consumer groups, consumer habits, especially focusing on the production and analysis module, analysis module prices and consumer modules.

Abstract: The paper describes a framework for exemplar-based texture synthesis. The main idea is reducing synthesis time consuming and advancing synthesis quality by some optimization methods. Many optimizations such as searching along a spiral path, edge expansion, L2 distance computing predigesting, accelerate synthesis speed and the final results also advanced. Experiments show that synthesis results are quite satisfactory and effective.

Abstract: The global exponential stability for switched neutral systems with time-varying delays and nonlinear perturbations is investigated in this paper. LMI-based delay-dependent criterion is proposed to guarantee exponential stability for our considered systems under any switched signal. Lyapunov-Krasovskii functional and Leibniz-Newton formula are applied to find the stability results. Free weighting matrix and linear matrix inequality (LMI) approaches are used to solve the proposed conditions.

Abstract: By the uses of finite element method and finite volume method, we calculated the solid domain and fluid domain of windward leading edge which is flying under one condition. And the paper proved that heat pipes which covered on the leading edge have effect on thermal protection. The maximum temperature of the head decreased 12.2%. And the minimum temperature of after-body increased 8.85%. Achieving the transfer of heat from head to after-body, the front head of the thermal load was weakened and the ability of leading edge thermal protection was strengthen. The effect of the thickness of heat pipe, black level of covering materials and equivalent thermal conductivity of heat pipes on the wall temperature were discussed for the selection of thermal protection materials of windward leading edge to provide a frame of reference.

Abstract: TiAl/Ti2AlC composites were successfully fabricated by hot-press-assisted reactive synthesis method from elemental powder mixtures of Ti, Al and C. The effect of C addition on the microstructures and mechanical properties of TiAl/Ti2AlC composites was investigated in detail. The results show that the Rockwell hardness, flexural strength and fracture toughness of the composites are modified by incorporation of in situ formed Ti2AlC. When the C content was 0.44 wt %, the flexural strength and the fracture toughness reach the maximum values of 658.7 MPa and 10.03 MPa•m1/2, respectively. The reinforcing mechanism was also discussed.

Abstract: Full dense and highly pure TiAl/Ti5Si3 in situ composite was successfully synthesized by reactive synthesis from the powder mixtures of Ti, Al and Si. The reaction process was investigated in detail by the X-ray diffraction analysis (XRD) and differential scanning calorimetry (DSC). The microstructural characteristics of the TiAl/Ti5Si3 in situ composite were also studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the as fabricated composite possesses three phases, namely, TiAl, Ti3Al and Ti5Si3. The matrix phases are mainly equiaxed TiAl with a minor lamellar Ti3Al phase. Ti5Si3 particles with size less than 1 μm are distributed uniformly in matrix grains as a reinforcing phase.

Abstract: Poly(ethylene glycol)-carbon nanotubes (PEG-CNTs) were successfully prepared. Results of four-ball tribotester indicated that both the load-carrying capacity and anti-wear of the PEG-CNTs were superior to those PEG owing to the additive reinforced by CNTs. The nanocomposite thin films have been fabricated on mica by spin casting technique. AFM investigations provide insights into the roughness and microtribological properties on a micro scale. The polymer in the film is the guarantee of flat surface, and the rigid CNTs enhance load-bearing property of the thin film.

Abstract: With the unchanged thermal gradient and withdrawal speed, the effect of melt overheating history on the microstructure of Ni-base single crystal superalloy is investigated. The results show that the dendrite structure and γ' phase in interdendritic area is obviously refined when overheating temperature increased from 1500 °C to 1640 °C and then to 1780 °C. However, the microstructure is coarsen with the holding time is increased from 30 min to 45min and then to 60min when melt is overheated at 1780 for 30min.

Abstract: Materials used for microelectronic devices need to have more multifunctional properties, such as excellent mechanical, thermal, and dielectric properties at the same time. In this paper, copper phthalocyanine/polyimide (CuPc/PI) composite films with high dielectric permittivity (k=9.9 with the volume fraction of CuPc is 28% at 100Hz) and high thermal stability are prepared by an in-situ polymerization process. The composite films show good dielectric properties and is almost independent of frequency in the measured frequency range up to 104 Hz. Notablely, The composites remain stable until the temperature reaches 500oC. In addition, the inclusion of CuPc slow down the composite degradation rate when the temperature is higher than 550oC. The resultant high performance of such polymer composites makes them attractive for technological applications in flexible high-k components.