某毫米波雷达发射机的热设计

介绍了一种车载毫米波气象雷达发射机的热设计.该发射机野外环境下工作时处于无人值守状态,需要做好野外防护工作,同时,该发射机随天线转动,尺寸要求严格且只能采用风冷.全密封的结构设计、模块化的组件设计及冷板技术的应用,使得该发射机既满足了野外工作的要求,又具有良好的散热性能.     

Binding nature of polystyrene and PVC 50:50% with CP and NP 50:50% ion exchangeable,mechanically and thermally stable membrane

Organic polymers with inorganic materials make a flexible and thermally stable composite ion exchangeable membrane. Such composite was effectively prepared by a sol–gel process. Polymers focus the binding as well as flexibility where as inorganic materials provide the ion exchange property, thermal stability and performance. TEM/SEM-supported EDS, XRD, FTIR and TGA/DTA characterization were used to show the structural configuration and thermal property. Through these above studies it is clear that the membrane has smooth, porous, cracks free and breakage free surface and it was found to be cation-selective nature. To show the theoretical value of ionic potential Teorell–Meyer–Sievers method was used which helps to obtain other parameters of composite membrane.     

Numerical simulation of asymmetric flow of coupled heat and mass transfer in a square cavity

The heat and mass transfer of fluid in a square cavity with a solutal and thermal source is numerically investigated. For different Rayleigh numbers, buoyancy ratio, Soret and Dufour numbers, the bifurcation characteristics of heat and mass transfer in a symmetrical square cavity are studied systematically. The results show that there is a critical Ra_c for onset of bifurcation that changes the fluid flow pattern. When Ra < Ra_c, the streamline, temperature and concentration are symmetrically distributed; when Ra > Ra_c, the transition from a symmetrical state to a stable asymmetric state is observed. The fluid is more prone to bifurcation with increasing of buoyancy. An increment to the Soret and Dufour effects enhances heat transfer symmetry and increases the critical Rayleigh number for breaking symmetry.     

Plasticizing effect of biodegradable dipropylene glycol bibenzoate and epoxidized linseed oil on diglycidyl ether of bisphenol A based epoxy resin

Major limitation for use of epoxy thermosets in engineering applications is its sudden brittle failure. In the present study dipropylene glycol dibenzoate (DPGDB) based plasticizer is used to modify diglycidyl ether of bisphenol A (DEGEBA) based epoxy resin system via simple blending technique. Bio-based epoxidized linseed oil was also used to modify epoxy resin system and compared with DPGDB modified resin. For DPGDB modified resin storage modulus and loss modulus of the epoxy system modified with 10% plasticizer increased by 7.54% and 12.24%, respectively. The primary mechanism responsible for such behavior is improved crosslinking density. With 5% plasticizer loading, flexural strength increased by 21%. There was an improvement of 312.74% in strain at failure for 10% plasticizer loading, while preserving its mechanical strength. It was found that DPGDB based modification was better than epoxidized linseed oil modification.     

Isobaric thermal expansivities of mixtures ofm-cresol and quinoline from 0.1 to 400 MPa at 303 to 503 K

Isobaric thermal expansivities, α _p (p, T), of five binary mixtures ofm-cresol with quinoline (0.1499, 0.2998, 0.5005, 0.6325, and 0.8501 mol fraction ofm-cresol) were measured in a pressure-controlled scanning calorimeter over the pressure range from just above the saturation vapor pressures to 400 MPa, and at 303.15, 353.15, 403.15, 453.15, and 503.15 K. Molecular association ofm-cresol with itself and ofm-cresol with quinoline exerts large effects on the pressure and temperature behavior of α _p isotherms. The extent of association changes significantly with conditions in all except the 2∶1 mixture as demonstrated by the crossing of isotherms at lower pressures as the temperature increases. In the 2∶1m-cresol quinoline mixture the extent of association is not perturbed significantly by temperature change and the mixture behaves like a simple liquid, exhibiting a unique crossing point of α _p isotherms.     

Thermal conductivity measurements and molecular association in a series of alcohol vapors: Methanol,ethanol, isopropanol,and t-butanol

Thermal conductivity measurements on the vapors of methanol, ethanol, isopropanol, and t-butanol are reported as a function of temperature (330–420 K) and pressure (11–240 kPa). The thermal conductivity versus pressure isotherms for all four alcohols exhibit upward curvatures at the lower temperatures and nearly linear increases at higher temperatures. This behavior is indicative of a dimeric species and one or more polymeric clusters in the vapor in addition to the monomer. Quantum mechanical calculations have indicated that tetramers are the most likely polymeric species. Detailed analyses of the data provide thermodynamic data (H,S) for the dimerization and tetramerization reactions and show interesting correlations with the size of the monomer unit.     

Thermal decomposition of SRC-II middle distillate under surface vaporizing conditions

Decomposition of SRC-II middle distillate under surface vaporizing conditions was studied as a function of temperature (heating rate), vapour phase residence time and oxygen level. The stressed and unstressed fuel was analysed by capillary gas chromatography. Decomposition was found to be greatest at low temperature. Boiling mode did not appear to affect the extent of decomposition. Decomposition was weakly related to chemical class and strongly related to component volatility. The effect of gas phase residence time and oxygen level were negligible at the conditions studied. It is concluded that decomposition occurs primarily within the liquid and at the vaporizer surface.     

高铝质强化日用瓷釉料

通过调整软质熔剂和硬质熔剂的种类和数量 ,研制出了适合刚玉质强化瓷的釉面硬度 7373MPa、白度 75 .9%、光泽度 89.3%且高热稳定性的透明釉料