PR状态方程的二元混合制冷剂热力性质计算

基于PR状态方程法和剩余函数法建立了混合制冷剂在过冷区、两相区以及过热区的热力学参数计算模型,将混合制冷剂R410A的计算结果与NIST数据库进行比对以验证模型精度.在此基础上,对二元混合制冷剂CO2/R600a(33.546/66.454,mass％)在不同相区的热力性质进行了推算,其计算结果可以用于以CO2/R600a为制冷剂的制冷系统的热力计算分析和性能优化.     

Thermal,mechanical, and morphological properties of soybean oil-based polyurethane/epoxy resin interpenetrating polymer networks (IPNs)

A series of interpenetrating polymer networks (IPNs) based on epoxy (EP) resin and polyurethane (PU) prepolymer derived from soybean oil-based polyols with different mass ratios were synthesized. The structure, thermal properties, damping properties, tensile properties, and morphology of soybean oil-based PU/EP IPNs were characterized by Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), universal test machine, and scanning electron microscopy (SEM). DSC and DMA results show that the glass transition temperature of the soybean oil-based PU/EP IPN decreases with the increase of PU prepolymer contents. Soybean oil-based PU/EP IPNs have better damping properties than that of the pure epoxy resin. The tensile strength and modulus of PU/EP IPNs decrease, while elongation at break increases with the increase of PU prepolymer contents. SEM observations reveal that phase separation appears in PU/EP IPNs with higher PU prepolymer contents.     

极端环境下7055铝合金摩擦磨损及表面质量研究

本文在–60℃和300℃两种极端环境下对经过二次时效处理的7055铝合金进行高速切削试验,采用超景深三维显微系统对刀具磨损形貌进行分析,用探针式三维表面形貌仪对切削加工表面形貌进行分析,并对切削前后的7055铝合金进行TEM微观组织分析,研究了7055铝合金在两种极端环境下的刀具摩擦磨损及表面质量.研究结果表明:在–60℃时,刀具磨损的主要形式为磨粒磨损,并出现崩刃,在300℃时,刀具磨损主要形式为氧化磨损和黏着磨损;在–60℃时,材料经过了深冷处理,硬度、脆性增强,切削加工表面质量较差;在300℃时,材料经过了回归热处理,脆硬性降低,韧性增强,切削过程中不断生成氧化膜,极大程度上提高了表面质量,延长了刀具寿命;–60℃时,TEM微观组织显示,材料弥散相变细小,在300℃时,TEM微观组织显示,材料弥散相出现大量消失,即发生回归现象.     

The Generalized p-Normal Operators and p-Hyponormal Operators on Banach Space

In this paper, the authors discuss the generalized p-normal and p-hyponormal operators on Banach space. Some results in this paper are the generalization of Sen’s results on generalized p-selfadjoint operator and some open questions of Sen’s are answered. For the generalized p-normal operator’s, the following formulae are obtained: r(T)=||T||,||(T-\Lambda I)^-1||=\frac{1}{dist(\Lambda,\sigma(T))}.     

P-type 3C-SiC nanowires and their optical and electrical transport properties

We report for the first time the fabrication of p-type SiC nanowire field-effect transistors (FETs) using an individual Al-doped 3C-SiC nanowire with a single crystalline structure. The Raman spectroscopy of the as-grown p-type wire indicates that the linewidth and peak intensity of LO-phonon bands are sensitive to temperature variations.