微扰理论的应用研究(I)——水-正丁醇二元体系热力学计算

本文对流体分子中的色散能和排斥能采用Lennard-Jones位能函数和Barker-Henderson微扰理论进行计算;偶极定向能采用空间取向平均和微扰理论处理,并用Monte Carlo分子模拟数据进行了验证;还考虑了诱导偶极能.在此基础上,计算了H_2O-nC_4H_9HO二元体系液相组分活度系数,结果满意.     

低温快速锌系磷化剂在涂装前处理中的应用

介绍了CZ99-03(3)锌系磷化剂在批量生产中的应用效果,并对工艺管理和磷化故障处理方法作了阐述。     

工程车辆等比三段式液压机械的复合传动

针对目前工程车辆液力机械传动换挡过程中存在的传动比不连续的问题,提出了一种新型的等比三段式液压机械复合传动系的方案,并对其速度特性、动力性、经济性等进行了分析。对比分析液压机械复合传动与液力机械传动的结果表明,液压机械复合传动系统能够自动调节变量泵倾角,实现发动机与动态负载的匹配,传动系统的经济性和动力性均得到了改善,动力特性曲线光滑、平缓,对于改进工程车辆传动系的性能具有重要的现实意义。     

Preparation of M-Ba-ferrite fine powders by sugar-nitrates process

In this paper, fine M-type barium hexaferrite (M-Ba-ferrite) particles were synthesized from sugar and nitrates by simple route, which revealed the feasibility of using sugar as chelating agent in forming solid precursors of BaFe₁₂O₁₉. The effects of factors, such as the molar ratio of Fe/Ba, calcination temperature and time, on the morphology, the phase component and the magnetic properties of M-type barium hexaferrite particles were studied by means of X-ray diffraction, infrared spectroscopy, transmission electron microscopy and physical property measurement system. The results showed that the molar ratio of Ba²⁺ to Fe³⁺ influenced significantly on the formation of the single phase barium ferrite. The hexagonal platelet barium ferrite particles with a specific saturation magnetization of 64.48 emu/g, remanence magnetization (Mr) of 33.84 emu/g, and coercive force (Hc) of 1848.85 Oe were obtained when the molar ratio of Fe/Ba was 11.5 and the calcination temperature was 1100 °C for 2 h.     

The formation of ilmenite FeTiO3 powders by a novel liquid mix and H2/H2O reduction process

FeTiO₃ powder was prepared via a liquid mix and H₂/H₂O reduction process. First, an intermediate compound was synthesized by a liquid mix process. This precursor compound to FeTiO₃ was characterized by thermal analysis (TG/DTA) and Fourier Transform Infrared spectroscopy (FT-IR). Second, the precursor was annealed in the air, H₂/H₂O(g) mixing gas stream, respectively. The obtained powder was characterized by X-ray diffraction (XRD), energy dispersive X-ray analysis spectroscopy (EDAX) and scanning electron microscope (SEM). It was showed that pure and homogenous FeTiO₃ was successfully obtained below 600 °C.     

The ferroelectric and optical properties of (Pb0.92La0.08)(Zr0.65Ti0.35)O3 thin films deposited by radio-frequency magnetron sputtering

Ferroelectric (Pb_0.92La_0.08)(Zr_0.65Ti_0.35)O₃ (PLZT) films have been prepared on Pt/Ti/SiO₂/Si and fused quartz substrates using radio-frequency (rf) magnetron sputtering at a deposition temperature of 650°C. X-ray diffraction analysis shows that the PLZT thin films on platinized silicon are polycrystalline with (100)-preferential orientation. A Al/PLZT/Pt capacitor has been fabricated and it shows that the films have excellent ferroelectric character, with saturation polarization (P _s), remanent polarization (P _r) and coercive field (E _c) of 32.8μC/cm², 24.3μC/cm² and 142 kV/cm, respectively. The PLZT thin films exhibit good insulating property and the leakage current density of the films on platinized silicon is only about 0.86 × 10⁻⁷ A/cm² at 200 kV/cm. By the optical transmission spectra measurements, the energy gap (E _g) of the PLZT films on fused quartz is found to be about 3.54 eV. The optical constants (n and k) of the films in the wavelength range of 250–900 nm are obtained by a Filmetrics F20 reflectance spectrometer.     

深处的激情

在澳大利亚一片森林的深处，当弯曲钢架结构的假日别墅内泛起火光的时候，它确实将世界照亮了，《Wallpaper》总第83期讲述一段深处的激情。[编者按]     

几种常用制冷剂的过冷制冷循环特性分析

详细分析了过冷制冷循环特性和空调常用的四种制冷剂(R22、R134a、R407C、R410A)的过冷度对制冷循环制冷量、耗功和性能系数COP的影响,并拟合了过冷度对循环性能参数影响的关系式。针对冰蓄冷系统给出了过冷度控制数值和冷量提高的程度。     

Performance and optimization of multistage partial parallel interference cancellation for wideband CDMA systems in multipath fading channels

In this paper, a closed-form bit error rate (BER) of hard-decision multistage partial parallel interference cancellation (PPIC) having perfect and imperfect channel estimation for complex spreading code-division multiple access (CDMA) over multipath Rayleigh channels was derived. The effects of receiving BER, power ratio of pilot to data channels, multiple-access interference (MAI) and multipath interference, additive white Gaussian noise, and other factors affecting channel estimation error are analyzed. The expression determining the optimal interference cancellation weight at path level for PPIC is first derived. Then, the oscillatory behavior of user-level-optimized PIC and the convergence of perfect channel estimation PIC and path-level-optimized PIC are validated. Results indicate that all factors determining the optimal weight certainly affect the BER performance of PPIC and that the lower BER limit of multistage PPIC depends on the adjustable factors, which include power ratio, observation length, and signal-to-noise ratio, and an unchangeable factor, i.e., number of users. In addition, the variance of MAI for complex spreading sequence is obtained, and the analytical expression can also be employed to predict the performance of multicode CDMA.