汽轮发电机组基础动力分析方法与标准综述

近年来,国内引进了多种大容量汽轮发电机组,同时国内设计院等相关单位也在参与国外工程的设计和建设。为此,有必要掌握国内外流行的大型汽轮发电机组基础设计标准中的动力分析方法。介绍了汽机基础结构分析用的4 种计算模型,强迫振动分析的扰力取值和阻尼系数比,以及强迫振动控制标准,最后,概述了各种标准的动力分析方法。     

干燥温度对醇提余甘子多酚含量及其抗氧化活性的影响

为探究干燥方式(冷冻真空干燥、热风干燥)和干燥温度(冻干、40、60、80、100℃)对余甘子多酚活性成分的影响,利用高效液相色谱(HPLC)检测不同干燥处理后余甘子醇提液中没食子酸、柯里拉京、鞣花酸、诃子鞣酸的含量,并测定其总多酚含量和抗氧化活性(ABTS+自由基清除能力和DPPH自由基清除能力)。结果表明,随着干燥温度的升高,余甘子中没食子酸、柯里拉京、鞣花酸、诃子鞣酸含量均增加,100℃热风干燥时达最高(分别为12.83、6.04、16.89、13.48 mg/g)。总多酚含量与抗氧化活性(ABTS+·清除能力和DPPH·清除能力)也随干燥温度升高而增加,80℃热风干燥时达最高(分别为200.92、695.76、725.05 mg/g)。此外,试验结果表明柯里拉京、诃子鞣酸和总多酚的含量与余甘子醇提样品ABTS+自由基清除能力呈显著或极显著正相关(P<0.05或P<0.01)。本次试验中,与热风干燥相比,冷冻干燥的样品中4种多酚单体和总多酚含量以及抗氧化活性无明显优势,综合考虑,80℃热风干燥为余甘子的最佳干燥方式。     

一种无烟气烟草制品秀爽的吸入毒理学评价

  目的  对一种无烟气烟草制品秀爽进行吸入毒理学评价。  方法  120只SD大鼠根据体重分性别随机分4组:对照组（n=30）、低剂量组（n=30）、中剂量组（n=30）、高剂量组（n=30）。对照组为空气暴露组,实验组吸入暴露剂量分别相当于人吸入暴露量的10倍、30倍、100倍。每天暴露1次,连续暴露14 d,恢复4 W。暴露期及恢复期每天观察各组大鼠一般状况、精神状态,腺体分泌,皮肤和粘膜颜色,呼吸状态,粪便性状,生殖器等情况及其它非常态症状。  结果  暴露期及恢复期,各组大鼠一般状况良好、自主活动正常、皮肤被毛清洁,亦未见其它毒性反应;各组大鼠体重正常增长,对照组和暴露组雌、雄鼠体重增长趋势未见显著性差异;眼科检查与大体解剖均无异常。  结论  秀爽对大鼠生长发育、生长代谢、重要脏器未造成影响。      

Local polynomial estimator for narrowband interference suppression in TH-UWB systems

Ultra-wideband (UWB) technology has been considered to offer an innovative solution for future short-range high-speed wireless communications. These systems use very low transmission power, spread over a bandwidth of several gigahertz. The very low transmission power and the large bandwidth used, enable UWB radio systems to co-exist with other narrowband systems over the same frequency band without interfering the narrowband systems. Nevertheless, these narrowband systems may cause interference which may jam the UWB receiver completely. Since standard narrowband interference suppression techniques are not applicable, techniques for interference suppression have to be developed. In this paper, the method of the local polynomial estimator in time-hopping impulse radio (TH-IR) for UWB communication is considered, which should not estimate any parameter of channel. And the narrowband interference (NBI) is modeled as a stationary process. Theoretical analysis of this algorithm reveals that it can eliminate the narrowband interference almost completely and can be computed by simple expression. Moreover, the sampling rate is very low.     

Notes on “the lower and upper approximations in a fuzzy group” and “rough ideals in semigroups”

In this note, we show by examples that Propositions 2.4 and 2.5 in [N. Kuroki, P.P. Wang, The lower and upper approximations in a fuzzy group, Information Sciences 90 (1996) 203] and Theorem 2.5 in [N. Kuroki, Rough ideals in semigroups, Information Sciences 100 (1997) 139] are incorrect and offer their modified versions.     

超声辅助提取红阳猕猴桃茎多糖的工艺研究

研究了红阳猕猴桃茎多糖的超声辅助提取工艺,通过单因素实验分别考察了液料比、提取时间、提取温度和提取次数对红阳猕猴桃茎多糖提取率的影响,并通过正交实验确定最优提取工艺为：液料比50 ∶ 1（mL∶ g）、提取时间40 min、提取温度60℃、提取次数3次,在此条件下,红阳猕猴桃茎多糖提取率为2.84％,较常规加热法（2.37％）提高了0.47％.     

Effects of MnO2 and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba0.85Ca0.15Ti0.90Zr0.10O3 lead-free ceramics

Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ + xmol% MnO₂ lead-free ceramics have been prepared by a conventional sintering method and the effects of MnO₂ and sintering temperature on microstructure, ferroelectric, and piezoelectric properties of Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ lead-free ceramics have been studied. The addition of 0.25 mol% MnO₂ promotes grain growth, improves the ferroelectricity of the ceramics and strengthens ferroelectric tetragonal–ferroelectric orthorhombic phase transition near 40 °C. Because of the coexistence of tetragonal and orthorhombic phases and the combinatory effects of soft and hard doping of Mn ions, the ceramic with x = 0.25 exhibits the optimum piezoelectric properties (d ₃₃ = 306 pC/N and k _p = 42.2 %, respectively). Excess MnO₂ inhibits the grain growth and degrades the ferroelectric and piezoelectric properties of the ceramics. Sintering temperature has an important influence on the microstructure, tetragonal–orthorhombic phase transition near 40 °C, ferroelectric and piezoelectric properties of the ceramics. The increase in sintering temperature leads to large grains and more noticeable tetragonal–orthorhombic phase transition near 40 °C, enhances ferroelectricity and thus improves effectively the piezoelectricity of the ceramics. The Ba_0.85Ca_0.15Ti_0.90Zr_0.10O₃ ceramic sintered at 1350 °C possesses the optimum piezoelectric constant d ₃₃ value of 373 pC/N.     

Corrosion behaviour of Al–29at%Co alloy in aqueous NaCl

Microstructure and corrosion behaviour of a binary Al–29 at%Co alloy have been studied. The alloy was prepared by arc-melting of Al and Co in high purity Ar and rapidly solidified on a water-cooled Cu mould. The alloy chemical composition and microstructure were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Furthermore, the corrosion behaviour was studied by potentiodynamic polarization in aqueous NaCl (0.6 mol dm⁻³) at room temperature. The alloy was found to consist of three phases: hexagonal Al₅Co₂, Z-phase and AlCo (β). The corrosion resistance of different intermetallic phases is characterized. The results are compared to previously published results of Al–TM (TM = transition metal) alloys.     

Room-temperature synthesis of crystallized LiCoO2 thin films by electrochemical technique

LiCoO₂ thin films have been directly synthesized on cobalt substrate in LiOH solution at room temperature by electrochemical method. The obtained LiCoO₂ thin films were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of electrochemical reaction time, current density and concentration of LiOH solution on the crystal structure and morphology of the obtained LiCoO₂ thin films was discussed emphatically. Our results show that the as-synthesized LiCoO₂ films all are pure hexagonal structure. The crystallinity, densification and uniformity of the films increase with increasing electrochemical reaction time, current density as well as concentration of LiOH solution and then decrease. The preferable electrochemical reaction conditions were optimized as: electrochemical reaction time is 50 h, current density is 1 mA cm⁻² and concentration of LiOH solution is 3 mol dm⁻³.