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1.
Power-law exponents are derived for the anomalous thermal properties of solids in which crystal defects act as the centres of nucleation and growth for the transition to the molten or liquid crystalline state. The predictions are borne out by piezothermal or calorimetric data on n-hexadecane, p-azoxyanisole, bismuth and selenium.  相似文献   
2.
3.
《Tetrahedron letters》1986,27(37):4415-4418
1-Aryl(alkyl)-1,2,4 λ3-diazaphospholes are obtained by reaction of the title educts with tris-(trimethylsilyl)-phosphane resp. 1-chloro-2-phenyl-2-trimethylsilyl-1-phosphaethene  相似文献   
4.
Commercial CaO was modified simply with benzyl bromide. The modified CaO had good water resistance, and characterization by FTIR and TG revealed the modifier was chemically bonded to the CaO surface. Commercial CaO and CaO modified with benzyl bromide were investigated as catalysts for the Henry reaction between benzaldehyde and nitromethane. It was found that the catalytic activity of the modified CaO was greatly improved, with high conversion of benzaldehyde to the (E)-phenyl nitroolefin and 1-phenyl-2-nitroethanol, and with different selectivity from commercial CaO. The effect of modification and reaction conditions on yield, selectivity, and mechanism were studied thoroughly.  相似文献   
5.
介绍了PN结物理特性综合实验原理,利用绘图软件Matlab对实验数据进行曲线拟合,得到了PN结伏安特性函数表达式和PN结正向压降与温度间关系的拟合曲线,计算了常温下玻尔兹曼常数和PN结温度传感器灵敏度及T=0 K时的半导体近似禁带宽度。  相似文献   
6.
郭晖 《应用光学》2007,28(1):12-15
为了实现光阴极光谱响应向短波延伸,分析了Ga1-xAlxAs/GaAs三代微光光阴极光谱响应向短波延伸的机理,提出了准禁带宽度的概念,讨论了Ga1-xAlxAs的禁带宽度随铝组份x值的增加而逐渐变宽的变化规律,计算了不同铝组份下光阴极光谱响应的短波限。通过提高光阴极材料的铝组份,做出了宽光谱响应像管,并给出了相应的光谱响应曲线。通过与标准三代微光像管光谱响应对比,发现:所得光谱响应曲线不仅向短波方向得以延伸,而且理论设计与实验结果吻合很好。  相似文献   
7.
Based on the techniques of Hilbert–Huang transform (HHT) and support vector machine (SVM), a noise-based intelligent method for engine fault diagnosis (EFD), so-called HHT–SVM model, is developed in this paper. The noises of a sample engine under normal and several fault states are first measured and denoised by using the wavelet packet threshold method to initially lower the noise level with negligible signal distortion. To extract fault features of the engine, then, the HHT is selected and applied to the measured noise signals. A nine-dimensional vector, which consists of seven intrinsic mode functions (IMFs) from the empirical mode decomposition (EMD), maximum value of HHT marginal spectrum and its corresponding frequency component, is specified to represent each engine fault feature. Finally, an optimal SVM model is established and trained for engine failure classification by using the fault feature vectors of the noise signals. Cross-validation results show that the proposed noise-based HHT–SVM method is accurate and effective for engine fault diagnosis. Due to outstanding time–frequency characteristics and pattern recognition capacity of the HHT and SVM, the newly proposed HHT–SVM can be used to deal with both the stationary and nonstationary signals, and even the transient ones. In the view of applications, the HHT–SVM technique may be suggested not only to detect the abnormal states of vehicle engines, but also to be extended to other fields for failure diagnosis in engineering.  相似文献   
8.
Mesoporous nanocrystalline NiO-Al2O3 powders with high surface area were synthesized via ultrasound assisted co-precipitation method and the potential of the selected samples as catalyst was investigated in dry reforming reaction for preparation of synthesis gas. The prepared samples were characterized by N2 adsorption (BET), X-ray diffraction (XRD), Temperature programmed reduction and oxidation (TPR, TPO) and scanning electron microscopy (SEM) techniques. The effects of pH, power of ultrasound irradiation, aging time and calcination temperature on the textural properties of the catalysts were studied. The sample prepared under specified conditions (pH10, 70 W, without aging time and calcined at 600 °C) exhibited the highest surface area (249.7 m2 g−1). This catalyst was calcined at different temperature and employed in dry reforming of methane and the catalytic results were compared with those obtained over the catalysts prepared by impregnation and co-precipitation methods. The results showed that the catalyst prepared by ultrasound assisted co-precipitation method exhibited higher activity and stability with lower degree of carbon formation compared to catalysts prepared by co-precipitation and impregnation methods.  相似文献   
9.
叶顶间隙尺度的不确定性对压气机性能影响的CFD模拟   总被引:1,自引:0,他引:1  
本文研究了转子叶顶间隙尺度的不确定性对某轴流压气机的气动性能的影响。采用非嵌入式概率配置点法模拟间隙尺度不确定性在流场中的传播。先以二维随机方腔流动为模型,通过与蒙特卡洛模拟进行对比对非嵌入式概率配置点法进行验证。验证后采用该不确定性方法模拟了当叶顶间隙大小服从Beta分布时气动性能及流场参数的变化。  相似文献   
10.
本文介绍一台红外光学材料折射率温度系数测量装置。该装置是由温控系统、精密测角系统、光学系统和电器控制系统等组成的一台高精度全自动化测量系统,采用改进的自准直法测量折射率温度系数值。该装置达到的主要技术指标:工作波长为2~12μm,温度范围为-50~150℃,测量不确定度为3%,可满足各种红外光学材料折射率温度系数测量的要求。利用该装置对红外材料锗折射率温度系数值进行了测量,并对测量数据进行了报道。  相似文献   
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