300MW汽轮机末级采用弯叶片对反力度的影响

本文通过求解多级透平Ｓ２流面的欧拉方程组和计算三维无粘环形叶栅排的三阶精度ＴＶＤ格式的数值方法、以及模化吹风实验,对３００ＭＷ汽轮机末级在不同侧型面以及弯角的情况下反力度的变化进行了全面的分析．讨论了在Ｄ／ｌ较小的透平级中不同侧型面、不同倾角、以及子午面对反力度影响的新的物理现象．给出了在Ｄ／ｌ较小的透平级中采用不同的侧型面对反力度的影响规律．     

高能重离子碰撞中末态粒子的关联度与集合侧向流

提出了关联度概念,采用粒子群关联函数方法对Bevalac流光室1.2A GeV Ar+BaI₂碰撞事件中关联度不同的粒子对集合侧向流的作用进行了研究.研究表明:关联度是描述集合侧向流性质的一个重要参量.少数关联度较大的粒子(或碎片)可以产生集合侧向流效应,但高阶集合流关联却不受其支配,而是关联度不同的多数粒子(或碎片)集体贡献的结果.     

On a question of Brézis and Nirenberg concerning the degree of circle maps

One considers maps F of the unit circle into itself. For maps of class C ¹ or in the Sobolev class H?, the degree or winding number is equal to the sum of the series in terms of the Fourier coefficients c _n of F (e ^it ) = f (t). Here one studies the possible relation between this series (in symmetric arrangement) and the degree for arbitrary continuous maps F. It is shown that for such maps, the series may fail to be convergent or Abel summable. If the series does converge, the sum may have any value different from the degree of F.     

Influence of laser heating on the optical properties of a superhigh-modulus organoplastic material

The degree and azimuth of polarization and the indicatrix of the intensity of radiation (λ=0.63 μm) reflected by the surface of a monodirectional superhigh-modulus organoplastic material after structural transformations induced in it by CO₂-laser radiation are measured. It is shown that the space-polarization characteristics of the radiation reflected by the organoplastic material charred as a result of laser heating correspond to the parameters of radiation scattered by a nontransparent material with an isotropic surface in the approximation of geometrical optics. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 635–639, September–October, 1999.     

线性啁啾高斯型锁模脉冲的时间相干长度

本文首次提出并讨论了锁模激光脉冲的时间相干长度问题。从时间复相干度定义出发,导出了具有线性啁啾的高斯型锁模脉冲的时间相干长度表达式,可以看出,时间相干长度随着脉冲啁啾的增大而减小;与这种脉冲的时间宽度比较可以得出结论,在没有啁啾时,脉冲的时间相干长度等于脉冲时间宽度的二倍。     

Photoswitchable PEG‐CA hydrogels and factors that affect their photosensitivity

The photoswitching behavior of polyethylene glycol‐based hydrogels was determined by monitoring the changes in their swellability and absorption spectra upon exposure to alternating wavelengths of irradiation. Highly hydrophilic PEG‐based hydrogels were prepared by the irradiation of a cinnamylidene acetate‐terminated PEG solution (PEG‐CA). The degree of swelling of the PEG‐CA hydrogels was predictably modulated by alternating the wavelength of exposing irradiation. Exposing the PEG‐CA gels to >300 nm irradiation resulted in the decrease of their swellability, while short exposure to 254 nm led to more hydrophilic gels. That is, the physical properties of the PEG‐CA gels can be controlled by the selection of wavelength of irradiation. Interestingly, it was found that 254 nm irradiation could not only lead to the photoscission of the PEG‐CA gels, but also initiate a crosslinking reaction between PEG‐CA monomers. On the contrary, only photocrosslinking via a cyclobutane ring formation was observed under >300‐nm irradiation. Finally, the factors that could affect an efficient photoswitching behavior of the PEG‐CA gels were investigated. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1466–1476, 2000     

Synthesis and properties of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose

In this article, a series of O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl celluloses with different degree of substitution (DS) values was synthesized by a homogeneous reaction of cellulose with 2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl chloride in a 10% (w/w) dimethylacetamide/lithium chloride solution, combined with pyridine as the acid acceptor. The total DS values of the derivatives in anhydroglucose units was determined by ¹H and ¹³C NMR spectra, and ranged from 0.4 to 3.0, depending on the amount of acid chloride in the reaction. The effects of the total DS values and the O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl substituent distribution on the solubility of the derivatives were investigated. The lowest limit of the DS value for water‐soluble O‐2‐[2‐(2‐methoxyethoxy)ethoxy]acetyl cellulose was approximately 0.5, which is lower than that of methylcellulose. The amphiphilic derivatives with higher DS values than 1.7 exhibited a good solubility in both water and organic solvents, such as dimethyl sulfoxide, tetrahydrofuran, and chloroform. Sol‐gel transition in aqueous solution was observed for the amphiphilic derivatives with a higher DS value than 1.7; the precipitation temperature (T_p) decreased as the DS value increased, showing that the derivatives are highly temperature sensitive. The thermal properties of the fully substituted derivative were measured using polarized microscopy, DSC, and X‐ray diffraction; and are discussed in terms of phase transition of the sample derivatives. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 376–382, 2001     

TiO2烧结助剂对纳米η-Al2 O3制备Al2 O3-Cr2 O3固溶体的影响研究

以纳米η-Al₂O₃粉和工业铬绿为原料,以摩尔比1:1配比制备Al₂O₃-Cr₂O₃固溶体,以TiO₂为烧结助剂,在还原气氛下经1400 ℃、1500 ℃和1600 ℃固相烧结.研究了TiO₂的加入对纳米η-Al₂O₃制备Al₂O₃-Cr₂O₃固溶体的致密度、线收缩率、相组成、晶胞参数、互扩散程度和微观结构的影响.结果表明:TiO₂的加入能促进Al₂O₃-Cr₂O₃固溶体的致密化;当温度为1600 ℃,TiO₂的添加量为2wt;时,试样的体积密度最大为4.57 g·cm^-3,线收缩率为19.8;;TiO₂的加入能使Al₂O₃-Cr₂O₃固溶体中Al³⁺和Cr³⁺的互扩散程度增加;微观结构表明,TiO₂的加入能使Al₂O₃-Cr₂O₃固溶体晶粒之间结合更紧密,实验温度范围内,随着TiO₂添加量的增加晶粒从沿晶断裂向穿晶断裂转变,只在晶间和晶内存在极少量气孔,当温度为1600 ℃,TiO₂的添加量为2wt;时,晶粒大小较均匀,平均晶粒尺寸约10μm.     

近海风机叶片模态局部化产生机理及定量分析研究

在摄动理论的基础上,结合失谐度、模态密集度以及模态置信准则对模态局部化的产生机理做了定量描述,并用26自由度弹簧质点结构验证了其可行性。其次,用ANSYS建立了风机叶片模型,并通过改变材料的密度和弹性模量模拟了四种失谐情况,发现风机叶片刚度和质量的小量失谐也会对其模态振型产生显著的影响,同时通过定义新的模态局部因子来定量描述风机叶片结构的模态局部化程度。最后,对风机叶片失谐振型中谐调振型的成分进行了分析,研究表明,其成分越复杂,模态局部化程度也越强。