轴流风扇叶片端导叶作用的研究

本文采用数值方法研究了叶片端导叶对轴流风扇性能的影响。通过与普通开式轴流风扇比较,分析了叶片端导叶对内部流动作用的机理.数值计算结果表明:叶片端导叶的安装位置将影响轴流风扇气动效率,安装叶片端导叶不能提高风扇静压升,但是在压力面安装时能有效地减小风扇叶顶泄漏流与主流的掺混损失;在设计流量下,压力面安装叶片端导叶使泄漏涡的作用范围较小,涡核更靠近吸力面;吸力面安装叶片端导叶弱化了泄漏涡的强度但没有减小泄漏涡的作用范围。     

A procedure for measuring the flexibility of single wood-pulp fibres

A way of determining the flexibility of wood-pulp fibres is developed, which involves i) a precise measurement of the topology of single-fibres by using a confocal laser scanning microscope and ii) the measurement of the elastic modulus of the fibres by using a single-fibre fatigue cell. Reported in this paper are the initial results of tests carried out on black spruce fibres, which have been subjected to three different levels of mechanical refining energy, namely ∼1100, 2300, and 3500 kWh/t. It is found that the fibre flexibility rises significantly between the first and second energy levels, but it does not change to the same degree between the second and third ones. The described procedure of measuring the flexibility of fibres may be used to establish the appropriate refiner energy necessary for the production of a specific grade of paper. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 115–128, January–February, 2006.     

New dynamic axial compression columns with means for monitoring floating adapter position. Column design and utilisation in low pressure LC on soft packings

Summary The design of new dynamic, axial-compression columns with a system for continous packed bed adjustment and monitoring of the floating adapter position is described. The columns are meant for liquid chromatography at low pressures (up to 8 bar) in aqueous and organic media with stationary phases of all types. The columns have adapter position pickups for continuous automatic monitoring of the bed height (original “swellographic” monitoring). The column described with gas pressurisation was tested with soft Sephadex G-10 and G-25. In spite of the reduction in external porosity there was no dramatic increase in back-pressure. The column proved to provide long-term stability of the packed bed and improvement in resolution. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996     

进气畸变对压气机稳定性的影响

在低速大尺寸单级压气机实验器上,实验研究了动态进气畸变对压气机稳定边界的影响。并采取在静子叶片表面埋入微型压力传感器的方法,分析了压气机流场的动态压力特性。实验结果表明,动态总压畸变的旋转频率和旋转方向对压气机稳定性有很大的影响,当畸变相对转速n在0~+0．5之间时,压气机失速推迟;分析动态压力的频谱特性后知道,在压气机失速前一般存在与失速相关的压力扰动,动态总压畸变影响这种压力扰动,从而影响压气机的不稳定流动状态。     

3 GPa熔融盐固体介质三轴高温压力容器的轴压摩擦力标定

 在温度标定和围压标定的基础上,采用轴压循环方法,对3 GPa固体介质三轴高温高压实验系统的轴压摩擦力进行了标定,分析了围压、温度、轴向位移速率、装样方式（盐套类型）等实验条件对轴压摩擦力的影响。结果表明：静摩擦力、挤压摩擦力和滑动摩擦力3种轴压摩擦力对轴向应力的影响不同,其中静摩擦力和挤压摩擦力对轴向应力的影响很小,影响应力精度的主要是滑动摩擦力。静摩擦力及滑动摩擦力与围压正相关;静摩擦力与轴向位移速率正相关,但受其影响较小,滑动摩擦力不受其影响;静摩擦力和滑动摩擦力与温度负相关,并且受其影响较显著;盐套类型对轴压摩擦力的影响较大,当实验条件接近盐套熔点时,轴压摩擦力显著降低,当样品周围的盐套处于熔融状态时,轴压摩擦力最小。基于此,确定了标定轴压摩擦力的具体步骤,并对角闪岩的应力-应变曲线进行了轴压摩擦力标定。对比轴压摩擦力校正前、后的应力-应变曲线发现,经过轴压摩擦力校正的应力-应变曲线能更好地反映样品的实际变形情况。     

纵磁作用下真空电弧单阴极斑点等离子体射流三维混合模拟

真空电弧的特性直接受到从阴极斑点喷射出的等离子体射流的影响,对等离子体射流进行数值仿真有助于我们深入了解真空电弧的内部物理机制.然而,磁流体动力学和粒子云网格仿真方法受限于计算精度和计算效率的原因,无法有效地应用于真空电弧等离子体射流仿真模拟.本文开发了一套三维等离子体混合模拟算法,并在此基础上建立了真空电弧单阴极斑点...     

Ferroelectric liquid crystals with axially chiral 2,2′-spirobiindan-1,1′-dione cores

The axially chiral mesogens 5-alkoxy-5′-[(4-alkoxybenzoyl)oxy]-2,2′-spirobiindan-1,1′-dione (QL7-n) were synthesised as racemic mixtures and resolved as single enantiomers by preparative chiral phase HPLC. The shorter homologues (R)-QL7-8 and QL7-9 form enantiotropic N* and SmC* phases, whereas the longer homologues (R)-QL7-10 and QL7-12 form an enantiotropic SmC* phase only. Texture analysis showed that the helical pitch of the N* phase is below the wavelength range of visible light; a helical pitch of 187 nm was measured at T – T_NI = –5 K by selective reflection using enantiomerically enriched mixtures of (R)- and (S)-QL7-8 (0.35 ≤ ee ≤ 0.80). Spontaneous polarisations were measured as a function of temperature in the SmC* phase by the triangular wave method. P_S values at saturation range from 102 nC cm^–2 for (R)-QL7-8 to 120 nC cm^?2 for (R)-QL7-9, which are up to three times greater than the highest polarisation previously reported for an axially chiral SmC* mesogen. Optical tilt angles θ were measured as a function of temperature and showed a sharp rise consistent with first-order N*–SmC* or I–SmC* transitions, with values at saturation ranging from 42 to 44°.     

Stereochemical assignments of aldol products of 2‐arylimino‐3‐aryl‐thiazolidine‐4‐ones by 1H NMR

The aldol reactions of 2‐arylimino‐3‐aryl‐thiazolidine‐4‐ones with benzaldehyde carried out at ?78 °C were found to produce sec‐carbinols. Intramolecular hydrogen bonding within the aldol products forming a six‐membered ring enabled the assignment of stereochemistries of the major and minor diastereomers via analysis of the syn and anti ³J_H,H ¹H NMR coupling constants. Copyright © 2012 John Wiley & Sons, Ltd.     

几种吊钩中的力学问题探析

对吊装机械中使用的几种吊钩在吊装重物时的受力情况进行分析和比较,说明了各自的特点及其应用.     

Chiral Discrimination in Dimers of Diphosphines PH2PH2 and PH2PHF

A theoretical study of the conformational profile of two diphosphines, PH₂?PH₂ and PH₂?PHF, is carried using second‐order Møller–Plesset perturbation theory (MP2) computational methods. The chiral minima found are used to build homo‐ and heterochiral dimers. Six minima are found for the (PH₂?PH₂)₂ dimers and 27 for the (PH₂?PHF)₂ dimers. Pnicogen and hydrogen bonds, the non‐covalent forces that stabilize the complexes, are characterized by Atoms in Molecules (AIM) and Natural Bond Orbital (NBO) methodologies. Those with several pnicogen bonds are more stable than those with hydrogen bonds. The chirodiastaltic energies amount to a total of 1.77 kJ mol^?1 for the R_a:R_a versus R_a:S_a (PH₂?PH₂)₂ dimers, 0.81 kJ mol^?1 for the RS_a:RS_a versus RS_a:SR_a (PH₂?PHF)₂ dimers, and 2.93 kJ mol^?1 for the RR_a:RR_a versus RR_a:SS_a (PH₂?PHF)₂ dimers. In the first and second cases, the heterochiral complex is favored whereas in the third case, the homochiral complex is favored.