RADIOACTIVE OR NATURAL TRACER。TECHNIQUES FOR LEAK DETERMINING OF DAM ABUTMENT

Infiltration and localization of preferential infiltration zones at the dam abutment are measured using radioactive tracer tests of flow in boreholes,meanwhile interconnection between boreholes and the energing water points is analysed.The theory and practice of radioactive tracer synthetic detective method are described to give methods and calculation formulae used under the condition of stable flow in single well to measure permeability coefficient and hydrostatic heads.Major single hole techniques including measurement for seepage line,velocity,rate of seepage flow and relationship of recharge of groundwater in aquifers are introduced briefly.The possibilities offered by natureal tracers are analysed,uincluding electric-conduct,pH-value and temperature of water as well as stable isotopes(D,^18O) and tritium.Furthermore,the sensibilities of this theory and methods were confirmed by detecting seepage flow field of Xinanjiang Dam.     

Deformation transition of intact coal induced by gas injection

Gas migration in coal bed is a multiple-physical process, of which not only includes gas desorption/diffusion through coal matrix and gas Darcy flow through the cleat system, but also results in deform...     

Compression Stability of Reversed Austenite in 9Ni Steel

The effect of compressive stress on the stability of reversed austenite in 9Ni steel was investigated by uniaxial and hydrostatic compression.It was found that the uniaxial compressive pressure promoted the γ→α transformation,while the hydrostatic pressure suppressed the γ→α transformation.The pressure dependent transformation behavior can be explained according to thermodynamic analysis.     

导轨式自升降脚手架遥控系统

本文介绍了一种新型的模块化自升降脚手架遥控系统,该系统采用无线遥控模块实现提升过程控制,克服了普通自升降脚手架控制系统控制器过大,控制不灵活的缺点.对系统进行了可靠性分析,给出了遥控器和提升控制器原理图,程序流程图.     

Relation between the structure of matrices and their mechanical relaxation mechanisms during the glass transition of biomaterials: A review

It has been demonstrated that industrial polysaccharides (agarose, deacylated gellan and κ-carrageenan) form networks of reduced enthalpic content in the presence of high levels of non-crystallizing co-solute (e.g., glucose syrup) that exhibit time-temperature dependent behaviour of a typical rubberlike polymer. In contrast, amylose holds its structural characteristics unaltered and does not reach a state of molecular mixing with glucose syrup, with morphological features being those of a micro phase-separated mixture. Variation in phase morphology and density of intermolecular associations leads to entropic or enthalpic viscoelasticity in systems, and it was utilised to define distinct classes of food related biomaterials exhibiting an extensive glass transition region or absence of vitrification phenomena. The approach was extended to encompass the experimental parameters of a porous matrix and the application of hydrostatic pressure. In the former, work discusses discrepancies in the T_g - porosity relationship attributable to the different extent to which the two techniques of calorimetry and mechanical spectroscopy respond to degrees of molecular mobility. In the latter, it was shown that the time-temperature-pressure equivalence of synthetic amorphous polymers is not operational in the glass-like behaviour of high sugar systems in the presence of gelatin or gelling polysaccharides. The existing body of evidence allowed quantitative treatment of results based on the asymmetric distribution theory of molecular relaxation time that identifies the chemical fingerprint of the local motions operating at the vicinity of T_g. Furthermore, the diffusional mobility of a bioactive compound within a glassy matrix could be followed in relation to temperature induced changes in free volume using the time-temperature superposition principle.     

Hydrostatic pressure effects on the structural properties of condensed whey protein/lactose systems

Hydrostatic pressure effects on whey protein/lactose mixtures were recorded with subsequent analysis of their structural, molecular and glass transition properties in comparison to thermal effects at atmospheric pressure. Experimental techniques used were small deformation dynamic oscillation in shear, modulated differential scanning calorimetry, Fourier transform infrared spectroscopy, and theoretical modelling of glass transition phenomena. Levels of solids ranged from 30 to 80% (w/w) in formulations with a protein/co-solute ratio of four-to-one. Addition of lactose protects the secondary conformation of the protein under application of high hydrostatic pressure. Nevertheless, pressurized protein systems are able to form three-dimensional structures due to the reduction in polymeric free volume and the development of an efficient friction coefficient amongst tightly packed particles. Systems can be seen as developing a “molten globular state”, where the structural knots of pressure-treated networks remain in the native conformation but achieve intermolecular cross-linking owing to frictional contact. Furthermore, pressure treated assemblies of condensed whey protein preparations could match the viscoelasticity of the thermally treated counterparts upon cooling below ambient temperatures. That allowed examination of the physical state and morphology of a condensed preparation at 80% solids by the combined framework of reduced variables and free volume theory thus affording derivation of glass transition temperatures for pressurized and atmospheric samples.     

一种医用防护服面料的选择及制备方法

采用浸轧-涂层整理方法制备一种塔夫绸医用防护服面料,并探讨防水剂种类、防水剂用量、消光粉OK-412对涂层后织物性能的影响.结果 表明:当防水剂FD-8用量为3.0％,消光粉OK-412用量为2.0％时,整理后的织物各项指标较优:静水压＞10.00 kPa,透湿量＞2 500 g/(m2·24 h),沾水＞4级,抗静电...     

对切削提升系统的改造

本文对切削机的液压传动控制过程进行分析,对切削机存在的问题提出了改进措施。     

精密数控车床静压导轨性能仿真研究

静压导轨的静态性能会直接影响精密机床的精度,需要在设计阶段考虑各个设计参数对其静态性能的影响,以保证设计符合要求.根据流体力学以及闭式静压导轨的受力特点推导出油腔内部的压力计算公式;结合节流器特征方程建立承载能力与刚度分析方程,得到简化模型;利用Matlab仿真分析导轨及节流器设计参数对静压导轨静态性能的影响,得到各设计参数的最优取值.     

Error correction in hydrostatic spindles by optimal bearing tuning

In this paper a high precision grinding wheel is considered as a rigid rotor mounted on two hydrostatic bearings. The equations for small perturbations of the wheel on the bearings are derived in the form of a multi-input, multi-output transfer function matrix, enabling the frequency response function of the wheel to be determined. Thereafter an optimisation algorithm is proposed which considers speed, load and dimensions of the spindle, and computes optimal stiffness and damping of the bearings. The dynamic characteristics of the bearings, tuned for minimum radial displacement of the spindle, is achieved maximising thereby the accuracy of the grinding process. Simulation results show that by stiffness coarse adjustment, and fine adjustment of the damping in the bearings, a spindle with 35 μm manufacturing error, can produce components with 3 μm accuracy.