Materials for dry running air motors

Systems analysis, pin-on-disc testing, and motor tests have been used in an investigation of materials for oil-free operation of air motors. The performance achieved with carbon fibre reinforced composites (cfc) running against an Al₂O₃ ceramic and polyimide-amide against a chemically deposite nickel coating suggests that the attainable blade life in dry running motors could match the maintenance intervals of oil-lubricated motors     

Adhesive contact and kinetics of adherence between a rigid sphere and an elastomeric solid

The adhesive contact of rigid spherical punches on viscoelastic solids is studied using a solution of the axisymmetric Boussinesq problem, assuming an integral constant to be non-zero. The JKR theory, based on the energy balance, is then found. The stress tensor is computed by superposition of the Hertzian stress tensor and the flat punch stress tensor, and is plotted for two particular cases: zero and minimum negative applied loads. It is shown that, whatever the load, the existence of molecular attraction forces provokes infinite stresses at the edge of the contact area.Fracture mechanics concepts are used to study the kinetics of adherence. It is shown that the general equation used allows the kinetics of interfacial crack propagation to be predicted in all types of test: fixed load; displacement; loading velocity; and crosshead velocity. Finally, the problem of the tackiness of elastomers and the dwell time effect on adherence are examined.The experimental results collected in this review have been obtained for the contact surface glass ball/polyurethane. All the theoretical predictions are verified with a reproducibility of better than 2%.     

Permeation of naproxen from saturated solutions and commercial formulations through synthetic membranes

The release of naproxen through synthetic membranes, mounted in modified Franz-type diffusion cells, was evaluated, either from saturated solutions or from commercially available topical formulations containing 10% naproxen. The results obtained showed that the porous type synthetic membranes chosen (cellulose acetate and polyethersulphone) can be used for assessing product performance in quality control procedures. The formulations interacted with the solid membranes (silicone and EVA) to change their diffusional characteristics. However, transfer in the membrane, and not the formulation was rate controlling. These membranes could not therefore be used in assessing product release performance for quality control.     

Wind-tunnel development and trends in applications to civil engineering

A review is presented on wind tunnels capable of simulating natural winds, the boundary-layer wind tunnel (BLWT), and trends in their extensive use in civil-engineering practice. BLWTs and data-acquisition systems, as they evolved to meet needs in civil engineering, are described. Advancements are highlighted for the types of wind-load information now available to structural engineers and architects by BLWT tests using the advanced data-acquisition systems-the high-frequency base balance (H-FBB) and the synchronous multi-pressure sensing system (SM-PSS). Trends in applications of BLWT tests to determine wind effects on structures and to investigate wind-related environmental problems are described. Technical details of the BLWT, the H-FBB, the SM-PSS, and their proper use are available in references cited and are not restated in this review.     

A Class of Functions from P 2

A number of essential properties of a class G of Boolean functions are investigated; these functions are realized by functional elements that have one output and check tests of length two that detect single constant errors at inputs and outputs of these elements. The problem of completeness of this class and questions of its relation to closed base classes in P ₂ are considered. A lower estimate of the number of all the functions of n variables from this class is obtained.     

Tests of Sheet Materials for Structural Elements in Transverse Shear

An experimental procedure to evaluate the energy spent for fracture of a circular-clamped thin plate in transverse shear, induced by impact loading with a flat-face body, is briefly outlined. Test results for the specimens of the three materials: mild steel, thickness = 1.0 mm, a D16T aluminum alloy, = 0.75 mm, and a PA6 shock-resistant composite, = 2.0 mm, are given. The analysis of experimental and calculated stress-strain data (within the circular area between the clamping contour and the loading surface) demonstrates the qualitative relation between the energy spent for deformation to fracture and dynamic strength and plasticity. Test results allow one to compare different materials by the energy spent for their fracture under impact loading. The specific work of deformation in shear characterizes this value more comprehensively than that determined in flexure, induced by impact of a spherical body, and is applicable over an expanded range of loading rates.     

线材轧机粗轧机组后飞剪设计实践

介绍了邯钢三轧厂在线材轧机粗轧机组后的飞剪设计中,采用了硬齿面齿轮传动,零侧隙啮合液压缸锁紧与横移及简便实用的剪刃间隙调整机械,并介绍了该飞剪的使用效果及优缺点。     

Contaminant transport with adsorption and their inverse problems

In Constales et al. (water Resources Res. 39(30), 1303, 2003) dual-well tests are used to reconstruct the flow and dispersion parameters in contaminant transport. A tracer is introduced by the injection well, which is considered to be in steady-state regime with the extraction well. Then, from measurements of the time evolution of the extracted tracer (breakthrough curve) the required model data has been recovered. In Constales et al. (water Resources Res. 39(30), 1303, 2003), a very precise numerical method has been developed for the solution of the direct problem. In Kačur et al. (Comput. Meth. Appl. Mech. Engo. 194(2–5), 479–489, 2005); Remešiková (J. Comp. Appl. Math. 169(1), 101–116, 2004) an extension has been discussed which adds adsorption terms to the model. The inverse problem of determination of sorption isotherms in nonequilibrium mode was solved by a Levenberg–Marquardt iteration method. In the present paper we develop the adjoint system to evaluate the sensitivity of the solution (via the breakthrough curve) on the sorption parameters in equilibrium and nonequilibrium modes. Possible use of the adjoint system in determining the several parameters occuring in the model is a crucial point for iteration methods. The obtained model parameters then can be used in a 3D flow and transport model with adsorption. The numerical experiments we present, justify the used method.