Nonstationary equivalent linearization of nonlinear continuous systems

This paper presents a technique for obtaining the nonstationary stochastic response of a nonlinear continuous system. The method of equivalent linearization is generalized to continuous systems subjected to nonstationary random excitation. This technique allows replacement of the original nonlinear system with a time-varying linear continuous system. A numerical implementation is also described. In this procedure, the linear replacement system is discretized by the finite element method. Application to systems satisfying the one-dimensional wave equation with a constitutive nonlinearity is discussed. Results are presented for nonlinear stress-strain laws of a strain-hardening type.     

Concentration of biological liquids by dialysis with modified acrylonitrile copolymer membranes

Acrylonitrile copolymer membranes were subjected to partial hydrolysis in order to improve their dialysis characteristics. The partial hydrolysis time and temperature, as well as the concentration of the hydrolyzing agent, were the variable parameters. The changes in the chemical and physical characteristics of the membrane were proved by infrared spectroscopy, elemental analysis, differential scanning calorimetry, and Mercury intrusion porometry. After each degree of modification, the permeability of the membrane with respect to a solution of vitamin B₁₂ was determined under static conditions and at temperature of 298 K. The improvement in the permeability at a definite degree of hydrolysis is explained by the conversion of nitrile groups to amide and carboxyl groups, as well as increase of the volume of the pores with average radius. The efficiency of the modified PAN membranes for concentration of biological liquids (diluted serum) was studied. © 1994 John Wiley & Sons, Inc.     

纽约NM别墅

不同于大型的公共建筑,NM别墅是一个私人住宅项目,位于市中心约两小时车程远的纽约北部地区,此地区现在是纽约年轻人的度假之所,故能远离大城市的喧闹熙攘。其功能正是作为一个小家庭的夏季避暑别墅,基地环境为广大的草原,外围环绕着大片树林,整个7,000平方米的地形为一个缓绛的斜坡,拥有360度的     

Optical and structural study of thin film of polyazomethine with triphenylamine unit prepared via spin-coating method

A conjugated aromatic polyazomethine (PAZ) with triphenylamine (TPA) unit in the main chain was obtained by high temperature solution polycondensation of diformyltriphenylamine with o-dianisidine (Fast blue B). A major feature of the PAZ containing TPA unit in the main chain is their complete solubility in comparison with PAZ obtained from terephthaldicarboxaldehyde and o-dianisidine (abbreviated hereinafter as PAZ1). Both polymers were analyzed by thermogravimetric analysis and FTIR spectroscopy. UV–vis absorption, X-ray diffraction (X-ray) and Atomic Force Microscopy (AFM) techniques were used to probe the optical properties and morphology of the thin films of the PAZ prepared by spin-coating technique on the glass and quartz substrate. Thickness of the PAZ thin layer on the glass and quartz substrate were determined by ellipsometer at the range 150–220 nm. The optical band gap value (E _g) of the thin films PAZ was detected at 2.45 eV. The current–voltage (I–V) characteristic was measured to confirm semiconductor nature of the PAZ.     

Development of surface roughness optimisation and prediction for the process of wire electro-discharge grinding

This paper investigates the technological capabilities of a hybrid micro machining process for performing wire electro-discharge grinding (WEDG). In particular, micro wire electrical discharge machining (μWEDM) is employed in combination with a rotating submergible spindle to perform WEDG. In this research, first a machining strategy for workpiece preparation is presented. Then, the effects of different machining setup parameters on the achievable surface finish after WEDG are investigated. In particular, an experimental study was conducted to identify the most statistically significant setup parameters for performing the main cut that affect the resulting surface quality. A signal-to-noise (S/N) ratio analysis was conducted to optimise the technological parameters for performing WEDG. By modifying the discharge energy for main cuts when performing WEDG surface finish comparable to that of μWEDM can be achieved. In addition, a simple and cost-effective method for on-the-machine estimation of resulting surface roughness is proposed. Especially, by applying inductive learning a surface roughness prediction model for WEDG can be generate based on data acquired by monitoring on-line the process.     

Chemische wechselwirkung in schmelzdispersionen von polyethylenterephthalat und polypropylen

Composites of polyethyleneterephthalate (PETP) and polypropylene (PP) obtained by heat-treatment of melt dispersions of both polymers have been investigated using differential-thermal analysis. The exothermic peak on the thermogramms at 220–240°C was explained as a result of a chemical interaction of the polymers. The interactions are activated by the thermooxidation of the polypropylene. It was found that the thermostabilizers for PETP and PP act as inhibitors of the chemical interaction between these polymers.     

Limiting resistance of peat to transverse pipeline displacement

Use of V. G. Fedorovskii's solution concerning the limiting resistance of soil to the transverse displacement of a shallow pipeline is examined for beds of peat. Experimental and computed data are compared for moderately decomposed peat. Experimental test results are processed for pipes ranging from 76 to 426 mm in diameter and embedded to various depths below the surface of the peat.