The influence of neglecting small harmonic terms on estimation of dynamical stability of the response of non-linear oscillators

The effects of neglecting small harmonic terms on estimation of dynamical stability of the steady state solution determined in the frequency domain are considered in this paper. For that purpose, a simple single-degree-of-freedom piecewise linear system excited by a harmonic excitation is analyzed. In the time domain, steady state solutions are obtained by using the method of piecing the exact solutions (MPES) and in the frequency domain, by the incremental harmonic balance method (IHBM). The stability of the solutions obtained in the frequency domain by IHBM is determined by using Floquet–Liapounov theorem and by digital simulation of the corresponding perturbed motion. Received 20 July 1998     

Effect of crystal habit and superstructure on modulus of elasticity of isotactic polypropylene by AFM nanoindentation

In this study the effects of crystal habit, crystallinity and superstructure on the modulus of elasticity of isotactic polypropylene films were analyzed by atomic force microscope (AFM) nanoindentation. The modulus of elasticity, evaluated on the nanometer scale by AFM, showed a qualitatively similar dependence on the crystal habit, crystallinity and superstructure as the modulus of elasticity measured by dynamic-mechanical analysis and tensile testing. The observed values of both the surface stiffness measured by AFM and the macroscopic/bulk stiffness were distinctly larger in the presence of non-isometric lamellae organized in spherulite than in the presence of isometric nodular crystals, not organized in a spherulitic superstructure. The experimental data showed that the modulus of elasticity is not primarily influenced by the presence or absence of spherulite but by the molecular-deformation constraint associated to the crystal habit.     

Contour mapping of the spatiotemporal state of polarization of light

A novel interferometric polarimeter capable of mapping a spatiotemporal change in the state of polarization (SOP) of light is described. The polarimeter has a reference beam of light with two orthogonal linearly polarized components that interfere with the counterpart components of an elliptically polarized signal beam. The resultant interference pattern is recorded by a computer by the use of a wideband metal-oxide semiconductor video camera. The interference pattern reduces to the ellipticity and azimuth of the ellipse at an instant of time, by which the spatiotemporal change in the SOP is mapped. No optical elements are used for the control of polarization in the polarimeter, and this allows for the mapping of a rapid change in the SOP. Successful experiments are demonstrated by generating an elliptically polarized beam whose SOP varies in space and time.     

Effect of addition of carbon on magnetic properties of sputter-deposited CoCr film

The addition of carbon changes Ms, Hkeff and Hc(perp) of sputter-deposited CoCr films: Ms is always increased, while Hkeff and Hc(perp) are either increased or decreased by the addition of up to 0.32 at% carbon. How the substrate temperature and the Cr content in the film influence the effect of added carbon is investigated. Higher substrate temperature tends to stimulate the increase in Ms caused by the addition of carbon. A higher substrate temperature and higher Cr content tend to stimulate the increase in Hkeff and Hc(perp) and to prevent the decrease in Hkeff and Hc(perp) caused by the addition of carbon. The increase in Ms with the addition of carbon seems to be caused by an increase in the degree of compositional segregation. The increase and decrease in Hkeff may be attributed to an increase and decrease in Ku, respectively. The increase in Hc(perp) caused by the addition of carbon is probably due to the increase in Ku and/or to the refinement of the magnetic domain. The decrease in Hc(perp) may be attributed to the decrease in Ku even though the magnetic domain is refined.     

Modification of the optical properties of ZnO thin films by proton implantation

Optical properties of proton-implanted ZnO thin film prepared by radio-frequency (rf) magneton sputtering have been studied, the optical constants being obtained from the reflectance measurements by employing Cauchy–Urbach model. Increase in the ordinary refractive index after proton implantation was explained by that in the polarizability. Besides, a slight increase in the optical band gap by proton implantation was identified and discussed in terms of the hydrogen shallow donors introduced by the proton implantation.     

Modeling of continuous ultrasonic impregnation and consolidation of thermoplastic matrix composites

Ultrasonic propagation was used to provide heat and pressure in order to perform impregnation and consolidation during production of thermoplastic matrix composites. For this purpose, a new experimental set-up, integrating a laboratory filament winding machine with a horn and a compaction roller, was developed.The heat transfer phenomena occurring during continuous impregnation and consolidation were simulated solving by finite element (FE) analysis the energy balance equations in 2D accounting for the heat generated by ultrasonic waves, the melting characteristics of the matrix and the movement of the thermoplastic commingled roving.The temperature distribution in the composite, predicted by the numerical simulations, was validated by temperature measurements during the production of E-glass/polypropylene cylinders, with the optimized parameters obtained by the FE analysis. The ultrasonic consolidated composite cylinders were characterized by low void content and a shear modulus comparable with that obtained by the micromechanical analysis.     

Influence of Raw Material and Processes of Gelatins upon Photographic Characteristics of Dichromated Gelatin

Carbon tissues prepared using types of gelatin differing in raw material and process were sensitized by dichromate and their photographic characteristics were investigated. Sensitivity and gamma were dominantly determined by the higher molecular weight components of the gelatin, sharpness and resolving power were dominantly determined by viscosity; these properties were little affected by its origin.     

Ellipsometry of thin films of copper phthalocyanine

Ellipsometric measurements have provided qualitative information on the optical properties of CuPC films deposited on a thin gold layer substrate. Detailed interpretation was complicated by variations in the density of the deposited layers and the surface roughness of the substrate. Films less than 100 nm thick can be satisfactory represented by a single homogeneous isotropic layer. Thicker films appear to be equivalent to an isotropic inner layer and an anisotropic outer layer, where the latter results from bulk deposition of CuPC with the molecules in a predominant orientation to the surface. Reasonable agreement has been obtained between film thicknesses measured by weighing and by ellipsometry, assuming a single homogeneous anisotropic film for thickness in excess of 150 nm.     

Dependence of microstructure and hardness of TiAlN/VN hard coatings on the type of substrate rotation

In industrial PVD deposition systems the substrates usually move in a so-called planetary rotation in order to deposit a homogeneous coating on the whole surface area of the tools. In this study we compared microstructure, surface topography and hardness of the coatings, deposited in the same batch but using different types of rotation: one-fold, two-fold and three-fold. The coating was a multilayer TiAlN/VN, deposited by magnetron sputtering. Microstructure was studied on cross-sectioned samples using SEM, prepared either by fracture or by focused ion beam. Coatings prepared by two-fold and three-fold rotation were very similar, both in microstructure and in hardness. They had dense, only slightly columnar microstructure. In contrast, coatings prepared by single rotation had a pronounced columnar microstructure, and substantially lower hardness.     

Formation and Morphology of Anodic Oxide Films of Ti

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A Review of the Chemistry of Lith (Infectious) Development

Lith development is produced by a combination of two primary mechanisms; the dependence of induction time on exposure and the autocatalytic continuation phase of development by semiquinone. Each mechanism may be modified in its action by other components of the system. The induction time is influenced principally by bromide ion, both that which is initially present and that which is released from adjacent developing grains and adsorbates to the grain SUI face, advantageously by polyethylene oxides, disadvantageously by some dyes. Semiquinone development is affected by the sulphite ion concentration and system components whose reactions lead to more rapid formation of the semiquinone such as hydroxyl ion and gelatin (arginine).

Additionally, bleaching of the latent image in the low exposure region may play some part in producing a sharp toe to the characteristic curve.     

Evaluation of the anti-rutting potential of polymer-modified binders by means of creep-recovery shear tests

In the experimental study reported in this paper a creep-recovery shear test method was used to evaluate the anti-rutting potential of different polymer-modified bituminous binders. The effects of several factors related to modification were investigated, such as polymer type (SBS, styrene–butadiene–styrene vs. ethylene–vinyl–acetate), composition (styrene content), structure (linear vs. radial SBS) and dosage (3–6 % by weight of the base bitumen). The effect of short-term aging was also considered by comparing binder response before and after treatment with the rolling thin-film oven test. Following previous work on the development of the test protocol, experimental results were analyzed by referring to shear modulus curves G(t) and to permanent compliance (J _P), obtained by dividing residual strain at the end of the unloading phase by the stress applied during creep loading. Results indicated the effectiveness of the proposed method in discriminating between the behavior of the different polymer-modified binders and in capturing the effects caused by the factors considered in the investigation. Reliable rankings of the binders were established and were explained by referring to the specific behavior of employed modifiers.     

硫化物形态对超高强度钢冲击韧性的影响

本文对比分析了"真空感应+真空自耗重熔"和"电弧炉+VOD+真空自耗重熔"两种工艺冶炼的超高强度G50钢力学性能.利用扫描电镜和能谱分析等检测手段研究了不同冶炼工艺生产的G50钢中夹杂物类型和尺寸分布.研究结果表明:电弧炉+VOD+真空自耗重熔工艺冶炼的G50钢横向和纵向冲击韧性分别相对"VIM+VAR"工艺得到很大的改善,各向均匀性得到改善.电弧炉+VOD+真空自耗重熔工艺冶炼的G50钢中夹杂物颗粒状和椭圆形弥散均匀分布,阻碍空洞合并,导致冲击性能尤其是横向冲击性能得到极大的改善.     

Effect of calcinations temperature of CuO nanoparticle on the kinetics of decontamination and decontamination products of sulphur mustard

Present study investigates the potential of CuO nanoparticles calcined at different temperature for the decontamination of persistent chemical warfare agent sulphur mustard (HD) at room temperature (30 ± 2 °C). Nanoparticles were synthesized by precipitation method and characterized by using SEM, EDAX, XRD, and Raman Spectroscopy. Synthesized nanoparticles were tested as destructive adsorbents for the degradation of HD. Reactions were monitored by GC-FID technique and the reaction products characterized by GC-MS. It was observed that the rate of degradation of HD decreases with the increase in calcination temperature and there is a change in the percentage of product of HD degradation. GC-MS data indicated that the elimination product increases with increase in calcination temperature whereas the hydrolysis product decreases.     

Methods of determination of shear properties of textile composites

Shear properties of four types of composites possessing no planes of weak shear strength and stiffness are experimentally investigated. Shear characteristics measured by Iosipescu test and/or its modification Asymmetrical Four-Point Bending (AFPB) are compared with experimental results obtained in the work by seven other shear tests developed for the determination of shear modulus and shear strength of fibrous and layered composites. One of the article’s purposes is to estimate an applicability of Iosipescu and AFPB tests for the determination of shear properties of textile composites fabricated by different processing methods. A long-standing experience of investigations of 3-D textile composites accumulated in the Institute of Polymer Mechanics is generalized in the paper.     

Effects of protein-simulated body fluid mixing methods on characteristics of bone-like mineral

This study examined effects of protein mixing methods into modified simulated body fluid (mSBF) on the crystalline structure and morphology of bone-like mineral (BLM) coated on a poly(lactic-co-glycolic acid) template (PLGA). Using bovine serum albumin (BSA) as a model protein, four sample groups were prepared: the N-BLM group was coated by soaking substrates in mSBF without BSA; the B-BLM group was coated by soaking in mSBF with BSA added immediately before soaking; the Ca-BLM group was coated by soaking in Ca-mSBF prepared by premixing BSA with a CaCl₂ solution before preparing the mSBF; the P-BLM group was coated by soaking in P-mSBF made by premixing the BSA with a KH₂PO₄ solution. The B-BLM and Ca-BLM groups exhibited densely coated, thick BLM layers, whereas the P-BLM group exhibited loosely connected BLM clusters. The hydroxyapatite (HAp) crystallites of the B-BLM and Ca-BLM groups were aligned along the c-axis, but those of the P-BLM group were disordered and had a lower crystallinity. The alignment to the c-axis of Ca-BLM and the disordered orientation of P-BLM were caused by calcium ions bound to BSA in Ca-mSBF and phosphate ions bound to BSA in P-mSBF, respectively. These results show that the crystallinity and morphology of BLM can be controlled by the mixing of BSA in mSBF. The crystallinity of BLM is closely connected to its solubility. Therefore, the release characteristics of growth factors and cell regulation on BLM could be affected by the changes in the crystalinity of BLM.     

Local Minima and Gradients of Stiffness and Conductivity as Indicators of Strength Reduction of Brittle-Elastic Materials

It is often suggested in literature to use change in the effective elastic properties (stiffness loss) as an indicator of reduction of strength due to defects such as cracks and pores. We argue that the key parameter is not the reduction of the average (over the specimen) stiffness but its local minimal values caused by formation of defect clusters. These defect clusters can be identified by the emergence of spatial gradients of elastic stiffness on a smaller scale. A convenient tool of detecting these gradients is provided by the elasticity-conductivity connection: the electric conductance gradient is usually easier to measure than the stiffness gradient. This concept is supported by computational and experimental results reported in two accompanying papers published in the present issue (by Sevostianov et al and Caiulo and Kachanov).     

重结晶对PYX热性能和机械感度的影响

分别采用降温法和溶剂-反溶剂法对2,6-二苦氨基-3,5-二硝基吡啶（PYX）进行了重结晶研究。表征了不同重结晶方法所得PYX晶体的形貌和粒径,测定了重结晶前、后的晶体纯度,研究了重结晶对晶体热性能和机械感度的影响。结果表明:采用降温法在DMSO中得到的多为小颗粒团聚形成的不规则块状PYX晶体;采用溶剂-反溶剂法在DMF或DMSO中得到的多为片状PYX晶体,在DMSO/DMF混合溶剂中得到的多为规则的多边形块状PYX晶体。相比较而言,多边形块状PYX晶体的表面光滑度良好,粒径跨度最小,纯度最高,热稳定性较优,且兼具最低的撞击感度和摩擦感度,其热分解峰温和热爆炸临界温度较重结晶前分别提高了8.99 ℃和9.11 ℃,撞击感度和摩擦感度较重结晶前分别降低了16％和12％。