Connection between the mechanical characteristics of the human abdominal aorta and its biochemical composition

The basic characteristics of the mechanical properties of the subrenal portion of the abdominal aorta have been determined experimentally for biaxial stretching, and their change with increase in size has been established. Amounts of the five main biochemical components of the aorta wall have been determined and a correlational analysis between the mechanical characteristics and biochemical composition has been carried out.Paper presented at the First All-Union Conference on Engineering and Medical Biomechanics, Riga, October, 1975.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Riga Scientific-Research Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 4, pp. 722–729, July–August, 1975.     

Some physicomechanical properties of polyformaldehyde (acetal resins)

A method of testing polyformaldehyde (acetyl resin) film has been developed. Comparative tests have been carried out on the homopolymer and trioxane-dioxolan copolymer. Certain physicomechanical characteristics of these polymers have been obtained.Mekhanika Polimerov, Vol. 3, No. 5, pp. 812–820, 1967     

Dependence of elastic and strength characteristics of high-modulus composites on schemes of reinforcement

The elastic and strength characteristics of high-modulus composites with 12 different reinforcement schemes have been studied thoroughly. The effect of reinforcement schemes on change in elastic and strength characteristics of composites has been evaluated. A calculation of the elastic characteristics of high-modulus composites has been performed from the properties of the reinforcement and binder, and a comparison of the results with experimental data is given. Diagrams of deformation upon extension of the composites studied are given.All-Union Scientific-Research Institute of Aviation Materials, Moscow. Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 6, pp. 1019–1027, November–December, 1974.     

Inertia effects in circular squeeze film bearing using Herschel–Bulkley lubricants

Recent engineering trends in lubrication emphasize that in order to analyze the performance of bearings adequately, it is necessary to take into account the combined effects of fluid inertia forces and non-Newtonian characteristics of lubricants. In the present work, the effects of fluid inertia forces in the circular squeeze film bearing lubricated with Herschel–Bulkley fluids with constant squeeze motion have been investigated. Herschel–Bulkley fluids are characterized by an yield value which leads to the formation of a rigid core in the flow region. The shape and extent of the core formation along the radial direction is determined numerically for various values of Herschel–Bulkley number and power-law index. The bearing performances such as pressure distribution and load capacity for different values of Herschel–Bulkley number, Reynolds number, power-law index have been computed. The effects of fluid inertia and non-Newtonian characteristics on the bearing performances have been discussed.     

Mathematical modelling and analysis of bulk waves in rotating generalized thermoelastic media with voids

The present paper deals with the propagation of body waves in a homogenous isotropic, rotating, generalized thermoelastic solid with voids. The complex quartic secular equation has been solved by employing Descartes’ algorithm and perturbation method to obtain phase velocities, attenuations and specific loss factors of four attenuating and dispersive waves, which are possible to exist in such media. These wave characteristics have been computed numerically for magnesium crystal and presented graphically. Statistical analysis has been performed to compare the obtained computer simulated result in order to have estimate on the suitability of the method to compute various characteristics of the waves. This work may find applications in geophysics and gyroscopic sensors.     

A mathematical model for lifetime prediction of lacquer-paint coatings in sea water

Main features of the mechanism of lacquer-paint coatings destruction in sea water have been revealed. On this basis, a mathematical model has been developed and boundary value problems of mathematical physics have been formulated to calculate the determining processes on characteristic stages of coatings in sea water. The theoretical evaluation of coatings longevity depending on physical characteristics of the system has been made. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of the thickness of the surface layer on polymer blocks

A dependence of the thickness of the surface layer on the mechanical and wave characteristics of polymers has been obtained from joint solution of the equations of surface-wave motion and surface-layer equilibrium. From the dependence derived, the thicknesses of the surface layers have been calculated for four polymers. The dependence of surface-layer thickness on mechanical properties of the polymers and loading characteristics has been established.Institute of the Chemistry of High-Molecular-Weight Compounds, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Mekhanika Polimerov, No. 2, pp. 195–201, March–April, 1972.     

The structures of German mathematics textbooks

From a socio-cultural perspective it is argued that the modality of artefacts has, structuring effects on the activities in which the artefact is involved. The mathematics textbook is an artefact that has a major influence on the activity of learning mathematics. Against this setting, the structures of the units in German mathematics textbooks for different grades and ability levels have been analysed. Firstly, the different structural elements have been examined with regard to: characteristics in terms of content; linguistic characteristics; visual characteristics; their pedagogical functions within the learning process; and situative conditions. Secondly, the orders of the structural elements within the units of the different textbooks have been compared. The findings reveal that the structure of the units is very similar in different mathematics textbooks. The units are not only composed of analogous structural elements, but these elements are also arranged in almost the same sequence. In order to develop a deeper understanding of these findings the structure of the units has been compared to the influential learning theories of J. F. Herbart and H. Roth. On this basis it is argued that the structure of the units seems to reflect the phases of idealised learning processes in general. The issue is raised if this is an appropriate structure in order to provide opportunities to learn mathematics.     

基于满意度函数的多响应稳健优化模型及实证研究

针对传统的综合满意度模型在研究多响应时较少考虑噪声因素的问题,本文通过引入噪声因素对传统的满意度模型实施改进,进行多响应稳健优化分析。首先,构建包含可控因素和噪声因素的多质量特性的响应曲面模型;其次,借助传统综合满意度模型的构建方法,将多质量特性的响应曲面模型整合为改进的满意度模型;最后,将信噪比作为衡量改进的满意度模型稳健优化的指标,得到稳健优化的参数组合。实证研究表明:构建同时包含可控因素和噪声因素的改进的满意度模型是可行的,在此模型的基础上利用信噪比能够有效地找到多响应稳健优化的参数组合。     

Effect of the biochemical composition of the wall of the vessels of the human thigh on its mechanical properties

The principal characteristics of the mechanical properties of the walls of the human femoral artery and great saphenous vein and their variation with age have been experimentally determined. Macroscopic and microscopic analyses have revealed characteristic age-related changes in the artery and vein walls. The concentrations of six principal biochemical components of the vessel walls have been determined for each age group and the rank correlation coefficients for the principal mechanical properties and biochemical components have been analyzed.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga; Riga Institute of Traumatology and Orthopedics. Translated from Mekhanika Polimerov, No. 2, pp. 316–327, March–April, 1974.     

Free electron laser induced two-photon photoconductivity in Hg1-xCdxTe

The Beijing free electron laser ( BFEL) has been employed for the first time to study the nonlinear photoconductivity characteristics of the typical infrared photoelectronic material Hg_1-xCd_xTe Taking advantage of the high photon flux density of BFEL, we have investigated the photoconductivity characteristics in Hg^1-xCd_x Te induced by two-photon absorption by means of the photoconductivity technique, observed the photoconductivity signals saturation, and studied the two-photon photoconductivity characteristics on different bias voltages across the sample.     

Temperature-time analogy applied to thermorheologically complex polymer materials. 2. Mixtures of thermoplastic and thermosetting polymers (polymer-oligomer composites)

Conclusions 1. Stress-relaxation curves have been obtained for polymer-oligomer composites over a wide temperature range, and the temperature-time characteristics of properties of mixtures have been analyzed. The effect of each component on the mechanical characteristics of a mixture has also been examined.2. We have studied the temperature depenence of viscoelastic properties of mixtures of tetrafluoroethylene and vinylidene fluoride copolymer with epoxide-diphenylene propane resin. We have demonstrated that polymer-oligomer composites do not conform to the concept of thermorheologically simple behavior.3. The parameters of the temperature-time analogy were calculated with the aid of a computer for polymer-oligomer composites, examples of thermorheologically complex materials. It has been established, as a result, that the reduction factor depends strongly on time and the relaxation function depends strongly on the ratio of components.For communication 1, see [7].Okhtinsk Scientific-Industrial Combine, Plastpolimer, Leningrad. Translated from Mekhanika Polimerov, No. 3, pp. 430–434, May–June, 1978.     

Free electron laser induced two-photon photoconductivity in Hg1-xCdxTe

The Beijing free electron laser ( BFEL) has been employed for the first time to study the nonlinear photoconductivity characteristics of the typical infrared photoelectronic material Hg_1-xCd_xTe Taking advantage of the high photon flux density of BFEL, we have investigated the photoconductivity characteristics in Hg^1-xCd_x Te induced by two-photon absorption by means of the photoconductivity technique, observed the photoconductivity signals saturation, and studied the two-photon photoconductivity characteristics on different bias voltages across the sample.     

Effect of fiber tension on the unwinding resistance of hardening layers of glass-reinforced plastic

The shear fracture toughness characteristics of glass-reinforced plastics used for strengthening metal pressure vessels have been determined by testing metal-GRP rings. The shear fracture toughness characteristics are statistically estimated for a unidirectional GRP as a function of the winding tension.K. É. Tsiolkovskii Moscow Aviation Engineering Institute. Translated from Mekhanika Polimerov, No. 5, pp. 935–938, September–October, 1975.     

Effect of hot-drawing conditions on the orientation characteristics of carbon-chain fibers determined by the acoustic method

The orientation characteristics of polypropylene, polyacrylonitrile, and chlorinated PVC fibers, determined by the acoustic method, have been investigated in relation to the fiber drawing conditions (draw ratio, speed, and temperature). It is shown that there is a correlation between the mechanical characteristics and the degree of acoustic anisotropy.Tashkent Institute of the Textile and Light Industries. Translated from Mekhanika Polimerov, No. 3, pp. 552–554, May–June, 1971.     

On the investigation of free vibrations of nonthin cylindrical shells of variable thickness by the spline-collocation method

For determining the dynamic characteristics of free vibrations of circular unclosed cylindrical shells of variable thickness in two coordinate directions, we have used the spline-collocation method together with the method of discrete orthogonalization. The problem has been solved within the framework of the refined Timoshenko–Mindlin theory. We have also investigated the influence of different laws of change in the shell thickness on the character of its natural vibrations. Our calculations have been carried out for different geometrical and elastic parameters of the shell under study and different boundary conditions.     

Effect of the structure of stereospecific rubbers on their rheological properties

The authors discuss the viscosity properties of stereospecific rubbers and the relationship of these properties to structure. The dynamic characteristics of rubbers have been mearured on a board frequency interval, and it is shown that the moduli of elasticity and loss tangents vary considerably with frequency. The relationship between the rheological characteristics and structure of these rubbers and certain of their technological properties is examined.Mekhanika Polimerov, Vol. 4, No. 3, pp. 387–393, 1968     

Wear resistance of cured epoxy-novolac compositions

It has been established that changing the elasticity of rigid crosslinked epoxy-novolac block copolymers changes the friction mechanism and wear characteristics. The optimal conditions for obtaining block copolymers with the greatest wear resistance have been determined. The results of testing epoxy novolacs in neutral and alkaline media are presented.Leningrad Lensovet Technological Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1107–1109, November–December, 1969.     

Forced convective flow and heat transfer past an unconfined blunt headed cylinder at different angles of incidence

In the present paper, a numerical investigation has been carried out to study the forced convective flow and heat transfer characteristics past a blunt-headed cylinder in crossflow. Employing air as an operating fluid, calculations are carried out for a range of Reynolds number (Re) from 40 to 160. The angle of incidence is varied in the range of 0^∘ ≤ α ≤ 180 ^∘. The thermofluid features of flow and heat transport are analysed in detail for different angles of incidence. To analyse the aerodynamic characteristics, several parameters such as drag and lift coefficients, moment coefficient, Strouhal number, recirculation length, and local time-averaged vorticity flux have been calculated. Furthermore, a stability analysis has been undertaken by using the Stuart Landau equation to enumerate the critical Reynolds number at each angle of incidence. Heat transfer characteristics are studied by computing local and time-averaged values of Nusselt numbers. When compared to a rectangular cylinder, a blunt-headed cylinder exhibits an enhanced heat transfer rate. In the end, an entropy generation analysis has been carried out to study the effects of Re and angle of incidence on the efficiency of thermofluid transport characteristics.     

Effect of temperature and moisture on the creep of polymeric materials 1. One-dimensional extension under stationary temperature-moisture conditions

Creep tests have been carried out on PN-3 polyester resin for one-dimensional tension in the linear region of the stress-strain relation at various fixed values of the temperature and moisture content of the material. The temperature and moisture dependence of the instantaneous elasticity and creep characteristics of the material have been determined. It is shown that time-temperature-moisture superposition can apply in creep under various fixed temperature-moisture conditions.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 393–399, May–June, 1975.