Cellulose-Based Composite Films

The mechanical and optical properties of cellulose-based composite films are investigated.It is shown that the use of toluene diisocyanate as a coupling agent and Avicel fibers as reinforcing elements give films with the highest mechanical characteristics. Using differential scanning calorimetry, it is also found that the glass transition temperature T _g of all the materials studied is below the room temperature and that the T _g increased with cross-linking and introduction of Avicel.     

Age aspects of the torsional strength of compact bone tissue

The variation of the strength of specimens of human tibial compact bone tissue with age has been investigated. It is shown that the torsional strength _i ^* increases sharply in childhood, reaches a maximum at age 25–35, and then gradually falls. There is a correlation between _i ^* and the porosity of the bone tissue. The mode of fracture of the bone tissue has been studied in relation to its orientation with respect to the principal axes of anisotropy.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 3, pp. 493–503, May–June, 1975.     

Phonon spectroscopy and transport properties of Y1-x Nd x Sr2Cu2.7Mo0.3O7-δ

The Raman and infrared spectra, resistivity as well as thermoelectric power of Y_1-xNd_xSr₂Cu_2.7Mo_0.3 O₇ δ(.x =0, 0.1. 0.2. 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr₂Cu_2.7Mo_0.3O₇ δ cuprates are different from those of RBa₂Cu₃0₇ δ. The variations of the microstructure in Y_1-x Nd_xSr₂Cu_2.7Mo_0.3O₇ δ with Nd-doping affect the carrier distribution. so as a result the superconductivity changes. Furthermore, it is pointed out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic size effect in HTSC. Project supported by the National Natural Science Foundation of China and the National Center for R & D Superconductivity.     

Focus characteristics of long distance flying optics

The ABCD law for the complex parameterq of the TEM₀₀, Gaussian beam is generally not valid for high-order modes. It can be used for the high-order modes or their superposition when the spot sizew in the virtual part of the parameterq is substituted by the Rayleigh rangeZ _R, of a certain resonator. The focus characteristics of long distance flying optics are studied in this paper theoretically and experimentally for the TEM _mn Gaussian beams between the two types of resonators without and with distortion. It is very important for the applications of the flying optical processing, the laser space craft and the spatial filter in the large laser project.     

PRIMITIVITY IN MATRIX NEAR-RINGS

Abstract

The relationships between modules of a near-ring R and the matrix near-ring IM_n(R) are studied, especially as regards primitivity. It is shown that R is 2-primitive iff IM_n(R) is.     

Electronic space-charge neutralisation in a thermionic converter

The V-I characteristics and the space distribution of electron densityn _e , temperature T _e , ion densityn _i , etc., have been studied in a thermionic converter using (i) d.c. excitation, (ii) r.f. excitation, for the auxiliary discharge in blue Argon. The latter has been found to give higher yields. Higher yields have also been obtained when the r.f. signal was allowed to leak into the interaction space of the device. It has been shown that Ramsauer scattering accounts for a major part of the resistivity of the device.     

Recognition of Virtual Braids

The virtual braid group VB_n containing the Artin braid group B_n as a subgroup is studied. A familiar complete invariant on B_n is extended to VB_n. It is conjectured that the new invariant is also complete. Bibliography: 7 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 299, 2003, pp. 267–286.     

Solidification characteristics of Pd40Ni40P20 alloy under microgravity condition

The microstructure and solute distribution of Pd₄₀Ni₄₀P₂₀ alloy solidified both on board a Chinese retrievable satellite (μg) and on the earth (1g) were studied. It was found that the dendritic primary phase formed under microgravity condition was finer and shorter. In the central area of the sample some asteroidal patterns of the primary phase were present in the microstructure. The primary spacing of the dendrites at the cooling rate of 0. 056 K/s was smaller than that measured in the ground-based experiments at the same cooling rate, but almost the same as that cooled at 0.67 K/s on the ground. With these experimental results, mass transport coefficients both in space and on the earth were evaluated.     

The influence of heat transfer on peristaltic transport of a Jeffrey fluid in a vertical porous stratum

The peristaltic flow of a Jeffrey fluid in a vertical porous stratum with heat transfer is studied under long wavelength and low Reynolds number assumptions. The nonlinear governing equations are solved using perturbation technique. The expressions for velocity, temperature and the pressure rise per one wave length are determined. The effects of different parameters on the velocity, the temperature and the pumping characteristics are discussed. It is observed that the effects of the Jeffrey number λ₁, the Grashof number Gr, the perturbation parameter N = EcPr, and the peristaltic wall deformation parameter ϕ are the strongest on the trapping bolus phenomenon. The results obtained for the flow and heat transfer characteristics reveal many interesting behaviors that warrant further study on the non-Newtonian fluid phenomena, especially the shear-thinning phenomena. Shear-thinning reduces the wall shear stress.     

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.     

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.     

Analytic solutions to a class of nonlinear infinite-delay-differential equations

The infinite-delay-differential equations (IDDEs) are studied and the analytic solution of a class of nonlinear IDDEs is presented based on the characteristics of the reproducing kernel space W₂[0,∞). Besides, the exact solution is represented in the form of series. It is proved that the n-term approximation un(x) converges to the exact solution u(x) of the IDDEs. Moreover, the approximate error of un(x) is monotone decreasing. The results of experiments showed that the proposed method in this paper is computationally efficient.     

Joint application of time — Temperature and time — Stress analogies to constructing unified curves

The possibility of constructing unified curves by joint application of time—temperature and time—stress analogies has been examined. It has been shown that by using this method the time scale can be expanded in constructing the unified curves that serve as models of long-time creep of material on the basis of short-time tests. The dependence of the influencing factorsa _T anda _σ on stress and temperature has been studied.

     

Investigation of the strength of foil-backed film materials

A correlation between the adhesion and cohesion strength characteristics is established for combined materials of the polymer-adhesive-foil type with crystalline polymer as the adhesive. It is shown that the dependence of K_r and ?_b on the adhesion is nonmonotonic. There is a so-called "working" adhesion range for obtaining foil-backed combined materials with improved physicomechanical properties.     

Experimental determination of the shear modulus of compact bone tissue

Various methods of experimentally determining the shear moduli G₁₂, G₁₃, and G₂₃ of compact human bone tissue have been examined. The results of the study confirm the previous view that compact tissue has properties similar to those of a transversally isotropic material. It has been established that the shear modulus along the diaphysis of the tibia at the level of girdles 9–24 does not change significantly. There is a definite difference in the rigidity characteristics with respect to the regions of the cross section. The highest values for the shear modulus were established in the angle regions of the cross section. There is a linear dependence of the shear stress ₁₂ on the torsional angle ₁ within the experimental range of stresses (₁₂90 kg/cm²).Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, pp. 697–705, July–August, 1972.     

Initial-boundary value problems for incomplete singular perturbations of hyperbolic systems

The general problem studied has as a prototype the full non-linear Navier-Stokes equations for a slightly viscous compressible fluid including the heat transfer. The boundaries are of inflow-outflow type, i.e. non-characteristic, and the boundary conditions are the most general ones with any order of derivatives. It is assumed that the uniform Lopatinsky condition is satisfied. The goal is to prove uniform existence and boundedness of solution as the viscosity tends to zero and to justify the boundary layer asymptotics. The paper consists of two parts. In Part I the linear problem is studied. Here, uniform lower and higher order tangential estimates are derived and the existence of a solution is proved. The higher order estimates depend on the smoothness of coefficients; however this smoothness does not exceed the smoothness of the solution. In Part II the quasilinear problem is studied. It is assumed that for zero viscosity the overall initial-boundary value problem has a smooth solutionu ₀ in a time interval 0≦t≦T ₀. As a result the boundary laye, is weak and is uniformlyC ¹ bounded. This makes the linear theory applicable. an iteration scheme is set and proved to converge to the viscous solution. The convergence takes place for small viscosity and over the original time interval 0≦t≦T ₀.     

Properties of topologies of information retrieval systems

This paper studies topological properties of different topologies that are possible on the space of documents as they are induced by queries in a query space together with a similarity function between queries and documents. The main topologies studied here are the retrieval topology (introduced by Everett and Cater) and the similarity topology (introduced by Egghe and Rousseau).The studied properties are the separation properties T₀, T₁, and T₂ (Hausdorff), proximity and connectedness. Full characterizations are given for the diverse topologies to be T₀, T₁, or T₂. It is shown that the retrieval topology is not necessarily a proximity space, while the similarity topology and the pseudo-metric topology always are proximity spaces. A characterization of connectedness in terms of the Boolean NOT-operator is given, hereby showing the intimate relationship between IR and topology.     

Basis Property of the Eigenfunction System of the Gellerstedt Problem in the Elliptic Part of the Domain

The Gellerstedt eigenvalue problem with homogeneous boundary conditions on interior characteristics is studied. We prove that the eigenfunction system of this problem is a Riesz basis in the L₂ space in the elliptic domain.     

Mathematical modeling and numerical simulation of CO2 transport through hollow-fiber membranes

Chemical absorption of carbon dioxide was studied theoretically using hollow-fiber membrane contactors in this work. A 2D mathematical model was developed to study CO₂ transport through hollow-fiber membrane contactors. The model considers axial and radial diffusion in the membrane contactor. It also considers convection in the tube and shell side with chemical reaction. The finite element method (FEM) was used to solve the model equations. Modeling predictions were validated with the experimental data obtained from literature for CO₂ absorption in amine aqueous solutions as solvent. The modeling predictions were in good agreement with the experimental data for different values of gas and liquid velocities. The liquid solvents considered for this study include aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), N-methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP) and potassium carbonate (K₂CO₃). The simulation results indicated that amine aqueous solutions were better than K₂CO₃ aqueous solution for CO₂ absorption. Also simulation results revealed that the removal of CO₂ with aqueous solution of MEA was the highest among the amines solvents. The hollow-fiber membrane contactors showed a great potential in the area of CO₂ absorption.     

Synthesis and surface reactivity of phosphide nanocrystals

Gap and InP nanocrystals were synthesized from Na₃P and GaCI₃ at low temperature (80–100°C) and atmospheric pressure. The samples were characterized by XRD and TEM measurements. The surface reactivity of Gap nanocrystals was studied by heating in N₂. The weight of the nanocrystals increased at the temperature between 370°C and 480°C. It can be concluded that N, molecule was absorbed and reactivated on the surface of Gap nanocrystals. Keywords: gallium phosphide, indium phosphide, nanocrystal, surface reactivity.