The effect of fibre diameter on the mechanical properties of graphite fibres manufactured from polyacrylonitrile and rayon

A relationship between diameter and both Young's modulus and tensile strength of graphite fibres, manufactured from both polyacrylonitrile and rayon precursors is demonstrated. Thin fibres exhibit higher values of Young's modulus and tensile strength than thick fibres. The observed relationship is deduced to be a consequence of the “sheath” and “core” type structure which is characteristic of these fibres.     

Mechanisms of the mass transfer of “Loose” corrosion deposits in primary circuits of a water-cooled reactor and practical recommendations

This paper describes the mechanisms of the mass transfer of “loose” corrosion deposits in the primary circuits of water-cooled reactors. The revealed “peaks” of the amount of suspended corrosion particles in the reactor transients are reported are reported. Two ways of using this effect are suggested: first, for monitoring the amount of suspended corrosion particles in the circuit and the thickness of their deposits formed on the surfaces of the primary circuit equipment; second, for removing “loose” deposits containing radionuclides from primary circuits, i.e., for “non-chemical decontamination technology.”     

The propagation of linear waves in humid,gas-saturated media

The process of propagation of acoustic waves in humid, gas-saturated porous media is investigated in a two-velocity approximation. A dispersion relation is derived, which includes interphase interaction forces and heat transfer between the skeleton of porous medium, liquid, and gas. The effect of heat transfer between the phases on the propagation of the “fast” and “slow” waves is included by means of heat equation     

Heat transfer in regional extracorporal perfusion of limbs

Two problems of heat transfer in regional perfusion are analyzed, viz., in heating of limbs by hot blood and in normothermal perfusion in combination with local SHF hyperthermia. The efficiency of the procedure in the latter case and its inefficiency in the former case are shown. The coefficient of heat transfer between a circulatory system and biotissue is estimated. Academic Scientific Complex “A. V. Luikov Heat and Mass Transfer Institute, Academy of Sciences of Belarus,” Minsk; Scientific Research Institute of Oncology and Medical Radiology, Ministry of Public Health of Belarus,” Minsk, Belarus. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 3, pp. 434–442, May–June, 1996.     

Low frequency dielectric spectroscopy characterization of microcrystalline cellulose, tablets and paper

Cellulose fibres and particles in the form of powder, tablets and paper sheets have been investigated by very low frequency dielectric spectroscopy using a novel form of dielectric cell, in which two planar electrodes have been mounted in fixed positions at right angles. The broad pattern of response obtained from the samples is independent of the structural form of the cellulose sample, a loss peak in the 0.1–100 Hz range, and at lower frequencies a dispersion process which is dominated by an imperfect charge transport. Moisture has a significant influence on the rate of charge transport. In dry samples the dipolar loss peak was not evident but as the moisture content increased it appeared. Using a humidity normalizing technique the dielectric response for microcrystalline cellulose has been characterized over the equivalent of 14 decades in frequency. It has also been shown that there is a linear response between the capacitance and the density of microcrystalline cellulose samples. The consolidation of powder into tablets is discussed with respect of the observations of changes in capacitance, loss peak frequency and imperfect charge transport efficiency. Furthermore it was found possible to investigate differences between the dipolar relaxation rate “in” and “out” of the plane of paper in the stack. The relaxation time for dipoles “out” of the paper plane is 7 to 8 times longer than for dipoles “in” the paper plane. This revised version was published online in November 2006 with corrections to the Cover Date.     

The effect of fibre sizing on fibres and bundle strength in hybrid glass carbon fibre composites

Tests have been carried out on single carbon fibres supplied in the sized and unsized conditions, as well as impregnated tows and tows in a glass–carbon fibre hybrid composite of the same fibre. The results were analysed using a Weibull distribution for the strengths of the reinforcing fibres and composites. The tensile strength of the single fibres appeared to be unaffected by the sizing of the filaments. In the case of the impregnated tows, an increase in characteristic strength of 7% was observed for the unsized fibres. The strength of the impregnated tows in hybrid composites was seen to be 15% higher than those tested in air. This can be attributed to the “hybrid effect”. This revised version was published online in November 2006 with corrections to the Cover Date.     

CFD codes and applications at boeing

The use of computational methods for three-dimensional flow design and analysis at the Boeing Company is presented. A range of computational “tools” consisting of “production” tools for everyday use by project engineers, “expert user” tools for special applications by computational researchers, and a new “emerging” tool which may see considerable use in the near future is described. These methods include full potential and Euler solvers, some coupled to three-dimensional boundary layer analysis methods, for transonic flow analysis about nacelle, wing/body, wing/body/strut/nacelle, and complete airplane configurations. As the examples presented show, such a tool box of codes is necessary for the variety of applications typical of an industrial environment. Such a tool box of codes makes possible aerodynamic advances not previously achievable in a timely manner, if at all. With a few exceptions, this paper is a version of the paper entitled “TransonicCFD applications at Boeing”, by E N Tinoco, presented at the Transonic Symposium,nasa Langley, April 1988. The paper was presented at the Specialists’ meeting onCFD, held at National Aeronautical Laboratory, Bangalore, December 1988. This paper is based in part on work conducted for the Boeing Independent Research and Development Program.     

Uncertainty of measurement results in various scales

The relationship between the concepts of “error” and “uncertainty” of measurement results is examined. The concepts of “standard uncertainty,” “combined standard uncertainty,” and “expanded uncertainty” are shown to be inapplicable in nonmetric scales of quantities and properties, in which the general concept of “uncertainty” in the broad sense is recommended. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 2000.     

The mechanical behaviour of polyimide-copper laminates

The peel energies of flexible laminates consisting of polyimide films bonded to copper foil with a polymeric adhesive have been measured and the peel mechanisms investigated by conducting peel tests inside a scanning electron microscope. These laminates were prepared from polyimide films that had been subjected to either a “high-thermal history” or “low-thermal history” treatment during the production of the film. The laminates prepared from the “high-thermal history” polyimide films had higher recorded peel energies and the locus of failure during the peel test was mainly by cohesive fracture through the adhesive layer. The laminates prepared from the “low-thermal history” polyimide films tended to fail in a weak boundary layer of the polyimide film. The peel energies were lower and displayed a greater scatter. Thein situ peel tests have also identified various failure mechanisms which account for the different features observed on the peeled surfaces and the various types of peel energy traces which were recorded.     

Collaboration patterns in patent networks and their relationship with the transfer of technology: the case study of the CSIC patents

The aim of this article is to observe differences between research areas when it comes to establish collaboration ties with local, national or international partners. It also intends to determine in what extent the collaboration can influence the patent transfer. A collaboration network between CSIC researchers and their external collaborators was built. Several statistical tests were used to find significant differences between research areas. A multiple regression model was also utilized in order to know what type of collaboration is more successful to transfer a patent. The results show that there are two well defined groups. A “Bio” group with a high international collaboration pattern but less national participation; and a “Physicist” group supported by a high proportion of national partners but with few international connections. The regression analysis found that the national collaboration is the variable that most increase the patent transfer.     

Vapor condensation upon transversal flow around a cylinder (boundary heat-exchange laws)

The problem of vapor condensation upon transversal flow around a horizontal cylinder is considered. The analytical solutions for the “boundary heat-exchange laws” are obtained. The solutions show the dependence of the heat transfer coefficient on the corresponding factor (gravity, interfacial friction, longitudinal pressure gradient) under the assumption that there is no effect of other factors. The boundary laws obtained for moving vapor are shown to depend on pressure in the same manner, while the temperature differential has different effects in specified asymptotics. The theoretical results obtained are used for qualitative analysis of the available experimental data.     

Vacuum-tight sample transfer stage for a scanning electron microscopic study of stabilized lithium metal particles

A vacuum-tight transfer stage is described, that enables air or moisture sensitive specimens to be safely transferred from a protective environment, like that in a dry box, to a scanning electron microscope without exposing the sample to ambient conditions. The transfer stage concept described here is, in fact, applicable to the protected transfer of hygroscopic or air-sensitive samples to any vacuum-based analysis equipment where the transfer device opens automatically under vacuum to reveal the sample. This device concept is also applicable to the transfer of samples under vacuum from one glove box to another where the transfer chamber can be easily opened manually to reveal the sample. An example of one application of the device is provided by a controlled exposure study of stabilized lithium metal particles (SLMP) at various stages of shelf life. We found that a reaction coating formed on “fresh” SLMP after it was exposed to 100 Pa air for as short as 15 m. Such a reaction to air exposure was not observed on “aged” SLMP with a thickened carbonate surface coating after 4 and 6 months of shelf life. The case study of the surface coating on SLMP clearly demonstrated the excellent vacuum performance of the novel transfer stage.     

Wear of engineering ceramics by a soft abrasive

The wear behaviour of a number of engineering ceramics sliding against polyethyleneterephthalate (PET) has been examined. Microscopical examination of the worn surfaces has shown a wide distribution of size of grooves, from 50 nm to 1 μm. The smaller grooves seem to be made by anatase particles in the PET sheet. The larger grooves are made by particles ejected from the samples' surfaces by a fatigue mechanism. By relating the hardness of the engineering ceramics at a scale appropriate to the measured wear rates, some degree of agreement found. Further, it was found that the near-surface hardness of all the materials was lower than the macroscopic hardness values: the sole exception was anatase. Although the macroscopic hardness values of anatase were much lower than the alumina-based ceramics, the near-surface hardness values became relatively greater. In this way, what was originally thought to be a “soft” ceramic can now abrade a nominally “harder” one. The wear of the carbides is thought to be by an oxidation-assisted process. This revised version was published online in November 2006 with corrections to the Cover Date.     

Evaluation of structural-concrete design-concepts based on finite-element analysis

Finite element analysis incorporating a brittle constitutive model of concrete is used to investigate the validity of the concepts which underlie structural concrete design. It is shown that ignoring fundamental concepts forming the basis of current code provisions – such as, for example, the concepts of “aggregate interlock” and “dowel action” through which cracked concrete is considered to contribute significantly to shear resistance – does not impair the ability of the analysis to yield predictions of structural behaviour which correlates closely with experimental values. For the structural forms investigated, it is found that designing to current codes leads to unsafe solutions, since the analysis predicts premature brittle shear, instead of the intended ductile flexural, failure. On the other hand, designing to the concept of the “compressive force path” which allows for the brittle nature of concrete was found to achieve the design objectives for safety and adequate ductility.     

Tangential velocity profiles of granular material within horizontal rotating cylinders modelled using the DEM

Flow regimes of granular materials in horizontal rotating cylinders are industrially important since they have a strong influence on the rates of heat and mass transfer within these systems. The tangential velocity profile, which describes how the average particle velocity in the direction parallel to the surface of the bed varies along a radius perpendicular to the surface of the bed, has been examined for many experimental and simulated systems. This paper is concerned with tangential velocity profiles within rotating cylinders simulated using the discrete element method. For high fill levels good agreement is found between the simulated velocity profiles and the equation proposed by Nakagawa et al. (Exp Fluids 16:54–60, 1993) based on magnetic resonance measurements. At lower fill levels slip is observed between the cylinder wall and the particles in contact with it and also between the outer layer of particles and the bulk of the bed. It is demonstrated that this slip occurs when the particles in contact with the wall are able to rotate and that it may be prevented either by using non-spherical particles or by attaching “lifters” to the cylinder wall.     

Influence of fibre taper on the work of fibre pull-out in short fibre composite fracture

A model has been formulated to determine the work of pull-out, U, of an elastic fibre as it shear-slides out of a plastic matrix in a fractured composite. The fibres considered in the analysis have the following shapes: uniform cylinder and ellipsoidal, paraboloidal or conical tapers. Energy transfer at the fibre–matrix interface is described by an energy density parameter which is defined as the ratio of U to the fibre surface area. The model predicts that the energy required to pull out a tapered fibre is small because the energy transfer at the fibre–matrix interface to overcome friction is small. In contrast, the pull-out energy of a uniform cylindrical fibre is large because the energy transfer is large. The pull-out energies of the paraboloidal and ellipsoidal fibres lay between those for the uniform cylindrical and the conical fibres. With the exception of the uniform cylindrical fibre which yields a constant energy density, tapered fibres yield expressions for the energy density which depend on the fibre axial ratio, q. In particular, the energy density increases as q increases but converges at large q. By defining the critical axial ratio, q ₀, as the limit beyond which u is independent of the fibre slenderness, our model predicts the value of q ₀ to be about 10. These results are applied to explain the mechanisms regulating fibre composite fracture.     

Multivalent assembly of ultrasmall nanoparticles: One-, two-, and three-dimensional architectures of 2 nm gold nanoparticles

The assembly of nanoparticles (NPs) into complex structures is a fundamental topic in nanochemistry. Although progress has been made in this respect, the classical treatment of NPs as hard building blocks that lack the ability to anisotropically “bond” to each other limits the construction of more complex assemblies. More importantly, extension of methods of assembly of robust NPs to the assembly of ultrasmall ones with size below 2 nm is still challenging. Here we report the controlled self-assembly of ∼2 nm gold NPs into one-dimensional (1D) nanochain, two-dimensional (2D) nanobelt and three-dimensional (3D) nanocomet architectures by kinetically controlling the diffusion of ultrasmall gold NPs with anisotropic surfaces in solution. This process is presumed to allow selective ligand exchange with linkers at different binding sites on the NP surface, and results in “multivalent” interactions between NPs. Different from the assembly of “hard building blocks”, our results demonstrate the significance of surface effects for ultrasmall NPs (or clusters) in determining the structure of complex self-assemblies, and suggest the possibility of assembling these “molecule-like” ultrasmall nanocrystals into novel complex materials on a nanoscale approaching that of real atoms or molecules.      

Introducing the concept of “uncertainty in measurement” into domestic metrological practice

There are four options for introducing the uncertainty concept in Russia. Preference is given to the gradual replacement of “error characteristic,” “total mean-square error,” and “confidence limits of error” by the terms “uncertainty,” “combined standard uncertainty,” and “expanded uncertainty,” respectively. The incorrect and widespread perception that “uncertainty in measurement” is an alternative for “error” is pointed out. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 27–28, May, 2000.     

Stripes, non-fermi-liquid behavior, and high-T c superconductivity

The electronic structure of the high-T_c. cuprates is studied in terms of “large-U” and “small-U” orbitals. A striped structure and three types of quasiparticles are obtained, polaron-like “stripons” carrying charge, “svivons” carrying spin, and “quasielectrons” carrying both. The anomalous properties are explained, and specifically the behavior of the resistivity. Hall constant, and thermoelectric power. High-temperature superconductivity results from transitions between pair states of quasielectrons and stripons.     

Calculation of the effect of evaporating drops on the relative law of heat exchange with a disperse mist flow

On the basis of a two-layer scheme of wall turbulence, a relative law of heat exchange with a disperse mist flow is calculated. It is shown that the influence of drops on heat exchange leads to a finite “stepwise” increase in heat transfer compared to the case of a single-phase vapor flow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 510–513, May–June, 1997.