Using internal fibre geometry to improve the performance of pin-loaded holes in composite materials

The anisotropic nature of fibre reinforced composites leads to large stress concentrations around pin-loaded holes through standard weave cloths. Proper understanding of how this anisotropic nature affects the load distribution around holes can be utilised to reduce these concentrations if sufficient thought is given to the internal fibre geometry near to the hole. Such local reinforcements need not be highly complex and can be readily produced without excessive effort, producing significant improvements in performance.     

A comparative thermodynamic study of sorption systems: second law analysis

As a consequence of the phasing out of CFCs, sorption systems appear to be potential candidates to replace vapour compression systems. Amongst sorption systems there exists a choice between several systems, such as liquid absorption, solid adsorption and chemical reaction heat pumps. Nevertheless, few comparative studies between these systems have been undertaken so far. It is the aim of this paper to present such a study based on combined first and second law thermodynamical analysis of the different cycles. Simple entropy generation processes explain why the basic cycles for these systems yield performances much lower than the Carnot efficiency. The possibility of operating regenerative cycles with internal heat recovery and higher efficiencies has also been considered for typical common base conditions. Different entropy generation considerations have been visualised, such as thermal coupling (external/internal), non-uniform temperature component entropy production and other irreversible processes for the COP degradation in these systems. It is found that thermal coupling irreversibilities in solid sorption systems and other internal irreversibilities in liquid sorption systems with solution heat exchanger are dominant in the actual COP degradation with respect to the reversible Carnot COP.     

Measurement photography

Examples are presented of the partial and complete spatial self-orientation of plane optical images. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 28–32, May, 1996.     

Computational medicine: bioelectric field problems

Applications of large-scale computer modeling and simulation to a class of bioelectric field problems in a variety of biomedical research areas, from single cells to full human structures, are described. The authors focus on a specific subset of bioelectric field problems that have applications in electrocardiography and electroencephalography. The physics and physiology of bioelectric volume conductors are introduced. A specific computational example and the authors' view on the future direction of computational medicine are presented     

Thermal stability of Al/AlGaAs and Al/GaAs/AlGaAs (MBE) Schottky barriers

Outstanding stability has been observed in Al/Al/sub x/Ga/sub 1-x/As and Al/GaAs/Al/sub x/Ga/sub 1-x/As (x=0.25) Schottky barriers prepared by depositing Al in situ by MBE on annealing up to 400 degrees C. Conventionally evaporated barriers have been fabricated and compared with epitaxial ones. The changes in barrier height and ideality factor induced by annealing are reported.<>     

A simple and effective precoding scheme for noise whitening onintersymbol interference channels

A precoding scheme for noise whitening on intersymbol interference (ISI) channels is presented. This scheme is compatible with trellis-coded modulation and, unlike Tomlinson precoding, allows constellation shaping. It can be used with almost any shaping scheme, including the optimal SVQ shaping, as opposed to trellis precoding, which can only be used with trellis shaping. The implementation complexity of this scheme is minimal-only three times that of the noise prediction filter, hence effective noise whitening can be achieved by using a high-order predictor     

Torsion of an elastic space with a crack on the surface of revolution

Numerical methods for solving integral equations of an axisymmetric problem of torsion of an elastic space with cracks on the surface of revolution are suggested for the cases of cracks crossing the axis of symmetry and cracks that have no common points with this axis. We also present relations for calculating the stress intensity factors at crack tips. Numerical results are obtained for a conic or paraboloidal simply connected crack and for a doubly connected crack lying on a surface formed by the revolution of an arbitrarily oriented straight segment or a parabolic arc. The crack faces are either subjected to a constant load or free of any forces; the body is subjected to torsion at infinity.Karpenko Physico-Mechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 29, No. 6, pp. 87–93, November–December, 1993.     

Radiative-conductive heat transfer in a cylindrical monocrystal grown by the vertically oriented crystallization method

The steady-state two-dimensional problem of the radiative-conductive heat transfer in a cylindrical monocrystal is solved. The solution is obtained numerically by the time-independent technique. Convergence of the iteration process is achieved by including the relation between the intensity of the nonlinear source in the energy equation and the desired temperature field at a particular time step. An algorithm for calculating the intensity field and the nonlinear source is given. In calculating the first approximation of the temperature distribution, the method of moments is used. The results obtained are given.Moscow Institute of Railroad Transport Engineers, Moscow, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 1, pp. 76–82, January, 1994.     

Anomalous photoemission threshold in high-T c oxide superconductor with Cs and K submonolayers

The photoemission threshold and photocurrent spectra were investigated for Bi₂Sr₂CaCu₂O₈ crystals with K or Cs submonolayer films. The different films of K or Cs were deposited on the Bi-O surface in the temperature range 80–250 K. We observed an appreciable (up to 0.3 eV) energy shift of the threshold and a strong modification of the photocurrent spectra for different temperatures and submonolayer coverages. The appropriate model of such a phenomena is based on a quasimetallic K or Cs clusters effect and additional 2D-polaronic effect.