Improved coupled-mode theory of anisotropic optical waveguides

A coupled-mode equation for anisotropic waveguide systems of arbitrary cross section and general dielectric distribution is derived. Numerical results comparing the exact calculations to those of the method of Hardy et al. (Opt. Lett., vol.11, 742-4, 1986) show that the same accuracy can be obtained not only for TE, but also for TM mode coupling in the case of anisotropic waveguides, and the improved coupled-mode theory is applicable to the situation when moderately strong coupling occurs under the condition where the edge-to-edge separation of two coupled guides D₂ is about 0.1 μm     

Hierarchical Evolution of High Definition Television

This paper presents an economically attractive system for the hierarchical evolution of High Definition Television (HDTV) compatible with the NTSC installed base. It describes the two main signals of this system: HDMAC-60 and HDNTSC. The first, HDMAC-60, is a feeder signal for use between the program origination and program redistribution points, and used also as a DBS emission format. The second, HDNTSC, is a delivery signal for high definition terrestrial broadcast, CATV distribution and VCR plus laser video disc applications. We propose this emission system as a means for transmitting HDTV pictures to consumers on the North American continent.     

Shear transfer capacity along pumice aggregate concrete and high-performance concrete interfaces

This paper aims to present an experimental investigation on the behaviour of interfaces between pumice LWAC (lightweight aggregate concrete) and HPC (high-performance concrete-high-strength and fibre-reinforced), typically found in the faces and core, respectively, of hybrid precast structural sandwich panels. The evaluation of the experimental data resulted in the derivation of a semi-empirical relationship that relates the interface strength with materials strength, interface geometry and loading parameters. A brief overview of existing shear friction theories and proposed relationships, as well as a somparison among existing models and that proposed by the authors, are also outlined in the paper.     

Reconstruction of three-dimensional objects through matching oftheir parts

The problem of re-assembling an object from its parts or fragments has never been addressed with a unified computational approach, which depends on the pure geometric form of the parts and not on application-specific features. We propose a method for the automatic reconstruction of a model based on the geometry of its parts, which may be computer-generated models or range-scanned models. The matching process can benefit from any other external constraint imposed by the specific application     

Upgrading coal-derived liquids to diesel fuel

Distilled fractions of a coal-derived liquid from the H-Coal process were upgraded to diesel fuel by catalytic hydrotreatment. The total hydrotreated products were distilled into naphtha (<180°C) and diesel fuel fractions (>180°C) and the diesel fractions were analysed for hydrocarbon-type composition, hydrogen content and some diesel fuel properties. GC—MS-analyses were carried out on the hydrocarbon-type fractions to identify individual chemical compounds. To investigate the effect of different distillation cut points on diesel fuel yield and properties, cut points for one hydrotreated product were varied. The diesel fuel cetane numbers were correlated with percentage hydrogen, total aromatics and saturates. Cetane numbers above 40 were obtained for diesel fuels containing (i) more than 75% saturates, (ii) less than 15% total aromatics and (iii) a hydrogen content above 12.8%. Compounds identified by GC—MS-analyses (in the diesel fractions) were typical aromatic and cycloparaffin compounds. Normal-and iso-paraffin compounds were not detected. By varying the distillation cut point from 135 to 180°C, the cetane number of the residual diesel fraction improved from 37 to 44. This increase is ascribed to the removal of aromatic compounds in the 135–180°C boiling point range.     

The heater test at the Grimsel Rock Laboratory: The thermo-mechanical response of the rock mass to a heat flux

The Grimsel Test Site (Felslabor Grimsel — FLG) is situated at a depth of 450 m in the Juchlistock massif of the Bernese Oberland. It is managed by the National Cooperative for the Storage of Radioactive Waste (NAGRA-Switzerland).By means of a heater test, the power output of canisters filled with high-level waste is simulated. This heater test is performed by the German Gesellschaft für Strahlen- und Umweltforschung — GSF. Two electrical heaters, with a heatable length of 6 m, a diameter of 0.3 m and an available power of 4 kW/m, are installed in two vertical boreholes. One of them is located in the granite adjacent to a strongly fractured lamprophyre vein, the other one directly within this disturbed zone. They are operating since August 1986.The thermo-mechanical reaction of the rock mass is registered by a large number of measurement devices which are installed in an array of instrument boreholes around the heaters. They record the deformation and the alteration of rock stresses, the pore water pressure and the water conductivity caused by heating.     

Scrubbing Hydrogen Sulfide from Gases. A Rational Approach

Worsening of the environmental situation in many regions of Russia in recent decades is to a great degree due to production and refining of oil and gas with a high hydrogen sulfide content. Industrial methods of utilization of hydrogen sulfide are extremely irrational: it is either burned in flares or used for production of sulfur whose quality and quantity pose new problems related to its use.     

LOW-CYCLE FATIGUE AND CYCLIC CREEP OF METALS

Abstract— This paper deals with the effect of accumulated (oriented) plastic deformation (cyclic creep) on the life of metals under conditions of cyclic loading typically in the range of low-cycle fatigue. Specific features of cyclic creep of aluminium, titanium alloys and structural steels were investigated for the lives ranging from 05 to 2 × 10⁵ cycles to rupture as well as specific features of transition from quasistatic to fatigue fracture associated with the variation in the mode of deformation of metals. It is shown that under conditions of repeated stress-controlled loading in a wide range of low temperatures, the cyclic creep processes are the predominant ones determining life of metals over a wide range of cycles, and when calculating life under these conditions it is necessary to take into account the rate of these processes irrespective of the type of fracture: quasistatic or fatigue. An equation was obtained for calculating life under low-cycle loading conditions which takes into account the interrelationship between the life, the accumulated plastic strain, steady-state cyclic creep rate and the resistance of the material to cyclic creep.