Showing papers by "Chalmers University of Technology published in 1984"
TL;DR: A survey of finite element methods for convectiondiffusion problems and first-order linear hyperbolic problems can be found in this article, where the authors give a survey of some recent work by the authors.
706 citations
TL;DR: In this article, the optical properties of evaporated films of doped semiconducting In2O3 in the 2-6eV range were investigated, i.e., around the fundamental bandgap.
Abstract: In this paper we investigate the optical properties of evaporated films of doped semiconducting In2O3 in the 2-6-eV range, i.e., around the fundamental bandgap. The study serves two main purposes: to elucidate basic properties of a heavily n-doped semiconductor, and to improve our understanding of a technologically important material which is widely used when transmittance of visible or solar radiation needs to be combined with good electrical conduction or low thermal emittance.
552 citations
TL;DR: In this paper, the effect of additives on the properties of injection moulded composites based on polypropylene (PP) and high density polyethylene (HDPE) filled with wood and cellulose flour was investigated.
Abstract: This paper reports on the effect of additives on the properties of injection moulded composites based on polypropylene (PP) and high density polyethylene (HDPE) filled with wood and cellulose flour. Three types of additives were studied: dispersion aids, elastomeric additives, and adhesion promoting agents. Some of the dispersion aids were found to improve the filler dispersion and the impact strength. The modulus remained relatively unaffected while the strength was lowered. The high molecular weight elastomeric additives increased the impact strength and ductility, while the stiffness was reduced. An adhesion promotor based on a maleic anhydride modified polypropylene was found to behave as a true coupling agent, i.e. the strength and ductility increased, the melt strength was improved, and also the hot water resistance was raised. The experimentally determined composite moduli are found to agree relatively well with theoretical predictions. The effect of processing on the shape and size of the...
346 citations
TL;DR: A new class of algorithms which is based on rational functions of the matrix is described, and there are also new algorithms which correspond to rational functions with several poles.
343 citations
TL;DR: In this paper, extensive calculations of the ground state properties of hydrogen chemisorbed on transition metal surfaces are performed using the effective medium theory, and the results for the chemical energy on all the 3D, 4D and 5D metals presented are in good agreement with experiment.
310 citations
01 Jun 1984
TL;DR: The principles underlying an efficient implementation of a lazy functional language, compiling to code for ordinary computers, based on combinator-like graph reduction: the user defined functions are used as rewrite rules in the graph.
Abstract: This paper describes the principles underlying an efficient implementation of a lazy functional language, compiling to code for ordinary computers. It is based on combinator-like graph reduction: the user defined functions are used as rewrite rules in the graph. Each function is compiled into an instruction sequence for an abstract graph reduction machine, called the G-machine, the code reduces a function application graph to its value. The G-machine instructions are then translated into target code. Speed improvements by almost two orders of magnitude over previous lazy evaluators have been measured; we provide some performance figures.
234 citations
17 Apr 1984
TL;DR: An extension to Milner's polymorphic type system is proposed and proved correct and the class of languages with mutually recursive top-level definitions can be ascribed a more general type than before.
Abstract: An extension to Milner's polymorphic type system is proposed and proved correct. Such an extension appears to be necessary for the class of languages with mutually recursive top-level definitions. We can now ascribe a more general type to such definitions than before.
211 citations
TL;DR: In this article, the authors discuss methods for calculation of different flexibility levels, strategies for a more flexible view upon products and processes, and examples and results from different areas within the Swedish industry.
Abstract: Drastic changes in market demands and rapid technological development have created a need for more flexible production systems and more complex products with a larger degree of variation. There is strong pressure towards the use of more and more mechanized and automated equipment, from single NC-machines to complete manufacturing systems. At the same time, there is a need for flexibility towards changes in the products. These changes have to be made in a limited time, and without the need for large reinvestments in the production system. This means that more often there must be discussion regarding flexibility versus productivity before the production system is designed. T will discuss methods for calculation of different flexibility levels, strategies for a more flexible view upon products and processes, and examples and results from different areas within the Swedish industry.
165 citations
TL;DR: In this paper, the absorption of electrons with regard to its spatial distribution in the crystal and design a phenomenological model comprising two parameters which are adjusted to the absorptive scattering cross section of the ion cores and that of the interstitial region.
Abstract: In the present low-energy electron-diffraction (LEED) study of the copper (111) surface the inner potential and the surface relaxation are determined independently from the subthreshold effect and from Bragg-type diffraction. A "subthreshold effect" is a narrow LEED intensity structure occurring at a setting where new beams have an emergence threshold in the metal: a "subthreshold." We reconsider the absorption of electrons with regard to its spatial distribution in the crystal and design a phenomenological model comprising two parameters which are adjusted to the absorptive scattering cross section of the ion cores and that of the interstitial region. The two-parameter model for the interlayer attenuation indicates the existence of a transparent scattering channel "pseudoparallel" to the surface for beams emerging in the crystal. The channeling extends over all layers penetrated by the LEED electrons, giving the subthreshold effect a peak width of about 2 eV. Each observable subthreshold effect fixes a point on the energy-dependent inner potential; for the copper (111) surface we are able to measure the inner potential at 19.5-, 73.6-, and 109-eV incidence energy. A local excited-state potential of the Hedin-Lundqvist type produces for the copper (111) surface an inner-potential curve that agrees well with the measured points. From LEED spectra for the 00, 10, and 01 beams from the copper (111) surface in the energy range 16-190 eV we infer a top-layer spacing contracted (0.7 \ifmmode\pm\else\textpm\fi{} 0.5)% relative to the layer spacing in the bulk. The theoretical and experimental spectra are compared by means of metric distances, which are stable with respect to noise in the data and give a linear response to small variations of the structural parameters.
165 citations
TL;DR: A permanent skin penetration has made it possible to develop a bone-anchored hearing aid with all components in one housing and a lowering in thresholds means lower transducer distortion, lower electrical gain, and lower power consumption to produce a given sensation level.
Abstract: Some patients who need hearing aids are unable to use an aid which transmits the sound via the external ear canal but have to use a bone-conduction hearing aid. The pressure needed to apply the transducer often gives the patient discomfort, and the attenuating effect of the skin gives poor electroacoustical function of the aid. A permanent skin penetration has made it possible to develop a bone-anchored hearing aid with all components in one housing. Ten patients have been equipped with such an aid. This paper deals with a comparative hearing threshold measurement on 10 patients. Bekesy audiometry was performed and a conventional Oticon (A-type) transducer was used. In the frequency range 600 to 6 000 Hz, there was a lowering of 10-20 dB in thresholds when skin penetration was performed. This lowering in thresholds means lower transducer distortion, lower electrical gain, and lower power consumption to produce a given sensation level.
164 citations
TL;DR: In this article, the chemical properties of silicon carbide fibres relevant to the use of SiC fibres as a reinforcement in metal matrix composite materials are reviewed, with particular attention paid to the oxidation properties and interaction with metals and alloys with respect to chemical interactions and fibre/matrix bonding.
TL;DR: In this paper, the flux of dissolved silicate across the sediment-water interface of sediments incubated in situ under parallel benthic flux chambers was measured, assuming that lack of oxygen will cause the activity of infauna to cease and thereby limit solute transport to that accomplished by molecular diffusion.
Abstract: On the assumption that lack of oxygen will cause the activity of benthic infauna to cease and thereby limit solute transport to that accomplished by molecular diffusion, we have measured the flux of dissolved silicate across the sediment-water interface of sediments incubated in situ under parallel benthic flux chambers. In one chamber the oxygen concentration was allowed to go to zero, and in the other the oxygen and pH remained at ambient values. As long as oxygen was present in the chambers, the measured summer and fall fluxes were 210 times those calculated from porewater profiles assuming one-dimensional molecular diffusion. The differences in fluxes predicted from the densities of macrobenthos at two different sites agree well with the flux measurements. After oxygen depletion, the silicate fluxes decreased and approached the values calculated on the basis of molecular diffusion. In one experiment the ratio between the oxic and anoxic fluxes was nearly identical to the ratio between the effective diffusion coefficient, as measured under oxic conditions using 22Na as a tracer, and the whole-sediment molecular diffusion coefficient. In winter (- 1’C) measured and calculated Fickian fluxes agreed closely, indicating a negligible effect of benthos on solute transport.
TL;DR: In this article, a transparent electrochromic device was made by coating conducting glass with reactively evaporated tungsten oxide films and letting these specimens form the working electrode in an electrochemical cell containing an electrolyte of LiClO4 + propylene carbonate.
TL;DR: In this article, it was shown that the usual Kubo formula for thermal response functions is invalid if a magnetic field is present, due to a lack of time-reversal symmetry.
Abstract: We demonstrate that the usual Kubo formula for thermal response functions is invalid if a magnetic field is present. There exists a fundamental correction due to a lack of time-reversal symmetry. We show in particular that, in addition to being of general importance in the theory of transport, this leads to a novel thermoelectric effect in a weakly disordered two-dimensional electron gas subject to a quantizing magnetic field. The thermopower tensor is calculated within the self-consistent Born approximation using a generalized Mott formula, which is derived.
TL;DR: In this paper, a neon ion beam has been used to regrow epitaxially a ~1700-AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures.
Abstract: A neon ion beam has been used to regrow epitaxially a ~1700-\AA{}-thick amorphous surface layer in silicon on sapphire at low temperatures. The damaged layer was produced by implanting 80-keV silicon ions to a dose of $2\ifmmode\times\else\texttimes\fi{}{10}^{15}$ ions/${\mathrm{cm}}^{2}$ at room temperature. The channeling technique with 315-keV protons was used to investigate the depth distribution of the damage, and disorder depth profiles were extracted from the backscattering spectra using calculations based on multiplescattering theory. The epitaxial regrowth was quantitatively determined from the extracted profiles. Many of the parameters which influence the regrowth rate, such as dose, dose rate, target temperature, energy, and random or channeled direction for the annealing beam, were varied. The results were compared with energy deposition calculations which indicated strongly that the annealing rate depends on the energy deposited in elastic collisions by the annealing ion beam. A defect annealing model based on vacancy diffusion is discussed.
TL;DR: In this paper, the authors discuss the distribution and transport of actinides dans l'eau, l'air and le sol, and the formation of colloides.
TL;DR: This paper describes a general class of simple Viterbi detectors with reduced complexity compared to the optimum case, and finds the asymptotically optimum reduced-complexity receiver for a variety of transmitted schemes and various complexity reduction factors.
Abstract: Partial response continuous phase modulation (CPM) gives constant envelope digital modulation schemes with excellent power spectra. Both narrow main lobe and low spectral tails can be achieved. When these signals are detected in an optimum coherent maximum likelihood sequence detector (Viterbi detector), power efficient schemes can also be designed, sometimes at the expense of receiver complexity. This paper describes a general class of simple Viterbi detectors with reduced complexity compared to the optimum case. The key idea is that the approximate receiver is based on a less complex CPM scheme than the transmitted scheme. The asymptotically optimum reduced-complexity receiver is found for a variety of transmitted schemes and various complexity reduction factors, for a specific class of receivers and modulation indexes. A new distance measure is introduced for the performance analysis. Smooth schemes based on raised cosine pulses are analyzed and simulated for the case of simplified reception. A graceful performance degradation occurs with the reduction of complexity.
TL;DR: It is pointed out the importance of the modulational instability as a possible limiting factor for coherent optical-fiber transmission and the need to address this problem in the near future.
Abstract: We point out the importance of the modulational instability as a possible limiting factor for coherent optical-fiber transmission.
TL;DR: The adsorption of H 2 O on Cu(100 and Pd(100) at temperatures around 10 K has been investigated by electron-energy-loss spectroscopy (EELS).
TL;DR: On demontre l'existence d'operateurs de diffusion definis partout for certaines equations de Klein-Gordon non lineaires as discussed by the authors, l'operateur de diffusion
Abstract: On demontre l'existence d'operateurs de diffusion definis partout pour certaines equations de Klein-Gordon non lineaires
TL;DR: In this article, the elastic energy expression of de Gennes for non-chiral and chiral smectic-C phases is reformulated, and it is shown that the maximum size of a uniformly oriented sample is limited, not only by the chiral helix but also by a spontaneous bend of the layers.
Abstract: The elastic energy expression of de Gennes for the non-chiral and chiral smectic-C phases is reformulated, and it is shown that the maximum size of a uniformly oriented sample is limited, not only by the chiral helix but also by a spontaneous bend of the smectic layers. A description of the flexoelectric effects is given: 9 different vector fields are involved, and they all remain in non-chiral smectic-C phase. These vector fields are connected to the divergence terms in the elastic free energy. The complexity of the boundary conditions for ferroelectric liquid crystals is discussed, and the concepts ‘bookshelf geometry’ and ‘φ-can’ are introduced. It is shown how the φ-can may be used to describe various monostable and bistable configurations of smectic-C cells. The symmetry of the cell can determine the configuration. Some general rules concerning the optical behaviour of smectic-C cells are given.
TL;DR: The microstructure of powder metallurgical high speed steel (ASP 60) has been investigated by combined analytical electron microscopy and atom-probe field-ion microscopy as mentioned in this paper.
16 Jul 1984
TL;DR: It is proved, that the interleaved behaviour of the resulting nets is equivalent to Milner's semantics and it is shown that a large class of CCS programs can be represented by finite nets and that this is impossible for the whole CCS.
Abstract: We give a partial order semantics to (pure) CCS via a translation into Petri nets and prove, that the interleaved behaviour of the resulting nets is equivalent to Milner's semantics. We show that a large class of CCS programs can be represented by finite nets and that this is impossible for the whole CCS.
TL;DR: Etude des proprietes des solutions de l'equation modelisant l'ecoulement d'un gaz dans un milieu poreux as mentioned in this paper.
Abstract: Etude des proprietes des solutions de l'equation modelisant l'ecoulement d'un gaz dans un milieu poreux
TL;DR: In this paper, a powder metallurgical high speed steel, ASP 23, has been investigated by transmission electron microscopy and the crystallographic orientation relationship between the precipitated phases and the ferrite matrix was investigated.
TL;DR: In this paper, the shear flow of nematic liquid crystals with a positive value of the Leslie viscosity α3 is studied theoretically under the assumption that the director will remain in the plane of shear, the equations governing the flow are solved numerically and the director- and velocity profile are calculated.
Abstract: The shear flow of nematic Liquid crystals with a positive value of the Leslie viscosity α3 is studied theoretically. Under the assumption that the director will remain in the plane of shear, the equations governing the flow are solved numerically and the director- and velocity-profile are calculated. The validity of this “in-plane” assumption is discussed, and it is shown that there are at least two situations where it is correct. For some values of the shear the solution of the equations is multi-valued. By study of the entropy production of the system it is deduced which one of these solutions will be adopted by the system. It is also demonstrated that as a consequence of these multi-valued solutions the system in some cases will behave like a system is undergoing a first-order phase transition.
TL;DR: In this article, the authors developed a standard method for measurements of the polarization of ferroelectric chiral smectic C liquid crystalline materials using the field-reversal method.
Abstract: With the aim to develop a standard method for measurements of the polarization of ferroelectric chiral smectic C liquid crystalline materials, we have studied thin, well-aligned samples of MBRA-8 using the field-reversal method. The method also provides an estimate for the rotational viscosity and for the response times.
TL;DR: In this paper, the force output of the biceps brachii muscle during static isometric contractions was studied in 26 arms of 23 subjects in relation to the simultaneously recorded level of the electromyogram (EMG) and the intra-muscular pressure (IMP).
TL;DR: In this paper, the authors studied the dynamical response of metal surfaces to external electric fields which vary slowly in space and time and showed that a linear response function determined the influence of a metal surface on all dynamical processes occurring outside of it.
Abstract: We study the dynamical response of metal surfaces to external electric fields which vary slowly in space and time. It is shown that a linear response function $g({q}_{\ensuremath{\parallel}},\ensuremath{\omega})$ determines the influence of a metal surface on all dynamical processes occurring outside of it. We evaluate $g({q}_{\ensuremath{\parallel}},\ensuremath{\omega})$ approximately within the jellium model and compare the result with electron-energy-loss measurements on Cu(100) and Ni(100). Good agreement between theory and experiment is obtained, particularly for Cu(100). Finally, we give illustrative applications to the frictional force on a charged particle and the damping of excitations at surfaces.