Showing papers by "University of Ljubljana published in 1988"
TL;DR: In this article, a manufacturing system is treated as a simple two-dimensional elastic structure in which the cutting force is generated by material flow against the tool, and generalized empirical relations corresponding to orthogonal cutting are applied to describe the non-linear dependence of a cutting force on chip velocity and thickness.
Abstract: In the article a manufacturing system is treated as a simple two dimensional elastic structure in which the cutting force is generated by material flow against the tool. Generalized empirical relations corresponding to orthogonal cutting are applied to describe the non-linear dependence of a cutting force on chip velocity and thickness. The formulated mechanical model of a two dimensional coupled oscillator thus represents a typical example of a non-linear dissipative system, the dynamics of which require description in a four dimensional phase space. The numerical solutions of the governing dynamical equations reveal chaotic oscillations if the characteristic cutting parameter is selected in a region corresponding to intensive cutting. The properties of chaotic oscillations are illustrated by the time dependence of tool displacement, acceleration, cutting force, and power dissipated for material deformation or exchanged with an oscillating tool. The manufactured surface profile is found to resemble a wavy water surface. The phase portraits, Lissajoux figures and spectral densities of calculated signals indicate a similarity with quasiperiodic movement. The information dimension of a corresponding strange attractor, estimated by the correlation exponent, is approximately 3 for a typical example of cutting chaos. The tool displacement X in the direction of input velocity appears to be the most characteristic variable. Its return map is constructed by successive observations of maximal displacement values. The corresponding approximate analytical expression X n+1 =5 X n (1.1- X n )-0.70 is similar to the prototypical map which is frequently applied in the study of chaotic phenomena.
155 citations
TL;DR: In this paper, the certification of a second-generation biological reference material (freeze-dried human serum) for trace element determinations is described, which was prepared under rigorously controlled conditions to avoid extraneous additions.
138 citations
TL;DR: Functional electrical stimulation was applied in 50 spinal cord injury patients in an effort to restore standing and walking and after using the stimulation in a home environment for more than three months, the number of patients who continued to use the stimulation for walking declined, and 16 patients remained ambulatory.
Abstract: Functional electrical stimulation (FES) was applied in 50 spinal cord injury patients in an effort to restore standing and walking. All patients in the program with lesions from T4-T12 were able to stand by means of FES. Walking, utilizing a four-channel stimulator, was accomplished by 25 patients with lesions in the range from T4-T12. These 25 patients represent approximately 5% of all spinal cord injured patients treated in the authors' rehabilitation facility during this time period. After using the stimulation in a home environment for more than three months, the number of patients who continued to use the stimulation for walking declined, and 16 patients remained ambulatory. The discontinuance of FES was mainly because of the time required to put on and operate the FES system and difficulties adapting to a new home environment and living situation.
100 citations
TL;DR: In this paper, the authors measured the frequency and temperature dependence of the complex dielectric constant near the Smectic-A liquid-crystal phase (Sm-${C^{\mathrm{*}}$--Sm-A) transition for two ferroelectric liquid crystals with a very large spontaneous polarization.
Abstract: The frequency and temperature dependence of the complex dielectric constant was measured near the smectic-${C}^{\mathrm{*}}$--smectic-A liquid-crystal phase (Sm-${C}^{\mathrm{*}}$--Sm-A) transition for two ferroelectric liquid crystals with a very large spontaneous polarization. The dielectric strengths as well as the corresponding relaxation frequencies of the dielectric modes were determined. Due to the large polarization we were able to resolve the contributions from the soft mode and the Goldstone mode in a comparatively large temperature interval in the Sm-${C}^{\mathrm{*}}$ phase close to the transition to the Sm-A phase. In the Sm-A phase, the relaxation frequency and the inverse dielectric strength of the soft mode decrease linearly when approaching ${T}_{c}$. Comparing the experimental data with a recent theoretical calculation of the complex dielectric constant, we conclude that we have a fairly good understanding of the behavior of the complex dielectric constant in the whole Sm-${C}^{\mathrm{*}}$--Sm-A transition range.
98 citations
TL;DR: In this paper, the cause du developpement d'un synovio-sarcome au siege de l'arthroplastie totale de hanche is inconnue.
Abstract: Dans le cas decrit la cause du developpement d'un synovio-sarcome au siege de l'arthroplastie totale de hanche est inconnue. Il provient probablement de cellules conjonctives neoplasiques qui peuvent provenir d'elements du tissu inflammatoire reactionnel. Il faut noter le long intervalle (12 ans) entre l'exposition initiale des tissus aux materiaux implantes et l'apparition de la tumeur
68 citations
TL;DR: In this paper, it was shown that the charmless decays of B mesons into the final states ppπ± and ppπ+π− are not the result of penguin-type processes.
64 citations
59 citations
TL;DR: Measurements of the Larmor frequency dependence of T1, are consistent with a spin‐lattice relaxation rate of the form 1/Tl = Aω−1/2+ B as expected for the case in which the relaxation arises from water‐biopolymer cross‐relaxation, which should be proportional to the surface area of the lung.
Abstract: The NMR relaxation times T2, T2, and T1 were measured in isolated rat lungs as functions of external magnetic field B0, temperature, and lung inflation. The observed linear dependence on B0 of the tissue-induced free induction decay rate (T2)−1 provides independent confirmation of the air/water interface model of the lung. Furthermore, measurements of the Larmor frequency dependence of T1, are consistent with a spin-lattice relaxation rate of the form 1/Tl = Aω−1/2+ B as expected for the case in which the relaxation arises from water-biopolymer cross-relaxation, which should be proportional to the surface area of the lung. This prediction was verified by observations of an approximately linear dependence of 1/T1, on transpulmonary pressure and thus on the lung surface area. © 1988 Academic Press, Inc.
57 citations
TL;DR: In this article, the Papapetrou equation for a point-like particle has been derived from the extrinsic curvature term in the action, which forces the particle to move along a helical path.
48 citations
TL;DR: Le recouvrement de relaxation de RMN, induit par surface, d'eau echangeable dans des ciments passe d'une forme exponentielle simple observee dans la periode «dormante» a une forme expositionielle «tendue» dans les derniers stades du processus d'hydratation.
Abstract: Le recouvrement de relaxation de RMN, induit par surface, d'eau echangeable dans des ciments passe d'une forme exponentielle simple observee dans la periode «dormante» a une forme exponentielle «tendue» dans les derniers stades du processus d'hydratation. Les resultats refletent l'evolution temporelle de la geometrie fractale des ciments et peuvent aider a differencier les differents modeles possibles de l'hydratation des ciments
44 citations
TL;DR: In this article, the authors used the ARGUS detector at DORIS II to study the production of the charmed baryon Λ c in e + e − annihilation at centre-of-mass energies near 10 GeV.
TL;DR: In this article, the diffusion and distribution of oxygen in models of biological systems have been followed by a fast-scan 2D EPR imaging apparatus based on the use of two sets of gradient coils with computer control to select projections.
Journal Article•
TL;DR: The effects of long-term electrical stimulation on reflex hyperactivity and voluntary muscle control were studied and the absence of tonic activity resulted in improvement of voluntary control, particularly in the tibialis anterior muscle.
Abstract: The effects of long-term electrical stimulation on reflex hyperactivity and voluntary muscle control were studied. Eight hemiplegic patients with implanted peroneal stimulator were included. After six months of functional electrical stimulation (FES) there was a decrease of tonic activity in both tibialis anterior and triceps surae muscles. The phasic stretch reflex activity in the stimulated tibialis anterior muscle increased. The resulting resistance during passive movements decreased due to diminution of tonic activity. The absence of tonic activity also resulted in improvement of voluntary control, particularly in the tibialis anterior muscle.
TL;DR: A dielectric study of Rb1−x(NH4)xH2AsO4 -RADA mdash; mixed crystals has been made in a wide concentration range x as mentioned in this paper.
Abstract: A dielectric study of Rb1−x(NH4)xH2AsO4 - RADA mdash; mixed crystals has been made in a wide concentration range x. Both the real and the imaginary part of the dielectric constant were studied in the X-band between 5 K and 300 K and the phase diagram was determined. The proton glass state exists in the concentration range 0.1
TL;DR: Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, a search for the decays B → K ∗ γ has been made as discussed by the authors.
TL;DR: Assessment of the periodontal status showed calculus to be the predominant disorder in the age groups 18 and 35-44 yr, while loss of sextants prevailed in persons aged over 65 yr.
Abstract: A pilot oral health epidemiological survey using WHO assessment forms was conducted in Yugoslavia in the year 1986. The study population consisted of 2600 persons aged 6, 12, 15, 18, 35-44, and over 65 yr. The survey included 22 towns (11 developed and 11 underdeveloped) in the six Republics and two Provinces of Yugoslavia. The results showed the prevalence of dental caries in the Yugoslav population to be very high (98.7% in 12-yr-olds). The mean decayed, missing, and filled teeth (DMF) scores were as follows: 6.1 at age 12 yr, 9.6 at age 15, 10.9 at age 18, 18.0 at age 35-44, and 28.0 in persons aged over 65 yr. Assessment of the periodontal status showed calculus to be the predominant disorder in the age groups 18 and 35-44 yr, while loss of sextants prevailed in persons aged over 65 yr.
TL;DR: In this article, a general solution of the problem of characterisation of quadratic functionals posed by Vukman is given, where the characterisation is based on a general characterisation problem.
Abstract: In this note a general solution of the problem of the characterisation of quadratic functionals posed by Vukman is given.
TL;DR: In this article, the production cross sections for the Λ, Σ0, Ξ− and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays.
Abstract: The production cross sections for the Λ, Σ0, Ξ−, Σ0 (1385), Ξ0 (1530) and Ω− hyperons have been measured, both in the continuum and in direct ϒ decays. Baryon rates in direct ϒ decays are enhanced by a factor of 2.5 or more compared to the continuum. Such a large baryon enhancement cannot be explained by standard fragmentation models. The strangeness suppression for baryons and mesons turns out to be the same. A strong suppression of spin 3/2 states is observed.
TL;DR: The upper embeddability of Cartesian and strong graph bundles with non-trivial base and fibre is proved and sharp upper and lower bounds for Betti defficiency are obtained.
Abstract: The upper embeddability of Cartesian and strong graph bundles with non-trivial base and fibre is proved. A similar result is obtained for both versions of lexicographic bundles. As a corollary the upper embeddability of Cartesian, strong and lexicographic products is obtained. The results cannot be generalized to the Cartesian and strong bundles with discrete fibres, i.e., to covering graphs. In this case sharp upper and lower bounds for Betti defficiency are obtained.
01 Jan 1988-International Journal of Radiation Applications and Instrumentation. Part D. Nuclear Tracks and Radiation Measurements
TL;DR: In this paper, a dosemeter was developed utilizing chemically etched MA-ND/α (CR-39) detector which is thermally insulated and protected against solar irradiation, and the calibration showed that its response amounts to 0.21 ± 0.03 tracks cm -2 /Bqm -3 day and was found to be in good agreement with theoretical prediction.
TL;DR: Using nuclear quadrupole resonance and double resonance techniques, the temperature dependence of 35 Cl, 14 N and 17 O frequencies have been measured in some photochromic and thermochromic solid N -salicylidene anilines as discussed by the authors.
TL;DR: In this paper, two new adducts, 2KrF2·MnF4 and KrF 2·mf4, have been synthesized and shown to decompose in a dynamic vacuum at −45°C yielding KrF2 and 1 : 1 adduct, which is stable up to −25°C.
Journal Article•
TL;DR: In this paper, the authors used the ARGUS detector at the DORIS II storage ring to observe the charmed baryons Σ c ++ and Σc 0 through their decays to Λ c + π ±.
TL;DR: The first direct observation of B meson decays into baryons using the decay channel Λ c + → pK − π + was reported in this paper, where a branching ratio of (0.30±0.06)% was derived from an observed signal of 208±89 events.
TL;DR: The heat production rate and the simultaneous nitrate consumption and production and consumption of nitrite and nitrous oxide were monitored during the anaerobic growth of two types of dissimilatory nitrate reducers.
Abstract: The heat production rate and the simultaneous nitrate consumption and production and consumption of nitrite and nitrous oxide were monitored during the anaerobic growth of two types of dissimilatory nitrate reducers Pseudomonas fluorescens, a denitrifier, consumed nitrate and accumulated small amounts of nitrite or nitrous oxide The heat production rate increased steadily during the course of nitrate consumption and decreased rapidly concomitant with the depletion of the electron acceptors A mean experimental enthalpy change value of −800 kJ/mol of nitrate and a mean growth yield value of 33 g (dry weight)/mol of nitrate consumed were obtained for different concentrations of nitrate For Pseudomonas putrefaciens, a dissimilatory ammonium producer, the nitrate consumption resulted in an accumulation of nitrite and nitrous oxide Nitrite consumption commenced after depletion of the nitrate; consequently, two phases were noted in the heat production rate curve during growth A mean experimental enthalpy change value of −810 kJ/mol of nitrate was obtained for different concentrations of nitrate
TL;DR: The broadening of the rotationally averaged ND4+ deuteron lines in Rb0.56(ND4)0.44D2PO4 due to the gradual "acid" deuterons freeze-out allows for a direct determination of the Edwards-Anderson pseudospin glass order parameter q far above the nominal glass transition temperature TG as mentioned in this paper.
Abstract: The broadening of the rotationally averaged ND4+ deuteron lines in Rb0.56(ND4)0.44D2PO4 due to the gradual "acid" deuteron freeze-out allows for a direct determination of the Edwards-Anderson pseudospin glass order parameter q far above the nominal glass transition temperature TG. The data provide strong evidence for a model where the basic difference between magnetic spin glasses and proton or deuteron pseudospin glasses is the presence of an inherent random field resulting from the substitutional disorder. This field acts as an ordering field conjugate to the pseudospin glass order parameter q and is responsible for the smearing of the deuteron glass transition.
TL;DR: It can be concluded that most nitroxide properties described for homogeneous systems—cells and tissue homogenates—are also valid for heterogeneous systems, which is important for the application of nitroxides as metabolically active NMR contrast agents.
Abstract: The reduction rates of different nitroxides in rat lung tissue were measured by electron paramagnetic resonance. We confirmed that the reduction rate of nitroxide spin probe molecules is coupled with their structure and transport characteristics. Oxygen was found to slow down the reduction rate of nitroxides in rat lung tissues. On the basis of these findings it can be concluded that most nitroxide properties described for homogeneous systems—cells and tissue homogenates—are also valid for heterogeneous systems, which is important for the application of nitroxides as metabolically active NMR contrast agents. © 1988 Academic Press, Inc.
TL;DR: Pulsed field gradient NMR measurements of rat lung tissue have shown that the apparent water self‐diffusion coefficient is nearly an order of magnitude smaller than that of free water and moreover is not constant but vanes as the inverse square root of the diffusion time.
Abstract: Pulsed field gradient NMR measurements of rat lung tissue have shown that the apparent water self-diffusion coefficient is nearly an order of magnitude smaller than that of free water and moreover is not constant but varies as the inverse square root of the diffusion time. The mean square displacement of water molecules is similarly proportional to the square root of the diffusion time. Possible origins of this non-Brownian behavior are discussed.