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  • Articles  (1,209)
  • Articles: DFG German National Licenses  (1,209)
  • Engineering  (1,153)
  • 61.80  (29)
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  • 2010-2014
  • 1980-1984  (1,209)
  • 1950-1954
  • Mathematics  (963)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (246)
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  • Articles  (1,209)
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  • Articles: DFG German National Licenses  (1,209)
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  • 1
    Electronic Resource
    Electronic Resource
    Some perturbation results for the Linear Complementarity Problem (1982)
    Springer
    Mathematical programming 23 (1982), S. 181-192 
    Details
    ISSN: 1436-4646
    Keywords: Linear Complementarity Problem ; Stability ; Classes of Matrices
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract It has been shown previously that the Linear Complementarity Problem is stable when the defining matrix is positive semidefinite and when (locally) the set of solutions is nonempty and bounded. We enlarge the class of matrices for which this is true and also demonstrate how the boundedness condition leads to other stability type questions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01583787
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  • 2
    Electronic Resource
    Electronic Resource
    Laser induced reorder in Pb implanted Ge (1980)
    Springer
    Applied physics 22 (1980), S. 201-203 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 81.40
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Ge samples implanted with 40 keV Pb at a fluence of 3×1015/cm2 were irradiated with ruby laser single pulses of 15ns duration. Reordering of the damaged layer occurs for energy density irradiation above 0.6 J/cm2. The Pb atoms redistribute with a large component at the sample surface which is easily etched off. The remaining part of Pb impurities is substitutionally located, and the concentration exceeds the solid solubility limit by three order of magnitude. The formation of the metastable solution is explained in terms of a transient liquid layer produced during laser irradiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00886007
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  • 3
    Electronic Resource
    Electronic Resource
    The influence of intrisic defects on the degradation and luminescence of GaAs and other III–V compounds (1980)
    Springer
    Applied physics 23 (1980), S. 303-309 
    Details
    ISSN: 1432-0630
    Keywords: 42.80 ; 61.70 ; 61.80 ; 78.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A significant contribution to the degradation of GaAs-based lasers and light-emitting diodes arises from the formation of so-called dark line defects. It is shown that these defects are accumulations of non-radiative recombination centres around dislocations. The centres are identified as As vacancies, which are emitted by climbing dislocations, concomitantly with the absorption of Ga interstitials. From scanning deep-level transient spectroscopy observations it is concluded that the so-called DX centres are Ga interstitials. The driving force for dislocation climb and thus for dark-line-defect formation is a supersaturation of Ga interstitials originating from the growth of the GaAs crystals under Ga-rich conditions as a consequence of the high volatility of As. Phenomena in other III–V compound semiconductors related to the formation of dark line defects in GaAs are also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00914916
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  • 4
    Electronic Resource
    Electronic Resource
    The effect ofγ-irradiation on amorphous silicon field effect transistors (1983)
    Springer
    Applied physics 31 (1983), S. 19-22 
    Details
    ISSN: 1432-0630
    Keywords: 61.40 ; 61.80 ; 85.30 ; 85.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The paper deals with the effect ofγ-radiation from a Co60 source on the electronic properties of amorphous silicon field effect transistors. These thin film devices, deposited by the glow discharge technique, are being developed for addressable liquid crystal displays, logic circuits and other applications. 1 Mrad (Si) and 5 Mrad (Si) doses were used and the transistors were held at gate voltages between −8V and +8V during irradiation. Measurements on irradiated specimens showed shifts in threshold voltage of less than 3 V and a change in transconductance below 10%, both of which could be removed by annealing above 130 °C. These results are compared with presently available “radiation hardened” crystalline silicon device structures and it is concluded that in spite of the thicker gate insulation layer (0.3 μm of silicon nitride) of the amorphous devices, the latter are remarkably radiation tolerant, with little degradation in performance. Measurements on irradiatedα-Si films deposited on glass show pronounced conductivity changes, not observed in the transistors. It is suggested that these effects arise at the Si/glass interface, and are prevented by the presence of the silicon nitride film in the devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617183
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  • 5
    Electronic Resource
    Electronic Resource
    Monte-Carlo calculations of keV electron and positron slowing down in solids (1983)
    Springer
    Applied physics 32 (1983), S. 95-106 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 78.70 ; 29.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A Monte-Carlo simulation technique based on the screened Rutherford differential cross section for the elastic scattering and Gryzinski's semiempirical expression for the inelastic core and valence electron excitation is used to describe electrons and positrons slowing down in solids. The theoretical results are compared with the experimental backscattering, absorption and transmission results for aluminum, silicon, copper, and gold thin film and semi-infinite targets and good agreement is observed. The simulated stopping profiles are fitted with a simple analytic expression. The profiles are Laplace-transformed to give a useful data base for analyzing phenomena associated with slow positron re-emission from solids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617834
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  • 6
    Electronic Resource
    Electronic Resource
    Free-running ruby laser annealing of boron implanted silicon (1981)
    Springer
    Applied physics 26 (1981), S. 243-246 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 42.80 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An analytical treatment of the thermal phenomena during free-running ruby laser annealing of boron implanted silicon is presented. The heat equation was solved for a simplified shape of the pulse train consisting of a uniform succession of triangular spikes, identical in energy. During one spike the optical and thermal parameters of the sample were taken constant, but for each new spike, new values of these parameters were calculated taking into account their temperature dependence. Such a model predicts the melting of the top surface before the laser pulse has ended, for energy densities higher than 9×104 J/m2. RHEED confirms the presence of recristallization at about the same value of the laser-pulse energy densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617845
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  • 7
    Electronic Resource
    Electronic Resource
    Ion-beam mixing kinetics of Fe-Al multilayers studied by in situ electrical resistivity measurements (1984)
    Springer
    Applied physics 33 (1984), S. 77-82 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 72.15 ; 73.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The ion-beam mixing of Fe-Al evaporated multiple-layer films has been investigated by measuring continuously the electrical resistivity of the samples during the bombardment. The experimental curves exhibit a tendency toward a saturation process and allow the determination of the critical dose corresponding to the total mixing of the multiple-layer film. The variations of the volume fraction of intermixed atoms as a function of the ion dose have been deduced and a semi-empirical model is proposed to explain the observed kinetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617611
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature dependence of positron annihilation parameters in neutron irradiated molybdenum (1984)
    Springer
    Applied physics 33 (1984), S. 255-263 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime measurements have been performed for molybdenum samples containing different densities of voids and dislocation loops. The samples consisted of single crystal molybdenum exposed to 2.7×1018 fast neutrons/cm2 at 60°C, and subsequently annealed at 650°, 725°, 800°, and 875°C in vacuum (p〈10−7 Torr). After each annealing, where the densities of voids and loops were changed, positron lifetime measurements were performed in the temperature interval [−194°, 285°C]. In two-term fits of the measured spectra the longer lifetime, τe2-460 ps corresponds to an intensityI e2 increasing with sample temperature. The shorter lifetime τe1 decreases with increasing temperature. A three-state trapping model with and without detrapping is discussed, and appears to be incapable of explaining the observed temperature dependences. A four-state positron trapping model including detrapping is necessary and satisfactory. It describes positron trapping to voids and trapping to dislocation loops, which is followed by a competition between detrapping and positron transition to jogs or other dislocation-bound defects. Mathematical expressions of the four-state trapping model including detrapping are worked out and calculations of the intensityI e2 are compared with the experimental values ofI e2. By use of special models for the temperature dependence of trapping rates, numerical values can be determined for the positron-dislocation-binding energy and for specific positron trapping rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00614668
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  • 9
    Electronic Resource
    Electronic Resource
    Monte Carlo calculations of keV electron and positron slowing down in solids. II (1984)
    Springer
    Applied physics 35 (1984), S. 51-59 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 78.70 ; 29.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An improved Monte-Carlo simulation technique has been used to investigate positron and electron slowing down in solid matter. Elastic scattering is based on exact cross sections of effective crystalline potentials and inelastic processes are described by Gryzinski's semiempirical expression for each core and valence electron excitation. Calculations with normal and oblique angles of incidence have been made for positrons and electrons impinging on semi-infinite aluminium, copper, tungsten, and gold. Interesting differences have been found between positron and electron penetration and backscattering features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620300
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  • 10
    Electronic Resource
    Electronic Resource
    Binding of gas atoms to extended crystal defects in molybdenum studied by positrons (1982)
    Springer
    Applied physics 27 (1982), S. 247-250 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.80 ; 71.60
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The positron annihilation technique (P.A.T.) has been used in a study of interactions between gas impurities and crystal defects (vacancy loops and voids) in molybdenum. P.A.T. measurements were found to be very effective for this purpose. We propose that the observed effects are due to decoration of the void surface with nitrogen and vacancy loop decoration with hydrogen and nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00619087
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  • 11
    Electronic Resource
    Electronic Resource
    Radiation damage and annealing studies of ion bombarded cobalt (1984)
    Springer
    Applied physics 35 (1984), S. 99-102 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 34
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effects of implantation-induced radiation damage on the thermal oxidation of cobalt have been studied. Bombardment by both Co+ self-ions and by Xe+ has been studied as a function of ion dose, energy and annealing temperature. A major increase in oxidation was observed for doses of 〉1016 Co+ cm−2 in agreement with previous studies on Al. The oxidation behaviour as a function of annealing temperature was markedly different for Co+ and Xe+ bombarded samples. For Co+ bombarded samples, damage anneals rapidly in the temperature range 20–300°C due to thermally assisted repair of point defects and vacancy clusters. However, for Xe+ bombardment, it is proposed that the higher annealing temperatures required for damage repair arise due to the stabilisation of three-dimensional vacancy clusters by the oversized Xe atoms. The increase in oxidation after annealing in the temperature range 300–500°C is thought to be due to vacancy release mechanisms which may affect oxide nucleation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620637
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  • 12
    Electronic Resource
    Electronic Resource
    Oxidation inhibiting properties of Si3N4-layers produced by ion implantation (1980)
    Springer
    Applied physics 22 (1980), S. 393-397 
    Details
    ISSN: 1432-0630
    Keywords: 85.30 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The implantation of nitrogen into silicon to produce Si3N4 layers was investigated to find an alternative to CVD-Si3N4 layers used in ISOPLANAR-and LOCOS-technology. The technological properties of the implanted Si3N4 layers in respect to oxidation inhibition and etching are comparable or superior to CVD-Si3N4 layers. The implanted layers are more resistent against oxidation for nitrogen doses of 2.4×1017 cm−2 at 30keV. The etching behavior is comparable for both types of Si3N4-layers. In the implanted layers no pinholes are found and threre is no formation of a bird's beak, as is well known in the case of CVD-nitride.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00901063
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  • 13
    Electronic Resource
    Electronic Resource
    On the inelastic-loss approximation for keV-energy ion collisions in solids (1981)
    Springer
    Applied physics 24 (1981), S. 121-126 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Inelastic energy-loss in a single collisionT e and related stopping cross-sectionT e based on the Firsov model are evaluated for different screening functions in the elastic interaction potentials. Various approximations ofT e andS e for keV-ions in solids are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00902267
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  • 14
    Electronic Resource
    Electronic Resource
    Lattice defects of V3Si single crystals studied by positron annihilation (1981)
    Springer
    Applied physics 25 (1981), S. 65-70 
    Details
    ISSN: 1432-0630
    Keywords: 78.70 ; 61.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The sensitivity of positrons to point defects created by the irradiation of V3Si with neutrons is demonstrated. We found no indication of thermal vacancies by thermal equilibrium measurement up to 1273 K which indicates that the monovacancy formation enthalpy for V3Si isH 1V F ≧(1.84±0.14) eV. Investigations within the range of homogeneity for excess vanadium suppot the idea that substitutional defects are the dominating defect type, whereas for excess silicon a direct confirmation of existing structural vacancies as the dominating defect type is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935393
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  • 15
    Electronic Resource
    Electronic Resource
    Calculation of the temperature during electron pulse annealing of silicon (1981)
    Springer
    Applied physics 25 (1981), S. 139-142 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 78.30 ; 85.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract High power density electron beams offer new opportunities for studies of epitaxial growth of semiconductor materials. Assuming that the mechanism of epitaxial growth can be understood as a surface melting followed by supercooling regrowth, the heat flow equation has been applied to calculate the temperature reached after an electron beam pulse of power density between 0.5–2 J/cm2. Comparison with laser annealing is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00901286
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  • 16
    Electronic Resource
    Electronic Resource
    Depth of origin of sputtered atoms (1981)
    Springer
    Applied physics 25 (1981), S. 307-310 
    Details
    ISSN: 1432-0630
    Keywords: 79.20 ; 68.55 ; 61.80 ; 34
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Estimates are given for the distribution of the depth of origin of sputtered atoms in the low-fluence limit, as well as the corresponding distribution of atoms sputtered into a given energy interval. The former distribution is well described by an exponential profile, with the characteristic depth being consistent with previous results. The latter distribution is characterized by an energy-dependent depth scale and a shape that varies from exponential at low sputtered-atom energies to inverse-power form at higher energies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00902988
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  • 17
    Electronic Resource
    Electronic Resource
    γ-Ray (and electron) induced annealing of nuclear tracks in polymeric detectors (1981)
    Springer
    Applied physics 25 (1981), S. 337-345 
    Details
    ISSN: 1432-0630
    Keywords: 29 ; 34 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Energy loss profiles for secondary electrons and γ-rays are discussed and the interactions of γ-rays with the activated species within the core of a nuclear track investigated. Based on an electron-hole trapping mechanism experimental values for the activation energies of annealing for nuclear tracks in the range of 0.26 to 0.5 eV have been obtained. These compare favourably with theoretical expectations. The consequences of variations in the detection sensitivities of such detectors are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00902992
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  • 18
    Electronic Resource
    Electronic Resource
    Incorporation of oxygen atoms into As+ implanted silicon during cw CO2 laser annealing in O2 (1983)
    Springer
    Applied physics 31 (1983), S. 71-74 
    Details
    ISSN: 1432-0630
    Keywords: 42.60 ; 61.80 ; 78.50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By annealing Si layers amorphised by ion-implantation with a cw CO2 laser beam in oxygen rich environments, it has been possible to incorporate O atoms into the recrystallized lattice. Absorption measurements on such regrown layers by infrared spectrometry have shown that the impurities are preferentially bonded into substitutional lattice sites, rather than existing interstitially. Supplementary RHEED studies have indicated thatβ-cristobalite, a crystalline form of SiO2, has been formed. These investigations highlight the importance of the ambient during cw laser annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00616307
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  • 19
    Electronic Resource
    Electronic Resource
    Energy distributions of low energy H ions backscattered from graphite, stainless steel, and molybdenum (1982)
    Springer
    Applied physics 27 (1982), S. 263-268 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 79.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Energy distributions of H+ and H− backscattered from graphite, stainless steel and molybdenum were measured for low incident beam energies (150∼1500 eV). The energy distributions of H− resembled that of H+, while the intensity ratio of H− to H+ varied from material to material and with the incident proton energy. A peak in the energy distribution moved to the “cutoff” energy with decreasing incident energy, which can be attributed to an increase in nuclear stopping cross section and a decrease in electronic stopping cross section. The ratio of the peak energy to the incident energy is related to the reduced energy ɛ of incident beam independent of target materials in the measured region (0.03〈ɛ〈 3.3).
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    URL: http://dx.doi.org/10.1007/BF00619090
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  • 20
    Electronic Resource
    Electronic Resource
    A search for a thermal spike effect in sputtering (1983)
    Springer
    Applied physics 30 (1983), S. 83-86 
    Details
    ISSN: 1432-0630
    Keywords: 79.20 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The temperature dependence of the sputtering yield was measured for lOOkeV per atom bombardment of silver with molecular and atomic antimony ions. No exponential increase of the yield was found in the temperature range from 25° to 775 °C, although a pronounced nonlinear effect is observed when the yield of these projectiles is compared,Y(Sb 2 + )≈ 1.5×[2Y(Sb+)]. We conclude that there is no influence of the lattice temperature on collision spikes.
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    URL: http://dx.doi.org/10.1007/BF00614908
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  • 21
    Electronic Resource
    Electronic Resource
    Low-power multi-pulse laser annealing of α-Ge (1983)
    Springer
    Applied physics 30 (1983), S. 161-167 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80 ; 68.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this paper we want to show by means of Reflection High Energy Electron Diffraction (RHEED) techniques that the recrystallization processes taking place on amorphous germanium films irradiated with low-power superimposed ruby laser pulses occur gradually. Furthermore, in implanted α-Ge films the amorphous-crystalline front moves from the surface of the specimen towards the substrate, while the opposite occurs for glow-discharge deposited films. Moreover, electron microscope observations carried out with a double-stage carbon replica technique at different depths in the specimen show that defect migration is one of the competitive mechanisms in low-power laser annealing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00620535
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  • 22
    Electronic Resource
    Electronic Resource
    Positron lifetime measurements on electron irradiation damage in amorphous Pd80Si20 and Cu50Ti50 alloys (1982)
    Springer
    Applied physics 27 (1982), S. 31-33 
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    ISSN: 1432-0630
    Keywords: 61.40 ; 61.80 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron lifetime measurements were performed on amorphous Pd80Si20 and Cu50Ti50 alloys irradiated with 3MeV electrons at 20K. The irradiation was found to increase the mean positron lifetime in both specimens indicating the presence of vacancy-like radiation damage. Isochronal annealing between 77 K and 300 K resulted in a continuous reduction of the positron lifetime, which suggests a gradual recovery of the irradiation induced defects.
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    URL: http://dx.doi.org/10.1007/BF01197543
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  • 23
    Electronic Resource
    Electronic Resource
    Positron annihilation and Hall effect in electron irradiatedn-InP crystals (1982)
    Springer
    Applied physics 29 (1982), S. 219-223 
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    ISSN: 1432-0630
    Keywords: 61.80 ; 71.55 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Positron annihilation and Hall effect inn-InP crystals as a function of electron irradiation up to 1 · 1019 cm−2 and post-irradiated isochronal annealing up to 550 °C have been studied. It is concluded that in irradiatedn-InP samples positrons interact with negatively charged acceptor-type defect with level atE c −0.33 eV, probablyV In (primary defect). In post-irradiated isochronal annealed (up to 330 °C) samples ofn-InP positron trapping occurs preferably in secondary defects-vacancy clusters, which are formed in the temperature range (150–300 °C). Inn-InP crystals containing radiation induced defects the trapping rate was found to decrease with temperature in the range (300–77) K.
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    URL: http://dx.doi.org/10.1007/BF00615071
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  • 24
    Electronic Resource
    Electronic Resource
    Disclosure of defects in YAG crystals by the thermoluminescence method (1984)
    Springer
    Applied physics 35 (1984), S. 249-253 
    Details
    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80 ; 71.35 ; 78.55
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The topograms revealing the anisotropic distribution of defects in the volume of monocrystalline YAG samples have been obtained by the thermoluminescence (TL) technique. It has also been shown that the anisotropic distribution of the lattice defects affects strongly the shape of the TL curves. The greatest changes in the TL intensity were observed in the areas of the samples distributed symmetrically every 120°. It was noted that the selective distribution of the TL intensity is caused mainly by the presence of the (211) facets as well as growth striations formed during the growth process. The groups of lines observed in the TL spectrum have been ascribed to the Tb3+ ions, excited owing to the radiationless energy transfer from the bound exciton states (BES).
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    URL: http://dx.doi.org/10.1007/BF00617175
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  • 25
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    Interaction of a low-pressure mercury discharge with the discharge tube wall (1980)
    Springer
    Applied physics 23 (1980), S. 355-356 
    Details
    ISSN: 1432-0630
    Keywords: 61.80 ; 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The darkening of soda-lime glass envelopes of low-pressure mercury discharge tubes has nothing to do with the formation of sodium amalgam on the inner surface of the tube. It is, however, connected with the diffusion of mercury ions into the glass of the tube. By applying a high negative voltage to part of the outer surface of a burning tube a sodium depleted region is created at the corresponding part of the inner surface. After removal of the high-voltage electrode and continued normal operation the rate of darkening of the sodium-depleted part of the tube is about 50 times larger than the rate observed for the normal parts of the same tube.
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    Range and range straggling of oxygen implanted into silicon at energies between 2 and 20 MeV (1980)
    Springer
    Applied physics 21 (1980), S. 151-158 
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    ISSN: 1432-0630
    Keywords: 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Oxygen profiles in silicon implanted with energies between 2 and 20 MeV by means of a Tandem accelerator have been investigated with a microprobe after bevelling the sample surface. It is shown that the measured profiles correspond to the implantation profiles when the microprobe is operated with a well focussed 2 keV electron beam. The projected ion ranges and the profiles thus obtained are compared with theoretical profiles which have been calculated by a Monte Carlo simulation of the stopping procedure. Takingk=1.30k LSS for the electronic stopping coefficient in the LSS region up to 2.55 MeV and a constant value of 162 eV/Å for the electronic stopping at higher energies the calculation yields satisfactory range estimates, whereas the range straggling is systematically too small up to 13% in comparison with the experimental results.
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    Deep levels subsisting in ion implanted silicon after various transient thermal annealing procedures (1983)
    Springer
    Applied physics 31 (1983), S. 147-152 
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    ISSN: 1432-0630
    Keywords: 61.80 ; 85.30 ; 71.20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Deep-level transient spectroscopy has been used to investigate the defects remaining in ion implantedp-n junctions in silicon after various pulsed annealing techniques, including ruby and YAG lasers as well as pulsed electron beams (PEBA). The nature and distribution of the various identified levels are discussed for each procedure as a function of various experimental parameters.
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    Surface electric fields of tourmaline (1983)
    Springer
    Applied physics 31 (1983), S. 183-185 
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    ISSN: 1432-0630
    Keywords: 61.80 ; 85.30 ; 71.20
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    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The N2, O2, H2O, and CO2 molecules that have condensed on the surface of a pyroelectric tourmaline crystal were degassed successively by means of electron bombardment. The temperature dependence of the electrostatic field strength on the specimen surface was observed by electron diffraction; it decreased as the degassing advanced. The tourmaline surface behaved as a gas Chromatographic adsorbent.
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    Time-resolved defect production and annealing during electron-beam processing of silicon (1984)
    Springer
    Applied physics 33 (1984), S. 251-254 
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    ISSN: 1432-0630
    Keywords: 61.70 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In (100)p-Si radiation damage was produced by implanting B+ ions with an energy of 80keV, 90keV and 1.6MeV. The specimens were annealed by scanned electronbeam irradiation (20keV, 1–2mAcm−2). The formation, evolution and annihilation of defects during the irradiation process were investigated by employing DLTS and RBS measuring techniques. The results show a minimum of defect concentration and an efficiency of the electrical activation of B higher than 80% at an annealing time of 4.5 s. For irradiation times longer than 5 s it becomes evident, that the crystal surface acts as source of defects and contributes to an increase in defect concentration.
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    Vanadium oxidation as a result of cw CO2 laser irradiation in atmospheric air (1984)
    Springer
    Applied physics 35 (1984), S. 103-108 
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    ISSN: 1432-0630
    Keywords: 42.60 ; 68.55 ; 61.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract New results are reported concerning the vanadium oxidation by cw CO2 laser irradiation in air at atmospheric pressure. Particular emphasis is paid both to the initial stage and the development of the oxidation process under the action of the laser radiation. Some aspects are finally discussed concerning the quantitative theoretical interpretation of the experimentally recorded data.
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    Dynamics of a single species in a spatially varying environment: The stabilizing role of high dispersal rates (1982)
    Springer
    Journal of mathematical biology 16 (1982), S. 49-55 
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    ISSN: 1432-1416
    Keywords: Stability ; Diffusion ; Parabolic equations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Models for a single species that inhabits an environment that is spatially varying are presented. Simple necessary and sufficient conditions for stability, which are independent of the exact details of the dispersal process, are developed in the case of large diffusion rates. The results highlight the important stabilizing nature of diffusion in a spatially varying environment.
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    Lotka-Volterra equations: Decomposition, stability, and structure (1980)
    Springer
    Journal of mathematical biology 9 (1980), S. 65-83 
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    ISSN: 1432-1416
    Keywords: Nonnegative equilibria ; Stability ; Decompositions ; Sub-communities ; Structural perturbations ; Connective stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The major objective of this paper is to propose a new decomposition-aggregation framework for stability analysis of Lotka-Volterra equations employing the concept of vector Liapunov functions. Both the disjoint and the overlapping decompositions are introduced to increase flexibility in constructing Liapunov functions for the overall system. Our second objective is to consider the Lotka-Volterra equations under structural perturbations, and derive conditions under which a positive equilibrium is connectively stable. Both objectives of this paper are directed towards a better understanding of the intricate interplay between stability and complexity in the context of robustness of model ecosystems represented by Lotka-Volterra equations. Only stability of equilibria in models with constant parameters is considered here. Nonequilibrium analysis of models with nonlinear time-varying parameters is the subject of a companion paper.
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    Equilibrium solutions of age-specific population dynamics of several species (1981)
    Springer
    Journal of mathematical biology 11 (1981), S. 65-84 
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    ISSN: 1432-1416
    Keywords: Population dynamics ; Age-dependent models ; Equilibrium solutions ; Stability ; Evolution equations
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    Topics: Biology , Mathematics
    Notes: Summary A mathematical model describing the dynamics of a population consisting of several species is studied. The interactions in the population are assumed to be age-specific. Using an evolution equation approach, sufficient conditions for well-posedness in L 1 of the dynamics and for existence as well as for stability of equilibrium solutions are given.
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    Stability in a class of cyclic epidemic models with delay (1981)
    Springer
    Journal of mathematical biology 11 (1981), S. 95-103 
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    ISSN: 1432-1416
    Keywords: Epidemiology ; SIRS ; Deterministic models ; Distributed delays ; Stability
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    Topics: Biology , Mathematics
    Notes: Abstract A detailed analysis of a general class of SIRS epidemic models is given. Sufficient conditions are derived which guarantee the global stability of the endemic equilibrium solution. Further conditions are found which ensure instability for the equilibrium. Finally, the dependence of the stability on the contact number and the ratio of the mean length of infection to the mean removed time is considered.
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    Stability in a two host epidemic model (1982)
    Springer
    Journal of mathematical biology 14 (1982), S. 71-75 
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    ISSN: 1432-1416
    Keywords: Epidemiology ; Two host models ; Stability
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    Notes: Abstract An epidemic model is derived for a two host infectious disease. It is shown that if a non-trivial equilibrium solution exists, it is globally stable. This result is also proved for a similar one host model.
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    Analysis of a sterile insect release model with predation (1982)
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    Journal of mathematical biology 16 (1982), S. 33-48 
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    ISSN: 1432-1416
    Keywords: Sterile insect release ; Predation ; Stability ; Limit cycles ; Optimal control
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    Notes: Abstract A model for the sterile insect release method of pest control in which the target species is under predatory or parasitic regulation is analyzed. The equations are nondimensionalized and the rescaled parameters are interpreted. There are four types of equilibria, whose existence and stability depend on which of ten regions of parameter space contain the rescaled parameters, and in turn give minimal release rates to achieve eradication of the pest. In at least one region, Hopf bifurcation theory shows the existence of limit cycles, but they are found to be unstable. In addition, the optimal release rate to minimize a total cost functional for pest control by the sterile release method is studied. Both approaches show that when predation accounts for a large fraction of the natural deaths, the necessary release rate and total cost are higher than for weak predation. If the predators are removed without being replaced by any other source of mortality, the cost rises in all cases but rises much more dramatically for cases with strong predation. A definite danger of the sterile release method when some predatory control exists is that the predators are frequently driven extinct before the prey, so that the target species could explode to much higher levels and be more difficult to eradicate again after the sterile release is terminated.
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    Models of epidemics and endemicity in genetically variable host populations (1983)
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    Journal of mathematical biology 17 (1983), S. 289-304 
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    ISSN: 1432-1416
    Keywords: Endemicity ; Epidemics ; Genetics ; Deterministic models ; Stability
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    Notes: Abstract A discrete time genetics model is developed for populations that are undergoing selection due to infectious disease. It is assumed that the generation time of the host and infectious agent are non-synchronous and that only the host population is evolving. Two classes of epidemic processes are considered. The first class is for infectious agents that confer immunity following infection, while the second class is for those that do not confer immunity. The necessary and sufficient conditions are found in order for the disease to persist in a stable polymorphic host population. These conditions are shown to depend on the density of susceptibles, the selection coefficients, and the severity and class of the disease process.
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    Constant-rate stocking of predator-prey systems (1981)
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    Journal of mathematical biology 11 (1981), S. 1-14 
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    ISSN: 1432-1416
    Keywords: Ecological modelling ; Predator-prey systems ; Ordinary non-linear differential equations ; Stability
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    Topics: Biology , Mathematics
    Notes: Abstract We examine the qualitative effects of constant-rate stocking of either or both species in a predator-prey system. The hypotheses are made as mild as possible so that several types of systems with different qualitative alternatives may be studied.
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    Coexistence properties of some predator-prey systems under constant rate harvesting and stocking (1982)
    Springer
    Journal of mathematical biology 12 (1982), S. 101-114 
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    ISSN: 1432-1416
    Keywords: Predator-prey systems ; Harvesting ; Stability
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    Notes: Abstract The global behaviour of a class of predator-prey systems, modelled by a pair of non-linear ordinary differential equations, under constant rate harvesting and/or stocking of both species, is presented. Theoretically possible structures and transitions are developed and validated by computer simulations. The results are presented as transition loci in the F-G (prey harvest rate-predator harvest rate) plane.
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    A predator prey model with age structure (1982)
    Springer
    Journal of mathematical biology 14 (1982), S. 231-250 
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    ISSN: 1432-1416
    Keywords: Predator-prey ; Age structure ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A general predator-prey model is considered in which the predator population is assumed to have an age structure which significantly affects its fecundity. The model equations are derived from the general McKendrick equations for age structured populations. The existence, stability and destabilization of equilibria are studied as they depend on the prey's natural carrying capacity and the maturation periodm of the predator. The main result of the paper is that for a broad class of maturation functions positive equilibria are either unstable for smallm or are destabilized asm decreases to zero. This is in contrast to the usual rule of thumb that increasing (not decreasing) delays in growth rate responses cause instabilities.
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    Stability of stationary distributions in a space-dependent population growth process (1982)
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    Journal of mathematical biology 15 (1982), S. 37-50 
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    ISSN: 1432-1416
    Keywords: Reaction-diffusion system ; Stationary solution ; Stability
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    Topics: Biology , Mathematics
    Notes: Abstract We consider a spatial population growth process which is described by a reaction-diffusion equation c(x)u t = (a 2(x)u x ) x +f(u), c(x) 〉0, a(x) 〉 0, defined on an interval [0, 1] of the spatial variable x. First we study the stability of nonconstant stationary solutions of this equation under Neumann boundary conditions. It is shown that any nonconstant stationary solution (if it exists) is unstable if a xx⩽0 for all xε[0, 1], and conversely ifa xx〉0 for some xε[0, 1], there exists a stable nonconstant stationary solution. Next we study the stability of stationary solutions under Dirichlet boundary conditions. We consider two types of stationary solutions, i.e., a solution u 0(x) which satisfies u 0 x≠0 for all xε[0, 1] (type I) and a solution u 0(x) which satisfies u 0x = 0 at two or more points in [0, 1] (type II). It is shown that any stationary solution of type I [type II] is stable [unstable] if a xx ⩾0 [a xx ⩽0] for all xε[0, 1]. Conversely, there exists an unstable [a stable] stationary solution of type I [type II] if a xx 〈0 [a xx 〉0] for some xε[0, 1].
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    Effects of behavioral adaptation on a predator-prey model (1982)
    Springer
    Journal of mathematical biology 15 (1982), S. 239-247 
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    ISSN: 1432-1416
    Keywords: Predator-prey model ; Behavioral adaptation ; Stability
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    Topics: Biology , Mathematics
    Notes: Abstract The Volterra-Lotka predator-prey equations are modified so that the predator's ability to utilize the prey varies in proportion to the average number of encounters between the two species in the past. The behavior of this adaptive system is then described in terms of three parameters — the carrying capacity of the prey, the relative death rate of the predator, and the predator's memoryspan. The most stable situation is shown to occur when the carrying capacity of the prey is large, the predator's death rate is close to zero, and the predator is able to adapt quickly to changing levels of prey density.
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    On the stability of delay equation models of simple human stretch reflexes (1983)
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    Journal of mathematical biology 17 (1983), S. 331-349 
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    ISSN: 1432-1416
    Keywords: Stability ; Delay equations ; Stretch reflexes ; Mathematical studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Human stretch reflexes (SRs) are often too weak and ineffectual to provide adequate postural regulation or rhythmic movement boosting (e.g. in ankle pushoff at the end of stance phase in fast running). Recent improvements in methods of artificially enhancing skeletomotor responses, especially in therapeutic regimens, should not be widely employed until the clonus-resisting stability properties of SRs are better understood. We formulate an idealized linear servo model of a segmentally-mediated SR system which includes the often ignored electromechanical coupling delay. For typical closed-loop (delay/gain) ratios, the model is shown to be unstable for all values of loop gain when operating as a position servo, but maximally stable when operating as a velocity servo. We claim that the velocity servo or one of its nonlinear relatives is a better model for some well studied SRs than, e.g., Houk's stiff muscle hypothesis. We also present evidence that even feeble and quickly saturating monosynaptic postural servos are always unstable if operated as pure position regulators.
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    Existence of a globally asymptotically stable equilibrium in Volterra models with continuous time delay (1983)
    Springer
    Journal of mathematical biology 18 (1983), S. 93-102 
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    ISSN: 1432-1416
    Keywords: Stability ; Time delay ; Feasible equilibrium ; Partially feasible equilibrium
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    Topics: Biology , Mathematics
    Notes: Abstract A sufficient condition for the existence of a globally asymptotically stable equilibrium in Volterra models with continuous time delay is obtained, and some properties of the stable equilibrium are proven. Furthermore, some applications in which asymptotic stability only depends on the sign of the coefficients are considered.
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    Effects of mean current and shear on stability of depth distributions of marine phytoplankton (1980)
    Springer
    Journal of mathematical biology 10 (1980), S. 33-51 
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    ISSN: 1432-1416
    Keywords: Plankton ; Stability ; Perturbations
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    Topics: Biology , Mathematics
    Notes: Abstract Linear perturbation theory is used to examine the stability of steady-state distributions of marine phytoplankton in the presence of a mean current with shear. Solutions are obtained for the general initial-value problem and it is found that all distributions are asymptotically stable so long as the rate of shear is greater than the local production. On the other hand, the early time behavior indicates that the system can be altered, if accomplished soon enough, depending upon a relative combination of diffusion, advection and production. Quantitative assessments are made where data are available.
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    Persistence of predator-prey systems in an uncertain environment (1980)
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    Journal of mathematical biology 10 (1980), S. 65-77 
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    ISSN: 1432-1416
    Keywords: Predator-prey ; Persistence ; Stability ; Differential inequalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The time derivatives of prey and predator populations are assumed to satisfy a set of inequalities, instead of a precise differential equation, reflecting an uncertain environmental and/or lack of knowledge by the modeler. A system of differential equations is found whose solution gives the boundary of a persistent set, which is positive flow invariant for any system satisfying the inequalities. Conditions are given for the persistent set to be bounded away from both axes, which show that resonance effects cannot drive either predator or prey to extinction if that does not happen for an autonomous system satisfying the inequalities. In general predator-prey systems are more persistent when there is strong asymptotic stability, when there is correlation between prey and predator dynamics, when the effect of perturbations is density dependent, and are more persistent under perturbations of the prey than of the predator.
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    One-dimensional λ-ω target patterns: Empirical stability tests (1980)
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    Journal of mathematical biology 10 (1980), S. 97-100 
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    ISSN: 1432-1416
    Keywords: Reaction diffusion equations ; Wave-trains ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary Stability of a class of solutions to reaction-diffusion equations is studied numerically. It is found that the solutions do not persist under a variety of boundary conditions.
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    Stability analysis for models of diseases without immunity (1981)
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    Journal of mathematical biology 13 (1981), S. 185-198 
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    ISSN: 1432-1416
    Keywords: Epidemiology ; Deterministic models ; Distributed delays ; Thresholds ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary A cyclic, constant parameter epidemiological model is described for a closed population divided into susceptible, exposed and infectious classes. Distributed delays are introduced and the model is formulated as two coupled Volterra integral equations. The delays do not change the general nature of thresholds or asymptotic stability; in all cases considered the disease either dies out, or approaches an endemic steady state.
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    The community matrix in three species community models (1982)
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    Journal of mathematical biology 16 (1982), S. 25-31 
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    ISSN: 1432-1416
    Keywords: Stability ; Community matrix ; Lotka-Volterra models
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    Topics: Biology , Mathematics
    Notes: Abstract The explicit function of the community matrix of a three dimensional Lotka-Volterra model is delineated by a set of necessary and sufficient conditions for a positive equilibrium to be asymptotically stable. In the special case that the community matrix is quasi weakly diagonally dominant, it is shown that a positive determinant for the community matrix is not only necessary but is also sufficient for stability. The results are specific to three dimensional models and do not extend to communities of dimension greater than three.
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    Stability results for delayed-recruitment models in population dynamics (1984)
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    Journal of mathematical biology 19 (1984), S. 147-156 
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    ISSN: 1432-1416
    Keywords: Stability ; delay ; difference equations ; whale models
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    Topics: Biology , Mathematics
    Notes: Abstract This paper relates the stability properties of a class of delay-difference equations to those of an associated scalar difference equation. Simple but powerful conditions for testing global stability are presented which are independent of the length of the time delay involved. For models which do not have globally stable equilibria, estimates of stability regions are obtained. Some well known baleen whale models are used to illustrate the results.
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    Integral equation models for endemic infectious diseases (1980)
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    Journal of mathematical biology 9 (1980), S. 37-47 
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    ISSN: 1432-1416
    Keywords: Epidemiology ; Endemic infectious diseases ; Deterministic models ; Thresholds ; Distributed delays ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary Endemic infectious diseases for which infection confers permanent immunity are described by a system of nonlinear Volterra integral equations of convolution type. These constant-parameter models include vital dynamics (births and deaths), immunization and distributed infectious period. The models are shown to be well posed, the threshold criteria are determined and the asymptotic behavior is analysed. It is concluded that distributed delays do not change the thresholds and the asymptotic behaviors of the models.
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    The existence of globally stable equilibria of ecosystems of the generalized Volterra type (1980)
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    Journal of mathematical biology 10 (1980), S. 401-415 
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    ISSN: 1432-1416
    Keywords: Stability ; Volterra ecosystems ; Linear complementarity theory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In this paper, global asymptotic stability of ecosystems of the generalized Volterra type $$dx_i /dt = x_i \left( {b_{i - } \mathop \sum \limits_{j = 1}^n a_{ij} x_j } \right),{\text{ }}i = 1,...,n,$$ is investigated. We obtain the conditions for the existence of a nonnegative and stable equilibrium point of the system by applying a result of linear complementarity theory. The results of this paper show that there exists a class of systems that do not have multiple domains of attractions. This class is defined in terms of the species interactions alone, and does not involve carrying capacities or species net birth rates.
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    Clines in the presence of asymmetric migration (1981)
    Springer
    Journal of mathematical biology 11 (1981), S. 207-233 
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    ISSN: 1432-1416
    Keywords: Clines ; Population genetics ; Nonlinear diffusion problems ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract If a population, which consists of individuals having genetic variation at one locus, with two alleles A and a, evolves under the influence of migration and selection, gradients in the distribution of alleles may arise. We consider the effect of asymmetry in the migration and spatial dependence of the selection process, upon the emergence and stability of such gradients.
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    The diffusive Lotka-Volterra system with three species can have a stable non-constant equilibrium solution (1982)
    Springer
    Journal of mathematical biology 16 (1982), S. 103-112 
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    ISSN: 1432-1416
    Keywords: Bifurcation ; Competition ; Diffusive Lotka-Volterra system ; Predator-prey interaction ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Three examples of the diffusive 3-species Lotka-Volterra system with constant interaction parameters are given, and by bifurcation techniques shown to have stable spatially non-constant equilibrium solutions. One example is competitive; the second one predator-two-competing prey and the third involves two predators and a single prey.
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    Existence and stability of travelling wave solutions of a nonlinear integral operator (1983)
    Springer
    Journal of mathematical biology 16 (1983), S. 199-220 
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    ISSN: 1432-1416
    Keywords: Nonlinear integral operator ; Travelling wave ; Wave speed ; Asymptotic speed of propagation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract In this paper, we establish the existence and stability property of travelling wave solutions of a nonlinear integral operator in the inferior case.
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    Stable spatio-temporal oscillations of diffusive Lotka-Volterra system with three or more species (1983)
    Springer
    Journal of mathematical biology 18 (1983), S. 213-221 
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    ISSN: 1432-1416
    Keywords: Diffusive Lotka-Volterra system ; Hopf-bifurcation ; Spatiotemporal oscillation ; Stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A stability condition for Hopf-bifurcating solutions from the uniform equilibrium of clasical Lotka-Volterra interaction-diffusion equations is presented. Using this condition, it is shown that stable spatio-temporal oscillations exist in the framework of such equations.
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    Derivation of first-passage time distribution of a single lift for arbitrary traffic (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1-11 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The distribution of the first-passage time is of decisive importance in lift (elevator) design. It yields the easure of performance of the system, the expected number of stops, the interval (i. e. time elapsed between two successive departures from a given floor) and many other parameters and factors determining the required number of lifts in a building. The derivation is based on the transition probability matrix of the operation policy, and consists in solving a system of linear equations.
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    On the analysis of accuracy for two-equation transient problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 55-62 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Fourier analysis of numerical accuracy has traditionally concentrated on the propagation behaviour of various methods. When systems of equations in more than one unknown are involved, analysis of propagation accuracy alone is shown to be incomplete. A distribution factor is introduced to complement the Fourier analysis in these cases, and application of the concept to two problems commonly encountered in the water resources field is demonstrated. The distribution factor is shown to provide important information which cannot be obtained from the customary analysis of propagation accuracy.
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    The limitations of the patch test (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 177-188 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple approximation by nonconforming finite elements is presented that passes the patch test of Irons and Strang but does not yield approximate solutions converging to the solution of the given boundary value problem. It is constructed from continuous piecewise linear functions perturbed by step functions. Further, strange convergence properties of such approximations are explained in all details because they may be typical for the behaviour of nonconforming finite elements violating the basic precondition for convergence.
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    Primitive variable finite element formulations for steady viscous flows (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 209-223 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The solution of incompressible, viscous flow problems using the primitive variable finite element approach is formulated in a coherent and physically reasoned exposition. In particular, it is shown that terms associated with changes in momentum caused by lack of mass conservation should logically be included in the governing equations. Previous formulations have not considered this possibility. Numerical results are presented to show the effect of inclusion of these extra terms; however, it is concluded from the numerical results for the specific case which was tested that there is no obvious benefit obtained by including these terms.
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    A method for space truss analysis in the post-buckling range (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 237-247 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A dual load method of truss analysis is presented that allows highly nonlinear member behaviour to be followed. In particular, a brittle type of strut behaviour is considered. The method assumes that the inelastic strut response is known and that piecewise linearization of the behaviour is acceptable. An example is given to illustrate the type of problem that can be handled. The example involves negative stiffness of the members and consequently attention must be given to the equation solving procedure for the structure. A comparison is made with some observed test results.
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    An approximate laplace transform inversion using exponential series representation (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 291-295 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical Laplace transform inversion technique is described, which is a modification of the inversion method using an exponential series representation. By adding an auxiliary function and using Erdélyi's inversion formula, the proposed technique provides the inverse approximation with improved accuracy near t = 0. Numerical illustrations shows that this procedure also works in cases when the original method of schapery fails to give satisfactory results.
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    A first-order blending method for triangles based upon cubic interpolation (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 308-318 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method for interpolating in triangles is described. Bivariate cubic polynomials are utilized to define an interpolant which assumes arbitrary position and slope on the entire boundary of a triangular domain. Some examples and applications are discussed.
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    An investigation of first- and second-order mixed plate-bending elements (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 351-360 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Numerical convergence of first- and second-order plate-bending elements is investigated. Using iso-parametric formulation, general bilinear and biquadratic quadrilaterals, with the three moment components and the transverse deflection as dependent variables, are obtained. The same elements are also used as degenerate triangles by collapsing one side. A constant bending moment patch test, applied numerically to the elements, indicated poor performance for linear triangles, while the bilinear, quadratic and biquadratic elements behaved well, with exact results in uniform meshes. Further numerical examples showed the same general trend as the patch test. Although bilinear, quadratic and biquadratic elements were always able to yield the correct solutions with mesh refinements, the linear triangles were in general unable to do so.
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    Finite difference analysis for developing laminar flow in circular tubes applied to forced and combined convection (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 381-404 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The complete two-dimensional partial differential equations for developing laminar flow in a circular tube have been treated by a finite difference analysis. Property variation with temperature, especially that of viscosity, is allowed for in a flexible manner. The continuity and momentum equations, and then the energy equations, are solved by direct elimination at each axial step, and marching procedure used in the axial direction. A new technique is that the stepwise energy balance is rigidly satisfied throughout by using it as a constituent equation in place of the ‘explicit’ wall thermal boundary condition normally used.The analysis predicts the complete developing hydrodynamic and thermal fields, together with friction factors and heat transfer coefficients. It has been tested for a range of fluid velocity and thermal boundary conditions and for various fluids, including high viscosity oils, water and air.Data for constant wall heat flux have already been published. 1,2 Predictions for constant wall temperature presented here are for forced and combined convection and are compared with experimental data of Test3 and Zeldin and Schmidt4.
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    A numerical method for solving two-point boundary value problems for nonlinear ordinary differential equations (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 464-469 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A numerical method for solving two-point boundary value problems associated with systems of first-order nonlinear ordinary differential equations is described. It needs four function evaluations at each point and is of order h6, where h is the space chop. Results of computational experiments, which include perturbation of the initial conditions, comparing this method with other known methods are given.
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    A method for the automatic generation of triangular elements on a surface (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 470-476 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm is given to discretize a polygon or curved surface into triangular arrays. The method first involves the manual division of the array into quadrilaterals with specified numbers on rows and columns. The individual points are then filled in automatically and elements are automatically generated. A point of particular importance is that the number of columns or rows may be made to change. A subroutine is given to perform this task.
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    Design oriented analysis of imperfect truss structures - part II - approximate analysis (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 483-494 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An approximate analysis method for calculating local and system geometric imperfection influences on the displacements, stresses and buckling load of imperfect truss structures, is developed. The structural response, as a function of the design variables, is expressed in this approximate analysis which is much faster and cheaper than the ‘accurate’ analysis. The accurate analysis for a particular design is used as a base for each approximate analysis which then gives the response information needed for other designs in the neighbourhood about the base point design. Comparison of the approximate behaviour predictions with accurate results based on the more refined analysis methods shows that the quality of the proposed approximate analysis procedure is adequate for guiding a structural design procedure. It is evident that the approximate analysis is capable of describing the nonlinear behaviour of the structure, but when nonlinearity increases, the quality of the approximate analysis tends to deteriorate.
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    Reduction of the error in eccentric beam modelling (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 575-582 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The usual linear shape function for approximating axial displacement in beam finite elements used as eccentric stiffeners leads to an inconsistency which can result in large errors in the deflection of plates or composite beams. The introduction of an additional degree-of-freedom for these elements circumvents this problem.
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    A method for incorporating free boundaries with surface tension in finite element fluid-flow simulators (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 639-648 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A boundary-location method is developed for finite element simulation of steady, two-dimensional flows of Newtonian liquid with free boundaries. In the method, boundary shape and position and the velocity and pressure fields are determined simultaneously. Inertial, viscous, gravitational, and surface tension effects are included in the development. The complete set of nonlinear finite element equations is solved by a modified frontal method combined with Newton-Raphson iteration to speed convergence. The finite element used to illustrate the method approximates the pressure as a piecewise constant function and the velocity and free boundaries as piecewise linear functions. Example calculations for flow from a slit show that the method can be effective.
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    A one-step method for direct integration of structural dynamic equationsThis work has been made in the framework of ELFI program supported by ENEL. (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 685-699 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The choice on an efficient direct integration procedure for linear structural dynamic equations of motion is discussed. It is suggested that as accuracy parameter the truncation error on the exponential terms contained in the modal contributions of the exact solution be assumed. This error does not always coincide with the local truncation error. These considerations were used to design an unconditionally stable one-step method whose accuracy is 0(h4). Numerical comparisons with some well-known integration schemes showed the efficiency of the proposed method.
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    A generalized automatic mesh generation scheme for finite element method (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 713-731 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a generalized method which generates linear, triangular, quadrilateral and pentahedral elements for the finite element method. Depending on geometrical and material variations, the region to be discretized is manually divided into blocks such as lines, triangles, quadrilaterals, pentahedrons and hexahedrons in several appropriate co-ordinate systems. However, no connectivity information of the adjacent blocks is required by the user as input. The continuity of the generated nodal co-ordinates and element configurations at the block interface are automatically maintained to describe the geometry of structures, no matter how these five types of blocks are connected. Furthermore, a mesh grading algorithm which generates reliable mesh grade distributions in the interior of the triangular and quadrilateral blocks is established corresponding to the arbitrarily defined subdivision numbers for each edge line of blocks. This algorithm is extended to the mesh grading in the interior of the hexahedral and pentahedral blocks. Element numbers are also renumbered in this scheme, in addition to node numbers, in order to increase the computational efficiency of the global matrix assembly. Additional facilities, i.e. loading data generation, boundary condition data generation and so on, are also discussed. An illustrative and a practical example are given to demonstrate the capabilities of this scheme.
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    The interpolation function of a general serendipity rectangular element (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 773-778 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The shape functions of serendipity rectangular elements had originally to be found by inspection. More recently an algorithm has been developed to formalize the construction of these shape functions. Here a simple expression is found for the interpolation function of the most general serendipity element. The shape functions can be derived immediately.
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    Post-buckling behaviour of structures using a finite element-nonlinear eigenvalue technique (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 955-980 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A series of finite element algorithms for the calculation of the post-buckling behaviour of structures are proposed. The algorithms represent a finite element implementation of a variational principle for nonlinear eigenvalue problems. Incremental amplitude solution schemes are defined. Numerical results are presented for the post-buckling behaviour of specific structures with linear and nonlinear pre-buckling states.
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    On quadratic elements in finite element solutions of steady-state convection - diffusion equation (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1041-1052 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    Masthead (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980) 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
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    On the proper boundary conditions for the thermal entry problem (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 935-942 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 8 Ill.
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    Transition finite elements for three-dimensional stress analysis (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 991-1020 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents isoparametric formulation for the three-dimensional transition finite elements. The transition finite elements are necessary for applications requiring the use of three-dimensional isoparametric solid elements and the curved shell elements. These elements provide proper connections between the two portions of the structure modelled with three-dimensional solids and the curved shell elements. The element properties are derived and presented in detail. Numerical examples are also presented to demonstrate the accuracy and the applications of such elements in three-dimensional stress analysis.
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    A Serendipity cubic-displacement hybrid-stress element for thin and moderately thick plates (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1261-1278 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A hybrid-stress element is developed for the analysis of thin and moderately thick plates. The independent transverse displacement and rotations are interpolated by the 12-node cubic Serendipity shape functions. All components of stress are included and 36β stress assumption is used. The element stiffness possesses correct rank and numerical results indicate that the element does not lock in the thin-plate limit. Results obtained using the present element are compared with those obtained using a 12-node assumed-displacement based Mindlin plate element with reduced integration; the present hybrid-stress element is shown to yield superior accuracy for all cases considered. In addition, the accuracy of the present element is compared against that of analogous 4-node and 8-node hybrid-stress Mindlin plate elements.
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    The mathematics of finite elements and applications III (MAFELAB 78), Ed. J. R. Whiteman, Academic Press, London, 1979. ISBN 0.12.747253.3. Price: £15.00, $31.50 (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1280-1280 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150813
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    Comparison between a finite element and a composite method for a three-dimensional potential problem (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1083-1094 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper is concerned with the solution of the three-dimensional potential problem for electromagnetic river gauging. It extends previous ideas of joining finite elements in an interior region to one infinite external element treated by the boundary integral method1,2 to this case where there are two external infinite elements representing the river and the ground. The boundary continuity conditions on the infinite river-ground interface, as well as the internal-external interfaces, are dealt with by introducing a variational principle with relaxed continuity requirement3.
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    URL: http://dx.doi.org/10.1002/nme.1620150709
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    Thin reinforced concrete shells - special analysis problems, Victor Gioncu, Wiley Chichester, 1979, No. of pages: 500, Price: £16.50 (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1107-1107 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150712
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    Two-step explicit finite element method for storm surge propagation analysis (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1129-1148 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620150803
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    On boundary conditions for the numerical solution of hyperbolic differential equations (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1113-1127 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Various boundary methods are considered for the numerical solution of the linear wave equation. The solution in the interior region is obtained using the Lax-Wendroff method. The theory of Gustafsson, Kreiss and Sundström is used to establish stability and the theory of Sköllermo is used to compare the accuracies of the various methods. The accuracy predictions are compared with computed results.
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    URL: http://dx.doi.org/10.1002/nme.1620150802
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    Modal methods in finite element fluid-structure eigenvalue problems (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1161-1175 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The technique of fixed-interface modal synthesis used to solve large structural eigenvalue problems is extended to fluid-structure eigenvalue problems with a view to efficient solution of problems involving localized modifications. Three cases are considered: namely, those fluid or fluid-structure vibration problems directly analogous to the structural case; the modification of the fluid model of a structure enclosing a compressible fluid; and the modification of fluid and structural models of a structure enclosing an incompressible fluid. Examples of the three cases are given, as are estimates of the computation that can be saved when using the methods to avoid resolving modified eigenvalue problems. It is also shown that the hard-walled modes of a fluid enclosure can be used to modify the incompressible-fluid modes of the fluid-structure system to account for a degree of compressibility in the fluid. An example and computation estimates are given.
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    URL: http://dx.doi.org/10.1002/nme.1620150805
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    The hybrid-stress model for thin plates (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1239-1260 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The assumed-stress hybrid finite element model is examined for application to the bending analysis of thin plates. A hybrid-stress functional is defined by using a Mindlin-type displacement assumption and including all components of stress. The Euler equations and matrix formulation corresponding to this functional are examined to assess the effects of plate thickness, and a rationale is presented for the selection of stress assumptions so that locking is avoided in the thin plate limit. To illustrate these concepts, a series of linear displacement quadrilateral elements are derived and tested, and the best of these elements is identified for suggested implementation in general-purpose computer programs.
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    URL: http://dx.doi.org/10.1002/nme.1620150810
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    Automatic reduction of frontwidth for finite element analysis (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1315-1324 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An algorithm is presented for reducing the frontwidth of finite element meshes. The technique takes an arbitrary input scheme and reorders the elements so as to reduce the frontwidth. A number of examples are presented to demonstrate the reliability and effectiveness of the method.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620150904
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    A brief review of techniques for generating irregular computational grids (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1335-1341 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This review attempts to place in perspective the wide variety of computer methods which are available for constructing irregular computational grids. Several different approaches exist for each aspect of the construction task: creation of the points, recognition of neighbouring points that define grid elements, enumeration of the points with indices, optimization of the positions of the points for computational advantage, and variation of point density throughout the grid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620150906
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    A fully nonlinear analysis of heat and mass transfer problems in porous bodies (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1381-1393 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The finite element method is used to analyse heat and mass transfer problems in porous media, in which the thermophysical properties are allowed to vary as functions of temperature and moisture. An example is given of the application of the method to the problem of timber drying.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620150910
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    Finite element calculations on a micro-computer (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1570-1574 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method is presented for solving field problems using a finite element formulation, to be executed with the aid of a micro-computer. In order to reduce the requirements regarding memory space, the coefficients of the matrix defining the system of equations are not stored, but calculated when they are needed, in a modification of the usual finite element procedure. The method is applicable to all problems for which Gauss-Seidel iteration converges, and can handle problems involving more than 100 degrees-of-freedom on a computer with 8,000 bytes memory. Computing time may run up to several minutes per cycle of iteration, but on a small, personal computer, this is still acceptable.
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    URL: http://dx.doi.org/10.1002/nme.1620151013
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    Stresses in bonded connections using finite elements (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1659-1680 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A finite element formulation for the adhesive of a lap joint is presented. The element is based on the assumptions common to the theories of Goland and Reissner and Ojalvo and Eidinoff. Deficiencies of the lap joint theories of those workers and of a previous finite element formulation of the adhesive are pointed out and the covergence of the new formulation to their results is discussed. Experimentally determined extreme fibre strains in the adherends are compared with those determined numerically using the new finite element formulation.
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    URL: http://dx.doi.org/10.1002/nme.1620151108
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    Masthead (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980) 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620151201
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    Announcements (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1730-1733 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620151116
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    High order polynomial elements with isoparametric mapping (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1747-1769 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite elements with polynomial interpolation functions of a degree higher than 2 are used comparatively little on large FEM systems, except in shell elements. However, the author has had several years' experience in the use of the so-called ‘isoparametric, reduced Hermitian element’,4 Which has behaved excellently in an industrial as well as an educational environment. The reason for the interest in the Hermitian concept is that the overcompatibility of the element reduces the number of unknowns, the solution time and the discontinuities in stresses between elements.Explicit formulae for the family of interpolation polynomials of order q and degree p = 2q + 1 are given and hierarchical Hermite elements are introduced. The families of Hermite and serendipity elements are isomorphic and the latter may thus be extended to arbitrary high order.For some problems the equidistant node configuration in Lagrange elements of degree 3 and higher is not optimal with respect to smoothness, and a new type of element, the ‘Lobatto element’, is introduced.The methods consistently produce results of an accuracy which is above the requirements of usual engineering applications, but in graphics smoothness of curves is important for a convincing representation. The methods are of particular interest in industries working with structures composed of almost linear materials with well-known properties.
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    A study of three-node triangular plate bending elements (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1771-1812 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An assessment of flat triangular plate bending elements with displacement degrees-of-freedom at the three corner nodes only is presented, with the purpose of identifying the most effective for thin plate analysis. Based on a review of currently available elements, specific attention is given to the theoretical and numerical evaluation of three triangular 9 degrees-of-freedom elements; namely, a discrete Kirchhoff theory (DKT) element, a hybrid stress model (HSM) element and a selective reduced integration (SRI) element. New and efficient formulations of these elements are discussed in detail and the results of several example analyses are given. It is concluded that the most efficient and reliable three-node plate bending elements are the DKT and HSM elements.
    Additional Material: 21 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620151205
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    More on infinite elements (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1613-1626 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The method of infinite elements is briefly reviewed. New more logical and general formulations of infinite elements are presented. The simplicity of the programming is emphasized. Results are given for elasticity and potential problems. Future extensions are discussed.
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    URL: http://dx.doi.org/10.1002/nme.1620151105
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    Oscillation limits for weighted residual methods applied to convective diffusion equations (1980)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 15 (1980), S. 1681-1689 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Convection-diffusion equations are difficult to solve when the convection term dominates because most solution methods give solutions which oscillate in space. Previous criteria based on the one-dimensional convection-diffusion equation have shown that finite difference and Galerkin (linear or quadratic basis functions) will not give oscillatory solutions provided the Peclet number times the mesh size (Pe Δx) is below a critical value. These criteria are based on the solution at the nodes, and ensure that the nodal values are monotone. Similar criteria are developed here for other methods: quadratic Galerkin with upwind weighting, cubic Galerkin, orthogonal collocation on finite elements with quadratic, cubic or quartic polynomials using Lagrangian interpolation, cubic or quartic polynominals using Hermite interpolation, and the method of moments. The nodal values do not oscillate for collocation or moments methods with Hermite cubic polynomials regardless of the value of Pe Δx.A new criterion is developed for all methods based on the monotonicity of the solutions throughout the domain. This criterion is more restrictive than one based only on the nodal values. All methods that are second order (Δx2) or better in truncation error give oscillatory solutions (based on the entire domain) unless Pe Δx is below a critical value. This value ranges from 2 for finite difference methods to 4·6 for Hermite, quartic, collocation methods.
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    URL: http://dx.doi.org/10.1002/nme.1620151109
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    Some computational aspects of elastic-plastic large strain analysis (1981)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 17 (1981), S. 15-41 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The governing equations for large strain analysis of elastic-plastic problems are reconsidered. An improved form of these equations is derived, which is valid for small increments of strain and large increments of rotation. Special attention is paid to the integration procedures for these equations in the deformation history. It is shown that the tangent modulus procedure for integration of the constitutive equations is conditionally stable, and that implicit methods, such as the ‘mean normal’ method, are to be preferred. A novel procedure is introduced for the treatment of nonlinear geometric effects. The performance of various element types is examined, with specific attention to effects of ‘locking’ and distortion. Several applications are discussed to illustrate the various aspects of the formulation developed ein this paper.
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    URL: http://dx.doi.org/10.1002/nme.1620170103
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    Elasto visco-plastic flow with special attention to boundary conditions (1981)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 17 (1981), S. 97-112 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper we analyse a simple but non-trivial steady-state creeping elasto visco-plastic (Maxwell fluid) radial flow problem, paying particular attention to the effects of the boundary conditions. Solutions are obtained by integration of a governing equation on stress, using the Runge-Kutta method for initial value problems and finite differences for boundary value problems. A more general approach by the finite element method, which solves for the velocity field rather than the stress field, and which is applicable to a wide range of problems, is presented and tested using the radial flow example.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/nme.1620170108
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    Alternative integration formulae for triangular finite elements (1981)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 17 (1981), S. 133-139 
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    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Some new formulae are presented for numerical integration over triangular regions. These formulae, which are triangularly symmetric, involve four, six, and seven integration points, respectively. They were derived by determining co-ordinates and weight factors for which polynomial functions of up to a certain degree are integrated exactly. The effectiveness of the formulae is demonstrated by applying them to the integration of five non-polynomial functions, two of which are singular within the region of integration. Results obtained with the new formulae are compared with results obtained with other, comparable formulae. It is seen that the new formulae are more accurate than some existing ones with the same numbers of points.
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    URL: http://dx.doi.org/10.1002/nme.1620170111
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