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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 21 (1981), S. 319-330 
    ISSN: 1436-4646
    Schlagwort(e): Nonlinear Programming ; Geometric Programming ; Duality Theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The several published methods for mapping a dual solution estimate to a primal solution estimate in posynomial geometric programming provide no criteria for deciding how much deviation from primal feasibility, or discrepancy between the primal and dual objective function values, should be permitted before the primal solution estimate is accepted by the designer. This paper presents a new and simple dual-to-primal conversion method that uses the cost coefficients to provide a sound economic criterion for determining when to accept a primal solution estimate. The primal solution estimate generated is the exact solution to a modified primal obtained from the given primal by modifying the cost coefficients, with the exponent matrix left unchanged. The method is shown to have desirable properties when coupled with a convergent dual algorithm.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 22 (1982), S. 163-201 
    ISSN: 1436-4646
    Schlagwort(e): Geometric Programming ; Code Comparisons ; Numerical Testing ; Nonlinear Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Ten codes or code variants were used to solve the five equivalent posynomial GP problem formulations. Four of these codes were general NLP codes; six were specialized GP codes. A total of forty-two test problems was solved with up to twenty randomly generated starting points per problem. The convex primal formulation is shown to be intrinsically easiest to solve. The general purpose GRG code called OPT appears to be the most efficient code for GP problem solution. The reputed superiority of the specialized GP codes GGP and GPKTC appears to be largely due to the fact that these codes solve the convex primal formulation. The dual approaches are only likely to be competitive for small degree of difficulty, tightly constrained problems.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 21 (1981), S. 241-261 
    ISSN: 1436-4646
    Schlagwort(e): Dual problem ; Duality Theory ; Optimality Conditions ; Price Functions ; Nonlinear Programming ; Integer Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We survey some recent developments in duality theory with the idea of explaining and unifying certain basic duality results in both nonlinear and integer programming. The idea of replacing dual variables (prices) by price functions, suggested by Everett and developed by Gould, is coupled with an appropriate dual problem with the consequence that many of the results resemble those used in linear programming. The dual problem adopted has a (traditional) economic interpretation and dual feasibility then provides a simple alternative to concepts such as conjugate functions or subdifferentials used in the study of optimality. In addition we attempt to make precise the relationship between primal, dual and saddlepoint results in both the traditional Lagrangean and the more general duality theories and to see the implications of passing from prices to price functions. Finally, and perhaps surprisingly, it appears that all the standard algorithms terminate by constructing primal and dual feasible solutions of equal value, i.e., by satisfying generalised optimality conditions.
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 20 (1981), S. 22-32 
    ISSN: 1436-4646
    Schlagwort(e): Concave Programming ; Extreme Point Solutions ; Global Optimization ; Nonconvex Programming ; Nonlinear Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract A method is described for globally minimizing concave functions over convex sets whose defining constraints may be nonlinear. The algorithm generates linear programs whose solutions minimize the convex envelope of the original function over successively tighter polytopes enclosing the feasible region. The algorithm does not involve cuts of the feasible region, requires only simplex pivot operations and univariate search computations to be performed, allows the objective function to be lower semicontinuous and nonseparable, and is guaranteed to converge to the global solution. Computational aspects of the algorithm are discussed.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 23 (1982), S. 75-86 
    ISSN: 1436-4646
    Schlagwort(e): Constrained Optimization ; Global Convergence ; Nonlinear Programming ; Penalty Function ; Quasi-Newton Method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The recently proposed quasi-Newton method for constrained optimization has very attractive local convergence properties. To force global convergnce of the method, a descent method which uses Zangwill's penalty function and an exact line search has been proposed by Han. In this paper a new method which adopts a differentiable penalty function and an approximate line is presented. The proposed penalty function has the form of the augmented Lagrangian function. An algorithm for updating parameters which appear in the penalty function is described. Global convergence of the given method is proved.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 22 (1982), S. 82-92 
    ISSN: 1436-4646
    Schlagwort(e): Generic Programming ; Optimality Conditions ; Nonlinear Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Optimality conditions for families of nonlinear programming problems inR n are studied from a generic point of view. The objective function and some of the constraints are assumed to depend on a parameter, while others are held fixed. Techniques of differential topology are used to show that under suitable conditions, certain strong second-order conditions are necessary for optimality except possibly for parameter values lying in a negligible set.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 24 (1982), S. 137-161 
    ISSN: 1436-4646
    Schlagwort(e): Nonlinear Programming ; Exact Penalty Methods ; Successive Quadratic Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract In this paper we motivate and describe an algorithm to solve the nonlinear programming problem. The method is based on an exact penalty function and possesses both global and superlinear convergence properties. We establish the global qualities here (the superlinear nature is proven in [7]). The numerical implementation techniques are briefly discussed and preliminary numerical results are given.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 20 (1981), S. 110-121 
    ISSN: 1436-4646
    Schlagwort(e): Bounded Variables ; Constrained Optimization ; Nonlinear Programming ; Nonnegativity Constraints ; Transformation of Variables
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The problem of minimizing a nonlinear objective function ofn variables, with continuous first and second partial derivatives, subject to nonnegativity constraints or upper and lower bounds on the variables is studied. The advisability of solving such a constrained optimization problem by making a suitable transformation of its variables in order to change the problem into one of unconstrained minimization is considered. A set of conditions which guarantees that every local minimum of the new unconstrained problem also satisfies the first-order necessary (Kuhn—Tucker) conditions for a local minimum of the original constrained problem is developed. It is shown that there are certain conditions under which the transformed objective function will maintain the convexity of the original objective function in a neighborhood of the solution. A modification of the method of transformations which moves away from extraneous stationary points is introduced and conditions under which the method generates a sequence of points which converges to the solution at a superlinear rate are given.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 24 (1982), S. 123-136 
    ISSN: 1436-4646
    Schlagwort(e): Nonlinear Programming ; Exact Penalty Methods ; Successive Quadratic Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract In this paper we consider the final stage of a ‘global’ method to solve the nonlinear programming problem. We prove 2-step superlinear convergence. In the process of analyzing this asymptotic behavior, we compare our method (theoretically) to the popular successive quadratic programming approach.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 21 (1981), S. 331-347 
    ISSN: 1436-4646
    Schlagwort(e): Optimization ; Nonlinear Programming ; Unconstrained Optimization ; Discrete Optimal Control ; Differential Dynamic Programming
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Dynamic programming techniques have proven to be more successful than alternative nonlinear programming algorithms for solving many discrete-time optimal control problems. The reason for this is that, because of the stagewise decomposition which characterizes dynamic programming, the computational burden grows approximately linearly with the numbern of decision times, whereas the burden for other methods tends to grow faster (e.g.,n 3 for Newton's method). The idea motivating the present study is that the advantages of dynamic programming can be brought to bear on classical nonlinear programming problems if only they can somehow be rephrased as optimal control problems. As shown herein, it is indeed the case that many prominent problems in the nonlinear programming literature can be viewed as optimal control problems, and for these problems, modern dynamic programming methodology is competitive with respect to processing time. The mechanism behind this success is that such methodology achieves quadratic convergence without requiring solution of large systems of linear equations.
    Materialart: Digitale Medien
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 26 (1981), S. 107-113 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 78.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The isothermal recovery rates of vacancy-impurity complexes in an aluminium-1% magnesium alloy are measured in situ at eight temperatures from variations of colinear annihilation γ-rays versus time. These data analysed in terms of a time dependant β+-trapping model yield two apparent migration energies of 0.8 eV±0.1 eV and 0.9 eV±0.05 eV. The nature of the complexes is discussed and their binding energy is estimated.
    Materialart: Digitale Medien
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  • 12
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 27 (1982), S. 167-169 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 68 ; 74
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A simple method is presented to prepare very low pinning niobium foils on which geometrically well defined Nb3Sn-pinning structures of arbitrary shape are deposited. This facilitates the fabrication of samples for guided vortex motion experiments some of which are reported.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 28 (1982), S. 99-102 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 81.40
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Supersaturated surface alloys produced by very high dose (0.8−2.6×1017cm−2) implantation of As-ions into silicon and subsequent pulsed electron-beam annealing have been investigated by means of the channeling technique. The maximum solubility limit of 7×1021 As/cm3 has been determined. It exceeds the equilibrium solubility limit by more than a factor of 4. Angular scan measurements indicated that for doses above 1×1017cm−2 As atoms are displaced by about 0.12 Å from the regular lattice sites.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 28 (1982), S. 179-187 
    ISSN: 1432-0630
    Schlagwort(e): 78.70 ; 61.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Positron annihilation measurements of the coincidence count rate at the peak of the angular correlation curve (CCR) have been performed as a function of temperature for the alloy systemFeTi in a concentration range up to about 1.3 at. %. The concentration dependence of the effective vacancy formation enthalpy (H 1V F )eff suggests the existence of an attractive interaction between vacancies and the impurity atoms. It will be shown that the description of the vacancy concentration in an alloy according to the Lomer model is not valid in this case, because it neglects binding of vacancies to solute atom pairs and to higher agglomerates. The application of a model proposed by Dorn and Mitchell gives evidence that beyond the binding of a vacancy to a single solute atom in the concentration range investigated also aggregates of a vacancy bound to two and three foreign atoms must be taken into account. The analysis of the measurements according to the method of Hehenkamp and Sander gives values for the respective vacancy-solute-atom(s) binding enthalpies H 1 B =0.25eV, H 2 B =0.53eV and H 3 B =0.91eV. The discussion of the temperature and solute-atoms concentration dependence of the vacancy concentration suggests a much more complicated behaviour than for pure metals even at low solute-atom concentrations.
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  • 15
    ISSN: 1432-0630
    Schlagwort(e): 78.70 ; 61.70 ; 61.80
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: 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.
    Materialart: Digitale Medien
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  • 16
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 27 (1982), S. 257-261 
    ISSN: 1432-0630
    Schlagwort(e): 78.70 ; 61.70 ; 81
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The positron lifetime was measured in cadmium in the temperature range between 80 K and 500 K. For the first time a plateau was observed by this method in polycrystalline samples. The obtained data are well explained by depletion of shallow traps forT≤180 K and by self-trapping in the prevacancy region.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 24 (1981), S. 85-88 
    ISSN: 1432-0630
    Schlagwort(e): 68.50 ; 61.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A summary of the theoretical and experimental investigations carried out to understand the problem of epitaxy is given. The effect of deposition conditions and the nature of the substrate-deposit combination on the orientation of the final film is discussed. The importance of the nucleation and growth stages, reorientation and recrystallization effects and the influence of the impurities and defects in the substrate surface on the quality of the films deposited are presented.
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  • 18
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 29 (1982), S. 105-111 
    ISSN: 1432-0630
    Schlagwort(e): 71.55F ; 61.70 ; 73.40Q
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The annealing behavior of trap-centers was studied in float-zone silicon wafers containing A-swirl defects. Samples from areas of high and low A-swirl density were annealed in nitrogen ambient between 100° and 900 °C, and analysed using the Deep Level Transient Spectroscopy. The results indicate, that two levels atE c }-0.07 eV,σ n=4.6×10−16 cm2, andE c−0.49eV,σ n=6.6×10−16cm2 are caused by one defect, for which the silicon di-selfinterstitial is a likely interpretation. A level atE c }-0.11 eV was assigned to interstitial carbon. Both defects annealed out at about 170 °C. After 600 °C annealing an additional level atE c−0.2 eV was detected, which was attributed to an interstitial silicon carbon complex. Heat treatment at 800 °C generated a new level atE c−0.49 eV,σ n=2.9×10−16cm2 only in the area of high A-swirl defect density. This level was also observed after oxidation and subsequent annealing of silicon.
    Materialart: Digitale Medien
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 27 (1982), S. 49-56 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 78.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Trapping of positrons at vacancy-type defects in magnesium was studied by positron lifetime and Doppler-broadening measurements. Vacancy defects were produced by quenching, electron irradiation and deformation at low temperatures as well as by thermal agitation at elevated temperatures. In the first three cases we observed trapping at multiple vacancies, which anneal out between 77...400 K. Thermal equilibrium measurements show S-shape behaviour originating from positron trapping at magnesium monovacancies. However, changes in the positron parameters were very small, which is due to the weakness of the positron-vacancy interaction. A detrapping analysis yielded a positron-vacancy binding energy of the order of 0.3...0.4 eV.
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  • 20
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 78.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Positron-annihilation lineshape parameter measurements were performed during isothermal annealing of room temperature deformed iron. An isothermal annealing effect is seen in impure iron while in pure iron no effect is measured.
    Materialart: Digitale Medien
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 27 (1982), S. 149-152 
    ISSN: 1432-0630
    Schlagwort(e): 78.70 ; 61.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract A simple model is developed for the trapping of positrons at grain boundaries. It is shown that there is a linear relationship between any linear annihilation parameter and the inverse grain size. An effective grain boundary width is defined, which depends on the positron diffusion length and on the strength of the grain boundary for positrons. The effect of detrapping on this effective width is also considered. The model is tested by using the experimental results available in the literature.
    Materialart: Digitale Medien
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 27 (1982), S. 171-176 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 66 ; 85.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The paper presents a theoretical study of the diffusion of gold into dislocated silicon wafers in terms of the kick-out mechanism Au i ⇄Au s +I, where Au i , Au s , andI mean Au interstitials, substitutional Au atoms, and Si self-interstitials, respectively. In agreement with experiments it is found that the Au s concentration in the centre of a wafer,C s m , increases with the durationt of the diffusion anneal according toC s m =C s eq (k 0 t)1/2 except forC s m values in the vicinity of the solubility limitC s eq of Au s . Approximate analytical expressions fork 0 as a function of the densityN I of the dislocations acting asI sinks are given for the entire regime 0≦NI〈+t8.
    Materialart: Digitale Medien
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 29 (1982), S. 199-200 
    ISSN: 1432-0630
    Schlagwort(e): 61.70
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract Conditions are discussed under which an interstitial atom absorbed in the core of a gliding 60° dislocation belonging to the glide set can be transformed into an antisite defect. The mechanism considered may be responsible for an increase in the concentration of AsGa defects observed in GaAs single crystals after their plastic deformation.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Applied physics 28 (1982), S. 79-92 
    ISSN: 1432-0630
    Schlagwort(e): 61.70 ; 66.30 ; 85.30
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The information available on the diffusion of oxygen and on the formation of thermal donors in silicon is critically reviewed. In this context the effects of intrinsic point defects on the diffusion-controlled growth of oxygen precipitates is investigated in some detail. Seemingly contradictory experimental results on the diffusivity of oxygen in silicon at temperatures around 400° C are explained in terms offast-diffusing gas-like molecular oxygen in silicon. The concept of molecular oxygen is also invoked in a newly suggested model of thermal donor formation in silicon. The diffusivity of molecular oxygen in silicon is estimated to be around 10−9cm2s−1 at 450° C, almost nine orders of magnitude higher than the diffusivity of atomic oxygen in interstitial position.
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