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991.
In this paper, we analyze the exponential method of multipliers for convex constrained minimization problems, which operates like the usual Augmented Lagrangian method, except that it uses an exponential penalty function in place of the usual quadratic. We also analyze a dual counterpart, the entropy minimization algorithm, which operates like the proximal minimization algorithm, except that it uses a logarithmic/entropy proximal term in place of a quadratic. We strengthen substantially the available convergence results for these methods, and we derive the convergence rate of these methods when applied to linear programs.Research supported by the National Science Foundation under Grant DDM-8903385, and the Army Research Office under Grant DAAL03-86-K-0171. 相似文献
992.
S. K. Zavriev 《Journal of Global Optimization》1993,3(1):67-78
The paper is devoted to the convergence properties of finite-difference local descent algorithms in global optimization problems with a special -convex structure. It is assumed that the objective function can be closely approximated by some smooth convex function. Stability properties of the perturbed gradient descent and coordinate descent methods are investigated. Basing on this results some global optimization properties of finite-difference local descent algorithms, in particular, coordinate descent method, are discovered. These properties are not inherent in methods using exact gradients.The paper was presented at the II. IIASA-Workshop on Global Optimization, Sopron (Hungary), December 9–14, 1990. 相似文献
993.
Emanuele Galligani 《Numerical Algorithms》1993,5(11):549-555
Givenn pairwise distinct and arbitrarily spaced pointsP
i in a domainD of thex–y plane andn real numbersf
i, consider the problem of computing a bivariate functionf(x, y) of classC
1 inD whose values inP
i are exactlyf
i,i=1,,n, and whose first or second order partial derivatives satisfy appropriate equality and inequality constraints on a given set ofp pointsQ
l inD.In this paper we present a method for solving the above problem, which is designed for extremely large data sets. A step of this method requires the solution of a large scale quadratic programming (QP) problem.The main purpose of this work is to analyse an iterative method for determining the solution of this QP problem: such a method is very efficient and well suited for parallel implementation on a multiprocessor system.Work supported by MURST Project of Computational Mathematics, Italy. 相似文献
994.
Random walk on distant mesh points Monte Carlo methods 总被引:1,自引:0,他引:1
A new technique for obtaining Monte Carlo algorithms based on the Markov chains with a finite number of states is suggested. Instead of the classical random walk on neighboring mesh points, a general way of constructing Monte Carlo algorithms that could be called random walk on distant mesh points is considered. It is applied to solve boundary value problems. The numerical examples indicate that the new methods are less laborious and therefore more efficient.In conclusion, we mention that all Monte Carlo algorithms are parallel and could be easily realized on parallel computers. 相似文献
995.
用新颖的干粉方法合成系列沸石的研究已从五元环沸石延伸到具有四元环和六元环的方钠石。本研究运用干粉方法在Na2O-SiO2-Al2O3混合物中分别以乙醇胺和乙二胺-氟化物为模板,合成出了方钠石。有机模板剂以吸附态模板方式进入体系。用XRD数据、扫描电镜图及红外光谱测试结果对实验产品做了表征。结果表明,干粉体系制备的方钠石的晶胞参数小于水热体系和非水体系合成的方钠石的相应值。而以乙醇胺为模板制备的方钠石与以乙二胺-氟化物为模板的样品比较,后者具有较快的晶化速度、较小的晶胞体积和晶粒 相似文献
996.
We propose a new approach for high-throughput continuous titration based on a flow ratiometry. The method was applied to potentiometric titrations of acids and bases. A base solution, the flow rate FB of which was varied in response to controller output voltage Vc, was merged with an acid solution under constant total (acid + base) flow rate. Downstream, the pH of the mixed solution was measured with a flow-through glass electrode. Initially, Vc, and thus FB was increased linearly. At the instant the equivalence point (EP) was sensed, the ramp direction of Vc was reversed from upward to downward. The direction was reversed to upward when EP was sensed again. Such the feedback-based operation gives a triangular waveform of Vc, because there is a delay corresponding mainly to the transit time of merged solutions to reach the sensor. The value of Vc that gives EP composition, VE, was estimated by averaging the most recent maximum and minimum values of Vc. Next, fixed triangular waves of Vc was used to control FB. The amplitude and the scan rate of the waves were fixed narrower and faster, respectively, than those in the feedback-based operation in order to improve the throughput rate. The EP can be located as long as the scan range covers VE. These automated processes limited the titration to just the narrow range around EP, and thus realized extremely high throughput rate of maximally 17.6 titrations per minute (=3.4 s per titration) at R.S.D. = 0.35%. 相似文献
997.
Activity coefficients of hydrochloric acid have been determined from electromotive-force measurements of cells containing mixtures of hydrochloric acid and calcium chloride at constant total ionic strengthsI=0.1, 0.5, 1.0, 2.0, and 3.0 mole-kg–1 at 298.15°K. Interpretations based on Scatchard's and Pitzer's equations indicate that Pitzer's equations probably provide a more convenient guide to the thermodynamic properties of the mixed-electrolyte solutions. Activity coefficients for calcium chloride were derived from these equations. 相似文献
998.
A study of the structural stability of clusters made up of a single component has been carried out within the Embedded Atom Method. Perfect icosahedral and cuboctahedral Cu, Ni, Pd, and Ag clusters with up to 5083 atoms have been compared. The icosahedron is found to be the stable structure for small clusters, and a change of structure from icosahedral to cuboctahedral is found as the cluster size increases. A contraction of the interatomic distances results when the cluster size decreases. 相似文献
999.
1000.