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1.
Evolutionary algorithms are applied as problem-independent optimization algorithms. They are quite efficient in many situations. However, it is difficult to analyze even the behavior of simple variants of evolutionary algorithms like the (1+1) EA on rather simple functions. Nevertheless, only the analysis of the expected run time and the success probability within a given number of steps can guide the choice of the free parameters of the algorithms. Here static (1+1) EAs with a fixed mutation probability are compared with dynamic (1+1) EAs with a simple schedule for the variation of the mutation probability. The dynamic variant is first analyzed for functions typically chosen as example-functions for evolutionary algorithms. Afterwards, it is shown that it can be essential to choose the suitable variant of the (1+1) EA. More precisely, functions are presented where each static (1+1) EA has exponential expected run time while the dynamic variant has polynomial expected run time. For other functions it is shown that the dynamic (1+1) EA has exponential expected run time while a static (1+1) EA with a good choice of the mutation probability has polynomial run time with overwhelming probability. 相似文献
2.
M. A. Posypkin I. Kh. Sigal 《Computational Mathematics and Mathematical Physics》2006,46(12):2187-2202
The efficiency of parallel implementations of the branch-and-bound method in discrete optimization problems is considered. A theoretical analysis and comparison of two parallel implementations of this method is performed. A mathematical model of the computation process is constructed and used to obtain estimates of the maximum possible speedup. Examples of problems in which none of these two parallel implementations can speed up the computations are considered. 相似文献
3.
Bounds are given on the size of the parameter-space decomposition induced by multiple sequence alignment problems where phylogenetic information may be given or inferred. It is shown that many of the usual formulations of these problems fall within the same integer parametric framework, implying that the number of distinct optima obtained as the parameters are varied across their ranges is polynomially bounded in the length and number of sequences. 相似文献
4.
This paper presents a new generic Evolutionary Algorithm (EA) for retarding the unwanted effects of premature convergence. This is accomplished by a combination of interacting generic methods. These generalizations of a Genetic Algorithm (GA) are inspired by population genetics and take advantage of the interactions between genetic drift and migration. In this regard a new selection scheme is introduced, which is designed to directedly control genetic drift within the population by advantageous self-adaptive selection pressure steering. Additionally this new selection model enables a quite intuitive heuristics to detect premature convergence. Based upon this newly postulated basic principle the new selection mechanism is combined with the already proposed Segregative Genetic Algorithm (SEGA), an advanced Genetic Algorithm (GA) that introduces parallelism mainly to improve global solution quality. As a whole, a new generic evolutionary algorithm (SASEGASA) is introduced. The performance of the algorithm is evaluated on a set of characteristic benchmark problems. Computational results show that the new method is capable of producing highest quality solutions without any problem-specific additions. 相似文献
5.
Multi-objective optimization using evolutionary algorithms identifies Pareto-optimal alternatives or their close approximation by means of a sequence of successive local improvement moves. While several successful applications to combinatorial optimization problems are known, studies of underlying problem structures are still scarce. 相似文献
6.
Pappa A. Kyriakou S. Mikedi K. Tzamtzis N. Statheropoulos M. 《Journal of Thermal Analysis and Calorimetry》2004,78(2):415-426
The design, the abilities and a characteristic application of an in-house made interface for combining thermogravimetry (TG)
with mass spectrometry (MS) are presented. The TG-MS interface consists mainly of three co-axial tubes. The position of the
intermediate tube was determined after calculation of the temperature profile at the TG furnace exit tube. The inner tube
position was determined taking into consideration its protection against condensation of heavy molecules and the time delay
for the transfer of the evolved gases. This interface allows either continuous sampling and transferring of the evolved gases
from the TG to the MS or repetitive introduction of short sampling pulses of TG evolved gases to MS. The interface is capable
of coupling various commercial instruments. In the present work two configurations of this interface are demonstrated. Finally
an example of application of this interface on forest fuel pyrolysis is presented.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Based on the group theory analysis and quantum chemical calculations within the framework of SW X α method (in relativistic approximation for core electrons and non-relativistic for valence ones), the existence possibility of square planar complexes [M4C] and [M4C]2? (M = Al, Ga, In, Tl, Sc, and Y) in gas phase has been shown. The extraction of Kt2[M4C] square planar complexes of carbon in the crystal state is possible too. A high stability of these complexes, in comparison with usual tetrahedral, is achieved due to the formation of five-and four-center bonds (bonds M-M and M-C). 相似文献
8.
首次将微量热用于亚细胞层次的研究,测定了鲤鱼肝脏线粒体和亚线粒体代谢的热谱及其漆树漆酶的影响,并用MTD方程和演化计算技术对它们的代谢热动力学参数进行了全局优化。 相似文献
9.
Mirka Bergamo Tiziana Beringhelli Giuseppe D'Alfonso Luca Garavaglia Pierluigi Mercandelli Massimo Moret Angelo Sironi 《Journal of Cluster Science》2001,12(1):223-242
Three and tetranuclear ring clusters have been obtained by treatment of [Re2(CO)8(THF)2] with carbonyl-rhenates containing two terminal hydrides. The reaction with [ReH2(CO)4]- provided a selective route to the previously known [Re3(-H)2(CO)12]- triangular cluster anion 1. The reaction with [Re2H2(-H)(CO)8]- gave the novel [Re4(-H)3(CO)16]- anion 2, containing a rare example of a puckered-square metal cluster. Protonation of 1 is known to afford the neutral [Re3(-H)3(CO)12] species 3. Analogously the reaction of 2 with a strong acid afforded the previously known square metal clusters [Re4(-H)4(CO)16] 4. The reaction could not be reversed by treatment with bases. Photolysis of 4 gave the unsaturated complex [Re2(-H)2(CO)8] 5: this is the reverse of the dimerization reaction, that in THF at room temperature produces 4 from 5. Thermal treatment (reflux in cyclohexane for 24 h) left 4 almost unchanged. A single crystal X-ray analysis of [NEt4]2 showed a s/e/s/s (e=eclipsed, s=staggered) conformation of the Re(CO)4 units, leading to a puckered geometry of the ring, at variance with the square-planar geometry of 4 (all eclipsed). Two of the three hydrides of 2 have been located as bridging the Re–Re edges from inside the metal ring, as previously observed in 4. Density functional computations indicated a puckered conformation as the most stable for both 2 and 4, with very low activation energies for ring inversion (6.6 and 2.2 kcal·mol-1, respectively), but ruled out solid state fluxionality for 4, whose observed planar geometry must be attributed to packing stabilization. 相似文献
10.
M. Broschag T. M. Klaptke A. Schulz I. C. Tornieporth-Oetting P. Umbach P. S. White 《无机化学与普通化学杂志》1994,620(6):1132-1136
Fluorination of Cyanuric Chloride and Low-Temperature Crystal Structure of [(ClCN)3F]+[AsF6]? The low-temperature fluorination of cyanuric chloride, (ClCN)3, with F2/AsF5 in SO2F2 solution yielded the salt [(ClCN)3F]+ [AsF6]? ( 1 ) essentially in quantitative yield. Compound 1 was identified by a low-temperature single crystal X-ray structure determination: R 3 c, trigonal, a = b = 10.4246(23) Å, c = 15.1850(24) Å, V = 1429.1(4) Å 3, Z = 6, RF = 0.056, Rw = 0.076 (for significant reflections), RF = 0.088, Rw = 0.079 (for all reflections). Fluorination of neat (ClCN)3 with [NF4]+ [Sb2F11]? yielded NF3, CClF3, SbF3, N2 and traces of CF4. A qualitative scale for the oxidizing strength of the oxidative fluorinators NF4+ and (XCN)3F+ (X = H, F, Cl) has been computed ab initio. 相似文献