首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   24篇
  免费   1篇
化学   14篇
力学   1篇
数学   6篇
物理学   4篇
  2021年   2篇
  2018年   1篇
  2017年   2篇
  2016年   3篇
  2014年   1篇
  2013年   1篇
  2012年   3篇
  2011年   1篇
  2010年   2篇
  2008年   4篇
  2007年   1篇
  2006年   1篇
  2005年   1篇
  1995年   1篇
  1992年   1篇
排序方式: 共有25条查询结果,搜索用时 15 毫秒
1.
In hybrid electric vehicles, the electrical powertrain system has multiple energy sources that it can gather power from to satisfy the propulsion power requested by the vehicle at each instant. This paper focusses on the minimization of the fuel consumption of such a vehicle, taking advantage of the different energy sources. Based on global optimization approaches, the proposed heuristics find solutions that best split the power requested between the multi-electrical sources available. A lower bounding procedure is introduced to validate the quality of the solutions. Computational results show a significant improvement over previous results from the literature in both the computing time and the quality of the solutions.  相似文献   
2.
In this paper, both scatter search (SS) and genetic algorithms (GAs) are studied for the NP-Hard optimization variant of the satisfiability problem, namely MAX-SAT. First, we investigate a new selection strategy based on both fitness and diversity to choose individuals to participate in the reproduction phase of a genetic algorithm. The resulting algorithm is enhanced in two ways leading to two genetic algorithm variants: the first one uses a uniform crossover. The second one uses a specific crossover operator (to MAX-SAT). The crossover operator is combined with an improved stochastic local search (SLS). The crossover operator is used to identify promising regions while the stochastic local search performs an intensified search of solutions around these regions. Secondly, we propose a scatter search variant for MAX-SAT. Both the SS and the GAs implementations share the solution selection strategy, the improved SLS method and the combination operator. Experiments on several instances from MAX-SAT libraries are performed to show and compare the effectiveness of our approaches. The computational experiments show that both (SS) and (GAs) with a stochastic local search (SLS) improvement technique outperform a classical genetic algorithm (without SLS). The two metaheuristics are able of balancing search diversification and intensification which leads to good results. In general, the specific genetic algorithm with a (SLS) improvement technique and a specific combination method provides competitive results and finds solutions of a higher quality than a scatter search.  相似文献   
3.

Background  

Major depression is a serious mood disorder affecting millions of adults and children worldwide. While the etiopathology of depression remains obscure, antidepressant medications increase synaptic levels of monoamine neurotransmitters in brain regions associated with the disease. Monoamine transmitters activate multiple signaling cascades some of which have been investigated as potential mediators of depression or antidepressant drug action. However, the diacylglycerol arm of phosphoinositide signaling cascades has not been systematically investigated, even though downstream targets of this cascade have been implicated in depression. With the ultimate goal of uncovering the primary postsynaptic actions that may initiate cellular antidepressive signaling, we have examined the antidepressant-induced production of CDP-diacylglycerol which is both a product of diacylglycerol phosphorylation and a precursor for the synthesis of physiologically critical glycerophospholipids such as the phosphatidylinositides. For this, drug effects on [3H]cytidine-labeled CDP-diacylglycerol and [3H]inositol-labeled phosphatidylinositides were measured in response to the tricyclics desipramine and imipramine, the selective serotonin reuptake inhibitors fluoxetine and paroxetine, the atypical antidepressants maprotiline and nomifensine, and several monoamine oxidase inhibitors.  相似文献   
4.
The essential oils of fresh leaves of Eucalyptus globulus L. (Myrtaceae), and leaves and stems of Smyrnium olusatrum L. (Apiaceae), obtained by hydrodistillation in a Clevenger-type apparatus, were analyzed by GC/MS. Twenty compounds were characterized, representing 98.3% of the essential oil of E. globulus, with 1,8-cineole (48.6%), globulol (10.9%), trans-pinocarveol (10.7%), and alpha-terpineol (6.6%) as main components, while thirty-three compounds were characterized, representing 94.3% of the essential oil of S. olusatrum, with sabinene (27.1%), curzerene (13.7%), methyl-1-benzyl-2-oxocyclooctane carboxylate (12.3%), alpha-pinene (7.2%), cryptone (7.1%) and beta-pinene (5.7%) as the major components. The essential oils of E. globulus and S. olusatrum were tested against a wide range of fungal and bacterial strains. Both oils showed significant antimicrobial activity.  相似文献   
5.
In this paper, we introduce an improved Greedy Randomized Adaptive Search Procedure (GRASP) based heuristic for the multi-product multi-vehicle inventory routing problem (MMIRP). The inventory routing problem, which combines the vehicle-routing problem and the inventory control decisions, is one of the most important problems in combinatorial optimization field. To deal with the MMIRP, we develop a GRASP-based heuristic (GBH). Each GBH iteration consists of two sequential phases; the first phase is a Greedy Randomized Procedure, in which, the best tradeoff between the inventory holding cost and routing cost is looked. Then, in the second phase, as local search for the GRASP, we use the Tabu search (TS) meta-heuristic to improve the solution found in the first phase. The GBH two phases are repeated until some stopped criterion is met. Our proposed method is evaluated on two benchmark data sets, and successfully compared with two state-of-the-art algorithms.  相似文献   
6.
ABSTRACT

We have studied the reversible and irreversible part of the hysteresis loops as a function of slow cooling rate through the order–disorder transformation near 80?K for the deuterated (κ-D8-Br) κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor. We estimated the critical current density JC and the thermodynamic critical field HC from the magnetic hysteresis loops. Temperature dependence of the critical current density derived from the irreversible part using Bean’s model. The thermodynamic critical field HC has been obtained from the reversible part of the hysteresis loops.  相似文献   
7.
In this review article the synthesis of iron chalcogenides using single source precursors is discussed. The effect on morphology and phase of iron chalcogenides formed is studied by varying single source precursors, reaction temperature, reaction time, surfactants and their concentration. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
8.
9.
Following the work of G. Citti and F. Uguzzoni who studied Yamabe type problems on Heisenberg group domains, we consider here the following critical semi-linear equation on domains of the Heisenberg group ${{\mathbb{H}^1}}$ : $$(P) \left\{\begin{array}{lll}-{\Delta_{H}}u\quad =\quad K{u^{3}}\quad\,{\rm in}\,\,\Omega,\\ \quad\quad\,{u}\quad > \quad0\qquad\,\,\,\,{\rm in}\,\,\Omega,\\ \quad\quad\,{u}\quad = \quad 0 \quad\quad\,\,\,{\rm on}\,\partial \Omega, \end{array}\right. $$ where Δ H is the sublaplacian on ${{\mathbb{H}^1}}$ and K is a C 3 positive function defined on Ω. Using a version of the Morse Lemma at infinity, we give necessary conditions on K to insure the existence of solutions for (P).  相似文献   
10.
The influence of the charge compensating cation nature (Na+, Mg2+) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C for 2 h using 1 M magnesium chloride (MgCl2) aqueous solutions. XRF, ICP, and EDX analyses indicate a successful cationic exchange process without the modification of the zeolite structure as shown by XRD and solid-state NMR analyses. Composite materials (granulates and molded parts) were manufactured using to extrusion and injection processes. In the case of MgA zeolite, nitrogen adsorption–desorption experiments allowed us to measure a microporous volume, unlike NaA zeolite, which is non-porous to nitrogen probe molecule. SEM and EDX analyses highlighted the homogeneous distribution of zeolite crystals into the polymer matrix. Water adsorption capacities confirmed that the trends observed in the zeolite powder samples are preserved after dragging zeolites into composite formulations. Granulates and molded parts composite samples containing the magnesium exchanged zeolite showed an increase of their water adsorption capacity up to +27% in comparison to composite samples containing the non-exchanged zeolite. The MgA composite is more promising for water decontamination applications due to its higher water adsorption properties than the NaA composite.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号