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71.
《Optimization》2012,61(3):413-427
The hypergraph minimum bisection (HMB) problem is the problem of partitioning the vertices of a hypergraph into two sets of equal size so that the total weight of hyperedges crossing the sets is minimized. HMB is an NP-hard problem that arises in numerous applications – for example, in digital circuit design. Although many heuristics have been proposed for HMB, there has been no known mathematical program that is equivalent to HMB. As a means of shedding light on HMB, we study the equivalent, complement problem of HMB (called CHMB), which attempts to maximize the total weight of non-crossing hyperedges. We formulate CHMB as a quadratically constrained quadratic program, considering its semidefinite programming relaxation and providing computational results on digital circuit partitioning benchmark problems. We also provide results towards an approximation guarantee for CHMB. 相似文献
72.
We propose a new scheme for generating the superposition and entanglement of the coherent states and squeezed states by considering N superconducting charge qubits (or artificial two-level atoms) interacting with photons in a high finesse cavity on a chip, assisted by a strong driving field. By virtue of the parameters of this system, we can generate novel quantum states, for example, multiparty entangled states and Schro¨dinger cat states among the superconducting qubits, coherent states and squeezed state... 相似文献
73.
《Optimization》2012,61(3):405-412
In the paper exponential bounds for the instationary and stationary waiting time d.f.'s in GI/GI/1/∞, derived by several authors partly using martingale theory arguments, are improved with the help of monotonicity properties. Further it is shown that Ne?eptjrenko's bound for the rate of convergence of the mean waiting time in single server queues Is also valid for many server queues with ρ < 1. 相似文献
74.
电子回旋共振(ECR)中和器是微型ECR离子推力器的重要组成部分,其引出的电子用于中和ECR离子源的离子束流,避免了航天器表面电荷堆积,并且电子引出性能对推力器的整体性能起着重要作用.为了分析影响微型ECR中和器电子引出的因素,本文建立了二维轴对称PIC/MCC计算模型,通过数值模拟研究不同磁路结构对中和器的电子引出,及不同腔体长度对壁面电流损失的影响.计算结果表明, ECR区位置和引出孔附近磁场构型对中和器的电子引出性能至关重要.当ECR区位于天线上游,电子在迁移扩散中易损失,并且电子跨过引出孔前电势阱所需的能量更高.如果更多磁力线平行通过引出孔,中和器引出相同电子电流所需电压较小.当ECR区被天线切割或位于下游时,电子更易沿磁力线迁移到引出孔附近,从而降低了收集板电压.研究了同一磁路结构下不同腔体长度对电子引出的影响,发现增加腔体长度,使得更多平行轴线的磁力线通过引出孔从而避免电子损失在引出板表面,增加了引出电子电流.研究结果有助于设计合理的中和器磁路和腔体尺寸. 相似文献
75.
AbstractAlkyl substituents appended to polymers play the determining role on self-assembly and film-forming properties, and on device performance. In this work, we highlight the effects of the linear and branched flexible chains appended to the acceptor moiety (A) in D-A type copolymers. Two thieno[3,4-c]-pyrrole-4,6-dione (TPD) based copolymers PT1 and PT2 with different alkyl chains, were designed and synthesized. By comparison their UV-vis absorptions, HOMO/LUMO energy levels, as well as the characters in polymer solar cells, the influences of alkyl chains were investigated. Both copolymers showed molecular weights of 21?kDa and similar optical properties with a medium band gap of 1.93?eV, while PT2 with the branched chain exhibited a lower HOMO than that of PT1 (?5.43 vs???5.37?eV). In bulk heterojunction (BHJ) solar cells, PT1 with a linear chain presented a short circuit current (Jsc) of 6.76?mA cm?2, open circuit voltage (Voc) of 0.89?V and power conversion efficiency (PCE) of 2.92%. To the contrary, PT2 showed a Jsc of 3.53?mA cm?2, Voc of 0.99?V, delivering a relatively lower PCE of 2.05%. The result indicates that appending a linear alkyl chain to the TPD unit could sufficient enhance the Jsc value of the related polymer. 相似文献
76.
Novel composite carbon particles are developed that can self‐assemble as a coating on a substrate without a binder. These carbon particles were used as a coating to enhance thermal dissipation and their thermal conductivity, surface emissivity and cooling performance were measured. Carbon particles with both thiol and epoxy functional groups self‐assembled to form a coating on the surface of a heat sink without a binder, which greatly improved the thermal conductivity of the coating. Coating a heat sink with the carbon particles yielded a higher thermal conductivity and emissivity than could be obtained with the addition of binder in the conventional approach, and significantly enhanced the cooling performance. In addition, the cooling performance of the carbon nanotube outperformed all other particles when coated on a substrate, because it had the highest thermal conductivity and good radiation emissivity. We developed an equation to describe the various parameters affecting the cooling performance of the thermally dissipative coating. This equation was confirmed by the experimental data. 相似文献
77.
At presrent, the photoelectric switch is more and more widely used in the industrial automation equipment.It can be finished counting industrial products by using the characteristic of the photoelectric switch which can detect the objects without touching them. This design uses the modular design method,including power-supply module, The photoelectric conversion module, optocoupler isolation circuit module, power off protection module, matrix keyboard module, counting module and The display module. It mainly uses 51 single-chip microcomputer to control the system,uses the keilC51 software to design program,uses the Proteus software to complete the simulation. Through the experiment, it proves the design is feasible. 相似文献
78.
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80.
In recent times,nanoparticles(NPs)have received intense attention not only due to their potential applications as a candidate for drug delivery,but also because of their undesirable effects on human health.Although extensive experimental studies have been carried out in literature in order to understand the interaction between NPs and a plasma membrane,much less is known about the molecular details of the interaction mechanisms and pathways.As complimentary tools,coarse grained molecular dynamics(CGMD)and dissipative particle dynamics(DPD)simulations have been extensively used on the interaction mechanism and evolution pathway.In the present review we summarize computer simulation studies on the NP-membrane interaction,which developed over the last few years,and particularly evaluate the results from the DPD technique.Those studies undoubtedly deepen our understanding of the NP-membrane interaction mechanisms and provide a design guideline for new NPs. 相似文献