Detection of Photoemission of Electrons into Anthracene Crystals by Studying Recom ination Radiation

Evidence for photoemission of electrons from a calcium contact into anthracene crystals is presented. It is based on the observation of recombination radiation resulting from mutual annihilation of photoinjected electrons with holes which are supplied by an ohmic counter-electrode. The method avoids spurious effect's due to optical release of trapped electrons. The problem of photoemission of electrons from alkali-metals into anthracene crystals is discussed.     

Dependence of electronic and optical properties of multilayer SiC and GeC on stacking sequence and external electric field

The electronic and optical properties of different stacked multilayer SiC and GeC are investigated with and without external electric field (EEF). The band gaps of multilayer SiC and GeC are found smaller than that of monolayer SiC and GeC due to the interlayer coupling effect. When EEF is applied, the direct band gaps (ΔK–M) of multilayer SiC and direct band gaps (ΔK–K) of multilayer GeC all turn to indirect band gaps (ΔK–G) as the band at the G point drops dramatically toward zero. The imaginary part ε₂(ω)s of multilayer SiC and GeC show that new absorption peaks between 2–5 eV appear when the polarized direction is perpendicular to the layer plane, and new absorption peaks in infrared region appear as the EEF is higher than a certain point when the polarized direction is parallel to the layer plane. Our calculations reveal that different stacking sequences and EEF can provide a wide tunable band structures and optical properties for multilayer SiC and GeC.     

The stabilization of partially-premixed jet flames in the presence of high potential electric fields

Numerous research efforts have focused on flame stabilization and emissions. Based on initial experiments, specific mechanisms resulting from DC electric fields were chosen to be investigated, namely the chemical, thermal, and ionization mechanisms. Numerical simulations were performed on premixed propane-ozone-air flames to characterize ozone effects on flame speed resulting from the formation of ozone in high potential electric fields. These results were compared against partially premixed flame experiments to observe the dominant influences within leading edge stabilization within high potential electric fields. It was found that the electromagnetic or ionization influences, serve as the dominant effect on the combustion zone.     

A semidefinite programming approach to the hypergraph minimum bisection problem

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.     

Realization of superposition and entanglement of coherent and squeezed states in circuit quantum electrodynamics

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...     

Further bounds for waiting time distributions and their means in the case ρ<1

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.     

不同磁路下微型ECR中和器电子引出的模拟研究

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.     

外电场对2-氟-5-溴吡啶分子结构与电子光谱影响的研究

采用密度泛函B3LYP方法，在6-311++g(3df,3pd)基组水平上优化了不同外电场下2-氟-5-溴吡啶分子的基态稳定构型、电偶极矩和分子的总能量，在此基础上利用杂化CIS方法研究了外电场下2-氟-5-溴吡啶分子的前9个激发态的激发能、波长和振子强度受外电场的影响规律。结果表明：5C-9Br和3C-10F间键长受到X轴向外场影响最大，随着外电场的继续增加，可能最先趋于断裂；在外电场F=-0.005a.u.时总能量达到最大，而偶极矩达到最小；LUMO能级受外场影响较大，HOMO能级受外电场影响较小；激发波长、振子强度也受外电场影响，但随电场变化比较复杂。     

Selectivity of seismic electric signal (SES) of the 2000 Izu earthquake swarm: a 3D FEM numerical simulation model

Although seismic electric signal (SES) has been used for short-term prediction of earthquakes, selectivity of SES still remains as one of the mysterious features. As a case study, we made a numerical simulation based on a 3D finite element method (FEM) on the selectivity of SES observed in the case of the 2000 Izu earthquake swarm. Our numerical results indicated that the existence of conductive channel under Niijima island could explain the reported SES selectivity.