由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。     

Revealing pion and kaon structure via generalised parton distributions

Clear windows onto emergent hadron mass(EHM)and modulations thereof by Higgs boson interactions are provided by observable measures of pion and kaon structure,many of which are accessible via generalised parton distributions(GPDs).Beginning with algebraic GPD Ans?tze,constrained entirely by hadron-scaleπand K valence-parton distribution functions(DFs),in whose forms both EHM and Higgs boson influences are manifest,numerous illustrations are provided.They include the properties of electromagnetic form factors,impact parameter space GPDs,gravitational form factors and associated pressure profiles,and the character and consequences of allorders evolution.The analyses predict that mass-squared gravitational form factors are stiffer than electromagnetic form factors;reveal that K pressure profiles are tighter than profiles,with both mesons sustaining near-core pressures at magnitudes similar to that expected at the core of neutron stars;deliver parameter-free predictions for and K valence,glue,and sea GPDs at the resolving scale l=2GeV;and predict that at this scale the fraction of meson mass-squared carried by glue and sea combined matches that lodged with the valence degrees-of-freedom,with a similar statement holding for mass-squared radii.     

Phase relations in the ZnO-V2O5-K2O system

The subsolidus phase relations of a ZnO-V 2 O 5-K 2 O system are investigated by X-ray powder diffraction.There is 1 ternary compound,11 binary compounds and 14 three-phase regions in this system.The phase diagrams of V 2 O 5 K 2 O with the K 2 O content ranging from 0 to 71 mol% and pseudo-binary system of ZnO-K 2 ZnV 2 O 7 are also studied by X-ray powder diffraction and differential thermal analysis methods.     

Lax pair and vector semi-rational nonautonomous rogue waves for a coupled time-dependent coefficient fourth-order nonlinear Schrodinger system in an inhomogeneous optical fiber

Optical fibers are seen in the optical sensing and optical fiber communication. Simultaneous propagation of optical pulses in an inhomogeneous optical fiber is described by a coupled time-dependent coefficient fourth-order nonlinear Schr?dinger system, which is discussed in this paper. For such a system, we work out the Lax pair, Darboux transformation, and corresponding vector semi-rational nonautonomous rogue wave solutions. When the group velocity dispersion(GVD) and fourth-order dispersion(FOD) coefficients are the constants, we exhibit the first-and second-order vector semirational rogue waves which are composed of the four-petalled rogue waves and eye-shaped breathers. Both the width of the rogue wave along the time axis and temporal separation between the adjacent peaks of the breather decrease with the GVD coefficient or FOD coefficient. With the GVD and FOD coefficients as the linear, cosine, and exponential functions, we respectively present the first-and second-order periodic vector semi-rational rogue waves, first-and second-order asymmetry vector semi-rational rogue waves, and interactions between the eye-shaped breathers and the composite rogue waves.     

Gravitational collapse with standard and dark energy in the teleparallel equivalent of general relativity

A perfect fluid with self-similarity of the second kind is studied within the framework of the teleparallel equivalent of general relativity(TEGR).A spacetime which is not asymptotically flat is derived.The energy conditions of this spacetime are studied.It is shown that after some time the strong energy condition is not enough to satisfy showing a transition from standard matter to dark energy.The singularities of this solution are discussed.     

Breakdown voltage model and structure realization of a thin silicon layer with linear variable doping on a silicon on insulator high voltage device with multiple step field plates

Based on the theoretical and experimental investigation of a thin silicon layer(TSL) with linear variable doping(LVD) and further research on the TSL LVD with a multiple step field plate(MSFP),a breakdown voltage(BV) model is proposed and experimentally verified in this paper.With the two-dimensional Poisson equation of the silicon on insulator(SOI) device,the lateral electric field in drift region of the thin silicon layer is assumed to be constant.For the SOI device with LVD in the thin silicon layer,the dependence of the BV on impurity concentration under the drain is investigated by an enhanced dielectric layer field(ENDIF),from which the reduced surface field(RESURF) condition is deduced.The drain in the centre of the device has a good self-isolation effect,but the problem of the high voltage interconnection(HVI) line will become serious.The two step field plates including the source field plate and gate field plate can be adopted to shield the HVI adverse effect on the device.Based on this model,the TSL LVD SOI n-channel lateral double-diffused MOSFET(nLDMOS) with MSFP is realized.The experimental breakdown voltage(BV) and specific on-resistance(R on,sp) of the TSL LVD SOI device are 694 V and 21.3 ·mm 2 with a drift region length of 60 μm,buried oxide layer of 3 μm,and silicon layer of 0.15 μm,respectively.     

A new complex variable element-free Galerkin method for two-dimensional potential problems

In this paper, based on the element-free Galerkin (EFG) method and the improved complex variable moving least- square (ICVMLS) approximation, a new meshless method, which is the improved complex variable element-free Galerkin (ICVEFG) method for two-dimensional potential problems, is presented. In the method, the integral weak form of control equations is employed, and the Lagrange multiplier is used to apply the essential boundary conditions. Then the corresponding formulas of the ICVEFG method for two-dimensional potential problems are obtained. Compared with the complex variable moving least-square (CVMLS) approximation proposed by Cheng, the functional in the ICVMLS approximation has an explicit physical meaning. Furthermore, the ICVEFG method has greater computational precision and efficiency. Three numerical examples are given to show the validity of the proposed method.     

Phase properties of odd and even circular states

Phase properties of the even and odd circular states are studied within the Hermitian phase formalism of Pegg and Barnett. Exact analytical formulas for the distribution function and the variance of the phase operator are obtained and used to examine whether or not the even and odd circular states exhibit photon-number squeezing and phase squeezing.     

Neutron star cooling and GW170817 constraint within quark-meson coupling models

In the present work,we used five different versions of the quark-meson coupling(QMC)model to compute astrophysical quantities related to the GW170817 event and the neutron star cooling process.Two of the models are based on the original bag potential structure and three versions consider a harmonic oscillator potential to confine quarks.The bag-like models also incorporate the pasta phase used to describe the inner crust of neutron stars.With a simple method studied in the present work,we show that the pasta phase does not play a significant role.Moreover,the QMC model that satisfies the GW170817 constraints with the lowest slope of the symmetry energy exhibits a cooling profile compatible with observational data.     

Decoy-state method for quantum-key-distribution-based quantum private query

The quantum private query(QPQ)is a quantum solution for the symmetrically private information retrieval problem.We study the security of quantum-key-distribution-based QPQ with weak coherent pulses.The result shows that multiphoton pulses have posed a serious threat to the participant’s privacy in QPQ protocols.Then we propose a decoy-state method that can help the honest participant detect the attack by exploiting multiphoton pulses and improving the key distillation process to defend against such attack.The analysis demonstrates that our decoy-state method significantly improves the security of the QPQ with weak coherent pulses,which solves a major obstacle in the practical application of the QPQ.     

计及几何参数变化的离心压气机特性分析

本文采用CFD软件对微型燃机的离心叶轮进行数值模拟,讨论了叶片数及分流叶片位置对叶轮性能的影响,并进行了流场分析。在本文研究的情况中,叶片数增加使得性能曲线左移,单个叶片载荷减小,损失增加,叶轮效率下降, 但是增压效果得到改善。分流叶片位置靠近主叶片压力面时,性能曲线右移,流通能力提高,同时会使分流叶片的载荷增大,当分流叶片靠近主叶片压力面时,则情况相反。     

基于势流理论的回转体并联入水双空泡演化动力学研究

两回转体并联入水过程中,双空泡在空间上相互干扰,使得单个入水空泡呈现非对称特性.本文基于势流理论,在现有二维轴对称入水空泡计算模型的基础上,对空泡干涉区域的三维流动进行简化,将相对流动对空泡发展的约束简化为约束势,分析了两回转体轴线内外两侧的空泡形态变化;基于非线性假设,引入影响函数,给出了空泡在三维空间演化的计算模型,并分析了同步并联入水过程空泡的三维演化特性.结果表明：回转体入水过程流场速度势可以看作由一个随回转体运动的点源和位于空泡轴线处的线源叠加产生;在并联入水过程中,双空泡演化在空间呈镜面对称,空泡间的相互扰动可以通过引入有势壁面进行分析;并联入水空泡半径随极角的变化与空泡截面所处深度有关,在靠近闭合点附近的抑制演化区空泡截面半径随极角的增大而逐渐减小,远离闭合点处的抑制演化区空泡截面半径随极角的增大而增大,空泡加权半径规律相反.     

基于云测试的自动测试系统体系架构研究

为了解决面临保障任务时,我军现有保障设备对武器装备故障检测周期过长以及测试资源在测试周期中被单个故障装备长时间占用的问题,对基于云测试(Cloud Testing)的自动测试系统(ATS,Automatic Test System)的体系架构进行了研究。以软件可移植性、硬件可互换性和系统互操作性为设计原则,对面向信号测试领域的云测试系统的体系架构进行了分析;在充分研究现有ATS的体系架构及其存在的突出问题的基础上,提出了基于云测试的ATS的软、硬件模型。为构建基于云测试的自动测试系统的开发和相关关键技术的研究提供了以有益的借鉴并打下了坚实的基础。     

混合场介质表面单边次级电子倍增效应统计

综合考虑发射电子的发射能量、发射角度及微波场的相位分布等因素,运用统计方法,研究了介质表面单边次级电子倍增过程中次级电子数目、瞬时直流场、渡越时间、微波场的沉积功率等次级电子倍增特征物理量随碰撞次数的变化过程,仿真分析了不同夹角、不同反射系数对次级电子倍增的影响。研究结果表明:当倾斜直流场一定时,微波场的反射系数越小,雪崩击穿的延迟时间越长,饱和状态下的次级电子数目越大;微波场一定时,当直流电场平行于介质板表面时,直流电场幅值越大,雪崩击穿的延迟时间越长,饱和状态下的次级电子数目越大,但当电场强度超过一定值时,次级电子倍增现象不再发生,当直流场垂直介质板表面,直流电场幅值越大,雪崩击穿的延迟时间越长,饱和状态下的次级电子数目越小,幅值超过一定值时,次级电子倍增现象同样不会发生。     

耗散腔中Λ型原子与光场Raman相互作用体系的线性熵

为了研究耗散腔中原子与光场Raman相互作用体系中子系统间的熵交换,利用超算符方法通过对系统主方程求解,讨论了光场强度、腔的耗散系数及原子两能级的Stark位移对线性熵的影响.结果表明：光场越强,光场与其它子系统进行熵交换的时间越长|腔耗散系数越大,熵交换时间越短|改变两能级间的Stark位移使原子和场之间的耦合增强,而系统的耗散系数不变,此时,系统的熵交换加快且其稳态值变小.     

最相邻后车综合信息对交通流不稳定性的影响分析

基于抑制交通流不稳定性所需的条件,分析司机后视获得的最相邻后车综合信息对交通流不稳定性的影响. 在司机关注前车信息概率大于关注后车信息概率与司机敏感系数大于0的现实条件下,解析分析以及仿真分析得到了以下结论:1)最相邻后车车头距信息减小了交通流的不稳定性,且关注概率越大,减小作用越大;跟驰车与最相邻后车的速度差信息增加了交通流的不稳定性,且关注概率越大,增加作用越大. 2)最相邻后车综合信息对交通流的不稳定性的减小作用大于增加作用,即最相邻后车综合信息减小了交通流的不稳定性. 3)司机距离差敏感系数越大,最相邻后车综合信息对交通流的不稳定性减小作用越大. 4)司机速度差敏感系数越大,最相邻后车综合信息对交通流的不稳定性增加作用越大. 关键词： 交通堵塞 交通流不稳定性 最相邻后车综合信息 跟驰模型     

气体栓子超声多普勒信号的仿真研究

通过分析研究气体栓子的超声多普勒信号的特征及其成因,建立气体栓子的超声多普勒仿真模型,为后续的气体栓子与固体栓子的分类提供理论基础。先利用超声辐射力和液体黏滞阻力的模型计算气体栓子所受的超声辐射力和黏滞阻力,然后计算气体栓子在血管内的径向加速度和轴向加速度,并从加速度得到气体栓子在血管内的运动轨迹,最后建立气体栓子的计算机仿真模型。实验中仿真合成气体栓子和固体栓子的超声多普勒信号,对信号的分析结果表明,相比于固体栓子,仿真的气体栓子信号受到作用力而产生的加速度将导致气栓信号在多普勒声谱图上频域的展宽,当气体栓子由低速区域加速到高速区域再由高速区减速至低速区将会在声谱图上体现为"V"型,若只有单一的加速或减速运动将只表现为斜线型。将仿真的气栓信号与临床采集的气栓信号进行比较,发现两者的特征是吻合的,说明气栓超声多普勒信号的仿真方法是合理的。      

兴奋性作用诱发神经簇放电个数不增反降的分岔机制

非线性动力学在识别神经放电的复杂现象、机制和功能方面发挥了重要作用.不同于传统观念,本文提出了兴奋性作用可以降低而不是增加簇内放电个数的新观点.在簇放电模式休止期的适合相位施加强度合适的脉冲或自突触电流,能诱发簇内放电个数降低;电流的施加相位越早,所需的强度阈值越大,簇内放电个数越少.进一步,利用快慢变量分离获得的簇放电的动力学性质进行了理论解释.簇放电模式表现出低电位的休止期和高电位的放电的交替,存在于快子系统的鞍结分岔点和同宿轨分岔点之间;放电起始于鞍结分岔、结束于同宿轨分岔;越靠近同宿轨分岔从休止期跨越到放电所需的电流强度越大.因此,电流在休止期上的作用相位越早,就越靠近同宿轨分岔,因而从休止期跨越到放电需要的电流强度阈值越大,放电起始相位到同宿轨分岔之间的区间变小导致放电个数变少.研究结果丰富了非线性现象及机制,对兴奋性作用提出了新看法,给出了调控簇放电模式的新途径.     

凹槽铜基底表面与单层石墨烯的相互作用特性研究

基于石墨烯二维材料的诸多应用需要将其大面积、高质量地转移到目标基底上,迫切需要了解石墨烯在剥离和转移过程中与基底之间的相互作用特性.本文采用经典分子动力学方法探索了铜基底表面凹槽的几何特征尺寸对石墨烯吸附和剥离过程中凹槽基底对石墨烯吸附作用的影响机理和规律.结果表明:对于固定边界条件下的单层石墨烯,当基底表面的凹槽宽度固定不变时,吸附过程中基底对石墨烯的吸附力随二者间距的减小,呈现先增大后减小的趋势;其最大吸附力随凹槽深度的增加而增大,而当凹槽深度继续增大至石墨烯未能吸附进入凹槽底部的临界值时,吸附力迅速减小;剥离过程中,石墨烯完全剥离的临界作用力随凹槽深度的增加同样呈现先增大后减小的趋势,且与剥离前石墨烯与凹槽基底的相互作用面积有关;当基底表面凹槽的深度固定不变时,吸附和剥离过程中石墨烯-基底之间的吸附力随间距的变化规律取决于石墨烯在基底凹槽处的稳态吸附构型.     

拼接式望远镜主镜衍射效应研究

拼接式主镜的设计使超大口径望远镜的构想成为现实。为了研究拼接式望远镜的成像性能,精确分析和量化了拼接式主镜构型、平移误差、倾斜误差对衍射效应的影响,从拼接式光学系统的成像原理出发,基于齐次坐标变换建立了拼接式主镜的光瞳模型,并仿真分析了拼接主镜构型对衍射效应的影响。分析结果表明:对于不同构型的拼接主镜,其衍射效应受拼接主镜的填充因子和孔径间隔共同影响,填充因子越高,孔径间隔越小,系统成像质量越好。以典型的拼接主镜构型为例,分别仿真分析了单个子镜平移误差、倾斜误差和拼接主镜整体平移误差、倾斜误差对衍射效应的影响。分析结果表明:对于单个子镜,平移误差对远场衍射的影响具有周期性;对于拼接主镜整体,当子镜piston误差的均方根值小于0.039λ时,斯特列尔比大于0.95;当子镜tip-tilt误差的均方根值小于0.036λ时,斯特列尔比大于0.95。分析结果为拼接式望远镜的成像性能分析、主镜的构型设计、平移误差和倾斜误差的检测与调整等提供了依据。