915 resultados para Equation of prediction


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We study the relationship between the properties of the isovector giant dipole resonance of finite nuclei and the symmetry energy in the framework of the relativistic mean field theory with six different parameter sets of nonlinear effective Lagrangian. A strong linear correlation of excited energies of the dipole resonance in finite nuclei and symmetry energy at and below the saturation density is found. This linear correlation leads to the symmetry energy at the saturation density at the interval 33.0MeV <= S(po) <= 37.0 MeV. The comparison to the present experimental data in the soft dipole mode of (132) Sn constrains approximately the symmetry energy at p = 0.1 fm(-3) at the interval 21.2MeV similar to 22.5 MeV. It is proposed that a precise measurement of the soft dipole mode in neutron rich nuclei could set up an important constraint on the equation of state for asymmetric nuclear matter.

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Transport in a semiopen Kondo- correlated quantum dot is mediated through more than one quantum state. Using the Keldysh technique and the equation of motion method, we study the shot noise S for a wide range of source- drain voltages V-sd within a model incorporating the additional states as a background continuum, demonstrating the importance of the Fano interference. In the absence of the interference, the noise is revealed to be a probe of the second moment of the local density of states, and our theory reproduces the well- known peak structure around the Kondo temperature in the S-V-sd curve. More significantly, it is found that taking account of the background transmission, the voltage dependence of the noise exhibits rich peak- dip line shapes, indicating the presence of the Fano effect. We further demonstrate that due to its two- particle nature, the noise is more sensitive to the quantum interference effect than the simple current.

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Deconfinement phase transition and neutrino trapping in (proto)neutron star matter are investigated in a chiral hadronic model (also referred to as the FST model) for the hadronic phase (HP) and in the color-flavor-locked (CFL) quark model for the deconfined quark phase. We include a perturbative QCD correction parameter alpha(s) in the CFL quark matter equation of states. It is shown that the CFL quark core with K-0 condensation forms in neutron star matter with the large value of alpha(s). If the small value of alpha(s) is taken, hyperons suppress the CFL quark phase and the HP is dominant in the high-density region of (proto)neutron star matter. Neutrino trapping makes the fraction of the CFL quark matter decrease compared with those without neutrino trapping. Moreover, increasing the QCD correction parameter alpha(s) or decreasing the bag constant B and the strange quark mass m(s) can make the fraction of the CFL quark matter increase, simultaneously, the fraction of neutrino in protoneutron star matter increases, too. The maximum masses and the corresponding radii of (proto)neutron stars are not sensitive to the QCD correction parameter alpha(s).

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We consider the Randall-Sundrum brane-world model with bulk-brane energy transfer where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. It is remarkable that these curvature terms will not change the dynamics of the brane universe at low energy. Parameterizing the energy transfer and taking the dark radiation term into account, we find that the phantom divide of the equation of state of effective dark energy could be crossed, without the need of any new dark energy components. Fitting the two most reliable and robust SNIa datasets, the 182 Gold dataset and the Supernova Legacy Survey (SNLS), our model indeed has a small tendency of phantom divide crossing for the Gold dataset, but not for the SNLS dataset. Furthermore, combining the recent detection of the SDSS baryon acoustic oscillations peak (BAO) with lower matter density parameter prior, we find that the SNLS dataset also mildly favors phantom divide crossing.

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Antikaon condensation and kaon and antikaon production in protoneutron stars are investigated in a chiral hadronic model (also referred to as the FST model in this paper). The effects of neutrino trapping on protoneutron stars are analyzed systematically. It is shown that neutrino trapping makes the critical density of K- condensation delay to higher density and (K) over bar (0) condensation not occur. The equation of state (EOS) of (proto)neutron star matter with neutrino trapping is stiffer than that without neutrino trapping, As a result, the maximum masses of (proto)neutron stars with neutrino trapping are larger than those without neutrino trapping. If hyperons are taken into account, antikaon does not form a condensate in (Proto)neutron stars. Meanwhile, the corresponding EOS becomes much softer, and the maximum masses of (proto)neutron stars are smaller than those without hyprons. Finally, our results illustrate that the Q values for K+ and K- production in (proto)neutron stars are not sensitive to neutrino trapping and inclusion of hyperons.

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We investigate the composition and the equation of state of the kaon condensed phase in neutrino-free and neutrino-trapped star matter within the framework of the Brueckner-Hartree-Fock approach with three-body forces. We find that neutrino trapping shifts the onset density of kaon condensation to a larger baryon density, and reduces considerably the kaon abundance. As a consequence, when kaons are allowed, the equation of state of neutrino-trapped star matter becomes stiffer than the one of neutrino free matter. The effects of different three-body forces are compared and discussed. Neutrino trapping turns out to weaken the role played by the symmetry energy in determining the composition of stellar matter, and thus reduces the difference between the results obtained by using different three-body forces.

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An isospin-dependent quantum molecular dynamical model (IQMD) is developed, with the isospin degree of freedom in the momentum-dependent interaction(MDI) included in IQMD, to obtain an isospin- and momentum-dependent interaction (IMDI) in IQMD. We investigate the effect of IMDI on the isospin fractionation ratio and its dynamical mechanism in the intermediate energy heavy ion collisions. It is found that the IMDI induces the significant reductions in the isospin fractionation ratio for all of beam energies, impact parameters, neutron-proton ratios and mass number of colliding systems. However, the strong dependence of isospin fractionation ratio on the symmetrical potential is preserved, with the isospin degree of freedom included in the MDI, i.e. the isospin fractionation ratio is still a good probe for extracting the information about the equation of state of isospin asymmetrical nuclear matter.

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Based on the isospin-dependent transport model IBUU and on the scaling model according to nucleon effective mass, effects of elastic and inelastic NN scattering cross-sections on pi(-)/pi(+) in the neutron-rich reaction Ca-48 + Ca-48 at a beam energy of 400MeV/nucleon are studied. It is found that cross-section effects of both NN elastic and inelastic scatterings affect Delta(1232), pi(-) and pi(+) productions as well as the value of pi(-)/pi(+).

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Microscopic three-nucleon force consistent with the Bonn B two-nucleon potential is constructed, which includes Delta(1232), Roper, and nucleon-antinucleon excitation contributions. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined. At the high densities,the nuclear equation of state and the symmetry energy are calculated. The corresponding neutron star mass-radius relations are presented.

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本论文介绍了放射性核束物理研究的现状以及当前常用的几种同位旋相关的重离子微观输运理论,系统描述了非对称核物质的状态方程、中能重离子碰撞中的同位旋效应以及中子星的性质。基于 Hartree-Fock 理论和扩展的 Skyrme 相互作用,在核物质近似下得到了一个非相对论性的密度、温度和同位旋相关的核物质状态方程 (IEOS)。系统研究了核物质状态方程的同位旋效应。讨论了核子的平均场、核物质的不可压缩系数、核子的有效质量以及核物质临界温度的同位旋相关性,并且给出了核物质饱笔点处的饱和密度、不可压缩系数以及单核子结合能的抛物线规律。同时,探讨了对称能的温度和密度相关性,给出了零温度时对称能的解析表达式,并提出了对称能温度相关性的抛物线规律,发现对称能随着温度的升高而减小。另外,基于以上的同位旋相关的核物质状态方程,对 ALADIN's Caloric Curve 给出了一种静态解释。在传统量子分子动力学 (QMD) 模型的基础上,通过在相互作用平均场、两体碰撞、泡利阻塞、初始化以及碎片构造过程中适当地考虑同位旋自由度,得到了一个同位旋相关的 QMD 模型 (IQMD 模型)。利用IQMD模型系统研究了中能重离子碰撞中的同位旋效应。例如,中能重离子碰撞中同位旋自由度的弛豫、重离子碰撞中核子前平衡发射的同位旋效应、重离子碰撞中的集体流(包括直接流、转动流、挤出流和径向流)及其同位旋相关性、原子核多重碎裂的同位旋效应及其消失、重离子碰撞中的化学不稳定性以及中能重离子碰撞中如何选取事件的碰撞参数及其同位旋效应等。同样,在传统的 Boltzmann-Langevin 方程中适当地考虑同位旋自由度,得到了同位旋相关的Boltzmann-Langevin方程 (IBLE),利用IBLE研究了 ~(19)Na的产生截面。另外,利用IQMD模型探讨了多重碎裂的"neck" 机制以及重离子碰撞中局域势的有限程效应。基于前面给出的非相对论的核物质状态方程,系统研究了中子星的性质,如中子星的化学组份、质量、结合能、半径、密度剖面、转动惯量及表面红移等。结果表明,使用一些常用的 Skyrme 势参数能够给出与天文学观测相一致的结果。

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本论文基于重离子输运理论模型对当前人们感兴趣的超重核合成及非对称核物质状态方程做了研究。基于双核系统概念建立了一个描述超重核合成的理论模型。这个模型中通过求解Fokker-Planck方程来描述重离子碰撞过程的能量、角动量以及形变等的弛豫过程,从而合理地包含了重离子熔合过程中的动力学效应。在求解弹靶的质量扩散时采用了数值求解主方程的方法,避免对势能面做任何近似,因此能够充分地体现重离子熔合过程中弹靶的结构效应。本文利用这一模型计算了重离子熔合形成超重元素的最佳激发能、熔合几率、复合核的存活几率以及蒸发剩余核截面等,并给出了合成超重核的最佳弹靶组合。计算了超重核形成的最佳激发能,在符合已有最佳激发能实验数据的基础上预言了基于冷熔合反应合成114,116和118号元素的最佳激发能。计算了重离子熔合反应的熔合几率。结果表明,随着反应系统变得越来越重,重离子的熔合几率呈指数规律下降,准裂变变得越来越严重。这解释了实验上观测到的超重剩余核截面随体系的变重而急剧下降的现象。研究了重离子熔合截面的弹靶相关性。结果表明弹靶的质量非对称度越高越有利于熔合生成复合核,同时重离子熔合截面还强烈地依赖于弹靶结构。重离子的熔合过程是合成超重元素的关键因素之一,另一个影响超重核合成的因素是超重复合核的存活几率。基于统计模型,系统的研究了超重复合核存活几率的质量、能量、角动量等相关性。计算了基于冷熔合反应的蒸发剩余截面,得到的结果与实验基本符合,并预言了基于冷熔合反应生成114,116和115号元素的截面。在研究超重核蒸发剩余截面的弹靶相关性的基础上给出了合成超重核的最佳弹靶组合。计算表明,在挑选弹靶组合时使得合成的超重复合核是奇A核则会得到更高的奇数中子蒸发剩余核截面。计算给出了超重复合核的自旋布居及其对裂变位垒和鞍点态形变的依赖性。发现超重复合核的自旋布居强烈地依赖于复合核的裂变位垒,高的裂变位垒会给出宽的自旋布居;而超重复合核的自旋布居对鞍点态形变不是很敏感。另外研究了多核子转移反应合成超重元素的可能性。结果表明基于多核子转移反应合成大于108号的元素是很困难的。非对称核物质状态方程由于其对天体物理及理解奇异核结构的重要性,因此是人们长期以来一直感兴趣的研究内容,然而直到现在人们对核物质状态方程特别是高密核物质和非对称核物质状态状态方程仍了解甚少。基于Skyrme-Hartree-Fock理论以及同位旋相关的量子分子动力学(IQMD)模型研究了非对称核物质的化学不稳定性,结果表明非对称核物质可以发生化学不稳定性,且化学不稳定性发生的条件依赖于单粒子势能的密度相关形式。同时计算表明化学不稳定性是可以发生在真实的重离子碰撞过程中的,且在入射能量较高时化学不稳定性会消失。另外首次研究了高密核物质的化学不稳定性及其发生的条件。由于实验室很难达到很高密度的核物质,而中子星是由致密的极丰中子物质组成,因此提供了研究高密非对称核物质的自然实验室。基于Skyrme-Hartree-Fock理论研究了两种典型的非对称核物质状态方程(软对称势和硬对称势)对中子星中质子百分比的影响。另外研究了热中子星中质子百分比的温度相关性,发现热中子星中质子百分比随温度的升高而减小。基于IQMD模型研究了同位旋相分化现象的产生机制。通过与MSU的实验数据比较指出核物质应该有软的对称势。研究了重离子碰撞过程中的径向流现象,及其同位旋效应。计算了径向流产生的能量闭,并给出了实验上利用径向流产生的能量闭来提取非对称核物质状态方程的方法。

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本论文介绍了极端条件下核物质研究的现状以及目前常用的几种核多体方法,系统描述了冷、热非对称核物质的状态方程和刀稳定中子星物质中的15。态中子和质子超流性,特别是微观三体核力对此所产生的影响。通过引入微观三体核力,扩展了有限温度的BI.tleclcller-Hal'tree-Fock(FTBHF)理论。利用这一扩展的理沦,详细研究了同位旋非对称热核物质的状态方程、液气相变临界现象以及三体核力对此所产生的影响。在不同的中质比条件下,重点讨论了热核物质液气相变的临界温度和动力学不稳定区域的温度、同位旋相关性。由此表明,三体核力的引入在一定程度上降低了液气相变的临界温度值,在固定的温度和密度下,非对称核物质的压弧随同位旋非对称度的增加而单调的增力日,而且随着核物质温度的升高和非对称度的增加,动力学不稳定区域逐渐缩小。通过与其它理论模型(特别是Di1'ac-BHF方法)所预言的结果相比较,就目前扩展的包含三体核力修正的FTBHF理论与Dilac-BHF方法所计算的临界温度的差异问题,文中给出一种可能的解释。通过计算热核物质的单粒子结合能,给出了有限温度条件下对称能的计算方式,并且细致研究了不同温度、密度下的对称能以及三体核力在高密度区域对对称能的影响。结果表明,微观三体核力强烈影响着高密度区域的对称能,使其对温度的变化更加明显。此外,其它重要物理量(例如中子和质子的单粒子势能、有效质量等)的同位旋依赖性和温度、密度相关性在文中也被详细的讨论。利用质量算子的空穴线展井,表明了在基态关联所导致的对单核子势的重排修正项影响下的HLlgenholtz-VanHove(HVH)定理的恢复程度,并且进一步计算了中子和质子化学势。并且以包含兰体核力的FTBI-方法为基础,研究了热核物质中重排项的密度和温度依赖性并讨论了三体核力对重排项的影响。通过计算不同温度和密度下的核物质中单核子势和核子有效质量,特别是研究和讨论了基态关联效应和三体核力贡献对热核物质中单核子势的影响,表明了基态关联和三体核力对单核子势修正的重要性。利用BHF和BCS的理论方法,计算了β稳定中子星物质中处于150态的中子和质子的对关联能隙,着重研究和讨论了三体核力的影响。结果表明,三体核力对刀稳定物质中{s0态中子超流性的影响相对较小,但是对,S0态质子超流性具有重要影响,其效应随核子数密度的增大而迅速增强。三体核力的主要作用是强烈地抑制了高密度区刀稳定中子星物质中的150态质子超流性,而且三体核力对中子星物质中,So态超流相的抑制效应主要是通过质子或中子的有效对相互作用而起作用的。

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相对于非对称核物质状态方程,对称核物质的状态方程己基本确定。然而不同的微观·唯象多体方法对非对称核物质状态方程(尤其是对称能)的预言很不一致。利用动量相关的标量势与矢量势(对称势)及介质修正的核子一核子散射截面,在工Buuo4输运模型框架下我们对重粒子碰撞产生的丰中子核物质的状态方程进行了研究。我们发现在低密情况下对称能E32(p/po),核物质同位旋依赖部分的等压不可压缩系数为K-55OMeF时能够较好地再现NSCL/MSU实验数据。在高密情况下π~-/π~+谱的横动量与动能分布,π~-谱的动能分布,π-的多重数,中快度前平衡核子发射的中一质比,中快度前平衡核子发射的同位旋非对称度,发射核子的中一质微分流,中一质微分椭圆流以及质子椭圆流是对对称能敏感的几个探针。其中对对称能最理想的探针是π-/π+谱的横动量与动能分布、中快度前平衡核子发射的同位旋非对称度以及发射核子的中一质微分流。利用这些对对称能敏感的观测量,通过与实验数据的对照我们就可以得出关于对称能的高密行为的重要信息。

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The current equation of the electrocatalytic reaction at a microdisk electrode modified with redox species has been described and verified experimentally. There exists a linear relationship between plateau limiting current and the radius of the microdisk electrode for a catalytic process. The influence of the dimensions of the microdisk electrode on catalytic efficiency is discussed. The polyvinylferrocene (PVFc)-modified microdisk electrode prepared by the coating method was taken as a typical example, on which the electrocatalytic oxidation of ascorbic acid could be studied. The catalytic reaction rate constants were determined as an average value of 1.5 X 10(-7) cm3/mol s by this method, and are consistent with those obtained at a conventional electrode.

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介绍了ZMP的概念,比较常见的几种ZMP建模方法,提出将高效牛顿-欧拉算法(RENA)与ZMP的概念相结合的迭代ZMP建模方法,并利用该方法完成轮式仿人机器人的ZMP建模.通过模型分析,得出该轮式仿人机器人的ZMP简化计算公式.最后得出此类轮式仿人机器人的稳定性判据及稳定度的定义.