共查询到20条相似文献,搜索用时 31 毫秒
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恒星结构和演化理论是研究恒星内部的物理过程、结构和恒星如何演化的科学、文章介绍了恒星结构和演化模型的计算方法,恒星在赫罗图中的分布规律,恒星的形成和早期演化特性,质量不同的各类恒星从主序开始的演化进程,恒星演化的晚期阶段的产物;白矮星、超新星和中子星。 相似文献
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D. Yar-Mukhamedov 《Journal of Experimental and Theoretical Physics》2016,123(5):796-806
We perform an in-depth analysis of the evolution of galactic magnetic fields within a semi-analytic galaxy formation and evolution framework, determine various distinctive aspects of the evolution process, and obtain analytic solutions for a wide range of possible evolution scenarios. 相似文献
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There is an intrinsic relationship between the molecular evolution in primordial period and genomic or proteomic properties of contemporary species. The genomic data may help us understand the driving force of evolution of life at a molecular level. In the absence of evidence, numerous problems in molecular evolution had to fall into a twilight zone of speculation and controversy in the past. Here we show that delicate variation patterns of genomic base compositions and amino acid frequencies resulted from the genetic code evolution, which underlies the molecular evolution. The theoretical results agree with the experimental observations very well, not only in the evolutionary trends of amino acid frequencies and genomic base compositions but also in many detailed characters. Inversely, the genomic data of contemporary species can help us unravel the genetic code chronology and amino acid chronology. Our results may shed light on the intrinsic mechanism of molecular evolution and the genetic code evolution. 相似文献
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Xiaohui Li Yishan Wang Wei Zhao Wei Zhang Xiaohong Hu Cunxiao Gao Han Zhang Zhi Yang Hushan Wang Xianglin Wang Cheng Li Deyuan Shen 《Optics Communications》2012,285(6):1356-1361
Soliton molecules evolution is numerically investigated in a passively mode-locked fiber laser based on the nonlinear polarization rotation (NPR) technique. Peak-to-peak separation of soliton molecules can be controlled by changing either pump strength or cavity linear phase delay appropriately. Moreover, soliton molecules with intensity-independent evolution, separation-independent evolution and large intensity-vibrating evolution are numerically found, respectively. The characteristics of soliton molecules evolution versus linear phase delay or pump strength are given. Periodic stable evolution regimes are found. The separation-controllable soliton molecules can be attributed to the mutual effects of phase delay, Kerr nonlinearity and other parameters of the cavity. 相似文献
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A two state model on a one dimensional lattice is considered, where the evolution of the state of each site is determined by the states of that site and its neighboring sites. Corresponding to this original lattice, a derived lattice is introduced the sites of which are the links of the original lattice. It is shown that there is only one reaction on the original lattice, which results in the derived lattice being solvable through the full interval method. And that reaction corresponds to the one dimensional stochastic non-consensus opinion model. A one dimensional non-consensus opinion model with deterministic evolution has already been introduced. Here this is extended to be a model which has a stochastic evolution. Discrete time evolution of such a model is investigated, including the two limiting cases of small probabilities for evolution (resulting to an effectively continuous-time evolution), and deterministic evolution. The formal solution to the evolution equation is obtained and the large time behavior of the system is investigated. Some special cases are studied in more detail. 相似文献
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压缩真空场与耦合双原子Raman相互作用系统场熵的演化特性 总被引:1,自引:1,他引:0
利用全量子理论,研究了压缩真空场与耦合双原子Raman相互作用系统的场熵演化特性,讨论了系统耦合常数和光场初始压缩因子对场熵演化特性的影响.结果表明,场熵的时间演化规律与原子布居差的时间演化规律非常相似.当原子间的偶极-偶极相互作用较弱时,场熵演化呈现周期性的崩塌与回复现象;当原子间的偶极-偶极相互作用较强时,场熵演化呈现不规则振荡,崩塌与回复周期现象消失. 相似文献
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Steels L 《Physics of life reviews》2011,8(4):339-356
The paper surveys recent research on language evolution, focusing in particular on models of cultural evolution and how they are being developed and tested using agent-based computational simulations and robotic experiments. The key challenges for evolutionary theories of language are outlined and some example results are discussed, highlighting models explaining how linguistic conventions get shared, how conceptual frameworks get coordinated through language, and how hierarchical structure could emerge. The main conclusion of the paper is that cultural evolution is a much more powerful process that usually assumed, implying that less innate structures or biases are required and consequently that human language evolution has to rely less on genetic evolution. 相似文献
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基于BA无标度网络,构建了舆论和网络结构相互影响的自适应舆论演化模型.舆论的演化不仅受制于网络拓扑结构,而且也导致拓扑结构的变化.研究表明,演化达到稳态后,网络结构不再是初始的无标度网络而呈现泊松分布,而且随着时间的推移,系统中的舆论演化表现出很强的趋同效应,原来初始状态的几十个舆论,在长时间的演化后,大部分舆论灭亡,只有少数的舆论存留,且发展壮大.这种趋向与社会上的舆论、意见、信仰的演化大体上是符合的. 相似文献
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本文综述了作者的研究成果.近十年,作者将现有静态统计信息理论拓展至动态过程,建立了以表述动态信息演化规律的动态信息演化方程为核心的动态统计信息理论.基于服从随机性规律的动力学系统(如随机动力学系统和非平衡态统计物理系统)与遵守确定性规律的动力学系统(如电动力学系统)的态变量概率密度演化方程都可看成是其信息符号演化方程,推导出了动态信息(熵)演化方程.它们表明:对于服从随机性规律的动力学系统,动态信息密度随时间的变化率是由其在系统内部的态变量空间和传递过程的坐标空间的漂移、扩散和耗损三者引起的,而动态信息熵密度随时间的变化率则是由其在系统内部的态变量空间和传递过程的坐标空间的漂移、扩散和产生三者引起的.对于遵守确定性规律的动力学系统,动态信息(熵)演化方程与前者的相比,除动态信息(熵)密度在系统内部的态变量空间仅有漂移外,其余皆相同.信息和熵已与系统的状态和变化规律结合在一起,信息扩散和信息耗损同时存在.当空间噪声可略去时,将会出现信息波.若仅研究系统内部的信息变化,动态信息演化方程就约化为与表述上述动力学系统变化规律的动力学方程相对应的信息方程,它既可看成是表述动力学系统动态信息的演化规律,亦可看成是动力学系统的变化规律都可由信息方程表述.进而给出了漂移和扩散信息流公式、信息耗散率公式和信息熵产生率公式及动力学系统退化和进化的统一信息表述公式.得到了反映信息在传递过程中耗散特性的动态互信息公式和动态信道容量公式,它们在信道长度和信号传递速度之比趋于零的极限情况下变为现有的静态互信息公式和静态信道容量公式.所有这些新的理论公式和结果都是从动态信息演化方程统一推导出的. 相似文献
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色散渐减光纤中自相似脉冲传输区域的研究 总被引:1,自引:0,他引:1
从非线性薛定谔(NLS)方程出发,用分步傅里叶方法结合对数值解的波形分析,确定了色散渐减光纤(DDF)中能实现自相似脉冲传输的区域,并研究了初始脉冲和光纤参数对自相似区域和演化速度的影响。结果表明,初始脉冲能量的减小有利于扩宽自相似区域,但会使自相似演化进程略为减慢;初始脉宽有一个最佳值,在最佳值上自相似区域最宽,演化较快且输出脉冲和啁啾较为稳定;高斯脉冲比双曲正割脉冲更快转化为自相似脉冲,传输区域也更广。选择具有较小非线性参量的DDF可以获得较广的自相似区域,同时非线性参量的增大可以加快自相似演化,而群速度色散参量和增益系数必须选择在最佳值附近,才能获得最大自相似区域和最快演化速度。 相似文献
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众所周知,量子态的演化可用与其相应的Wigner函数演化来代替.因为量子态的Wigner函数和量子态的密度矩阵一样,都包含了概率分布和相位等信息,因此对量子态的Wigner函数进行研究,可以更加快速有效地获取量子态在演化过程的重要信息.本文从经典扩散方程出发,利用密度算符的P表示,导出了量子态密度算符的扩散方程.进一步通过引入量子算符的Weyl编序记号,给出了其对应的Weyl量子化方案.另外,借助于密度算符的另一相空间表示-Wigner函数,建立了Wigner算符在扩散通道中演化方程,并给出了其Wigner算符解的形式.本文推导出了Wigner算符在量子扩散通道中的演化规律,即演化过程中任意时刻Wigner算符的形式.在此结论的基础上,讨论了相干态经过量子扩散通道的演化情况. 相似文献
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With an example of Ag ultrafine particles, the "diffusion-trapping-reaction aggregation" model of ultrafine particles is proposed, and the spontaneous evolution of ultrafine particles is described. The evolution kinetic equation is established and the solitary wave solution of evolution kinetic equation is found and discussed in detail. 相似文献
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New approach for deriving the exact time evolution of density operator for diffusive anharmonic oscillator and its Wigner distribution function 下载免费PDF全文
Using the thermal entangled state representation, we solve the master equation of a diffusive anharmonic oscillator (AHO) to obtain the exact time evolution formula for the density operator in the infinitive operator-sum representation. We present a new evolution formula of the Wigner function (WF) for any initial state of the diffusive AHO by converting the calculation of the WF to an overlap between two pure states in an enlarged Fock space. It is found that this formula brings us much convenience to investigate the WF's evolution of any known initial state. As applications, this formula is used to obtain the evolution of the WF for a coherent state and the evolution of the photon-number distribution of the diffusive AHO. 相似文献
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阐述了以表述信息演化规律的信息(熵)演化方程为核心的非平 衡统计信息理论.推导出了 Shannon信息(熵)的非线性演化方程,引入了统计物理信息并 推导出了它的非线性演化方程.这两种信息(熵)演化方程一致表明:统计信息(熵)密度 随时间的变化率是由其在坐标空间(和态变量空间)的漂移、扩散和减损(产生)三者引起 的.由此方程出发,给出了统计信息减损率和统计熵产生率的简明公式、漂移信息流和扩散 信息流的表达式,证明了非平衡系统内的统计信息减损(或增加)率等于它的统计熵产生( 或减少)率、信息扩散与信息减损同时
关键词:
统计信息(熵)演化方程
统计信息减损率
统计熵产 生率
信息(熵)流
信息(熵)扩散
动态互信息 相似文献
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《理论物理通讯》2017,(3)
It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels. 相似文献