一类分数阶神经网络模型的稳定性与Hopf分支分析

分析了一类分数阶神经网络的稳定性与Hopf分支问题.基于分数阶稳定性判据,得到了分数阶神经网络模型局部渐近稳定的条件.并以q为分支参数,得到了分数阶系统产生Hopf的条件.最后数值仿真证明了我们的结论.     

1．5GHz锯材超导腔的研制

介绍铌材超导腔的研制进展，重点讨论了国产铌腔的材料改性，以及相应的超导腔性能的改进．叙述了１．５ＧＨｚ铌腔的腔形设计，分析了铌材的射频性能和机械性能，制定了铌腔制作与后处理的特定工艺．最后给出了１．５ＧＨｚ铌材超导腔的低温实验结果．     

1．5GHz锯材超导腔的研制

介绍铌材超导腔的研制进展，重点讨论了国产铌腔的材料改性，以及相应的超导腔性能的改进．叙述了１．５ＧＨｚ铌腔的腔形设计，分析了铌材的射频性能和机械性能，制定了铌腔制作与后处理的特定工艺．最后给出了１．５ＧＨｚ铌材超导腔的低温实验结果．     

国产铌材超导腔的研制和实验

通过对国产铌腔的研制和探索，掌握了超导腔的计算制造和实验研究的关键技术，进行铌材性后获得了铌腔后处理的特定工艺，在２．５Ｋ温度时，国产铌腔的加速梯度超过１０ＭＶ／ｍ，品质因素１０＾９。     

激光驱动高亮度电子束源

采用激光驱动光阴极和１００ｋＶ直流加速间隙可产生宽度为５０～１００ｐｓ的高亮度脉冲电子束，该装置主要由光阴极制备室和直流加速间隙组成，可以用化学气相沉积，离子注入和离子束增强沉积等方法制备光阴极，通过用ＥＧＵＮ和ＰＯＩＳＳＯＮ程序模拟，给出了直流间隙的物理设计，光源采用一台主被动双锁的Ｎｄ：ＹＡＧ激光器，可工作在１０６４、５３２和２６６ｎｍ三个波长，重复频率为１０Ｈｚ，此外，也论述了光阴极制备室与     

Synergy and Redundancy in a Signaling Cascade with Different Feedback Mechanisms

Feedback plays an important role in various biological signal transmission systems. In this paper, a signaling cascade system(including three layers: input(S), intermediate(V), output(X) components) is employed to study the fluctuations and net synergy in information transmission, in which the V component is regulated by itself or the X component, and each feedback on V is either positive or negative. The Fano factor, the net synergy, and the signalto-noise ratio(SNR) of signaling cascade with the four possible feedback types are theoretically derived by using linear noise approximation of the master equation, and the ability of information transmission through the signaling cascade is characterized by using the partial information decomposition of information theory. It is found that the signaling cascade exhibits different responses to the four feedback mechanisms, which depend on the relationships between degradation rates of components. Our results not only clarify the dependence of the Fano factor, net synergy, and SNR on the feedback regulations with the varying of degradation rates of components, but also imply that living cells could utilize different feedback mechanisms to adapt to the external fluctuating environments.     

外力作用下反馈耦合布朗棘轮的定向输运

本文研究了处于外力作用下双阱棘轮势中两个反馈耦合布朗粒子的定向输运性能. 通过对过阻尼朗之万方程的数值求解, 详细讨论了外力、热噪声与势阱的不对称参数等对耦合布朗粒子的平均速度、 有效扩散系数及Pe数的影响. 研究发现, 平均速度随外力呈周期性的变化规律. 同时耦合系统存在最优噪声强度会使定向输运达到最强. 值得指出的是棘轮系统可通过改变双阱势的结构来获得较强的定向流. 关键词： 耦合布朗棘轮 外力 双阱棘轮势 平均速度     

用于高平均功率自由电子激光器的DC–RF超导腔注入器

北京大学超导加速器实验室提出了新型DC?RF超导腔注入器的设计方案.该注入器由皮尔斯引出结构、1+1/2超导腔组成,可以提供高品质的、CW模式或高占空比(1%以上)的电子束.对该注入器进行了分析计算和设计研究,通过改变超导腔首腔腔形以增加聚焦效果,采取措施缩短阴极到超导腔的距离,从而有效地抑制束流发射度的增长.用PARMELA对该注入器进行束流动力学研究,以确定皮尔斯引出结构的形状以及超导腔的同步相位.计算结果表明这种用于高平均功率自由电子激光的注入器的设计方案是可行的.     

Effects of time delays in a mathematical bone model

In this paper we propose a mathematical model of bone remodeling with time delays of both osteoclast-derived paracrine signaling of tumor and tumor-derived paracrine signaling of osteoclast. The effects of time delays on the growth of tumor cells and bone system are studied in multiple myeloma-induced bone disease. In the case of small osteoclast-derived paracrine signaling, it is found that the growth of tumor cells slows down, the oscillation period of the ratio of osteoclasts to osteoblasts is extended with increasing time delay, and there is a competition between the delay and osteoclast-derived paracrine signaling. In the case of large tumor-derived paracrine signaling, the tumor-derived paracrine signaling can induce a more significant decline in tumor growth for long time delay, and thus slowing down the progression of bone disease. There is an optimal coupling between the tumor-derived paracrine signaling of osteoclasts and time delay during the progressions of bone diseases, which suppresses the tumor growth and the regression of bone disease.