AN INVARIANCE OF CDF EQUATION

ＡＮＩＮＶＡＲＩＡＮＣＥＯＦＣＤＦＥＱＵＡＴＩＯＮ￥ＴＩＡＮＣＨＯＵＡｂｓｔｒａｃｔ：ＴｈｉｓｐａｐｅｒｐｒｅｓｅｎｔｓａｎｅｗｉｎｖａｒｉａｎｃｅｆｏｒｔｈｅＣＤＦｅｑｕａｔｉｏｎ．Ｕｓｉｎｇｔｈｉｓｉｎｖａｒｉａｎｃｅ，ｔｈｅａｕｔｈｏｒｏｂｔａ...     

Existence of a Weak Solution for the Phase Change Problem with Joule's Heating

A phase change problem with Joule's heat ing describes tbe processes of electric heating in a conducting material. It is modeled as a coupled system of nonlinear partial differential equations with quadratic growth in the gradient. We establish the existence of a weak solution for the problem in two dimensions.     

SYMMETRIES AND GROUP-INVARIANT SOLUTIONS OF DIFFERENTIAL EQUATIONS

ＳＹＭＭＥＴＲＩＥＳＡＮＤＧＲＯＵＰ－ＩＮＶＡＲＩＡＮＴＳＯＬＵＴＩＯＮＳＯＦＤＩＦＦＥＲＥＮＴＩＡＬＥＱＵＡＴＩＯＮＳＴＩＡＮＣＨＯＵＡｂｓｔｒａｃｔ：Ｆｏｒａｄｉｆｆｅｒｅｎｔｉａｌｅｑｕａｔｉｏｎ，ａｔｈｅｏｒｅｔｉｃａｌｐｒｏｏｆｏｆｔｈｅｒ...     

二阶Melnikov函数及其应用

在Ｍｅｌｎｉｋｏｖ函数的种种应用中，目前常见到的仅是一阶形式。本文具体推导了二阶Ｍｅｌｎｉｋｏｖ函数的分析表达，提出了临界情况下考察双曲鞍点的稳定流形与不稳定流形相对位置的二阶判据，并成功地用于环面ｖａｎｄｅｒＰｏｌ方程的研究中。     

四阶和一般偶数阶奇异边值问题正解的存在性

在本文中得到了四阶和一般偶数阶非线性方程奇异边值问题正解的存在性。从而推广了［１］［２］中的结果。     

Solutions to the Equation of Non－Newtonian Polytropic Filtration Under Optimal Condition On Initial Values

Ｓｏｌｕｔｉｏｎｓ　ｔｏ　ｔｈｅ　Ｅｑｕａｔｉｏｎ　ｏｆ　Ｎｏｎ－Ｎｅｗｔｏｎｉａｎ　Ｐｏｌｙｔｒｏｐｉｃ　Ｆｉｌｔｒａｔｉｏｎ　Ｕｎｄｅｒ　Ｏｐｔｉｍａｌ　Ｃｏｎｄｉｔｉｏｎ　Ｏｎ　Ｉｎｉｔｉａｌ　ＶａｌｕｅｓＹｕａｎＨｏｎｇｊｕｎ（袁洪君）（Ｄｅ...     

用硅双结型色敏器件测量色温

提出了一种用硅双结型色敏器件测量色温的方法．在合理的测控电路下，硅双结型色敏器件的电流对数比与实验灯泡的色温值呈良好的单值对应，经单片机处理后可以得到分段线性关系．通过对电流对数比与波长随线的数据拟合，结果表明，用硅双结型色敏器件测量色温，其测量温度可以到10^4K以上，精度可以达到10K．本文的方法与传统方法相比减少了工作量，降低了费用，具有通用性和实用价值．     

非PLL相位平均型参考线原型验证

射频相位参考线是粒子加速器的重要组成部分之一,为射频低电平控制系统(LLRF)、束流诊断系统、定时系统等提供稳定的相位锁定参考信号。为减少远距离传输过程中由环境温度变化导致的射频传输线中的射频相位漂移,多个加速器装置中已经采用射频相位参考线提供射频相位参考,这些相位参考的实现方案主要是基于恒温控制和基于光纤锁相。与这些方案相比,采用相位平均方法不仅可以保持长距离节点之间的相位稳定,而且更易于现场安装与维护。现有的带有锁相环(PLL)的终端短路方式实现相位平均参考线的方案仍有一些节点数量限制等方面的不足,本文对相位平均参考线结构进行了去除PLL的简化设计并进行了验证,以期增加更多的相位分配节点以及降低对射频器件参数的要求。对非PLL的单端输入终端短路相位平均方案与两端输入各节点间互为参考的相位平均方案分别进行了实验测试,结果表明两者的相位RMS精度可以达到0.1°~0.3°。并对不同的相位平均实现方案中相位不稳定的产生原因进行了分析,结果表明,除环境温度外,同轴线缆材质、合成相位与幅度的不平衡合成等也是重要影响因素。     

Effect of mechanical force on domain switching in BiFeO_3 ultrathin films

Ferroelectric polarization can be switched by an external applied electric field and may also be reversed by a mechanical force via flexoelectricity from the strain gradient.In this study,we report the mechanical writing of an epitaxial BiFeO3(BFO)thin film and the combined action of an applied mechanical force and electric field on domain switching,where the mechanical force and electric field are applied using the tip of atomic force microscopy.When the applied force exceeds the threshold value,the upward polarization of the BFO thin film can be reversed by pure mechanical force via flexoelectricity;when an electric field is simultaneously applied,the mechanical force can reduce the coercive electric field because both the piezoelectricity from the homogeneous strain and the flexoelectricity from strain gradient contribute to the internal electric field in the film.The mechanically switched domains exhibit a slightly lower surface potential when compared with that exhibited by the electrically switched domains due to no charge injection in the mechanical method.Furthermore,both the mechanically and electrically switched domains exhibit a tunneling electroresistance in the BFO ferroelectric tunnel junction.     

An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.