Brans-Dicke引力理论的弱场近似

Brans-Dicke引力理论是重要的修正引力理论之一,其对于研究星体运动、宇宙演化以及解释宇宙现象等起着重要的作用.寻找Brans-Dicke引力理论场方程的解对于Brans-Dicke引力理论的研究和发展具有重要意义.但由于Brans-Dicke引力理论场方程本身的高度非线性性,使得一般情况下精确求解非常困难,特殊情况下也只能求得部分精确解.幸运的是大多数情况下引力场比较弱,且在低速的条件下求场方程的近似解相对容易.本文基于弱场低速条件,详细地求解了Brans-Dicke引力理论的弱场低速近似解.首先基于弱场条件,将标量场和度规写为一阶微扰展开的形式;然后将标量场和度规代入相应的场方程得到相应的线性场方程,通过选取特定的规范条件进一步简化线性场方程;最后求解出简化的线性场方程的低速近似解.本文的求解方法可以为Brans-Dicke引力理论的教学和研究提供有益的参考.     

任意n阶多边形电阻网络的电特性研究

文章采用基尔霍夫定律通过建立差分方程模型的方法研究了一类任意n阶多边形电阻网络的电学性质(节点电压,支路电流,等效电阻).首先采用基尔霍夫节点电流定律建立差分方程模型,同时建立边界条件方程,以此研究差分方程组的通解和特解,进而获得各节点电压公式,并且基于电压结果导出支路电流公式及等效电阻公式.本文的研究工作对于促进基础物理创新教学具有很好的理论意义与教学实践价值.     

希罗喷泉动力学分析

本文构建了一个希罗喷泉系统,利用修正后的非定常伯努利方程及连续性方程,在层流与非定常的基本假设下,解出其动力学方程;使用Mathematica软件并结合实验参数进行数值求解,推导了喷射高度随时间的理论变化关系,并探讨了喷射瓶的相对放置高度、横截面积、喷射管道直径以及喷口高度等参量对喷泉高度的影响.同时运用Tracker软件追踪喷泉高度,建立了空气弹簧的模型,完成了理论与实验的相互验证.     

Hydrodynamic forces and moments due to interaction of linear water waves with truncated partial-porous cylinders in finite depth

An exact analytical method is employed for studying the diffraction problems in an ocean due to the presence of a specific type of cylinders. In this current work, two models are studied: (i) a floating surface-piercing truncated partial-porous cylinder, (ii) a surface-piercing truncated partial-porous cylinder placed at the bottom. In both cases, the configuration of the composite cylinder is such that it consists of an impermeable inner cylinder rising above the free surface and a coaxial truncated porous cylinder around the lower part of the inner cylinder with the top of the porous cylinder being impermeable. By using linear water wave theory, a three-dimensional representation of the problem is developed based on eigenfunction expansion method. The condition on the porous boundary is defined by applying Darcy’s law. Pressure and velocity satisfy continuity conditions across the linear interface between the adjacent fluid domains. Hydrodynamic force, moment and wave run-up are calculated by using the velocity potentials. Comparisons are carried out with results of wave diffraction by a floating and bottom-mounted compound cylinder, i.e., when the whole cylinder is non-porous. Handy agreements are observed from these comparisons. Through numerical tests, various experiments are carried out to investigate the impact of various parameters, such as porous coefficients, draft ratio, the ratio of inner and outer radii, the water depth etc., on hydrodynamic force, moment and wave run-up. The results clearly indicate that an appropriate optimal ratio for various parameters may be considered in designing practical ocean structures with minimum adverse hydrodynamic effect. The appearance of resonance in the results and role of porosity in mitigating resonance effect are explained. Proposal to select various appropriate parameters for the best possible effect is put forward.     

Adsorption Capacity of Poly[4-Methacroyloxy-(4’-Carboxy-3-СHloro)-Azobenzene], In Situ Immobilized on the Silica Gel Surface to Toxic Metals Ions

Abstract

By mean of heterophase polimarzation on the silica gel surface has been made in situ immobilization of poly[4-methacroyloxy-(4’-carboxy-3-Сhloro)-azobenzene] and has been received new organic-mineral composit material. The fact of polymer immobilization has been confirmed by IR spectroscopic method and thermogravimetric analysis combined with mass spectrometry. According to the results of thermogravimetric analysis, has been found the mass of the immobilized polymer is 13.33%.

The synthesized composite revealed sorption activity to the ions of Cu (II), Pb (II) and Fe (III) micro quantities in a neutral water environment. Maximum sorption ions Cu (II), Pb (II) and Fe (III) degree is reached during first contact hour in static sorption condition. According to the results of isotherms sorption treatment has been determined the silica gel surface poly [4-methacryloxy- (4'-carboxy-3-chloro)-azobenzene] modification led to the sorbtion volum Cu (II) ions more than 1.5 times, for ions Pb (II) - 3.6 times, but for Fe (III) ions - almost 2 times.     

Multifunction switching by a flat structurally tunable acoustic metasurface for transmitted waves

In this paper a flat structurally tunable acoustic metasurface is constructed based on the helical unit cell. The length of the acoustic channel can be tuned by the screw-in depth of the helix. Accordingly, the wave phase for the transmitted acoustic wave can be tuned and the wavefront can be manipulated. Then multifunctions such as anomalous refraction, point focusing, beam focusing and self-bending can be realized and switched just by screwing in or out the helixes. At the same time, the broadband operating frequency is also realized. The experiments for anomalous refraction and point focusing are also performed, and the results show that the designed metasurface is effective. The present studies have important applications in dynamic manipulation of acoustic waves by metasurfaces.     

异黄酮同分异构体的ESI-IT-TOF质谱特征及区别

采用电喷雾-离子阱-飞行时间串联质谱(ESI-IT-TOF)技术, 在正/负离子检测模式下对芒柄花素及其同分异构体7-甲氧基异黄酮的质谱裂解规律进行了系统研究. 实验结果表明, 该化合物在正、负离子模式下均得到了5级高分辨质谱. 结果显示, 二者在负离子模式下的碎片相同, 而在正离子模式下的碎片裂解不同. 根据正负离子模式的5级高分辨质谱推导了两者的可能裂解规律, 丰富了异黄酮的ESI-MSn数据, 为其它异黄酮类化合物的分析鉴定提供了有效的质谱方法.     

丝氨酸组酰胺对5'-pTpTpCp-3'片段切割作用的量子化学计算

采用量子化学方法对丝氨酸组酰胺切割5'-pTpTpCp-3'的作用机理进行了研究. 通过计算得到了两者之间形成多氢键作用的有效分子识别模型以及相关分子结构参数. 从理论上解释了丝氨酸组酰胺对5'-pTpTpCp-3'切割的水解机理.     

利用二次球形配位构筑疏水型隧道框架结构

质子化N,N,N',N'-四苄基乙二胺(L)可与[MCl4]2-(M=Mn, Co, Cu)形成二次球形配合物. 通过N—H…Cl相互作用构筑了1D带状和2D层状框架结构, 层中配体L的苄基通过C—H…Cl相互作用分别采取水平和垂直取向, 使1D带状和2D层状呈现凸凹交替排列. 通过层间凸凹部位的C—H…H—C相互作用, 形成了层间空穴, 进而构筑成了3D疏水型隧道框架结构, 乙醇分子能够填充于隧道之中. 在L·2H+·[CuBr4]2-晶体中, 由于[CuBr4]2-没有与配体L的苄基形成C—H…Br氢键, 使配体L的苄基采取了同向取向. 因而, 形成的2D层状框架结构是平展的, 未形成3D疏水型隧道框架结构, 也未发现与乙醇分子的包结现象.     

融入用户社交关系与信任关系的应用推荐方法研究

随着近年来互联网技术的快速发展,应用获取平台都面临着信息过载的问题.面对大量应用,解决用户不能快速准确地找到满足其偏好的应用的问题迫在眉睫.已有的如Cosine、Pearson等协同过滤方法普遍存在稀疏性、冷启动和可扩展性等问题,从而对推荐结果产生影响.文章在考虑用户社交关系、偏好及信任关系的基础上,提出了融合用户社交...