The Gravitational “Plane Waves” of Liu & Zhou and the Nonexistence of Dynamic Solutions for Einstein’s Equation

Although both the electromagnetic wave and the gravitational wave can be produced approximately from Maxwell-type equations, there are subtle differences in their respective exact equations. Since gravitational wave carries energy-momentum, the exact field equation of a gravitational wave must have a nonzero source term along its path, whereas a field equation for an electromagnetic wave does not. This explains that there is no weak wave solution of Einstein equation. Historically, neither Einstein & Rosen nor the Physical Review was aware that the nonexistence of gravitational wave solutions is due to a violation of the principle of causality. It is pointed out that the criterion of Liu & Zhou on plane-waves is valid since the principle of causality requires the existence of weak limits. However, due to the influence of the popular but unverified assumption of the existence of dynamic solutions, they made careless errors in their calculations and incorrectly concluded that their plane-waves have weak limits. It is shown that “plane-waves” of Liu & Zhou, is actually unbounded in amplitude, and have no weak limit. Therefore, Liu & Zhou provide additional evidence in supporting the nonexistence of dynamic solutions. PAC Number: 04.20.-q, 04.20.Cv, 04.30.-w     

饱和多孔岩石弛豫衰减对时间和温度的依赖性

通过饱和多孔岩石的低频亚共振试验 ,得到了饱和多孔岩石的内耗峰是典型的弛豫峰的结论 .不同的饱和液体、不同的岩石导致不同的弛豫峰特征 ,饱和岩石的弛豫特性 ,是寻找油田、地热田和预测储层的物性基础 .试验结果表明 ,饱和多孔岩石都具有一个共同的特性———时间和温度的等效性 ,即降低温度与增加振动频率是等效的 ,这就是饱和多孔岩石的弛豫共性 .     

Equivalence of network-solution and PPP-solution

The technique of precise point positioning (PPP) is gradually becoming a popular method in GPS data-processing. In GPS observation equation, the unknown parameters can be separated into two parts: global parameters and local parameters. The global parameters include orbit, satellite clock and geodynamic parameters. The local parameters are site-occupation-spectific, such as position, tropospheric delay, etc. The formulas of local parameters are firstly derived under the network-solution and the PPP-solution conditions respectively. If the weight matrix of global parameters in PPP-solution is small enough, the cofactor matrices of local parameters are the same as that in network-solution. Then, 16 daily solutions are obtained in both PPP mode and network mode. Three sites are selected to compare the solutions. The experimental results demonstrated that the difference between two solutions in coordinates and tropospheric delays are only few millimeters. This level of difference can be neglected so that the solutions from both PPP mode and network mode can be taken as the same in the actual application.     

微分系统的等价性及其应用研究综述

自Mironenko教授创建反射函数理论以来,人们采用该理论定义了微分系统间的新的等价关系,由此建立了复杂微分系统与简单微分系统、非自治微分系统与自治微分系统的等价性,应用它将复杂系统的几何性态的研究可转化为简单或自治系统的几何性态的研究.经过专家们的共同研究取得了若干极具理论和应用价值的好成果.     

Magnetic equivalence of dipping beds,faults and anticlines

The interpretation of magnetic anomalies of dipping beds with an inclined top is ambiguous. The magnetic anomaly profile over a dipping bed can be produced by a series of beds of different dips and directions of magnetization. Further, these anomalies are equivalent to those of faults and anticlines. Thus, the magnetic anomaly profiles, assumed to be produced by one of the models, can also be produced by the other models. The ambiguity is resolved in case of dipping beds and faults, when the magnetization is caused purely by induction; but the case of anticlinal beds remains ambiguous.The magnetic equivalence of dipping beds, anticlines, and faults makes it possible to apply the available methods of interpretation of fault models to dipping beds and anticlines.     

埋置基础扭转振动的实用化计算

根据弹性半空间理论及基础振动试验和数值计算的最新成果,采用方程对等法推演出埋置块体基础扭转振动的实用化计算公式。采用该实用化计算公式和弹性半空间理论分别对复杂形状的埋置块体基础在谐和扰力矩作用下的扭转振动动力响应进行计算,并将计算结果进行了比较,两者结果吻合,振幅误差为9.13%。该实用化计算公式具有概念明确,计算简单的优点,对于任意形状、任意埋置状况的动力设备块体基础都实用,对于结构工程的地震响应计算具有参考意义。     

模糊聚类动态图的性质

模糊聚类分析在地学中有广泛应用。其核心问题之一是确定相似系数。目前有14种以上的定义,且多含有参数。为免除应用者选择之苦,本文证明对某几种相似系数定义中的不同参数值都代表相同的分类结构,只要适当选择一个参数值就够了。核心问题之二是作出聚类动态图。本文引入等价模糊矩阵的脊形变换得到脊形矩阵,已证明n阶脊形矩阵至多含有n个互异元素（包括主对角线元素1）,它们分布在1级对角线上。取这些数值作为人阀值就能作出聚类动态图。对于众多的分类集合U,脊形变换能使U的元素重新排列,使任一等价类的元素都相邻排列,便于计算机自动输出聚类动态图。     

基于递归学习的组合电路等价性检验方法研究

等价性检验方法通常包括功能性和结构性的验证方法。分析了等价性检验的一般方法；并讨论了基于递归学习的组合电路等价性检验方法；算法利用直接蕴含和间接蕴含的方法，解决了布尔可满足问题。实验结果表明了该方法的有效性和可行性。     

Thresholds of aeolian sand transport: establishing suitable values

This paper assesses the practical use and applicability of the time fraction equivalence method (TFEM; Stout & Zobeck, 1996) of calculating a wind speed threshold for sand grain entrainment in field situations. A modification of the original method is used and is applied to 1 Hz measurements of wind speed and sand transport on a beach surface. Calculated grain entrainment thresholds are tested in terms of the percentage of sand transport events that they explain. It was found that the calculated thresholds offered a poor representation of the occurrence of saltation activity, explaining only about 50% of the measured transport events. Results are discussed in terms of system response time, wind speed measurement height, undetected events and sampling period. A shear velocity threshold for grain entrainment was also calculated, but this also failed to explain a high proportion of the sand transport events. The best results (67–91% of transport events explained) were found by calculating a threshold based on time‐averaged (≈ 40 s) wind velocity measurements. The applicability of a single threshold to a natural grain population is discussed. A natural surface is likely to possess a range of thresholds varying over short time scales in response to parameters such as grain rearrangement and changes in moisture conditions. The results show that calculated thresholds based on 40 s time‐averaged data consistently explain a high proportion of the recorded sand transport events. This is because such a time‐averaged approach accounts for higher frequency variability inherent in the sand transport system.     

中国城市的网络地位及影响因素研究——基于上市公司500强企业网络视角

利用2016年中国上市公司500强企业网络数据和隶属联系方法构建城市网络,解析了中国城市的网络地位分异格局,并定量测度了城市网络地位的影响因素,在城市网络"行为-结构-绩效"分析框架下解释了地位分异的动力机制。研究发现:正则等价性模型识别的15个正则等价块分化为首位者、经纪人、接收者和孤立者4个地位类型;地位间关系呈现"核心-半边缘-边缘"结构特征,其中首位者地位的正则等价块形成凝聚子群并占据网络权力的核心,经纪人和接收者地位的块位于半边缘位置,孤立者地位的块处于网络权力的边缘;市场潜力、政治资源、知识资本、区位条件和发展基础是中国城市网络地位的关键影响因素;规模偏好、择优选择、地理临近和路径依赖构成了城市网络地位分异的动力机制。城市网络的发展倾向于扩大城市间发展差距,中国城市化政策和城市治理体系需要做出相应调整。