Dark matter,the Equivalence Principle and modified gravity

Dark matter (DM) is an essential ingredient of the present Standard Cosmological Model, according to which only 5% of the mass/energy content of our universe is made of ordinary matter. In recent times, it has been argued that certain cases of gravitational lensing represent a new type of evidence for the existence of DM. In a recent paper, Peter Kosso attempts to substantiate that claim. His argument is that, although in such cases DM is only detected by its gravitational effects, gravitational lensing is a direct consequence of Einstein's Equivalence Principle (EEP) and therefore the complete gravitational theory is not needed in order to derive such lensing effects. In this paper I critically examine Kosso's argument: I confront the notion of empirical evidence involved in the discussion and argue that EEP does not have enough power by itself to sustain the claim that gravitational lensing in the Bullet Cluster constitutes evidence for the DM Hypothesis. As a consequence of this, it is necessary to examine the details of alternative theories of gravity to decide whether certain empirical situations are indeed evidence for the existence of DM. It may well be correct that gravitational lensing does constitute evidence for the DM Hypothesis—at present it is controversial whether the proposed modifications of gravitation all need DM to account for the phenomenon of gravitational lensing and if so, of which kind—but this will not be a direct consequence of EEP.     

中国大地震规律初探——爆炸地质动力学理论在地震研究中的应用

地震是地球断裂构造释放能量的窗口,含能量积聚、触发、爆发和沉寂过程。地震是震源断裂结构的爆裂过程,断裂结构内压力超过岩层的断裂强度和重力之和时,地震随之爆发。对地震的触发,太阳活动影响最大,月球和太阳引力也有影响。断裂结构内的磁场异变和赵锬的形变矢量观察具有临震警报意义。     

自动变速器传动路线分析在异响故障诊断中的应用

本文结合自动变速器的结构原理对其传动路线进行了分析,并深入分析了异响故障的主要原因和诊断思路。     

供热堆中影响重力注硼速度的因素

重力注硼系统不仅设备简单、经济，而且具有固有安全的特点。本文采用一组双组分两相流体五方程式描述系统的物理过程，分析影响注硼速度的因素。分析结果说明：在所关心的范围内，反应堆压力容器内不凝结气体的分压力和注硼管直径的影响最大。     

广东省异常血红蛋白研究Ⅺ 三例Hb G Honolulu的一级结构与功能研究

用快原子轰击抽谱技术测定3例Hb G Honolulu(α_2~(30Gly→Gln)β_2)的一级结构。经氧平衡曲线测定,发现此异常血红蛋白氧亲和力与Hb A的相同,2,3-DPG对它的效应亦正常。     

钟摆机构重心和转动惯量算法探讨

本文提出了一种复杂零件重心和转动惯量的实用算法。所研究的零件可以由板状多边形、圆、扇形、圆锥和圆台等叠合而成。这种广义的叠合也包括了在形体上挖孔以及镶嵌不同密度的材料。该算法适用于计算机编程,其要点是以零件图形某一边界的某一拐点为公共端点进行图形分割,从而使基本图形分割具有规律性。按该法编写的软件比手工计算效率提高了50～100倍,尤其适用于对钟摆重心和转动惯量的计算。     

APPLEⅡ微机在用自由落体测定重力加速度实验中的应用

用AppleⅡ微机的游戏接口与自由落体装置相连,通过微机测定自由落体下落时间,计算重力加速度的数值。     

关于n维单形的一类不等式

本文首先得到关于高维二面角余弦平方和的一个不等式，给出了不等式的最小下界，随后研究了ｎ维单形中线长的一个不等式，得到了一些有盗的结果。     

双曲拱坝的累计自重应力

通过用三维有限元方法按计划施工顺序计算了某高双曲拱坝在自重、灌浆及水压荷载下的累计应力．并研究了不同施工阶段的累计自重应力的特点及改善、利用该应力的工程措施．