引力波探测领域研究态势及热点分析

对宇宙中的引力波进行探测,可以帮助人类发现天体源深处和高密度部分所发生物理过程的完整信息,并绘制全新的"天体分布太空图";激光干涉仪引力波探测器的发展提升了全球范围内的引力波探测研究热度.美国、德国、英国、法国、意大利、日本、澳大利亚、印度和中国等国家纷纷设立了引力波探测计划和项目,并开展了大量的研究工作.本文基于文献...     

支撑引力波探测的信息技术基础设施:LIGO的经验与启示

2016年2月,美国"激光干涉引力波天文台"(LIGO)科学合作组织等机构共同宣布,人类首次直接探测到了引力波,这是前沿物理的重大进展,在多方面具有革命性意义。在LIGO探测到引力波的背后,超级计算、数据网格、志愿者计算等信息技术基础设施发挥了关键性支撑作用,关键经验包括:(1)构建多模式、多样化的计算资源体系;(2)打造便捷、高效的科学工作流系统;(3)探索先进算法、提高数据分析效率。我国正在推动"阿里"、"太极"、"天琴"等三大引力波探测计划,LIGO如何通过建设和使用信息技术基础设施为引力波探测提供有效支持的成功经验,对于我国引力波探测计划取得成功具有重要的参考价值,包括:(1)从整体上构建信息技术基础设施支撑体系;(2)重视开发科学工作流系统;(3)将先进算法作为核心目标;(4)重视科研信息化人才队伍建设。     

欧洲超大型引力波探测仪投入使用

由法国和意大利合作、在意大利建造的“室女座”引力波探测仪日前投入使用。欧洲科学家希望 ,这台设备能够帮助印证爱因斯坦在 1 91 6年最早提出的引力波理论。根据爱因斯坦的广义相对论 ,当物体做加速运动时就会对原有的引力场产生干扰从而辐射出引力波 ,这就好像将一块石头扔到平静的水面上出现的波纹一样。后来的科学家引申了这一理论认为 ,任何运动物体都在无时无刻地辐射引力波 ,引力波在宇宙中无处不在。这种波在真空中以光速传播 ,穿透性极强 ,携带能量以及与波源体有关的信息 ,因而可以用质量体系做“天线” ,接收并探测天体发射来…     

嫦娥三号探测器技术进步与推动

嫦娥三号探测器的任务目标是实现我国在地球以外天体的首次软着陆和巡视探测,在探测器研制技术特点分析的基础上,分析了各项关键技术已取得的突破,以及嫦娥三号的技术推动作用．     

VLBI软件相关处理机研究进展及其在深空探测中的应用

甚长基线干涉测量（VLBI）是重要的射电天文技术，具有极高的空间分辨率，是国际上广泛采用的深空探测器高精度测量手段，相关处理机则是VLBI数据预处理的核心设备.由于VLBI观测数据的相关处理具有数据密集和计算密集的双重特点，目前绝大多数均由专用的大规模高速硬件相关处理机承担.随着通用计算机性能的迅猛发展，基于通用商用计算机的VLBI软件相关处理机的研究逐渐得到重视，并发展迅速，成为VLBI技术领域新的研究热点.软件相关处理机具有制造价低、复制容易、升级简便等特点，有可能在不久的将来，以深空探测领域为切入点，得以普遍应用，并且在常规天文数据相关处理中替代现有的硬件相关处理机。     

天文学家在黑洞周围初步发现引力波存在的证据

美国科学家近日在美国加利福尼亚州圣迭戈召开的美国天文学会年会上报告说，他们初步发现了引力波存在的证据。某些黑洞旋转时拖动周围的时空结构，可能产生引力波，使黑洞周围物质“随波逐流”。     

VLBI相时延及其在深空探测器测定轨中的应用

甚长基线干涉测量(very long baseline interferometry,VLBI)技术是深空探测器测定轨的方法之一,也是行星无线电科学研究的重要手段.VLBI相时延通过解算相关相位的整周模糊度解算出探测器的VLBI时延观测量,可有效地降低相位随机误差的影响,从而提高时延测量的精度.本文论述了解算相位整周模糊度的条件和方法,给出相时延的解算方法,并分析比较了相时延与群时延的随机误差水平.以嫦娥二号(CE2)卫星飞往拉格朗日L2点的探测任务为例,求解了两个月内10次VLBI观测的相时延并分析了数据质量.相时延和群时延分别联合测速测距数据的定轨结果表明,在150万公里的距离上相时延用于探测器的定轨是可行的.     

涂硼MRPC热中子探测器性能的模拟研究

介绍了涂硼MRPC热中子探测器的原理,利用蒙特卡罗方法模拟研究了涂硼MRPC热中子探测器对于不同能量中子的响应以及不同涂层厚度对于0.025eV热中子的转换效率,分析了其对射线的响应,并计算了该探测器的时间分辨和本征探测效率.通过模拟结果给出了涂硼MRPC热中子探测器对于0.025eV热中子的探测效率.对转换效率进行理论计算验证,模拟结果和理论计算值吻合较好.     

前言——天问一号火星探测器专题

天问一号任务是我国行星探测工程的首次任务,在国际上首次通过一次任务实现火星"环绕、着陆、巡视"的三步跨越,是我国航天事业发展的又一具有里程碑意义的进展.天问一号探测器由环绕器和着陆巡视器组成,环绕器对火星开展全球性、综合性的环绕探测,着陆巡视器释放火星车在火星表面开展区域巡视探测.2020年7月23日,探测器在海南文昌...     

包含有界切换增益的空间惯性传感器输出调节积分模型参考自适应控制

基于输出调节的多变量模型参考自适应控制(model reference adaptive control, MRAC)用于解决系统状态不可直接获取时,多变量系统向参考系统的稳定输出跟踪问题.在空间引力波探测航天器内部惯性传感器静电悬浮控制中,考虑到其作为航天器平台惯性基准的稳定需求,双质量块动力学中存在的不连续干扰影响,以及应对不同工作模式的瞬态切换,提出一种基于积分输出调节MRAC的静电悬浮控制方案,引入有界的切换自适应校正增益及自适应积分修正项,用于系统不连续情况下的抗输入饱和、瞬态抑制及惯性传感器非敏感轴各自由度向参考状态的稳定逼近.基于Filippov集与广义梯度的Lyapunov分析验证该方案下,不连续系统中各闭环信号的收敛性,数值仿真验证样例空间引力波探测航天器中,作为关键载荷的双质量块空间惯性传感器各非敏感轴自由度针对位移噪声及残余加速度及切换瞬态的良好抑制效果.     

高分辨雷达扩展目标检测算法研究

针对高分辨雷达扩展目标检测问题,本文建立了高分辨雷达回波模型,推导了在目标信息完全已知的理想条件下的最优检测器形式,给出了检测算法的性能上界.讨论了广义似然比检验在目标信息不同程度缺失情况下的检测器形式,给出了可实现检测器的检测性能上界.基于广义似然比检验,提出了一种基于散射点个数估计的双门限检测器.仿真表明该方法检测性能优于现有检测方法.     

一种基于自体集层次聚类的否定选择算法

否定选择算法是用于产生人工免疫检测器的重要算法,然而传统的否定选择过程需要将随机生成的候选检测器与全部自体数据进行匹配以排除识别了自体的无效检测器,该匹配过程导致检测器的生成效率过低,极大地限制了免疫算法的应用.为此,文中提出了一种基于自体集层次聚类的否定选择算法CB-RNSA.算法首先对自体数据进行层次聚类预处理,然后用聚类中心取代自体数据点与候选检测器进行匹配,以减少距离计算代价.在生成检测器的过程中,候选检测器被限定在非自体空间的低覆盖率区域内,以降低检测器冗余.对检测器的非自体空间覆盖率进行了概率分析,给出了中止生成检测器的条件,该条件较传统的预设检测器数量的中止条件更为合理.理论分析表明CB-RNSA的时间复杂度与自体集规模无关,从而解决了经典的否定选择算法的时间复杂度随自体数量呈指数增长这一难题,极大地提高了大自体样本空间下的检测器生成效率.对比实验结果表明:在相同的实验数据集与期望覆盖率下,CB-RNSA的检测率比经典的RNSA与V-detector算法分别提高了12.3%与7.4%,误警率分别降低了8.5%与4.9%,产生检测器的时间代价分别降低了67.6%和75.7%.     

基于模型突变检测的管道泄漏检测定位方法

为了改进负压波法在管道微弱泄漏的检测和定位中的效果,提出了基于模型突变检测的特征提取和泄漏定位算法。首先运用广义似然比检测理论,建立压力信号变化的统计检验模型,计算广义似然比比率r和下降幅度d作为压力信号突变发生的敏感特征,并通过求得的压力变化时间点进行泄漏定位。针对缓慢泄漏时压力信号变化的特点,提出了相应的改进模型,更精确的求出缓慢泄漏压力信号的下降拐点。实验证明,参数r和d对不同变化类型的压力信号有较好的区分度,利用管道内压力和流量信号的特征值作为神经网络的特征向量可以实现管道的微弱泄漏识别,且基于改进模型的定位算法在缓慢泄漏定位中有较好的定位结果和稳定度。     

便携式生命探测仪的研究

生命的无损检测技术是以人体特性为基础,通过研究电磁波束照射人体而反射信号的波形规律,了解人体受到微动所调制而使得回波信号的某些参数的变化特性,从而提取出人体生命参数。描述了以DSP＆FPGA为核心构造的人体信号的探测装置的研究。通过回波的频率和相位特性分析,确定了生命信号检测系统的最佳参数。在此基础上设计了一套便携式生命探测仪,硬件系统主要由DSP处理器、LCD图形显示器、雷达电磁波单元等组成。软件系统由信号处理算法模块、显示模块、信号发射与接收模块等构成。     

Stratosphärische Wellenvorgänge als Ursache der Witterungssingularitäten

Summary The existence of symmetries in the calender of singularities in the average annual weather trend and the fixation of the symmetry points in atmospheric pressure within the calender prove the causal connection between singularities and pressure waves. The maximum of the amplitude of an important wave (with a period of 30.5 days) is situated in the atmospheric layers above 20 km, that of waves with a period of 15 (or 18) days in the altitude of the tropopause. The same waves are found byGötz in the annual ozone trend. They extend over the whole northern hemisphere.The length of these collective pressure waves are single rational divisors of the year. The singularities will be understood as higher harmonic oscillations of the annual period, partly located in the high stratosphere.     

Judgement aggregation in scientific collaborations: The case for waiving expertise

The fragmentation of academic disciplines forces individuals to specialise. In doing so, they become experts over their narrow area of research. However, ambitious scientific projects, such as the search for gravitational waves, require them to come together and collaborate across disciplinary borders. How should scientists with expertise in different disciplines treat each others’ expert claims? An intuitive answer is that the collaboration should defer to the opinions of experts. In this paper we show that under certain seemingly innocuous assumptions, this intuitive answer gives rise to an impossibility result when it comes to aggregating the beliefs of experts to deliver the beliefs of a collaboration as a whole. We then argue that when experts’ beliefs come into conflict, they should waive their expert status.     

Lamellipodia mediate the heterogeneity of central olfactory ensheathing cell interactions

The growth and guidance of primary olfactory axons are partly attributed to the presence of olfactory ensheathing cells (OECs). However, little is understood about the differences between the subpopulations of OECs and what regulates their interactions. We used OEC-axon assays and determined that axons respond differently to peripheral and central OECs. We then further purified OECs from anatomically distinct regions of the olfactory bulb. Cell behaviour assays revealed that OECs from the olfactory bulb were a functionally heterogeneous population with distinct differences which is consistent with their proposed roles in vivo. We found that the heterogeneity was regulated by motile lamellipodial waves along the shaft of the OECs and that inhibition of lamellipodial wave activity via Mek1 abolished the ability of the cells to distinguish between each other. These results demonstrate that OECs from the olfactory bulb are a heterogeneous population that use lamellipodial waves to regulate cell–cell recognition.     

A conceptual discussion on electromagnetic units – Extending mechanical units towards a global system of units

A comparative review of the different systems of units that are most usual in electromagnetism leads to the proposal of a new system of units. In this system, the gravitational constant acquires the role of an interaction constant, both for gravitational and electromagnetic interaction, as a result of a redefinition of electric charge. In this way, the new system of units extends in a natural manner to mechanics. The comparison between the gravitational and electromagnetic interactions is of particular relevance.     

Fantastic Beasts and where (not) to find them: Local gravitational energy and energy conservation in general relativity

This paper critically examines energy-momentum conservation and local (differential) notions of gravitational energy in General Relativity (GR). On the one hand, I argue that energy-momentum of matter is indeed locally (differentially) conserved: Physical matter energy-momentum 4-currents possess no genuine sinks/sources. On the other hand, global (integral) energy-momentum conservation is contingent on spacetime symmetries. Local gravitational energy-momentum is found to be a supererogatory notion. Various explicit proposals for local gravitational energy-momentum are investigated and found wanting. Besides pseudotensors, the proposals considered include those of Lorentz and Levi-Civita, Pitts and Baker. It is concluded that the ontological commitment we ought to have towards gravitational energy in GR mimics the natural anti-realism/eliminativism towards apparent forces in Newtonian Mechanics.     

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.