Constraints on the photon charge from observations of extragalactic sources     

V. V. Kobychev  S. B. Popov 《Astronomy Letters》2005,31(3):147-151

Having analyzed high-resolution observations of extragalactic compact radio sources with modern systems of radio telescopes, we obtained an estimate of the upper limit for the photon electric charge, e_γ ? 3×10^?33 of the elementary charge (assuming the photon charge to be energy independent). This is three orders of magnitude better than the limit obtained from radio pulsar timing. We also set a limit on the charge of a gamma-ray (energy ～0.1 MeV) photon. In the future, the estimate based on extragalactic sources can be improved significantly.  相似文献   

On the character of distribution of chemical elements in nature     

Jozef Guba 《Mathematical Geology》1986,18(4):429-432

Distribution of chemical elements in nature is controlled by the general physical-chemical state of natural processes, a result of the effort to reach thermodynamic equilibrium. Natural processes, forming geologic objects (e.g., rocks, ores) usually do not reach total chemical equilibrium. This is reflected in distributions of chemical elements in nature. We recognize symmetric as well as asymmetric distributions. The question arises, what distribution in nature is most commonly followed? Evidently, this should be a distribution of chemical elements in thermodynamic equilibrium throughout the system, thus with maximum entropy. This paper notes that Gauss's normal distribution may be derived from statistic explanation of entropy as a function of contnt of chemical elements in a system with application of Einstein's formula.  相似文献   

DLG制图数据生产中AutoCAD自动填充的实现方法     

陈秀萍  黄彦锋  吕翠华 《测绘科学》2012,(4):175-177

DLG制图数据是1∶10 000基础测绘3D产品的重要组成部分,在DLG制图数据的生产时常采用Auto-CAD的DWG格式。而AutoCAD在生产DLG制图数据时不能有效处理拓扑问题,同时在AutoCAD中的面色填充,一直以来都没有一个简便而快速的方法。本文在总结实际生产经验的基础上,利用Python编程语言实现了Auto-CAD面状地物的自动填充,在实际生产中提高了效率,保证了DLG制图数据产品的质量。  相似文献   

获取与处理类测绘标准的重组规划探讨     

刘艳  武广臣 《东北测绘》2012,(2):223-225

获取与处理类测量规范是测绘标准体系的核心部分,然而,这些测量规范存在着内容重复、引用复杂、系统性差等缺点,因此,建议将现行的获取与处理类测量规范进行重组。通过分析,将该类测量规范规划为两部分：基础测量规范与专业测量规范,重组后的测量规范系统性强、引用简单、索引明确,对指导测绘生产具有重要意义。  相似文献   

关于数字城市地理空间框架建设的研究   总被引：1，自引：0，他引：1  

黄峥 《东北测绘》2012,(10):159-160,166

随着我国城市化进程的发展,城市规模不断扩大,传统的城市管理方法远远不能满足现代城市管理的要求。随着＂数字中国＂战略的提出,＂数字城市＂应运而生。当前以＂数字城市＂为标志的城市信息化建设正在全国范围内迅速开展,网络基础设施和空间信息基础设施是数字城市建设中两个最为重要的基础设施,而地理空间框架是空间信息基础设施的重要组成部分,是经济社会信息化发展的基础支撑平台。  相似文献   

基于WalkGIS的地形数据建库加工整理模式     

张玲  李育平 《北京测绘》2012,(1):39-40,46

以1∶500基础地理信息数据加工整理模式为研究对象,对数据整理的技术要求和整理方法进行了清晰的阐述,总结出一套基于WalkGIS平台的基础地理信息数据库建库数据加工整理模式,为数据整理工作提供参考。  相似文献   

An interacting O + O supergiant close binary system: Cygnus OB2-5 (V729 Cyg)     

《New Astronomy》2014

  相似文献   

Intermediate‐term variations in solar radius during solar cycle 23     

H. Kili  O. Golbasi  F. Chollet 《Astronomische Nachrichten》2009,330(4):351-357

In this study, we look for the mid‐term variations in the daily average data of solar radius measurements made at the Solar Astrolabe Station of TUBITAK National Observatory (TUG) during solar cycle 23 for a time interval from 2000 February 26 to 2006 November 15. Due to the weather conditions and seasonal effect dependent on the latitude, the data series has the temporal gaps. For spectral analysis of the data series, thus, we use the Date Compensated Discrete Fourier Transform (DCDFT) and the CLEANest algorithm, which are powerful methods for irregularly spaced data. The CLEANest spectra of the solar radius data exhibit several significant mid‐term periodicities at 393.2, 338.9, 206.5, 195.2, 172.3 and 125.4 days which are consistent with periods detected in several solar time series by several authors during different solar cycles. The knowledge relating to the origin of solar radius variations is not yet present. To see whether these variations will repeat in next cycles and to understand how the amplitudes of such variations change with different phases of the solar cycles, we need more systematic efforts and the long‐term homogeneous data. Since most of the periodicities detected in the present study are frequently seen in solar activity indicators, it is thought that the physical mechanisms driving the periodicities of solar activity may also be effective in solar radius variations (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

New magnetic field measurements of β Cephei stars and slowly pulsating B stars     

S. Hubrig  M. Briquet  P. De Cat  M. Schller  T. Morel  I. Ilyin 《Astronomische Nachrichten》2009,330(4):317-329

We present the results of the continuation of our magnetic survey with FORS 1 at the VLT of a sample of B‐type stars consisting of confirmed or candidate β Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B‐type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three β Cephei stars and two stars suspected to be β Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3σ has been diagnosed in two normal B‐type stars, the nitrogen‐rich early B‐type star HD 52089 and in the B5 IV star HD 153716. Roughly one third of β Cephei stars have detected magnetic fields: Out of 13 β Cephei stars studied to date with FORS 1, four stars possess weak magnetic fields, and out of the sample of six suspected β Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: Roughly half of the 34 SPB stars have been found to be magnetic and among the 16 candidate SPBs eight stars possess magnetic fields. In an attempt to understand why only a fraction of pulsating stars exhibit magnetic fields, we studied the position of magnetic and non‐magnetic pulsating stars in the H‐R diagram. We find that their domains in the H‐R diagram largely overlap, and no clear picture emerges as to the possible evolution of the magnetic field across the main sequence. It is possible that stronger fields tend to be found in stars with lower pulsating frequencies and smaller pulsating amplitudes. A somewhat similar trend is found if we consider a correlation between the field strength and the v sin i ‐values, i.e. stronger magnetic fields tend to be found in more slowly rotating stars (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

On the origin of exponential galaxy discs     

Aaron A. Dutton 《Monthly notices of the Royal Astronomical Society》2009,396(1):121-140

  相似文献