Principles for selecting a list of reference radio sources for a celestial coordinate system

Time series of the coordinates of radio sources defining the celestial coordinate frame are analyzed. Methods for selecting such sources so as to enhance the stability of the frame are considered. Some of these sources, including so-called “defining” sources, demonstrate significant proper motions. Since the stability of the celestial coordinate frame is determined by an absence of global rotation relative to the defining sources (no net rotation), variation in their coordinates will lead to a rotation of the axes of the celestial coordinate frame. The parameters of this rotation are calculated for two physical models for the motions of extragalactic radio sources. The motions displayed by the first group of sources are linear and uniform. Since the apparent speeds of radio sources are often close to, and sometimes exceed, the speed of light, it is supposed that such radio sources have relativistic jets or plasma clouds that move with speeds roughly equal to the speed of light. The observed uniform, linear motion can then be explained by precession of the jet. The second group of sources display non-linear motions, interpreted as a manifestation of the acceleration of matter by the jet. It is assumed that a cloud of particles that moves into the path of the jet is accelerated to relativistic speeds by the jet. A list of sources that should form a very stable coordinate system for several decades into the future is composed based on these two models.     

Radio identification and continuum spectra of decameter-wavelength sources

The paper describes a method for the radio identification of decameter-wavelength sources based on their continuum spectra and analysis of their coordinates in relatively large error boxes surrounding a specified position on the sky. The distribution of continuum spectra and identifications in other wavelength ranges are analyzed for the resulting radio catalog. Using identifications with the FIRST and NVSS surveys, the statistics of the spectral index-size and spectral index-flux density distributions for steep-spectrum sources have been studied, and a catalog of ultrasteep-spectrum (α相似文献   

Detection of sources of periodic radio emission with the Large Phased Array of the Lebedev Physical Institute

A method for searching for new periodic radio sources is described. The method is based on the spectral analysis of data from daily monitoring of the sky on the Large Phased Antenna (LPA) of the Pushchino Radio Astronomy Observatory at 111 MHz in a 2.5-MHz band. The 96-beam directivity pattern of the LPA is used. The signal is received in six 0.42-MHz frequency channels with a sampling rate of 0.1 s. The duration of the processed survey is four months. The particulars of detecting periodic sources with the LPA are considered. In total, 16 such radio sources have been detected, for which equatorial and Galactic coordinates, periods, and dispersion measures are given.     

The Role of Pressure as a Source of Gravity and Wormholes

The role of pressure as a source of gravity in general relativity is considered. In homogeneous, anisotropic cosmological models, the anisotropic pressure components along different coordinate axes are included as terms in the equations determining the accelerations along these axes; in this sense, this situation is similar to how the mass density is included in these equations. A change in the pressure component along one of the coordinates leads to an anisotropic change in the accelerations along all three coordinates. However, the pressure components are not present in the equation determining the initial conditions. On the other hand, with an inhomogeneous matter density distribution, the mass density and pressure play fundamentally different roles as sources of gravity. The consequences of this are considered.     

基于GIS的区域地质编图方法

本文以地理信息系统在小比例尺区域地质编图中的应用为基础,结合《亚洲中部及邻区系列地质图》的编制,详细阐述了应用ArcInfo、MapGis等GIS软件进行数字地质编图的方法.对地理空间数据和专业地质空间数据的编制做了详细介绍,其中包括各种要素制图综合、属性库制作、编码设计、现势资料的补充等.根据数据源的不同,制定了不同的技术路线和工作方法.将来自不同国家的数据源进行数据转换、投影变换和误差校正,转换为统一的数据格式和投影坐标系统.对基于GIS的区域地质编图方法及数据源做了具体分析.     

The influence of galactic aberration on precession parameters determined from VLBI observations

The influence of proper motions of sources due to Galactic aberration on precession models based on VLBI data is determined. Comparisons of the linear trends in the coordinates of the celestial pole obtained with and without taking into account Galactic aberration indicate that this effect can reach 20 μ as per century, which is important for modern precession models. It is also shown that correcting for Galactic aberration influences the derived parameters of low-frequency nutation terms. It is therefore necessary to correct for Galactic aberration in the reduction of modern astrometric observations.     

Search for class I methanol maser emission toward several supernova remnants

Observations at 44 GHz in the 7₀−6₁ A ⁺ methanol line have been carried out on the 20-m telescope of the Onsala Space Observatory (Sweden) in the directions of the poorly studied region G27.4–0.2 and of several supernova remnants, at the coordinates of the OH(1720) maser satellite emission, with the aim of searching for Class I methanol maser emission in these sources. The region G27.4–0.2 has beenmapped, and contains maser sources and two supernova remnants with similar coordinates and radial velocities, which may accelerate condensation of the ambient gas-dust medium. This may play a role in enhancing the probability of methanol formation and maser emission. This is the first detection of 44 GHz maser emission in this source, and this maser is among the 10% of the strongest Class I methanol masers, within the uncertainties in the integrated flux (of a total of 198 currently knownmasers). A 27′ × 27′ region around the maser has been mapped at 44 GHz in steps of 1′. The 44-GHz emission forms only within the previously known maser region. Further studies in water lines are needed to estimate the influence of shocks from supernovae. No 44-GHz Class I methanol maser emission was detected at the 3σ level at the coordinates of the OH(1720) satellite emission in six supernova remnants; i.e., the presence of OH(1720) emission is not a sufficient condition for the detection of Class I methanol masers.     

Effects of instability of the Earth and celestial coordinate systems on Earth orientation parameters

Unknown secular and long-term changes in the Earth orientation parameters attributed to instability (possible rotation) of both the Earth and celestial coordinate systems (ECS and CCS) are studied. Rotation of the CCS due to changes in the coordinates of extragalactic sources resulting from gravitational lensing can lead to errors of the order of several microarcseconds in the orientation parameters. The rotation of the ECS due to the crust pressing on the mantle diminishes the tidal retardation of the Earth's rotation and produces long-term variations in the duration of the day (with a period of about 1500 years) and in the motion of the pole relative to the Earth's surface.     

The Mesozoic granitoid magmatism and metallogeny of the Central Asian and Pacific Belts junction area

Materials pertaining to Mesozoic granitoids in the Central Asian and Pacific Belts junction area and the adjacent platforms are summarized. Maps of the location of massifs, the extensiveness of granitoid magmatism, the manifestations of Mesozoic plumes, and the relief of the asthenosphere surface have been compiled. The locations of the major ore deposits are plotted on the maps. The distribution chart has been constructed for these deposits in the coordinates of the crust and lithosphere. The depth of the occurrence of the sources for large and superlarge gold, tin, polymetallic, molybdenum, tungsten, and uranium deposits has been estimated. Areas showing promise for the discovery of large deposits are defined.     

Study on the sensitivity of the vertical cooling (heat sink) on the displacements of the mid-tropospheric ridge using a linear model

A linear model of the response of a stratified atmosphere to isolated heat sources in spherical coordinates is used to study the maintenance of the mean position of the mid tropospheric ridge and its displacement. It is well known that the performance of the southwest Indian monsoon is related to the latitudinal position of the April 500 hPa ridge along 75‡E. It was demonstrated that an anomalous cooling associated with the increased snow cover in Eurasia can result in moderate southward displacement of the mid-tropospheric ridge. The results of this study indicate that the vertically integrated cooling rate (strength of heat sink) has more effect on the southward displacement of the ridge when the sink is closer to the ridge.     

Catalog of Supermassive Black Holes for Interferometric Observations

The paper presents a catalog of supermassive black holes (SMBHs) sharpened for interferometric observations at millimeter and submillimeter wavelengths, based on open sources. The catalog includes the object’s name, coordinates, angular size, and mass, the angular size of the gravitational radius of the SMBH, and the integrated radio flux associated with the radiosource concluding the SMBH at 20?900 GHz, planned for the Event Horizon Telescope, the future space mission Millimetron, and others. The catalog is intended for use during planning of interferometric observations of SMBH shadows.

     

Use of Spherical Trigonometry to Compute Near-Well Flow through Irregular Grid Block Boundaries

This paper concerns the computation of near-well flow in numerical reservoir simulation with unstructured grids. In particular, it uses spherical trigonometry to derive analytical expressions for the flow towards a well modeled as either a number of point sources or a constant-flux line source. The expression for the point source representation is based on projections of the grid block boundaries on spheres with unit radius around the sources. The expression for the line source is based on projection on a prolate spheroid. The computation of the surface area is done through transformation to prolate spheroidal coordinates and subsequent projection on a sphere at infinity. The point source expression for a single source is exact for grid block boundaries with straight edges; the line source expression is an approximation. Both representations are fully volume conserving, such that the sum of the fluxes through the grid block boundaries surrounding a source adds up exactly to the total source flow rate. Both representations can be used to accurately model complicated wells in the form of segments. The point source representation is simpler to implement and not necessarily less accurate than the line source representation.     

Tsunamigenic zones in the Mediterranean Sea

A list of 300 tsunamis and similar phenomena known in the Mediterranean is given. Data reliability and wave intensity are estimated; mechanisms of tsunami generation are indicated and data from literature sources on the coordinates and magnitudes of tsunamigenic earthquakes are cited. Eighteen zones of excitation and manifestation of tsunamis are identified which can be integrated into four groups with respect to the recurrence period and maximum intensity of the tsunamis. The strongest tsunamis are excited in the Aegean Sea, and the Hellenic and Calabrian island arcs. The focal depth of the earthquake-generating tsunamis in the Mediterranean is, on average, less than that in the Pacific. Correspondingly, the magnitude of tsunamigenic earthquakes is lower. According to preliminary estimates, the Mediterranean tsunamis attenuate with distance more rapidly than do those in the Pacific Ocean.     

A sky survey at 102.5 MHz: Radio sources at declinations 27.5°–33.5° and 67.5°–70.5°

The results of observations on the Large Phased Array of the Lebedev Physical Institute made as part of a survey of the northern sky at 102.5 MHz are reported. Survey source lists for the declination ranges 27.5°–33.5° and 67.5°–70.5° are given, together with their coordinates, flux densities, and identifications with 4C objects. In total, there are 920 sources with flux densities S _102.5≥3.0 Jy in the two zones, which cover 0.73 star. The observing and data-reduction methods are described, and the reliability and completeness of the catalog are estimated.     

太原盆地重金属元素地球化学分布特征

研究了太原盆地土壤中8种重金属元素As,Cd,Cr,Hg,Ni,Pb,Zn,Cu的来源及分布规律,首次计算了太原盆地区域土壤背景值,分析了盆地中重金属元素的污染状况;认为Hg,Cd,As的污染情况最为严重.用太原市和太原盆地的深、浅层数据作出8种重金属元素的多重分形图,对8种重金属元素在生态环境中的影响作用进行了统计分析,总结了重金属元素的分形规律,得出各影响因素的相对重要性.     

起伏地形上规则二度体复重磁场正演和直接反演

上接211页13　n个无限薄板叠加场反演13.1　复场展开以Mj代替2Mmj和2fMgj,以F(S)代替G′(S)和T(S),得复场F(S)= nj=1Mjσj-S=- nj=1MjS-σj。(13.1)展开上式,即F(S)=-1(S-σ1)(S-σ2)…(S-σn)×{M1(S-σ2)(S-σ3)…(S-σn)+M2(S-σ1)(S-σ3)…(S-σn)+…+Mn(S-σ1)(S-σ2)…(S-σn-1)}。(13.2)根据(9.2)、(9.9)式有(S-σ1)(S-σ2)…(S-σn)=-1F(S){Φ1+Φ2+…+Φn};Φ1=M1{Sn-1-x1(1)Sn-2+x2(1)Sn-3-　　　　…+(-1)n-1x(n-1)(1)},Φ2=M2{Sn-1-x1(2)Sn-2+x2(2)Sn-3-　　　　…+(-1)n-1x(n-1)(2)},Φn=Mn{Sn-1-x1(n)S…     

Thermoelastic stress due to a rectangular heat source in a semi-infinite medium. Presentation of an analytical solution

The thermoelastic response due to a time-dependent rectangular heat source in a semi-infinite medium is analyzed. The problem originates from studies of nuclear waste repositories in rock. Canisters containing heat-emitting nuclear waste are deposited over a large rectangular area deep below the ground surface. The solution for a time-dependent heat source is obtained from the corresponding instantaneous heat source by superposition. The thermoelastic problem for the instantaneous rectangular heat source in a infinite surrounding is solved exactly. An important step is the introduction of so-called quadrantal heat sources. The solution for the rectangle is obtained from four quadrantal solutions. The solution for the quadrantal heat source depends on the three dimelasionless coordinates only. Time occurs in the scale factors only. The condition of zero normal and shear stresses at the ground surface is fulfilled by using a mirror heat source and a boundary solution. The boundary solution accounts for the residual normal stress at the ground surface. Using a Hertzian potential, a surprisingly simple solution is obtained. The final analytical solution is quite tractable considering the complexity of the initial problem. The solution may be used to test numerical models for coupled thermoelastic processes. It may also be used in more detailed numerical simulations of the process near the heat sources as boundary conditions to account for the three-dimensional global process.     

手持GPS坐标系转换方法

导航型手持GPS目前在中小比例地质调查等领域得到广泛应用,由于坐标系之间存在差异,在实际应用过程中,必须将手持机的WGS84坐标系转换为我国应用的BJ54或西安80坐标系。坐标转换的准确与否,直接影响到工程测量定位的精度,传统的坐标转换计算所需要的起算资料不易收集,计算过程过于繁琐,非专业人员难以掌握。本文根据收集的三角点BJ54坐标(或西安80坐标),和现场测定的过渡坐标,求出各参数在本工作地区的变化率,建立参数方程,反向求出适合于当地的各项改正参数,方法简便易行,为手持GPS定位的坐标转换方法提出一种新的思路。