Quasi-simultaneous VLBI and RATAN-600 observations of active galactic nuclei

VLBI observations of several quasars and BL Lacertae objects were carried out at 1.66 GHz in November–December 1999 using six antennas (Medvezh'i Ozera, Svetloe, Pushchino, Noto, HartRAO, and Shanghai). Maps of six sources (0420+022, 0420-014, 1308+326, 1345+125, 1803+784, and DA 193) obtained with milliarcsecond resolution are presented and discussed, together with their broad-band (1–22 GHz) spectra obtained on the RATAN-600 radio telescope at epochs close to those of the VLBI observations. Comparison of the VLBI maps with maps of these sources obtained on standard VLBI networks and with the RATAN-600 quasisimultaneous total-flux measurements indicates the reliability of the results obtained on this Low Frequency VLBI Network and the good efficiency of this network.     

Velocity field in the spiral-wave pattern observed in rotating shallow-water experiments

The paper presents the first quantitative results of a laboratory study of the velocity field in a two-arm spiral-wave pattern generated in a steady-state fashion by a hydrodynamical instability in a differentially rotating, thin layer of liquid. The liquid layer has a free surface, and the rotational profile includes an interval where the velocity drops abruptly, as in the gaseous disks of spiral galaxies. The properties of anticyclonic vortices observed between the arms of this pattern at the corotation radius are considered.     

The magnetic-field geometry in polar ray structures of the solar corona

Variations in the positions of the intersection points of tangents to ray structures in the polar corona of the Sun during the solar cycle are considered. At first glance, the decrease in the distance q between the tangent intersection point and the center of the solar disk during activity maximum contradicts harmonic analyses that indicate that the relative weight of higher harmonics in the global field increases during this period. Indeed, the higher the harmonic number in an axisymmetric field, the closer the intersection point of the field-line tangents (the magnetic focus) to the solar surface. It is shown that q for a field composed of two harmonics with opposite polarities at the poles can be smaller than q for either of them taken alone. A simple model representing the global field using the third and seventh harmonics is analyzed; this model can reproduce quite satisfactorily the observed dynamics of magnetic foci of the polar field.     

A statistical analysis of methanol maser groups

An analysis of the flux densities of the 5₁-6₀ A ⁺ (6.7 GHz) and 2₀-3_?1 E (12.2 GHz) class II methanol maser lines in a large and homogeneous sample of maser sources has been carried out. For convenience, the maser lines were divided into three groups: group I contains spectral features for the lines most prominent in the 5₁-6₀ A ⁺ (6.7 GHz) transition, group II contains spectral features for the lines strongest in the 2₀-3_?1 E (12.2 GHz) transition, group III contains spectral features for which the velocities of the emission maxima of the two lines coincide. The same dependence was found for group II and group III: log S _6.7=(0.79±0.05)×log S _12.2+(0.79±0.05). The spectral features in group I do not obey this relation, and deviations from a linear dependence are considerably greater. It is suggested that methanol class II masers be divided into a subclass IIa, which has special conditions favoring 6.7 GHz masers, and a subclass IIb, which is comprised of the 12.2 GHz masers and those 6.7 GHz masers that necessarily accompany them under the same conditions.     

Thermal decomposition of NH4-analcime

The thermal decomposition of ammonium-exchanged natural analcime is characterized by gas chromatography, IR spectroscopy and X-ray diffraction. The de-ammoniation and dehydroxylation proceed in parallel throughout the decomposition, which evidences the instability of the protonated analcime framework. The mechanism of degassing of NH₄-analcime changes throughout its decomposition. At the initial step, the mechanism of de-ammoniation consists in thermal dissociation of NH₄⁺ molecule onto NH₃ and proton (framework OH group) and diffusion of NH₃ out of the structure. Subsequent decomposition and removal of the OH groups lead to a progressive loss of crystallinity. At this step, an apparent activation energy for NH₃ desorption is estimated to be 145(±13) kJ mol^–1. This value is within the upper limit of the activation energy characteristic for the NH₃ desorption from proton centres in large-pore zeolites. At the final step, the adsorption of NH₃ and protons onto the defect centres in the amorphosed aluminosilicate framework results in a significant increase of an apparent activation energy for the de-ammoniation and dehydroxylation up to 270(±20) kJ mol^–1.     

The Classification of Calcium Phosphates of Phosphorites

Lithology and Mineral Resources -     

Are isolated stable rigid clasts in shear zones equivalent to voids?

Particles in shear enclose important information about a rock's past and can potentially be used to decipher the kinematic history and mechanical behavior of a certain outcrop or region. Isolated rigid clasts in shear zones often exhibit systematic inclinations with respect to the shear-plane at small angles, tending towards the instantaneous stretching direction of the shear zone. This shape preferred orientation cannot be easily explained by any of the analytical theories used in geology. It was recently recognized that a weak mantle surrounding the clast or a slipping clast–matrix interface might be responsible for the development of the observed inclinations. Physical considerations lead us to conjecture that such mantled, rigid clasts can be effectively treated as voids that are not allowed to change their shape. The resulting equivalent void conjecture agrees well with numerical and field data and has the following important geological implications. (i) Clasts in shear zones can have stable positions in simple shear without the requirement of an additional pure shear component. (ii) The stable orientation can be approached either syn- or antithetically; hence, the clast can rotate against the applied shear sense. (iii) The strain needed to develop a strong shape preferred orientation is small (γ≈1) and therefore evaluations based on other theories may overestimate strain by orders of magnitude. (iv) The reconstruction of far-field shear flow conditions and kinematic vorticity analysis must be modified to incorporate these new findings.     

幂函数对建筑物沉降的回归分析

通过实例推导幂函数对建筑物沉降进行回归分析，并且得出较为精确的结果，同时也说明在选择回归函数的时候，还会受到很多条件影响。     

Data Fusion in Distributed Multi-sensor System

This paper presents a data fusion method in distributed multi-sensor system including GPS and INS sensors“ data processing. First, a residual X^2-test strategy with the corresponding algorithm is designed.Then a coefficient matrices calculation method of the information sharing principle is derived. Finally, the federated Kalman filter is used to combine these independent, parallel, real-time data. A pseudolite (PL) simulation example is given.     

图像控制点数据库的设计与实现

地面控制点数据是航天航空图像摄影测量几何处理的必需数据。文中首先比较了控制点数据的存储管理方式，即采用文件系统方式与数据库方式的优缺点；接着分析了控制点图像数据的特征，从而提出了图像控制点数据的数据库存储方案，讨论了图像控制点数据库的查询方法；最后结合文中的方法，设计并且实现了一个控制点图像数据库管理与应用实验系统。通过分析认为，建立控制点图像数据库是重复利用控制点资源的有效途径。