Hot-spot evolution and the global tectonics of venus

The global tectonics of Venus may be dominated by plumes rising from the mantle and impinging on the lithosphere, giving rise to hot spots. Global sea-floor spreading does not take place, but direct convective coupling of mantle flow fields to the lithosphere leads to regional-scale deformation and may allow lithospheric transport on a limited scale. A hot-spot evolutionary sequence comprises (i) a broad domal uplift resulting from a rising mantle plume, (ii) massive partial melting in the plume head and generation of a thickened crust or crustal plateau, (iii) collapse of dynamic topography, and (iv) creep spreading of the crustal plateau. Crust on Venus is produced by gradual vertical differentiation with little recycling rather than by the rapid horizontal creation and consumption characteristic of terrestrial sea-floor spreading.     

Relation of major volcanic center concentration on venus to global tectonic patterns

Global analysis of NASA Magellan image data indicates that a major concentration of volcanic centers covering approximately 40 percent of the surface of Venus occurs between the Beta, Atla, and Themis regiones. Associated with this enhanced concentration are geological characteristics commonly interpreted as rifting and mantle upwelling. Interconnected low plains in an annulus around this concentration are characterized by crustal shortening and infrequent volcanic centers that may represent sites of mantle return flow and net down-welling. Together, these observations suggest the existence of relatively simple, largescale patterns of mantle circulation similar to those associated with concentrations of intraplate volcanism on Earth.     

Lightning and plasma wave observations from the galileo flyby of venus

During the Galileo flyby of Venus the plasma wave instrument was used to search for impulsive radio signals from lightning and to investigate locally generated plasma waves. A total of nine events were detected in the frequency range from 100 kilohertz to 5.6 megahertz. Although the signals are weak, lightning is the only known source of these signals. Near the bow shock two types of locally generated plasma waves were observed, low-frequency electromagnetic waves from about 5 to 50 hertz and electron plasma oscillation at about 45 kilohertz. The plasma oscillations have considerable fine structure, possibly because of the formation of soliton-like wave packets.     

A radar snapshot of venus

A radar brightness map of Venus has been obtain d. It reveals interesting surface features and much structure over a large area.     

Kaup-Kupershmidt-Parker-Dye方程的确切行波解(英文)

通过应用Cosgrove方法研究了Kaup-Kupershmidt-Parker-Dye方程的相应的四维行波系统,得到了一些新的确切显式紧孤子、非紧孤子、周期解和非周期解.同时对一些已知平衡点的局部动力学行为进行了讨论.     

Ice caps on venus?

The data on Venus obtained by Mariner V and Venera 4 are interpreted as evidence of giant polar ice caps holding the water that must have come out of the volcanoes with the observed carbon dioxide, on the assumption that Earth and Venus are of similar composition and volcanic history. The measurements by Venera 4 of the equatorial surface temperature indicate that the microwave readings were high, so that the polar ice caps may be allowed to exist in the face of the 10-centimeter readings of polar temperature. Life seems to be distinctly possible at the edges of the ice sheets.     

Suppressing wall turbulence by means of a transverse traveling wave

Direct numerical simulations of wall-bounded flow reveal that turbulence production can be suppressed by a transverse traveling wave. Flow visualizations show that the near-wall streaks are eliminated, in contrast to other turbulence-control techniques, leading to a large shear stress reduction. The traveling wave can be induced by a spanwise force that is confined within the viscous sublayer; it has its maximum at the wall and decays exponentially away from it. We demonstrate the application of this approach in salt water, using arrays of electromagnetic tiles that produce the required traveling wave excitation at a high efficiency.     

Encounter with venus

This report is an introduction to the accompanying collection of initial results from the successful Pioneer Venus orbiter and mutiprobe missions that encountered Venus on 4 December and 9 December 1978, respectively. The mission features are briefly described and furnish data accumulated over the first 30 days of the mission.     

基于FIMD和小波变换电缆双端行波测距新方法

针对电力电缆故障定位误差较大问题,提出基于FIMD和小波变换模极大值导数双端行波测距新方法。利用PSCAD仿真软件建立电力电缆模型,变换各测量点电流突变量相模,分解变换后模分量FIMD。利用小波变换对分解所得IMF1分量求取模极大值导数,找出暂态信号奇异点。根据首个暂态行波奇异点,确定初始行波到达线路两端时间,计算故障距离。结果表明,该方法测定电缆故障距离精度高、具有应用可行性。     

基于单端行波法的输电线路故障测距系统的设计

快速准确故障定位是保证电力系统安全运行的有效途径之一。文章根据单端行波测距原理,设计出专门的硬件启动电路进行故障检测,采用高速、高精度的A/D转换芯片进行数据转换,高速数据处理芯片DSP进行数据处理和故障波头的提取,实现了输电线路故障点的快速、准确的定位。     

Resonance rotation of venus

Combination of two types of radar data shows the orbital plane and equator of Venus to be included by less than 2 degrees, and the sidereal rotation period to be 243.09 +/- 0.18 days (retrograde)-remarkably close to the 243.16-day period for which the spin would be in resonance with the relative orbital motions of Earth and Venus. In this resonance, Venus would make, on average, four axial rotations as seen by an Earth observer between successive close approaches of the two planets. Estimates of the instantaneous spin period, accurate within about 0.01 day, would provide important information on the difference of Venus's equatorial moments of inertia, on their orientation, and on the magnitude of the tidal torque exerted on Venus by the sun.     

Mariner 10 venus encounter

The Mariner 10 spacecraft encountered Venus at 1701 G.M.T. on 5 February 1974. The preplanned encounter science sequence was executed satisfactorily, accomplishing all objectives despite a number of spacecraft problems that had occurred in the early phases of the flight. Seven experiments were conducted, including observations of the solar wind interaction region, extreme ultraviolet and infrared emissions, radio occultation, and imaging.     

Nature of the ultraviolet absorber in the venus clouds: inferences based on pioneer venus data

Several photometric measurements of Venus made from the Pioneer Venus orbiter and probes indicate that solar near-ultraviolet radiation is being absorbed throughout much of the main cloud region, but little above the clouds or within the first one or two optical depths. Radiative transfer calculations were carried out to simulate both Pioneer Venus and ground-based data for a number of proposed cloud compositions. This comparison rules out models invoking nitrogen dioxide, meteoritic material, and volatile metals as the source of the ultraviolet absorption. Models involving either small ( approximately 1 micrometer) or large ( approximately 10 micrometers) sulfur particles have some serious difficulties, while ones invoking sulfur dioxide gas appear to be promising.