Collisional processes among interplanetary dust grains: An unlikely origin for the β meteoroids

The question of the collisional production of the β meteoroids is reexamined incorporating recent experimental results (A. Fugiwara, G. Kamimoto, A. Tsukamoto, 1977, Icarus31, 277–288). The collisional model yields a flux of fragments supported by the conservation of mass flux which does not account by far for the observed flux of submicron grains. Particles larger than about 100 μm will be destroyed by collisions inside 1 AU, well before they can get near the Sun. The existence of two independent populations of interplanetary dust grains as proposed by L. B. Le Sergeant and Ph. L. Lamy (1978, Nature266, 822–824; 1980, Icarus43, 350–372) appears reinforced. It is proposed that the bulk of submicron grains does not necessarily travel in hyperbolic orbits and that β meteoroids may be a phenomenon—possibly transitory—of limited importance.     

强化管理盘活资产多元经营提高效益

行政事业单位的内部招待所走向市场后,必须摒弃旧的传统观念,变资产管理为资产经营、变行政管理为质量控制、变传统管理为制度管理.     

广饶县地面沉降成因及预测分析

地面沉降是指由于自然因素或人类工程活动引发的地下松散岩层固结压缩,并导致一定区域范围内地面高程降低的地质现象,是一种缓变性地质灾害。广饶县地处东营市南端,根据2004—2016年地面沉降监测资料,其沉降中心累计沉降量已超过了1 500mm,最大沉降速率超过70mm/a,属地面沉降强发育。通过对地面沉降发生、发展规律和引发地面沉降的成因进行了分析,并在现状条件下对地面沉降趋势进行了预测分析。     

美国不动产征收典型案例分析及启示

美国宪法第五修正案规定不动产征收改变了以往封建社会不动产征收为统治阶级服务的目的而转向公共利益。但最初的制度设计随着政府角色定位改变、社会经济发展繁荣等多种因素难以充分应对公共政策制定和实施过程中遇到的各种问题。该文通过分析美国不动产征收权的形成背景及对其产生影响的典型案例,探析美国不动产征收权的形成与演化。结果表明,随着社会经济多元化发展以及公共用途内涵的不断扩展,美国政府通过案例来补充和完善法律在最初界定不动产征收相关条款的概括和不足。政府在行使不动产征收权的时候,虽然部分涉及与经营性用地结合来实现提高本地居民收入、增加就业机会和改善局部市政环境等目标,但如何协调政府行为与公共利益的关键在于建立合理的公共参与制度来反映公众诉求和监督政府行为,以实现个体权益保护的目的。美国不动产征收制度的演化与发展为我国征地制度改革提供了一定的理论借鉴和案例支撑。     

Large-Scale Variation of Solar Wind Electron Properties from Quasi-Thermal Noise Spectroscopy: Ulysses Measurements

The transport of energy in space plasmas, especially in the solar wind, is far from being understood. Measuring the temperature of the electrons and their non-thermal properties is essential to understand the transport properties in collisionless plasmas. Quasi-thermal noise spectroscopy is a reliable tool for measuring the electron temperature accurately since it is less sensitive to the spacecraft perturbations than particle detectors. We apply this method to Ulysses radio data obtained during the first pole-to-pole fast latitude scan in the high-speed solar wind, using a kappa function to describe the electron velocity distribution. We deduce the variations with heliocentric distance between 1.5 and 2.3 AU in the fast solar wind at high latitude in terms of three fitting parameters: the electron density varies as n _e??R ^?1.96±0.08, the electron temperature as T _e??R ^?0.53±0.15, and the kappa index of the distribution remains constant at ??=2.0±0.2. These observations agree with the predictions of the exospheric theory.     

Hypsometry of Titan

Cassini RADAR topography data are used to evaluate Titan’s hypsometric profile, and to make comparisons with other planetary bodies. Titan’s hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the ‘glacial buzz-saw’ that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa.     

系统聚类方法在房地产周期分析中的应用

选取了9项房地产经济波动指标，经过相关性分析，确定房地产经济综合指标体系，并运用聚类分析方法对我国房地产经济波动进行了分析，为进一步分析研究我国房地产周期提供了方法和手段。     

Mapping Titan's surface features within the visible spectrum via Cassini VIMS

Titan shows its surface through many methane windows in the 1–5 $\mathrm{\mu }\mathrm{m}$ region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 $\mathrm{\mu }\mathrm{m}$. We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and $1.046\mathrm{\mu }\mathrm{m}$ and apply an RGB color scheme to the 0.754, 0.827 and $0.937\mathrm{\mu }\mathrm{m}$ windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of $0.938\mathrm{\mu }\mathrm{m}$. We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as $5\text{‐}\mathrm{\mu }\mathrm{m}$ bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast.     

10 Hygiea: ISO Infrared Observations

Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8-11.6 and 7-45 μm, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo-physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated.     

The chemistry of magmatic gases from Erta'Ale,Ethiopia

The chemical composition of the gases emitted from a hornito close to the active lava lake of Erta'Ale, Ethiopia, as derived from chemical analyses on 18 samples collected on 23 January 1974, was found to be (in mol-%): H₂O: 79.4, CO₂: 10.4, total S: 7.36, HCl: 0.42, H₂: 1.49, N₂: 0.18, Ar: 0.001, CO: 0.46, and COS: 0.009. Thermodynamic considerations, based on the equilibria CO₂ + H₂ ? CO + H₂O and CO₂ + 3H₂ + SO₂ ? COS + 3H₂O show that the analytical values represent the equilibrium composition of a gas mixture at the measured temperature of around 1130°C under close to the surface pressure conditions. Comparison of the Erta'Ale gas emissions with those from other volcanoes suggests a close similarity in their chemical composition. This similarity is considered to be due to common processes governing the release of gaseous species from a magma.