Scattering properties of planetary regolith analogs

The physics of scattering of electromagnetic waves by media in which the particles are in contact, such as planetary regoliths, has been thought to be relatively well understood when the particles are larger than the wavelength. However, this is not true when the particles are comparable with or smaller than the wavelength. We have measured the scattering parameters of planetary regolith analogs consisting of suites of well-sorted abrasives whose particles ranged from larger to smaller than the wavelength. We measured the variation of reflectance as the phase angle varied from 0.05° to 140°. The following parameters of the media were then deduced: the single scattering albedo, single scattering phase function, transport mean free path, and scattering, absorption, and extinction coefficients. A scattering model based on the equation of radiative transfer was empirically able to describe quantitatively the variation of intensity with angle for each sample. Thus, such models can be used to characterize scattering from regoliths even when the particles are smaller than the wavelength. The scattering parameters were remarkably insensitive to particle size. These results are contrary to theoretical predictions, but are consistent with earlier measurements of alumina abrasives that were restricted to small phase angles. They imply that a basic assumption made by virtually all regolith scattering models, that the regolith particles are the fundamental scattering units of the medium, is incorrect. Our understanding of scattering by regoliths appears to be incomplete, even when the particles are larger than the wavelength.     

Spectral analysis of the 91bg-like Type Ia SN 2005bl: low luminosity, low velocities, incomplete burning

The properties of underluminous Type Ia supernovae (SNe Ia) of the 91bg subclass have yet to be theoretically understood. Here, we take a closer look at the structure of the dim SN Ia 2005bl. We infer the abundance and density profiles needed to reproduce the observed spectral evolution between −6 d and  +12.9 d  with respect to B maximum. Initially, we assume the density structure of the standard explosion model W7; then we test whether better fits to the observed spectra can be obtained using modified density profiles with different total masses and kinetic energies. Compared to normal SNe Ia, we find a lack of burning products especially in the rapidly expanding outer layers  ( v ≳ 15 000 km s⁻¹)  . The zone between ∼8500 and 15 000 km s⁻¹ is dominated by oxygen and includes some amount of intermediate-mass elements. At lower velocities, intermediate-mass elements dominate. This holds down to the lowest zones investigated in this work. This fact, together with negligible-to-moderate abundances of Fe-group elements, indicates large-scale incomplete Si burning or explosive O burning, possibly in a detonation at low densities. Consistently with the reduced nucleosynthesis, we find hints of a kinetic energy lower than that of a canonical SN Ia: the spectra strongly favour reduced densities at  ≳13 000 km s⁻¹  compared to W7, and are very well fitted using a rescaled W7 model with original mass  (1.38 M_⊙)  , but a kinetic energy reduced by ∼30 per cent (i.e. from  1.33 × 10⁵¹  to  0.93 × 10⁵¹ erg  ).     

土层地震反应传递函数的模拟

探讨了用单一土层模型替换复杂场地求解土层场地传递函数的方法,并用ＳＭＡＲＴ－１台阵地震记录对这一方法的可行性进行了研究和讨论,结果表明,只要选取适当的地震波入射角Ψ和土介质的滞回阻尼比ｄ,简化模型的传递函数与实际传递函数能符合得较好,这一方法可用来近似估计缺少详细土质勘测资料地区的土层地震反应的传递函数。     

A data‐based mechanistic modelling (DBM) approach to understanding dynamic sediment transmission through Wyresdale Park Reservoir,Lancashire, UK

This paper outlines the application of a new data‐based mechanistic (DBM) modelling methodology to the characterization of the sediment transmission dynamics in a small upland reservoir, Wyresdale Park, Lancashire. The DBM modelling strategy exploits advanced statistical procedures to infer the dynamic model structure and its associated parameters directly from the instrumented data, producing a parametrically efficient, continuous time, transfer function model which relates suspended sediment load at the reservoir inflow to the outflow at the event scale. The associated differential equation model parameters have physical attributes which can be interpreted in terms of sediment transmission processes and associated reservoir trap efficiency. Sedigraph analysis suggests that wind‐induced resuspension episodically supplies an additional load to the reservoir outlet. The stochastic nature of the DBM model makes it ideal for evaluating the effects of uncertainty through Monte Carlo simulations (MCS) for discharge and sediment transmission. Copyright © 2000 John Wiley & Sons, Ltd.     

中国沙漠（地）生态系统水文调控功能及其服务价值评估

荒漠生态系统是整个生物圈中分布较广的一个系统,是陆地生态系统中一个重要的子系统。开展荒漠生态系统服务价值研究和评价,对荒漠生态系统重要性认识和管理具有重要的现实意义。本文基于中国沙漠（地）生态系统的生态水文过程、水平衡机理和水文调控功能等,对其在淡水提供、原盐生产、水源涵养和气候调节方面的物质流——水资源进行了核算,结合不同类型生态服务价值通量,初步评估了中国荒漠生态系统在水文调控方面的服务价值。结果表明:中国沙漠（地）生态系统水文调控方面的生态服务价值为每年5 510.05亿元,其中供给服务价值370.42亿元,调节服务价值5 139.63亿元,分别占总服务价值的6.72%和93.28%。     

主体功能区划的研究现状与思考

对主体功能区划相关理论、实践方法进行了梳理和分析,综述了主体功能区划研究动态和存在问题,在此基础上,对主体功能区划进一步研究中需要解决的几个问题,如主体功能区概念内涵、主体功能区划与相关规划的关系与衔接、区域发展政策保障、主体功能区划实践技术方法中争议较多的问题如划分单元、划分方法与指标等进行了探讨。