宽频带模态识别算法中极点的自动选取

摘在试验模态分析中,确定系统阶次以及极点的正确选择是一个非常重要的问题。到目前为止,这项工作一般是由人工来完成。但是在复杂或者大阻尼结构中,这个过程尤其繁琐并且耗时。本文中采用模糊聚类方法对极点进行分类,实现了极点的自动选取,减少了人工选取的工作量。     

FeSO4稳定铬污染土的铬赋存形态及浸出特性研究

采用硫酸亚铁（FeSO4）对Cr(VI)污染土进行稳定化处理。研究了Fe(II)/Cr(VI)摩尔比和养护龄期对污染土稳定过程中的铬赋存形态及浸出特性的影响规律。结果表明：随着Fe(II)/Cr(VI)摩尔比和养护龄期的增加,Cr(VI)和总Cr的浸出浓度降低,稳定土中Cr(VI)的含量降低,当摩尔比为3时,Cr(VI)和总Cr的浸出浓度均低于我国《危险废弃物鉴别标准 浸出毒性鉴别》（GB/T50853―2007）的限值;当摩尔比为10时,稳定土中Cr(VI)的含量低于我国《土壤环境质量标准》（GB15618―2008）中工业和商业用地的限值（30 mg/kg）;当摩尔比为20时,低于居住用地限值（5 mg/kg）。形态提取试验结果表明：FeSO4改变稳定土中铬的赋存形态,可促使铬从弱酸态向可还原态和可氧化态转化,而对残渣态的铬影响不大。Cr(VI)的浸出浓度与稳定土中的Cr(VI)含量均存在指数函数关系,且浸出试验不能全面、客观地评价铬污染土稳定效果。     

砾岩边坡稳定性分析与防治工程

沪蓉国道主干线宜昌至恩施段高速公路,是国家“五纵七横“交通网的重要组成部分,其砾岩边坡稳定性分析与防治工程是重要的研究课题。本文以砾岩岩体结构面模拟研究,岩体力学参数估算为基础,结合砾岩特征及边坡地质环境条件,提出砾岩边坡稳定性评价的地质模型,并采用数值模拟与计算,得出砾岩边坡稳定性分析的确切结果。砾岩边坡岩土工程加固设计是关系到该高速公路安全、经济、适用的重要内容,紧密结合砾岩边坡的地质环境和砾岩岩体特征,采用信息化设计,运用生态化设计理念,充分发挥岩土工程技术优势,保护环境,提出合理的岩土工程加固设计方案。本研究成果对砾岩边坡防治工程提出了系统的研究思路,对沪蓉国道主干线宜昌至恩施段高速公路砾岩边坡的设计与施工具重要意义。     

The nonlinear stabilization of a zonal shear flow instability

Abstract

The development of initially small perturbations in a weakly supercritical zonal shear flow on a β-plane is studied. Two different scenarios of evolution are possible. If the supercriticality is sufficiently small, the growth of a perturbation is stopped in the viscous critical layer regime; for this case the evolution equation (corrected by the inclusion of a quintic nonlinearity) is derived. At greater supercriticality the nonlinearity cannot stop the growth of the perturbation in a linear (viscous or unsteady) critical layer regime, and the evolution is more complicated. Transition to a nonlinear critical layer regime leads to a reduction in the growth rate and to a slowing (but not a stopping) of the increase in amplitude, A. These are connected to the formation of a plateau (S=constant) of width L=O(A ^½) in the profile of absolute vorticity, S. Careful analysis reveals that the growth in amplitude ceases only when the whole instability domain (where the slope of unperturbed S-profile is positive) becomes covered again by the plateau.     

Evaluation of Carcinogenic Risk Due to Accidental Ingestion of PAHs in Contaminated Soils

Polycyclic aromatic hydrocarbons (PAHs) are types of hazardous contaminants, which their ingestion could cause severe consequences on human health. Leakages from storage tanks, underground pipelines, and evaporation ponds are the main sources of soil and groundwater contaminations at the Tehran Oil Refinery area (TOR site), located in south of Tehran, Iran. In this study, soil samples were collected from different locations at and adjacent to a polluted stream in the south of the refinery. The samples were analyzed for two hazardous PAH compounds, namely benzo[a]anthracene and acenaphthene. The clean up levels due to the accidental ingestion of contaminated soils at the site were also investigated in accordance to the U.S.EPA guidelines. Comparing the soil analysis results indicated that the benzo[a]anthracene concentrations in the samples varied from 53 to 299 mg/kg, which were higher than the clean up level of 1.17 mg/kg. Thus, soil remediation is required for this contaminant. The acenaphthene analysis results denoted that the average concentration of this contaminant was below the clean up level of 116.67 mg/kg, indicating that no treatment for this contaminant is necessary at the TOR site. Also, because the slope of the ground extends to the south of the stream, which stimulates the migration of the contaminants in this direction due to advection and dispersion mechanisms, the average of benzo[a]anthracene concentrations in south samples was higher than north samples (i.e., C_avg(S) = 160 ppm, C_avg(N) = 113 ppm). Various treatment techniques such as thermal desorption, soil vapor extraction (SVE), and solidification/stabilization (S/S) were investigated for this site. Due to moderate to high plasticity and relatively low permeability of the soil and low volatility of benzo[a]anthracene, however S/S method is recommended as a practical approach for the remediation of the soil at the site.     

静压灌浆技术在某化验楼地基加固中的应用

某化验楼因不均匀沉降,造成墙体和地面开裂,根据该楼地基松散填土具有高压缩性、性质差异大、欠固结等地质特性,采取静压灌浆法加固该地基,使其地基土承载力标准值提高了2～3倍,静压灌浆后建筑物停止沉降,效果显著。     

随机微分方程的稳定性理论:方法概述

从所应用的主要方法出发,回顾了随机连续系统的各种稳定性理论结果,并探讨了这些稳定性之间的关系.     

Biogenic soil crusts and soil depth: a long‐term case study from the Central Negev desert highland

Wind‐blown soil degradation is a major problem in arid regions. Biogenic soil crust consists of a dense growth of many small organisms covering bare desert soil surfaces in arid regions worldwide. These organisms perform essential services in the ecosystem, for example, soil surface stabilization and carbon and nitrogen fixation. A unique service provided by biogenic crusts is the incorporation of large quantities of deposited atmospheric particles, leading to a significantly enhanced rate of increase in soil depth in windy and arid environments. A long‐term study (over 42 months) was conducted to investigate the contribution of a biogenic crust to the accumulation of atmospheric particles in an arid zone. Undisturbed and treated biogenic crusts were studied for their capacity to incorporate deposited particles. Atmospheric particles were found to accumulate on marble dust collectors at a rate of 120 g m^?2 year^?1 and on sterilized crust at a rate of 208 g m^?2 year^?1, while the accumulation rate on live, intact crusts was 277 g m^?2 year^?1, suggesting a soil depth accretion rate on an undisturbed biogenic crust of 10 mm every 33 years. Maintenance of a healthy biogenic crust in dry land environments should, therefore, be a major consideration for improving soil quality and increasing soil depth in arid regions.     

Global Triptych: a bottom-up approach for the differentiation of commitments under the Climate Convention

Abstract

In the coming years the international debate on commitments for the second commitment period under the Kyoto Protocol will intensify. In this study, the Global Triptych approach is put forward as an input for international decision-making concerning the differentiation of commitments by 2020. It is a sector- and technology-oriented approach, and we calculated quantitative emission limitation objectives and global emissions starting from bottomup information on long-term reduction opportunities. Central to the calculations were long-term sustainability targets for the year 2050, formulated for (1) energy efficiency in the energy-intensive industry, (2) greenhouse gas intensity of electricity production, and (3) per capita emissions in the domestic sectors. Calculated emission limitation objectives for 13 world regions ranged from about ?30% to more than +200%. The ranking of world regions in the differentiation turned out to be independent of the levels chosen for the long-term sustainability targets. The objectives seem sufficient to maintain the long-term possibility of stabilizing atmospheric greenhouse gas concentrations at about 550 ppm CO₂-eq, but will require severe emission reductions. These may be relaxed to a certain degree if stabilization at 650 ppm CO₂-eq is aimed for. We conclude that the bottom-up character of the approach made it possible to examine important basic principles of the Climate Convention, including equity, the needs and circumstances of developing countries, cost-effectiveness and sustainable development.     

National GHG emissions reduction pledges and 2°C: comparison of studies

This article provides further detail on expected global GHG emission levels in 2020, based on the Emissions Gap Report (United Nations Environment Programme, December 2010), assuming the emission reduction proposals in the Copenhagen Accord and Cancun Agreements are met. Large differences are found in the results of individual groups owing to uncertainties in current and projected emission estimates and in the interpretation of the reduction proposals. Regardless of these uncertainties, the pledges for 2020 are expected to deliver emission levels above those that are consistent with a 2°C limit. This emissions gap could be narrowed through implementing the more stringent conditional pledges, minimizing the use of ‘lenient’ credits from forests and surplus emission units, avoiding double-counting of offsets and implementing measures beyond current pledges. Conversely, emission reduction gains from countries moving from their low to high ambition pledges could be more than offset by the use of ‘lenient’ land use, land-use change and forestry (LULUCF) credits and surplus emissions units, if these were used to the maximum. Laying the groundwork for faster emission reduction rates after 2020 appears to be crucial in any case.