基础弹性刚度变化对铁路简支梁桥地震响应的影响研究

以某特大铁路简支梁桥为例 ,考虑m值变化对基础弹性刚度的影响 ,笔者建立了铁路简支梁桥单墩有限元计算分析模型 ;运用大型通用软件ANSYS ,采用时程分析方法 ,对不同地震输入激励条件下的桥墩动力响应进行计算研究 ;研究结果表明 ,m值变化引起的基础竖向刚度的变化对桥梁结构地震响应的影响较大。笔者的研究成果为硬土质基础的铁路简支梁桥的抗震安全设计 ,提供了重要参考。     

Surface runoff losses of copper and zinc in sandy soils

Increased anthropogenic inputs of Cu and Zn in soils have caused considerable concern relative to their effect on water contamination. Copper and Zn contents in surface soil directly influence the movement of Cu and Zn. However, minimal information is available on runoff losses of Cu and Zn in agricultural soils, and soil-extractable Cu and Zn in relation to runoff water quality. Field experiments were conducted in 2001 to study dissolved Cu and Zn losses in runoff in Florida sandy soils under commercial citrus and vegetable production and the relationship between soil-extractable Cu and Zn forms and dissolved Cu and Zn concentrations in runoff water. Five extraction methods were compared for extracting soil available Cu and Zn. Concentrations of dissolved Cu and Zn in runoff were measured and runoff discharge was monitored. Mean dissolved Cu in field runoff water was significantly correlated with the extractable Cu obtained only by 0.01 mol L(-1) CaCl2, Mehlich 1, or DTPA-TEA methods. Dissolved Zn in runoff water was only significantly correlated with extractable Zn by 0.01 mol L(-1) CaCl2. The highest correlations to dissolved Cu in runoff were obtained when soil-available Cu was extracted by 0.01 mol L(-1) CaCl2. The results indicate that 0.01 mol L(-1) CaCl2-extractable Cu and Zn are the best soil indexes for predicting readily released Cu and Zn in the sandy soils. Both runoff discharge and 0.01 mol L(-1) CaCl2-extractable Cu and Zn levels had significant influences on Cu and Zn loads in surface runoff.     

Rapid degradation of butachlor in wheat rhizosphere soil

The degradative characteristics of butachlor in non-rhizosphere, wheat rhizosphere, and inoculated rhizosphere soils were measured. The rate constants for the degradation of butachlor in non-rhizosphere, rhizosphere, and inoculated rhizosphere soils were measured to be 0.0385, 0.0902, 0.1091 at 1 mg/kg, 0.0348, 0.0629, 0.2355 at 10 mg/kg, and 0.0299, 0.0386, 0.0642 at 100 mg/kg, respectively. The corresponding half-lives for butachlor in the soils were calculated to be 18.0, 7.7, 6.3 days at 1 mg/kg, 19.9, 11.0, 2.9 days at 10 mg/kg, and 23.2, 18.0, 10.8 days at 100 mg/kg, respectively. The experimental results show that the degradation of butachlor can be enhanced greatly in wheat rhizosphere, and especially in the rhizosphere inoculated with the bacterial community designated HD which is capable of degrading butachlor. It could be concluded that rhizosphere soil inoculated with microorganisms-degrading target herbicides is a useful pathway to achieve rapid degradation of the herbicides in soil.     

Enzymatic characterization of organic phosphorus in animal manure

Information on the forms of P present in animal manure may improve our ability to manage manure P. In most investigations of manure P composition, only inorganic and total P are determined, and the difference between them is assigned as organic P. In this study, we explored the possibility of identifying and quantifying more specific organic P forms in animal manure with orthophosphate-releasing enzymes. Pig (Sus scrofa) manure and cattle (Bos taurus) manure were first sequentially fractionated into water-soluble P, NaHCO3-soluble P, NaOH-soluble P, HCl-soluble P, and residual P. The fractions were separately incubated with wheat phytase, alkaline phosphatase, nuclease P1, nucleotide pyrophosphatase, or their combinations. The released orthophosphate was determined by a molybdate blue method. Part of the organic P in those fractions could be identified by the enzymatic treatments as phytate (i.e., 39% for pig manure and 17% for cattle manure in water-soluble organic P), simple phosphomonoesters (i.e., 43% for pig manure and 15% for cattle manure in NaOH-soluble organic P), nucleotide-like phosphodiesters (2-12%), and nucleotide pyrophosphate (0-4%). Our data indicate that the enzymatic treatment is an effective approach to identify and quantify the organic P forms present in animal manures.     

Carbon disulfide at a Chinese viscose factory external and internal exposure assessment

This article presents the results of carbon disulfide exposure measurements in a Chinese viscose rayon factory. The objectives of the study were to identify the external exposure levels at a large factory and to investigate the 2-thiothiazolidine-4-carboxylic acid (TTCA) concentrations in the urine of the subjects who were exposed to carbon disulfide in the working place atmosphere. The metabolism of carbon disulfide in the exposed subjects was also studied in order to demonstrate the best points in time for the internal exposure sampling. The measurement of the amount of personal exposure to carbon disulfide in the air of the workplace was performed by GC-FPD; the presence of TTCA in the workers urine was analyzed by use of a modified HPLC method. The kinetics of TTCA excretion was studied by analyses at different time-points both during and after exposure to carbon disulfide in the subjects. A total of 155 personal samples were obtained. The carbon disulfide concentration in the staple viscose hall was 13.72 +/- 1.12 mg m-3 in terms of the geometric mean +/- geometric standard deviation, and was 20.05 +/- 1.33 mg m-3 in the filament spinning hall. The TTCA values in the subjects who worked in the staple spinning hall were 1.18 +/- 0.43 mg g-1 creatinine and 1.07 +/- 0.38 mg g-1 creatinine for subjects working in the filament spinning hall. The best time for TTCA sampling is at the end of the working shift, the TTCA excretion was stable for a period of 4-12 h after exposure of the subjects to the carbon disulfide. It might be that the Chinese have different anthropometric characteristics; a sampling bias may therefore appear among different races.     

提高节理面c和φ对岩坡开挖变形的影响

为了反映岩质边坡在节理面注浆后的变形效应,首先,通过室内试验,分析注浆前后岩体变形和破坏的全过程,以探讨其抗剪性能(粘结力c和内摩擦角φ)的变化;然后,基于理想弹塑性本构模型的Mohr-Cou-lomb准则,运用拉格朗日元数值方法(FLAC3D),对岩坡注浆前后变形效应(水平位移、垂直位移、剪应变增量)进行模拟。结果表明:注浆加固后,岩体的位移场变得均匀和连续,节理面处的较大位移受到抑制,边坡的整体性得到提高,有利于边坡的稳定性。     

信息安全评估的模型和方法研究

提出了信息系统安全评估及弱点管理的工作模型;明确了信息安全评估中涉及的资产、资产价值、威胁、弱点等基本概念;给出了资产赋值、威胁、弱点量化原则;同时对信息系统安全评估及弱点管理的工作模型,及综合的风险计算模型和公式给以介绍。研究工作旨在为信息安全评估工作和后续的弱点管理工作提供理论依据和参考,以提高风险评估的质量和效果,为企业的信息安全评估提供了支撑平台。同时对安全信息库的建设方式、企事业单位的信息安全评估管理体系的建设提出建议。     

Nitrogen removal from landfill leachate via ex situ nitrification and sequential in situ denitrification

Ex situ nitrification and sequential in situ denitrification represents a novel approach to nitrogen management at landfills. Simultaneous ammonia and organics removal was achieved in a continuous stirred tank reactor (CSTR). The results showed that the maximum nitrogen loading rate (NLR) and the maximum organic loading rate (OLR) was 0.65 g N l^?1 d^?1 and 3.84 g COD l^?1 d^?1, respectively. The ammonia and chemical oxygen demand (COD) removal was over 99% and 57%, respectively. In the run of the CSTR, free ammonia (FA) inhibition and low dissolved oxygen (DO) were found to be key factors affecting nitrite accumulation. In situ denitrification was studied in a municipal solid waste (MSW) column by recalculating nitrified leachate from CSTR. The decomposition of MSW was accelerated by the recirculation of nitrified leachate. Complete reduction of total oxidized nitrogen (TON) was obtained with maximum TON loading of 28.6 g N t^?1 TS d^?1 and denitrification was the main reaction responsible. Additionally, methanogenesis inhibition was observed while TON loading was over 11.4 g N t^?1 TS d^?1 and the inhibition was enhanced with the increase of TON loading.