列车运行控制系统安全保障与认证方法研究

为了保证轨道交通系统的运行安全性,系统必须在其投入运行之前进行安全认证,只有取得相应的安全授权才能投入运行。结合CENELEC国际标准和我国应用实践,提出以安全验证和确认为基础的安全保障与认证方法,将安全验证和确认的方法贯穿于系统研制开发生命周期内的每一个阶段,监控系统研制开发的每一个活动,评审系统研制开发的每一个文档,保证相关文档之间的追溯性,针对系统的所有需求进行完备性和充分性测试,才能够确保列车运行控制系统能安全、可靠地投入使用。列车运行控制系统是轨道交通系统的重要组成部分,关系其运行安全和效率2,010年底采用安全验证和确认的方法成功地将LCF-300型列车运行控制系统应用于北京轨道交通亦庄线和昌平线,并顺利通过英国劳氏公司的第三方安全认证。     

COD在线监测仪器比对监测采样误差分析研究

化学需氧量(COD)和悬浮物(SS)是衡量污水对外界环境的污染程度的重要指标.化学需氧量是指在强酸并加热条件下,用重铬酸钾作为氧化剂处理水样时所消耗氧化剂的量.悬浮物即"不可滤残渣"是指将水过滤后留在过滤材料上的物质.针对引起比对分析监测结果中采样环节误差的原因,从理化概念入手,分析了环境样品随沉降时间不同引起的CODcr值的变化,以及CODcr值与SS值的相关性,并提出了相应的对策.以提高COD在线监测结果的科学性、可靠性,使其更好地发挥COD在线监测仪在环境管理中的作用,为污染减排和污染物总量控制工作提供准确、科学的技术支持.     

Sulfur dioxide dispersion and source contribution to receptors of downtown Patras, Greece

Background The development of the city of Patras, including harbour relocation, in conjunction with the protection of the regional ecosystems, requires air quality assessment and management. For this reason, a model applicable in the Patras area is necessary and valuable. The goal of this study was to validate a model suitable for predicting the dispersion of sulfur dioxide (SO₂), based on particular activity, topography and weather conditions. Methods We used the US-EPA ISCLT3 integral dispersion model to predict SO₂ concentrations for Patras, Greece. We assumed that the major contribution to Patras air pollution came from central heating, harbour and traffic. We calculated traffic emissions using COPERTIII. Results and Discussion Assigning suitable values of the mixing height, the model predicted the local and spatial distribution of the mean monthly SO₂ concentrations in downtown Patras, as well computed the contribution of the SO₂ emissions originating from each particular source at each receptor location on a seasonal and annual basis. The comparison between predictions and measurements shows that the model performance for estimating the SO₂ concentrations and period pattern is satisfactory. Conclusion The mixing height was the critical parameter for calibrating the model. Model validation promises satisfactory predictions for SO₂ pollution levels on monthly basis. Recommendations and Outlook The model could be used in predicting SO₂ concentrations and source contribution for several downtown Patras receptors using pertinent meteorological and emission information. It could be also extended to predict the dispersion of other primary air pollutants. The calibrated model predictions could be used to fill gaps in monitoring data, saving money and time, and help in assess and manage air quality as Patras develops.     

A Simple Model for Urban Background Pollution

A simple urban background pollution model is presented. Contributions from the individual area sources, subdivided into a grid net of a resolution of 2km × 2km, are integrated along the wind direction path assuming linear dispersion with the distance to the receptor point. Horizontal dispersion is accounted for by averaging the calculated concentrations over a certain, wind speed dependent wind direction sector, centred on the average wind direction. Formation of the nitrogen dioxide due to oxidation of nitrogen monoxide by ozone is calculated using a simple chemical model based on assumption of a photochemical equilibrium on the time scale of the pollution transport across the city area. The rate of entrainment of fresh rural ozone is governed by this time scale. The model is suitable for calculations of urban background when the dominating source is the road traffic. For this source the emissions take place at ground level, and a good approximation is to treat the emissions as area sources, but with an initial vertical dispersion determined by the height of the buildings.     

OSPM - A Parameterised Street Pollution Model

For many practical applications, as e.g. in support of air pollution management, numerical models based on solution of the basic flow and dispersion equations are still too complex. Alternative are models that are basically parameterised semi-empirical models making use of a priori assumptions about the flow and dispersion conditions. However, these models must, be thoroughly tested and their performance and limitations carefully documented. The Danish Operational Street Pollution Model (OSPM) belongs to this category of parameterised models. In the OSPM, concentrations of exhaust gases are calculated using a combination of a plume model for the direct contribution and a box model for the recirculating part of the pollutants in the street. Parameterisation of flow and dispersion conditions in street canyons was deduced from extensive analysis of experimental data and model tests. Results of these tests were used to further improve the model performance, especially with regard to different street configurations and a variety of meteorological conditions.     

Validation of an Invertebrate Community Index for Urban Streams for an Alabama Coastal Plains Watershed1

Abstract: The purpose of this study was to validate the application of an invertebrate community index (ICI) to assess the biological integrity of urban streams. Validation involved comparing chemical and habitat data to ICI scores from 20 urban streams and four least‐impacted streams in the Choctawhatchee and Pea River watersheds located in Southeast Alabama. Chemical and habitat data were collected to support whether the ICI accurately predicts the health of the streams. A significant difference between urban and least‐impacted ICI scores, habitat evaluation scores, chemical variables, taxa richness, and Shannon‐Wiener diversity were observed when urban sites were compared with least‐impacted sites using Mann‐Whitney U‐test. Urban sites having low ICI scores, low species richness and diversity, and poor habitat showed greater impairment than least‐impacted sites. Cluster analysis of macroinvertebrate assemblages indicated two clusters. Significant differences between clusters in habitat evaluations, chemical parameters, and ICI scores showed that some urban sites were more degraded than other urban sites in the study. Differentiation between least‐impacted and urban sites indicated that the ICI provided valid biotic assessments. Therefore, this study validated that the ICI is capable of predicting the biological integrity of urban streams in the Choctawhatchee and Pea River watersheds.     

Method validation for control determination of mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry

A method for the determination of total mercury in fresh fish and shrimp samples by solid sampling thermal decomposition/amalgamation atomic absorption spectrometry (TDA AAS) has been validated following international foodstuff protocols in order to fulfill the Brazilian National Residue Control Plan. The experimental parameters have been previously studied and optimized according to specific legislation on validation and inorganic contaminants in foodstuff. Linearity, sensitivity, specificity, detection and quantification limits, precision (repeatability and within-laboratory reproducibility), robustness as well as accuracy of the method have been evaluated. Linearity of response was satisfactory for the two range concentrations available on the TDA AAS equipment, between approximately 25.0 and 200.0 μg kg^?1 (square regression) and 250.0 and 2000.0 μg kg^?1 (linear regression) of mercury. The residues for both ranges were homoscedastic and independent, with normal distribution. Correlation coefficients obtained for these ranges were higher than 0.995. Limits of quantification (LOQ) and of detection of the method (LDM), based on signal standard deviation (SD) for a low-in-mercury sample, were 3.0 and 1.0 μg kg^?1, respectively. Repeatability of the method was better than 4%. Within-laboratory reproducibility achieved a relative SD better than 6%. Robustness of the current method was evaluated and pointed sample mass as a significant factor. Accuracy (assessed as the analyte recovery) was calculated on basis of the repeatability, and ranged from 89% to 99%. The obtained results showed the suitability of the present method for direct mercury measurement in fresh fish and shrimp samples and the importance of monitoring the analysis conditions for food control purposes. Additionally, the competence of this method was recognized by accreditation under the standard ISO/IEC 17025.     

Quantitative analysis of acetamiprid and imidacloprid residues in tomato fruits under greenhouse conditions

Abstract

A selective liquid chromatographic analytical method was studied for determination of two neonicotinoids, acetamiprid and imidacloprid, in tomato fruits under greenhouse conditions in Egypt. The fruits were extracted and cleaned up by QuEChERS method followed by HPLC determination. The method showed a good linearity with a determination coefficient (R²) of higher than 0.99 for the 0.0125–0.15 µg/mL concentration range. The method was validated using a blank tomato spiked at 5, 25 and 50 mg/kg and the recovery percentages were 83.71, 94.52 and 97.49% for acetamiprid and 88.59, 89.63 and 90.18% for imidacloprid, respectively. The rates of dissipation of both pesticides were studied and the preharvest intervals (PHIs) were calculated. Imidacloprid dissipated faster than acetamiprid and half-life periods were 1.30 and 2.07 days, respectively. Acetamiprid and imidacloprid residues were below the already established European maximum residue limits (EU MRLs) (0.5 mg/kg) 3 and 5 days after application, respectively.