Tracer Flux Balance at an Urban Canyon Intersection

Despite their importance for pollutant dispersion in urban areas, the special features of dispersion at street intersections are rarely taken into account by operational air quality models. Several previous studies have demonstrated the complex flow patterns that occur at street intersections, even with simple geometry. This study presents results from wind-tunnel experiments on a reduced scale model of a complex but realistic urban intersection, located in central London. Tracer concentration measurements were used to derive three-dimensional maps of the concentration field within the intersection. In combination with a previous study (Carpentieri et al., Boundary-Layer Meteorol 133:277–296, 2009) where the velocity field was measured in the same model, a methodology for the calculation of the mean tracer flux balance at the intersection was developed and applied. The calculation highlighted several limitations of current state-of-the-art canyon dispersion models, arising mainly from the complex geometry of the intersection. Despite its limitations, the proposed methodology could be further developed in order to derive, assess and implement street intersection dispersion models for complex urban areas

An operational method for assessing traffic-related air pollution in urban streets

Urban air quality has been a topic of major public concern and scientific research in recent years. Several theoretical and experimental studies have focused on the assessment of air quality within street canyons and other microenvironments (intersections, motorways, parking spaces, etc.), where population exposure to traffic-related pollutants is relatively high. The aim of this study was to develop a practical methodology for assessing traffic-related air pollution in urban streets, after testing available monitoring and modelling techniques. To meet this objective, a large amount of original air quality, meteorological and traffic data were collected during four intensive short-term and one long-term monitoring campaigns carried out in the region of Paris from December 1998 to December 2001. These campaigns covered three representative street canyon sites (Bd. Voltaire, Rue de Rennes, Av. Leclerc - PI. Basch) as well as a motorway service station (RN10 petrol station). Passive and active monitoring techniques were used to sample a wide range of inorganic (CO, NO X and Os) and organic gases (benzene, toluene, xylene, ethylbenzene, formaldehyde, acetaldehyde, etc.) at different heights and distances from the kerb. Indicative background measurements were also taken during the same sampling periods. Furthermore, relevant meteorological (synoptic and local) and traffic information was obtained on each site. The analysis of the data gave insights into the dispersion and transformation processes taking place within the streets. Channelling effects induced by parallel to the road axis winds gave rise to relatively high kerbside pollution levels. On the other hand, perpendicular synoptic winds generated air vortices within the canyons, which resulted in steep crossroad concentration gradients. In that case, higher pollution levels were observed on the leeward than on the windward side of the streets. A significant reduction of concentrations with height above the ground was also observed within two of the street canyons (Bd. Voltaire and Av. Leclerc). In all cases, roadside concentrations were several times higher than the corresponding urban background values. This spatial variability indicates a strong transport effect on the pollutant distribution within urban canyons, caused by the synoptic wind and influenced by the geometry of the street. That may have serious implications in terms of population exposure and compliance with air quality legislation. In this context, the siting of permanent monitoring equipment becomes crucial. A relationship between CO and benzene as well as an exponential expression linking pollutant concentrations at different heights within the canyons were empirically deduced. Five dispersion models of different levels of complexity (STREET-SRI, OSPM, AEOLIUS, CAR-International, and CALINE4) were used to calculate CO and benzene concentrations at the campaign sites. The Computational Fluid Dynamic code PHOENICS was also tested for one location. The comparison between observed and predicted values revealed the advantages and drawbacks of each model in association with the configuration of the street and the meteorological conditions. Furthermore, a sensitivity and uncertainty analysis involving three of the available models (STREET-SRI, OSPM and AEOLIUS) was carried out. OSPM was slightly modified in order to allow user access to certain internally coded parameters. An operational method combining multi-site sampling and dispersion modelling was finally proposed for assessing air quality in urban streets, taking into account the pronounced spatial and temporal variability of traffic-related air pollution, the modelling uncertainty, the practical constraints related to measurements and models, and the needs of decision makers. This methodology may find wider application in air quality management, urban and transport planning, and population exposure studies

Traffic pollution modelling in a complex urban street

This study explores for the first time, the applicability of the Danish Operational Street Pollution Model (OSPM) in the city of Buenos Aires where street canyons are very irregular. The model is applied in an irregular and asymmetric street canyon of a five-lane avenue near a street intersection. Urban background concentrations estimated by the DAUMOD model are considered. Meteorological information registered at the domestic airport located in the city is used in calculations. Three months of hourly NOx, NO 2 and CO estimated concentrations are compared with measurements inside the street canyon. Statistical evaluation of model results shows that OSPM performance is quite good.Fil: Venegas, Laura Esperanza. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional; ArgentinaFil: Mazzeo, Nicolas Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional; Argentin

La modelación y la gestión en el mejoramiento de la calidad del aire

This paper provides a review of international trends used in connection with modeling and management of urban air quality. According to specialized literature on this topic, the most common actions are dose-response evaluation, modeling, monitoring, emission control, and planning. The methodology implemented consisted of a procedure for managing measures to control atmospheric pollutants from fixed and mobile sources in order to pursue initiatives aimed at minimizing the risks posed by air pollution to health and the environment. This resulted in an atmospheric emission inventory, which can be used for improving air quality management efforts, and three different kinds of software applications that can be used as technical support tools for receiving, analyzing, and monitoring data. As a conclusion, the procedure for the Environmental Territorial Authority (ETA) to manage measures for controlling atmospheric pollutants from fixed and mobile sources is a promising management tool aimed at minimizing the health and environmental risks associated with air pollutionEl artículo analiza las tendencias internacionales utilizadas sobre la modelación y la gestión implementada en el manejo de la calidad del aire urbano. La literatura especializada establece que las acciones más empleadas son la evaluación dosis-respuesta, modelación, monitoreo, control de emisiones y planificación. La metodología que se implementó fue un procedimiento para la gestión de las medidas de control de contaminantes atmosféricos de fuentes móviles y fijas para adelantar una gestión, orientada a minimizar los riesgos que presenta la contaminación del aire en el ambiente y la salud. Como resultado, se obtiene un inventario de emisiones atmosféricas para mejorar la gestión en el manejo de la calidad del aire, y tres software como soporte técnico para las fases de recepción, análisis y control de datos. Se concluye que el procedimiento para gestionar las medidas de control de contaminantes atmosféricos de fuentes móviles y fijas en la Autoridad Territorial Ambiental (ATA) se perfila como una herramienta de gestión orientada a minimizar los riesgos que presenta la contaminación del aire en el ambiente y la salud

Air pollution in urban canyons

La contaminación del aire es un problema creciente en los grandes centros urbanos. En las ciudades, las emisiones provenientes del tránsito automotor pueden generar niveles elevados de concentración de contaminantes. Los mayores niveles se presentan en el interior de los cañones urbanos, donde la dilución atmosférica de los contaminantes emitidos por los vehículos está limitada significativamente por los edificios que bordean las calles. La Tesis tiene como objetivo principal presentar el desarrollo y la evaluación de un modelo operacional (Semi-Empirical Urban Street (SEUS)) destinado a estimar la concentración de contaminantes pasivos y de NO2 (adicionando un esquema fotoquímico) en aire dentro de cañones urbanos. SEUS es un modelo que requiere poca información de entrada. Puede ser implementado fácilmente en una planilla de cálculo, no requiriendo grandes tiempos computacionales. Las variables de entrada de SEUS son el caudal másico de emisión por unidad de longitud, el ancho del cañón, la escala de velocidad dispersiva (suma de la turbulencia natural del aire y de la inducida por el movimiento de los automotores) y la concentración de fondo urbana. Se desarrollan formas funcionales empíricas de parámetros incluidos en las formulaciones de las dos turbulencias mencionadas. Se analiza la sensibilidad de los resultados de SEUS de las variables de entrada. El modelo es evaluado con información proveniente de tres cañones urbanos. Diferentes indicadores estadísticos muestran que existe buena concordancia entre los valores estimados y observados. Asimismo se compara las estimaciones obtenidas aplicando SEUS con las de otros modelos.Air pollution is an increasing problem in urban areas. In cities, emissions from vehicles can generate high pollution concentration levels. The highest levels are present inside urban canyons, where atmospheric dilution of pollution emitted by vehicles is significantly limited by buildings surrounding the streets. The development and evaluation of an operational model (Semi-Empirical Urban Street (SEUS)) for estimate the passive air pollution and NO2 concentrations (adding a simple photochemistry scheme) inside street urban canyons are presented. SEUS is a semi-empirical model which requires small input information. It can be applied to different wind directions. Because of its simplicity it can be easily implemented in a spreadsheet, without requiring large computational times. The input variables are: the emission rate, the width of the canyon, the dispersive velocity scale (ambient turbulence plus traffic-induced turbulence) and the background concentration. The dispersive velocity scale depends on turbulent motions related to wind and traffic. Functional forms of empirical parameters are developed including the two types of turbulence mentioned above. The sensitivity of the SEUS results is analyzed in light of the input variables. This model is tested with data from three urban canyons. Different statistical indicators show that there is good agreement between estimated and observed values. Estimations using SEUS with other model estimations are also compared.Fil: Dezzutti, Mariana Clara. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Water rights and related water supply issues

Presented during the USCID water management conference held on October 13-16, 2004 in Salt Lake City, Utah. The theme of the conference was "Water rights and related water supply issues."Includes bibliographical references.Proceedings sponsored by the U.S. Department of the Interior, Central Utah Project Completion Act Office and the U.S. Committee on Irrigation and Drainage.Consensus building as a primary tool to resolve water supply conflicts -- Administration to Colorado River allocations: the Law of the River and the Colorado River Water Delivery Agreement of 2003 -- Irrigation management in Afghanistan: the tradition of Mirabs -- Institutional reforms in irrigation sector of Pakistan: an approach towards integrated water resource management -- On-line and real-time water right allocation in Utah's Sevier River basin -- Improving equity of water distribution: the challenge for farmer organizations in Sindh, Pakistan -- Impacts from transboundary water rights violations in South Asia -- Impacts of water conservation and Endangered Species Act on large water project planning, Utah Lake Drainage Basin Water Delivery System, Bonneville Unit of the Central Utah Project -- Economic importance and environmental challenges of the Awash River basin to Ethiopia -- Accomplishing the impossible: overcoming obstacles of a combined irrigation project -- Estimating actual evapotranspiration without land use classification -- Improving water management in irrigated agricultue -- Beneficial uses of treated drainage water -- Comparative assessment of risk mitigation options for irrigated agricutlrue -- A multi-variable approach for the command of Canal de Provence Aix Nord Water Supply Subsystem -- Hierarchical Bayesian Analysis and Statistical Learning Theory II: water management application -- Soil moisture data collection and water supply forecasting -- Development and implementation of a farm water conservation program within the Coachella Valley Water District, California -- Concepts of ground water recharge and well augmentation in northeastern Colorado -- Water banking in Colorado: an experiment in trouble? -- Estimating conservable water in the Klamath Irrigation Project -- Socio-economic impacts of land retirement in Westlands Water District -- EPDM rubber lining system chosen to save valuable irrigation water -- A user-centered approach to develop decision support systems for estimating pumping and augmentation needs in Colorado's South Platte basin -- Utah's Tri-County Automation Project -- Using HEC-RAS to model canal systems -- Potential water and energy conservation and improved flexibility for water users in the Oasis area of the Coachella Valley Water District, California

Data bases and data base systems related to NASA's aerospace program. A bibliography with indexes

This bibliography lists 1778 reports, articles, and other documents introduced into the NASA scientific and technical information system, 1975 through 1980

Investigating value propositions in social media: studies of brand and customer exchanges on Twitter

Social media presents one of the richest forums to investigate publicly explicit brand value propositions and its corresponding customer engagement. Seldom have researchers investigated the nature of value propositions available on social media and the insights that can be unearthed from available data. This work bridges this gap by studying the value propositions available on the Twitter platform. This thesis presents six different studies conducted to examine the nature of value propositions. The first study presents a value taxonomy comprising 15 value propositions that are identified in brand tweets. This taxonomy is tested for construct validity using a Delphi panel of 10 experts – 5 from information science and 5 from marketing. The second study demonstrates the utility of the taxonomy developed by identifying the 15 value propositions from brand tweets (nb=658) of the top-10 coffee brands using content analysis. The third study investigates the feedback provided by customers (nc=12077) for values propositioned by the top-10 coffee brands (for the 658 brand tweets). Also, it investigates which value propositions embedded in brand tweets attract ‘shallow’ vs. ‘deep’ engagement from customers. The fourth study is a replication of studies 2 and 3 for a different time-period. The data considered for studies 2 and 3 was for a 3-month period in 2015. In the fourth study, Twitter data for the same brands was analysed for a different (nb=290, nc=8811) 3-month period in 2018. This study thus examines the nature of change in value propositions across brands over time. The fifth study was on generalizability and replicates the investigation of brand and customer tweets (nb=635, nc=7035) in the market domain of the top-10 car brands in 2018. Lastly, study six conducted an evaluation of a software system called Value Analysis Toolkit (VAT) that was constructed based on the research findings in studies 1 - 5. This tool is targeted at researchers and practitioners who can use the tool to obtain value proposition-based insights from social media data (brand value propositions and the corresponding feedback from customers). The developed tool is evaluated for external validity using 35 students and 5 industry participants in three dimensions (tool’s analytics features, usability and usefulness). Overall, the contributions of this thesis are: a) a taxonomy to identify value propositions in Twitter (study 1) b) an approach to extract value proposition-based insights in brand tweets and the corresponding feedback from customers in the process of value co-creation (studies 2 - 5) for the top-10 coffee and car brands, and c) an operational tool (study 6) that can be used to analyse value propositions of various brands (e.g., compare value propositions of different brands), and identify which value propositions attract positive electronic word of mouth (eWOM). These value proposition-based insights can be used by social media managers to devise social-media strategies that are likely to stimulate positive discussions about a brand in social media

U.S. Commission on Immigration Reform

The U.S. Commission on Immigration Reform was created by Congress to assess U.S. immigration policy and make recommendations regarding its implementation and effects. Mandated in the Immigration Act of 1990 to submit an interim report in 1994 and a final report in 1997, the Commission has undertaken public hearings, fact-finding missions, and expert consultations to identify the major immigration-related issues facing the United States today.LBJ School of Public Affair