Bridge frost prediction by heat and mass transfer methods

Frost on roadways and bridges can present hazardous conditions to motorists, particularly when it occurs in patches or on bridges when adjacent roadways are clear of frost. To minimize materials cost, vehicle corrosion, and negative environmental impacts, frost-suppression chemicals should be applied only when, where, and in appropriate amounts needed to maintain roadways in a safe condition for motorists. Accurate forecasts of frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. A finite-difference algorithm (BridgeT) has been developed that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. BridgeT simulates bridge temperatures at numerous points within the bridge (including its upper and lower surface) at each time step of the weather forecast model and calculates volume per unit area (i.e., depth) of frost deposited, melted, or sublimed. This model produces forecasts of bridge surface temperature, frost depth, and bridge condition (i.e., dry, wet, icy/snowy). Early-morning observations of untreated bridges near Ames, Iowa, during the past two winter seasons establishes a database of bridge frost occurrences and non-occurrences. When frost was detected, observations were continued until the frost disappeared, thereby providing additional information on duration and timing of onset and demise of frost. Bridge frost predictions and bridge surface temperature are compared with observed and measured values to assess BridgeT\u27s skill in forecasting bridge frost and associated conditions. Sensitivity studies were conducted to assess the impacts of input quality and bridge property specification

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

Bridge frost prediction by heat and mass transfer methods

Frost on roadways and bridges can present hazardous conditions to motorists, particularly when it occurs in patches or on bridges when adjacent roadways are clear of frost. To minimize materials cost, vehicle corrosion, and negative environmental impacts, frost-suppression chemicals should be applied only when, where, and in appropriate amounts needed to maintain roadways in a safe condition for motorists. Accurate forecasts of frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. A finite-difference algorithm (BridgeT) has been developed that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. BridgeT simulates bridge temperatures at numerous points within the bridge (including its upper and lower surface) at each time step of the weather forecast model and calculates volume per unit area (i.e., depth) of frost deposited, melted, or sublimed. This model produces forecasts of bridge surface temperature, frost depth, and bridge condition (i.e., dry, wet, icy/snowy). Early-morning observations of untreated bridges near Ames, Iowa, during the past two winter seasons establishes a database of bridge frost occurrences and non-occurrences. When frost was detected, observations were continued until the frost disappeared, thereby providing additional information on duration and timing of onset and demise of frost. Bridge frost predictions and bridge surface temperature are compared with observed and measured values to assess BridgeT's skill in forecasting bridge frost and associated conditions. Sensitivity studies were conducted to assess the impacts of input quality and bridge property specification.</p

Bridge Frost Prediction by Heat and Mass Transfer Methods

Frost on roadways and bridges can present hazardous conditions to motorists, particularly when it occurs in patches or on bridges when adjacent roadways are clear of frost. To minimize materials costs, vehicle corrosion, and negative environmental impacts, frost-suppression chemicals should be applied only when, where, and in the appropriate amounts needed to maintain roadways in a safe condition for motorists. Accurate forecasts of frost onset times, frost intensity, and frost disappearance (e.g., melting or sublimation) are needed to help roadway maintenance personnel decide when, where, and how much frost-suppression chemical to use. A finite-difference algorithm (BridgeT) has been developed that simulates vertical heat transfer in a bridge based on evolving meteorological conditions at its top and bottom as supplied by a weather forecast model. BridgeT simulates bridge temperatures at numerous points within the bridge (including its upper and lower surface) at each time step of the weather forecast model and calculates volume per unit area (i.e., depth) of deposited, melted, or sublimed frost. This model produces forecasts of bridge surface temperature, frost depth, and bridge condition (i.e., dry, wet, icy/snowy). Bridge frost predictions and bridge surface temperature are compared with observed and measured values to assess BridgeT's skill in forecasting bridge frost and associated conditions.This article is published as Greenfield, Tina M., and Eugene S. Takle. "Bridge frost prediction by heat and mass transfer methods." Journal of applied meteorology and climatology 45, no. 3 (2006): 517-525. DOI:10.1175/JAM2356.1. Posted with permission.</p

Provisioning the Early Bronze Age City of Tell es-Safi/Gath, Israel: Isotopic Analyses of Domestic Livestock Management Patterns

It is often assumed that domestic animals in early urban Near Eastern centres either are a reflection of the local pastoral economy, or were raised at a distance by pastoral specialists. In this paper, we test these assumptions through detailed isotopic analyses (carbon, oxygen and strontium) of caprines (sheep and goat) from Tell es-Safi/Gath, an Early Bronze Age urban centre in central Israel. The isotopic analyses demonstrate that the bulk of the caprines were raised within the general vicinity of the site, suggesting that the majority of food resources were largely produced at the local level, within the territory of the city-state, and not at a distance by specialised pastoralists. It is the rare specimen that comes from a great distance and would have entered the local system through long distance trade networks