Design, characterization, and fabrication of solar-retroreflective cool-wall materials

Raising urban albedo increases the fraction of incident sunlight returned to outer space, cooling cities and their buildings. We evaluated the angular distribution of solar radiation incident on exterior walls in 17 U S. climates to develop performance parameters for solar-retroreflective walls, then applied first-principle physics and ray-tracing simulations to explore designs. Our analysis indicates that retroreflective walls must function at large incidence angles to reflect a substantial portion of summer sunlight, and that this will be difficult to attain with materials that rely on total internal reflection. Gonio-spectrophotometer measurements of the solar spectral bi-directional reflectivity of a bicycle reflector showed little to no retroreflection at large incidence angles. Visual comparisons of retroreflection to specular first-surface reflection for four different retroreflective safety films using violet and green lasers suggest their retroreflection to be no greater than 0.09 at incidence angles up to 45°, and no greater than 0.30 at incidence angles of up to 70°. Attempts to produce a two-surface retroreflector with orthogonal mirror grooves by cutting and polishing an aluminum block indicate that residual surface roughness impedes retroreflection. Ongoing efforts focus on forming orthogonal surfaces with aluminized Mylar film, a material with very high specular reflectance across the solar spectrum. We investigated (1) folding or stamping a free film; (2) adhering the film to a pre-shaped substrate; or (3) attaching the film to a flat ductile substrate, then shaping. The latter two methods were more successful but yielded imperfect right angles

A Three-Way Decision Approach to Email Spam Filtering

Abstract. Many classification techniques used for identifying spam emails, treat spam filtering as a binary classification problem. That is, the in-coming email is either spam or non-spam. This treatment is more for mathematical simplicity other than reflecting the true state of nature. In this paper, we introduce a three-way decision approach to spam filtering based on Bayesian decision theory, which provides a more sensible feed-back to users for precautionary handling their incoming emails, thereby reduces the chances of misclassification. The main advantage of our ap-proach is that it allows the possibility of rejection, i.e., of refusing to make a decision. The undecided cases must be re-examined by collect-ing additional information. A loss function is defined to state how costly each action is, a pair of threshold values on the posterior odds ratio is systematically calculated based on the loss function, and the final deci-sion is to select the action for which the overall cost is minimum. Our experimental results show that the new approach reduces the error rate of classifying a legitimate email to spam, and provides better spam pre-cision and weighted accuracy. Key words: spam filter, three-way decision, naive Bayesian classifica-tion, Bayesian decision theory, cost

Fertility, education and development: further evidence from India

There has been a significant decline in fertility in many parts of India since the early 1980s. This paper reexamines the determinants of fertility levels and fertility decline, using panel data on Indian districts for 1981 and 1991. We find that women's education is the most important factor explaining fertility differences across the country and over time. Low levels of child mortality and son preferences also contribute to lower fertility. By contrast, general indicators of modernization and development such as urbanisation, poverty reduction, and male literacy bear no significant association with fertility. En passant, we probe a subject of much confusion - the relation between fertility decline and gender bias

Experimental validation for thermal transmittances of window shading systems with perimeter gaps

Virtually all residential and commercial windows in the U.S. have some form of window attachment, but few have been designed for energy savings. ISO 15099 presents a simulation framework to determine thermal performance of window attachments, but the model has not been validated for these products. This paper outlines a review and validation of the ISO 15099 centre-of-glass heat transfer correlations for perimeter gaps (top, bottom, and side) in naturally ventilated cavities through measurement and simulation. The thermal transmittance impact due to dimensional variations of these gaps is measured experimentally, simulated using computational fluid dynamics, and simulated utilizing simplified correlations from ISO 15099. Results show that the ISO 15099 correlations produce a mean error between measured and simulated heat flux of 2.5 ± 7%. These tolerances are similar to those obtained from sealed cavity comparisons and are deemed acceptable within the ISO 15099 framework

Water availability: A regional water quality problem

The limits to water availability are set, not only by the quantity of water in storages or streams but, more fundamentally, by acceptable levels of environmental health. An interpretation of water quality as inclusive of biological quality infers that environmental health and water quality are interdependent. Consequently, to make effective judgements of water availability managers of water resources need information that presents environmental condition in its regional context. This paper presents the results of research that explores the use of stream turbidity as an indicator of environmental condition, identifies a regional statistical model, and constructs a method to display the distribution of model predictions over a large region of south-eastern Australia. The practical advantage of this approach is that it provides managers with the ability to identify sites that differ significantly from modelled water quality and flag them for further investigation. The major project outputs are a map of regional catchments showing standardised residuals and a raster representation of the state of Victoria in which cell values indicate predicted stream turbidity. Important to this project was the novel use of Geographic Information System technology to process national and regional scale digital data sets using tools developed for catchment scale hydrological models

Experimental validation and model development for thermal transmittances of porous window screens and horizontal louvred blind systems

Virtually every home in the US has some form of shades, blinds, drapes, or other window attachment, but few have been designed for energy savings. In order to provide a common basis of comparison for thermal performance it is important to have validated simulation tools. This paper outlines a review and validation of the ISO 15099 centre-of-glass thermal transmittance correlations for naturally ventilated cavities through measurement and detailed simulations. The focus is on the impacts of room-side ventilated cavities, such as those found with solar screens and horizontal louvred blinds. The thermal transmittance of these systems is measured experimentally, simulated using computational fluid dynamics analysis, and simulated utilizing simplified correlations from ISO 15099. Correlation coefficients are proposed for the ISO 15099 algorithm that reduces the mean error between measured and simulated heat flux for typical solar screens from 16% to 3.5% and from 13% to 1% for horizontal blinds

Mapping the spatial extent of environmental health: An approach using stream turbidity

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