Design drivers for affordable and sustainable housing in developing countries

Current demand for housing worldwide has reached unprecedented levels due to factors such as human population growth, natural disasters and conflict. This is felt no more so than in developing countries which have experienced disproportionate levels of demand due to their innate vulnerability. Many current approaches to housing delivery in developing countries continue to utilize inappropriate construction methods and implementation procedures that are often problematic and unsustainable. As such affordability and sustainability are now vital considerations in the international development debate for housing the poor in developing countries in order to meet the long term sustainable development goals and needs of housing inhabitants. This paper utilized an extensive scoping study to examine the various facets impacting on design decision making relative to sustainable and affordable housing delivery in developing country contexts. Aspects of affordability, sustainability, design decision making, appropriate technology use, cultural awareness, as well as current barriers to affordable and sustainable construction in developing countries are examined in detail. Results highlighted the capability of indigenous knowledge, skills and materials as well as selected appropriate technology transfer and cultural awareness by foreign bodies can be utilized in innovative ways in addressing current housing needs in many developing country contexts

Cubic Curves, Finite Geometry and Cryptography

Some geometry on non-singular cubic curves, mainly over finite fields, is surveyed. Such a curve has 9,3,1 or 0 points of inflexion, and cubic curves are classified accordingly. The group structure and the possible numbers of rational points are also surveyed. A possible strengthening of the security of elliptic curve cryptography is proposed using a `shared secret' related to the group law. Cubic curves are also used in a new way to construct sets of points having various combinatorial and geometric properties that are of particular interest in finite Desarguesian planes.Comment: This is a version of our article to appear in Acta Applicandae Mathematicae. In this version, we have corrected a sentence in the third paragraph. The final publication is available at springerlink.com at http://www.springerlink.com/content/xh85647871215644

Harmonic analysis of the stability of reverse routing in channels

International audienceNormal downstream routing of a flood flow is a highly stable process for Froude numbers less than 1 and hence the results are reliable. In contrast, reverse routing in an upstream direction, which may be required for flow control, is potentially unstable. This paper reports the results of a study of the practical limits on channel lengths for reverse routing. Harmonic analysis is applied to the full non-linear solution of the St. Venant equations for three different wave patterns and two different wave periods, for a particular channel with a Froude number of 0.5. Reverse routing can be done for prismatic channels longer than 100 km. For long periods (>10 hours) the shape of the upstream hydrograph is recovered well. However, when the wave period is short (<1 hour), the high frequency components of the upstream hydrograph and, thus, its shape, are not recovered. These limits are influenced by the channel morphology and shape of the wave. Further work is needed to determine how these factors interact

Root selection methods in flood analysis

International audienceIn the 1970s, de Laine developed a root-matching procedure for estimating unit hydrograph ordinates from estimates of the fast component of the total runoff from multiple storms. Later, Turner produced a root selection method which required only data from one storm event and was based on recognising a pattern typical of unit hydrograph roots. Both methods required direct runoff data, i.e. prior separation of the slow response. This paper introduces a further refinement, called root separation, which allows the estimation of both the unit hydrograph ordinates and the effective precipitation from the full discharge hydrograph. It is based on recognising and separating the quicker component of the response from the much slower components due to interflow and/or baseflow. The method analyses the z-transform roots of carefully selected segments of the full hydrograph. The root patterns of these separate segments tend to be dominated by either the fast response or the slow response. This paper shows how their respective time-scales can be distinguished with an accuracy sufficient for practical purposes. As an illustration, theoretical equations are derived for a conceptual rainfall-runoff system with the input split between fast and slow reservoirs in parallel. These are solved analytically to identify the reservoir constants and the input splitting parameter. The proposed method, called "root separation", avoids the subjective selection of rainfall roots in the Turner method as well as the subjective matching of roots in the original de Laine method. Keywords: unit hydrograph,identification methods, z-transform, polynomial roots, root separation, fast andslow response, Nash cascade</p

A modified Muskingum routing approach for floodplain flows: theory and practice

Hydrological or hydraulic flood routing methods can be used to predict the floodplain influences on a flood wave as it passes along a river reach. While hydraulic routing uses both the equation of continuity and the equation of momentum to describe the dynamics of river flows, the simpler data requirements of hydrological routing makes it useful for preliminary estimates of the time and shape of a flood wave at successive points along a river. This paper presents a modified linear Muskingum hydrological routing method where the floodplain effects on flood peak attenuation and flood wave travel time are included in routing parameters. Developing the routing parameters initially involved routing hydrographs of different flood peak and duration through a 1-dimensional model of a generalised river reach in which a range of geometrical and resistance properties were varied. Comparison of upstream and simulated downstream hydrographs for each condition investigated, allowed the attenuation and travel time (storage constant, K, in standard Muskingum routing) of the flood wave to be estimated. Standard Muskingum 1 routing was then used to develop downstream hydrographs for each K value together with assumed storage weighting factors (x) ranging from 0 to 0.5. Flood peak attenuations were again determined through comparison of the upstream and routed downstream hydrographs and with these, linear relationships between x and these attenuations were developed. Actual weighting factors, corresponding to storage constants, were subsequently determined using these relationships for all attenuations determined from the 1-dimensional model simulations. Using multi-variate regression analysis, the computed values of K and x were correlated to catchment and hydrograph properties and expressions for determining both K and x in terms of these properties were developed. The modified Muskingum routing method based on these regressed expressions for K and x was applied to a case study of the River Suir in Ireland where good agreement between measured and routed hydrographs was observed.Deposited by bulk importTS 11.02.1

The Economic Stimulus: Gauging the Early Effects of ARRA Funding on Health Centers and Medically Underserved Populations and Communities

During times of economic crisis, community health centers and other health care safety net providers become even more vital to the communities they serve. The current downturn, with its high levels of unemployment and enormous impact on family incomes, carries major implications for health insurance coverage. The American Recovery and Reinvestment Act (ARRA), signed into law on February 17, 2009, provided slightly more than two billion dollars to community health centers for capital improvements, expansion (or retention) of personnel and services, and adoption of health information technology. All of these uses not only support health centers\u27 mission to serve populations with limited access to health care, such as the uninsured, low-income populations, minorities, and the homeless, but also generate new economic activities in communities hit hardest by the recession: More than 1,100 health centers throughout the United States have received ARRA funding to date. These centers are projected to serve 21 million persons in 2011, including nearly three million new patients as a direct result of ARRA funding. By targeting health centers, ARRA effectively provides needed health resources to populations at higher risk of poor health. Community health centers receiving ARRA funding tend to be located in areas with higher rates of unemployment and recent job losses. The average unemployment rate among counties with health center ARRA grantees was 9.6 percent compared to an average rate of 9.0 percent in all other counties; the average unemployment rate grew by 4.4 percent in counties with health centers compared to 4.0 percent in all other counties. The $1.85 billion invested to date in health centers under ARRA translates into$3.2 billion in new economic activity in these communities, suggesting that health centers are able to rapidly transform an infusion of funding into new services and expanded jobs. These findings indicate that ARRA has achieved its goal of directing resources into those communities that tend to bear the heaviest burden of an economic downturn, and have low community incomes, a disproportionate percentage of low wage workers, inadequate primary care access, and elevated health risks. However, the challenge lies in sustaining this expansion and assuring that the ability of health centers to respond to community needs is maintained even as overall economic circumstances begin to improve. Reforms contained in both the House and Senate bills, such as expanded Medicaid coverage for low income patients and direct investment in health center expansions, hold the greatest promise for operational sustainability and growth

Assessing the applicability of the Revised Universal Soil Loss Equation (RUSLE) to Irish Catchments

Elevated suspended sediment concentrations in fluvial environments have important implications for system ecology and even small concentrations may have serious consequences for sensitive ecosystems or organisms, such as freshwater pearl mussels (<i>Margaritifera margaritifera</i>). Informed decision making is therefore required for land managers to understand and control soil erosion and sediment delivery to the river network. However, given that monitoring of sediment fluxes requires financial and human resources which are often limited at a national scale, sediment mobilisation and delivery models are commonly used for sediment yield estimation and management. The Revised Universal Soil Loss Equation (RUSLE) is the most widely used model for overland flow erosion and can, when combined with a sediment delivery ratio (SDR), provide reasonable sediment load estimations for a catchment. This paper presents RUSLE factors established from extant GIS and rainfall datasets that are incorporated into a flexible catchment modelling approach. We believe that this is the first time that results from a RUSLE application at a national scale are tested against measured sediment yield values available from Ireland. An initial assessment of RUSLE applied to Irish conditions indicates an overestimation of modelled sediment yield values for most of the selected catchments. Improved methods for model and SDR factors estimation are needed to account for Irish conditions and catchment characteristics. Nonetheless, validation and testing of the model in this study using observed values is an important step towards more effective sediment yield modelling tools for nationwide applications