Two calculation procedures for the determination of composition and mass thickness of thin samples by x-ray spectrometry

Two procedures are described for calculating the composition and mass thickness of thin samples from measured x-ray intensities. One procedure is suitable for use with a programmable hand calculator but gives correct results only for very thin samples. The other procedure utilizes the NRLXRF program and produces correct results for thin and thick films

Gate Delay Fault Test Generation for Non-Scan Circuits

This article presents a technique for the extension of delay fault test pattern generation to synchronous sequential circuits without making use of scan techniques. The technique relies on the coupling of TDgen, a robust combinational test pattern generator for delay faults, and SEMILET, a sequential test pattern generator for several static fault models. The approach uses a forward propagation-backward justification technique: The test pattern generation is started at the fault location, and after successful ¿local¿ test generation fault effect propagation is performed and finally a synchronising sequence to the required state is computed. The algorithm is complete for a robust gate delay fault model, which means that for every testable fault a test will be generated, assuming sufficient time. Experimental results for the ISCAS'89 benchmarks are presented in this pape

Climate Change and Global Agricultural Potential Project: A Case of Kenya

Kenya is endowed with a wide range of agro-ecological conditions, varying from hot arid lowlands to cool humid highlands. As expected, the results of the impact analysis of climate change and increases of atmospheric carbon dioxide, therefore show a wide spectrum of impacts on land resources make-up and agricultural production. At the sub-national level results of impacts on agricultural productivity vary substantially both in terms of magnitude and direction. At present, agricultural production in the low altitude areas in Kenya is mainly constrained by water availability, highland areas are constrained by low temperatures and locally by water availability, while in parts of central and western Kenya rainfall in excess of optimal levels occurs. Rising temperatures, without corresponding increases in precipitation to balance the increased plant water requirements due to higher evapotranspiration may lead to dramatic reductions in agricultural production potential, especially in eastern and southern Kenya, i.e., in parts of Eastern province, North-Eastern province and Coast province. In central and western Kenya temperature increases would result in larger extents of lands with cultivation potential, because some higher altitude areas would become suitable for cropping. This, together with potentials for higher cropping intensities in these highland areas, more than outweighs effects of diminished moisture conditions, even in scenarios assuming no change in precipitation. Under such conditions in the presently humid areas (>270 days of growing period), diminished wetness, in instances, could reduce the potential impact of pest and disease constraints. Results of the impact assessment suggest that the national level food productivity potential of Kenya may well increase with higher levels of atmospheric CO2 and climate change induced increases in temperature, provided this is accompanied by some increase in precipitation as predicted by several global circulation models. If no balanced increase in precipitation were to take place then the impact on agricultural productivity in the semi-arid parts of Kenya could be devastating. Although land productivity in Kenya as a whole appears most likely positively affected by climate change, impacts vary considerably depending on location. Negative impacts are expected to occur in Coast province and North-Eastern province. The main reasons being: -- Exceeding optimal temperature ranges for photosynthesis and growth; -- Shortening of cereal growth cycles and periods of yield formation; -- Increased water stress. For Central province, Nairobi area, important parts of Eastern province, Nyanza province and Western province the impacts are mostly positive. However, some negative impacts in western Kenya may occur due to pest and disease damage and worsening of workability conditions due to increased wetness. The high-potential agricultural lands in central and western Kenya will dominate the agricultural production potential even more under projected climate change conditions. The main reasons of positive impacts appear to be: -- Temperature increase in the mid/high altitudes, enlarging the area with crop production potential; -- Increased cropping intensity potentials; -- CO2 fertilization. In Rift Valley province, comprising of a wide range of thermal and moisture conditions, impacts are mixed. Negative impacts are, for instance, expected in Laikipia and Narok while positive impacts are anticipated in Nakuru and West Pokot. Despite of overall positive effects for Kenya as a whole, impacts of climate change on land productivity may intensify regional disparities. Therefore, preparedness is critical in order to: -- take advantage of potential blessings of climate change and increased atmospheric CO2 concentrations; -- mitigate likely negative impacts in low-lying and semi-arid areas; -- cope with the socio-economic consequences of changing patterns of land productivity. These observations are consistent with short and medium term considerations for sustainable development, emphasizing the critical need for careful planning and protection of high potential areas

Climate Change and Agricultural Vulnerability

The challenge of agriculture in the 21st century requires a systemic integration of the environmental, social and economic pillars of development to meet the needs of present generations without sacrificing the livelihoods of future generations. Over the next 50 years, the world population is projected to increase by some 3 billion, primarily in the developing countries. Yet, even today, some 800 million people go hungry daily, and more than a billion live on less than a dollar a day. This food insecurity and poverty affecting one-quarter of the world's population is a sad indictment of the failure to respond adequately in a time of unprecedented scientific progress and economic development. There is no way we can meet food security and poverty concerns without first addressing the issues of sustainable agricultural and rural development. The methodology and results reported in this study form a first comprehensive and integrated global ecological-economic assessment of the impact of climate change on agro-ecosystems in the context of the world food and agricultural system. The Food and Agriculture Organization of the United Nations (FAO) and the International Institute for Applied Systems Analysis (IIASA) have developed a comprehensive methodology based on environmental principles, referred to as the agro-ecological zones methodology. This GIS-based framework combines crop modeling and environmental matching procedures to identify crop-specific environmental limitations under various levels of inputs and management conditions. This has facilitated comprehensive and geographically detailed assessments of climate-change impacts and agricultural vulnerability. The sensitivity of agro-ecosystems to climate change, as determined by the FAO/IIASA Agro-ecological Zones (AEZ) model, was assessed within the socio-economic scenarios defined by the Intergovernmental Panel on Climate Change (IPCC) Special Report on Emissions (SRES). For this purpose, IIASA's global linked model of the world food system was used. This modeling framework, referred to as the Basic Linked System (BLS), comprises a representation of all major economic sectors, and views national agricultural systems as embedded in national economies, which in turn interact with each other at the international level. The BLS is a global general equilibrium model system for analyzing agricultural policies and food system prospects in an international setting. BLS views national agricultural systems as embedded in national economies, which interact with each other through financial flows and trade at the international level. The national models linked in the BLS cover about 80% of the most important attributes related to the world food system, such as population, land, agricultural production, demand, and trade. The remaining countries of the world are grouped into 14 regional models to provide closure for the world system, both geographically and economically. The national models simulate the behavior of producers, consumers, and the government. They distinguish two broad sectors: agriculture and non-agriculture. Agriculture produces nine aggregate commodities. The combination of AEZ and BLS provides an integrated ecological-economic framework for the assessment of the impact of climate change. We consider climate scenarios based on experiments with four General Circulation Models (GCM), and we assess the four basic socioeconomic development pathways and emission scenarios as formulated by the IPCC in its Third Assessment Report. The main results of the study include climate-change impacts on the prevalence of environmental constraints to crop agriculture; climate variability and the variability of rain-fed cereal production; changes in potential agricultural land; changes in crop production patterns; and the impact of climate change on cereal production potential. Results of the AEZ-BLS integrated ecological-economic analysis of climate change on the world food system includes quantification of scale and location of hunger, international agricultural trade, prices, production, land use, etc. The analysis assesses trends in food production, trade, and consumption, and the impact on poverty and hunger of alternative development pathways and varying levels of climate change. The methodology and database developed in this study provides a foundation for detailed country studies, incorporating country-level information. The climate change issue is global, long term and involves complex interaction between climatic, environmental, economic, political, institutional, social and technological processes. It has significant international and intergenerational implications in the context of equity and sustainable development. Climate change will impact on social, economic and environmental systems and shape prospects for sustainable agricultural and rural development. Adaptation to climate change is essential to complement climate change mitigation, and both have to be central to an integrated strategy to reduce risks and impacts of climate change. Most of the discussion on climate change has focused on mitigation measures, for example the Kyoto Protocol. Not much attention has been given to climate change adaptation, which will be critical for many developing countries. The developing world has not realized that this issue needs to be on the global agenda and for developed countries this is not a priority, as they have the means and resources to adapt to future climate change. National governments and the international community must give agriculture and rural sector the highest priority in terms of resource allocation and adoption of development polices that are locally relevant and globally consistent. Only then progress can be made to eradicate hunger and poverty in the world

Assessment of Potential Productivity of Tree Species in China, Mongolia and the Former Soviet Union: Methodology and Results

Over the past twenty years, the term agro-ecological zones methodology (AEZ) has become widely used for global regional and national assessments of agricultural potentials. The AEZ methodologies and procedures have recently been extended and newly implemented to make use of the latest digital geographical databases, and to cope with the specific characteristics of seasonal temperate and boreal climates. This report presents details of a companion model of AEZ that enables assessments of potential productivity of forest tree species. It is referred to a FAEZ. The FAEZ methodology follows an environmental approach; it provides a standardized framework for the characterization of climate, soil and terrain conditions relevant to forest production and it uses environmental matching procedures to identify limitations of prevailing climate, soil and terrain for a range of tree species and assumed management objectives. The model for the estimation of biomass increments is based on two well established and robust models: the Chapman-Richard biomass increment model, and the AEZ potential biomass model. FAEZ includes an inventory of ecological adaptability characteristics as well as an inventory of specific ecological and environmental requirements for 52 boreal and temperate forest tree species. The natural resources inventory is based on the up-to-date LUC-GIS database of climate, soil, terrain and vegetation covering China, Mongolia and former Soviet Union. Results of potential productivity for tree species in North, Central and East Asia are presented under three different sets of assumptions of forest resources management and exploitation, namely: conservation forestry, traditional production forestry and biomass plantation forestry