Energetics of a simple microscopic heat engine

We model a microscopic heat engine as a particle hopping on a one-dimensional lattice in a periodic sawtooth potential, with or without load, assisted by the thermal kicks it gets from alternately placed hot and cold thermal baths. We find analytic expressions for current and rate of heat flow when the engine operates at steady state. Three regions are identified where the model acts either as a heat engine or as a refrigerator or as neither of the two. At quasistatic limit both efficiency of the engine and coefficient of performance of the refrigerator go to that for Carnot engine and Carnot refrigerator, respectively. We investigate efficiency of the engine at two operating conditions (at maximum power and at optimum value with respect to energy and time) and compare them with those of the endoreversible and Carnot engines.Comment: 6 pages and 8 figure

Noise-created bistability and stochastic resonance of impurities diffusing in a semiconductor layer

We investigate the dynamics of impurities walking along a semiconductor layer assisted by thermal noise of strength $D$ and external harmonic potential $V(x)$. Applying a nonhomogeneous hot temperature in the vicinity of the potential minimum may modify the external potential into a bistable effective potential. We propose the ways of mobilizing and eradicating the unwanted impurities along the semiconductor layer. Furthermore, the thermally activated rate of hopping for the impurities as a function of the model parameters is studied in high barrier limit. Via two state approximation, we also study the stochastic resonance (SR) of the impurities dynamics where the same noise source that induces the dynamics also induces the transition from mono-stable to bistable state which leads to SR in the presence of time varying field.Comment: Accepted for publication in EPJ

Farmers' collective action and agricultural transformation in Ethiopia

Rural Ethiopia rolled-out a program for the establishment of farmers’ collective action groups known as ‘Farmers’ Development Groups’ (FDGs), in 2007, based on presumed common interest of smallholder farmers. Although the government trusts that FDGs fetch fast and widescale agricultural transformation as part of the participatory agricultural extension system, systematic study and evidence on what motivates smallholder farmers to act collectively, the group dynamics, long term impact and transformative potential of the agricultural extension groups is scarce. Using the expectancy-value theory in social-psychology, this study explores what drives smallholders to act collectively; their participation level and benefits in groups, particularly for women and the youth; and the extent to which farmers’ groups attain intended agricultural transformation goals of productivity and commercialization. The study collected a mix of qualitative and quantitative data in 2016, through 46 key informant interviews; 8 focus group discussions with farmers, and a survey of randomly selected 120 smallholder farmers (30 percent women) in four sample woredas (districts) of Ethiopia. The findings of the study are drawn through a content analysis, and descriptive and correlation analysis of the qualitative and quantitative data, respectively. The study findings show that social identity, and not ‘common interest’ motivates smallholder farmers to join and participate in FDGs. The study provides evidence that participation in FDGs enhances smallholder farmers’ adoption and use of agricultural technologies, where 96 and 84 percent of the farmers who received extension messages in the group on crop and livestock production, respectively, applied the message. Consequently, by 2015 more than 85 percent of the survey respondent farmers reported above 10 percent increase in crop and livestock productivity. Nevertheless, the nature of the incremental changes brought by the collective actions are not transformative, nor sustainable. Extension groups have limited contribution to commercialization of smallholders, where only 20 percent of the FDG members participate in output marketing. More so, FDGs avail limited collective opportunity for the landless youth, and married female farmers in a rural society where difference in power, status and privilege prevail. It also limits deviation of thought among the rural community. Limited access to inputs and technology; large family size; limited access to farm land; over dependence of the extension system on ‘model’ farmers and public extension agents, and poorly designed sustainability features bound the transformative potential of FDGs. The study forwards a set of five recommendations to unleash the potential of FDGs: reconsider the group design to be identity congruent; ensure inclusiveness for young and female farmers; empower and motivate voluntary group leaders; encourage collective marketing and; invest in sustainability features of the group.Development StudiesPh. D. (Development Studies

Spatial Variability and Isotopic Studies of the Prairie -Forest Transition Soil in Louisiana.

The calcareous prairies of Louisiana are among the most endangered ecosystems in North America. The major threat to this ecosystem is the invasion by woody and herbaceous plants, primarily eastern red cedar (Juniperus virginiana ). The restoration and management of these rare plant communities require a thorough understanding of the soils supporting them. Geostatistical, fractal, and stable isotopic procedures were integrated to study the soil and vegetation spatial variability. The prairie soil was alkaline, the forest soil was acidic, and the transition soil was neutral. The spherical model described the spatial variability of virtually all the soil properties considered with a spatial dependence expressed over a range of 20 to 30 m. The estimated fractal dimension for each soil property indicated short-range variation domination. Calcite was the major constituent of the soil carbonate. The delta13C values of the carbonate showed that it is of secondary origin. The delta13 C values of soil organic matter (SOM) and pedogenic carbonate covary, indicating an isotopic equilibrium between SOM and the pedogenic carbonate. The carbon isotope data from SOM within the 0--10 cm depth suggested that the prairies are composed of a mixture of approximately equal proportions of C3 and C4 plants. The relative proportion of C3 and C4 plants varied with season. The C4 plants dominated in the summer and the C3 plants in the spring. Comparison of delta13C values from the forest, transition, and prairie with depth suggested that the invasion of C3 trees and shrubs observed within the transition might not be a recent phenomenon. SOM delta 13C below 40--50 cm indicated that in the past a C4 community might have dominated the site. Plant leaves from prairie, transition, and forest showed similar delta 15N signals. Compared with the leaves, the soil was enriched with 15N. The order of enrichment of the 0--10 cm relative to corresponding leaves was forest soil \u3e transition soil \u3e prairie soil. The delta 15N and Ca were significantly affected by vegetation type. The differences in the soil delta15N is a clear indication that the vegetation within the transition zone (invading woody and herbaceous plants) is altering the N cycling towards more forest-like conditions

Exploring the operation of a tiny heat engine

We model a tiny heat engine as a Brownian particle that moves in a viscous medium in a sawtooth potential (with or without load) assisted by $\it {alternately}$ placed hot and cold heat baths along its path. We find closed form expression for the steady state current as a function of the model parameters. This enables us to deal with the energetics of the model and evaluate either its efficiency or its coefficient of performance depending upon whether the model functions either as a heat engine or as a refrigerator, respectively. We also study the way current changes with changes in parameters of interest. When we plot the phase diagrams showing the way the model operates, we not only find regions where it functions as a heat engine and as a refrigerator but we also identify a region where the model functions as neither of the two.Comment: 8 pages and 13 figure

Determinants of Agricultural Technology adoption: the case of improved groundnut varieties in Malawi

This paper applies the Average Treatment Effect (ATE) framework on data obtained from a random cross-section sample of 594 farmers in Malawi to document the actual and potential adoption rates of improved groundnut varieties and their determinants conditional on farmers’ awareness of the technology. The fact that not all farmers are exposed to the new technologies makes it difficult to obtain consistent estimates of population adoption rates and their determinants using direct sample estimates and classical adoption models such as probit or tobit. Our approach tries to control for exposure and selection bias in assessing the adoption rate of technology and its determinants. Results indicate that only 26% of the sampled farmers grew at least one of the improved groundnut varieties. The potential adoption rate of improved groundnut for the population is estimated at 37% and the adoption gap resulting from the incomplete exposure of the population to the improved groundnut is 12%. We further find that the awareness of improved varieties is mainly influenced by information access variables, while adoption is largely influenced by economic constraints. The findings are indicative of the relatively large unmet demand for improved groundnut varieties suggesting that there is scope for increasing the adoption rate of improved groundnut varieties in Malawi once the farmers are made aware of the technologies and if other constraints such as lack of access to credit are addressed.groundnuts, adoption, Average Treatment Effect, Malawi, Crop Production/Industries,

Causes and Remedy of Squatting in Burayu Town, Ethiopia

The first dilemma that millions of poor in urban areas of the developing world face and which is likely to persist for a long period is the question of adequate housing. In this regard, 70 per cent of the urban population of Ethiopia is living in slums and squatter settlements. This article is on accessibility of land for residential purpose and existing squatter settlements in Burayu town in Oromia National Regional State, Ethiopia. The population of Burayu town is 100,200 (2010) and the town is located about 15 kilo meters from the city limits of Addis Ababa metropolis, the capital of Ethiopia. The town is characterized by many land related problems like proliferation of squatter settlements, expansion of slums and other illegal land developments. This article tries to identify the root causes for squatting and assess the major local government responses in Burayu town. By the combination of random and purposive sampling method, 246 squatter households were selected from different sections of the town and quantitative data and qualitative information were collected from primary as well as secondary sources to analyze. The result shows that on the contrary to many studies conducted on similar areas, the root cause for development and expansion of squatter settlements in Burayu town is not economic poverty of the squatter households. Rather, the main reason found is cumbersome procedures and very poor performance of Land Development and Management Agency to deliver the land to the aspirants. Inability of the local government to cope up with the fast urbanization and increasing demand of land for housing is obvious. Keywords: Squatter, Accessibility and Squatter Settlement

Urban Environment and Squatting: One Affecting the Other The Case of Burayu Town, Ethiopia

Squatting is the process of illegally occupying land or buildings without the explicit permission of the owner. It is clear that squatter settlements help some households in solving their shelter problems. But, rising evidences on the other side indicate that squatter settlements are the causes for remarkable public costs many of which are related to environmental degradation. Burayu town is one of the fastest growing towns in Oromia National Regional State of Ethiopia. The town is located about 15 kilometers from the center of Addis Ababa metropolis, the capital of Ethiopia. The population of Burayu town was 4,138 in 1984; 10,027 in 1994; 63,873 in 2007 (Census) and has grown to more than 150,000 in 2013 (estimated), showing that the population of the town has increased very rapidly especially during the past about seven years. The town is characterized by many environmental related problems like proliferation of squatter settlements, expansion of slums and other illegal land developments. The objective of this article is therefore to identify the collision of squatting on urban environment in relation to location of the squatter houses and generation and mismanagement of different kinds of wastes. By random purposive sampling method, 246 squatter households were selected and quantitative data and qualitative information were collected from primary as well as secondary sources and analyzed. The result points out that, squatter houses are negatively related to the town’s environment. 58.1 per cent of the squatter houses are located in environmentally sensitive areas which are prohibited by the Structure Plan Preparation Manual prepared by Ethiopian Ministry of Urban Development and Construction, 2012. They generate different kinds of wastes and the management of wastes in squatter settlements is not sustainable. Key Words: Squatting and squatter house