| 31. |
- Tórrez, Norvin, et al.
(författare)
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Modelling and Simulation of Crossflow Moving Bed Grain Dryers
- 1998
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Ingår i: Drying Technology. - : Informa UK Limited. - 0737-3937 .- 1532-2300. ; 16:9-10, s. 1999-2015
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Tidskriftsartikel (refereegranskat)abstract
- The drying of grain in dryers of a crossflow moving bed type was theoretically and experimentally studied. Two different dryer configurations were analyzed, a dryer with central air distribution and another with multiple air duels. Experimental information was obtained in pilot-size dryers. A mathematical model to simulate the process was developed. Hindered drying was accounted for by using the concept of relative drying rate. An adjustable factor, specific to the dryers, was used to account for the uncertainties of the contact area and the transfer coefficients encountered in the literature. Agreement between experimental results and simulations was fairly good. Simulations showed that distance between inlet air and outlet devices, air to solid flow ratio and dryer height to cross section ratio have great influence on the process. The mathematical model may be a useful tool for process exploration and optimization of this type of dryers.
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| 32. |
- Vidaurre, Marcia, et al.
(författare)
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Continuous drying of a solid wetted with ternary mixtures
- 1997
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Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 43:3, s. 681-692
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Tidskriftsartikel (refereegranskat)abstract
- The influence on drying selectivity of the continuous-contact mode between a solid wetted with ternary mixtures and a gas stream was theoretically studied. The liquid mixtures, ethanol–isopropanol–water and water–ethanol–acetone, were used. A mathematical model describing a gas-phase-controlled process was developed, and the influence of the process variables was studied by simulations. In addition to the inlet composition of the moisture and temperature of the solid, gas composition has the most important effect on selectivity. Small changes of gas composition, either imposed or spontaneous, may modify completely the process trajectory. The extent of these effects depends on the ratio between the flow rates of inlet gas and liquid contained in the solid. Because of their effects on the evolution of temperature and composition, the operating pressure and energy sources other than convection are also useful in controlling the selectivity. Since all these variables determine the composition of the remaining liquid and thereby product quality, their influence should be predictable. The model may be a valuable tool for exploring the process, provided that drying is gas-phase-controlled.
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| 33. |
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| 34. |
- Martínez, Claudia, et al.
(författare)
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Extraction Kinetics of Neem Seed Flakes
- 1998
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Ingår i: IACChE'98. - Mayagüez, Puerto Rico : University of Puerto Rico at Mayagüez (UPRM).
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Konferensbidrag (refereegranskat)
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| 35. |
- Scharp, Cecilia
(författare)
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Strategic groundwater protection
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Groundwater is an undervalued natural resource that isexperiencing a large number of threats to both its quantity andquality. Different types of land-use activities releasepotentially harmful substances that may be transported down tothe groundwater and have a negative impact on its quality.Society has been gradually recognising the need for bettergroundwater protection based on land-use decisions. Theobjective of this thesis has been to develop and test aframework forstrategic groundwater protection that providesprotection at both the general resource level and at particularwells and springs (abstraction points). The frameworkhighlights protection zones with specific managementrequirements and couples these to matrices with land-useregulations. The framework is developed in a process thatinvolves major stakeholders at different project stages, inline with the intention in the Dublin Statement. The frameworkhas been developed and tested in the Managua groundwater systemin Nicaragua which is a volcanic aquifer of crucial importancefor supplying water to about 1.5 million people. The frameworkis composed of four components: (i)groundwater vulnerability assessment,(ii)estimation of potential contamination load,(iii)assessment of a protection value,and (iv)delineation of wellhead protection zones. It is possibleto extract useful information from a variety of combinations ofthe assessments. Application of the Geographic InformationSystem IDRISI was used in the analyses to facilitate theoverlay procedures. Thecontamination liability,which is a combination ofvulnerability and potential contamination load, provides aninstantaneous image of areas at risk of contamination. At theresource level, groundwater vulnerability and the protectionvalue together formgroundwater protection categories, which indicate thedegree of urgency for regulating land use. Wellhead protectionzones are delineated based on a combination of capture-zonemodelling and particle tracking. Matrices with land-useregulations are outlined and coupled to protection categoriesand wellhead protection zones. Maps accompanied by manuals andguidelines are the physical result, which can then be used inplanning and decision-making situations. A general planningprocess for stakeholder participation in groundwater protectionhas been outlined based on the experience of the work done.This process involves stakeholders at various levels throughworkshops, group meetings, seminars and short courses,depending on the planning stage and the level of expertiserequired.Keywords:groundwater protection, groundwatervulnerability, protection value, contamination load, wellheadprotection zoning, stakeholder participation, Nicaragua
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| 36. |
- Johansson, Anna
(författare)
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Tjock och vacker - kvinnlighet och kroppsstorlek bland nicaraguanska kvinnor
- 1996
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Ingår i: Sociologisk forskning. - : Sveriges Sociologförbund. - 0038-0342 .- 2002-066X. ; 33:2-3, s. 51-70
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Tidskriftsartikel (refereegranskat)abstract
- Fat and beautiful - femininity and body size among Nicaraguan womenThis article aims to illuminate and discuss body size as a central element in the social construction of a feminine body. It also emphases the variations in the social definitions and experiences of womens body size; historical and social as well as cultural ones. The dominant body ideal today in Western culture is the slender and fat free body. Women are to a higher extent then men subdued to the disciplinary practices of fat reduction, to what some feminist researchers call ”the tyranny of slenderess”. These ideals and practices are historically rooted in a Western discourse and are formed within a culture of affluence and mass consumption. At the same time they are also influencing (or colonizing?) the so called Third World, as part ofthe cultural flows of global modernity. This is true also for Nicaragua, a country where I have carried out fieldwork during the latest years. Still, among the Nicaraguan lower class mestizo women with whom I have lived, fatness is defined as beautiful and as a sign of health, while slenderness is considered a sign of suffering. As I am disciplined within the Western ”fat is bad” discourse, the ethnographic situation of fieldwork involved both a meeting and confrontation of different ideals and practices of the feminine body. Finally, in highlighting definitions and significance of bodysize which are different from the Western ones there might lie a possibility of challenge and resistance of the discourses which are dominating our definitions and experiences of our own and others bodies.
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| 37. |
- Erikson, Rolf
(författare)
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Phytoplankton and bacterioplankton dynamics in a polymictic tropical lake
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phytoplankton and bacterioplankton dynamics in lakes are regulated by a multitude of factors such as light, temperature, water column mixing, nutrients, organic substrates, grazing, and food web structure. Tropical lakes are especially interesting to study because of the relative constancy of several of these factors. This thesis deals with interactions between phytoplankton, bacterioplankton and environmental factors in tropical, polymictic Lake Xolotlán, Nicaragua.Phytoplankton biomass per unit area showed only small temporal and spatial variations, with an average of 65 g C m-2. The photic zone:mixing depth ratio was relatively constant at 0.19, which is a critical lower limit for algal survival. Frequent mixing of the water column caused the algae to spend much time in darkness, thereby loosing by respiration what was gained by photosynthesis during short periods in the photic zone, and this caused high algal mortality.Areal primary production was limited by the biomass of actively photosynthesizing algal cells in the photic zone and varied within the range 6.0-7.5 g C m-2 d-l. The depth of the photic zone was mainly regulated by light extinction by active algae, but also by dead algae. The rates of light saturated and light limited photosynthesis were close to theoretical maximum values.Bacterial production (1 g C m-2 d-1) was comparable to known empirical models, but the bacterial biomass (5 g C m-2) was much greater than predicted. This resulted in a very low production per biomass. Bacterial biomass and production were significantly correlated to algal degradation products suggesting that bacteria were regulated by algal mortality. Allochtonous organic carbon was an insignificant source of substrate for the bacteria. This study shows that bacteria were sinks for organic carbon and regenerators of nutrients. By rapid decomposition of dead algae they made nutrients available for new algal growth, thus maintaining a high biomass specific primary production. Both algal and bacterial mortality by grazing was very low. The system was thus characterized by a tight coupling between algae and bacteria with little transfer of carbon and energy to higher trophic levels.
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| 38. |
- Neergaard, Anders
(författare)
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Grasping the Peripheral State : A Historical Sociology of Nicaraguan State Formation
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis has two aims. The first one is to contribute to the field of political and historical sociology through an understanding of the processes of state formation in a Third World country. The second aim is to describe and analyze the development of the Nicaraguan state from independence to 1990. In the first part of the dissertation theories of the nation-state and state formation are discussed and criticized. The Eurocentric origin and bias of the nation-state concept is seen as a significant problem in conceptualizing and understanding state formation in the Third World. Taking into consideration the experience of state formation in Western Europe, a theoretical frame work is presented that operationalize the concept of nation-state and the process of state formation. This frame work is further elaborated by discussions of some central aspects pertaining to countries of the Third World that differentiate them from the Western European experience. Nation-state formation is thus seen as a process in the international, "national" and state arenas encompassing the strengthening and the coordination of repressive, extractive and integrative capacities of the state. A central aspect in understanding state capacities is through the conceptual pair of infrastructural and despotic power. The empirical study focuses on the development (state formative processes) of the Nicaraguan state from independence in 1823 until the Sandinista electoral defeat in 1990. The role of the colonial legacy, the world capitalist economy and the international system of states in influencing the shape of the Nicaraguan state is analyzed. Through the history of Nicaraguan state formation, phases are outlined with different state formative characteristics. State disintegrative phases are represented by the city-states of early independent Nicaragua and the protectorate years at the beginning of the 20th century. Reproductive peripheralness is seen as dominant during the second half of the 19th century and the Somoza dynasty. Finally projects of nation-state formation are to be found during the Zelaya regime and during the Sandinista regime. The importance of the agroexport economy, foreign interventions and a fractured social formation is seen as an important factor blocking the development of a Nicaraguan nation-state. Through the notion of the peripheral state and frameworked in the concepts of extractive, repressive and integrative capacities the author provides new theoretical insights on Third World states dynamics in creating and maintaining a national arena, squeezed between international and local forces. The author shows that the peripheral state is not a traditional state form but a modern state form interdependent on the successful consolidation of nation-stateness in the First World.
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