The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform
Philip A Eckhoff - One of the best experts on this subject based on the ideXlab platform.
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malaria parasite diversity and transmission intensity affect development of parasitological immunity in a mathematical model
Malaria Journal, 2012Co-Authors: Philip A EckhoffAbstract:The development of parasitological immunity against malaria affects the ability to detect infection, the efficiency of the local human parasite Reservoir at infecting mosquitoes, and the response to reintroduction of parasites to previously cleared areas. Observations of similar age-trends in detected prevalence and mean parasitaemia across more than an order-of-magnitude of variation in baseline transmission complicate simple exposure-driven explanations. Mathematical models often employ age-dependent immune factors to match the observed trends, while the present model uses a new detailed mechanistic model of parasite transmission dynamics to explain age-trends through the mechanism of parasite diversity. Illustrative simulations are performed for multiple field sites in Tanzania and Nigeria, and observed age-trends and seasonality in parasite prevalence are recreated in silico, proffering possible mechanistic explanations of the observational data. Observed temporal dynamics in measured parasitaemia are recreated for each location and age-prevalence outputs are studied. Increasing population-level diversity in malaria surface antigens delays development of broad parasitological immunity. A local parasite population with high diversity can recreate the observed trends in age-prevalence across more than an order of magnitude of variation in transmission intensities. Mechanistic models of human immunity and parasite antigen diversity can recreate the observed temporal patterns for the development of parasitological immunity across a wide range of transmission intensities. This has implications for the distribution of disease burden across the population, the human transmission Reservoir, Design of elimination campaigns, and development and roll-out of potential vaccines.
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malaria parasite diversity and transmission intensity affect development of parasitological immunity in a mathematical model
Malaria Journal, 2012Co-Authors: Philip A EckhoffAbstract:Background: The development of parasitological immunity against malaria affects the ability to detect infection, the efficiency of the local human parasite Reservoir at infecting mosquitoes, and the response to reintroduction of parasites to previously cleared areas. Observations of similar age-trends in detected prevalence and mean parasitaemia across more than an order-of-magnitude of variation in baseline transmission complicate simple exposure-driven explanations. Methods: Mathematical models often employ age-dependent immune factors to match the observed trends, while the present model uses a new detailed mechanistic model of parasite transmission dynamics to explain age-trends through the mechanism of parasite diversity. Illustrative simulations are performed for multiple field sites in Tanzania and Nigeria, and observed age-trends and seasonality in parasite prevalence are recreated in silico, proffering possible mechanistic explanations of the observational data. Results: Observed temporal dynamics in measured parasitaemia are recreated for each location and age-prevalence outputs are studied. Increasing population-level diversity in malaria surface antigens delays development of broad parasitological immunity. A local parasite population with high diversity can recreate the observed trends in age-prevalence across more than an order of magnitude of variation in transmission intensities. Conclusions: Mechanistic models of human immunity and parasite antigen diversity can recreate the observed temporal patterns for the development of parasitological immunity across a wide range of transmission intensities. This has implications for the distribution of disease burden across the population, the human transmission Reservoir, Design of elimination campaigns, and development and roll-out of potential vaccines.
Ahmad Ghassemi - One of the best experts on this subject based on the ideXlab platform.
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a review of some rock mechanics issues in geothermal Reservoir development
Geotechnical and Geological Engineering, 2012Co-Authors: Ahmad GhassemiAbstract:Rock mechanics and geomechanical studies can provide crucial information for economic geothermal Reservoir development. Although significant progress has been made in Reservoir geomechanics, technical challenges specific to the geothermal area (high temps, data collection, experimentation issues) have prevented widespread use of geomechanics in geothermal Reservoir development. However, as the geothermal industry moves to develop more challenging resources using the concept of enhanced geothermal systems (EGS), and to maximize productivity from conventional resources, the need for improved understanding of geomechanical issues and developing specific technologies for geothermal Reservoirs has become critical. Rock mechanics research and improved technologies can impact areas related to in-situ stress characterization, initiation and propagation of artificial and natural fractures, and the effects of coupled hydro-thermo-chemo-mechanical processes on fracture permeability and induced seismicity. Rock mechanics/geomechanics research, including experimental and theoretical investigations as well as numerical and analytical solutions, has an important role in optimizing Reservoir Design and heat extraction strategies for sustainable geothermal energy development. A number of major areas where rock mechanics research can facilitate geothermal systems development are reviewed in this paper with particular emphasis on EGS Design and management.
Haizhen Zhai - One of the best experts on this subject based on the ideXlab platform.
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evaluation of heat production from single fracture hot dry rock with applications for egs Reservoir Design
Social Science Research Network, 2021Co-Authors: Haizhen ZhaiAbstract:Enhanced Geothermal Systems (EGS) are the most effective methods for extracting geothermal energy from deep hot dry rock (HDR). The EGS Reservoir framework is envisioned as independent-multiple fractures connecting injection and production wells. The Reservoir is further conceptually represented by a single fracture with homogeneous features, and a unit fracture is defined as having extendibility to a larger surface area for heat extraction. An analytical solution for the thermal-hydraulic coupling process is derived with a 1-D steady state conductive heat flow in the HDR with perpendicular water flow in the single fracture and transient heat transfer from rock to water. The heat produced from the HDR via water flow in the idealized single fracture is demonstrated by arithmetic equations. The lifetime of an EGS Reservoir in these reference conditions is 23.2 years and is confined by the produced water temperature of 150°C for commercial utilization. The heat recovery factor is 12.4%. With a power plant capacity of 5 Mw installed, the total area for extracting recoverable heat within the projected lifetime of a fracture surface of 1.58×106m2was determined. The discussion shows the ability of the model to estimate heat production and Reservoir scale.
Sam Sandoval Solis - One of the best experts on this subject based on the ideXlab platform.
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Reliability Based Optimum Reservoir Design by Hybrid ACO-LP Algorithm
Water Resources Management, 2015Co-Authors: Abbas Afshar, Fariborz Masoumi, Sam Sandoval SolisAbstract:Optimal Design of irrigation and water supply Reservoirs under reliability constraints may be categorized as large combinatorial optimization problems. In this paper, the reliability based optimum Design of a single water supply Reservoir is formulated as a mixed integer programming and a hybrid algorithm is introduced for its solution. To eliminate iterative procedures in reliability-based Reservoir Design and operation, the reliability requirements are directly embedded into the modeling framework and treated as different sets of constraints. Adaptive penalty method is used for constraint handling in the solution methodology. The proposed algorithm couples an ant colony optimization (ACO) optimizer with a virtual linear programing (LP) model for the solution of the resulted NP-hard mixed integer nonlinear programming problem. Dez Reservoir for irrigation water supply with 480 months of inflow is used to demonstrate the method and its performance. The structure and solution methodology is verified by the solution to the inverse problem. It is shown that the proposed hybrid model can efficiently solve the problem for various combinations of reliability measures in a multiple period modeling scheme. It is illustrated that under some circumstances and specific reliability values, the mixed integer nonlinear programming (MINLP) solver may even fail to address a feasible and local optimal solution. Although operating rule is not included in the operational scheme, the procedure is capable of identifying coefficients for decision rules with any proposed structure.
Ximing Cai - One of the best experts on this subject based on the ideXlab platform.
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reexamination of critical period for Reservoir Design and operation
Journal of Water Resources Planning and Management, 2009Co-Authors: Jiing Yun You, Ximing CaiAbstract:Reservoir operating rules are often based on deterministic models using critical period (CP) analysis, which results in very conservative decisions. CP is defined as the historical hydrologic period that includes the lowest flow or the most severe drought, which represents functionally as the full-empty cycle of Reservoir storage under a given firm yield. This paper compares CP with another time scale, the forecast horizon (FH) underlying hedging rule policies for Reservoir operation. When the decisions in the initial few periods are not affected by forecast data beyond a certain period, the period is known as FH, and the number of the initial periods is known as the decision horizon. When a Reservoir operation policy follows the concept of CP, CP is used as FH and the optimal yield generated within the FH is the firm yield. FH as long as the CP is not realistic because in the real world data for a such a long future period is unavailable; and using CP as FH is not effective either, because CP—the longest...