1,269 research outputs found
A System Complexity Approach to Swarm Electrification
The study investigates a bottom-up concept for microgrids. Financial analysis is performed through a business
model approach to test for viability when replacing a researched energy expenditure baseline in Bangladesh. A
literature review compares the approach to current trends in microgrids. A case study of Bangladesh illustrates the
potential for building on the existing infrastructure base of solar home systems. Opportunities are identified to improve
access to reliable energy through a microgrid approach that aims at community-driven economic and infrastructure
development by building on network effects generated through the inclusion of localized economies with strong
producer-consumer linkages embedded within larger systems of trade and exchange. The analysed approach
involves the linking together of individual stand-alone energy systems to form a microgrid that can eventually
interconnect with present legacy infrastructure consisting of national or regional grids. The approach is likened to
the concept of swarm intelligence, where each individual node brings independent input to create a conglomerate of
value greater than the sum of its parts
Crustal Evolution and Petrogenesis of Silicic Plutonic Rocks within the Oman Ophiolite – Petrological and Geochemical Investigations
Modelling UV irradiances on arbitrarily oriented surfaces: effects of sky obstructions
International audienceA method is presented to calculate UV irradiances on inclined surfaces that additionally takes into account the influence of sky obstructions caused by obstacles such as mountains, houses, trees, or umbrellas. Thus the method allows calculating the impact of UV radiation on biological systems, such as for instance the human skin or eye, in any natural or artificial environment. The method, a combination of radiation models, is explained and the correctness of its results is demonstrated. The effect of a natural skyline is shown for an Alpine ski area, where the UV irradiance even on a horizontal surface may increase due to reflection at snow by more than 10%. In contrast in a street canyon the irradiance on a horizontal surface is reduced down to 30% in shadow and to about 75% for a position in the sun
Predictive Modeling of Cholera Outbreaks in Bangladesh
Despite seasonal cholera outbreaks in Bangladesh, little is known about the
relationship between environmental conditions and cholera cases. We seek to
develop a predictive model for cholera outbreaks in Bangladesh based on
environmental predictors. To do this, we estimate the contribution of
environmental variables, such as water depth and water temperature, to cholera
outbreaks in the context of a disease transmission model. We implement a method
which simultaneously accounts for disease dynamics and environmental variables
in a Susceptible-Infected-Recovered-Susceptible (SIRS) model. The entire system
is treated as a continuous-time hidden Markov model, where the hidden Markov
states are the numbers of people who are susceptible, infected, or recovered at
each time point, and the observed states are the numbers of cholera cases
reported. We use a Bayesian framework to fit this hidden SIRS model,
implementing particle Markov chain Monte Carlo methods to sample from the
posterior distribution of the environmental and transmission parameters given
the observed data. We test this method using both simulation and data from
Mathbaria, Bangladesh. Parameter estimates are used to make short-term
predictions that capture the formation and decline of epidemic peaks. We
demonstrate that our model can successfully predict an increase in the number
of infected individuals in the population weeks before the observed number of
cholera cases increases, which could allow for early notification of an
epidemic and timely allocation of resources.Comment: 43 pages, including appendices, 5 figures, 1 table in the main tex
Ion-temperature-gradient sensitivity of the hydrodynamic instability caused by shear in the magnetic-field-aligned plasma flow
Optical properties of aerosols and clouds: The software package OPAC
The software package OPAC (Optical Properties of Aerosols and Clouds) is described. It easily provides optical properties in the solar and terrestrial spectral range of atmospheric particulate matter. Microphysical and optical properties of six water clouds, three ice clouds, and 10 aerosol components, which are considered as typical cases, are stored as ASCII files. The optical properties are the extinction, scattering, and absorption coefficients, the single scattering albedo, the asymmetry parameter, and the phase function. They are calculated on the basis of the microphysical data (size distribution and spectral refractive index) under the assumption of spherical particles in case of aerosols and cloud droplets and assuming hexagonal columns in case of cirrus clouds. Data are given for up to 61 wavelengths between 0.25 and 40 mu m and up to eight values of the relative humidity. The software package also allows calculation of derived optical properties like mass extinction coefficients and Angstrom coefficients. Real aerosol in the atmosphere always is a mixture of different components. Thus, in OPAC it is made possible to get optical properties of any mixtures of the basic components and to calculate optical depths on the base of exponential aerosol height profiles. Typical mixtures of aerosol components as well as typical height profiles are proposed as default values, but mixtures and profiles for the description of individual cases may also be achieved simply
A two-fluid model describing the finite-collisionality, stationary Alfvén wave in anisotropic plasma
The stationary inertial Alfvén (StIA) wave (Knudsen, 1996) was predicted for cold, collisionless plasma. The model was generalized (Finnegan et al., 2008) to include nonzero values of electron and ion collisional resistivity and thermal pressure. Here, the two-fluid model is further generalized to include anisotropic thermal pressure. A bounded range of values of parallel electron drift velocity is found that excludes periodic stationary Alfvén wave solutions. This exclusion region depends on the value of the local Alfvén speed VA, plasma beta perpendicular to the magnetic field β⊥ and electron temperature anisotropy
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