Magnetic flux emergence and associated dynamic phenomena in the Sun

We present a review of the process of magnetic flux emergence in the Sun. We focus on observations and numerical experiments that explore the dynamical rise of magnetic fields from the solar interior to the corona. We describe the response of the highly stratified solar atmosphere on flux emergence and, consequently, we present a comprehensive picture of the coupling between solar dynamic events and flux emergence. We discuss potential applications of this process in other astrophysical environments.     

A Numerical Model for Two-Dimensional Flood Routing in Complex Terrains

In this paper, a new powerful numerical hydrodynamic in-house model is presented and tested. The model simulates flood routing in two dimensions. It is based on the solution of Shallow Water Equations using the Finite Difference Method according to the explicit McCormack numerical scheme which has shock capturing capability. The innovation of the proposed model lies in the modification of McCormack scheme by incorporating artificial viscosity through a diffusion factor in order to avoid oscillations as proposed by various researchers. Additionally, a threshold of water depth is introduced in order to distinguish the wet and dry cells of the computational domain. The model is capable of producing maps for the inundation extent, water depths and depth-averaged water velocities. Finally, the paper presents extensive testing of the model by comparison with analytical solution, experimental results and with the output of another software package in real world flood simulation studies.     

Emissions from photovoltaic life cycles.

Photovoltaic (PV) technologies have shown remarkable progress recently in terms of annual production capacity and life cycle environmental performances, which necessitate timely updates of environmental indicators. Based on PV production data of 2004-2006, this study presents the life-cycle greenhouse gas emissions, criteria pollutant emissions, and heavy metal emissions from four types of major commercial PV systems: multicrystalline silicon, monocrystalline silicon, ribbon silicon, and thin-film cadmium telluride. Life-cycle emissions were determined by employing average electricity mixtures in Europe and the United States during the materials and module production for each PV system. Among the current vintage of PV technologies, thin-film cadmium telluride (CdTe) PV emits the least amount of harmful air emissions as it requires the least amount of energy during the module production. However, the differences in the emissions between different PV technologies are very small in comparison to the emissions from conventional energy technologies that PV could displace. As a part of prospective analysis, the effect of PV breeder was investigated. Overall, all PV technologies generate far less life-cycle air emissions per GWh than conventional fossil-fuel-based electricity generation technologies. At least 89% of air emissions associated with electricity generation could be prevented if electricity from photovoltaics displaces electricity from the grid.     

Land use and electricity generation: A life-cycle analysis

Renewable-energy sources often are regarded as dispersed and difficult to collect, thus requiring substantial land resources in comparison to conventional energy sources. In this review, we present the normalized land requirements during the life cycles of conventional- and renewable-energy options, covering coal, natural gas, nuclear, hydroelectric, photovoltaics, wind, and biomass. We compared the land transformation and occupation matrices within a life-cycle framework across those fuel cycles. Although the estimates vary with regional and technological conditions, the photovoltaic (PV) cycle requires the least amount of land among renewable-energy options, while the biomass cycle requires the largest amount. Moreover, we determined that, in most cases, ground-mount PV systems in areas of high insolation transform less land than the coal-fuel cycle coupled with surface mining. In terms of land occupation, the biomass-fuel cycle requires the greatest amount, followed by the nuclear-fuel cycle. Although not detailed in this review, conventional electricity-generation technologies also pose secondary effects on land use, including contamination and disruptions of the ecosystems of adjacent lands, and land disruptions by fuel-cycle-related accidents.     

Error analysis and optimal estimation procedures in identification of nonlinear volterra systems

In the problem of nonlinear system identification, the white-noise (crosscorrelation) method has become increasingly popular during the last five years. Since the ideal white noise is physically unrealizable, the method employs quasi-white test signals which approximate its statistical properties to a satisfactory and determinable degree. A family of such signals (CSRS) which has been recently introduced appears to be most advantageous in nonlinear system identification. Its principal advantage is that it allows the thorough and effective error analysis and, consequently, the optimization of the identification procedure. This paper presents that error analysis and outlines the optimal procedures which ought to be followed for the optimal application of the method to nonlinear Volterra systems identification.     

Noncontact optical imaging in mice with full angular coverage and automatic surface extraction

During the past decade, optical imaging combined with tomographic approaches has proved its potential in offering quantitative three-dimensional spatial maps of chromophore or fluorophore concentration in vivo. Due to its direct application in biology and biomedicine, diffuse optical tomography (DOT) and its fluorescence counterpart, fluorescence molecular tomography (FMT), have benefited from an increase in devoted research and new experimental and theoretical developments, giving rise to a new imaging modality. The most recent advances in FMT and DOT are based on the capability of collecting large data sets by using CCDs as detectors, and on the ability to include multiple projections through recently developed noncontact approaches. For these to be implemented, we have developed an imaging setup that enables three-dimensional imaging of arbitrary shapes in fluorescence or absorption mode that is appropriate for small animal imaging. This is achieved by implementing a noncontact approach both for sources and detectors and coregistering surface geometry measurements using the same CCD camera. A thresholded shadowgrammetry approach is applied to the geometry measurements to retrieve the surface mesh. We present the evaluation of the system and method in recovering three-dimensional surfaces from phantom data and live mice. The approach is used to map the measured in vivo fluorescence data onto the tissue surface by making use of the free-space propagation equations, as well as to reconstruct fluorescence concentrations inside highly scattering tissuelike phantom samples. Finally, the potential use of this setup for in vivo small animal imaging and its impact on biomedical research is discussed.     

Use of natural clinoptilolite for the removal of lead, copper and zinc in fixed bed column

This work deals with the removal of lead, copper and zinc from aqueous solutions by using natural zeolite (clinoptilolite). Fixed bed experiments were performed, using three different volumetric flow rates of 5, 7 and 10bed volume/h, under a total normality of 0.01N, at initial pH of 4 and ambient temperature (25 degrees C). The removal efficiency increased when decreasing the flow rate and the following selectivity series was found: Pb(2+)>Zn(2+)> or =Cu(2+). Conductivity measurements showed that lead removal follows mainly ion exchange mechanism, while copper and zinc removal follows ion exchange and sorption mechanism as well.