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Relativistic Rotating Boltzmann Gas Using the Tetrad Formalism

Abstract

We consider an application of the tetrad formalism introduced by Cardall et al. [Phys. Rev. D 88 (2013) 023011] to the problem of a rigidly rotating relativistic gas in thermal equilibrium and discuss the possible applications of this formalism to rel- ativistic lattice Boltzmann simulations. We present in detail the transformation to the comoving frame, the choice of tetrad, as well as the explicit calculation and analysis of the components of the equilibrium particle ow four-vector and of the equilibrium stress-energy tensor.

Open access
A Solid State Pyranometer

Abstract

The construction of a solid state device-based pyranometer designated to broadband irradiance measurements is presented in this paper. The device is built on the physical basis that the temperature difference between two bodies of identical shape and external surface area, identically exposed to the incident radiation, but having different absorption and heat transfer coefficients (e.g. one body is painted white and the other is painted black), is proportional to the incident irradiance. This proportionality may be put in evidence if the two bodies consisting of identical arrays of correspondingly painted semiconductor diodes, due to the thermal behaviour of their p-n junction. It is theoretically predicted and experimentally confirmed that the voltage drop across a diode passed through a constant forward current linearly decreases with the temperature of the junction. In other words, a signal proportional to the irradiance of the light source may be obtained via conventional analog electronics. The calibration of the apparatus, as performed by means of a professional device (LP PYRA 03), indicates a good linearity.

Open access
The Aharonov-Bohm Effect and Transport Properties in Graphene Nanostructures

Abstract

This paper investigates the possibility to improve the filtering process of flue gas by separation of suspended nanoparticle using dielectrophoresis. The study focuses on the particles having an average radius of about 50-150 nm, that cannot be filtrated by classical techniques but have a harmful effect for environment and human health. The size distribution nanoparticles collected from the flue gas filters of a hazardous waste incinerator plant were evaluated. Based on obtained experimental data and a proposed mathematical model, the concentration distribution of nanoparticle suspended in flue gas inside a microfluidic separation device was analyzed by numerical simulations, using the finite element method. The performances of the device were described in terms of three new specific quantities related to the separation process, namely Recovery, Purity and Separation Efficiency. The simulations could provide the optimal values of control parameters for separation process, and aim to be a useful tool in designing microfluidic devices for separating nanoparticle from combustion gases.

Open access
The Aharonov-Bohm Effect and Transport Properties in Graphene Nanostructures

Abstract

In this paper we discuss interplays between the Aharonov-Bohm effect and the transport properties in mesoscopic ring structures based on graphene. The interlayer interaction leads to a change of the electronic structure of bilayer graphene ring such that the electronic energy dispersion law exhibits a gap, either by doping one of the layers or by the application of an external perpendicular electric field. Gap adjustments can be done by varying the external electric field, which provides the possibility of obtaining mesoscopic devices based on the electronic properties of bilayer graphene. This opens the way to controllable manipulations of phase-coherent mesoscopic phenomena, as well as to Aharonov-Bohm oscillations depending on the height of the potential step and on the radius of the ring. For this purpose one resorts to a tight-binding model such as used to the description of conductance.

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Analysis of Metal Content in Soil in Timis County

Abstract

The paper reports on the presence of various metals in soil in Timis county. A set of 18 samples were collected from different points of interest. The metal content of the samples was investigated using a handheld XRF Niton XLp 300 GOLDD analyzer. Special attention was paid to the metals with harmful potential to humans. Based on the obtained results, a set of conclusions on the environment’s health was drawn.

Open access
Comparison Between Measurements and WRF Numerical Simulation of Global Solar Irradiation in Romania

Abstract

The paper presents a comparative analysis between the surface global irradiation measured for Romania and the predicted irradiation obtained by numerical simulation. The measured data came from the Romanian National meteorological Administration. Based on a preliminary analysis that took into account several criteria among which, performance, cost, popularity and meteorological and satellite data accessibility we concluded that a combination GFS-WRF(NMM) or GFS-WRF(ARW) is most suitable for short term global solar irradiation forecasting in order to assess the performance of the photovoltaic power stations (Badescu and Dumitrescu, 2012, [1], Martin et al., 2011, [2]).

Open access
Fractal Analysis on Morphology of Laser Irradiated Vanadium Surfaces Under Different Ambient

Abstract

Pulsed laser irradiated vanadium surface morphology under different ambient has been prepared and characterized using fractal dimension analysis method on scanning electron microscopy (SEM) images. In presence of different ambient, self-periodic and self-similar surface patterns (e.g. dots, islands, and pins) were grown and appeared in different shapes. The fractal dimension (FD) of this developed vanadium nanostructure was calculated by fractal box count method (FBM). The calculated fractal dimension (FD, Df) shows dependence on the different type on ambient and the number of laser shots.

Open access
Improving The Accuracy of the Empirical Clear Sky Solar Irradiance Models

Abstract

This paper is focused on improving the quality of nowcasting solar irradiance by enhancing the clear sky component of the model. A simple linear correction for the average atmospheric transmittance is proposed. The correction is based on the most recent measurements recorded prior the forecasting moment. The proposed procedure was tested against data measured on the Solar Platform of the West University of Timisoara. Overall results demonstrates a notable improvement in the clear sky model accuracy.

Open access
Intercomparison of Radon in Soil Instruments at Reference Site in Czech Republic

Abstract

Intercomparison exercises of radon instruments play an important part when it comes to domestic survey as well as international or national mapping in dwellings, soil or water. Therefore, it is of prime interest to improve and standardize technical methods of measurement and also to verify quality assurance through comparison between different instruments and techniques. In the present paper is described the latest intercomparison exercise performed between the Laboratory of Environmental Radioactivity (hereafter called LER) of our department and other 15 different teams around Europe. The test has been held at two radon reference sites located 60 km SW of Prague, Czech Republic.

Open access
Neural Flows in Hopfield Network Approach

Abstract

In most of the applications involving neural networks, the main problem consists in finding an optimal procedure to reduce the real neuron to simpler models which still express the biological complexity but allow highlighting the main characteristics of the system. We effectively investigate a simple reduction procedure which leads from complex models of Hodgkin-Huxley type to very convenient binary models of Hopfield type. The reduction will allow to describe the neuron interconnections in a quite large network and to obtain information concerning its symmetry and stability. Both cases, on homogeneous voltage across the membrane and inhomogeneous voltage along the axon will be tackled out. Few numerical simulations of the neural flow based on the cable-equation will be also presented.

Open access