Stochastic processes with finite correlation time: modeling and application to the generalized Langevin equation

The kangaroo process (KP) is characterized by various forms of the covariance and can serve as a useful model of random noises. We discuss properties of that process for the exponential, stretched exponential and algebraic (power-law) covariances. Then we apply the KP as a model of noise in the generalized Langevin equation and simulate solutions by a Monte Carlo method. Some results appear to be incompatible with requirements of the fluctuation-dissipation theorem because probability distributions change when the process is inserted into the equation. We demonstrate how one can construct a model of noise free of that difficulty. This form of the KP is especially suitable for physical applications.Comment: 22 pages (RevTeX) and 4 figure

Balanços energéticos agropecuários: uma importante ferramenta como indicativo de sustentabilidade de agroecossistemas.

No Brasil, pouca atenção se tem dado às formas e caminhos com que os fluxos energéticos se distribuem nos sistemas produtivos. Na agropecuária, a atenção tem sido voltada a novas fontes de energia (biomassa) ou em tecnologia alternativa, visando a racionalização do uso de energia fóssil ou elétrica. Entretanto, a agricultura tem se desenvolvido baseada fortemente na utilização intensiva de máquinas agrícolas, com conseqüente uso de combustíveis fósseis. Um fator de estrangulamento muito forte no consumo energético geral tem sido a utilização massiva de fertilizantes derivados do petróleo nos agroecossistemas. Estudos de Balanços Energéticos visam determinar os pontos de estrangulamento energético fundamentando a busca por tecnologias poupadoras de energia, especialmente aquelas de origem fóssil (combustível, fertilizante, agrotóxicos, energia despendida na fabricação das máquinas e implementos, etc.). No Brasil, a Região Sul, é onde se encontram vários trabalhos buscando uma agricultura mais auto-sustentável, do ponto de vista da utilização da energia. Em vista da possibilidade de eventuais futuras crises energéticas, o presente trabalho procura analisar o estado-da-arte dos estudos em Balanço Energético, no Brasil e no Mundo, como uma ferramenta de indicação da sustentabilidade dos sistemas agropecuários

Highly-parallelized simulation of a pixelated LArTPC on a GPU

The rapid development of general-purpose computing on graphics processing units (GPGPU) is allowing the implementation of highly-parallelized Monte Carlo simulation chains for particle physics experiments. This technique is particularly suitable for the simulation of a pixelated charge readout for time projection chambers, given the large number of channels that this technology employs. Here we present the first implementation of a full microphysical simulator of a liquid argon time projection chamber (LArTPC) equipped with light readout and pixelated charge readout, developed for the DUNE Near Detector. The software is implemented with an end-to-end set of GPU-optimized algorithms. The algorithms have been written in Python and translated into CUDA kernels using Numba, a just-in-time compiler for a subset of Python and NumPy instructions. The GPU implementation achieves a speed up of four orders of magnitude compared with the equivalent CPU version. The simulation of the current induced on 10^3 pixels takes around 1 ms on the GPU, compared with approximately 10 s on the CPU. The results of the simulation are compared against data from a pixel-readout LArTPC prototype

Electron impact double ionization of neon

Electron-impact double ionization from the valence shell of neon has been measured at an incident electron energy of 3662.5 eV. Double-coincidence (e, (3-1)e) measurements have been made between the scattered electron and each of the ejected electrons in turn, ejected energies were 10 eV and 90 eV, respectively, at ejection angles of 45, 60, 90, 120 and 135 degrees with respect to the incident electron beam. Absolute four-fold-differential cross-sections have been derived from the measured data and can be interpreted in terms of a fast, single-step, shake-off process

Electron impact double ionization in magnesium

Experimental investigations of double ionization provide information on the mechanism by which two electrons can be simultaneously removed from an atom. Information on the two-electron momentum distribution function of the electrons can also be obtained from the experiments. Results for the double ionization of magnesium are summarized and new (e,3e) data presented. Under a variety of experimental conditions evidence has been found for orientation and polarization effects. In addition, the recoil momentum of the residual doubly-charged ion is often large implying large momentum transfer to the core or ionizing collisions that occur close to the nucleus

Multifunktionale Mikrometer- und Millimeterwellen-Module 4M. Teilprojekt: Thermisch-mechanische Charakterisierung innovativer Millimeterwellen-Module Abschlussbericht

Aim of the overall project was to combine recent technologies for complex millimeter wave applications as well in the field of traffic control as in that of sensors in automotive and communication technologies. A high electrical, thermal, and mechanical reliability had to be ensured. Precise knowledge of the thermal and mechanical behaviour of the components under construction is an important requirement for design optimisation. Therefore, the design process had to be supported decisively by numerical simulations basing on FEM. Within the IZM part of the project, the well-known and proved macroscopic methodology was adapted onto the specific RF requirements. The main topics of the IZM project were to ensure correct material descriptions for the FE calculations including the corresponding temperature dependent parameters, the evaluation of unavoidable technological tolerances, and recommendations for design improvements as well as detail optimisation. The moulded plastic samples of the LO filtre have been analysed by means of high precision optical and laser optical measurements in orer to characterise tolerances, shape precision, and surface quality. Material properties have been determined for important materials built in the project demonstrators comparing measured and computed results basing on the same samples and comparable loading conditions. This way, a new methodology could be estbalished regarding the special requirements of millimeter wave technology. Sensitivity analyses have been carried out basing on parameter variations by means of FEM. (orig.)Available from TIB Hannover: F00B812+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung (BMBF), Bonn (Germany)DEGerman