Search results for " Heating"
showing 10 items of 150 documents
Multi-Objective Optimization of Urban Microgrid Energy Supply According to Economic and Environmental Criteria
2019
This study is focused on the optimization of the annual cost and greenhouse impact related to the supply of natural gas and electricity of an urban microgrid through the installation of components as renewable energy sources, energy storage units and converters. As input parameters of the optimization model, the energy demand of a medium density urban district was estimated, while average costs and emissions of equipment were collected in market reports and literature. The outputs of the model are the optimal size and the schedule of each component. Moreover, optimization analysis was carried out for two different scenarios, comparing Italian and Vietnamese energy system cost and environmen…
Study of voltage decrease in organic light emitting diodes during the initial stage of lifetime
2016
Abstract We report the results of lifetime DC testing at constant current of not-encapsulated organic light emitting diodes (OLEDs) based on Tris (8 idroxyquinoline) aluminum (Alq3) as emitting material. In particular, a voltage decrease during the initial stage of the lifetime test is observed. The cause of this behavior is also discussed, mainly linked to initial Joule self-heating of the device, rising its temperature above room temperature until thermal equilibrium is reached at steady state.
Dielectric Characterization of Fruit Nectars at Low RF Frequencies
2015
Dielectric properties of apple, apricot, peach, and pear nectars were studied in the frequency range from 15 kHz to 30 MHz and the temperature range from 25 to 60 degrees C. Both the relative dielectric constants and the dielectric loss factors decreased by increasing frequency and increased linearly with increasing temperature with values in the order 10(4)-10(2) and 10(5)-10(2), respectively. The power dissipation densities and the power penetration depths were found to increase linearly with temperature. Power dissipation densities remained essentially constant for all the samples while power penetration depths decreased significantly on increasing frequency. The dependence of each of th…
Reconnection nanojets in the solar corona
2020
P.A. acknowledges STFC support from grant numbers ST/R004285/2 and ST/T000384/1 and support from the International Space Science Institute, Bern, Switzerland to the International Teams on ‘Implications for coronal heating and magnetic fields from coronal rain observations and modeling’ and ‘Observed Multi-Scale Variability of Coronal Loops as a Probe of Coronal Heating’. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 647214). P.T. was also supported by contracts 8100002705 and SP02H1701R from Lockheed-Martin to the Smithsonian Astrophysical Observatory (SAO), and NASA c…
On the Coronal Temperature in Solar Microflares
2020
We present a study of solar imaging and spectral observations of a microflare, focusing on the temperature diagnostics provided by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, and the Extreme-Ultraviolet Imaging Spectrometer (EIS) on board Hinode. Our data analysis, in particular from the emission in the 131 and 94 Å channels, indicates that the heated plasma reaches temperatures of ≿10 MK, at odds with a previous analysis of the same event, and we discuss the reason for the discrepancy. A particularly interesting aspect is the likely presence of the Fe XXIII 263.76 Å line, though weak, in EIS spectra in the early phases of the event, supporting the presen…
Modeling a coronal loop heated by magnetohydrodynamic turbulence nanoflares
2005
We model the hydrodynamic evolution of the plasma confined in a coronal loop, 30,000 km long, subject to the heating of nanoflares due to intermittent magnetic dissipative events in the MHD turbulence produced by loop footpoint motions. We use the time-dependent distribution of energy dissipation along the loop obtained from a hybrid shell model, occurring for a magnetic field of about 10 G in the corona; the relevant heating per unit volume along the loop is used in the Palermo-Harvard loop plasma hydrodynamic model. We describe the results, focusing on the effects produced by the most intense heat pulses, which lead to loop temperatures between 1 and 1.5 MK.
Direct measurement of the electron‐phonon relaxation rate in thin copper films
2004
We have used normal metal-insulator-superconductor (NIS) tunnel junction pairs, known as SINIS structures, for ultrasensitive thermometry at sub-Kelvin temperatures. With the help of these thermometers, we have developed an ac-technique to measure the electron-phonon (e-p) scattering rate directly, without any other material or geometry dependent parameters, based on overheating the electron gas. The technique is based on Joule heating the electrons in the frequency range DC-10 MHz, and measuring the electron temperature in DC. Because of the nonlinearity of the electron-phonon coupling with respect to temperature, even the DC response will be affected, when the heating frequency reaches th…
Electron-phonon interaction in thin copper and gold films
2004
We have studied the electron-phonon (e-p) interaction in thin Cu and Au films at sub-Kelvin temperatures with the help of the hot electron effect, using symmetric normal metal-insulator-superconductor tunnel junction pairs as thermometers. By Joule heating the electron gas and measuring the electron and the lattice temperatures simultaneously, we show that the electron-phonon scattering rate follows a $T^{4}$ temperature dependence in both metals. The result is in accordance with the theory of e-p scattering in disordered films with vibrating boudaries and impurities, in contrast to the $T^{3}$-law expected for pure samples, and $T^{2}$-law for static disorder.
Microwave heating as a tool for coupling Marangoni and Hickman instabilities
2007
The aim of this paper is the linear stability analysis of an evaporating interface in order to justify hydrodynamic behaviors observed during evaporation of water and ethanol simultaneously under microwave irradiation and reduced pressure. In relation to the local character of the thermal conversion of electromagnetic energy, and of the thermal dependency of the dielectric loss, it seems possible under microwave heating to induce a specific hydrodynamic compared to those induced by conventional heating.
Joule heating and the thermal evolution of old neutron stars
1998
We consider Joule heating caused by dissipation of the magnetic field in the neutron star crust. This mechanism may be efficient in maintaining a relatively high surface temperature in very old neutron stars. Calculations of the thermal evolution show that, at the late evolutionary stage ($t \geq 10$ Myr), the luminosity of the neutron star is approximately equal to the energy released due to the field dissipation and is practically independent of the atmosphere models. At this stage, the surface temperature can be of the order of $3 \times 10^{4} - 10^{5}$K. Joule heating can maintain this high temperature during extremely long time ($\geq 100$ Myr), comparable with the decay time of the m…