Search results for " Fault"
showing 10 items of 239 documents
Critical analysis of conventional thermoeconomic approaches to the diagnosis of multiple faults in air conditioning units: Capabilities, drawbacks an…
2013
Abstract Faults diagnosis in air conditioning systems is a crucial activity, since malfunctions may induce heavy degradation of performance. Among the available techniques, thermoeconomic diagnosis has played a marginal role due to the difficulties encountered when applying the methodology to refrigeration plants. In this paper a critical analysis on capabilities and limits of thermoeconomic diagnosis is proposed. The reference plant is a 120 kWc air-cooled air conditioning system; a simulator is used to evaluate thermodynamic data under normal and faulty conditions, setting up “virtual experiments” to simulate each fault. Five malfunctions are imposed, either individually or simultaneously…
Prediction of Weak Topological Insulators in Layered Semiconductors
2012
We report the discovery of weak topological insulators by ab initio calculations in a honeycomb lattice. We propose a structure with an odd number of layers in the primitive unit-cell as a prerequisite for forming weak topological insulators. Here, the single-layered KHgSb is the most suitable candidate for its large bulk energy gap of 0.24 eV. Its side surface hosts metallic surface states, forming two anisotropic Dirac cones. Though the stacking of even-layered structures leads to trivial insulators, the structures can host a quantum spin Hall layer with a large bulk gap, if an additional single layer exists as a stacking fault in the crystal. The reported honeycomb compounds can serve as…
FPGA-based concurrent watchdog for real-time control systems
2003
A straightforward and efficient implementation of a custom concurrent watchdog processor for real-time control systems is presented. Emphasis is given to the techniques used for on-line checking the main processor activity without adding overhead, and to the advantages of a field programmable gate array implementation.
Growth and defect studies of CdTe particles
2013
The paper reports the epitaxial growth of cadmium telluride (CdTe) particles by thermal deposition on cleaved planes of (001)NaCl and (001)KBr. Using high resolution transmission electron microscopy and electron diffraction it was shown that CdTe particles could have different orientation and phase (cubic or hexagonal) depending on the substrate temperature. Their most common defects are twins and stacking faults.
Tectonometamorphic evolution of high-pressure rocks from the island of Amorgos (Central Aegean, Greece)
2007
Structural and metamorphic data from the island of Amorgos (central Aegean Sea) show evidence for the existence of two distinct high-pressure units, the Metabasite Unit and the Basal Conglomerate Unit. These are exposed at the base of a thick marble sequence and overlying flysch deposits. The Metabasite Unit is characterized by a mineral assemblage of blue amphibole, garnet and clinopyroxene, indicating P – T conditions of 500–600 °C and >13 kbar. It is juxtaposed below carpholite-bearing metaconglomerates and quartz-rich micaschists of the Basal Conglomerate Unit, for which metamorphic conditions of 300–450 °C and 10–14 kbar are estimated. The contact between the two units is interpreted a…
New zeolite-like RUB-5 and its related hydrous layer silicate RUB-6 structurally characterized by electron microscopy.
2020
RUB-5 and its related hydrous layer silicate RUB-6 were synthesized in the 1990s, but so far their structures have remained unknown due to their low crystallinity and disorder. The combination of 3D electron diffraction, X-ray powder diffraction, high-resolution transmission electron microscopy, structural modelling and diffraction simulations has enabled a comprehensive description of these two nanomaterials, revealng a new framework topology and a unique silica polymorph.
STACKING-FAULTS IN VERY FINE PALLADIUM PARTICLES SUPPORTED ON PUMICE
1990
By means of an X-ray diffraction study, carried out with best-fitting procedures, of the asymmetry and peak maximum shifts of some reflections, stacking-faults in the FCC lattice of very fine palladium particles supported on pumice were detected using the Warren-Wagner-Cohen theoretical approach.
Geochemical investigations applied to active fault detection in a volcanic area: the North-East Rift on Mt. Etna (Sicily, Italy)
1999
Geochemical investigations were performed on the Northeast Rift of Mt. Etna, a prominent volcanic structure of this volcano. Low-temperature fumaroles were found on the upper part of this area and the isotopic compositions of C(CO2) and He suggest a likely magmatic origin of the emitted gases. On the contrary, very low degassing was found in the lower part of the NE-Rift, with CO2 concentrations generally very close to those in air. This pattern is probably due to sealing of the eruptive fissures by the repeated injections of magma solidified into dikes and by consequent shallow hydrothermal alteration of the fissured rocks due to residual magma degassing. High soil CO2 concentrations were …
Fractal Dimension Logarithmic Differences Method for Low Voltage Series Arc Fault Detection
2021
Series arc faults introduce singularities in the current signal and changes over time. Fractal dimension can be used to characterize the dynamic behaviour of the current signal by providing a degree of signal chaos. This measure of irregularity exhibits changes in signal behaviour that can suitably be used as a basis for series arc fault detection. In this paper, an efficient low voltage series arc fault detection method based on the logarithmic differences of the estimate of the fractal dimension of the current signal using the multiresolution length-based method is presented. The discrete wavelet transform and the hard thresholding denoising with the universal threshold are also used. Exp…
HybridS: A Scheme for Secure Distributed Data Storage in WSNs
2008
In unattended wireless sensor networks (WSNs), data is stored locally or at designated nodes upon sensing, and users can access it on demand. This paradigm can improve energy efficiency by making use of the upcoming cheap and large flash memory, as well as system robustness. Nevertheless, the security and dependability of distributed storage are critical for the applicability of such WSNs. In this paper, we propose a secure and dependable data storage scheme by taking advantages of secret sharing and Reed-Solomon code, which has computational security and yet maintains optimal data size. The extensive analysis verifies our scheme can provide secure and dependable data storage in WSNs in the…