Search results for "Wire"
showing 10 items of 1383 documents
Towards quantum phase slip based standard of electric current
2019
An accurate standard of electric current is a long-standing challenge of modern metrology. It has been predicted that a superconducting nanowire in the regime of quantum fluctuations can be considered as the dynamic equivalent of a chain of conventional Josephson junctions. In full analogy with the quantum standard of electric voltage based on the Josephson effect, the quantum phase slip phenomenon in ultrathin superconducting nanowires could be used for building the quantum standard of electric current. This work presents advances toward this ultimate goal.
Optical properties and microstructure of 2.02-3.30 eV ZnCdO nanowires: effect of thermal annealing
2013
International audience; ZnCdO nanowires with up to 45% Cd are demonstrated showing room temperature photoluminescence (PL) down to 2.02 eV and a radiative efficiency similar to that of ZnO nanowires. Analysis of the microstructure in individual nanowires confirms the presence of a single wurtzite phase even at the highest Cd contents, with a homogeneous distribution of Cd both in the longitudinal and transverse directions. Thermal annealing at 550 C yields an overall improvement of the PL, which is blue-shifted as a result of the homogeneous decrease of Cd throughout the nanowire, but the single wurtzite structure is fully maintained.
Direct observation of elemental segregation in InGaN nanowires by X-ray nanoprobe
2011
Using synchrotron radiation nanoprobe, this work reports on the elemental distribution in single Inx Ga1–xN nanowires (NWs) grown by molecular beam epitaxy directly on Si(111) substrates. Single NWs dispersed on Al covered sapphire were characterized by nano-X-ray fluorescence, Raman scattering and photoluminescence spectroscopy. Both Ga and In maps reveal an inhomogeneous axial distribution inside sin- gle NWs. The analysis of NWs from the same sample but with different dimensions suggests a decrease of In segregation with the reduction of NW diameter, while Ga distribution seems to remain unaltered. Photoluminescence and Raman scattering measurements carried out on ensembles of NWs exhibi…
Potential of Automated Digital Hemispherical Photography and Wireless Quantum Sensors for Routine Canopy Monitoring and Satellite Product Validation
2021
To better characterize the temporal dynamics of vegetation biophysical variables, a variety of automated in situ measurement techniques have been developed in recent years. In this study, we investigated automated digital hemispherical photography (DHP) and wireless quantum sensors, which were installed at two sites under the Copernicus Ground Based Observations for Validation (GBOV) project. Daily estimates of plant area index (PAI) and the fraction of absorbed photosynthetically active radiation (FAPAR) were obtained, which realistically described expected vegetation dynamics. Good correspondence with manual DHP and LAI-2000 data (RMSE = 0.39 to 0.90 for PAI, RMSE = 0.07 for FAPAR) provid…
Performance analysis of Alamouti-coded OFDM systems over spatio-temporally correlated underwater acoustic channels
2017
In this paper, we analyze the performance of Alamouti-coded orthogonal frequency division multiplexing (OFDM) systems over time-varying underwater acoustic (UWA) channels. A realistic UWA channel model has been considered, which can be correlated in either time or space or simultaneously in both domains. An exact analytical expression for the bit error probability (BEP) is necessary to analyze accurately the performance of Alamouti-coded OFDM systems over the spatio-temporally correlated UWA channel model. Hence, by using this UWA channel model, an expression has been derived for the BEP of Alamouti-coded OFDM systems assuming that the receiver knows perfectly the channel state information.…
Effect of Metal Complexation on the Conductance of Single-Molecular Wires Measured at Room Temperature
2014
The present work aims to give insight into the effect that metal coordination has on the room-temperature conductance of molecular wires. For that purpose, we have designed a family of rigid, highly conductive ligands functionalized with different terminations (acetylthiols, pyridines, and ethynyl groups), in which the conformational changes induced by metal coordination are negligible. The single-molecule conductance features of this series of molecular wires and their corresponding Cu(I) complexes have been measured in break-junction setups at room temperature. Experimental and theoretical data show that no matter the anchoring group, in all cases metal coordination leads to a shift towar…
Communication cost of channel estimation interpolation for group-based vehicular communications in cellular networks
2020
Las comunicaciones inalámbricas para aplicaciones vehiculares en sistemas celulares de quinta generación (5G) deben ser de baja latencia y alta fiabilidad. Entre otros factores, la cantidad de información de control que debe intercambiarse entre cada vehículo y la estación base puede penalizar la latencia de la comunicación. Varios casos de uso vehicular 5G implican comunicaciones dentro de grupos de vehículos, por ejemplo el pelotón de vehículos. Este trabajo se centra en explotar la estructura y características de este servicio vehicular particular basado en grupos para disminuir el intercambio de información de control relacionado con la etapa de estimación del canal necesaria para las c…
Peer-to-peer cooperative GNSS-based localization for stationary reference nodes in wireless sensor networks
2017
Most localization algorithms in wireless sensor networks rely on a few reference nodes with known locations to estimate the locations of unknown nodes. The locations of reference nodes can be either manually configured or, more practically, obtained by means of some satellite-based positioning system(s). However, satellite-based locations may be inaccurate and imprecise, which results in reduced location accuracy of localization algorithms. This paper proposes a peer-to-peer cooperative GNSS-based localization algorithm for stationary reference nodes to improve their relative location accuracy and precision. The algorithm applies simple statistical methods and GNSS-based information from mu…
Wireless NoC for Inter-FPGA Communication: Theoretical Case for Future Datacenters
2020
Integration of FPGAs in datacenters might have different motivations from acceleration to energy efficiency, but the goal of better performance tops all. FPGAs are being utilized in a variety of ways today, tightly coupled with heterogenous computing resources, and as a standalone network of homogenous resources. Open source software stacks, propriety tool chain, and programming languages with advanced methodologies are hitting hard on the programmability wall of the FPGAs. The deployment of FPGAs in datacenters will neither be sustainable nor economical, without realizing the multi-tenancy in multiple FPGAs. Inter-FPGA communication among multiple FPGAs remained relatively less addressed p…
Security and Privacy in Wireless IoT
2018
The 13 articles in this special section focus on security and privacy in wireless Internet of Things (IoT). IoT is a paradigm that involves networked physical objects with embedded technologies to collect, communicate, sense, and interact with the external environment through wireless or wired connections. With rapid advancements in IoT technology, the number of IoT devices is expected to surpass 50 billion by 2020, which has also drawn the attention of attackers who seek to exploit the merits of this new technology for their own benefits. There are many potential security and privacy threats to IoT, such as attacks against IoT systems and unauthorized access to private information of end u…