scholarly journals Scattering Evaluation of Equivalent Surface Impedances of Acoustic Metamaterials in Large FDTD Volumes Using RLC Circuit Modelling

2021 ◽  
Vol 11 (17) ◽  
pp. 8084
Author(s):  
Eric Ballestero ◽  
Brian Hamilton ◽  
Noé Jiménez ◽  
Vicent Romero-García ◽  
Jean-Philippe Groby ◽  
...  
Keyword(s):  
Surface Impedance ◽  
Complex Impedance ◽  
Acoustic Metamaterials ◽  
Zero Crossings ◽  
Physical Conditions ◽  
Novel Approach ◽  
Rlc Circuit ◽  
Computing Environments ◽  
Difference Time ◽  
Vast Range

Most simulations involving metamaterials often require complex physics to be solved through refined meshing grids. However, it can prove challenging to simulate the effect of local physical conditions created by said metamaterials into much wider computing sceneries due to the increased meshing load. We thus present in this work a framework for simulating complex structures with detailed geometries, such as metamaterials, into large Finite-Difference Time-Domain (FDTD) computing environments by reducing them to their equivalent surface impedance represented by a parallel-series RLC circuit. This reduction helps to simplify the physics involved as well as drastically reducing the meshing load of the model and the implicit calculation time. Here, an emphasis is made on scattering comparisons between an acoustic metamaterial and its equivalent surface impedance through analytical and numerical methods. Additionally, the problem of fitting RLC parameters to complex impedance data obtained from transfer matrix models is herein solved using a novel approach based on zero crossings of admittance phase derivatives. Despite the simplification process, the proposed framework achieves good overall results with respect to the original acoustic scatterer while ensuring relatively short simulation times over a vast range of frequencies.

scholarly journals Hybrid two-mode squeezing of microwave and optical fields using optically pumped graphene layers

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Montasir Qasymeh ◽  
Hichem Eleuch
Keyword(s):  
Microwave Field ◽  
Microwave Frequency ◽  
Optically Pumped ◽  
Optical Fields ◽  
Graphene Layers ◽  
Novel Approach ◽  
Small Uncertainty ◽  
Electrical Modulation ◽  
First Time ◽  
Vast Range

Abstract A measurable quadrature of a squeezed quantum state manifests a small uncertainty below the Heisenberg limit. This phenomenon has the potential to enable several extraordinary applications in quantum information, metrology and sensing, and other fields. Several techniques have been implemented to realize squeezed electromagnetic states, including microwave fields and optical fields. However, hybrid squeezed modes (that incorporate both microwave and optical fields) have not yet been proposed despite their vital functionality to combine the two worlds of quantum superconducting systems and photonics systems. In this work, for the first time, we propose a novel approach to achieve two-mode squeezing of microwave and optical fields using graphene based structure. The proposed scheme includes a graphene layered structure that is driven by a quantum microwave voltage and subjected to two optical fields of distinct frequencies. By setting the optical frequency spacing equal to the microwave frequency, an interaction occurs between the optical and microwave fields through electrical modulation of the graphene conductivity. We show that significant hybrid two-mode squeezing, that includes one microwave field and one optical field, can be achieved. Furthermore, the microwave frequency can be tuned over a vast range by modifying the operation parameters.

Answering Continuous Description Logic Queries

2016 ◽  
pp. 893-938
Author(s):  
Carlos Bobed ◽  
Fernando Bobillo ◽  
Sergio Ilarri ◽  
Eduardo Mena
Keyword(s):  
Mobile Computing ◽  
Description Logic ◽  
Description Logics ◽  
Data Access ◽  
Location Data ◽  
Novel Approach ◽  
Continuous Description ◽  
Efficient Data ◽  
Continuous Query Processing ◽  
Computing Environments

During the last years, mobile computing has been the focus of many research efforts, due mainly to the ever-growing use of mobile devices. In this context, there is a need to manage dynamic data, such as location data or other data provided by sensors. As an example, the continuous processing of location-dependent queries has been the subject of thorough research. However, there is still a need of highly expressive ways of formulating queries, augmenting in this way the systems' answer capabilities. Regarding this issue, the modeling power of Description Logics (DLs) and the inferring capabilities of their attached reasoners could fulfill this new requirement. The main problem is that DLs are inherently oriented to model static knowledge, that is, to capture the nature of the modeled objects, but not to handle changes in the property values (which requires a full ontology reclassification), as it is common in mobile computing environments (e.g., the location is expected to vary continually). In this paper, the authors present a novel approach to process continuous queries that combines 1) the DL reasoning capabilities to deal with static knowledge, with 2) the efficient data access provided by a relational database to deal with volatile knowledge. By marking at modeling time the properties that are expected to change during the lifetime of the queries, the authors'system is able to exploit both the results of the classification process provided by a DL reasoner, and the low computational costs of a database when accessing changing data (mobile environments, semantic sensors, etc.), following a two-step continuous query processing that enables us to handle continuous DL queries efficiently. Experimental results show the feasibility of the authors' approach.

Dual Functional Energy Harvesting and Vibration Control: Electromagnetic Resonant Shunt Series Tuned Mass Dampers

2012 ◽  
Author(s):  
Lei Zuo ◽  
Wen Cui
Keyword(s):  
Energy Harvesting ◽  
Vibration Control ◽  
Vibration Suppression ◽  
Primary System ◽  
Dual Functional ◽  
Novel Approach ◽  
Rlc Circuit ◽  
Gradient Based ◽  
And Performance ◽  
Resonant Shunt

This paper proposes a novel approach for dual-functional energy harvesting and vibration control by integrating the tuned mass damper (TMD) and electromagnetic shunted resonant damping. The viscous dissipative element between the TMD and primary system is replaced by an electromagnetic transducer shunted with a resonant RLC circuit. An efficient gradient based method is presented for the parameter optimization in the control framework for vibration suppression and energy harvesting. A case study is performed based on the Taipei 101 TMD. It is founded that by tuning the TMD resonance and circuit resonance close to that of the primary structure, the electromagnetic resonant shunt TMD achieves the enhanced effectiveness and robustness of double-mass series TMDs, without suffering from the significantly amplified motion stroke. It is also observed that the parameters and performance optimized for vibration suppression are close to those optimized for energy harvesting, and the performances are not sensitive to the resistance of the charging circuit or electrical load.

Answering Continuous Description Logic Queries

2014 ◽  
Vol 10 (3) ◽  
pp. 1-44 ◽  
Author(s):  
Carlos Bobed ◽  
Fernando Bobillo ◽  
Sergio Ilarri ◽  
Eduardo Mena
Keyword(s):  
Mobile Computing ◽  
Description Logic ◽  
Description Logics ◽  
Data Access ◽  
Location Data ◽  
Novel Approach ◽  
Continuous Description ◽  
Efficient Data ◽  
Continuous Query Processing ◽  
Computing Environments

During the last years, mobile computing has been the focus of many research efforts, due mainly to the ever-growing use of mobile devices. In this context, there is a need to manage dynamic data, such as location data or other data provided by sensors. As an example, the continuous processing of location-dependent queries has been the subject of thorough research. However, there is still a need of highly expressive ways of formulating queries, augmenting in this way the systems' answer capabilities. Regarding this issue, the modeling power of Description Logics (DLs) and the inferring capabilities of their attached reasoners could fulfill this new requirement. The main problem is that DLs are inherently oriented to model static knowledge, that is, to capture the nature of the modeled objects, but not to handle changes in the property values (which requires a full ontology reclassification), as it is common in mobile computing environments (e.g., the location is expected to vary continually). In this paper, the authors present a novel approach to process continuous queries that combines 1) the DL reasoning capabilities to deal with static knowledge, with 2) the efficient data access provided by a relational database to deal with volatile knowledge. By marking at modeling time the properties that are expected to change during the lifetime of the queries, the authors'system is able to exploit both the results of the classification process provided by a DL reasoner, and the low computational costs of a database when accessing changing data (mobile environments, semantic sensors, etc.), following a two-step continuous query processing that enables us to handle continuous DL queries efficiently. Experimental results show the feasibility of the authors' approach.

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