Search results for " Electronics"
showing 10 items of 580 documents
Safeguarding the Ultra-dense Networks with the aid of Physical Layer Security: A review and a case study
2016
In the wake of the extensive application of the fourth generation system, investigations of new technologies have been moving ahead vigorously to embrace the next generation communications in 2020. Thereinto, the technique of ultra-dense networks (UDNs) serves as a key enabler in meeting the roaring mobile traffic demands. With the prevalence of mobile Internet services especially those involve the mobile payment, security has gained an unprecedented amount of attention and become a highlighted feature for the fifth generation. Resource allocation, one of the most significant tools on getting over the obstacle of ubiquitous interference as well as elevating the spectrum/energy efficiency, h…
An approach to the optimum design of the magnetic circuit of a PM linear electrical generator driven by stochastical forces
2006
Linear electrical generator has been recently studied for the exploitation of sea waves energy. In order to maximize the energy extraction, the stochastic features of the energy source must be included in the mathematical model of the system. A PM linear electrical generator has been designed and built. The design has been optimized by including in the mathematical model used for the optimization the following aspects: 1. the dynamic and stochastic features of the waves; 2. a dynamic model of the hydraulic conversion system; 3. a parametric circuit model of the magnetic circuit as well as of the electric windings; 4. a circuit model of the power electronics converter used to connect the gen…
Green Synthesis, Molecular Characterization and Associative Behavior of Some Gemini Surfactants without a Spacer Group.
2013
A series of new gemini surfactants without a spacer group, disodium 2,3-dialkyl-1,2,3,4-butanetetracarboxylates, were synthesized in a green chemistry context minimizing the use of organic solvents and applying microwaves (MW) when activation energy was required. Once the desired architecture was confirmed by means of the nuclear magnetic resonance technique (1H-NMR, 1H-1H COSY) for all the studied surfactants, the critical micellization concentration was determined by conductance measurements. The diffusion coefficient of micelles formed by the four compounds was characterized using pulsed field gradient (PFG)-NMR. Diffusion coefficients were found to be dependent on the concentration and …
A Novel Systolic Parallel Hardware Architecture for the FPGA Acceleration of Feedforward Neural Networks
2019
New chips for machine learning applications appear, they are tuned for a specific topology, being efficient by using highly parallel designs at the cost of high power or large complex devices. However, the computational demands of deep neural networks require flexible and efficient hardware architectures able to fit different applications, neural network types, number of inputs, outputs, layers, and units in each layer, making the migration from software to hardware easy. This paper describes novel hardware implementing any feedforward neural network (FFNN): multilayer perceptron, autoencoder, and logistic regression. The architecture admits an arbitrary input and output number, units in la…
Optimizing the Performance of Data Warehouse by Query Cache Mechanism
2022
Fast access of data from Data Warehouse (DW) is a need for today’s Business Intelligence (BI). In the era of Big Data, the cache is regarded as one of the most effective techniques to improve the performance of accessing data. DW has been widely used by several organizations to manage data and use it for Decision Support System (DSS). Many methods have been used to optimize the performance of fetching data from DW. Query cache method is one of those methods that play an effective role in optimization. The proposed work is based on a cache-based mechanism that helps DW in two aspects: the first one is to reduce the execution time by directly accessing records from cache memory, and th…
Decoupled Downlink-Uplink Coverage Analysis with Interference Management for Enriched Heterogeneous Cellular Networks
2016
Heterogeneous cellular networks (HetCNets) offer a promising solution to cope with the current cellular coverage crunch. Due to the large transmit power disparity, while following maximum power received (MPR) association scheme, a larger number of users are associated with macro-cell BS (MBS) than small-cell BSs (SBSs). Therefore, an imbalance load arrangement takes place across the HetCNets. Hence, using cell range expansion-based cell association, we can balance the load across the congested MBS. However, using MPR association scheme, users’ offloading leads to two challenges: 1) macro-cell interference , in which the MBS interferes with the offloaded users, and 2) coupled downlink-uplink…
Analysis of load balancing and interference management in heterogeneous cellular networks
2017
To meet the current cellular capacity demands, proactive offloading is required in heterogeneous cellular networks (HetCNets) comprising of different tiers of base stations (BSs), e.g., small-cell BSs (sBSs) and conventional macro-cell BSs (mBSs). Each tier differs from the others in terms of BS transmit power, spatial density, and association bias. Consequently, the coverage range of each tier BSs is also different from others. Due to low transmit power, a fewer number of users are associated to an sBS as compared with mBS. Thus, inefficient utilization of small-cell resources occurs. To balance the load across the network, it is necessary to push users to the underloaded small cells from …
LOFT - A large observatory for x-ray timing
2010
The high time resolution observations of the X-ray sky hold the key to a number of diagnostics of fundamental physics, some of which are unaccessible to other types of investigations, such as those based on imaging and spectroscopy. Revealing strong gravitational field effects, measuring the mass and spin of black holes and the equation of state of ultradense matter are among the goals of such observations. At present prospects for future, non-focused X-ray timing experiments following the exciting age of RXTE/PCA are uncertain. Technological limitations are unavoidably faced in the conception and development of experiments with effective area of several square meters, as needed in order to…
Vircator Technologies Comparison and Novel Anode Analysis
2021
High Power Microwave (HPM) sources are widely used as signal sources in radar, jammer, and Counter Improvised Explosive Devices (CIED). Such devices usually are heavy and bulky, characteristics that are in conflict with the small weight and power (SWaP) approach so that it is practically impossible to mount such HPMs on several platforms with reduced spaces (e.g., avionic, UAVs). During the last century, several devices have been proposed, all of them heavy due to the components that they need such as the magnetic material of the Magnetron, Klystron, or Gyrotron. Considering the HPM sources for pulsed applications, the VIRtual CAThode oscillatOR (Vircator) represents the best candidate due …
Jahn-Teller effect in molecular electronics: quantum cellular automata
2017
The article summarizes the main results of application of the theory of the Jahn-Teller (JT) and pseudo JT effects to the description of molecular quantum dot cellular automata (QCA), a new paradigm of quantum computing. The following issues are discussed: 1) QCA as a new paradigm of quantum computing, principles and advantages; 2) molecular implementation of QCA; 3) role of the JT effect in charge trapping, encoding of binary information in the quantum cell and non-linear cell-cell response; 4) spin-switching in molecular QCA based on mixed-valence cell; 5) intervalence optical absorption in tetrameric molecular mixed-valence cell through the symmetry assisted approach to the multimode/mul…