Analytical Studies of Fragmented-Spectrum Multi-Level OFDM-CDMA Technique in Cognitive Radio Networks

In this paper, we present a multi-user resource allocation framework using fragmented-spectrum synchronous OFDM-CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, a channel sensing and estimation method is used to obtain information of subcarrier availability. Given this information, some real-valued multi-level orthogonal codes, which are orthogonal codes with values of $\{\pm1,\pm2,\pm3,\pm4, ... \}$, are provided for emerging new users, i.e., cognitive radio users. Additionally, we have obtained a closed form expression for bit error rate of cognitive radio receivers in terms of detection probability of primary users, CR users' sensing time and CR users' signal to noise ratio. Moreover, simulation results obtained in this paper indicate the precision with which the analytical results have been obtained in modeling the aforementioned system.Comment: 6 pages and 3 figure

Типологические особенности глагольной подсистемы современного немецкого языка

Показаны типологические особенности в морфологии глагола современного немецкого языка, а именно: явление синкретизма, системная избыточность, отраженные категории и существование синтоморфологии. Они выявляются при сопоставлении морфологической подсистемы современного немецкого языка с соответствующими подсистемами русского и английского языков и служат показателями аналитических тенденций в его системе, отражая на синхронном срезе постепенный переход ряда функций от морфологии к синтаксису

Cellular Underwater Wireless Optical CDMA Network: Potentials and Challenges

Underwater wireless optical communications is an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access (UW-OCDMA) network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes (OOC) are employed as signature codes of underwater mobile users. Fundamental key aspects of the network such as its backhaul architecture, its potential applications and its design challenges are presented. In particular, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Furthermore, a promising underwater localization and positioning scheme based on this cellular network is presented. Finally, probable design challenges such as cell edge coverage, blockage avoidance, power control and increasing the network capacity are addressed.Comment: 11 pages, 10 figure

Benefiting from Energy-Hub Flexibilities to Reinforce Distribution System Resilience : A Pre- and Post-Disaster Management Model

The proliferation of power-to-gas technology can propound a tailored platform to physically integrate power systems and natural gas grids. These integrated energy systems with different spatial-temporal properties not only could provide significant flexibilities to properly mitigate existing and imminent challenges, but also could increase the robustness of power systems in facing unpredicted conditions. Keeping this in mind, this article outlines a novel conservative two-stage model to improve the resilience of distribution systems against extreme hurricanes. To this end, at the first stage, a pre-disaster scheduling is executed to increase preparedness and robustness of the power system before approaching the tornado. The preparedness index is defined as the sum of energy stored in the electric vehicles and natural gas storages that should be maximized. Subsequently, at the second stage after the recognition of the tornado, some proactive post-disaster actions such as grid partitioning, network reconfiguration, demand-side management, and distributed series reactors are applied to minimize the degradation and vulnerability of the power system. An integrated gas and electricity power flow is proposed in a linear computationally efficient fashion capable of modeling the worst-case scenario. The effectiveness of the model is examined on a distribution grid with multiple energy hubs.© 2022 Authors. Published by IEEE. This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

A Parallel Fast-Track Service Restoration Strategy Relying on Sectionalized Interdependent Power-Gas Distribution Systems

In the distribution networks, catastrophic events especially those caused by natural disasters can result in extensive damage that ordinarily needs a wide range of components to be repaired for keeping the lights on. Since the recovery of system is not technically feasible before making compulsory repairs, the predictive scheduling of available repair crews and black start resources not only minimizes the customer downtime but also speeds up the restoration process. To do so, this paper proposes a novel three-stage buildup restoration planning strategy to combine and coordinate repair crew dispatch problem for the interdependent power and natural gas systems with the primary objective of resiliency enhancement. In the proposed model, the system is sectionalized into autonomous subsystems (i.e., microgrid) with multiple energy resources, and then concurrently restored in parallel considering cold load pick-up conditions. Besides, topology refurbishment and intentional microgrid islanding along with energy storages are applied as remedial actions to further improve the resilience of interdependent systems while unpredicted uncertainties are addressed through stochastic/IGDT method. The theoretical and practical implications of the proposed framework push the research frontier of distribution restoration schemes, while its flexibility and generality support application to various extreme weather incidents.©2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.fi=vertaisarvioitu|en=peerReviewed

Idiopathic generalized epilepsies and efficiency of advanced magnetic resonance imaging techniques in present era; perspectives in future

Epilepsy is a common disorder worldwide, with a prevalence of 4.5/1000 (0.45%) for youngsters and youths, and 1.54/1000 (0.15%) for the adult Chinese population in Hong Kong. up to 15% of epileptic patients can still leak the screening process of any structural lesion. In addition, the structural lesions detected on structural MR images may not reveal the correct degree and practical position of the abnormalities, especially with respect to malformations of cortical development. These include magnetic resonance spectroscopy (MRS) and perfusion weighted imaging (PWI). The widespread application of most of these techniques in clinical practice depends on the availability of high-performance MR imagers with the ability to accomplish fast echo-planar pulse sequences (echo-planar imaging), as well as substantial data processing capabilities. Using and PWI in study of microcirculation of tissues and vascular of lesional area on mechanisms by which selective drugs work and will provide new treatment targets for drug development. Finally, there is coupling of cerebral blood flow and metabolism, MR perfusion can act as a surrogate marker of metabolism as measured by MRS

Spatiotemporal Splitting of Distribution Networks into Self-Healing Resilient Microgrids using an Adjustable Interval Optimization

The distribution networks can convincingly break down into small-scale self-controllable areas, namely microgrids to substitute microgrids arrangements for effectively coping with any perturbations. To achieve these targets, this paper examines a novel spatiotemporal algorithm to split the existing network into a set of self-healing microgrids. The main intention in the grid-tied state is to maximize the microgrids profit while equilibrating load and generation at the islanded state by sectionalizing on-fault area, executing resources rescheduling, network reconfiguration and load shedding when the main grid is interrupted. The proposed problem is formulated as an exact computationally efficient mixed integer linear programming problem relying on the column & constraint generation framework and an adjustable interval optimization is envisaged to make the microgrids less susceptible against renewables variability. Finally, the effectiveness of the proposed model is adequately assured by performing a realistic case study.© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.fi=vertaisarvioitu|en=peerReviewed