456 research outputs found

    Optimal Wideband LPDA Design for Efficient Multimedia Content Delivery over Emerging Mobile Computing Systems

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    An optimal synthesis of a wideband Log-Periodic Dipole Array (LPDA) is introduced in the present study. The LPDA optimization is performed under several requirements concerning the standing wave ratio, the forward gain, the gain flatness, the front-to-back ratio and the side lobe level, over a wide frequency range. The LPDA geometry that complies with the above requirements is suitable for efficient multimedia content delivery. The optimization process is accomplished by applying a recently introduced method called Invasive Weed Optimization (IWO). The method has already been compared to other evolutionary methods and has shown superiority in solving complex non-linear problems in telecommunications and electromagnetics. In the present study, the IWO method has been chosen to optimize an LPDA for operation in the frequency range 800-3300 MHz. Due to its excellent performance, the LPDA can effectively be used for multimedia content reception over future mobile computing systems

    Radiometric Wireless Sensor Network Monitoring of Partial Discharge Sources in Electrical Substations

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    A wireless sensor network (WSN) with the potential to monitor and locate partial discharge (PD) in high-voltage electricity substations using only received signal strength (RSS) is proposed. The advantages of an RSS-based operating principle over more traditional methods (e.g., time-of-arrival and time-difference-of-arrival) are described. Laboratory measurements of PD that emulate the operation of a PD WSN are presented. The hardware architecture of a prototype PD WSN is described and the particular challenges of an RSS-based location approach in an environment with an unknown, and spatially varying, path-loss index are discussed. It is concluded that an RSS-based PD WSN is a plausible solution for the monitoring of insulation integrity in electricity substations

    Low complexity wireless sensor system for partial discharge localisation

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    This study describes a key element of any modern wireless sensor system: data processing. The authors describe a system consisting of a wireless sensor network and an algorithmic software for condition-based monitoring of electrical plant in a live substation. Specifically, the aim is to monitor for the presence of partial discharge (PD) using a matrix of inexpensive radio sensors with limited processing capability. A low-complexity fingerprinting technique is proposed, given that the sensor nodes to be deployed will be highly constrained in terms of processing power, memory and battery life. Two variants of artificial neural network (ANN) learning models (multilayer perceptron and generalised regression neural network) that use regression as a form of function approximation are developed and their performance compared to K-nearest neighbour and weighted K-nearest neighbour models. The results indicate that the ANN models yield superior performance in terms of robustness against noise and may be particularly suited for PD localisation

    Cerebral fat embolism and the "starfield" pattern: a case report

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    Nearly all long-bone fractures are accompanied by some form of fat embolism. The rare complication of clinically significant fat embolism syndrome, however, occurs in only 0.9-2.2% of cases. The clinical triad of fat embolism syndrome consists of respiratory distress, altered mental status, and petechial rash. Cerebral fat embolism causes the neurologic involvement seen in fat embolism syndrome. A 19-year-old African-American male was admitted with gunshot wounds to his right hand and right knee. He had diffuse hyperactive deep tendon reflexes, bilateral ankle clonus and decerebrate posturing with a Glasgow Coma Scale (GCS) score of 4T. Subsequent MRI of the brain showed innumerable punctate areas of restricted diffusion consistent with "starfield" pattern. On a 10-week follow up he has a normal neurological examination and he is discharged home. Despite the severity of the neurologic insult upon initial presentation, the majority of case reports on cerebral fat embolism illustrate that cerebral dysfunction associated with cerebral fat embolism is reversible. When neurologic deterioration occurs in the non-head trauma patient, then a systemic cause such as fat emboli should be considered. We describe a patient with non-head trauma who demonstrated the classic "starfield" pattern on diffusion-weighted MRI imaging

    Exponential Log-Periodic Antenna Design Using Improved Particle Swarm Optimization with Velocity Mutation

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    An improved particle swarm optimization (PSO) method applied to the design of a new wideband log-periodic antenna (LPA) geometry is introduced. This new PSO variant, called PSO with velocity mutation (PSOvm), induces mutation on the velocities of those particles that cannot improve their position. The proposed LPA consists of wire dipoles with lengths and distances varied according to an exponential rule, which is defined by two specific parameters called length factor and spacing factor. The LPA is optimized for operation in 790-6000MHz frequency range, in order to cover the most usual wireless services in practice, and also to provide in this range the highest possible forward gain, gain flatness below 2dB, secondary lobe level below –20dB with respect to the main lobe peak, and standing wave ratio below 2. To demonstrate its superiority in terms of performance, PSOvm is compared to well-known optimization methods. The comparison is performed by applying all the methods on several test functions and also on the LPA optimization problem defined by the above-mentioned requirements. Furthermore, the radiation characteristics of the PSOvm-based LPA give prominence to the effectiveness of the proposed exponential geometry compared to the traditional Carrel’s geometry

    An Efficient Algorithm for Partial Discharge Localization in High-Voltage Systems Using Received Signal Strength

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    The term partial discharge (PD) refers to a partial bridging of insulating material between electrodes that sustain an electric field in high-voltage (HV) systems. Long-term PD activity can lead to catastrophic failures of HV systems resulting in economic, energy and even human life losses. Such failures and losses can be avoided by continuously monitoring PD activity. Existing techniques used for PD localization including time of arrival (TOA) and time difference of arrival (TDOA), are complicated and expensive because they require time synchronization. In this paper, a novel received signal strength (RSS) based localization algorithm is proposed. The reason that RSS is favoured in this research is that it does not require clock synchronization and it only requires the energy of the received signal rather than the PD pulse itself. A comparison was made between RSS based algorithms including a proposed algorithm, the ratio and search and the least squares algorithm to locate a PD source for nine different positions. The performance of the algorithms was evaluated by using two field scenarios based on seven and eight receiving nodes, respectively. The mean localization error calculated for two-field-trial scenarios show, respectively, 1.80 m and 1.76 m for the proposed algorithm for all nine positions, which is the lowest of the three algorithms

    Gated pipelined folding ADC based low power sensor for large-scale radiometric partial discharge monitoring

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    Partial discharge is a well-established metric for condition assessment of high-voltage plant equipment. Traditional techniques for partial discharge detection involve physical connection of sensors to the device under observation, limiting sensors to monitoring of individual apparatus, and therefore, limiting coverage. Wireless measurement provides an attractive low-cost alternative. The measurement of the radiometric signal propagated from a partial discharge source allows for multiple plant items to be observed by a single sensor, without any physical connection to the plant. Moreover, the implementation of a large-scale wireless sensor network for radiometric monitoring facilitates a simple approach to high voltage fault diagnostics. However, accurate measurement typically requires fast data conversion rates to ensure accurate measurement of faults. The use of high-speed conversion requires continuous high-power dissipation, degrading sensor efficiency and increasing cost and complexity. Thus, we propose a radiometric sensor which utilizes a gated, pipelined, sample-and-hold based folding analogue-todigital converter structure that only samples when a signal is received, reducing the power consumption and increasing the efficiency of the sensor. A proof of concept circuit has been developed using discrete components to evaluate the performance and power consumption of the system

    Diagnostic Potential of Free-Space Radiometric Partial Discharge Measurements

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    The work reported in this paper addresses the calibration of four types of partial discharge (PD) emulator required for the development of a PD Wireless Sensor Network (WSN). Three partial discharge (PD) emulators have been constructed: a floating-electrode emulator, and two internal PD emulators. Both DC and AC HV power supplies are used to initiate PD which is measured using concurrent free-space radiometry (FSR) and a galvanic contact method based on the IEC 60270 standard. A new method of estimating absolute PD activity level from a radiometric measurement is proposed

    REACH MUSC: A Telemedicine Facilitated Network for Stroke: Initial Operational Experience

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    REACH Medical University of South Carolina (MUSC) provides stroke consults via the internet in South Carolina. From May 2008 to April 2011 231 patients were treated with intravenous (IV) thrombolysis and 369 were transferred to MUSC including 42 for intra-arterial revascularization [with or without IV tissue plasminogen activator (tPA)]. Medical outcomes and hemorrhage rates, reported elsewhere, were good (Lazaridis et al., 2011). Here we report operational features of REACH MUSC which covers 15 sites with 2,482 beds and 471,875 Emergency Department (ED) visits per year. Eight Academic Faculty from MUSC worked with 165 different physicians and 325 different nurses in the conduct of 1085 consults. For the 231 who received tPA, time milestones (in minutes) were: Onset to Door: 62 (mean), 50 (median); Door to REACH Consult: 43 and 33, Consult Request to Consult Start: was 9 and 7, Consult Start to tPA Decision: 31 and 25; Decision to Infusion: 20 and 14, and total Door to Needle: 98 and 87. The comparable times for the 854 not receiving tPA were: Onset to Door: 140 and 75; Door to REACH Consult: 61 and 41; Consult Request to Consult Start: 9 and 7, Consult Start to tPA Decision: 27 and 23. While the consultants respond to consult requests in <10, there is a long delay between arrival and Consult request. Tracking of operations indicates if we target shortening Door to Call time and time from tPA decision to start of drug infusion we may be able to improve Door to Needle times to target of <60. The large number of individuals involved in the care of these patients, most of whom had no training in REACH usage, will require novel approaches to staff education in ED based operations where turnover is high. Despite these challenges, this robust system delivered tPA safely and in a high fraction of patients evaluated using the REACH MUSC system
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