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Power Loss (power + loss)
Selected AbstractsPower loss with the Aestiva/5 anaesthetic machineANAESTHESIA, Issue 4 2010A. R. Jones No abstract is available for this article. [source] A simple method to calculate the signal-to-noise ratio of a circular-shaped coil for MRICONCEPTS IN MAGNETIC RESONANCE, Issue 6 2006K. Ocegueda Abstract The introduction of the ultrafast imaging sequences has renewed the interest in development of RF coils. The theoretical frame of the SNR of MRI coils is a challenge because it requires a deep mathematical background to master the associated concepts. Here, a simpler method is proposed based on Legendre polynomials. This approximation method, together with a quasi-static approach, was used to derive a signal-to-noise ratio expression for a circular-shaped coil. Legendre polynomials were used instead of a weighting function to simplify the vector potential of the power loss, and an SNR formula was then derived. The simplified version of the SNR formula of a circular coil was compared with the weighting function-derived SNR expression using the quasi-static approach. SNR-vs.-depth plots were computed to theoretically compare both SNR formulas. Results showed a strong agreement between SNR values for the circular-shaped coil. This approach can be used as a tool to derive SNR expressions for more complex geometries. © 2006 Wiley Periodicals, Inc. Concepts Magn Reson Part A 28A: 422,429, 2006 [source] An efficient hybrid evolutionary algorithm based on PSO and ACO for distribution feeder reconfigurationEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2010Taher Niknam Abstract A new formulation based on norm2 method for the multi objective distribution feeder reconfiguration (DFR) is introduced in order to minimize the real power loss, deviation of the nodes' voltage, the number of switching operations, and to balance the loads on the feeders. In the proposed method, since the objective functions are not the same and commensurable, the objective functions are considered as a vector and the aim is to maximize the distance (norm2) between the objective function vector and the worst objective function vector while the constraints are met. The status of the tie and sectionalizing switches are considered as the control variables. The proposed DFR problem is a multi objective and non-differentiable optimization problem so a hybrid evolutionary algorithm based on Particle Swarm Optimization (PSO) and Ant Colony Optimization (ACO), called HPSO, is proposed to solve it. The feasibility of the HPSO algorithm and the proposed DFR is demonstrated and compared with the solutions obtained by other approaches and evolutionary methods such as genetic algorithm (GA), ACO and the original PSO, over different distribution test systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Non-superconducting fault current limitersEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2009M. Tarafdar Hagh Abstract This paper proposes the use of non-superconducting DC reactor type fault current limiter (NSFCL) instead of superconducting fault current limiters (SFCLs) which has high cost and technology. Proposed FCL consists of three similar sets, each including a diode bridge and a single non-superconducting DC reactor. The device is connected in series with distribution line and it has almost no effect on the normal system operation. It is not necessary to use a control circuit and it has a simple and cheap power circuit. Design characteristics, analytical analysis and overall transient and steady-state performance of NSFCL in normal and fault conditions are presented in this paper. The comparison between experimental and simulation results indicate good agreements. The results confirm that the power loss of NSFCL is a very small percentage of distribution line power. Also, the system current and load voltage distortions due to using NSFCL is explained and simulated. Copyright © 2008 John Wiley & Sons, Ltd. [source] Multistage designs in the genomic era: Providing balance in complex disease studiesGENETIC EPIDEMIOLOGY, Issue S1 2007Marie-Pierre Dubé Abstract In this summary paper, we describe the contributions included in the Multistage Design group (Group 14) at the Genetic Analysis Workshop 15, which was held during November 12,14, 2006. Our group contrasted and compared different approaches to reducing complexity in a genetic study through implementation of staged designs. Most groups used the simulated dataset (problem 3), which provided ample opportunities for evaluating various staged designs. A wide range of multistage designs that targeted different aspects of complexity were explored. We categorized these approaches as reducing phenotypic complexity, model complexity, analytic complexity or genetic complexity. In general we learned that: (1) when staged designs are carefully planned and implemented, the power loss compared to a single-stage analysis can be minimized and study cost is greatly reduced; (2) a joint analysis of the results from each stage is generally more powerful than treating the second stage as a replication analysis. Genet. Epidemiol. 31 (Suppl. 1):S118,S123, 2007. © 2007 Wiley-Liss, Inc. [source] Influence of oil type on the performance characteristics of a two-axial groove journal bearingLUBRICATION SCIENCE, Issue 9 2009D. M. C. McCarthy Abstract The use of environmentally adapted lubricants (EALs) is a subject of growing interest to industry as legislation increasingly demands the replacement of mineral oil lubricants. Vegetable-based fluids are widely seen as providing lubricants from a renewable source, as well as meeting demands for improved biodegradability. However, at present, utilization of such fluids is limited due to their rapid oxidation. EALs produced from other base stocks (i.e. synthetic esters) have been shown to provide performance benefits in hydrodynamic thrust bearings. In the present study, a hydrodynamic journal bearing test rig has been employed to compare the performance of three EALs (a VG32 saturated ester, rapeseed base fluid and a propylene glycol dioleate) relative to three mineral turbine oils (ISOVG32, ISOVG46 and ISOVG68) in the hydrodynamic regime. Results are given in terms of temperature, power loss and minimum film thickness. The impact of oil viscosity index is also discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Calculation of sliding power loss in spur gear contactsLUBRICATION SCIENCE, Issue 1 2002Arto Lehtovaara Abstract An engineering-level calculation model for sliding power loss in spur gear contacts is presented. Teeth contact through the line of action is modelled as a constantly changing roller contact whose radius, speed, and load can be calculated from the gear geometry under the given operating conditions. The gear mesh cycle is approximated by a large number of elastohydrodynamic contacts. A constant film thickness and a Hertzian pressure distribution are assumed in each contact. The model includes non-Newtonian lubricant behaviour together with temperature and mixed lubrication effects in contact. The numerical solver is reasonably fast in evaluating effectively the sliding power loss dependence on the essential gear and lubricant parameters. The features and behaviour trends of the calculated sliding power losses have a close similarity with published results obtained from measurements and experiment-based power loss models with mineral oil. The limiting shear stress of the lubricant is observed to have an essential role in the power loss behaviour especially at high loads. [source] Dispersion characteristics of LiTi-Ferrite radomeMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2010Naveen Kumar Saxena Abstract The dispersion characteristics of a magnetically switchable LiTi-Ferrite radome is presented. A thin layer of LiTi-ferrite is used as superstrate or radome layer, which control the radiation, reception, and scattering from a printed antenna or array by applying a DC magnetic bias field in the plane of the ferrite, orthogonal to the RF magnetic field. In this analysis, absorbing and transmission power coefficients are calculated to obtain the power loss in radome layer and transmitted power, respectively. The absorbing power coefficient verifies the switching behavior of radome for certain range of applied external magnetic field (Ho), which depends on the resonance width parameter (,H) of ferrite material. By properly choosing the bias field, quasi TEM wave propagation in the ferrite layer can be made to be zero or negative over a certain frequency range, results in a switching behavior in the ferrite layer. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 52,54, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24828 [source] A combined imaging, microthermal and spectroscopic study of a multilayer packaging systemPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2004I. Woodward Abstract The effectiveness of a packaging solution for the pharmaceutical and food industry is dependent on the integrity of the constituent layers and the interfaces formed between them. The deconvolution and analysis of the many intimate layers found in packaging is analytically challenging, requiring techniques capable of identifying sub-micron regions. Here we have characterized the chemical and physical nature of the layers in a multilayer packaging system along with the interfaces, using a combination of high-resolution atomic force microscopy (AFM), microthermal analysis using scanning thermal microscopy (SThM), and Fourier transform infrared (FT-IR) spectroscopy. In particular, localized thermal analysis is shown to reveal the thermal transitions of the individual layers, but it was found that care must be exercised when melting through one layer to the next, as this can result in overestimates of melting temperatures of the underlying layer due to excess power loss from the SThM probe to the already molten top layer surrounding the probe. Copyright © 2004 John Wiley & Sons, Ltd. [source] A Beam-splitting Device for Use with Fiber-coupled Laser Light Sources for Photodynamic Therapy,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2002Leroy M. Wood ABSTRACT A device that divides light into eight, four or two beams of equivalent power with only minor total power loss was designed, built and tested. The apparatus accepts light from a 200 ,m diameter, 0.16 numerical aperture, silica,silica multimode optical fiber connected to one of several laser light sources for photodynamic therapy (PDT) of cancer. The incorporation of a variable iris diaphragm into the optical couplers allows the power of the beams to be independently set. Each of the beams can be coupled to a 400 or 600 ,m diameter optical fiber to deliver the therapeutic light to the patient. This device is used in our institute for PDT of patients with either numerous small malignant tumors or single tumors with large surface area. [source] Design of a Small Centrifugal Blood Pump With Magnetic BearingsARTIFICIAL ORGANS, Issue 9 2009Said Jahanmir Abstract Design of a blood pump with a magnetically levitated rotor requires rigorous evaluation of the magnetic bearing and motor requirements and analysis of rotor dynamics and hydraulic performance with attention to hemolysis and thrombosis potential. Given the desired geometric dimensions, the required operating speed, flow in both the main and wash flow regions, and magnetic bearing performance, one of several design approaches was selected for a new prototype. Based on the estimated operating speed and clearance between the rotor and stator, the motor characteristics and dimensions were estimated. The motor stiffness values were calculated and used along with the hydraulic loading due to the fluid motion to determine the best design for the axial and radial magnetic bearings. Radial and axial stability of the left ventricular assist device prototype was verified using finite element rotor dynamic analysis. The analysis indicated that the rotor could be completely levitated and spun to the desired operating speed with low power loss and no mechanical contact. In vitro experiments with a mock loop test setup were performed to evaluate the performance of the new blood pump prototype. [source] Performance Characterization of a Rotary Centrifugal Left Ventricular Assist Device With Magnetic SuspensionARTIFICIAL ORGANS, Issue 5 2008Said Jahanmir Abstract:, The MiTiHeart (MiTiHeart Corporation, Gaithersburg, MD, USA) left ventricular assist device (LVAD), a third-generation blood pump, is being developed for destination therapy for adult heart failure patients of small to medium frame that are not being served by present pulsatile devices. The pump design is based on a novel, patented, hybrid passive/active magnetic bearing system with backup hydrodynamic thrust bearing and exhibits low power loss, low vibration, and low hemolysis. Performance of the titanium alloy prototype was evaluated in a series of in vitro tests with blood analogue to map out the performance envelop of the pump. The LVAD prototype was implanted in a calf animal model, and the in vivo pump performance was evaluated. The animal's native heart imparted a strong pulsatility to the flow rate. These tests confirmed the efficacy of the MiTiHeart LVAD design and confirmed that the pulsatility does not adversely affect the pump performance. [source] Concept for a New Hydrodynamic Blood Bearing for Miniature Blood Pumps,ARTIFICIAL ORGANS, Issue 10 2004Thomas Kink Abstract: The most crucial element of a long-term implantable rotary blood pump is the rotor bearing. Because of heat generation and power loss resulting from friction, seals within the devices have to be avoided. Actively controlled magnetic bearings, although maintenance-free, increase the degree of complexity. Hydrodynamic bearings for magnetically coupled rotors may offer an alternative solution to this problem. Additionally, for miniature pumps, the load capacity of hydrodynamic bearings scales slower than that of, for example, magnetic bearings because of the cube-square-law. A special kind of hydrodynamic bearing is a spiral groove bearing (SGB), which features an excellent load capacity. Mock-loop tests showed that SGBs do not influence the hydraulic performance of the tested pumps. Although, as of now, the power consumption of the SBG is higher than for a mechanical pivot bearing, it is absolutely contact-free and has an unlimited lifetime. The liftoff of the rotor occurs already at 10% of design speed. Further tests and flow visualization studies on scaled-up models must demonstrate its overall blood compatibility. [source] A small temperature rise may contribute towards the apparent induction by microwaves of heat-shock gene expression in the nematode Caenorhabditis ElegansBIOELECTROMAGNETICS, Issue 2 2006Adam S. Dawe Abstract We have previously reported that low intensity microwave exposure (0.75,1.0 GHz CW at 0.5 W; SAR 4,40 mW/kg) can induce an apparently non-thermal heat-shock response in Caenorhabditis elegans worms carrying hsp16-1::reporter genes. Using matched copper TEM cells for both sham and exposed groups, we can detect only modest reporter induction in the latter exposed group (15,20% after 2.5 h at 26 °C, rising to ,50% after 20 h). Traceable calibration of our copper TEM cell by the National Physical Laboratory (NPL) reveals significant power loss within the cell (8.5% at 1.0 GHz), accompanied by slight heating of exposed samples (,0.3 °C at 1.0 W). Thus, exposed samples are in fact slightly warmer (by ,0.2 °C at 0.5 W) than sham controls. Following NPL recommendations, our TEM cell design was modified with the aim of reducing both power loss and consequent heating. In the modified silver-plated cell, power loss is only 1.5% at 1.0 GHz, and sample warming is reduced to ,0.15 °C at 1.0 W (i.e., ,0.1 °C at 0.5 W). Under sham:sham conditions, there is no difference in reporter expression between the modified silver-plated TEM cell and an unmodified copper cell. However, worms exposed to microwaves (1.0 GHz and 0.5 W) in the silver-plated cell also show no detectable induction of reporter expression relative to sham controls in the copper cell. Thus, the 20% "microwave induction" observed using two copper cells may be caused by a small temperature difference between sham and exposed conditions. In worms incubated for 2.5 h at 26.0, 26.2, and 27.0 °C with no microwave field, there is a consistent and significant increase in reporter expression between 26.0 and 26.2 °C (by ,20% in each of the six independent runs), but paradoxically expression levels at 27.0 °C are similar to those seen at 26.0 °C. This surprising result is in line with other evidence pointing towards complex regulation of hsp16-1 gene expression across the sub-heat-shock range of 25,27.5 °C in C. elegans. We conclude that our original interpretation of a non-thermal effect of microwaves cannot be sustained; at least part of the explanation appears to be thermal. Bioelectromagnetics 27:88,97, 2006. © 2005 Wiley-Liss, Inc. [source] Optimal methodology for distribution systems reconfiguration based on OPF and solved by decomposition techniqueEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2010H. M. Khodr Abstract This paper presents a new and efficient methodology for distribution network reconfiguration integrated with optimal power flow (OPF) based on a Benders decomposition approach. The objective minimizes power losses, balancing load among feeders and subject to constraints: capacity limit of branches, minimum and maximum power limits of substations or distributed generators, minimum deviation of bus voltages and radial optimal operation of networks. The Generalized Benders decomposition algorithm is applied to solve the problem. The formulation can be embedded under two stages; the first one is the Master problem and is formulated as a mixed integer non-linear programming problem. This stage determines the radial topology of the distribution network. The second stage is the Slave problem and is formulated as a non-linear programming problem. This stage is used to determine the feasibility of the Master problem solution by means of an OPF and provides information to formulate the linear Benders cuts that connect both problems. The model is programmed in GAMS. The effectiveness of the proposal is demonstrated through two examples extracted from the literature. Copyright © 2009 John Wiley & Sons, Ltd. [source] A detailed analysis of hotspots and insulation breakdown phenomena in power inductor windings at high frequency regimes: overcurrents and overvoltagesEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2008J. A. Brandão Faria Abstract This research paper is the last of a group of three papers dedicated to the analysis and computation of the high-frequency electromagnetic behaviour of inductor windings where a multiconductor transmission line approach is used. The present work is essentially concerned with application aspects linked up with the important engineering problem of windings insulation damage, which can occur either because of excessive temperature (winding hotspots) or because of excessive electric field strength (dielectric breakdown). For single and multilayer windings we present here a wealth of information in graphical and tabular form concerning the distribution of voltages, currents, electric charges, charge densities, electric field components and power losses along the inductor winding turns, operating at the critical resonance frequencies characteristic of the structure (which is the worst possible scenario). This information is analysed and processed in order to allow for a detection of the winding zones where breakdown phenomena and hotspots could most probably occur. Copyright © 2007 John Wiley & Sons, Ltd. [source] A new algorithm for reactive power management and pricing in an open access environmentEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2008G. Reza Yousefi Abstract In deregulated electricity markets, reactive power is one of the ancillary services that is provided by the Independent System Operator (ISO). In this paper we propose a new algorithm to ,tune' reactive power resources with the objectives of minimizing active power losses and optimizing system voltage profile and stability. In our solution, we assume that reactive power resources are either owned by or are under long-term contracts with the ISO. The optimization problem is solved as an Extended Multi-objective Optimal Power Flow (EMOPF) problem using Lexico Graphic Method (LGM). Thereafter, using the concept of Fair Resource Allocation (FRA), the cost of reactive power is allocated to existing transactions. The application of the algorithm to a test system is also presented. Copyright © 2007 John Wiley & Sons, Ltd. [source] Linear-programming-based method for optimum schedule of reactive power sources in integrated AC-DC power systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2003M. Abdel-Salam This paper is aimed at obtaining the optimal flow of reactive power which corresponds to minimum real power losses in integrated AC-DC power systems including one DC link. The DC power or DC current, drawn by the link at its rectifier side is introduced as a new control variable added to the normal control variables, i.e. transformer tap-settings, generator terminal voltages and reactive-power outputs, and switchable reactive power sources. The constraints include the reactive power limits of the generators, limits on the load bus voltages and the operating limits of the control variables. Dual linear programming is applied to minimize an objective function for system losses. Application of the proposed method on different test AC-DC systems confirmed that less system losses is achieved with the introduction of the DC control variable. [source] Testing a Vapour-fed PBI-based Direct Ethanol Fuel CellFUEL CELLS, Issue 5 2009J. Lobato Abstract This work is focused on the application and performance of a high temperature PBI-based direct ethanol fuel cell, studying the influence of some operating variables such as the temperature, ethanol concentration and oxygen partial pressure. An increase in the temperature resulted in an improvement of the cell performance due to the enhanced electrodic kinetic and electrolyte conductivity. An ethanol/water weight ratio between 0.25 and 0.5 was found to be suitable for providing both enough water and fuel availability to make the ethanol oxidation possible. Measurements of the ethanol crossover at different temperatures and concentrations were carried out. An intermittent lifetime test showed that the cell, after several hours, was able to reach stability. Moreover, its performance was completely reversible with no perceptible losses for 7,days. Finally, tests using bio-ethanol as fuel were performed, with no significant power losses. This final feature is of special interest from a practical ,green' point of view. [source] Numerical solution of eddy current problems in ferromagnetic bodies travelling in a transverse magnetic fieldINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2003W. Peterson Abstract Eddy currents are investigated in a ferromagnetic bar travelling in a transverse magnetic field. Such an open boundary field problem is analysed by a hybrid approach based on Galerkin finite element formulation coupled with a separation of variables. A steady state is considered, introducing time-periodic boundary conditions. The resultant system of non-linear equations is solved by an iterative procedure based on Brouwer's fixed-point theorem. Numerical results are presented for a bar of circular cross-section made of cast steel or cast iron. Selected examples of the field distribution and characteristics of eddy-current power losses are enclosed in graphic form. Copyright © 2003 John Wiley & Sons, Ltd. [source] A fast power loss calculation method for long real time thermal simulation of IGBT modules for a three-phase inverter systemINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2006Z. Zhou Abstract A fast power losses calculation method for long real time thermal simulation of IGBT module for a three-phase inverter system is presented in this paper. The speed-up is obtained by simplifying the representation of the three-phase inverter at the system modelling stage. This allows the inverter system to be simulated predicting the effective voltages and currents whilst using large time-step. An average power losses is calculated during each clock period, using a pre-defined look-up table, which stores the switching and on-state losses generated by either direct measurement or automatically based upon compact models for the semiconductor devices. This simulation methodology brings together accurate models of the electrical systems performance, state of the art-device compact models and a realistic simulation of the thermal performance in a usable period of CPU time and is suitable for a long real time thermal simulation of inverter power devices with arbitrary load. Thermal simulation results show that with the same IGBT characteristics applied, the proposed model can give the almost same thermal performance compared to the full physically based device modelling approach. Copyright © 2006 John Wiley & Sons, Ltd. [source] Calculation of sliding power loss in spur gear contactsLUBRICATION SCIENCE, Issue 1 2002Arto Lehtovaara Abstract An engineering-level calculation model for sliding power loss in spur gear contacts is presented. Teeth contact through the line of action is modelled as a constantly changing roller contact whose radius, speed, and load can be calculated from the gear geometry under the given operating conditions. The gear mesh cycle is approximated by a large number of elastohydrodynamic contacts. A constant film thickness and a Hertzian pressure distribution are assumed in each contact. The model includes non-Newtonian lubricant behaviour together with temperature and mixed lubrication effects in contact. The numerical solver is reasonably fast in evaluating effectively the sliding power loss dependence on the essential gear and lubricant parameters. The features and behaviour trends of the calculated sliding power losses have a close similarity with published results obtained from measurements and experiment-based power loss models with mineral oil. The limiting shear stress of the lubricant is observed to have an essential role in the power loss behaviour especially at high loads. [source] Spatially resolved evaluation of power losses in industrial solar cells by illuminated lock-in thermographyPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 5 2004Joerg Isenberg Abstract The principles of a recently introduced measurement technique for power losses in solar cells, illuminated lock-in thermography (ILT), are reviewed. The main advantage of ILT over dark lock-in Thermography (DLT) is measurement under realistic operational conditions of solar cells. The main focus of this paper is to demonstrate the wide range of applications of ILT in identifying the causes of power losses in solar cells. For this purpose different evaluation methods are presented. A method for the evaluation of improvement potentials within a given cell technology is demonstrated. It is shown that different types of series resistance may be localized. Small areas of recombination losses (e.g., grain boundaries) can routinely be detected, which is not possible in dark lock-in thermography. Good correspondence with light-beam-induced current images is found. A realistic evaluation of the impact of recombination losses on solar cell performance is demonstrated on two examples. Finally, process- or treatment-induced recombination losses are investigated. In summary ILT is shown to be an extremely powerful tool in localizing, identifying and quantifying power losses of solar cells under realistic illumination conditions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Incorporation of Electronics within a Compact, Fully Implanted Left Ventricular Assist DeviceARTIFICIAL ORGANS, Issue 11 2002Kevin Bourque Abstract: The promise of expanded indications for left ventricular assist devices in the future for very long-term applications (10+ years) prompts sealed (i.e. fully implanted) systems and less-obtrusive and more reliable implanted components than their external counterparts in percutaneous configurations. Furthermore, sealed systems increase the fraction of total power losses dissipated intracorporeally, a disadvantage that must be carefully managed. We set out to incorporate the motor drive and levitation control electronics within the HeartMate III blood pump without substantially increasing the pump's size. Electronics based on a rigid-flex satellite printed circuit board (PCB) arrangement that could be folded into a very compact, dense package were designed, fabricated, and tested. The pump's lower housing was redesigned to accommodate these PCBs without increasing any dimension of the pump except the height, and that by only 5 mm. The interconnect cable was reduced from 22 wires to 10 (two fully redundant sets of 5). An ongoing test of the assembled pump in vitro has demonstrated no problems in 5 months. In addition, a 20-day in vivo test showed only 1°C temperature rises, equivalent to pumps without incorporated electronics at similar operating conditions. [source] | ||||||||||||||||