			Home About us Contact

Power Requirements (power + requirement)

Distribution by Scientific Domains

Chemistry	41%
Engineering	23%
Medical Sciences	17%

Selected Abstracts

Detection of Left Ventricle Function From a Magnetically Levitated Impeller Behavior

ARTIFICIAL ORGANS, Issue 5 2006
Hideo Hoshi
Abstract:, The magnetically levitated (Mag-Lev) centrifugal rotary blood pump (CRBP) with two-degrees-of-freedom active control is promising for safe and long-term support of circulation. In this study, Mag-Lev CRBP controllability and impeller behavior were studied in the simulated heart failure circulatory model. A pneumatically driven pulsatile blood pump (Medos VAD [ventricular assist device]-54 mL) was used to simulate the left ventricle (LV). The Mag-Lev CRBP was placed between the LV apex and aortic compliance tank simulating LV assistance. The impeller behavior in five axes (x, y, z, ,, and ,) was continuously monitored using five eddy current sensors. The signals of the x - and y -axes were used for feedback active control, while the behaviors of the other three axes were passively controlled by the permanent magnets. In the static mock circuit, the impeller movement was controlled to within ±10,±20 µm in the x- and y -axes, while in the pulsatile circuit, LV pulsation was modulated in the impeller movement with the amplitude being 2,22 µm. The amplitude of impeller movement measured at 1800 rpm with the simulated failing heart (peak LV pressure [LVP] = 70 mm Hg, mean aortic pressure [AoPmean] = 55 ± 20 mm Hg, aortic flow = 2.7 L/min) was 12.6 µm, while it increased to 19.2 µm with the recovered heart (peak LVP = 122 mm Hg, AoPmean = 100 ± 20 mm Hg, aortic flow = 3.9 L/min). The impeller repeated the reciprocating movement from the center of the pump toward the outlet port with LV pulsation. Angular rotation (,, ,) was around ±0.002 rad without z -axis displacement. Power requirements ranged from 0.6 to 0.9 W. Five-axis impeller behavior and Mag-Lev controller stability were demonstrated in the pulsatile mock circuit. Noncontact drive and low power requirements were shown despite the effects of LV pulsation. The impeller position signals in the x - and y -axes reflected LV function. The Mag-Lev CRBP is effective not only for noncontact low power control of the impeller, but also for diagnosis of cardiac function noninvasively. [source]

Field metabolic rates of black-browed albatrosses Thalassarche melanophrys during the incubation stage

JOURNAL OF AVIAN BIOLOGY, Issue 6 2004
Scott A. Shaffer
Field metabolic rates (FMR) and activity patterns of black-browed albatrosses Thalassarche melanophrys were measured while at sea and on nest during the incubation stage at Kerguelen Island, southwestern Indian Ocean. Activity-specific metabolic rates of five albatrosses at sea (FMRat-sea) were measured using doubly labeled water (DLW), and by equipping birds with wet-dry activity data loggers that determined when birds were in flight or on the water. The metabolic rates of four birds incubating their eggs (FMRon-nest) were also measured using DLW. The mean±SD FMRat-sea of albatrosses was 611±96 kJ kg,1 d,1 compared to FMRon-nest of 196±52 kJ kg,1 d,1. While at sea, albatrosses spent 52.9±8.2% (N=3) of their time in flight and they landed on the water 41.2±13.9 times per day. The FMR of black-browed albatrosses appear to be intermediate to that of three other albatross species. Based on at-sea activity, the power requirement of flight was estimated to be 8.7 W kg,1 (or 4.0×predicted BMR), which is high compared to other albatross species, but may be explained by the high activity levels of the birds when at sea. The FMRat-sea of albatrosses, when scaled with body mass, are lower than other seabirds of similar body size, which probably reflects the economical nature of their soaring flight. [source]

A new recovery process of carbon dioxide from alkaline carbonate solution via electrodialysis

AICHE JOURNAL, Issue 12 2009
Hiroki Nagasawa
Abstract Bipolar membrane electrodialysis is applied to CO2 recovery from alkaline carbonate solution. CO2 in flue gas is captured by an alkaline hydroxide absorbing solution to form an alkaline carbonate solution. The captured CO2 is recovered from the alkaline carbonate solution via bipolar membrane electrodialysis, and the alkaline solution is regenerated simultaneously. To reduce the power requirement for CO2 recovery, this study considers optimal design and operation. Three membrane arrangements were compared, and the results indicate the membrane arrangement comprising a bipolar membrane and cation exchange membrane is the most energy saving. With further optimization of operation conditions, the minimum power requirement for CO2 recovery was reduced to 2.1 MJ/kg-CO2 (or 2.1 GJ/t-CO2). © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

A low local oscillator power K-band mixer based on tunneling diodes

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2009
Iacopo Magrini
Abstract In this article, we will demonstrate a low local oscillator (LO) power K-band mixer based on a tunneling diode technology. Due to its unique diode characteristics, no DC supply is needed, whereas an LO power as low as ,2 dBm is required for nominal functionality. The energy-efficient MMIC prototype integrates a pair of heterojunction interband tunnel diodes and a 90° coplanar broadband coupler. The prototype is optimized within the 19,26 GHz band, with an IF ranging from zero to 7 GHz. In addition, when compared with other mixers, it has the lowest LO power requirement with a conversion loss ranging from 6 to 10 dB, an input compression point of ,3 dBm and an intercept 2nd and 3rd order intermodulation point of 22 and 12 dBm, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1140,1143, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24228 [source]

A digitally controlled band-switching VCO using switching inductors and capacitors in 0.18 ,m CMOS

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2008
Tienyu Chang
Abstract In this article, a digitally controlled band-switching voltage controlled oscillator (VCO) is designed and fabricated using TSMC 0.18 ,m CMOS technology. Design considerations regarding the power requirement and the phase noise of the VCO are discussed. Eight bands are set by three bits, with one bit controlling switching inductors, and two bits controlling switching capacitors. The VCO covers 2.9,3.45 GHz and 3.6,4.3 GHz using varactors for continuous frequency tuning. Phase noise of the VCO stays constant around ,110 dBc/Hz at 1 MHz offset for all bands. The fabricated VCO consumes 11 mA of current with 1.8 V supply voltage and has a small size of 730 ,m × 660 ,m. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1970,1973, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23496 [source]

Giant repeated ejections from GRS 1915+105

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2000
R. P. Fender
We report simultaneous millimetre and infrared observations of a sequence of very large amplitude quasi-periodic oscillations from the black hole X-ray binary GRS 1915+105. These oscillations are near the end of a sequence of over 700 repeated events as observed at 15 GHz, and are simultaneous at the mm and infrared wavelengths to within our time resolution (4 min), consistent with the respective emitting regions being physically close near the base of the outflow. One infrared event appears to have no mm counterpart, perhaps owing to highly variable absorption. The overall radio,mm,infrared spectrum around the time of the observations does suggest some absorption at lower frequencies. We calculate the energy and mass-flow into the outflow for a number of different assumptions, and find that the time-averaged power required to produce the observed synchrotron emission cannot be much lower than 3×1038 erg s,1, and is likely to be much larger. This minimum power requirement is found regardless of whether the observed emission arises in discrete ejections or in an internal shock in a quasi-continuous flow. Depending on the similarity of the physical conditions in the two types of ejection, GRS 1915+105 may be supplying more power (and mass, if both have the same baryonic component) to the jet during periods of repeated oscillations than during the more obvious larger events. [source]

Integrated control method for a fuel cell hybrid system

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
Hongwen He
Abstract To apply a fuel cell engine (FCE) on a hybrid electric vehicle, an integrated control method is put forward according to the driving characteristics of the vehicle. The FCE's output power is self-regulated to minimize hydrogen consumption and at the same time to meet the driving power requirement of the vehicle. For the difference of the power output dynamics, the actual power difference between the FCE and the vehicle load is compensated passively by a secondary power battery pack. Vehicle experiments show that the fuel cell hybrid system works well without any adverse influence on the vehicle power performance. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Electrochemical Sensing of Explosives

ELECTROANALYSIS, Issue 4 2007
Joseph Wang
Abstract This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field-deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low-cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low-cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (,Lab-on-Chip') devices for on-site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems. [source]

Electrochemical Detection for Capillary Electrophoresis Microchips: A Review

ELECTROANALYSIS, Issue 13 2005
Joseph Wang
Abstract Electrochemistry detection offers considerable promise for capillary-electrophoresis (CE) microchips, with features that include remarkable sensitivity, portability, independence of optical path length or sample turbidity, low cost and power requirements, and high compatibility with modern micromachining technologies. This article highlights key strategies in controlled-potential electrochemical detectors for CE microchip systems, along with recent advances and directions. Subjects covered include the design of the electrochemical detection system, its requirements and operational principles, common electrode materials, isolation from the separation voltage, derivatization reactions, typical applications, and future prospects. It is expected that electrochemical detection will become a powerful tool for CE microchip systems and will lead to the creation of truly portable (and possibly disposable) devices. [source]

Fabrication of a Multilayered Low-Temperature Cofired Ceramic Micro-Plasma-Generating Device

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2006
Amanda Baker
Plasma technology is currently being used in innumerable industrial applications. Some of the common uses of this technology include surface cleaning and treatment, sputtering and etching of semiconductor devices, excitation source for chemical analyses, cutting, environmental cleanup, sterilization, and phototherapy. The harsh conditions that these devices must endure require robust refractory materials systems for their fabrication and reliability. Low-temperature cofired ceramic (LTCC) material systems provide a durable and cost-effective platform for the manufacture of such devices, and allow for possible integration into meso-scale microsystems. Our designs are based on RF microstriplines that capacitively couple and ionize small gas discharge sites over the top electrode. In this paper, we have built several iterations of this micro-plasma generating device using LTCC material systems. The impact of electrode ink selection and processing, lamination methods, dielectric layer thickness, and electrode design has been investigated. Several micro-plasma-generating devices were then evaluated for power requirements, output stability, and long-term reliability. [source]

RF MEMS-based tunable filters

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 5 2001
James Brank
Abstract This paper overviews the application of RF MEMS switches in tunable filters as well as circuit developments for bandpass filters covering 110 MHz to 2.8 GHz. RF MEMS have several desirable features, including small size, low power requirements, and low loss. The basic operation of Raytheon's RF MEMS capacitive membrane switch is described. An overview of the technique used to integrate the switch into a variable capacitor structure with sixteen capacitance states is provided. Variable capacitor structures are used to construct multipole lumped bandpass filter designs, each with sixteen states. Finally, measured data from two representative five- and six-pole bandpass filters are presented. Characterization data demonstrates that the insertion loss for the five-pole filter using on-chip inductors was between 6.6 and 7.3 dB, and between 3.7 and 4.2 dB for the six-pole filter using off-chip inductors. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 276,284, 2001 [source]

Joint spectrum and power optimization in the design of the UMTS satellite component

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2001
Ernestina Cianca
Abstract The paper provides a power and spectrum joint analysis of the universal mobile telecommunications system (UMTS) satellite component, based on the wideband code division multiple access (W-CDMA) air interface. In fact, power and spectral efficiency may become highly conflicting requirements in a satellite system and a trade-off analysis is needed to drive a proper dimensioning of the satellite. The proposed approach allows a dimensioning of the satellite component either in terms of orbit and power budget or in terms of additional capacity for the terrestrial section, for specified orbit and power limitations. The impact of candidate frequency bands, orbit type and diversity on both spectral and power requirements of the satellite component is evaluated. For given traffic requirements, power-vs-spectrum trade-off is proposed which ensures a proper resources utilization. The efficiency evaluation accounts for: beams overlapping, ortho gonality, voice activity factor, diversity and cross-polarization frequency reuse. Perfect power control is assumed and the effect of the excess power required by the shadowed users is accounted for in the interference calculation. Furthermore, still in the frame of a proper resource exploitation, a possible optimization of capacity through the use of unpaired bands in the two link directions is analysed. Copyright © 2001 John Wiley & Sons, Ltd. [source]

The Orbitrap: a new mass spectrometer

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 4 2005
Qizhi Hu
Abstract Research areas such as proteomics and metabolomics are driving the demand for mass spectrometers that have high performance but modest power requirements, size, and cost. This paper describes such an instrument, the Orbitrap, based on a new type of mass analyzer invented by Makarov. The Orbitrap operates by radially trapping ions about a central spindle electrode. An outer barrel-like electrode is coaxial with the inner spindlelike electrode and mass/charge values are measured from the frequency of harmonic ion oscillations, along the axis of the electric field, undergone by the orbitally trapped ions. This axial frequency is independent of the energy and spatial spread of the ions. Ion frequencies are measured non-destructively by acquisition of time-domain image current transients, with subsequent fast Fourier transforms (FFTs) being used to obtain the mass spectra. In addition to describing the Orbitrap mass analyzer, this paper also describes a complete Orbitrap-based mass spectrometer, equipped with an electrospray ionization source (ESI). Ions are transferred from the ESI source through three stages of differential pumping using RF guide quadrupoles. The third quadrupole, pressurized to less than 10,3 Torr with collision gas, acts as an ion accumulator; ion/neutral collisions slow the ions and cause them to pool in an axial potential well at the end of the quadrupole. Ion bunches are injected from this pool into the Orbitrap analyzer for mass analysis. The ion injection process is described in a simplified way, including a description of electrodynamic squeezing, field compensation for the effects of the ion injection slit, and criteria for orbital stability. Features of the Orbitrap at its present stage of development include high mass resolution (up to 150 000), large space charge capacity, high mass accuracy (2,5 ppm), a mass/charge range of at least 6000, and dynamic range greater than 10.3 Applications based on electrospray ionization are described, including characterization of transition-metal complexes, oligosaccharides, peptides, and proteins. Use is also made of the high-resolution capabilities of the Orbitrap to confirm the presence of metaclusters of serine octamers in ESI mass spectra and to perform H/D exchange experiments on these ions in the storage quadrupole. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Lactate efflux and the neuroenergetic basis of brain function

NMR IN BIOMEDICINE, Issue 7-8 2001
Robert G. Shulman
Abstract In the unstimulated brain energy is primarily supplied by the oxidation of glucose. However the oxygen-to-glucose index (OGI), which is the ratio of metabolic rates of oxygen to glucose, CMRO2/CMRglc, diverges from the theoretical value of 6 as activity is increased. In vivo measurements of brain lactate show its concentration to increase with stimulation. The decreasing OGI with stimulation had led to the suggestion that activation, unlike resting activity, is supported by anaerobic glycolysis. To date a unifying concept that accommodates glucose oxidation at rest with lactate generation and OGI decrease during stimulation of brain is lacking. Furthermore, energetics that change with increasing activity are not consistent with a neuroenergetic model that has been proposed from 1- 13C-glucose MRS experiments. That model, based upon in vivo MRS measurements and cellular studies by Pellerin and Magistretti, showed that glutamate neurotransmitter cycling was coupled to glucose oxidation over a wide range of brain activities from rest down to deep anesthesia. Here we reconcile these paradoxical observations by suggesting that anaerobic glucose consumption (which can provide energy rapidly) increases with activation to meet the power requirements of millisecond neuronal firing. It is proposed, in accord with our neuroenergetic model, that the extra glucose mobilized rapidly for glial clearance of glutamate, is not needed for the oxidative processes that are responsible for neuronal firing and glutamate release, and consequently it is effluxed as lactate. A stoichiometric relation between OGI and lactate concentration is derived from the neuroenergetic model, showing that the enhanced glucose uptake during activation is consistent with neuronal activity being energetically supported by glucose oxidation. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Solids suspension agitation in square tanks

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2008
Emily T. Mitchell
Abstract The Zwietering correlation for the just-suspended speed has been modified to include baffling and geometric effects (impeller-to-tank diameter ratio and impeller off-bottom clearance) for two impeller types (high-efficiency and pitched-blade). Baffles are generally not required when using square tanks although they improve solids suspension performance of pitched-blade turbines. Comparison of square tank solids suspension to that in a fully baffled cylindrical tank has also been made. Very little difference was observed in the power number, but the just-suspended speed, torque, and power requirements were higher in the square tank. On a modifié la corrélation de Zwietering pour la vitesse de suspension minimale afin d'inclure les effets des contrepales et de la geométrie (rapport du diamètre turbine sur réservoir et dégagement de la turbine par rapport au fond) pour deux types de turbines (à efficacité élevée et à pales inclinées). II n'est généralement pas nécessaire d'installer des contrepales dans le cas de réservoirs carrés bien que celles-ci améliorent la performance de la suspension de solides dans le cas des turbines à pales inclinées. On a également comparé la suspension de solides dans un réservoir carré à celle d'un réservoir cylindrique muni de quatre chicanes. Une très faible différence a été observée dans le nombre de puissance, mais la vitesse de suspension minimale, le couple et la demande en puissance sont plus élevés dans le réservoir carré. [source]