Reduced Power Requirements Research Articles

Power requirements for vibrotactile piezo-electric and electromechanical transducers.

Human-machine information transfer through tactile excitation has addressed new applications in virtual reality, robotics, telesurgery, sensory substitution and rehabilitation for the handicapped in the past few years. Power consumption is an important factor in the design of vibrotactile displays, because it affects energy needs and the size, weight, heat dissipation and cost of the associated electronics. An experimental study is presented on the power required to reach tactile thresholds in electromechanical and piezo-electric transducers. Three different waveforms are considered, with an excitatory period formed by a burst of rectangular 50% duty cycle pulses (R50), rectangular low duty cycle pulses (RLO) and sinusoidal pulses (SIN). Ten different pulse repetition periods (RPs) were considered in the range 1/550-1/25 s. The voltage and current waveforms applied to the transducers at sensation thresholds in a group of 12 healthy subjects were sampled and stored in a digital oscilloscope. The average power was determined for each subject, and differences of two orders of magnitude were measured between the electromechanical and the piezo-electric transducer power consumption. Results show that, for the electromechanical transducer, a smaller power consumption of 25 microW was determined for RP = 1/25 s and the RLO waveform. In the case of the piezo-electric transducer, power of 0.21 microW was determined for SIN excitation and RP = 1/250 s. These results show the advantages of reducing power requirements for vibrotactile displays, which can be optimised by the choice of appropriate types of transducer, excitatory waveforms and pulse repetition periods.

Non-metallic mag drive

Iwaki Walchem has launched a new line of magnetic drive pumps called MX. The range introduces a volute casing to non-metallic magnetic drive pumps that the company claims can dramatically increase hydraulic efficiency and reduce power requirements. A bearing flush circuit reduces internal heat build-up, giving the MX dry run capability and increasing pump life. All stress bearing portions of the MX are reinforced to improve pressure resistance and mechanical strength. Flows to 150gpm are available, heads to 120ft. MX offers a smaller package, corrosion-resistant, sealless construction, and comes with a two-year warranty on all parts. This is a short news story only. Visit www.worldpumps.com for the latest pump industry news

소요동력 절감을 위한 트랙터 로터리의 개발 - 이물질 감김방지 및 흙부착방지 장치 -

소요동력 절감을 위한 트랙터 로터리의 개발 - 이물질 감김방지 및 흙부착방지 장치 -

High-pressure discharges with imposed stability resulting in reduced power requirements

High-pressure plasma discharge columns that are long and straight, as well as uniform in the axial direction, have been generated in a steady state. These discharges, stabilized by rotation of the containment envelope about a horizontal axis, have reduced heat transport to the wall due to the absence of buoyancy-driven radial convection and the elimination of eddies caused by sheared flow. These “rotating tube discharges” may take the form of electric arcs powered with dc or low-frequency ac; or of electrodeless plasmas, heated by electromagnetic waves at rf or microwave frequencies.

The use of plastic optical fibres and shape memory alloys for damage assessmentand damping control in composite materials

This paper reports the use of a plastic fibre sensor for detecting impactdamage in carbon fibre epoxy cantilever beams by monitoring their dampingresponse under free vibration loading conditions. The composite beamswere impacted at impact energies up to 8 J. The residual strengths andstiffnesses of the damaged laminates were measured in order to relatereductions in their mechanical properties to changes in their dampingcharacteristics. Here, optical fibre sensors were surface bonded to carbon fibrecomposite beams which were subjected to free vibration tests to monitortheir dynamic response.In the second part of this study, Ni–Ti shapememory alloy (SMA) wires were employed to control and modify thedamping response of a composite beam. The SMA wires were initiallytrained to obtain the desired shape when activated. Here, the trained SMAwires were heated locally using a nickel/chromium wire that was wrappedaround the trained region of the SMA. By using this method to activatethe SMA wire (as opposed to direct electrical heating), it is possible toobtain localized actuation without heating the entire length of the wire.This procedure minimizes any damage to the host material that mayresult from local heat transfer between the SMA wire and the compositestructure. In addition, the reduction in power requirements to achieve SMAactivation permits the use of small-size power packs which can in turnlead to a potential weight reduction in weight-critical applications. Thefindings of this study demonstrate that a trained SMA offers a superiordamping capability to that exhibited by an ‘as-supplied’ flat-annealed wire.

OPTIMIZED MOTOR CONTROL ENHANCES MECHANICAL RELIABILITY OF PULSATILE ELECTROMECHANICAL VAD

In bridge to heart transplantation as well as permanent support of end-stage heart failure patients, a compact, totally implantable, electromechanical pulsatile VAD suitable for 50–60Kg patients has been developed. The diameter and thickness of the VAD are 90cm and 56cm, yielding the 275 cc volume and 400g weight. The pump can provide maximum flow of 8 L/min against 100 mmHg. For long term reliable operation of VAD in vivo, overall system reliability must be proven through in vitro mechanical as well as in vivo anti-thrombogenic performance studies. For mechanical reliability, an attention was paid to reduce the impact forces to bearings that support the roller-screw actuator. Motor speed patterns were programmed to reduce the impact forces at both end-systolic and end-diastolic points. The bench testing showed a remarkable reduction in power requirement to 4–5 Watts at 4 L/min flow against 100mmHg afterload. For durability testing, the VAD was submerged in a 37 degree C water bath simulating the biological environment. Motor current and VAD internal temperature were continuously monitored to detect changes in the system performance. The VAD temperature did not exceed 2 degree C than the surrounding, and the power requirement remained at 4–5 watts. Currently, one system is running without failure over 2.5 month period. This VAD is now moving toward clinical readiness testing including anti-thrombogenic performance in long term animal studies.

Modelling and characterization of a piezoceramic inertial actuator

An inertial actuator (also known as a proof mass actuator) applies forces to a structure by reacting them against an “external” mass. This approach to actuation may provide some practical benefits in the active control of vibration and structure-borne noise: system reliability may be improved by removing the actuator from a structural load path; effective discrete point-force actuation permits ready attachment to curved surfaces, and an inherent passive vibration absorber effect can reduce power requirements. This paper describes a class of recently developed inertial actuators that is based on mechanical amplification of displacements of an active piezoceramic element. Important actuator characteristics include resonance frequencies, clamped force, and the drive voltage to output the force frequency response function. The paper addresses one particular approach to motion amplification, the “dual unimorph,” in detail. A model of actuator dynamic behavior is developed using an assumed-modes method, treating the piezoelectrically induced stresses as external forces. Predicted actuator characteristics agree well with experimental data obtained for a prototype actuator. The validated actuator dynamic model provides a tool for design improvement.

Low-power digital neuron for SOM implementations

A digital implementation of the self-organising map (SOM) is shown to have reduced power requirements through a strategy of increasing silicon area while reducing the number of clock cycles required to process each element of an input vector. Designs requiring two clock cycles, one clock cycle, and half clock cycle per element of the input vector have been constructed and analysed. The designs offer a reduction in power of a factor of 3 for an increase in silicon area of some 33%.

CORN CANOPY TEMPERATURES MEASURED WITH A MOVING INFRARED THERMOMETER ARRAY

Measurement of water stress and scheduling of irrigation are both enabled by noncontact infrared thermometers(IRTs). Technological advances have miniaturized IRTs and reduced power requirements so that inexpensive selfpoweredunits are now commercially available. The objective of this work was to test a linear array of IRT sensors mounted on acenterpivot irrigation machine, and to use this IRT array to examine spatial variation in water stress of corn under fourirrigation treatments imposed on a highly variable field with a center pivot equipped for sitespecific irrigation andagrochemical application. An array of 26 IRTs was mounted on the pivot, which was run dry for a full circle on 7 days duringthe 1999 corn growing season. Procedures were developed to adjust for time lag during the 3.5hr measurement period.Significant differences were obtained among the varying water treatments, as expected, but also among plots within the samesoil map unit and among soil map unit means. Distinct spatial patterns, not necessarily related to the 1:1200scale soil map,were observed. These results emphasize the necessity to consider soil water relations during the development of managementrecommendations for sitespecific agriculture.

Low power state assignment and flipflop selection for finite state machine synthesis—a genetic algorithmic approach

Current renewed emphasis for more aggressive logic designs with lesser area, delay, and power demands exploration of alternative avenues that could lead to better designs, albeit at the higher cost of computation. The author explores the avenue of genetic algorithm for a holistic view for synthesis of finite state machine (FSM) targeting power reduction by incorporating both state assignment and sequential element selection. Exhaustive experimentation performed on a large suite of benchmarks has established the fact that this tool results in state encodings with on average 46.08% reduction in power requirement over NOVA, without any significant increase in the number of product terms. The effectiveness of judicious flipflop selection has been demonstrated by showing that the approach with all D-flipflops as the sequential element requires 33.78% more power than the approach with a choice of D and T flipflop types. Moreover, as compared to the technique presented in LPSA, the algorithm presented here requires 38.96% less power when using a mix of D and T flipflops. The quality of the solution obtained and the high rate of convergence have established the effectiveness of the genetic algorithm in solving this particular NP-complete problem. Further, the inherent parallelism of genetic algorithm makes the proposed scheme ideal for solving the problem in a multiprocessor environment.

The 42V power system with energy management in the matrix architecture of the vehicle’s electrical system

Based on the matrix architecture of the electrical system in the motor vehicle, this article examines the possibilities that are available for reducing the power requirements of the electrical components. Improving the electrical efficiency, increasing the system voltage, reducing power requirements and a subtle adaptation of the operating periods of electrical functions to the operation of the vehicle are all means by which the energy balance can be positively influenced.

Average power reduction techniques for multiple-subcarrier intensity-modulated optical signals

We describe two classes of simple, effective techniques for reducing the average optical power requirement in intensity-modulated optical systems using multiple BPSK or QPSK subcarriers. The first class of techniques involves block coding between the information bits to be transmitted and the symbol amplitudes modulated onto the subcarriers in order to increase the minimum value of the multiple-subcarrier electrical waveform. The second class of techniques involves replacing the fixed DC bias by a bias signal that varies on a symbol-by-symbol basis. These two classes of techniques can be applied separately or in tandem. The reduction in power requirement increases with the number of subcarriers and, with eight subcarriers, can be as high as about 3.6 dB and 3.2 dB with BPSK and QPSK, respectively. The techniques described are applicable as long as all subcarriers originate from a single transmitter and are symbol-synchronized.

Compact low field magnetic resonance imaging magnet: Design and optimization

Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80–100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These “dedicated” apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

Application of biofiltration in the crude oil processing industry

For the purification of industrial waste water from the crude oil processing industry, a multiple stage treatment plant is recommended. Biofiltration takes place as a secondary treatment stage. Under plug-flow conditions residual compounds can be treated efficiently with a reduced power requirement. Specialized microorganisms, utilizing compounds which are not readily biodegradable, are immobilized on burned clay. Usually toxic peaks do not inhibit the microorganisms in the biofilm. This depends on the short retention time of the water in fixed bed systems and on the characteristic of the biofilm. Dissolved, colloidal or particulate non-biodegradable substances will be adsorbed on the biofilm and can be removed by backwashing the reactor. A description of the treatment plants at BP-oiltech Hamburg and Shell Refinery Hamburg is given. The design of the fixed film reactors is discussed.

Application of biofiltration in the crude oil processing industry

For the purification of industrial waste water from the crude oil processing industry, a multiple stage treatment plant is recommended. Biofiltration takes place as a secondary treatment stage. Under plug-flow conditions residual compounds can be treated efftciendy with a reduced power requirement. Specialized microorganisms, utilizing compounds which are not readily biodegradable, are immobilized on burned clay. Usually toxic peaks do not inhibit the microorganisms in the biofdm. This depends on the short retention time of the water in fixed bed systems and on the characteristic of the biotilm. Dissolved, colloidal or particulate non-biodegradable substances will be adsorbed on the biofilm and can be removed by backwashing the reactor. A description of the treatment plants at BP-oiltech Hamburg and Shell Refinery Hamburg is given. The design of the fixed film reactors is discussed.

Deterministic channel modeling and long range prediction of fast fading mobile radio channels

In wireless communication systems, the direct signal and the reflected signals form an interference pattern resulting in a received signal given by the sum of these components. They are distinguished by their Doppler shifts at the mobile. Since the parameters associated with these components are slowly varying, the fading coefficients can be accurately predicted far ahead. This novel approach to fading channel prediction is combined with transmitter signal optimization to mitigate the effects of deep fades, which severely limit the performance of mobile radio systems. This capability will potentially help to reduce power requirements for wireless channels and improve the system performance.

Heat Transfer in Two-Phase Solid-Liquid Food Flows: A Review

Higher quality food can be produced by continuous aseptic processes rather than by the essentially batch process of in-container sterilization of particulate foods. In continuous aseptic processing, a food mixture passes continuously through a heathold- cool system, and is then packaged in presterilized containers. This results in shorter processing times, higher production rates, superior product quality, reduced power requirements, and improved process control. The design of such a plant requires knowledge of the rates of heat exchange (both fluid-particle and wall-fluid) which take place within the process. At present there is a severe lack of understanding of two-phase solid-liquid food flows, and suitable commercial sterilization schedules must be determined experimentally for every food product processed. Until enough knowledge of real flows has been gained, food manufacturers will adhere to conservative approaches in the design of each stage in a heathold-cool system. Following the recent review on the fluid mechanics of solid-liquid food flows6, this paper reviews the current state-of-the-art in the area of heat transfer. The fluid-particle and the wall-fluid heat transfer coefficients are crucial design parameters. Measurement techniques and mathematical models for estimating them are reviewed, the application of existing knowledge to the design of continuous aseptic processes is discussed, and research needs are highlighted.

Performance studies of narrow-beam trisector cellular systems

This paper analyzes and compares two different approaches to base station sectorization: the traditional wide-beam trisector cell (WBTC); and the newer (but not well-characterized) narrow-beam trisector cell (NBTC). Unlike the WBTC architecture using three 100/spl deg/-120/spl deg/ antennas in a base station, the NBTC architecture (also called "clover-leaf") uses three 60/spl deg/-70/spl deg/ antennas at each base. We obtain new results on the quantitative performance of both architectures, taking into account the impact of (1) actual (rather than ideal) antenna patterns, (2) channel utilization factor, (3) site diversity, (4) non-ideal cell site locations, and (5) the influences of reuse factor and shadow fading. We show that the performance of NBTC systems exceeds that of WBTC systems, both in signal-to-interference ratio (SIR) statistics and signal coverage. The improvement in coverage translates to a reduced power requirement of about 2 dB for the same cell size, or equivalently, to a 25% larger cell coverage area for the same power. The improvement in SIR performance corresponds to a gain of 2-3 dB in the 90/sup th/ SIR percentile. This gain can be translated to significantly improved grade-of-service in cellular environments, with no attendant cost.

Recycling of waste of aluminum foil into sheet materials

The principal method of recycling secondary metals, in particular aluminum, is remelting. However, remelting of aluminum swarf, and in particular of foil trimmings, is marked by low effectiveness because of extensive oxidation (in the processing of thin foil loss by oxidation amounts to 80%), low productivity of the metallurgical equipment on account of low volume-weight characteristics of foil trimmings compared with lumpy scrap metal, and high power requirements of metallurgical conversion. The shortcomings of the traditional technology can be eliminated by recycling foil trimmings by methods of powder metallurgy. This eliminates completely remelting and loss of metal by oxidation, simplifies the technological cycle, and reduces power requirements. We investigated the process of recycling aluminum foil marque A6 (GOST 21631-76) 14 and 30 {mu}m thick which is widely used in the food industry. The amount of waste occurring in its production may attain 15% of the annual output. In the initial state the waste of foil for food are trimmings of thin aluminum strip crushed into fragments of arbitrary shape whose maximal size in plan is 5-8 cm. To be processed by methods of powder metallurgy, such waste has to be converted into smaller fragments that fill well the cavity ofmore » the die when pressed in closed molds or the deformation zone in rolling or other methods of compaction in open tools.« less

Rapid stochastic acceleration of protons to energies above 100 TeV in the accretion column of Hercules X-1

Abstract An investigation into the acceleration of protons by scattering off relativistic Alfven waves in the accretion column of Hercules X-1 is presented. The mechanism is shown to achieve mean particle energies of 30 TeV under very reasonable assumptions about the environment, and 250 TeV is available under some circumstances. The highest individual energy attained is almost 1 PeV. The protons emerge in the form of a narrow beam directed at the inner edge of the accretion disk, which is favourable because of the reduced power requirement and presence of target material for γ-ray production.