8,735 research outputs found
The generation of dual wavelength pulse fiber laser using fiber bragg grating
A stable simple generation of dual wavelength pulse fiber laser on experimental method is proposed and demonstrated by using Figure eight circuit diagram. The generation of dual wavelength pulse fiber laser was proposed using fiber Bragg gratings (FBGs) with two different central wavelengths which are 1550 nm and 1560 nm. At 600 mA (27.78 dBm) of laser diode, the stability of dual wavelength pulse fiber laser appears on 1550 nm and 1560 nm with the respective peak powers of -54.03 dBm and -58.00 dBm. The wavelength spacing of the spectrum is about 10 nm while the signal noise to ratio (SNR) for both peaks are about 8.23 dBm and 9.67 dBm. In addition, the repetition rate is 2.878 MHz with corresponding pulse spacing of about 0.5 ÎŒs, is recorded
Sensor failure detection for jet engines using analytical redundance
Analytical redundant sensor failure detection, isolation and accommodation techniques for gas turbine engines are surveyed. Both the theoretical technology base and demonstrated concepts are discussed. Also included is a discussion of current technology needs and ongoing Government sponsored programs to meet those needs
Noise-based logic: Binary, multi-valued, or fuzzy, with optional superposition of logic states
A new type of deterministic (non-probabilistic) computer logic system
inspired by the stochasticity of brain signals is shown. The distinct values
are represented by independent stochastic processes: independent voltage (or
current) noises. The orthogonality of these processes provides a natural way to
construct binary or multi-valued logic circuitry with arbitrary number N of
logic values by using analog circuitry. Moreover, the logic values on a single
wire can be made a (weighted) superposition of the N distinct logic values.
Fuzzy logic is also naturally represented by a two-component superposition
within the binary case (N=2). Error propagation and accumulation are
suppressed. Other relevant advantages are reduced energy dissipation and
leakage current problems, and robustness against circuit noise and background
noises such as 1/f, Johnson, shot and crosstalk noise. Variability problems are
also nonexistent because the logic value is an AC signal. A similar logic
system can be built with orthogonal sinusoidal signals (different frequency or
orthogonal phase) however that has an extra 1/N type slowdown compared to the
noise-based logic system with increasing number of N furthermore it is less
robust against time delay effects than the noise-based counterpart.Comment: Accepted for publication by Physics Letters A, on December 23, 200
Image formation in synthetic aperture radio telescopes
Next generation radio telescopes will be much larger, more sensitive, have
much larger observation bandwidth and will be capable of pointing multiple
beams simultaneously. Obtaining the sensitivity, resolution and dynamic range
supported by the receivers requires the development of new signal processing
techniques for array and atmospheric calibration as well as new imaging
techniques that are both more accurate and computationally efficient since data
volumes will be much larger. This paper provides a tutorial overview of
existing image formation techniques and outlines some of the future directions
needed for information extraction from future radio telescopes. We describe the
imaging process from measurement equation until deconvolution, both as a
Fourier inversion problem and as an array processing estimation problem. The
latter formulation enables the development of more advanced techniques based on
state of the art array processing. We demonstrate the techniques on simulated
and measured radio telescope data.Comment: 12 page
Sensor failure detection for jet engines
Revisions to the advanced sensor failure detection, isolation, and accommodation (DIA) algorithm, developed under the sensor failure detection system program were studied to eliminate the steady state errors due to estimation filter biases. Three algorithm revisions were formulated and one revision for detailed evaluation was chosen. The selected version modifies the DIA algorithm to feedback the actual sensor outputs to the integral portion of the control for the nofailure case. In case of a failure, the estimates of the failed sensor output is fed back to the integral portion. The estimator outputs are fed back to the linear regulator portion of the control all the time. The revised algorithm is evaluated and compared to the baseline algorithm developed previously
Limits on Fundamental Limits to Computation
An indispensable part of our lives, computing has also become essential to
industries and governments. Steady improvements in computer hardware have been
supported by periodic doubling of transistor densities in integrated circuits
over the last fifty years. Such Moore scaling now requires increasingly heroic
efforts, stimulating research in alternative hardware and stirring controversy.
To help evaluate emerging technologies and enrich our understanding of
integrated-circuit scaling, we review fundamental limits to computation: in
manufacturing, energy, physical space, design and verification effort, and
algorithms. To outline what is achievable in principle and in practice, we
recall how some limits were circumvented, compare loose and tight limits. We
also point out that engineering difficulties encountered by emerging
technologies may indicate yet-unknown limits.Comment: 15 pages, 4 figures, 1 tabl
Autonomous Vehicle Coordination with Wireless Sensor and Actuator Networks
A coordinated team of mobile wireless sensor and actuator nodes can bring numerous benefits for various applications in the field of cooperative surveillance, mapping unknown areas, disaster management, automated highway and space exploration. This article explores the idea of mobile nodes using vehicles on wheels, augmented with wireless, sensing, and control capabilities. One of the vehicles acts as a leader, being remotely driven by the user, the others represent the followers. Each vehicle has a low-power wireless sensor node attached, featuring a 3D accelerometer and a magnetic compass. Speed and orientation are computed in real time using inertial navigation techniques. The leader periodically transmits these measures to the followers, which implement a lightweight fuzzy logic controller for imitating the leader's movement pattern. We report in detail on all development phases, covering design, simulation, controller tuning, inertial sensor evaluation, calibration, scheduling, fixed-point computation, debugging, benchmarking, field experiments, and lessons learned
Register-transfer-level power profiling for system-on-chip power distribution network design and signoff
Abstract. This thesis is a study of how register-transfer-level (RTL) power profiling can help the design and signoff of power distribution network in digital integrated circuits. RTL power profiling is a method which collects RTL power estimation results to a single power profile which then can be analysed in order to find interesting time windows for specifying power distribution network design and signoff.
The thesis starts with theory part. Complementary metal-oxide semiconductor (CMOS) inverter power dissipation is studied at first. Next, power distribution network structure and voltage drop problems are introduced. Voltage drop is demonstrated by using power distribution network impedance figures. Common on-chip power distribution network structure is introduced, and power distribution network design flow is outlined. Finally, decoupling capacitors function and impact on power distribution network impedance are thoroughly explained.
The practical part of the thesis contains RTL power profiling flow details and power profiling flow results for one simulation case in one design block. Also, some methods of improving RTL power estimation accuracy are discussed and calibration with extracted parasitic is then used to get new set of power profiling time windows. After the results are presented, overall RTL power estimation accuracy is analysed and resulted time windows are compared to reference gate-level time windows. RTL power profiling result analysis shows that resulted time windows match the theory and RTL power profiling seems to be a promising method for finding time windows for power distribution network design and signoff.Rekisterisiirtotason tehoprofilointi jÀrjestelmÀpiirin tehonsiirtoverkon suunnittelussa ja verifioinnissa. TiivistelmÀ. TÀssÀ työssÀ tutkitaan, miten rekisterisiirtotason (RTL) tehoprofilointi voi auttaa digitaalisten integroitujen piirien tehonsiirtoverkon suunnittelussa ja verifioinnissa. RTL-tehoprofilointi on menetelmÀ, joka analysoi RTL-tehoestimoinnista saadusta tehokÀyrÀstÀ hyödyllisiÀ aikaikkunoita tehonsiirtoverkon suunnitteluun ja verifiointiin.
Työ alkaa teoriaosuudella, jonka aluksi selitetÀÀn, miten CMOS-invertteri kuluttaa tehoa. Seuravaksi esitellÀÀn tehonsiirtoverkon rakenne ja pahimmat tehonsiirtoverkon jÀnnitehÀviön aiheuttajat. JÀnnitehÀviötÀ havainnollistetaan myös piirikaavioiden ja impedanssikÀyrien avustuksella. LisÀksi integroidun piirin tehonsiirtoverkon suunnitteluvuo ja yleisin rakenne on esitelty. Lopuksi teoriaosuus kÀsittelee yksityiskohtaisesti ohituskondensaattoreiden toiminnan ja vaikutuksen tehonsiirtoverkon kokonaisimpedanssiin.
Työn kokeellisessa osuudessa esitellÀÀn ensin tehoprofiloinnin vuo ja sen jÀlkeen vuon tulokset yhdelle esimerkkilohkolle yhdessÀ simulaatioajossa. LisÀksi tÀssÀ osiossa kÀsitellÀÀn RTL-tehoestimoinnin tarkkuutta ja tehdÀÀn RTL-tehoprofilointi loisimpedansseilla kalibroidulle RTL-mallille. Lopuksi RTL-tehoestimoinnin tuloksia ja saatuja RTL-tehoprofiloinnin aikaikkunoita analysoidaan ja verrataan porttitason mallin tuloksiin. RTL-tehoprofiloinnin tulosten analysointi osoittaa, ettÀ saatavat aikaikkunat vastaavat teoriaa ja ettÀ RTL-tehoprofilointi nÀyttÀÀ lupaavalta menetelmÀltÀ tehosiirtoverkon analysoinnin ja verifioinnin aikaikkunoiden löytÀmiseen
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