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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
121

A Comparison of Two Hydrologic Modeling Approaches for the Estimation of Flood Frequency Distributions / A Comparison of Two Hydrologic Modeling Approaches

Senior, Matthew 12 1900 (has links)
Several previous studies have compared design storms with continuous simulation results for the purposes of estimating flood frequency distributions. These previous studies were limited in scope to primarily urban single lumped catchments. This thesis attempted to perform a more detailed comparison of design storm and continuous simulation flood frequency distributions by extending the analysis to different basin types, as well as examining the effect of more complex watershed systems and storage elements (detention ponds). It was found that design storms could reasonably reproduce continuous simulation flood frequency distributions if an appropriate distribution and antecedent conditions were selected. Design storms were found to compare increasingly well to continuous simulation results in more complex watershed systems and through storage elements. / Thesis / Master of Applied Science (MASc)
122

Local regulation of increased milk yield due to early lactation increased milking frequency

Hardin, Diana Kaitlyn 31 July 2015 (has links)
Increased milking frequency (IMF) during early lactation increases milk yield not only during the IMF period, but also after the cow is returned to twice daily milking (2X). The increase in yield is locally regulated within the gland; however the mechanism for the increase in yield is unknown. The objective of this study was to demonstrate a difference in milk and component yield, both during the IMF period and throughout the remainder of lactation, and examine potential local mechanisms driving the increase in production. Eight multiparous dairy cows were assigned to unilateral frequent milking [UFM ; 2X left udder half and 4-times-daily milking (4X) right udder half] for the first 21 days of lactation. Both udder halves were milked 2X for the remainder of lactation. Early lactation IMF significantly increased milk, fat, and protein yields in the right udder halves by 2.27 kg/d, 73.5 g/d, and 68 g/d respectively through the first 210 DIM (P < 0.001). At d 21, the right udder halves had a significant increase in activated signal transducer and activator of transcription 5 (STAT5), as well as a reduction in activated Akt (P ≤ 0.05). There was no difference in STAT3 expression at d 21. There was no significant difference in gene expression of prolactin, insulin-like growth factor 1 (IGF-1), insulin-like growth factor binding protein 5 (IGFPB5), or chitinase 3-like-1 (CHI3L1) in mammary tissue at d 21 or 60; and no difference in protein expression of STAT5, Akt, or STAT3 in mammary tissue at d 60. / Master of Science
123

A DIGITAL INTEGRATOR FOR AN S-BAND HIGH-SPEED FREQUENCY-HOPPING PHASE-LOCKED LOOP

Holtzman, Melinda, Johnson, Bruce, Lautzenhiser, Lloyd 10 1900 (has links)
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Phase-locked loop (PLL) frequency synthesizers used for high-speed data transmission must rapidly hop and lock to new frequencies. The fundamental problem is that the settling time depends inversely on the loop bandwidth, and increasing the bandwidth causes unwanted noise interference and stability problems for the circuit. We demonstrate the feasibility of replacing the analog integrator in the PLL with a digital integrator. This circuit has advantages of increased hopping speed, ability to compensate for temperature drift and system stability. PLL lock-in was demonstrated in a prototype circuit designed and built with both discrete components and with a programmable logic device.
124

A HIGH-ACCURACY AND LOW-COMPLEXITY CARRIER-OFFSET-FREQUENCY ESTIMATOR

Palmer, Joseph 10 1900 (has links)
ITC/USA 2007 Conference Proceedings / The Forty-Third Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2007 / Riviera Hotel & Convention Center, Las Vegas, Nevada / A single-tone frequency estimator for a non-uniformly sampled sinusoid is proposed. A nonuniformly sampled sinusoid may be generated from the received training sequences of a telemetry link. The frequency of the sinusoid matches the carrier-frequency-offset (CFO) of the received signal, and estimation of this quantity allows a receiver to compensate for the CFO. The performance bounds of this type of estimator have been investigated in the literature, though little work has been published on practical algorithms. The estimator proposed in this paper is a generalization of phase-increment estimators previously described in the literature. It exhibits a low computational complexity yet converges to theoretical bounds at high SNR. The paper argues that a periodic training sequence structure, combined with the new estimator, allows for a high-accuracy and lowcomplexity CFO compensator.
125

Digital FDM for the HSTSS DAC Program

Doerr, Michael B., Hallidy, William H., Jr.,, McMillian, Gary B., Burke, Lawrence W., Jr., Faust, Jonah N. 10 1900 (has links)
International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper presents the design of an innovative approach to Frequency Division Multiplexing (FDM) for the STRICOM Hardened Subminiature Telemetry and Sensor System (HSTSS) Data Acquisition Chipset (DAC) program. An ASIC (Application Specific Integrated Circuit) is being developed by Systems & Processes Engineering Corporation (SPEC) that implements this new digital FDM approach for telemetry applications. The FDM ASIC provides six channels that are IRIG-106 compatible, and may be used in conjunction with a Delay/Repeater ASIC. Together these ASICs make a complete instrumentation system for those applications requiring very small size, simplicity of use, and low cost, e.g. munitions/armament testing.
126

HIGH SPEED, WIDE BANDWIDTH SIGNAL DETECTION AND FREQUENCY ESTIMATION

Caprio, James R., Nystrom, Lennart 10 1900 (has links)
International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada / A digital frequency discriminator (DFD) of the delay-correlator type is described. The device is shown to have an instantaneous frequency measurement capability on very short pulses. The theoretical performance of the DFD in a noisy background is derived and shown to compare favorably with measured results.
127

SPATIO-TEMPORAL VARIATION IN ACTIVATION INTERVALS DURING VENTRICULAR FIBRILLATION

Moghe, Sachin Anil 01 January 2002 (has links)
Spatio-temporal variation in activation rates during ventricular fibrillation (VF)provides insight into mechanisms of sustained re-entry during VF. This study had three objectives related to spatio-temporal dynamics in activation rates during VF. The first objective was to quantify spatio-temporal variability in activation rates,that is, in dominant frequencies, computed from epicardial electrograms recorded during VF in swine. Results showed that temporally and spatially, dominant frequencies variedas much as 20% of the mean dominant frequency, and the mean dominant frequencies increased during first 30 sec of VF. These results suggest that activation rates are nonstationary during VF. The second objective of the study was to develop a new stimulation protocol for quantifying restitution of action potential duration (APD) by independently controlling diastolic intervals (DI). A property of cardiac cells that determines spatio-temporal variability in dominant frequencies is restitution of APD, which relates APD to the previous DI. Independent control of DI permits explicit determination of the role of memory in restitution. Restitution functions quantified using mathematical models of activation and our stimulation protocol, showed significant hysteresis. That is, for adiastolic interval, the action potential durations were as much as 15% longer during periods when the DI were decreasing than when the DI were increasing. We verified the feasibility of implementing our protocol experimentally in isolated and perfused rat hearts with action potentials recorded using floating glass microelectrodes. The third objective of our study was to verify that spatio-temporal variability in dominant frequencies during VF could be modified using spatially distributed pacing strength stimuli. Simulated VF was induced in 400x400 and 400x800 matrices of cells. Electrical function of cells was simulated using the Luo-Rudy model. Stimulators were arranged in the matrices such that there were 5 rows of line stimulators. Results showed that it was possible to modify activations in almost 54% of the area and to modify spatio-temporal variability in activation during VF into a desired pattern by the use of synchronized pacing from multiple sites. These results support further exploration of distributed stimulation approach for potential improvements in defibrillation therapy.
128

Scattering and propagation of electromagnetic waves in planar and curved periodic structures - applications to plane wave filters, plane wave absorbers and impedance surfaces

Forslund, Ola January 2004 (has links)
The subject of this thesis is scattering of electromagneticwaves from planar and curved periodic structures. The problemspresented are solved in the frequency domain. Scattering from planar structures with two-dimensionalperiodic dependence of constitutive parameters is treated. Theconstitutive parameters are assumed to vary continuously orstepwise in a cross section of a periodically repeating cell.The variation along a longitudinal coordinate z is arbitrary. Ageneral skew lattice is assumed. In the numerical examples, lowloss and high loss dielectric materials are considered. Theproblem is solved by expanding the .elds and constitutiveparameters in quasi-periodic and periodic functionsrespectively, which are inserted into Maxwell’s equations.Through various inner products de.ned with respect to the cell,and elimination of the longitudinal vector components, a linearsystem of ordinary di.erential equations for the transversecomponents of the .elds is obtained. After introducing apropagator, which maps the .elds from one transverse plane toanother, the system is solved by backward integration.Conventional thin metallic FSS screens of patch or aperturetype are included by obtaining generalised transmission andre.ection matrices for these surfaces. The transmission andre.ection matrices are obtained by solving spectral domainintegral equations. Comparisons of the obtained results aremade with experimental results (in one particular case), andwith results obtained using a computer code based on afundamentally di.erent time domain approach. Scattering from thin singly curved structures consisting ofdielectric materials periodic in one dimension is alsoconsidered. Both the thickness and the period are assumed to besmall. The .elds are expanded in an asymptotic power series inthe thickness of the structure, and a scaled wave equation issolved. A propagator mapping the tangential .elds from one sideto the other of the structure is derived. An impedance boundarycondition for the structure coated on a perfect electricconductor is obtained. Keywords:electromagnetic scattering, periodicstructure, frequency selective structure, frequency selectivesurface, grating, coupled wave analysis, electromagneticbandgap, photonic bandgap, asymptotic boundary condition,impedance boundary condition, spectral domain method,homogenisation
129

Frequency discriminator detection in frequency-selective fading environments.

Rohani-Mehdiabadi, Bijan January 1998 (has links)
In recent years, millions of customers all over the world have been subscribing to mobile telephony services which are based on modern digital transmission. At the high transmission bit rates that these systems use, the mobile radio channel exhibits frequency-selective fading characteristics. Under such conditions, the received signal could experience significant intersymbol interference (ISI) from severe distortion to the waveform of the received baseband signal. Therefore, such techniques as adaptive waveform equalisation or adaptive maximum likelihood sequence estimation (MLSE) are used in modern digital mobile radio telephone systems to combat this undesirable ISI. These adaptive schemes have almost always been used in conjunction with coherent demodulation in the receivers.This study examines the application of noncoherent demodulation, in the form of frequency discriminator detection, as an alternative to coherent demodulation. The GSM (Global System for Mobile Communications) standard has been used as the basis for this investigation. It has been shown analytically that in the presence of frequency-selective fading, a propagation environment common to the GSM system, the use of frequency discriminator detection gives rise to nonlinear ISI in the demodulated signal. It has also been shown that frequency-selective fading could cause large unwanted "spikes" to appear in the demodulated signal, thus leading to a severe degradation in the bit-error-rate (BER) performance. Consequently, several waveform distortion cancellation schemes for combatting the nonlinear ISI have been formulated. The BER performances of these proposed schemes, under various propagation conditions, have been studied by computer simulation.Furthermore, it has been observed that the undesirable "spikes", that occur in the demodulated signal due to frequency-selective fading, could be ++ / suppressed by the use of inverse-limiting in conjunction with frequency discriminator detection. As a result, an effective adaptive detection scheme has been formulated, based on modelling the combination of the GMSK modulator, the mobile channel, the frequency discriminator, and any transmit and receive fitters, as a finite-state machine. The transmitted data is then detected using an MLSE. The BER performance of this proposed adaptive detection scheme has been extensively investigated by computer simulation. This has been carried out assuming various propagation conditions, including the two-ray fading channel model with equal path powers and relative delays of up to four bit periods, the maximum relative delay considered in the GSM system. Also, the effectiveness of the proposed adaptive detection scheme in combatting IS] has been investigated by computer simulation based on the six-ray GSM empirical propagation models for typical urban (TU), hilly terrain (HT) and rural area (RA) environments. The computer simulated results confirm that the voice grade performance required for the GSM system could be achieved by the proposed adaptive detection scheme in all the recommended GSM propagation models considered. Furthermore, the BER performance of the receiver remains unaffected by a carrier frequency offset of up to 2 kHz.
130

The Effects of Mobile Phone Radiation on the Human Central Nervous System

Perentos, Nicholas, nperentos@gmail.com January 2009 (has links)
The effects of mobile phone-like electromagnetic radiation on the human brain activity are examined. The research focuses on both radio frequency (RF) exposures and the much less studied low frequency (ELF) exposures (less than 40 kHz) arising from the battery operation of GSM handsets. The first single blind study recruited a small sample of twelve human volunteers. The eyes closed resting EEG activity is monitored after radio frequency exposure. With SAR levels of 2 W/kg, results reveal no statistical changes in any of the examined frequency bands for neither pulsed modulated RF signals nor continuous wave RF signals. In the second double blind study, a sample of 72 volunteers is recruited and an improved protocol comprised of separate pulsed RF, continuous RF and pulsed ELF exposures is employed. Exposures are delivered through a custom made handset capable of independent RF and ELF exposures. Findings include a reduced alpha band frequency activity during pulsed radio frequency and low frequency radiations exposures but no changes under the continuous RF radiation. Changes are present both during as well as after exposure, while greater changes are observed during exposures. The study of some non linear measures of the resting EEG revealed no changes under any of the active exposures. As the observed changes are very close to the normal EEG variation during resting conditions, their biological significance and health impact is not immediately obvious. However, their mere demonstration points to a low level interaction mechanism which may deserve further study.

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