International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Calculating the power spectral density (PSD) at the transducer or data acquisition system offers advantages in a network-based telemetry system. The PSD is provided in real time to the users. The conversion to PSD can either be lossless (allowing a complete reconstruction of the transducer signal) or lossy (providing data compression). Post-processing can convert the PSD back to time histories if desired. A complete reconstruction of the signal is possible, including knowledge of the signal level between the sample periods. Properly implemented, this method of data collection provides a sharp anti-aliasing filter with minimal added cost. Currently no standards exist for generating PSDs on the vehicle. New standards could help telemetry system designers understand the benefits and limitations calculating the power spectral density in a network-based telemetry system.

Pilot Induced Oscillations (PIO) are described as pilot-aircraft dynamic couplings which can lead to instability in an otherwise stable system. Previous and ongoing research has attempted to explain, predict, and avoid such oscillations. In contrast to other research, this effort backs away from pilot models and PIO avoidance and focuses on the characteristics of the pilot before, during, and after a PIO. Often, PIO''s can be explained by limit cycles occurring in a non-linear system where the non-linearities cause a sustained, constant amplitude oscillation. The primary instigators in such a PIO are usually a non-linear element (i.e. rate limit saturation) and a trigger event (i.e. pilot mode switching or increased pilot gain). By performing analysis in the frequency domain, determining such oscillations becomes easier. Using spectrograms and power spectral density functions, the frequency content of a signal in the pilot-aircraft system can also be investigated. An F-14 flight test was recently performed where the hydraulic system was modified to determine the feasibility of trying to recover the aircraft (land on carrier) during such an extreme hydraulic failure. During testing, a severe PIO occurred because of the tight tracking task used during aerial refueling. While performing spectrograms and power spectral analysis, an increase in power concentration at the PIO frequency was observed. With a linear approximation of the F-14 aircraft dynamics, a closed-loop system containing the aircraft, actuator, and pilot dynamics is developed so that limit cycle analysis can be performed. With stable limit cycle solutions found possible, a pilot-in-the-loop simulation is performed to verify the pilot model used in limit cycle analysis. Using the flight test data, limit cycle analysis, and pilot-in-the-loop simulation, a connection between variation in pilot behavior and PIO predicted by the increase in power concentration is investigated. The resulting connection showed that an increase in pilot gain along with a transition from observing pitch attitude to pitch rate are the possible trigger events causing the PIO. The use of spectrograms as a PIO predictor is shown to be possible, provided the necessary calculations can be completed in real-time. / Master of Science

O tratamento clareador pode resultar em alterações na rugosidade superficial do esmalte dental, as quais podem ser vistas a olho nu como alterações de cor, opacidade e perda de brilho. O objetivo deste estudo foi analisar in vitro a alteração de rugosidade, cor e brilho de superfícies de esmalte dental humano após clareamento com um produto a base de peróxido de hidrogênio (PH) 38% e após polimento com fluoreto de sódio 2% neutro (FS2%) ou pasta dentifrícia contendo partículas de nano-hidroxiapatita. Para isso, coroas de incisivos centrais humanos foram preparadas e tiveram suas faces vestibulares analisadas em microscópio de força atômica (MFA), o qual determinou os valores de rugosidade [Ra, RMS, Z range e Power Spectral Density (PSD)] iniciais. A cor e o brilho destas amostras foram determinados por um espectrofotômetro. Todas as amostras foram clareadas com PH 38% por 135 minutos. Os valores de Ra, RMS, Z range e PSD foram estabelecidos pelo MFA e a cor e o brilho determinados pelo espectrofotômetro. As amostras foram divididas em dois grupos: Flúor, que recebeu um polimento com gel de FS2%; e nHA, que recebeu um polimento com pasta dentifrícia contendo partículas de nano-hidroxiapatita. Os valores de Ra, RMS, Z range, PSD, cor e brilho pós-polimento foram determinados pelo MFA e espectrofotômetro. Após o clareamento, os valores de Ra, RMS, Z range e PSD não apresentaram alteração estatisticamente significante, os valores de L* aumentaram e C* diminuiu significativamente em todas as amostras. O brilho superficial não apresentou alteração significativa após o clareamento. O grupo Flúor não apresentou alteração de rugosidade significativa para Ra, RMS, Z range e PSD após o polimento. Os valores de L*, C* e brilho superficial também não apresentaram alterações significativas após o polimento das superfícies clareadas. No grupo nHA, os valores de Ra e RMS não apresentaram alteração significativa após o polimento das superfícies clareadas, porém os valores de Z range e PSD apresentaram alteração estatisticamente significante. Em comparação à superfície clareada, L* e C* não apresentaram alteração significante após o polimento, porém o brilho superficial foi significativamente maior. O tratamento clareador de consultório mostrou ser eficiente quanto à alteração de cor e não gerou aumento na rugosidade superficial do esmalte dental. Um polimento com pasta dentifrícia contendo partículas de nano-hidroxiapatita realizado após o clareamento é capaz de aumentar o brilho e diminuir a rugosidade superficial do esmalte dental. / Bleaching treatment may result in dental enamel surface roughness alterations, which might be seen as color alterations, opacity and gloss loss. The aim of this research was to in vitro investigate roughness, color and gloss alterations of human dental enamel surfaces after bleaching treatment with 38% hydrogen peroxide (HP) and after polishing with neutral 2% sodium fluoride or dental tooth paste containing nano-hydroxiapatite particles. Human central incisors were prepared and buccal surfaces were analyzed by an atomic force microscope (AFM), which determined roughness values [Ra, RMS, Z range and Power Spectral Density (PSD)]. Surface color and gloss were determined by a spectrophotometer. All samples were bleached with 38% HP for 135 minutes. AFM determined Ra, RMS, Z range and PSD after bleaching. Color and gloss were determined by the spectrophotometer. Samples were distributed in two different groups: Fluor, which was polished with neutral 2% sodium fluoride, and nHA, which was polished with dental tooth paste containing nano-hydroxyapatite particles. Ra, RMS, Z range, PSD, color and gloss values were determined by AFM and spectrophotometer after polishing. After bleaching, Ra, RMS, Z range and PSD didnt show any statistical difference. L* increased and C* decreased significantly in all samples after bleaching. Surface gloss didnt show significant alteration after bleaching. Fluor group didnt show surface roughness alteration considering Ra, RMS, Z range and PSD after polishing. L*, C* and gloss didnt change after bleached surfaces are polished with neutral 2% sodium fluoride. Ra and RMS of nHA group didnt change significantly after polishing, but Z range and PSD showed significant alteration. Despite L* and C* didnt change, gloss increased significantly after polishing with dental tooth paste containing nano-hydroxyapatite. In-office bleaching treatment showed to be efficient as for color enhancement and didnt cause roughness alteration in dental enamel surface. An after-bleaching polishing with dental tooth paste containing nano-hydroxyapatite particles may increase gloss and decrease surface roughness of dental enamel.

O tratamento clareador pode resultar em alterações na rugosidade superficial do esmalte dental, as quais podem ser vistas a olho nu como alterações de cor, opacidade e perda de brilho. O objetivo deste estudo foi analisar in vitro a alteração de rugosidade, cor e brilho de superfícies de esmalte dental humano após clareamento com um produto a base de peróxido de hidrogênio (PH) 38% e após polimento com fluoreto de sódio 2% neutro (FS2%) ou pasta dentifrícia contendo partículas de nano-hidroxiapatita. Para isso, coroas de incisivos centrais humanos foram preparadas e tiveram suas faces vestibulares analisadas em microscópio de força atômica (MFA), o qual determinou os valores de rugosidade [Ra, RMS, Z range e Power Spectral Density (PSD)] iniciais. A cor e o brilho destas amostras foram determinados por um espectrofotômetro. Todas as amostras foram clareadas com PH 38% por 135 minutos. Os valores de Ra, RMS, Z range e PSD foram estabelecidos pelo MFA e a cor e o brilho determinados pelo espectrofotômetro. As amostras foram divididas em dois grupos: Flúor, que recebeu um polimento com gel de FS2%; e nHA, que recebeu um polimento com pasta dentifrícia contendo partículas de nano-hidroxiapatita. Os valores de Ra, RMS, Z range, PSD, cor e brilho pós-polimento foram determinados pelo MFA e espectrofotômetro. Após o clareamento, os valores de Ra, RMS, Z range e PSD não apresentaram alteração estatisticamente significante, os valores de L* aumentaram e C* diminuiu significativamente em todas as amostras. O brilho superficial não apresentou alteração significativa após o clareamento. O grupo Flúor não apresentou alteração de rugosidade significativa para Ra, RMS, Z range e PSD após o polimento. Os valores de L*, C* e brilho superficial também não apresentaram alterações significativas após o polimento das superfícies clareadas. No grupo nHA, os valores de Ra e RMS não apresentaram alteração significativa após o polimento das superfícies clareadas, porém os valores de Z range e PSD apresentaram alteração estatisticamente significante. Em comparação à superfície clareada, L* e C* não apresentaram alteração significante após o polimento, porém o brilho superficial foi significativamente maior. O tratamento clareador de consultório mostrou ser eficiente quanto à alteração de cor e não gerou aumento na rugosidade superficial do esmalte dental. Um polimento com pasta dentifrícia contendo partículas de nano-hidroxiapatita realizado após o clareamento é capaz de aumentar o brilho e diminuir a rugosidade superficial do esmalte dental. / Bleaching treatment may result in dental enamel surface roughness alterations, which might be seen as color alterations, opacity and gloss loss. The aim of this research was to in vitro investigate roughness, color and gloss alterations of human dental enamel surfaces after bleaching treatment with 38% hydrogen peroxide (HP) and after polishing with neutral 2% sodium fluoride or dental tooth paste containing nano-hydroxiapatite particles. Human central incisors were prepared and buccal surfaces were analyzed by an atomic force microscope (AFM), which determined roughness values [Ra, RMS, Z range and Power Spectral Density (PSD)]. Surface color and gloss were determined by a spectrophotometer. All samples were bleached with 38% HP for 135 minutes. AFM determined Ra, RMS, Z range and PSD after bleaching. Color and gloss were determined by the spectrophotometer. Samples were distributed in two different groups: Fluor, which was polished with neutral 2% sodium fluoride, and nHA, which was polished with dental tooth paste containing nano-hydroxyapatite particles. Ra, RMS, Z range, PSD, color and gloss values were determined by AFM and spectrophotometer after polishing. After bleaching, Ra, RMS, Z range and PSD didnt show any statistical difference. L* increased and C* decreased significantly in all samples after bleaching. Surface gloss didnt show significant alteration after bleaching. Fluor group didnt show surface roughness alteration considering Ra, RMS, Z range and PSD after polishing. L*, C* and gloss didnt change after bleached surfaces are polished with neutral 2% sodium fluoride. Ra and RMS of nHA group didnt change significantly after polishing, but Z range and PSD showed significant alteration. Despite L* and C* didnt change, gloss increased significantly after polishing with dental tooth paste containing nano-hydroxyapatite. In-office bleaching treatment showed to be efficient as for color enhancement and didnt cause roughness alteration in dental enamel surface. An after-bleaching polishing with dental tooth paste containing nano-hydroxyapatite particles may increase gloss and decrease surface roughness of dental enamel.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Feher Keying (FK) signals are clock shaped baseband waveforms with the potential to attain very high spectral efficiencies. Two FK signals which have different level rectangular waveforms (named as FK-1) or sinusoidal waveforms (named as FK-2) for two binary symbols are considered in this paper. These signals have periodic components in the time domain. Therefore they have cyclostationary properties. This means that spectral correlation exists in the frequency domain. For each type of waveforms, spectral correlation has been investigated. FK signals can be expressed mathematically into two parts in the frequency domain – discrete part and continuous part. The discrete part has one or more discrete impulse(s) in their spectra and the continuous part has periodically the same shape of harmonics in their spectra. The correlations of their spectra have been obtained mathematically and by simulation. It is shown that FK signals have high correlation related to the symbol rate. Finally, some suggestions how these properties can be used to improve their performance by devising better demodulators are discussed. These properties can be used for interference rejection at the receiver, which results in low bit error rate performance.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Performances of a subclass of a new spectral efficient modulation scheme, designated as Feher Keying [1], or FK, is evaluated. The Power Spectral Density (PSD) and Bit Error Rate (BER) characteristics of FK are presented. FK has ultra high spectral efficiency and satisfies the frequency mask for WLAN defined in FCC part 15, and it has a simple structure for high bit rate implementation.

As optical designs become more sophisticated and incorporate aspheric and free form surfaces, the need to specify limits on mid-spatial frequency manufacturing errors becomes more critical, particularly as we better understand the effects of these errors on image quality. While there already exist methods based on Fourier analysis to specify these errors in most commercial interferometry software, the method of calculation and the power spectral density (PSD) results remain obscure to many in the optical design and manufacturing field. We suggest that the structure functions (SF) contains the same information as in the Fourier based PSD but in a way that is much more transparent to analysis, interpretation and application as a specification. The units of measure are more familiar and the concept behind the analysis is simpler to understand. Further, the information contained in the structure function (or PSD) allows a complete specification of an optical surface from the finest measurable detail of roughness to the overall figure. We discuss the origin of the structure function in the field of astronomy to describe the effects of air turbulence on image quality, the simple mathematical definition of the structure function and its easy means of calculation and how its results should be scaled depending on the location of the optical surface in a system from pupil to image plane. Finally, we give an example of how to write a specification of an optical surface using the structure function.

Many real-world applications use random numbers generated by pseudo-random number and true random number generators (TRNG). Unlike pseudo-random number generators which rely on an input seed to generate random numbers, a TRNG relies on a non-deterministic source to generate aperiodic random numbers. In this research, we develop a novel and generic software-based TRNG using a random source extracted from compute architectures of today. We show that the non-deterministic events such as race conditions between compute threads follow a near Gamma distribution, independent of the architecture, multi-cores or co-processors. Our design improves the distribution towards a uniform distribution ensuring the stationarity of the sequence of random variables. We improve the random numbers statistical deficiencies by using a post-processing stage based on a heuristic evolutionary algorithm. Our post-processing algorithm is composed of two phases: (i) Histogram Specification and (ii) Stationarity Enforcement. We propose two techniques for histogram equalization, Exact Histogram Equalization (EHE) and Adaptive EHE (AEHE) that maps the random numbers distribution to a user-specified distribution. EHE is an offline algorithm with O(NlogN). AEHE is an online algorithm that improves performance using a sliding window and achieves O(N). Both algorithms ensure a normalized entropy of (0:95; 1:0]. The stationarity enforcement phase uses genetic algorithms to mitigate the statistical deficiencies from the output of histogram equalization by permuting the random numbers until wide-sense stationarity is achieved. By measuring the power spectral density standard deviation, we ensure that the quality of the numbers generated from the genetic algorithms are within the specified level of error defined by the user. We develop two algorithms, a naive algorithm with an expected exponential complexity of E[O(eN)], and an accelerated FFT-based algorithm with an expected quadratic complexity of E[O(N2)]. The accelerated FFT-based algorithm exploits the parallelism found in genetic algorithms on a homogeneous multi-core cluster. We evaluate the effects of its scalability and data size on a standardized battery of tests, TestU01, finding the tuning parameters to ensure wide-sense stationarity on long runs. / October 2016

The present work introduces novel methodologies for damage detection and health monitoring of structural and mechanical systems. The new approach uses the angular velocity inside different mathematical forms, via a gyroscope, to detect, locate, and relatively quantify damage. This new approach has been shown to outperform the current state-of-the-art acceleration-based approach in detecting damage on structures. Additionally, the current approach has been shown to be less sensitive to environmental acoustic noises, which present major challenges to the acceleration-based approaches. Furthermore, the current approach has been demonstrated to work effectively on arch structures, which acceleration-based approaches have struggled to deal with. The efficacy of the new approach has been investigated through multiple forms of structural damage indices. The first methodology proposed a damage index that is based on the changes in the second spatial derivative (curvature) of the power spectral density (PSD) of the angular velocity during vibration. The proposed method is based on the output motion only and does not require information about the input forces/motions. The PSD of the angular velocity signal at different locations on structural beams was used to identify the frequencies where the beams show large magnitude of angular velocity. The curvature of the PSD of the angular velocity at these peak frequencies was then calculated. A damage index is presented that measures the differences between the PSD curvature of the angular velocity of a damaged structure and an artificial healthy baseline structure. The second methodology proposed a damage index that is used to detect and locate damage on straight and curved beams. The approach introduces the transmissibility and coherence functions of the output angular velocity between two points on a structure where damage may occur to calculate a damage index as a metric of the changes in the dynamic integrity of the structure. The damage index considers limited-frequency bands of the transmissibility function at frequencies where the coherence is high. The efficacy of the proposed angular-velocity damage-detection approach as compared to the traditional linear-acceleration damage-detection approach was tested on straight and curved beams with different chord heights. Numerical results showed the effectiveness of the angular-velocity approach in detecting damage of multiple levels. It was observed that the magnitude of the damage index increased with the magnitude of damage, indicating the sensitivity of the proposed method to damage intensity. The results on straight and curved beams showed that the proposed approach is superior to the linear-acceleration-based approach, especially when dealing with curved beams with increasing chord heights. The experimental results showed that the damage index of the angular-velocity approach outweighed that of the acceleration approach by multiple levels in terms of detecting damage. A third methodology for health-monitoring and updating of structure supports, which resemble bridges’ bearings, is introduced in this work. The proposed method models the resistance of the supports as rotational springs and uses the transmissibility and coherence functions of the output response of the angular velocity in the neighborhood of the bearings to detect changes in the support conditions. The proposed methodology generates a health-monitoring index that evaluates the level of deterioration in the support and a support-updating scheme to update the stiffness resistance of the supports. Numerical and experimental examples using beams with different support conditions are introduced to demonstrate the effectiveness of the proposed method. The results show that the proposed method detected changes in the state of the bearings and successfully updated the changes in the stiffness of the supports.

Ultra Wideband (UWB) is an emerging technology for use in the indoor wireless personal area networks and ad hoc networks. The more common form of UWB which uses sub-nanosecond pulses without any form of carrier signal is considered in this research. UWB signals have a large bandwidth with allocated frequency spectrum from 3.1 GHz to 10.6 GHz and maximum power restricted to -41dBm/MHz. The IEEE 802.11a is a popular standard for high data rate wireless local area networks (WLANs). The operating frequency of the IEEE 802.11a WLAN is 5 GHz which is right inside the allocated UWB frequency spectrum. One of the main obstacles facing the implementation of UWB devices is the challenge of reducing interference caused by UWB to other systems and vice versa. The potential operating areas/frequencies of the IEEE 802.11a WLAN and UWB systems overlap and therefore the problem of UWB interference to the IEEE 802.11a WLANs and vice versa becomes significant. In this research we have focused on studying the effect of UWB interference on IEEE 802.11a WLANs. The different UWB parameters that affect the interference caused by UWB to IEEE 802.11a WLAN have been considered for determining their effect on the performance of the IEEE 802.11a WLAN. The effect of UWB multipath on the performance of the IEEE 802.11a WLAN has been observed. The UWB parameters have also been compared based on their effect on the performance of the IEEE 802.11a system in the presence of UWB multipath. Additionally, two different interference mitigation techniques that reduce UWB interference to the IEEE 802.11a WLANs have been studied.