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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.
1331

Design And Characterization Of Multi-Layer Coplanar Waveguid Baluns And Inductors

Obeidat, Khaled 01 July 2003 (has links)
This work examined the design and characterization of multilayer coplanar waveguide baluns and inductors. This work derives a design procedure that helps RF engineers design cost effective multilayer coplanar waveguide (CPW) spiral balun that works in the frequency range 1-8 GHz. The accuracy of the developed procedure has been proven by designing two balun circuits of different dimensions and simulating them using available commercial software, Momentum (MoM) and Empire (FDTD). The simulation results have shown good balun performance over the desired frequency range. Furthermore some of the designed balun circuits have been fabricated and measured and the results agree with the simulations. The smaller balun (2.4 mm x 1.4 mm) with a minimum spacing of 25mm works very good in the frequency range 4-8 GHz with a 4 GHz operational bandwidth (OBW) and 5o phase difference and 0.5 dB amplitude imbalance. The larger balun (5.6mm x 3.0 mm) with minimum spacing of 100mm works well in the frequency range 2-4 GHz with a 2 GHz operational bandwidth (OBW) and 10o phase difference and 0.5 dB amplitude imbalance. Such a large-size balun is suitable for a new fabrication technique called Direct-Write. This thesis focuses on techniques that can be used to enhance balun performance, it has been shown through this work that adding some capacitance at certain points in the balun circuit will decrease both the phase difference and the amplitude imbalance of the balun. Some of these techniques were discovered through the thesis work and the other techniques were used before, but for different balun structures. An additional study to the effect of the ground plane on the spiral inductor model is included herein. Formulas for the inductance nominal value in the existing CPW ground plane for some spiral inductors are derived here, in addition to the derivation of an RF spiral inductor model that is independent of the ground plane. The importance of this model lies in its necessity in designing an antenna dipole loaded with lumped elements (in the absence of ground plane) to control the antenna electrical length without changing its physical length.
1332

Prepulse Inhibition and the Acoustic Startle Response in Nine Inbred Mouse Strains

O'steen, Jennifer Robin 25 March 2003 (has links)
This study examined the effects of genetic background on the acoustic startle response (ASR) and its modulation by prepulse inhibition (PPI) by comparing nine inbred strains of mice. The ASR, a jerk-like motor reflex, is elicited by bursts of noise or tones with sound pressure levels of 80-90 dB and greater. PPI is a type of modulation of the ASR, requires no training, and results in observable response in both mice and humans. Data were obtained from nine inbred mouse strains, sixteen per strain, which were shipped at approximately 3-5 weeks old from The Jackson Laboratory. In general, ASRs were generally smaller when the startle stimulus was less intense. PPI was relatively weak for the 4 kHz prepulse, and stronger with prepulses of 12 kHz and 20 kHz. However, means varied widely across strains for both ASR and PPI, suggesting a strong influence of genetic background on these behaviors. In addition to genetic influences, peripheral hearing loss and central auditory processing factors must be taken into consideration.
1333

Copper Gallium Diselenide Solar Cells: Processing, Characterization and Simulation Studies

Panse, Pushkaraj 28 March 2003 (has links)
The goal of this research project was to contribute to the understanding of CuGaSe2/CdS photovoltaic devices, and to improve the performance of these devices. The initial part of the research dealt with the optimization of a Sequential Deposition process for CuIn(Ga)Se2 absorber formation. As an extension of this, a recipe (Type I Process) for CuGaSe2 absorber layer fabrication was developed, and the deposition parameters were optimized. Electrical characterization of the thin films and completed devices was carried out using techniques such as Two-Probe and Three-Probe Current-Voltage, Capacitance-Frequency, Capacitance-Voltage, and Spectral Response measurements. Structural/chemical characterization was done using XRD and EDS analysis. Current densities of up to 15.2 mA/cm2, and Fill Factors of up to 58% were obtained using the Type I CuGaSe2 Process. VOC's, however, were limited to less than 700 mV. Several process variations, such as changes in the rate/order/temperature of depositions and changes in the thickness of layers, resulted in little improvement. With the aim of breaking through this VOC performance ceiling, a new absorber recipe (Type II Process) was developed. VOC's of up to 735 mV without annealing, and those of up to 775 mV after annealing, were observed. Fill Factors were comparable to those obtained with Type I Process, whereas the Current Densities were found to be reduced (typically, 10-12 mA/cm2, with the best value of 12.6 mA/cm2). This performance of Type II devices was correlated to a better intermixing of the elements during the absorber formation. To gain an understanding of the performance limitations, two simulation techniques, viz. SCAPS and AMPS, were used to model our devices. Several processing experiments and SCAPS modeling indicate that a defective interface between CuGaSe2 and CdS, and perhaps a defective absorber layer, are the cause of the VOC limitation. AMPS simulation studies, on the other hand, suggest that the back contact is limiting the performance. Attempts to change the physical back contact, by changes in the absorber processing, were unsuccessful. Processing experiments and simulations also suggest that the CuGaSe2/CdS solar cell involves a true heterojunction between these two layers.
1334

Monaural Speech-in-Noise Thresholds Using the Hearing in Noise Test (HINT)

Parrish, Denise 01 November 2003 (has links)
Understanding speech in background noise is occasionally difficult for normal hearing listeners and is often impossible for the listener with sensorineural hearing loss. The ability to understand speech in noise depends upon multiple factors such as the characteristics of the speech signal, the signal-to-noise ratio, and the listener's degree of hearing impairment. A routine hearing evaluation usually does not provide ample information about a listener's functional communication abilities. The Hearing-in-Noise Test (HINT) developed by The House Ear Institute provides an efficient and reliable method for evaluating an individual's suprathreshold speech understanding ability in quiet and in noise. The purpose of this pilot study was to investigate monaural speech reception thresholds for sentences (RTS) in quiet and in noise using the standardized Hearing-in-Noise Test (HINT). Data was collected from one clinical setting using twenty-five subjects with bilateral normal hearing (WNL) and twenty subjects with bilaterally symmetrical sensorineural hearing loss (SNHL). Subject age ranged from 40 to 65 years. The study results were generally in agreement with the HINT norms. It was concluded that administering the HINT monaurally under headphones could differentiate between normal hearing individuals and individuals with cochlear hearing loss. The SNHL group exhibited higher RTSs than the WNL group in both quiet and in noise. The mean RTS difference between the two groups in quiet was 14.56 dB while the mean RTS difference in noise was only 2.85 dB. Surprisingly, the difference between the two subject groups in quiet was greater than was expected.
1335

Falun Gong in the United States: An Ethnographic Study

Porter, Noah 18 July 2003 (has links)
Falun Gong, also known as Falun Dafa, has been described in many ways. It has been called qigong, one of many schools of physical exercises that aim at improving health and developing "supernatural abilities". Scholars and mainstream media have referred it to as a "spiritual movement" or religion, although practitioners claim it is not a religion. It has been called a cult, in the pejorative sense rather than in a sociological context, by the Chinese government and by some Western critics. In the writings of Li Hongzhi, the founder of Falun Gong, it is referred to in different ways, though primarily as a "cultivation practice". The question of how to define Falun Gong is not just an academic issue; the use of the cult label has been used to justify the persecution of practitioners in China. To a limited degree, the Chinese Government is able to extend the persecution overseas. How society defines Falun Gong has implications for action on the level of policy, as well as the shaping of social, cultural, and personal attitudes. This research project addresses what Falun Gong is through ethnography. Research methods included participant-observation, semi-structured ethnographic interviews (both in-person and on-line), and content analysis of text and visual data from Falun Gong books, pamphlets, and websites. Research sites included Tampa, Washington D.C., and "cyberspace". In order to keep my research relevant to the issues and concerns of the Falun Gong community, I was in regular contact with the Tampa practitioners, keeping them abreast of my progress and asking for their input. My findings are contrary to the allegations made by the Chinese Government and Western anti-cultists in many ways. Practitioners are not encouraged to rely on Western medicine, but are not prohibited from using it. Child practitioners are not put at risk. Their organizational structure is very loose. Finally, the Internet has played a vital role in Falun Gong's growth and continuation after the crackdown.
1336

Implementation of an Acoustic Echo Canceller Using Matlab

Raghavendran, Srinivasaprasath 15 October 2003 (has links)
The rapid growth of technology in recent decades has changed the whole dimension of communications. Today people are more interested in hands-free communication. In such a situation, the use a regular loudspeaker and a high-gain microphone, in place of a telephone receiver, might seem more appropriate. This would allow more than one person to participate in a conversation at the same time such as a teleconference environment. Another advantage is that it would allow the person to have both hands free and to move freely in the room. However, the presence of a large acoustic coupling between the loudspeaker and microphone would produce a loud echo that would make conversation difficult. Furthermore, the acoustic system could become instable, which would produce a loud howling noise to occur. The solution to these problems is the elimination of the echo with an echo suppression or echo cancellation algorithm. The echo suppressor offers a simple but effective method to counter the echo problem. However, the echo suppressor possesses a main disadvantage since it supports only half-duplex communication. Half-duplex communication permits only one speaker to talk at a time. This drawback led to the invention of echo cancellers. An important aspect of echo cancellers is that full-duplex communication can be maintained, which allows both speakers to talk at the same time. This objective of this research was to produce an improved echo cancellation algorithm, which is capable of providing convincing results. The three basic components of an echo canceller are an adaptive filter, a doubletalk detector and a nonlinear processor. The adaptive filter creates a replica of the echo and subtracts it from the combination of the actual echo and the near-end signal. The doubletalk detector senses the doubletalk. Doubletalk occurs when both ends are talking, which stops the adaptive filter in order to avoid divergence. Finally, the nonlinear processor removes the residual echo from the error signal. Usually, a certain amount of speech is clipped in the final stage of nonlinear processing. In order to avoid clipping, a noise gate was used as a nonlinear processor in this research. The noise gate allowed a threshold value to be set and all signals below the threshold were removed. This action ensured that only residual echoes were removed in the final stage. To date, the real time implementation of echo an cancellation algorithm was performed by utilizing both a VLSI processor and a DSP processor. Since there has been a revolution in the field of personal computers, in recent years, this research attempted to implement the acoustic echo canceller algorithm on a natively running PC with the help of the MATLAB software.
1337

Curating Illustrations of Lewis Carroll’s <em>Alice’s Adventures in Wonderland</em>

Persohn, Lindsay 29 March 2018 (has links)
In the 150 years since Lewis Carroll and John Tenniel (1865/1866) first published Alice's Adventures in Wonderland, various illustrators have found inspiration in this story to recreate its images again and again. Since Carroll and Tenniel, Wonderland has concerned itself with sociocultural ideas and the work of artists who re-illustrated this story provide ways to trace history of these ideas. Accordingly, the purpose of this project was to examine connections and breaks with tradition in illustration that contribute to an evolution of meaning in the Wonderland story. Additionally, through this project, I worked to interpret ideas from different artists in different times and spaces in an attempt to understand intersecting ideas of culture and Wonderland illustration. Through this work, I developed the concept of curation as a visual research methodology in order to make sense of and share my discoveries. Wonderland offers a rich context to explore and elucidate the arts-based qualitative methodology of curation because of its literary merits, artistic interpretations, and persistence and pervasion worldwide over the last century and a half. Curation allowed me flexibility in thinking about thematic interpretations of the illustrations I studied. Specific curatorial methods led me to identify the scene of Alice's decent to Wonderland, visual characterizations of the Hatter character, and depictions of the playing card characters as signals of sociocultural changes. When examined together, these interpretations point to an ever-shifting relationship between author, illustrators, and readers in classic, illustrated novels. Specifically, through the illustrations in Wonderland, Alice is no longer portrayed as a particular girl and illustrators over time have placed readers as the subject of the adventures. In recent times, Wonderland has gained some ability to cross over from its pages into the real world and take a look at its readers. This shift in perspective in Wonderland speaks to a current sociocultural environment wherein reality is hyper-subjective and nothing is quite as it seems.
1338

Study and Edition of <em>La dama presidente</em> by Francisco de Leiva Ramírez de Arellano

Valdés, Diana 30 October 2017 (has links)
Entre los grandes autores de teatro del siglo XVII se puede encontrar a Francisco de Leiva Ramírez de Arellano. El siglo en el que vivió es uno de suma importancia en el mundo del teatro, ya que los escritores del momento crearon cánones estilísticos que cambiaron la forma de escribir estas obras para siempre. De Leiva, que fue seguidor de la escuela de Calderón, se conocen unas catorce obras de teatro y un entremés, y se sabe que sus obras no tuvieron mayor éxito hasta el siglo XVIII. En la modernidad su nombre es poco conocido y sus trabajos han sido escasamente publicados. Esta tesis intentará desenterrar una obra de Leiva, La dama presidente, para entender mejor el teatro español de su tiempo.
1339

Border-Crossing Travels Across Literary Worlds: My Shamanic Conscientization

Neumeister, Scott 15 November 2018 (has links)
Border-Crossing Travels Across Literary Worlds is an autocritographical journey that places a group of U.S. literary texts into critically conscious dialogue with the “text” of my life. As a white, American, middle-class, cishetero, able-bodied man, I historicize, contextualize, analyze, and deconstruct the process by which my ten years of graduate academic studies at the University of South Florida fostered my ongoing awakening to critical consciousness—the personal and political evolution Paolo Freire terms “conscientization.” I present the analytical insights I realized about landmark feminist and womanist texts I encountered during my graduate studies that resonate with the prominent literary works and events from my youth. By identifying personal contexts and identity-aware frameworks for how I read these influential texts in my past, I give concrete examples of how hegemonic systems of gender, race, class, sexuality, and ability operate within such writing. I also demonstrate how utilizing feminist and womanist theoretical lenses allows a scholar to re-vision and recover problematic texts. Across all my autocritographical travels, I imagine my own life experiences, as well as the positionality of my selected texts’ protagonists, in terms of the archetype of the shaman—a liminal, border-crossing person who walks between worlds to function in the capacity as a messenger, intermediary, and balance-bringing healer.
1340

Glycosylation Modulates Cardiac Excitability by Altering Voltage-Gated Potassium Currents

Schwetz, Tara A 10 July 2009 (has links)
Neuronal, cardiac, and skeletal muscle electrical signaling is achieved through the highly regulated activity of several types of voltage-gated ion channels to produce an action potential (AP). Voltage-gated potassium (Kv) channels are responsible for repolarization of the AP. Kv channels are uniquely and heavily glycosylated proteins. Previous reports indicate glycosylation modulates gating of some Kv channel isoforms; often, terminal sialic acid residues alter Kv channel gating. Here, we questioned whether alterations in glycosylation impact Kv channel gating, thus altering APs and cardiac excitability. ST3Gal-IV, a sialyltransferase expressed at uniform levels throughout the heart, adds sialic acids to N- and O-glycans through alpha 2-3 linkages. Electrocardiograms (ECGs) suggest that cardiac conduction/rhythm are altered in ST3Gal-IV(-/-) animals, which show an increased incidence of arrhythmic beats. AP waveform parameters and two components of IK, the transient outward, Ito, and the slowly inactivating, IK,slow, were compared in neonatal control versus ST3Gal-IV(-/-) and glycosidase treated atrial and ventricular myocytes. Action potential durations (APDs) measured from ST3Gal-IV(-/-) and glycosidase treated atrial myocytes were lengthened significantly (~25-150%) compared to control; however, ventricular APDs were unaffected by changes in glycosylation. Consistently, atrial Ito and IK,slow activation were shifted to more depolarized potentials (by ~9-17 mV) in ST3Gal-IV(-/-) and glycosidase treated myocytes, while ventricular K+ currents were unaltered. Those channels responsible for producing Ito and IK,slow were examined under conditions of full and reduced glycosylation. Sialylation and N-glycosylation uniquely and differently impact gating of two mammalian Shaker family Kv channel isoforms, Kv1.4 and Kv1.5; Kv1.4 gating was unaffected by changes in channel glycosylation, while N-linked sialic acids, acting through electrostatic mechanisms, fully account for glycan effects on Kv1.5 gating. In addition, sialic acids modulate the gating of three Kv channel isoforms that are not N-glycosylated, Kv2.1, Kv4.2, and Kv4.3, through apparent electrostatic mechanisms. Click chemistry was utilized to confirm that these three isoforms are O-glycosylated and sialylated; thus, O-linked sialylation modulates gating of Kv2.1, Kv4.2, and Kv4.3. This study suggests that regulated or aberrant glycosylation alters the gating of channels producing IK in a chamber-specific manner, thus altering the rate of cardiac repolarization and potentially leading to arrhythmias.

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