To see the other types of publications on this topic, follow the link: Enhancement techniques.
Dissertations / Theses on the topic 'Enhancement techniques'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Enhancement techniques.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Krishnan, Gayathri. "Skin penetration enhancement techniques." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1471.
Full textAbstract:
Transdermal drug delivery is an effective alternative to conventional oral and injectable drug delivery routes. It offers painless and convenient once daily or even once weekly dosing for a variety of clinical indications. The major limitation to successful transdermal drug delivery is the efficient barrier properties of the skin. Significant research efforts have been focused on developing strategies to overcome these barrier properties. These strategies include the use of physical and chemical penetration enhancers. Physical skin penetration enhancers use an external energy source to alter the barrier properties of the skin. The current research focuses on some of these physical skin penetration enhancers on a range of drug molecules and peptides.The first technology investigated was Dermaportation that utilised pulsed electromagnetic energy. This technology enhanced the epidermal permeation of naltrexone in vitro as compared to passive diffusion. A 5-fold increase in naltrexone permeation was observed during Dermaportation application when compared to passive administration. Multiphoton tomography-fluorescence life-time imaging microscopy (MPT-FLIM) analysis of the permeation of gold nanoparticles in the presence of Dermaportation revealed increased penetration across ex vivo human skin. These results demonstrated that the channels created by dermaportation must be larger than the 10 nm diameter of the applied nanoparticles.The second technology investigated was an unpowered magnetic film array technology (ETP), which utilised unpowered magnetic energy. Chapter 3 presents enhanced epidermal permeation of urea with ETP. A 4-fold increase in urea penetration was observed across human epidermis in the in vitro permeation study. Optical resonance tomography was used to visualise the changes in epidermal thickness due to urea permeation as an indication of increased hydration. The results revealed an increase in epidermal thickness at 30 min, to 16% for ETP induced urea permeation as compared to 3% with urea from occlusion. These results further substantiated our previous findings that magnetic energy creates hydrophilic diffusion channels or pores in the skin.The third technology investigated was low-frequency sonophoresis that utilises cavitation bubbles as a force to create channels for drug delivery in the skin. Chapter 4 presents enhanced human skin permeation of 5-aminolevuleninic acid in vitro and curcumin dye in vivo with low-frequency sonophoresis. Two different sources of ultrasound devices that generated low-frequency sonophoresis were investigated. MPT-FLIM analysis was utilised to investigate the effects of sonophoresis on human skin in vivo. This revealed that there was substantial disturbance in the epidermal cells due to cavitation by sonophoresis. Permeation of curcumin was found in the deeper layers of the epidermal membrane with 55 kHz sonophoresis and was confined to the more superficial layers of skin with 21 kHz sonophoresis. Permeation of 5-aminolevuleninic acid across human skin increased significantly when compared to passive permeation.The fourth technology investigated in this research was iontophoresis which utilises a small electric current to drive charged and uncharged molecules across the skin. Chapter 5 presents enhanced epidermal permeation of a range of model therapeutic and cosmetic peptides. Various key parameters such as pH, concentration and presence of counterions and co-ions that are essential for effective iontophoretic delivery of these peptides were investigated. The iontophoretic delivery of 5- aminolevulenic acid revealed a 15-fold enhancement when compared to passive diffusion. For dipeptide (Ala-Trp) the mean cumulative amount increased iontophoretic delivery from 0.4±0.4, 0.1μg/cm2 to 16.0±8.8, 3.6μg/cm2 (Mean±SD, SEM) was observed when the donor pH was reduced from 7.4 to 5.5. The corresponding current intensity (0.38mA/cm2) normalised flux was 36.1±19.5, 11.2μg/(mA.h) for iontophoretic Ala-Trp. For the tetrapeptide (Ala-Ala-Pro-Val) the mean cumulative amount that permeation with 2h iontophoresis was 350.4±45.9, 15.3μg/cm2 (Mean±SD, SEM) compared to zero passive permeation. A 4-fold increase in acetyl hexapeptide-3 delivery occurred with iontophoresis compared with passive application. In addition it was observed that lowering of donor solution pH and the presence of counterions and co-ions reduced the iontophoretic delivery of acetylhexapeptide-3. Iontophoresis provided a significant enhancement factor for the decapeptide, triptorelin acetate with a 16-fold increase in epidermal permeation compared with passive permeation. The iontophoretic permeation was concentration dependent with mean cumulative amounts of 48±28, 14 μg/cm2 (Mean±SD, SEM) achieved with 9 mM concentration of triptorelin acetate.Overall the technologies investigated in this research work presented enhanced permeation of drug molecules and peptides. In addition MPT-FLIM was demonstrated to be an efficient visualisation tool for permeation within the skin. This research demonstrates the effectiveness of physical skin permeation enhancement techniques and extends our understanding of these technologies.
2
Khakifirooz, Ali. "Transport enhancement techniques for nanoscale MOSFETs." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42907.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 155-183).
Over the past two decades, intrinsic MOSFET delay has been scaled commensurate with the scaling of the dimensions. To extend this historical trend in the future, careful analysis of what determines the transistor performance is required. In this work, a new delay metric is first introduced that better captures the interplay of the main technology parameters, and employed to study the historical trends of the performance scaling and to quantify the requirements for the continuous increase of the performance in the future. It is shown that the carrier velocity in the channel has been the main driver for the improved transistor performance with scaling. A roadmapping exercise is presented and it is shown that new channel materials are needed to lever carrier velocity beyond what is achieved with uniaxially strained silicon, along with dramatic reduction in the device parasitics. Such innovations are needed as early as the 32-nm node to avoid the otherwise counter-scaling of the performance. The prospects and limitations of various approaches that are being pursued to increase the carrier velocity and thereby the transistor performance are then explored. After introducing the basics of the transport in nanoscale MOSFETs, the impact of channel material and strain configuration on electron and hole transport are examined. Uniaixal tensile strain in silicon is shown to be very promising to enhance electron transport as long as higher strain levels can be exerted on the device. Calculations and analysis in this work demonstrate that in uniaxially strained silicon, virtual source velocity depends more strongly on the mobility than previously believed and the modulation of the effective mass under uniaxial strain is responsible for this string dependence.
(cont) While III-V semiconductors are seriously limited by their small quantization effective mass, which limits the available inversion charge at a given voltage overdrive, germanium is attractive as it has enhanced transport properties for both electrons and holes. However, to avoid mobility degradation due to carrier confinement as well as L - interband scattering, and to achieve higher ballistic velocity, (111) wafer orientation should be used for Ge NFETs. Further analysis in this work demonstrate that with uniaixally strained Si, hole 3 ballistic velocity enhancement is limited to about 2x, despite the fact that mobility enhancement of about 4x has been demonstrated. Hence, further increase of the strain level does not seem to provide major increase in the device performance. It is also shown that relaxed germanium only marginally improves hole velocity despite the fact that mobility is significantly higher than silicon. Biaxial compressive strain in Ge, although relatively simple to apply, offers only 2x velocity enhancement over relaxed silicon. Only with uniaxial compressive strain, is germanium able to provide significantly higher velocities compared to state-of-the-art silicon MOSFETs. Most recently, germanium has manifested itself as an alternative channel material because of its superior electron and hole mobility compared to silicon. Functional MOS transistors with relatively good electrical characteristics have been demonstrated by several groups on bulk and strained Ge. However, carrier mobility in these devices is still far behind what is theoretically expected from germanium. Very high density of the interface states, especially close to the conduction band is believed to be responsible for poor electrical characteristics of Ge MOSFETs. Nevertheless, a through investigation of the transport in Ge-channel MOSFETs and the correlation between the mobility and trap density has not been undertaken in the past.
(cont) Pulsed I -V and Q-V measurement are performed to characterize near intrinsic transport properties in Ge-channel MOSFETs. Pulsed measurements show that the actual carrier mobility is at least twice what is inferred from DC measurements for Ge NFETs. With phosphorus implantation at the Ge-dielectric interface the difference between DC and pulsed measurements is reduced to about 20%, despite the fact that effects of charge trapping are still visible in these devices. To better understand the dependence of carrier transport on charge trapping, a method to directly measure the inversion charge density by integrating the S/D current is proposed. The density of trapped charges is measured as the difference between the inversion charge density at the beginning and end of pulses applied to the gate. Analysis of temporal variation of trapped charge density reveals that two regimes of fast and slow charge trapping are present. Both mechanisms show a logarithmic dependence on the pulse width, as observed in earlier literature charge-pumping studies of Si MOSFETs with high- dielectrics. The correlation between mobility and density of trapped charges is studied and it is shown that the mobility depends only on the density of fast traps. To our knowledge, this is the first investigation in which the impact of the fast and slow traps on the mobility has been separated. Extrapolation of the mobility-trap relationship to lower densities of trapped charges gives an upper limit on the available mobility with the present gate stack if the density of the fast traps is reduced further. However, this analysis demonstrates that the expected mobility is still far below what is obtained in Si MOSFETs. Further investigations are needed to analyze other mechanisms that might be responsible for poor electron mobility in Ge MOSFETs and thereby optimize the gate stack by suppressing these mechanisms.
by Ali Khakifirooz.
Ph.D.
3
Williams, Daniel Dee. "Design analysis techniques for software quality enhancement." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Summer2007/d_williams_072407.pdf.
Full text
4
Al-Atabany, Walid Ibrahim. "Image enhancement techniques for bioelectronic visual aids." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.528303.
Full text
5
Dale-Jones, Ralph. "Contrast enhancement using grey scale transformation techniques." Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387342.
Full text
6
Thái, Minh Thanh 1976. "Resolution enhancement techniques for antenna pattern measurements." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86572.
Full text
7
MacCormack, Stuart. "Photorefractive techniques for diode laser brightness enhancement." Thesis, University of Southampton, 1991. https://eprints.soton.ac.uk/403318/.
Full textAbstract:
The experimental investigation of a number of techniques using photorefractive materials to increase the spectral and spatial brightness of the output from high power semiconductor laser arrays are discussed. The topics of semiconductor lasers and photorefractive materials are reviewed briefly, and the experimental and theoretical background of array transverse modes and laser array injection locking are discussed fully. Single longitudinal mode operation of a 100mW array coupled to a simple, hemispherical external cavity is reported. A side mode suppression ratio of 14dB was achieved. A spatial brightness enhancement by a factor of 10 is reported for a 1W laser array coupled to a phase conjugate external cavity. A number of techniques for the combination of multiple array outputs into a single beam were investigated. A power of 108mW (220mW, Fresnel corrected) was obtained in a diffraction limited, single mode laser beam using photorefractive two-beam coupling with an injection locked 1W laser array pump. Results on the operation of a reflection geometry phase conjugate master-oscillator, power-amplifier using a 500mW diode laser array are presented. The observation of coherent energy transfer between the outputs from the separate stripes of a laser array is discussed, and an external photorefractive beam combining element is proposed. Phase conjugate fidelity results are presented for a double pass, phase conjugate, multimode fibre amplifier geometry. The experiments suggest that phase conjugate modal unscrambling will still take place in the presence of ~6dB gain. A scheme for a high efficiency, high power multimode fibre amplifier is proposed.
8
Ullah, Muhammad Obaid Obaid Ullah. "Link enhancement techniques for future multicarrier systems." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/link-enhancement-techniques-for-future-multicarrier-systems(255d3239-2ec7-45d5-b3e6-9bd73caa8377).html.
Full textAbstract:
Orthogonal Frequency Division Multiplexing (OFDM) is very effective in combating the distortive effects of wireless channel and promises high data rate capabilities with reasonable complexity and accuracy. Other advantages of OFDM include significantly simple equalizer requirement, high spectral efficiency, computationally inexpensive implementation, increased immunity to impulse noise, ability to support adaptive modulation schemes and high flexibility in resource allocation. This thesis investigates two vital issues regarding the OFDM system design requirements, namely, Channel Estimation (CE) and Carrier Frequency Offset Estimation (CFOE). The accuracy of these two estimators plays a crucial role in the overall performance of OFDM systems. Whether it is a single antenna or a multi-antenna OFDM system, accurate channel estimation (CE) is required for coherent reception. The channel estimation requirement is further exacerbated in the case of OFDM systems with multiple transmit and/or receive antennas as the signals are simultaneously transmitted / received and consequently arrive at the receiver through many channels. CE techniques for OFDM systems are broadly classified into pilot-aided and blind techniques. As compared to blind algorithms, pilot-aided CE algorithms are more robust to high Doppler frequency, and hence, are useful for high mobility applications. One of the major drawbacks of OFDM is its sensitivity to time and frequency synchronization errors. Owing to its inherent cyclic symbol structure, the time synchronization requirements are somewhat relaxed for OFDM systems. Conversely, the frequency synchronization requirements are more stringent because of its tightly packed subcarriers. The frequency offset results in loss of orthogonality of subcarriers which subsequently causes significant performance degradation. Therefore, it is imperative to estimate the CFO and thereafter eliminate or minimize its effects. This thesis proposes a new set of techniques for pilot-aided CE namely “undersampledchannel estimation” for OFDM systems. In such techniques, the number of pilots used to sample the channel are less than those allowed by Nyquist sampling theorem. Virtually blind (VB) CE uses only one pilot to estimate the channel frequency response (CFR). The performance of VB CE is hindered by the occurrence of CFR inversion (CFRI). Uniformly spaced fixed additional pilots and dynamically assigned additional pilots were then augmented with the only pilot in order to take more samples of channel and to stop propagating CFRIeffect further. For joint blind channel and control signal estimation for OFDM systems, the detectability of control information dependent (CID) pilot sequences is highly dependent on the type of sequences used. An algorithm to design a new set of pilot sequences with better detectability is proposed in this thesis.
9
Castillo, Solis Maria De los angeles. "Dielectric resonator antennas and bandwidth enhancement techniques." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/dielectric-resonator-antennas-and-bandwidth-enhancement-techniques(44b64ce4-dc73-496a-b656-dc4b9c910291).html.
Full textAbstract:
In this thesis a technique that is being used in another area of technology to optimize light reception in a photographic camera was also applied to the dielectric resonator antenna. The technique consisting of the use of thin film to couple the media and camera impedances resulted in a dielectric resonator antenna bandwidth enhancement technique. The bandwidth enhancement technique was found when thin film dielectric layer structure was used to couple the dielectric resonator and its feed mechanism. Remarkable good performance was detected with a coplanar waveguide fed cylindrical dielectric resonator antenna which resulted in an improvement to its fractional bandwidth from 7.41% to 50.85%. Extensive experimental work was undertaken in order to explore the extent offered in bandwidth performance by using thin film dielectric layer structure in the dielectric resonator antenna performance. The experimental tasks were designed in order to investigate the influence of the thin film dielectric layer structure in relation to its size, shape, thickness, position and direction. Experimental results were supported with simulation work with the computer simulation technology microwave studio. The pieces of the material used for undertaking this experimental work were manually handcrafted. Four different dielectric resonator antenna designs were used in order to carry out the experimental work including the coplanar waveguide fed cylindrical dielectric resonator antenna. The other three dielectric resonator antennas were implemented using the same microstrip feed mechanism. Improved performance in bandwidth was achieved for all the designs. Optimization of the incoming signal was observed when a piece of thin film dielectric layer structure was placed in position between the feed mechanism and the dielectric resonator antenna. The optimization was observed as an enhancement in both the return loss level and the bandwidth of work. Different unexpected operational modes from were activated, such modes being called perturbed modes. Two different shapes were used in this project. Cylindrical dielectric resonator antenna (ɛr = 37) from a commercial provider and two novel rectangular dielectric resonator antennas. The novel rectangular dielectric resonator antennas were created with the methodology presented in this thesis. The rectangular dielectric resonator antennas were elaborated with transparent ceramic material (ɛr = 7) and TMM10i (ɛr = 9.8) from the Rogers Corporation company. The bandwidth enhancement technique was tested in novel embedded dielectric resonator antennas. A coplanar waveguide fed embedded cylindrical dielectric resonator antenna achieved a maximum bandwidth enhancement of 156.77% around f = 3.79 GHz with a thin film dielectric layer structure modified rectangular piece on one edge. Escalation to dielectric resonator antenna design at millimeter wave frequencies was achieved by using thin film dielectric layer structure bandwidth enhancement technique and a handcrafted printed circuit board millimeter wave feed mechanism. The millimeter wave feed mechanisms were achieved using a low cost alternative technique conceived as part of this project. Millimeter wave dielectric resonator antennas were implemented using thin film dielectric layers structure. The antennas deliver an adequate performance in bandwidth. The work presented in this thesis demonstrates dielectric resonator antenna simpler geometry, simple couple schemes, small size, low profile, light weight, and ease of excitation and orientation. Other parameters have also been investigated covering reduced complexity, high degree of flexibility, ease of fabrication and the use of low cost technology to escalate to millimeter wave frequencies.
10
Messina, Giuseppe. "Advanced Techniques for Image Analysis and Enhancement." Thesis, Università degli Studi di Catania, 2011. http://hdl.handle.net/10761/190.
Full textAbstract:
The research activities, described in this thesis, have been mainly focused on images analysis and quality enhancement. Specifically the research regards the study and development of algorithms for color interpolation, contrast enhancement and red-eye removal, which have been exclusively oriented to mobile devices. Furthermore an images analysis for forgeries identification and image enhancement, usually directed by investigators (Forensic Image Processing) has been conducted. The thesis is organized in three main parts: Image Processing for Embedded Devices; Image Analysis and Enhancement; Forensics Image Processing.Le attivita' di ricerca, descritte in questa tesi, sono state principalmente focalizzate sull'analisi delle immagini ed il miglioramento della qualita'. In particolare la ricerca riguarda lo studio e lo sviluppo di algoritmi di interpolazione del colore, miglioramento del contrasto e rimozione degli occhi rossi, che sono stati esclusivamente sviluppati per l'utilizzo su dispositivi "mobile". Inoltre e' stata documentata un analisi delle immagini per l'identificazione dei falsi e per il miglioramento della qualita' immagini, a fini investigativi (Forensics Image Processing). La tesi e' organizzata in tre parti: Image Processing for Embedded Devices; Image Analysis and Enhancement; Forensics Image Processing.
11
Parsa, Vijay. "Interference reduction techniques for somatosensory evoked potential enhancement." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23871.pdf.
Full text
12
Crozier, Philip Mark. "Enhancement techniques for noise affected telephone quality speech." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321115.
Full text
13
Ma, Xu. "Optimization of resolution enhancement techniques in optical lithography." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 252 p, 2009. http://proquest.umi.com/pqdweb?did=1885756601&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
14
Lambert, T. "Digital Enhancement Techniques for Underwater Video Image Sequences." Thesis, Honours thesis, University of Tasmania, 2005. https://eprints.utas.edu.au/253/1/tristanlthesis.pdf.
Full textAbstract:
Due to concern about the current state of the world's oceans, several large scale scientific projects have begun to investigate the condition of our oceans. These projects are making use of underwater video sequences to monitor marine species. The move to using underwater video monitoring introduces labour intensive manual processing techniques. This leads to the need for an automated system capable of processing the data at a much greater speed. This project investigated whether the development of suitable image processing techniques could be used for pre-processing underwater images from a fish farm and locating fish within these images using computer vision techniques.
Using underwater images leads to some serious problems when compared to images from a clearer environment. Visibility in an underwater environment is poor, even when using state of the art equipment. After reviewing the broad field of computer vision and current underwater projects, an image pre-processing system was developed in MATLAB using suitable image processing and analysis techniques.
The application developed was able to successfully locate an acceptable number of fish within the underwater images. The project demonstrated that automated analysis of underwater video images is needed and is possible. Automatic processing of large quantities of video image sequences will be of great benefit in the future. It will allow scientific researchers to study the ocean environment and its species more effectively. Pre-processing is an essential component of the overall process that will lead to automation of underwater video data analysis for marine science applications.
15
ZINI, SIMONE. "Image Enhancement and Restoration using Machine Learning Techniques." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2022. http://hdl.handle.net/10281/378899.
Full textAbstract:
Le fotocamere digitali acquisiscono, manipolano e salvano in memoria informazioni elettronicamente tramite un sensore e unitá di calcolo integrate, rendendo la fotografia accessibile agli utenti finali i quali non necessitano di basi di conoscenza di chimica o delle specifiche operazioni meccaniche che erano necessarie per lo sviluppo con la fotografia analogica.
Diversi tipi di degradazioni e artefatti possono affliggere le immagini acquisite tramite camere digitali, riducendo la fedeltà percepita delle immagini e rendendo piú difficili operazioni di visione artificiale che possono essere operate sulle immagini acquisite.
Tre elementi possono essere identificati come possibili sorgenti di artefatti in un'immagine: il contenuto della scena, le limitazioni hardware della camera e la pipeline di elaborazione dell’immagine, dall’acquisizione al salvataggio in memoria.
Alcuni artefatti non sono direttamente trattati all’interno della tipica pipeline di camera, come ad esempio la presenza di nebbia o pioggia che possono ridurre la visibilitá della scena acquisita. Questi artefatti , per essere trattati, necessitano di metodologie ad hoc che sono generalmente applicate come operazioni post-processing.
Altri tipi di artefatti sono legati ai processi di elaborazione dell’immagine e all'intera pipeline di camera integrata nelle camere. Questi artefatti includono il rumore proveniente dal sensore, dominanti cromatiche indesiderate, basso contrasto e artefatti di compressione.
L’obiettivo di questa tesi è l'identificazione e la progettazione di nuovi e piú robusti moduli di elaborazione e restauro dell’immagine capaci di migliorare la qualitá delle immagini acquisite dalle camere digitali, in particolare in scenari critici quali condizioni climatiche avverse, condizione di bassa illuminazione etc…
Gli artefatti identificati sono divisi in due macro gruppi: “artefatti in-camera” e “artefatti esterni”
Nel primo gruppo sono stati identificati e trattati quattro argomenti: la rimozione del rumore proveniente dal sensore della camera, il processo di bilanciamento automatico del bianco, il miglioramento automatico del contrasto e la rimozione di artefatti di compressione JPEG. Il processo di progettazione di questi moduli ha tenuto conto di aspetti di efficienza, in termini di calcolo e memoria occupata, in relazione alla possibilità di integrare tali moduli in future configurazioni di pipeline di camera.
Il secondo gruppo di artefatti è legato alla presenza di elementi nella scena che possono causare una degradazione in termini di fedeltà dell’immagine e/o usabilità. In particolare il lavoro presentato nella tesi è focalizzato su artefatti provenienti dalla presenza di pioggia nella scena scattata.
La tesi, dopo una descrizione della tipica pipeline di elaborazione delle camere digitali, analizza i diversi tipi di artefatti che possono affliggere la qualità di una immagine, e descrive la progettazione delle soluzioni proposte. Tutti gli approcci proposti sono basati su tecniche di apprendimento automatico, come ad esempio Reti Neurali Convoluzionali o procedure di ottimizzazione Bayesiana, e sono stati validati sperimentalmente su dataset standard.
I contributi principali di questa tesi possono essere riassunti in tre punti: integrazione di approcci classici di imaging con tecniche di ottimizzazione basate su machine learning, progettazione e sviluppo di nuovi approcci e architetture di deep learning per il restauro e l'elaborazione di immagini e analisi di metodi di image processing basati su deep learning in task di computer vision.Digital cameras record, manipulate, and store information electronically through sensors and built-in computers, which makes photography more available to final users which do not anymore need to rely on the use of chemicals and knowledge of mechanical procedures to develop their pictures. Different types of degradation and artifacts can affect images acquired using digital cameras, decreasing the perceptual fidelity of images and making harder many image processing and analysis tasks that can be performed on the collected images. Three elements can be identified as possible sources of artifacts in an image: the scene content, the hardware limitations and flaws, and finally the operations performed by the digital camera processing pipeline itself, from acquisition to compression and storing. Some artifacts are not directly treated in the typical camera processing pipeline, such as the presence of haze or rain that can reduce visibility of the scene in the depicted images. These artifacts require the design of ad hoc methods that are usually applied as post-processing on the acquired images. Other types of artifacts are related to the imaging process and to the image processing pipeline implemented on board of digital cameras. These include sensor noise, undesirable color cast, poor contrast and compression artifacts. The objective of this thesis is the identification and design of new and more robust modules for image processing and restoration that can improve the quality of the acquired images, in particular in critical scenarios such as adverse weather conditions, poor light in the scene etc… . The artifacts identified are divided into two main groups: “in camera-generated artifacts" and “external artifacts and problems". In the first group it has been identified and addressed four main issues: sensor camera noise removal, automatic white balancing, automatic contrast enhancement and compression artifacts removal. The design process of the proposed solutions has considered efficiency aspects, due to the possibility of directly integrating them in future camera pipelines. The second group of artifacts are related to the presence of elements in the scene which may cause a degradation in terms of visual fidelity and/or usability of the images. In particular the focus is on artifacts induced by the presence of rain in the scene. The thesis, after a brief review of the digital camera processing pipeline, analyzes the different types of artifacts that can affect image quality, and describes the design of the proposed solutions. All the proposed approaches are based on machine learning techniques, such as Convolutional Neural Networks and Bayesian optimization procedure, and are experimentally validated on standard images datasets. The overall contributions of this thesis can be summarized in three points: integration of classical imaging approaches with machine learning optimization techniques, design of novel deep learning architectures and approaches and analysis and application of deep learning image processing algorithms in other computer vision tasks.
16
Morris, Robert W. "Enhancement and recognition of whispered speech." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180338/unrestricted/morris%5frobert%5fw%5f200312%5fphd.pdf.
Full text
17
Udayashankara, V. "DSP Techniques for Performance Enhancement of Digital Hearing Aid." Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/156.
Full textAbstract:
Hearing impairment is the number one chronic disability affecting people in the world. Many people have great difficulty in understanding speech with background noise. This is especially true for a large number of elderly people and the sensorineural impaired persons. Several investigations on speech intelligibility have demonstrated that subjects with sensorineural loss may need a 5-15 dB higher signal-to-noise ratio than the normal hearing subjects. While most defects in transmission chain up to cochlea can nowadays be successfully rehabilitated by means of surgery, the great majority of the remaining inoperable cases are sensorineural hearing impaired, Recent statistics of the hearing impaired patients applying for a hearing aid reveal that 20% of the cases are due to conductive losses, more than 50% are due to sensorineural losses, and the rest 30% of the cases are of mixed origin. Presenting speech to the hearing impaired in an intelligible form remains a major challenge in hearing-aid research today. Even-though various methods have been suggested in the literature for the minimization of noise from the contaminated speech signals, they fail to give good SNR improvement and intelligibility improvement for moderate to-severe sensorineural loss subjects. So far, the power and capability of Newton's method, Nonlinear adaptive filtering methods and the feedback type artificial neural networks have not been exploited for this purpose. Hence we resort to the application of all these methods for improving SNR and intelligibility for the sensorineural loss subjects. Digital hearing aids frequently employ the concept of filter banks. One of the major drawbacks of this techniques is the complexity of computation requiring more number of multiplications. This increases the power consumption. Therefore this Thesis presents the new approach to speech enhancement for the hearing impaired and also the construction of filter bank in Digital hearing aid with minimum number of multiplications. The following are covered in this thesis.
One of the most important application of adaptive systems is in noise cancellation using adaptive filters. The ANC setup requires two input signals (viz., primary and reference). The primary input consists of the sum of the desired signal and noise which is uncorrelated. The reference input consists of mother noise which is correlated in Some unknown way with noise of primary input. The primary signal is obtained by placing the omnidirectional microphone just above one ear on the head of the KEMAR mannikan and the reference signal is obtained by placing the hypercardioid microphone at the center of the vertebral column on the back. Conventional speech enhancement techniques use linear schemes for enhancing speech signals. So far Nonlinear adaptive filtering techniques are not used in hearing aid applications. The motivation behind the use of nonlinear model is that it gives better noise suppression as compared to linear model. This is because the medium through which signals reach the microphone may be highly nonlinear. Hence the use of linear schemes, though motivated by computational simplicity and mathematical tractability, may be suboptimal. Hence, we propose the use of nonlinear models to enhance the speech signals for the hearing impaired: We propose both Linear LMS and Nonlinear second order Volterra LMS schemes to enhance speech signals. Studies conducted for different environmental noise including babble, cafeteria and low frequency noise show that the second-order Volterra LMS performs better compared to linear LMS algorithm. We use measures such as signal-to-noise ratio (SNR),
time plots, and intelligibility tests for performance comparison.
We also propose an ANC scheme which uses Newton's method to enhance speech signals. The main problem associated with LMS based ANC is that their convergence is slow and hence their performance becomes poor for hearing aid applications. The reason for choosing Newton's method is that they have high performance adaptive-filtering methods that often converge and track faster than LMS method. We propose two models to enhance speech signals: one is conventional linear model and the other is a nonlinear model using a second order Volterra function. Development of Newton's type algorithm for linear mdel results in familiar Recursive least square (RLS) algorithm. The performance of both linear and non-linear Newton's algorithm is evaluated for babble, cafeteria and frequency noise. SNR, timeplots and intelligibility tests are used for performance comparison. The results show that Newton's method using Volterra nonlinearity performs better than RLS method.
ln addition to the ANC based schemes, we also develop speech enhancement for the hearing impaired by using the feedback type neural network (FBNN). The main reason is that here we have parallel algorithm which can be implemented directly in hardware. We translate the speech enhancement problem into a neural network (NN) framework by forming an appropriate energy function. We propose both linear and nonlinear FBNN for enhancing the speech signals. Simulated studies on different environmental noise reveal that the FBNN using the Volterra nonlinearity is superior to linear FBNN in enhancing speech signals. We use SNR, time plots, and intelligibility tests for performance comparison.
The design of an effective hearing aid is a challenging problem for sensorineural hearing impaired people. For persons with sensorineural losses it is necessary that the frequency response should be optimally fitted into their residual auditory area. Digital filter enhances the performance of the hearing aids which are either difficult or impossible to realize using analog techniques. The major problem in digital hearing aid is that of reducing power consumption. Multiplication is one of the most power consuming operation in digital filtering. Hence a serious effort has been made to design filter bank with minimum number of multiplications, there by minimizing the power consumption. It is achieved by using Interpolated and complementary FIR filters. This method gives significant savings in the number of arithmetic operations.
The Thesis is concluded by summarizing the results of analysis, and suggesting scope for further investigation
18
Wong, Kim Fai. "Speed enhancement techniques for comparator-based switched-capacitor circuits." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2493500.
Full text
19
Yuksel, Basak. "Towards The Enhancement Of Biped Locomotion And Control Techniques." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609899/index.pdf.
Full textAbstract:
The omnipresent tendency to &ldquolive easy&rdquo
is a sign of our need for automatization. To enable for such a &ldquo
comfortable and safe&rdquo
world, the automatic systems have to be developed that satisfies the necessities of life. Biologically inspired robots, especially the humanoids, are thus the key, and research in this area focuses on the improvement of such systems. Lately, it has been shown by high dexterity examples that the humanoid robots achieved to a mature level even if there are still open issues to be improved, especially in the control and stability of the bipeds. The purpose of this thesis is to study biped locomotion in different floor conditions, such as stairs and obstacles
to improve the research done in this area
to contribute to the development of autonomous biped robots, dynamic modeling, gait planning, supervisory and guidence control, stability analysis of biped robots
and to implement new control algorithms for biped locomotion, especially by using optimization and high level intelligent control techniques. The locomotion aimed to be realized results from complex, high-dimensional, nonlinear and dynamically related interactions between the robot and its environment. The mathematical modeling of the physical system is realized based on a 5-link 7 DOF biped robot model walking on a 3D planar surface and the dynamic simulation is performed using MATLAB. In terms of control, several different methods applied, comparison and the performance of each method are given. The 3D dynamic simulation software is developed, which allows the user to operate the biped systems within a 3D virtual environment.
20
Zou, Xinlei. "Bandwidth enhancement techniques for probe-fed microstrip patch antennas." Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27106.
Full textAbstract:
Many bandwidth enhancement techniques for microstrip patch antennas have been developed since the 1970's. Except for an IEEE collection of reprints which appeared in 1995, relatively little work has been done to review and categorize these techniques. As a result, the published research and design of broadband microstrip antennas has become somewhat unsystematic. In this thesis, papers on broadband microstrip antennas have been reviewed. Using full-wave electromagnetic simulation, the important performance parameters such as the bandwidth, realized gain, antenna efficiency, radiation efficiency and radiation patterns of broadband microstrip patch antennas have been considered. Based on these results, bandwidth enhancement techniques have been categorized in two broad classes, namely those applicable when electrically-thick low-permittivity substrates are used, and those applicable to electrically-thin high-permittivity substrates. These broad classes have been sub-divided into several sub-classes in a structured manner that aids the understanding of the bandwidth enhancement methods. A summary of these techniques, linked to a comparison of resulting microstrip patch antenna performance obtained from full-wave analysis of the sub-classes, is provided. It is also shown, through a specific example, how the increased understanding afforded by this categorization can lead to the development of new broad bandwidth geometries that can offer some advantages over existing ones.
21
Curnow, Alison. "Photodynamic therapy with 5-aminolaevulinic acid-techniques for enhancement." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312641.
Full text
22
Winski, R. "Adaptive techniques for signal enhancement in the human electroencephalogram." Thesis, Keele University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372829.
Full text
23
Nahma, Lara. "A Study into Speech Enhancement Techniques in Adverse Environment." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/76002.
Full textAbstract:
This dissertation developed speech enhancement techniques that improve the speech quality in applications such as mobile communications, teleconferencing and smart loudspeakers. For these applications it is necessary to suppress noise and reverberation. Thus the contribution in this dissertation is twofold: single channel speech enhancement system which exploits the temporal and spectral diversity of the received microphone signal for noise suppression and multi-channel speech enhancement method with the ability to employ spatial diversity to reduce reverberation.
24
Kamkar-Rouhani, Abolghasem. "Development and application of processing techniques for signal enhancement using multisystem resistivity measurements." Thesis, Curtin University, 1998. http://hdl.handle.net/20.500.11937/1314.
Full textAbstract:
DC electrical surveying involves the injection of current into the earth, and the measurement of the electrical potential differences this produces. A number of electrode configurations such as the Schlumberger and Wenner arrays, dipole-dipole and pole-pole geometries are in common use for electrical surveying. New acquisition systems enable the convenient collection of data with a number of common configurations at the same time. It is found however that while the recovery of layered structure from electrical surveys can be effective, the sensitivity and resolving power of such systems in detecting the presence of anomalous three-dimensional (3-D) bodies is poor. This is mainly due to the dominance of conduction pathways through the layered earth compared to the influence of small 3-D conductivity anomalies.Theoretical relationships between the responses of various survey geometries to the layered earth may be established as is shown in this thesis, but their response to 3-D targets differs strongly. This thesis introduces a new procedure for anomalous target detection by the computation of an apparent resistivity residual using multi-electrode configuration survey data. This procedure, applicable to a variety of electrode geometries, reduces the dominance of the layered earth response and enhances the signal from 3-D structures.In the development and testing of this new apparent resistivity residual, numerically modelled data were used. In order to obtain suitable test data of high accuracy it was necessary to make improvements to modelling software. For this purpose, recently developed techniques in numerical modelling such as the biconjugate gradient method, new digital linear filters for computation of Hankel transforms, and spectral formalism were employed in an integral equation approach for the software developed in this thesis.The computed apparent resistivity residual was found to depend on the array type and dimensions, the nature of the anomalous zone, geological layer geometries, and resistivity contrasts of the layers involved. While the apparent resistivity residual signature requires some measure of interpretation, it is shown to enhance the resolution and detectability of 3-D targets in a layered environment.The presence of random noise produces some degradation in the performance of the residual technique, but a normalisation procedure has been developed to alleviate the problem. A preliminary field trial showed that survey profiles of apparent resistivity residual were able to locate a subsurface conductive anomaly in an area in Western Australia.A transitional zone is defined as a layer in the earth where resistivity varies as a continuous function of depth. A theoretical formulation for the electrical response of an earth structure composed of anomalous 3-D bodies in the presence of transitional layers is introduced. Tests on synthetic survey data showed that the apparent resistivity residual is an effective anomaly detector in transitional layer environments.A multi-system method of computing an apparent resistivity residual has been developed theoretically and tested on both synthetic and field data. This new approach when applied to resistivity profiling is more sensitive to, and gives greater resolution of, localised anomalies than is possible using conventional profiling procedures.
25
Pritchard, Thomas Anthony John. "3G Wideband-CDMA : subspace splitting techniques for downlink performance enhancement." Thesis, Imperial College London, 2005. http://hdl.handle.net/10044/1/11211.
Full text
26
Yin, Zhanping. "Protocol enhancement and network formation techniques in IEEE 802.15.3 WPANs." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31760.
Full textAbstract:
Designed for high rate wireless personal area networks (WPANs), the IEEE 802.15.3 protocol enables peer-to-peer communications between devices (DEVs) with quality of service (QoS) support. This thesis presents several performance enhancement methods and scatternet formation techniques for 802.15.3 networks. Considering piconet coverage and multi-rate carriers, we first propose a Third-Party Handshake Protocol (3PHP) for fast peer discovery and connection reestablishment. With the active involvement of the piconet coordinator (PNC), 3PHP guarantees full piconet connectivity, and achieves faster peer discovery by removing the peer discovery overhead and eliminating costly upper layer routing between directly unreachable DEVs by a more reliable and efficient MAC layer forwarding. Second, we develop intra-piconet route optimization algorithms in the PNC with application awareness through self-learning the achievable data rates between DEVs, which significantly increase the system performance in terms of reducing transmission time and increasing effective data rate, and thus reduce power consumption and increase piconet capacity. Furthermore, we propose a frame aggregation strategy for efficient frame transmissions in 802.15.3 Contention Period (CPs), and model the CP in each superframe as a contention resolution problem. We further propose a novel Adaptive CP Suspend (ACS) scheme that significantly shortens the effective region in a CP, thus greatly reducing the system energy cost by allowing DEVs to sleep during the suspended parts of the CPs. ACS adapts to varying channel traffic and collision situations by employing a CP counter at the PNC. Finally, we investigate the 802.15.3 scatternet formation problem. Configuration of scatternets needs to consider the piconet size and channel reuse, given the number of logical channels available. We first evaluate the effect of piconet size on the expected scatternet connection rate, and show that a medium sized piconet radius yields the best scatternet connection data rate taking into account of channel reuse. Moreover, we propose a stochastic scattenet formation algorithm to avoid neighbor information gathering in 802.15.3 networks. With only 20% more piconets than the ideal but impracticable greedy algorithm, the stochastic method scales well with network size, achieves better connectivity, requires less maintenance and is robust and stable with respect to changes in the WPAN.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
27
Lundell, Johan. "Efficiency Enhancement Techniques for a 0.13 µm CMOS DECT PA." Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-96235.
Full textAbstract:
Different efficiency enhancement techniques for a 1.9 GHz DECT power amplifier (PA) have been investigated. Generally, a higher efficiency can be achieved by varying the supply voltage and/or the bias of the PA or by making topology and/or class changes. In this work, changes in bias and topology have been studied. Focus has been on enhancing efficiency at power back-off to increase talk-time for handset applications. The PA used in this study was a two stage 0.13 μm CMOS PA for 2.5 V operation. In its original configuration, it delivered 28.3 dBm of maximum output power with a PAE of 43.5 % (simulated). At 10 dB power back-off the PAE was only 15.9 %. The largest improvement was obtained using a topology change with the amplifying transistor split into two parallel transistors (class A and B) with variable bias. The PA delivered 29.1 dBm to the load with a PAE of 45.1 %, and 18 % PAE at power back-off; a relative improvement at this level with 13 %. The new PA topology does not require any additional area.
28
Jabloun, Firas. "Perceptual and Multi-Microphone Signal Subspace Techniques for Speech Enhancement." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95577.
Full textAbstract:
The performance of speech communication systems, such as hands-free telephony, is known to seriously degrade under adverse acoustic environments. The presence of noise can lead to the loss of intelligibility as well as to the listener's fatigue. These problems can generally make the existing systems unsatisfactory to the customers especially that the offered services usually put no restrictions on where they can actually be used. For this reason, speech enhancement is vital for the overall success of these systems on the market.In this thesis we present new speech enhancement techniques based on the signal subspace approach. In this approach the input speech vectors are projected onto the signal subspace where it is processed to suppress any remaining noise then reconstructed again in the time domain. The projection is obtained via the eigenvalue decomposition of the speech signal covariance matrix.The main problem with the signal subspace based methods is the expensive eigenvalue decomposition. In this thesis we present a simple solution to this problem in which the signal subspace filter is updated at a reduced rate resulting in a significant reduction in the computational load. This technique exploits the stationarity of the input speech signal within a frame of 20-30 msec to use the same eigenvalue decomposition for several input vectors. The original implementation scheme was to update the signal subspace filter for every such input vector. The proposed technique was experimentally found to offer significant computational savings at almost no performance side-effects.The second contribution of this thesis is the incorporation of the human hearing properties in the signal subspace approach using a sophisticated masking model. It is known that there is a tradeoff between the amount of noise reduction achieved and the resulting signal distortion. Therefore, it would be beneficial to avoid suppressing any noise components as long as they are not perceived by theIl est connu que la performance des systèmes de communication par la voix se détériore lorsqu'ils sont utilisés dans des environnements acoustiques peu favorables. En effet, la présence du bruit cause la perte de l'intelligibilité et engendre la fatigue chez les auditeurs. Ces problèmes peuvent rendre les systèmes existant sur le marché inintressants pour les clients surtout que les services offerts par les compagnies de télécommunication ne comportent aucune restriction sur les endroits où ils seront utilisés. Dans ce contexte, les algorithmes qui visent à améliorer la qualité du signal parole sont très importants du fait qu'ils permettent à ces systèmes de satisfaire les attentes du marché. Dans cette thèse, nous présentons des nouvelles techniques, visant à rehausser la qualité de la voix, qui sont basées sur l'approche de sous-espace du signal (SES). Selon cette approche, les vecteurs du signal sont projetés sur le sous-espace du signal où ils sont traités afin d'éliminer le bruit restant. Après ce traitement, les vecteurs seront reconstruits dans le domaine du temps. La projection est obtenue grâce à la décomposition en valeurs propres de la matrice de covariance du signal parole. Le problème avec l'approche SES est que le coût, en terme de temps de calcul, relié à la décomposition en valeurs propres est élevé. Dans cette thèse, nous proposons une technique simple pour résoudre ce problème. Cette technique réduit considérablement le temps de calcul car le filtre en sous-espace est mis à jour moins fréquemment. Initialement, l'implémentation de l'approche SES consistait à recalculer un nouveau filtre pour chaque vecteur. L'originalité de notre technique réside dans l'exploitation de la stationnarité du signal parole dans un intervalle de 20-30 msec afin d'utiliser la même décomposition en valeurs propres pour plusieurs vecteurs. Les expériences menées montrent que notre nouvelle technique réduit consid
29
Canagarajah, Cedric Nishanthan. "Digital signal processing techniques for speech enhancement in hearing aids." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260433.
Full text
30
Achi, Peter Y. "Speech Enhancement Techniques for Large Space Habitats Using Microphone Arrays." Thesis, University of Louisiana at Lafayette, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10813016.
Full textAbstract:
The astronauts? ability to communicate easily among themselves or with the ship?s computer should be a high priority for the success of missions. Long-duration space habitats--whether spaceships or surface bases--will likely be larger than present-day Earth-to-orbit/Moon transfer ships. Hence an efficient approach would be to free the crew members from the relative burden of having to wear headsets throughout the spacecraft. This can be achieved by placing microphone arrays in all crew-accessible parts of the habitat. Processing algorithms would first localize the speaker and then perform speech enhancement. The background "noise" in a spacecraft is typically fan and duct noise (hum, drone), valve opening/closing (click, hiss), pumps, etc. We simulate such interfering sources by a number of loudspeakers broadcasting various sounds: real ISS sounds, a continuous radio stream, and a poem read by one author. To test the concept, we use a linear 30-microphone array driven by a zero-latency professional audio interface. Speaker localization is obtained by time-domain processing. To enhance the speech-to-noise ratio, a frequency-domain minimum-variance approach is used.
31
Ogunnika, Olumuyiwa Temitope 1978. "Efficiency enhancement techniques for RF and millimeter wave power amplifiers." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78455.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-126).
Power amplifiers are the circuit blocks in wireless transceivers that require the largest power budget because of their relatively low efficiencies. RF designers cannot depend solely on the development better semiconductor devices in advanced deeply scaled process technologies to obtain improved power amplifier performance. The development of new and better circuits, architectures and design methodologies to maximally exploit the available semiconductor devices is very important as well. This thesis investigates a number of techniques that can be used to improve the efficiency of power amplifiers and break the power-frequency tradeoff in power amplifier design. The first technique emphasizes the use of a class E tuned output network as an efficiency enhancement tool for power amplifiers regardless of their bias conditions. A Class E tuned CMOS power amplifier (PA) operating in the 60 GHz band was designed. Design, layout, and parasitic modeling considerations to attain high-efficiency millimeter-wave PA operation are discussed. Both single-ended and differential versions of the single-stage PA were implemented in a 32 nm SOI CMOS process. Peak power added efficiency of 27% (30%), power gain of 8.8 dB (10 dB), and saturated output power > 9 dBm (12.5 dBm) were measured at 60 GHz from the single-ended (differential) PA with 0.9 V supply. The second technique investigated the efficacy of resistance compression networks in an energy recycling network operating at multi-gigahertz frequencies. The resistance compression network reduces the variation in resonant rectifier input impedance seen at the isolation port of an isolating power combiner. The system was operated at 2.14 GHz and was built around Schottky barrier diodes custom fabricated in a 0.13 [mu]m CMOS process. It is the first experimental demonstration that resistance compression networks can be used for energy recycling in multi-gigahertz applications.
by Olumuyiwa Temitope Ogunnika.
Ph.D.
32
Chatlani, Navin. "Advanced signal enhancement techniques with application to speech and hearing." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23117.
Full textAbstract:
Advanced signal enhancement techniques with application to speech and hearing are presented that are applied to areas including adaptive noise cancellation (ANC) in noisy speech signals, single channel noise reduction for speech enhancement, voice activity detection (VAD) and noise reduction in binaural hearing aids. The performance enhancement of the new techniques over competing approaches is presented. For the domains of ANC and single channel noise reduction, the use of Empirical Mode Decomposition (EMD) is the underpinning technique employed. A novel approach to dual-channel speech enhancement using Adaptive Empirical Mode Decomposition (SEAEMD) is also presented, when a noise reference is available. The new SEAEMD system incorporates the multi-resolution approach EMD with ANC for effective speech enhancement in stationary and non-stationary noise environments. Two novel Empirical Mode Decomposition based filtering (EMDF) algorithms are presented for single channel speech enhancement. The first system is designed to be particularly effective in low frequency noise environments. The second generalized EMDF system is designed to operate under other noisy conditions, with results presented for babble noise, military vehicle noise and car interior noise. It is shown that the proposed EMDF techniques enhance the speech more effectively than current speech enhancement approaches that use effective noise estimation routines. Speech systems such as hearing aids require fast and computationally inexpensive signal processing technologies. A new and computationally efficient 1-dimensional local binary pattern (1-D LBP) signal processing procedure is designed and applied to (i) signal segmentation and (ii) the VAD problem. Both applications use the underlying features extracted from the 1-D LBP. The simplicity and low computational complexity of 1-D LBP processing are demonstrated. A novel binaural noise reduction system is presented for steering the focus direction of a hearing aid (2 microphones per hearing aid) to additional directions as well as 0/180 degrees. The system places a spatial null in the direction of the target speaker to obtain a noise estimate. The noisy speech signal is then filtered to perform noise reduction, and thus focus on the target speaker located at the desired direction. The results demonstrate its performance at attenuating multiple directional interferers.
33
Goodman, Allan Paul. "Creativity-enhancement techniques for professional design students : an integrated approach." Thesis, Kansas State University, 1988. http://hdl.handle.net/2097/16724.
Full text
34
Bachtobji, Soumaya. "Performance Analysis of Enhancement Techniques for 3-D Cellular Networks." Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1028.
Full textAbstract:
Les réseaux 5G présentent de nombreux défis et opportunités pour la conception des réseaux sans fil denses. Par conséquent, des efforts de recherche substantiels sont consacrés aux problèmes de la modélisation 3-D dans les réseaux HetNets basés sur les mmWave et la récupération d’énergie respectivement. Ainsi, la modélisation et l’amélioration des performances des réseaux cellulaires hétérogènes 3-D pour la prochaine génération méritent une étude approfondie, qui est l’objectif principal de cette thèse. Le travail de recherche présenté dans cette thèse a deux axes principaux. Premièrement, nous nous concentrons sur la modélisation en 3D des réseaux de communication sans fil. Ces modèles décrivent non seulement le système lorsque les blocages sont négligés, mais permettent également de modéliser les obstacles (tels que les bâtiments) afin d'étudier leur effet et de proposer une solution pour les surmonter. Deuxièmement, de nouvelles techniques de transmission sont proposées pour améliorer les performances des systèmes de communication sans fil urbains. Ainsi, nous introduisons une technique basée sur la récupération d’énergie (EH) tel que l’objectif est de réduire le délai de transmission et améliorer la capacité ergodique. Sur cette base, le délai de transmission moyen et les expressions de capacité ergodique sont détaillés et dérivés. Enfin, en considérant une hypothèse de canal nakagami-m pour les communications à ondes millimétriques, nous proposons un nouveau schéma min / max pour améliorer le taux de réussite de la transmission. Ce schéma est basé sur la sélection d’un relais disponible pouvant assister à la transmissionWith the explosive growth of mobile data demand, cellular networks have experienced several major evolutions, from the first generation to the present the fifth generation new radio cellular networks. These networks can cover a larger geographical area, with high network capacity, and low power consumption. For the next generation, the cellular networks consist in deploying a big number of small cells, such as femto-cells and picocells, which offers a lager zone of radio coverage. In fact, cell densification presents a simple and efficient solution to increase the network capacity, which relies on densely reusing the spectrum across a geographical area and hence brings base stations closer to users. Thus, the 3-D modeling and the performance enhancement of the increasingly heterogeneous cellular networks become important issues. The current thesis focuses on the study and the enhancement of 3-D cellular networks. The research work introduced in this thesis has two main axes. First, we focus on three-dimensional modeling of wireless communication networks. These models, not only describe the system when the blockages effect are neglected, but also capable of modeling the obstacles (such as buildings) in order to study their effect and propose solution to overcome. Second, new transmission schemes are proposed to enhance the performances of the urban wireless communication systems
35
Cluff, Stephen T. "A unified approach to GPU-accelerated aerial video enhancement techniques /." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd2780.pdf.
Full text
36
Huang, Danian. "Enhancement of automatic interpretation techniques for recognising potential field sources." Thesis, University of Leeds, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.719809.
Full text
37
Cluff, Stephen Thayn. "A Unified Approach to GPU-Accelerated Aerial Video Enhancement Techniques." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/1680.
Full textAbstract:
Video from aerial surveillance can provide a rich source of data for analysts. From the time-critical perspective of wilderness search and rescue operations, information extracted from aerial videos can mean the difference between a successful search and an unsuccessful search. When using low-cost, payload-limited mini-UAVs, as opposed to more expensive platforms, several challenges arise, including jittery video, narrow fields of view, low resolution, and limited time on screen for key features. These challenges make it difficult for analysts to extract key information in a timely manner. Traditional approaches may address some of these issues, but no existing system effectively addresses all of them in a unified and efficient manner. Building upon a hierarchical dense image correspondence technique, we create a unifying framework for reducing jitter, enhancing resolution, and expanding the field of view while lengthening the time that features remain on screen. It also provides for easy extraction of moving objects in the scene. Our method incorporates locally adaptive warps which allows for robust image alignment even in the presence of parallax and without the aid of internal or external camera parameters. We accelerate the image registration process using commodity Graphics Processing Units (GPUs) to accomplish all of these tasks in near real-time with no external telemetry data.
38
Walker, Jacqueline. "Frame synchronization techniques and jitter generation : analysis, modelling and enhancement." Thesis, Curtin University, 1997. http://hdl.handle.net/20.500.11937/1715.
Full textAbstract:
Synchronization means the aligning of the significant instants of one signal to the significant instants of another. In digital systems, where timing transfer between systems is required, synchronization is an important function. In this thesis new results on the performance and design of synchronization processes are presented. An inescapable consequence of the synchronization of external autonomous inputs in digital systems is the possibility of failure of digital devices used to capture the external signal. The anomalous behaviour of these devices is referred to as metastability. The most commonly used approach to controlling the problem of metastability is the use of synchronizers. A synchronizer can be designed to reduce the probability of metastable: failure but cannot eliminate it altogether. New high performance synchronizer designs are presented and analysed in this thesis. Another consequence of synchronization is the resulting disturbance of the significant epochs of timing signals. This disturbance is referred to as jitter. The characterization of jitter produced in synchronization processes is important in the design of digital systems. In this thesis, jitter characteristics are derived for two important applications that arise in digital communications systems. The characterization provides new insight into the dependence of the jitter on system parameters.
39
Walker, Jacqueline. "Frame synchronization techniques and jitter generation : analysis, modelling and enhancement." Curtin University of Technology, Co-operative Research Centre for Broadband Telecommunications and Networking Telecommunications, 1997. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10841.
Full textAbstract:
Synchronization means the aligning of the significant instants of one signal to the significant instants of another. In digital systems, where timing transfer between systems is required, synchronization is an important function. In this thesis new results on the performance and design of synchronization processes are presented.An inescapable consequence of the synchronization of external autonomous inputs in digital systems is the possibility of failure of digital devices used to capture the external signal. The anomalous behaviour of these devices is referred to as metastability. The most commonly used approach to controlling the problem of metastability is the use of synchronizers. A synchronizer can be designed to reduce the probability of metastable: failure but cannot eliminate it altogether. New high performance synchronizer designs are presented and analysed in this thesis.Another consequence of synchronization is the resulting disturbance of the significant epochs of timing signals. This disturbance is referred to as jitter. The characterization of jitter produced in synchronization processes is important in the design of digital systems. In this thesis, jitter characteristics are derived for two important applications that arise in digital communications systems. The characterization provides new insight into the dependence of the jitter on system parameters.
40
Saleem, Amina. "Image enhancement using a perceptual fusion approach." Paris 13, 2012. http://scbd-sto.univ-paris13.fr/intranet/edgalilee_th_2012_saleem.pdf.
Full textAbstract:
Due to limitations in image acquisition and transmission systems, image enhancement is established as an important area in image processing. Removing noise and blur, improving contrast to reveal details, coding artifact reduction and luminance adjustment are some image processing tasks that fall in the broader category of image enhancement operations. The problem of image enhancement is not a trivial task, since each image has its own characteristics and different image applications demand different enhancement requirements. It is therefore, hard to find a universal enhancement technique that would satisfy such diverse requirements. This justifies the presence of number of enhancement methods and ongoing research to find methods that can achieve different enhancement goals at the same time. Generally, image enhancement algorithms are developed to achieve some attributes of enhancement at the expense of some others. In our thesis, we develop a framework for fusion based image enhancement which is presented as a solution to the deficiencies of image enhancement algorithms. Fusion based methods for contrast enhancement, multi-focus image fusion and deblocking are developed with applications to tone mapping for HDR and natural enhancement of color imagesLa qualité de l’image perceptuelle depend essentiellement des conditions d’observation et d’acquisition, et les limitations des systems de numérisation et de transmission. On a souvent recours aux méthodes de restauration d’image et de réduction des artéfacts générés durant l’acquisition, le codage ou la transmission. Cependant, l’amélioration de la qualité d’image est un problème difficile en soi en raison de l’absence de critères objectifs bien établis pour juger des résultats. En effet, la qualité d’image est avant tout une notion subjective qui dépend de plusieurs paramètres psycho-visuels incontrôlables. De plus, chaque image a ses propres charactéristiques, et les solutions proposées dépendent aussi des applications visées. Par exemple, le réhaussement de contraste peut s’avérer efficace dans certaines zones de l’image, mais néfaste dans d’autres. Il est donc difficile de trouver une technique d’amélioration universelle qui puisse satisfaire les diverses exigences inhérentes au signal d’image. L’objectif de ce travail est de développer des méthodes basées sur une nouvelle approche où l’on fait appel à la fusion d’information et la modélisation des mécanismes de la perception visuelle. Dans ce cadre, nous proposons des méthodes de réhaussement de contraste, de filtrage et de bruit, de réductions des artefacts de codage et d’ajustement et d’équilibrage de tonalité chromatique dans le cas d’images, « HDRI ». Les performances des méthodes développées peuvent pallier les limitations des solutions de l’état de l’art et ouvrent ainsi de grandes perspectives
41
Hayworth, Mark Steven. "Enhancement, tracking, and analysis of digital angiograms." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184371.
Full textAbstract:
This dissertation presents image processing methods designed to enhance images obtained by angiography, and applied image analysis methods to quantify the vascular diameter. An iterative, non-linear enhancement technique is described for enhancing the edges of blood vessels in unsubtracted angiographic images. The technique uses a median filter and the point spread function of the imaging system to increase the resolution of the image while keeping down noise. Evaluation of the images by radiologists showed that they preferred the processed images over the unprocessed images. Also described is a heuristic, recursive, vessel tracking algorithm. The tracker is intended for use with digital subtraction angiography images. The vascular system is characterized by a tree data structure. Tree structures are inherently recursive structures and thus recursive programming languages are ideally suited for building and describing them. The tracker uses a window to follow the centerlines of the vessels and stores parameters describing the vessels in nodes of a binary tree. Branching of the vascular tree is handled automatically. A least squares fit of a cylindrical model to intensity profiles of the vessel is used to estimate vessel diameter and other parameters. The tracker is able to successfully track vessels with signal-to-noise ratios down to about 4. Several criteria are applied to distinguish between vessel and noise. The relative accuracy of the diameter estimate is about 3% to 8% for a signal-to-noise ratio of 10; the absolute accuracy depends on the magnification (mm per sample). For the clinically significant case of a 25% stenosis (narrowing of the vessel), the absolute error in estimating the percent stenosis is 3.7% of the normal diameter and the relative error is 14.8%. This relative error of 14.8% is a substantial improvement over relative errors of 30% to 70% produced by other methods.
42
Kamkar-Rouhani, Abolghasem. "Development and application of processing techniques for signal enhancement using multisystem resistivity measurements." Curtin University of Technology, Department of Exploration Geophysics, 1998. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10895.
Full textAbstract:
DC electrical surveying involves the injection of current into the earth, and the measurement of the electrical potential differences this produces. A number of electrode configurations such as the Schlumberger and Wenner arrays, dipole-dipole and pole-pole geometries are in common use for electrical surveying. New acquisition systems enable the convenient collection of data with a number of common configurations at the same time. It is found however that while the recovery of layered structure from electrical surveys can be effective, the sensitivity and resolving power of such systems in detecting the presence of anomalous three-dimensional (3-D) bodies is poor. This is mainly due to the dominance of conduction pathways through the layered earth compared to the influence of small 3-D conductivity anomalies.Theoretical relationships between the responses of various survey geometries to the layered earth may be established as is shown in this thesis, but their response to 3-D targets differs strongly. This thesis introduces a new procedure for anomalous target detection by the computation of an apparent resistivity residual using multi-electrode configuration survey data. This procedure, applicable to a variety of electrode geometries, reduces the dominance of the layered earth response and enhances the signal from 3-D structures.In the development and testing of this new apparent resistivity residual, numerically modelled data were used. In order to obtain suitable test data of high accuracy it was necessary to make improvements to modelling software. For this purpose, recently developed techniques in numerical modelling such as the biconjugate gradient method, new digital linear filters for computation of Hankel transforms, and spectral formalism were employed in an integral equation approach for the software developed in this thesis.The computed apparent ++resistivity residual was found to depend on the array type and dimensions, the nature of the anomalous zone, geological layer geometries, and resistivity contrasts of the layers involved. While the apparent resistivity residual signature requires some measure of interpretation, it is shown to enhance the resolution and detectability of 3-D targets in a layered environment.The presence of random noise produces some degradation in the performance of the residual technique, but a normalisation procedure has been developed to alleviate the problem. A preliminary field trial showed that survey profiles of apparent resistivity residual were able to locate a subsurface conductive anomaly in an area in Western Australia.A transitional zone is defined as a layer in the earth where resistivity varies as a continuous function of depth. A theoretical formulation for the electrical response of an earth structure composed of anomalous 3-D bodies in the presence of transitional layers is introduced. Tests on synthetic survey data showed that the apparent resistivity residual is an effective anomaly detector in transitional layer environments.A multi-system method of computing an apparent resistivity residual has been developed theoretically and tested on both synthetic and field data. This new approach when applied to resistivity profiling is more sensitive to, and gives greater resolution of, localised anomalies than is possible using conventional profiling procedures.
43
Akgun, Toygar. "Resolution enhancement using natural image statistics and multiple aliased observations." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22675.
Full textAbstract:
Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Yucel Altunbasak; Committee Member: Ghassan Alregib; Committee Member: Marcus Spruill; Committee Member: Patricio A. Vela; Committee Member: Russell M. Mersereau.
44
Turan, Arif Ergun. "Analysis And Comparison Of The Contrast Enhancement Techniques For Infrared Images." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614057/index.pdf.
Full textAbstract:
Today, infrared cameras are used especially for target tracking and surveillance operations. However, they have a high dynamic range output, and the standard display devices cannot handle them. In order to show them on common devices, the dynamic range is cropped. Thus, the contrast of the image is reduced. This is called as the High Dynamic Range (HDR) Compression. Although several algorithms have been proposed for preserving details during the HDR compression process, it cannot be used to enhance the local contrasts of image contents.
In this thesis, we compare the performances of contrast enhancement techniques, which are suitable for real time applications. The methods experimented are generally histogram based methods. Some modifications are also proposed in order to reduce computational complexity of the process. Performances of these methods are compared with common objective quality metrics on different image sets.
45
Srinivas, Tara. "Evaluation and enhancement of computational techniques in indoor air quality analysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63557.pdf.
Full text
46
Robinson, James W. "Application of patch-based super-resolution techniques to CCTV video enhancement." Thesis, Staffordshire University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.402457.
Full text
47
Landberg, Markus. "Enhancement Techniques for Lane PositionAdaptation (Estimation) using GPS- and Map Data." Thesis, Linköpings universitet, Datorseende, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-110812.
Full textAbstract:
A lane position system and enhancement techniques, for increasing the robustnessand availability of such a system, are investigated. The enhancements areperformed by using additional sensor sources like map data and GPS. The thesiscontains a description of the system, two models of the system and two implementedfilters for the system. The thesis also contains conclusions and results oftheoretical and experimental tests of the increased robustness and availability ofthe system. The system can be integrated with an existing system that investigatesdriver behavior, developed for fatigue. That system was developed in aproject named Drowsi, where among others Volvo Technology participated.Ett filpositioneringssystem undersöks och förbättringstekniker för ökandet av robusthetoch tillgängligheten av ett sådant system genom att använda ytterligaresensorkällor som kartdata och GPS. Detta examensarbete presenterar beskrivningenav ett system, två modeller och två implementerade filter. Examensarbetetinnehåller också slutsatser och resultat av teoretiska och experimentella testersom plottar och grafer av ökad robusthet och tillgängligheten av systemet. Dettasystem kan bli integrerat med ett framtaget system som tittar på körrelaterat beteendevid trötthet. Systemet är utvecklat i ett projekt kallat Drowsi, där blandandra Volvo Technology deltog.
48
Sepehr, H. "Advanced adaptive signal processing techniques for low complexity speech enhancement applications." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1306808/.
Full textAbstract:
This thesis research is focused on using subband and multi rate adaptive signal processing techniques in order to develop practical speech enhancement algorithms. This thesis comprises of research on three different speech enhancement applications. Firstly, design of a novel method for attenuation of a siren signal in an emergency telephony system (by use of single source siren noise reduction algorithms) is investigated. The proposed method is based on wavelet filter banks and series of adaptive notch filters in order to detect and attenuate the siren noise signal with minimal effect on quality of speech signal. Results of my testing show that this algorithm provides superior results in comparison to prior art solutions. Secondly, effect of time and frequency resolution of a filter bank used in a statistical single source noise reduction algorithm is investigated. Following this study, a novel method for improvement of time domain noise reduction algorithm is presented. The suggested method is based on detection of transient elements of speech signal followed by a time varying signal dependent filter bank. This structure provides a high time resolution at points of transient in a noisy speech signal hence temporal smearing of the processed signal is avoided. Additionally, this algorithm provides high frequency resolution at other times which results in a good performing noise reduction algorithm and benchmarking results against a prior art algorithm and a commercially available noise reduction solution show better performance of proposed algorithm. The time domain nature of algorithm provides a low processing delay algorithm that is suitable for applications with low latency requirement such as hearing aid devices. Thirdly, a low footprint delayless subband adaptive filtering algorithm for applications with low processing delay requirement such as echo cancellation (EC) in telephony networks is proposed. The suggested algorithm saves substantial memory and MIPS and provides significantly faster convergence rate in comparison with prior art algorithms. Finally, challenges and issues for implementation of real-time audio signal processing algorithms on DSP chipsets (especially low power DSPs) are briefly explained and some applications of research conducted in this thesis are presented.
49
Farrugia, Kevin Joseph. "An evaluation of enhancement techniques for footwear impressions made on fabric." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=16878.
Full text
50
Melicher, Milos. "An Enhancement of Existing RF Data Links Using Advanced Diversity Techniques." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605912.
Full textAbstract:
ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaThe theoretical capacity of communication channel in the presence of additive white Gaussian noise (AWGN) as defined by Shannon's channel capacity theorem has been well understood since 1940s. This theorem bounds the bit error rate (BER) of RF data links achievable for a particular noise level. The development in digital technology over the last decade has made it possible not just to design devices that operate close to the Shannon's limit, but also to explore techniques, such as best source and best data selectors, for further improvements in performance of RF data links where frequency, spatial or polar diverse reception is possible. This paper discusses an approach to improving quality of data links using an advanced diversity technique that does not select one source at a time but aligns and combines soft values from each. It shows how the overall bit error rate of RF data link can be improved by combining signals from multiple receivers and/or transmitters. Test results showing practical performance improvements are presented and discussed.