Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 45 for “"Image noise"”.
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Shoeprint image noise reduction and retrieval
… 35% of all crime scenes. More and more shoeprint images have been collected, leading to a few of shoeprint image databases. The constantly increasing of the size of these databases leads to a problem that it takes too much time to classify or retrieve them manually. In addition, when a shoeprint …
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Statistical methods for quantification of voxel-level image noise in PET/CT imaging
… and validated methods for estimating PET image noise are helpful for interpretation of the image and assessment of uncertainty in biomarkers associated with user-defined tissue regions of interest. However, estimation of voxel-level noise characteristics such as variance/covariance is very …
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Development of an Image Noise Estimation Method and a Sub-Imaging Based Wiener Method
… part is an investigation of several popular image restoration techniques. The techniques are used to restore 2-D image data, f(x, y), that has been blurred by a known point spread function (PSF), b(x, y) and corrupted by an unknown amount of noise, n(x, y). Several sample images are restored …
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A Phantom Study for Attenuation Change and Detection of Calcification in Lung Nodules According to Variation of Examination Techniques in Low Dose CT
… reconstruction. Mean attenuation of nodules and image noise were compared between the standard-dose and low-dose images. Diagnostic accuracy of visual assessment by two readers for discrimination of hyperdense nodule was analyzed using CT images of standard and 5 selected low-dose settings. …
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Assessment of New Innovations In Pet/Ct For Respiratory Motion Correction
… respiratory motion blur is unavoidable in PET images especially in the lower lung and upper abdomen. This leads to reductions in measured radiotracer concentration and lesion detectability all of which can potentially result in incorrect management of patients. Multiple methods exist to correct …
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Twin-image problems in optical scanning holography
… part of this dissertation investigates twin-image noise in optical scanning holography. In optical scanning holography, holographic information of an object is generated by 2-D active optical scanning. The optical scanning beam can be a time-dependent Gaussian apodized Fresnel zone pattern. …
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Automatic age progression and estimation from faces
… proposed, most of the methods are affected by image noise, illumination variations, and facial expressions. Furthermore, most of the algorithms use a pattern caricaturing approach which infers ages by manipulating the target image and a template face formed by averaging faces at the intended …
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Optical Scanning Holography for 3-D Imaging of Fluorescent Objects in Turbid Media
… and a digital decoding method for removing twin-image noise in optical scanning holography. The holographic method studied can be applied to 3-D biomedical imaging of fluorescent objects in turbid media as well as diffusely reflecting objects.
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Perception and Control Methods for Improving the Autonomy of Off-Road Robots
… settings where underexposure, motion blur, or image noise can degrade VO performance depending on the exposure parameters selected by the camera. This thesis contributes VO-AutoExpose, an auto-exposure algorithm that, unlike existing ones, predicts exposure parameters maximizing VO performance …
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Estimation of nonlinear mechanical properties of atherosclerotic plaques
… algorithm with finite element methods. Plaque images derived from optical coherence tomography were employed to construct finite element models which were subsequently used in conjunction with a genetic algorithm to determine the parameters in a nonlinear constitutive model. A new multi-frame …
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Development and implementation of efficient noise suppression methods for emission computed tomography
… methods rely on regularization terms to suppress image noise and render radiotracer distribution with good image quality. The choice of regularization method substantially affects the appearances of reconstructed images, and is thus a critical aspect of the reconstruction process. Major …
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Image Quality Optimisation and Dose Management in CT, SPECT/CT, and PET/CT
… absorbed dose and maintaining or improving image quality in CT, SPECT/CT, and PET/CT. One way to achieve optimisation is to use automatic exposure control (AEC) systems in CT. The reduction in radiation absorbed dose ranges from 35-60% for an anthropomorphic chest phantom, depending on the …
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Connected operators for unsupervised image segmentation
Image segmentation forms the first stage in many image analysis procedures including image sequence re-timing and the emerging field of content based retrieval. By dividing the image into a set of disjoint connected regions, each of which is homogeneous with respect to some measure of the image …
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Enhancing and Reconstructing Digitized Handwriting
… reconstructing, restoring, and enhancing digital images; however, many require <i> a priori </i> knowledge of the imaging system. In this study, only partial <i> a priori </i> knowledge is available, and therefore unknown parameters must be estimated before restoration, reconstruction, or …
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Video Mosaicking Using Ancillary Data to Facilitate Size Estimation
… a mosaicking system designed to generate image mosaics that facilitate size estimation of 3-dimensional objects by improving data obtained with a multi-sensor video camera. The multi-sensor camera is equipped with a pulse laser-rangefinder and internally mounted inclinometers that measure …
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Software and hardware improvements for digital solar magnetograph system
… Their high resolution, high rate of image acquisition and convenience for off-line image processing have provided significant improvements to solar physics research. In this project, two digital magnetograph systems established at Big Bear Solar Observatory (BBSO) have been described. …
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De-noising of Real-time Dynamic Magnetic Resonance Images by the Combined Application of Karhunen-Loeve Transform (KLT) and Wavelet Filtering
… (KW) filtering is presented to de-noise dynamic cardiac magnetic resonance images that simultaneously takes advantage of the intrinsic spatial and temporal redundancies of real-time cardiac cine. This new image filtering technique combines two well-established methods: temporal …
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Entrainment Characteristics of Turbulent Round Gas Jets Submerged in Water
… with limited success. In this work, Particle Image Velocimetry (PIV) and shadowgraph flow visualization experiments have been conducted on submerged round gas jets of varying speeds and nozzle diameters with the goal of improving our understanding of the entrainment process in a two-phase …
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Orthogonally coded array for high-speed synthetic aperture radar (SAR) imaging
… and developed to optimize the tradeoffs between image quality, resolution, image production speed, and system hardware complexity. For certain imaging applications, in which weakly scattering targets are of interest, image noise may distort or hide important and desirous features. For such …
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