Browsing by Subject "Imaging systems"
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Item Item An analysis of the effect of confirmation bias on industrial radiography(Texas Tech University, 1997-05) Romero, Henry AbrahamThis experiment was undertaken to ascertain the current performance, the variables affecting performance, and performance improvements of a dynamic visual inspection process, real time radiography, used at a Department of Energy laboratory. The system was being used to determine contents of 5 5-gallon mixed waste drums prior to storage. This experiment started with a task analysis in which critical tasks necessary for successful completion of a barrel assessment were determined. One of the factors expected to shape the performance was the provision of a shipper's manifest. The reason is that the manifest induces a confirmation bias on the part of the operator concerning what to expect in the barrel. A literature review was performed concerning perception and industrial inspection processes. From this review, it was determined that this process had not been adequately studied in the literature. One of the main differences was that the confirmation bias was elicited in the literature by the use of tachistoscopic cues which were not feasible in this process. A repeated-measures design experiment was developed that utilized specifically created drums to test the confirmation bias as well as effects of experience and Mental Fatigue. The responses from this experiment were categorized into three binomial distributions: correct identifications, misclassifications. and detection failures. The results were that this experiment failed to note an effect due to the confirmation bias. In addition, this experiment failed to note impact from the Mental Fatigue or experience variables. In examining experience effects, it appears that between three and nine months time on task, the performance of the operators reached a level and did not significantly improxe. However, individual differences alone could have accounted for these results.Item An experimental and theoretical investigation of nonequilibrium behavior of electrons in gases(Texas Tech University, 1984-05) Young, Chris MorrowNot availableItem Brownian motion at fast time scales and thermal noise imaging(2008-12) Huang, Rongxin, 1978-; Florin, Ernst-LudwigThis dissertation presents experimental studies on Brownian motion at fast time scales, as well as our recent developments in Thermal Noise Imaging which uses thermal motions of microscopic particles for spatial imaging. As thermal motions become increasingly important in the studies of soft condensed matters, the study of Brownian motion is not only of fundamental scientific interest but also has practical applications. Optical tweezers with a fast position-sensitive detector provide high spatial and temporal resolution to study Brownian motion at fast time scales. A novel high bandwidth detector was developed with a temporal resolution of 30 ns and a spatial resolution of 1 °A. With this high bandwidth detector, Brownian motion of a single particle confined in an optical trap was observed at the time scale of the ballistic regime. The hydrodynamic memory effect was fully studied with polystyrene particles of different sizes. We found that the mean square displacements of different sized polystyrene particles collapse into one master curve which is determined by the characteristic time scale of the fluid inertia effect. The particle’s inertia effect was shown for particles of the same size but different densities. For the first time the velocity autocorrelation function for a single particle was shown. We found excellent agreement between our experiments and the hydrodynamic theories that take into account the fluid inertia effect. Brownian motion of a colloidal particle can be used to probe three-dimensional nano structures. This so-called thermal noise imaging (TNI) has been very successful in imaging polymer networks with a resolution of 10 nm. However, TNI is not efficient at micrometer scale scanning since a great portion of image acquisition time is wasted on large vacant volume within polymer networks. Therefore, we invented a method to improve the efficiency of large scale scanning by combining traditional point-to-point scanning to explore large vacant space with thermal noise imaging at the proximity of the object. This method increased the efficiency of thermal noise imaging by more than 40 times. This development should promote wider applications of thermal noise imaging in the studies of soft materials and biological systems.Item Coarse segmentation of cervical and lumbar vertebrae using a customized version of the Generalized Hough Transform(Texas Tech University, 2003-12) Gururajan, ArunkumarThe objective of this thesis is to develop a framework for a robust coarse segmentation scheme, to segment the cervical and lumbar vertebrae in radiographic images. Previous research customized the Generalized Hough transform (GHT) for segmenting the radiographic images of cervical vertebrae, and tested the same on a dataset of 50 images. The key factor for the successful performance of GHT, is the availability of suitable edge information for the target shape that is to be segmented. This thesis is an effort to effectively address the low-level vision schemes involved in the preprocessing stage of GHT, and also to extend and test the proposed coarse segmentation scheme on a sizeable set of cervical and lumbar spine images.Item Geomorphic interpretation of digital spot imagery: Hanaupah Canyon alluvial fan, Death Valley, California(Texas Tech University, 1988-08) Goodwin, Peter BNot availableItem Optical near-field effects for submicron patterning and plasmonic optical devices(2007) Battula, Arvind Reddy, 1979-; Chen, ShaochenMetallic films with narrow and deep subwavelength gratings or holes having a converging-diverging channel (CDC) can exhibit enhanced transmission resonances for wavelengths larger than the periodicity of the grating or hole. Using the finite element method, it is shown that by varying the gap size at the throat of a CDC, the spectral locations of the transmission resonance bands can be shifted close to each other and have high transmittance in a very narrow energy band. Additionally, the transmission of light can be influenced by the presence of the externally applied magnetic field H. The spectral locations of the transmission peak resonances depend on the magnitude and the direction of H. The transmission peaks have blue-shift with the increase in H. A new multilayer thermal emitter has been analyzed in the visible wavelength range. The proposed emitter has large temporal and spatial coherence extending into the far field. The thermal emitter is made up of a cavity that is surrounded by a thin silver grating having a CDC on one side and a one-dimensional (1D) photonic crystal (PhC) on the other side. The large coherence length is achieved by making use of the coherence properties of the surface waves. Due to the nature of surface waves the new multilayer structure can attain the spectral and directional control of emission with only ppolarization. The resonance condition inside the cavity is extremely sensitive to the wavelength, which would then lead to high emission in a very narrow wavelength band. In addition a new tunable plasmonic crystal (tPLC) was proposed, where the plasmonic or polaritonic mode of a metallic array can be combined with the photonic mode of a hole array in a dielectric slab for achieving negative refraction and still posses an extra degree of freedom for tuning the tPLC as a superlens to operate at different frequencies. The tunability of the single planar tPLC slab is demonstrated numerically for subwavelength imaging (FWHM 0.38[lambda]~ 0.42[lambda]) by just varying the fluid in the hole array, thereby enabling the realization of ultracompact tunable superlens and paving the way for a new class of lens. An aggressive pursuit for decreasing the minimum feature size in high bandgap materials has lead to various challenges in nanofabrication. However, it is difficult to achieve critical dimensions at sub-wavelength scale using traditional optical lithography. A new technique to create submicron patterns on hard-to-machine materials like silicon carbide (SiC) and borosilicate glass with a laser beam is demonstrated. Here the principle of optical near-field enhancement between the spheres and substrate when irradiated by a laser beam has been used for obtaining the patterning.Item Plasmonic nanoparticles for imaging intracellular biomarkers(2007-05) Kumar, Sonia, 1978-; Richards-Kortum, Rebecca, 1964-; Sokolov, Konstantin V. (Associate professor)Molecular optical imaging enables the ability to non-invasively image biological function. When used in conjunction with optical contrast agents, molecular imaging can provide biomarker-specific information with subcellular spatial resolution. Plasmonic nanoparticles are unique optical contrast agents due to the fact that the intensity and peak wavelength of scattering is dependant on interparticle spacing. This distance dependance puts these nanosensors in a position to probe molecular interactions by exploiting contrast between isolated and closely spaced nanoparticles. This dissertation presents the first intracellular molecular imaging platform using multifunctional gold nanoparticles which incorporate both cytosolic delivery and targeting moieties on the same particle. In order to produce robust nanosensors, a novel conjugation strategy was developed involving a heterofunctional linker capable of rigidly attaching various components to the nanoparticle surface. Since most biomarkers of interest are localized intracellularly, the delivery functionality was a key focus. It was achieved using the TAT-HA2 fusion peptide which has been previously shown to enhance both endosomal uptake and subsequent release into the cytosol. The feasibility of these nanoparticles as intracellular sensors was proposed by attempting to image actin rearrangement in live fibroblasts. The assembly of nanoparticles at the leading of motile cells was which was potentially due to actin targeting resulted in a red shift in scattering maxima due to plasmon resonance coupling between particles as well as a dramatic increase in scattering intensity. Although several challenges still exist, the potential for these contrast agents as nanosensors for the presence of proteins implicated in viral carcinogenesis is also introduced.