Browsing by Subject "Detection"
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Item A study of environmental fate and application of commercially available carbon nanotubes(2012-08) Li, Shibin; Canas, Jaclyn; Anderson, Todd; Jonathan, Maul; Green, Micah J.; Zobeck, Ted M.Carbon nanotubes (CNTs) are a group of carbon-based nanomaterials which can be conceptualized as one or more micrometer-scale-graphene sheets rolled into a nanoscale-cylinder. With special properties, especially large aspect ratio and quantum effects, CNTs have been used widely in various areas, such as materials science, electronics, pharmaceutical, and environmental sciences. As exceptional CNT properties are the key to the promotion of CNT applications in many aspects of our lives, these same properties are also cause for concern regarding the toxicological effects on organisms and the environment. Recent toxicity studies with CNTs have raised attention to the risks associated with CNTs to the environment and humans. It has also been suggested that not only toxicity of CNTs but also the fate, especially possible interactions with other contaminants, in a real environment should be understood to better serve future risk assessments. Currently, there are limited studies focused on CNT fate in the environment. In this research, fate and application studies of CNTs were conducted. The effect of CNTs on the fate of polyaromatic hydrocarbons (PAHs) was investigated in a soil system. Through sorption and desorption studies, it was discovered that CNTs had a strong sorption capacity for PAHs, which was three orders of magnitude higher than that of natural soils. However, at a concentration of 2 mg/g, CNTs did not change PAH sorption capacity in soil. This study also proposed ‘the rule of mixtures’ as a tool for prediction of PAH sorption behaviors in CNT-contaminated soil. Through leaching studies, CNTs at a concentration of 5 mg/g significantly changed PAH leaching behavior in soil. Properties of both sorbent (CNTs) and sorbate (PAHs) influenced PAH retention behavior in soil. Overall, CNTs with different concentrations led to distinct PAH fate behavior in soil. Future studies are needed to investigate PAH fate behavior in a CNT concentration-dependent manner. Bioaccumulation of CNTs in earthworms was also investigated. A novel microwave-induced heating method to detect CNTs in plants was recently developed. In this study, this method was modified to detect CNTs in earthworms; this is the first available method for quantification of CNTs in earthworms. The method was used to assess bioaccumulation of CNTs in earthworms and the calculated bioaccumulation factor was 0.015 ± 0.004, which indicated that CNTs are not bioaccumulative. In addition to these studies related to the fate and interactions of CNTs in the environment, one study was conducted to evaluate one potential application of CNTs. No studies have investigated the application of CNTs in passive sampling devices (PSDs) for contaminants in soil. Two PSDs with different sorbents (C18 and CNTs) were developed. The C18-PSD was a good biomimetic tool for PAH accumulation in soil, with a rapid equilibrium rate and good correlation with PAH bioaccumulation. With a cheaper price and higher sensitivity, CNTs-PSDs are a promising tool for estimating bioavailable PAHs in soil. However, future studies are needed to improve PAH extraction efficiency from CNTs. In summary, this research provided critical fate data needed for future CNT environmental risk assessment and regulation in soil. In addition, this study also provided data regarding the use of C18-PSDs and MWNTs-PSDs as potential biomimetic tools in PAH risk assessment.Item Algorithms for detecting missing voltage and motor starting events(2016-08) Cho, Wanki; Santoso, Surya; Baldick, RossThe objective of this work is to develop algorithms to detect voltage variation events in power quality data and to figure out their characteristics. Voltage variation events covered in this work are missing voltage and motor starting events. The first part of this work describes the fundamental concept, characteristics and sources of voltage variation events. Next, this work describes the algorithms to detect voltage variation events. The verification of the algorithms is performed using simulated data from PSCAD/EMTDC and actual field data. The results show that the performance of the algorithms and the characteristics of voltage variation events are satisfactory. This work contributes to the development of detecting voltage variation events from a real distribution system and the analysis of voltage variation events.Item Analysis of smuggler movement on multiple transportation networks(2011-05) Goshev, Stefan Antoanov; Morton, David P.; Popova, ElmiraWe analyze an interdiction problem in which a nuclear-material smuggler can traverse multiple transportation networks, wherein each edge has an indigenous probability of evasion. Our objective is to determine the optimal locations of a limited number of radiation detectors at United States ports of entry across multiple networks (maritime, road and rail) so as to minimize the smuggler's total probability of evasion, from origin to destination. We choose geographically diverse potential origins and give the smuggler freedom to move across and between transportation networks. Further, we consider two different models of smuggler behavior in this context. Our analysis aims to provide a complete prioritization and picture of the threat at all ports of entry, leading to insight into good practical locations for detectors.Item Automated analysis of linear array images for the detection of human papillomavirus genotypes(2011-05) Wilhelm, Matthew S.; Nutter, Brian; Mitra, SunandaPersistent infections with carcinogenic Human Papillomavirus (HPV) are a necessary cause for cervical cancer, which is the fifth most deadly cancer for women worldwide. Approximately 20 million Americans are currently infected with HPV, but only a subset will develop cervical cancer. While a negative HPV test indicates a very low risk for cervical cancer, a positive test cannot discriminate between an innocuous transient infection and a prevalent cancer. Additional information such as HPV genotype and HPV viral load is thought to improve the ability to predict which women will develop cervical cancer. The visual interpretation of hybridization-strip-based HPV genotyping results, however, is heterogeneous and poorly standardized. The need for accurate and repeatable results has led to work toward the development of a robust automated image analysis package for HPV genotyping strips.Item Axial illumination based optical detection in Micro LC(Texas Tech University, 1995-12) Abbas, Ahmad AbdullaNot availableItem Computer algorithm to detect and predict machine faults using cloud-based vibration data(2015-05) Olivares Villamediana, Ignacio Javier; Fernandez, Benito R.; Bukowitz, DavidIn this research a machine fault detection and diagnostic algorithm is presented. The algorithm uses time wave-form acceleration data stored in a server for cloud computing to calculate RMS and Peak values from it and give information to the user for maintenance schedule. Detection algorithm analyses the change in time of the acceleration signals and establish urgency and severity of the studied machines. Furthermore, the diagnosis sub-system studies also the change in time of the signals in frequency domain to give a forecast of the possible existing fault by discarding faults throughout a predetermined decision table. Simulated and real cases are performed to show the efficiency and results of using the algorithm as well.Item Development of a fluorescence model for the determination of constants associated with binding, quenching, and FRET efficiency and development of an immobilized FRET-peptide sensor for metal ion detection(2012-08) Casciato, Shelly Lynn, 1984-; Holcombe, James A.; Liljestrand, Howard M.This thesis presents a modeling program to obtain equilibrium information for a fluorescent system. Determining accurate dissociation constants for equilibrium processes involving a fluorescent mechanism can prove to be quite challenging. Typically, titration curves and non-linear least squares fitting of the data using computer programs are employed to obtain such constants. However, these approaches only consider the total fluorescence signal and often ignore other energy transfer processes within the system. The current model considers the impact on fluorescence from equilibrium binding (viz., metal-ligand, ligand-substrate, etc.), quenching and resonance energy transfer. This model should provide more accurate binding constants as well as insights into other photonic processes. The equations developed for this model are discussed and are fit to experimental data from titrimetric experiments. Since the experimental data are generally in excess of the number of parameters that are needed to define the system, fitting is operated in an overdetermined mode and employs error minimization (either absolute or relative) to define goodness of fit. Examples of how changes in certain parameters affect the shape of the titrimetric curve are also presented. The detection of metal ions is very important, causing a need for the development of a metal ion sensor that provides selectivity, sensitivity, real-time in situ monitoring, and a flexible design. In order to be able to perform in situ monitoring of trace metal ions, FRET-pair labeled peptides were attached to a Tentagel[trademark] resin surface. After soaking in nonmetal and metal solutions (pH = 7.5), the resin beads gave an enhanced response in the presence of Hg²⁺ and Zn²⁺. Using a t-test, the signals of the beads that were soaked in a solution of each of these metal ions (and that of Cd²⁺) were determined to be significantly different from beads soaked in a solution without metal. However, the standard deviation between a set the beads was too large in order to differentiate a bead that was soaked in nonmetal solution versus one soaked in a metal containing solution.Item Development of a heat-balance model for the characterization of wax blockage in flowlines(Texas A&M University, 2006-04-12) Ombu, Ebiaye ValerieThe presence of a blockage in a pipeline will alter the fluid dynamics of a flowing system in terms of the heat, mass and velocity characteristics. The analysis of the fluid dynamics is based on balances taken on the overall system to qualitatively and quantitatively assess the effects of the blockage. Pioneer work in the area of mass and momentum effects of blockages led to the development of blockage type curves useful in characterizing blockages from limited information. This work is an extension of previous work and is based on the application of a simplistic energy balance approach to characterize blockages in pipelines. The resulting heat models for the case of both a partially and fully-blocked flowline correctly predict the effect of wax deposition. Dimensionless temperature-based blockage maps developed here can be used in modeling unique cases where only two of the three necessary conditions are given. The heat model matches results from commercial software within a limited range of restricted flow conditions.Item Interdicting smuggler movement with transparent and non-transparent assets(2012-05) Hawley, Megan Lynn; Morton, David P.; Popova, ElmiraWe analyze an interdiction problem in which a nuclear-material smuggler can traverse the rail and road ports of entry (POEs) along the Mexican and Canadian borders of the United States. Our objective is to determine the optimal locations of a limited number of transparent and non-transparent assets so as to minimize the smuggler’s total probability of evasion, from origin to destination. We choose origins in Mexico and Canada and give the smuggler a diverse set of destinations to choose from. Our analysis aims to provide a complete prioritization and picture of the threat at Mexican and Canadian POEs, leading to insight into practical locations for transparent and non-transparent assets.Item Real-time detection of illegally parked vehicles using 1-D transformation(2007-08) Lee, Jong Taek, 1983-; Aggarwal, J.K. (Jagdishkumar Keshoran), 1936-With decreasing costs of high quality surveillance systems, human activity detection and tracking has become increasingly practical. Accordingly, automated systems have been designed for numerous detection tasks, but the task of detecting illegally parked vehicles has been left largely to the human operators of surveillance systems. This thesis provides a methodology for detecting this event in real-time by applying a novel image projection that reduces the dimensionality of the image data and thus reduces the computational complexity of the segmentation and tracking processes. After event detection, we invert the transformation to recover the original appearance of the vehicle and to allow for further processing that may require the two dimensional data. The proposed algorithm is able to successfully recognize illegally parked vehicles in realtime in the i-LIDS bag and vehicle detection challenge datasets.Item Retina-V1 model of detectability across the visual field(2014-08) Bradley, Chris Kent; Geisler, Wilson S.A practical model is proposed for predicting the detectability of targets at arbitrary locations in the visual field, in arbitrary gray-scale backgrounds, and under photopic viewing conditions. The major factors incorporated into the model include: (i) the optical point spread function of the eye, (ii) local luminance gain control (Weber's law), (iii) the sampling array of retinal ganglion cells, (iv) orientation and spatial-frequency dependent contrast masking, (iv) broadband contrast masking, (vi) and efficient response pooling. The model is tested against previously reported threshold measurements on uniform backgrounds (the ModelFest data set and data from Foley et al. 2007), and against new measurements reported here for several ModelFest targets presented on uniform, 1/f noise, and natural backgrounds, at retinal eccentricities ranging from 0 to 10 deg. Although the model has few free parameters, it is able to account quite well for all the threshold measurements.Item Short lived radionuclide modeling from nuclear weapons test sites and nuclear power plant accidents(2014-08) Helfand, Jonathan David; Biegalski, Steven R.Nuclear accidents and weapons tests are monitored by a worldwide network of air sensors, seismic detectors and several other techniques. At the site of the incident, contaminants are distributed and can provide insight into the time of the incident and type of incident. That information can then be used to affect policy decisions or better understand health risks. In order to evaluate a post nuclear test scenario, we must better understand the background readings at potential test sites where false positive or false negative allegations are more likely (e.g. the Nevada Test Site, the Chernobyl Nuclear Power Plate, etc.) Data from these sites have been compiled and compared to high purity germanium detector background readings and activities from a hypothetical nuclear weapon test. The results indicate that the following nuclides would be the best indicator of a recent nuclear test: ⁸⁹Sr, ⁹¹Y, ⁹⁵Zr, ¹⁰³Ru, ¹²⁶Sb, ¹²⁹[superscript m]Te, ¹⁴⁷Nd, ¹⁵⁶Eu. Nuclides such as ⁹¹Sr or ⁹⁷Zr have a steady state concentration due to plutonium spontaneous fission thus would not be a good indication of a recent nuclear test.Item Underground distribution cable incipient fault diagnosis system(Texas A&M University, 2007-04-25) Jaafari Mousavi, Mir RasoulThis dissertation presents a methodology for an efficient, non-destructive, and online incipient fault diagnosis system (IFDS) to detect underground cable incipient faults before they become catastrophic. The system provides vital information to help the operator with the decision-making process regarding the condition assessment of the underground cable. It incorporates advanced digital signal processing and pattern recognition methods to classify recorded data into designated classes. Additionally, the IFDS utilizes novel detection methodologies to detect when the cable is near failure. The classification functionality is achieved through employing an ensemble of rule-based and supervised classifiers. The Support Vector Machines, designed and used as a supervised classifier, was found to perform superior. In addition to the normalized energy features computed from wavelet packet analysis, two new features, namely Horizontal Severity Index, and Vertical Severity Index are defined and used in the classification problem. The detection functionality of the IFDS is achieved through incorporating a temporal severity measure and a detection method. The novel severity measure is based on the temporal analysis of arrival times of incipient abnormalities, which gives rise to a numeric index called the Global Severity Index (GSI). This index portrays the progressive degradation path of underground cable as catastrophic failure time approaches. The detection approach utilizes the numerical modeling capabilities of SOM as well as statistical change detection techniques. The natural logarithm of the chronologically ordered minimum modeling errors, computed from exposing feature vectors to a trained SOM, is used as the detection index. Three modified change detection algorithms, namely Cumulative Sum, Exponentially Weighted Moving Averages, and Generalized Likelihood Ratio, are introduced and applied to this application. These algorithms determine the change point or near failure time of cable from the instantaneous values of the detection index. Performance studies using field recorded data were conducted at three warning levels to assess the capability of the IFDS in predicting the faults that actually occurred in the monitored underground cable. The IFDS presents a high classification rate and satisfactory detection capability at each warning level. Specifically, it demonstrates that at least one detection technique successfully provides an early warning that a fault is imminent.