UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item LURKING IN THE SHADOWS OF HOME: HOMELESSNESS, CARCERALITY, AND THE FIGURE OF THE SEX OFFENDER(2017) Wooten, Terrance; Hanhardt, Christina B; American Studies; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation is a multi-methodological and interdisciplinary project that examines how those who have been designated as "sex offenders" and are homeless in the Maryland/DC area are managed and regulated by various technologies of governance such as social policies, sex offender registries, and civil commitment statutes. By looking at the cultural, social, and political geography of shelters, the suburbs, and the city, I challenge scholars to reconsider how we understand stigma, belonging, and home. More broadly, I consider how the very construction of home is bound up in processes of sexual regulation and management that produce certain people as homeless by virtue of their proximity to sexual impropriety, deviance, and blackness. Put otherwise, some people are made to be or kept homeless as a result of their sexual practices or non-normative gender presentations, particularly when they are in direct conflict with dominant discourses about and legal definitions of acceptable sexual and gendered behavior. Access to home is equally mitigated by race. There has been, and continues to be, a long history of racial minorities searching for, being denied, and yet building home in geopolitical spaces that often articulate them as outside of home—as, in fact, homeless. I examine how those processes happen in tandem with and in contradistinction to modes of regulation organized around sexual deviance and difference. Drawing on scholarship in African American studies, carceral studies, and gender and sexuality studies, this project makes three critical interventions: 1) it frames sexuality as a central category of analysis necessary for understanding homelessness; 2) it offers new perspectives on the ways homeless sex offenders navigate and resist modes of racialized hypersurveillance; and 3) it argues that the structure of homeless shelters and housing policies are inherently designed to manage deviance. I draw on interviews of homeless service providers and homeless sex offenders, placing them in conversation with sex offender laws, public media, and popular film to map out the multiple contexts that structure the lives of homeless sex offenders. In doing so, I offer an alternative framework for policy interventions that attempt to address homelessness without centering the issue of race and sexuality.Item Surveillance in Cyberspace: Applying Natural and Place Manager Surveillance to System Trespassing(2016) Remrey, Lizabeth Paige; Maimon, David; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Research on the criminological side of system trespassing (i.e. unlawfully gaining access to a computer system) is relatively rare and has yet to examine the effect of the presence of other users on the system during the trespassing event (i.e. the time of communication between a trespasser’s system and the infiltrated system). This thesis seeks to analyze this relationship drawing on principles of Situational Crime Prevention, Routine Activities Theory, and restrictive deterrence. Data were collected from a randomized control trial of target computers deployed on the Internet network of a large U.S. university. This study examined whether the number (one or multiple) and type (administrative or non-administrative) of computer users present on a system reduced the seriousness and frequency of trespassing. Results indicated that the type of user (administrative) produced a restrictive deterrent effect and significantly reduced the frequency and duration of trespassing events.Item Restrictive Deterrence and the Severity of Hackers' Attacks on Compromised Computer Systems(2014) Wilson II, Theodore Henry; Maimon, David; Criminology and Criminal Justice; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)There is a lack of consensus within the literature assessing whether surveillance is effective in reducing the seriousness of criminal events, with almost no prior study investigating its operation in cyberspace. This thesis seeks to address both of these domains while drawing on the deterrence perspective. Data were obtained from an experiment conducted over seven months at a large, public university within the United States. Specifically, a series of virtual computers with known vulnerabilities were deployed into the university's computer network as part of a randomized controlled trial. This thesis seeks to examine 1) whether a surveillance banner reduces the severity of offending through inhibiting hackers from escalating to active engagement with the system upon gaining access on the first session and 2) whether the deterrent effect of a surveillance banner persists beyond the first session. This surveillance banner produced a restrictive deterrent effect for the first and second sessions.Item Lightfield Analysis and Its Applications in Adaptive Optics and Surveillance Systems(2012) Eslami, Mohammed Ali; Davis, Christopher C; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An image can only be as good as the optics of a camera or any other imaging system allows it to be. An imaging system is merely a transformation that takes a 3D world coordinate to a 2D image plane. This can be done through both linear/non-linear transfer functions. Depending on the application at hand it is easier to use some models of imaging systems over the others in certain situations. The most well-known models are the 1) Pinhole model, 2) Thin Lens Model and 3) Thick lens model for optical systems. Using light-field analysis the connection through these different models is described. A novel figure of merit is presented on using one optical model over the other for certain applications. After analyzing these optical systems, their applications in plenoptic cameras for adaptive optics applications are introduced. A new technique to use a plenoptic camera to extract information about a localized distorted planar wave front is described. CODEV simulations conducted in this thesis show that its performance is comparable to those of a Shack-Hartmann sensor and that they can potentially increase the dynamic range of angles that can be extracted assuming a paraxial imaging system. As a final application, a novel dual PTZ-surveillance system to track a target through space is presented. 22X optic zoom lenses on high resolution pan/tilt platforms recalibrate a master-slave relationship based on encoder readouts rather than complicated image processing algorithms for real-time target tracking. As the target moves out of a region of interest in the master camera, it is moved to force the target back into the region of interest. Once the master camera is moved, a precalibrated lookup table is interpolated to compute the relationship between the master/slave cameras. The homography that relates the pixels of the master camera to the pan/tilt settings of the slave camera then continue to follow the planar trajectories of targets as they move through space at high accuracies.Item SYMMETRY IN HUMAN MOTION ANALYSIS: THEORY AND EXPERIMENTS(2006-06-27) Ran, Yang; Chellappa, Rama; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Video based human motion analysis has been actively studied over the past decades. We propose novel approaches that are able to analyze human motion under such challenges and apply them to surveillance and security applications. Part I analyses the cyclic property of human motion and presents algorithms to classify humans in videos by their gait patterns. Two approaches are proposed. The first employs the omputationally efficient periodogram, to characterize periodicity. In order to integrate shape and motion, we convert the cyclic pattern into a binary sequence using the angle between two legs when the toe-to-toe distance is maximized during walking. Part II further extends the previous approaches to analyze the symmetry in articulation within a stride. A feature that has been shown in our work to be a particularly strong indicator of the presence of pedestrians is the X-junction generated by bipedal swing of body limbs. The proposed algorithm extracts the patterns in spatio-temporal surfaces. In Part III, we present a compact characterization of human gait and activities. Our approach is based on decomposing an image sequence into x-t slices, which generate twisted patterns defined as the Double Helical Signature (DHS). It is shown that the patterns sufficiently characterize human gait and a class of activities. The features of DHS are: (1) it naturally codes appearance and kinematic parameters of human motion; (2) it reveals an inherent geometric symmetry (Frieze Group); and (3) it is effective and efficient for recovering gait and activity parameters. Finally, we use the DHS to classify activities such as carrying a backpack, briefcase etc. The advantage of using DHS is that we only need a small portion of 3D data to recognize various symmetries.Item Sensor, Motion and Temporal Planning(2006-05-31) Lim, Ser-Nam; Davis, Larry S; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)We describe in this dissertation, planning strategies which enhance the accuracy with which visual surveillance can be conducted and which expand the capabilities of visual surveillance systems. Several classes of planning strategies are considered: sensor planning, motion planning and temporal planning. Sensor planning is the study of the control of cameras to optimize information gathering for performing vision algorithms. The study of camera control spans camera placement strategies, active camera (specifically, Pan-Tilt-Zoom or PTZ cameras) control, and, in some cases, camera selection from a collection of static cameras. Camera placement strategies have been employed previously for enhancing vision algorithms such as 3D reconstruction, area coverage in surveillance, occlusion and visibility analysis, etc. We will introduce a two-camera placement strategy that is utilized by a background subtraction algorithm, allowing it to achieve video rate performance and invariance to several illumination artifacts, such as lighting changes and shadows. While camera placement strategies can improve the performance of vision algorithms significantly, their utilities are limited in situations where it is more cost-effective to utilize existing camera networks instead. In these situations, we can employ camera selection strategies that choose, from the camera network, cameras that yield the best performance when utilized for performing surveillance tasks. We illustrate this with an algorithm that detects and tracks people under severe occlusions by selecting the best stereo pairs for counting people in a scene. The study of sensor planning is also closely related to motion and temporal planning. Motion and temporal planning involves predicting trajectories of objects into the future based on previously observed tracks, and is very useful for modeling interactions between moving objects in the scene. This is utilized by an active camera system that we have developed for reasoning about periods of occlusions. Doing so allows the system to select cameras and PTZ settings that with high probability can be used to capture unobstructed video segments. Finally, we will introduce a left-package system. This system first detects abandoned package in the scene and goes back in time to determine the time window when the package was first left. Steps can then be taken to retrieve images or video segments collected during the time window for identifying the person who left the package. We present the left-package detection sub-system and will show that it can detect abandoned packages even under severe occlusions without any hard thresholding steps.Item KEY-FRAME APPEARANCE ANALYSIS FOR VIDEO SURVEILLANCE(2005-08-19) Yoon, Kyongil; Davis, Larry; Computer Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Tracking moving objects is a commonly used approach for understanding surveillance video. However, by focusing on only a few key-frames, it is possible to effectively perform tasks such as image segmentation, recognition, object detection, and so on. In this dissertation we describe several methods for appearance analysis of key-frames, which includes region-based background subtraction, a new method for recognizing persons based on their overall extrinsic appearance, regardless of their (upright) pose, and appearance-based local change detection. To encode the spatial information into an appearance model, we introduce a new feature, path-length, which is defined as the normalized length of the shortest path in the silhouette. The method of appearance recognition uses kernel density estimation (KDE) of probabilities associated with color/path-length profiles and the Kullback-Leibler (KL) distance to compare such profiles with possible models. When there are more than one profile to match in one frame, we adopt multiple matching algorithm enforcing a 1-to-1 constraint to improve performance. Through a comprehensive set of experiments, we show that with suitable normalization of color variables this method is robust under conditions varying viewpoints, complex illumination, and multiple cameras. Using probabilities from KDE we also show that it is possible to easily spot changes in appearance, for instance caused by carried packages. Lastly, an approach for constructing a gallery of people observed in a video stream is described. We consider two scenarios that require determining the number and identity of participants: outdoor surveillance and meeting rooms. In these applications face identification is typically not feasible due to the low resolution across the face. The proposed approach automatically computes an appearance model based on the clothing of people and employs this model in constructing and matching the gallery of participants. In the meeting room scenario we exploit the fact that the relative locations of subjects are likely to remain unchanged for the whole sequence to construct more a compact gallery.