Data management in environmental monitoring sensor networks

Gupchup, Jayant The Johns Hopkins University 2012 해외박사(DDOD)

Data gathered from multi-month to multi-year battery-powered environmental monitoring sensor networks present numerous challenges. This thesis explores three problems. First, design issues related to loading, storing and data integrity are studied in detail. An end-to-end system addressing these tasks by decoupling deployment-specific and deployment-independent phases is presented. This solution places a strong emphasis on the ability to trace the origins of every collected measurement for provenance and scientific reproducibility. Second, we explore the problem of assigning accurate global timestamps to the measurements collected using the motes' local clocks. In deployments lacking a persistent gateway, a data-driven approach is employed to assign timestamps to within 10 parts per million. Building on these experiences, we developed a novel low-power approach to accurately timestamp measurements in the presence of random, frequent mote reboots. The system is tested in simulation and on a real deployment in a Brazilian rain forest. It is able to achieve an accuracy in the order of seconds for more than 99% of measurements even when a global clock source is missing for days to months. Lastly, this thesis explores a generic data-driven approach to reduce communication costs in order to increase network lifetime. In particular, spatial correlation among sampling stations is leveraged to adaptively retrieve data from a small subset of informative sensors rather than all instrumented locations. Soil temperature data collected every half hour for four months from 50 locations is used to evaluate this system. The method achieves a factor of two reduction in collected data with a median error of 0.06°C and 95th percentile error of 0.325°C. This work is part of the Life Under Your Feet project developed at the Hopkins Inter-Networking Research (HiNRG) and eScience Labs at the Johns Hopkins University. At the time of writing, the data collected for this project is available at http://www.lifeunderyourfeet.org.

Paradigms for service robotics

Suthakorn, Jackrit The Johns Hopkins University 2003 해외박사(DDOD)

Most of the robots produced to date have been <italic>industrial</italic> robots. These robots have taken the place of human laborers in hazardous, boring, or otherwise dangerous manufacturing tasks. The number of robots being used in industrial production has grown significantly. In contrast, the use of personal robots, often called service robots, is still limited. Service robots perform tasks for people rather than serving an industrial manufacturer. Of late, the idea of service robotics has become a more interesting topic for both robotics researchers and the general public. The objective of this dissertation is to explore various concepts and applications in service robotics. This research is separated into three parts. <italic>Binary robotic manipulators</italic>. Continuous actuators, such as motors, actuate most robotic manipulators. These actuators require complex and expensive control and sensor systems. In this study, Discretely Actuated Hyper-Redundant (DAHR) manipulators are shown to be viable candidates for use in many applications. This study consists of describing the DAHR concept, formulating and numerically implementing a new inverse kinematics algorithm for this type of robotic manipulator using only the “mean” of the workspace density function; constructing a prototype, and performing experiments with the prototype. <italic>Robotic library systems</italic>. The robotic library system described here is a part of a unique robotics project called “Comprehensive Access to Printed Materials” (CAPM) at the Johns Hopkins University. The goal of the CAPM project is to design and build a prototype robotic library system for an off-site shelving facility of the JHU. The design, descriptions, and experimental results of a prototype mobile manipulator are reported. <italic>Self-replicating robots</italic>. The concept of a self-replicating machine was introduced more than fifty years ago by John yon Neumann. However, prior to the work performed in this dissertation, a fully autonomous self-replicating mechanical system, such as a self-replicating robot, had yet to be implemented. In this study, a set of underlying principles of self-replicating robotic systems is introduced. A series of prototype designs and their experimental results is described in stages beginning with a remote-controlled replicating robotic system, a semi-autonomous replicating robotic system, and finally a fully autonomous self-replicating system.

Singular behavior of minimal surfaces and mean curvature flow

Kleene, Stephen James The Johns Hopkins University 2010 해외박사(DDOD)

This document records three distinct theorems that the author proved, along with his collaborators, while a graduate student at The Johns Hopkins University. The author, with M. Calle and J. Kramer, generalized a sharp estimate of Tobias Colding and William Minicozzi for the extinction time of convex hyper-surfaces in euclidean space moving by their mean curvature vector to a much broader class of evolutions studied by Ben Andrews in (1). Also, the author gave an alternate proof, first given by D. Hoffman and B. White in (17), of very poor limiting behavior for sequences of minimal surfaces in euclidean three space. Finally, the author, together with N. Moller in (23) constructed a new family of asymptotically conical ends that satisfy the mean curvature self shrinking equation in euclidean three space in all dimensions.

Flow problems in hyperbolic space

Xiao, Ling The Johns Hopkins University 2013 해외박사(DDOD)

The aim of this dissertation is threefold and it records three distinct results that the author along with her collaborators proved, during her time as a graduate student at The Johns Hopkins University. Firstly, with L. Lin, in [33] we defined a new modified mean curvature flow (MMCF) in hyperbolic space Hn+1 . We showed the existence, uniqueness and convergence of the MMCF of complete embedded star-shaped hypersurfaces with prescribed asymptotic boundary at infinity. The proofs of our main theorems closely follow the work of Guan and Spruck [16], and may be thought of as a parabolic analogue. Secondly, in [37] the author investigated the existence, convergence and uniqueness of the modified curvature flow of convex hypersurfaces (MCFC) in hyperbolic space with a prescribed asymptotic boundary. Finally, the author extended her result in [37] to the case of finding the general curvature flow of complete hypersurfaces (MGCF) in hyperbolic space with a prescribed asymptotic boundary at infinity. This is part of the project of generalizing Guan and Spruck's result in [20].

Measuring the willingness to pay user fees for interpretive services at a national forest

Goldhor-Wilcock, Barbara Ashley The Johns Hopkins University 2000 해외박사(DDOD)

An understanding of willingness to pay (WTP) for nonmarket environmental goods is useful for planning and policy, but difficult to determine. WTP for interpretive services was investigated using interviews with 361 participants in guided nature tours. Immediately after the tour, participants were asked to state their WIT for the tour. Responses were predominantly $5 (42%), $2 (14%) and $10 (13%). A predetermined amount was added to the open-ended (OE) WTP offer and respondents were asked if they were willing to pay a larger amount. Acceptance of the larger amount depended strongly on the relative increase over the initial WTP. If the increase was smaller than the initial offer, most respondents agreed, whereas if the increment was larger, most did not agree, suggesting that the initial offer was approximately half of the true WTP. The two WTP questions were used to define lower and upper bounds for each respondent's true WTP. A censored interval regression was used to estimate a WTP distribution with mean $11.30 and median $10.00. The median is twice that of the OE WTP, further suggesting that the OE response understated value by 50 percent. The estimated true WTP distribution and the OE WTP distribution have a weak, but statistically significant, dependence on some demographic, travel, and benefit variables, although these relations have negligible practical significance over the observed range of the variables. To evaluate whether the WTP amounts were based on a true economic tradeoff, respondents were asked to explain their WTP responses. For the initial OE question, 38% gave explanations that could be interpreted as an economic tradeoff, whereas 33% gave reasons that were clearly irrelevant. For the second, dichotomous choice (DC), question, 59% gave reasons suggesting a relevant economic judgement. A DC question may provoke apparently relevant answers, regardless of the underlying reasoning (a majority simply said “it was (not) worth it”). The DC reasoning may also be influenced by the preceding OE question, which provides a comparative base. Combining OE and DC questions in a single survey may encourage relevant reasoning, while also helping to identify the true WTP and consumer surplus.

Artificial gene delivery systems: Kinetics, stability, and schematic characterization to facilitate identification of promising formulations

Lai, Eva The Johns Hopkins University 2001 해외박사(DDOD)

Synthetic vectors are an attractive alternative form of gene therapy with minimal or no immune responses. However, generating a therapeutic effect has been difficult to achieve. In an effort to enhance transfection efficiency, most studies have been focusing on targeting, increasing the circulation time, tracing the intracellular pathway, examining the tissue distribution, determining the DNA complex structures, designing gene expression vectors, and synthesizing gene carriers. Targeting and enhancing the circulation time involve surface modifications of synthetic vectors even though the basic formation process is not well understood. The determination of the intracellular pathway and tissue distribution are essential parts to understanding the delivery process, but the lack of physical characterizations limits the usefulness of data. Structural characterizations are important, but most undermine the work by failing to correlate with transfection efficiency. Synthesis of novel gene carriers and expression systems has improved transfection efficiency, but the current screening method is based mostly on a trial and error process that is time consuming, expensive, and arduous. Thus, this research investigates the formation process, examines stability, characterizes vectors properties, and develops a systemic characterization approach to identify potential vectors. The formation of DNA/poly-L-lysine and DNA/cationic liposomes systems is probed by time-resolved multiangle laser light scattering. Two kinetic pathways are observed and found to depend on mass concentration or charge ratio. The kinetic rates of DNA/cationic liposomes lipoplex are determined and found to increase with DNA concentration. By monitoring the physical properties changes, the experimental results indicate the lipoplex instability during long-term storage is actually due to a degradation process, as opposed to the universally assumed aggregation dilemma. Thus, the results provide new insights for designing synthetic vectors with greater stability. Experimental studies demonstrate the DNA loading correlates with gene expression efficiency, even when transfection occurs in the presence of serum. DNA loading was also investigated to determine its role in transfection efficiency for the DOTAP/DOPE lipoplex system with distinct microstructures. The varying transfection efficiencies reported for distinct microstructures are found to also correlate with DNA loading. Thus, there may be a universal characteristic parameter to facilitate the identification of promising synthetic vectors formulations.

Connectivity in image processing and analysis: Theory, multiscale extensions and applications

Braga-Neto, Ulisses de Mendonca The Johns Hopkins University 2002 해외박사(DDOD)

Connectivity plays an important role in image processing and analysis, and particularly in problems related to image segmentation, image filtering, image coding, motion analysis, multiscale signal decomposition, pattern recognition, and other application areas. In this dissertation, we study a general theory of connectivity in image processing and analysis. Connectivity is classically defined using either a topological or a graph-theoretic framework, and their fuzzy analogs. We provide a thorough review of several existing definitions of connectivity. Although these classical concepts have been extensively applied in image processing and analysis, they are unfortunately incompatible. The theory of connectivity classes, first proposed in the late eighties for binary images, and recently extended to arbitrary complete lattices, circumvents the shortcomings of classical definitions by providing a consistent unified theoretical framework that includes the majority of the existing concepts of connectivity. We review this theory, expand it with new results and examples, and demonstrate its usefulness in applications based on connected operators. We also propose the notion of multiscale connectivity. We provide a novel theoretical framework for multiscale connectivity, which includes the theory of connectivity classes in complete lattices as a special, single-scale case. Among the items we propose and study in connection with multiscale connectivities is the integration of connectivity with multiscale methods that are currently routinely employed in image processing and analysis applications. In particular, we define several multiscale tools based on multiscale connectivities, such as multiscale signal decompositions, hierarchical segmentation, hierarchical clustering and multiscale features. Several examples of application of these multiscale tools are provided using synthetic and real images.

Development and mechanistic studies of a bifunctional catalyst system: Lewis acid-Lewis base co-catalysis

Shah, Meha H The Johns Hopkins University 2006 해외박사(DDOD)

Bifunctional catalysis has come to the forefront of synthetic chemistry in recent years. Herein is described the development of a bifunctional catalyst system involving a Lewis acid and Lewis base. We chose an achiral metal ion as our Lewis acid which could coordinate to a chiral Lewis base, namely benzoylquinine. Utilizing these two catalysts in our b-lactam methodology we hoped to enhance our yields, but were concerned about the affect on diastereo- and enantioselectivity. After screening many achiral Lewis acids we found that the triflate salts of In(III), Zn(II), and Sc(III), along with our chiral ligand, benzoylquinine, considerably enhanced the yields of our reaction without negatively affecting the enantioselectivity of our beta-lactam products. Mechanistic studies were then performed to determine the role of the catalysts in our system. Kinetic and stereochemical evidence compiled allowed us to propose a detailed mechanism by which the reaction occurs and confirm our hypothesis of imine activation. This methodology was then used to synthesize a variety of beta-lactams as possible inhibitors of prostate specific antigen (PSA). Along with the Denmeade group at Johns Hopkins Medicine we were able to develop some interesting candidates for inhibition of PSA and provide some insight on the structure of the protease itself.

Direct visualization by eye of far-red and near-infrared fluorescence through an optical microscope

Siddiqi, Mahmud Ahmad The Johns Hopkins University 2002 해외박사(DDOD)

I have developed and implemented a general method for the direct visualization by eye of far-red and near-infrared (NIR) fluorescence through an optical microscope. The method employs a gallium arsenide (GaAs) image intensifier, typically utilized in low-light or ‘night vision’ applications. The intensifier converts far-red and NIR light into electrons and then into green light, which is visible to the human eye. I have designed, constructed, and tested a working prototype of a GaAs image intensifier-based device for optical microscopy. The prototype makes possible the direct, real-time viewing by eye of normally invisible far-red and NIR fluorescence from a wide variety of fluorochromes, using the full field of view of the microscope to which it is applied. No modifications to the microscope are required in order to use the prototype, which is fully compatible with all current fluorescence techniques. Because of the high sensitivity of the image intensifier, the prototype will also facilitate imaging of a wide variety of photosensitive specimens, including live cells and embryos, by allowing the use of vastly reduced illumination levels in both fluorescence and brightfield microscopy.

A phenomenological case study of new teachers' experiences at an independent school

Matsuzaki, William Masatu The Johns Hopkins University 2013 해외박사(DDOD)

Current research has shown that about one-third of new teachers in the United States leave the profession within the first three years, thus, making it a priority to support new teachers in the classroom. To address this issue, research is needed to better understand the needs and experiences of novice educators in a variety of educational settings. Through the use of in-depth, semi-structured interviews and review of the school's professional development program, this multiple case study investigated the career paths of seven novice teachers in a private educational institution. The study sought to gain understanding of how novice teachers at an independent school perceived the usefulness of professional supports for their own classroom performance and how they negotiated the school environment. The study showed that a teacher's age and gender, professional preparation, and workload affected his or her perceptions of the usefulness of the supports provided at the focal school. In addition, administrators' leadership styles were found to influence the novice teachers' perceptions of professional support. The study suggests that differentiated support for novice teachers and professional training for school administrators may be critical elements of effective new teacher programs. Specific recommendations are made for single-sex independent schools based on the literature and analysis of the interviews.