The inverse electromagnetic scattering problem in a piecewise homogeneous medium

This paper is concerned with the problem of scattering of time-harmonic electromagnetic waves from an impenetrable obstacle in a piecewise homogeneous medium. The well-posedness of the direct problem is established, employing the integral equation method. Inspired by a novel idea developed by Hahner [11], we prove that the penetrable interface between layers can be uniquely determined from a knowledge of the electric far field pattern for incident plane waves. Then, using the idea developed by Liu and Zhang [21], a new mixed reciprocity relation is obtained and used to show that the impenetrable obstacle with its physical property can also be recovered. Note that the wave numbers in the corresponding medium may be different and therefore this work can be considered as a generalization of the uniqueness result of [20].Comment: 19 pages, 2 figures, submitted for publicatio

Imagining the Unimagined Metropolis: Privilege, Liminality, and Peripheral Communities in the Contemporary Urban Situation

Various works of psychogeographic literature explore privileged and non-privileged communities and spaces through narrative and character development. Novels of this sort—specifically those by China Miéville, Neil Gaiman, and J.G. Ballard—feature narratives where their respective protagonists undergo a liminal metamorphosis and transform from a monotonous, albeit privileged urbanite into a free-associating inhabitant of the urban periphery: the unimagined, non-privileged space of urban detritus. By engaging with these authors’ novels alongside the works of the Situationists, Walter Benjamin, Rob Nixon and others, the goal of this thesis is to explore how the dominant urban epistemologies are subverted—whether or not they should be subverted—while also analysing the representation of non-privileged communities and how they resist the dominant epistemology in an attempt to imagine the unimagined metropolis. Literature is uniquely suited to exploring this topic, with the act of comparing texts itself revealing the volatile nature of the urban environment

Project-Based Learning in Introductory Psychology: Modern Adaptations To an Academic Classic

This study used a quasi-experimental design to examine the effectiveness of a project-based learning (PjBL) course design on meaningful learning, student goal orientation, engagement, and perceived classroom motivational climate in an introductory psychology course. Project-based learning was examined in comparison to a traditional, lecture and multiple-choice exam course design in introductory psychology over the course of one semester (N = 247). Generally, there is limited research examining PjBL in large introductory classes, specifically in relation to concrete outcomes such as meaningful learning and perceived classroom climate (Gurung et al., 2016). Therefore, the purpose of the study was to add to the limited research that exists and work to encourage the use of alternative designs like PjBL in large introductory courses. I decided to employ a PjBL design in introductory psychology because it is a course that has remained generally unchanged in the last few decades. It typically involves large class sizes, daily lectures, minimal active learning opportunities, and multiple-choice exams once every four weeks. I believe it has become a “classic” as defined by John Dewey (Dewey, 1933). It has become something that people no longer find true wonder or intrigue in and simply recognize it as existing in one way. As an introductory psychology instructor, I quickly realized the affordances of the course and felt the traditionally accepted format was not maximizing these students’ potential benefits. The research that does exist related to PjBL and introductory courses (i.e., Hard et al., 2018) and research that speaks to the power of introductory psychology in general (i.e., Gurung et al., 2016) encouraged me to pursue alternative methods and examine their potential benefits related to valuable academic outcomes such meaningful learning, goal orientation, engagement, and classroom motivational climate. Findings from the current study yielded no statistically significant differences between the PjBL condition and traditional condition regarding meaningful learning, goal orientation, or engagement (measured through transformative experience), suggesting that other motivational and learning outcomes may want to be examined. However, significant differences were found when examining perceived classroom motivational climate. These differences are in line with existing motivational climate research (i.e., Appleton et al., 2016; Dweck & Leggett, 1988) and speak to the potential value of authentic, autonomy-supportive course designs in improving student climate perceptions

Contemplation of a Place, Slow and Constant

This thesis focuses on the complex nature of experience and the ability to capture its essence through forms of representation. I start with a narrative to give the reader my personal his- tory and context that drive my work. I then go on to examine the moment in which an experience exceeds the mundane and becomes significant. I also examine the object by focusing on its ability to act as a remnant of an experience, and therefore, it becomes a means of self-reflection. I use the work Box with the Sound of its own making by Robert Morris and Inhabited for a Survey (First Floor Plan from Self-Portrait as a Building) by Mark Manders in correlation with my own to explain the role of objects in the recollection of memory. Lastly, I analyze a work by Thomas Demand, titled Poll, to focus on the photograph’s lack of ability to represent a moment fully

"Oxide-free" tip for scanning tunneling microscopy

We report a new tip for scanning tunneling microscopy and a tip repair procedure that allows one to reproducibly obtain atomic images of highly oriented pyrolytic graphite with previously inoperable tips. The tips are shown to be relatively oxide-free and highly resistant to oxidation. The tips are fabricated with graphite by two distinct methods

Lateral Signals in Piezoresponse Force Microscopy at Domain Boundaries of Ferroelectric Crystals

In piezoresponse force microscopy a lateral signal at the domain boundaries is occasionally observed. In recent years, a couple of experiments have been reported and varying explanations for the origin of this lateral signal have been proposed. Additionally, elaborated theoretical modeling for this particular issue has been carried out. Here we present experimental data obtained on different crystallographic cuts of $\rm LiNbO_3$, $\rm BaTiO_3$, and $\rm KTiOPO_4$ single crystals. We could thereby rule out some of the explanations proposed so far, introduce another possible mechanism, and quantitatively compare our results to the existing modeling

MENTOR: Human Perception-Guided Pretraining for Iris Presentation Detection

Incorporating human salience into the training of CNNs has boosted performance in difficult tasks such as biometric presentation attack detection. However, collecting human annotations is a laborious task, not to mention the questions of how and where (in the model architecture) to efficiently incorporate this information into model's training once annotations are obtained. In this paper, we introduce MENTOR (huMan pErceptioN-guided preTraining fOr iris pResentation attack detection), which addresses both of these issues through two unique rounds of training. First, we train an autoencoder to learn human saliency maps given an input iris image (both real and fake examples). Once this representation is learned, we utilize the trained autoencoder in two different ways: (a) as a pre-trained backbone for an iris presentation attack detector, and (b) as a human-inspired annotator of salient features on unknown data. We show that MENTOR's benefits are threefold: (a) significant boost in iris PAD performance when using the human perception-trained encoder's weights compared to general-purpose weights (e.g. ImageNet-sourced, or random), (b) capability of generating infinite number of human-like saliency maps for unseen iris PAD samples to be used in any human saliency-guided training paradigm, and (c) increase in efficiency of iris PAD model training. Sources codes and weights are offered along with the paper.Comment: 8 pages, 3 figure

Lower Bounds for Structuring Unreliable Radio Networks

In this paper, we study lower bounds for randomized solutions to the maximal independent set (MIS) and connected dominating set (CDS) problems in the dual graph model of radio networks---a generalization of the standard graph-based model that now includes unreliable links controlled by an adversary. We begin by proving that a natural geographic constraint on the network topology is required to solve these problems efficiently (i.e., in time polylogarthmic in the network size). We then prove the importance of the assumption that nodes are provided advance knowledge of their reliable neighbors (i.e, neighbors connected by reliable links). Combined, these results answer an open question by proving that the efficient MIS and CDS algorithms from [Censor-Hillel, PODC 2011] are optimal with respect to their dual graph model assumptions. They also provide insight into what properties of an unreliable network enable efficient local computation.Comment: An extended abstract of this work appears in the 2014 proceedings of the International Symposium on Distributed Computing (DISC