Topological Mapping and Navigation in Real-World Environments

We introduce the Hierarchical Hybrid Spatial Semantic Hierarchy (H2SSH), a hybrid topological-metric map representation. The H2SSH provides a more scalable representation of both small and large structures in the world than existing topological map representations, providing natural descriptions of a hallway lined with offices as well as a cluster of buildings on a college campus. By considering the affordances in the environment, we identify a division of space into three distinct classes: path segments afford travel between places at their ends, decision points present a choice amongst incident path segments, and destinations typically exist at the start and end of routes. Constructing an H2SSH map of the environment requires understanding both its local and global structure. We present a place detection and classification algorithm to create a semantic map representation that parses the free space in the local environment into a set of discrete areas representing features like corridors, intersections, and offices. Using these areas, we introduce a new probabilistic topological simultaneous localization and mapping algorithm based on lazy evaluation to estimate a probability distribution over possible topological maps of the global environment. After construction, an H2SSH map provides the necessary representations for navigation through large-scale environments. The local semantic map provides a high-fidelity metric map suitable for motion planning in dynamic environments, while the global topological map is a graph-like map that allows for route planning using simple graph search algorithms. For navigation, we have integrated the H2SSH with Model Predictive Equilibrium Point Control (MPEPC) to provide safe and efficient motion planning for our robotic wheelchair, Vulcan. However, navigation in human environments entails more than safety and efficiency, as human behavior is further influenced by complex cultural and social norms. We show how social norms for moving along corridors and through intersections can be learned by observing how pedestrians around the robot behave. We then integrate these learned norms with MPEPC to create a socially-aware navigation algorithm, SA-MPEPC. Through real-world experiments, we show how SA-MPEPC improves not only Vulcan’s adherence to social norms, but the adherence of pedestrians interacting with Vulcan as well.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144014/1/collinej_1.pd

Alan Touring, the Campus Tourbot

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (leaves 125-127).Alan Touring, the Campus Tourbot, is a robotic tour-guide/tourist robot for parts of the MIT campus. Work on the robot began in January 2006, and for the past 31 months, I have devoted thousands of hours to designing, implementing, and testing the robot. This thesis describes the hardware and software systems created for the robot, performs an evaluation of the robot's functionality, and discusses the public's reactions to the robot when they encountered it driving through their world. As with any robotic system, the development of the Tourbot involved trial-and-error. A critique of some major design decisions that were made and how these decisions affected the development of the robot is performed. Suggestions for how the development process could have been improved based on lessons that I learned are then offered.by Collin Eugene Johnson.M.Eng

Self-fertilization, Larval Dispersal, and Population Structure in the Marine Bryozoan Bugula stolonifera

Although the process by which fertilization occurs in bryozoans is well described, the ability to self-fertilize and the subsequent ecological consequences are poorly understood. Culturing experiments were conducted examining the effects of selfing on offspring survival and reproduction in the simultaneous hermaphrodite Bugula stolonifera collected from Eel Pond, Woods Hole, MA. Results from these experiments document significant decreases in survival and fecundity of selfed offspring, compared to outcrossed controls, suggesting that these animals are not routinely self-fertilizing in Eel Pond. How these arborescent colonies minimize selfing remains unclear, but it is hypothesized that conspecific aggregations could serve to minimize the chances that a colony utilizes its own sperm for fertilization. The genetic composition of these aggregations was investigated using a newly developed microsatellite library. As larvae routinely metamorphose on conspecific colonies, the possibility that larvae select or avoid their maternal colony was also investigated. Analyses of genetic structure document homogeneity throughout these aggregations on extremely small spatial scales, suggesting high amounts of larval dispersal within aggregations. When combined with results from parentage-exclusion and kinship analyses, these results indicate that a colony's nearest neighbors are not composed of siblings, potentially minimizing inbreeding. Molecular analyses were then used to determine if the high larval dispersal within aggregations resulted in high mixing between aggregations. Sites within Eel Pond separated by 100-300 m were routinely sampled from 2009 to 2011, and analyses were conducted to investigate potential inter- and intra-annual genotypic differentiation within and between aggregations. Results document that although low levels of mixing could result in increased homogeneity between some aggregations, barriers to genetic exchange prevent mixing between most sites. Further, inter-annual comparisons within sites document that significant differentiation can occur between reproductive seasons. Hence, any potential homogeneity achieved between sites during one reproductive season will likely be lost by the beginning of the next reproductive season. Additionally, while sampling in Eel Pond in 2010, I document the first occurrence from the western Atlantic Ocean of another aggregating arborescent bryozoan, Tricellaria inopinata. The growth and reproductive biology of these animals was monitored throughout 2011; results suggest that this introduction is likely to persist

An Extended TOE Framework for Cybersecurity-adoption Decisions

High-profile cybersecurity incidents, such as the 2019 Capital One data breach and the 2017 Equifax breach, have engendered doubts about firms’ trustworthiness and resulted cybersecurity becoming a critical risk factor firms must address. Breaches can precipitate extreme consequences for affected firms’ managers, shareholders, and customers. Unsurprisingly, data breaches represent IT leaders’ biggest concern. In this paper, we report on a qualitative field study in which we interviewed C-level executives and IT consultants to investigate cybersecurity concerns and factors that influence adoption decisions for cybersecurity. We found that the traditional technology-organization-environment (TOE) framework does not fully capture the range of issues in the cybersecurity context. Thus, we propose a new extended TOE framework that pertains specifically to cybersecurity-adoption decisions. This extended framework includes new dimensions, cyber catalysts, practice standards, and new factors under the traditional technology, organization, and environment dimensions

Star Formation in Quasar Disk

Using a version of the ZEUS code, we carry out two-dimensional simulations of self-gravitating shearing sheets, with application to QSO accretion disks at a few thousand Schwarzschild radii, corresponding to a few hundredths of a parsec for a 10^8 solar-mass black hole. Radiation pressure and optically thick radiative cooling are implemented via vertical averages. We determine dimensionless versions of the maximum surface density, accretion rate, and effective viscosity that can be sustained by density-wave turbulence without fragmentation. Where fragments do form, we study the final masses that result. The maximum Shakura-Sunyaev viscosity parameter is approximately 0.4. Fragmentation occurs when the cooling time is less than about twice the shearing time, as found by Gammie and others, but can also occur at very long cooling times in sheets that are strongly radiation-pressure dominated. For accretion at the Eddington rate onto a 10^8 solar-mass black hole, fragmentation occurs beyond four thousand Schwarzschild radii, r_s. Near this radius, initial fragment masses are several hundred suns, consistent with estimates from linear stability; final masses after merging increase with the size of the sheet, reaching several thousand suns in our largest simulations. With increasing black-hole mass at a fixed Eddington ratio, self-gravity prevails to smaller multiples of r_s, where radiation pressure is more important and the cooling time is longer compared to the dynamical time; nevertheless, fragmentation can occur and produces larger initial fragment masses. We also find energy conservation is likely to be a challenge for all eulerian codes in self-gravitating regimes where radiation pressure dominates.Comment: 34 pages, 8 figures. Submitted to Ap

Backgrounding of LGBT in Newspaper Coverage in Malaysia

In Malaysia, Lesbian, Gay, Bisexual dan Transgender (LGBT) face moral sanctions and legal challenges because it is prohibited by Islam and not condoned by major religions. A search using Google Trends show that there was a spike of interest on “LGBT in Malaysia” in 2009 and 2019, but there has been sustained interest since 2014. The present study examined framing of LGBT in four online newspapers in Malaysia. The specific objectives of the study were to determine the percentage of episodic and thematic framing in the newspapers, and to compare the topics that are reported in LGBT news. LGBT seems to be backgrounded in newspaper coverage by Astro Awani, Free Malaysia Today, Malaysiakini and The Star Online because only 60 articles published in 2019 were related to LGBT. The analysis showed that 81.67% of the articles were episodic frames and 18.33% were thematic frames. Malaysiakini had relatively more thematic articles while Astro Awani had the lowest percentage of thematic articles on LGBT. Over half (61.67%) of the articles were on LGBT news stories in Malaysia while other articles reported LGBT-linked persons or events in other countries. The local topics reported on LGBT were specific events which generated views on LGBT from politicians, religious leaders, and activists. The coverage of LGBT topics in other countries included criminalisation and societal discrimination of LGBT, and support for LGBT. The findings suggest caution in news on LBGT, with newspapers treading a thin line between affirming human rights and taking the official position of the country on LGBT

Framing of LGBT in Online Newspapers in Malaysia

In Malaysia, Lesbian, Gay, Bisexual dan Transgender (LGBT) face moral sanctions and legal challenges because it is prohibited by Islam and not condoned by other major religions. A search using Google Trends show that there was a spike of interest on “LGBT in Malaysia” in 2009 and 2019, but there has been sustained interest since 2014. The present study examined framing of LGBT in four online newspapers in Malaysia. The specific objectives of the study were to determine the percentage of episodic and thematic framing in the newspapers, and to compare the topics that are reported in LGBT news. A total of 60 newspaper articles published in 2019 were identified from Astro Awani, Free Malaysia Today, Malaysiakini and The Star Online. The analysis showed that 81.67% of the articles were episodic frames and 18.33% were thematic frames. The four newspapers differ in the proportion of episodic and thematic articles on LGBT. The main events related to LGBT were the Women’s Day March in Kuala Lumpur on 9 March 2019 and the vote against the International Labour Organisation agreement. Many news articles reported politicians, religious leaders, activists and companies expressing either support or condemnation of LGBT. Over half (61.67%) of the articles were on LGBT news stories in Malaysia while other articles reported LGBT-linked persons or events in other countries. The findings suggest caution in news on LBGT, with newspapers treading a thin line between affirming human rights and taking the official position of the country on LGBT

Microstructure Effects for Casimir Forces in Chiral Metamaterials

We examine a recent prediction for the chirality-dependence of the Casimir force in chiral metamaterials by numerical computation of the forces between the exact microstructures, rather than homogeneous approximations. We compute the exact force for a chiral bent-cross pattern, as well as forces for an idealized "omega"-particle medium in the dilute approximation and identify the effects of structural inhomogeneity (i.e. proximity forces and anisotropy). We find that these microstructure effects dominate the force for separations where chirality was predicted to have a strong influence. To get observations of chirality free from microstructure effects, one must go to large separations where the effect of chirality is at most $\sim10^{-4}$ of the total force.Comment: 5 pages, 4 figure