Material characterization and process development for indium-arsenide / indium-gallium-antimonide channel, high electron mobility transistors for low power, high speed applications

Efforts to push the performance of transistors for millimeter-wave and microwave applications have borne fruit through device size scaling and the use of novel material systems. III-V semiconductors and their alloys hold a distinct advantage over silicon because they have much higher electron mobility which is a prerequisite for high frequency operation. InGaAs/InP pseudomorphic heterojunction bipolar transistors (HBTs) have demonstrated fT of 765 GHz at room temperature and InP based high electron mobility transistors (HEMTs) have demonstrated fMax of 1.2 THz. The 6.1 A lattice family of InAs, GaSb, AlSb covers a wide variety of band gaps and is an attractive future material system for high speed device development. Extremely high electron mobilities ~ 30,000 cm^2 V^-1s^-1 have been achieved in modulation doped InAs-AlSb structures. The work described in this thesis involves material characterization and process development for HEMT fabrication on this material system.

D3M: multicast listener mobility support mechanisms over distributed mobility anchoring architectures

The explosion in mobile data traffic is a driver for future network operator technologies, given its large potential to affect both network performance and generated revenue. The concept of distributed mobility management (DMM) has emerged in order to overcome efficiency-wise limitations in centralized mobility approaches, proposing not only the distribution of anchoring functions but also dynamic mobility activation sensitive to the applications needs. Nevertheless, there is not an acceptable solution for IP multicast in DMM environments, as the first proposals based on MLD Proxy are prone to tunnel replication problem or service disruption. We propose the application of PIM-SM in mobility entities as an alternative solution for multicast support in DMM, and introduce an architecture enabling mobile multicast listeners support over distributed anchoring frameworks in a network-efficient way. The architecture aims at providing operators with flexible options to provide multicast mobility, supporting three modes: the first one introduces basic IP multicast support in DMM; the second improves subscription time through extensions to the mobility protocol, obliterating the dependence on MLD protocol; and the third enables fast listener mobility by avoiding potentially slow multicast tree convergence latency in larger infrastructures, by benefiting from mobility tunnels. The different modes were evaluated by mathematical analysis regarding disruption time and packet loss during handoff against several parameters, total and tunneling packet delivery cost, and regarding packet and signaling overhead.

Magnetoresistance in a High Mobility Two-Dimensional Electron System as a Function of Sample Geometry

In a high mobility two-dimensional electron gas (2DEG) realized in a GaAs/Al0.3Ga0.7As quantum well we observe changes in the Shubnikov-de Haas oscillations (SdHO) and in the Hall resistance for different sample geometries. We observe for each sample geometry a strong negative magnetoresistance around zero magnetic field which consists of a peak around zero magnetic field and of a huge magnetoresistance at larger fields. The peak around zero magnetic field is left unchanged for different geometries.

Beyond hope: Rhetorics of mobility, possibility, and literacy

When writing teachers enter the classroom, they often bring with them a deep faith in the power of literacy to rectify social inequalities and improve their students’ social and economic standing. It is this faith—this hope for change—that draws some writing teachers to locations of social and economic hardship. I am interested in how teachers and theorists construct their own narratives of social mobility, possibility, and literacy. My dissertation analyzes the production and expression of beliefs about literacy in the narratives of a diverse group of writing teachers and theorists, from those beginning their careers to those who are published and widely read. The central questions guiding this study are: How do teachers’ and theorists’ narratives of becoming literate intersect with literacy theories? and How do such literacy narratives intersect with beliefs in the power of literacy to improve individuals’ lives socially, economically, and personally? I contend that the professional literature needs to address more fully how teachers’ and theorists’ personal histories with literacy shape what they see as possible (and desirable) for students, especially those from marginalized communities. A central focus of the dissertation is on how teachers and theorists attempt to resolve a paradox they are likely to encounter in narratives about literacy. On one hand, they are immersed in a popular culture that cherishes narrative links between literacy and economic advancement (and, further, between such advancement and a “good life”). On the other hand, in professional discourse and in teacher preparation courses, they are likely to encounter narratives that complicate an assumed causal relationship between literacy and economic progress. Understanding, through literacy narratives, how teachers and theorists chart a practical path through or around this paradox can be beneficial to literacy education in three ways. First, it can offer direction in professional development and teacher education, addressing how teachers negotiate the boundaries between personal experience, theory, and pedagogy. Second, it can help teachers create spaces wherein students can explore the impact of paradoxical views about the role of literacy on their own lives. Finally, it can offer direction in public policy discourse, extending awareness of what we want—and need—from English language arts education in the twenty-first century. To explore these issues, I draw on case studies and ethnographic observation as well as narrative inquiry into teachers’ and theorists’ published literacy narratives. I situate my findings within three interrelated frames: 1) the narratives of new teachers, 2) the published works of literacy educators and theorists, and 3) my own literacy narrative. My first chapter, “Beyond Hope,” explores the tenuous connections between hope and critique in literacy studies and provides a methodological overview of the study. I argue that scholarship must move beyond a singular focus on either hope or critique in order to identify the transformative potential of literacy in particular circumstances. Analyzing literacy narratives provides a way of locating a critically informed sense of possibility. My second chapter, “Making Teachers, Making Literacy,” explores the intersection between teachers’ lives and the theories they study, based on qualitative analysis of a preservice course for secondary education English teachers. I examine how these preservice English teachers understood literacy, how their narratives of becoming literate and teaching English connected—and did not connect—with theoretical and pedagogical positions, and how these stories might inform their future work as practitioners. Centering primarily on preservice teachers who resisted Nancie Atwell’s pedagogy of possibility because they found it too good to be true, this research concentrates on moments of disjuncture, as expressed in class discussion and in one-on-one interviews, when literacy theories failed to align with aspiring teachers’ understandings of their own experiences and also with what they imagined as possible in disadvantaged educational settings. In my third and fourth chapters, I analyze the narratives of celebrated teachers and theorists who put forth an agenda that emphasizes possibilities through literacy, examining how they negotiate the relationship between their own literacy stories and literacy theories. Specifically, I investigate the narratives of three proponents of critical literacy: Mike Rose, Paulo Freire, and Myles Horton, all highly respected literacy teachers whose working-class backgrounds influenced their commitment to teaching in disenfranchised communities. In chapter 3, “Reading Lives on the Boundary,” I demonstrate how Mike Rose’s 1989 autobiographical text, Lives on the Boundary, juxtaposes rhetorics of mobility with critiques of such possibility. Through an analysis of work published in professional journals, I offer a reception history of Rose’s narrative, focusing specifically on how teachers have negotiated the tension between hope and critique. I follow this analysis with three case studies, drawn from a larger sampling, that inquire into the personal connections that writing teachers make with Lives on the Boundary. The teachers in this study, who provided written responses and participated in audio-recorded follow-up interviews, were asked to compare Rose’s story to their own stories, considering how their personal literacy histories influenced their teaching. My findings illustrate how a group of teachers and theorists have projected their own assessments of what literacy and higher education can and cannot accomplish onto this influential text. In my fourth chapter, “Horton and Freire’s Road as Literacy Narrative,” I concentrate on Myles Horton and Paulo Freire’s 1990 collaborative spoken book, We Make the Road by Walking. Central to my analysis are the educators’ stories about their formative years, including their own primary and secondary education experiences. I argue that We Make the Road by Walking demonstrates how theories of literacy cannot be divorced from personal histories. I begin by examining the spoken book as a literacy narrative that fuses personal and theoretical knowledge, focusing specifically on its authors’ ideas on theory. Drawing on Bakhtin’s notion of the chronotope—the intersection of time and space within narrative—I then explore the literacy narratives emerging from the production process of the book, in a video production about Horton and Freire’s meeting, and ultimately in the two men’s reflections on their childhood years (Dialogic). Interspersed with these accounts is archival material on the book’s editorial production that illustrates the value of increased dialogue between personal history and theories of literacy. My fifth chapter is both a reflective analysis and a qualitative study of my work at a men’s medium-high security prison in Illinois, where I conducted research and served as the instructor of an upper-level writing course, “Writing for a Change,” in the spring of 2009. Entitled “Doing Time with Literacy Narratives,” this chapter explores the complex ways in which literacy and incarceration are configured in students’ narratives as well as my own. With and against students’ stories, I juxtapose my own experiences with literacy, particularly in relation to being the son of an imprisoned father. In exploring the intersections between such stories, I demonstrate how literacy narratives can function as a heuristic for exploring beliefs about literacy between teachers and students both inside and outside of the prison-industrial complex. My conclusion pulls together the various themes that emerged in the three frames, from the making of new teachers to the published literacy narratives of teachers and theorists to my own literacy narrative. Writing teachers encounter considerable pressure to align their curricula with one or another theory of literacy, which has the effect of negating the authority of knowledge about literacy gleaned from experience as readers and writers. My dissertation contends that there is much to be gained by finding ways of articulating theories of literacy that encompass teachers’ knowledge of reading and writing as expressed in personal narratives of literacy. While powerful cultural rhetorics of upward social mobility often neutralize the critical potential of teachers’ own narratives of literacy—potential that has been documented by scholars in writing studies and allied disciplines—this is not always the case. The chapters in this dissertation offer evidence that hopeful and critical positions on the transformational possibilities of literacy are not mutually exclusive.

Mobility in vehicular networks with multiple access points to the infrastructure

Nowadays there is a huge evolution in the technological world and in the wireless networks. The electronic devices have more capabilities and resources over the years, which makes the users more and more demanding. The necessity of being connected to the global world leads to the arising of wireless access points in the cities to provide internet access to the people in order to keep the constant interaction with the world. Vehicular networks arise to support safety related applications and to improve the traffic flow in the roads; however, nowadays they are also used to provide entertainment to the users present in the vehicles. The best way to increase the utilization of the vehicular networks is to give to the users what they want: a constant connection to the internet. Despite of all the advances in the vehicular networks, there were several issues to be solved. The presence of dedicated infrastructure to vehicular networks is not wide yet, which leads to the need of using the available Wi-Fi hotspots and the cellular networks as access networks. In order to make all the management of the mobility process and to keep the user’s connection and session active, a mobility protocol is needed. Taking into account the huge number of access points present at the range of a vehicle for example in a city, it will be beneficial to take advantage of all available resources in order to improve all the vehicular network, either to the users and to the operators. The concept of multihoming allows to take advantage of all available resources with multiple simultaneous connections. This dissertation has as objectives the integration of a mobility protocol, the Network-Proxy Mobile IPv6 protocol, with a host-multihoming per packet solution in order to increase the performance of the network by using more resources simultaneously, the support of multi-hop communications, either in IPv6 or IPv4, the capability of providing internet access to the users of the network, and the integration of the developed protocol in the vehicular environment, with the WAVE, Wi-Fi and cellular technologies. The performed tests focused on the multihoming features implemented on this dissertation, and on the IPv4 network access for the normal users. The obtained results show that the multihoming addition to the mobility protocol improves the network performance and provides a better resource management. Also, the results show the correct operation of the developed protocol in a vehicular environment.

Household language, residential segregation and social mobility: continuity and change in eThekwini, South Africa

This article uses South African census data for 1996, 2001 and 2011 to explore the relationship between language and social mobility in the metropolitan region of eThekwini (including what was previously known as Durban). We focus particular attention on variables selected to shed light on residential segregation and social mobility, such as education level, income, race and in-migration. Data on adults at ward level (using 2011 ward boundaries) in eThekwini is used to develop a comparative spatial context for this analysis. Our main finding is that English appears in eThekwini to be the household language of the social elite as well as the language of upward mobility and empowerment.

The Mobility Turn in the Social Science

The paper describes the latest upsurge in the interest in the different forms of mobility in the contemporary world. In the social science this process is often called the mobility turn. In the text it is argued that theoretical underpinnings of the mobility turn are rooted mainly in the different variants of theories of globalization. The text describes: mobility as one of the key elements in the varying concepts of globalization; ways in which mobility was analyzed in the globalization literature; main sources of the mobility turn; crucial arguments in favor of introducing “mobilities” as a separate field of research; and the most important critical remarks concerning the mobility turn.

Collaborative Management of Intermodal Mobility

Part 21: Mobility and Logistics

Social Mobility and Demand for Redistribution. A Comparative Analysis

The literature on preferences for redistribution has paid little attention to the effect of social mobility on the demand for redistribution, which is in contrast with the literature on class-voting, where studies on the effect of social mobility has been very common. Some works have addressed this issue but no systematic test of the hypotheses connecting social mobility and preferences has been done. In this paper we use the diagonal reference models to estimate the effect of origin and destination class on preferences for redistribution in a sample of European countries using data from the European Social Survey. Our findings indicate that social origin matters to a little extent to explain preferences, as newcomers tend to adopt the preferences of the destination class. Moreover, we have found only limited evidence supporting the acculturation hypothesis and not support for the status maximization hypothesis. Furthermore, the effect of social origin varies largely between countries. In a second step of the analysis we investigate what are the national factors explaining this variation. The empirical evidence we present leads to conclude that high rates of upward social mobility sharply reduce the effect of social origin on preferences for redistribution

Electroreflectance characterization of AlInGaN/GaN high-electron mobility heterostructures

Room temperature electroreflectance (ER) spectroscopy has been used to study the fundamental properties of AlxInyGa${}_{1-x-y}$N/AlN/GaN heterostructures under different applied bias. The (0001)-oriented heterostructures were grown by metal-organic vapor phase epitaxy on sapphire. The band gap energy of the AlxInyGa${}_{1-x-y}{\rm{N}}$ layers has been determined from analysis of the ER spectra using Aspnes' model. The obtained values are in good agreement with a nonlinear band gap interpolation equation proposed earlier. Bias-dependent ER allows one to determine the sheet carrier density of the two-dimensional electron gas and the barrier field strength.

NEIGHBORHOOD PERCEPTION OF SAFETY AND THE MOBILITY GAP BETWEEN MEN AND WOMEN IN OLD AGE

Thesis (Master, Community Health & Epidemiology) -- Queen's University, 2016-10-02 21:02:07.735

A probabilistic approach to user mobility prediction for wireless services.

Mobile and wireless networks have long exploited mobility predictions, focused on predicting the future location of given users, to perform more efficient network resource management. In this paper, we present a new approach in which we provide predictions as a probability distribution of the likelihood of moving to a set of future locations. This approach provides wireless services a greater amount of knowledge and enables them to perform more effectively. We present a framework for the evaluation of this new type of predictor, and develop 2 new predictors, HEM and G-Stat. We evaluate our predictors accuracy in predicting future cells for mobile users, using two large geolocation data sets, from MDC [11], [12] and Crawdad [13]. We show that our predictors can successfully predict with as low as an average 2.2% inaccuracy in certain scenarios.

Mobility and satisfaction with lower-limb prostheses and orthoses among users in Sierra Leone: A cross-sectional study

Objectives: To investigate patients' mobility and satisfaction with their lower-limb prosthetic or orthotic device and related service delivery in Sierra Leone; to compare groups of patients regarding type and level of assistive device, gender, area of residence, income; and to identify factors associated with satisfaction with the assistive device and service. Methods: A total of 139 patients answered questionnaires, including the Quebec User Evaluation of Satisfaction with Assistive Technology questionnaire (QUEST 2.0). Results: Eighty-six percent of assistive devices were in use, but half needed repair. Thirty-three percent of patients reported pain when using their assistive device. Patients had difficulties or could not walk at all on: uneven ground (65%); hills (75%); and stairs (66%). Patients were quite satisfied with their assistive device and the service (mean 3.7 out of 5 in QUEST), but reported 886 problems. Approximately half of the patients could not access services. In relation to mobility and service delivery, women, orthotic patients and patients using above-knee assistive devices had the poorest results. The general condition of the assistive device and patients' ability to walk on uneven ground were associated with satisfaction with the assistive devices and service. Conclusion: Patients reported high levels of mobility while using their device although they experienced pain and difficulties walking on challenging surfaces. Limitations in the effectiveness of assistive devices and limited access to follow-up services and repairs were issues desired to be addressed.