Sub-sampled and Differentially Private Hamiltonian Monte Carlo

Hamiltonian Monte Carlo is a powerful Markov Chain algorithm, which is able to traverse complex posterior distributions accurately. One of the method's disadvantages is it's reliance on gradient evaluations over the full data, which quickly becomes computationally costly when the data sets grow large. By mini-batching the data set for stochastic gradient approximations we can speed up the algorithm, albeit with a reduced posterior accuracy. We illustrate by using a toy example, that the stochastic version of the method is unable to explore the exact posterior, and we show how an added friction term greatly alleviates this, when the term is adjusted carefully. We use the added stochastic error to our advantage, by turning the results differentially private. The randomness in the results masks the appearance of any single data point in the used data set, creating a way to more secure handling of sensitive data. In the case of stochastic gradient Hamiltonian Monte Carlo, we are able to achieve reasonable privacy bounds with little to no decrease in optimization performance, although finding a good the differentially private approximation of the target posterior becomes harder. In addition, we compare the previously considered privacy accounting methods to assay the privacy bounds to a new privacy loss distribution method, which is able to determine a tighter privacy profile than, for example, the moments accountant method

Privacy Preserving Randomized Gossip Algorithms

In this work we present three different randomized gossip algorithms for solving the average consensus problem while at the same time protecting the information about the initial private values stored at the nodes. We give iteration complexity bounds for all methods, and perform extensive numerical experiments.Comment: 38 page

Computer Mediated Communication: Providing Pastoral Care to Youth in “A High Tech” World

This study used a hermeneutical methodology to explore how Computer Mediated Communication (CMC) can be used to provide pastoral care to youth in a high tech world. The research was motivated by the writers desire to find ways to be in communication with youth and provide pastoral care to them during their adolescent years. The thesis will explore computer mediated communication and its usefulness in providing pastoral care to youth by exploring the benefits and limitations, how it can be abused, namely cyber bullying, how it can provide an opportunity for mentoring and a theological reflection on how it can work in the church. The hermeneutical research leads the reader through information on CMC, the hazards of using this type of technology and the benefits that this technology lends for providing pastoral care in the parish

Data: Implications for Markets and for Society

Every day, massive amounts of data are gathered, exchanged, and used to run statistical computations, train machine learning algorithms, and inform decisions on individuals and populations. The quick rise of data, the need to exchange and process it, to take data privacy concerns into account, and to understand how it affects decision-making, introduce many new and interesting economic, game theoretic, and algorithmic challenges. The goal of this thesis is to provide theoretical foundations to approach these challenges. The first part of this thesis focuses on the design of mechanisms that purchase then aggregate data from many sources, in order to perform statistical tasks. The second part of this thesis revolves around the societal concerns associated with the use of individuals' data. The first such concern we examine is that of privacy, when using sensitive data about individuals in statistical computations; we focus our attention on how privacy constraints interact with the task of designing mechanisms for acquisition and aggregation of sensitive data. The second concern we focus on is that of fairness in decision-making: we aim to provide tools to society that help prevent discrimination against individuals and populations based on sensitive attributes in their data, when making important decisions about them. Finally, we end this thesis on a study of the interactions between data and strategic behavior. There, we see data as a source of information that informs and affects agents' incentives; we study how information revelation impacts agent behavior in auctions, and in turn how a seller should design auctions that take such information revelation into account.</p

Proceedings of the 2009 Joint Workshop of Fraunhofer IOSB and Institute for Anthropomatics, Vision and Fusion Laboratory

The joint workshop of the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation IOSB, Karlsruhe, and the Vision and Fusion Laboratory (Institute for Anthropomatics, Karlsruhe Institute of Technology (KIT)), is organized annually since 2005 with the aim to report on the latest research and development findings of the doctoral students of both institutions. This book provides a collection of 16 technical reports on the research results presented on the 2009 workshop

The social impact of closed circuit television (CCTV) inside mental health wards

CCTV (Closed Circuit Television) camera use has been a feature of the mental health ward since the 1990s. However, how CCTV surveillance is simultaneously controlling and caring inside the mental health ward has been missing in sociological research. In addition, the use of cameras is also impacted by the nature of patients being cared for inside the ward, that is, those subjects who have a limited cognitive capacity because of the nature of their mental health condition, to understand the panoptic effects of the cameras.Ethnographic research, inside three psychiatric intensive care units (PICUs), was undertaken in order to examine the actual use of cameras.Research findings are centred on the perception of violence and mental disorder, the ability of the cameras to undermine the ‘face’ and ethics of care, and subjective experiences of patients. Data analysis is influenced by Foucault’s triangulation of sovereign power, disciplinary power and governmentality and how CCTV shapes patient and staff behaviour, how it coheres with other techniques adopted inside the ward and Foucault’s analysis of pastoral power. The findings suggest that CCTV cameras can be used to the benefit of patients inside the ward, for example, in undertaking less intrusive observations when patients are placed in seclusion. However, their uses can also result in a range of unintended outcomes for patients, for example, through their capacity to criminalise mental health difficulties and potentially minimise the life chances of those people who are already marginalised in society because of their mental health status

Enhancing Privacy and Fairness in Search Systems

Following a period of expedited progress in the capabilities of digital systems, the society begins to realize that systems designed to assist people in various tasks can also harm individuals and society. Mediating access to information and explicitly or implicitly ranking people in increasingly many applications, search systems have a substantial potential to contribute to such unwanted outcomes. Since they collect vast amounts of data about both searchers and search subjects, they have the potential to violate the privacy of both of these groups of users. Moreover, in applications where rankings influence people's economic livelihood outside of the platform, such as sharing economy or hiring support websites, search engines have an immense economic power over their users in that they control user exposure in ranked results. This thesis develops new models and methods broadly covering different aspects of privacy and fairness in search systems for both searchers and search subjects. Specifically, it makes the following contributions: (1) We propose a model for computing individually fair rankings where search subjects get exposure proportional to their relevance. The exposure is amortized over time using constrained optimization to overcome searcher attention biases while preserving ranking utility. (2) We propose a model for computing sensitive search exposure where each subject gets to know the sensitive queries that lead to her profile in the top-k search results. The problem of finding exposing queries is technically modeled as reverse nearest neighbor search, followed by a weekly-supervised learning to rank model ordering the queries by privacy-sensitivity. (3) We propose a model for quantifying privacy risks from textual data in online communities. The method builds on a topic model where each topic is annotated by a crowdsourced sensitivity score, and privacy risks are associated with a user's relevance to sensitive topics. We propose relevance measures capturing different dimensions of user interest in a topic and show how they correlate with human risk perceptions. (4) We propose a model for privacy-preserving personalized search where search queries of different users are split and merged into synthetic profiles. The model mediates the privacy-utility trade-off by keeping semantically coherent fragments of search histories within individual profiles, while trying to minimize the similarity of any of the synthetic profiles to the original user profiles. The models are evaluated using information retrieval techniques and user studies over a variety of datasets, ranging from query logs, through social media and community question answering postings, to item listings from sharing economy platforms.Nach einer Zeit schneller Fortschritte in den Fähigkeiten digitaler Systeme beginnt die Gesellschaft zu erkennen, dass Systeme, die Menschen bei verschiedenen Aufgaben unterstützen sollen, den Einzelnen und die Gesellschaft auch schädigen können. Suchsysteme haben ein erhebliches Potenzial, um zu solchen unerwünschten Ergebnissen beizutragen, weil sie den Zugang zu Informationen vermitteln und explizit oder implizit Menschen in immer mehr Anwendungen in Ranglisten anordnen. Da sie riesige Datenmengen sowohl über Suchende als auch über Gesuchte sammeln, können sie die Privatsphäre dieser beiden Benutzergruppen verletzen. In Anwendungen, in denen Ranglisten einen Einfluss auf den finanziellen Lebensunterhalt der Menschen außerhalb der Plattform haben, z. B. auf Sharing-Economy-Plattformen oder Jobbörsen, haben Suchmaschinen eine immense wirtschaftliche Macht über ihre Nutzer, indem sie die Sichtbarkeit von Personen in Suchergebnissen kontrollieren. In dieser Dissertation werden neue Modelle und Methoden entwickelt, die verschiedene Aspekte der Privatsphäre und der Fairness in Suchsystemen, sowohl für Suchende als auch für Gesuchte, abdecken. Insbesondere leistet die Arbeit folgende Beiträge: (1) Wir schlagen ein Modell für die Berechnung von fairen Rankings vor, bei denen Suchsubjekte entsprechend ihrer Relevanz angezeigt werden. Die Sichtbarkeit wird im Laufe der Zeit durch ein Optimierungsmodell adjustiert, um die Verzerrungen der Sichtbarkeit für Sucher zu kompensieren, während die Nützlichkeit des Rankings beibehalten bleibt. (2) Wir schlagen ein Modell für die Bestimmung kritischer Suchanfragen vor, in dem für jeden Nutzer Aanfragen, die zu seinem Nutzerprofil in den Top-k-Suchergebnissen führen, herausgefunden werden. Das Problem der Berechnung von exponierenden Suchanfragen wird als Reverse-Nearest-Neighbor-Suche modelliert. Solche kritischen Suchanfragen werden dann von einem Learning-to-Rank-Modell geordnet, um die sensitiven Suchanfragen herauszufinden. (3) Wir schlagen ein Modell zur Quantifizierung von Risiken für die Privatsphäre aus Textdaten in Online Communities vor. Die Methode baut auf einem Themenmodell auf, bei dem jedes Thema durch einen Crowdsourcing-Sensitivitätswert annotiert wird. Die Risiko-Scores sind mit der Relevanz eines Benutzers mit kritischen Themen verbunden. Wir schlagen Relevanzmaße vor, die unterschiedliche Dimensionen des Benutzerinteresses an einem Thema erfassen, und wir zeigen, wie diese Maße mit der Risikowahrnehmung von Menschen korrelieren. (4) Wir schlagen ein Modell für personalisierte Suche vor, in dem die Privatsphäre geschützt wird. In dem Modell werden Suchanfragen von Nutzer partitioniert und in synthetische Profile eingefügt. Das Modell erreicht einen guten Kompromiss zwischen der Suchsystemnützlichkeit und der Privatsphäre, indem semantisch kohärente Fragmente der Suchhistorie innerhalb einzelner Profile beibehalten werden, wobei gleichzeitig angestrebt wird, die Ähnlichkeit der synthetischen Profile mit den ursprünglichen Nutzerprofilen zu minimieren. Die Modelle werden mithilfe von Informationssuchtechniken und Nutzerstudien ausgewertet. Wir benutzen eine Vielzahl von Datensätzen, die von Abfrageprotokollen über soziale Medien Postings und die Fragen vom Q&A Forums bis hin zu Artikellistungen von Sharing-Economy-Plattformen reichen

A Pilot Study of a Sex Education Program in a Sheltered Workshop Using a Cognitive-Behavioral Model Based on Rational Emotive Therapy

This pilot study was developed to teach people with mental retardation about their own sexuality, appropriate community behaviors, and to develop within them a basic sense of responsibility for their own actions. Problems in social/sexual behaviors have been consistently quoted as reasons for high recidivism rates, as well as difficulties in community living, vocational placement, and other generalized stereotypes about mental retardation. Often the public remains uninformed about, does not recognize, and/or feels that sexual rights for people with any mental differences should not exist. Additionally, when any form of sexuality was expressed by such people it resulted in shock and/or punishment. This in turn perpetuated the old coustodial models, and the teaching of general effective living skills for eventual community re-integration remained inadequate. Included within this pilot study were problem solving techniques based on Rational Emotive Therapy which were extended into sexuality and then generalized to other non-sexual areas. The basic philosophy behind the project was that people who attend a sheltered workshop are able to think and learn appropriate behavior, can accept responsibilities for themselves, and can learn how to solve their own personal problems with minimal support. In the area of sexuality the paper concentrates on sexual knowledge and attitudes. A literature review shows that few researchers have asked the people themselves what they think or feel about sex. Several problems were revealed: Most of the literature covers philosophical positions or anecdotes. The few appropriate tests available have no published norms. Much of the material available remains inadequate and overpriced. Other areas covered include problems in sex education programs; attitudes of institutions; parental reaction to sexuality and retardation; birth control, children, and marriage; and the legal aspects of sterilization. A growing number of professionals have indicated that therapy can work if the counselor remains active, directive, structures meetings, is more verbal, uses repetition, accepts limitations, tolerates frustration, and works within narrow goals. While true insight is rare, a person can be taught several alternatives in solving his problems himself. The approach of Rational Emotive Therapy is explained and shows how it can be adapted. Another section provides materials a counselor/educator could use to create a program for his own use. This includes philosophy, readings, format, games, slide presentations, comic books, posters, and curriculums. A chapter on research shows a short questionaire format used to judge group needs and as a method for ongoing group evaluation. Results show the test to be reliable (r=.70). More than 70% know the concepts involved in making a woman pregnant and defining terms. Some problems were seen in V.D. knowledge, homosexuality, who to have sex with, making decisions, and creating alternatives. The end result is a cognitive-behavioral based sex education program which stresses acceptance of self responsibility, concept of self as adults, decision-making, and basic problem solving skills. The basic philosophy emphasizes that these are people with retardation not retarded people

LIPIcs, Volume 277, GIScience 2023, Complete Volume

LIPIcs, Volume 277, GIScience 2023, Complete Volum