| 15541. |
- Lobo Vesga, Elisabet, 1993
(författare)
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A Programming Language for Data Privacy with Accuracy Estimations
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Differential privacy offers a formal framework for reasoning about the privacy and accuracy of computations on private data. It also offers a rich set of building blocks for constructing private data analyses. When carefully calibrated, these analyses simultaneously guarantee the privacy of the individuals contributing their data, and the accuracy of the data analyses results, inferring useful properties about the population. The compositional nature of differential privacy has motivated the design and implementation of several programming languages aimed at helping a data analyst in programming differentially private analyses. However, most of the programming languages for differential privacy proposed so far provide support for reasoning about privacy but not for reasoning about the accuracy of data analyses. To overcome this limitation, in this work we present DPella, a programming framework providing data analysts with support for reasoning about privacy, accuracy, and trade-offs. The distinguishing feature of DPella is a novel component that statically tracks the accuracy of different data analyses. In order to make tighter accuracy estimations, this component leverages taint analysis for automatically inferring statistical independence of the different noise quantities added for guaranteeing privacy. We evaluate our approach by implementing several classical queries from the literature and showing how data analysts can figure out the best manner to calibrate privacy to meet the accuracy requirements.
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| 15542. |
- Lobo Vesga, Elisabet, 1993
(författare)
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Language-Based Differential Privacy with Accuracy Estimations and Sensitivity Analyses
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the development of programming frameworks to enforce, by construction, desirable properties of software systems. Particularly, we are interested in enforcing differential privacy -- a mathematical notion of data privacy -- while statically reasoning about the accuracy of computations, along with deriving the sensitivity of arbitrary functions to further strengthen the expressiveness of these systems. To this end, we first introduce DPella, a programming framework for differentially-private queries that allows reasoning about the privacy and accuracy of data analyses. DPella provides a novel component that statically tracks the accuracy of different queries. This component leverages taint analysis to infer statistical independence of the different noises that were added to ensure the privacy of the overall computation. As a result, DPella allows analysts to implement privacy-preserving queries and adjust the privacy parameters to meet accuracy targets or vice-versa. In the context of differentially-private systems, the sensitivity of a function determines the amount of noise needed to achieve a desired level of privacy. However, establishing the sensitivity of arbitrary functions is non-trivial. Consequently, systems such as DPella provided a limited set of functions -- whose sensitivity is known -- to apply over sensitive data, thus hindering the expressiveness of the language. To overcome this limitation, we propose a new approach to derive proofs of sensitivity in programming languages with support for polymorphism. Our approach enriches base types with information about the metric relation between values and applies parametricity to derive proof of a function's sensitivity. These ideas are formalized in a sound calculus and implemented as a Haskell library called Spar, enabling programmers to prove the sensitivity of their functions through type-checking alone. Overall, this thesis contributes to the development of expressive programming frameworks for data analysis with privacy and accuracy guarantees. The proposed approaches are feasible and effective, as demonstrated through the implementation of DPella and Spar.
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| 15543. |
- Lobovkina, Tatsiana, 1975
(författare)
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Lipid Nanotube Networks: Shape Transitions and Insights into the Dynamics of Self-Organization
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nanotube-vesicle networks (NVNs) are simplified models of cell membrane tubular systems which are dynamic transportation routs for molecular cargoes in biological cells. The presented work describes dynamic properties of NVNs such as self-organization, shape and topology transformations; moreover, specific geometric properties of the networks are used for controlling enzymatic reactions.A nanotube-vesicle network is a network of surface-adhered lipid vesicles (5-25 m in radius) connected by suspended lipid nanotubes (100-200 nm in radius). Vesicle size, nanotube length, and connectivity of a network can be controlled with high precision. Initially, the network is trapped in a high free energy state. By proper means, it is possible to trigger network self-organization towards a lower free energy state.Network evolution begins with merging of two adjacent nanotubes, and formation of a single nanotube three-way junction. Based on experimental observations of fluorescently labeled nanotubes and a theoretical model, the nanotube three-way junction is shown to propagate with a zipper-like mechanism, described in Paper I of this thesis. Lipids from two merging branches flow through the junction and form an extension on the third nanotube branch. Depending on the starting arrangement of the nanotubes, a NVN can evolve towards entangled and knotted geometries; or it can form a system of branching nanotubes. Paper II describes the formation of knotted nanotubes. The estimated size of the knot is comparable with the radius of a lipid nanotube. It is also demonstrated that such a knot can be used as a mechanical tweezer to capture and transport submicrometer-sized objects. In the experiments described in Paper III, NVNs are shown to form tree-like structures. The nanotubes arrange into symmetric three-way junctions with angles of 120o between the nanotubes. Moreover, the process of self-organization in the networks reveals a strong similarity with some optimization problems, such as the Euclidian Steiner Tree Problem. Paper IV suggests a method to form circular lipid nanotubes. The presented method gives new opportunities for preparing, manipulating and studying shape transitions of vesicles with non-spherical topology.Finally in Paper V, the geometry of a NVN is used to control the dynamics of an enzymatic reaction. Here, the vesicles are used as containers for reacting molecules, and the nanotubes serve as transportation routes. The narrow nanotube entrances act as transport barriers for the enzyme molecules. In such a reaction-diffusion system, the reaction occurs as a cascade through the containers and displays wave-like behavior.
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| 15544. |
- Lock, Jonathan, 1987
(författare)
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Towards Optimal Real-Time Automotive Emission Control
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The legal bounds on both toxic and carbon dioxide emissions from automotive vehicles are continuously being lowered, forcing manufacturers to rely on increasingly advanced methods to reduce emissions and improve fuel efficiency. Though great strides have been made to date, there is still a large potential for continued improvement. Today, many subsystems in vehicles are optimized for static operation, where subsystems in the vehicle perform well at constant operating points. Extending optimal operation to the dynamic case through the use of optimal control is one method for further improvements. This thesis focuses on two subtopics that are crucial for implementing optimal control; dynamic modeling of vehicle subsystems, and methods for generating and evaluating computationally efficient optimal controllers. Though today's vehicles are outfitted with increasingly powerful computers, their computational performance is low compared to a conventional PC. Any controller must therefore be very computationally efficient in order to feasibly be implemented. Furthermore, a sufficiently accurate dynamic model of the subsystem is needed in order to determine the optimal control value. Though many dynamic models of the vehicle's subsystems exist, most do not fulfill the specific requirements set by optimal controllers. This thesis comprises five papers that, together, probe some methods of implementing dynamic optimal control in real-time. Two papers develop optimal control methods, one introduces and studies a cold-start model of the three-way catalyst, one paper extends the three-way catalyst model and studies optimal cold-start control, and one considers fuel-optimally controlling the speed of the engine in a series-hybrid. By combining the method and model papers we open for the potential to reduce toxic emissions by better managing cold-starts in hybrid vehicles, as well as reducing carbon dioxide emissions by operating the engine in a more efficient manner during transients.
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| 15545. |
- Lockett, Nigel, et al.
(författare)
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The contribution of universities to student and graduate entrepreneurs' social capital: a current fairytale?
- 2016
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Ingår i: Engage HEI Conference, University of Central Lancashire, UK, May 19-20.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper explores how universities contribute to the acquisition of social capital of their student and graduate entrepreneurs. The objective is to identify under what circumstances universities facilitate this in the context of entrepreneurial learning. The study builds on collaboration between three European universities: Chalmers University of Technology, Universidad de Malaga and University of Leeds.Entrepreneurial learning and education literature underpin this study. Stemming from this, the theoretical framework is complemented by research about the impact of social capital on entrepreneurs’ development, and its relevance to the concept of the entrepreneurial university.A qualitative methodological approach involving critical incident technique is used to map student and graduate entrepreneurs’ entrepreneurial journey based on a timeline, specifying stakeholders associated with critical events (entrepreneurial activities of any kind). A visual aid technique was used throughout the interview to assist interviewees in recalling their verbal history. 24 individuals fulfilling criteria: (1) university final year students or first year after graduation; (2) have or were engaged in some entrepreneurial activity; (3) 50% completed some formal entrepreneurship education were interviewed. Nvivo was used to analyse the data through narrative analysis of the social informal learning; i.e. how interviewees learned from others what they needed to learn in order to carry out their entrepreneurial activities. Preliminary analyses of the data identified that entrepreneurship education programmes in these universities engage experienced entrepreneurs to connect students to the ‘real world’, providing them an initial network of role models, as well as skills to develop their own network. It seems that respondents’ entrepreneurial learning follows a pattern. Early stages of the entrepreneurial journey relied on informal learning. As respondents’ entrepreneurial activities expand to include a more complex structure and wider network of stakeholders, they became aware of their need of a more formal learning. To satisfy this need, respondents engaged in non-formal education programmes and, when necessary, they enrolled in formal education programmes. Nevertheless, respondents also used other informal learning sources to cover their self-perceived knowledge gaps. Consequently, this illustrates how interdisciplinarity and entrepreneurship reaches beyond business school learning.Results also suggest that the intertwining of social capital and learning in entrepreneurship occurs before university, from the very first moment that respondents engage in some type of entrepreneurial activity. However, the university is vital in facilitating integrated understanding and developed maturity to manage the complexity of formal, non-formal and informal learning. This comprehensive understanding becomes an essential part of the respondents’ entrepreneurial social capital.This paper contributes by exposing the previously missing value of social networking in entrepreneurship education at universities. At an institutional-level, it legitimises university inclusion of social networking activities into formal and non-formal entrepreneurship education, and encouragement of informal entrepreneurship learning. Moreover, at an individual-level, it motivates educators to embed these activities within the curriculum in order to facilitate entrepreneurial learning. Considering that social networking goes beyond simply building a contact list and that it is part of the social capital necessary for the entrepreneurial journey, this study exposes the previously missing value of social networking in entrepreneurial education programmes. It encourages educators to embed social networking activities into the curriculum to facilitate entrepreneurial learning. The study highlights the importance of social capital acquired at university, as part of student/graduate entrepreneurial journeys. This revitalises the role of the university as a key enabler of economic, social and cultural impact through student/graduate entrepreneurs. Thus, the fairy tale question is answered: universities contribution to student and graduate entrepreneurs’ social capital is no longer a fantasy.Future research needs to be focus on understanding the student/graduate entrepreneurial journey, considering not only entrepreneurial activities as critical incidents, but also other interactions in the entrepreneur’s life. Moreover, the inclusion of other countries and universities to identify a clearer pattern of how universities contribute to acquisition of social capital of their student and graduate entrepreneurs.
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| 15546. |
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| 15547. |
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| 15548. |
- Logg, Anders, 1976
(författare)
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An Overview of the FEniCS Project
- 2008
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Ingår i: 21st Nordic Seminar on Computational Mechanics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 15549. |
- Logg, Anders, 1976
(författare)
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Att lösa en differentialekvation
- 2008
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Ingår i: Människor och matematik. - 9789185143085 ; , s. 95-109
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 15550. |
- Logg, Anders, 1976
(författare)
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Automated Solution of Differential Equations
- 2007
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Ingår i: Sixth International Congress on Industrial Applied Mathematics (ICIAM07) and GAMM Annual Meeting, Z\"urich. - 1617-7061.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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