Lower Bounds on the Communication Complexity of Shifting

We study the communication complexity of the SHIFT (equivalently, SUM-INDEX) function in a 3-party simultaneous message model. Alice and Bob share an n-bit string x and Alice holds an index i and Bob an index j. They must send messages to a referee who knows only n, i and j, enabling him to determine x[(i+j) mod n]. Surprisingly, it is possible to achieve nontrivial savings even with such a strong restriction: Bob can now make do with only ceil(n/2) bits. Here we show that this bound is completely tight, for all n. This is an exact lower bound, with no asymptotics involved

Periferias residenciales difusas y calidad de vida: un análisis comparado de situaciones representativas de la región metropolitana de Madrid y buenas prácticas internacionlaes

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Filosofía y Letras, Departamento de Geografía. Fecha de lectura: 12-12-201

Automated Structural and Spatial Comprehension of Data Tables

Data tables on the Web hold large quantities of information, but are difficult to search, browse, and merge using existing systems. This dissertation presents a collection of techniques for extracting, processing, and querying tables that contain geographic data, by harnessing the coherence of table structures for retrieval tasks. Data tables, including spreadsheets, HTML tables, and those found in rich document formats, are the standard way of communicating structured data for typical computer users. Notably, geographic tables (i.e., those containing names of locations) constitute a large fraction of publicly-available data tables and are ripe for exposure to Internet users who are increasingly comfortable interacting with geographic data using web-based maps. Of particular interest is the creation of a large repository of geographic data tables that would enable novel queries such as "find vacation itineraries geographically similar to mine" for use in trip planning or "find demographic datasets that cover regions X, Y, and Z" for sociological research. In support of these goals, this dissertation identifies several methods for using the structure and context of data tables to improve the interpretation of the contents, even in the presence of ambiguity. First, a method for identifying functional components of data tables is presented, capitalizing on techniques for sequence labeling that are used in natural language processing. Next, a novel automated method for converting place references to physical latitude/longitude values, a process known as geotagging, is applied to tables with high accuracy. A classification procedure for identifying a specific class of geographic table, the travel itinerary, is also described, which borrows inspiration from optimization techniques for the traveling salesman problem (TSP). Finally, methods for querying spatially similar tables are introduced and several mechanisms for visualizing and interacting with the extracted geographic data are explored

A User-Based Look at Visualization Tools for Environmental Data and Suggestions for Improvement - An Inventory among City Planners in Gothenburg

With a growing interest in environmental data and the need to consider various environmental factors earlier in the planning processes, it becomes more important to disseminate this type of information to different target groups in a comprehensible way. To support easier decision making, many cities and municipalities are increasingly using digital city models where it is possible to integrate different types of information based on simulation and visualization of future scenarios. Such tools have high potential, but the visual representation of data still needs to be developed. In this paper, we investigate how professionals within urban planning currently use visualization to communicate environmental data, and what their needs are regarding tools and visual representation. We discuss challenges for representing environmental data in urban development processes, with the aim of contributing to a better understanding of these issues. We base our investigation on a literature study, an inventorying survey and a focus group discussion with professionals within urban planning. This study provides an end-user perspective among urban planners and valuable insights on tool usage and visualization. Results show that applications used for environmental visualization still can be improved regarding, e.g., user friendliness and information handling, which may increase their efficiency

Too much pressure? Driving and restraining forces and pressures relating to the state of connected and autonomous vehicles in cities

Connected and Autonomous Vehicles (CAVs) are predicted by many analysts to transform the transport system over the coming decades. Which direction and path this transformation will take remains highly uncertain, as do the related environmental effects. In the present study we examine the introduction of CAVs in cities in terms of the indirect or underlying processes (drivers) and the direct expressions of interest that are related to specific actions, events or processes (pressures). The drivers and pressures are identified in interviews with stakeholders from across the quadruple helix (academia, industry, government and civil society). We then use an analytical framework that combines the drivers and pressures of the DPSIR (Driving forces, Pressures, States, Impacts, Responses) model and force field analysis. This framework is used to map survey data on the strength of the driving and restraining forces and pressures behind the introduction of CAVs in cities, and to identify which stakeholders are involved in this socio-technical transition. Results showed that there was a strong belief across stakeholder groups that CAVs should be connected with mobility planning strategies. This need for planning has been discussed at length in other contexts, and now our results show that respondents find this need is also present in the Swedish context. An unexpected finding was that those who are sceptical to CAVs may form unique groups with a broad range of stakeholder types, for example elderly people, cyclists, people who are concerned because of conspiracies related to new technology, and those who are concerned about environmental effects

Towards a systemic understanding of compact city qualities

The compact city concept remains a key policy response to multiple societal challenges. Based on theoretical and empirical research, this article seeks to a) develop a systemic understanding of compact city qualities; b) map alleged compact city qualities from the literature onto this framework; c) map qualities mentioned by stakeholders in two European cities onto the same framework; and d) apply the developed framework to analyse how compounded compact city qualities relate to policy challenges, such as carbon neutrality, poverty alleviation, neighbourhood revitalization, or community engagement. It is based on literature reviews and interviews with stakeholders in Barcelona and Rotterdam

Linking research, education and citizen codesign: compact cities as social intensification

Both research and policy argue for more compact cities, but there is little clarity regarding which urban qualities must be made more compact to achieve the purported benefits. This paper discusses an example of how to conduct immersive and localised studies by connecting research and education to community outreach. Three potential positive outcomes of linking are examined: (a) linking may improve research activities, (b) linking may have a positive impact on student learning, and (c) better valorisation of research results may be achieved. Within a master’s course, architectural students used codesign methods to investigate how the compact city concept can be understood and applied at the neighbourhood level; this assignment was formulated within a research project. The researchers performed observations and feedback tutorials, and the students applied mixed methods, including a literature review, meetings with researchers and stakeholders, site analysis, interviews and a pop-up workshop with residents, strategy development, design proposals, and feedback meetings with critics and local stakeholders. The results show that this linking may contribute significantly to research activities, as the results of a collaborative process between students and local residents were noteworthy. Rather than focusing on the physical environment, the residents argued that the starting point for urban development should be the social aspects. The residents helped the students understand what social aspects to focus on and how to think about certain locations. In terms of education, the collaboration gave students access to the latest research. Better valorisation of research results was achieved with actors at the local level. However, higher up in the municipal hierarchy, valorisation remained a challenge. Linking research and education to community outreach is not particularly common, even if linking all three activities has the potential to lead to systemic change

Synergies and trade-offs of Barcelona compact city qualities

Supplementary figure to the article Towards a systemic understanding of compact city qualities by Jaan-Henrik Kain, Marco Adelfio, Jenny Stenberg and Liane Thuvander, published in Journal of Urban Design in 2021

Transforming brownfields into urban greenspaces: A working process for stakeholder analysis

Urban greenspaces (UGS) provide a range of ecosystem services and are instrumental in ensuring the liveability of cities. Whilst incorporating UGS in increasingly denser cities is a challenge to planners, brownfields form a latent resource with the potential of being converted into UGS. Transformation of brownfields to greenspaces, however, requires engagement of a variety of stakeholders, from providers to users. The overall aim of this study was to support effective and realistic realisations of UGS in the context of urban brownfields’ regeneration and stakeholder engagement. A working process was developed to: 1) integrate methods relevant for UGS realisation for a) identification and categorising of relevant stakeholders, b) mapping their interests and resources, c) identifying various challenges, and d) matching those challenges with the mapped resources over the timeline of UGS development; and 2) apply these methods to assess relevance and shortcomings. The methods were applied to a study site in Sweden, and data was collected using a questionnaire survey. The survey received 31 responses and the respondents’ comments indicated that the combination of several uses, especially integrated with an urban park, is preferable. Visualisation was an important component for data analysis: stakeholder categorisation was effectively visualised using a Venn diagram, and the needed mobilisation of resources among stakeholders to manage identified challenges was visualised using a timeline. The analysis demonstrates the need for collaboration between stakeholders to achieve an effective realisation of UGS and how multiple methods can be used in concert to map stakeholders, preferences, challenges, and resources for a particular site. The application at a study site provided site-specific data but the developed stakeholder categorisation, and the method for matching identified challenges with the stakeholders’ resources using a timeline, can be generalised to applications at other sites