454 research outputs found
Stau
No full textWie kann es sein, dass wir in einem High-tech-Land, in dem fast jeder ein Navigationsgerät und ein Smartphone hat, immer noch auf verstopften Straßen im Stau festhängen? Campus Reporter Nils Birschmann hat dazu den Experten Prof. Alexander Zipf der Universität Heidelberg befragt.
Der Beitrag erschien in der Sendereihe "Campus-Report" - einer Beitragsreihe, in der über aktuelle Themen aus Forschung und Wissenschaft der Universitäten Heidelberg, Mannheim, Karlsruhe und Freiburg berichtet wird. Zu hören ist "Campus-Report" montags bis freitags jeweils um ca. 19.10h im Programm von Radio Regenbogen. (Empfang in Nordbaden: UKW 102,8. In Mittelbaden: 100,4 und in Südbaden: 101,1
Zipf zipped
No full textIn this paper, I provide a quantitative review of the empirical literature on Zipf's law for cities; the meta-analysis combines 515 estimates from 29 studies. I find that the combined estimate of the Zipf coefficient is significantly larger than 1.0. This finding implies that cities are on average more evenly distributed than suggested by (a strict interpretation of) Zipf's law. I also identify several features that account for differences across the individual point estimates. --Zipf's law,size distribution of cities,rank size rule,meta-analysis
HeiGIT
No full textSmartphones können alles - man kann damit sogar telefonieren. Viel spannender sind inzwischen allerdings die Unmengen an Daten, die unsere mobilen Geräte jede Minute produzieren. An der Universität Heidelberg wird jetzt das Heidelberger Institute for Geoinformation Technology (HeiGIT) aufgebaut, das erforscht, was man alles Sinnvolles mit den Geodaten aus Smartphones anfangen kann. Zum Beispiel schnelle Unterstützung von Rettungsteams. Campus Reporter Nils Birschmann hat sich dort umgesehen und sich mit Prof. Dr. Alexander Zipf unterhalten.
Der Beitrag erschien in der Sendereihe "Campus-Report" - einer Beitragsreihe, in der über aktuelle Themen aus Forschung und Wissenschaft der Universitäten Heidelberg, Mannheim, Karlsruhe und Freiburg berichtet wird. Zu hören ist "Campus-Report" montags bis freitags jeweils um ca. 19.10h im Programm von Radio Regenbogen. (Empfang in Nordbaden: UKW 102,8. In Mittelbaden: 100,4 und in Südbaden: 101,1
Prof. Dr. Alexander Zipf Spatio-Temporal Data Modelling for "4D"-Databases
No full textConventional GIS are usually quite static, as they do not cover dynamic aspects of geo-objects in their data model. The information on the modeled domain is usually separated into model of geometric space (2D/3D) and thematic aspects (attributes). But if someone wants to develop a system that is capable of modeling objects of the environment including their history, presenc
Measuring and modelling Internet diffusion using second level domains: the case of Italy
No full textThe last 10 years witnessed an exponential growth of the Internet. According to Hobbes' Internet Timeline, the Internet hosts are about 93 million, while in 1989 they were 100,000. The same happens for second level domain names. In July 1989 the registered domains were about 3,900 while they were over 2 million in July 2000. This paper reports about the construction of a database containing daily observations on registrations of second level domain names underneath the it ccTLD in order to analyse the diffusion of Internet among families and businesses. The section of the database referring to domains registered by individuals is analysed. The penetration rate over the relevant population of potential adopters is computed at highly disaggregated geographical level (province). A concentration analysis is carried out to investigate whether the geographical distribution of Internet is less concentrated than population and income suggesting a diffusive effect. Regression analysis is carried out using demographic, social, economic and infrastructure indicators. Finally we briefly describe the further developments of our research. At the present we are constructing a database containing domains registered by firms together with data about the registrants; the idea is to use this new database and the previous one in order to check for the existence of power laws both in the number of domains registered in each province and in the number of domains registered by each firm.Domain names, Internet metrics, Diffusion, Power laws, Zipf s law
ZIPFFIT: stata module to fit the Zipf distribution or the Zipf-Mandelbrot distribution by maximum likelihood. Stata program archived at Boston college’s software statistics components archive
No full textzipffit fits the 1 parameter Zipf distribution or the two parameter Zipf-Mandelbrot distribution by ML using a right truncated zeta distribution
Comparison of Simulated Fast and Green Routes for Cyclists and Pedestrians
No full textRoutes with a high share of greenery are attractive for cyclist and pedestrians. We analyze how strongly such green routes differ from the respective fast routes using the openrouteservice. Greenness of streets was estimated based on OpenStreetMap data in combination with Sentinel-II imagery, 3d laser scan data and administrative information on trees on public ground. We assess the effect both at the level of the individual route and at the urban level for two German cities: Dresden and Heidelberg. For individual routes, we study how strongly green routes differ from the respective fast routes. In addition, we identify parts of the road network which represent important green corridors as well as unattractive parts which can or cannot be avoided at the cost of reasonable detours. In both cities, our results show the importance of urban green spaces for the provision of attractive green routes and provide new insights for urban planning by identifying unvegetated bottlenecks in the street network for which no green alternatives exist at this point
Zipf's Law in Passwords
No full textDespite three decades of intensive research efforts, it remains an open question as to what is the underlying distribution of user-generated passwords. In this paper, we make a substantial step forward toward understanding this foundational question. By introducing a number of computational statistical techniques and based on 14 large-scale data sets, which consist of 113.3 million real-world passwords, we, for the first time, propose two Zipf-like models (i.e., PDF-Zipf and CDF-Zipf) to characterize the distribution of passwords. More specifically, our PDF-Zipf model can well fit the popular passwords and obtain a coefficient of determination larger than 0.97; our CDF-Zipf model can well fit the entire password data set, with the maximum cumulative distribution function (CDF) deviation between the empirical distribution and the fitted theoretical model being 0.49%similar to 4.59% (on an average 1.85%). With the concrete knowledge of password distributions, we suggest a new metric for measuring the strength of password data sets. Extensive experimental results show the effectiveness and general applicability of the proposed Zipf-like models and security metric.National Key Research and Development Plan [2016YFB0800603, 2017YFB1200704]; National Natural Science Foundation of China [61472016, 61472083]SCI(E)ARTICLE112776-27911
Towards the Statistical Analysis and Visualization of Places (Short Paper)
No full textThe concept of place recently gains momentum in GIScience. In some fields like human geography, spatial cognition or information theory, this topic already has a longer scholarly tradition. This is however not yet completely the case with statistical spatial analysis and cartography. Despite that, taking full advantage of the plethora of user-generated information that we have available these days requires mature place-based statistical and visualization concepts. This paper contributes to these developments: We integrate existing place definitions into an understanding of places as a system of interlinked, constituent characteristics. Based on this, challenges and first promising conceptual ideas are discussed from statistical and visualization viewpoints
Zipf's law, 1/f noise, and fractal hierarchy
No full textFractals, 1/f noise, and Zipf's laws are frequently observed within the natural living world as well as in social institutions, representing three signatures of complex systems. All these observations are associated with scaling laws and therefore have created much research interest in many diverse scientific circles. However, the inherent relationships between these scaling phenomena are not yet clear. In this paper, theoretical demonstration and mathematical experiments based on urban studies are employed to reveal the analogy between fractal patterns, 1/f spectra, and the Zipf distribution. First, the multifractal process empirically suggests the Zipf distribution. Second, a 1/f spectrum is mathematically identical to Zipf's law. Third, both spectra and Zipf's law can be converted into a self-similar hierarchy. Fourth, fractals, 1/f spectra, Zipf's law can be rescaled with similar exponential laws and power laws. The self-similar hierarchy is a more general scaling method which can be used to unify different scaling phenomena and rules in both physical and social systems such as cities, rivers, earthquakes, fractals, 1/f noise, and rank-size distributions. The mathematical laws of this hierarchical structure can provide us with a holistic perspective of looking at complexity and complex systems. (C) 2011 Elsevier Ltd. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000300595500007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Mathematics, Interdisciplinary ApplicationsPhysics, MultidisciplinaryPhysics, MathematicalSCI(E)EI8ARTICLE163-734
- …
