104,703 research outputs found
Contributions to Workshop Eurobike in Helsinki
No full textIn this report three subjects relevant for the study of bicycle traffic are presented, giving the state of the art in The Netherlands. They were presented at a workshop of Eurobike, a consortium preparing to carry out practically oriented research about bicycle traffic in European urban areas. The general set-up of the National Travel Survey is described. This survey also includes trips made by bicycle. Some details are given about the size of the survey, the change in method to collect the data in 1985 and the response rate. The modal split as a function of trip distance and the distribution function for bicycle traffic are given as examples of results that can be derived from the survey. In the safety part statistics are given about the general fatality rate of cyclists and other modes of traffic. Two studies to determine criteria for the need for separate cycle paths are described. A study proposal for analysing safety and behaviour in tenns of risk for a mix of fast and slow traffic on an arterial is presented. The third subject is the cycle planning model Quo-Vadis that can be used to determine the best possible cycling network and the best allocation of the budget for bicycle facilities. A short description of the model and its required input is presented. The traffic model part can determine cycle intensities over the period 7 AM to 7 PM on every link of the network and the origins and destinations of the flow. The evaluation part can be used to evaluate an existing network and to assess the effect of measures improving the network. The combination of the model with accident data and the determination of yard-sticks for safety can give indications of how to improve safety.Transport and PlanningCivil Engineering and Geoscience
Twentieth Anniversary of the Dakar-Talks
No full text5 A4 pages in pdf formatProf H R Botman, rektor en visekanselierThe original publication is available at http://www.sun.ac.za/university/Management/rektor/speeches.htmlTwentieth Anniversary of the Dakar-Talks, Prof H. R. Botma
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Kwaliteit afwikkeling op vrijliggende fietspaden: Toepassingen van een hindermodel
No full textRapport in opdracht van Rijkswaterstaat, Dienst Verkeerskunde. In dit onderzoek is een simulatiemodel ontwikkeld voor de kwaliteit van de verkeersafwikkeling op vrijliggende fietspaden, zowel voor één- als voor tweerichtigsverkeer. Het kwaliteitscriterium is de mate van hinder of discomfort die gebruikers van het fietspad bij manoeuvres als inhalen en ontmoeten ondervinden. In het model worden drie soorten padgebruikers onderscheiden: solo fietsers, duo fietsers en bromfietsers. Met het model worden de frequenties van de manoeuvres bepaald. Aan de verschillende soorten manoeuvres is een zekere mate van hinder toegekend, afhankelijk van de betrokken partijen en de padbreedte. Deze hoeveelheden hinder en hun onderlinge gewichten zijn verkregen door middel van een enquête onder deskundigen. Op deze manier kan de totale hinder over een wegvak van een zekere lengte per passerende tweewieler worden berekend. In een veldonderzoek zijn op 4 fietspaden van 7h30 tot 18h de gebruikers geënquêteerd en is hen gevraagd naar de hinder die ze ervaren hadden op het zojuist bereden wegvak. Dit is verwerkt tot een verloop van het percentage gehinderden over de tijd van de dag. Tijdens de enquêtes is de intensiteit en samenstelling geregistreerd. Deze is gebruikt als input voor het hindermodel en op deze manier kan men het verloop van de modelhinder over de tijd bepalen. Vervolgens is een relatie gezocht tussen de ervaren en de modelhinder. Op fijne tijdschaal is het niet gelukt een dergelijke relatie te leggen. Op meer globaal niveau is wel een evenredigheidsfactor tussen ervaren hinder en modelhinder vastgesteld. Met behulp hiervan en een gekozen acceptabel percentage gehinderden ajn toelaatbare intensiteiten af te leiden voor de diverse soorten paden en samenstellingen. In het bijzonder het effect van het aandeel bromfietsen en in duo rijdende fietsen op de toelaatbare intensiteiten is bepaald.Transport and PlanningCivil Engineering and Geoscience
Het rij- en inhaalgedrag op versmalde rijstroken
No full textA new measure to improve the traffic performance on particular network parts of motorways during the peak periods substantially, is the 'dynamic carriageway'. This means that there are two or three lanes available for low-density traffic and three or four lanes for high-density traffic, while maintaining the emergency lane. A number of problems arose during the research for the 'dynamic carriageway'. One of them is the lack of clarity about the impacts of narrow lanes on the traffic flow. This is observed in an exploring simulation study with an extended version of the microscopic simulation model MIXIC. This version tries to model the driving and overtaking behaviour on narrow lanes. Because of the lack of quantitative data this proved to be impossible so far. This thesis shows what data is still missing in order to describe the driving and overtaking behaviour on narrow lanes ofmotorways effectively. At the same time a check is performed how missing data could be collected. First of all the extended version ofMIXIC is closely examined. On basis ofthis an impression is obtained of the aspects which are considered to be of importance for describing the driving and overtaking behaviour. Also an impression is obtained of the data which is of importance to describe these aspects. In addition it becomes clear what (quantitative) data is still missing. An additional literature study did hardly yield new (quantitative) data. Nevertheless this study presents some quality information about the missing data. Besides, there is also information presented about other aspects that could be useful to describe the driving and overtaking behaviour. With the obtained knowledge about the overtaking behaviour a model is designed, which describes the choice of a driver whether he executes an overtaking manoeuvre or not. As a result 'overtaking' has been placed into perspective with the processes 'car-following' and 'lane-changing'. After that a model is designed which describes the actions of a driver during a passing manoeuvre. In this second model the driver of the passing vehicle considers, depending on the lane in which he drives, the vehicles and the fixed objects, which are located within a certain longitudinal distance of the passing vehicle. While executing the passing manoeuvre the driver takes decisions about the position and speed of his vehicle. On basis of the collected knowledge ofMIXIC, literature and models so far, a definitive list of missing data is formed. This data relates, amongst other things, to the positions of the vehicles within their lane in relation to moving and fixed objects. It also relates to the (minimal) lateral distances in case the vehicles drive next to each other and the influence of the different characteristics of the vehicles that are involved in the passing manoeuvre. To determine how the necessary data can be collected a comparison is made between a number of instruments. These instruments are a video-observation, the Differential Global Positioning System, an instrumented vehicle and a driving simulator. Finally the instruments video-observation and driving simulator are chosen. With the first instrument drivers are hardly influenced and many observations can be made relative easy and cheap. This way a large quantity of data can be collected about the lateral positions of the vehicles. With the second instrument several aspects can be examined separately, which shows a detailed picture of the course of the passing manoeuvre in terms of position and speed. The use of these instruments is described in two separated methods. Video-observation can be performed on several locations and collects pictures of different combinations of vehicles and fixed objects. Aided by for instance a software package the lateral positions of the vehicles can be determined from the pictures. In successive phases the overtaking manoeuvre can be examined and visualised in detail by a driving simulator. A number of subjects are for that confronted with various situations. Analysis of the recorded data may result in a collection of desired data. If both instruments are used as described, the missing data can be obtained. From this point forward the driving and overtaking behaviour on narrow lanes of motorways can be modelled and validated. After carrying out a part of the research by video-observation on a location with lanes of normal width without the influence of a fixed object (motorway A2) and another part on a location with narrow lanes with the influence of a fixed object (motorway A12), the results show that the lateral position of vehicles is influenced by other vehicles as well as fixed objects as the distance between a fixed object and the roadway. The effect of a fixed object on a vehicle is considerably less than the effect of other vehicles. The effect of one vehicle on the lateral position of another vehicle differs; two passenger cars do influence each other, but a lorry does influence a passenger car to a greater extend. With regard to the distribution of the lateral positions within a lane, it turns out that the distribution in all considered situations is Normal. To be able to predict the separate quantitative effect of the width of the lane and the influence of a fixed object on the lateral positions, a third measurement on a location with narrow lanes without the influence of a fixed object has to be carried out (motorway A27).Transport & PlanningCivil Engineering and Geoscience
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
The construction of Karen Karnak: The multi-author-function
No full textThis thesis is situated within the comparatively recent developments of Web 2.0 and the emergence of interactive WikiMedia, and explores the mode of authorship within a Read/Write culture compared to that of a Read/Only tradition. The hypothesis of this study is that the role of the audience has become merged with the author, and as such, represents new functions and attributes, distinct from a more conventional concept of authorship, in which the roles of audience and author are more separate. Read/Write and participatory culture, as defined by this study, is focused on collaboration, and includes the influences of D.I.Y. culture, Open-Source practices and the production of text by multiple authors. Multi-authorship presents a re-thinking of several concepts which support the notion of the individual author, since the focus of multi-authorship is not on attribution and ownership of a finished text, but on the continued malleability of a text. Modes of multi-authorship, demonstrated in the use of the pseudonyms Alan Smithee and Karen Eliot, represent declarative authors whose names signify multiple origins, whilst concurrently indicating a distinct body of work. The function of these names form an important context to this study, since primary research involves the construction of an experimental mode of multi-authorship utilising WikiMedia technology and the interaction of thirty nine participants, who are invited to create a body of work under the collective pseudonym Karen Karnak. The data generated by this experiment is analysed using aspects of Michel Foucault's author-function to identify and determine power structures inherent in the WikiMedia context. The interplay of power structures, including concepts such as identity, ownership and the body of work, affect the resulting mode of authorship and contribute to the construction of Karen Karnak, suggesting further areas of research into the emerging multi-author
Up scaling of the BDI production
No full textDe begeleider en/of auteur heeft geen toestemming gegeven tot het openbaar maken van de scriptie.
The supervisor and/or the author did not authorize public publication of the thesis.
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