30 results on '"Kochan, B."'
Search Results
2. Presentation and evaluation of an integrated model chain to respond to traffic- and health-related policy questions
- Author
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Lefebvre, W., Degrawe, B., Beckx, C., Vanhulsel, M., Kochan, B., Bellemans, T., Janssens, D., Wets, G., Janssen, S., de Vlieger, I., Int Panis, L., and Dhondt, S.
- Published
- 2013
- Full Text
- View/download PDF
3. Assessing the environmental impact associated with different trip purposes
- Author
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Beckx, C., Lefebvre, W., Degraeuwe, B., Vanhulsel, M., Kochan, B., Bellemans, T., Dhondt, S., and Int Panis, L.
- Published
- 2013
- Full Text
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4. Unit cell calculations under fully characterized stress states
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Kochan, B., Tekoglu, C., Kochan, B., and Tekoglu, C.
- Abstract
The available numerical methods for performing finite element unit cell calculations under stress states evolving in a predefined manner restrict the most general stress state to a single shear stress component superimposed on three normal stress components. The present study builds on and extends state of the art such that the behavior of a unit cell under the most complex stress states, comprising three shear and three normal stress components, can be explored. The proposed method is implemented in the commercial finite element software Abaqus. Three-dimensional cubic unit cells containing either a void or a particle at the center and subjected to various stress states showed that the developed method is accurate and computationally efficient. Furthermore, simulations using voided unit cells demonstrate that ductile failure is an anisotropic process, with anisotropy intensifying in the presence of shear loads. That is, void growth and strain localization leading to ductile fracture are influenced by the relative ratios of all shear stress components as well as the stress triaxiality and the Lode parameter.
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- 2022
5. Nachweis von Hepatitis-C-Virus-RNA in Gerinnungspräparaten
- Author
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Geulen, O., Kupfer, B., Brackmann, H.-H., Kochan, B., Schneweis, K. E., Matz, B., Kaiser, R., Scharrer, Inge, editor, and Schramm, Wolfgang, editor
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- 1998
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6. Neue Aspekte in der Diagnostik der HCV-Infektion bei Hämophilen
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Jonas, M., Kaiser, R., Simmonds, R., Lechmann, M., Spengler, U., Oldenburg, J., Brackmann, H. H., Kochan, B., Schneider, A., Schneweis, K. E., Matz, B., Scharrer, Inge, editor, and Schramm, Wolfgang, editor
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- 1996
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7. Charakterisierung der HCV-Infektion bei Hämophilen
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Jonas, M., Kaiser, R., Simmonds, P., Oldenburg, J., Brackmann, H. H., Kochan, B., Scholt, B., Lechmann, M., Spengler, U., Schneweis, K. E., Matz, B., Scharrer, Inge, editor, and Schramm, Wolfgang, editor
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- 1994
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8. Influence of sous vide technology on various types of poultry meat
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Pasichnyi, V., primary, Garmash, D., additional, Ramik, O., additional, and Kochan, B., additional
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- 2018
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9. Investigating Pedestrian Walkability using a Multitude of Seoul Data Sources
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Lee, Won, Ectors, W, Bellemans, T, Kochan, B, Janseens, D, Wets, G, Choi, K, Joh, C-H, Lee, Won, Ectors, W, Bellemans, T, Kochan, B, Janseens, D, Wets, G, Choi, K, and Joh, C-H
- Abstract
Currently walking is a multidisciplinary and emerging point of attention for urban sustainability and for ensuring the quality of pedestrian environments. In order to understand pedestrian behaviour, walkability researches estimate the factors which affect the level of pedestrian satisfaction. Past studies focused on the relationship between environmental factors and pedestrian behavioural outcomes. In this study, we developed pedestrian satisfaction multinomial logit models using various datasets, examining the relative impact of five differently themed sets of attributes: personal, walk-facilities, land-use, pedestrian volumes, and weather-related variables. The results show that the personal variability attributes were selected as most significant. We investigated effects of personal variability, such as the spatial cognition level and travel purpose, and detailed effects of environmental features. In addition, crowdedness, land-use types, and residential information were investigated. The results from this study offer contributions by providing evidence of the importance of personal and contextual variables in influencing the pedestrian walkability.
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- 2018
10. Optimizing Copious Activity Type Classes based on Classification Accuracy and Entropy Retention
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Ectors, W, Reumers, S, Lee, WD, Kochan, B, Janssens, D, Bellemans, T, Wets, G, Ectors, W, Reumers, S, Lee, WD, Kochan, B, Janssens, D, Bellemans, T, and Wets, G
- Abstract
Despite the advantages, big transport data are characterized by a considerable disadvantage as well. Personal and activity-travel information are often lacking, making it necessary to deduce this information with data mining techniques. However, some studies predict many unique activity type classes (ATCs), while others merge multiple activity types into larger ATCs. This action enhances the activity inference estimation, but destroys important activity information. Previous studies do not provide a strong justification for this practice. An objectively optimized set of ATCs, balancing model prediction accuracy and preserving activity information from the original data, becomes essential. Previous research developed a classification methodology in which the optimal set of ATCs was identified by analyzing all possible ATC combinations. However, for the US National Household Travel Survey (NHTS) 2009 data set which comprises 36 ATCs (home activity excluded), this approach is practically impossible in a finite amount of time since there would be 3.82*10^30 unique combinations. The aim of this paper is to optimize which original ATCs should be grouped into a new class, and this for data sets for which it is impossible or impractical to simply calculate all ATC combinations. The proposed method defines an optimization parameter (based on classification accuracy and information retention) which is maximized in an iterative search algorithm. The optimal set of ATCs for the NHTS 2009 data set was determined. A comparison finds that this optimum is considerably better than many expert opinion activity type classification systems. Convergence was confirmed and performance gains were benchmarked.
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- 2018
11. Vernieuwing stedelijke verkeersmodellen: wij raken nooit uitgeleerd!
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Clerx, W., Romph, E. de, and Kochan, B.
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2016 Urban Mobility & Environment ,SUMS - Sustainable Urban Mobility and Safety ,Traffic ,Urbanisation ,ELSS - Earth, Life and Social Sciences ,Mobility & Logistics - Abstract
De grote steden in Nederland worden de komende jaren geconfronteerd met een toenemende groei. Dit vergt nu reeds beslissingen over de inrichting van de stad. Voor de onderbouwing van deze beslissingen worden meestal verkeersmodellen gebruikt. Echter, veel vragen die bestuurders op dit moment hebben kunnen onvoldoende beantwoord worden met de huidige modellen. Met name als het gaat om nieuwe ontwikkelingen zoals e-bikes, auto-delen, autonome auto’s en MaaS. Hierdoor wordt nu nog teruggegrepen op experimenten. De potentie van sommige van deze ontwikkelingen is echter zo groot en zo ingrijpend dat de behoefte aan modellen die hier inzicht in verschaffen nog steeds groot is. Om hier grip op te krijgen moeten die modellen wel aan een aantal eisen voldoen. Ze moeten: • Gedesaggregeerd zijn (incl. life-style-achtige kenmerken) en daarmee meer grip op individueel gedrag geven. • Ketenverplaatsingen kunnen modelleren, omdat verplaatsing complexer worden en fietsen en openbaar vervoer belangrijker worden om de leefbaarheid van steden te borgen. Door de verschuiving van “auto-faciliteren” naar leefkwaliteit is er een grotere behoefte aan integrale modellen waarin de impact op bereikbaarheid, leefbaarheid, gezondheid en economische vitaliteit integraal beoordeelt kunnen worden. Agent of Activity Based Modellen hebben de potentie om te voldoen aan deze eisen en zouden de toekomstige generatie modellen kunnen vormen. Het is echter niet eenvoudig om de huidige generatie van geaggregeerde stedelijke modellen zomaar te vervangen voor Activity Based Modellen (ABM). Er zijn weliswaar een aantal academische pilots geweest maar er is nog nooit een volledig ABM voor een stad gebouwd. De Gemeente Rotterdam en TNO zijn de eerste stappen aan het zetten om zo’n model te maken. Als startpunt wordt hiervoor FEATHERS gebruikt, een ABM ontwikkeld aan de Universiteit van Hasselt. Alle stappen voor de bouw van zo’n model worden doorlopen zodat ervaring wordt opgebouwd en inzicht wordt verkregen of ABM deze beloftes kan waarmaken. De eerste ervaringen leren ons dat de potentie groot is, maar ook dat er nog een aantal problemen opgelost moeten worden, zoals de omgang met extern verkeer, de inter-huishoud relaties en de nauwkeurigheid van de dagboekjes. Om ABM in Nederland echt van de grond te tillen is het van belang dat de Nederlandse steden, de centrale overheid en de kennisinstellingen hierin samen optrekken. Dit maakt het mogelijk om grotere stappen gezamenlijk te zetten en te borgen dat deze kennis en technologie in de praktijk toegepast gaat worden. Dit is van groot belang om de steden te ondersteunen met de juiste instrumenten gezien de transities de ze de komende decennia gaan doormaken.
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- 2017
12. Developing an optimised activity type annotation method based on classification accuracy and entropy indices
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Ectors, W, Reumers, S, Lee, WD, Choi, K, Kochan, B, Janssens, D, Bellemans, T, Ectors, W, Reumers, S, Lee, WD, Choi, K, Kochan, B, Janssens, D, and Bellemans, T
- Abstract
The generation of substantial amounts of travel and mobility related data has spawned the emergence of the era of big data. However, this data generally lacks activity-travel information such as trip purpose. This deficiency led to the development of trip purpose inference (activity type imputation / annotation) techniques, of which the performance depends on the available input data and the (number of) activity type classes to infer. Aggregating activity types strongly increases the inference accuracy and is usually left to the discretion of the researcher. As this is open for interpretation, it undermines the reported inference accuracy. This study developed an optimised classification methodology by identifying classes of activity types with an optimal balance between improving model accuracy, and preserving activity information from the original data set. A sensitivity analysis was performed. Additionally, several machine learning algorithms are experimented with. The proposed method may be applied to any study area.
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- 2017
13. Field evaluation of personal digital assistant enabled by global positioning system: impact on quality of activity and diary data
- Author
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Bellemans, T., Kochan, B., Janssens, D., Wets, G., Timmermans, H.J.P., Stopher, P., and Urban Planning and Transportation
- Abstract
Tom Bellemans, Bruno Kochan, Davy Janssens, Geert Wets and Harry Timmermans (2008), ‘Field Evaluation of Personal Digital Assistant Enabled by Global Positioning System: Impact on Quality of Activity and Diary Data’, Transportation Research Record: Journal of the Transportation Research Board, No. 2049, Washington, DC, USA: Transportation Research Board, National Academy of Sciences, 136–43
- Published
- 2016
14. PARKAGENT: sensitivity analysis & integration with FEATHERS
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Khaliq, A., Kochan, B., van der Waerden, P.J.H.J., Janssens, D., Khaliq, A., Kochan, B., van der Waerden, P.J.H.J., and Janssens, D.
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- 2016
15. Faces of migration: migrants and the transformation of Amsterdam
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Kloosterman, R.C., Kochan, B., and Geographies of Globalizations (GoG, AISSR, FMG)
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- 2014
16. Validation of Activity-based Travel Demand Model using Smart-card Data in Seoul, South Korea
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Cho, S, Lee, WD, Hwang, J-H, Kochan, B, Knapen, L, Bellemans, T, Choi, K, Joh, C-H, Cho, S, Lee, WD, Hwang, J-H, Kochan, B, Knapen, L, Bellemans, T, Choi, K, and Joh, C-H
- Abstract
This study aims to validate an activity-based travel demand model, FEATHERS, using smart-card data which is collected in Seoul, South Korea, and to discuss some limits and challenges in the prediction of public traffic demands. To achieve the goal, global/local trip pattern indices and a hot-spot analysis were applied for the validation test as a comparison method in this study. Using those methods, the public traffic demands predicted by the simulation in the study area were evaluated comparing with ones in the smart-card data. As a result, FEATHERS Seoul shows the enough performance in predicting the global pattern of the public traffic demands, but a low performance in a local pattern, particularly in some areas with a mixture land-use type and/or a frequent public transit. This is because the current model does not handle such a complicate type of land-use and also a multi-modal trip in the simulation process. In conclusion, this study addressed the limits of the current model through the validation test using smart-card data and suggested some solution to the improvement in the specific models As a future work, we will apply smart-card data for the validation of the models operated in FS, such as a location choice model and a trip mode choice model.
- Published
- 2015
17. Assessing the Marginal Impact of a Trip on Population Exposure to Air Pollution
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Beckx, C., Lefebvre, W., Degraeuwe, B., Vanhulsel, M., Dhondt, S., Kochan, B., Bellemans, T., Jansen, S., Int Panis, L., and De Vlieger, I.
- Abstract
Purpose: There are different reasons to assume that not every vehicle kilometre yields the same environmental impact. For instance, some vehicle kilometres are driven at high speeds on highways, while others are driven at low speeds in urban environments. This will have an impact on the resulting exhaust missions. Furthermore, the timing of a trip determines its impact on the resulting concentration levels. Pollutants emitted during trips at night will have a larger impact on the ground-level concentrations than emissions exhausted during the day, due to the greater atmospheric stability. And, concerning the impact on exposure, emissions produced in cities will affect a larger number of people than emissions exhausted in sparsely populated areas. These aspects are examined in this paper using an integrated model chain involving an activity based traffc demand model (to assess people's travel behavior), an emission model (to convert the trips into emissions) and a pollutant concentration module(to stimulate detailed concentration maps and assess the impact of each trip on the resulting concentration level). By combining the model output with detailed population information, the marginal impact of a trip on the population exposure to NO2 was assessed. Results demonstrate that not every vehicle kilometre and not every trip motive yields the same impact on the population exposure.
- Published
- 2012
18. Integration of population mobility in the evaluation of air quality measures on local and regional scales
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Dhondt, S., primary, Beckx, C., additional, Degraeuwe, B., additional, Lefebvre, W., additional, Kochan, B., additional, Bellemans, T., additional, Int Panis, L., additional, Macharis, C., additional, and Putman, K., additional
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- 2012
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19. Making greener cities - a practical guide. Development of urban green spaces to improve the quality of life in cities and urban regions
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Smaniotto Costa, C., Morgenstern, D., Kasperidus, H.D., Mathey, J., Thiele, K., Caserio, M., Grayson, N., Coles, R., Wohlleber, S., Farcher, S., Rößler, S., Niedetzky, A., Weiße, A., Bognar, A., Edlich, B., Müller, B., Kochan, B., Rodenburg, C., Eichhorn, D., Goede, E., van Leeuwen, E., Udvarheyi, G., Gaggero, G., Varese, G., Ruzzeddu, G., Kasperidus, Hans Dieter, Kunath, I., Niemela, J., Breuste, J., Seidel, K., Nagy, K., Papp, K., Zabó, K., Thiele, Kathleen, Kettner, K., Mikle, K., Baumgart, M., Gallina, N., Gattuli, O., Nijkamp, P., Somogyi, R., Wohlleber, Sandra, Gamboni, S., Venn, S., Scharpen, S., Levent, T.B., Bertelli, U., Kovacs, Z., Smaniotto Costa, C., Morgenstern, D., Kasperidus, H.D., Mathey, J., Thiele, K., Caserio, M., Grayson, N., Coles, R., Wohlleber, S., Farcher, S., Rößler, S., Niedetzky, A., Weiße, A., Bognar, A., Edlich, B., Müller, B., Kochan, B., Rodenburg, C., Eichhorn, D., Goede, E., van Leeuwen, E., Udvarheyi, G., Gaggero, G., Varese, G., Ruzzeddu, G., Kasperidus, Hans Dieter, Kunath, I., Niemela, J., Breuste, J., Seidel, K., Nagy, K., Papp, K., Zabó, K., Thiele, Kathleen, Kettner, K., Mikle, K., Baumgart, M., Gallina, N., Gattuli, O., Nijkamp, P., Somogyi, R., Wohlleber, Sandra, Gamboni, S., Venn, S., Scharpen, S., Levent, T.B., Bertelli, U., and Kovacs, Z.
- Abstract
Das Handbuch des EU-Projektes "URGE - Förderung von Grünflächen zur Verbesserung der Lebensqualität in Städten und urbanen Räumen" bildet eine Synthese von Arbeiten, in die Erfahrungen aus vielen Teilen Europas eingeflossen sind, und präsentiert eine Sammlung von Instrumenten, die im Projekt erarbeitet wurden. Sie wurden gezielt für die Planung städtischen Grüns entwickelt und bieten verschiedene Zugangsweisen sowohl für die Analyse urbaner Grünstrukturen wie für die Bewertung der einzelnen Grünfläche. Anhand gelungener Beispielen u.a. aus den Partner- und Referenzstädten gibt das Handbuch Anleitungen zur Verbesserung der Grünsituation in den Städten. Der Text der gedruckten Version ist in englischer Sprache gehalten, die beiliegende CD ROM enthält die Planungsinstrumente betreffenden Textpassagen in weiteren Sprachen, darunter im Deutschen, bereit.
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- 2004
20. Dynamic Activity-Travel Diary Data Collection Using a GPS-Enabled Personal Digital Assistant
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Kochan, B., primary, Bellemans, T., additional, Janssens, D., additional, and Wets, G., additional
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- 2006
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21. Activity based models for countrywide electric vehicle power demand calculation.
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Knapen, L., Kochan, B., Bellemans, T., Janssens, D., and Wets, G.
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- 2011
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22. Non-linear electrical effects in epitaxial graded-gap CdxHg1−xTe layers
- Author
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Szatkowski, J., primary, Kaczmarski, K., additional, Kochan, B., additional, Sierański, K., additional, and Pawlikowski, J.M., additional
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- 1980
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23. Non-linear electrical effects in epitaxial graded-gap Cd xHg 1− xTe layers
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Szatkowski, J., Kaczmarski, K., Kochan, B., Sierański, K., and Pawlikowski, J.M.
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- 1980
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24. Do Londoners make their own plans?
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Edwards, M., Scanlon, K., and Kochan, B.
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- 2010
25. Implementation and validation of a modeling framework to assess personal exposure to black carbon.
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Dons E, Van Poppel M, Kochan B, Wets G, and Int Panis L
- Subjects
- Adult, Female, Humans, Male, Urbanization, Air Pollutants toxicity, Environmental Exposure, Epidemiologic Methods, Models, Theoretical, Soot toxicity
- Abstract
Because people tend to move from one place to another during the day, their exposure to air pollution will be determined by the concentration at each location combined with the exposure encountered in transport. In order to estimate the exposure of individuals in a population more accurately, the activity-based modeling framework for Black Carbon exposure assessment, AB(2)C, was developed. An activity-based traffic model was applied to model the whereabouts of individual agents. Exposure to black carbon (BC) in different microenvironments is assessed with a land use regression model, combined with a fixed indoor/outdoor factor for exposure in indoor environments. To estimate exposure in transport, a separate model was used taking into account transport mode, timing of the trip and degree of urbanization. The modeling framework is validated using weeklong time-activity diaries and BC exposure as revealed from a personal monitoring campaign with 62 participants. For each participant in the monitoring campaign, a synthetic population of 100 model-agents per day was made up with all agents meeting similar preconditions as each real-life agent. When these model-agents pass through every stage of the modeling framework, it results in a distribution of potential exposures for each individual. The AB(2)C model estimates average personal exposure slightly more accurately compared to ambient concentrations as predicted for the home subzone; however the added value of a dynamic model lies in the potential for detecting short term peak exposures rather than modeling average exposures. The latter may bring new opportunities to epidemiologists: studying the effect of frequently repeated but short exposure peaks on long term exposure and health., (© 2013.)
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- 2014
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26. Evaluating the road safety effects of a fuel cost increase measure by means of zonal crash prediction modeling.
- Author
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Pirdavani A, Brijs T, Bellemans T, Kochan B, and Wets G
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- Humans, Models, Theoretical, Predictive Value of Tests, Risk Assessment, Travel, Accidents, Traffic statistics & numerical data, Automobile Driving statistics & numerical data, Gasoline economics, Safety
- Abstract
Travel demand management (TDM) consists of a variety of policy measures that affect the transportation system's effectiveness by changing travel behavior. The primary objective to implement such TDM strategies is not to improve traffic safety, although their impact on traffic safety should not be neglected. The main purpose of this study is to evaluate the traffic safety impact of conducting a fuel-cost increase scenario (i.e. increasing the fuel price by 20%) in Flanders, Belgium. Since TDM strategies are usually conducted at an aggregate level, crash prediction models (CPMs) should also be developed at a geographically aggregated level. Therefore zonal crash prediction models (ZCPMs) are considered to present the association between observed crashes in each zone and a set of predictor variables. To this end, an activity-based transportation model framework is applied to produce exposure metrics which will be used in prediction models. This allows us to conduct a more detailed and reliable assessment while TDM strategies are inherently modeled in the activity-based models unlike traditional models in which the impact of TDM strategies are assumed. The crash data used in this study consist of fatal and injury crashes observed between 2004 and 2007. The network and socio-demographic variables are also collected from other sources. In this study, different ZCPMs are developed to predict the number of injury crashes (NOCs) (disaggregated by different severity levels and crash types) for both the null and the fuel-cost increase scenario. The results show a considerable traffic safety benefit of conducting the fuel-cost increase scenario apart from its impact on the reduction of the total vehicle kilometers traveled (VKT). A 20% increase in fuel price is predicted to reduce the annual VKT by 5.02 billion (11.57% of the total annual VKT in Flanders), which causes the total NOCs to decline by 2.83%., (Copyright © 2012 Elsevier Ltd. All rights reserved.)
- Published
- 2013
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27. Integrated health impact assessment of travel behaviour: model exploration and application to a fuel price increase.
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Dhondt S, Kochan B, Beckx C, Lefebvre W, Pirdavani A, Degraeuwe B, Bellemans T, Int Panis L, Macharis C, and Putman K
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- Adolescent, Adult, Air Pollution prevention & control, Environmental Policy, Female, Gasoline statistics & numerical data, Humans, Male, Middle Aged, Models, Theoretical, Morbidity, Risk Assessment, Taxes, Transportation statistics & numerical data, Travel psychology, Travel statistics & numerical data, Walking statistics & numerical data, Young Adult, Air Pollution statistics & numerical data, Gasoline economics, Health Impact Assessment, Health Policy, Transportation economics, Travel economics
- Abstract
Transportation policy measures often aim to change travel behaviour towards more efficient transport. While these policy measures do not necessarily target health, these could have an indirect health effect. We evaluate the health impact of a policy resulting in an increase of car fuel prices by 20% on active travel, outdoor air pollution and risk of road traffic injury. An integrated modelling chain is proposed to evaluate the health impact of this policy measure. An activity-based transport model estimated movements of people, providing whereabouts and travelled kilometres. An emission- and dispersion model provided air quality levels (elemental carbon) and a road safety model provided the number of fatal and non-fatal traffic victims. We used kilometres travelled while walking or cycling to estimate the time in active travel. Differences in health effects between the current and fuel price scenario were expressed in Disability Adjusted Life Years (DALY). A 20% fuel price increase leads to an overall gain of 1650 (1010-2330) DALY. Prevented deaths lead to a total of 1450 (890-2040) Years Life Gained (YLG), with better air quality accounting for 530 (180-880) YLG, fewer road traffic injuries for 750 (590-910) YLG and active travel for 170 (120-250) YLG. Concerning morbidity, mostly road safety led to 200 (120-290) fewer Years Lived with Disability (YLD), while air quality improvement only had a minor effect on cardiovascular hospital admissions. Air quality improvement and increased active travel mainly had an impact at older age, while traffic safety mainly affected younger and middle-aged people. This modelling approach illustrates the feasibility of a comprehensive health impact assessment of changes in travel behaviour. Our results suggest that more is needed than a policy rising car fuel prices by 20% to achieve substantial health gains. While the activity-based model gives an answer on what the effect of a proposed policy is, the focus on health may make policy integration more tangible. The model can therefore add to identifying win-win situations for both transport and health., (Copyright © 2012 Elsevier Ltd. All rights reserved.)
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- 2013
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28. Differential expansion of T-cell receptor variable beta subsets after antigenic stimulation in patients with different outcomes of hepatitis C infection.
- Author
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Woitas RP, Sippel M, Althausen EM, Brackmann HH, Kochan B, Matz B, Rockstroh JK, Sauerbruch T, and Spengler U
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- Adolescent, Adult, Aged, Cell Culture Techniques, Cell Division immunology, Cytokines biosynthesis, Female, Hepatitis C Antigens immunology, Humans, Immunologic Memory, Male, Middle Aged, Hepatitis C, Chronic immunology, Receptors, Antigen, T-Cell, alpha-beta blood, T-Lymphocyte Subsets immunology
- Abstract
Persistent antigenic stimulation during chronic hepatitis C may alter the T-cell receptor variable chain beta (TCR BV) repertoire as well as the cytokine responses of hepatitis C virus (HCV)-specific T lymphocytes. We analysed the distribution of the TCR BV subsets 2.1, 3.1, 5.1, 6.1, 8, 13.1, 13.6, 14.1, 17.1, 21.3 in relation to intracytoplasmic expression of interleukin-2, interferon-gamma, interleukin-4 and interleukin-10. Using flow cytometry, CD45RO+ memory T cells of 27 patients with chronic hepatitis C, eight patients with resolved HCV infection and 16 non-HCV-related controls were studied with and without stimulation by the HCV core, NS3, NS4, NS5a and NS5b proteins. Patients with chronic and resolved hepatitis C differed by larger basal TCR BV2.1+, BV6.1+, BV17.1+ and BV21.3+ subsets in chronic hepatitis C, which were correlated to the numbers of T cells with spontaneous interleukin-2 and interferon-gamma production (r=0.51-0.73, P<0.05). Upon HCV-specific stimulation these subsets did not expand, whereas a marked in vitro expansion of TCR BV8+ T cells in response to all HCV proteins was selectively noted in chronic hepatitis C (P<0.05). This expansion of TCR BV8+ memory T cells was significantly correlated to HCV-induced interleukin-10 expression (r=0.58-0.98, P<0.01). Thus, differential involvement of selected TCR BV subsets may be related to the outcome of HCV infection.
- Published
- 2002
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29. Hepatitis C virus infection and genotypes among human immunodeficiency virus high-risk groups in Cameroon.
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Ndjomou J, Kupfer B, Kochan B, Zekeng L, Kaptue L, and Matz B
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- Adolescent, Adult, Aged, Aged, 80 and over, Cameroon epidemiology, Child, Female, Genotype, HIV Antibodies blood, HIV Infections complications, Hepatitis C virology, Hepatitis C Antibodies blood, Humans, Male, Middle Aged, Prevalence, RNA, Viral blood, Risk Factors, HIV Infections epidemiology, Hepacivirus classification, Hepacivirus genetics, Hepatitis C epidemiology, Molecular Epidemiology
- Abstract
Parenteral transmission of HCV is well established but other possible routes such as heterosexual transmission are still questioned. The Central African region is characterised by a high HCV endemicity without any evidence on the route of transmission. The information on HCV genotypes that circulate in this area is also limited and controversial. HIV infection is very frequent in this region and mostly acquired via the heterosexual route. The aim of this work was to investigate the trend of HCV infection and genotypes among HIV high-risk groups from Cameroon. Four hundred eighty-two patients including 229 tuberculosis clinic attendants, 184 sexually transmitted disease clinic attendants, and 69 HIV clinical suspects from another clinic were enrolled. All plasma samples were screened for antibodies to HCV and HCV RNA. Genotypes were assigned by sequencing a 5'UTR amplified fragment. The overall prevalence of HCV markers was 11.6% and a significant increasing trend with respect to age was observed. A proportion of 64.1% (34/53) of HCV antibody positive samples was viraemic. HCV RNA was found in 3 samples that were indeterminate in RIBA 3.0. One was negative in the antibody screening test and the two others were weakly positive. The data on HCV genotypes revealed that genotype 1 was involved in 57% of viraemias, genotype 2 in 24%, while genotypes 4 and 5a accounted for 16 and 3%, respectively. In contrary to the predominance of genotype 4 reported in some African countries and even the neighbouring countries, these data demonstrate clearly that HCV infection in Cameroon is dominated by genotypes 1 and 2. No association was found between the HCV markers and the presence of HIV infection. It is concluded, therefore, that the heterosexual route plays a minor role in HCV transmission in this country., (Copyright 2002 Wiley-Liss, Inc.)
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- 2002
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30. Antigen-specific cytokine response to hepatitis C virus core epitopes in HIV/hepatitis C virus-coinfected patients.
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Woitas RP, Rockstroh JK, Beier I, Jung G, Kochan B, Matz B, Brackmann HH, Sauerbruch T, and Spengler U
- Subjects
- Adult, Aged, CD3 Complex metabolism, Cytokines immunology, Female, Flow Cytometry, HIV Infections immunology, HIV Infections virology, HIV-1 genetics, HIV-1 physiology, Hepacivirus genetics, Hepacivirus physiology, Hepatitis C immunology, Hepatitis C virology, Humans, Immunodominant Epitopes, Ki-1 Antigen metabolism, Lymphocyte Activation, Male, Middle Aged, RNA, Viral blood, T-Lymphocytes immunology, Th1 Cells immunology, Th2 Cells immunology, Viral Core Proteins immunology, Cytokines biosynthesis, Epitopes, T-Lymphocyte immunology, HIV Infections complications, Hepatitis C complications, Hepatitis C Antigens immunology
- Abstract
Objective: Epidemiological data indicate that hepatitis C virus (HCV) infection runs a more rapid and severe course of disease in HIV-coinfected patients, probably because of an altered immune response., Design: We investigated whether HCV-specific cytokine responses are affected by HIV coinfection., Methods: Using triple colour flow cytometry on peripheral blood lymphocytes after stimulation with the four major immunodominant HCV core T cell epitopes, CT1-CT4, we determined intracytoplasmic production of IFN-gamma, IL-2, IL-4, IL-10 and CD30 expression, a putative surrogate marker of type 2 cells. Fifteen patients with asymptomatic HIV/HCV coinfection (group A), 15 patients with chronic HCV infection (group B) and 10 HIV-infected patients without hepatitis C (group C) were included in the study., Results: In group A, HCV antigens induced significantly higher IL-2 and IFN-gamma production than groups B and C (P < 0.05). Groups A and B showed a similar induction of CD30, which was significantly higher than in group C (P < 0.001). Remarkably, in group A HCV antigens induced IL-4 production in addition to IL-10 and IFN-gamma in the CD30 subset, whereas in groups B and C no IL-4 induction was observed in this T cell subset (P < 0.002)., Conclusion: Our data suggest that asymptomatic HIV coinfection importantly alters the HCV-specific cytokine response towards a greater production of proinflammatory type 1 cytokines. Moreover, the antiviral activity of type 1 cytokines may be modified by an increased production of type 2 cytokines in the CD30 subset. The altered cytokine pattern may contribute to the adverse natural course of hepatitis C in HIV coinfection.
- Published
- 1999
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