| 1. |
- Ceccato, Vania, 1968-, et al.
(författare)
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A new information theoretical measure of global and local spatial association
- 2002
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Ingår i: The Review of Regional Research. - 0173-7600. ; 22:1, s. 13-40
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Tidskriftsartikel (refereegranskat)abstract
- In this paper a new measure of spatial association, the S statistics, is developed.The proposed measure is based on information theory by defininga spatially weighted information measure (entropy measure) that takes thespatial configuration into account. The proposed S-statistics has an intuitiveinterpretation, and furthermore fulfils properties that are expected from anentropy measure. Moreover, the S statistics is a global measure of spatialassociation that can be decomposed into Local Indicators of Spatial Association(LISA). This new measure is tested using a dataset of employmentin the culture sector that was attached to the wards over Stockholm Countyand later compared with the results from current global and local measuresof spatial association. It is shown that the proposed S statistics share manyproperties with Moran’s I and Getis-Ord Gi statistics. The local Si statisticsshowed significant spatial association similar to the Gi statistic, but has the advantage of being possible to aggregate to a global measure of spatialassociation. The statistics can also be extended to bivariate distributions.It is shown that the commonly used Bayesian empirical approach can beinterpreted as a Kullback-Leibler divergence measure. An advantage of Sstatisticsis that this measure select only the most robust clusters, eliminatingthe contribution of smaller ones composed by few observations and that mayinflate the global measure.
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| 2. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
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Modeling of tensile index using uncertain data sets
- 2020
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 35:2, s. 231-242
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this investigation is to analyze and model tensile index. Two approaches are used, one based on training and validation data, while the other novel approach tests models using all possible combinations of data points. This approach is focused on small data sets which have here been obtained from nineteen pulp samples at different refining conditions in a full-scale TMP production line with a CD-76 refiner as a primary stage. From each pulp sample twenty handsheet strips for tensile index measurements were performed. Initially, specific energy and the external variables (dilution water feed rates and plate gaps) are used as predictors in a modeling approach based on an adjusted R 2 {R^{2}} approach. Thereafter, the resulting models are compared with a combination of specific energy and internal variables (primarily consistencies) obtained from temperature measurements inside the refining zones using a soft sensor concept. It is found that specific energy and internal variables as predictors outperform the external variables when estimating tensile index.
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| 3. |
- Bengtsson, Fredrik, 1989, et al.
(författare)
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On the modeling of pulp properties in CTMP processes
- 2021
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Ingår i: Nordic Pulp and Paper Research Journal. - : Walter de Gruyter GmbH. - 2000-0669 .- 0283-2631. ; 36:2, s. 234-248
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Tidskriftsartikel (refereegranskat)abstract
- The goal of this paper is to model the pulp properties fiber length, shives width and freeness. This will be done utilizing specific energy, flat zone inlet consistency and the internal variables, consistencies and fiber residence times estimated from refining zone soft sensors. The models are designed using more than 3600 hours of data from a RGP82CD refiner. The pulp properties are sampled using a measurement device positioned after the latency chest. Such measurements are noisy and irregularly sampled which opens for a number of challenges to overcome in modeling procedures. In this paper it is shown that the models for shives width and fiber length are capable of predicting most of the major dynamics. However, for freeness no reliable linear models can be derived. When estimating fiber length, the specific energy together with flat zone inlet consistency, fiber residence times and the consistency in the conical zone were the dominant inputs. For shives width it was found that a similar set of inputs resulted in the best models, except that the consistencies during normal process conditions did not significantly influence shives width. Furthermore, fiber residence times were shown to have considerably more pronounced impact on fiber length compared with shives width estimates.
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| 4. |
- Berghauser Pont, Meta, 1972, et al.
(författare)
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PST
- 2019
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Annan publikation (mjukvara/multimedium) (övrigt vetenskapligt/konstnärligt)abstract
- PST is a tool for performing space syntax and regular accessibility analyses. It currently consists of two main parts - a C++ and Python library called Pstalgo and a plugin for the desktop application QGIS.PST is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. The GNU General Public License is intended to guarantee your freedom to share and change all versions of a program--to make sure it remains free software for all its users.For latest download visit either the Chalmers publication page, or find "Releases" on the Github page.
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| 5. |
- Blom Västberg, Oskar, 1987-, et al.
(författare)
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A joint between-day and within-day activity based travel demand with forward looking individuals
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Including day-to-day planning to account for systematic variability in activity participation has the potential to further improve travel demand models. This paper introduce a dynamic discrete choice model of day-to-day and within-day planning in a joint framework. No model up to date jointly treats within-day and day-to-day planning with individuals that take future days into account. The model is estimated using a combination of a small survey with week long data and a larger single day travel survey. A static, myopic and forward looking version of the model is estimated. There is a big improvement in model fit when moving from a static to a dynamic model, but allowing forward-looking behaviour gives a relatively small additional improvement. As a policy test, grocery stores are closed on Sundays. The myopic model predicts that people as a consequence will shop more on Mondays-Thursdays and therefore unintuitively also less on Saturdays. The forward looking model also predicts increased shopping on weekdays but mainly that people will shop more on Saturdays anticipating that stores are closed on Sundays.
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| 6. |
- Blom Västberg, Oskar, 1987-, et al.
(författare)
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Discount factors greater than or equal to one in infinite horizon dynamic discrete choice models
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, the theory on infinite horizon DDCM's is extended to allow for discount factors greater than or equal to one. The proposed methods are applied to Rust's (1987) bus engine replacement model, where a discount factor of 1.075 is identified using grid search. The infinite horizon problem with and without a terminal state are treated separately. Sufficient conditions are given for the existence of solutions to Bellman's equation in the terminal state problem and to a normalized version of Bellman's equation in the non-terminal state setting. If a terminal state exists, acting according to Bellman's equation still yields the maximum expected total utility under derived conditions on the one-stage utility functions and reachability of the terminal state. In the non-terminal state problem, $\beta=1$ implies that individuals maximize the average cost per stage, but for $\beta>1$ no rationale for acting according to Bellman's equation, even when it has a solution, has been found.
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| 7. |
- Dharmowijoyo, Dimas B. E., et al.
(författare)
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Analysing the complexity of day-to-day individual activity-travel patterns using a multidimensional sequence alignment model : A case study in the Bandung Metropolitan Area, Indonesia
- 2017
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Ingår i: Journal of Transport Geography. - : Elsevier BV. - 0966-6923 .- 1873-1236. ; 64, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Using a panel regression model and a multidimensional three-week household time-use and activity diary, this study analyses the complexity of the day-to-day variability in individuals' activity-travel patterns by applying a multidimensional sequence alignment model. It is found that the variability between weekend and weekday pairs is much greater than between weekday-weekday pairs or weekend-weekend pairs. The variability of other household members' activity-travel patterns is found to significantly influence an individual's activity-travel patterns. The results also show that the variability in the activity-travel patterns of workers and students is greater when conducting a particular discretionary activity on weekdays. Due to performing discretionary activities more often and for longer, non-workers tend to have more predictable activity-travel patterns. Undertaking multitasking activities within different activities on weekdays significantly impacted the different degrees of variability in an individual's activity-travel patterns. Having different health and built environment characteristics also corresponds with different degrees of predictability of the activity-travel patterns, particularly in the worker/student case.
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| 8. |
- Eriksson, Karin, 1976, et al.
(författare)
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Pre-study on the establishment of a research collaboration between industrial energy systems and process control at Chalmers
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the project described in this report has been to create a platform for collaboration between the research areas of industrial energy systems and process control at Chalmers. The authors of this report, belonging to the division of Heat and Power Technology, the Automatic control group and to CIT Industriell Energi, are convinced that a close collaboration between these areas could generate benefits for the process industry including •Improved efficiency with respect to energy•Improved opportunities to ensure satisfying operability•Improved process stability and product uniformity•Intensified utilization of available process equipment•Increased profitabilityIn accordance with the project scope, an inventory of relevant academic literature and of past and ongoing activities within the relevant research community has been conducted. Firstly, this inventory recognizes that researchers at Lehigh University (US), NTNU (Norway) and Carnegie Mellon University (US) have been strongly involved in the establishment of a research field commonly referred to as Integrated design and control. It is found that the research questions that are in the interest of the project partners largely can be attributed to this field. Other related labels used, and investigated as part of the project, are plant-wide control and heat exchanger network control. In a specific section of the report, definitions of important terms like operability, controllability and flexibility are given and commented on. Secondly, international research groups of special interest that has been identified are presented. In this category, I2C2 at University of Auckland and CAPEC at Technical University of Denmark can be mentioned. Relevant publications of the above mentioned research groups and their associates have been studied and are commented on in the report. Special emphasize has been put on review papers and on recent publications. Furthermore, the project has mapped the competences, experience and interest of the project partners. On this basis, the following keywords were identified:•Retrofit•Bio-based processes•Pulp and paper industry•Real life case studies•Industrial co-operation•Economic evaluation•Simulation•Scale up challengesThis list was used during discussions on research questions and project ideas for future collaboration. This project has provided the partners an opportunity to obtain deeper insight into each other’s knowledge and experiences, and, moreover, research areas of common interest have been recognized. To further develop the collaboration, the next step seems to imply joint participation in specific research projects. Research questions of interest and ideas for future projects are presented in the full report. This relates to the prevailing possibilities to apply for research grant - an issue that is addressed lastly in this report. In relation to this it should be noted that there is a program on Industrial Process Automation, supported by Vinnova, the Swedish Energy Agency and Formas, that is soon to be launched. A strategy for monitoring calls from this program as well as other relevant programs was formulated. As a result of the work in this project, it has also been possible to formulate proposals for two specific PhD-student projects within the Preem-Chalmers cooperation. These proposals take the outcome of this project into account and include opportunities to further develop the collaboration between industrial energy systems and process control at Chalmers.
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| 9. |
- Franklin, Joel P., et al.
(författare)
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Traveller Responses to the Stockholm Congestion Pricing Trial: Who Changed, Where Did They Go, and What Did It Cost Them?
- 2016
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Ingår i: Travel Demand Management and Road User Pricing. - : Taylor and Francis. ; , s. 215-238
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Among transport economists and traffic planners, congestion pricing has long been advocated as an efficient means to reduce road congestion. Yet, up until recent years, the idea had rarely been implemented, with Singapore and Trondheim the only examples of congestion pricing systems that vary by time of day.2 In the last few years, however, new congestion pricing systems have been introduced in various forms, with London and Stockholm being the most ambitious systems in the sense that the congestion charges apply to the entire urban core. With the Stockholm system now in place, we have a chance to measure some real effects of congestion pricing on daily travel patterns.
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| 10. |
- Fredriksson, Joel, et al.
(författare)
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Analyzing non-linear contributions to predictive performance in a neural network based scheduling model
- 2023
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Ingår i: Proceedings 14th International Conference on Ambient Systems, Networks and Technologies Networks, ANT 2023 and The 6th International Conference on Emerging Data and Industry 4.0, EDI40 2023. - : Elsevier BV. ; , s. 680-685
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Konferensbidrag (refereegranskat)abstract
- This paper aims to investigate whether increasing non-linear opportunities in a neural network-based scheduling model improves its predictive performance. More specifically, this paper experiments on a trip distribution model that is part of an activity-based scheduling model called Skyline-seqNN from the ongoing thesis A neural network scheduling model. The motivation behind that model s proposed structure is to lay the groundwork for a neural network discrete choice model (DCM) that achieves to model travel demand on a detailed level while also being suitable for experimental analysis. Similar to a four-step model framework in the sequential aspect, the model system from the referenced paper utilizes the three sub-models; trip generation, trip distribution, and mode choice using a utility-maximizing micro-simulation approach. The trip generation model first decides whether, at every 10-minute interval between 05:00 am and 11:00 pm, an individual in the next time step should stay and continue the current activity or take an activity-defined trip. The distribution and mode choice models are used whenever a trip is selected. The trip distribution model decides the trip s destination by evaluating travel times and land use descriptions of each zone. The mode choice model learns the probability distribution of modes given each mode s travel time to the selected destination zone. Tests performed in this paper show how successive non-linear opportunities between input features in the trip distribution model increase its predictive performance. The data used for training and evaluation comes from a travel questionnaire from 2015 per-formed in Stockholm containing 10819 individuals and days.
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