| 1. |
- Andersson, Mats, et al.
(författare)
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Road Friction Estimation
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This project is part of the Swedish IVSS program. The aim of IVSS is to stimulate research and development for the road safety of the future. Road conditions with low friction have been identified as a frequent cause of traffic accidents. Therefore, technology to automaticallydetect changes in road conditions and alert the driver or take proper actions with active driver support systems would be a key contribution to increased road safety.The aim of this project was to investigate the possibilities to estimate the tire to road friction.Three different approaches have been developed and evaluated, from concept to early prototypes in test vehicles. In the first method, the estimation of the coefficient of friction is based on the forces and torques that are produced at the front tires at cornering maneuvers.The second method is based on a physical model of the tire behavior and estimates road friction from information on the forces that are produced at straight driving. The third method is based on an optical sensor that classifies the road surface ahead of the vehicle.The three methods have been successfully evaluated in proving ground and public road tests in summer and winter conditions with different tires, and have been compared with reference measurements. The conclusion is that all three methods can be used for tire to road frictionestimation and are recommended for further development and industrialization.
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| 2. |
- Eppanapelli, Lavan Kumar, 1988-, et al.
(författare)
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Estimation of Liquid Water Content of Snow Surface by Spectral Reflectance
- 2018
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Ingår i: Journal of cold regions engineering. - : American Society of Civil Engineers (ASCE). - 0887-381X .- 1943-5495. ; 32:1
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Tidskriftsartikel (refereegranskat)abstract
- This study measures the spectral reflectance from snow with known liquid water content (LWC) in a climate chamber using two optical sensors, a near-infrared (NIR) spectrometer and a Road eye sensor. The spectrometer measures the backscattered radiation in the wavelength range of 920–1,650 nm. The Road eye sensor was developed to monitor and classify winter roads based on reflected intensity measurements at wavelengths of 980, 1,310, and 1,550 nm. Results of the study suggest that the spectral reflectance from snow is inversely proportional to the LWC in snow. Based on the effect of LWC on the spectral reflectance, three optimum wavelength bands are selected in which snow with different LWCs is clearly distinguishable. A widely used remote sensing index known as the normalized difference water index (NDWI) is used to develop a method to estimate the surface LWC for a given snow pack. The derived NDWI values with respect to the known LWC in snow show that the NDWI is sensitive to the LWC in snow and that the NDWI and LWC are directly proportional. Based on this information, the NDWI is used to estimate the surface LWC in snow from measurements on a ski track using the Road eye sensor. The findings suggest that the presented method can be applied to estimate the surface LWC in order to classify snow conditions potentially for ski track and piste applications.
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| 3. |
- Eppanapelli, Lavan Kumar, 1988-, et al.
(författare)
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Estimation of specific surface area of snow based on density and multispectral infrared reflectance
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Ingår i: Journal of cold regions engineering. - 0887-381X .- 1943-5495.
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a multiple regression method for predicting snow SSA based on multispectral reflectance and snow density. Multispectral near-IR reflectance from snow was measured at wavelengths 980 nm, 1,310 nm and 1,550 nm. In total, 16 different artificially prepared snow samples were investigated using two optical sensors, a spectrometer and a Road eye sensor. Both the sensors measured backscattered radiance from snow and measurements were carried out in a climate chamber. Snow types with variations in physical properties such as grain distribution, surface texture, SSA, density and depth are considered. Variations in snow density were obtained through compaction and aging process. Correlation between the snow density and reflectance is investigated and influence of snow density and multispectral reflectance on snow SSA is also investigated. A generalized linear model is developed to predict the snow SSA with a coefficient of determination equal to 98\%. The preliminary validation of results show that the SSA can be accurately estimated from the density and multispectral reflectance. The model results indicate that the snow density has minor effect on the variations in snow SSA. Results suggest that snow with varying physical properties can be qualitatively characterized based on the presented approach, which is of interest for applications such as winter roads classification and pistes classification.
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| 4. |
- Eppanapelli, Lavan Kumar, 1988-, et al.
(författare)
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Investigation of snow single scattering properties of snow based on first order Legendre phase function
- 2017
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Ingår i: Optics and lasers in engineering. - : Elsevier. - 0143-8166 .- 1873-0302. ; 91, s. 151-159
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Tidskriftsartikel (refereegranskat)abstract
- Angularly resolved bidirectional reflectance measurements were modelled by ap- proximating a first order Legendre expanded phase function to retrieve single scattering properties of snow. The measurements from 10 different snow types with known density and specific surface area (SSA) were investigated. A near infrared (NIR) spectrometer was used to measure reflected light above the snow surface over the hemisphere in the wavelength region 900 nm to 1650 nm. A solver based on discrete ordinate radiative transfer (DISORT) model was used to retrieve the estimated Legendre coefficients of the phase function and a cor- relation between the coefficients and physical properties of different snow types is investigated. Results of this study suggest that the first two coefficients of the first order Legendre phase function provide sufficient information about the physical properties of snow where the latter captures the anisotropic behaviour of snow and the former provides a relative estimate of the single scattering albedo of snow. The coefficients of the first order phase function were com- pared with the experimental data and observed that both the coefficients are in good agreement with the experimental data. These findings suggest that our approach can be applied as a qualitative tool to investigate physical properties of snow and also to classify different snow types.
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| 5. |
- Odelius, Johan, et al.
(författare)
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Industrial internet applications for efficient road winter maintenance
- 2017
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Ingår i: Journal of Quality in Maintenance Engineering. - : Emerald Group Publishing Limited. - 1355-2511 .- 1758-7832. ; 23:3, s. 355-367
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: For the expected increase in the capacity of existing transportation systems and efficient energy utilisation, smart maintenance solutions that are supported by online and integrated condition monitoring systems are required. Industrial Internet is one of the smart maintenance solutions, which enables real-time acquisition and analysis of asset condition by linking intelligent devices with different stakeholdersￜ applications and databases. This paper presents some aspects of Industrial Internet application as required for integrating weather information and floating road condition data from vehicle mounted sensors to enhance effective and efficient winter maintenance.Design/methodology/approach: The concept of real-time road condition assessment using in-vehicle sensors is demonstrated in a case study of a 3.5 km road section located in northern Sweden. The main floating data sources were acceleration and position sensors from a smartphone positioned on the dash board of a truck. Features extracted from the acceleration signal were two road roughness estimations. To extract targeted information and knowledge, the floating data were further processed to produce time series data of the road condition using Kalman filtering. The time series data were thereafter combined with weather data to assess the condition of the road.Findings: In the case study, examples of visualisation and analytics to support winter maintenance planning, execution, and resource allocation were presented. Reasonable correlation was shown between estimated road roughness and annual road survey data to validate and prove the presented results wider applicability.Originality/value: The paper describes a concept of floating data for an industrial internet application for efficient road maintenance. The resulting improvement in winter maintenance will promote dependable, safe and sustainable transportation of goods and people, especially in northern Nordic region with harsh and sometimes unpredictable weather conditions.
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| 6. |
- Andren, Lina J., et al.
(författare)
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Avoiding Arrays of Odd Order by Latin Squares
- 2013
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Ingår i: Combinatorics, probability & computing. - : Cambridge University Press (CUP). - 0963-5483 .- 1469-2163. ; 22:2, s. 184-212
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Tidskriftsartikel (refereegranskat)abstract
- We prove that there is a constant c such that, for each positive integer k, every (2k + 1) x (2k + 1) array A on the symbols 1, ... , 2k + 1 with at most c(2k + 1) symbols in every cell, and each symbol repeated at most c(2k + 1) times in every row and column is avoidable; that is, there is a (2k + 1) x (2k + 1) Latin square S on the symbols 1, ... , 2k + 1 such that, for each i, j is an element of {1, ... , 2k + 1}, the symbol in position (i, j) of S does not appear in the corresponding cell in Lambda. This settles the last open case of a conjecture by Haggkvist. Using this result, we also show that there is a constant rho, such that, for any positive integer n, if each cell in an n x n array B is assigned a set of m andlt;= rho n symbols, where each set is chosen independently and uniformly at random from {1, ... , n}, then the probability that B is avoidable tends to 1 as n -andgt; infinity.
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| 7. |
- Andrén, Lina J., 1980-, et al.
(författare)
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Avoiding arrays of odd order by Latin squares
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We prove that there exists a constant c such that for each pos- itive integer k every (2k+1)×(2k+1) array A on the symbols 1,...,2k+1 with at most c(2k + 1) symbols in every cell, and each symbol repeated at most c(2k+1) times in every row and column is avoidable; that is, there is a (2k+1)×(2k+1) Latin square S on the symbols 1,...,2k+1 such that for each cell (i, j) in S the symbol in (i, j) does not appear in the corresponding cell in A. This settles the last open case of a conjecture by Häggkvist.
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| 8. |
- Andrén, Lina, et al.
(författare)
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Restricted completion of sparse partial Latin squares
- 2019
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Ingår i: Combinatorics, probability & computing. - : Cambridge University Press. - 0963-5483 .- 1469-2163. ; 28:5, s. 675-695
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Tidskriftsartikel (refereegranskat)abstract
- An n × n partial Latin square P is called α-dense if each row and column has at most αn non-empty cells and each symbol occurs at most αn times in P. An n × n array A where each cell contains a subset of {1,.., n} is a (βn, βn, βn)-array if each symbol occurs at most βn times in each row and column and each cell contains a set of size at most βn. Combining the notions of completing partial Latin squares and avoiding arrays, we prove that there are constants α, β > 0 such that, for every positive integer n, if P is an α-dense n × n partial Latin square, A is an n × n (βn, βn, βn)-array, and no cell of P contains a symbol that appears in the corresponding cell of A, then there is a completion of P that avoids A; that is, there is a Latin square L that agrees with P on every non-empty cell of P, and, for each i, j satisfying 1 ≤ i, j ≤ n, the symbol in position (i, j) in L does not appear in the corresponding cell of A.
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| 9. |
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| 10. |
- Asratian, Armen, et al.
(författare)
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Cyclic deficiency of graphs
- 2019
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Ingår i: Discrete Applied Mathematics. - : ELSEVIER. - 0166-218X .- 1872-6771. ; 266, s. 171-185
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Tidskriftsartikel (refereegranskat)abstract
- A proper edge coloring of a graph G with colors 1, 2, . . . , t is called a cyclic interval t-coloring if for each vertex v of G the edges incident to v are colored by consecutive colors, under the condition that color 1 is considered as consecutive to color t. In this paper we introduce and investigate a new notion, the cyclic deficiency of a graph G, defined as the minimum number of pendant edges whose attachment to G yields a graph admitting a cyclic interval coloring; this number can be considered as a measure of closeness of G of being cyclically interval colorable. We determine or bound the cyclic deficiency of several families of graphs. In particular, we present examples of graphs of bounded maximum degree with arbitrarily large cyclic deficiency, and graphs whose cyclic deficiency approaches the number of vertices. Finally, we conjecture that the cyclic deficiency of any graph does not exceed the number of vertices, and we present several results supporting this conjecture. (C) 2018 Elsevier B.V. All rights reserved.
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