| 1. |
- Lohse, M., et al.
(författare)
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Evaluating extrovert and introvert behaviour of a domestic robot – a video study
- 2008
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Ingår i: Proceedings of the 17th IEEE International Symposium on Robot and Human Interactive Communication, RO-MAN. - New York : IEEE. - 9781424422128 ; , s. 488-493
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Konferensbidrag (refereegranskat)abstract
- Human-Robot Interaction (HRI) research is here presented into social robots that have to be able to interact with inexperienced users. In the design of these robots many research findings of human-human interaction and human-computer interaction are adopted but the direct applicability of these theories is limited because a robot is different from both humans and computers. Therefore, new methods have to be developed in HRI in order to build robots that are suitable for inexperienced users. In this paper we present a video study we conducted employing our robot BIRON (BIelefeld RObot companioN) which is designed for use in domestic environments. Subjects watched the system during the interaction with a human and rated two different robot behaviours (extrovert and introvert). The behaviours differed regarding verbal output and person following of the robot. Aiming to improve human-robot interaction, participants' ratings of the behaviours were evaluated and compared.
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| 2. |
- Bolin, David, 1983, et al.
(författare)
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Fast estimation of spatially dependent temporal vegetation trends using Gaussian Markov random fields
- 2009
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Ingår i: Computational Statistics and Data Analysis. - : Elsevier BV. - 0167-9473. ; 53:8, s. 2885-2896
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for efficient methods for estimating trends in spatio-temporal Earth Observation data. A suitable model for such data is a space-varying regression model, where the regression coefficients for the spatial locations are dependent. A second order intrinsic Gaussian Markov Random Field prior is used to specify the spatial covariance structure. Model parameters are estimated using the Expectation Maximisation (EM) algorithm, which allows for feasible computation times for relatively large data sets. Results are illustrated with simulated data sets and real vegetation data from the Sahel area in northern Africa. The results indicate a substantial gain in accuracy compared with methods based on independent ordinary least squares regressions for the individual pixels in the data set. Use of the EM algorithm also gives a substantial performance gain over Markov Chain Monte Carlo-based estimation approaches. © 2008 Elsevier B.V. All rights reserved.
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| 3. |
- Olofsson, P., et al.
(författare)
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Mapping NPP for a coniferous forest in southern sweden using data from Terra/MODIS
- 2005
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Konferensbidrag (refereegranskat)abstract
- Net primary production (NPP) is modeled for a coniferous forest in southern Sweden for 2001. The model is based on the light-use efficiency concept where NPP is calculated as a product of absorbed photosynthetically active radiation (APAR) and a light-use efficiency factor (ε). APAR is estimated from the fraction of APAR (FAPAR) multiplied with the daily total amount of incoming PAR. FAPAR is obtained by linear transformation of 250 m NDVI from Terra/MODIS. Prior to the transformation, the NDVI has been seasonally adjusted by fitting local asymmetric Gauss functions to the time series. ε is modeled daily as a function of temperature, latitude and time. The model is evaluated against an NPP time series obtained from flux measurements of net ecosystem exchange (NEE) and measurements of respiration carried out simultaneously at the site (r 2 = 0.78 for modeled and measured NPP). FAPAR is evaluated against measurements 2004.
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| 4. |
- Olsson, L, et al.
(författare)
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A recent greening of the Sahel - Trends, patterns and potential causes
- 2005
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Ingår i: Journal of Arid Environments. - : Elsevier BV. - 1095-922X .- 0140-1963. ; 63:3, s. 556-566
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Tidskriftsartikel (refereegranskat)abstract
- For the last four decades there has been sustained scientific interest in contemporary environmental change in the Sahel (the southern fringe of the Sahara). It suffered several devastating droughts and famines between the late 1960s and early 1990s. Speculation about the climatology of these droughts is unresolved, as is speculation about the effects of land clearance on rainfall and about land degradation in this zone. However, recent findings suggest a consistent trend of increasing vegetation greenness in much of the region. Increasing rainfall over the last few years is certainly one reason, but does not fully explain the change. Other factors, such as land use change and migration, may also contribute. This study investigates the nature of a secular vegetation trend across the Sahel and discusses several potential causative factors.
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