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- Craig, Cora L, et al.
(författare)
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International physical activity questionnaire : 12-country reliability and validity
- 2003
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Ingår i: Medicine & Science in Sports & Exercise. - 0195-9131 .- 1530-0315. ; 35:8, s. 1381-1395
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Physical inactivity is a global concern, but diverse physical activity measures in use prevent international comparisons. The International Physical Activity Questionnaire (IPAQ) was developed as an instrument for cross-national monitoring of physical activity and inactivity.METHODS: Between 1997 and 1998, an International Consensus Group developed four long and four short forms of the IPAQ instruments (administered by telephone interview or self-administration, with two alternate reference periods, either the "last 7 d" or a "usual week" of recalled physical activity). During 2000, 14 centers from 12 countries collected reliability and/or validity data on at least two of the eight IPAQ instruments. Test-retest repeatability was assessed within the same week. Concurrent (inter-method) validity was assessed at the same administration, and criterion IPAQ validity was assessed against the CSA (now MTI) accelerometer. Spearman's correlation coefficients are reported, based on the total reported physical activity.RESULTS: Overall, the IPAQ questionnaires produced repeatable data (Spearman's rho clustered around 0.8), with comparable data from short and long forms. Criterion validity had a median rho of about 0.30, which was comparable to most other self-report validation studies. The "usual week" and "last 7 d" reference periods performed similarly, and the reliability of telephone administration was similar to the self-administered mode.CONCLUSIONS: The IPAQ instruments have acceptable measurement properties, at least as good as other established self-reports. Considering the diverse samples in this study, IPAQ has reasonable measurement properties for monitoring population levels of physical activity among 18- to 65-yr-old adults in diverse settings. The short IPAQ form "last 7 d recall" is recommended for national monitoring and the long form for research requiring more detailed assessment.
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| 3. |
- Larsson, Erik G., et al.
(författare)
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Removal of surface returns in ground-penetrating radar data
- 2001
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Ingår i: Proceedings of SPIE Vol. 4394. - : SPIE. ; , s. 764-775
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Konferensbidrag (refereegranskat)abstract
- Techniques using ground-penetrating radar (GPR) for the detection of targets such as abandoned landmines or unexploded ordnance (UXO) buried under the ground surface continue to receive considerable attention especially in the area of signal processing. In this paper we consider the problem of eliminating the so-called ground-bounce effect, which is due to the specular ground surface reflections of the radar signal. The ground-bounce returns are often significantly stronger than the reflection from a target and pose a challenging problem. Existing techniques commonly assume that the ground response is constant as the radar equipment moves along a track. By using measured data, we show that this is, for several reasons, an unrealistic assumption. Instead, we consider a semi-parametric model for the ground-bounce that is in better agreement with observed data. Furthermore, we show how this model can be used to derive an accurate and robust but yet conceptually simple algorithm for the removal of the ground return. We demonstrate our technique using data recorded by an ultra-wideband GPR on a U.S. Army test range.
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