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| 2. |
- Grennberg, Anders, et al.
(författare)
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Secondary sound classification for the assessment of focus positioning in shock-wave lithotripsy
- 1993
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Ingår i: IX Nordic Meeting on Medical and Biological Engineering. - Lund : Medicinsk Teknik.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A problem encountered when using acoustic shock-waves for kidney stone disintegration is that the positioning of the focus relative to a stone, for the best possible fragmenting effect, is crtitical. The standard methods for focus positioning are ultrasound or x-ray imaging. These methods are, however, not always sufficient and a better indication of a well positioned focus would be valuable. The secondary sound emitted as a result of each shock-wave has been found to contain valuable information. A skilled operator is able to hear from the timbre of these sound pulses when the positioning of the focus is adequate. A method for the automatic evaluation of secondary sounds, using a computer, is developed in this work.
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| 3. |
- Löfdahl, Lennart, 1948, et al.
(författare)
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Influence of Different Sensor Configurations on the Turbulent Quantities in a Complex Three-Dimensional Flow Field
- 1993
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Ingår i: ASME-Fluid Engineering Conference, Washington DC.
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Konferensbidrag (refereegranskat)abstract
- Measurements of the Reynolds stress tensor have been carried out in a complex three-dimensional boundary layer using different techniques. Single-, cross- and three-hot-wire probes were employed together with a silicon based double chip sensor. All measurements were performed at a Reynolds number of 1.2 x ___ per meter. The turbulent stresses were determined at a reference position in a two-dimensional part of the flow field and at three locations with different strength of the three-dimensionality. A good agreement was found in the turbulent quantities measured with the different methods, however, the influence of prong interference, measuring volumes and velocity gradients were noted.
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| 4. |
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| 5. |
- Olsson, Lennart, et al.
(författare)
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Analysis and classification of secondary sounds from the disintegration of kidney-stones with acoustic shock waves
- 1991
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Ingår i: Ultrasound in Medicine and Biology. - 0301-5629 .- 1879-291X. ; 17:5, s. 491-495
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Tidskriftsartikel (refereegranskat)abstract
- Secondary sound emission, partly in the audible frequency range, from shock wave disintegration of kidney stones has been recorded during the treatment of two patients. A skilled operator can determine by listening if the stone is hit by the shock-wave or not. Spectral analysis of these recordings show differences between sounds which can be used to evaluate the fragmenting effect on the stone. Results are presented of a preliminary discriminating method based on parameters in an autoregressive signal model.
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| 6. |
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| 7. |
- Olsson, Lennart
(författare)
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Desertification in Africa - Critique and an Alternative Approach
- 1993
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Ingår i: GeoJournal. - 1572-9893. ; 31:1, s. 23-32
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Tidskriftsartikel (refereegranskat)abstract
- This article critically reviews the international debate on desertification, its status, rate as well as causes and consequences. The article rejects the commonly used concept of a degrading environment, but tries to explain the environmental problems as symptoms of a wider economic and political crisis. An alternative approach applying systems analysis of the entire socio-eco-system to the study of desertification and land degradation is discussed, with examples from the Western Sudan
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| 8. |
- Olsson, Lennart, et al.
(författare)
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Fourier series for analysis of temporal sequences of satellite sensor imagery
- 1994
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 1366-5901 .- 0143-1161. ; 15:18, s. 3735-3741
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Tidskriftsartikel (refereegranskat)abstract
- Fourier Series and the derivative were used in this study for analysing time series of remotely-sensed data. The technique allows fundamental characteristics of time series data to be quantified. In Fourier analysis a function in space or time is broken down into sinusoidal components, or harmonics. The first and second harmonics are a function of the mono or bi-modality of the curve, demonstrated in the study on Global Vegetation Index data classified into typical mono and bi-modal vegetation index zones. The last harmonic explains close to 100 per cent of the variance in the curve. Other important parameters of the time series, such as extreme points and rate of change, can be extracted from the derivative of the Fourier Series. Fourier Series may form a basis for a quantitative approach to the problem of handling temporal sequences of remotely-sensed data.
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| 9. |
- Olsson, Lennart
(författare)
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On the Causes of Famine - Drought, Desertification and Market Failure in the Sudan
- 1993
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Ingår i: Ambio: a Journal of Human Environment. - 0044-7447. ; 22, s. 395-404
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Tidskriftsartikel (refereegranskat)abstract
- Many natural scientists foster the idea of a degrading environment, caused by over-exploitation of the resources, being the cause of famine and poverty in Africa. In accordance with this, policies aimed at restoring the environment are formulated. This article analyses the main causes of famine, i.e. drought, desertification and the food market, with examples from the 1984-85 famine in the Sudan. The food security situation is scrutinised from both a natural and a societal point of view. It demonstrates the close connection between climatic variation and food production and reveals the myth of desertification. It also demonstrates the role of a malfunctioning market, in combination with an unjust credit system, in causing the famine. While crop production were half the normal, prices were five to six times higher than normal - that was the real cause of the tragedy. In order to find solutions for preventing a return of the 1984/85 situation, the idea of a degrading environment must be abandoned in favour of a more profound analysis of the interrelations between the atmosphere, the biosphere and the society.
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| 10. |
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