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- Anderson, Johan, 1973, et al.
(author)
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A comparison of drift wave stability in stellarator and tokamak geometry
- 2002
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In: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 9:5, s. 1629-
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Journal article (peer-reviewed)abstract
- The influence of plasma geometry on the linear stability of electrostatic ion-temperature-gradient driven drift modes (ITG modes) is investigated. An advanced fluid model is used for the ions together with Boltzmann distributed electrons. The derived eigenvalue equation is solved numerically. A comparison is made between an H – 1NF [Fusion Technol. 17, 123 (1990)] like stellarator equilibrium, a numerical tokamak equilibrium and the analytical s - alpha equilibrium. The numerical and the analytical tokamak are found to be in good agreement in the low inverse aspect ratio limit. The growth rates of the tokamak and stellarator are comparable whereas the modulus of the real frequency is substantially larger in the stellarator. The threshold in Ln/LT for the stellarator is found to be somewhat larger. In addition, a stronger stabilization of the ITG mode growth is found for large L n / R in the stellarator case.
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| 2. |
- Candefjord, Stefan, 1981, et al.
(author)
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A wearable microwave instrument can detect and monitor traumatic abdominal injuries in a porcine model
- 2021
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 11:1
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Journal article (peer-reviewed)abstract
- Abdominal injury is a frequent cause of death for trauma patients, and early recognition is essential to limit fatalities. There is a need for a wearable sensor system for prehospital settings that can detect and monitor bleeding in the abdomen (hemoperitoneum). This study evaluates the potential for microwave technology to fill that gap. A simple prototype of a wearable microwave sensor was constructed using eight antennas. A realistic porcine model of hemoperitoneum was developed using anesthetized pigs. Ten animals were measured at healthy state and at two sizes of bleeding. Statistical tests and a machine learning method were used to evaluate blood detection sensitivity. All subjects presented similar changes due to accumulation of blood, which dampened the microwave signal (p< 0.05). The machine learning analysis yielded an area under the receiver operating characteristic (ROC) curve (AUC) of 0.93, showing 100% sensitivity at 90% specificity. Large inter-individual variability of the healthy state signal complicated differentiation of bleedings from healthy state. A wearable microwave instrument has potential for accurate detection and monitoring of hemoperitoneum, with automated analysis making the instrument easy-to-use. Future hardware development is necessary to suppress measurement system variability and enable detection of smaller bleedings.
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| 4. |
- Candefjord, Stefan, 1981, et al.
(author)
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Microwave technology for detecting traumatic intracranial bleedings: tests on phantom of subdural hematoma and numerical simulations
- 2017
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In: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 1741-0444 .- 0140-0118. ; 55:8, s. 1177-1188
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Journal article (peer-reviewed)abstract
- Traumatic brain injury is the leading cause of death and severe disability for young people and a major public health problem for elderly. Many patients with intracranial bleeding are treated too late, because they initially show no symptoms of severe injury and are not transported to a trauma center. There is a need for a method to detect intracranial bleedings in the prehospital setting. In this study, we investigate whether broadband microwave technology (MWT) in conjunction with a diagnostic algorithm can detect subdural hematoma (SDH). A human cranium phantom and numerical simulations of SDH are used. Four phantoms with SDH 0, 40, 70 and 110 mL are measured with a MWT instrument. The simulated dataset consists of 1500 observations. Classification accuracy is assessed using fivefold cross-validation, and a validation dataset never used for training. The total accuracy is 100 and 82–96 % for phantom measurements and simulated data, respectively. Sensitivity and specificity for bleeding detection were 100 and 96 %, respectively, for the simulated data. SDH of different sizes is differentiated. The classifier requires training dataset size in order of 150 observations per class to achieve high accuracy. We conclude that the results indicate that MWT can detect and estimate the size of SDH. This is promising for developing MWT to be used for prehospital diagnosis of intracranial bleedings.
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| 9. |
- Dahlbäck, Robin, 1985, et al.
(author)
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A 340 GHz CW non-linear imaging system
- 2010
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In: Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010. - 9781424466559
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Conference paper (peer-reviewed)abstract
- A CW sub-millimetre wave imaging system is presented. The system operates around 340GHz with a 6.5% relative bandwidth and uses a non-linear imaging algorithm.
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