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- Rahmani, M. A., et al.
(författare)
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Thermal management and design optimization of heatsink for cooling performance improvement during transient heat generation
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 61, s. 1665-1668
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Tidskriftsartikel (refereegranskat)abstract
- Heatsinks have long been used for cooling of electronic components to maintain them under the maximum allowed operational temperature. Forced air cooling with heatsink is suitable and enough efficient for low power applications cooling. Varieties of heatsinks are proposed by specialized industries to cool different kinds of electronic components. However, in most cases we need the appropriate heatsink to each specific case and particularly under transient heat generation that can be caused by many electronic or power electronic devices. The heat transport and evacuation process is tightly related to the heatsink performance. This paper examines the cooling characteristics of a heatsink used in a specific industrial application. The investigation is performed using Computational Fluid Dynamics (CFD) and the heat transfer performance of the heatsink is mainly determined by the Nusselt number which can be calculated from the numerical results. Analysis and discussion of the numerical results and especially the level of Nusselt number obtained at the contact surface of the heatsink with the surrounding cooling air allow optimization of the industrial heatsink shape to meet the requested cooling performance. Comparison of cooling performance before and after heatsink design optimization showed noticeable improvement.
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| 2. |
- Allwood, Jens, et al.
(författare)
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Developing a tagset and tagger for the African languages of South Africa with special reference to Xhosa
- 2003
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Ingår i: Southern African Linguistics and Applied Language Studies. - 1607-3614 .- 1727-9461. ; 21:4, s. 223-237
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Tidskriftsartikel (refereegranskat)abstract
- There are currently two distinct but not necessarily mutually exclusive approaches to the retrieval of information from linguistic corpora. ’Corpus-driven’ approaches rely solely on the corpus itself to yield significant patterns. With the exception of orthographic spacing, no additional annotations to a ’raw’ corpus are used to guide searches and the retrieval of information from the corpus. Typically, key word in context (KWIC) analyses are applied to relevant concordance lines to extract statistically significant lexical and grammatical patterns. In ’corpus-based’ approaches, on the other hand, information is retrieved from an enriched corpus on the basis of annotations in the form of linguistic tags and annotations. That is, the annotations are used to direct the searches to specific grammatical and lexical phenomena in a corpus. In this article, we propose a corpus-based approach and a tagset to be used on a corpus of spoken language for the African languages of South Africa. A number of problematic linguistic phenomena such as fixed expressions, agglutination, morphemic merging and spoken language phenomena such as interrupted words etc., often have some effect on tagging principles. These problematic phenomena are discussed and illustrated. The development of the tagset is based on the morphosyntactic properties of Xhosa for reasons that are outlined in the article. Manual tagging of a large corpus would be quite a daunting and time-consuming task, not to mention the potential for various kinds of errors. This problem is solved in a two-step process. Firstly, a computer-based drag-and-drop tagger was developed to facilitate the manual tagging of a so-called training corpus. This training corpus then forms the input to the development of an automatic tagger. The principles and procedures for the development of an automatic tagger for African languages are also discussed. ©2003 NISC Pty Ltd.
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| 4. |
- Dahlqvist Leinhard, Olof, et al.
(författare)
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Is Increased Normal White Matter Glutamate Concentration a Precursor of Gliosis and Disease Progression in Multiple Sclerosis?
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: The multiple sclerosis (MS) severity scale (MSSS) is a new scoring procedure to clinically characterize the rate of disease progression in MS, rather than the disability of the patient. The latter is often characterized using the expanded disability status score (EDSS). The progress rate of the disease, magnetic resonance imaging (MRI)-based measures of ‘black hole lesions’, and atrophy have all been shown to be predicted well by MSSS. In this study we investigated possible relationships between brain metabolite concentrations, measured using proton (1H) magnetic resonance spectroscopy (MRS), and MSSS. Purpose: Our aims were to quantitatively investigate the metabolite concentrations in normal appearing white matter (NAWM) in MS-patients, and also to investigate possible correlations between disease subtype, EDSS and MSSS and metabolite concentrations. To minimize the interference from lesion contamination in the MRS measurement, a refined novel analysis procedure had to be developed in order to correct for partial volume effects in tissues near plaques. Materials and Methods: Forty eight patients with Clinically Definite MS (CDMS), and 18 normal control subjects (NC) were included retrospectively from several MRS studies. T1, T2, and proton density MRI, and four white matter 1H MRS single voxel PRESS (Point-REsolved SpectroScopy) spectra were acquired in each subject using echo time 35 ms and repetition time 6000 ms on a 1.5 T MR-scanner. A total of 108 examinations were acquired from patients and 18 from NC. Absolutely quantified NAWM metabolite concentrations were determined using a mixed linear model (MLM) analysis that included the degree of T2 lesion contamination in each voxel. The T2 lesion contamination of the MRS voxels was also used as an estimate of ‘lesion load’ at each exam. The corrected metabolite concentrations were then correlated with clinical measures of the patients’ status, including EDSS and MSSS. Results: The axonal marker N-acetyl aspartate (NAA) did not correlate with either EDSS or MSSS. The glial cell markers creatine and myo-inositol correlated positively with EDSS. Creatine and glutamate correlated positively with MSSS. The ‘estimated lesion load’ correlated positively not only with EDSS, but also with the number of bouts since disease onset. Importantly, it did not correlate with MSSS. Conclusion: The most interesting findings were the unchanged concentrations of NAA, and the concomitant increase of creatine and myo-inositol during the course of disease progression in MSpatients. These not only indicated a constant axonal density, but also that a simultaneous development of gliosis occurred. These processes are most likely linked to demyelination, as well as development of white matter atrophy, a process in which the demyelinated volume is replaced by the surrounding tissue leading to a net loss of white matter. As a consequence of this process, axons in NAWM are probably damaged, which leads to a higher concentration of glia cells relative to the axonal volume. The positive correlation that was found between MSSS, and the glutamate and creatine concentrations in NAWM, in combination with a complete lack of correlation between lesion load and MSSS, suggests that altered glutamate metabolism, and subsequent demyelination and gliosis, is an important pathophysiological mechanism in MS.
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| 6. |
- Lehmann, Vicky, et al.
(författare)
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Negative and positive consequences of adolescent cancer 10 years after diagnosis : An interview-based longitudinal study in Sweden
- 2014
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Ingår i: Psycho-Oncology. - : Wiley-Blackwell. - 1057-9249 .- 1099-1611. ; 23:11, s. 1229-1235
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The aim of this study was to provide insight into survivor-reported negative and positive consequences of cancer during adolescence 10 years after diagnosis and compare these with consequences reported 3 and 4 years after diagnosis. METHODS: Three, 4, and 10 years after diagnosis, survivors of adolescent cancer were interviewed about negative and positive consequences due to their cancer experience. Manifest content analysis was used to identify categories of reported consequences. Categories of consequences 10 years after diagnosis were compared with consequences reported 3 and 4 years after diagnosis. RESULTS: Seven categories of negative consequences were identified: bodily concerns, existential thoughts about loss and life (new at 10 years), psychological problems, difficulties interacting with others, health worries (new), fertility concerns (new), and frustrations about health care (new); and six categories of positive consequences: positive view of life, positive view of self, compassion for others (new), close relationships, gained knowledge about disease and health care, and financial gains. Consistent with previous time points, bodily concerns were reported most often. The majority of survivors (n = 22) reported both negative and positive consequences of their former disease. Few reported only negative (n = 2) or only positive consequences (n = 4). CONCLUSIONS: Ten years after diagnosis, most survivors reported both negative and positive consequences. New themes, relevant to young adulthood and long-term survival, were identified. Health care professionals treating young adult survivors may anticipate and address problems regarding physical health, fertility, and health care but may also reinforce positive affect by addressing survivors’ positive views of life, sense of self, and close relationships.
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| 7. |
- Lundin, Fredrik, et al.
(författare)
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Pre-Postoperative 1H-MRS-Changes in Frontal Deep White Matter and the Thalamus in Idiopathic Normal Pressure Hydrocephalus
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In a previous study we found a significantly decreased N-acetylaspartate (NAA) and total N-acetyl groups (tNA) in the thalamus in patients with idiopathic normal pressure hydrocephalus (iNPH) compared with healthy individuals (HI). No significant difference between the groups could be found in the frontal deep white matter (FDWM). The primary aim of this study was to investigate if these metabolites in the thalamus were normalised after shunt surgery. The secondary aim was to investigate postoperative metabolic changes in FDWM.Subjects and Methods: Fourteen iNPH-patients, mean age 74 years, and 15 HI, also mean age 74 years, were examined. Assessment of motor scores was performed before and after shunt surgery. Absolute quantitative 1H-MRS (1.5 T, VOI 2.5-3 mL) was performed on the patients in the FDWM and in the thalamus, before and three months after shunt surgery, and also once on the HI. The following metabolites were analysed: tNA, NAA, total creatine (tCr), total choline (tCho), myo-inositol (mIns), glutamate (Glu), and lactate (Lac) concentrations. MRI volumetric calculations of the lateral ventricles were also performed.Results: At three months postoperatively, we found no significant changes of tNA or NAA in the thalamus. In contrast, in FDWM, there was a significant increase of tCho (p=0.01) and a borderline significant decrease of mIns (p=0.06). 12/14 patients were shunt responders (motor function). Median reduction of the lateral ventricle was 16%. A weak correlation between motor score (MOS) and ventricular reduction was observed.Conclusion: Normalisation of thalamic tNA and NAA could not be detected postoperatively. The increased tCho and decreased mIns in the FDWM postoperatively might relate to clinical improvement.
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| 8. |
- Smith, Göran, et al.
(författare)
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Cykeleffekt - Slutrapport för förstudie
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det finns sedan länge en bred politisk samsyn i Sverige kring att andelen cykelresor bör ökas. Trots detta är det svårt att påvisa någon övergripande positiv trend. En bidragande orsak är att det i dagsläget saknas grundläggande kunskap om hur utformning, drift och underhåll av cykelinfrastruktur påverkar cyklisterna och cykeltrafiken. Kunskapsluckorna gör det svårt för trafikplanerare att prioritera mellan olika typer av åtgärder samt att motivera sina val gentemot beslutsfattare. Det leder i sin tur till att utväxlingen av tilldelade resurser inte maximeras.Det överliggande syftet med forskningsinitiativet Cykeleffekt är att komplettera befintliga handböcker om cykelinfrastruktur med kunskap om vilken effekt olika typer av infrastrukturåtgärder ämnade att främja cykling har. För att möjliggöra forskningen krävs en samverkansplattform mellan kommuner och forskningsinstanser samt tillgång till faktiska infrastrukturåtgärder/-objekt att studera. Huvudmålet med den här förstudien var därför att bedöma potentialen för att koppla den typen av forskningsprojekt till det nybildade kommunnätverket Svenska Cykelstäder.För att kunna bedöma forskningspotentialen utfördes: en kort litteraturöversikt över befintlig kunskap om effekten av åtgärder och identifierade metoder för att utreda effektsamband; en konkretisering av nätverkets upplägg och agenda samt; en kartläggning av medlemskommunerna planerade åtgärder och intresse i att beforska effektsamband.Litteraturstudien pekade på att kunskapen om effekten av cykelinfrastrukturåtgärder är låg men att det finns metoder för att möjliggöra den forskning som krävs för att ta fram hypoteser om effektsamband. Det konkretiserade nätverket ansågs vara en lämplig plattform att koppla samma forskningsinstanser och kommunala cykelplanerare kring sådan forskning. Kommunerna uttryckte dessutom stort intresse för att delta i framtida forskningsprojekt och det finns gott om planerade infrastrukturåtgärder att beforska inom nätverket. I kontakten med kommunerna framkom det även att de tror att de skulle kunna utnyttja sina resurser för att öka andelen cykling bättre om de hade större tillgång till dokumenterad kunskap om effektsamband. Sammantaget bedömdes forskningspotentialen därav som god.Som slutprodukt för förstudien utvecklades ett förslag till syfte, mål, upplägg och genomförandeplan för fortsatt forskning med koppling till Svenska Cykelstäder.
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