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Search Results: 1 - 10 of 208440 matches for " L. Westerlund "
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Simulation of the thermal borehole resistance in groundwater filled borehole heat exchanger using CFD technique
A-M. Gustafsson, L. Westerlund
International Journal of Energy and Environment , 2010,
Abstract: The thermal borehole resistance in a groundwater-filled borehole heat exchanger (BHE) is affected of both conductive and convective heat transfer through the borehole water. To calculate this heat transport, different models are required compared to calculation of only conductive heat transfer in a back-filled BHE. In this paper some modelling approximations for groundwater-filled, single U-pipe BHEs were investigated using a 3D CFD model. The purpose is to find approximations that enable to construct a fast, simple model including the convective heat transfer that may be used in thermal response test analyses and BHE design programs. Both total heat transfer calculations (including convective and conductive heat transport) and only conductive heat transfer calculations were performed for comparison purposes. The approximations that are investigated are the choice of boundary condition at the U-pipe wall and using a single pipe in the middle of the borehole instead of the U-pipe. For the total heat transfer case, it is shown that the choice of boundary condition hardly affects the calculated borehole thermal resistance. For the only conductive heat transfer case, the choice of boundary condition at the pipe wall gives large differences in the result. It is also shown that using an annulus model (single pipe in the middle of the borehole) results in similar heat transfer as the U-pipe model provided that the equivalent radius is chosen appropriately. This approximation can radically decrease the number of calculation cells needed.
CFD optimization of a pellet burner
Westerlund Lars B.,Hermansson Roger L.,Cervantes Michel J.
Thermal Science , 2012, DOI: 10.2298/tsci110609135w
Abstract: Increased capacity of computers has made CFD technology attractive for the design of different apparatuses. Optimization of a pellet burner using CFD was investigated in this paper. To make the design tool work fast, an approach with only mixing of gases was simulated. Other important phenomena such as chemical reactions were omitted in order to speed up the design process. The original design of the burner gave unsatisfactory performance. The optimized design achieved from simulation was validated and the results show a significant improvement. The power output increased and the emission of unburned species decreased but could be further reduced. The contact time between combustion gases and secondary air was probably too short. An increased contact time in high temperature conditions would possibly improve the design further.
Non-Listening and Self Centered Leadership – Relationships to Socioeconomic Conditions and Employee Mental Health
T?res Theorell, Anna Nyberg, Constanze Leineweber, Linda L. Magnusson Hanson, Gabriel Oxenstierna, Hugo Westerlund
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0044119
Abstract: Background The way in which leadership is experienced in different socioeconomic strata is of interest per se, as well as how it relates to employee mental health. Methods Three waves of SLOSH (Swedish Longitudinal Occupational Survey of Health, a questionnaire survey on a sample of the Swedish working population) were used, 2006, 2008 and 2010 (n = 5141). The leadership variables were: “Non-listening leadership” (one question: “Does your manager listen to you?” - four response categories), “Self centered leadership” (sum of three five-graded questions – “non-participating”, “asocial” and “loner”). The socioeconomic factors were education and income. Emotional exhaustion and depressive symptoms were used as indicators of mental health. Results Non-listening leadership was associated with low income and low education whereas self-centered leadership showed a weaker relationship with education and no association at all with income. Both leadership variables were significantly associated with emotional exhaustion and depressive symptoms. “Self centered” as well as “non-listening” leadership in 2006 significantly predicted employee depressive symptoms in 2008 after adjustment for demographic variables. These predictions became non-significant when adjustment was made for job conditions (demands and decision latitude) in the “non-listening” leadership analyses, whereas predictions of depressive symptoms remained significant after these adjustments in the “self-centered leadership” analyses. Conclusions Our results show that the leadership variables are associated with socioeconomic status and employee mental health. “Non-listening” scores were more sensitive to societal change and more strongly related to socioeconomic factors and job conditions than “self-centered” scores.
Tinnitus Severity Is Reduced with Reduction of Depressive Mood – a Prospective Population Study in Sweden
Sylvie Hébert, Barbara Canlon, Dan Hasson, Linda L. Magnusson Hanson, Hugo Westerlund, T?res Theorell
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0037733
Abstract: Tinnitus, the perception of sound without external source, is a highly prevalent public health problem with about 8% of the population having frequently occurring tinnitus, and about 1–2% experiencing significant distress from it. Population studies, as well as studies on self-selected samples, have reported poor psychological well-being in individuals with tinnitus. However, no study has examined the long-term co-variation between mood and tinnitus prevalence or tinnitus severity. In this study, the relationship between depression and tinnitus prevalence and severity over a 2-year period was examined in a representative sample of the general Swedish working population. Results show that a decrease in depression is associated with a decrease in tinnitus prevalence, and even more markedly with tinnitus severity. Hearing loss was a more potent predictor than depression for tinnitus prevalence, but was a weaker predictor than depression for tinnitus severity. In addition, there were sex differences for tinnitus prevalence, but not for tinnitus severity. This study shows a direct and long-term association between tinnitus severity and depression.
Categorizing the Growth Strategies of Small Firms
Seppo Leminen,Mika Westerlund
Technology Innovation Management Review , 2012,
Abstract: This study investigates the link between a small firm’s investment in R&D and its growth strategy. A firm’s growth strategy refers to the means by which the organization plans to achieve its objective to grow in volume and turnover. We categorize firm growth strategies into eight distinctive clusters: opportunity explorers, radical innovators, business developers, business expanders, profit makers, business rebuilders, stagnators, and downsizers. We argue that understanding a firm’s growth orientation provides a way to assess the returns of its R&D investments, because an organization’s intangible growth strategies and tangible inputs are connected.
Managing the Challenges of Becoming an Open Innovation Company: Experiences from Living Labs
Mika Westerlund,Seppo Leminen
Technology Innovation Management Review , 2011,
Abstract: High-technology firms have paved the way for user-driven innovations, but now even traditional industries are becoming increasingly open. This shift is a great challenge for companies with instituted practices, policies, and customer relationships. In this article, we identify four distinct steps in becoming an open innovation company based on our recent research into firms’ experiences with living lab experiments in the information and communication technology (ICT) sector. We describe these phases and illustrate the divergent roles that users play in each one. We conclude with a discussion on the differences between the management challenges of conventional development projects versus the open innovation model. For all firms that wish to become open innovators, we recommend that their managers promote an open organizational mindset and apply groupware that supports increased openness, because traditional project management tools are insufficient for open innovation.
A Framework for HI Spectral Source Finding Using Distributed-Memory Supercomputing
Stefan Westerlund,Christopher Harris
Physics , 2014, DOI: 10.1017/pasa.2014.18
Abstract: The latest generation of radio astronomy interferometers will conduct all sky surveys with data products consisting of petabytes of spectral line data. Traditional approaches to identifying and parameterising the astrophysical sources within this data will not scale to datasets of this magnitude, since the performance of workstations will not keep up with the real-time generation of data. For this reason, it is necessary to employ high performance computing systems consisting of a large number of processors connected by a high-bandwidth network. In order to make use of such supercomputers substantial modifications must be made to serial source finding code. To ease the transition, this work presents the Scalable Source Finder Framework, a framework providing storage access, networking communication and data composition functionality, which can support a wide range of source finding algorithms provided they can be applied to subsets of the entire image. Additionally, the Parallel Gaussian Source Finder was implemented using SSoFF, utilising Gaussian filters, thresholding, and local statistics. PGSF was able to search on a 256GB simulated dataset in under 24 minutes, significantly less than the 8 to 12 hour observation that would generate such a dataset.
Performance Analysis of GPU-Accelerated Filter-Based Source Finding for HI Spectral Line Image Data
Stefan Westerlund,Christopher Harris
Physics , 2015, DOI: 10.1007/s10686-015-9445-2
Abstract: Searching for sources of electromagnetic emission in spectral-line radio astronomy interferometric data is a computationally intensive process. Parallel programming techniques and High Performance Computing hardware may be used to improve the computational performance of a source finding program. However, it is desirable to further reduce the processing time of source finding in order to decrease the computational resources required for the task. GPU acceleration is a method that may achieve significant increases in performance for some source finding algorithms, particularly for filtering image data. This work considers the application of GPU acceleration to the task of source finding and the techniques used to achieve the best performance, such as memory management. We also examine the changes in performance, where the algorithms that were GPU accelerated achieved a speedup of around 3.2 times the 12 core per node CPU-only performance, while the program as a whole experienced a speedup of 2.0 times.
The healthcare environment—The importance of aesthetic surroundings: Health professionals’ experiences from a surgical ward in Finland  [PDF]
Britt-Maj Wikstr?m, Emma Westerlund, Jaana Erkkil?
Open Journal of Nursing (OJN) , 2012, DOI: 10.4236/ojn.2012.23029
Abstract: There is a growing acceptance of the vital role patient centered design plays in shaping the environment. Art can be of use in every area of health care. It is within the power of each person to share and interpret experience by means of the arts, by viewing the work of others, and by using feelings and imagination. Health professionals [n = 24 of a total of n = 35], answered the Wheel Questionnaire test instrument. It measures structure, motivation/engagement, and degree of emotional investment in a situation. Participants were requested to describe, in their own words, their perception of the enrichment of the ward interiordesign and the double-sided photos with a short poetic text, and the photo-book placed at each patient room. The results demonstrate that participants are motivated, structured and emotionally engaged when describing the new enrichment. The domains and themes are: Social interaction domain; rising thoughts and conversations. Comfort domain; atmosphere. Aesthetic do main; enrichment of the working environment. It could be concluded that the surgical ward environmental enrichment stimulated conversations between health professionals and between health professionals and patients and should be regarded as an important aspect in hospital planning.
Palaeoproterozoic mafic and intermediate metavolcanic rocks in the Turku area, SW Finland
Markku V?is?nen,Gustav Westerlund
Bulletin of the Geological Society of Finland , 2007,
Abstract: Twenty two samples were analysed from mafic and intermediate volcanic rocks from the Turku area along ~60 km long north-south geotraverse. Geographically and lithologically the samples were divided into the Pargas, Turku and Vahto groups. The Pargas and Turku groups consist of mafic units and intercalations within migmatitic gneisses. Their geochemical compositions are very similar. In average, they show quite flat REE curves and the multielement diagrams show moderate LILE enrichments, minor negative Ta-Nb anomalies and straight HFSE curves. We infer these as transitional between MORB and VAB. The Vahtogroup consists of thicker volcanic sequences in connection with synorogenic plutonic rocks. The data show enriched LREEs, LILEs, Th and P combined with negative Ta-Nb anomalies, i.e. the Vahto group shows subduction component. We interpret that the Vahto volcanicrocks belong to the H me belt. The geochemical data indicate that the Pargas and Turku groups were formed in extensional, possibly back-arc or intra-arc setting while the Vahto group was formed at continental volcanic arc.
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