| 1. |
- Moghadas, Shahab, et al.
(författare)
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Snowmelt modeling in urban areas : sensitivity analysis of the energy and mass balance method
- 2012
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Konferensbidrag (refereegranskat)abstract
- Flooding is one of the main concerns in seeking safe and sustainable urban areas. In many cases the design criteria are based on intense rainfall. It is, therefore, assumed that the peak flow in cities’ drainage systems is due to heavy and fast rainfalls. However snowmelt pattern could be more important for places with cold climate; therefore the need of a better snowmelt and runoff simulation becomes more important particularly when the effects of climate change needs to be considered. Two main methods are basically used for urban snowmelt simulation i.e. temperature index and energy budged methods. Studies done previously show that the energy balance method gives a better estimation for volume and time compare to the temperature index. For urban areas though, it is argued that the data demanding of the energy balance method can be a disadvantage and it could affect the model precision. However, the advances in geographical information systems (GIS) and the requirement for better time resolution than daily have increased the tendency of applying it for urban snow melt. There are couples of studies during recent years e.g. (Ho& Valeo 2005) applying energy budget method in urban areas, even though the efforts basically focused on developing routines and comparing it with the degree day method. There is still a gap in parameter sensitivity analysis especially with two main features of urban snowmelt modeling; firstly, the importance of input data along with difficulties in providing them; and secondly the classification of snow in urban areas based on snow properties. These two concerns were the motives to go one step ahead and to conduct a sensitivity analysis. The aim of the study is therefore to investigate the dependency of the simulation results to the different model parameters as built-in parameters and input data. Such analysis eventually can be used for snow classification which along with GIS technology can provide a reliable platform to simulate snowmelt over an urban catchment more precisely than what the current models are capable of today. Here in this study, a model namely Utah Energy Balance Snow Model (UEB) is used. The model uses a complete energy and mass balance routine to simulate snow accumulation and melt at a point scale. Except using the measured climatic values to run the model, the routines in this model has the capability of producing (simulating) solar radiation and albedo if the measured values are not available. The model has simulated the snow accumulation and melts in rural area with reasonable accuracy in previous studies i.e. (Tarboton et al. 1995). For this research, three snow deposits from 1991 and 1992 are taken to calibrate the model with. The pilot snow packs are identical to municipal snow deposit with density more than natural snow, around 700 Kg/m3. The snowmelt runoff has been measure between March and Jun 1991 and 1992. The necessary input values are collected from Meteorological and Hydrological Institute (SMHI) for the same periods. All input parameters are available on hourly and 3 hourly periods. The method is to run the model with real values collected from SMHI and calibrate it versus the measured data. The model is run using modified parameters to investigate the possible change in the simulation result. Eventually an analysis is done on each parameter and the dependency of the model. An analysis also is done by running the model with different time resolution, i.e. hourly, 3-hourly, and 6-hourly and to investigate the effect of time span in modeling snowmelt and simulation precision.
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| 2. |
- Nyberg, Anna, et al.
(författare)
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Destructive managerial leadership and psychological well-being among employees in Swedish, Polish, and Italian hotels
- 2011
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Ingår i: Work. - : IOS Press. - 1051-9815 .- 1875-9270. ; 39:3, s. 267-281
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of this cross-sectional exploratory study was to investigate destructive managerial leadership in the hotel industry in Sweden, Poland, and Italy in relation to psychological well-being among employees.Methods and Participants: 554 questionnaires were collected from employees in all occupational groups within hotels. The Copenhagen Psychosocial Questionnaire (COPSOQ) measured working conditions, particularly iso-strain or high work demands combined with low control and poor social support, and psychological well-being, defined in terms of mental health, vitality, and behavioural stress. Items adapted from the Global Leadership and Organisational Behaviour Effectiveness (GLOBE) research program questionnaire measured autocratic, malevolent, and self-centred leadership styles. Differences in ratings between countries were estimated, as well as the relationship between destructive managerial leadership on an organisation level and employee psychological well-being on an individual level. The relationship between destructive leadership and psychological well-being among employees was adjusted for employees' reported iso-strain.Results: Autocratic and malevolent leadership were at the organisation level related to low vitality among employees and self-centred leadership was significantly associated with poormental health, low vitality, and high behavioural stress. Autocratic and malevolent leadership were more strongly related to iso-strain than was self-centred leadership. Variations in leadership practice between countries were seen in autocratic and malevolent leadership.Conclusion: This exploratory study suggests a significant association between destructive managerial leadership on the organisation level and poor psychological well-being among employees on an individual level. Interventions to decrease iso-strain and enhance psychological well-being among employees could be directed at an organisation level.
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| 3. |
- Baltzer, Maria, et al.
(författare)
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Involvement and structure : A qualitative study of organizational change and sickness absence among women in the public sector in Sweden
- 2011
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Ingår i: BMC Public Health. - : Springer Science and Business Media LLC. - 1471-2458. ; 11, s. 318-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Organizational changes in modern corporate life have become increasingly common and there are indications that they often fail to achieve their ends. An earlier study of 24,036 employees showed that those who had repeatedly been exposed to large increases in staffing during 1991-1996 had an excess risk of both long-term sickness absence and hospital admission during 1997-1999, while moderate expansion appeared to be protective. The former was most salient among female public sector employees. We used qualitative interviews to explore work environment factors underlying the impact of organizational changes (moderate and large expansions in staffing) on sickness absence from an employee perspective. METHOD: We interviewed 21 strategically selected women from the earlier study using semi-structured telephone interviews focusing on working conditions during the organizational changes. We identified 22 themes which could explain the association between organizational changes and sickness absence. We then used Qualitative Comparative Analysis (QCA) to reduce the number of themes and discover patterns of possible causation. RESULTS: The themes that most readily explained the outcomes were Well Planned Process of Change (a clear structure for involvement of the employees in the changes), Agent of Change (an active role in the implementation of the changes), Unregulated Work (a lack of clear limits and guidelines regarding work tasks from the management and among the employees), and Humiliating Position (feelings of low status or of not being wanted at the workplace), which had been salient throughout the analytic process, in combination with Multiple Contexts (working in several teams in parallel) and Already Ill (having already had a debilitating illness at the beginning of 1991), which may indicate degree of individual exposure and vulnerability. Well Planned Process of Change, Agent of Change and Multiple Contexts are themes that were associated with low sickness absence. Unregulated Work, Humiliating Position and Already Ill were associated with high sickness absence. CONCLUSIONS: These findings suggest that promising areas for future research and improvement in change management could be the structured involvement of the employees in the planning of organizational changes, and the development of methods to avoid highly unregulated working conditions.
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| 4. |
- Ferrie, Jane E., et al.
(författare)
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Differences in the association between sickness absence and long-term sub-optimal health by occupational position : a 14-year follow-up in the GAZEL cohort
- 2011
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Ingår i: Occupational and Environmental Medicine. - : BMJ. - 1351-0711 .- 1470-7926. ; 68:10, s. 729-733
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Tidskriftsartikel (refereegranskat)abstract
- Objectives Although sickness absence is a strong predictor of health, whether this association varies by occupational position has rarely been examined. The aim of this study was to investigate overall and diagnosis-specific sickness absence as a predictor of future long-term sub-optimal health by occupational position. Methods This was a prospective occupational cohort study of 15 320 employees (73% men) aged 37–51. Sickness absences (1990–1992), included in 13 diagnostic categories, were examined by occupational position in relation to self-rated health measured annually during 1993–2006. Results 60% of employees in higher occupational positions and 22% in lower positions had no sickness absence. Conversely, 9.5% of employees in higher positions and 40% in lower positions had over 30 sick-leave days. Repeated-measures logistic regression analyses adjusted for age, sex and chronic disease showed employees with over 30 days absence, compared to those with no absence, had approximately double the risk of sub-optimal health over the 14-year follow-up in all occupational positions. 1–30 days sick-leave was associated with greater odds of sub-optimal health in the high (OR 1.48; 95% CI 1.27 to 1.72) and intermediate (1.29; 1.15 to 1.45) but not lower occupational positions (1.06; 0.82 to 1.38). Differences by occupational position in the association between sickness absence in 13 specific diagnostic categories and sub-optimal health over the ensuing 14 years were limited to stronger associations observed with cancer and mental disorders in the higher occupational positions. Conclusions The association between sickness absence of more than 30 days over 3 years and future long-term self-rated health appears to differ little by occupational position.
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| 5. |
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| 6. |
- Fransson, Eleonor, 1971-, et al.
(författare)
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Comparison of alternative versions of the job demand-control scales in 17 European cohort studies : the IPD-Work consortium
- 2012
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Ingår i: BMC Public Health. - : Springer Science and Business Media LLC. - 1471-2458. ; 12, s. 62-
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Tidskriftsartikel (refereegranskat)abstract
- Background: Job strain (i.e., high job demands combined with low job control) is a frequently used indicator of harmful work stress, but studies have often used partial versions of the complete multi-item job demands and control scales. Understanding whether the different instruments assess the same underlying concepts has crucial implications for the interpretation of findings across studies, harmonisation of multi-cohort data for pooled analyses, and design of future studies. As part of the 'IPD-Work' (Individual-participant-data meta-analysis in working populations) consortium, we compared different versions of the demands and control scales available in 17 European cohort studies. Methods: Six of the 17 studies had information on the complete scales and 11 on partial scales. Here, we analyse individual level data from 70 751 participants of the studies which had complete scales (5 demand items, 6 job control items). Results: We found high Pearson correlation coefficients between complete scales of job demands and control relative to scales with at least three items (r > 0.90) and for partial scales with two items only (r = 0.76-0.88). In comparison with scores from the complete scales, the agreement between job strain definitions was very good when only one item was missing in either the demands or the control scale (kappa > 0.80); good for job strain assessed with three demand items and all six control items (kappa > 0.68) and moderate to good when items were missing from both scales (kappa = 0.54-0.76). The sensitivity was > 0.80 when only one item was missing from either scale, decreasing when several items were missing in one or both job strain subscales. Conclusions: Partial job demand and job control scales with at least half of the items of the complete scales, and job strain indices based on one complete and one partial scale, seemed to assess the same underlying concepts as the complete survey instruments.
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| 7. |
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| 8. |
- Fransson, Eleonor, 1971-, et al.
(författare)
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Job strain as a risk factor for leisure-time physical inactivity : an individual-participant meta-analysis of up to 170,000 men and women
- 2012
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Ingår i: American Journal of Epidemiology. - Cary : Oxford University Press. - 0002-9262 .- 1476-6256. ; 176:12, s. 1078-1089
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Forskningsöversikt (refereegranskat)abstract
- Unfavorable work characteristics, such as low job control and too high or too low job demands, have been suggested to increase the likelihood of physical inactivity during leisure time, but this has not been verified in large-scale studies. The authors combined individual-level data from 14 European cohort studies (baseline years from 19851988 to 20062008) to examine the association between unfavorable work characteristics and leisure-time physical inactivity in a total of 170,162 employees (50 women; mean age, 43.5 years). Of these employees, 56,735 were reexamined after 29 years. In cross-sectional analyses, the odds for physical inactivity were 26 higher (odds ratio 1.26, 95 confidence interval: 1.15, 1.38) for employees with high-strain jobs (low control/high demands) and 21 higher (odds ratio 1.21, 95 confidence interval: 1.11, 1.31) for those with passive jobs (low control/low demands) compared with employees in low-strain jobs (high control/low demands). In prospective analyses restricted to physically active participants, the odds of becoming physically inactive during follow-up were 21 and 20 higher for those with high-strain (odds ratio 1.21, 95 confidence interval: 1.11, 1.32) and passive (odds ratio 1.20, 95 confidence interval: 1.11, 1.30) jobs at baseline. These data suggest that unfavorable work characteristics may have a spillover effect on leisure-time physical activity.
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| 9. |
- Galfi, Helen, et al.
(författare)
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Indicator bacteria variation in separate sewersystems in Östersund, Sweden - Preliminary results : [La variation des indicateurs bactériens et des flux de MES dans les systèmes séparatifs d'eaux pluviales à Östersund, en Suède - Résultats préliminaires]
- 2013
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Konferensbidrag (refereegranskat)abstract
- Faecal bacteria are a major pollution threat of water bodies designated for multipurpose use including drinking water sources or recreational purposes. Even though stormwater discharges may contribute significantly to microbiological pollution, they have not been fully investigated in the European context. We have studied the presence of indicator bacteria and total suspended solids (TSS) in stormwater discharged from four urban catchments, with areas between 5 and 40 ha, in Östersund, Sweden. The aim was to determine local variation of standard bacteria strains and TSS in Swedish urban catchments with specific land uses. Further, intra event variations were investigated. During dry weather, indicator bacteria concentrations in sewers conveying baseflow did not exceed 100 CFU/100 mL. During storm runoff, total coliform and int. enterococci concentrations increased 102 to 103 times, compared to those in baseflow. Compared to these two parameters, considerably lower concentrations were observed for E. coli and C. perfringens. Bacteria concentrations differed significantly among the sampling sites and partly, a first flush phenomenon was observed. Partly, significant correlations between TSS and indicator bacteria were observed. These were catchment specific and need a more detailed assessment. Further research will focus on seasonal variations and influential factors.
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| 10. |
- Gustafsson, Anna-Maria, et al.
(författare)
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CFD-modelling of natural convection in a groundwater-filled borehole heat exchanger
- 2010
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311 .- 1873-5606. ; 30:6-7, s. 683-691
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Tidskriftsartikel (refereegranskat)abstract
- In design of ground-source energy systems the thermal performance of the borehole heat exchangers is important. In Scandinavia, boreholes are usually not grouted but left with groundwater to fill the space between heat exchanger pipes and borehole wall. The common U-pipe arrangement in a groundwater-filled BHE has been studied by a three-dimensional, steady-state CFD model. The model consists of a 3 m long borehole containing a single U-pipe with surrounding bedrock. A constant temperature is imposed on the U-pipe wall and the outer bedrock wall is held at a lower constant temperature. The occurring temperature gradient induces a velocity flow in the groundwater-filled borehole due to density differences. This increases the heat transfer compared to stagnant water. The numerical model agrees well with theoretical studies and laboratory experiments. The result shows that the induced natural convective heat flow significantly decreases the thermal resistance in the borehole. The density gradient in the borehole is a result of the heat transfer rate and the mean temperature level in the borehole water. Therefore in calculations of the thermal resistance in groundwater-filled boreholes convective heat flow should be included and the actual injection heat transfer rate and mean borehole temperature should be considered. (C) 2009 Elsevier Ltd. All rights reserved.
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