| 1011. |
- Helander, Jakob, et al.
(författare)
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Performance Analysis of Millimeter-Wave Phased Array Antennas in Cellular Handsets
- 2016
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1536-1225 .- 1548-5757. ; 15, s. 504-507
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Tidskriftsartikel (refereegranskat)abstract
- This letter discusses the usage of high-gain steerable antenna arrays operating at millimeter-wave (mmWave) frequencies for future cellular networks (5G). Based on the probable outline of the 5G networks, a method for characterizing phased array antennas in cellular handsets has been introduced. For analyzing the performance, the total scan pattern of the array configuration together with its respective coverage efficiency are essential to consider in order to compare different antenna designs and topology approaches with each other. Two design approaches and subarray schemes of these have been considered in order to illustrate the relevance of such a characterization method. The results show the importance of evaluating potential array antennas in such manners. The method can be applied to much more complex system models, where polarization diversity, hand and body effect, and statistical modeling of the channel may be included.
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| 1012. |
- Helgstrand, Magnus, et al.
(författare)
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QSim, a program for NMR simulations
- 2004
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Ingår i: Journal of Biomolecular NMR. - 0925-2738 .- 1573-5001. ; 30:1, s. 71-80
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Tidskriftsartikel (refereegranskat)abstract
- We present QSim, a program for simulation of NMR experiments. Pulse sequences are implemented and analyzed in QSim using a mouse driven interface. QSim can handle almost any modern NMR experiment, using multiple channels, shaped pulses, mixing, decoupling, phase-cycling and pulsed field gradients. Any number of spins with any spin quantum number can, in theory, be used in simulations. Relaxation is accounted for during all steps of pulse sequences and relaxation interference effects are supported. Chemical kinetics between any numbers of states can be simulated. Both classical and quantum mechanical calculations can be performed. The result of a simulation can be presented either as magnetization as a function of time or as a processed spectrum.
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| 1013. |
- Hellström, Fredrik, 1971-, et al.
(författare)
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Numerical computations of steady and unsteady flow in bended pipes
- 2007
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Ingår i: Collection of Technical Papers - 37th AIAA Fluid Dynamics Conference. - Reston, Virigina : American Institute of Aeronautics and Astronautics. - 9781563478970 - 1563478978 ; , s. 1850-1859
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Konferensbidrag (refereegranskat)abstract
- The steady and pulsative turbulent flows in curved pipes have been computed with two different modeling approaches; the Reynolds Averaged Navier-Stokes (RANS) technique and Large Eddy Simulations (LES). The results from computations of the flow in a single bended pipe have been compared to experimental data. The comparisons show poor agreement for the RANS technique at the exit of the bend, while the LES computations show better agreement with the measured velocity profiles. LES in contrast to RANS, can also provide much more details about the dynamics of the flow. It is also shown that small uncertainties in the inlet boundary conditions can result in significant variations in the flow field. Different types of small amplitude secondary flow at the inlet affect the flow downstream of the bend. The approach enables one to state that for the experiments under consideration the lack of data on the secondary flow prevents a direct validation of the LES results. The pulsatile flow in a double bended pipe has also been investigated and the vortex cores are visualized to enable a better insight into the unsteady flow field and the effects of the inflow pulsations.
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| 1014. |
- Helsing, Johan, et al.
(författare)
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A Seventh-Order Accurate and Stable Algorithm for the Computation of Stress Inside Cracked Rectangular Domains
- 2004
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Ingår i: International Journal for Multiscale Computational Engineering. - 1543-1649. ; 2:1, s. 47-68
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Tidskriftsartikel (refereegranskat)abstract
- A seventh-order accurate and extremely stable algorithm for the rapid computation of stress fields inside cracked rectangular domains is presented. The algorithm is seventh-order accurate since it incorporates basis functions, taking the asymptotic shape of the stress fields close to crack tips and corners into account at least up to order six. The algorithm is stable since it is based on a Predholm integral equation of the second kind. The particular form of the integral equation represents the solution as the limit of a function which is analytic inside the domain. This allows for an efficient implementation. In an example, involving 112 discretization points on an elastic square with a center crack, values of normalized stress intensity factors and T-stress with a relative error of 10(-6) are computed in seconds on a workstation. More points reduce the relative error down to 10(-15), where it saturates in double precision arithmetic. A large-scale setup with up to 1024 cracks in an elastic square is also studied, using up to 740,000 discretization points. The algorithm is intended as a basic building block in general-purpose solvers for fracture mechanics. It can also be used as a substitute for benchmark tables.
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| 1015. |
- Hemphälä, Hillevi, et al.
(författare)
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A visual ergonomics intervention in mail sorting facilities : Effects on eyes, muscles and productivity
- 2012
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Ingår i: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 43:1, s. 217-229
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Tidskriftsartikel (refereegranskat)abstract
- Visual requirements are high when sorting mail. The purpose of this visual ergonomics intervention study was to evaluate the visual environment in mail sorting facilities and to explore opportunities for improving the work situation by reducing visual strain, improving the visual work environment and reducing mail sorting time. Twenty-seven postmen/women participated in a pre-intervention study, which included questionnaires on their experiences of light, visual ergonomics, health, and musculoskeletal symptoms. Measurements of lighting conditions and productivity were also performed along with eye examinations of the postmen/women. The results from the pre-intervention study showed that the postmen/women who suffered from eyestrain had a higher prevalence of musculoskeletal disorders (MSD) and sorted slower, than those without eyestrain. Illuminance and illuminance uniformity improved as a result of the intervention. The two post-intervention follow-ups showed a higher prevalence of MSD among the postmen/women with eyestrain than among those without. The previous differences in sorting time for employees with and without eyestrain disappeared. After the intervention, the postmen/women felt better in general, experienced less work induced stress, and considered that the total general lighting had improved. The most pronounced decreases in eyestrain, MSD, and mail sorting time were seen among the younger participants of the group.
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| 1016. |
- Hemphälä, Hillevi, et al.
(författare)
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Optimal correction in spectacles : Intervention effects on eyestrain and musculoskeletal discomfort among postal workers
- 2014
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Ingår i: Work. - 1051-9815 .- 1875-9270. ; 47:3, s. 329-337
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The static posture of postal workers when sorting mail can lead to musculoskeletal discomfort. Research has shown a connection between eyestrain and upper-body musculoskeletal discomfort in general, including postal workers. A previous study of postal workers found that most of those with eye strain were in need of a new correction in their existing spectacles.OBJECTIVE: Evaluate intervention effects on eyestrain and musculoskeletal discomfort with new spectacles for postal workers.METHODS: Postal workers subjectively reported eyestrain, musculoskeletal discomfort and their opinions of the visual environment via questionnaires pre- and post-intervention. After an eye examination the postal workers were divided into two groups: those who needed new spectacles and those who did not.RESULTS: Those who needed new spectacles showed a higher prevalence of eyestrain and musculoskeletal discomfort pre-intervention. Post-intervention, the postal workers rated their vision better and the average eyestrain and musculoskeletal discomfort decreased for both groups. These workers also experienced a decrease in discomfort on the left (static) side of the neck while sorting mail.CONCLUSION: An intervention providing the optimal correction reduces eyestrain and decreases musculoskeletal discomfort, especially from the neck.
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| 1017. |
- Hemphälä, Hillevi, et al.
(författare)
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Vision ergonomics at recycling centres
- 2010
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Ingår i: Applied Ergonomics. - : Elsevier BV. - 0003-6870 .- 1872-9126. ; 41:3, s. 368-375
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Tidskriftsartikel (refereegranskat)abstract
- All municipalities in Sweden offer their inhabitants a service for disposing of large-size and hazardous waste at local recycling centres. Opening hours at these centres include hours of darkness. The aims of this study were to 1) describe user and employee experiences of lighting and signs at Swedish recycling centres, 2) measure and assess the lighting system at the two recently built recycling centres in Linkoping and to assess the legibility and visibility of the signs used and 3) propose recommendations regarding lighting and signs for recycling centres. Interviews and questionnaires were used to assess experiences of employees and users, and light measurements were performed. By observing users, activities with different visual demands at different areas within the recycling centres were identified. Based on the literature, standards and stakeholder experiences, recommendations regarding lighting systems and sign design, illuminance, luminance and uniformity are proposed for recycling centres.
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| 1018. |
- Hemphälä, Hillevi, et al.
(författare)
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Visual ergonomics interventions in mail sorting facilities
- 2012
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Ingår i: Work. - 1051-9815 .- 1875-9270. ; 41:1, s. 3433-3437
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Tidskriftsartikel (refereegranskat)abstract
- This study was performed between 2004 and 2011 at mail sorting facilities in Sweden. During this time, different interventions were performed. The first was a lighting intervention that had a positive impact on the postal workers, especially those with eyestrain. A new lighting system also improved the illuminance and gave better light distribution. The second intervention involved new personal spectacles for the postal workers who needed them and this had a positive effect on eyestrain. The third intervention involved a specific type of sorting spectacles for the postal workers who already used progressive lenses privately. The reading distances that the postal workers had while sorting the mail was inverted to the distances in their regular progressive lenses. The new sorting spectacles had a positive effect on head postures and on muscular activity.
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| 1019. |
- Hemphälä, Hillevi, et al.
(författare)
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Working spectacles for sorting mail
- 2014
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Ingår i: Work. - 1051-9815 .- 1875-9270. ; 47:3, s. 319-327
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Sorting mail into racks for postmen is visually demanding work. This can result in backward inclination of their heads, especially more pronounced for those who use progressive addition lenses. OBJECTIVE: To evaluate the effects of customized working spectacles on the physical workload of postmen. METHODS: Twelve male postmen sorted mail on two occasions: once using their private progressive spectacles and once using customized sorting spectacles with inverted progressive lenses. Postures and movements of the head, upper back, neck, and upper arms were measured by inclinometry. The muscular load of the trapezius was measured by surface electromyography. RESULTS: With the customized sorting spectacles, both the backward inclination of the head and backward flexion of the neck were reduced (3 degrees), as well as the muscular load of the right upper trapezius, compared to sorting with private spectacles. However, with the sorting spectacles, there was a tendency for increased neck forward flexion, and increased sorting time. CONCLUSION: The reduction in work load may reduce the risk for developing work-related musculoskeletal disorders due to the positive reduction of the backward inclination of the head. But the tendency for increased neck forward flexion may reduce the positive effects. However, the magnitude of the possible reduction is difficult to predict, especially since quantitative data on exposure-response relationships are unknown. Alternative working spectacles with inverted near progressive lenses ought to be evaluated. They should still result in a positive reduced backward inclination of the head and may not cause any increased forward flexion.
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| 1020. |
- Henning, Martin, 1978, et al.
(författare)
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Urban-rural population changes and spatial inequalities in Sweden
- 2022
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Ingår i: Regional Science Policy and Practice. - : Wiley. - 1757-7802. ; 15:4, s. 878-892
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Tidskriftsartikel (refereegranskat)abstract
- This paper documents regional population changes in Sweden since 1860 and investigates how these changes link to regional economic development (regional GDP). We combine long-term decade population data for the historical counties (1860-2020) with detailed annual population observations for municipalities (1968-2021). As industrialization picked up speed, this benefited regions all around the country in terms of production, at the same time as regional population patterns started to diverge. After a slowdown in the regional GDP convergence processes during the low-growth period of the 1980s, 'double divergence,' in both population and regional GDP per capita, has characterized Swedish growth patterns since the 1990s.
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