| 2741. |
- Hellman, Fredrik, et al.
(författare)
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Numerical upscaling for heterogeneous materials in fractured domains
- 2021
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Ingår i: Esaim - Mathematical Modelling and Numerical Analysis - Modelisation Mathematique Et Analyse Numerique. - : EDP Sciences. - 0764-583X .- 2822-7840 .- 1290-3841. ; 55
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Tidskriftsartikel (refereegranskat)abstract
- We consider numerical solution of elliptic problems with heterogeneous diffusion coefficients containing thin highly conductive structures. Such problems arise e.g. in fractured porous media, reinforced materials, and electric circuits. The main computational challenge is the high resolution needed to resolve the data variation. We propose a multiscale method that models the thin structures as interfaces and incorporate heterogeneities in corrected shape functions. The construction results in an accurate upscaled representation of the system that can be used to solve for several forcing functions or to simulate evolution problems in an efficient way. By introducing a novel interpolation operator, defining the fine scale of the problem, we prove exponential decay of the shape functions which allows for a sparse approximation of the upscaled representation. An a priori error bound is also derived for the proposed method together with numerical examples that verify the theoretical findings. Finally we present a numerical example to show how the technique can be applied to evolution problems.
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| 2742. |
- Hellman, Fredrik, et al.
(författare)
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Well-posedness and finite element approximation of mixed dimensional partial differential equations
- 2024
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Ingår i: BIT NUMERICAL MATHEMATICS. - 0006-3835 .- 1572-9125. ; 64:1
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Tidskriftsartikel (refereegranskat)abstract
- In this article, a mixed dimensional elliptic partial differential equation is considered, posed in a bulk domain with a large number of embedded interfaces. In particular, well-posedness of the problem and regularity of the solution are studied. A fitted finite element approximation is also proposed and an a priori error bound is proved. For the solution of the arising linear system, an iterative method based on subspace decomposition is proposed and analyzed. Finally, numerical experiments are presented and rapid convergence using the proposed preconditioner is achieved, confirming the theoretical findings.
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| 2743. |
- Hellsing, Marie, 1983, et al.
(författare)
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An Experimental Field Study of the Effects of Listening to Self-selected Music on Emotions, Stress, and Cortisol Levels
- 2016
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Ingår i: Music and Medicine. - 1943-8621 .- 1943-863X. ; 8:4, s. 187-198
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Tidskriftsartikel (refereegranskat)abstract
- Music listening may evoke meaningful emotions in listeners and may enhance certain health benefits. At the same time, it is important to consider individual differences, such as musical taste, when examining musical emotions and in considering their possible health effects. In a field experiment, 21 women listened to their own preferred music on mp3-players daily for 30 minutes during a two week time period in their own homes. One week they listened to their own chosen relaxing music and the other their own chosen energizing music. Self-reported stress, emotions and health were measured by a questionnaire each day and salivary cortisol was measured with 6 samples two consecutive days every week. The experiment group was compared to a control group (N = 20) who were instructed to relax for 30 minutes everyday for three weeks, and with a baseline week when they relaxed without music for one week (before the music intervention weeks). The results showed that when participants in the experiment group listened to their own chosen music they reported to have experienced significantly higher intensity positive emotions and less stress than when they relaxed without music. There was also a significant decrease in cortisol from the baseline week to the second music intervention week. The control group’s reported stress levels, perceived emotions and cortisol levels remain stable during all three weeks of the study. Together these results suggest that listening to preferred music may be a more effective way of reducing feelings of stress and cortisol levels and increasing positive emotions than relaxing without music.
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| 2744. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Comparison of plantar pressure in three types of insole given to patients with diabetes at risk of developing foot ulcers – A two-year, randomized trial
- 2014
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Ingår i: Journal of Clinical and Translational Endocrinology. - : Elsevier BV. - 2214-6237. ; 1:4, s. 121-132
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Tidskriftsartikel (refereegranskat)abstract
- Background: Special insoles and shoes designed to prevent foot ulcers caused by repetitive high pressures are recommended for patients with diabetes who have any of the following risk factors: neuropathy; peripheral vascular disease; foot deformities; previous ulcers; amputation; and skin pathologies. However, there is a need for increased knowledge regarding: a) differences in the peak pressure (PP) and pressure time integral (PTI) for different types of insoles; and b) the properties of the pressure distribution for insoles used over a period of several months. We present the results of a randomized trial to compare the plantar pressures of three commonly used insoles. Objectives: The primary objective was to compare the PP and PTI between three types of insoles. The secondary objective was to explore the long-term pattern of peak plantar pressure distribution and variations in specific regions of interest (ROI). The tertiary objective was to investigate the impacts of insole adjustments, how much the insoles were used, and the levels of patient satisfaction. Methods In a 2-year trial, 114 patients with type 1 (N = 31) or type 2 (N = 83) diabetes (62 men and 52 women; mean age, 57.7 ± 15.4 years; duration of diabetes, 12.3 ± 11.2 years; neuropathy, 38%), were randomized to be supplied with one of three different insoles. The ethylene vinyl acetate (EVA) insoles were used in outdoor walking shoes. The 35 EVA group (N = 39) received soft custom-made insoles composed of EVA of 35 shore A hardness, the 55 EVA group (N = 37) received custom-made insoles composed of EVA of 55 shore hardness, and the control group (N = 38) received prefabricated insoles composed of a hard core with a top layer of soft 12 shore hardness microfiber. Using F-Scan®, the in-shoe plantar pressures were measured at seven ROI (hallux, metatarsal head 1, metatarsal head 2, metatarsal head 4, metatarsal head 5, lateral aspect of the mid-foot, heel) on five occasions during the study period. The plantar-pressure variables used were PP (main outcome) and PTI. The plantar patterns of load were explored, satisfaction and usage of the insoles were rated by the participants, and insole adjustments were recorded. Results:A mixed model analysis estimated lower PP values in the heel regions for the 35 EVA and 55 EVA insoles (171 ± 13 and 161 ± 13 kPa, respectively) than for the prefabricated insoles (234 ± 10 kPa) (p
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| 2745. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Exploring the Role of Complexity in Health Care Technology Bottom-Up Innovations : Multiple-Case Study Using the Nonadoption, Abandonment, Scale-Up, Spread, and Sustainability Complexity Assessment Tool
- 2024
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Ingår i: JMIR Human Factors. - : JMIR Publications. - 2292-9495. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: New digital technology presents new challenges to health care on multiple levels. There are calls for further research that considers the complex factors related to digital innovations in complex health care settings to bridge the gap when moving from linear, logistic research to embracing and testing the concept of complexity. The nonadoption, abandonment, scale-up, spread, and sustainability (NASSS) framework was developed to help study complexity in digital innovations.OBJECTIVE: This study aims to investigate the role of complexity in the development and deployment of innovations by retrospectively assessing challenges to 4 digital health care innovations initiated from the bottom up.METHODS: A multicase retrospective, deductive, and explorative analysis using the NASSS complexity assessment tool LONG was conducted. In total, 4 bottom-up innovations developed in Region Västra Götaland in Sweden were explored and compared to identify unique and shared complexity-related challenges.RESULTS: The analysis resulted in joint insights and individual learning. Overall, the complexity was mostly found outside the actual innovation; more specifically, it related to the organization's readiness to integrate new innovations, how to manage and maintain innovations, and how to finance them. The NASSS framework sheds light on various perspectives that can either facilitate or hinder the adoption, scale-up, and spread of technological innovations. In the domain of condition or diagnosis, a well-informed understanding of the complexity related to the condition or illness (diabetes, cancer, bipolar disorders, and schizophrenia disorders) is of great importance for the innovation. The value proposition needs to be clearly described early to enable an understanding of costs and outcomes. The questions in the NASSS complexity assessment tool LONG were sometimes difficult to comprehend, not only from a language perspective but also due to a lack of understanding of the surrounding organization's system and its setting.CONCLUSIONS: Even when bottom-up innovations arise within the same support organization, the complexity can vary based on the developmental phase and the unique characteristics of each project. Identifying, defining, and understanding complexity may not solve the issues but substantially improves the prospects for successful deployment. Successful innovation within complex organizations necessitates an adaptive leadership and structures to surmount cultural resistance and organizational impediments. A rigid, linear, and stepwise approach risks disregarding interconnected variables and dependencies, leading to suboptimal outcomes. Success lies in embracing the complexity with its uncertainty, nurturing creativity, and adopting a nonlinear methodology that accommodates the iterative nature of innovation processes within complex organizations.
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| 2746. |
- Hellstrand Tang, Ulla, 1956, et al.
(författare)
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Foot deformities, function in the lower extremities, and plantar pressure in patients with diabetes at high risk to develop foot ulcers
- 2015
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Ingår i: Diabetic Foot & Ankle. - : Informa UK Limited. - 2000-625X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Objective : Foot deformities, neuropathy, and dysfunction in the lower extremities are known risk factors that increase plantar peak pressure (PP) and, as a result, the risk of developing foot ulcers in patients with diabetes. However, knowledge about the prevalence of these factors is still limited. The aim of the present study was to describe the prevalence of risk factors observed in patients with diabetes without foot ulcers and to explore possible connections between the risk factors and high plantar pressure. Patients and methods : Patients diagnosed with type 1 ( n= 27) or type 2 ( n= 47) diabetes (mean age 60.0±15.0 years) were included in this cross-sectional study. Assessments included the registration of foot deformities; test of gross function at the hip, knee, and ankle joints; a stratification of the risk of developing foot ulcers according to the Swedish National Diabetes Register; a walking test; and self-reported questionnaires including the SF-36 health survey. In-shoe PP was measured in seven regions of interests on the sole of the foot using F-Scan ® . An exploratory analysis of the association of risk factors with PP was performed. Results : Neuropathy was present in 28 (38%), and 39 (53%) had callosities in the heel region. Low forefoot arch was present in 57 (77%). Gait-related parameters, such as the ability to walk on the forefoot or heel, were normal in all patients. Eighty percent had normal function at the hip and ankle joints. Gait velocity was 1.2±0.2 m/s. All patients were stratified to risk group 3. Hallux valgus and hallux rigidus were associated with an increase in the PP in the medial forefoot. A higher body mass index (BMI) was found to increase the PP at metatarsal heads 4 and 5. Pes planus was associated with a decrease in PP at metatarsal head 1. Neuropathy did not have a high association with PP. Conclusions: This study identified several potential risk factors for the onset of diabetic foot ulcers (DFU). Hallux valgus and hallux rigidus appeared to increase the PP under the medial forefoot and a high BMI appeared to increase the PP under the lateral forefoot. There is a need to construct a simple, valid, and reliable assessment routine to detect potential risk factors for the onset of DFU.
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| 2747. |
- Hellström, Björn, 1959, et al.
(författare)
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Modelling the shopping soundscape
- 2011
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Ingår i: Journal of Sonic Studies. - Leiden : Leiden University Press. - 2212-6252. ; 1
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Tidskriftsartikel (refereegranskat)abstract
- This article’s pivotal theme is: “How to compose a site-specific sound-art installation for a commercial space in order to improve conditions, while taking perceptual, social, aesthetical, temporal and spatial criteria into account” The interdisciplinary, art-based research approach is derived from the concept of acousmatics, i.e. the process of apprehending any sound, the source of which is invisible. Acousmatic perception concerns the everyday identification process; when lacking visual contact with the sound source, we automatically seek references, such as social (what produces the sound and what is my relation to it?), aesthetical, spatial and temporal (e.g. orientation and demarcation). The acousmatic concept identifies phenomena based on individually, culturally and spatially conditioned experiences. Today, a shopping culture dominates urban space. Indoor malls expose us to all types of acousmatically perceived sounds: jingles, signals, music and muzak from public loudspeakers, mobile devices, etc. In this respect, one could claim that the soundscape of the shopping culture embodies an acousmatic environment. In 2009, the research and sound-art group Urban Sound Institute (USIT) created a permanent sound installation in a shopping mall (Gallerian) located in downtown Stockholm. This installation serves as a case study for the present paper. The artistic assignment involved the creation of a meeting place without material devices as well as the enhancement of the overall atmosphere. The research objective was to elucidate different qualities of the sound installation in regard to the acousmatics of the shopping mall, promoting discussions on the articulation of sound-space configurations in relation to time and site-specific context, issues on musical-architectural qualities as well as objective, subjective and inter-subjective interrelationships between the experience of the sound-art installation and the experience of the shopping mall soundscape. Other applied, interrelated concepts are metabolic environment and masking- and cutting effects.
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| 2748. |
- Hellström, Kristina M, 1971, et al.
(författare)
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Mitigation of Fireside Corrosion in Power Plants: The Combined Effect of Sulfur Dioxide and Potassium Chloride on the Corrosion of a FeCrAl Alloy
- 2014
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 0887-0624 .- 1520-5029. ; 28:9, s. 6116-6129
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion behavior of a FeCrAl alloy (Kanthal APMT) was investigated in 5% O-2 with 40% H2O plus 300 ppm of SO2 at 600 degrees C in the presence or absence of KCl, and the results were also compared to exposures performed without SO2 and KCl. The influence of preoxidation was also examined. The kinetics was followed using mass gain measurements, and the formed corrosion products were examined using XRD, SEM/EDX, AES, IC, and SIMS. The oxidation rate of Kanthal APMT was very low in O-2/N-2/H2O + 300 ppm of SO2, and the outward alumina growth appeared to be suppressed. Interestingly, no sulfur was detected at the scale/metal interface. KCl strongly accelerated the corrosion of Kanthal APMT in O-2/H2O/N-2 at 600 degrees C, forming K2CrO4 and gaseous HCl. Chromate formation depletes the protective scale in Cr, triggering the formation of a fast growing iron-rich scale. Adding SO2 suppressed the corrosion due to the conversion of the corrosive KCl to the stable K2SO4. If any K2CrO4 was formed on the surface of the material initially, it was also rapidly converted to K2SO4. Preoxidation of Kanthal APMT had a strong beneficial effect on the subsequent exposure at 600 degrees C in the presence of KCl and SO2, resulting in the formation of K2SO4 and the evaporation of HCl and KCl. In summary, the alumina-forming FeCrAl material Kanthal APMT is not completely inert to KCl in an oxidizing SO2-containing atmosphere at 600 degrees C. However, the corrosion rate is significantly lower than that of the commonly used chromia-forming alloy, 304L. Preoxidation decreases the corrosion rate even further, making Kanthal APMT a promising candidate material for combustion plant components, particularly from a corrosion point of view.
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| 2749. |
- Hellsvik, Johan, et al.
(författare)
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General method for atomistic spin-lattice dynamics with first-principles accuracy
- 2019
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Ingår i: Physical Review B. - : American Physical Society. - 2469-9969 .- 2469-9950. ; 99:10
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Tidskriftsartikel (refereegranskat)abstract
- We present a computationally efficient and general first-principles based method for spin-lattice simulations for solids and clusters. The method is based on a coupling of atomistic spin dynamics and molecular dynamics simulations, expressed through a spin-lattice Hamiltonian, where the bilinear magnetic term is expanded up to second order in displacement. The effect of first-order spin-lattice coupling on the magnon and phonon dispersion in bcc Fe is reported as an example, and we observe good agreement with previous simulations. We also illustrate the coupled spin-lattice dynamics method on a more conceptual level, by exploring dissipation-free spin and lattice motion of small magnetic clusters (a dimer, trimer, and tetramer). The method discussed here opens the door for a quantitative description and understanding of the microscopic origin of many fundamental phenomena of contemporary interest, such as ultrafast demagnetization, magnetocalorics, and spincaloritronics.
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| 2750. |
- Helsing, Johan, et al.
(författare)
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An efficient full-wave solver for eddy currents
- 2022
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Ingår i: Computers & Mathematics with Applications. - : Elsevier BV. - 0898-1221. ; 128, s. 145-162
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Tidskriftsartikel (refereegranskat)abstract
- An integral equation reformulation of the Maxwell transmission problem is presented. The reformulation uses techniques such as tuning of free parameters and augmentation of close-to-rank-deficient operators. It is designed for the eddy current regime and works both for surfaces of genus 0 and 1. Well-conditioned systems and field representations are obtained despite the Maxwell transmission problem being ill-conditioned for genus 1 surfaces due to the presence of Neumann eigenfields. Furthermore, it is shown that these eigenfields, for ordinary conductors in the eddy current regime, are different from the classical Neumann eigenfields for superconductors. Numerical examples, based on the reformulation, give an unprecedented 13 -digit accuracy both for transmitted and scattered fields.
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