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1.
  • Aranda, Jesus Javier Lechuga (författare)
  • Towards Self-Powered Devices Via Pressure Fluctuation Energy Harvesters
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The growing interest in the Internet of Things has created a need for wireless sensing systems for industrial and consumer applications. In hydraulic systems, a widely used method of power transmission in industry, wireless condition monitoring can lead to reduced maintenance costs and increase the capacity for sensor deployment. A major problem with the adoption of wireless sensors is the battery dependence of current technologies. Energy harvesting from pressure fluctuations in hydraulic systems can serve as an alternative power supply and enable self-powered devices. Energy harvesting from pressure fluctuations is the process of converting small pressure fluctuations in hydraulic fluid into a regulated energy supply to power low power electronics. Previous studies have shown the feasibility of pressure fluctuation harvesting. However, for the development of self-powered sensor systems, the methods and techniques for converting pressure fluctuations into electrical energy should be further investigated.This thesis explores the methods, limitations, opportunities and trade-offs involved in the development of pressure fluctuation energy harvesters in the context of self-powered wireless devices. The focus is on exploring and characterizing the various mechanisms required to convert pressure fluctuations into electrical energy. In this work, an energy harvesting device consisting of a fluid-to-mechanical interface, an acoustic resonator, a piezoelectric stack, and an interface circuit is proposed and evaluated. Simulations and experimental analysis were used to analyse these different components for excitation relevant to hydraulic motors.The results of this work provide new insights into the development of power supplies for self-powered sensors for hydraulic systems using pressure fluctuation energy harvesters. It is shown that with the introduction of the space coiling resonator for pressure fluctuation amplification and a detailed analysis of the fluid interface and power conditioning circuits, the understanding of the design and optimization of efficient pressure fluctuation energy harvesters is further advanced.
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2.
  • Olande, Oduor (författare)
  • Students' narratives from graphical artefacts : Exploring the use of mathematics tools and forms of expression in students' graphicacy
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The research concerns presented in this dissertation addresses aspects of students’ interaction with commonly occurring graphical artefacts in teaching and learning environments. In particular, focus is on how the students make sense of these artefacts in relation to subject specific tools and forms of expression.The dissertation comprises of four studies guided by a semiotics cultural- historical perspective to cognition. The first study which is largely quantitative, analyses the percentage scores from students’ responses to selected items from OECD PISA surveys for items containing graphical elements. The second and the third studies in keeping with a more sociocultural perspective to learning as point of departure, examine the students’ collaborative interaction around tasks containing graphical elements. The fourth study explores the nature of students’ solutions from the Swedish national test in mathematics based on a tools and forms of expression sensitive empirically derived construct of Identification contra Critical-analytical approach to graphicacy.The main outcomes of these studies can be summarised as follows: first there is justification for re-examining the predominant characterisation of students’ interaction with graphical artefacts. Secondly, while it is not uncommon for students to take a more visual-perceptive and intuitive approach to graphicacy, results from task items interactions indicate that a Critical-analytical approach seems to be more reliable and capable of yielding desirable outcomes. The outcomes of these studies call for vigilance on the type of tasks used in relation to graphicacy and how these can be used to foster students’ Critical-analytical disposition.
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3.
  • Olsson, Helén, 1961- (författare)
  • Att minska risken för våld och att främja återhämtning i den rättspsykiatriska vården : Patienters och personalens erfarenheter av vägen mot återhämtning
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Detta avhandlingsarbete är utfört inom en rättspsykiatrisk vårdkontext och återspeglar patienters[1] och personals[2] erfarenheter och upplevelser av vändpunkter i samband med minskad risk för våld och återhämtning. Med utgångspunkt från ett holistiskt och salutogent hälsovetenskapligt perspektiv har avhandlingen ett tvärvetenskapligt förhållningssätt.   Teoretiska ämnesdiscipliner såsom psykiatrisk omvårdnad, kriminologi och sociologi har influerat arbetet.Avhandlingens övergripande syfte var att utifrån de salutogena aspekterna i det rättspsykiatriska omvårdnadsarbetet undersöka vad som är relaterat till vändpunkter i samband med minskad risk för våld och vad som bidrar till återhämtning. Avhandlingen baseras på fyra olika studier. Syftet med den inledande kvantitativa delstudien (I) var att identifiera och jämföra rättspsykiatriska patienter som sänkt sin bedömda risk för våld med 30 % eller mer enligt riskbedömningsinstrument HCR-20. Resultatet visade att den bedömda risken för våld minskade över tid. En demografisk analys genomfördes för att studera skillnader mellan de patienter som sänkt sin bedömda risk för våld och de som inte sänkt sin risk. Det framgick att rättspsykiatriska patienter som bedömts med hjälp av riskbedömningsinstrumentet HCR-20, minskade den bedömda risken för våld, både på kort och på lång sikt. Den rättspsykiatriska vården fungerade bäst när det gällde att förbättra de kliniska riskfaktorerna (C-skalan).Riskhanteringen (R-skalan) gällande eventuell utskrivning och framtida friförmåner visade inte samma goda progress. Demografiska karaktäristika såsom ålder, alkohol och drogmissbruk och psykiatriska diagnoser var inte relaterade till minskad risk för våld, dock var kvinnliga patienter och patienter utan psykopatidiagnos mer benägna att sänka sin risk för våld. Ett urval av de patienter som minskade sin risk för våld med 30 % eller mer utgjorde basen för delstudie II och III.I delstudie II intervjuades tretton rättspsykiatriska patienter om upplevelser och erfarenheter kring vad som bidrar till minskad respektive ökad risk för våld inne på en rättspsykiatrisk avdelning. Data analyserades med hjälp av en tolkande beskrivning (Interpretive Description). Studien visade att orsakerna till ökad respektive minskad risk för våld var processrelaterad, där interaktioner mellan personal och patienter bidrog till en utveckling som antingen präglades av välbefinnande eller disharmoni. Delstudie II utgjorde en viktig kunskapskälla som präglade ansatsen i delstudie III och IV. Detta med hänvisning till att flertalet patienter i delstudie II lämnade intressanta beskrivningar av vändpunkter i samband med minskad risk för våld och återhämtning.Sålunda intervjuades i delstudie III, tio rättspsykiatriska patienter om deras upplevelser av förändringsprocesser i samband med vändpunkter och återhämtning. Dataanalysen skedde med hjälp av en kvalitativ innehållsanalys. Processen beskrevs utifrån tre faser där man i högriskfasen upplevde kaotiska och överväldigande känslor. Vändpunkten upplevdes som ett känsligt skede som präglades av att tvingas hitta en ny, konstruktiv väg i livet. Återhämtningsfasen präglades av ett accepterande och en mognad. Stöd och erkännande från omgivningen ansåg främja dessa processer.Delstudie IV bestod av intervjuer med tretton personal. Syftet var att belysa upplevelser och erfarenheter kring rättspsykiatriska patienters vändpunkter och återhämtning. Kvalitativ innehållsanalys användes för att analysera data. Beskrivningar kring hur en vändpunkt kunde bevaras och främjas baserades på vikten av att vara uppmärksam, lyhörd och att inte skynda på processen. En vändpunkt upplevdes genom att patienten uppvisade synbara positiva förändringar. Sammansättningen på personalen och patienterna ansågs påverka atmosfären på avdelningen, och bidrog till huruvida processen mot vändpunkter och återhämtning underlättades eller försvårades.Avhandlingen visar hur ett ständigt växelspel mellan patienter och mellan personal bidrog till huruvida vårdatmosfären upplevdes såsom hälsofrämjande eller ej. Vidare framgår att processer kring vändpunkter i samband med minskad risk för våld och återhämtning präglades av känslor av sårbarhet och utsatthet. Processen beskrevs som ett känsligt förlopp som behövde understödjas av förtroendefulla relationer med andra, samt möjligheter att få vistas i en trygg miljö.[1] Den vetenskapliga litteraturen använder sig av begrepp såsom client, consumer, service user eller forensic patient för att beteckna människor som är inskrivna inom den rättspsykiatriska vården. Inom det psykiatriska svenska fältet kan begreppen brukare, vårdtagare eller patient förekomma. I denna avhandling kommer begreppet patient och vårdtagare omväxlande att användas för att beteckna de människor som är föremål för den rättspsykiatriska vården. De patienter som deltagit i avhandlingens två delstudier kommer omväxlande att benämnas såsom deltagare eller patienter, för att åstadkomma en varierande och läsvänlig text.[2] I denna avhandling anser begreppet personal den personalkategori som arbetar med omvårdnad inom en rättspsykiatrisk kontext. Det är främst sjuksköterskor och skötare som inkluderas i begreppet omvårdnadspersonal inom den vetenskapliga litteraturen. Sjuksköterskor benämns såsom registered mental health nurses eller registered nurses. Övrig omvårdnadspersonal tituleras till exempel som nurse manager eller assistant nurses. När begreppen personal, vårdare eller omvårdnadspersonal används i denna avhandling avses då den personalkategori som arbetar närmast patienten med omvårdnad och ingen åtskillnad kommer att göras mellan de båda yrkesgrupperna. Personalen som deltar i delstudie IV har omväxlande kallats för personal eller vårdare.
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4.
  • Nydahl, Erik, 1983- (författare)
  • I fyrkens tid : Politisk kultur i två ångermanländska landskommuner
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Abstract   Nydahl, Erik; I fyrkens tid. Politisk kultur i två ångermanländska landskommuner 1860-1930 [Voting by income: The political culture of two Swedish municipalities, 1860–1930] Department of Humanities, Mid Sweden University, SE-871 88 Härnösand, Sweden ISBN: 978-91-86694-05-0, ISSN 1652-893X, Doctoral thesis nr: 100 (2010). Swedish text with a summary in English   This dissertation analyses the development of political culture in two Swedish municipalities between the 1860s and the 1930s – a period during which Swedish society underwent major changes. The purpose is to examine the direct and indirect consequences of an evolving industrial society's economic, social and political structures on political culture at local levels. The following factors are the base of the study. At the start of the 1860s, a long-standing Swedish tradition of local self-government was reinforced through a major reform, the Local Government Ordinance of 1862 (1862 års kommunalförfattningar). From this point, each parish formed its own municipality. The new municipalities were given the right to levy taxes and made responsible for welfare and schools, thereby becoming a prominent arena for the exercise of power at local levels. The municipal reform of 1862 was carried out at a time when Swedish society was transitioning as the industrialisation process accelerated during the latter part of the 1800s. Gradually, the old structure of an agricultural society was cast aside in favour of a new, modern industrial society. Naturally, also the municipalities changed – directly and indirectly. For some municipalities, adjustments were significant; for others, less so. Part of this process was the reformation of voting rights from plutocratic to public and equal. Another part was the reorganisation of municipal government from direct government via municipal meetings to representative government via municipal councils. Two main issues are formulated and answered in the dissertation. The one addresses who or which had the power over local politics and how the situation changed over time. The second addresses in what way municipal representation changed form with the modernisation of the municipalities. The empirical survey comprises a comparative case study between two municipalities in the northern part of Sweden. The one municipality, Ytterlännäs, was early the site for large-scale sawmill industry. The second municipality, Stigsjö, retained its agricultural structure throughout the entire period in question. The comparison makes it possible to analyse the impending industrial society from two different poles. In the 1800s, local politics was considered to be a completely different sort than politics at a national level. The difference was that local politics, referred to as “the municipal”, was seen as non-political and unaffiliated with those conflicts addressed at national levels, referred to as “the political”. The dissertation demonstrates two different models of how modern municipal politics evolved from the municipal meetings of the 1800s. While the starting point was the same in both municipalities, the paths diverged in the early 1870s. In the agricultural municipality of Stigsjö, it was “business as usual”. In the industrial municipality of Ytterlännäs, however, confrontation arose between enterprises and farmers and eventually, a labour movement emerged demanding the right of participation. The dissertation shows that the distinction between “municipal” and “political” was obliterated in the beginning of the 1900s, paving the way for a new concept – municipal politics. This process occurred in a very palpable way in Ytterlännäs but eventually, Stigsjö was forced to conform. The new municipal politics was, so to speak, the final station in both municipalities. In conjunction with party politicisation of local politics, the criteria and seats for the municipal representatives changed. When party affiliation became an important criterion, professional affiliation became less relevant. Party bloc seats replaced the independent seats, and representatives were eventually paid remuneration.     Keywords: Political culture, politics, voting right, municipal politics, industrial society, industrialisation, elected representatives, representation, temperance movement, labour movement, popular movements, political parties, modernisation
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5.
  • Abbasi, Seyed (författare)
  • Determinants of social inequalities in cardiovascular disease among Iranian patients
  • 2018
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Background and objectives: Cardiovascular disease (CVD) is the single largest cause of mortality in the world. Similar to other health issues, CVD is generally affected either by individual risk factors, which may influence the risk for developing an illness or its complications, or by social indicators (social determinants of health). There is evidence from developed countries which shows that the so-called "upstream factors"—including social determinants such as political, social, spiritual, cultural, and economic factors—may affect the prevalence and incidence of CVD. Scarce evidence from studies in low- and middle-income countries also suggests that social factors may affect the distribution of CVD across population groups. However, there is a dearth of such data in Iran, where only a few small-sizedstudies have focused on the social determinants of health. Therefore, the present thesis sought to fill this gap by assessing the effects of socioeconomic status (SES) on the distribution of CVD and the relevant inequalities within the Iranian context.Methods: This thesis is based on four studies, which used data from the Tehran Heart Center’s Databases. In Study I, a total of 44,820 patients who underwent coronary angiography at Tehran Heart Center between 2005 and 2010 were recruited. Then, their pre- and post-procedural data—including demographics, CVD risk factors, symptoms, and laboratory tests—were compared between men and women. In Study II, 6,246 patients with acutecoronary syndrome who were hospitalized between March 2004 and August 2011 were included and, based on their education and their employment status, were divided into high- and low-SES groups. Thereafter, the effect of SES on the in-hospital death of the patients was evaluated. In Study III, 20,165 patients with documented coronary artery disease who underwent coronary angiography at Tehran Heart Center were enrolled and CVD risk factors and severity (measured by the Gensini score) were assessed among the six major Iranian ethnic groups. In Study IV, 9,088 patients with acute coronary syndrome who were hospitalized at Tehran Heart Center between May 2007and June 2014 were recruited and the association between in-hospital death due to acute coronary syndrome and place of residence (rural/urban) was assessed using logistic regression adjusted for potential confounders.Results: In this thesis, the data analyses were based on the hypothesis that there is a potential association between the different socioeconomic indicators and the selected cardiovascular outcomes. In Study I, among the recruited participant, 25,363 men and 11,995 women had coronary artery disease and the women not only were significantly older, less educated, and more overweight but also had higher blood levels of triglyceride, cholesterol, low-density lipoprotein, high-density lipoprotein, and fasting blood sugar than the men. Moreover, hypertension and diabetes mellitus showed the strongest association in the women with coronary artery disease (OR=3.45, 95% CI: 3.28to 3.61 and OR=2.37, 95% CI: 2.26 to 2.48, respectively). In addition, the frequency of post-procedural recommendations for non-invasive procedures was higher in the women than in the men (20.1% vs 18.6%; P<0.001). In StudyII, of the 6,246 recruited patients with acute coronary syndrome, 3,290individuals were considered low-SES and 2,956 high-SES individuals. In-hospital death occurred in 79 (1.26%) patients: 1.9% in the low-SES and 0.6% in the high-SES groups. After adjustment for the possible cofounders, our multivariate analysis demonstrated a significant effect of the patients’ SES on their in-hospital death and a lower in-hospital mortality rate was shown in the high-SES patients (OR=0.30, 95% CI: 0.09 to 0.98; P=0.046). In Study III, the Fars (8.7%) and Gilak (8.6%) ethnic groups had the highest frequency of having at least four simultaneous risk factors. Additionally, the mean Gensini score was lowest in the Lurs (67.5±52.8) and highest among the Gilaks (77.1±55.9). The multivariable regression analysis indicated that the Gilaks showed the worst CVD severity (β: 0.056, 95% CI: 0.009 to 0.102; P=0.018), followed by the Turks (β: 0.032, 95% CI: 0.005 to 0.059; P=0.020), and the lowest CVD severity, was detected in the Lurs (β: -0.087, 95% CI: -0.146 to -0.027;P=0.004). Study IV showed that while smoking (P=0.002), positive family history of coronary artery disease (P=0.003), higher body mass index (P=0.013),and hyperlipidemia (P=0.026) were more prevalent in the urban patients, the rural patients showed lower educational levels (P<0.001) and higher frequency of unemployment (P=0.009). Meanwhile, in-hospital death occurred in 135 (1.5%) patients: 125 (1.5%) urban and 10 (1.2%) rural. To adjust the effects of the possible confounders, we utilized the Firth regression model, which showed no significant difference regarding in-hospital death betweenthe rural and urban patients (OR=1.57, 95% CI: 0.376 to 7.450; P=0.585).Conclusions: The aim of this thesis was to investigate the effects of social determinants (particularly SES) on CVD and its modifiable risk factors among Iranian patients. Results showed that medical treatment for CVD was more recommended (by treating physicians) to the women than the men, and the low-SES patients with acute coronary syndrome were more likely to die in the hospital than their high-SES counterparts. In addition, the thesis found heterogeneity in the distribution of the traditional risk factors for CVD as well as CVD severity in the major Iranian ethnic groups. Further, there were no differences concerning the in-hospital death rates due to acute coronary syndrome between the urban and rural patients after adjustment for the potential confounders.
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6.
  • Afewerki, Samson, 1985- (författare)
  • Development of catalytic enantioselective C-C bond-forming and cascade transformations by merging homogeneous or heterogeneous transition metal catalysis with asymmetric aminocatalysis
  • 2014
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Chiral molecules play a central role in our daily life and in nature, for instance the different enantiomers or diastereomers of a chiral molecule may show completely different biological activity. For this reason, it is a vital goal for synthetic chemists to design selective and efficient methodologies that allow the synthesis of the desired enantiomer. In this context, it is highly important that the concept of green chemistry is considered while designing new approaches that eventually will provide more environmental and sustainable chemical synthesis.The aim of this thesis is to develop the concept of combining transition metal catalysis and aminocatalysis in one process (dual catalysis). This strategy would give access to powerful tools to promote reactions that were not successful with either transition metal catalyst or the organocatalyst alone. The protocols presented in this thesis based on organocatalytic transformations via enamine or iminium intermediates or both, in combination with transition metal catalysis, describes new enantioselective organocatalytic procedures that afford valuable compounds with high chemo- and enantioselectivity from inexpensive commercial available starting materials. In paper I, we present a successful example of dual catalysis: the combination of transition metal activation of an electrophile and aminocatalyst activation of a nucleophile via enamine intermediate. In paper II, the opposite scenario is presented, here the transition metal activates the nucleophile and the aminocatalyst activates the electrophile via an iminium intermediate. In paper III,we present a domino Michael/carbocyclisation reaction that is catalysed by a chiral amine (via iminium/enamine activation) in combination with a transition metal catalysts activation of an electrophile. In paper IV, the concept of dual catalysis was further extended and applied for the highly enantioselective synthesis of valuable structural scaffolds, namely poly-substituted spirocyclic oxindoles. Finally, in paper V the concept of dual catalysis was expanded, by investigating more challenging and environmentally benign processes, such as the successful combination of a heterogeneous palladium and amine catalysts for the highly enantioselective synthesis of functionalised cyclopentenes, containing an all carbonquaternary stereocenter, dihydrofurans and dihydropyrrolidines.
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7.
  • Ahlin, Karin, 1963- (författare)
  • Benefits of Digital Technical Information
  • 2020
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • In our daily work life, we use a wealth of information, including a category of information produced as a part of products and their life-cycle phases, named digital technical information (DTI). Manufacturing organizations focus more often on the product than on DTI, because DTI’s impact seems almost invisible, despite its crucial role to the product and its life-cycle phases, development, production, maintenance, and destruction. Hence, the aim of this thesis is to describe DTI’s benefits and the research questions: “What are the benefits of the DTI?” and “What are the perceptions of how to measure benefits of DTI?” The thesis contains five studies related to identifying and measuring DTI’s benefits. The empirical material is based on semi-structured interviews and group interviews within five organizations and a survey among manufacturing organizations in Sweden.I used three characteristics of the DTI and two pairs of previously known benefit categories to analyse the benefits. The analysis shows that the benefits are recognized in the particular product’s life cycle phase where the DTI is published. However, the DTI continues to offer benefits in the product’s other life cycle phases. In relationship to the product, the benefits evolve from supporting an individual product to supporting more general product lines or all products and a more complex product is said to increase DTI’s benefits. DTI’s structure adds benefits as synthesized or aggregated DTI, where the DTI is synthesized or aggregated automatically or manually. The categorization predetermined benefits related to the change are less numerous than the emerging benefits. The predetermined benefits are strategic by nature, and the emerging ones are mainly used to achieve operational goals. Measuring DTI’s benefits is of importance for a formal comparison of its development and is of special interest for managers. Perceptions from the initial stages on how to measure show that to establish common interpretations among the stakeholders of the measurement process is of importance, especially when it comes to what is viewed as a benefit. The benefits are viewed as intangible by the respondents, which creates difficulties when one is evaluating, using conventional measurement methods. The only perceived way to measure is when DTI reduces co-worker’s workload and efficiency is achieved. The thesis’s contribution to academia consists of the analysis of DTI’s benefits, showing details of the relationships between the DTI and its benefits. For practice, the contributions focus on the systematic evaluation process, which can be used for further development of the DTI and comparison of the evolvement of the DTI itself and relating to other resources. One proposal for future research is to use the analysed benefits and compare various approaches to digitizing DTI, e.g. Industry 4.0. Another proposal is to list, in detail, various ways on how to measure DTI’s benefits and their usefulness. The latter can positively impact on any intangible benefits due to the general approach we have established of how to measure those benefits.
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8.
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9.
  • Ahmad, Waqas (författare)
  • High Efficiency Light Field Image Compression : Hierarchical Bit Allocation and Shearlet-based View Interpolation
  • 2021
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Over the years, the pursuit of capturing the precise visual information of a scenehas resulted in various enhancements in digital camera technology, such as highdynamic range, extended depth of field, and high resolution. However, traditionaldigital cameras only capture the spatial information of the scene and cannot pro-vide an immersive presentation of it. Light field (LF) capturing is a new-generationimaging technology that records the spatial and angular information of the scene. Inrecent years, LF imaging has become increasingly popular among the industry andresearch community mainly for two reasons: (1) the advancements made in optical and computational technology have facilitated the process of capturing and processing LF information and (2) LF data have the potential to offer various post-processing applications, such as refocusing at different depth planes, synthetic aperture, 3Dscene reconstruction, and novel view generation. Generally, LF-capturing devicesacquire large amounts of data, which poses a challenge for storage and transmissionresources. Off-the-shelf image and video compression schemes, built on assump-tions drawn from natural images and video, tend to exploit spatial and temporalcorrelations. However, 4D LF data inherit different properties, and hence there is aneed to advance the current compression methods to efficiently address the correla-tion present in LF data.In this thesis, compression of LF data captured using a plenoptic camera andmulti-camera system (MCS) is considered. Perspective views of a scene capturedfrom different positions are interpreted as a frame of multiple pseudo-video se-quences and given as an input to a multi-view extension of high-efficiency videocoding (MV-HEVC). A 2D prediction and hierarchical coding scheme is proposedin MV-HEVC to improve the compression efficiency of LF data. To further increasethe compression efficiency of views captured using an MCS, an LF reconstructionscheme based on shearlet transform is introduced in LF compression. A sparse set of views is coded using MV-HEVC and later used to predict the remaining views by applying shearlet transform. The prediction error is also coded to further increase the compression efficiency. Publicly available LF datasets are used to benchmark the proposed compression schemes. The anchor scheme specified in the JPEG Plenocommon test conditions is used to evaluate the performance of the proposed scheme. Objective evaluations show that the proposed scheme outperforms state-of-the-art schemes in the compression of LF data captured using a plenoptic camera and an MCS. Moreover, the introduction of shearlet transform in LF compression further improves the compression efficiency at low bitrates, at which the human vision sys-tem is sensitive to the perceived quality.The work presented in this thesis has been published in four peer-reviewed con-ference proceedings and two scientific journals. The proposed compression solu-tions outlined in this thesis significantly improve the rate-distortion efficiency forLF content, which reduces the transmission and storage resources. The MV-HEVC-based LF coding scheme is made publicly available, which can help researchers totest novel compression tools and it can serve as an anchor scheme for future researchstudies. The shearlet-transform-based LF compression scheme presents a compre-hensive framework for testing LF reconstruction methods in the context of LF com-pression.
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10.
  • Ainegren, Mats (författare)
  • Roller skis' rolling resistance and grip characteristics : influences on physiological and performance measures in cross-country skiers
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The aim of this thesis was to investigate roller ski characteristics; classical and freestyle roller skis’ rolling resistance coefficients (μR) and classical style roller skis’ static friction coefficients (μS), and to study the influence of different μR and μS on cross-country skiers’ performance and both physiological and biomechanical indices. The aim was also to study differences in skiing economy and efficiency between recreational skiers, female and male junior and senior elite cross-country skiers.The experiments showed that during a time period of 30 minutes of rolling on a treadmill (warm-up), μR decreased significantly (p<0.05) to about 60-65 % and 70-75 % of its initial value for freestyle and classical roller skis respectively. Also, there was a significant influence of normal force on μR, while different velocities and inclinations of the treadmill only resulted in small changes in μR.The study of the influence on physiological variables of a ~50 % change in μR showed that during submaximal steady rate exercise, external power, oxygen uptake, heart rate and blood lactate were significantly changed, while there were non-significant or only small changes to cycle rate, cycle length and ratings of perceived exertion. Incremental maximal tests showed that time to exhaustion was significantly changed and this occurred without a change in maximal power, maximal oxygen uptake, maximal heart rate and blood lactate, and that the influence on ratings of perceived exertion was non-significant or small.The study of classical style roller skis μS showed values that were five to eight times more than the values of μS reported from on-snow skiing with grip-waxed cross-country skis.The subsequent physiological and biomechanical experiments with different μS showed a significantly lower skiing economy (~14 % higher v̇O2), higher heart rate, lower propulsive forces coming from the legs and shorter time to exhaustion (~30 %) when using a different type of roller ski with a μS similar to on-snow skiing, while there was no difference between tests when using different pairs of roller skis with a (similar) higher μS.The part of the thesis which focused on skiing economy and efficiency as a function of skill, age and gender, showed that the elite cross-country skiers had better skiing economy and higher gross efficiency (5-18 %) compared with the recreational skiers, and the senior elite had better economy and higher efficiency (4-5 %) than their junior counterparts, while no differences could be found between the genders.
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