Östernäs - väcker åter liv i Ljusdal

Den här uppsatsen visar ett alternativt gestaltningsprogram för utvecklingsområdet Östernäs. Arbetsområdet ligger centralt i tätorten Ljusdal och har direkt kontakt med Kyrksjön och rekreationsområde, men avskärmas från centrum genom starka barriärer. I examensarbetet undersöker jag hur man genom olika arkitektoniska strategier kan koppla samman området Östernäs med Ljusdals centrum. Syftet med uppsatsen är att skapa ett gott stadsliv. Målet är att genom förslaget visa exempel på hur ett kompakt centrum kan gynna det sociala livet. Arbetet bygger på en modell där inventering och studier av kartor, historia, översiktsplan, detaljplan, medborgardialog och program skapat den informationskälla och den bas som det övriga arbetet vilar på. Informationen har sedan legat till grund för uppsatsens mål, att skapa ett gott stadsliv genom ett kompakt centrum. Ett antal analyser har utförts för att lyfta fram och tydliggöra områdets problem. Problemen har sedan resulterat i forskningsfrågan hur man kopplar samman Östernäs med övriga centrum. För att svara på forskningsfrågan har jag sökt strategier inom litteratur och likvärdiga utvecklingsområden. Strategierna har sammanställts i en konceptuell skiss som visar riktlinjer för hur området Östernäs kan kopplas samman med Ljusdals centrum. Utifrån konceptskiss och program som bygger på önskemål från kommun, medborgare, samt riktlinjer från analyser och egna idéer har jag tagit fram en programskiss för att disponera områdets ytor. Programskissen har legat till grund för det slutliga förslaget. Svaret på forskningsfrågan är att det går att koppla samman Östernäs med övriga centrum genom arkitektoniska strategier. För att göra detta kan man använda en rad olika verktyg, vilka jag klassificerat under tre övergripande rubriker: skapa ett enhetligt intryck, skapa gemensamma rum och sammanlänkande riktningar. För att skapa ett enhetligt intryck kan man arbeta med en upprepning av färg, form, storlek, skala, textur, markbeläggning, rytm, koncentration och detaljrikedom. För att öka känslan av ett gemensamt rum kan man arbeta med ett gemensamt golv, gemensamma väggar, gemensamt tak, en gemensam länk/sluss/ knutpunkt, gemensamma stråk, gemensamma aktiviteter samt något som kallas för interlock och innebär att två former överlappar varandra och skapar en ny. För att skapa sammanlänkande riktningar kan man arbeta med gemensamma stråk, skapa visuella kontakter, gemensamma fokuspunkter, landmärken och axlar. I det här examensarbetet har jag använt dessa verktyg för att skapa en konceptskiss och därefter ett förslag på hur området Östernäs kan kopplas samman med Ljusdals centrum

Dynamic characterization of cellulose nanofibrils in sheared and extended semi-dilute dispersions

New materials made through controlled assembly of dispersed cellulose nanofibrils (CNF) has the potential to develop into biobased competitors to some of the highest performing materials today. The performance of these new cellulose materials depends on how easily CNF alignment can be controlled with hydrodynamic forces, which are always in competition with a different process driving the system towards isotropy, called rotary diffusion. In this work, we present a flow-stop experiment using polarized optical microscopy (POM) to study the rotary diffusion of CNF dispersions in process relevant flows and concentrations. This is combined with small angle X-ray scattering (SAXS) experiments to analyze the true orientation distribution function (ODF) of the flowing fibrils. It is found that the rotary diffusion process of CNF occurs at multiple time scales, where the fastest scale seems to be dependent on the deformation history of the dispersion before the stop. At the same time, the hypothesis that rotary diffusion is dependent on the initial ODF does not hold as the same distribution can result in different diffusion time scales. The rotary diffusion is found to be faster in flows dominated by shear compared to pure extensional flows. Furthermore, the experimental setup can be used to quickly characterize the dynamic properties of flowing CNF and thus aid in determining the quality of the dispersion and its usability in material processes.Comment: 45 pages, 13 figure

Demonstrating the Performance and Emission Characteristics of a Variable Compression Ratio, Alvar-Cycle Engine

This paper is a direct continuation of a previous study that addressed the performance and design of a variable compression engine, the Alvar-Cycle Engine [1]. The earlier study was presented at the SAE International Conference and Exposition in Detroit during February 23- 26, 1998 as SAE paper 981027. In the present paper test results from a single cylinder prototype are reviewed and compared with a similar conventional engine. Efficiency and emissions are shown as function of speed, load, and compression ratio. The influence of residual gas on knock characteristics is shown. The potential for high power density through heavy supercharging is analyzed

Non-Hermitian Hamiltonians in field theory

This thesis is centred around the role of non-Hermitian Hamiltonians in Physics both at the quantum and classical levels. In our investigations of two-level models we demonstrate [1] the phenomenon of fast transitions developed in the PT -symmetric quantum brachistochrone problem may in fact be attributed to the non-Hermiticity of evolution operator used, rather than to its invariance under PT operation. Transition probabilities are calculated for Hamiltonians which explicitly violate PT -symmetry. When it comes to Hilbert spaces of infinite dimension, starting with non-Hermitian Hamiltonians expressed as linear and quadratic combinations of the generators of the su(1; 1) Lie algebra, we construct [2] Hermitian partners in the same similarity class. Alongside, metrics with respect to which the original Hamiltonians are Hermitian are also constructed, allowing to assign meaning to a large class of non-Hermitian Hamiltonians possessing real spectra. The finding of exact results to establish the physical acceptability of other non-Hermitian models may be pursued by other means, especially if the system of interest cannot be expressed in terms of Lie algebraic elements. We also employ [3] a representation of the canonical commutation relations for position and momentum operators in terms of real-valued functions and a noncommutative product rule of differential form. Besides exact solutions, we also compute in a perturbative fashion metrics and isospectral partners for systems of physical interest. Classically, our efforts were concentrated on integrable models presenting PT - symmetry. Because the latter can also establish the reality of energies in classical systems described by Hamiltonian functions, we search for new families of nonlinear differential equations for which the presence of hidden symmetries allows one to assemble exact solutions. We use [4] the Painleve test to check whether deformations of integrable systems preserve integrability. Moreover we compare [5] integrable deformed models, which are thus likely to possess soliton solutions, to a broader class of systems presenting compacton solutions. Finally we study [6] the pole structure of certain real valued nonlinear integrable systems and establish that they behave as interacting particles whose motion can be extended to the complex plane in a PT -symmetric way.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Six iterative reconstruction algorithms in brain CT- A phantom study on image quality at different radiation doses.

OBJECTIVE: To evaluate the image quality produced by six different iterative reconstruction (IR) algorithms in four CT systems in the setting of brain CT, using different radiation dose levels and iterative image optimisation levels. METHODS: An image quality phantom, supplied with a bone mimicking annulus, was examined using four CT systems from different vendors and four radiation dose levels. Acquisitions were reconstructed using conventional filtered back-projection (FBP), three levels of statistical IR and, when available, a model-based IR algorithm. The evaluated image quality parameters were CT numbers, uniformity, noise, noise-power spectra, low-contrast resolution and spatial resolution. RESULTS: Compared with FBP, noise reduction was achieved by all six IR algorithms at all radiation dose levels, with further improvement seen at higher IR levels. Noise-power spectra revealed changes in noise distribution relative to the FBP for most statistical IR algorithms, especially the two model-based IR algorithms. Compared with FBP, variable degrees of improvements were seen in both objective and subjective low-contrast resolutions for all IR algorithms. Spatial resolution was improved with both model-based IR algorithms and one of the statistical IR algorithms. CONCLUSION: The four statistical IR algorithms evaluated in the study all improved the general image quality compared with FBP, with improvement seen for most or all evaluated quality criteria. Further improvement was achieved with one of the model-based IR algorithms. ADVANCES IN KNOWLEDGE: The six evaluated IR algorithms all improve the image quality in brain CT but show different strengths and weaknesses