Made available in DSpace on 2014-07-29T15:03:40Z (GMT). No. of bitstreams: 1 Dissertacao Isa Lorena.pdf: 2675574 bytes, checksum: 324410a337fb201f2446d151678a3e01 (MD5) Previous issue date: 2009-11-24 / This research is carried out to study the influence of aggregate source on the initial tangent modulus of deformation of concrete (Eci), to correlate the resistance to compression (fc) with the module Eci and compare the results of this research with the equations proposed by international standards and the Brazilian. To this end, it was used three levels of resistance to 28 days: 20MPa, 30Mpa and 40Mpa and ranged up the aggregate source in the types lithological micaschist, Granulito and Basalt. Set the type of cement, sand, water, and additive content of mortar. All materials are used in dosages of Goiânia and the surrounding region in order to determine the behavior of these materials in concrete that is produced in the region. The experimental program of this research is divided into two parts. The first is to determine the curves of strength of each aggregate source test of resistance to compression in the age of three, seven and 28 days, while the second part determines the initial tangent modulus of deformation on the ages of seven and 28 days. For the first part of the experimental program were molded 54 body-of-evidence and tested for resistance to compression. For the second part was molded 90 body-of-evidence, where 36 were tested for resistance to compression and 54 with the initial tangent modulus of deformation. With the end of testing was performed a statistical analysis of results obtained through software STATISTIC. In the analysis it was the influence of aggregate source in the initial tangent modulus of deformation (Eci), noting influences the levels of resistance adopted and distinct variations in the influence of aggregate source studied on the Eci, by increasing order of the results of module: micaschist, granulito and basalt. The results also indicated that the NBR 6118 (ABNT, 2003) overestimates the values of modulus of deformation of concrete. / Esta pesquisa desenvolve-se para estudar a influência do agregado graúdo sobre o módulo de deformação tangente inicial do concreto (Eci), correlacionar a resistência à compressão (fc) com o módulo Eci e comparar os resultados desta pesquisa com as equações propostas pelas normas internacionais e pela brasileira. Para esse fim, utilizaram-se três níveis de resistência aos 28 dias: 20MPa, 30Mpa e 40Mpa e variou-se o agregado graúdo nos tipos litológicos Micaxisto, Granulito e Basalto. Fixou o tipo de cimento, areia, água, aditivo e teor de argamassa. Todos os materiais utilizados nas dosagens são da região de Goiânia e entorno com o objetivo de determinar o comportamento desses materiais nos concretos que são produzidos na região. O programa experimental desta pesquisa é dividido em duas partes. A primeira visa determinar as curvas de dosagem de cada agregado graúdo através de ensaios de resistência à compressão nas idades de três, sete e 28 dias, enquanto que a segunda parte determina o módulo de deformação tangente inicial nas idades de sete e 28 dias. Para a primeira parte do programa experimental foram moldados 54 corpos-de-prova e todos ensaiados à resistência à compressão. Para a segunda parte foram moldados 90 corpos-deprova, onde 36 foram ensaiados à resistência à compressão e 54 com o módulo de deformação tangente inicial. Com o termino dos ensaios foi realizado uma análise estatística dos resultados obtidos através do software STATISTIC. Com a análise constatou-se a influência do agregado graúdo sobre o módulo de deformação tangente inicial (Eci), observando sucintas influências dos níveis de resistências adotados e distintas variações na influência dos agregados graúdos estudados sobre o Eci, apresentando em ordem crescente dos resultados do módulo: micaxisto, granulito e basalto. Os resultados também indicaram que a NBR 6118 (ABNT, 2003) superestima os valores do módulo de deformação dos concretos. Com os resultados encontrados para cada agregado graúdo foi possível encontrar as relações entre os resultados da equação proposta pela NBR 6118 (ABNT, 2003) e ACI (ACI, 1999) além de estimar os valores do módulo de elasticidade de acordo com os tipos litológicos estudados por essa pesquisa.

Abstract The main objective of this thesis was to research and develop a sensitive characterization method for dielectric powdery substances which could be utilized in various industrial and research fields. With modern electromagnetic simulation tools and the presented experimental measurements, the characterization of dielectric powders using an indirectly coupled open-ended coaxial cavity resonator operating in TEM mode at 4.5 GHz was found to have potential. The modelling and the experimental measurement results of commonly used dielectric powders revealed that, from the nine classical mixing rules, it was possible to derive reliable inclusion permittivity values when using the properties of the perturbed resonator and the Bruggeman symmetric and the Looyenga mixing theories. In addition, the determination accuracy of the inclusion permittivity was found to be greatly improved with the correction factor included into the previously presented permittivity equation of the quarter wave coaxial resonator. Determination of the dielectric losses was found to be reliable when using the differences between the perturbed and unperturbed resonator and the general mixing model equation. The sensitivity of the characterization method was researched with both humidity exposed and surfactant treated modified SiO2, Al2O3 and ZrO2 powders. Experimental results showed that the effect of adsorbed water on the particles was most pronounced when measuring the dielectric losses of the inclusions. Furthermore, a clear correlation with the theory of the general mixing model was found. Thus, in addition to the changed dielectric properties between dry and humidity exposed powders, it was also possible to determine the moisture content with reasonable accuracy. This correlated well with the traditional, mass based, determination. Stearic acid coating of the particles induced only a small change in inclusion permittivity but a notable change in dielectric losses. Unlike the cases with the larger particle sized SiO2 and Al2O3, the dielectric loss of ZrO2 inclusions, with stearic acid coating, was decreased significantly from 6.2 × 10-3 to 3.8 × 10-3. When characterizing magnesium and calcium titanate composite powders, with CaTiO3 molar ratios of 0.0, 0.02, 0.05 and 0.1, the method was found to have good sensitivity and accuracy. Additions of CaTiO3 exhibited a clear increase in net inclusion permittivities from 13.4 up to 14.9 and in dielectric loss tangents from 7.1 × 10-3 up to 8.5 × 10-3. In addition, a good correlation was found in the theoretical determination of the CaTiO3 molar ratios using the resonator measurement results and the general mixing model. The characterization method was proved to be capable of measuring the dielectric properties and detecting even very slight changes in the powders. Thus, the method could be utilized in various types of powdery material characterization, for example, in the analysis and quality control of different composite powders. / Tiivistelmä Väitöstyön päätavoitteena oli tutkia ja kehittää herkkä jauhemaisten eristemateriaalien karakterisointimenetelmä, jota voitaisiin hyödyntää usealla teollisuuden ja tutkimuksen alueella. Hyödyntäen nykyaikaisia sähkömagnetiikan simulointityökaluja sekä kokeellisia mittauksia, havaittiin TEM -moodissa 4,5 GHz taajuudella toimivan avoimen epäsuorasti kytketyn koaksiaalionteloresonaattorin soveltuvan karakterisoimaan eristejauheita. Sähkömagneettinenmallinnus yhdessä yleisesti käytettyjen eristejauheiden kokeellisten mittausten kanssa osoitti, että partikkelin permittiivisyysarvot voitiin johtaa luotettavasti. Tällöin käytettiin näytemateriaalilla täytetyn resonaattorin ominaisuuksia, sekä yhdeksästä vertaillusta klassisesta sekoitusyhtälöstä Bruggeman symmetristä ja Looyengan sekoitusteorioita. Tämän lisäksi tarkkuutta voitiin parantaa huomattavasti lisäämällä korjauskerroin aikaisemmin julkaistuun neljännesaalto-koaksiaaliresonaattorin permittiivisyyden määrittävään yhtälöön. Eristehäviöiden määrittäminen havaittiin luotettavaksi, kun käytettiin mitattavalla materiaalilla muutetun ja tyhjän resonaattorin ominaisuuksien eroja, sekä general mixing model -yhtälöä. Karakterisointimenetelmän herkkyys tutkittiin ilmankosteudelle altistetuilla, sekä pintakäsittelyllä muutetuilla SiO2, Al2O3 ja ZrO2 -jauheilla. Mittaustulokset osoittivat, että partikkelin pinnalle adsorpoituneen veden vaikutus oli kaikkein korostunein, kun mitattiin partikkelien eristehäviöitä. Tämän lisäksi havaittiin myös selkeä korrelaatio general mixing model -teorian kanssa. Näin ollen muuttuneiden eristeominaisuuksien määritysten lisäksi voitiin määrittää jauheen kosteussisältö riittävällä tarkkuudella. Tulokset korreloivat hyvin perinteisen massaeroihin perustuvan määrittämisen kanssa. Partikkelien pinnoitus steariinihapolla aiheutti ainoastaan pienen muutoksen permittiivisyyteen mutta merkittävän muutoksen eristehäviöihin. Toisin kuin suuremman partikkelikoon SiO2:lla ja Al2O3:lla ZrO2 -partikkelin eristehäviö laski huomattavasti steariinihappopinnoituksen jälkeen, 6,2 × 10-3:sta 3,8 × 10-3:een. Karakterisoitaessa magnesium- ja kalsiumtitanaattikomposiittijauheita käyttämällä CaTiO3 -moolisuhteita 0,0, 0,02, 0,05 ja 0,1 menetelmällä havaittiin olevan hyvä herkkyys ja tarkkuus mitattavan materiaalin muutoksille. CaTiO3 -määrän lisäykset aiheuttivat selkeän nousun partikkelien kokonaispermittiivisyyksissä, joka kasvoi 13,4:sta 14,9:ään, sekä häviötangentissa, joka kasvoi 7,1 × 10-3:sta aina 8,5 × 10-3:een. Tämän lisäksi resonaattorin mitattuihin ominaisuuksiin sekä general mixing model -yhtälöön perustuvan teoreettisen määrityksen havaittin korreloivan hyvin CaTiO3 -moolisuhteisiin. Karakterisointimenetelmän osoitettiin soveltuvan eristeominaisuuksien mittaukseen sekä havaitsemaan jopa erittäin pienet muutokset jauheiden eristeominaisuuksissa. Menetelmää voitaisiin hyödyntää usean tyyppisissä jauhemateriaalien ominaisuuksien määrityksissä, kuten esimerkiksi erilaisten komposiittijauheiden analysoinnissa ja laaduntarkkailussa.

La tomodensitométrie est une technique très utile qui permet de mener avec succès des analyses non-invasives dans plusieurs types d'applications, par exemple médicales ou industrielles. L'analyse manuelle des structures d'intérêt présentes dans une image peut prendre beaucoup de temps, être laborieuse et parfois même impossible à faire en raison de sa complexité. C'est pour cela que dans cette thèse, nous proposons et développons des algorithmes nécessaires à cette analyse, basés sur la géométrie discrète et la topologie. Ces algorithmes peuvent servir dans de nombreuses applications, et en particulier au niveau de l'analyse quantitative automatique de l'arbre bronchique humain, sur la base d'images de tomodensitométrie. La première partie introduit les notions fondamentales de la topologie et de la géométrie discrètes utiles dans cette thèse. Ensuite, nous présentons le principe de méthodes utilisées dans de nombreuses applications : les algorithmes de squelettisation, de calcul de l'axe médian, les algorithmes de fermeture de tunnels et les estimateurs de tangentes. La deuxième partie présente les nouvelles méthodes que nous proposons et qui permettent de résoudre des problèmes particuliers. Nous avons introduit deux méthodes nouvelles de filtrage d'axe médian. La première, que nous appelons "hierarchical scale medial axis", est inspirée du "scale axis transform", sans les inconvénients qui sont propres à la méthode originale. La deuxième est une méthode nommée "discrete adaptive medial axis", où le paramètre de filtrage est adapté dynamiquement aux dimensions locales de l'objet. Dans cette partie, nous introduisons également des estimateurs de tangente nouveaux et efficaces, agissant sur des courbes discrètes tridimensionnelles, et que nous appelons "3Dlambda maximal segment tangent direction". Enfin, nous avons montré que la géométrie discrète et les algorithmes topologiques pouvaient être utiles dans le problème de l'analyse quantitative de l'arbre bronchique humain à partir d'images tomodensitométriques. Dans une chaîne de traitements de structure classique par rapport à l'état de l'art, nous avons appliqué des méthodes de topologie et de géométrie discrète afin de résoudre des problèmes particuliers dans chaque étape du processus de l'analyse quantitative. Nous proposons une méthode robuste pour segmenter l'arbre bronchique à partir d'un ensemble de données tomographiques (CT). La méthode est basée sur un algorithme de fermeture de tunnels qui est utilisé comme outil pour réparer des images CT abîmées par les erreurs d'acquisition. Nous avons aussi proposé un algorithme qui sert à créer un modèle artificiel d'arbre bronchique. Ce modèle est utilisé pour la validation des algorithmes présentés dans cette thèse. Ensuite nous comparons la qualité des différents algorithmes en utilisant un ensemble de test constitué de fantômes (informatiques) et d'un ensemble de données CT réelles. Nous montrons que les méthodes récemment présentées dans le cadre des complexes cubiques, combinées avec les méthodes présentées dans cette thèse, permettent de surmonter des problèmes indiqués par la littérature et peuvent être un bon fondement pour l'implémentation future des systèmes de quantification automatique des particularités de l'arbre bronchique / Computed tomography is a very useful technic which allow non-invasive diagnosis in many applications for example is used with success in industry and medicine. However, manual analysis of the interesting structures can be tedious and extremely time consuming, or even impossible due its complexity. Therefore in this thesis we study and develop discrete geometry and topology algorithms suitable for use in many practical applications, especially, in the problem of automatic quantitative analysis of the human airway trees based on computed tomography images. In the first part, we define basic notions used in discrete topology and geometry then we showed that several class of discrete methods like skeletonisation algorithms, medial axes, tunnels closing algorithms and tangent estimators, are widely used in several different practical application. The second part consist of a proposition and theory of a new methods for solving particular problems. We introduced two new medial axis filtering method. The hierarchical scale medial axis which is based on previously proposed scale axis transform, however, is free of drawbacks introduced in the previously proposed method and the discrete adaptive medial axis where the filtering parameter is dynamically adapted to the local size of the object. In this part we also introduced an efficient and parameter less new tangent estimators along three-dimensional discrete curves, called 3D maximal segment tangent direction. Finally, we showed that discrete geometry and topology algorithms can be useful in the problem of quantitative analysis of the human airway trees based on computed tomography images. According to proposed in the literature design of such system we applied discrete topology and geometry algorithms to solve particular problems at each step of the quantitative analysis process. First, we propose a robust method for segmenting airway tree from CT datasets. The method is based on the tunnel closing algorithm and is used as a tool to repair, damaged by acquisition errors, CT images. We also proposed an algorithm for creation of an artificial model of the bronchial tree and we used such model to validate algorithms presented in this work. Then, we compare the quality of different algorithms using set of experiments conducted on computer phantoms and real CT dataset. We show that recently proposed methods which works in cubical complex framework, together with methods introduced in this work can overcome problems reported in the literature and can be a good basis for the further implementation of the system for automatic quantification of bronchial tree properties

La dérivée est un concept important dans les cours de calcul. Dans certains pays comme au Canada et en France, il est enseigné au niveau collégial tandis qu’en Afrique et en particulier au Cameroun, on l’enseigne au niveau secondaire car la dérivée intervient dans l’étude des variations d’une fonction. Cette thèse dont le titre est : Analyse praxéologique des pratiques des enseignants et de leur utilisation de ressources pour l’enseignement de la dérivée. Une étude de cas dans l’enseignement secondaire général au Cameroun part du constat selon lequel de nombreux élèves et étudiants rencontrent des difficultés avec la notion de dérivée et que ces difficultés s’observent dans leurs résultats scolaires et académiques. Au vu de l’importance de la dérivée pour les différents parcours universitaires en sciences, nous nous intéressons aux pratiques des enseignants de mathématiques et notamment leurs praxéologies didactiques autour de la dérivée mais aussi, nous voulons comprendre les raisons qui justifient les choix faits par ces enseignants. La recherche essaie de répondre à la question de savoir quelles sont les pratiques des enseignants et les ressources utilisées par ces derniers pour l’enseignement de la dérivée? La recherche se propose ainsi d’identifier les praxéologies que les enseignants développent dans leur utilisation des ressources pour préparer leurs leçons et pour enseigner la dérivée. Nous ne nous limitons pas aux praxéologies observables mais nous aimerons comprendre les raisons qui justifient les choix opérés par ces enseignants et les contraintes institutionnelles auxquelles ils font face. Deux cadres théoriques encadrent cette recherche : la Théorie Anthropologique de la Didactique (TAD) qui nous permet d’analyser les types de tâches, les techniques, les technologies et les théories justifiant les technologies employées dans les ressources des enseignants et dans leurs pratiques enseignantes. De même, nous utilisons l’Approche Documentaire du Didactique (ADD) afin d’analyser les ressources institutionnelles et les autres ressources que les enseignants utilisent pour enseigner la dérivée. Pour analyser l’utilisation des ressources des enseignants, nous mettons un accent sur les objectifs et les sous-objectifs visés, les règles d’action, les invariants opératoires et les inférences éventuelles. Sur le plan méthodologique, nous utilisons une étude de cas impliquant trois enseignants qui enseignent la dérivée aux élèves de première. Nous utilisons des entretiens semi-dirigés afin d’analyser les choix que font les enseignants lors de la préparation des cours mais et surtout les raisons qui justifient ces choix; les observations vidéo-filmées permettent de savoir comment les enseignants introduisent la dérivée en un point et sur un intervalle et l’analyse des documents tels que les programmes de mathématiques, les manuels scolaires et d’autres ressources des enseignants employés dans la préparation des cours. Le principal résultat de cette thèse est l’identification du poids des ressources institutionnelles et de l’examen de fin d’année sur les praxéologies mathématiques et sur la manière dont les enseignants utilisent ces ressources. Nous discutons de ce résultat en tenant compte du rapport personnel des enseignants et des praxéologies développées dans les manuels et lors de l’enseignement. / Derivatives are one of the most important topics studied in high school (in many countries) and postsecondary mathematics. Many students must learn this topic to pursue their university studies and as a gateway to learn other mathematical topics in various other fields. In Cameroon, secondary teaching lasts from 12 to 18 years old. In this context, what in other countries is considered as pre-university courses, or college, in Cameroon is still called secondary. Derivatives are introduced in the last but one year of this cycle, called première (students are 17), after the topics of function, limit, and continuity. In this thesis, we examined teachers’ practices and their use of resources while teaching derivatives. This study in general secondary education in Cameroon starts from the observation that many pupils and students encounter difficulties with the notion of derivative and that these difficulties are observed in their academic results. The research attempts to identify the tasks, techniques and technologies developed in the resources used by these teachers. It also tries to describe the patterns of use of resources by closely observing the objectives pursued, the rules of action and the operational invariants put in place when using resources. We do not limit ourselves to describing the practices of teachers, but we would like to understand the reasons that justify their choices and the institutional constraints they face. Since we are interested in teachers’ practices and their use of resources to teach derivatives, we use elements of the anthropological theory of the didactic (ATD) to analyze the types of tasks, the techniques, technologies, and theories justifying the technologies used in teachers' resources and teaching practices. By using DA, we understand that teachers, to prepare their teaching, use variety of resources. These resources aiming to teach this content together with the schemes of use of these resources result in a document and these schemes of use of resources is influenced by the teacher’s own personal relationship. The participants in this study were three teachers who teach derivatives to first-class students. We use semi-structured interviews to analyse the choices teachers make when preparing courses, but above all the reasons that justify these choices and video to observe how teachers introduce the derivative. The video shows how teachers introduce the derivative at a point and on an interval. Others analyses helps us understanding how this content is introduced on math programs, textbooks and other teacher resources used in the preparation of courses. The main result of this thesis is the identification of the weight of institutional resources and the end-of-year examination on mathematical praxeology’s and on the way, teachers use these resources. We discuss this result considering the personal relationship of teachers and the praxeology’s developed in textbooks and during teaching.

In Nonlinear Finite Element Analysis (FEA) applied to structures, displacements at which the tangent stiffness matrix KT becomes singular are called critical points, and correspond to instabilities such as buckling or elastoplastic softening (e.g., necking). Prior to the introduction of Arc Length Methods (ALMs), critical points posed severe computational challenges, which was unfortunate since behavior at instabilities is of great interest as a precursor to structural failure. The original ALM was shown to be capable in some circumstances of continued computation at critical points, but limited success and unattractive features of the formulation were noted and addressed in extensive subsequent research. The widely used Crisfield Cylindrical and Spherical ALMs may be viewed as representing the 'state-of-the-art'. The more recent Stiff Arc Length method, which is attractive on fundamental grounds, was introduced in 2004, but without implementation, benchmarking or performance assessment. The present thesis addresses (a) implementation and (b) performance comparisons for the Crisfield and Stiff methods, using simple benchmarks formulated to incorporate elastoplastic softening. It is seen that, in contrast to the Crisfield methods, the Stiff ALM consistently continues accurate computation at, near and beyond critical points.

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Development of the power gridtowards a more reliable and smarter system requires frequent on-line monitoring of the power components. Power transformers and their bushings are particularly important components in a power transmission system and their insulation degradation may lead to catastrophic failures. Time consuming and costly replacement of these components raise the importance of their frequent monitoring. A fault in a power transformer bushing can also involve in the failure of the transformer. Therefore, on-line diagnostics of power transformers and their bushings is of great interest. Several methods exist for diagnostics of these components. However, some of them can only be done off-line in maintenance periods, and the existing on-line methods generally provide less information, especially on the internal solid insulation parts. In this project, a new technique for on-line diagnostics of the power transformer and the bushing insulation is proposed. In this technique, natural transients happening in the power system such as lightning and switching surges can be used as stimuli for on-line dielectric response measurements. This technique can provide information on insulation close to what Dielectric Spectroscopy offers in off-line measurements. The wide-ranging frequency content of power system transients is their advantage for being usedas stimuli when measuring the Dielectric Response. The response can have particular signatures due to different types of defects in the insulation varying with frequency. Oil-impregnated paper as a major insulation component in power transformer and its bushing has been investigated in this project. Moisture content and temperature, as two important degradation factors in this type of insulation, have been studied to evaluate the performance of the proposed technique in the diagnostics of the oil-impregnated paper. The results are verified with the dielectric response obtained through commercial instruments. The results show that the proposed technique has the ability to track the changes in dielectric response due to the moisture content and temperature. Measurements were done at both highvoltage (40kV) and low voltage (10V) levels, and the corresponding circuit models to achieve reasonable accuracy for the results are discussed. Moving on from the material samples, a further study was done on three service-aged 150 kV bushings to investigate the feasibility of the technique on the diagnostics of power transformer bushings. Their dielectric response measured by the transient stimuli showed good agreement with their response obtained by the commercial instruments. The effect of the transformer winding on the transient response of the bushing is a further aspect of the real conditions for on-line diagnostics. This has been investigated through the simulation of transient models for transformers and bushings, and possible solutions for distinguishing the responses are presented. The proposed new on-line diagnostics technique by utilizing natural transients can provide information about the insulation system in a certain range of frequency without interrupting the operation or requiring an external voltage source. However, the validity range of the results depends on the bandwidth of the applied transients and other measurement considerations. This approach can be valuable in frequent monitoring of dielectric properties of the power transformers and their bushings as a complement to the other available on-line techniques. / <p>QC 20140409</p>

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Konsistensen på en gel bestående av tvärbunden hyaluronsyra beror av tre faktorer: total koncentration hyaluronsyra, gelningsgrad och tvärbindningsdensitet. För att utföra detta projekt erhölls tre olika geler med olika tvärbindningsdensitet. Dessa geler späddes dels med lösning av fri, icke tvärbunden, HA från 100 % gelningsgrad till 90 % och 80 %. De olika gelningsgraderna späddes också med natriumkloridlösning från den totala koncentrationen HA, 35 mg HA/g gel, till 25 mg/g och 15 mg/g. Projekts huvudfråga är att kartlägga gelens reologiska egenkaper då både total koncentration HA och gelningsgrad varieras. För att kunna kartlägga detta har en reometer brukats där följande tre tester körts: tidssvep, frekvenssvep och amplitudsvep. Från erhållen data har sedan två parametrar som representerar gelkompositionernas viskösa egenskaper (G'') och elastiska egenskaper (G') observerats. Även mätning av extruderingskraft har genomförts för att dra vidare paralleller och slutsatser mellan extruderingskraften och de reoligiska egenskaperna. Ur resultaten ses att förlusttangenten tenderar att sjunka när gelningsgraden ökar, d.v.s. gelerna blir då mer viskösa och mindre elastiska. Förlusttangenten sjunker även vid ökande total koncentration HA vilket betyder att G’ ökar mer än G’’ i vardera punkt som gör att förlusttangenten minskar.Det gick även att avläsa att de viskösa egenskaperna i gelen ökar då total koncentration hyaluronsyra minskar samt att de viskösa egenskaperna i gelerna minskar vid en sjunkande gelningsgrad. Mellan gelningsgrad 90-100 % och total koncentration HA 25-35 mg HA/g har analyserna som gjorts i detta projekt gett följande slutsatser. Konsistensen på gel A och C är mer påverkade av gelningsgraden än total koncentration HA. För gel B kan ingen dominerande parameter utläsas. / The softness of a gel made of crosslinked HA (HA = hyaluronic acid) depends onthree factors. One is the amount of free hyaluronic acid in the gel. Another is thedensity of the crosslinked network, which is the molecular entanglements in the gel.The third is the total concentration of HA. In this project a rheometer is used to measure the rheological properties by runningthe following tests: time sweep, frequency sweep and amplitude sweep. From theobtained data, parameters related to viscous properties (G’’) and elastic properties(G’) of the gels were observed. 27 different compositions of gels with three differentconcentrations (35 mg HA/g, 25 mg HA/g, 15 mg HA/g), three different gel contents(100%, 90%, 80%) and three different densities of crosslinked network (A, B, C) wereanalyzed. To draw further conclusions an analysis of extrusion force was performedas well. The results from the frequency sweeps show that the loss tangent for a gel increasedas the total concentration of HA was reduced and that the loss tangent for a gelincreased as the gel content was decreased. This indicates that the gels become moreviscous when either the concentration of HA or the gel content was decreased. Anincrease in concentration of HA results in an increase of G' and an increase of gelcontent also results in an increase of G'. The results from the amplitude sweeps showthat xG' (xG' = storage modulus at the crossover point between G' and G'') increasesas either the concentration of HA or the gel content is increased. For xStrain (xStrain= deformation of the gel at the crossover point) and xStress (xStress = the stressapplied to the gel at the crossover point) no clear trend can be seen regarding the gelcontent. But an increase in concentration of HA results in an increase of both xStrainand xStress. The results from the analysis of extrusion force show that an increase intotal concentration HA increases the force.