The evolution of landscapes and seascapes in time is the result of the constant interaction between flows and topography. Flows change topography, which in turn change the flow. This feedback causes evolution processes to be highly non-linear and complex. When full analytical derivations of the co-evolution of topography and flow are not possible without oversimplifications, as is the case in river bends, recent large topographical datasets and modern computers allow for correlations between horizontal (planview) and cross-sectional geometry of channels. Numerical analysis in the Mississippi and Trinity rivers indicate that the type of correlation between river radius of curvature and bankfull channel width depends on the migration behavior of the river. In other cases, channel topography may only have a second-order effect on its own evolution, as is the case for fully depositional turbidity currents, and the evolution of aeolian field topography may only be a function of this topography. I show that in these situations, changes in topography may be decoupled from details of the flow field and modeled very easily with a good accuracy. / text

In many previous physiological and psychoacoustic studies, Schroeder-phase masking (using Schroeder harmonic complexes to mask other sounds) has proven useful in understanding different aspects of cochlear function, particularly the phase curvature of the cochlea and cochlear nonlinearity. The common method of measuring Schroeder-phase masking functions uses a very time consuming three-alternative forced choice (3AFC) process, which limits its research and clinical usefulness. This thesis describes a fast method for measuring Schroeder-phase masking functions that we developed to address this problem. By adapting the Békésy tracking technique, we demonstrate how the measurement time can be reliably shortened by almost 80% in comparison to the commonly-used method. Using the fast method, we have demonstrated that the difference in masking effectiveness produced by different phases of Schroeder maskers (known as the ‘phase effect’) is reduced in conditions where cochlear non-linearity is expected to be reduced (i.e. at low intensity levels and in sensorineural hearing loss subjects) – findings which are consistent with previous studies. The possible involvement of other mechanisms in producing the Schroeder phase effect (particularly the medial olivocochlear (MOC) reflex) is discussed. Given the shorter testing time and higher resolution data it can give, the fast method can be a useful tool in estimating cochlear phase curvature. The reduction in testing time in particular may significantly aid the investigation of different aspects of cochlear function which might have been limited by the long testing time given by the commonly-used method.

The interaction between the driver, the car and the road is essential for the road safety. This case study focuses on the road condition and its effect regarding road safety issues. By studying and isolating the road condition aspect and its contributing role to the accident occurrence, the aim is to explore their relationship, as well as highlight the road parameters that are commonly associated with accident occurrence. This result will be used to develop and increase awareness of the impact of poor road alignment and poor road surface conditions on traffic safety, in order to prevent these accidents from occurring. The road parameters chosen for this study include side friction, cross slope and rut bottom cross slope, road texture, curvature, drainage gradient and rutting. The case study was limited to lv 360 in Västerbotten, where all accidents with an unclear cause of the accident were studied, between 2003 and 2012 were carefully studied and assessed based on the condition of the road at the time of the accident. The study was based on accident data from Transportstyrelsens accident database STRADA and road data was obtained from Vecturas Profilograf. Analysis of the various road parameters and their respective safety limits, identified many hazardous sections on lv 360. Low side friction values, insufficient drainage gradient and incorrect cross slopes are some of the shortcomings that were found. The results show that 70% of all accidents occurred on curves where the vehicle either skidded or went off the road. Furthermore, the results show that the side friction demand in 65% of the accidents far exceeded the designed side friction supply according to VGU. Insufficient side friction associated with curves shows an evident relation with the accident occurrence. The analysis shows that 80% of the accidents had deficiencies in two or more road parameters. Improperly designed cross slopes in curves – where the slope instead of resisting the lateral force, contributed to it – was found to create dangerous circumstances for the traffic. These were also found at lv 360, why the cross slope design according to the results, directly affects the accident rate – particularly at curves. Improper cross slope in sections where the gradient is low often result in insufficient drainage gradient, and consequently a high skid risk. These were common on entry and exit points of curves, where the cross slope shifts between straight sections and curves and thus passes zero. The results show that the drainage gradient in 70 % of the accidents was too low and in many cases fell below VGU's requirement of 0.5 % before and after the curve. / Samarbetet mellan föraren, bilen och vägen är essentiellt för trafiksäkerheten. Denna fallstudie fokuserar på vägens tillstånd och dess roll inom trafiksäkerhetsarbetet. Genom att studera och isolera vägaspekten och dess bidragande roll till olycksförekomsten, är målet att tydliggöra relationen mellan dessa, samt belysa de vägparametrar som vanligen associeras med trafikolyckor. Detta för att utveckla och utöka medvetenheten kring effekten av dålig linjeföring och bristfälliga vägytegenskaper, för att i framtiden kunna förebygga dessa olyckor. De parametrar som studerades är bland annat sidofriktionen, tvärfallet och spårbottentvärfallet, texturen, kurvaturen, snedlutningen och spårdjupet. Arbetet avgränsades till länsväg (lv) 360 i Västerbotten, där alla olyckor med en oklar olycksorsak mellan åren 2003 och 2012 studerades, och bedömdes efter vägens tillstånd vid olyckan. Studien baserades på olycksuppgifter från Transportstyrelsens olycksdatabas STRADA och vägmätningar utförda av Vecturas Profilograf. Vid analys av de olika väg parametrarna och deras respektive gränsvärden, identifierades många brister på länsväg 360. Låga sidofriktionsvärden, otillräcklig snedlutningar och felaktiga tvärfall vid kurvor är några av de brister som påhittades. Resultatet visar att 70 % av alla olyckor inträffade i kurvor där fordonet antingen fått sladd eller åkt av vägen. Vidare visar resultatet att sidofriktionsbehovet i 65 % av olyckorna långt översteg den dimensionerande sidofriktionen enligt regelverket Vägar och Gators Utformning (VGU). För liten sidofriktion i samband med kurvor visar en tydlig koppling till olycksförekomsten. Analysen visar dessutom att 80 % av olyckorna hade brister i två eller fler vägparametrar. Felaktigt utformat tvärfall vid kurvor – där lutningen istället för att motverka sidokraften bidrar till den – skapar livsfarliga förutsättningar för trafiken. Även dessa påträffades på länsväg 360, varför tvärfallets utformning enligt resultatet direkt påverkar på olyckstalet, i synnerhet vid kurvor. För litet tvärfall i de sektioner där även längslutningen är låg innebär dessutom otillräcklig snedlutning (resultanten av tvärfallet och längslutningen) och medför stora risker för halka. Dessa är vanliga vid in- och utfarter av kurvor, där tvärfallet övergår mellan raksträcka och kurva och passerar noll. Resultatet visar att 70 % av olyckorna hade för låg snedlutning samt att flera sträckor i många fall underskred VGU:s krav på 0,5 % före och efter kurvan. Som lösning föreslås hastighetssänkning och varningsskyltar vid skarpa kurvor samt att stor kraft bör läggas på korrekt utförda tvärfall som tar hänsyn till sidokraften.

<p>The surface of cell membranes can display a high degree of lateral heterogeneity. This non-uniform distribution of constituents is characterized by mobile nanodomain clusters called rafts. Enriched by saturated phospholipids, cholesterol and proteins, rafts are considered to be vital for several important cellular functions such as signalling and trafficking, morphological transformations associated with exocytosis and endocytosis and even as sites for the replication of viruses. Understanding the evolving distribution of these domains can provide significant insight into the regulation of cell function. Giant vesicles are simple prototypes of cell membranes. Microdomains on vesicles can be considered as simple analogues of rafts on cell membranes and offer a means to study various features of cellular processes in isolation. </p><p>In this work, we employ a continuum approach to model the evolution of microdomains on the surface of Giant Unilamellar Vesicles (GUVs). The interplay of species transport on the vesicle surface and the mechanics of vesicle shape change is captured using a chemo-mechanical model. Specifically, the approach focuses on the regime of vesicle dynamics where shape change occurs on a much faster time scale in comparison to species transport, as has been observed in several experimental studies on GUVs. In this study, shape changes are assumed to be instantaneous, while species transport, which is modeled by phase separation and domain coarsening, follows a natural time scale described by the Cahn--Hilliard dynamics.</p><p>The curvature energy of the vesicle membrane is defined by the classical Canham--Helfrich--Evans model. Dependence of flexural rigidity and spontaneous curvature on the lipid species is built into the energy functional. The chemical energy is characterized by a Cahn--Hilliard type density function that intrinsically captures the line energy of interfaces between two phases. Both curvature and chemical contributions to the vesicle energetics are consistently non-dimensionalized.</p><p>The coupled model is cast in a diffuse-interface form using the phase-field framework. The phase-field form of the governing equations describing shape equilibrium and species transport are both fourth-order and nonlinear. The system of equations is discretized using the finite element method with a uniform cubic-spline basis that satisfies global higher-order continuity. For shape equilibrium, geometric constraints of constant internal volume and constant surface area of the vesicle are imposed weakly using the penalty approach. A time-stepping scheme based on the unconditionally gradient-stable convexity-splitting technique is employed for explicit time integration of nonlocal integrals arising from the geometric constraints.</p><p>Numerical examples of axisymmetric stationary shapes of uniform vesicles are presented. Further, two- and three-dimensional numerical examples of domain formation and growth coupled to vesicle shape changes are discussed. Simulations qualitatively depicting curvature-dependent domain sorting and shape changes to minimize line tension are presented. The effect of capturing the difference in time scales is also brought out in a few numerical simulations that predict a starkly different pathway to equilibrium.</p> / Dissertation

Darbe pasiūlyta tempiamojo betono įtempių - deformacijų priklausomybė trumpalaikio ir ilgalaikio apkrovimo atveju. Pasiūlyta priklausomybė gauta, taikant EC2 momentų–kreivių priklausomybių apskaičiavimo metodiką. Atlikta lenkiamųjų gelžbetoninių elementų įtempių ir deformacijų priklausomybių analizė. Apžvelgti tokių elementų deformacijų skaičiavimo metodai ir matematiniai modeliai, apžvelgti paskelbti literatūros šaltiniai, susijusę su lenkiamųjų gelžbetoninių elementų deformacijomis. Skaitinio eksperimento pagalba sudaryta lenkiamųjų gelžbetoninių elementų duomenų imtis, išnagrinėta trumpalaike ir ilgalaike apkrova veikiami lenkiamieji gelžbetoniniai elementai, deformacijos ir jas lemiantys faktoriai, atlikta jų analizė. Taikant VGTU tiltų ir specialiųjų statinių katedroje pasiūlytą sluoksnių metodą iš skaitinių eksperimentų gautų momentų-kreivių diagramų gautos supleišėjusio tempiamojo betono įtempių-deformacijų priklausomybės. Parinkti pagrindiniai teorinės diagramos parametrai, priklausomai nuo betono klasės, armavimo procento bei valkšnumo koeficiento. Gautoji priklausomybė pritaikyta gelžbetoninių sijų kreivių apskaičiavimui sluoksnių metodu. Gautieji rezultatai palyginti su empirinėmis EC2 normų prikalsumybėmis gautais rezultatais. Palyginamoji gautų skaičiavimo rezultatų analizė parodė gerą abiem metodais gautų rezultatų atitikimą. Gautoji priklausomybė gali būti pritaikyta netiesiniuose skaičiavimuose, taikant baigtinių elementų metodą. / The paper suggests tension concrete stress-strain dependence of the short-term and long-term case-load of the EC2 method. Bending reinforced concrete elements of stress and strain dependence are analyzed. Presented overview of such elements deformation calculation methods and mathematical models, highlight the relevance literature review, relating to bending reinforced concrete elements. Collected bending reinforced concrete elements (numerical experiments) data, examined short-term and long term effects of load to bended reinforced concrete elements, deformations and the determining factors, performed their analysis. For the purposed of VGTU bridges and special structures department’s constitutive model from the numerical experiments obtained moment-curvature relationships derived the charts of cracked pulling concrete stress-strain dependence. Choose the basic theoretical parameters of the relationships, depending on the class of concrete, reinforcement rates, and creep coefficient. The calculation results are compared with the experimental beam data. Performed calculation results of the analysis showed quite accurate results with the derived dependencies.

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This thesis presents a new system that reconstructs the 3D representation of dental casts. To maintain the integrity of the 3D representation, a standard model is built to cover the blind spots that the camera cannot reach. The standard model is obtained by scanning a real human mouth model with a laser scanner. Then the model is simplified by an algorithm which is based on iterative contraction of vertex pairs. The simplified standard model uses a local parametrization method to obtain the curvature information. The system uses a digital camera and a square tube mirror in front of the camera to capture multi-view images. The mirror is made of stainless steel in order to avoid double reflections. The reflected areas of the image are considered as images taken by the virtual cameras. Only one camera calibration is needed since the virtual cameras have the same intrinsic parameters as the real camera. Depth is computed by a simple and accurate geometry based method once the corresponding points are identified. Correspondences are selected using a feature point based stereo matching process, including fast normalized cross-correlation and simulated annealing.

We numerically investigate crystalline order on negative Gaussian curvature capillary bridges. In agreement with the experimental results in [W. Irvine et al., Nature, Pleats in crystals on curved surfaces, 2010, 468, 947] we observe for decreasing integrated Gaussian curvature, a sequence of transitions, from no defects to isolated dislocations, pleats, scars and isolated sevenfold disclinations. We especially focus on the dependency of topological charge on the integrated Gaussian curvature, for which we observe, again in agreement with the experimental results, no net disclination for an integrated curvature down to −10, and an approximately linear behavior from there on until the disclinations match the integrated curvature of −12. In contrast to previous studies in which ground states for each geometry are searched for, we here show that the experimental results, which are likely to be in a metastable state, can be best resembled by mimicking the experimental settings and continuously changing the geometry. The obtained configurations are only low energy local minima. The results are computed using a phase field crystal approach on catenoid-like surfaces and are highly sensitive to the initialization.

In tunnel excavation, the use of rockbolts has long been a popular means of reinforcement in rock masses to prevent the rock opening from caving in. The idea has evolved from the earliest form of rockbolt made of wood to the more up-to-date form of pre-tensioned or grouted steel rockbolts. A major breakthrough in the design of rockbolt models was made by Aydan (1989). This rockbolt element was modelled in coupled form, with one sub-element representing the steel bolt, and the other sub-element the grout. This representation was necessary to model the complex action in the continuous rock mass near the joint. In elasticity problems, the large displacement formulation of a beam element is derived from the fundamental theory, and the bending phenomenon of a thin rod is analysed by the finite element discretizations of the bar elements and the beam elements. Experiments show that the deformation characteristics of the latter representation resemble a more realistic life behaviour. Based on this finding, this thesis proposes a modification to Aydan's two-dimensional rockbolt element, with the beam elements discretising the steel bolt. The different mechanical responses of a perfectly elastic rockbolt are considered, and the large displacement formulation of the new rockbolt element is derived by combining those of Aydan's rockbolt element and the beam element. The mechanics of the Aydan element and the new rockbolt element are described, and their performances are compared in an identical situation. It is found that in the two two-dimensional examples used in this thesis, the modified element ensures the continuity of curvature of the rockbolt, and in general, can act as support across a discontinuity or joint between rock masses well. In conjunction with the displacement method in the finite element procedures, a conventional iteration solution procedure is first described to solve the nonlinear incremental stiffness equation. However, it is found that this procedure is cumbersome, and requires a large amount of comptutations. Some limited storage quasi-Newton minimization algorithms are considered as an alternative.