We consider random simplicial complexes constructed on a Poisson point process within a convex set in a Euclidean space, especially the Vietoris-Rips complex and the Cech complex both of whose 1-skeleton is the Gilbert graph. We investigate at first the Vietoris-Rips complex by considering the volume-power functionals defined by summing powers of the volume of all k-dimensional faces in the complex. The asymptotic behaviour of these functionals is investigated as the intensity of the underlying Poisson point process tends to infinity and the distance parameter goes to zero. This behaviour is observed in different regimes. Univariate and multivariate central limit theorems are proven, and analogous results for the Cech complex are then given. Finally we provide a Poisson limit theorem for the components of the f-vector in the sparse regime.

Nobel Biocare is one of the world’s leading companies that produce dental implants. This thesis was executed at the part of the company located in Karlskoga, Sweden.To be sure that the implants manufactured at Nobel Biocare will heal as good as possible when being implanted in a patient, the implant has to go through a coating process where the implants, after a few preparing steps, are going through a salt treatment. This salt treatment will in the end simplify the healing process for the patient. Between every process there is a time limit for how long the implants may rest, a so-called transfer time limit. This time is too short and leads to unnecessary cassations.The purpose of the thesis was to investigate what will happen if the transfer time limit of today increases from eight hours to sixty hours. What will be crucial for the results of the thesis is wether any contamination will occur on the surface of the dental implant or not.To investigate if any possible contamination occurs during the longer transfer time limit the implants were, after a coating process, examined with the help of a laboratry in Great Britain, where XPS analysis of different materials are performed.This thesis has the limitations of examining only the product TiUltra and has only investigated the longer transfer time limit during the coating process of the implants.The result of the thesis is that no contamination occured on the surface, and therefore there now is a basis available for technical documents to increase the transfer time limit from eight hours to sixty hours. This could also be implemented in other areas of the production, where there are similar problems. This thesis could be the base of new test plans for those areas. / Nobel Biocare är ett av de världsledande företag som tillverkar tandimplantat. Examensarbetet genomfördes hos den del av företaget som ligger i Karlskoga.För att de implantat som Nobel Biocare tillverkar ska läka så bra som möjligt när de väl är inopererade hos en patient genomgår dessa implantat en ytbehandling där ett saltlager, efter ett antal förberedande steg, läggs på ytan, som i slutändan förenklar läkeprocessen för den patient som får implantatet inopererat. Mellan varje processteg finns en tidsbegränsning för hur längre implantaten får vila, en så kallas transfer time limit. Denna tid är i dagsläget för kort och leder till onödiga kassationer.Syftet med examensarbetet var att undersöka vad som händer om den satta transfer time limit ökas från åtta timmar till 60 timmar. Det som kommer vara avgörande för resultatet är om någon kontaminering på ytan av implantaten uppstår eller inte.För att undersöka om eventuell kontaminering uppstod under en längre transfer time limit har de implantat som genomgått ytbehandlingsprocessen undersökts med hjälp av ett laboratorium i Storbritannien som utför XPS-analyser av olika material.Arbetets avgränsning är satt till produkten TiUltra och ska enbart undersöka en ökad transfer time limit under ytbehandlingsprocessen av implantaten.Resultatet av arbetet blev att ingen kontaminering uppstod på ytan och därmed finns tekniskt underlag för att kunna öka transfer time limit från åtta timmar till 60 timmar. Detta är något som skulle kunna implementeras på fler ställen i produktionen där liknande problem finns. Då skulle detta arbete och dess upplägg för test av förlängd transfer time limit kunna ligga som underlag för planeringar av nya tester.

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Potential predation between fishes of recreational interest has incited many bitter conflicts between angler groups. Large predators, such as esocids, are often at the center of these conflicts because of their capacity to alter fish populations. Such a conflict certainly exists between the Muskellunge Esox masquinongy and Smallmouth Bass Micropterus dolomieu fisheries of the New River, Virginia. Following the institution of a 42-in minimum-length limit (MLL) on Muskellunge, bass anglers feared that increased Muskellunge abundance might be negatively affecting Smallmouth Bass via increased predation. In order to ascertain the impacts of the 42-in MLL, I estimated the demographics, abundance, and food habits of Muskellunge combined with bioenergetics modeling to assess changes (i) in the quality of the Muskellunge fishery and (ii) in Muskellunge predation on Smallmouth Bass. Additionally, given the likelihood of future regulations to incite similar concerns from bass anglers, I modeled alternative length-limit regulations (iii) to assess their potential to improve fishery quality, thereby laying the groundwork for managers to address angler concerns before they arise. I found substantial increases in population size structure and in average adult density of Muskellunge since the institution of the 42-in MLL, but bioenergetics modeling did not indicate a notable increase in the consumption of Smallmouth Bass. I also found that high MLLs (e.g., 48-in) were likely to promote the largest increases in trophy production of Muskellunge compared to low MLLs or protected-slot limits (PSLs). This study suggests that the current Muskellunge population likely plays a small role in shaping Smallmouth Bass population dynamics and production in the New River; and lays the groundwork for predicting how the impact of Muskellunge on Smallmouth Bass might change under alternative regulations. / Master of Science / Management of fish for recreation can be challenging when multiple species are of interest, particularly when potential exists for one species to negatively influence another and stimulates conflict between users. Large predators are often at the center of these conflicts because of their ability to change fish populations via predation. This type of conflict certainly exists between the Muskellunge <i>Esox masquinongy</i> and Smallmouth Bass <i>Micropterus dolomieu</i> fisheries of the New River, Virginia. The perceived influence of increased Muskellunge predation on Smallmouth Bass and the bass fishery following the institution of a 42-in minimum-length limit (MLL), has created tension between users. In order to ascertain the impacts of the 42-in MLL, I estimated Muskellunge population structure, abundance, and food habits and combined them with diet modeling to assess changes (i) in the number and size of Muskellunge and (ii) in Muskellunge predation on Smallmouth Bass. Additionally, given the likelihood of future regulations to incite similar concerns from bass anglers, I also used regulation modeling to assess (iii) the potential of other regulations to change the number and size of Muskellunge. I found that the size structure (i.e., the proportion of large Muskellunge in the population) and the number of Muskellunge increased after the 42-in MLL, but I did not find a notable increase in the amount of Smallmouth Bass eaten by Muskellunge. I also found that more-restrictive regulations (i.e., a 48-in MLL) could further increase the size structure and number of Muskellunge. My results suggest that the current Muskellunge population probably plays a small role in shaping the Smallmouth Bass population of the New River, and I lay the groundwork for predicting how that role might change under other regulations.

Prediction as a tool in engineering has been used in taking right judgement in many of the professional activities. This being the fact, the role and significance of prediction in geotechnical practice needs no emphasis. Bulk of all man made structures are either made of soil or are resting on natural soil, involving large quantities of soil. Thus, it is often necessary for the geotechnical engineer to quickly characterize the soil and determine their engineering properties, so as to assess the suitability of the soil for any specific purpose. Obtaining these properties requires undisturbed samples, which involves time and money, and also elaborate laboratory procedures. Thus, it is desirable to find simpler and quicker methods of testing, using the data of which the engineering properties can be predicted satisfactorily especially so, for preliminary design purposes. Most often this can be achieved from simple tests known as inferential tests, and the engineering properties namely, compressibility, swell/collapse, hydraulic conductivity, strength and compaction characteristics can be obtained from empirical/semi-empirical correlations. The index tests namely the Atterberg limits form the most important inferential soil tests with very wide universal acceptance. These tests are relatively simple to perform and have provided a basis for explaining most engineering properties of soils in geotechnical practice. In this direction, this investigation has been carried out to correlate the engineering properties with the simple index properties and their indices, namely, the liquid limit, plastic limit, shrinkage limit, plasticity index and shrinkage index (liquid limit - shrinkage limit). Any good correlation in the prediction of engineering properties with the index properties will enhance the use of simple test for prediction purposes. This thesis is an attempt towards this direction. It is often necessary to identify the basic mechanisms controlling the engineering properties from a micro-mechanistic point of view and correlate with the index properties, thereby facilitating prediction of engineering properties better. Though attempts have been made in the past to predict the engineering properties of soils from the index properties/indic­es, they are not quite satisfactory. This thesis is an attempt to predict the engineering properties of fine-grained soils from the index properties taking into consideration the mechanisms controlling them. Since, the index properties are used for prediction of engineering properties, the existing methods of determining the same have been examined carefully and critically. It's satisfactory determination is found important because other indices namely plasticity index, Ip and shrinkage index, Is = (wL - ws), are determined based on it. Also the liquid limit is one of the important and widely used parameter in various existing correlations. In this direction, two new methods of determining the liquid limit have been developed, namely (i) absorption water content and liquid limit of soils and (ii) liquid limit from equilibrium water content under Ko-stress. In the absorption water content method, the water absorbed by an oven dried soil pat at equilibrium gives a good correlation with the liquid limit of soils. Here, the water holding capacity at equilibrium goes well with the mechanism of liquid limit, which is also the water holding capacity of a soil at a particular small but measurable shear strength. A good relationship is found to exit between the absorption water content, wA and the liquid limit, wL, and it is given as : WA = 0.92 wL (i) In the second method, namely, the liquid limit from equilibrium water content under K0-stress, which is the equilibrium water content under a Ko stress of 0.9 kPa is found to be equal to the liquid limit obtained from the cone penetration method of determining the liquid limit It is found that this method of determining the liquid limit overcomes the limitations of the conventional methods of determining the liquid limit, also easy to determine with a simple apparatus and has good repeatability. Determination of plastic limit of the soils by the rolling thread method often poses a problem especially when the soil is less plastic. Hence, to overcome this problem, a new method has been proposed to predict the plasticity index in terms of the flow index. The relationship between the plasticity index and the flow index by the cone penetration cup method is found to be better than by the percussion cup method. Since, the cone penetration method of the liquid limit determination is more popular than the percussion cup method, the flow index from the cone method is recommended to determine the plasticity index from the correlation as given below: (/p)c = 0.74 Ifc (ii) Thus, the plastic limit can be determined with the plasticity index, thereby dispensing with the determination of plastic limit by the thread method. The determination of consolidation characteristics form an important aspect in the design of foundations and other earth retaining structures. The determination of consolidation characteristics namely the compression index, the coefficient of consolidation and the coefficient of secondary compression is time consuming. So, researchers have resorted to correlating the compressibility behaviour with simple index properties. While attempts have been made in the past to correlate the compressibility behaviour with various index properties individually, all the important properties affecting the compressibility behaviour has not been considered together in any single study to examine which of the index property/properties of the soils correlates better with the compressibility behaviour, especially with the same set of test results. Number of existing correlations with the liquid limit alone as a primary index property correlating with the compression index have limitations in that they do not consider the plasticity characteristics of the soils fully. The index parameter, shrinkage index, Is has a better correlation with the compression index, Cc and also the coefficient of volume change, mv than plasticity index. Coefficient of consolidation, Cv has also shown to correlate well with shrinkage index than the plasticity index. Even the coefficient of secondary compression, Cαε has shown to have a better correlation with shrinkage index than the plasticity index. However, liquid limit has a poor correlation with all the compressibility characteristics. The correlation of Cc and Cv with shrinkage index, Is is as given below: Cc = 0.007 (Is + 18) (iii) Cv = 3x10-2 (Is)-3.54 (in m2/sec) Further, to reduce the testing time of conventional consolidation test in order to obtain the compressibility characteristics, a new method known as rapid method of consolidation has been proposed, which is very effective in enormously reducing the time of consolidation without sacrificing the accuracy of the end results. The time required in the rapid method of consolidation testing could be as low as 4 to 5 hours to complete the whole test as compared to 1 to 2 weeks as the case may be by the conventional consolidation test. Using any curve fitting procedure the degree of consolidation, U for any pressure increment can be found out. Thus, the effective pressure at that stage can be calculated and further the pressure incremented without further delay. This procedure is repeated for every pressure increment with a load increment ratio of unity till the desired pressure level is reached. Even for a highly compressible soil like BC soil with a liquid limit of 73.5 %, the consolidation test could be completed within 5 hours by the rapid method, without any sacrifice of the accuracy of the results as compared to 7 days by the conventional method to reach a pressure of 800 kPa. Hydraulic conductivity is one of the basic engineering properties of soils. Of late hydraulic conductivity of fine-grained soils has assumed greater importance in waste disposal facilities. From the present investigation it is found that hydraulic conductivity with water for each pair of soils having nearly the same liquid limit but different plasticity properties is found to be vastly different, but found to correlate well with shrinkage index. A method to predict the hydraulic conductivity of fine -grained soils as a function of void ratio is proposed with the use of shrinkage index as given below: k = C [ ] (in m/sec) (v) 1 + e C = 2.5 x 10-4 (/s)-5.89 and n = 4 (vi) It has also been brought out that as the dielectric constant of the pore fluid decreases; there is a drastic increase in the intrinsic permeability of soil. These changes are attributed to the significant reduction in the thickness of diffuse double layer, which in turn is mainly dependent on the dielectric constant of the pore fluid. The quantification of the change in the hydraulic conductivity with the change in the pore fluids of extreme dielectric constant, i.e., from water to carbon tetrachloride could be expressed in terms of the volume of water held in the diffuse double layer and the same has a good correlation with shrinkage index. With the advancement in the knowledge of the engineering behaviour of fine-grained soils, there is an increasing trend toward larger involvement of fine-grained soils in earth structures and foundations. Though extensive work has been done in the past to understand the swelling behaviour of expansive soils and the mechanisms involved therein, it is yet not satisfactory. From the literature it can be seen that lot of work has been done to correlate the swell potential with various physical properties. The simple means of identifying the swelling type of soils is by means of free swell tests with the ratio of free swell with carbon tetrachloride to the free swell of water. The same has found to correlate well with the percent swell/collapse of the ten soils used in the present investigation. However, it was found that shrinkage index has a better correlation with the swell/collapse behaviour of fine-grained soils, compared to the liquid limit or the plasticity index. In this study, it is also shown that neither the liquid limit nor the plasticity index can qualitatively describe the swell/collapse behaviour of fine-grained soils. This has been attributed primarily to two different mechanisms governing montmorillonitic and kaolinitic soils separately. Even swelling pressure has shown to have a good correlation with shrinkage index. It is found that the compression index of the samples consolidated from the swollen condition correlates well with the shrinkage index. Laboratory determination of the compaction characteristics are very much important for use in earth work constructions. It is found that only the plastic limit bears a good correlation with the compaction characteristics namely optimum moisture content and maximum dry unit weight. This conclusion is also supported by the data from the literature. The correlations are given as: OMC = 0.92 wp (in percent) (viii) and ydmax = 0.23 (93.3 - wp) (inkN/m3) (ix) Liquid limit, plasticity index and shrinkage index do not bear any correlation with the compaction characteristics. It is quite possible that, the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, possibly the good correlation. A simple method to predict the compaction curve is proposed based on the plastic limit of the soils. Of all the important engineering properties, both volume change (compressibility and swelling) and hydraulic conductivity have good correlation with the shrinkage index. However, the compaction characteristics correlate well with the plastic limit. Herein, an hypothesis is proposed to possibly explain why shrinkage index has shown to be a better parameter to correlate with most of the engineering properties with the exception of the compaction characteristics. The liquid limit is a parameter which takes part of the plasticity characteristics of a soil. Recently it has been well brought out that shrinkage limit is primarily a function of how the varying grain sizes are distributed in a soil. Thus, shrinkage limit takes care of the gradation of the soil fractions in it. Thus, by considering the shrinkage index, which is the difference of the liquid limit water content on one end and shrinkage limit water content on the other end, the primary physical properties of the soils namely the plasticity and the grain size distribution are considered. This possibly explains the good correlation of shrinkage index with the engineering properties of fine-grained soils. However, compaction being a moulding of the soils into a compact state, it has a good correlation with the plastic limit, which is the optimum water content of a saturated soil at which it behaves as a plastic material, and thus can be moulded to any shape, thereby the soil can be compacted or moulded to the densest possible state at that water content. Hence, the good correlation. As the present investigation gives the correlative equations to predict the engineering properties of fine-grained soils from the appropriate index properties, which are obtained from simple and quick laboratory tests, it is hoped that this will go a long way in being a handy tool for a practicing geotechnical engineer in the preliminary assessment of fine-grained soils and thereby take appropriate judgement in various aspects of geotechnical constructions with it.

<p>High performance fighter aircraft such as the F-16 experience aeroelastic Limit Cycle Oscillations (LCO) when they carry certain combinations of under-wing stores. This `store-induced LCO' causes serious problems including airframe fatigue, pilot discomfort and loss of operational effectiveness. The usual response has been to restrict the stores carriage envelope based on flight test experience, and accept the accompanying reduction in mission performance.</p><p>Although several nonlinear mechanisms - structural as well as aerodynamic, have been proposed to explain the LCO phenomenon, their roles are not well understood. Consequently, existing models are unable to predict accurately AND reliably the most critical LCO properties, namely onset speed and response level. On the other hand, the more accurate Computational Fluid Dynamics (CFD) based time marching methodology yields results at much greater expense and time. Clearly, there is a critical need to establish methods that are more rapid while providing accurate predictions more in line with flight test results than at present. Such a capability will also aid in future aircraft design and usage.</p><p>This work was undertaken to develop a better understanding of nonlinear aeroelastic phenomena, and their relation to classical flutter and divergence, with a particular focus on store-induced LCO in high performance fighter aircraft. The following systems were studied: (1) a `simple' wing with a flexible and nonlinear root attachment, (2) a `generic' wing with a flexible and nonlinear wing-store attachment and (3) the F-16 aircraft, again with nonlinear wing-store attachments.</p><p>While structural nonlinearity was present in all cases, steady flow aerodynamic nonlinearity was also included in the F-16 case by the use of a Computational Fluid Dynamics model based on the Reynolds Averaged Navier Stokes (RANS) equations. However, dynamic linearization of the CFD model was done for the present computations. The computationally efficient Harmonic Balance (HB) nonlinear solution technique was a key component of this work, with time marching simulations and closed form solutions being used selectively to confirm the findings of the HB solutions. The simple wing and the generic wing were both modeled as linear beam-rods whose displacements were represented using the primitive modes method. The wing aerodynamic model was linear (quasi-steady for the simple wing and based on the Vortex Lattice Method for the generic wing), and the store aerodynamics were omitted.</p><p>The presence of a cubic restoring force (of hardening or softening type, in stiffness or in damping) at the root of the simple wing led to several interesting results and insights. Next, various nonlinear mechanisms including cubic restoring force, freeplay and friction were introduced at the wing-store attachment of the generic wing and these led to a still greater variety in behavior. General relationships were established between the type of nonlinearity and the nature of the resulting response, and they proved very useful for tailoring the F-16 study and interpreting its results.</p><p>The Air Force Seek Eagle Office/Air Force Research Laboratory provided a modal structural model of an LCO-prone store configuration of the F-16 aircraft with stores included. In order to investigate a range of stores attachment configurations, the analysis required modification of the stiffness and damping of the wing-store attachment. Since the Finite Element model of the wing and store structure was not available, the modification was achieved by subtracting the store and adding it back with the necessary changes to the store or attachment using a dynamic decoupling/coupling technique. The modified models were subjected to flutter/LCO analysis using the Duke Harmonic Balance CFD RANS solver, and the resulting flutter boundaries were used in combination with the HB method to derive LCO responses due to the wing-store attachment nonlinearity.</p><p>Comparisons were made between the simulation results and the F-16 flight test LCO data. While multiple sources of nonlinearity are probably responsible for the wide range of observed LCO behavior, it was concluded that cubic softening stiffness and positive cubic damping were the more likely structural mechanisms causing LCO, in addition to nonlinear aerodynamics.</p> / Dissertation

Autor no autoriza el acceso a texto completo de su documento hasta el 15/1/2021. / Ingeniero Civil Industrial / Se presenta un modelo dinámico de múltiples mercados financieros, organizados como limit order markets, en el cual agentes endógenamente toman decisiones óptimas para maximizar el valor esperado de sus ganacias. Los agentes toman sus decisiones considerando incentivos propios, condiciones de mercado, potenciales decisiones de trading futuras y diferentes estrategias adoptadas por otros agentes. Para efectos de la presente investigación, se compara el escenario de un único mercado financiero ( single market ) con un escenario de dos mercados interconectados que compiten por el flujo de órdenes ( multi markets ). Los resultados indican que la posibilidad de transar en múltiples mercados, beneficia ampliamente a agentes sin valoración privada por el activo, ya que buscan oportunidades de transar en ambos mercados, mientras que perjudica el bienestar de agentes con motivación intrínseca para transar, dado que obtienen peores condiciones de negociación. Por otro lado, se observa una reducción en varias medidas de liquidez en multi markets, lo que sugiere la existencia de externalidades positivas asociadas a mercados consolidados.

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