Academic literature on the topic 'Bottom of variable thickness'
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Journal articles on the topic "Bottom of variable thickness"
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Yuriy, Khomyak, Naumenko Ievgeniia, Zheglova Victoriia, and Popov Vadim. "MINIMIZING THE MASS OF A FLAT BOTTOM OF CYLINDRICAL APPARATUS." Eastern-European Journal of Enterprise Technologies 2, no. 1 (92) (2018): 42–50. https://doi.org/10.15587/1729-4061.2018.126141.
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In the bodies of cylindrical apparatuses that operate under pressure, one of the weak elements is a flat bottom whose thickness is increased by 4…5 times in comparison with the wall thickness. This is due to the fact that the bottom is exposed to a more unfavorable bending deformation compared to the wall that «works» on stretching. In order to reduce specific metal consumption for the bottom, we propose the optimization of the shape of a radial cross-section by a rational redistribution of the material: to increase thickness of the bottom in the region of its contact with the wall and to significantly reduce it in the central zone. To describe a variable thickness of the bottom, we applied the Gauss equation with an arbitrary parameter that determines the intensity of change in the thickness in radial direction. We have obtained a general solution to the differential equation of the problem on bending a bottom at a given law of change in its thickness, which is represented using the hypergeometric Kummer’s functions. A technique for concretizing the resulting solution was proposed and implemented, based on the application of conditions of contact between a cylindrical shell and a bottom. The solution derived was used to minimize the mass of the bottom. We have designed a zone of transition from the bottom to the wall whose strength was verified by the method of finite elements under actual conditions
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Xin, Tengda, Hua Wang, Cunyan Cui, and Jiguang Zhao. "An optimal design model for the wall thickness of the propellant tank." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 234, no. 2 (2019): 445–56. http://dx.doi.org/10.1177/0954410019867218.
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The propellant tank is a vital part for the liquid rocket, and the optimal design of the propellant tank is a significant research to develop the heavy rocket. This paper aims at providing an optimal design model for tank wall thickness. Through establishing the tank mathematical model, analyzing the stress distributions of tank, and defining the equivalent stress of tank, the wall thickness parameters of tank roof, cylinder, and bottom are obtained. The effects of tank parameters on the wall thickness are analyzed to determine the distribution rules of tank roof, cylinder, and bottom wall thickness parameters. Combined with the safety factor that is defined as the ratio of the material's ultimate stress to the maximum equivalent stress, the optimal design model with invariable tank roof and bottom wall thicknesses and variable tank cylinder wall thickness is established. Finally, the optimal design model is verified by comparing the optimal tank with the original tank. The results show that the optimal design model can effectively decrease the mass of the tank and improve the stress distribution of the tank.
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Taibi, Mohammed, Younes Abouelhanoune, and Fouad Dimane. "Transient Heat Transfer Analysis in Metal Plates with Variable Thickness." Journal of Physical Science 35, no. 1 (2024): 1–12. http://dx.doi.org/10.21315/jps2024.35.1.1.
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Nonlinear transient heat transfer via conduction–radiation is a dynamic topic of long-standing interest with applications ranging from aeronautical and mechanical engineering to industrial and civil security. To gain a better understanding of the performances of materials having thermal proprieties that change during nonlinear heat transfer, several studies using the finite element method (FEM) have been conducted. Such studies apply nonlinear thermal material characteristics to describe the complete system under different loading conditions in each region by adjusting the temperature values for the other three edges and the thickness parameter with Dirichlet boundary conditions. As a result, while modeling and simulating temperature distributions for such situations, nonlinearities generated by temperature-dependent thermal conductivity must be considered. In this work, we focus on the analysis of coupled transient heat transfer through two metal plates with temperature-dependent thermal characteristics in which the temperature is fixed along the bottom edge and heat is transferred from both the top and bottom faces of the two plates. FEM is employed to solve the nonlinear heat equation and compute the temperature as a function of time for variable thickness. The study examines the effect of modifying the thickness parameter values on the temperature distribution over time for various edge values over 5,000 s.
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Kang, Jae-Hoon. "Vibration Analysis of Complete Conical Shells with Variable Thickness." International Journal of Structural Stability and Dynamics 14, no. 04 (2014): 1450001. http://dx.doi.org/10.1142/s0219455414500011.
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A three-dimensional (3D) method of analysis is presented for determining the free vibration frequencies of complete (not truncated) conical shells with linearly varying thickness. The complete conical shells free or clamped at the bottom edge with a free vertex are investigated. Unlike conventional shell theories, which are mathematically 2D, the present method is based upon the 3D dynamic equations of elasticity. Displacement components ur, uθ and uz in the radial, circumferential and axial directions, respectively, are taken to be periodic in θ and in time, and expressed by algebraic polynomials in the r- and z-directions. Potential (strain) and kinetic energies of the complete conical shell are formulated. The Ritz method is used to solve the eigenvalue problem, yielding the upper bound values of the frequencies by minimization. As the degree of the polynomials is increased, frequencies converge to the exact values, with four-digit exactitude demonstrated for the first five frequencies. The frequencies from the present 3D method are compared with those from other 3D approaches and 2D shell theory by previous researchers.
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Barton, N. G., C. H. Li, and S. J. Spencer. "Control of a surface of discontinuity in continuous thickness." Journal of the Australian Mathematical Society. Series B. Applied Mathematics 33, no. 3 (1992): 269–89. http://dx.doi.org/10.1017/s0334270000007050.
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AbstractThis paper examines the control of an interface between a suspension of sedimenting particles in liquid and a bed of dense-packed particles at the bottom of the suspension. The problem arises in the operation of continuous thickeners (e.g. in mineral processing) and is here mathematically described by a first order inhomogeneous partial differential equation for the concentration C(x, t) of particles. The controlled variable is the height H* of the bed, and the control variables are the volume fluxes injected at the feed level and removed at the bed. A strategy to control the interface is devised, and control is confirmed and demonstrated by a series of numerical experiments.
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Kim, Do Bum, and Byong Jeong Choi. "Evaluation of Flexural Strength about Shape of the Steel Plate-Concrete Composite Beam with Bolt." Advanced Materials Research 1021 (August 2014): 144–47. http://dx.doi.org/10.4028/www.scientific.net/amr.1021.144.
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The composite beam is efficient and easy to construction. But deformation capacity is degraded with thickness of bottom tension plate. The composition ratio by shear connector have a decisive effect on deformation capacity. This research evaluated the flexural strength and deflection with variable of thickness and protrusion length. The effect of composite ratio and shear connector was analyzed through fracture behaviors and distribution of strain through two point loading test.
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Ivošević, Špiro, Romeo Meštrović, and Nataša Kovač. "A Probabilistic Method for Estimating the Percentage of Corrosion Depth on the Inner Bottom Plates of Aging Bulk Carriers." Journal of Marine Science and Engineering 8, no. 6 (2020): 442. http://dx.doi.org/10.3390/jmse8060442.
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This paper presents an approach for the model estimating the probabilistic percent corrosion depth for inner bottom plates of fuel oil tanks located in the double bottom of aging bulk carriers. Assuming that corrosion begins after four years of exploitation, a statistical approach to investigations on the ratio of the corrosion rate and the average initial inner bottom plate’s thickness of considered bulk carriers is given. We consider this ratio to be a random variable since it is included in the usual linear corrosion model. By applying adequate statistical tests to the available empirical dataset, three best fitted three-parameter distributions for estimating the cumulative density function and the probability density function of the random variable were obtained. These three distributions were further used to estimate the studied percentage of corrosion depth. Lastly, we present the corresponding numerical and graphical results concerning the obtained statistical and empirical results and give concluding remarks.
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Arcone, Steven A., and Allan J. Delaney. "Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar." Journal of Glaciology 33, no. 115 (1987): 330–40. http://dx.doi.org/10.1017/s0022143000008923.
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AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.
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Arcone, Steven A., and Allan J. Delaney. "Airborne River-Ice Thickness Profiling with Helicopter-Borne UHF Short-Pulse Radar." Journal of Glaciology 33, no. 115 (1987): 330–40. http://dx.doi.org/10.3189/s0022143000008923.
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AbstractThe ice-thickness profiling performance of a helicopter-mounted short-pulse radar operating at approximate center frequencies of 600 and 900 MHz was assessed. The antenna packages were mounted 1.2 m off the skid of a small helicopter whose speed and altitude were varied from about 1.8 to 9 m/s and 3 to 12 m. Clutter from the helicopter offered minimal interference with the ice data. Data were acquired in Alaska over lakes (as a proving exercise) and two rivers, whose conditions varied from open water to over 1.5 m of solid ice with numerous frazil-ice formations. The most readily interpretable data were acquired when the ice or snow surface was smooth. Detailed surface investigations on the Tanana River revealed good correlations of echo delay with solid ice depth, but an insensitivity to frazil-ice depth due to its high water content. On the Yukon River, coinciding temporally coherent surface and bottom reflections were associated with solid ice and smooth surfaces. All cases of incoherent surface returns (scatter) occurred over ice rubble. Rough-surface scattering was always followed by the appearance of bottom scattering but, in many cases, including a hanging-wall formation of solid frazil ice, bottom scattering occurred beneath coherent, smooth-surface reflections. Areas of incoherent bottom scattering investigated by drilling revealed highly variable ice conditions, including frazil ice. The minimum ice thickness that could be resolved from the raw data was about 0.2 m with the 600 MHz antenna and less than 0.15 m with the 900 MHz antenna.
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Luan, Yingcheng, Yuan Ma, Weiguang Zhang, Yuqing Zhang, Tao Ma, and Jusang Lee. "Adaptability evaluation of pavement structure to replacement treatment subgrade of black cotton soil." Transportation Safety and Environment 2, no. 1 (2020): 69–80. http://dx.doi.org/10.1093/tse/tdaa004.
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Abstract Aiming at the typical engineering problem of black cotton soil (BCS) subgrade under the alternation of dry and wet climate in the region of Nairobi, Kenya, this paper takes the pavement structure as the research object, and the numerical calculation model of BCS subgrade is established based on the consolidation coupling theory of unsaturated soil. Taking the modulus and thickness of the subbase as variables, the deformation characteristics and additional stresses of different pavement structures are analysed. Then the adaptability of different pavement structures to replacement treatment subgrade of BCS is evaluated by gray incidence decision analysis method. The results show that whatever the pavement structure is, neither subgrade modulus nor thickness is sensitive to the pavement surface deformation, and the deformation differences between each pavement structure are more obvious in wet season; the additional stress at control layer bottom and pavement surface decreases with the increase of subbase modulus, whereas the stress may increase at subbase bottom; the additional stress at subbase bottom, control layer bottom and pavement surface all decreases with the increase of subbase thickness for pavement Structure I and II. For pavement Structure III, the change of subbase thickness is not sensitive to the additional stress at the control layer bottom and pavement surface, whereas the stress at subbase bottom increases with the increase of subbase thickness. It is concluded that the most adaptable structure is pavement Structure I, which can minimize the comprehensive level of pavement settlement and additional stress.
Dissertations / Theses on the topic "Bottom of variable thickness"
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MATTUCCI, LUCA MARIA. "Numerical study of cold rolling process with variable thickness." Doctoral thesis, Università Politecnica delle Marche, 2018. http://hdl.handle.net/11566/256367.
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Il principale obiettivo tecnologico di questo progetto di ricerca è lo sviluppo di una tecnologia di laminazione a freddo innovativa, tramite la distribuzione di aree di diverso spessore sul prodotto finito, in modo che il materiale possa essere distribuito al meglio dove è necessario, per soddisfare i requisiti di resistenza e/o rigidezza. Per quanto riguarda il processo di laminazione a freddo, l'obiettivo è quello di effettuare un upgrade della soluzione 1D, nota anche come profile- rolling, già presente in molte aree industriali: il processo di laminazione a zone denominato patch-rolling. Esso rappresenta un'innovazione assoluta consentendo di ottenere zone di maggiore spessore già in fase di laminazione a freddo, nel rispetto delle dimensioni richieste e del posizionamento risultante dalle mappe delle sollecitazioni. L'obiettivo è dunque quello di sviluppare uno strumento di supporto in grado non solo di indicare la fattibilità delle patch, come richiesto dal progetto, ma anche di suggerire eventuali modi che come la dimensione delle patch, variazione di spessore, raggio di raccordo ecc. La prima fase del progetto è stata la scelta del materiale dalle migliori prestazioni per i processi di laminazione e stampaggio. A tale scopo, diversi materiali sono stati caratterizzati mediante test mono-assiali e di formabilità. I primi hanno permesso di identificare le curve di flusso plastico e le principali caratteristiche meccaniche del materiale, mentre quelle di formabilità hanno permesso di valutare l'influenza dell'anisotropia e tracciare i diagrammi limite di formabilità grazie a metodi ottici avanzati. La fase successiva, quindi, è stata lo sviluppo di un modello agli elementi finiti del processo di laminazione a patch in cui venivano richieste solo le proprietà meccaniche del materiale. Dopo che il modello è stato con figurato e convalidato con successo, sono state studiate diverse configurazioni di patch con il modello FEM già descritto. A causa della deformazione non bilanciata nel senso della lunghezza del laminato, è stato sviluppato anche un modello analitico più semplice e veloce in MatLAB R per fornire un'anteprima della forma del laminato con il solo ne di valutare la qualità della distribuzione delle patch. Quindi, lo studio di come i principali fattori (variabili principali) coinvolti nel processo di laminazione influenzino la fattibilità del processo stesso, è stato eseguito attraverso una sperimentazione FEM organizzata secondo le tecniche del Design of Experiments (DoE). L'analisi dei risultati del DoE ha permesso di sviluppare e analizzare un'applicazione di casi reali, a partire dalla distribuzione delle patch no alla realizzazione del prototipo.<br>The main technological aim of this research project is the development of an innovative cold rolling technology with the distribution of different thickness areas on the finished product, so the material can be best distributed where it is needed, to satisfy strength and/or stiffness requirements. Regarding the cold rolling process, the aim is to achieve a better optimisation of the 1D solution, also known as profile-rolling, already seen in many industrial areas: the multi-thickness rolling process named patch-rolling. It represents an absolute innovation by allowing the higher thickness zones already used in the process of cold rolling to be obtained, with respect to the requested sizes and positioning resulting from the stress map. To this purpose the goal is to develop a support tool able not only to indicate the feasibility of the patches, as requested by the project, but also which suggests any amendments needed such as dimension of the patches, thickness variation, fillet radius etc. The first stage of the project was the choice of the material with best performances in both rolling and stamping processes. To this purpose, several possible challengers were deeply investigated through uni-axial and formability tests. First ones were led to identify the flow plastic curves and principal mechanical characteristics of the material while the formability ones allowed the anisotropy influence and the Forming Limit Diagrams to be evaluated thanks
to advanced optical methods. The next stage, indeed, was the development of a finite element method model of the patch-rolling process in which only mechanical properties of the material were requested. After the model was successfully set-up and validated, several patch-configurations were investigated with the FEM model already described. Due to the unbalanced length-wise direction deformation of the work-piece a more simple and fast analytical model was also developed in MatLAB R to provide a pre-view of the shape of the laminated work-piece only to evaluate the quality of the patch distribution. Then the study of how the principal factors (main variables) involved in the rolling process may affect the feasibility of the process itself, was performed through a FEM experimentation organized according to the Design of Experiments (DoE) techniques. The analysis of the results of the DoE allowed a real case application to be developed and analysed, starting from the patch distribution until the prototype realisation.
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Adcock, Susan T. "A parameterisation of geostrophic eddies over variable bottom topography." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314318.
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Portz, Ron. "Transverse jet penetration in supersonic flows with variable boundary layer thickness." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010827.
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Lasseigne, Alexis. "Optimization of variable-thickness composite structures. Application to a CROR blade." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEM006/document.
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Cette thèse aborde la problématique de la conception optimale de structures composites stratifiées d’épaisseur variable. Les variables d’empilement définissent un problème d’optimisation combinatoire et des espaces de décisions de grande taille et potentiellement multimodaux. Les algorithmes d’optimisation stochastiques permettent de traiter ce type de problème et de tirer profit des performances et de l’anisotropie des plis composites pour l’allègement des structures composites stratifiées. Le but de cette étude est double : (i) développer un algorithme d’optimisation dédié aux composites stratifiés d’épaisseur variable et (ii) estimer le potentiel des composites stratifiés pour la maîtrise des performances aérodynamiques d’une pale de CROR composite.Dans la première partie de cette thèse, un algorithme évolutionnaire est spécialisé pour l’optimisation de tables de drapage et la gestion d’un ensemble de règles de conception représentatif des pratiques de l’industrie. Pour se faire, un encodage spécifique des solutions est proposé et des opérateurs de variations spécialisés sont développés.Dans la deuxième partie, l’algorithme est enrichi d’une technique de guidage basée sur l’exploitation d’un espace auxiliaire afin d'accroître son efficacité et d’intégrer davantage de connaissances des composites dans la résolution du problème.Finalement, la méthode est appliquée pour la conception d’une pale de CROR composite à l’échelle de la maquette de soufflerie. Au préalable, des processus itératifs de mise à froid et mise à chaud de la pale sont mis en place afin d’estimer la forme de la pale au repos et l’état de contraintes dans la pale en fonctionnement<br>This thesis deals with the optimal design of variable-thickness laminated composite structures. The stacking variables define a combinatorial optimization problem and large decision spaces which are potentially multimodal. Stochastic optimization algorithms allow solving this type of problem and allow taking advantage from the performance and the anisotropic nature of unidirectional composite plies to lighten laminated composite structures.The purpose of this study is twofold: (i) developing an optimization algorithm dedicated to variable-thickness laminated composites and (ii) assessing the potential of laminated composites in influencing the aerodynamic performances of a composite CROR blade.Firstly, an evolutionary algorithm is specialized in order to optimize layup tables and handle a set of design guidelines which is representative of industrial practices. In this purpose, a specific encoding of the solutions is suggested and specialized variation operators are developed.Secondly, the algorithm is enriched with a guiding technique based on the exploitation of an auxiliary space in order to improve its efficiency and to include further composites-related knowledge for the resolution of the problem.Finally, the method is applied for the design of a reduced-scale composite CROR blade intended for wind-tunnel testing. Beforehand, iterative processes are implemented to estimate the shape of the non-operating blade and the stress state within the operating blade
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Ekmekjian, Nazareth (Nazareth Vahe). "Architecture sandwiched : tuning anisotropy through variable thickness and hetereogeneous laminar assemblies." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99272.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Architecture, 2015.<br>Cataloged from PDF version of thesis. Page 61 blank.<br>Includes bibliographical references (pages 58-59).<br>Much of architecture's earliest material palettes and construction methods are often referred to today as legacy materials - those primarily consisting of various types of stone and masonry construction. While these materials are often conceptually thought of as being solid, monolithic, and even homogeneous, in actuality they rely on logics of assembly more akin to contemporary sandwich structures, which are laminar assemblies typically composed of two or more stressed skins and either a solid or cellular core that binds them together. While it is still common to use ancient materials in contemporary architecture, the construction methods and techniques used several hundred years ago are no longer appropriate for today's buildings. This thesis however, argues for a newfound relevance of their influence on contemporary and even future material selections and methods. Specifically, this thesis explores the potentials of composite sandwiches varying in thickness and material in search of architectural possibilities whose structural, formal, and aesthetic implications are a result of tuning multiple influences. Variable thickness is used here as a strategy for enabling a range of architectural and tectonic conditions, all within the same heterogeneous but integrated laminar assemblies. While most commercial products in the realm of composite sandwiches are of uniform thickness in section, this thesis suggests a method for constructing sandwiched elements with variable thickness. This is done primarily through a process of infill and backfill using expanding urethane foam as a medium which creates the so called "core" of the sandwich between two skins. This investigation works through a series of small scale prototypes, each of which focus on a particular tectonic, spatial, or structural condition. These mock ups are meant to serve as didactic artifacts, providing feedback with which to incorporate and speculate upon larger architectural propositions through drawing and representation. The end result is a set of architectural proposals which suggest the beginnings of new design methodologies.<br>by Nazareth Ekmekjian.<br>S.M.
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Awrejcewicz, Jan, Lidiya Kurpa, and T. Shmatko. "Nonlinear vibration of orthotropic shallow shells of the complex shape with variable thickness." Thesis, Wydawnictwo Politechniki Łódzkiej, 2011. http://repository.kpi.kharkov.ua/handle/KhPI-Press/37115.
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Early R-functions theory [1] combined with variational methods have been applied to linear [2] and nonlinear vibration problems [3,4] of the shallow shells theory of the constant thickness. In the present study, we first apply R-functions theory in order to investigate the geometrically nonlinear vibrations of orthotropic shallow shells of complex shape with variable thickness. Mathematical formulation is made in the framework of classical geometrically nonlinear theory of thin shallow shells. For a discretization of the original system in time, approximation of unknown functions is carried out by using a single mode approach. In order to construct a system of basic functions, the proposed algorithm includes sequence of the linear problems such as finding eigen functions of the linear vibrations of shallow shells with variable thickness and auxiliary tasks of the elasticity theory. The linear problems are solved by the R-functions method. The developed approach allows reducing the original problem to the corresponding problem of solving nonlinear ordinary differential equations (ODEs), whose coefficients are presented in analytical form. In order to solve the obtained system of ODEs the Bubnov-Galerkin method is applied. The proposed algorithm is implemented within an automated system POLE-RL [1]. Numerical examples of large-amplitude flexible vibrations of shallow orthotropic shells with complex shape and variable thickness are introduced demonstrating merits and advantages of the R-functions method. Comparison of the obtained results regarding shells with rectangular plans with the other methods confirms the reliability of the proposed method.
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Brunke, Michael A., Patrick Broxton, Jon Pelletier, et al. "Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)." AMER METEOROLOGICAL SOC, 2016. http://hdl.handle.net/10150/612995.
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One of the recognized weaknesses of land surface models as used in weather and climate models is the assumption of constant soil thickness because of the lack of global estimates of bedrock depth. Using a 30-arc-s global dataset for the thickness of relatively porous, unconsolidated sediments over bedrock, spatial variation in soil thickness is included here in version 4.5 of the Community Land Model (CLM4.5). The number of soil layers for each grid cell is determined from the average soil depth for each 0.9 degrees latitude x 1.25 degrees longitude grid cell. The greatest changes in the simulation with variable soil thickness are to baseflow, with the annual minimum generally occurring earlier. Smaller changes are seen in latent heat flux and surface runoff primarily as a result of an increase in the annual cycle amplitude. These changes are related to soil moisture changes that are most substantial in locations with shallow bedrock. Total water storage (TWS) anomalies are not strongly affected over most river basins since most basins contain mostly deep soils, but TWS anomalies are substantially different for a river basin with more mountainous terrain. Additionally, the annual cycle in soil temperature is partially affected by including realistic soil thicknesses resulting from changes in the vertical profile of heat capacity and thermal conductivity. However, the largest changes to soil temperature are introduced by the soil moisture changes in the variable soil thickness simulation. This implementation of variable soil thickness represents a step forward in land surface model development.
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Dadfar, Humaira. "The influence of variable B horizon thickness (tonguing) on solute transport through undisturbed soil columns." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq24456.pdf.
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El-Kaabazi, Nihal. "Free vibration of cylindrical shells with constant and variable thickness using the Wittrick-Williams algorithm." Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/55072/.
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With the rapid development of computer programming and systems, complex analytical shell problems are being tackled more than ever before. Finite element analysis has been the most widely used numerical method in modelling shell structures. In this thesis a more reliable and accurate method is demonstrated, in which the dynamic stiffness is derived from the exact differential equations, resulting in fewer elements and reduced computing time. Free undamped vibration analysis for constant and variable thickness cylindrical shells is carried out by deriving the dynamic stiffness matrix directly from the three differential equilibrium equations after transforming them to three ordinary differential equations and using the boundary value solver COLSYS. The natural frequencies and mode shapes are determined by using the Wittrick-Williams algorithm. A method of handling the effect of fixed end member frequencies below a limiting trial frequency is presented. Numerical examples for beams with constant and variable thicknesses and shells with constant and variable thicknesses are shown, and the method is validated by convergence studies and the handling of fixed end frequencies. A comparison of shell problem results with those of other authors is given, and a parametric study is carried out by varying the length to radius, radius to thickness, and thickness variation ratios. Results are obtained for different circumferential and axial harmonic numbers. Mode shapes are explained, for different shell thickness ratios and end conditions, and significant conclusions are drawn. From all the study and results obtained in this thesis it is ascertained that using the Wittrick-Williams algorithm in combination with COLSYS is a successful approach, and good agreements are effectively achieved for free undamped vibration of cylindrical shells with constant and variable thickness.
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Kang, Jae-Hoon. "Three-dimensional vibration analysis of thick shells of revolution with arbitrary curvature and variable thickness /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487945015615814.
Full textBooks on the topic "Bottom of variable thickness"
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R, Heyd A., and United States. National Aeronautics and Space Administration., eds. Characterization of SiGe/Ge heterostructures and graded layers using variable angle spectroscopic ellipsometry. National Aeronautics and Space Administration, 1996.
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Dejak, Steven Ivan. Long-time dynamics of Korteweg-de Vries solitary waves over a variable bottom. 2006.
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Wyatt, Laura A., and Michael Doherty. Morphological aspects of pathology. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199668847.003.0003.
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Osteoarthritis (OA) is the commonest condition to affect synovial joints, but although any synovial joint can be affected, most studies of pathology relate to large joints (knees and hips). OA involves the whole joint and pathological alterations typically occur in all joint tissues. Established OA is characterized by a mixture of tissue loss and new tissue production resulting in focal loss of articular hyaline cartilage together with bone remodelling and osteophyte formation. Articular cartilage may show increased thickness in the earliest stages of OA with increased numbers of hypertrophic chondrocytes, followed by progressive decline in matrix components, thickness, and chondrocyte number. Surface fibrillation and vertical clefts become evident in mid- to end-stage OA and eventual complete loss of cartilage can occur, predominantly in maximum load-bearing regions, with subsequent eburnation and furrowing of bone. Bone remodelling may lead to alteration of bone shape and variable trabecular thickness in subchondral bone, whilst subchondral microfractures may result in localized osteonecrosis, fibrosis, and ‘cysts’. Endochondral ossification of new fibrocartilage produced predominantly at the joint margin produces characteristic bony osteophytes. The synovium shows areas of hyperplasia with varying amounts of lymphocyte aggregates and inclusion of osteochondral ‘loose’ bodies, and the outer fibrous capsule thickens to help stabilize the compromised joint. Synovial fluid increases in volume but decreases in viscosity. Periarticular changes include type II muscle atrophy and enthesophytes.
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Bickel, Balthasar, and Fernando Zúñiga. The ‘Word’ in Polysynthetic Languages. Edited by Michael Fortescue, Marianne Mithun, and Nicholas Evans. Oxford University Press, 2017. http://dx.doi.org/10.1093/oxfordhb/9780199683208.013.52.
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Polysynthesis presupposes the existence of ‘words’, a domain or unit of phonology and syntax that is extremely variable within and across languages: what behaves as a ‘word’ with respect to one phonological or syntactic rule or constraint may not behave as such with respect to other rules or constraints. Here we develop a system of variables that allows cataloguing all verb-based domains in a language in a bottom-up fashion and then determining any potential convergence of domains in an empirical way. We apply the system to case studies of Mapudungun and Chintang. These confirm earlier observations that polysynthetic languages do not operate with unified units of type ‘word’ in either phonology or syntax.
Book chapters on the topic "Bottom of variable thickness"
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Bhaskar, K., and T. K. Varadan Retd. "Variable Thickness Plates." In Plates. John Wiley & Sons, Ltd, 2014. http://dx.doi.org/10.1002/9781118894705.ch12.
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Bhaskar, K., and T. K. Varadan. "Variable Thickness Plates." In Plates. Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-69424-1_12.
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Zhou, Ding, and Yepeng Xu. "Plates of Variable Thickness." In Encyclopedia of Thermal Stresses. Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_185.
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Kobelev, Vladimir. "Disk Springs with Variable Thickness." In Fundamentals of Springs Mechanics. Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-58584-5_6.
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Vullo, Vincenzo, and Francesco Vivio. "Non-Linearly Variable Thickness Disks." In Mechanical Engineering Series. Springer Milan, 2012. http://dx.doi.org/10.1007/978-88-470-2562-2_7.
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Lazari, L., and S. T. S. Al-Hassani. "Explosive Welding of Variable Thickness Plates." In Metallurgical Applications of Shock-Wave and High-Strain Rate Phenomena. CRC Press, 2024. http://dx.doi.org/10.1201/9781003573661-62.
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Sahni, Manoj, and Ritu Sahni. "Analysis of Orthotropic Variable Thickness Rotating Disc." In Lecture Notes in Mechanical Engineering. Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8767-8_40.
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Barton, Oscar, and Robert Reiss. "Approximate Fundamental Frequency of Variable Thickness Composite Plates." In Computational Mechanics ’95. Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79654-8_377.
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Bakker, Mark, and Vincent Post. "Steady one-dimensional unconfined flow with variable saturated thickness." In Analytical Groundwater Modeling. CRC Press, 2022. http://dx.doi.org/10.1201/9781315206134-3.
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Hirano, S., Y. Hirata, M. Matsuda, T. Morooka, S. Nakayama, and S. Kuriki. "Direct flux-noise measurement of Nb variable-thickness-bridges." In Advances in Superconductivity XI. Springer Japan, 1999. http://dx.doi.org/10.1007/978-4-431-66874-9_282.
Full textConference papers on the topic "Bottom of variable thickness"
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Shukla, Pavan K., Andrew Nordquist, Fernando Farelas, Naim Kabir, and Ingrid Pederson. "Cathodic Protection Systems Analysis for Aboveground Storage Tanks." In CONFERENCE 2025. AMPP, 2025. https://doi.org/10.5006/c2025-00425.
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Abstract Cathodic protection (CP) is widely used to protect against soil-side corrosion of aboveground storage tanks (ASTs). However, design practices, field installations and implementations, and operational parameters can be suboptimal, leading to soil-side corrosion of the AST bottoms even with CP in place. For example, in anode ring CP systems, the loop-to-loop separation distance requires that the entire bottom plate is adequately saturated with CP current. This requirement also means that the sandpad thickness must be considered during the system design phase, and failure to do so can lead to deficiencies in the design. Similarly, failure of the anode rings during operation may lead to suboptimal current distribution. Therefore, a CP current distribution model is needed to study design variables, field installation and implementation conditions, and operation parameters and their effects on the CP current distribution such that a given tank has optimal corrosion control. A finite element method was used to develop the CP current distribution model. The model was exercised for various options such as varying sandpad thickness across the pad surface and sandpad resistivity variations. The model results were used to develop CP design and installation guidelines for various configurations.
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LaBerge, Kelsen, Joel Johnston, Robert Handschuh, and Gary Roberts. "Evaluation of a Variable Thickness Hybrid Composite Bull Gear." In Vertical Flight Society 74th Annual Forum & Technology Display. The Vertical Flight Society, 2018. http://dx.doi.org/10.4050/f-0074-2018-12859.
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For several years, NASA Glenn Research Center and the U.S. Army Research Laboratory have been investigating hybrid (composite/steel) gear technology for use in vertical lift drive systems. The hybrid gear concept replaces the structural portion of a gear between the shaft and the gear rim with a lightweight carbon fiber composite, in an effort to reduce the overall weight of a gear and increase the drive system power density. Past research includes both small-scale and large-scale hybrid gear concepts, all of which have a constant composite thickness throughout. The design described in this paper is of a variable thickness, such that the composite is thickest at the inner diameter and this thickness is gradually reduced toward the outer diameter. The resulting "stair stepped" design stems from dropping plies of the braided carbon fiber prepreg composite fabric gradually with increased radius. Additionally, the interlock pattern at the inner metallic adapter was adjusted slightly from previous designs to obtain a better stress distribution on the inner metallic adapter. The manufactured variable thickness web was tested both in static torsion tests and operationally in a relevant gearbox environment. The results of these experiments will be presented and compared to a baseline steel configuration.
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Xie, Xiaopeng, Gangyi Zou, Liang Xu, et al. "Method of design and optimization process of variable curvature mirror with variable thickness distribution." In Optical Design and Testing XIV, edited by Rengmao Wu, Yongtian Wang, and Tina E. Kidger. SPIE, 2024. http://dx.doi.org/10.1117/12.3035424.
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Sherwani, Muhammad A. "Use of Vapor Corrosion Inhibitor for Tank Bottom Protection." In CONFERENCE 2022. AMPP, 2022. https://doi.org/10.5006/c2022-17879.
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Abstract The use of Volatile Corrosion Inhibitors (VCI) to protect Aboveground Storage Tank (AST) bottom plates against soil-side corrosion is one of the emerging corrosion prevention methods, specifically for tanks constructed on oily sand pad. Oily sand pad and the presence of air gaps underneath the bottom plates lead to severe corrosion and high metal thickness loss. In such cases, the cathodic protection cannot be fully considered as effective due to Cathodic Protection (CP) current shielding. These situations sometimes result in serious failures on multiple fronts, such as; containment losses, system shutdowns, extensive repairs, environmental impact and safety concerns in case of flammable fluids. Recently, East West Pipeline Department (EWPD) of Saudi Aramco has deployed this technology to one of the crude oil storage tanks, which showed high metal thickness loss during its out of service inspection. Soil-side corrosion rustled in major repairs of bottom plates and ultimately caused enormous unplanned activities in term of time as well as cost. This paper mainly focuses on the methodology of VCI installation, corrosion monitoring system and the expected results of protection.
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Hamza, Ameer, and Rakan M. Samman. "Corrosion Challenges on Tank Bottom Plate." In CONFERENCE 2023. AMPP, 2023. https://doi.org/10.5006/c2023-19387.
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Abstract Subsequent failure due to corrosion, particularly on storage tanks bottom plates for molten sulphur tanks, is one of the main factors upsetting any production facilities. Maintaining adequate level of corrosion protection for the bottom plates soil side is always challenging due to complex corrosion phenomena. Failure of storage tanks during production stage due to such corrosion phenomena can be catastrophic which would result in serious consequences subject to health, safety, environmental, cost, economic impact, damage to assets and company reputation. As per current industrial practice, above ground storage tanks’ bottom plates are designed to be protected externally with ICCP system. However, the CP effectiveness often becomes challenging due to presence of air gap, improper selection of sand, improper CP design and formation of acidic environment. Such factors eventually lead to ineffectiveness of CP system due to restricted current flow. The situation aggravates in the tanks which is handling molten sulphur whenever there is moisture ingress occurs through annular area of the concrete foundation and settles underneath the bottom plate surfaces. This paper focuses on sulphur tank failure due to multiple corrosion damage mechanism acting on this tank from soil side that had resulted in heavy loss of thickness and deep pitting.
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Yu, Huan, Wenchao Chen, Zijian Cai, Fuheng Zhang, Peng Xin, and Hao Gu. "Optimization of Variable Thickness Rotationally-symmetric Dielectric Radome Based on Physical Optics." In 2024 Photonics & Electromagnetics Research Symposium (PIERS). IEEE, 2024. http://dx.doi.org/10.1109/piers62282.2024.10618309.
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Esber, Ahmad, and Sunday Olutunde Oyadiji. "Design of a variable-thickness morphing wing for enhanced UAV aerodynamic performance." In Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2025, edited by Maria Pina Limongelli, Ching Tai Ng, and Didem Ozevin. SPIE, 2025. https://doi.org/10.1117/12.3057857.
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Azzuni, Eyas, and Sukru Guzey. "Design of Cylindrical Steel Storage Tanks: A Linear Elastic Analysis Approach." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63202.
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A cylindrical steel storage tank is a cylindrical shell subjected to internal hydrostatic pressure due to the stored liquid product. The hydrostatic pressure causes the shell to experience circumferential stress. This circumferential stress can lead to the yielding of the shell if its thickness is not designed properly. The design of step-walled steel storage tanks requires the calculation of the required thickness of each shell course. A conservative way of calculating each course’s thickness is using the one-foot method (1FM). This method calculates the required thickness to withstand the hydrostatic pressure one foot above the bottom edge of the shell course under consideration. Another method, which is more refined than the 1FM, is the variable-design-point method (VDM), which finds the point in the course where the maximum circumferential stress is. VDM calculates the required shell thickness to withstand that maximum circumferential stress. However, VDM does not capture the circumferential stress resulting from the bottom edge yielding moment accurately for some thank geometries. A new linear analysis approach using thin-shell theory is presented in this paper. The approach captures the plastic yielding moment of the bottom edge accurately, and may produce more economical and safe designs than 1FM and VDM.
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Belibassakis, K. A., and G. A. Athanassoulis. "A Fast Convergent Modal-Expansion of the Wave Potential With Application to the Hydrodynamic and Hydroelastic Analysis of Floating Bodies in General Bathymetry." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79681.
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A non-linear coupled-mode system of horizontal equations has been derived with the aid of Luke’s (1967) variational principle, modelling the evolution of nonlinear water waves in intermediate depth and over a general bathymetry Athanassoulis & Belibassakis (2002, 2008). Following previous work by the authors in the case of linearised water waves (Athanassoulis & Belibassakis 1999), the vertical structure of the wave field is exactly represented by means of a local-mode series expansion of the wave potential. This series contains the usual propagating and evanescent modes, plus two additional modes, the free-surface mode and the sloping-bottom mode, enabling to consistently treat the non-vertical end-conditions at the free-surface and the bottom boundaries. The coupled-mode system fully accounts for the effects of non-linearity and dispersion. The main feature of this approach that a small number of modes (of the order of 5–6) are enough for the precise numerical solution, provided that the two new modes (the free-surface and the sloping-bottom ones) are included in the local-mode series. The consistent coupled-mode system has been applied to numerical investigation of families of steady nonlinear travelling wave solutions in constant depth (Athanassoulis & Belibassakis 2007) showing good agreement with known solutions both in the Stokes and the cnoidal wave regimes. In the present work we focus on the hydroelastic analysis of floating bodies lying over variable bathymetry regions, with application to the non-linear scattering of water waves by large floating structures (of VLFS type or ice sheets) characterised by variable thickness (draft), flexural rigidity and mass distributions, modelled as thin plates of variable thickness, extending previous approaches (see, e.g., Porter & Porter 2004, Belibassakis & Athanassoulis 2005, 2006, Bennets et al 2007). Numerical examples are presented, showing that useful results can be obtained for the analysis of large floating elastic bodies or structures very efficiently by keeping only a few terms in the expansion. Ideas for extending our approach to 3D are also discussed.
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Behera, Chaitanya, Sandip Mahajan, Carlos Annia, et al. "Challenges, Opportunities and Threats of Deep Bottoms-Up Water Injection in Heavy Oil Reservoir: Lessons Learnt from the G Field, South Oman." In SPE 2020 Symposium Compilation. SPE, 2021. http://dx.doi.org/10.2118/203783-ms.
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Abstract This paper presents the results of a comprehensive study carried out to improve the understanding of deep bottom-up water injection, which enabled optimizing the recovery of a heavy oil field in South Oman. Understanding the variable water injection response and the scale of impact on oil recovery due to reservoir heterogeneity, operating reservoir pressure and liquid offtake management are the main challenges of deep bottoms-up water injection in heavy oil fields. The offtake and throughput management philosophy for heavy oil waterflood is not same as classical light oil. Due to unclear understanding of water injection response, sometimes the operators are tempted to implement alternative water injection trials leading to increase in the risk of losing reserves and unwarranted CAPEX sink. There are several examples of waterflood in heavy oil fields; however, very few examples of deep bottom water injection cases are available globally. The field G is one of the large heavy oil fields in South Oman; the oil viscosity varies between 250cp to 1500cp. The field came on-stream in 1989, but bottoms-up water-injection started in 2015, mainly to supplement the aquifer influx after 40% decline of reservoir pressure. After three years of water injection, the field liquid production was substantially lower than predicted, which implied risk on the incremental reserves. Alternative water injection concepts were tested by implementing multiple water injection trials apprehending the effectiveness of the bottoms-up water injection concept. A comprehensive integrated study including update of geocellular model, full field dynamic simulation, produced water re-injection (PWRI) model and conventional field performance analysis was undertaken for optimizing the field recovery. The Root Cause Analysis (RCA) revealed many reasons for suboptimal field performance including water injection management, productivity impairment due to near wellbore damage, well completion issues, and more importantly the variable water injection response in the field. The dynamic simulation study indicated negligible oil bank development due to frontal displacement and no water cut reversal as initial response to the water injection. Nevertheless, the significance of operating reservoir pressure, liquid offtake and throughput management impact on oil recovery cann't be precluded. The work concludes that the well reservoir management (WRM) strategy for heavy oil field is not same as the classical light oil waterflood. Nevertheless, the reservoir heterogeneity, oil column thickness and saturation history are also important influencing factors for variable water injection response in heavy oil field.
Reports on the topic "Bottom of variable thickness"
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Wadman, Heidi, and Jesse McNinch. Elevation of underlying basement rock, Ogdensburg Harbor, NY. Engineer Research and Development Center (U.S.), 2021. http://dx.doi.org/10.21079/11681/40843.
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Over six linear miles of shallow acoustic reflection geophysical data were collected in an 800 ft by 300 ft survey region at Ogdensburg Harbor, Ogdensburg, NY. To better accommodate modern commercial vessels and expand the harbor’s capacity, the current navigable depth of -19 ft Low Water Depth (LWD) needs to be increased to -28 ft LWD, and an accurate map of the nature of the riverbed material (e.g., unconsolidated sediment, partially indurated glacial till, or bedrock) is required to effectively plan for removal. A total of 28 boreholes were previously collected to map the stratigraphy, and the effort revealed significant spatial variability in unit thickness and elevation between adjacent boreholes. To accurately map this variable stratigraphy, chirp sub-bottom profiles were collected throughout the region, with an average line spacing of 13 ft. These sub-bottom data, validated and augmented by the borehole data, resulted in high-resolution spatial maps of stratigraphic elevation and thickness for the study area. The data will allow for more accurate assessment of the type and extent of different dredging efforts required to achieve a future uniform depth of -28 ft LWD for the navigable region.
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Al-Qadi, Imad, Jaime Hernandez, Angeli Jayme, et al. The Impact of Wide-Base Tires on Pavement—A National Study. Illinois Center for Transportation, 2021. http://dx.doi.org/10.36501/0197-9191/21-035.
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Researchers have been studying wide-base tires for over two decades, but no evidence has been provided regarding the net benefit of this tire technology. In this study, a comprehensive approach is used to compare new-generation wide-base tires (NG-WBT) with the dual-tire assembly (DTA). Numerical modeling, prediction methods, experimental measurements, and environmental impact assessment were combined to provide recommendations about the use of NG-WBT. A finite element approach, considering variables usually omitted in the conventional analysis of flexible pavement was utilized for modeling. Five hundred seventy-six cases combining layer thickness, material properties, tire load, tire inflation pressure, and pavement type (thick and thin) were analyzed to obtained critical pavement responses. A prediction tool, known as ICT-Wide, was developed based on artificial neural networks to obtain critical pavement responses in cases outside the finite element analysis matrix. The environmental impacts were determined using life cycle assessment. Based on the bottom-up fatigue cracking, permanent deformation, and international roughness index, the life cycle energy consumption, cost, and green-house gas (GHG) emissions were estimated. To make the outcome of this research effort useful for state departments of transportation and practitioners, a modification to AASHTOWare is proposed to account for NG-WBT. The revision is based on two adjustment factors, one accounting for the discrepancy between the AASHTOware approach and the finite element model of this study, and the other addressing the impact of NG-WBT.
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Holdsworth, E., R D Knight, L J Valiquette, A. R. R. Landon-Browne, and H. A. J. Russell. An assessment of variable sample thickness for pXRF analysis of unconsolidated sediment. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328195.
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Christoforidou, Eirini, Antonio Bobet, Tommy Nantung, and Philippe L. Bourdeau. Use of Geosynthetics on Subgrade and on Low and Variable Fill Foundations. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317437.
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There are significant problems during construction to establish an adequate foundation for fills and/or subgrade for pavements when the natural ground has low-bearing soils. Geosynthetics such as geogrids, geotextiles, and/or geocells could provide a less time-consuming, costly alternative for establishing an adequate foundation for the fill and/or subgrade. There is extensive evidence in the literature and on DOTs practices about the suitability of using geotextiles in pavements as separators. Previous studies have also shown that the use of geogrids in flexible pavements as a reinforcing mechanism could decrease the thickness of the base layer and/or increase the life of the pavement. In this study, analyses of selected pavement designs using Pavement ME—while considering geogrid-enhanced base or subgrade resilient modulus values—showed that geogrid-reinforcement, when placed at the interface between subgrade and base, did not produce significant benefits and only a modest increase in pavement life was predicted. In addition, parametric finite element analyses were carried out to investigate the potential benefits of placing a geogrid at the base of a fill over a localized weak foundation zone. The analyses showed that the use of geogrids is beneficial only when: (a) the stiffness of the weak foundation soil is about an order of magnitude smaller than the rest of the foundation soil; and (b) the horizontal extent of the weak foundation soil is at least 30% of the base of the embankment foundation. The largest decrease in differential settlements at the surface of the fill, resulting from geogrid-reinforcement, was less than 20% and, therefore, it is unlikely that the sole use of geogrids would be sufficient to mitigate differential settlements. Based on previous studies, a geocell mattress, which is a three-dimensional geosynthetic filled with different types of materials, could act as a stiff platform at the base of an embankment and bridge over weak zones in the foundation. However, given the limited experience in Indiana on the use of geocells, further research is required to demonstrate that geocells can be effectively used in place of other reinforcement methods.
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Wadman, Heidi, and Jesse McNinch. Spatial distribution and thickness of fine-grained sediment along the United States portion of the upper Niagara River, New York. Engineer Research and Development Center (U.S.), 2021. http://dx.doi.org/10.21079/11681/41666.
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Over 220 linear miles of geophysical data, including sidescan sonar and chirp sub-bottom profiles, were collected in 2016 and 2017 by the US Army Corps of Engineers and the US Fish and Wildlife Service in the upper Niagara River. In addition, 36 sediment grab samples were collected to groundtruth the geophysical data. These data were used to map the spatial distribution of fine-grained sediment, including volume data in certain locations, along the shallow shorelines of the upper Niagara River. Overall, the most extensive deposits were spatially associated with either small tributaries or with man-made structures that modified the natural flow of the system. Extensive beds of submerged aquatic vegetation (SAV) were also mapped. Although always associated with a fine-grained matrix, the SAV beds were patchy in distribution, which might reflect subtle differences in the grain size of the sediment matrix or could simply be a function of variations in species or growth. The maps generated from this effort can be used to guide sampling plans for future studies of contamination in fine-grained sediment regions.
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Campbell, Seth, Zoe Courville, Samantha Sinclair, and Joel Wilner. Brine, englacial structure and basal properties near the terminus of McMurdo Ice Shelf, Antarctica. Engineer Research and Development Center (U.S.), 2022. http://dx.doi.org/10.21079/11681/45303.
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We collected ∼1300 km of ground-penetrating radar profiles over McMurdo Ice Shelf, Antarctica, using frequencies between 40 and 400 MHz to determine extent, continuity and depth to the brine. We also used profiles to determine meteoric ice thickness and locate englacial features, which may suggest ice shelf instability. The brine extends 9–13 km inland from the ice shelf terminus and covers the entire region between Ross, White and Black Islands. Jump unconformities and basal fractures exist in the brine and ice shelf, respectively, suggesting prior fracturing and re-suturing. One 100 MHz profile, the most distal from the ice shelf edge while still being situated over the brine, simultaneously imaged the brine and bottom of meteoric ice. This suggests a negative brine salinity gradient moving away from the terminus. The meteoric ice bottom was also imaged in a few select locations through blue ice in the ablation zone near Black Island. We suggest that brine, sediment-rich ice and poor antenna coupling on rough ice attenuates the signal in this area. When combined with other recent mass-balance and structural glaciology studies of MIS, our results could contribute to one of the most high-resolution physical models of an ice shelf in Antarctica.
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Kanakamedala, Deven, Jungil Seo, Amit H. Varma, Robert J. Connor, and Anna Tarasova. Shear and Bearing Capacity of Corroded Steel Beam Bridges and the Effects on Load Rating. Purdue University, 2023. http://dx.doi.org/10.5703/1288284317634.
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Corrosion in the girders of steel girder bridges often occurs due to the deicing salts, water, and other debris that leak through the deck joints into the web and bottom flange at the girder ends. Corrosion causes loss of cross-sectional area leading to a reduction in section properties of the member, which eventually results in a reduction in structural resistance against shear and bearing. In this study, seven full-scale tests were performed on decommissioned steel girders acquired from bridges scheduled for demolition in Indiana. Two of the four girders had severe corrosion with cracks and holes in the bottom of the web induced by corrosion, while four girders had moderate section loss induced artificially. All seven girders were subjected to shear loading to determine the residual shear and bearing capacity. Test results revealed a reduction in strength due to section loss compared to nominal sections. Failure modes observed during these four large-scale experiments were shear buckling, shear rupture, and web local crippling. Finite element models were developed and benchmarked to the experimental results. Parametric studies were performed for unstiffened and stiffened girders and included different corrosion scenarios by varying parameters such as corrosion height, length, and thickness loss. Results were analyzed to investigate the effect of each parameter and a modification factor was developed to estimate the residual shear and bearing capacity of corroded girders.
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Speranza, Vito, Sara Liparoti, Giuseppe Titomanlio, and Roberto Pantani. Modeling of polymer processing of thermoplastic polymers: application to the injection molding process. Universidad de los Andes, 2024. https://doi.org/10.51573/andes.pps39.gs.im.5.
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In the transformation operations of polymeric materials, there is a complex interplay between transport phenomena and crystallization. In particular, the polymer in the molten state is a viscoelastic fluid with rheological parameters depending on temperature, pressure, crystallinity, and molecular stretch. The molecular stretch is a tensor variable with values determined by the history of the flow, temperature, and pressure fields. During polymer processing operations, several phenomena proceed simultaneously by interacting with each other. The combination and interplay of the models that describe each of the phenomena mentioned above provides the evolution of all the relevant quantities and, therefore, also the overall model that describes the evolution of the solidification that generally proceeds starting from the walls (where the temperature is lower and furthermore the shear is higher). This work presents an overall model of the behavior of an isotactic polypropylene during the injection molding process. The model includes the kinetics of spherulitic and fibrillar crystallization and their dependence on the level of molecular stretch; the modeling is carried out up to the prediction of molecular stretch and morphology distributions along the molded part thickness. The model predictions satisfactorily describe the evolution of temperature and pressure during the process and the fundamental aspects of the morphology distribution inside the part.
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Scholz, Florian. Sedimentary fluxes of trace metals, radioisotopes and greenhouse gases in the southwestern Baltic Sea Cruise No. AL543, 23.08.2020 – 28.08.2020, Kiel – Kiel - SEDITRACE. GEOMAR Helmholtz Centre for Ocean Research Kiel, 2020. http://dx.doi.org/10.3289/cr_al543.
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R/V Alkor Cruise AL543 was planned as a six-day cruise with a program of water column and sediment sampling in Kiel Bight and the western Baltic Sea. Due to restrictions related to the Covid-19 pandemic, the original plan had to be changed and the cruise was realized as six oneday cruises with sampling in Kiel Bight exclusively. The first day was dedicated to water column and sediment sampling for radionuclide analyses at Boknis Eck and Mittelgrund in Eckernförde Bay. On the remaining five days, water column, bottom water, sediment and pore water samples were collected at eleven stations covering different types of seafloor environment (grain size, redox conditions) in western Kiel Bight. The data and samples obtained on cruise AL543 will be used to investigate (i) the sedimentary cycling of bio-essential metals (e.g., nickel, zinc, and their isotopes) as a function of variable redox conditions, (ii) the impact of submarine groundwater discharge and diffusive benthic fluxes on the distribution of radium and radon as well as greenhouse gases (methane and nitrous oxide) in the water column, and (iii) to characterize and quantify the impact of coastal erosion on sedimentary iron, phosphorus and rare earth element cycling in Kiel Bight.
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Zhu, Xian-Kui, Tom McGaughy, and Brian Leis. PR-185-163609-R01 Model Error Assessment for Pipeline Metal-loss Defects Phase II. Pipeline Research Council International, Inc. (PRCI), 2018. http://dx.doi.org/10.55274/r0011506.
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This project included seven, full-scale burst tests conducted on a single grade and size of pipe to evaluate a metal-loss defect assessment model developed under EWI Project No. 54922CSP, "Assessment of Corrosion Model Error for Metal Loss Defects in Pipelines" (PRCI Project EC-2-6). The goal of the modeling and full-scale test efforts was to minimize error and reduce the conservatism of Level-1 corrosion assessment models, with the eventual benefit of potentially reducing unwarranted maintenance efforts without increasing operator risk. Seven tests were performed on a recent vintage of API 5L X70M (L485M) grade pipe having an outside diameter of 24 in. (610 mm) and nominal wall thickness of 0.50 in. (12.7 mm). The seven test pipes contained machined flat-bottomed defects for which the Shape Factor is 1, to focus on the role of the planar defect size and its depth and avoid the complexities of river-bottom shaped defects that are beyond the current scope. Defect lengths ranged between 3 and le; L/(Dt)0.5 and le; 10, at bounding values of width taken at arc angles of 20 and 60 degrees, and depth at d/t of 30% and 80%. The simulated corrosion was centered in pups approximately 12 ft (~3.7 m) in length, which is sufficient to prevent any interaction between the end caps with the defects. The pipes were then end-capped and pressurized with water to failure. The actual failure pressures were evaluated relative to predictions based on the model developed in EC-2-7 coupled with the reference stress developed in PRCI Project EC-2-6.