Bibliografías temáticas / Geometrical uncertainties

Índice

  1. Artículos de revistas
  2. Tesis
  3. Capítulos de libros
  4. Actas de conferencias
  5. Informes

Literatura académica sobre el tema "Geometrical uncertainties"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 1 de febrero de 2022

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros

Elija tipo de fuente:

Consulte las listas temáticas de artículos, libros, tesis, actas de conferencias y otras fuentes académicas sobre el tema "Geometrical uncertainties".

Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.

También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.

Artículos de revistas sobre el tema "Geometrical uncertainties"

1

Stroom, Joep. "Safety margins for geometrical uncertainties in radiotherapy". Medical Physics 27, n.º 9 (septiembre de 2000): 2194. http://dx.doi.org/10.1118/1.1289899.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
2

Schwarz, M. "SP-0199: Geometrical uncertainties and proton treatment planning". Radiotherapy and Oncology 111 (2014): S79. http://dx.doi.org/10.1016/s0167-8140(15)30304-2.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
3

Mailhe, J., J. M. Linares, J. M. Sprauel y P. Bourdet. "Geometrical checking by virtual gauge, including measurement uncertainties". CIRP Annals 57, n.º 1 (2008): 513–16. http://dx.doi.org/10.1016/j.cirp.2008.03.112.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
4

Mileusnic, Dusan. "Verification and correction of geometrical uncertainties in conformal radiotherapy". Archive of Oncology 13, n.º 3-4 (2005): 140–44. http://dx.doi.org/10.2298/aoo0504140m.

Texto completo
Resumen
Geometrical errors are presented as deviation between intended geometry of radiotherapy plan and real geometry of radiotherapy treatment. Total geometrical error is build up of smaller errors, which can be generally classified as set-up, organ motion, organ delineation, and technical condition related errors. The clear distinction must be made between systematic and random component of these errors and its amount should be encountered in treatment planning process. Errors? measuring for specific patient group with electronic portal imaging device and proper correction strategy enables to predict, minimize, and keep under control the amount for most of geometrical errors; it also improves the preciseness of treatment and consequent results. Nature and characteristics of most frequent geometrical errors are discussed and clinically applicable methods for their proper managing are described in this paper.
Los estilos APA, Harvard, Vancouver, ISO, etc.
5

Agarwal, Nitin y N. R. Aluru. "A stochastic Lagrangian approach for geometrical uncertainties in electrostatics". Journal of Computational Physics 226, n.º 1 (septiembre de 2007): 156–79. http://dx.doi.org/10.1016/j.jcp.2007.03.026.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
6

Li, Zhao Kun, Hua Mei Bian, Li Juan Shi y Xiao Tie Niu. "Reliability-Based Topology Optimization of Compliant Mechanisms with Geometrically Nonlinearity". Applied Mechanics and Materials 556-562 (mayo de 2014): 4422–34. http://dx.doi.org/10.4028/www.scientific.net/amm.556-562.4422.

Texto completo
Resumen
A new reliability-based topology optimization method for compliant mechanisms with geometrical nonlinearity is presented. The aim of this paper is to integrate reliability and geometrical nonlinear analysis into the topology optimization problems. Firstly, geometrical nonlinear response analysis method of the compliant mechanisms is developed based on the Total-Lagrange finite element formulation, the incremental scheme and the Newton-Raphson iteration method. Secondly, a multi-objective topology optimal model of compliant mechanisms considering the uncertainties of the applied loads and the geometry descriptions is established. The objective function is defined by minimum the compliance and maximum the geometric advantage to meet both the stiffness and the flexibility requirements, and the reliabilities of the compliant mechanisms are evaluated by using the first order reliability method. Thirdly, the computation of the sensitivities is developed with the adjoint method and the optimization problem is solved by using the Method of Moving Asymptotes. Finally, through numerical calculations, reliability-based topology designs with geometric nonlinearity of a typical compliant micro-gripper and a multi-input and multi-output compliant sage are obtained. The importance of considering uncertainties and geometric nonlinearity is then demonstrated by comparing the results obtained by the proposed method with deterministic optimal designs, which shows that the reliability-based topology optimization yields mechanisms that are more reliable than those produced by deterministic topology optimization.
Los estilos APA, Harvard, Vancouver, ISO, etc.
7

Remeijer, P. "MANAGEMENT OF GEOMETRICAL UNCERTAINTIES IN RADIOTHERAPY: MARGINS AND CORRECTION STRATEGIES". Radiotherapy and Oncology 92 (agosto de 2009): S124. http://dx.doi.org/10.1016/s0167-8140(12)72915-8.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
8

Stroom, Joep C. y Ben J. M. Heijmen. "Geometrical uncertainties, radiotherapy planning margins, and the ICRU-62 report". Radiotherapy and Oncology 64, n.º 1 (julio de 2002): 75–83. http://dx.doi.org/10.1016/s0167-8140(02)00140-8.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
9

Bel, A., M. van Herk y J. V. Lebesque. "Target margins for random geometrical treatment uncertainties in conformal radiotherapy". Medical Physics 23, n.º 9 (septiembre de 1996): 1537–45. http://dx.doi.org/10.1118/1.597745.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
10

MATSUMOTO, Masahide y Etsuo IWAYA. "Interval Finite Element Analysis of Structural Systems with Uncertainties. Static Analyses of Truss Structures with Geometrical Uncertainties." Transactions of the Japan Society of Mechanical Engineers Series A 67, n.º 662 (2001): 1576–82. http://dx.doi.org/10.1299/kikaia.67.1576.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
Más fuentes

Tesis sobre el tema "Geometrical uncertainties"

1

Minev, Ekaterin. "Grid method studies of the geometrical uncertainties in free form and micro processes". Thesis, Cardiff University, 2012. http://orca.cf.ac.uk/32291/.

Texto completo
Resumen
This research is devoted to the engineering of a generic, reliable and cost-effective method for the investigation of accuracy in layer based fabrication technologies. It begins with a review of the causes of deviations and uncertainties in component parts, analyses of the existing approaches for accuracy investigation and their limitations and disadvantages. The main focus of the research is the development of an original and convenient methodology capable of defining the dimensional uncertainties and accuracy of the technologies and the distribution of dimensional errors within the entire build area. The Grid Methodology is based on the discretisation of the object to allow the measurement, calculation, visualisation and analysis of part distortion in terms of linear and shear deviations from nominal. A single test piece and routine measurement procedure are utilised to estimate the distribution of the above entities; calculated in a similar way to the geometrical characteristics of strains in solid mechanics. The methodology was applied to research the causes of inaccuracy in the vertical direction of SLS Polystyrene. The presence of a critical dimension in height from where the distortion changes from shrinkage to extension was revealed and explained. The methodology was also utilised to estimate the necessary scaling factors to improve part accuracy, based on the calculated distortions. Implementation of the Grid Method to Micro Projection Stereolithography resulted in the ability to describe and estimate curling distortion in terms of angular deviations from nominal and separate it from linear distortions. - ii - Furthermore the application of the GM to the emerging micro-nano manufacturing sector has been shown to support the assessment of process capability. This provides a means of calculating process tolerances using results obtained from the single test piece. Investigation of the accuracy capabilities of three micro-processes was performed and their compatibility for designing process chains presented.
Los estilos APA, Harvard, Vancouver, ISO, etc.
2

Picou, Anthony. "Robust analysis under uncertainties of bladed disk vibration with geometrical nonlinearities and detuning". Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2038.

Texto completo
Resumen
Le désaccordage intentionnel, plus communément appelé detuning, a été identifié comme une possible technonologie pour réduire la sensibilité du comportement dynamique de roues aubagées soumises au désaccordage involontaire, aussi appelé mistuning, causé par les dispersions matérielle d'une aube à une autre engendrées lors du processus de fabrication et par la variabilité des propriétés mécaniques des matériaux. Le désaccordage intentionnel est mis en place par l'introduction de motifs à partir desquels différents types de secteurs générateurs, ayant des propriétés géométriques et matérielles différentes, sont assemblés. Cependant, les récentes innovations technologiques impliquant l'utilisation d'aubes de plus en plus flexibles et plus légères conduisent à de grands niveaux de déplacements et de déformations, requiérant l'utilisation des équations dynamiques non linéaires tenant compte des non-linéarités géométriques. Ce travail est dédié à l'analyse robuste des effets des non-linéarités géométriques sur la dynamique non linéaire de roues aubagées désacccordées intentionnellement, en rotation, en présence de désaccordage involontaire. Le désaccordage involontaire correspond à des incertitudes dans le modèle numériques et sont prises en compte par une approche probabiliste. Cette thèse de nouveaux résultats concernant la dynamique non linéaire des roues aubagées désaccordées intentionnellement en présense de non-linéarités géométriques et en présence de désaccordage involontaire. Les analyses dynamiques sont effectuées dans le domaine temporel et analysées dans le domaine fréquentiel. L'analyse fréquentielle des réponses non-linéaires mettent en évidence des réponses significatives en dehors de la bande d'excitation. Les intervalles de confiance des réponses stochastiques permettent d'analyser la robustesse du modèle vis-à-vis des incertitudes, c'est-à-dire du niveau de désaccordage involontaire. La roue aubagées utilisée pour les simulations numériques est composée de 24 secteurs pour lesquels différents motifs de roues aubagées désaccordées intentionnellement sont analysés, avec ou sans désaccordage involontaire
The intentional mistuning, also called detuning has been identified as an efficient technological way for reducing the sensitivity of the forced response of bladed disks to unintentional mistuning (simply called mistuning), caused by the manufacturing tolerances and the small variations in the mechanical properties from blade to blade. The intentional mistuning consists in detuning the bladed disk structure by using partial or alternating patterns of different sector types. However, the recent technological improvements that include the use of more flexible and lighter blades can lead to large strains/displacements, which requires the use of nonlinear dynamic equations involving geometric nonlinearities. This work is devoted to the robust analysis of the effects of geometric nonlinearities on the nonlinear dynamic behavior of rotating detuned bladed disks in presence of mistuning. The detuning corresponds to uncertainties in the computational model, and are taken into account by a probabilistic approach. This thesis presents a series of novel results in dynamics of rotating bladed disks with mistuning and detuning in presence of nonlinear geometrical effects. The structural responses are computed in the time domain and are analyzed in the frequency domain. The frequency analysis exhibits responses outside the frequency band of excitation. The confidence region of the stochastic responses allows the robustness to be analyzed with respect to uncertainties, that is to say with respect to the level of mistuning. The bladed disk structure, which is used for the numerical simulations, is made up of 24 blades for which several different detuned patterns are investigated with and without mistuning
Los estilos APA, Harvard, Vancouver, ISO, etc.
3

Sykes, Jonathan. "Quantification of geometric uncertainties in image guided radiotherapy". Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/3864/.

Texto completo
Resumen
The aim of this thesis is to determine if the geometric uncertainties that are introduced into the image guided radiotherapy (IGRT) process by Cone Beam CT (CBCT) based IGRT equipment are sufficiently small that they do not pose a significant risk of geometrical error in treatment delivery. This was performed by quantifying and investigating the geometric uncertainties introduced by; (1) calibration of the image geometry, (2) correction of patient position performed by automatic treatment couch systems and (3) automatic image registration of the localisation image with a reference image. In addition, the feasibility of providing user feedback on the likelihood of accurate image registration was investigated. A method was developed using supervised machine learning based on the shape of the image registration algorithm's similarity metric surface. The geometric uncertainties introduced by image calibration and couch positioning were both shown to be less than 1 mm and therefore do not contribute significantly to the overall uncertainties in the IGRT process. Image registration performance for image guidance based on the bony anatomy of the skull was shown to be reproducible, accurate and robust with errors typically less than 1 mm. Moreover, image registration performance did not deteriorate significantly as imaging dose was reduced. For image guidance based on the soft tissues of the prostate, image registration performance was satisfactory for some CBCT images resulting in errors less than 2 mm. However, with the majority of CBCT images, image registration was highly irreproducible with high frequencies of failure. The user feedback of image registration quality was able to correctly classify 84% of image registrations into categories of good, acceptable and unacceptable. No unacceptable classifications were classed as good. CBCT based IGRT equipment does not introduce significant risks into the IGRT process however, appropriate quality assurance measures should be implemented to safeguard against equipment failure and drift since previous system calibration. Automatic image registration of the soft-tissues of the prostate cannot be relied upon for clinical use and therefore it should be used in conjunction with manual methods.
Los estilos APA, Harvard, Vancouver, ISO, etc.
4

Fleming, Alan Duncan. "Analysis of uncertainties and geometric tolerances in assemblies of parts". Thesis, University of Edinburgh, 1988. http://hdl.handle.net/1842/6626.

Texto completo
Resumen
Computer models of the geometry of the real world have a tendency to assume that the shapes and positions of objects can be described exactly. However, real surfaces are subject to irregularities such as bumps and undulations and so do not have perfect, mathematically definable forms. Engineers recognise this fact and so assign tolerance specifications to their designs. This thesis develops a representation of geometric tolerance and uncertainty in assemblies of rigid parts. Geometric tolerances are defined by tolerance zones which are regions in which the real surface must lie. Parts in an assembly can slop about and so their positions are uncertain. Toleranced parts and assemblies of toleranced parts are represented by networks of tolerance zones and datums. Each arc in the network represents a relationship implied by the tolerance specification or by a contact between the parts. It is shown how all geometric constraints can be converted to an algebraic form. Useful results can be obtained from the network of tolerance zones and datums. For example it is possible to determine whether the parts of an assembly can be guaranteed to fit together. It is also possible to determine the maximum slop that could occur in the assembly assuming that the parts satisfy the tolerance specification. Two applications of this work are (1) tolerance checking during design and (2) analysis of uncertainty build-up in a robot assembly plan. I n the former, a designer could check a proposed tolerance specification to make sure that certain design requirements are satisfied. In the latter, knowledge of manufacturing tolerances of parts being manipulated can be used to determine the constraints on the positions of the parts when they are in contact with other parts.
Los estilos APA, Harvard, Vancouver, ISO, etc.
5

Xu, Huijun. "A study of coverage optimized planning incorporating models of geometric uncertainties for prostate cancer". VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3061.

Texto completo
Resumen
A fundamental challenge in the treatment planning process of multi-fractional external-beam radiation therapy (EBRT) is the tradeoff between tumor control and normal tissue sparing in the presence of geometric uncertainties (GUs). To accommodate GUs, the conventional way is to use an empirical planning treatment volume (PTV) margin on the treatment target. However, it is difficult to determine a near-optimal PTV margin to ensure specified target coverage with as much normal tissue protection as achievable. Coverage optimized planning (COP) avoids this problem by optimizing dose in possible virtual treatment courses with GU models directly incorporated. A near-optimal dosimetric margin generated by COP was reported to savvily accommodate setup errors of target and normal tissues for prostate cancer treatment. This work further develops COP to account for (1) deformable organ motion and (2) delineation uncertainties for high-risk prostate cancer patients. The clinical value of COP is investigated by comparing with two margin-based planning techniques: (i) optimized margin (OM) technique that iteratively modifies PTV margins according to the evaluated target coverage probability and (ii) fixed margin (FM) technique that uses empirically selected constant PTV margins. Without patient-specific coverage probability estimation, FM plans are always less immune to the degraded effect of the modeled GUs than the COP plans or the OM plans. Empirical PTV margins face more risks of undesirable target coverage probability and/or excessive dose to surrounding OAR. The value of COP relative to OM varies with different GUs. As implemented for deformable organ motions, COP has limited clinical benefit. Due to optimization tradeoffs, COP often results in target coverage probability below the prescribed value while OM achieves better target coverage with comparable normal tissue dose. For delineation uncertainties, the clinical value of COP is potentially significant. Compared to OM, COP successfully maintains acceptable target coverage probability by exploiting the slack of normal tissue dose in low dose regions and maximally limiting high dose to normal tissue within tolerance.
Los estilos APA, Harvard, Vancouver, ISO, etc.
6

Cazoulat, Guillaume. "Radiothérapie guidée par l'image du cancer de la prostate : vers l'intégration des déformations anatomiques". Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00992354.

Texto completo
Resumen
Ce travail de thèse porte sur la quantification et la prise en compte des variations anatomiques en cours de radiothérapie guidée par l'image pour le cancer de la prostate. Nous proposons tout d'abord une approche basée population pour quantifier et analyser les incertitudes géométriques, notamment à travers des matrices de probabilité de présence de la cible en cours de traitement. Nous proposons ensuite une méthode d'optimisation des marges suivant des critères de couverture géométrique de la cible tumorale. Cette méthode permet d'obtenir des marges objectives associées aux différents types d'incertitudes géométriques et aux différentes modalités de repositionnement du patient. Dans un second temps, nous proposons une méthode d'estimation de la dose cumulée reçue localement par les tissus pendant un traitement de radiothérapie de la prostate. Cette méthode repose notamment sur une étape de recalage d'images de façon à estimer les déformations des organes entre les séances de traitement et la planification. Différentes méthodes de recalage sont proposées, suivant les informations disponibles (délinéations ou points homologues) pour contraindre la déformation estimée. De façon à évaluer les méthodes proposées au regard de l'objectif de cumul de dose, nous proposons ensuite la génération et l'utilisation d'un fantôme numérique reposant sur un modèle biomécanique des organes considérés. Les résultats de l'approche sont présentés sur ce fantôme numérique et sur données réelles. Nous montrons ainsi que l'apport de contraintes géométriques permet d'améliorer significativement la précision du cumul et que la méthode reposant sur la sélection de contraintes ponctuelles présente un bon compromis entre niveau d'interaction et précision du résultat. Enfin, nous abordons la question de l'analyse de données de populations de patients dans le but de mieux comprendre les relations entre dose délivrée localement et effets cliniques. Grâce au recalage déformable d'une population de patients sur une référence anatomique, les régions dont la dose est significativement liée aux événements de récidive sont identifiées. Il s'agit d'une étude exploratoire visant à terme à mieux exploiter l'information portée par l'intégralité de la distribution de dose, et ce en fonction du profil du cancer.
Los estilos APA, Harvard, Vancouver, ISO, etc.
7

Acharya, Srikanth B. "A multivariate statistical analysis on sampling uncertainties of geometric and dimensional errors for circular features /". Cincinnati, Ohio University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1113427839.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
8

ACHARYA, SRIKANTH B. "A MULTIVARIATE STATISTICAL ANALYSIS ON THE SAMPLING UNCERTAINTIES OF GEOMETRIC AND DIMENSIONAL ERRORS FOR CIRCULAR FEATURES". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1113427839.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
9

Kalyankuppam, Selvaraj Jothybasu. "Modelling the effect of geometric uncertainties, clonogen distribution and IMRT interplay effect on tumour control probability". Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/17533/.

Texto completo
Resumen
Geometric uncertainties are inevitable in radiotherapy. These uncertainties in tumour position are classified as systematic (Ε) and random (δ) errors. To account for these uncertainties, a margin is added to the clinical target volume (CTV) to create the planning target volume (PTV). The size of the PTV is critical for obtaining an optimal treatment plan. Dose-based (i.e., physical) margin recipes as a function of systematic and random errors based on coverage probability of a certain level of dose (90% or 95% of the prescription dose) have been published and widely used. However, with a TCP-based margin it is possible to consider fractionation and the radiobiological characteristics, especially the dose-response slope (50) of the tumour. Studies have shown that the density of the clonogens decrease from the boundary of the gross tumour volume (GTV). In such a scenario, dose that is lower than in the GTV should be sufficient to eradicate these clonogens. Thus a smaller PTV margin with a gradual dose fall off can be used if the clonogen density in the GTV-CTV region is found to be lower than in GTV. Studies have reported tiny tumour islets outside the CTV region. These tiny tumour islets can be eradicated in some cases by the incidental dose outside the PTV due to the nature of the photon beam irradiation, but if they are not in the beam path the treatment outcome is compromised. In this thesis, a Monte Carlo approach is used to simulate the effect of geometric uncertainties, number of fractions and dose-response slope (gamma50) using the 'enhanced Marsden' TCP model on the treatment outcome. Systematic and random errors were drawn from a pseudo-random number generator. The dose variations caused by tumour displacements due to geometric uncertainties in the CTV are accumulated each fraction on a voxel-by-voxel basis. Required margins for ≤ 1% mean population TCP (TCPpop) for four-field (4F) brick and a highly conformal spherical dose distribution for varying number of fractions, different γ50 and different combinations of Ε and δ are investigated. It is found that TCP-based margins are considerably smaller than dose-based recipes in most cases except for tumours with a steep dose-response slope (high γ50) and a small number of fractions for both 4F and spherical dose distributions. For smaller geometric uncertainties (Ε = δ = 1 mm) margins can be close to zero for the 4F technique due to high incidental dose outside the PTV. It is evident from the analyses that margins depend on the number of fractions, γ50, the degree of dose conformality in addition to Ε and δ. Ideally margins should be anisotropic and individualized, taking into account γ50, number of fractions, and the dose distribution, as well as estimates of Ε and γ. No single 'recipe' can adequately account for all these variables. Using an exponential clonogen distribution in the GTV-CTV region, possible PTV margin reduction is demonstrated. Moreover, the effect of extra-CTV tumour islets is studied using a prostate IMRT plan. The islets were randomly distributed around the CTV with in a radius of 3 cm to represent different patients. The doses were rescaled up to 102 Gy to obtain the dose-response curve (DRC). Interestingly, the obtained DRC showed a biphasic response where 100% TCP could not be achieved just by escalating the dose. Another potential problem encountered in intensity-modulated radiotherapy (IMRT) is the problems caused by the 'interplay' effect between the respiration-induced tumour motion and the multileaf collimator (MLC) leaves movement during treatment. Several dosimetric studies in the literature have shown that 'interplay' effects blur the dose distribution by producing 'hot' and 'cold' dose inside the tumour. Most of these studies were done in a phantom with ion chambers or films, which provide only 1D or 2D dose information. If 3D dose information is available, a TCP based analysis would provide a direct estimate of interplay on the clinical outcome. In this thesis, an in-house developed dose model enabled us to calculate the 3D time-resolved dose contribution to each voxel in the target volume considering the change in segment shapes and position of the target volume. Using the model, delivered dose is accumulated in a voxel-by-voxel basis inclusive of tumour motion over the course of treatment. The effect of interplay on dose and TCP is studied for conventionally and hypofractionated treatments using DICOM datasets. Moreover, the effect of dose rate on interplay is also studied for single-fraction treatments. Simulations were repeated several times to obtain mean population TCP (TCPpop) for each plan. The average variation observed in mean dose to the target volumes were -0.76 ± 0.36% for the 20 fraction treatment and -0.26 ± 0.68%, -1.05 ± 0.98% for the 3- and single-fraction treatments respectively. For the 20-fraction treatment, the drop in TCPpop was -1.05 ± 0.39%, whereas for the 3 and single fraction treatments it was -2.8 ± 1.68% and -4.0 ± 2.84% respectively. By reducing the dose rate from 600 to 300 MU/min for the single-fraction treatments, the drop in TCPpop was reduced by ~ 1:5%. In summary, the effect of interplay on treatment outcome is negligible for conventionally fractionated treatments, whereas a considerable drop in TCP is observed for the 3- and single-fraction treatments. Where no motion management techniques such as tracking or gating are available for hypo-fractionated treatments, reduced dose rate could be used to reduce the interplay effect.
Los estilos APA, Harvard, Vancouver, ISO, etc.
10

Tilly, David. "Probabilistic treatment planning based on dose coverage : How to quantify and minimize the effects of geometric uncertainties in radiotherapy". Doctoral thesis, Uppsala universitet, Medicinsk strålningsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-304180.

Texto completo
Resumen
Traditionally, uncertainties are handled by expanding the irradiated volume to ensure target dose coverage to a certain probability. The uncertainties arise from e.g. the uncertainty in positioning of the patient at every fraction, organ motion and in defining the region of interests on the acquired images. The applied margins are inherently population based and do not exploit the geometry of the individual patient. Probabilistic planning on the other hand incorporates the uncertainties directly into the treatment optimization and therefore has more degrees of freedom to tailor the dose distribution to the individual patient. The aim of this thesis is to create a framework for probabilistic evaluation and optimization based on the concept of dose coverage probabilities. Several computational challenges for this purpose are addressed in this thesis. The accuracy of the fraction by fraction accumulated dose depends directly on the accuracy of the deformable image registration (DIR). Using the simulation framework, we could quantify the requirements on the DIR to 2 mm or less for a 3% uncertainty in the target dose coverage. Probabilistic planning is computationally intensive since many hundred treatments must be simulated for sufficient statistical accuracy in the calculated treatment outcome. A fast dose calculation algorithm was developed based on the perturbation of a pre-calculated dose distribution with the local ratio of the simulated treatment’s fluence and the fluence of the pre-calculated dose. A speedup factor of ~1000 compared to full dose calculation was achieved with near identical dose coverage probabilities for a prostate treatment. For some body sites, such as the cervix dataset in this work, organ motion must be included for realistic treatment simulation. A statistical shape model (SSM) based on principal component analysis (PCA) provided the samples of deformation. Seven eigenmodes from the PCA was sufficient to model the dosimetric impact of the interfraction deformation. A probabilistic optimization method was developed using constructs from risk management of stock portfolios that enabled the dose planner to request a target dose coverage probability. Probabilistic optimization was for the first time applied to dataset from cervical cancer patients where the SSM provided samples of deformation. The average dose coverage probability of all patients in the dataset was within 1% of the requested.
Los estilos APA, Harvard, Vancouver, ISO, etc.
Más fuentes

Capítulos de libros sobre el tema "Geometrical uncertainties"

1

Remeijer, Peter. "Geometrical Uncertainties in Radiotherapy". En NATO Science for Peace and Security Series B: Physics and Biophysics, 135–40. Dordrecht: Springer Netherlands, 2009. http://dx.doi.org/10.1007/978-90-481-3097-9_12.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
2

Wyrozębski, Marcin, Łukasz Łaniewski-Wołłk y Jacek Rokicki. "Second-Order Derivatives for Geometrical Uncertainties". En Uncertainty Management for Robust Industrial Design in Aeronautics, 347–61. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-77767-2_22.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
3

Mailhé, Jean, Jean-Marc Linares, Jean-Michel Sprauel y Jean-Paul Raynal. "Impact of the Sampling Strategy on Geometrical Checking Uncertainties". En Product Lifecycle Management, 299–315. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118557921.ch16.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
4

Perel, R. L. "Uncertainties of Responses Calculated with a “Tuned” Library: Geometrical and Algebraic Insights". En Reactor Dosimetry: 14th International Symposium, 161–78. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2012. http://dx.doi.org/10.1520/stp49610t.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
5

Perel, R. L. "Uncertainties of Responses Calculated with a “Tuned” Library: Geometrical and Algebraic Insights". En Reactor Dosimetry: 14th International Symposium, 161–78. 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959: ASTM International, 2012. http://dx.doi.org/10.1520/stp155020120013.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
6

Liu, Dishi, Daigo Maruyama y Stefan Görtz. "Geometrical Uncertainties—Accuracy of Parametrization and Its Influence on UQ and RDO Results". En Uncertainty Management for Robust Industrial Design in Aeronautics, 785–98. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-77767-2_51.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
7

Wunsch, Dirk, Rémy Nigro, Grégory Coussement y Charles Hirsch. "Non-intrusive Probabilistic Collocation Method for Operational, Geometrical, and Manufacturing Uncertainties in Engineering Practice". En Uncertainty Management for Robust Industrial Design in Aeronautics, 143–67. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-77767-2_9.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
8

Linares, Jean-Marc y Jean Michel Sprauel. "Uncertainties in Tolerance Analysis and Specification Checking". En Geometric Tolerancing of Products, 341–74. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118587027.ch13.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
9

Inui, Masatomo, Kazuhiro Maida y Yuji Hasegawa. "Cutter Accessibility Analysis of a Part with Geometric Uncertainties". En Frontiers of Assembly and Manufacturing, 35–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-14116-4_4.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
10

Sprauel, Jean Michel, Jean Marc Linares y Pierre Bourdet. "Contribution of nonlinear optimization to the determination of measurement uncertainties". En Geometric Product Specification and Verification: Integration of Functionality, 237–44. Dordrecht: Springer Netherlands, 2003. http://dx.doi.org/10.1007/978-94-017-1691-8_24.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.

Actas de conferencias sobre el tema "Geometrical uncertainties"

1

Wunsch, Dirk, Charles Hirsch, Rémy Nigro y Gregory Coussement. "Quantification of Combined Operational and Geometrical Uncertainties in Turbo-Machinery Design". En ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43399.

Texto completo
Resumen
The NASA rotor 37 is investigated accounting for as many as 9 simultaneous operational and geometrical uncertainties. The combined influence of uncertainties on input quantities such as the total inlet pressure, static outlet pressure, tip gap or leading and trailing edge angles on output quantities is studied. These simulations provide results which go far beyond the standard deterministic simulation. A probabilistic collocation method in combination with a sparse grid quadrature is introduced into the software suite FINE™ propagating combined operational and geometrical uncertainties in complex 3D CFD simulations. The modification of the parameterized geometry and the consequent re-meshing is provided by a fully automatic tool, which also couples with the flow solver and provides post-treatment routines. It is this automation, which makes this kind of study feasible. A manual modification of geometry, manual meshing and simulation set-up accounting for a multitude of simultaneous uncertainties is simply unfeasible for as many as hundreds of complex 3D turbo-machinery simulations. This work represents thus a break-through in the uncertainty management towards the application of uncertainty propagation in the daily engineering practice.
Los estilos APA, Harvard, Vancouver, ISO, etc.
2

Chalot, Frederic, Quang Dinh, Erick Herbin, Ludovic Martin, Michel Ravachol y Gilbert Roge. "Estimation of the Impact of Geometrical Uncertainties on Aerodynamic Coefficients Using CFD". En 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference
16th AIAA/ASME/AHS Adaptive Structures Conference
10t. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-2068.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
3

da Silva, Maíra Martins y Hiparco Lins Vieira. "FAILURE MAPS FOR A KINEMATICALLY REDUNDANT PLANAR PARALLEL MANIPULATOR UNDER GEOMETRICAL UNCERTAINTIES". En COB2019. ABCM, 2019. http://dx.doi.org/10.26678/abcm.cobem2019.cob2019-0149.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
4

Strano, Matteo, Bianca Maria Colosimo y Enrique Del Castillo. "Improved design of a three roll tube bending process under geometrical uncertainties". En THE 14TH INTERNATIONAL ESAFORM CONFERENCE ON MATERIAL FORMING: ESAFORM 2011. AIP, 2011. http://dx.doi.org/10.1063/1.3589488.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
5

Picou, Anthony, Evangéline Capiez-Lernout, Christian Soize y Moustapha Mbaye. "Mistuning Analysis of a Detuned Bladed-Disk With Geometrical Nonlinearities". En ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-90820.

Texto completo
Resumen
Abstract This work concerns the nonlinear numerical analysis of mistuned blades for a rotating detuned bladed-disk structure with geometrical nonlinearities. The detuning phenomenon is taken into account through a deterministic approach by modifying material properties of some blades. A nonlinear reduced-order model is obtained by setting up a basis using a double projection method. The mistuning uncertainties are implemented through a nonparametric probabilistic approach for which the level of uncertainties is controlled by a hyperparameter. A numerical application is carried out on a bladed-disk structure made up of 24 blades whose finite element model has about 800,000 dofs exhibiting complex dynamic behaviors.
Los estilos APA, Harvard, Vancouver, ISO, etc.
6

Ji, Wooseok, Anthony Waas, Peter Gustafson, Wei Ng, Evan Pineda, Pavana Prabhakar y Ravi Raveendra. "Computational modeling of failure in composite structures including uncertainties in material and geometrical properties". En 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-1722.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
7

Quagliarella, Domenico, Andrea Serani, Matteo Diez, Michele Pisaroni, Penelope Leyland, Luca Montagliani, Umberto Iemma et al. "Benchmarking Uncertainty Quantification Methods Using the NACA 2412 Airfoil with Geometrical and Operational Uncertainties". En AIAA Aviation 2019 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-3555.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
8

Mohtashami, V. y A. A. Shishegar. "Effects of geometrical uncertainties on ray tracing results for site-specific indoor propagation modeling". En 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC). IEEE, 2013. http://dx.doi.org/10.1109/apwc.2013.6624914.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
9

Gouttière, Alexandre, Dirk Wunsch, Rémy Nigro, Virginie Barbieux y Charles Hirsch. "Robust Design Optimization of an Industrial 1.5 Stage Axial Compressor Under Operational and Geometrical Uncertainties". En ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58603.

Texto completo
Resumen
Abstract A robust design optimization of a 1.5 stage axial compressor with secondary flows from Safran Aero Boosters is investigated. A total of 9 simultaneous operational and geometrical uncertainties are propagated for the nominal design point as well as for two off-design points, close to stall and choke conditions respectively. These uncertainties, including mass flow rates of the secondary flows, tip gap size of the rotor and highly correlated profiles on the inlet condition, are propagated by the Non-Intrusive Probabilistic Collocation method. In order to understand the effects of the uncertainties on the performances and to minimize the computational cost of the robust optimization, a preliminary uncertainty quantification (UQ) study of the original design is performed to identify and rule out less influential uncertainties. Contrary to what was expected, the imposed geometrical uncertainties on the tip gap are identified to have the relatively smallest influence on the performances by means of scaled sensitivity derivatives. The global objective of the robust design optimization is to minimize the standard deviations of the main compressor performances at all three operating points and to preserve the mean values of these performances. Because the objective functions are standard deviations, this study is only possible in a robust optimization setting, by propagating the simultaneous operational and geometrical uncertainties. A total of 9 stochastic objectives and 15 stochastic constraints are taken into account. The best optimal design preserves the mean performances of the compressor, while the standard deviations are minimized compared with the original design, ensuring a more robust operation. This effect is very pronounced in the off-design points.
Los estilos APA, Harvard, Vancouver, ISO, etc.
10

Peradotto, Edoardo, Alfonso M. Panunzio, Loïc Salles y Christoph Schwingshackl. "Stochastic Methods for Nonlinear Rotordynamics With Uncertainties". En ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43534.

Texto completo
Resumen
The calculated dynamic response of an excited rotating system can be significantly affected by uncertainties in its mechanical properties, such as mass, stiffness, geometrical imperfections, or loadings. For this reason, it is essential to understand and quantify the influence of uncertain parameters on the predicted rotor response. This paper aims to optimize the propagation of random input uncertainties for a rotordynamic problem and assess their influence on the dynamic behaviour of an unbalanced rotor. The Harmonic balance method (HBM) and a non-intrusive Polynomial Chaos Expansion (PCE) are used to evaluate the stochastic response of a finite element rotor. The proposed stochastic approach is based on a numerical quadrature calculation of integrals for finding the coefficients of the PCE. The method is initially applied to evaluate the stochastic response of a linear rotodynamic system, leading to the original concept of stochastic Campbell diagram and further extended to nonlinear rotordynamic problems, using the Asymptotic Numerical Method (ANM).
Los estilos APA, Harvard, Vancouver, ISO, etc.

Informes sobre el tema "Geometrical uncertainties"

1

Geometric Uncertainties in Daily Online IGRT. British Institute of Radiology, 2020. http://dx.doi.org/10.1259/geo-unc-igrt.

Texto completo
Los estilos APA, Harvard, Vancouver, ISO, etc.
También puede estar interesado en las bibliografías ampliadas sobre el tema "Geometrical uncertainties" para tipos de fuentes particulares:
Artículos de revistas Tesis
Ofrecemos descuentos en todos los planes premium para autores cuyas obras están incluidas en selecciones literarias temáticas. ¡Contáctenos para obtener un código promocional único!

Pasar a la bibliografía