Bibliographies thématiques / Polygonal plates

Littérature scientifique sur le sujet « Polygonal plates »

Auteur : Grafiati
Publié le 18 mai 2024

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Articles de revues sur le sujet "Polygonal plates"

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Alda, Javier, et Francisco Javier González. « Polygonal Fresnel zone plates ». Journal of Optics A : Pure and Applied Optics 11, no 8 (26 juin 2009) : 085707. http://dx.doi.org/10.1088/1464-4258/11/8/085707.

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Nallim, L. G., B. M. Luccioni et R. O. Grossi. « A Rayleigh-Ritz approach to transverse vibration of isotropic polygonal plates with variable thickness ». Proceedings of the Institution of Mechanical Engineers, Part K : Journal of Multi-body Dynamics 216, no 3 (1 septembre 2002) : 213–22. http://dx.doi.org/10.1177/146441930221600302.

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This paper presents a simple, computationally efficient and highly accurate numerical model for the study of free vibration behaviour of polygonal plates with variable thickness. The approach developed is based on the Rayleigh-Ritz method and the use of non-orthogonal right triangular coordinates. The deflection of the plate is approximated by a set of beam characteristic orthogonal polynomials generated using the Gram-Schmidt procedure. The algorithm is quite general and can be used to study plates with any combinations of clamped, simply supported and free edge support conditions and also different taper and geometric parameters. Several examples are solved and some results are compared with existing values in the literature. New results are also presented for tapered polygonal plates with different geometrical shapes and combinations of boundary conditions. For some polygonal plates, their mode shapes of free vibration are shown. The study of this problem is of practical importance for a better understanding of the vibration of polygonal plates which are commonly encountered in modern technology.
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Liew, K. M., et C. M. Wang. « Elastic buckling of regular polygonal plates ». Thin-Walled Structures 21, no 2 (janvier 1995) : 163–73. http://dx.doi.org/10.1016/0263-8231(94)00031-t.

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Alda, Javier, et Glenn Boreman. « Optimization of polygonal Fresnel zone plates ». Microwave and Optical Technology Letters 50, no 2 (février 2008) : 536–41. http://dx.doi.org/10.1002/mop.23125.

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Krommer, Michael, et Hans Irschik. « Post-Buckling of Piezoelectric Thin Plates ». International Journal of Structural Stability and Dynamics 15, no 07 (31 août 2015) : 1540020. http://dx.doi.org/10.1142/s0219455415400209.

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In the present paper, the geometrically nonlinear behavior of piezoelastic thin plates is studied. First, the governing equations for the electromechanically coupled problem are derived based on the von Karman–Tsien kinematic assumption. Here, the Berger approximation is extended to the coupled piezoelastic problem. The general equations are then reduced to a single nonlinear partial differential equation for the special case of simply supported polygonal edges. The nonlinear equations are approximated by using a problem-oriented Ritz Ansatz in combination with a Galerkin procedure. Based on the resulting equations the buckling and post-buckling behavior of a polygonal simply supported plate is studied in a nondimensional form, where the special geometry of the polygonal plate enters via the eigenvalues of a Helmholtz problem with Dirichlet boundary conditions. Single term as well as multi-term solutions are discussed including the effects of piezoelectric actuation and transverse force loadings upon the solution. Novel results concerning the buckling, snap through and snap buckling behavior are presented.
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Chuikov, R. S., S. S. Chuikov, A. S. Stavyshenko et V. D. Samohvalov. « Increasing the operational life of the cutting tool based on stress relieving ». MATEC Web of Conferences 298 (2019) : 00007. http://dx.doi.org/10.1051/matecconf/201929800007.

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The paper covers the results of studying the influence of internal stresses arising in the manufacture of changeable polygonal plates of TC type hard alloys on the resistance of the cutting tool and the possibility of relieving them by preheating the cutting plates before cutting. A method and a special design are proposed for preheating changeable polygonal plates in order to relieve internal stresses in tool hard alloys and increase the resistance of the cutting tool.
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Wang, C. M., S. Kitipornchai et J. N. Reddy. « Relationship Between Vibration Frequencies of Reddy and Kirchhoff Polygonal Plates With Simply Supported Edges ». Journal of Vibration and Acoustics 122, no 1 (1 octobre 1997) : 77–81. http://dx.doi.org/10.1115/1.568438.

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This paper presents an exact relationship between the natural frequencies of Reddy third-order plate theory and those of classical Kirchhoff plate theory for simply supported, polygonal isotropic plates, including rectangular plates. The relationship for the natural frequencies enables one to obtain the solutions of the third-order plate theory from the known Kirchhoff plate theory for the same problem. As examples, some vibration frequencies for rectangular and regular polygonal plates are determined using this relationship. [S0739-3717(00)01601-9]
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Wah, Thein. « Flexure of Polygonal Plates with Circular Holes ». Journal of Ship Research 29, no 03 (1 septembre 1985) : 209–11. http://dx.doi.org/10.5957/jsr.1985.29.3.209.

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A procedure is developed for determining the stresses in a polygonal plate with a circular hole. Classical plate theory is assumed. The boundary conditions are satisfied exactly term by term. Numerical results are given.
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Wang, C. M. « Buckling of polygonal and circular sandwich plates ». AIAA Journal 33, no 5 (mai 1995) : 962–64. http://dx.doi.org/10.2514/3.12664.

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Wah, Thein. « Stresses in polygonal plates with circular holes ». Engineering Fracture Mechanics 23, no 3 (janvier 1986) : 489–93. http://dx.doi.org/10.1016/0013-7944(86)90157-8.

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Thèses sur le sujet "Polygonal plates"

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Gunda, Rajendra. « Harmonic Green's functions of wedges and polygonal plates using the ray tracing technique / ». The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487949150070192.

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Cuenca, Jacques. « Wave models for the flexural vibrations of thin plates : model of the vibrations of polygonal plates by the image source method : vibration damping using the acoustic black hole effect ». Le Mans, 2009. http://cyberdoc.univ-lemans.fr/theses/2009/2009LEMA1011.pdf.

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Les vibrations de flexion des structures minces sont étroitement liées au rayonnement sonore et à l'endommagement des structures. Ainsi, des méthodes de modélisation des vibrations et des techniques d'amortissement sont indispensables dans divers domaines scientifiques et techniques. La première partie de la thèse traite du développement d'un modèle des vibrations de flexion de plaques minces polygonales excitées ponctuellement, basé sur la méthode des sources image. Le modèle développé permet de prédire les vibrations d'une plaque et d'un assemblage de plaques dont la géométrie et les conditions aux limites sont arbitraires. La particularité de la méthode est que la précision des simulations s'améliore avec la fréquence et l'amortissement structural, ce qui est contraire à la méthode des éléments finis ou aux méthodes dites modales. Un outil de mesure du module d'Young et du facteur d'amortissement de panneaux fortement amortis est également proposé. La deuxième partie de la thèse traite de l'amortissement des vibrations par l'effet de ``trou noir acoustique''. La célérité des ondes de flexion dépend de l'épaisseur de la structure dans laquelle elles se propagent. Ainsi, une onde se propageant dans une plaque d'épaisseur décroissante ralentit et, dans certaines conditions, peut s'arrêter complètement. Un modèle est développé, permettant d'estimer les valeurs optimales des paramètres des matériaux utilisés afin de maximiser l'amortissement. Les résultats numériques, ainsi que des études expérimentales, montrent une réduction de niveau vibratoire atteignant 20 décibels
Flexural vibrations of thin structures are strongly related to sound radiation and structural damage, for which they deserve careful attention in many domains of science and engineering. Two aspects of crucial importance are the development of accurate tools for the prediction and analysis of vibrations and efficient vibration damping. In the first part of the thesis, a model of the flexural vibrations of thin convex polygonal plates based on the image source method is presented. The developed approach allows to predict the vibrations of individual plates and plate assemblies of arbitrary convex polygonal geometry and having arbitrary boundary conditions. The method is particularly suitable for mid- and high-frequency dynamics, in that its accuracy is improved with an increase in frequency or structural damping. A tool for estimating the Young's modulus and structural damping ratio of highly damped flat panels is also proposed. The second part of the thesis concerns vibration damping using the acoustic black hole effect. It is weel-known that a flexural wave travelling in a thin plate or beam slows down in a zone of decreasing thickness. Thus, if the thickness decreases sufficiently smoothly to zero, the wave stops travelling, without being reflected back. Such is the principle of the so-called acoustic black hole effect. A model of the flexural vibrations of such profile is proposed, allowing to determine optimal geometrical and material properties in order to maximise vibration damping. Simulated and measured responses show a reduction of vibration level up to 20 decibels
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Jedlička, Lukáš. « Interaktivní umísťování virtuální dlahy na 3D modely kostí ». Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2008. http://www.nusl.cz/ntk/nusl-235898.

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This Master's Project deals with creation of virtual Splint (Orthopedic plate) model and with placement of virtual Splint model onto 3D Bone model. It handles with creating of interpolation curves in 3D (especially Subdivision method) and motion along a curve. This work is only in Czech.
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Chattopadhyay, Arka Prabha. « Elastic buckling behavior of plate and tubular structures ». Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8702.

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Master of Science
Department of Mechanical and Nuclear Engineering
Kevin B. Lease
Xiao J. Xin
The study of buckling behavior of tubular and cellular structures has been an intriguing area of research in the field of solid mechanics. Unlike the global Euler buckling of slender structures under compressive loads, tubular and cellular structures deform with their walls buckling as individual supported plates. The aspect ratio and the dimensional characteristics of the tube define the buckling behavior of any tube structure. In this thesis, a thorough study on the buckling of polygon tubular structures with different cross sections is discussed. In the first study, the theoretical buckling formulation of a square tube using the energy method is reviewed from existing solutions in literature. The elastic critical load of a square tube derived from the theoretical solution is then compared with results of finite element elastic buckling simulations. The formation of lobes along the height of the walls at different aspect ratios of the tube is investigated and compared to theory. Also, the buckling behavior of multi-wall structures is studied and the relationship between these structures and a rectangular simply supported plate is established. A brief study on the buckling behavior of rhombic tubes is also performed. The results of the simulation match closely with the theoretical predictions. The study is then extended to quadrilateral tubes with cross-sections in the shape of square, rectangle, rhombus and parallelogram. The theory of buckling of these tubes is explicitly defined using classical plate mechanics based on the previous works presented in literature. Also, the possibility of global Euler buckling in the tubular structures after a certain critical height is discussed. The prediction from the theory is validated using extensive finite element elastic buckling simulations and experimental tests on square and rhombic tube specimens. The results of the simulations and experiments are observed to be consistent with the theory. Using the formulation of plate buckling under different boundary conditions, the buckling behavior of triangular tubes is also determined. A theoretical formulation for calculating the critical load of triangular tubes is derived. The theoretical critical loads for a range of aspect ratios are compared with corresponding finite element simulation results. The comparisons reveal high degree of similarity of the theoretical predictions with the simulations.
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Pineau, Chantal. « Facteurs limitant la croissance des plantes graminoïdes et des mousses dans les polygones de tourbe utilisés par la grande oie des neiges ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ44938.pdf.

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El, Bouzid Hassan. « Méthodes d'éléments finis raffinés pour quelques problèmes aux limites dans des domaines non-réguliers ». Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/78c75dce-f930-4497-9077-c57356a9fac0.

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Dans ce travail, nous proposons différentes méthodes d'éléments finis raffines pour deux types de problèmes: le premier concerne des problèmes aux limites dans des polygones et le second le système de Stokes dans des polygones ou des polyèdres. Les solutions de ces problèmes présentent des singularités, en conséquence, l'utilisation d'une méthode d'éléments finis classique n'aboutit pas à un ordre optimal de convergence. En dimension 2, la forme explicite de ces singularités permet d'adopter certaines stratégies de façon à restaurer l'ordre optimal de convergence ; parmi celles-ci, citons la méthode de raffinement de maillage, la méthode d'adjonction de singularités et la méthode des fonctions singulières duales. En dimension 3, la structure des singularités étant plus complexe, seule la méthode de raffinement de maillage est actuellement applicable pour des domaines polyèdraux généraux. Pour le premier type de problèmes, les méthodes utilisées jusqu'à présent sont en général conformes, ce qui, dans le cas du problème des plaques, induit un cout de résolution assez important. Pour minimiser ce cout, nous proposons ici d'utiliser la méthode d'éléments finis non conformes raffinés. Sont étudiés notamment dans cette thèse: le problème de Dirichlet pour l'operateur de Laplace et l'équation des plaques encastrées. Pour le second, nous analysons une méthode d'éléments finis mixtes raffinés (conformes et non conformes) afin d'approcher la solution du système de Stokes. Les majorations d'erreurs optimales du cas des domaines reguliers sont démontrées pour les deux types de problèmes considérés.
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Marchand-Roy, Mylène. « L'effet fertilisant de la grande oie des neiges : cinq ans de suivi de l'azote et du phosphore dans les polygones de tourbe de l'île bylot au nunavut ». Master's thesis, Université Laval, 2009. http://hdl.handle.net/20.500.11794/20683.

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Des expériences de fertilisation à court terme ont montré que la présence d 'un tapis de mousses était une contrainte au recyclage de l'azote (N) et du phosphore (P) par les plantes graminoïdes des polygones de tourbe de l'Arctique, dont se nourrissent des herbivores comme les oies. Cette contrainte retarderait l'effet fertilisant de leurs fèces qui sont riches en nutriments facilement assimilables (N et P) par les plantes broutées. Dans ce contexte, une expérience de fertilisation à long terme, cumulant 14 traitements (N, P, N+P, fèces et glycine), a été menée dans les polygones de tourbe de l ' île Bylot, un site du Haut-Arctique canadien. Le but était de simuler la présence annuelle de la Grande Oie des neiges qui vient s 'y alimenter chaque été. Nos résultats montrent, qu 'après cinq ans de fertilisation avec 'Une quantité de fèces qui équivaut au double de celle produite par la population d 'oies actuelle, on a une forte tendance pour l'augmentation de la croissance des plantes graminoïdes. Par contre, c'est seulement avec une fertilisation en N inorganique supérieure (~ 1 g Nfm2 fan), pour venir saturer le tapis de mousses, que l'on a un effet significatif sur leur croissance. De plus, la décomposition de la matière organique est alors favorisée. L'étude dévoile aussi que l ' absorption de l'N et du P par la végétation n'est pas clairement favorisée par des apports combinés en ces nutriments en comparaison à des apports de l'un ou l'autre seuls. Par contre, la fréquence d'application d'une même quantité de fertilisant (individuelle vs. annuelle) influence la croissance des mousses, alors qu'elle ne montre pas de différence sur celle des graminoïdes. En effet, les mousses ont profité davantage du fractionnement d'une dose de fertilisant à chaque année, que de l'application complète de la même dose, la première année de l'expérience. Donc, par leur présence annuelle, il semble que l ' effet fertilisant des oies soit plus important sur la croissance des mousses que sur celle des graminoïdes broutées. Ces plantes vasculaires, également, ne compensent que partiellement la perte de tissu liée au broutement, ce qui abaisse leur couvert et donne probablement accès à plus de lumière pour les mousses. À l'île Bylot, la présence des oies favoriserait donc le maintien d'un couvert de bryophytes caractéristique des polygones de tourbe arctiques.
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Abgrall, Corentin. « Réponse de la flore, de la faune du sol et de leur substrat à l'introduction d'espèces exotiques envahissantes végétales ». Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR056/document.

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Les espèces exotiques envahissantes végétales sont des plantes introduites et naturalisées hors de leur aire de répartition native et capables de maintenir et d’accroitre leur population. Certaines sont considérées comme transformatrices de par leur effet sur les écosystèmes : leur structure, leur fonctionnement ainsi que leur communauté végétale et animale. Ces transformations peuvent rendre certaines de ces espèces nuisibles de par leurs impacts écologiques et économiques important. Les travaux réalisés dans le cadre de cette thèse et présentés ici ont pour objectif d’approfondir les connaissances sur l’impact des invasions biologiques. La faune du sol, la végétation native et leur substrat ainsi que son fonctionnement ont été étudiés à différentes échelles spatiales. Deux espèces exotiques, envahissantes en Europe, ont été considérées comme modèles pour ces travaux : le robinier faux-acacia (Robinia pseudoacacia) et la renouée du japon (Reynoutria japonica). Premièrement, une méta-analyse globale a permis de démontrer l’effet positif des invasions biologiques végétales sur l’abondance de certains groupes de la faune du sol, notamment les consommateurs primaires, en fonction de la structure de l’habitat (ouvert ou fermé). Ensuite, une étude à large échelle sur le robinier faux-acacia a permis d’illustrer les différences qui peuvent exister dans la réponse des écosystèmes forestiers aux invasions le long d’un gradient latitudinal. Ce gradient, composé de quatre régions distinctes en Europe de l’Ouest présente des différences de climat et de végétation dominante, ces différences modifiant l’impact du robinier faux-acacia. Une étude approfondie sur le robinier faux-acacia en Normandie a permis de mieux comprendre l’effet du robinier faux-acacia sur les communautés animales et végétales ainsi que sur le fonctionnement des écosystèmes par comparaison avec deux essences natives dominantes. Finalement, une manipulation expérimentale en laboratoire a démontré l’impact des composés allélopathiques de la renouée du Japon sur une partie de la faune du sol. Cette étude a montré que certaines espèces exotiques envahissantes sont susceptibles d’influencer la faune, et les réseaux trophiques, du sol par leur métabolisme secondaire. Ces travaux illustrent l’intérêt, dans le contexte des invasions biologiques végétales, de l’étude simultanée des compartiments aériens et souterrains à différentes échelles spatiales
Invasive alien plants are species introduced and naturalized outside of their native distribution range and which have the capacity to maintain and expand their population. Some of these species are considered to be ecosystem transformers by altering their structure, functioning as well as resident animal and plant communities. These induced alterations make some of these species undesirable through their ecological and economical impacts. The work presented in this thesis aimed at a better understanding of the impact of biological invasions by alien plants. The soil fauna, native vegetation and their substrate, as well as ecosystem functioning, were studied at different spatial scales. Two exotic alien species, invasive in Europe, were considered as biological models for this work: the black locust (Robinia pseudoacacia) and the Japanese knotweed (Reynoutria japonica). Firstly, a global meta-analysis demonstrated the positive impact that plant invasions can exert on the abundance of some groups within the soil fauna, notably primary consumers, within different types of habitats (open or closed). Then, a large-scale study on the black locust revealed the differences that can can occur in the response of forest ecosystems to invasions along a latitudinal gradient. Study sites along this gradient, distributed amog four distinct regions in western Europe, exhibit differences in climate and dominant native vegetation which can alter the impact of the black locust. A detailed study on black locust impact in Normandy demonstrated the impact of R. pseudoacacia on native plant and soil fauna communities, as well as some ecosystem functions, in comparison to two native tree species. Finally, a laboraty experiment demonstrated the impact that allelopathic compounds extracted from Japanese knotweed rhizomes can have on some organisms within the soil fauna. This study showed that some invasive alient plants can influence the soil fauna, and soil food webs, through their secondary metabolism. This thesis illustrates that simultaneous study of both aboveground and belowground ecosystem compartments at different spatial scales is of interest in the context of biological invasions
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Aganj, Ehsan. « Multi-view Reconstruction and Texturing=Reconstruction multi-vues et texturation ». Phd thesis, Ecole des Ponts ParisTech, 2009. http://pastel.archives-ouvertes.fr/pastel-00517742.

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Dans cette thèse, nous étudions les problèmes de reconstruction statique et dynamique à partir de vues multiples et texturation, en s'appuyant sur des applications réelles et pratiques. Nous proposons trois méthodes de reconstruction destinées à l'estimation d'une représentation d'une scène statique/dynamique à partir d'un ensemble d'images/vidéos. Nous considérons ensuite le problème de texturation multi-vues en se concentrant sur la qualité visuelle de rendu..
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Marchand-Roy, Mylène. « L'effet fertilisant de la grande oie des neiges : cinq ans de suivi de l'azote et du phosphore dans les polygones de tourbe de l'île bylot au nunavut / ». 2009. http://www.theses.ulaval.ca/2009/26062/26062.pdf.

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Livres sur le sujet "Polygonal plates"

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Park, Chong-Wook. Taxonomy of Polygonum section Echinocaulon (Polygonaceae). Bronx, N.Y., U.S.A : New York Botanical Garden, 1988.

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McIver, James D. Natural enemies of invasive knotweeds in the Pacific Northwest. Morgantown, W. Va : FHTET, USDA Forest Service, 2010.

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Electromagnetic scattering from a polygonal thin metallic plate using quadrilateral meshing. [Hampton, Va : Langley Research Center, 2003.

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(Editor), Fran Lloyd, et Catherine O'Brien (Editor), dir. Secret Spaces, Forbidden Places : Rethinking Culture (Polygons). Berghahn Books, 2001.

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National Aeronautics and Space Administration (NASA) Staff. Electromagnetic Scattering from a Polygonal Thin Metallic Plate Using Quadrilateral Meshing. Independently Published, 2018.

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(Editor), Fran Lloyd, et Catherine O'Brien (Editor), dir. Secret Spaces, Forbidden Places : Rethinking Culture (Polygons : Cultural Diversities and Intersections, 4). Berghahn Books, 2001.

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U.S. Fish and Wildlife Service. Region 1, dir. Recovery plan for two insects (Polyphylla barbata and Trimerotropis infantilis) and four plants (Chorizanthe pungens var. hartwegiana, Chorizanthe robusta var. hartwegii, Erysimum teretifolium, and Polygonum hickmanii) from the Santa Cruz mountains : Technical and agency draft. Portland, Or : U.S. Fish and Wildlife Service, Region 1, 1997.

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Jacoby, Henry Sylvester. Text-Book on Roofs and Bridges : Stresses in Simple Trusses. 3. Ed. Creative Media Partners, LLC, 2018.

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Text-Book on Roofs and Bridges : Stresses in Simple Trusses. 3. Ed. Creative Media Partners, LLC, 2022.

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Text-Book on Roofs and Bridges : Stresses in Simple Trusses. 3. Ed. Creative Media Partners, LLC, 2022.

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Chapitres de livres sur le sujet "Polygonal plates"

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Heuer, R., H. Irschik et F. Ziegler. « Large Amplitude Random Vibration of Polygonal Plates ». Dans Nonlinear Stochastic Mechanics, 285–96. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-84789-9_25.

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Banerjee, M. M., J. Mazumdar et Jayatu K. Bhuyan. « Nonlinear Vibrations of Polygonal-Shaped Plates : Use of Conformal Mapping Function ». Dans Lecture Notes in Mechanical Engineering, 423–31. Singapore : Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-8049-9_26.

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Rafetseder, Katharina, et Walter Zulehner. « On a New Mixed Formulation of Kirchhoff Plates on Curvilinear Polygonal Domains ». Dans Lecture Notes in Computational Science and Engineering, 869–77. Cham : Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-319-96415-7_82.

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Irschik, H., R. Heuer et F. Ziegler. « Free and Forced Vibrations of Polygonal Mindlin-Plates by an Advanced BEM ». Dans Advanced Boundary Element Methods, 179–88. Berlin, Heidelberg : Springer Berlin Heidelberg, 1988. http://dx.doi.org/10.1007/978-3-642-83003-7_19.

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Bhattacharyya, Bharati, et B. M. Johri. « Order Polygonales ». Dans Flowering Plants, 92–94. Berlin, Heidelberg : Springer Berlin Heidelberg, 1998. http://dx.doi.org/10.1007/978-3-662-11754-5_17.

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Kiss, György, et Tamás Szőnyi. « Generalized polygons, Möbius planes ». Dans Finite Geometries, 229–54. Boca Raton : CRC Press, Taylor & Francis Group, 2020. : Chapman and Hall/CRC, 2019. http://dx.doi.org/10.1201/9781315120072-10.

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Khare, C. P. « Polygonum aviculare Linn. » Dans Indian Medicinal Plants, 1. New York, NY : Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-70638-2_1256.

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Khare, C. P. « Polygonum bistorta Linn. » Dans Indian Medicinal Plants, 1. New York, NY : Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-70638-2_1257.

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Khare, C. P. « Polygonum glabrum Willd. » Dans Indian Medicinal Plants, 1. New York, NY : Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-70638-2_1258.

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Khare, C. P. « Polygonum hydropiper Linn. » Dans Indian Medicinal Plants, 1. New York, NY : Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-70638-2_1259.

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Actes de conférences sur le sujet "Polygonal plates"

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Higuchi, Hiroshi, Robert Anderson et Jinzhong Zhang. « Initial three-dimensional wake structures behind various polygonal plates ». Dans Fluid Dynamics Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 1994. http://dx.doi.org/10.2514/6.1994-2283.

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York, C. « Elastic buckling interaction in regular arrays of thin polygonal plates ». Dans 19th AIAA Applied Aerodynamics Conference. Reston, Virigina : American Institute of Aeronautics and Astronautics, 2001. http://dx.doi.org/10.2514/6.2001-1331.

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Nemirovsky, Yu V. « Permissible dynamic deformations of hybrid polymetallic plates with fixed polygonal circuits ». Dans NUMERICAL METHODS FOR SOLVING PROBLEMS IN THE THEORY OF ELASTICITY AND PLASTICITY (EPPS 2021). AIP Publishing, 2021. http://dx.doi.org/10.1063/5.0073256.

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Campos, Nivaldo Benedito Ferreira, et José Maria Dos Santos. « A SPECTRAL ELEMENT FORMULATION FOR THE DYNAMIC ANALYSIS OF POLYGONAL THIN PLATES ». Dans XXXVI Iberian Latin American Congress on Computational Methods in Engineering. Rio de Janeiro, Brazil : ABMEC Brazilian Association of Computational Methods in Engineering, 2015. http://dx.doi.org/10.20906/cps/cilamce2015-0833.

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Achdjian, Hossep, Emmanuel Moulin, Farouk Benmeddour, Jamal Assaad et Jacques Cuenca. « Prediction of average propagation characteristics in polygonal reverberant plates for experimental feature extraction ». Dans 2012 IEEE International Ultrasonics Symposium. IEEE, 2012. http://dx.doi.org/10.1109/ultsym.2012.0671.

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Santos Duarte, Diego, et Ivan Menezes. « An Educational MATLAB Code for Topology Optimization of Thick-Thin Plates using Arbitrary Polygonal Meshes ». Dans 27th Brazilian Congress of Thermal Sciences and Engineering. ABCM, 2023. http://dx.doi.org/10.26678/abcm.cobem2023.cob2023-1154.

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Pishnery, Joseph E., et Craig P. Lusk. « A Statically Balanced Shape Shifting Surface ». Dans ASME 2012 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/detc2012-70689.

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This paper presents a concept for producing a Statically Balanced Shape-Shifting Surface (SB-SSS). In this context, an SB-SSS is a surface that can require near-zero magnitude force changes to accomplish a change in shape while retaining effectiveness as a physical barrier. This paper focuses on how to statically balance a specifically-designed compliant mechanism and how to incorporate this mechanism into a polygonal cell. The mechanism consists of a compliant Peaucellier-Lipkin linkage layered with a pre-stressed link as the balancer. Prior art is presented that can show how a polygonal cell can be incorporated into a surface via a tiling array. Specifically shaped overlapping thin plates are used to retain the physical barrier requirement. The demonstration of a virtually zero-force Shape-Shifting Surface (SSS) suggests that SSS’s can be designed with a wide range of force-displacement properties, i.e. ranging from that of a square of the parent material to the zero-force mechanism presented here. Applications for an SB-SSS may be macro-scale or micro-scale and may include sensors, biomedical applications, defense applications, and variable stiffness materials.
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Kim, Kyu Tae, Sang Gi Ko et Jong Man Han. « Effects of Microstructural Inhomogeneity on HIC Susceptibility and HIC Evaluation Methods for Linepipe Steels for Sour Service ». Dans 2014 10th International Pipeline Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/ipc2014-33341.

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It has been well documented that slab internal quality is one of the key factors for reduced susceptibility of hydrogen induced cracking (HIC) in line pipe steels designed for sour gas service. In addition, the creation of a homogeneous microstructure which is heavily influenced by the slab internal quality is also a critical key parameter to reduce the HIC susceptibility in higher strength line pipe steel grade X60 and above. For the application of deep sea linepipe exposed to higher external pressure environments, heavy gauge in combination with higher strength steel is essential. Homogeneity of the steel microstructure is a key to success for thicker plates used in sour service HIC applications in combination with a deep sea environment. In this paper, various microstructures were compared along with an evaluation of the effects of the various microstructures on HIC susceptibility in grades X52, X65 and X70 designed for sour service. The various microstructures compared consisted of polygonal ferrite and pearlite in the X52 and polygonal ferrite, pearlite, acicular ferrite and bainite in the X65 and X70. The effect of microstructural inhomogeneity on HIC susceptibility was comparatively lower for the X52 than that of the X65 and X70. The microstructure of grade X65 and X70 were different due to the different conditions of rolling and cooling that were applied. Grades X65/X70 had a microstructure of polygonal ferrite/pearlite with bainite islands that resulted in a high crack length ratio (CLR) value caused by different hardness regions across the microstructural matrix. A homogeneous fine acicular ferrite microstructure produced by optimizing temperature control during rolling and cooling showed no hydrogen induced cracking. In addition, this alloy/process/microstructure design resulted in improved toughness results in low temperature drop weight tear test (DWTT). This paper will describe the successful production results of plate and pipe for high strength heavier gauge line pipe steels with highly homogeneous microstructures designed for sour service by controlling chemical design and process conditions in rolling and cooling. In addition, HIC evaluation methods utilizing both a traditional NACE TM0284 method versus that of a Scan-UT method were conducted and compared. A proposal to make the NACE TM0284 testing method more reliable by using Scan-UT method will be presented.
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Lusk, Craig, et Paul Montalbano. « Design Concepts for Shape-Shifting Surfaces ». Dans ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/detc2011-47402.

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This paper presents concepts for Shape-Shifting Surfaces (SSSs), i.e. surfaces that retain their effectiveness as physical barriers while undergoing changes in shape. These shape changes could be motions like expanding, shrinking, twisting, encircling, wiggling, swallowing or constricting that make the surface more effective at performing its function. The SSSs are a novel concept, and are composed of tiled arrays of polygonal cells, each cell consisting of specifically-designed compliant flexures attached to specifically-shaped overlapping thin plates or shells. Applications for such surfaces are anticipated at the micro-scale in cellular engineering and at the macro-scale for biomedical applications, recreational uses, national security, and environmental protection; each will be stem from the foundational concepts described in this paper.
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Ahn, Seong Soo, Woo Yeon Cho, Tae-Yang Yoon et Jang-Yong Yoo. « Mechanical Properties and Bending Behaviors of Low Temperature Toughness Linepipe Steels ». Dans ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29501.

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API-X70 and X80 steel with good low temperature toughness were developed. The microstructure and mechanical properties of API-X70 steel plate and pipe were investigated and the buckling behavior of X80 steel pipe was evaluated through large scale deformation tester. API-X70 steels with 30 mm thickness were manufactured by finished rolling below Ar3. The microstructure was composed of polygonal ferrite with subgrain network, degenerated pearlite and bainite. The yield strengths of API-X70 pipes were lower than those of plates, while the tensile strengths were similar in both states. The Charpy upper shelf energy of API-X70 steel plate was about 350 J and the energy transition temperature was below −100 °C. The separations were observed on the DWTT fracture surface of API-X70 steel plate. The DWTT 85 SA% transition temperature of plate was below −30 °C. It was conjectured that the separation associated with the low temperature rolling might increase the strength without deterioration of DWTT properties. API-X80 steels with 19mm thickness were fabricated with finished rolling above Ar3 and pipes with 30” diameter were made with R/B process. The deformation capacity of X80 linepipe was evaluated by large scale deforming machine operating under the loading of bending and axial compression force. It was showed that 2nd moment term should be calculated more correctly to measure the accurate critical compressive strain of pipe in the loading of bending and axial compression force. The compressive axial force had a little effect on the peak moment but changed the deformation pattern and state of critical compressive strain of linepipe. It was found that X80 linepipe used in this study was within the specification of DNV and API codes in terms of buckling capacity.
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Rapports d'organisations sur le sujet "Polygonal plates"

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Thoma, David. Landscape phenology, vegetation condition, and relations with climate at Canyonlands National Park, 2000–2019. Sous la direction de Alice Wondrak Biel. National Park Service, juin 2023. http://dx.doi.org/10.36967/2299619.

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Quantitatively linking satellite observations of vegetation condition and climate data over time provides insight to climate influences on primary production, phenology (timing of growth), and sensitivity of vegetation to weather and longer-term patterns of weather referred to as climate. This in turn provides a basis for understanding potential climate impacts to vegetation—and the potential to anticipate cascading ecological effects—such as impacts to forage, habitat, fire potential, and erosion—as climate changes in the future. This report provides baseline information about vegetation production and condition over time at Canyonlands National Park (NP), as derived from satellite remote sensing. Its objective is to demonstrate methods of analysis, share findings, and document historic climate exposure and sensitivity of vegetation to weather and climate as a driver of vegetation change. This report represents a quantitative foundation of vegetation–climate relationships on an annual timestep. The methods can be modified to finer temporal resolution and other spatial scales if further analyses are needed to inform park planning and management. The knowledge provided in this report can inform vulnerability assessments for Climate Smart Conservation planning by park managers. Patterns of pivot points and responses can serve as a guide to anticipate what, where, when, and why vegetation change may occur. For this analysis, vegetation alliance groups were derived from vegetation-map polygons (Von Loh et al. 2007) by lumping vegetation types expected to respond similarly to climate. Relationships between vegetation production and phenology were evaluated for each alliance map unit larger than a satellite pixel (~300 × 300 m). We used a water-balance model to characterize the climate experienced by plants. Water balance translates temperature and precipitation into more biophysically relevant climate metrics, such as soil moisture and drought stress, that are often more strongly correlated with vegetation condition than temperature or precipitation are. By accounting for the interactions between temperature, precipitation, and site characteristics, water balance helps make regional climate assessments relevant to local scales. The results provide a foundation for interpreting weather and climate as a driver of changes in primary production over a 20-year period at the polygon and alliance-group scale. Additionally, they demonstrate how vegetation type and site characteristics, such as soil properties, slope, and aspect, interact with climate at local scales to determine trends in vegetation condition. This report quantitatively defines critical water needs of vegetation and identifies which alliance types, in which locations, may be most susceptible to climate-change impacts in the future. Finally, this report explains how findings can be used in the Climate Smart Conservation framework, with scenario planning, to help manage park resources through transitions imposed by climate change.
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Thoma, David. Landscape phenology, vegetation condition, and relations with climate at Capitol Reef National Park, 2000–2019. Sous la direction de Alice Wondrak Biel. National Park Service, mars 2023. http://dx.doi.org/10.36967/2297289.

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Quantitatively linking satellite observations of vegetation condition and climate data over time provides insight to climate influences on primary production, phenology (timing of growth), and sensitivity of vegetation to weather and longer-term patterns of weather referred to as climate. This in turn provides a basis for understanding potential climate impacts to vegetation—and the potential to anticipate cascading ecological effects, such as impacts to forage, habitat, fire potential, and erosion, as climate changes in the future. This report provides baseline information about vegetation production and condition over time at Capitol Reef National Park (NP), as derived from satellite remote sensing. Its objective is to demonstrate methods of analysis, share findings, and document historic climate exposure and sensitivity of vegetation to weather and climate as a driver of vegetation change. This report represents a quantitative foundation of vegetation–climate relationships on an annual timestep. The methods can be modified to finer temporal resolution and other spatial scales if further analyses are needed to inform park planning and management. The knowledge provided in this report can inform vulnerability assessments for Climate Smart Conservation planning by park managers. Patterns of pivot points and responses can serve as a guide to anticipate what, where, when, and why vegetation change may occur. For this analysis, vegetation alliance groups were derived from vegetation-map polygons (Von Loh et al. 2007) by lumping vegetation types expected to respond similarly to climate. Relationships between vegetation production and phenology were evaluated for each alliance map unit larger than a satellite pixel (~300 × 300 m). We used a water-balance model to characterize the climate experienced by plants. Water balance translates temperature and precipitation into more biophysically relevant climate metrics, such as soil moisture and drought stress, that are often more strongly correlated with vegetation condition than temperature or precipitation are. By accounting for the interactions between temperature, precipitation, and site characteristics, water balance helps make regional climate assessments relevant to local scales. The results provide a foundation for interpreting weather and climate as a driver of changes in primary production over a 20-year period at the polygon and alliance-group scale. Additionally, they demonstrate how vegetation type and site characteristics, such as soil properties, slope, and aspect, interact with climate at local scales to determine trends in vegetation condition. This report quantitatively defines critical water needs of vegetation and identifies which alliance types, in which locations, may be most susceptible to climate-change impacts in the future. Finally, this report explains how findings can be used in the Climate Smart Conservation framework, with scenario planning, to help manage park resources through transitions imposed by climate change.
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Wolfe, S. A., H. B. O'Neill, C. Duchesne, D. Froese, J M Young et S. V. Kokelj. Ground ice degradation and thermokarst terrain formation in Canada over the past 16 000 years. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329668.

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Thermokarst results from thawing of excess ground ice in permafrost sediments. Thermokarst processes and landforms are controlled by ground ice type, amount and distribution, as well as the patterns of ground ice loss over time. Recent acceleration of varied thermokarst processes across diverse Canadian permafrost terrains make for a challenging task in predicting landscape-scale thaw trajectories. Using existing ground ice models, we examined the modelled amounts and spatial extent of ground ice loss relative to ground ice maxima in the last ca. 16 ka BP for relict, segregated and wedge ice. We relate observed thermokarst features to the nature of ground ice development and loss in different environments (cold continuous permafrost, discontinuous permafrost, and no current permafrost). In cold, continuous permafrost areas where ground ice loss has been limited over the last 16 ka BP, thermokarst processes include active layer detachments and slumps in segregated and relict ice, gullying and ponding in ice wedge troughs, and the cyclical development of shallow thermokarst ponds in segregated ice. With ground ice loss in discontinuous permafrost, thermokarst processes are wide-ranging. Slumps, subsidence, and collapse of lithalsas, palsas and peat plateaus occur from thawing of segregated ice, thermokarst ponds from melting wedge and segregated ice, and involuted terrain from melting and creep of relict or segregated ice. In former permafrost terrain, evidence of thermokarst includes former ice wedge polygons, collapsed lithalsas, and irregular hummocky terrain. The relations between modelled ground ice loss and observed thermokarst landscapes assist in understanding present-day processes and in predicting future thermokarst landform evolution with a changing climate.
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Kull, Kathleen, Craig Young, Jennifer Haack-Gaynor, Lloyd Morrison et Michael DeBacker. Problematic plant monitoring protocol for the Heartland Inventory and Monitoring Network : Narrative, version 2.0. National Park Service, mai 2022. http://dx.doi.org/10.36967/nrr-2293355.

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Problematic species, which include invasive, exotic, and harmful species, fragment native ecosystems, displace native plants and animals, and alter ecosystem function. In National Parks, such species negatively affect park resources and visitor enjoyment by altering landscapes and fire regimes, reducing native plant and animal habitat, and increasing trail maintenance needs. Recognizing these challenges, Heartland Inventory and Monitoring (I&M) Network parks identified problematic plants as the highest-ranking vital sign across the network. Given the need to provide early detection of potential problematic plants (ProPs) and the size of network parks, the Heartland I&M Network opted to allocate available sampling effort to maximize the area searched. With this approach and the available sampling effort in mind, we developed realistic objectives for the ProP monitoring protocol. The monitoring objectives are: 1. Create a watch list of ProPs known to occur in network parks and a watch list of potential ProPs that may invade network parks in the future, and occasionally update these two lists as new information is made available. 2. Provide early detection monitoring for all ProPs on the watch lists. 3. Search at least 0.75% and up to 40% of the reference frame for ProP occurrences in each park. 4. Estimate/calculate and report the abundance and frequency of ProPs in each park. 5. To the extent possible, identify temporal changes in the distribution and abundance of ProPs known to occur in network parks. ProP watch lists are developed using the best available and most relevant state, regional, and national exotic plant lists. The lists are generated using the PriorityDB database. We designed the park reference frames (i.e., the area to be monitored) to focus on accessible natural and restored areas. The field methods vary for small parks and large parks, defined as parks with reference frames less than and greater than 350 acres (142 ha), respectively. For small parks, surveyors make three equidistant passes through polygon search units that are approximately 2-acres (0.8 ha) in size. For large parks, surveyors record each ProP encountered along 200-m or 400-m line search units. The cover of each ProP taxa encountered in search units is estimated using the following cover scale: 0 = 0, 1 = 0.1-0.9 m2, 2 = 1-9.9 m2, 3 = 10-49.9 m2, 4 = 50-99.9 m2, 5 = 100-499.9 m2, 6 = 499.9-999.9 m2, and 7 = 1,000-4,999.9 m2. The field data are managed in the FieldDB database. Monitoring is scheduled to revisit most parks every four years. The network will report the results to park managers and superintendents after completing ProP monitoring.
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Muldavin, Esteban, Yvonne Chauvin, Teri Neville, Hannah Varani, Jacqueline Smith, Paul Neville et Tani Hubbard. A vegetation classi?cation and map : Guadalupe Mountains National Park. National Park Service, 2024. http://dx.doi.org/10.36967/2302855.

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A vegetation classi?cation and map for Guadalupe Mountains National Park (NP) is presented as part of the National Park Service Inventory & Monitoring - Vegetation Inventory Program to classify, describe, and map vegetation communities in more than 280 national park units across the United States. Guadalupe Mountains NP lies in far west Texas and contains the highest point in the state, Guadalupe Peak (8,751 ft; 2,667 m). The mountain escarpments descend some 5,000 ft (1,500 m) to the desert basins below forming a complex geologic landscape that supports vegetation communities ranging from montane coniferous forests down to desert grasslands and scrub. Following the US National Vegetation Classi?cation (USNVC) standard, we identi?ed 129 plant associations hierarchically tiered under 29 groups and 17 macrogroups, making it one of the most ecologically diverse National Park Service units in the southwestern United States. An aspect that adds to this diversity is that the park supports communities that extend southward from the Rocky Mountains (?ve macrogroups) and Great Plains (one macrogroup) and northward from the Chihuahuan Desert (two macrogroups) and Sierra Madre Orientale of Mexico (three macrogroups). The remaining six macrogroups are found in the Great Basin (one macrogroup), and throughout the southwestern United States (remaining ?ve macrogroups). Embedded in this matrix are gypsum dunelands and riparian zones and wetlands that add further complexity. We describe in detail this vegetation classi?cation, which is based on 540 vegetation plots collected between 2006 and 2010. Full descriptions and diagnostic keys to the plant associations along with an overall plant species list are provided as appendices. Based on the vegetation classi?cation and associated plot data, the vegetation map was developed using a combined strategy of automated digital object-oriented image classi?cation and direct-analog image interpretation of four-band National Agricultural Imagery Program (NAIP) aerial photography from 2004 and 2008 and Landsat Thematic Mapper satellite imagery. The map is designed to facilitate ecologically-based natural resource management at a 1:24,000 scale with 0.5-ha minimum map unit size. The map legend is hierarchically structured: the upper Level 1 consists of 16 map units corresponding in most cases to the USNVC group level, and an additional map unit describing built-up land and agriculture; Level 2 is composed of 48 nested map units re?ecting various combinations of plant associations. A ?eld-based accuracy assessment using 341 vegetation plots revealed a Level 1 overall accuracy of 79% with 90% CI of 74?84% and 68% with 90% CI of 59?76% at Level 2. An annotated legend with summary descriptions of the units, distribution maps, aerial photo examples of map unit polygons, and representative photos are provided in Appendix D. Large wall-size poster maps at 1:35,000 scale were also produced following NPS cartographic standards. The report, plot data, and spatial layers are available at National Park Service Vegetation Mapping Program https://www.nps.gov/im/vegetation-inventory.htm). Outcomes from this project provide the most detailed vegetation classi?cation and highest resolution mapping for Guadalupe Mountains NP to date to support many uses including ?re, recreation, vegetation, and wildlife management, among others. The upper Level 1 map is particularly suited to landscape-scale, park-wide planning and linkages to its sister park, Carlsbad Caverns NP. The Level 2 mapping provides added detail for use at a more localized project scale. The overall accuracy of the maps was good, but because Guadalupe Mountains NP is primarily wilderness park, there were logistical challenges to map development and testing in remote areas that should be considered in planning management actions. In this context, some map units would bene?t from further development and accuracy assessment. In particular, a higher resolution mapping of McKittrick Creek riparian habitat at 1:6,000 scale or ?ner is recommended for this important habitat in the park. In addition, developing a structural canopy height model from LiDAR imagery would be useful to more accurately quantify woody canopy density and height to support ?re management and other habitat management issues. With respect to understanding vegetation dynamics in this time of rapid environmental change, the 540 vegetation plots themselves are su?ciently georeferenced and have the data resolution to be useful in detecting change at the decadal scales across much of the park. To this end, an additional recommendation would be to install more plots to ?ll the gaps among the main vegetation units of the park, both spatially and thematically. Overall, the Vegetation and Classi?cation Map for Guadalupe Mountains NP will support the park?s management e?orts and enhance regional understanding of vegetation and ecology of ecosystems of the southwestern United States.
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