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Articles de revues sur le sujet "Multilayered timber structures"
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Vardaxis, Nikolaos-Georgios, Delphine Bard Hagberg et Jessica Dahlström. « Evaluating Laboratory Measurements for Sound Insulation of Cross-Laminated Timber (CLT) Floors : Configurations in Lightweight Buildings ». Applied Sciences 12, no 15 (29 juillet 2022) : 7642. http://dx.doi.org/10.3390/app12157642.
Texte intégralRésumé :
Cross-laminated timber (CLT) floors with supplementary layers or floating floors comprise a common solution in new multistory timber structures. However, bare CLT components provide poor sound insulation, especially in low frequencies during structure-borne sound propagation. Thus, floor configurations in wooden buildings deploy more layers for improved acoustic behavior. Twelve contemporary CLT floors were analyzed after laboratory measurements of airborne sound reduction and impact sound transmission utilizing the following indicators: Rw, Rw, 100, Rw, 50, Ln,w, Ln,w,100, and Ln,w,50 (per ISO 10140, ISO 717). An increase in sound insulation was achieved thanks to added total mass and thickness, testing layers of the following: elastic mat for vibration isolation, wool insulation, gypsum boards, plywood, concrete screed, and wooden parquet floor. The results indicate that multilayered CLT floors can provide improvements of up to 22 dB for airborne sound and 32 dB for impact sound indicators compared with the bare CLT slab. Floating floor configurations with dry floor solutions (concrete screed) and wooden parquet floors stand out as the optimal cases. The parquet floor provides a 1–2 dB improvement only for impact sound indicators in floating floor setups (or higher in three cases).
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Čechavičius, Rimantas. « INVESTIGATIONS IN THE STRENGTH OF PRESTRESSED MULTILAYERED BEAMS UNDER THE ACTION OF LONG-TERM SHEAR/MEDINIŲ IŠ ANKSTO ĮTEMPTŲJŲ DAUGIASLUOKSNIŲ SIJŲ STIPRUMAS VEIKIANT ILGALAIKĖMS SKERSINĖMS JĖGOMS ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 4, no 2 (30 juin 1998) : 109–16. http://dx.doi.org/10.3846/13921525.1998.10531389.
Texte intégralRésumé :
The results of long-term experiments are presented in the paper. As a result of the experiments, invention SU 1025831 was developed under the name “The method of manufacture of a timber load-bearing element” (E 04 C 3/12, priority since July 11, 1981). The objective of the experiments performed was to check the method of increase of load bearing capacity of glulam beams under the influence of long-term shear. 14 beams were tested: nine of them were multilayered and 5 made of board-package and square-sawn timber. All the beams failed because of the action of shear forces. Two beams were tested by static short loading, the rest twelve by long-term loading. Three beams, that have not failed because of the action of long-term loading, then were tested by short-term loading. From the tests of multilayered, glulam and solid square-sawn timber beams the decrease of the relative strength wood split alongside fibres under the action of long-term shear is bigger than that given in literature in case of standard experiments. Relationship of the level of decrease of this strength with the duration of long-term loading may be calculated according to the equation (2). The influence of long-term loading on the load-bearing capacity of these beams depends on the intensity of actions: if such a load does not cause the plastic deformations in the beam, their load-bearing capacity does not decrease and vice versa—the appearance of plastic deformations and micro-cracks means the decrease of load bearing capacity of the beam under a short-term shear. A short description of invention SU 1025831 is also presented in the paper. The invention is devoted to the perfection of the former invention No 954237. The latter one suggested an increase of load-bearing capacity of glulam elements under a short-term shear. Under a long-term load, or in case of fire, when the temperature and moisture around is changing, the strength of prestressed joint of these beams may not be fully guaranteed because of the influence of inner stresses and possible micro-cracking. With the purpose to increase the strength of beams under a long-term shear the author offers additionally to install pivots (Fig 6, 3) after giving prestress and full polymerisation. This method does not only increase the load-bearing capacity of multilayered elements under a long-term shear, but also ensures a higher reliability and fire resistance of such structures.
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Čechavičius, Rimantas. « INVESTIGATIONS IN THE STRENGTH OF GLULAM MULTILAYERED BEAMS UNDER A SHORT-TIME SHEAR/MEDINIŲ KLIJUOTŲ DAUGIASLUOKSNIŲ SIJŲ STIPRUMO TYRIMAI VEIKIANT TRUMPALAIKĖMS SKERSINĖMS SKERSINĖMS JĖGOMS ». JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 4, no 1 (31 mars 1998) : 5–11. http://dx.doi.org/10.3846/13921525.1998.10531373.
Texte intégralRésumé :
The author of the article has performed wide-range tests of glulam beams. The objective of the tests is increasing of load bearing capacity of such beams under shear. As a result 5 inventions have been suggested and confirmed. In total 44 beams of various types were tested under the action of short and long-time loadings. These investigations have verified a new method for increasing load bearing capacity of glulam beams. The essence of the method was the utilisation of prestressed elements in multilayered beams. It allows to increase load bearing capacity of such elements under shear and decrease or eliminate the influence of lateral tension stresses on their resistance. Totally, 30 beams have been tested for the influence of short-time forces: 6 of them are multilayered with pre-stressed elements, made by the offer of invention No 954237; 8 analogous beams for comparison of the results are made of squared timber, board package, multilayered without prestressed elements; 16 different beams for additional investigations of methods of experiments and closer definition of separate technological factors. All beams failed because of shear. It has been proved by experiments that plywood brass in multilayered beams not only increases the strength of the beam, but also prevents the element from a sudden failure, increases its reliability. Longitudinal cracks have appeared in the zones of neutral axes of prestressed multilayered beams before the failure of them, while the load was 0,93–0,98 of ultimate the width of the crack was 0,7–0,8 mm, and the shear deformation was 2–6 mm at the moment of failure. The strength of the beams under short-time shear depending on the level of prestressing force (σy = = 1,5…2,25 MPa) increased 9–10% and crack resistance increased 9–22% in comparison with unpresstressed beams. A short description of invention No 954237 has also been given (see Fig 6). Layers of a load bearing multilayered element with wood fibres oriented along the axis of the member (1) are precompressed laterally to the wood fibres (5). Compression force should not cause stresses (σy) higher than the point of wood proportionality in lateral direction. These layers (1) are glued with the layers where wood fibres are directed laterally to the axis of the element (2) and they are shorter in value Δ ≥ σy · h/E90 than layers (1). Horizontal prestressing of multilayered element (4) has to ensure a qualitative cohesion. It is possible to use structural plywood instead of wood layers with fibres lateral to the axis of the element. The use of this method does not only increase the resistance of glulam elements to short-time shear, but also ensures a better reliability of such structures.
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Mamani, Veronica Jesus Pilco, et Kenneth Ayala Castro. « Artificial Degradation of Two Wooden Species of Different Density and Their Use for Optimization of Thermal Comfort in Climatic Areas of Marine and Mesoandean Desert ». Revista de Gestão Social e Ambiental 18, no 12 (11 décembre 2024) : e010290. https://doi.org/10.24857/rgsa.v18n12-061.
Texte intégralRésumé :
Objective: The objective of this study was to evaluate the behavior of two species of wood of different density and the most commercialized in the southern regions of Peru: Schizolobium excelsum (pashaco) and Aniba gigantiflora (mohena), in order to choose the appropriate timber species for housing coating and contribute to thermal comfort. Wood is known to be a widely used material in construction due to its mechanical, aesthetic and sustainable properties. However, its durability is compromised by environmental factors. The degradation of wood can manifest itself in the form of cracking, erosion and discoloration, affecting its structural integrity and appearance. On the other hand, several studios have designed multilayered facades as an architectural strategy that seeks to optimize the thermal comfort of the interior spaces. Previous studies have shown that the configuration of multilayer facades with wood can result in a significant improvement of the thermal performance of buildings, for this purpose the best timber species must be chosen. Context: In this context, samples of two timber species were selected and evaluated in their natural state and coated with commercial surface protector, and wood thermally treated at 180 °C; these samples were subjected to accelerated degradation in a QUV equipment under conditions of UV radiation (0.89 W/m2 nm at 340 nm), humidity (by condensation and spray) and high temperatures (up to 60 °C), according to EN 927-6:2018 (European Committee for Standardization, 2018) for a total of 2016 hours. Results: The results showed statistically that the wood in its natural state, and with commercial coating presented cracking, fissures, erosion and discoloration. However, the heat treated wood presented better results of resistance against cracks. Finally, the species Schizolobium excelsum (density 0.33 g/cm3) is more resistant to exposed climatic conditions. Chosen the best timber species, it was configured as part of the multi-layer facade system composed of: heat treated wood, elastomer, air, OSB board and polyurethane insulators and its behavior was simulated to optimize thermal comfort in homes of marine desert climates and Andean meso with THERM software. The result showed an internal temperature concentration of 20 °C versus 0 °C of external temperature, this result considering only structures of walls of the house. Implications of the research: The implications of the research is at the level of material development, since the results reflect the need to develop coatings and treatments for wood that offer greater protection against degradation that respond to demands for durability and sustainability. Another implication is at the level of design strategy, the configuration of multi-layer facade with heat treated wood, can be adopted in architectural design to improve thermal comfort in marine or Mesoandean desert climatic areas. Originality: The originality of this inside research in which an accelerated degradation equipment was used, which allowed to have a realistic frame of reference to evaluate the behavior of materials in adverse climatic conditions. Likewise, it was possible to identify the timber species, more resistant to extreme climatic factors and by simulating the thermal behavior of this material, it is concluded that it is viable against other timber species.
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Cachim, Paulo. « ANN prediction of fire temperature in timber ». Journal of Structural Fire Engineering 10, no 2 (10 juin 2019) : 233–44. http://dx.doi.org/10.1108/jsfe-06-2018-0012.
Texte intégralRésumé :
Purpose Fire degradation is an extremely important risk that threatens timber structures. It is therefore normal that timber design codes include provisions for the design and verification of structures under fire loading. Eurocode 5 is no exception to this, but the simplified methods presented in the code show some inconsistencies, and the advanced method is not practical to use for design purposes. Artificial neural networks (ANNs) have the ability to model complex problems and have been used in a variety of construction engineering problems. They can learn from a subset of data, and then they can be used to predict the results for other input parameters. The purpose of this study is to present the possibility of the use of ANNs for the prediction of temperatures in rectangular timber cross sections, under fire exposure. Design/methodology/approach In this work, a multilayer feedforward ANN has been trained to predict the temperatures within a timber cross section, using as input the size of the cross section, the timber density, the time of exposure and the coordinates of the point within the cross section. Findings The results obtained clearly indicate that ANN can be used to predict the temperatures in a timber cross section subjected to fire. Originality/value ANNs have not been used for the prediction of temperatures in timber cross sections. The use of ANN makes the temperature prediction under a standard fire loading in a cross section extremely easy to implement in any code. These results can be used to calculate the strength of the elements after fire.
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Ibragimov, Aleksandr, Lubov Gnedina, Ksenia Zaytseva, Nikita Ushakov et Konstantin Popkov. « Heat and mass transfer in laminated glued timber bar ». E3S Web of Conferences 244 (2021) : 09009. http://dx.doi.org/10.1051/e3sconf/202124409009.
Texte intégralRésumé :
The main prerequisites for the development of wooden housing construction in Russia are given, which determined the goal of this study - to develop a mathematical model of heat and mass transfer (moisture transfer) in glued timber for rational design of enclosing structures. Lamellas can be classified as a capillary ‒ porous body. leaning on theory of academician A.V. Lykov, the formulation of the problem of heat and mass transfer in a multilayer glued laminated timber is presented a system of equations describing non-stationary heat, mass and pressure transfer under real possible operating conditions of enclosing structures is considered. An analytical method is proposed for calculating both individual lamellas and the entire multilayer glued beam. The proposed technique allows the method of solving the inverse problem to directly calculate the resistance value of the entire bar from the unsteady temperature field. The system of equations describing the process is nonlinear and analytically insoluble. To solve the problem, a combined method for solving boundary value problems of heat transfer was used, which is based on a combination of elements of analytical and numerical solutions. A feature of the problem under consideration is that the middle lamella has heat-conducting inclusions in the form of a bough. Method is that the entire heat transfer process is divided into a number of small time intervals. Within each interval, we assume that the temperature is constant at the interface between layers and a constant heat flux through the contacting surfaces, i.e. perfect thermal contact.
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Mestnikov, Aleksey, et Anastasia Egorova. « Energy efficiency of timber-frame buildings in cold climates ». E3S Web of Conferences 592 (2024) : 03033. http://dx.doi.org/10.1051/e3sconf/202459203033.
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Ensuring human life in harsh cold climate conditions is one of the priority objectives for the development of the Arctic states. Among numerous building structures used in the construction of energy-efficient buildings, wood-frame panels occupy one of the leading places in the world. They have inherent positive characteristics such as versatility, manufacturability, lightness, high thermal protection qualities and relatively low cost. The main features include a high dependence of their fire resistance and energy efficiency on the choice of materials and structures. In the paper to improve energy efficiency and fire resistance of timber-frame buildings the method of two-layer thermal insulation in permanent formwork made of non-combustible glass magnesite boards with the use of heterogeneous thermal insulation materials is proposed. These include polystyrene foam with a low coefficient of thermal conductivity and non-combustible insulating foam concrete. To substantiate the increase of energy efficiency of the enclosing structures, the results of thermal calculation are given, thermograms of field inspection of the quality of thermal insulation are shown. At rational selection of materials and construction the energy efficiency of the offered multilayer wooden-frame wall (thermal resistance 5.66 (m2 × °C)/W) is increased almost two times (by 1.82) in comparison with a single-layer wall from monolithic foam concrete of similar buildings in conditions of St. Petersburg. The results of experimental research on improving the technology of obtaining heat-insulating foam concrete with improved indicators of shrinkage deformation, strength and curing processes are presented.
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Han, Liuyang, Guanglan Xi, Wei Dai, Qun Zhou, Suqin Sun, Xiangna Han et Hong Guo. « Influence of Natural Aging on the Moisture Sorption Behaviour of Wooden Structural Components ». Molecules 28, no 4 (17 février 2023) : 1946. http://dx.doi.org/10.3390/molecules28041946.
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A greater understanding of moisture sorption behaviour of aged wooden structural components, which has a close relationship with dimensional stability, is required to effectively evaluate and preserve historical artefacts. This study focused on the effects of aging on Baotou beam samples from a Chinese historical wooden building. An analysis of the sorption isotherms and hysteresis loops of a naturally aged, decayed sample (AOS), an aged sound sample (AIS), and a reference sample (RS), using classical sorption isotherm models revealed that the moisture sorption behaviour of samples from the same growth ring in a Baotou beam can differ significantly. AOS showed higher hygroscopicity than AIS, and both these samples were more hygroscopic than RS. Furthermore, the mono/multilayer moisture contents of AOS were always higher than those of AIS and RS. In addition, Fourier transform infrared, second-derivative infrared, and two-dimensional correlation infrared spectroscopy were used to investigate chemical changes in the samples. The relative hemicellulose and lignin contents of the samples changed significantly with wood aging. Furthermore, AOS exhibited the highest calcium oxalate content, which may be associated with fungal infections. Overall, these results provide valuable insights into the effects of aging on wood samples and the dimensional stability of timber structures, which could inform future research on methods for the preservation or restoration of aging timber structures.
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Niederwestberg, Jan, Jianhui Zhou, Ying Hei Chui et Dongsheng Huang. « Bamboo/Wood Composites and Structures Shear and Normal Strain Distributions in Multilayer Composite Laminated Panels under Out-of-Plane Bending ». Advances in Civil Engineering 2021 (31 janvier 2021) : 1–15. http://dx.doi.org/10.1155/2021/6637853.
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Innovative mass timber panels, known as composite laminated panels (CLP), have been developed using lumber and laminated strand lumber (LSL) laminates. In this study, strain distributions of various 5-layer CLP and cross-laminated timber (CLT) were investigated by experimental and two modelling methods. Seven (7) different panel types were tested in third-point bending and short-span shear tests. During the tests, the digital imaging correlation (DIC) technique was used to measure the normal and shear strain in areas of interest. Evaluated component properties were used to determine strain distributions based on the shear analogy method and finite element (FE) modelling. The calculated theoretical strain distributions were compared with the DIC test results to evaluate the validity of strain distributions predicted by the analytical model (shear analogy) and numerical model (FE analysis). In addition, the influence of the test setup on the shear strain distribution was investigated. Results showed that the DIC strain distributions agreed well with the ones calculated by the shear analogy method and FE analysis. Both theoretical methods agree well with the test results in terms of strain distribution shape and magnitude. While the shear analogy method shows limitations when it comes to local strain close to the supports or gaps, the FE analysis reflects these strain shifts well. The findings support that the shear analogy is generally applicable for the stress and strain determination of CLP and CLT for structural design, while an FE analysis can be beneficial when it comes to the evaluation of localized stresses and strains. Due to the influence of compression at a support, the shear strain distribution near the support location is not symmetric. This is confirmed by the FE method.
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Titunin, Andrey. « Thermal conductivity coefficient determination of wooden glued structures taking into account macrostructure and wood density ». Smart composite in construction 5, no 1 (23 mars 2024) : 8–18. http://dx.doi.org/10.52957/2782-1919-2024-5-1-8-18.
Texte intégralRésumé :
The paper considers calculated and experimental methods of determining the thermal conductivity coefficient of wooden glued structures. The author shows that when designing the thermal protection of building enclosure structures in the form of CLT-panels or wooden glued laminated timber, one uses reference data on the thermal conductivity coefficient for pine or spruce. In practice, the value of the thermal conductivity coefficient may be less than the reference value; as a consequence, the thickness of the building enclosing structures is overestimated. This is not reasonable in terms of material intensity of construction. When considering wood as an anisotropic material, the peculiarities of the macrostructure and differences in the density of individual layers, as well as the wood species, should be taken into account when determining the parameters of structures. Based on the physical description of the thermal conductivity process and the fundamental laws of heat and mass transfer, the author proposes that it is necessary to adjust the results of calculations to the actual values of the thermal conductivity coefficient of multilayer wooden glued structures. The paper presents the results of experimental determination of the thermal conductivity coefficient of pine and aspen wood using steady-state and unsteady heat flow methods. It is shown that, depending on the density and wood species, experimental values of the thermal conductivity coefficient from 0.102 to 0.115 W·m-1∙K-1 can be obtained.
Thèses sur le sujet "Multilayered timber structures"
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Bui, Tuan Anh. « Experimental and numerical uncertain vibration analysis of multilayered timber structures assembled using compressed wood dowels ». Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0202.
Texte intégralRésumé :
Cette thèse présente une étude expérimentale et numérique sur les aptitudes en service en ce qui concerne le comportement vibratoire de planchers réalisés en bois d’ingénierie sans colle (AFEWP), à savoir les poutres en bois lamellé sans adhésif (AFLB) et les panneaux en bois lamellé-croisé sans adhésif (AFCLT), assemblés par des tourillons en bois densifié (CWD). Les analyses modales expérimentales ont été réalisées en conditions libres-libre à l'aide d'un marteau instrumenté. Les fréquences naturelles, les modes propres et les coefficients d'amortissement ont été évalués expérimentalement. De plus, des poutres en bois lamellé-collé similaires ont été fabriquées et testées à des fins de comparaison. Un modèle EF 3D a été développé et validé par comparaison avec des données expérimentales, puis utilisé pour prédire le comportement vibratoire d'un système de plancher à grande échelle réalisé avec un panneau AFCLT mesurant 4,5 m x 5,5 m. Une étude paramétrique a été réalisée en utilisant le modèle EF pour identifier les paramètres qui influent sur la rigidité et les fréquences propres du plancher. Les résultats obtenus ont été analysés au regard des critères de conception exigés par Eurocode 5 en ce qui concerne le confort vibratoire des planchers bois. Un modèle EF simplifié a ensuite été développé pour réduire les coûts de calcul. Le niveau de variabilité des résultats des AFEWP a été également étudié et discuté. La variabilité numérique des fréquences des AFEWP a été étudiée en utilisant la méthode MSP (Modal Stability Procedure). Les résultats de la méthode MSP ont d'abord été comparés aux résultats EF dans le cas nominal. Les résultats statistiques (valeur moyenne, écart type, coefficient de variation et distribution) obtenus par la méthode MSP ont été confrontés aux résultats de simulation directe de Monte Carlo ainsi qu’aux données expérimentales. Une estimation rapide des erreurs entre la méthode MSP et la simulation directe de Monte Carlo a été développée. Enfin, la variabilité (moyenne et écart-type des fréquences) du comportement vibratoire du système de plancher à grande échelle a été étudiée en utilisant la méthode MSPThis study presents an experimental and numerical investigation on the vibrational serviceability performance of novel adhesive free engineered wood products (AFEWPs), namely adhesive free laminated timber beams (AFLB) and adhesive free cross-laminated timber panels (AFCLT), assembled through thermo-mechanically compressed wood dowels (CWD). The experimental modal analyses were carried out under free-free conditions using a hammer impact. Natural frequencies, mode shapes, and damping ratio were assessed experimentally. In addition, similar glued timber beams (conventional glulam) were manufactured and tested for comparison purpose. A 3D FE model was developed and validated by comparison against experimental data and then used to predict the vibrational behavior of a realistic flooring system made with AFCLT panel measuring 4.5 m x 5.5 m. A parametric study was performed on the FE model to maximize the floor stiffness. The predicted FE results were discussed with regard to the Eurocode 5 vibrational serviceability design requirements showing acceptable vibrational performance. A simplified FE model was then developed to reduce computational cost. The variability level of the results for the AFEWPs was also studied and discussed. The numerical variability of frequencies of the AFEWPs was investigated based on the development of the Modal Stability Procedure (MSP). The MSP result was first compared with the FE result in the nominal case. Then, the statistic results (mean value, standard deviation, coefficient of variation and distribution) obtained from the MSP were compared with the results from the classical method (direct Monte Carlo simulation) and experimental results. A quick error estimation between the MSP and the direct Monte Carlo simulation was developed. Finally, the mean and standard deviation of the frequencies of the realistic AFCLT flooring system were predicted by the MSP
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Paroissien, Jeanne. « Développement de modèles éléments finis de types volumique, volume-coque et volume-poutre pour l’analyse du comportement des structures multicouches en bois assemblées par des goujons ». Electronic Thesis or Diss., Compiègne, 2025. http://www.theses.fr/2025COMP2844.
Texte intégralRésumé :
Les structures multicouches en bois, assemblées par des goujons en bois densifié, constituent une solution durable et innovante pour le secteur de la construction. Le développement de modèles prédictifs par éléments finis nécessite une représentation volumique de la géométrie pour modéliser le comportement mécanique complexe de ces structures. Cependant, les modèles volumiques sont couteux, notamment dans le cadre des études de variabilité et d’optimisation. Dans cette thèse, des approches de types volumique, volume-coque et volume-poutre, sont développées pour obtenir des modèles précis et qui peuvent être qualifiés de juste nécessaires. L’étude du comportement mécanique des structures multicouches en bois révèle que les lamelles adoptent un comportement de coque tandis que les goujons se comportent comme des poutres. Des champs de déplacement d’ordre supérieur dans l’épaisseur des lamelles et dans la section des goujons sont identifiés. Pour respecter ces champs de déplacement tout en gardant une représentation volumique, deux méthodes ont été développées. Une première méthode exploite des éléments volumiques standards en appliquant des théories de coque à travers l’épaisseur des lamelles et des théories de poutre à travers les sections des goujons. Une seconde méthode exploite un élément hexaédrique à 32 nœuds et s’inspire des principes des éléments volume-coque et volume-poutre, avec un seul élément dans l’épaisseur des lamelles et un seul élément dans la section des goujons. Les résultats démontrent que les méthodes proposées dans cette thèse mènent à des outils de modélisation efficaces pour les structures multicouches en bois assemblées par des goujons en bois densifié. Ces méthodes ouvrent également de nouvelles pistes de développements futurs et des perspectives d’application à d’autres types de structuresMultilayered timber structures, assembled using densified wood dowels, represent a sustainable and innovative solution for the construction sector. The development of predictive finite element models requires a solid representation of the geometry for modelling the complex mechanical behaviour of these structures. However, solid models are costly, especially in the context of variability studies and optimization. In this thesis, solid, solid-shell, and solid-beam approaches are developed to obtain accurate models that can be considered as the best compromise. The study of the mechanical behaviour of multilayered timber structures reveals that the layers adopt a shell-like behaviour, while the dowels behave like beams. Higher-order displacement fields through the thickness of the layers and through the cross-section of the dowels are identified. To meet these displacement fields while maintaining a solid representation, two methods have been developed. A first method exploits standard solid elements by applying shell theories through the thickness of the layers and beam theories through the sections of the dowels. A second method uses a 32-node hexahedral element and is inspired by the principle of solid-shell and solid-beam elements, with a single element through the thickness of the layers and a single element through the section of the dowels. The results demonstrate that the methods proposed in this thesis lead to effective modelling tools for multilayered timber structures assembled with densified wood dowels. These methods offer perspectives for future developments and applications to other types of structures
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Naureen, Shagufta. « Top-down Fabrication Technologies for High Quality III-V Nanostructures ». Doctoral thesis, KTH, Halvledarmaterial, HMA, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-117766.
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III-V nanostructures have attracted substantial research effort due to their interesting physical properties and their applications in new generation of ultrafast and high efficiency nanoscale electronic and photonic components. The advances in nanofabrication methods including growth/synthesis have opened up new possibilities of realizing one dimensional (1D) nanostructures as building blocks of future nanoscale devices. For processing of semiconductor nanostructure devices, simplicity, cost effectiveness, and device efficiency are key factors. A number of methods are being pursued to fabricate high quality III-V nanopillar/nanowires, quantum dots and nano disks. Further, high optical quality nanostructures in these materials together with precise control of shapes, sizes and array geometries make them attractive for a wide range of optoelectronic/photonic devices. This thesis work is focused on top-down approaches for fabrication of high optical quality nanostructures in III-V materials. Dense and uniform arrays of nanopillars are fabricated by dry etching using self-assembly of colloidal SiO2 particles for masking. The physico-chemistry of etching and the effect of etch-mask parameters are investigated to control the shape, aspect ratios and spatial coverage of the nanopillar arrays. The optimization of etch parameters and the utilization of erosion of etch masks is evaluated to obtain desired pillar shapes from cylindrical to conical. Using this fabrication method, high quality nanopillar arrays were realized in several InP-based and GaAs-based structures, including quantum wells and multilayer heterostructures. Optical properties of these pillars are investigated using different optical spectroscopic techniques. These nanopillars, single and in arrays, show excellent photoluminescence (PL) at room temperature and the measured PL line-widths are comparable to the as-grown wafer, indicating the high quality of the fabricated nanostructures. The substrate-free InP nanopillars have carrier life times similar to reference epitaxial layers, yet an another indicator of high material quality. InGaAs layer, beneath the pillars is shown to provide several useful functions. It effectively blocks the PL from the InP substrate, serves as a sacrificial layer for generation of free pillars, and as a “detector” in cathodoluminescence (CL) measurements. Diffusion lengths independently determined by time resolved photoluminescence (TRPL) and CL measurements are consistent, and carrier feeding to low bandgap InGaAs layer is evidenced by CL data. Total reflectivity measurements show that nanopillar arrays provide broadband antireflection making them good candidates for photovoltaic applications. A novel post etch, sulfur-oleylamine (S-OA) based chemical process is developed to etch III-V materials with monolayer precision, in an inverse epitaxial manner along with simultaneous surface passivation. The process is applied to push the limits of top-down fabrication and InP-based high optical quality nanowires with aspect ratios more than 50, and nanostructures with new topologies (nanowire meshes and in-plane wires) are demonstrated. The optimized process technique is used to fabricate nanopillars in InP-based multilayers (InP/InGaAsP/InP and InP/InGaAs/InP). Such multilayer nanopillars are not only attractive for broad-band absorption in solar cells, but are also ideal to generate high optical quality nanodisks of these materials. Finally, the utility of a soft stamping technique to transfer free nanopillars/wires and nanodisks onto Si substrate is demonstrated. These nanostructures transferred onto Si with controlled densities, from low to high, could provide a new route for material integration on Si.QC 20130205
Livres sur le sujet "Multilayered timber structures"
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Dmitrii, Lozovanu, et SpringerLink (Online service), dir. Optimization and Multiobjective Control of Time-Discrete Systems : Dynamic Networks and Multilayered Structures. Berlin, Heidelberg : Springer-Verlag Berlin Heidelberg, 2009.
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Bianconi, Ginestra. Synchronization, Non-linear Dynamics and Control. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198753919.003.0015.
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This chapter is entirely devoted to characterizing non-linear dynamics on multilayer networks. Special attention is given to recent results on the stability of synchronization that extend the Master Stability Function approach to the multilayer networks scenario. Discontinous synchronization transitions on multiplex networks recently reported in the literature are also discussed, and their application discussed in the context of brain networks. This chapter also presents an overview of the major results regarding pattern formation in multilayer networks, and the proposed characterization of multivariate time series using multiplex visibility graphs. Finally, the chapter discusses several approaches for multiplex network control where the dynamical state of a multiplex network needs to be controlled by eternal signals placed on replica nodes satisfying some structural constraints.
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Brataas, A., Y. Tserkovnyak, G. E. W. Bauer et P. J. Kelly. Spin pumping and spin transfer. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198787075.003.0008.
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This chapter discusses the interaction between currents and magnetization, which can cause undesirable effects such as enhanced magnetic noise in read heads made from magnetic multilayers. While most research has been carried out on metallic structures, current-induced magnetization dynamics in semiconductors or even insulators has been pursued as well. These issues have attracted many physicists because, on top of the practical aspects, the underlying phenomena are fascinating. Berger and Slonczewski are acknowledged to have started the field in general through their introduction of the concept of current-induced magnetization dynamics by the transfer of spin. The reciprocal effect, i.e., spin pumping, was expected long ago, but it took some time before Tserkovnyak et al. developed a rigorous theory of spin pumping for magnetic multilayers, including the associated increased magnetization damping.
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Elliott, Mark, et Robert Thomas. Public Law. Oxford University Press, 2020. http://dx.doi.org/10.1093/he/9780198836742.001.0001.
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Public Law is an advanced text that comprehensively covers the key topics in the field of public law. The book presents an analysis of the law and institutions of public law, and places the legal issues within the wider socio-political context within which the constitution operates. Three key themes that permeate the content allow readers to approach the subject in a structured way. The key themes are the significance of executive power in the contemporary constitution and the challenge of ensuring that those who wield it are held to account, the shift in recent times from a political to a more legal constitution and the implications of this change, and the increasingly ‘multilayered’ character of the British constitution.
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Elliott, Mark, et Robert Thomas. Public Law. Oxford University Press, 2017. http://dx.doi.org/10.1093/he/9780198765899.001.0001.
Texte intégralRésumé :
Public Law is an advanced text that comprehensively covers the key topics in the field of public law. The book presents an analysis of the law and institutions of public law, and places the legal issues within the wider socio-political context within which the constitution operates. Three key themes that permeate the content allow readers to approach the subject in a structured way. The key themes are the significance of executive power in the contemporary constitution and the challenge of ensuring that those who wield it are held to account, the shift in recent times from a political to a more legal constitution and the implications of this change, and the increasingly ‘multilayered’ character of the British constitution.
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Eckes, Christina, Päivi Leino-Sandberg et Anna W. Ghavanini, dir. The Dynamics of Powers in the European Union. Hart Publishing, 2024. http://dx.doi.org/10.5040/9781509971626.
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Separation of powers is the time-tested touchstone of the legitimate exercise of power in modern democracies. This collection examines decision-making in the EU’s multilayered and polycentric constitutional structure through this lens. The focus on separation of powers reveals how strong executive powers collaborate in the EU as a single source of public power, which is not sufficiently counterbalanced by parliaments or the judiciary. The collection explores 3 policy fields marked by crisis: the economic and monetary union (EMU), migration, and trade. Drawing on expertise from across these sectors, with a strong conceptual thread linking all the contributions, this important work illustrates how different branches of government co-determine each others’ powers.
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Reimitz, Helmut. Contradictory Stereotypes. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199394852.003.0006.
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Entering the postclassical world, this chapter examines what happened when Roman power structures were inhabited by so-called barbarian, do-nothing kings. Focusing in particular on the multilayered depiction of Chilperic I (c. 539–589) in the Histories of Gregory of Tours, the chapter shows that the Merovingian kings are rebuked not only for barbarous and un-Christian behaviors but also, surprisingly, for being ‘too Roman’. These critiques originate with local political and ecclesiastical elites, who feared a destabilizing displacement of their own authority and jurisdiction as the Merovingians strove to centralize their state after the model of Rome. Once again, therefore, foreignness of various kinds becomes the marker of a bad king, this time reflecting the interplay between the complex sociopolitical developments of the sixth century and the Roman imperial tradition.
Chapitres de livres sur le sujet "Multilayered timber structures"
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ElMahgoub, Khaled, Fan Yang et Atef Elsherbeni. « Multilayered Periodic Structures ». Dans Scattering Analysis of Periodic Structures Using Finite-Difference Time-Domain Method, 61–91. Cham : Springer International Publishing, 2012. http://dx.doi.org/10.1007/978-3-031-01713-1_5.
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Liu, Wentao, Zongyi Shao, Ying Meng, Zongshu Li et Zheng Sui. « Hot-Pressing Sintering and Analytical Characterization of Coated Particle-Dispersed Fuel Pellets ». Dans Springer Proceedings in Physics, 1095–103. Singapore : Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_92.
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AbstractCoated particle-dispersed fuel pellets have the characteristics of high thermal conductivity and multilayer protection against fission products, which are an important component of ATF fuel. In this paper, by carrying out research on the dressing process of TRISO particles, it is realized that SiC powder completely encapsulates TRISO particles. The hot-pressing sintering method was used to study the influence of different sintering aids, different hot-pressing sintering holding time, different hot-pressing sintering temperature, different hot-pressing sintering pressure and different powder particle size on the density of pellets. The power with a particle size of 10nm is sintered at 3% sintering aid, 1690 ℃, 1.5h holding time, 80 MPa vacuum hot pressing, and a full ceramic micro-encapsulated fuel core with a relative density of 95% or more is prepared, and the internal particle structure is complete.
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Darbinyan, Asya. « “Special Kind of Refugees” : Assisting Armenians in Erzincan, Bayburt, and Erzurum ». Dans Documenting the Armenian Genocide, 103–22. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-36753-3_6.
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AbstractOver 200,000 Armenians became displaced persons during the First World War as a result of the war on the Caucasus battlefront and the genocide in the Ottoman Empire. Drawing upon previously untapped material from Armenian, Georgian, and Russian archives and libraries, this chapter reflects on that mass population movement, examines the resulting humanitarian crisis, and analyzes Armenian refugee relief work. It shows that because of the complex structure of the empire, the nature of humanitarianism in imperial Russia was multilayered and heterogeneous. To control and coordinate the large population movements in the eastern occupied regions of the Ottoman Empire and in Transcaucasia, imperial Russian authorities needed to organize and facilitate proper registration of refugees: a challenging task in times of war, epidemics, and humanitarian crises. They also had to define who was and who wasn’t a refugee.This chapter reflects on Russian military and civil authorities’ responses to the refugee movements in newly occupied areas of the Ottoman Empire—Erzincan, Bayburt, Erzurum— in summer 1916 and emphasizes the new directions and challenges of relief work. It shows how the relief committees and agencies adjusted to the changing dynamics on the warfront and in the occupied regions and shaped their relief strategies and methods according to the emerging needs of various categories of refugees. Hence, it contributes to key discussions in interdisciplinary research on refugees and to the emerging literature on relations between humanitarianism and imperialism. Finally, it offers a more nuanced understanding of Armenian-Russian relations in this period.
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Franco, Renan Louro Cardoso, Carsten Eichert, Charlotte Lücking, Lars Biermann, Mandy Paschetag et Stephan Scholl. « revolPET® : An Innovative “Back-to-Monomer” Recycling Technology for the Open Loop Value Chain of PET and Polyester Composite Packaging and Textiles ». Dans Lecture Notes in Mechanical Engineering, 175–83. Cham : Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-28839-5_20.
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AbstractNowadays there is a need for innovative solutions for composite materials in the packaging and textile sectors. These are formed by multilayer structures that improve technical performance however complicates recycling. Consequently, they are mostly sent to energy recovery or downgrade recycling processes. To avoid this, new recycling technologies are needed.The innovative “back-to-monomer” recycling technology “revolPET®” represents a solution for this challenge. In the process, the polyethylene terephthalate (PET) is selectively depolymerized to recover the monomers ethylene glycol (EG) and terephthalic acid (TA) for a new PET production. By an alkaline hydrolysis, the PET reacts continuously with a strong base in a twin-screw extruder. The average residence time in the extruder is less than one minute with a process yield up to 95%. Due to the mild depolymerization conditions, the other polymers remain chemically unchanged and can be easily separated. The produced monomers are regained in virgin quality and can achieve a 33% reduction on the greenhouse gases emissions if compared with the crude oil production route.In this contribution, the technology on a pilot scale as well as the results of the first scale-up investigations are presented and discussed with respect to technical maturity and environmental benefit.
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Stanchina, Gabriella. « 2. Mou Zongsan and the Critique of the Cognitive Mind ». Dans The Art of Becoming Infinite, 69–112. Cambridge, UK : Open Book Publishers, 2025. https://doi.org/10.11647/obp.0442.02.
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The second chapter analyzes in depth Mou’s Critique of the Cognitive Mind. As the most mature work characterizing his earlier fifteen years of endeavor in logic and epistemology, it embraces the works of Russell, Wittgenstein, and Whitehead as reference points. Furthermore, even the title itself implies a close commitment to Kant’s Critique of Pure Reason. The work serves as a bridge between Mou’s early interest in logic and language and the subsequent moral metaphysical development of his thought. In describing the inner life of the human mind, Mou skillfully interweaves Chinese and Western thought, which is a feature of the rest of his philosophical writings. In Critique of the Cognitive Mind, Mou shifts his attention toward the internal and subjective processes of the mind, maintaining the search for an objective and universally valid foundation as a tension that runs through the entire process of ego formation. The method Mou adopted to forge his original philosophy of mind distances itself from the multilayered architecture of Kant’s first Critique. Rather, it recalls a phenomenological quest, starting in medias res from the interdependence of perception and reality and accompanying the living autopoietic evolution of the mind. Given this mutual connection between mind and the world, Mou affirms that, even at the most basic level of cognitive interaction, reality is not scattered as autonomous fragments waiting to be set in order by the mind through the law of causation. On the contrary, it reveals itself as a unified whole, with a cohesive structure and an inherent meaning. According to Mou, the most basic expression of the mind is perception, that is, a self-aware dynamism of manifestation, structurally intertwined with the flux of the universe. We can perceive the originality of Mou’s approach here, reminding us that the majority of previously discussed Western theories of mind share an unformulated assumption—knowledge is the primary modality of our relationship with reality. According to this assumption, we learn about the world through basic mental operations of grasping, defining, and exploring its nature. Therefore, the primeval approach to reality is a disengaged inquiry into an object that appears in its otherness and externality. Mou challenges the elementariness of this experience by arguing that the human mind is always practically engaged in reality. Active participation and interest in the world imply that cognitive endeavors are only complete when guided by a moral, practical, and holistic approach to reality. Through this lens, the mind reveals itself as an unceasingly active dynamism. The prominence conferred on activity, dynamicity, and creativity is the cornerstone of Mou’s investigation of the mind and subjectivity. According to Mou, the mind is not an objective entity that we can examine and locate inside our brain, but a self-transcending movement of manifestation. The strict interrelation between the flux of the phenomenal world and the mind, as the creative locus of its manifestation, defines the task and responsibility of the mind. Its lively function is to preserve the integrity of this manifestative event and provide an ultimate place for its object to settle and disclose itself as an objective and universal totality of meaning. To provide an objective foundation for the perceived phenomenal word, the mind is able to spontaneously emanate structuring frames, such as space and time at the level of imagination, and finally the logical self, which synthesizes and produces all categories. The self-reflection of the logical self through which the mind, returning to itself, possesses and guarantees its own objectivity, is the supreme achievement of a cognitive mind. For Mou, the dynamism of the mind is a rhythmic succession of self-limitation and transcendence over those very limits. In the search for objectivation, the mind molds and fixes content through spatio-temporal and logical frames. This graspable, solidified content, which is the product of the self-limitation of the mind, should be liquefied. This is because the mind transcends and dissolves its partial cognitive products to restore its structural dynamicity and creativity. This capacity of mind to continuously emerge from its self-limitation is termed “intuition” by Mou. However, from his previous studies on logics, Mou derives that “the cognitive mind, both in self-limitation and in springing out, cannot obtain a final principle through which the system of knowledge can be completely verified.”[ Mou Zongsan (牟宗三), Renshi xin zhi pipan. 認識心之批判 (Critique of the Cognitive Mind), 2 vols, II, 560, in Mou Zongsan xiansheng quanji. 牟宗三先生全集 (Complete Works of Mou Zongsan), vols XVIII–XIX, Taipei: Lianhe baoxi wenhua jijin hui, 2003.] The faculty of understanding, through the emanation of forms a priori, becomes progressively wider but cannot achieve full verification without exception, that is, a concrete universality. Only intuition, in the very instant of eliminating any boundary, accomplishes full verification in a flash, leaving us with a glimpse of the infinite completeness of the universe. Depending on the self-limitations from which it emerges, intuition is transient and elusive. This is the final and unsurpassable boundary of the cognitive mind. However, the possibility of infinite self-realization adumbrated in intuition allows us to hypothesize the existence of a higher level of the mind. This mind should have a trans-cognitive, ontological character, being simultaneously both subjective and substantive. It will be able to unfold itself in everything and its self-knowing will be the same as that of its infinite being. The conclusion of Mou’s cognitive research is, therefore, that epistemology is ultimately incomplete and unsatisfying because it cannot find in itself the universal principle and motive of the mind and universe. In the rest of his works, Mou searches in Chinese tradition for another way to pursue truth. The exploration of this vertical, moral-metaphysical approach represents Mou’s greatest and most original contribution to philosophy of the mind. The mind cannot be reduced to an object of knowledge because it is an ever-flowing process of manifestation. What is manifested through one’s mental process is the world as a meaningful and interrelated totality. The mind can evolve through the rhythmic processes of self-limitation and self-transcendence. The ultimate aim of our inner life—realizing the full synthesis of mind and reality, subject, and object—is unattainable at the mere cognitive level.
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Surowitz Eugene J. « Analytic General Intelligence : Constructing Space+Time for the Lowen Model ». Dans Frontiers in Artificial Intelligence and Applications. IOS Press, 2011. https://doi.org/10.3233/978-1-60750-959-2-365.
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The Lowen Model presents a graph of cycles among macroscopic processes of the mind. Developing of that model by adopting the feedback loop as the fundamental element, we can assemble various basic structures via space+time diagrams which can be used to form large, extended systems. The introduction of diagrammatic methods drastically eases the development and expression of structural concepts. Multilayer systems are formed from the basis elements by concatenating or gluing along common links to make them of arbitrary scale. Different types of multilayered systems are generated by the choice of which sections of the basis elements are glued together. A focus-bilens multilayer contains a middle layer of nodes that are not directly connected to each other. Generating graphs within this layer is hypothesized to provide a sufficient mechanism to implement the Lowen model's capacities; their dynamics are not addressed here.
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S. Bhat, Ramesh. « Fabrication of Multi-Layered Zn-Fe Alloy Coatings for Better Corrosion Performance ». Dans Liquid Metals [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99630.
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Zn-Fe compositionally modulated multilayer alloy (CMMA) coatings were developed onto low carbon steel from acid sulphate bath; and their corrosion resistance was calculated using Tafel polarization and impedance methods. The deposit layers were formed galvanostatically by single bath technique (SBT), using square current pulses. An optimal configuration for the growth of most corrosion resistant Zn-Fe coating was proposed and discussed. At maximum switching cathode current density (SCCD) (2.0–5.0 A dm−2), the deposit with 300 layers showed ~43 times superior corrosion resistance than the same thickness of monolayer coating. The improved corrosion resistance of multilayered coatings is due to small change in iron content, leading to change the phase structure of the alternate-layers of the alloy coatings. The surface morphology and structure of film and roughness of the deposit were assessed using Scanning Electron Microscopy and Atomic Force Microscopy. Thus, superior corrosion resistance of Zn-Fe multilayer coatings was used for industrial applications including defense, machinery and automobile etc.
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Erlingsson S. « Numerical modelling of unbound granular materials in thin pavements structures ». Dans Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2005. https://doi.org/10.3233/978-1-61499-656-9-1699.
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New pavement design methods are under development where the aim is to predict functional and structural conditions of the road over time. To be able to take advantage of these new design methods a better understanding of the ability to calculate the response of pavement structures due to vehicle load is needed were the mechanical properties of the constituent materials are properly presented. For thin pavement structures the granular materials, base and subbase layers, play an essential role in the overall structural performance. However they show a complex elasto-plastic behaviour under external loading. An instrumented thin surface dressed pavement structure has been tested in accelerated testing by using a Heavy Vehicle Simulator (HVS). The response of the structure due to traffic loading was measured and thereafter two different numerical techniques used to predict the structural behaviour, the Multilayer Elastic Theory (MLET) and the Finite Element (FE) method. Both linear and nonlinear elastic analyses have been carried out to simulate the response of the structure. It was found that analyses where the nonlinear base behaviour is taken into account gave better agreement with measurements compared to a linear elastic analyses. Based on the calculated response of vertical strain in the pavement structure as well as from results from Repeated Load Triaxial (RLT) testing a simple power law function is used to estimate the development of rutting in the pavement structure and compared to actual measurements. Good agreement was found between the actual measurements and the calculations.
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Yue, Zhi. « An experimental study of column connections in Chinese multilayer timber structure heritages ». Dans Structural Analysis of Historical Constructions : Anamnesis, Diagnosis, Therapy, Controls, 1425–32. CRC Press, 2016. http://dx.doi.org/10.1201/9781315616995-194.
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Kelly, M. J. « The two-dimensional electron gas ». Dans Low-Dimensional Semiconductors, 102–33. Oxford University PressOxford, 1995. http://dx.doi.org/10.1093/oso/9780198517818.003.0005.
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Abstract In this chapter, we describe the two main systems that have driven research into low-dimensional physics over the last two decades. The metal-oxide-semiconductor field-effect transistor (MOSFET) was patented over 50 years ago, but the technology of oxidizing a Si surface in a way that left few remaining unsatisfied bonds (which have undesirable electrical activity) was perfected only in the 1960s, just in time for its exploitation in modern integrated circuitry where it has been the key active device (Nicollian and Brews 1982). High electron mobilities in GaAs-AlGaAs multilayers with selective doped layers were discovered in 1978 (Dingle et al. 1978), and this selective doping principle has become incorporated into the high-electronmobility transistor (HEMT), at present the lowest noise transistor available, and used in amplifying weak signals, with the particular domestic application of receiving television signals from space. The commercial success of these two structures has increased the levels of research investment in multilayer structures more generally. In both structures, we have electrons that are ‘trapped’ at an interface, but are free to move (with metallic-like conduction properties) along the interface. The physics of these electron systems has been of wide interest, while attempts to improve the performance of these structures as devices have led to many of the new materials and device technologies that we now take for granted. Historically, the Si-Si02 system dominated research in the 1970s (Ando et al. 1982), while the GaAs-AlGaAs heterojunction dominated research in the 1980s. Although most of this book is about III-V epitaxial multilayers, experience with the Si MOSFET set the scene for much of the research that followed.
Actes de conférences sur le sujet "Multilayered timber structures"
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Kang, Yilin, Naixing Feng, Yuxian Zhang, Xiaoli Feng, Huan Wang, Jiuyang Fan, Lixia Yang et Zhixiang Huang. « Analysis of Transmission Coefficients in Multilayer Media Structures Using Scale Compressed Finite-Difference Time-Domain Method ». Dans 2024 Photonics & Electromagnetics Research Symposium (PIERS), 1–4. IEEE, 2024. http://dx.doi.org/10.1109/piers62282.2024.10618214.
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Karimi, Arash, Erica Heller, Zachery B. Harris et Hassan Arbab. « Measurement of sub-wavelength coating thicknesses in multilayered carbon-fiber structures by sparse deconvolution of polarized terahertz time-domain pulses ». Dans Terahertz, RF, Millimeter, and Submillimeter-Wave Technology and Applications XVIII, sous la direction de Laurence P. Sadwick et Tianxin Yang, 38. SPIE, 2025. https://doi.org/10.1117/12.3045073.
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Joensen, K. D., P. Gorenstein, P. Høghøj et F. E. Christensen. « X-ray Supermirrors : Novel multilayer structures for broad band hard X-ray applications ». Dans Physics of X-Ray Multilayer Structures. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/pxrayms.1994.tha.3.
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With the increased availability of hard X-ray (≥ 20 keV) synchrotron sources and a concurrent wish for hard X-ray telescopes. the need for hard X-ray optics has become considerable. For some applications crystals and periodic multilayers are desirable; for others the bandwidth of these may be too narrow. A wider bandwidth can be obtained by using total reflection from heavy elements. This approach. however, is impractical for harder X-rays since it is limited by the inverse proportionality between the critical angle of total reflection and the energy. One solution to this broad-band reflection problem may be the supermirror: a multilayer structure where the bi-layer thickness is gradually changed from top to bottom. In such a structure radiation with different wavelengths will have the criteria for constructive interference fulfilled at different depths in the multilayer. If the bi-layer thicknesses are changed sufficiently slowly. simultaneous diffraction of a continuum of X-ray energies can be obtained. The multilayered supermirror was originally designed for neutron applications1 such as increasing the throughput of guide-tubes. For neutrons, where absorption is extremely low for most materials. reflectivities up to95 can be obtained in a continuous band up to 3 times the critical angle or energy2. For X-rays. the absorption is considerably larger and this strongly influences the performance of the X-ray supermirror.
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MacGowan, B. J., S. Mrowka, T. Barbee, L. B. Da Silva, D. C. Eder, J. A. Koch, L. Pan, J. Underwood et P. E. Young. « Investigation of the effect of large x-ray fluences on multilayer structures ». Dans Physics of X-Ray Multilayer Structures. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/pxrayms.1992.mc1.
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The use of multilayer mirrors in x-ray laser cavities is complicated by extremely intense optical and x-ray pulses that damage the multilayer mirror before it has done its job. The issue of damage of the mirror by x-ray emission from the plasma amplifier has been studied experimentally using short duration (500 psec) bursts of soft x-rays from a laser produced Au plasma. Different damage/failure mechanisms have been observed and identified for Mo/Si, MoSi2/Si, W/C, WC/C and Cr3C2/C multilayers and damage thresholds quantified. The effect of the x-ray flux on the peak mirror reflectivity together with the position and shape of the bandpass has been resolved both temporally and spectrally. The shape of the bandpass has been fitted to solutions to the Fresnel equations for aperiodic stacks in order to infer the time history of the stack. Rapid diffusion of Mo into Si in Mo/Si multilayers has been observed to occur in time scales of order 70 psec.
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Rosen, R. S., D. G. Stearns, M. A. Viliardos, M. E. Kassner et S. P. Vernon. « Interdiffusion Kinetics in Mo/Si Multilayers ». Dans Physics of X-Ray Multilayer Structures. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/pxrayms.1992.tha2.
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Mo/Si multilayers (ML's) are attractive for x-ray optics due to the relatively high associated reflectivity. However, the reflectivity is known to decrease with the formation of diffuse interlayer regions resulting from interdiffusion at the Mo-Si interfaces [1-2]. Most of the previous studies have reported interdiffusion coefficients [1-5] and effective activation energies [2-4] over a range of temperature assuming that the interdiffusion coefficient is invariant with annealing time. At temperatures of 560-580 °C, hexagonal molybdenum-disilicide (h-MoSi2) grows with a square-root time dependence at the Mo-Si interface [6]. This suggests diffusion-limited growth with a time-invariant interdiffusion coefficient. However, at temperatures of 300-400 °C, the interlayer structure is known to change with annealing time from amorphous to crystalline [1-3], suggesting the possibility that the rate-controlling mechanism(s) for interdiffusion may also change with annealing time and/or temperature. Therefore, it is the objective of this study to perform a series of annealing treatments of Mo/Si ML's at temperatures lower than those previously reported to determine the Mo-Si interdiffusion kinetics as a function of time.
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Freeman, R. R. « Crystal Balls and Technology ». Dans Physics of X-Ray Multilayer Structures. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/pxrayms.1994.mc.1.
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Just what direction lithography will take in the future is the product of advances in technology times the wishes of the user community. Since all we can influence is technology, we have to prepare ourselves for disappointments in the final answer.
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Walton, C., et J. B. Kortright. « Effect of substrate bias on roughness of Mo/SiO2 multilayers ». Dans Physics of X-Ray Multilayer Structures. Washington, D.C. : Optica Publishing Group, 1994. http://dx.doi.org/10.1364/pxrayms.1994.mc.10.
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Multilayers of Mo and SiO2 were grown by magnetron sputtering with layer d-spacings of 20-40Å and fraction Mo about γ= 0.4. Dc biases of -120V were applied during the entire deposition time for some samples. Layer roughness was studied by specular and non-specular x-ray diffraction. In the non-specular scans the bias was observed to increase the peak-background ratio from about 102 to about 103. This is interpreted to show a decrease in interface roughness due to the bias.
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Ferraiuolo, Michele, Oronzio Manca et Aniello Riccio. « A Procedure to Evaluate the Thermal Response of a Multilayered Thermal Protection System Subjected to Aerodynamic Heating ». Dans ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12327.
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Next generation reusable re-entry vehicles must be capable of sustaining consistent repeated aero-thermal loads without damage or deterioration. This means that such structures must tolerate the high temperatures engendered by aero-thermal re-entry fluxes due to the establishment of a hypersonic regime over the body. Thermal Protection Systems (TPS) are used to maintain a reusable launch vehicle’s structural temperature within acceptable limits during re-entry flights; that is, internal temperature should not overcome the temperature limit use of the internal structure. TPS are usually composed by several layers made of different materials. Heat transfer through a multilayer insulation during atmospheric re-entry involves combined modes of heat transfer: heat conduction through the solid, heat radiation to the outer space etc. In the frame of TPS design activities a procedure based on one dimensional analytical solutions of transient nonlinear analyses has been developed in order to estimate the temperature variation with time and space of a multilayered body subjected to aerodynamic heating inside a radiating space. Since internal temperature values of TPSs of re-entry vehicles cannot exceed certain values, that procedure allows to quickly evaluate those temperature values and to preliminary size layer thicknesses before preparing and performing Finite Element analyses.
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Xie, Hui, Keli Sun, Ettore Mirto, Joe Gremillion, Sarwa Tan, Kent Harms, Jianguo Liu et Yao Feng. « An Advanced Ultrahigh-Definition Directional Electromagnetic Propagation Logging Tool for Mapping While Drilling and Multilayered Formation Evaluation ». Dans 2022 SPWLA 63rd Annual Symposium. Society of Petrophysicists and Well Log Analysts, 2022. http://dx.doi.org/10.30632/spwla-2022-0050.
Texte intégralRésumé :
Logging-while-drilling (LWD) electromagnetic (EM) propagation measurements and interpretation techniques have been widely used for reservoir boundary detection in geosteering applications. With more formation information provided near the wellbore during drilling operations, it can still be challenging to obtain an accurate resistivity formation profile in complex scenarios such as multilayered geological structures. This is particularly evident in in high-angle and horizontal (HA/HZ) wells drilled in thin-laminated formations. This paper will present a newly developed LWD mapping-while-drilling service to enable advanced geosteering and formation evaluation in multilayered geological structures. A new electromagnetic multilayer mapping-while-drilling (MLM) tool was designed to measure a complete set of electromagnetic responses in complex formation geometry and anisotropy environment. This tool consists of an industry’s first combination of multi-spaced axial, tilted, and transverse current loop-antennas operating in a multifrequency configuration. The tool measurements are designed so that formation resistivity and geological structure change can be observed directly while drilling. The existing tool offers conventional apparent resistivity, symmetrized, and anti-symmetrized directional measurements. The new tool also provides calibrated deep-resistivity channels acquired from tilted-axial array and anisotropy measurements taken from the transverse antenna. These additional data provide deeper formation measurements and demonstrate stronger sensitivity to anisotropy and bed boundaries. Moreover, the tool also generates real-time high-resolution deep-resistivity images while drilling, which could be beneficial in geosteering. Using these various measurements and a series of state-of-the-art interpretation workflows, a full multilayered formation model can be obtained to show bed boundaries, dipping angle, azimuth, formation resistivity, as well as resistivity anisotropy. Within a 35-ft radius around the wellbore, up to 8 formation layers can be reconstructed. High-definition formation property maps are derived on the curtain-section plot to facilitate operation decisions in complex geosteering environments. Furthermore, a vertical resistivity (Rv) log and a horizontal resistivity (Rh) log can be produced along the well trajectory to display the formation profile for petrophysical evaluation purposes. The interpretation application has been optimized so that the solutions can be provided during drilling operations. Some field data examples will be presented to demonstrate the enhanced mapping and formation evaluation capabilities offered by this new LWD directional electromagnetic propagation tool and interpretation workflow in HA/HZ wells. Compared with the existing tools in the industry, which only show the first boundary near the wellbore most of the time, this recent technology provides significantly more formation layering details, especially in the presence of sedimentary changes or geological discontinuities along the drilling path.
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Yadagiri, G., K. K. Goswami, K. S. Gurumurthy, Satyam et K. N. Shankara. « Co-Firing Technology for Buried Resistors ». Dans ASME 2003 International Electronic Packaging Technical Conference and Exhibition. ASMEDC, 2003. http://dx.doi.org/10.1115/ipack2003-35336.
Texte intégralRésumé :
The complexity and performance of the electronic components and systems is increasing and placing greater demands on compact packaging and interconnection technologies. Multilayer thick film technology is one of the important technologies adopted in the miniaturization of electronic systems. Normally only interconnections are made in the intermediate layers. The possibility of fabricating resistors along with interconnections in the intermediate layers using conventional thick film materials using co-firing process has been examined in this paper. Normally multilayer structures are fabricated by printing / drying / firing of each layer separately starting from the bottom most layer (sequential processing). In this process the bottom layers undergo sintering many times. To avoid many firing cycles and to save power and processing time, a study is taken up to examine the effects of co-firing on the multilayer structure with embedded resistors. The results of the study are presented in this paper.
Rapports d'organisations sur le sujet "Multilayered timber structures"
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Rivera-Casillas, Peter, et Ian Dettwiller. Neural Ordinary Differential Equations for rotorcraft aerodynamics. Engineer Research and Development Center (U.S.), avril 2024. http://dx.doi.org/10.21079/11681/48420.
Texte intégralRésumé :
High-fidelity computational simulations of aerodynamics and structural dynamics on rotorcraft are essential for helicopter design, testing, and evaluation. These simulations usually entail a high computational cost even with modern high-performance computing resources. Reduced order models can significantly reduce the computational cost of simulating rotor revolutions. However, reduced order models are less accurate than traditional numerical modeling approaches, making them unsuitable for research and design purposes. This study explores the use of a new modified Neural Ordinary Differential Equation (NODE) approach as a machine learning alternative to reduced order models in rotorcraft applications—specifically to predict the pitching moment on a rotor blade section from an initial condition, mach number, chord velocity and normal velocity. The results indicate that NODEs cannot outperform traditional reduced order models, but in some cases they can outperform simple multilayer perceptron networks. Additionally, the mathematical structure provided by NODEs seems to favor time-dependent predictions. We demonstrate how this mathematical structure can be easily modified to tackle more complex problems. The work presented in this report is intended to establish an initial evaluation of the usability of the modified NODE approach for time-dependent modeling of complex dynamics over seen and unseen domains.
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Russo, Margherita, Fabrizio Alboni, Jorge Carreto Sanginés, Manlio De Domenico, Giuseppe Mangioni, Simone Righi et Annamaria Simonazzi. The Changing Shape of the World Automobile Industry : A Multilayer Network Analysis of International Trade in Components and Parts. Institute for New Economic Thinking Working Paper Series, janvier 2022. http://dx.doi.org/10.36687/inetwp173.
Texte intégralRésumé :
In 2018, after 25 years of the North America Trade Agreement (NAFTA), the United States requested new rules which, among other requirements, increased the regional con-tent in the production of automotive components and parts traded between the three part-ner countries, United States, Canada and Mexico. Signed by all three countries, the new trade agreement, USMCA, is to go into force in 2022. Nonetheless, after the 2020 Presi-dential election, the new treaty's future is under discussion, and its impact on the automo-tive industry is not entirely defined. Another significant shift in this industry – the acceler-ated rise of electric vehicles – also occurred in 2020: while the COVID-19 pandemic largely halted most plants in the automotive value chain all over the world, at the reopen-ing, the tide is now running against internal combustion engine vehicles, at least in the an-nouncements and in some large investments planned in Europe, Asia and the US. The definition of the pre-pandemic situation is a very helpful starting point for the analysis of the possible repercussions of the technological and geo-political transition, which has been accelerated by the epidemic, on geographical clusters and sectorial special-isations of the main regions and countries. This paper analyses the trade networks emerg-ing in the past 25 years in a new analytical framework. In the economic literature on inter-national trade, the study of the automotive global value chains has been addressed by us-ing network analysis, focusing on the centrality of geographical regions and countries while largely overlooking the contribution of countries' bilateral trading in components and parts as structuring forces of the subnetwork of countries and their specific position in the overall trade network. The paper focuses on such subnetworks as meso-level structures emerging in trade network over the last 25 years. Using the Infomap multilayer clustering algorithm, we are able to identify clusters of countries and their specific trades in the automotive internation-al trade network and to highlight the relative importance of each cluster, the interconnec-tions between them, and the contribution of countries and of components and parts in the clusters. We draw the data from the UN Comtrade database of directed export and import flows of 30 automotive components and parts among 42 countries (accounting for 98% of world trade flows of those items). The paper highlights the changes that occurred over 25 years in the geography of the trade relations, with particular with regard to denser and more hierarchical network gener-ated by Germany’s trade relations within EU countries and by the US preferential trade agreements with Canada and Mexico, and the upsurge of China. With a similar overall va-riety of traded components and parts within the main clusters (dominated respectively by Germany, US and Japan-China), the Infomap multilayer analysis singles out which com-ponents and parts determined the relative positions of countries in the various clusters and the changes over time in the relative positions of countries and their specialisations in mul-tilateral trades. Connections between clusters increase over time, while the relative im-portance of the main clusters and of some individual countries change significantly. The focus on US and Mexico and on Germany and Central Eastern European countries (Czech Republic, Hungary, Poland, Slovakia) will drive the comparative analysis.