Bibliografie tematiche / Wood structure / Tesi
Segui questo link per vedere altri tipi di pubblicazioni sul tema: Wood structure.

Tesi sul tema "Wood structure"

Autore: Grafiati
Pubblicato: 4 giugno 2021
Ultima modifica: 10 febbraio 2022

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili

Scegli il tipo di fonte:

Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Wood structure".

Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.

Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.

Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.

1

Kultikova, Elena V. "Structure and Properties Relationships of Densified Wood". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35810.

Testo completo
Abstract (sommario):
The objective of this research was to investigate the effect of applied compressive strain in various environments, on the strength and stiffness of compressed wood samples. It is believed that transverse compression of wood at specific conditions of temperature and moisture will result in improved mechanical properties, which can be attributed to increased density and perhaps other physical or chemical changes.

Specimens of both mature and juvenile southern pine (Pinus taeda) and yellow-poplar (Liriodendron tulipifera) were compressed radially at three different temperature, and moisture content conditions relevant to the glass transition of wood.

Ultimate tensile stress and longitudinal modulus of elasticity were obtained by testing compressed, uncompressed and control samples in tension parallel-to-grain. Strain measurements were performed using laboratory-built clip-on strain gauge transducers. Results of the tensile tests have shown an increase in the ultimate tensile stress and modulus of elasticity after all densification treatments.

Scanning electron microscopy was employed for observing changes in cellular structure of densified wood. Existence of the cell wall fractures was evaluated using image processing and analysis software. Changes in cellular structure were correlated with the results of the tensile test.

Chemical composition of wood samples before and after desorption experiments was determined by acid hydrolysis followed by high performance liquid chromatography (HPLC). The results of the chemical analysis of the wood specimens did not reveal significant changes in chemical composition of wood when subjected to 160 °C, pure steam for up to 8 hours.

The results of this research will provide information about modifications that occur during wood compression and will result in better understanding of material behavior during the manufacture of wood-based composites. In the long run, modification of wood with inadequate mechanical properties can have a significant effect on the wood products industry. Low density and juvenile wood can be used in new high-performance wood-based composite materials instead of old-growth timber.
Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri
2

Donkor, Ben N. "Stem wood structure of four Ghanaian Khaya species". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0004/MQ33365.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
3

Doroudiani, Saeed. "Microcellular wood-fibre thermoplastic composites, processing-structure-properties". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq41016.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
4

Hsu, Ching Yi. "Radiata pine wood anatomy structure and biophysical properties". Thesis, University of Canterbury. Forestry, 2003. http://hdl.handle.net/10092/7202.

Testo completo
Abstract (sommario):
Several important characteristics such as density, acoustic velocity, modulus of elasticity and tracheid dimensions are examined in stemwood, branchwood and rootwood in young (age 3 and 7) Pinus radiata. Stemwood air-dry density decreases little from ground level to the top of the tree falling gradually from 415 kg/m³ to 405 kg/m³. Branchwood air-dry density is higher than stemwood density. The branchwood density is approximately 480 kg/m³ close to the stem and then decreases sharply to ca. 410 kg/m³ near the branch tips. Rootwood density at 12% moisture content is similar to stemwood density ranging between 420 and 405 kg/m³. Density varies from stemroot junction to root tip in lateral roots (420 to 405 kg/m³) but changes little along tap roots (405 kg/m³) In stemwood, the air-dry modulus of elasticity increases from ground level (ca. 2.5-3.5 GPa) to approximately 4 metres (ca. 5.5-6.5 GPa) and then decreases thereafter to 7 metres (ca. 2.5-3.5 GPa). The air-dry MOE of branchwood decreases linearly with tree height up the stem from approximately 4.5 GPa at 1 metre to 3 GPa at 6 metres. Roots are the least stiff part of the tree. The air-dry MOE value decreases along roots from the stem-root junction (ca. 1.9 GPa) to the root tip area (0.5 GPa) in lateral roots, and from 1.4 GPa to 0.4 GPa in tap roots. In stemwood and rootwood the tracheid dimensions change with distance from ground level in both directions with significant different patterns. For stemwood, the tracheid length decreases with height up the stem. The mean tracheid length is approximately 1.70 mm at breast height whereas it is 1.55 mm and 1.40 mm at 2.4 metres and 4.6 metres respectively. Rootwood tracheids are much longer (nearly double) than stemwood tracheids. The tracheid length increases with increasing distances from the stem-root junction. The mean tracheid length adjacent to the stemroot junction area is approximately 2.2 mm whereas for the middle and root tip areas it is 2.6 mm and 3.3 mm respectively. Compression wood is a common feature of stem and branchwood. However, this atypical tissue is absent in roots except in some restricted instances where compression wood extends a short distance from the stem down into the root. Branchwood in green condition can be used to predict volume-weighted stemwood qualities at 12% moisture content when specific conditions are applied (select a straight portion of first branch segment from the largest diameter branch at breast height, R2 = 0.64). However, this approach has little practical appeal as equally good or better correlations can be obtained using Fakopp on standing trees (R2 = 0.75). Therefore future work should focus solely on the use of time of flight instruments such as Fakopp on stemwood.
Gli stili APA, Harvard, Vancouver, ISO e altri
5

Joffre, Thomas. "Structure and Mechanical Behaviour of Wood-Fibre Composites". Doctoral thesis, Uppsala universitet, Tillämpad mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229290.

Testo completo
Abstract (sommario):
Wood fibres have several advantages compared to man-made synthetic fibres: they have high specific stiffness, are renewable, relatively inexpensive, available in industrial quantities and biodegradable. However, to increase and diversify their utilisation, it is necessary to increase the understanding on what controls their mechanical properties. In this work, the hygroelastic behaviour of isolated wood fibres has been investigated using an analytical model and a finite element model based on three dimensional images obtained using synchrotron-based X-ray micro-computed tomography. It was thus possible to show how the cell wall responds to a mechanical load or a change in ambient relative humidity. The wood fibres were then mixed with a biopolymer aiming to produce a cost-efficient, 100% renewable composite material. The microstructure of the produced composites has been characterised using X-ray microtomography and digital image processing. It was for instance possible to measure the moisture-induced swelling of fibres embedded in a polymeric matrix. The experimental results have then been successfully compared with prediction obtained with a finite element model. The length of the fibres inside the composite has also been measured from three dimensional images, aiming to understand how each step of the processing chain is affecting the degradation of the aspect ratio of the reinforcing fibres. The presence of defects inside the composite has also been quantified using X-ray microtomography. The effects of the defects on the tensile strength have been predicted using an analytical model. The results have been compared with the measured tensile strength on each sample, showing that the size and orientation of the critical defect controls the tensile strength of the material. Finally, wood-fibre mats without any matrix material were compressed in the chamber of a microtomographic scanner. Sequential images were taken during the test. Using digital volume correlation, it was possible to calculate the local strain field inside the material. The effects of heterogeneities on the strain field have then been investigated. The applied compressive load resulted in transport of material from high to low density regions.
Gli stili APA, Harvard, Vancouver, ISO e altri
6

Owens, Elis M. "Fungal community structure and functioning in decomposing wood". Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375959.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
7

Feeney, F. "Ultrasonic characterisation of the structure and properties of wood". Thesis, University of Surrey, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300305.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
8

Shi, Jingbo. "Water sorption hysteresis and wood cell wall nanopore structure". Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61782.

Testo completo
Abstract (sommario):
The origin of sorption hysteresis in the wood-water system is still under debate. In this study, cell walls are considered as micro-mesoporous materials and capillary condensation in the entire hygroscopic region is proposed as an alternative sorption mechanism. Initially, the pore connectivity was investigated by observing five experimentally generated hysteresis patterns at 25 and 40oC. Consistent patterns were found for the species-temperature combinations. Further, the satisfactory congruency and wiping-out properties indicate the dominance of independent cell wall pores. After this experimental phase, the geometric interpretations derived from the Preisach model, the mathematical form of the independent domain model, was used tο explain the observed hysteresis patterns. Additionally, a modification to the aforementioned model was suggested that involves a numerical implementation, which avoids the use of unknown parameters. The low prediction errors and well-maintained wiping-out property support the suitability of our approach. In the next phase, grand canonical Monte Carlo (GCMC) technique was applied in a simplified wood-water system to simulate sorption isotherms and hysteresis at 25 and 40°C. In the simulation system, wood is represented by a cell wall model that is composed of solid substances and evenly distributed independent cylindrical nanopores with sizes in the range of 0.6 – 2.2nm. Two types of pore-wall compositions regarding polysaccharides and lignin have been considered. The hydroxyl groups are modeled as negative energy pits attached to walls whereas water is represented by the SPC/E model. Results demonstrated that hysteresis can be well explained by the existence of metastable states associated with capillary condensation and evaporation of water in cell wall pores. The alternative sorption mechanism driven by capillary condensation is also strongly supported by the simulation. In the last phase, the cell wall pore size distributions in the hygroscopic range were explored for the three species from a “trial and error” calculation approach. This approach was indirectly examined by comparing derived volumetric strain of cell walls and the density of adsorbed water in the hygroscopic range with literature data. The qualitative agreement indicates the soundness of assumptions made on the cell wall swelling process and proposed calculation procedures.
Forestry, Faculty of
Wood Science, Department of
Graduate
Gli stili APA, Harvard, Vancouver, ISO e altri
9

Uhlin, Karen Ingegerd. "The influence of hemicelluloses on the structure of bacterial cellulose". Diss., Available online, Georgia Institute of Technology, 1990:, 1990. http://etd.gatech.edu/theses/available/ipstetd-11/uhlin%5Fki.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
10

Rotsaert, Frederik A. J. "Structure-function studies on the flavocytochrome cellobiose dehydrogenase from phanerochaete chrysosporium /". Full text open access at:, 2003. http://content.ohsu.edu/u?/etd,18.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
11

Nordin, Lars-Olof. "Wood fiber composites : from processing and structure to mechanical performance". Doctoral thesis, Luleå : Univ, 2004. http://epubl.ltu.se/1402-1544/2004/09/.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
12

Hibberd, Martin Sidney. "The technology and structure of the British wood furniture industry". Thesis, University of Sussex, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323015.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
13

Saumure, Raymond A. "Growth, mutilation, and age structure of two populations of wood turtles, Clemmys insculpta, in southern Québec". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29779.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
14

Howell, Caitlin L. "Understanding Wood Biodegradation through the Characterization of Crystalline Cellulose Nanostructures". Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/HowellCL2008.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
15

Ashaari, Zaidon. "The structure and properties of rattan in relation to treatment with boron preservatives". Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282681.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
16

Griffith, G. S. "Fungal community structure and development in attached angiosperm twigs". Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305126.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
17

Zhou, Yonghui. "Interface optimisation and bonding mechanism of rubber-wood-plastic composites". Thesis, Brunel University, 2018. http://bura.brunel.ac.uk/handle/2438/16095.

Testo completo
Abstract (sommario):
The incorporation of waste tyre rubber into thermoplastics to develop a class of polymer composites with both elastomeric and thermoplastic behaviour has gained a lot of attention and is becoming one of the most straightforward and preferred options to achieve the valorisation of waste tyres. In view of the unique properties rubber possesses and the rapid expansion and versatile application of wood plastic composites (WPC) materials, the inclusion of tyre rubber as raw material into WPC to develop an entirely new generation of WPC, namely rubber-wood-plastic composites (RubWPC), was presumed to be another highly promising solution to turn waste tyres into value-added materials. This research starts with the interfacial optimisation of Rubber-PE composites and WPC by the use of maleated and silane coupling agents, aiming at addressing their poor constituent compatibility and interfacial bonding, thus enabling the optimal design of RubWPC. Chemical, physical and mechanical bonding scenarios of both untreated and treated composites were revealed by conducting ATR-FTIR, NMR, SEM and FM analyses. The contribution of the optimised interface to the bulk mechanical property of the composites were assessed by carrying out DMA and tensile property analysis. The influence of the coupling agent treatments on the in situ mechanical property of WPC was first determined by nanoindentation analysis, which led to a thorough understanding of the interfacial characteristics and the correlation between in situ and bulk mechanical properties. This research focuses on the novel formulation of RubWPC and the understanding of bonding mechanism. Chemical bonding and interface structure studies revealed that interdiffusion, molecular attractions, chemical reactions, and mechanical interlocking were mutually responsible for the enhancement of the interfacial adhesion and bonding of the coupling agent treated RubWPC. The improved interface gave rise to the increase of bulk mechanical properties, while the continuous addition of rubber particle exerted an opposite influence on the property of RubWPC. The composite with optimised interface possessed superior nanomechanical properties due to the resin penetration into cell lumens and vessels and the reaction between cell walls and coupling agents.
Gli stili APA, Harvard, Vancouver, ISO e altri
18

Tank, Jennifer Leah. "Microbial activity on wood in streams : exploring abiotic and biotic factors affecting the structure and function of wood biofilms /". Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-144954/.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
19

Visscher, George E. "Wood Anatomy of Metasequoia - Separation from Glyptostrobus and Function/Structure Considerations". Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/VisscherGH2002.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
20

Figueroa, Michael. "Dynamic Analysis of a Light Wood-Framed Structure during Fire Conditions". Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-theses/777.

Testo completo
Abstract (sommario):
The purpose of this project is to create a theoretical dynamic analysis model to assess the dynamic response of light, wood-framed structures before and after fire conditions. This information is useful for predicting the damage to structural integrity due to a fire. The mass and stiffness matrices used for the dynamic model are derived from a standard residential building created for an existing project at WPI funded through the DHS/FEMA/USFA Assistance to Firefighters Grant program. The damping matrix is derived via the Rayleigh Damping Method using the mass and stiffness matrices obtained through SAP. Then, theoretical impact forces are applied to the developed dynamic model, and the acceleration response is estimated using Matlab. Both acceleration time history and frequency responses are used as the evaluation method. Finally, the dynamic model is integrated with a fire simulation model to investigate the impact of fire conditions on dynamic responses of residential buildings. The results show that frequencies can shift due to the structural degradation due to fire.
Gli stili APA, Harvard, Vancouver, ISO e altri
21

Henman, G. S. "'Shake' defects and wood structure variations in British oaks (Quercus spp.)". Thesis, Bangor University, 1991. https://research.bangor.ac.uk/portal/en/theses/shake-defects-and-wood-structure-variations-in-british-oaks-quercus-spp(124e6162-d6f4-4e61-a985-ad5e4edef257).html.

Testo completo
Abstract (sommario):
The overall aim was to gain information required for improvement of wood quality in British oaks (Quercus robur and petraea). Specific aims were 1) to investigate the nature and incidence of shake in British oaks; 2) to quantify variations in oak wood structure and properties, identifying which characteristics are under genetic control and which associated with growth rate; 3) to make prescriptions for selection and silviculture of oak, with a view to improving wood quality in future British crops. Site surveys (including soil analyses) of 42 woodlands were carried out. An index of severity was devised to standardise shake assessment within individual trees. Wood structure was analysed in oaks from shake-prone and sound woodlands. Associations of wood structure and property variations with genotype and growth rate were analysed in oaks from a seed origin trial. Environmental factors were strongly associated with shake. High shake incidence occurred on sites which gave poor rooting conditions for oak: shallow, nutrient poor soils with low clay content and low calcium availability, and with soil texture and/or site topography leading to seasonal droughtiness or waterlogging. Woodland type (shake-prone or sound) was a stronger influence than tree condition (shaken or sound) on wood structure: oaks from shake-prone woodlands had wider rings, smaller earlywood percentage, larger wide rays and larger earlywood vessel radial diameters. Density, sapwood width, earlywood vessel frequency and proportions of wide rays and of latewood vessels and fibres varied between seed origins; these variables therefore have selection potential for improvement of oak wood quality. Many parameters also varied with growth rate, and earlywood vessel radial diameter was strongly associated with current ring width. A model of shake development is proposed in which various predispositions (structural weaknesses) and triggers (mechanical stresses) influence a tree over time. It is proposed that predispositions are caused by environmental factors at the time of wood formation, resulting in physiological stress or cambial damage. Genotype may modify response or susceptibility to environment. Predispositions may be extended by secondary weakening. Triggers of shake are thought to be natural internal growth stresses supplemented by the action of external forces (such as wind). Recommendations are made for site choice and silviculture of future British oak crops.
Gli stili APA, Harvard, Vancouver, ISO e altri
22

Mandlekar, Neeraj Kumar. "Integration of wood waste to develop multifunctional fully biobased textile structure". Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I062/document.

Testo completo
Abstract (sommario):
Les textiles jouent un rôle important dans notre vie quotidienne. La plupart des fibres textiles et des tissus sont fabriqués à partir de polymères à base de pétrole, des matériaux inflammables et potentiellement dangereux. Afin de conférer le caractère ignifuge aux fibres textiles; entre autres, les composés halogénés sont plus efficaces et largement utilisés pour améliorer le comportement ignifuge des matières textiles. Cependant, en raison de la toxicité des composés halogénés et de l'épuisement progressif des ressources pétrolières, les communautés scientifiques et industrielles sont obligées de trouver des solutions alternatives. Par conséquent, on s’intéresse de plus en plus aux ressources durables, en particulier au développement de systèmes ignifugeants fabriqués à partir de ressources biologiques et respectueux de l’environnement non halogénés. Dans le contexte de l’utilisation de ressources biologiques, une attention particulière a été appelée pour la biomasse. Après la cellulose, la lignine est le deuxième polymère de biomasse le plus abondant et le principal à base d'unités aromatiques. En particulier, la lignine est avantageuse car c’est un coproduit des industries de la pâte à papier et de la fabrication du papier et non une ressource qui nécessite une production spécifique. En fait, sa structure chimique hautement aromatique permet d’améliorer différentes propriétés fonctionnelles telles que la résistance aux UV, l’antioxydant et l’ignifugation des polymères. Récemment, la lignine a fait l’objet d’une grande attention en tant qu’additif retardateur de flamme d'origine biologique en raison de son aptitude élevée à la formation de carbone après la décomposition thermique. Cette capacité de formation de carbone de la lignine en fait un candidat de choix comme source de carbone pour un système intumescent avec un autre additif ignifuge. Lors du chauffage, les matériaux intumescents ignifuges (FR) forment une couche carbonisée cellulaire expansée; agissant comme une barrière physique contre le transfert de chaleur et de masse, qui protège le matériau sous-jacent de l'action du flux de chaleur et de la flamme.Au meilleur de nos connaissances, aucune étude n'a été publiée concernant l'introduction de la lignine en tant que source de carbone dans les structures textiles pour leur conférer des propriétés ignifugeantes. Par conséquent, dans cette étude, la lignine a été introduite dans la structure textile lors de la composition. Cette thèse porte sur le développement de la structure textile ignifuge entièrement biosourcée. Pour atteindre cet objectif, l'approche en plusieurs étapes est adoptée. Dans une première étape, la matrice polymère biosourcée a été sélectionnée pour produire la structure textile et la méthode d’incorporation de la lignine a été étudiée et optimisée. Ensuite, les propriétés ignifuges apportées par la lignine ont été caractérisées et améliorées en ajoutant un additif ignifuge dans les formulations (par exemple, utilisation de sources acides pour développer un système intumescent pouvant améliorer la résistance des textiles au feu). Dans la deuxième phase du projet, la lignine a été combinée à la source d'acide d'origine biologique pour développer une nouvelle génération de structures durables (100% biosourcées) destinées aux marchés du textile. La principale avancée technologique consiste à utiliser et à combiner différents composants biosourcés utilisés dans d'autres industries, telles que l'industrie du plastique, afin de développer des solutions textiles
It has been chosen to study valorization of low-cost industrial lignin as additive in designing the flame retardant (FR) system for polyamide 11 (PA) to develop biobased textile structure. The main focus of this thesis work is to consider lignin as carbon source and introduce in a textile structure in combination with phosphinate salt (FR agent). In the primary study, chemically different industrial lignins were incorporated in PA by extrusion to investigate the charring and fire retardant behaviour of the prepared binary blends. In addition, the introduction of sulphonated lignins significantly reduced the peak of the heat release rate (PHRR) and of the total heat release (THR), and a noticeable increase of the char residue was observed after forced combustion test. In the next approach, lignin was exploited as carbon source in combination with commercially available phosphinate FR (i.e., ZnP and AlP). To achieve this objective, a preliminary study carried out with laboratory grade lignin (LS) combined with ZnP to investigate the thermal stability and fire performance as well as the possible synergy between lignin and ZnP and with the polymer matrix. The results obtained in this study permitted to continue further, the practical implementation of lignin and multifilament production. In the next step, flame retarded blends were developed with direct addition of low-cost industrial lignins (LL and DL) with phosphinate FR. For the systematic understanding, various FR formulations were developed by varying the lignin and FR loading and characterized. Thermal decomposition analysis showed that the presence of lignin decreases the initial decomposition temperature (T5%) due to the decomposition of lignin which starts at a lower temperature region with the evolution of less thermally stable compounds and the maximum decomposition temperature (Tmax) shifts to higher temperature region, at this stage the formation of phenolic, carbonyls, hydrocarbons and CO2 along with phosphinate compounds occurs. Meanwhile, in the condensed phase thermally stable aromatic charred layer is formed because of lignin decomposition and phosphate compounds formation due to the presence of phosphinate metal salt. A higher amount of char residue is obtained when LL combined with ZnP/AlP as compared to the DL and ZnP/AlP blends. It is assumed that, during decomposition of LL, the sulfonate compounds release SO2 and transformed into thermally stable Na2SO4, hence giving rise to the stable char residue. The fire properties were assessed by cone calorimeter tests revealed the combination of lignin and phosphinate FR significantly reduced the PHRR and other fire-related parameters due to the formation of a protective char layer. The presence of lignin not only improve fire retardancy but also reduced the evolution of carbon monoxide (CO). More enhanced fire retardant properties were obtained with LL and ZnP/AlP combination reaches to 10 wt% in ternary blends, which not only promotes char formation but also confer the stability to char in the condensed phase. Furthermore, the most enhanced forced combustion results were obtained with LL and AlP (in particular, PA80-LL10-AlP10). Multifilament yarns were successfully produced for PA-DL-ZnP and PA-LL-ZnP combinations. However, the blends of AlP with lignin were not spinnable because of low compatibility and dispersion level of AlP in the polymer. Optical microscopy and tensile tests were performed to study the physical properties of multifilaments. A double layer (interlock structure) knitted fabrics were developed to evaluate fire behaviour analysis on fabric samples
Gli stili APA, Harvard, Vancouver, ISO e altri
23

Gu, Hongmei. "Structure Based, Two-dimensional, Anisotropic, Transient Heat Conduction model for Wood". Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28938.

Testo completo
Abstract (sommario):
The importance of precise values for the parameters used in heat and mass transfer models has been demonstrated by many research studies. Thermal conductivity values used in previous models are usually empirical and fluctuate. Theoretical analysis and estimations of wood thermal conductivities in the radial and tangential directions were conducted with the geometric models built up from the macro- and micro-structure observations. Theoretically, thermal conductivity in the radial direction is about 1.5 to 2.5 times of the tangential direction for softwood species with moisture content (MC) below Fiber Saturation Point (FSP). When MC is over the FSP, tangential radial thermal conductivity both increase dramatically and are linear function of MC. The two thermal conductivity values are close with a ratio of near one estimated by the model for MC above the FPS. In hardwood species, radial thermal conductivity estimated by the model is 1.5 times of the tangential thermal conductivity. Validation tests for model estimations of thermal conductivities in the radial and tangential directions for three wood species showed the reliability of the geometric models developed in this project. Correlations between the wood thermal conductivity and structure parameters, such as latewood percentage and cell wall percentage, were examined. Linear relationships for the thermal conductivity and average temperature in wood were established in both radial and tangential directions of three wood species. A two-dimensional transient heat conduction model was developed utilizing thermal conductivity values derived from geometric models. The anisotropic material property affect on heat transport in radial and tangential directions was discussed using an assumed situation. The simulation run showed slightly faster heat flow in the radial direction than in the tangential direction due to higher thermal conductivity in the radial direction. Validation tests on practical wood blocks showed the 2D model with the use of theoretical thermal conductivity values can predict good temperature distribution in wood during the heating process. However, in the practical wood samples with curved rings on the cross section, no significant difference was found in the two transverse directions. Mathematica software was introduced in this study for the intense and complicated math calculations and model programming. Mathematica was found to be a powerful technique for solving sophisticated math problems. It had abundant and flexible plotting options for providing optimized presentations for the results. These advantages make Mathematica popular for engineering modeling research.
Ph. D.
Gli stili APA, Harvard, Vancouver, ISO e altri
24

Maryoko, Hadi. "Earthquake Resisting Timber Structure System Composed of Indonesian Engineered Wood Products". Kyoto University, 2013. http://hdl.handle.net/2433/175087.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
25

Li, Ruonan. "Surface properties and pore structure of superheated steam dried paper". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55414.

Testo completo
Abstract (sommario):
Effects of superheated steam drying were determined for surface properties and pore structure of paper, properties which are important in the end use of paper. Two furnishes were investigated, thermomechanical pulp (TMP) and a TMP/kraft pulp blend. Drying of handsheets under matched conditions in air was used as the basis of comparison.
TMP paper dried in superheated steam has a slightly higher surface roughness, by about 0.5 $ mu$m at a roughness around 8 $ mu$m. This difference decreases with drying fluid temperature. It is also reduced by about half after a very light blade coating. Surface roughness of paper from 50/50 TMP/kraft blend is unaffected.
Superheated steam drying reduces substantially the linting propensity of TMP paper, by about 30%-60% depending on the criteria used. Improved lignin softening by higher web temperature from the beginning of drying in superheated steam drying is believed an important mechanism in improving bonding of surface fines and short fibre fragments.
The Z-direction bond strength of TMP paper after surface treatment with water is about 20% higher for sheets dried in steam. Time for water absorption is 100%-150% longer for superheated steam dried TMP paper and contact angle of water is also substantially increased.
Superheated steam drying substantially reduces the volume of micropores of diameter 0.2-0.6 $ mu$m while having no significant effect on larger pores. Thus superheated steam drying affects only the pore structure of the micronetwork. The decrease of micropore volume in superheated steam drying is associated with an increase of Z-direction bond strength and a decrease of light scattering coefficient.
Gli stili APA, Harvard, Vancouver, ISO e altri
26

Tsai, K. T. "An investigation into the fatigue behaviour of wood : Laminates for Wind Energy Converter blade design". Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379572.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
27

Du, Han. "An Extension to Östasiatiska museet ----- transforming from traditional Asian wood structure language". Thesis, KTH, Arkitektur, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-241458.

Testo completo
Abstract (sommario):
There is always a strong character of OKU( which means depth) inside the traditional Japanese wood construction, which fascinating me a lot. My thesis is about study the structure and spatial language and translating traditional language to formulate a space with that quality of depth/ oku.Site is been choose in far east museum in Skeppsholmen, and my the- sis is working on an addition to the original far east museum. As it was ropewalk manufactory early days, long and narrow, it doesn’t have its own identification, that’s why nowadays it’s more like a belonging facility attached to modern museum and being ignored by most citizens.
Gli stili APA, Harvard, Vancouver, ISO e altri
28

Li, Guizhen. "Wood structure and properties of clonal plantlets and seedlings of Pinus radiata". Thesis, University of Canterbury. Plant and Microbial Sciences, 2000. http://hdl.handle.net/10092/5927.

Testo completo
Abstract (sommario):
The ontogeny of vascular cambium and the wood formation in the 8 month-old Pinus radiata have been examined. The results showed that the procambium develops from the subapical meristem parenchyma, which is converted to pro cambial cells by periclinal division about 0.5 mm from the shoot tip. The interfascicular cambium originates from the interfascicular parenchyma, which is also derived from the subapical meristem. Transverse sections show that the interfascicular parenchyma convert to interfascicular cambial cells requires activation by the fascicular cambium. The vascular cambium was established by the fascicular cambium connecting with the interfascicular cambium. Compression wood formation is related to the plantlet's response to stress. The magnitude and distribution of compression wood is related to whether the stem is free-growing, staked vertically, or tied to an inclined stake, the three situations generating 27%, 14% and 49% compression wood as assessed by image analysis of thin sections. Stiffness, density, tracheid length, cell numbers/mm2, and percent cell wall area were tested for plantlets of clones 8 and 31 grown under three treatments. Compared to the free grown plantlets, the angled plantlets were shorter, thinner, contained more compression wood with thicker cell walls and more cells/mm2, and had shorter denser tracheids to formed weaker wood. By contrast the tied plantlets were taller and thinner, having fewer cells/mm2 with each tracheid being longer and less dense (thinner cell walls), but of similar stiffness to the free grown ones. Compression wood was stiffer than opposite wood because of its higher density, and the angled plantlets were weaker than the free and tied plantlets due to their shorter tracheids. Stiffness is related to density in angled plantlets, and related to tracheid length in the free and tied plantlets. Tracheid length is negatively related to density, cells/mm2, and percent cell wall. Density is related to percent cell wall and cells/mm2, and the percent cell wall and cells/mm2 related each other. Stiffness, microfibril angle, density, and maximum crushing strength have been studied for 1 and 2 year-old seedlings from seedlots 10 and 28. The results indicated that stiffness increased and microfibril angle decreased from one year-old to two year-old material. A relationship between maximum crushing strength and density and a negative relationship between stiffness and microfibril angle existed in two years old plantlets. Stiffness and maximum crushing strength related each other in both one and two years old plantlets. Overall, this work proved to be a scoping trial. While the results could have been anticipated in general terms they do provide a useful description of very young wood. The extent of compression wood varied greatly between treatments, but even in the best case (tied) it takes up a significant proportion of the stem cross-section. However, the technical challenges, especially in the measurement of mechanical properties in such small samples remains a formidable challenge.
Gli stili APA, Harvard, Vancouver, ISO e altri
29

Gonzalez, Rubio Hector Larsen David R. "Stand structure development effects on wood quality of Melina (Gmelina arborea roxb.)". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6171.

Testo completo
Abstract (sommario):
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 15, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. David Larsen Vita. Includes bibliographical references.
Gli stili APA, Harvard, Vancouver, ISO e altri
30

Forbes, Craig L. "Competitive strategy and structure in the United States wood household furniture industry". Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-02052007-081246/.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
31

Jackson, Asti Joy. "Structure of Sound". Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/73778.

Testo completo
Abstract (sommario):
This thesis creates a complementarity relationship with the use of timber and concrete as primary structural and accent materials. Key elements of this thesis include (1) The development of a wood latticing system (2) Stairs that posses a strong sculptural language (3) The Lantern, a free standing lobby/box office, clad in wood and glass (4) Circulation towers that accommodate balcony seating. Studies of these elements went through many iterations resulting in over one hundred drawings. Progression of these drawings are directed to the interpretation of building form and the interaction with the site. These concepts are then implemented in the design of a multifaceted music venue located on a hillside in the New River Valley. Minutes from the college town of Blacksburg, Virginia this event complex caters to an array of musical functions. Spaces include The Lantern, which is a multipurpose lobby/lounge, the main auditorium, and an outdoor amphitheater.
Master of Architecture
Gli stili APA, Harvard, Vancouver, ISO e altri
32

Beatini, Salvatore J. "Using DNA fingerprinting to assess genetic structure of the vernal pool amphibian rana sylvatica". Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0428103-153026.

Testo completo
Abstract (sommario):
Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: wood frog; vernal pool conservation; fragmented habitat; Rana sylvatica; DNA fingerprinting. Includes bibliographical references (p. 38-40).
Gli stili APA, Harvard, Vancouver, ISO e altri
33

Burgers, Agnès. "Caractérisations physico-mécaniques de bois "sans défauts" pour la conception mécanique : application aux pins de la région méditerranéenne française". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTS014/document.

Testo completo
Abstract (sommario):
L’utilisation des bois pour des usages structuraux en ingénierie mécanique, sous forme de bois massifs ou éléments reconstitués, suppose une bonne connaissance des propriétés des composants bois élémentaires utilisés. Faute de cela, les bois restent exclus du monde moderne de la conception mécanique.En Languedoc-Roussillon, les pins constituent la ressource forestière principale (30 % des bois sur pieds). La valorisation de cette ressource est un enjeu majeur pour l’interprofession de la filière bois. L’objectif de ce travail de thèse est d’examiner la possibilité de prédire les propriétés de base des bois de pin « sans défauts », à partir de mesures non destructives disponibles. L’étude a été réalisée sur quatre des espèces de pins les plus présentes : pin sylvestre, pin à crochets, pin laricio et pin maritime.Les indicateurs de base retenus sont la densité (obtenue par mesure de masse et de volume), le module spécifique (obtenu par mesure vibratoire) et des indicateurs issus de la spectroscopie proche infrarouge (NIRS). Les propriétés technologiques étudiées sont les neuf constantes de la matrice élastique (obtenues par mesures ultrasonores sur une éprouvette unique), les coefficients de retrait et retraits totaux ainsi que la résistance en rupture en compression axiale (obtenus par les essais normalisés).L’analyse des données permet de construire des modèles prédictifs des propriétés de base, uniques pour l’ensemble des pins étudiés, à partir des indicateurs mesurés sur chaque échantillon de bois « sans défauts ».Il est alors possible d’associer à une pièce de bois donnée, une fiche technique des propriétés utiles à la conception mécanique. Les indicateurs choisis étant facilement mesurables dans le milieu industriel, le transfert de la méthode est envisageable. Chaque pièce de bois d’intérêt (i.e. avec peu de défauts) pourrait être rapidement caractérisée. Associé à une bonne traçabilité (par code barre par exemple) cette démarche permettrait d’identifier clairement chaque pièce et ses propriétés, donnant ainsi la possibilité au concepteur de sélectionner les matériaux les mieux adaptés à ses besoins
Using wood for mechanical engineering as solid wood or glued solid timber (or glued laminated timber) requires a good knowledge of the properties of each elementary piece. Due to this lack of knowledge, woods are still not used in modern mechanical design.In the Languedoc-Roussillon French region, pines are the dominant forest resource (approx. 30 % of standing wood). The development of this resource is a major interest for the inter-branch organisation. The aim of this PhD work is to examine the possibility to predict basic useful properties of pine clear wood, based on available non-destructive methods. The study has been made on four of the most present species: Laricio black pine, Maritime pine, Mountain pine and Scots pine.Basic relevant indicators are the density (obtained by mass and volume measurements), the specific modulus of elasticity (obtained by vibrational measurements) and indicators from Near Infrared Resonance Spectroscopy (NIRS). Technological properties are the nine components of the elastic matrix (obtained by resonant ultrasonic measurements on a single specimen), hygroscopic dilatations and compressive breaking strength along the fibres (obtained in standard testing conditions).Data analysis allows to build some predictive models, unique for the whole pine selection, of basic properties, from indicators measured on each specimen of clear wood.Therefore it is possible to associate to a given piece of wood, a technical specification sheet of useful properties for mechanical design. Selected indicators are common measurements in industry and knowledge transfer is conceivable. Each interesting piece of wood (i.e. with few defects) could be rapidly characterized. Related to a good traceability this process could lead to identify clearly each piece and its properties, giving the possibility to the designer to select the best materials to his or her needs
Gli stili APA, Harvard, Vancouver, ISO e altri
34

Ljungdahl, Jonas. "Structure and properties of Vasa oak". Licentiate thesis, Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4016.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
35

Filchev, Ivan. "Buckling and geometric nonlinear FE analysis of pitched large-spanroof structure of wood". Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54324.

Testo completo
Abstract (sommario):
An arched structure provides an effective load carrying system for large span structures. When it comes to long span roof structures, timber arches are one of the best solutions from both structural and aesthetical point of view. Glulam arched structures are often designed using slender elements due to economic consideration. Such slender cross-section shape increases the risk of instability. Instability analysis of straight members such as beam and column are explicitly defined in Eurocode. However, for instability of curved members no analytical approach is provided in the code, thus some numerical method is required. Nonetheless, an approximation is frequently used to obtain the effective buckling length for the arched structures in the plane of arches. In this master thesis a linear buckling analysis is carried out in Abaqus to obtain an optimal effective buckling length both in-plane and out-of-plane for circular glulam arched structures. The elastic springs are used to simulate the overall stiffness of the bracing system. The results obtained by the FE simulations are compared with a simple approximation method. Besides, the forces acting on the bracings system is obtained based on 3D geometric nonlinear stress analysis of the timber trusses. Our findings conclude that the approximation method overestimates the effective buckling length for the circular glulam arched structures. In addition, the study indicates that the position of the lateral supports along the length of the arch is an important design aspect for buckling behaviour of the arched structures. Moreover, in order to acquire an effective structure lateral supports are needed both in extrados and intrados. Furthermore, instead of using elastic spring elements to simulate the overall stiffness of the bracing system, a full 3D simulation of two parallel arches was performed. It was shown that the springs are stronger than the real bracing system for the studied arch.
Gli stili APA, Harvard, Vancouver, ISO e altri
36

Schreiner, Linda [Verfasser]. "Characterization of conifer wood regarding its odor-active constituents, their structure-odor relationships, and the influence of wood odors on humans / Linda Schreiner". München : Verlag Dr. Hut, 2020. http://d-nb.info/1220568031/34.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
37

Aebischer, Danille P. "Basic density and shrinkage of oak in relation to wood structure and cambial age". Thesis, Bangor University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285465.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
38

Eriksson, Daniel. "Wood - an anatomical structure in the tree and an engineering material in industry : prediction of material properties in managed Scots pine stands in the forest /". Umeå : Dept. of Forest Ecology and Management, Swedish University of Agricultural Sciences, 2008. http://epsilon.slu.se/200873.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
39

Bahrani, Babak. "Effects of weathering on performance of intumescent coatings for structure fire protection in the wildland-urban interface". Thesis, The University of North Carolina at Charlotte, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1606131.

Testo completo
Abstract (sommario):

The objective of this study was to investigate the effects of weathering on the performance of intumescent fire-retardant coatings on wooden products. The weathering effects included primary (solar irradiation, moisture, and temperature) and secondary (environmental contaminants) parameters at various time intervals.

Wildland urban interface (WUI) fires have been an increasing threat to lives and properties. Existing solutions to mitigate the damages caused by WUI fires include protecting the structures from ignition and minimizing the fire spread from one structure to another. These solutions can be divided into two general categories: active fire protection systems and passive fire protection systems. Passive systems are either using pre-applied wetting agents (water, gel, or foam) or adding an extra layer (composite wraps or coatings). Fire-retardant coating treatment methods can be divided into impregnated (penetrant) and intumescent categories. Intumescent coatings are easy to apply, economical, and have a better appearance in comparison to other passive fire protection methods, and are the main focus of this study.

There have been limited studies conducted on the application of intumescent coatings on wooden structures and their performance after long-term weathering exposure. The main concerns of weathering effects are: 1) the reduction of ignition resistance of the coating layer after weathering; and 2) the fire properties of coatings after weathering since coatings might contribute as a combustible fuel and assist the fire growth after ignition.

Three intumescent coatings were selected and exposed to natural weathering conditions in three different time intervals. Two types of tests were performed on the specimens: a combustibility test consisted of a bench-scale performance evaluation using a Cone Calorimeter, and a thermal decomposition test using Simultaneous Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) method (also known as SDT). For each coating type and weathering period, three different radiative heat flux levels were used in the combustibility tests. Data obtained from the tests, including flammability and thermal properties, were gathered, analyzed, and compared to non-weathered specimens.

The results revealed visible effects of weathering on pre (and up to)-ignition flammability and intumescent properties, especially decreases in Time-to-Ignition (TTI), Time-to-Intumescence (tintu.), and (maximum) Intumescence Height (Hintu.) values in weathered specimens. These results showed that the ignition resistance of the coating layers decreased after weathering exposure. On the other hand, the obtained results from weathered specimens for the post-ignition flammability properties, especially Peak Heat Release Rate (PHRR) and Effective Heat of Combustion (EHC) did not show a significant difference in comparison to the non-weathered samples. These results demonstrated that the weathered coating layer would not likely to act as an additional combustible fuel to increase fire spread.

Gli stili APA, Harvard, Vancouver, ISO e altri
40

Zafra-Camón, Guillermo. "Calculation of global properties of a multi-layered solid wood structure using Finite Element Analysis". Thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298677.

Testo completo
Abstract (sommario):
Finite Element Method (FEM) is a powerful numerical tool which, combined with the fast development of Computer Science in the lastdecades, had made possible to perform mechanical analysis of a widerange of bodies and boundary conditions. However, the complexity of some cases may turn the calculationprocess too slow and sometimes even unaffordable for most computers. This work aims to simplify an intricate system of layers withdifferent geometries and material properties by approximating itthrough a homogeneous material, with unique mechanical parameters.Besides the Finite Element analysis, a theoretical model is created, in order to understand the basis of the problem, and, as a firstapproach, check whether the assumptions made in the FEM model areacceptable or not. This work intends to make a small contribution to the understandingof the mechanical behaviour of the Vasa vessel, which will eventuallylead to the design of a new support structure for the ship. The preservation of the Vasa is a priority for the Swedish Property Board, as it is one of the main monuments of Sweden.
Gli stili APA, Harvard, Vancouver, ISO e altri
41

Jonsson, Christian. "Detection of annual rings in wood". Thesis, Linköping University, Department of Science and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-15804.

Testo completo
Abstract (sommario):

This report describes an annual line detection algorithm for the WoodEye quality control system. The goal with the algorithm is to find the positions of annual lines on the four surfaces of a board. The purpose is to use this result to find the inner annual ring structure of the board. The work was done using image processing techniques to analyze images collected with WoodEye. The report gives the reader an insight in the requirements of quality control systems in the woodworking industry and the benefits of automated quality control versus manual inspection. The appearance and formation of annual lines are explained on a detailed level to provide insight on how the problem should be approached. A comparison between annual rings and fingerprints are made to see if ideas from this area of pattern recognition can be adapted to annual line detection. This comparison together with a study of existing methods led to the implementation of a fingerprint enhancement method. This method became a central part of the annual line detection algorithm. The annual line detection algorithm consists of two main steps; enhancing the edges of the annual rings, and tracking along the edges to form lines. Different solutions for components of the algorithm were tested to compare performance. The final algorithm was tested with different input images to find if the annual line detection algorithm works best with images from a grayscale or an RGB camera.

Gli stili APA, Harvard, Vancouver, ISO e altri
42

Osei, Nana Akwasi. "Large wood in fluvial systems : quantity, structure and landforms, sediment retention, and riparian seed bank development". Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8813.

Testo completo
Abstract (sommario):
This thesis investigates the characteristics and impacts of large wood accumulations within river reaches of different size and style. Four reaches were studied: (i) a wide, braided, headwater reach, characterised by dead wood (Tagliamento River, Italy); (ii) a lower gradient, wide, braided reach, characterised by resprouting wood (Tagliamento River, Italy); (iii) a low gradient, single thread reach with a natural supply of dead wood (Highland Water, UK), and (iv) a low gradient, single thread reach that has been restored by felling trees into the river (River Bure, UK). In each reach, quantities of wood, types of accumulation and their association with sediment retention, landform and propagule bank development were investigated, generating four main findings: 1. There were marked differences in the size and character of large wood accumulations among the four reaches. 2. Retention of fine sediment and organic matter by wood was observed on all four reaches, giving rise to notable spatial heterogeneity in surface sediments. 3. Sediment retention resulted in the development of different landforms among the four reaches. In the two multi-thread reaches, accretion of finer sediment around large wood led to island development. In the naturally-functioning single-thread reach, wood jams spanned the river channel, accumulating sediment and organic matter to produce unvegetated wood jams, and inducing other landforms, notably pools and bars. Such geomorphic heterogeneity was anticipated in the restored reach, but to date this has not significantly occurred. 4. Spatio-temporal variations were observed in propagule abundance and species richness within different wood-related mesohabitats. Higher abundance and species richness were associated with finer, more organic sediments retained within wood accumulations and related mesohabitats. In the restored reach such associations were not statistically significant, further indicating that responses to wood emplacement take longer than the 4 years since restoration. iv Overall, this research has strengthened the evidence concerning the differing nature of wood accumulations in rivers of different size and style, and it has demonstrated the importance of large wood for retaining organic matter and plant propagules, resources essential for riparian vegetation succession and for the success of river restoration efforts.
Gli stili APA, Harvard, Vancouver, ISO e altri
43

Girardon, Stéphane. "Amélioration des performances mécaniques des assemblages bois sur bois vissés par préparation des interfaces : application à la réalisation d'éléments de structure". Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0188/document.

Testo completo
Abstract (sommario):
L'assemblage de planches par technique de collage est utilisé pour réaliser des éléments de structure en bois performants. Le collage permet d'obtenir des rigidités et des résistances d'assemblages excellentes. Cependant, ces produits sont souvent polluants à différents degrés et ne permettent pas de s'adapter à une cadence industrielle de fabrication, notamment à cause des temps de pressage. Le niveau de performance s'effondre lorsque l'assemblage par collage est remplacé par des organes de type tige, tels que des pointes, vis ou tourillons en bois, mais ils confèrent un temps de mise en oeuvre instantané. Dans ces types d'assemblages mécaniques, la surface de contact entre les planches n'est plus du tout utilisée pour transmettre des efforts. L'objectif de ce travail est de montrer comment la préparation mécanique des interfaces permet de fortement améliorer le comportement de ces assemblages. La finalité étant de produire des éléments de structure sans composés organiques volatiles (COV), dont la fabrication serait réalisable par un robot industriel, de manière flexible et en utilisant des essences mixtes de bois locaux. La première partie de cette étude est consacrée à répertorier et analyser les différents systèmes reconstitués en bois, ainsi que de montrer comment mener un dimensionnement en tenant compte du caractère imparfait de la connexion. Cette partie montre que la prise en compte du caractère non linéaire des liaisons mécaniques dans les systèmes reconstitués est souvent très imprécise et conduit à des écarts de dimensionnement importants. La deuxième partie décrit une méthodologie pour pallier à ce manque, développée à partir de la modélisation non linéaire d'un élément de construction de type poutre. Cette approche conduit à proposer des raideurs sécantes précises de la liaison permettant le calcul linéaire exact pour les ingénieurs. Cette méthodologie permet de caractériser la raideur d'une liaison par une approche liée au comportement plutôt qu'une approche normative générale. Suite à la mise en évidence de la souplesse de la liaison par organes, une troisième partie expose une réflexion sur l'utilisation des surfaces en contact pour transmettre les efforts. Un traitement mécanique de type rainurage est réalisé à l'interface de contact des pièces à assembler. Il permet de transmettre des efforts de cisaillement et de torsion dans le plan de croisement des planches. Le maintien des éléments en contact est également étudié en développant un principe de vis conique en bois. Pour valider ces principes, des campagnes d'essais sont réalisées afin de mesurer les performances obtenues par le rainurage, la vis conique en bois et leurs utilisations simultanées. La dernière partie est consacrée à la mise en oeuvre de l'assemblage amélioré dans des éléments de structure afin d'en confirmer son potentiel. Le premier élément est une poutre ajourée, le second est un élément de mur contreventant. Les résultats d'essais sont comparés à des modèles numériques incluant le comportement non linéaire des assemblages rainurés vissés. Ces réalisations en grandeurs réelles permettent de valider également leur faisabilité par un robot industriel
Plank bonding connection is used to produce efficient structural timber. The bonding achieves excellent rigidity and connection resistance. However, these products are often pollutants and are incompatible with industrial production rates due to the pressing time. Their performances collapse when the adhesive connection is replaced by rodlike fasteners, such as nails, screws or wooden dowels, but these connections allow a quick assembly. In these assemblies the contact surfaces between planks are not used for transmitting loads. The purpose of this study is to point out how mechanical preparation of the interfaces improves the performance of timber connections. The aim is to produce structural members without volatile organic compounds (VOC), achievable by an industrial robot allowing for flexibility, and using mixed wood local species. The first part of this study consists in identifying and analyzing reconstituted wood systems, as well as showing how to conduct a design by taking into account the partial composite action of connectors. This part explains that the chosen behavior of the mechanical connections in reconstituted systems is frequently very imprecise and leads to significant differences in design. The second part describes a methodology to overcome this lack, developed from the nonlinear modeling of a beamtype component. This approach leads to determine the fastener's secant stiffness for an exact linear calculation for engineers. The outcome of this methodology is the quantification of the fastener's secant stiffness by a related behavior rather than a general normative behavior. Due to the flexibility of members, a third part presents a reflection on the use of the contact surfaces for transmitting loads. The plank interfaces were machined in order to obtain grooves. This binding allows the transmission of shear and torsion forces in the intersection plane of the planks. Maintaining the contact is managed by the development of a wooden conical screw. To validate these principles, test campaigns were carried out to measure the performance of the groove, the wooden conical screw and their simultaneous use. The last section deals with the implementation of the improved assembly in structural members in order to confirm its potential. The first element type is a castellated beams and the second one is a bracing wall. Experimental results are compared with numerical models including the nonlinear grooved screwed connection behavior. Furthermore, these full scale elements validate the feasibility by an industrial robot
Gli stili APA, Harvard, Vancouver, ISO e altri
44

Chowdhury, Sudip. "Advancing characterization techniques for structure-property determination of in-situ lignocelluloses". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/39189.

Testo completo
Abstract (sommario):
The global progression towards sustainable energy, materials and chemicals requires novel and improved analytical tools to understand and optimize lignocellulosic biomass utilization. In an effort to advance lignocellulose characterization, gain insights into biomass processing, and obtain novel perspectives on cell wall ultrastructure, this study utilizes three principal polymer characterization techniques, namely compressive-torsion dynamic mechanical analysis (DMA), deuterium quadrupolar nuclear magnetic resonance (2H NMR) and rheo-infrared spectroscopy. A novel parallel-plate compressive-torsion DMA protocol is developed to analyze very small solvent-plasticized biomass specimens with or without mechanical integrity. The benefits and limitations of this technique are demonstrated by comparing it to a conventional tensile-torsion DMA while analyzing various solvent-plasticized lignocelluloses. The rheology of wood in various organic solvents is studied through dynamic thermal scans, Time/temperature superposition (TTS) and fragility analysis. Plasticizing solvents and wood grain orientation significantly affected the lignin glass-transition temperature. Dynamic TTS reveals that while all storage modulus data shift smoothly, the thermorheological complexity of solvent-plasticized wood becomes evident in loss component master curves. It is argued that the plasticized lignocellulose TTS is insightful and potentially useful, although it fails to satisfy the classic TTS validity criteria. Subsequently, it is justified that the fragility analysis is a better suited treatment than the WLF model to investigate cooperative segmental motions of plasticized wood. Deuterium quadrupolar NMR reveals a new perspective on the orientation of amorphous wood polymers and two distinct amorphous polymer domains: a highly oriented phase in the S2 layer of the secondary cell wall and an isotropic phase postulated to occur in the compound middle lamella (CML). If the origin of the isotropic phase is confirmed to arise from the CML, then this technique provides a way to independently investigate the morphology and phase dynamics of CML and S2 in an intact tissue, and should bring novel insights into deconstructive strategies specific to the oriented and unoriented domains. Finally the effects of a wood-adhesion promoter (hydroxymethyl resorcinol, HMR) on in-situ wood polymers are studied to elucidate the still unresolved HMR-lignocellulose interactions. DMA, creep-TTS and 2H NMR reveal that HMR increases the crosslink density and restricts the mobility of wood amorphous phase. Rheo-IR spectroscopy shows that the molecular stress-transfer mechanism is altered within the wood cell wall.
Ph. D.
Gli stili APA, Harvard, Vancouver, ISO e altri
45

Lin, Wing Shan Linda. "Effect of moisture and other volatiles on the cellular structure of plastic/wood-fiber composite foams". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ63121.pdf.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
46

Nord, Tomas. "Structure and developments in the solid wood value chain : dominant saw milling strategies and industrialized housing". Licentiate thesis, Luleå, 2005. http://epubl.luth.se/1402-1757/2005/57.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
47

Hult, Eva-Lena. "CP/MAS ¹³C-NMR spectroscopy applied to structure and interaction studies on wood and pulp fibers /". Stockholm, 2001. http://media.lib.kth.se:8080/kthdisseng.html.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
48

Ochieng, Judith Auma. "The role of disturbances in mangrove wood formation and forest structure: Effect of large sedimentation events". Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/232475.

Testo completo
Abstract (sommario):
Disturbance can take various forms and are characteristic of any ecosystem including mangroves. When maintained within certain allowable limits, disturbances permits maintenance of a given stable state which is equivalent to resilience hence the ecological status is not compromised. Disturbances may disrupt the natural balance of processes within such ecosystems including changes in sediment budgets and salinity and tidal regimes. As such, it may trigger a series of responses in tree establishment and development. While such responses may be displayed in loss of stability of a forest and may culminate in irreversible degradation of the system, disturbances could also result in improved performance of physiological processes and consequently tree growth. It may equally lead to the development of adaptive mechanisms to counteract the resultant otherwise stressful effects. Sediment accretion is one of the important natural processes within the mangrove environment particularly in the face of relative sea level rise. In each case, sediment fluxes are gradual and while the trees thrive from the benefits of terrestrial sediment, the system ensures balance in elevation for possible sea level rise scenario. However, abrupt and/or rapid sediment input leading to partial burial of the trees may be detrimental to the trees development in the short term and the entire ecosystem in the long run. But how are ecophysiological processes affected before the mangroves trees die from partial sediment burial? What is the threshold below which normal tree functioning is ensured.The main objective of this study was to understand the impacts of disturbance on mangrove trees, as individuals and as an assemblage. Specifically the study targeted large sedimentation on selected ecophysiological processes (phenology, water transport), root development and general physiognomy and hence its impact on wood formation in mangroves. A survey was also done on the extent of wood exploitation and other human activities, in order to obtain background information on the environmental management in the area and hence to help create an integrated picture of the evolving mangrove ecosystem in the human-nature context.Main question: What is the significance of sedimentation in shaping the ecological status of mangrove forests?
Doctorat en Sciences
Author's maiden name: Judith Auma OKELLO
Due to a technical Di-Fusion bug it was not possible to input the correct date of the defense. The correct date is Thursday 30 June 2016.
info:eu-repo/semantics/nonPublished
Gli stili APA, Harvard, Vancouver, ISO e altri
49

Macias, Diego. "Topological (Bio)Timber: An Algorithm and Data Approach to 3d Printing a Bioplastic and Wood Architecture". University of Cincinnati / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1491305462260965.

Testo completo
Gli stili APA, Harvard, Vancouver, ISO e altri
50

Forsström, Jennie. "Fundamental Aspects on the Re-use of Wood Based Fibres : Porous Structure of Fibres and Ink Detachment". Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-84.

Testo completo
Abstract (sommario):

In this work, different aspects on the re-use of wood based fibres have been studied, focusing on ink detachment of flexographic ink from model cellulose surfaces and changes in porous structure of kraft fibres following different treatments. New model systems for evaluation of ink detachment and ink-cellulose interactions were used. Ink detachment was studied using Impinging jet cell equipment, taking into consideration the influence of storage conditions, surface roughness and surface energy of the cellulose substrate. A micro adhesion measurement apparatus (MAMA) was used to directly study ink-cellulose interactions, from which the adhesive properties between ink and cellulose, having various surface energies, could be derived. UV-light, elevated temperatures, longer storage time, decreased surface energy, i.e. making the cellulose surface more hydrophobic, and high surface roughness all negatively affected ink detachment. Attenuated total reflectance - fourier transform infra red (ATR-FTIR) and atomic force microscopy (AFM) was used to evaluate structural and chemical changes of ink and cellulose upon storage at elevated temperature or under UV-light. After storage at elevated temperatures, ATR-FTIR spectra indicated that a hydrolysis or an oxidative reaction took place as a peak at 1710 cm-1 appeared. AFM revealed that storage at elevated temperatures caused the latex particles present in the ink to form a film, most likely due to annealing. Less ink detached from hydrophobic cellulose surfaces. Ink detachment decreased for rougher cellulose substrates due to an increased molecular contact area.

Fibre pore structure and water retaining ability influenced fibre/fibre joint strength and different paper strength properties. Investigations took into account the effect of pulp yield, counter-ion types, pH, salt, hornification and strength enhancing additives. Nuclear magnetic resonance relaxation (NMR), inverse size exclusion chromatography (ISEC) and water retention value (WRV) measured the changes that occur in the fibre wall upon varying the conditions. Each different measuring technique contained unique information such that a combination of the techniques was necessary to give as complete a picture as possible over the changes that occurred in the fibre wall upon varying the conditions for the fibre. A correlation between fibre pore radius and sheet strength properties was found, suggesting that fibres with larger pores allow for a larger molecular contact area between fibres to be formed during drying and consolidation of the paper. Fibre/fibre joint strength, fibre flexibility, and the number of efficient fibre/fibre contacts also controlled sheet strength. The effect of different strength enhancing additives on fibre pore structure and paper strength was investigated. Larger pores in the fibres allowed for additives to penetrate into the fibre wall. Additives with low molecular mass (Mw) penetrated into the fibre wall to a larger extent than additives with a high Mw, causing an embrittlement of the fibre. However, low Mw additives gave higher sheet tensile strength despite a leveling out in strength at high additions, indicating that the fibre wall can only adsorb a limited amount of chemical. Polyallylamine hydrochloride (PAH) and polyelectrolyte complexes (PEC) of PAH and polyacrylic acid (PAA) were added separately to the pulp. PEC significantly improved both tensile strength and Z-strength, whereas PAH alone did not increase the strength properties to the same extent unless the sheets were heated to 150°C for 10 minutes. The results suggested that the effect of PEC was dominated by an improvement in fibre/fibre joint strength, whereas the effect of PAH was significantly affected by an improvement of the intra-fibre bond strength

Gli stili APA, Harvard, Vancouver, ISO e altri
Ti possono interessare anche gli elenchi di altri tipi di fonti sul tema "Wood structure":
Articoli di riviste Libri
Offriamo sconti su tutti i piani premium per gli autori le cui opere sono incluse in raccolte letterarie tematiche. Contattaci per ottenere un codice promozionale unico!

Vai alla bibliografia