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Soil attributes and wood quality for pulp production in plantations of Eucalyptus grandis clone; Atributos do solo e qualidade da madeira para produção de celulose em plantações clonais de Eucalyptus grandis

GAVA, José Luiz; GONÇALVES, José Leonardo de Moraes
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.12%
The soil attributes can affect the wood quality of eucalypt, which may result in considerable effect on cellulose production. This study evaluated the effect of different physical and chemical soil attributes on wood quality of Eucalyptus grandis for cellulose production. Five sites were selected at the Western Plateau of the State of São Paulo, planted with one clone of Eucalyptus grandis, with ages ranging between 6.5 and 7.0 years. Four soil types, with texture ranging from sandy to very clayey were found. At each site, three experimental plots were allocated with 100 trees each. Trees representative of each class frequency of diameter at breast height were harvested. Their biomass and wood components were characterized. The wood productivity and quality was affected by physical attributes of soil, mainly clay content, which is directly related to the amount of available water. Basic wood density did not changed at different soil types. Total lignin content decreased and holocellulose content exponentially increased as soil clay content increased (until about 350 to 400 g kg-1 of clay). The wood extractives content was not affected by soil attributes. Screened cellulose yield exponentially increased with soil clay content.; Os atributos edáficos podem afetar a qualidade da madeira de eucalipto...

Agrupamento das espécies madeireiras ocorrentes em pequenas áreas sob manejo florestal do projeto de colonização Pedro Peixoto (AC) por similaridade das propriedades físicas e mecânicas. ; Grouping of the wood species occurring in small farms under forest management on the Pedro Peixoto colonization project (AC), by similarity of the physical and mechanical properties.

Araújo, Henrique José Borges de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 04/09/2002 PT
Relevância na Pesquisa
46.17%
O manejo florestal sustentado mostra-se uma solução tecnológica adequada para a região amazônica. A exploração seletiva das espécies madeireiras tradicionais vem ocasionando a escassez dessas espécies. É necessário melhorar o aproveitamento dos recursos florestais amazônicos, aproveitando o máximo de suas potencialidades. As espécies de madeira exploradas para fins comerciais são poucas, sendo que há muitas outras com potencial de uso. Vários fatores mostram que o estado do Acre tem aptidão para atividades florestais. O objetivo do presente trabalho é agrupar, por similaridade das propriedades físicas e mecânicas, as madeiras ocorrentes em áreas sob manejo florestal, identificando espécies com potencial de uso e comercialização. A revisão bibliográfica abordou aspectos relacionados ao mercado internacional de madeiras, ao consumo da produção madeireira amazônica, ao uso sustentado dos recursos florestais, a novas espécies de madeira, à caracterização geral do material Madeira, e, à análise estatística multivariada. A área do estudo é composta por 12 pequenas propriedades localizadas no estado do Acre. A área total sob manejo florestal das propriedades é de 431 ha. O plano de manejo florestal prevê a exploração de 8...

Influência do desbaste e da adubação na qualidade da madeira serrada de Eucalyptus grandis Hill ex-Maiden.; Influence of thinning and fertilization on Eucalyptus grandis (Hill ex-Maiden) sawn wood quality.

Lima, Israel Luiz de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/05/2005 PT
Relevância na Pesquisa
46.09%
O presente trabalho teve como objetivo geral estudar a influência do manejo florestal no rendimento e na qualidade tecnológica da madeira serrada de uma população plantada de Eucalyptus grandis, de 21 anos de idade, manejada pelo sistema de desbastes seletivos com aplicação de fertilizantes na época do início dos desbastes. Os fatores utilizados foram três intensidades de desbastes seletivos (37, 50 e 75%), presença ou ausência de fertilizantes, três classes de diâmetro e três posições verticais ao longo da altura do fuste comercial.As influências dos fatores e de suas combinações nas tensões de crescimento das árvores foram avaliadas de forma indireta através das rachaduras de extremidade de tora, rachadura de extremidade de tábua úmidas e secas, encurvamento e arqueamento de tábua úmida e deslocamento da medula em relação à sua normal posição central. Foram avaliadas, também, porcentagem de casca e conicidade de toras, que são variáveis que interferem no rendimento em madeira serrada; massa específica da madeira à umidade de equilíbrio ao ar; módulo de elasticidade estrutural na flexão estática não destrutiva, determinado em tábuas secas de dimensões comerciais e um sistema de classificação de tábuas segundo diferentes classes de qualidade. O deslocamento da medula...

Avaliação da qualidade da madeira das espécies Acacia crassicarpa, Acacia mangium, Eucalyptus nitens, Eucalyptus globulus e Populus tremuloides; Evaluation of the wood quality of species Acacia crassicarpa, Acacia mangium, Eucalyptus nitens, Eucalyptus globulus and Populus tremuloides

Antunes, Fernanda Schablatura
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 10/06/2009 PT
Relevância na Pesquisa
46.25%
As madeiras utilizadas para produção de polpa celulósica podem ser divididas em dois grupos em função da fibra: folhosas (fibra curta) e coníferas (fibra longas), as espécies de folhosas são destinadas especialmente a papéis de escrita e impressão. As principais espécies de folhosas utilizadas para produção de polpa de fibra curta em outros países são o Eucalyptus globulus (Península Ibérica e Chile), Eucalyptus nitens (Chile), Populus tremuloides (Canadá), Acacia mangium, Acacia crassicarpa (Indonésia). Este projeto tem por objetivo: avaliar e comparar o desempenho de madeiras utilizadas mundialmente para produção de polpa celulósica de fibra curta considerando parâmetros de qualidade da madeira tais como composição química, densidade básica, características anatômicas da madeira; com objetivo de fornecer informações estratégicas para o setor nacional de celulose e papel, visando o conhecimento e posicionamento em competitividade destas madeiras no mercado mundial. Para a realização deste trabalho foram coletadas 5 árvores de cada espécie as quais foram utilizados cavacos cortados manualmente obtidos de discos; com relação à madeira foram determinadas densidade básica, composição química e dimensões de fibras. Os resultados foram analisados estatisticamente sendo comparadas as diferentes espécies referentes à qualidade da madeira.; Wood used for pulp production may be divided in two major groups regarding fiber function: hardwood (short fiber) and softwood (long fibers). Hardwood species are mainly designated to writing and printing papers. Hardwood principal species used for production of short fiber pulp in other countries are Eucalyptus globulus (Iberian Peninsula and Chile)...

A supramolecular proposal of lignin structure and its relation with the wood properties

Abreu,Heber S.; Latorraca,João V.F.; Pereira,Regina P.W.; Monteiro,Maria Beatriz O.; Abreu,Fábio A.; Amparado,Kelysson F.
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2009 EN
Relevância na Pesquisa
46.12%
In spite of the great importance of cellulose the lignin is considered the second most abundant substance of the wood. However, little attention has been given it, mainly to wood properties. The lignin as well as other structural compounds (cellulose and hemicelluloses), has obviously an important role on the wood properties, probably due its composition and existent bonds. In general lignins have β-O-4 (Alkyl Aril Ether) as majoritary bond. This bond in a continued structure form big molecules with spiral conformation as virtual model. Based on this idea, lignins that have high/low β-O-4 content may have differentiated spiraled structures,suggesting different behaviors on the wood properties,which shows that the lignins (Guaicyl:Syringyl (GS)) of angiosperms, for example, which have higher β-O-4 content would present higher spiral conformation than gymnosperms lignins(HG). On the other hand HG lignins have chance of being more anchored on the matrix compound than GS lignins. In this context, the β-O-4 bonds of lignins possibly affect the wood properties, therefore, it is considered relevant for wood technology science discussion.

Soil attributes and wood quality for pulp production in plantations of Eucalyptus grandis clone

Gava,José Luiz; Gonçalves,José Leonardo de Moraes
Fonte: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" Publicador: São Paulo - Escola Superior de Agricultura "Luiz de Queiroz"
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2008 EN
Relevância na Pesquisa
46.12%
The soil attributes can affect the wood quality of eucalypt, which may result in considerable effect on cellulose production. This study evaluated the effect of different physical and chemical soil attributes on wood quality of Eucalyptus grandis for cellulose production. Five sites were selected at the Western Plateau of the State of São Paulo, planted with one clone of Eucalyptus grandis, with ages ranging between 6.5 and 7.0 years. Four soil types, with texture ranging from sandy to very clayey were found. At each site, three experimental plots were allocated with 100 trees each. Trees representative of each class frequency of diameter at breast height were harvested. Their biomass and wood components were characterized. The wood productivity and quality was affected by physical attributes of soil, mainly clay content, which is directly related to the amount of available water. Basic wood density did not changed at different soil types. Total lignin content decreased and holocellulose content exponentially increased as soil clay content increased (until about 350 to 400 g kg-1 of clay). The wood extractives content was not affected by soil attributes. Screened cellulose yield exponentially increased with soil clay content.

Modification of static bending strength properties of Eucalyptus grandis heat-treated wood

Cademartori,Pedro Henrique Gonzalez de; Schneid,Eduardo; Gatto,Darci Alberto; Beltrame,Rafael; Stangerlin,Diego Martins
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 EN
Relevância na Pesquisa
46.09%
The present study describes the effect of thermal rectification on physical and mechanical properties of Eucalyptus grandis wood at different levels of temperature and time. Samples of Eucalyptus grandis wood (10 × 10 × 200 mm) were heat-treated at 180, 200, 220 and 240 °C during 4 and 8 hours. The mechanical properties of heat-treated and untreated samples were determined by static bending tests. The physical properties were determined by weight loss and swelling tests. The results showed that modulus of elasticity, modulus of rupture, weight loss, volumetric swelling and linear swelling were affected significantly by the thermal rectification. However, the length of exposure influenced just weight loss, while the temperature influenced all the studied properties of heat-treated wood. More significant modifications with treatments at a temperature of 200 °C or higher were found in the properties of heat-treated wood.

A distributed bipolar device for monolithic analog-to-digital conversion

Mangelsdorf, Christopher Wood
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 284 leaves; 15701917 bytes; 15701674 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.06%
by Christopher Wood Mangelsdorf.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1984.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Includes bibliographical references.

A comparative analysis of emissions from bagasse charcoal and wood charcoal

Ramírez, Andrés, 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 27 leaves; 1102484 bytes; 1100975 bytes; application/pdf; application/pdf
ENG
Relevância na Pesquisa
46.19%
Haiti is the poorest country in the Western hemisphere and is in need of cheap cooking fuel source. Currently, lump charcoal, the cooking fuel of Haiti, is made by carbonizing trees in ditches before selling the charcoal at market. However, Haiti is now 98% deforested and must find a way to prepare their food that does not destroy their land. The idea for this new fuel comes from compressed and extruded carbonized bagasse, which was produced using an extruder developed in a senior product development class at MIT. Using this bagasse fuel, experiments were conducted to compare the combustion characteristics of the bagasse charcoals with wood charcoal. Unfortunately, the heat released by the bagasse charcoal did not compare favorably with that of the wood charcoal, failing to raise 1 L of water to boiling while the wood charcoal raised the water to boiling for 25 minutes. Since the bagasse charcoal performed similarly to Kingsford brand charcoal, the emissions released were compared between these two fuels. Based on their averages, the bagasse charcoal emitted 1.4 times more CO, 1.6 times more SO₂ and 2.3 times more particulates but only 17% of the NOx emitted by Kingsford.; by Andrés Ramírez.; Thesis (S.B.)--Massachusetts Institute of Technology...

Seismic design of a current woodframe structure and study of innovative products and damping systems in wood construction; Study of innovative products and damping systems in wood construction

Mahjoub, Nina A. (Nina Azadeh)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 97 p.
ENG
Relevância na Pesquisa
46.28%
Wood structures have seen resurgence in popularity over the past several decades, especially in Western States of America, such as California. The industry keeps creating new structural wood products of exceptional strength, versatility, and reliability. Woodframe structures offer a more sustainable answer, but need to be carefully detailed in high seismic zone. The objective of this work is to describe the seismic design of a current woodframe structure. Moreover, this thesis aims to present the innovation occurring in the market of wood construction. New engineered wood products are introduced as well as a review of the new developments and researches that are being made to incorporate damping systems such as viscoelastic and hysteretic dampers, in the ultimate goal of obtaining an optimum earthquake-resistant wood structure.; by Nina A. Mahjoub.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (p. 96-97).

Nanostructured gene and drug delivery systems based on molecular self-assembly

Wood, Kris Cameron
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 202 p.
ENG
Relevância na Pesquisa
46.06%
Molecular self-assembly describes the assembly of molecular components into complex, supramolecular structures governed by weak, non-covalent interactions. In recent years, molecular self-assembly has been used extensively as a means of creating materials and devices with well-controlled, nanometer-scale architectural features. In this thesis, molecular self-assembly is used as a tool for the fabrication of both gene and drug delivery systems which, by virtue of their well-controlled architectural features, possess advantageous properties relative to traditional materials used in these applications. The first part of this thesis describes the solution-phase self-assembly of a new family of linear-dendritic "hybrid" polymers with plasmid DNA for applications in gene therapy. It begins with an overview of the design of next-generation, non-viral gene delivery systems and continues through the synthesis and validation of hybrid polymer systems, which possess modular functionalities for DNA binding, endosomal escape, steric stabilization, and tissue targeting. This part of the thesis concludes with applications of these systems to two areas of clinical interest: DNA vaccination and tumor targeted gene therapy.; (cont.) The second part of this thesis describes the directed self-assembly of polymeric thin films which are capable of degrading in response to either passive or active stimuli to release their contents. It begins with a description of passive release thin films which degrade by basic hydrolysis to release precise quantities of model drug compounds. These systems can be engineered to release their contents on time scales ranging from hours to weeks and can also be designed to release multiple drugs either in series or in parallel. Later...

All inorganic colloidal quantum dot LEDs; All inorganic colloidal QD light emitting devices

Wood, Vanessa Claire
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 89 p.
ENG
Relevância na Pesquisa
46.06%
This thesis presents the first colloidal quantum dot light emitting devices (QD-LEDs) with metal oxide charge transport layers. Colloidally synthesized quantum dots (QDs) have shown promise as the active material in optoelectronic devices because of their tunable, narrow band emission. To date, the most efficient QD-LEDs involve a monolayer of closely packed QDs sandwiched between organic charge transport layers. However, these organic materials are subject to degradation due to atmospheric oxygen and water vapor. In contrast, metal-oxide films used in this work are chemically and morphologically stable in air and can withstand numerous organic solvents, which increases the flexibility of device processing. Furthermore, they can sustain higher carrier injection rates needed to realize an electrically pumped colloidal QD laser. This thesis details the characterization techniques, such as Atomic Force Microscopy, photoluminescence spectroscopy, Hall Effect measurements, X-Ray Diffraction, and Ultraviolet Photoelectron Spectroscopy, used to design efficient QD-LEDs. It reviews the steps used to optimize device performance and obtain a transparent device architecture with external quantum efficiency of 0.15% and a peak luminance of 7000 Cd/m2. This manifests a 100-fold improvement in efficiency over any previously reported all inorganic QD-LED structure.; by Vanessa Claire Wood.; Thesis (S.M.)--Massachusetts Institute of Technology...

Exploring kinetics and thermodynamics in fast-ion conductors and hydrogen-storage materials using ab-initio molecular dynamics

Wood, Brandon C. (Brandon Christopher)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 190 p.
ENG
Relevância na Pesquisa
46.06%
We investigate the interplay between various kinetic processes and thermodynamic factors in three materials--silver iodide (AgI), cesium hydrogen sulfate (CsHSO4), and sodium alanate (NaAlH4)-using ab-initio molecular dynamics simulations. The time-averaged and instantaneous silver substructure in the fast-ion conductor AgI is analyzed, resulting in a set of ordering rules that govern the distribution of the mobile silvers in the first coordination shell surrounding an iodine. We find evidence of an independent phase transition of the silver ions which drives the structural transformation to the high-mobility phase. A thermodynamic motivation for the existence of fast-ion conduction is suggested in terms of an entropic stabilization associated with the decrease in silver mobility upon melting. We also find a unique chemical signature for the fourth nearest-neighbor silver to an iodine. This fourth silver is weakly bound and relatively unconstrained, and we isolate it as the predominant agent in the diffusion process. Next, a detailed statistical analysis is performed on simulations of the fuel-cell electrolyte CsHSO4 to isolate the interplay between the dynamics of the O-H chemical bonds, the ... H hydrogen bonds, and the SO4 tetrahedra in promoting proton conduction. A high reversal rate limits the apparent success rate of the otherwise rapid chemical-bond dynamics...

Wasted opportunities : inequality and fragmentation in the 2010 South Africa World Cup; Inequality and fragmentation in the 2010 South Africa World Cup

Wood, Astrid
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166, [1] p.
ENG
Relevância na Pesquisa
46.06%
(cont.) This thesis will examine the possibilities for cities to use the 2010 World Cup to hasten city development. The first chapter will detail the 2010 World Cup plan and the local stakeholders as well as the lessons learned from previous World Cups. The next chapter will examine the obstacles South Africa faces as it prepares for the 2010 World Cup and characteristics that make this host country different from previous World Cup hosts. Chapter three will describe the development strategy and explain how World Cup infrastructure can change the city. The next chapter will illustrate the World Cup conflict resulting from these development decisions. The final chapter will explain the reasons why local organizers are wasting this opportunity, instead exacerbating inequality and fragmentation, and conclude with suggestions for future World Cup planners.; Planning and preparations for the 2010 South Africa FIFA World Cup are well underway and there is little doubt that South Africa will impress sports fans and spectators with the modern stadiums and tourist facilities. The 2010 World Cup is an opportunity to hasten social, cultural, environmental, economic, and physical growth. South African cities should use 2010 to improve the public realm and create new economic opportunities for South Africans.Megaevents like the 2010 World Cup can generate economic investment and build an international image...

Motion artifact reduction for wearable photoplethysmogram sensors using micro accelerometers and laguerre series adaptive filters

Wood, Levi Benjamin
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 74 p.
ENG
Relevância na Pesquisa
46.06%
The photoplethysmogram (PPG) is an extremely useful wearable sensing medical diagnostic tool. However, the PPG signal becomes highly corrupted when the wearer is in motion, rendering the measured signal useless. This thesis develops an adaptive motion artifact reduction scheme to recover the underlying physiologic information from the corrupted signal using a collocated accelerometer as a motion reference and adaptively estimating the motion-to-artifact system dynamics. It has previously been shown that this artifact reduction scheme can be utilized, but many tunable parameters were required to model the system dynamics and performance was poor. This work quantifies algorithm performance based on confidence in the estimated system dynamics, which shows low confidence using the previous parameterization when the wearer is jogging. To improve confidence, the form of the system dynamics is established and a Laguerre series is implimented to compactly represent the system dynamics using just a few parameters that can be confidently estimated. Using the new model, heart rate and amplitude can be estimated from typical jogger data with variance similar to separate PPG sensors located on contralateral motionless hands. The standard artifact reduction scheme does not work when the physiologic signal is correlated with wearer motion. Since the signals may become correlated...

Propriedades tecnol??gicas da madeira termorretificada de tr??s esp??cies de Eucalyptus; Technological properties of thermally modified wood from three Eucalyptus species

CADEMARTORI, Pedro Henrique Gonzalez de
Fonte: Universidade Federal de Pelotas; Ci??ncia e Engenharia de Materiais; Programa de P??s-Gradua????o em Ci??ncia e Engenharia de Materiais; UFPel; BR Publicador: Universidade Federal de Pelotas; Ci??ncia e Engenharia de Materiais; Programa de P??s-Gradua????o em Ci??ncia e Engenharia de Materiais; UFPel; BR
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
46.12%
This study aimed to evaluate physicomechanical and chemical behaviour of Eucalyptus grandis, Eucalyptus saligna e Eucalyptus cloeziana thermally modified wood. To achieve this, six trees of each species were randomly selected and samples measuring 1.6 x 1.6 x 25cm were prepared. The samples were thermally modified through exposure to nine treatments in an oven and in an autoclave steriliser. The process conditions in the oven were: temperatures between 180 and 240??C and time of exposure of 4h, whereas for the treatments in autoclave a constant temperature (127??C) and pressure (1.5kgf/cm??) were used for 1h. The evaluation of the physical properties was done through the performance of weight loss, equilibrium moisture content, stability dimensional and specific gravity tests. Colour changes and wettability were measured by colorimetric and contact angle techniques, respectively. Regarding mechanical properties, thermally modified wood was evaluated through the performance of static bending tests and non-destructive ultrasonic tests. Chemical modifications were qualitatively measured through infrared spectroscopy (ATR-IR). The main results showed that thermal treatments significantly influenced weight loss, equilibrium moisture content and dimensional stability. On the other hand...

An analysis of technology transition within the Department of Defense

Tew, Donnie; Wallace, Kevin
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Formato: xviii, 55 p. : ill. ; 28 cm.
Relevância na Pesquisa
46.03%
Joint Applied Project; Joint Applied Project; Appropriate methods and the proper execution thereof are critical to the success of technology transition. A significant hurdle in this process is the phase in which the Science and Technology community is prepared to hand-off a technology, which has not achieved a sufficiently high enough Technology Readiness Level (TRL), Manufacturing Readiness Level (MRL), or System Readiness Level (SRL) for the Engineering and Manufacturing community. This analysis concentrated on three technology transition factors: Organization, Policy, and Metrics (OPM). Organizational transformation encompasses the recent expansion of technology transition groups and initiatives within DoD. Additionally, the overall mindset of cooperative development and open communication are detailed within the Organizational focal area. The Policy focal area delves into the various DoD technology transition governing principles included in the DoD 5000, the Defense Acquisition Guidebook, and other governing documents. Lastly, the Technology Metrics focal area concentrates on the importance of technology maturation and how to qualitatively and objectively assess technologies. Thorough research was conducted on these areas to demonstrate DoD's recent efforts to bridge the gap and provide innovative solutions to the Warfighter within a reduced timeframe. Additionally...

Adverse effects of heartwood on the mechanical properties of wood-wool cement boards manufactured from radiata pine wood

Semple, Kate; Evans, Philip
Fonte: Society of Wood Science and Technology Publicador: Society of Wood Science and Technology
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.12%
Wood-wool cement boards (WWCBs) that are manufactured commercially in Australia from radiata pine occasionally contain localized areas in which there is poor bonding between wood and cement. The cause of this defect, which leads to the rejection of boards before they are sold, is not known, but it has been suggested that it may be due to the use of blue-stained wood or heartwood in the manufacture of boards. In this study, both wood types were tested for their effects on the hydration of Portland cement and the mechanical properties of WWCBs. Blue-stained sapwood slightly retarded the hydration of cement but had no significant (P < 0.05) effect on lhe mechanical properties of boards. In contrast, heartwood severely retarded cement hydration, and boards made from heartwood had little structural integrity. The appearance of such boards resembled the defective portions of commercially produced boards, and therefore it can be concluded that the defect arises from the inhibitory effect of heartwood on cement hydration. The problem could be eliminated by processing logs from young radiata pine trees, less than 12-15 years old, which will contain little or no heartwood.

Manufacture of wood-cement composites from Acacia Mangium: mechanistic study of compounds improving the compatability of Acacia Mangium heartwood with Portland cement

Semple, Kate; Cunningham, Ross; Evans, Philip David
Fonte: Society of Wood Science and Technology Publicador: Society of Wood Science and Technology
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
46.12%
Numerous inorganic compounds were screened to identify those capable of minimizing the inhibitory effect of Acacia mangium heartwood on the setting of cement. It was hypothesized that the most effective compounds would be ones that could accelerate the hydration of cement and form complexes with inhibitory phenolic extractives found in the heartwood of A. mangium. Our hypothesis proved correct since compounds such as SnCl4, AlCl3, and FeCl3 and/or their ionic species that were able to bond with the phenolic heartwood constituents of A. mangium as well as accelerate cement hydration were generally more effective at strengthening cement hydration in the presence of A. mangium heartwood than compounds that simply accelerated cement hydration. Compounds containing Ni2+, Ag+, Fe3+, and Co2+, that bonded to phenolic constituents of A. mangium heartwood, but lacked the ability to strongly accelerate cement hydration increased maximum hydration temperature attained in wood-cement mixes. The findings suggest that complexation of phenolic heartwood extractives may be an important mechanism by which inorganic compounds reduce the inhibitory effect of certain wood species on the hydration of cement. A combination of compounds including a cost-effective accelerator (such as CaCl2 or MgCl2) and an efficient chelating agent (containing such ions as Al3+...

Atributos do solo e qualidade da madeira para produção de celulose em plantações clonais de Eucalyptus grandis; Soil attributes and wood quality for pulp production in plantations of Eucalyptus grandis clone

Gava, José Luiz; Gonçalves, José Leonardo de Moraes
Fonte: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz Publicador: Universidade de São Paulo. Escola Superior de Agricultura Luiz de Queiroz
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; Formato: application/pdf
Publicado em 01/01/2008 ENG
Relevância na Pesquisa
46.12%
Os atributos edáficos podem afetar a qualidade da madeira de eucalipto, o que pode resultar em considerável efeito sobre a produção de celulose. Este trabalho teve como objetivo avaliar o efeito de atributos físicos e químicos do solo na qualidade da madeira de Eucalyptus grandis usada para polpação celulósica. Foram selecionadas cinco áreas no planalto ocidental do Estado de São Paulo, Brasil, plantadas com um mesmo clone de Eucalyptus grandis, com idades variando entre 6,5 e 7,0 anos de idade. Quatro classes de solo, com textura arenosa a muito argilosa, foram encontradas. Em cada uma das cinco áreas, foram demarcadas, aleatoriamente, 3 parcelas com 100 plantas cada. Em cada parcela, foram colhidas árvores representativas das diferentes classes de diâmetro à altura do peito para avaliação de suas biomassas e para a análise de extrativos e componentes da madeira. Os atributos físicos do solo, sobretudo o teor de argila, diretamente relacionado à quantidade de água disponível, foram os que mais afetaram a produtividade e a qualidade da madeira. A densidade básica da madeira não se alterou nas diferentes classes de solo. O teor de lignina total diminuiu e o de holocelulose aumentou exponencialmente com o aumento do teor de argila do solo (até cerca de 350 a 400 g kg-1 de argila). O teor de extrativos da madeira não foi afetado pelos atributos do solo. O rendimento de celulose depurada relacionou-se exponencialmente com o teor de argila do solo.; The soil attributes can affect the wood quality of eucalypt...