Methodology and device to obtain torsional shear strength of glued joints

This paper presents a methodology to obtain the shear strength of glued joints, at the torsion moment. In the current standards this strength is measured by compression tests. The device designed for this purpose are also presented. The motivation for this test is related to the possibility of execution of glued wooden structures with joints under bending moment, shear force and normal force simultaneously. It was admitted the hypothesis that the joint strength can be different depending on the test type. The methodology is relatively simple and in order to obtain the results classic equations from Mechanics of Materials were used. The strength results of 198 test specimens, tested by standard methodology, were compared, with an equal number of specimens made and tested with the proposed methodology, resulting in 396 tests. 208 specimens were glued with resorcinol-formaldehyde and 188 with castor oil-based adhesive. The wood used was Eucalyptus sp. The specimens were made according to seven series involving gluing with the following angles between the fibers: 0°, 15°, 30°, 45°, 60°, 75° and 90°. Regardless of the adhesive type, there was a significant difference for the strengths presented by the two methods. From the seven angles studied, it was noticed a difference in six of them, except for the 30° series. The compression shear strength was severely affected by the gluing angle, with increasing losses towards higher angles. On the contrary, the strength offered by the joints tested by torsion did not seem affected by the gluing angle.Keywords: wood; adhesive; characterization; procedure

Specific density and dimensional variation of a Eucalyptus urophylla x Eucalyptus grandis clonal hybrid

Espécies de rápido crescimento como as do gênero Eucalyptus apresentam sérios problemas durante as diversas fases de processamento de desdobro, secagem e beneficiamento. Assim, este trabalho objetivou estudar as propriedades físicas da madeira de um híbrido clonal de Eucalyptus urophylla x Eucalyptus grandis de duas idades, provenientes de regeneração florestal por talhadia simples e por reforma, em diferentes intensidades de desbaste, com diâmetros entre 28,0 e 30,0 cm. Os resultados indicaram que o extrato de maior idade com intervenção de dois desbastes (E2) apresentou os maiores valores médios da ao longo do fuste e na direção medula-casca, além de menores contrações volumétricas médias e menor fator anisotrópico médio (1,66). Apesar de o extrato E1, com talhadia e 70 meses de idade, cujo fator anisotrópico médio foi igual a 1,92, ser próximo do extrato E3, em que foi realizada apenas uma reforma aos 70 meses de idade, com fator anisotrópico igual a 2,04 ao longo do fuste, o extrato E1 apresentou os menores resultados de densidade básica média e retratibilidade média na primeira tora em relação à segunda. O mesmo comportamento foi verificado na contração volumétrica. O coeficiente de anisotropia na tora 2 foi menor do que na tora 1, nos extratos E1 e E3.Fast growing species as those belonging to the gender Eucalyptus present serious problems during the various phases of sawing, drying and processing. Thus, this work aimed to study the physical wood properties of a clonal hybrid of Eucalyptus urophylla x Eucalyptus grandis at two ages originated from coppice and replacement regeneration at different thinning intensities, with diameters between 28.0 and 30.0cm. The results showed that the extract of older aged wood with two thinning interventions (E2) presented the highest mean values for specific gravity along the stem and in the position pith to bark, as well as lower average volumetric contractions and lower average anisotropic factor (1.66). Although extract E1, with coppice at the age of 70 months and anisotropic factor equal to 1.92, was close to extract E3, with only one replacementat the age of 70 months and anisotropic factor equal to 2.04 along the stem, it presented the lowest specific gravity and average shrinkage values for log 1 in relation to log 2. The same behavior was verified for volumetric contraction. The anisotropy factor in log 1 was lower in relation to log 2 in extracts E1 and E3

Eucalyptus growth under the effect of artificial defoliation

O objetivo deste trabalho foi avaliar os efeitos do desfolhamento total, realizado após o plantio e ao longo do primeiro ano de cultivo, sobre o crescimento de Eucalyptus grandis, desde a implantação até ao corte do povoamento. Foram avaliados cinco tratamentos: sem desfolhamento; um desfolhamento aos 56 dias após o plantio (DAP); dois desfolhamentos, aos 56 e 143 DAP; dois desfolhamentos, aos 56 e 267 DAP; e três desfolhamentos, aos 56, 143 e 278 DAP. Foram mensurados os diâmetros do tronco a 1,3 m e a altura total de 60 árvores por tratamento, em oito avaliações, do 21º ao 92º mês de cultivo. O crescimento médio em cada tratamento foi descrito por modelos de regressão não lineares e comparados por testes de identidade para comparar as tendências entre a testemunha e os demais tratamentos. O desfolhamento causou reduções significativas nas taxas de crescimento em diâmetro e altura das plantas, e diminuição expressiva no faturamento ao final da rotação, mesmo quando realizado uma única vez, no início do plantio. Maiores danos, no entanto, foram verificados após consecutivos desfolhamentos ao longo do primeiro ano de cultivo. A manutenção de áreas que tenham sofrido desfolhamento total na fase inicial de plantio pode tornar-se uma medida economicamente inviável.The objective of this work was to evaluate the effects of total defoliation at planting initial stages, and along the first year of cultivation, on Eucalyptus grandis growth, from planting to plantation cut. Five treatments were tested: without defoliation; one defoliation, at 56th day after planting (DAP); two defoliations, at 56th and 143rd DAP; two defoliations, at 56th and 267th DAP; and three defoliations, at 56th, 143rd and 278th DAP. Trunk diameter at 1.30-m height and the total height of 60 trees were measured from the 21st to the 92nd cultivation months. The average growth of each treatment was described by nonlinear models and compared by identity tests in order to estimate the tendencies between control and the other treatments in each variable. Defoliation significantly reduces diameter of the trunk and height growth rates, and expressively decreases the income at the plantation cut. However, greater losses were verified after consecutive defoliation, along the first cultivation year. Maintaining areas that suffered severe defoliations at initial planting stages can become economically unfeasible

Análise cinética da cura de adesivos de taninos das cascas de três espécies de eucalyptus por calorimetria diferencial exploratória (dsc)

O objetivo deste trabalho foi analisar a cinética de cura de adesivos à base de taninos de Eucalyptus grandis, Eucalyptus saligna e Eucalyptus urophylla por calorimetria diferencial exploratória (DSC), comparando-a com a cinética de cura de adesivos comerciais: fenol-formaldeído e de taninos de acácia-negra (Acacia mollissima D.Wild). Verificou-se que o adesivo de taninos de Eucalyptus urophylla apresentou os parâmetros cinéticos (energia de ativação, entalpia, temperatura de pico e ordem de reação) mais próximos aos do adesivo comercial de taninos de acácia-negra, que foram totalmente diferentes do adesivo à base de fenol-formaldeído. Com base nestes parâmetros constatou-se que, em relação aos outros dois, o adesivo de taninos de Eucalyptus urophylla é o mais adequado para colagem, uma vez que em condições industriais ele necessitará de uso mínimo de energia e de tempo de prensagem durante o processo de colagem.This work aimed to analyze the cure kinetics of Eucalyptus grandis, Eucalyptus saligna and Eucalyptus urophylla tannins based adhesives by differential scanning calorimetry (DSC). Another objective was to compare cure kinetics of Eucalyptus tannin adhesives with the cure kinetics of phenol-formaldehyde and Wattle black (Acacia mollissima D. Wild) tannin commercial adhesives. It was observed that the Eucalyptus urophylla tannin adhesives presented kinetic parameters (activation energy, entalpia, peak temperature and reaction order) similar to the Wattle black commercial tannin adhesives but were different from the phenol-formaldehyde adhesives. Based on these parameters it was concluded that the Eucalyptus urophylla tannin adhesives are more adequate for wood bonding than the other two Eucalyptus tannin adhesives. Under industrial conditions, Eucalyptus urophylla tannin adhesive will need a minimum energy and pressing

Crescimento de eucalipto sob efeito de desfolhamento artificial

O objetivo deste trabalho foi avaliar os efeitos do desfolhamento total, realizado após o plantio e ao longo do primeiro ano de cultivo, sobre o crescimento de Eucalyptus grandis, desde a implantação até ao corte do povoamento. Foram avaliados cinco tratamentos: sem desfolhamento; um desfolhamento aos 56 dias após o plantio (DAP); dois desfolhamentos, aos 56 e 143 DAP; dois desfolhamentos, aos 56 e 267 DAP; e três desfolhamentos, aos 56, 143 e 278 DAP. Foram mensurados os diâmetros do tronco a 1,3 m e a altura total de 60 árvores por tratamento, em oito avaliações, do 21º ao 92º mês de cultivo. O crescimento médio em cada tratamento foi descrito por modelos de regressão não lineares e comparados por testes de identidade para comparar as tendências entre a testemunha e os demais tratamentos. O desfolhamento causou reduções significativas nas taxas de crescimento em diâmetro e altura das plantas, e diminuição expressiva no faturamento ao final da rotação, mesmo quando realizado uma única vez, no início do plantio. Maiores danos, no entanto, foram verificados após consecutivos desfolhamentos ao longo do primeiro ano de cultivo. A manutenção de áreas que tenham sofrido desfolhamento total na fase inicial de plantio pode tornar-se uma medida economicamente inviável.The objective of this work was to evaluate the effects of total defoliation at planting initial stages, and along the first year of cultivation, on Eucalyptus grandis growth, from planting to plantation cut. Five treatments were tested: without defoliation; one defoliation, at 56th day after planting (DAP); two defoliations, at 56th and 143th DAP; two defoliations, at 56th and 267th DAP; and three defoliations, at 56th, 143th and 278th DAP. Trunk diameter at 1.30-m height and the total height of 60 trees were measured from the 21st to the 92th cultivation months. The average growth of each treatment was described by nonlinear models and compared by identity tests in order to estimate the tendencies between control and the other treatments in each variable. Defoliation significantly reduces diameter of the trunk and height growth rates, and expressively decreases the income at the plantation cut. However, greater losses were verified after consecutive defoliation, along the first cultivation year. Maintaining areas that suffered severe defoliations at initial planting stages can become economically unfeasible

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe