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Effects of particles thickness and veneer reiforced layer in the properties of oriented strand boards OSB
Setsuo Iwakiri,Leopoldo Karman Saldanha,Carlos Eduardo Camargo de Albuquerque,Lourival Marin Mendes
CERNE , 2009,
Abstract: This work evaluated the effects of particle thickness and veneer reinforced layer on the physical and mechanicalproperties of OSB made of Pinus taeda L. The boards were manufactured with particle thickness of 0.4, 0.7 and 1.0 mm and phenolformaldehyderesin in the proportion of 6% of solid content. To the veneer reinforced layer was used veneer from Pinus taeda with 2.0mm of thickness. The increase in the slenderness (length/thickness) ratio of thins particles, results in the higher values of MOE andMOR in the cross direction. The increase in the particles thickness contributed to higher values of the board internal bond. Thedifferent particles thickness did not clearly affected on the physical properties of OSB. The veneer reinforced layer results in the higheraverage values of MOE and MOR in the cross direction. All of the results of MOE and MOR obtained for boards with differentthickness attend tominimum values required per CSA 0437 (CSA, 1993). For the internal bond, the results were satisfactory to boardsmanufactured with particles thickness of 0.7 and 1.0 mm. According to the results the main conclusions were: (i) The increase in theparticles thickness contributed to lower values of MOE and MOR, and higher values of the board internal bond; (ii) the veneerreinforced layer increased MOE and MOR values in the cross direction.
Utilization of Non -oven Jute felt - A natural Fiber as a Substitution of Wood Veneer for Manufacture of Plywood  [PDF]
Mr. S.C.Sahoo,Mr. Amitava Sil,Mr. P.K.Khatua
International Journal of Recent Technology and Engineering , 2012,
Abstract: In this study the suitability of using core veneer made from renewable natural fiber i.e. Non-oven jute felt, which is the second most widely used natural fiber for manufacturing of plywood was investigated to minimize the gap between demand and supply of wood veneer. The renewable natural hard jute fibre was impregnated with phenolic resin and was used for the manufacture of plywood. Plywood of 4 mm, 6 mm, 12 mm and 18 mm thick were manufactured by using phenolic resin impregnated jute felt having thickness 16mm of 1850 GSM (approx.) as a core in place of the natural wood veneer. From the study, it can be inferred that PF Resin impregnated Non oven jute felt as a natural fibre can suitably replace the wooden glue core veneer to manufacture ply board up to 80% as an alternative substitute of wood. The physico-mechanical properties such as surface roughness, moisture content, density, water absorption, swelling, compressive strength, tensile strength, static bending strength, glue shear strength, of the plywood manufactured by using jute felt as core veneer with different resin dilution have been studied. Data revels that most of the physico-mechanical properties of the plywood showed satisfactory results meeting the requirement of different grades of plywood tested as per IS: 1734 - 1983. The accelerated study of the glued core after impregnation with jute felt have been carried out for three months before plywood manufacture after storing it in proper temperature and humidity. The data revealed that there is no appreciable change in bond quality and mechanical properties of the plyboard manufactured after storing the veneer up to 30 days. The study concluded that wood substituted jute composites could be an ideal solution with ever depleting forest reserves where utilization of renewable resources will be beneficiary for plywood industries to meet the challenges during scarcity of veneer by reducing the cost of imported veneer.
Compressive Direction Finding Based on Amplitude Comparison  [cached]
Ruiming Yang,Yipeng Liu,Qun Wan,Wanlin Yang
Journal of Networks , 2011, DOI: 10.4304/jnw.6.3.498-504
Abstract: This paper exploits recent developments in sparse approximation and compressed sensing to efficiently perform the direction finding. The new method is proposed based on unimodal characteristic of antenna pattern and sparse property of received data. Unlike the conventional methods based peak-searching and symmetric constraint, the sparse reconstruction algorithm requires less pulse and takes advantage of compressive sampling. Simulation results validate the performance of the proposed method is better than the conventional methods.
Compressive Direction Finding Based on Amplitude Comparison  [PDF]
Ruiming Yang,Yipeng Liu,Qun Wan,Wanlin Yang
Mathematics , 2010,
Abstract: This paper exploits recent developments in compressive sensing (CS) to efficiently perform the direction finding via amplitude comprarison. The new method is proposed based on unimodal characteristic of antenna pattern and sparse property of received data. Unlike the conventional methods based peak-searching and symmetric constraint, the sparse reconstruction algorithm requires less pulse and takes advantage of CS. Simulation results validate the performance of the proposed method is better than the conventional methods.
The Comparison of the Film Thickness and Compressive Strength Between Ariadent and Harvard Zinc Phosphate Cement.  [cached]
M - Sabouhi,N Hekmat,N Baiatabadi
Journal of Isfahan Dental School , 2005,
Abstract: Introduction. Recently, the Ariadent Zinc phosphate cement has been introduced to market with low cost. Some dentists purchase this product because of low cost and others avoid buying it because of unreliable quality. The two important properties of ideal dental cement are to have the minimum film thickness (less than 25 micron) and to have favorable compressive strength. The purpose of this study was to determine the mean and to compare the film thickness and compressive strength of Ariadent and Harvard Zinc phosphate cement.Materials and Methods. In this experimental study evaluation was made based on Iranian standard number 2725. To measure film thickness of each cement, the first step was to prepare two glass slabs and their thickness was measured with micrometer, then each cement was prepared according to standard procedure and was put between the glass slabs. The difference between glass slabs with and without cement was measured. This procedure was repeated 3 times and average of three measurements were obtained and determined as mean of cement film thickness. To determine the compressive strength of each cement at first a mold was fabricated according to standard procedures. Then each prepared cement was poured in to the mold. After 24 hours each of five prepared specimens was Put under load and the average compressive strength was calculated.Results. The mean film thickness for Arident Zinc phosphate was 42.33 4.50 micron and for Harvard cement was 24.33 5.70. The mean compressive strength of Ariadent Zinc phosphate cement was 44.90 4.11 MPa and for Harvard cement was 62.85 5.19 MPa. The statistical analysis (t-student) revealed significant difference between two phosphate cement.Discussion. In this study mean film thickness of Iranian Ariadent Zinc phosphate cement was more than standard level (25 micron) and the mean compressive strength was less than standard level (70 MPa). These results indicated that Ariadent cement was of low quality and below standard. But Harvard Zinc phosphate cement had a standard film thickness and its compressive strength was close to standard and this is a reason for acceptable quality of Harvard Zinc phosphate cement.Keywords. Cement, Compressive strength, film thickness, Zinc phosphate cement
Alternating Direction Algorithms for $\ell_1$-Problems in Compressive Sensing  [PDF]
Junfeng Yang,Yin Zhang
Mathematics , 2009,
Abstract: In this paper, we propose and study the use of alternating direction algorithms for several $\ell_1$-norm minimization problems arising from sparse solution recovery in compressive sensing, including the basis pursuit problem, the basis-pursuit denoising problems of both unconstrained and constrained forms, as well as others. We present and investigate two classes of algorithms derived from either the primal or the dual forms of the $\ell_1$-problems. The construction of the algorithms consists of two main steps: (1) to reformulate an $\ell_1$-problem into one having partially separable objective functions by adding new variables and constraints; and (2) to apply an exact or inexact alternating direction method to the resulting problem. The derived alternating direction algorithms can be regarded as first-order primal-dual algorithms because both primal and dual variables are updated at each and every iteration. Convergence properties of these algorithms are established or restated when they already exist. Extensive numerical results in comparison with several state-of-the-art algorithms are given to demonstrate that the proposed algorithms are efficient, stable and robust. Moreover, we present numerical results to emphasize two practically important but perhaps overlooked points. One point is that algorithm speed should always be evaluated relative to appropriate solution accuracy; another is that whenever erroneous measurements possibly exist, the $\ell_1$-norm fidelity should be the fidelity of choice in compressive sensing.
Some Comparative Properties of Reconstituted Poplar Veneer Replicating Wenge With Classic Veneer of the Same Species
Lidia GURAU
Pro Ligno , 2010,
Abstract: Eco-friendly alternative options to traditional wood veneer have become available around the world in reconstituted veneers. This paper is exploring some properties of reconstituted poplar veneer replicating wenge in indirect testing, which meant to evaluate the bending properties of veneered particleboards and in direct testing that envisaged the veneer density and water absorption. The properties of reconstituted poplar replicating wenge were compared with those of poplar and wenge veneer tested in the same conditions. The results show a slightly lower MOE and MOR for the particleboard veneered with reconstituted veneer compared to the classic veneer, in spite of a higher veneered panel density. The reason may be a discontinuous structure of the engineered veneer compared to the traditional veneer. However, the addition of veneer to particleboards has increased their MOE app. 1.4-1.7 times and doubled their MOR. Smaller standard deviation values of the MOE, MOR and density were recorded for the particleboard veneered with reconstituted poplar replicating wenge compared with the ones veneered with poplar or natural wenge, which may indicate a more homogenous structure for the reconstituted veneer compared with the natural veneers. The reconstituted poplar veneer replicating wenge had higher density than the poplar veneer and it absorbed less water. However, compared with natural wenge, the replica made of poplar had lower performances. Further tests could examine the finishing behaviour of reconstituted veneer and its resistance to scratches and spots.
VENEER BLOCK CONDITIONING MANUAL FOR VENEER AND PLYWOOD PRODUCTION
Steinhagen,H. Peter;
Maderas. Ciencia y tecnología , 2005, DOI: 10.4067/S0718-221X2005000100006
Abstract: veneer blocks are heat-conditioned in water or steam in an effort to plasticize (“soften”) the wood. when a sufficiently heated block is cut into veneer, the veneer will bend over the lathe's knife without splitting. this leads to improved volume recovery as the greatest conditioning benefit. since conditioning adds to the production cost, a site-specific economic analysis will be necessary to determine profit margins. this manual is based on selected literature sources. it briefly addresses the cost/benefit of block conditioning, heat-conditioning systems, energy demand, target temperatures, and conditioning times
VENEER BLOCK CONDITIONING MANUAL FOR VENEER AND PLYWOOD PRODUCTION
H. Peter Steinhagen
MADERAS : Ciencia y Tecnología , 2005,
Abstract: Veneer blocks are heat-conditioned in water or steam in an effort to plasticize (“soften”) the wood. When a sufficiently heated block is cut into veneer, the veneer will bend over the lathe's knife without splitting. This leads to improved volume recovery as the greatest conditioning benefit. Since conditioning adds to the production cost, a site-specific economic analysis will be necessary to determine profit margins. This manual is based on selected literature sources. It briefly addresses the cost/benefit of block conditioning, heat-conditioning systems, energy demand, target temperatures, and conditioning times
Influence of veneer quality on beech LVL mechanical properties
Abdelhakim Daoui,Clément Descamps,Rémy Marchal,Abdellatif Zerizer
MADERAS : Ciencia y Tecnología , 2011,
Abstract: The quality of peeled veneers is generally quoted considering 3 main criteria: surface roughness, thickness variations and lathe checking. This last criterion impacts on mechanical properties of by-products. It is well known that lathe checking occurrence can be reduced applying a good hygrothermal treatment of the round-wood before peeling coupled with optimised setting of pressure bar on the peeling lathe. It is also well known that thicker the veneer is and more difficult it is to reduce lathe checking and the other veneer defects. The tendency being to manufacture more eco-friendly engineering wood products using less glue, it is of interest to design such products with thicker layers and so less glue lines. But using ticker veneers should lead to a deterioration of final products mechanical properties. To quantify this effect, we have made 20-21mm thick LVL (Laminated Veneer Lumber) boards of beech (Fagus sylvatica) with various compositions (veneers 1, 3 or 5 mm thick). In order to obtained veneers enclosing different grades, several bolts of a same tree have been peeled following 4 different modalities changing wood conditioning temperature (20 / 70°C) and pressure bar settings (bar acting or not). The quality of all the veneers has been quantified before gluing. In total, 12 sets of boards have been produced for non destructive and destructive mechanical tests. The main results of these exploratory experiments are: a quite low weakening of LVL mechanical properties when increasing veneer thickness. the non destructive prediction of MOE by vibration seems not so good on LVL with thick veneers, especially in the case of edgewise loading, probably because of the presence of important lathe checks. in some configuration, and especially when using thick veneers, it could be benefit to load LVL flatwise rather than edgewise. for the measurement of shear strength on LVL, the 5-point bending test increases its efficiency when increasing veneer thickness. To properly order in a hierarchy the different veneer criteria impacting on LVL mechanical properties, new tests should be repeated on different LVL boards homogeneous for given criteria of veneer quality.
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