Physics and Mechanical Wood
mostafa kohantorabi; Mehran Roohnia; Shadabeh Fathi
Abstract
In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture ...
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In this study, 10 samples of beech wood, without apparent defect, with dimensions of 360 × 16 × 16 cm (length × radial × tangential) were selected, and after being exposed to variable temperature (60, 80, 100, 120, 140, 160, and 180°C) and moisture content conditions (moisture content in conditions of: saturated with water (EMC=35±5%), equilibrium moisture content exposed to air (EMC=19±5%), and conditioning moisture content in a climatic chamber (EMC=12±2%), they underwent free flexural vibration test in two longitudinal-tangential and longitudinal-radial planes, and some of the physical, mechanical, and acoustical properties in both planes were investigated. The results showed that the correlation coefficient of the first three modes of flexural vibration in both planes under climatic chamber had a similar situation, but when the samples were in the water-saturated condition, they showed an adverse behavior in each plane. The effect of increasing the temperature above 100°C caused stresses resulting from shrinkage leading to the development of micro-cracks and reduction in the modulus of elasticity of cell walls and ultimately reduction in wave propagation ability of wood, thus increase in the damping vibration values in both longitudinal-tangential and longitudinal-radial planes of the samples. Also, the concurrent changes in modulus of elasticity and damping vibration in both vibration planes are a desirable indicator for monitoring the process from the primary logging process stages to processes such as wood drying and heat treatment.
Mahmood Kazemi; Hamideh Asadpoor; Shamsaldin Balapoor
Abstract
During 2008, a severe deluge in Sari caused huge damages and Cupressus sempervirens l. var. horizantalis trees in botany garden of Natural Sciences College were also fallen by the overflow. To perform the study the fallen trees disks and cores of standing trees were prepared. Using Lintab Measurement ...
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During 2008, a severe deluge in Sari caused huge damages and Cupressus sempervirens l. var. horizantalis trees in botany garden of Natural Sciences College were also fallen by the overflow. To perform the study the fallen trees disks and cores of standing trees were prepared. Using Lintab Measurement Table, the width of each growth ring per year and their average were calculated. The raw data related to rings growth were standardized by method of ARSTAN and index average of growth rings was recorded. To study the relationship between climatic variables and C. sempervirens rings growth, data of Babolsar and Tajan synoptic stations were found. The observation results of fallen trees in flat sites showed that C. sempervirens is not resistant against deluge and in the places which ground water table is raised; C. sempervirens is not suggested for planting. Numerical results also indicated that the mean growth ring is about 3.62 mm per year. Taking into account the bark width, the average of trunk diameter after 40 years was about 30 cm. Temperature increase during the Past years had caused the trend of growth width to reduce. Also the relation of index average of growth with rainfall showed that precipitation is an effective factor on C. sempervirens growth and as a result, the average of rainfall in April had a positive and significance effect on C. sempervirens growth (R= 0.61 and P<0.01).
Shamsaldin Balapoor; Mahmood Kazemi
Abstract
Plants such as tree species respond to their surrounding environmental variations over their biological life cycle. One of the techniques to study the tree response to environmental conditions is dendrochronolog. In this study, 20 samples were prepared from 10 Zelkova carpinifolia trees in Badleh-Sari ...
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Plants such as tree species respond to their surrounding environmental variations over their biological life cycle. One of the techniques to study the tree response to environmental conditions is dendrochronolog. In this study, 20 samples were prepared from 10 Zelkova carpinifolia trees in Badleh-Sari area. The effects of climate variables (precipitation and temperature) on annual rings of Zelkova carpinifolia trees were examined. Samples rings cross-date was determined using dendrochronological method. Also a chronology of 78 years period was made (1932-2012 AD). Mean Sensitivity (MS), mean correlation coefficient between the samples (trees), EPS and SNR, were determined as 20%, 0.5, 0.88 and 4.11 respectively. Analysis of the relationship between growth and climate over the period of 1951 – 2005, using response function (RF) showed that temperature did not significantly affect growth but total precipitation in February had positive effect (r = 0.45 p <0.001) on the growth of Zelkova carpinifolia. Analysis of trees growth response to precipitation in February showed that precipitation in the periods 1976–1994 had significant impact on the growth. However, in recent years (2011-2006) the rate of effectiveness of the precipitation on tree growth was decreased. Finally it could be mentioned that Zelkova can be a useful tree species for dendroclimatological purposes in terms of high rate of MS, EPS and SNR.
Pulp and paper
Omid Hosseinzadeh; Ahmad Jahan latibari
Abstract
The influence of pulping temperature and time on strength properties of bagasse soda pulp was investigated. Two cooking temperatures)175ْC,185 ْC (and three cooking times (20,30,40 minutes) were selected .The other variables were kept constant at 18 % NaOH and l/w=8. Tensile strength, tear strength ...
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The influence of pulping temperature and time on strength properties of bagasse soda pulp was investigated. Two cooking temperatures)175ْC,185 ْC (and three cooking times (20,30,40 minutes) were selected .The other variables were kept constant at 18 % NaOH and l/w=8. Tensile strength, tear strength index and folding endurance of hand sheets measured . Factorial experiment and randomized block design was used for statistical analysis and DMRT was used for grouping the means. The results indicate that, application of intermediate cooking intensity produced better pulp than more intense pulping at highest pulping time and temperature. However, more intense pulping produced better folding endurance and pulp prepared at 30 minutes cooking time showed better folding endurance than pulp produced at 20 minutes. The highest tear index was obtain at 185 ْC and 20minutes and lowest at 185ْC and 40 minutes. Results indicate that undamaged fibers will product highest tear index. The highest folding endurance was produced at 175 ْC and 30 minutes and the lowest at 185ْC and 30 minutes .Increasing pulping time reduced tensile index and the highest and lowest tensile index obtained at 20 and 40 minutes pulping time respectively.
