Cultivation of fast-growing industrial trees is one of the solutions to overcome the wood resources lack. To invest optimally in this field, some cases such as annual growth rate of the cultivated species, species adaptation to the climate of the region, adaptation to t More
Cultivation of fast-growing industrial trees is one of the solutions to overcome the wood resources lack. To invest optimally in this field, some cases such as annual growth rate of the cultivated species, species adaptation to the climate of the region, adaptation to the soil of the culture site, and also the quality of the produced wood and its applicability in lignocellulosic industries must be regarded. One of the recently introduced extremely fast-growing poplar cultivars is the Mofid hybrid poplar (Populus euphratica Oliv. × P. alba L.). Since low-density wood and wood waste, are used as the main source in the particle board production, in this study, the use of 4-year-old “Mofid” hybrid poplar wood as raw material in particle board production was investigated. To make particle board, the screened chips had been resined with 12% resin by a rotary gluer and then pressed for 5 min at a temperature of 170°C and a pressure of 32 kg/cm2. The examined tests included density, thickness swelling, bending strength, and internal bonding strength. The results showed that the produced particle board samples with “Mofid” poplar wood had acceptable mechanical and physical properties and they were more or less similar to the paulownia particle board samples (control group).
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Concentrated major stresses in area of beam-to-column welded connections of steel moment frames have been proposed in the high density demands as a critical factor in connection vulnerabilities. Reducing the stress concentration in the connections can be accompl More
Concentrated major stresses in area of beam-to-column welded connections of steel moment frames have been proposed in the high density demands as a critical factor in connection vulnerabilities. Reducing the stress concentration in the connections can be accomplished with the intentionally weakening of the cross section of the beam connected to the column. By this method, the plastic hing is formed in the weakened section and the demand is included on the connecting components. In this study, the effect of the panel rigidity on the behavior of the beam connection with the reduced bending strength section with the tube has been investigated. Eight connections of various thicknesses have been investigated. Connections are analyzed using finite element modeling under static loading. In this research, it is observed that with increasing the thickness of the web panel zone, the loss of the strength curve decreases and the connection experiences more drift. Also by increasing the thickness the von mises stress in the panel zone decreased. The values of stress and displacement were observed in the tube web in larger thicknesses are bigger. The failure of the column and the connection panel zone in the connections decreased with the increase of the connection panel zone thickness. The lowest energy dissipation is related to the weakest panel zone connection. By increasing the thickness of the panel zone connection, it would be expected that more energy would be lost from the connection. In general, according to the results obtained in this study, application of thickness less than the calculated value in seismic design is not recommended.
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خم شدن ساقه و دمگل تحت تاثیر وزن گل یکی از مشکلات اصلی پس از برداشت در ژربرا (Gerbera jamesonii Bolus.) است و گاهی اوقات باعث شکستگی ساقه و یا اختلال در جذب آب می­شود. در این تحقیق، تیمار سیلیسیوم و اسید سالیسیلیک به منظور افزایش مقاومت مکانیکی ساقه گل استفاده شد. ن More
خم شدن ساقه و دمگل تحت تاثیر وزن گل یکی از مشکلات اصلی پس از برداشت در ژربرا (Gerbera jamesonii Bolus.) است و گاهی اوقات باعث شکستگی ساقه و یا اختلال در جذب آب می­شود. در این تحقیق، تیمار سیلیسیوم و اسید سالیسیلیک به منظور افزایش مقاومت مکانیکی ساقه گل استفاده شد. نتایج نشان داد که خمیدگی ساقه با مصرف سیلیسیوم و تیمار اسید سالیسیلیک کاهش یافت. مقاومت برشی و مقدار لیگنین توسط تیمار سالیسیلیک اسید در هر دو بخش بالا و پایین ساقه افزایش یافت. به نظر می­رسد که مقدار لیگنین ساقه با مقاومت برشی در قسمت بالایی ارتباط داشت. علاوه بر این، مقدار سیلیسیوم در بافت ساقه گل به طور قابل­توجهی با مصرف سیلیسیوم افزایش یافت و مقاومت مکانیکی قسمت پایین ساقه با میزان سیلیسیوم بافت همبستگی داشت. این نتایج نشان داد که مصرف سیلیسیوم و تیمار اسید سالیسیلیک می­تواند باعث افزایش مقاومت مکانیکی ساقه گل و بهبود کیفیت گل بریده ژربرا گردد.
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