RESUMOO objetivo deste trabalho foi avaliar a resistência ao cisalhamento na linha de cola de juntas de Eucalyptus sp. coladas com diferentes adesivos e diferentes gramaturas. Para a colagem das juntas foi utilizada a madeira de Eucalyptus sp., dois adesivos de cura a quente (fenol-formaldeído e melamina-formaldeído), quatro adesivos de cura a frio [resorcinol-formaldeído, silicato de sódio, PVA (acetato de polivinila) e poliuretano à base de mamona], empregando-se gramaturas de 150 g, 200 g e 250 g/m 2 em face dupla. Foram determinados aresistência ao cisalhamento e à falha na madeira, e cisalhamento em condição úmida. Os resultados obtidos indicaram que os adesivos de mamona e resorcinol apresentaram maior resistência ao cisalhamento na linha de cola na condição seca. Os adesivos de mamona e fenol-formaldeído apresentaram maior percentual de falha na madeira na condição seca.Palavras-chave: adesivo de mamona, silicato de sódio, colagem. Shear in the Glue Line of Eucalyptus sp. Bonded with Different Adhesives and Weights ABSTRACTThis work aimed to evaluate the shear strength of glue line joints of Eucalyptus sp bonded with different adhesives and weights. Bonding of Eucalyptus sp was performed using two hot-curing adhesives (phenol-formaldehyde and melamine-formaldehyde), four cold-curing adhesives (resorcinol-formaldehyde, sodium silicate, PVA (polyvinyl acetate) and castor oil-based polyurethane, the weights were 150, 200 and 250 g/m 2 double sided.Shear strength and failure in wood and shear in wet conditions were determined. According to the results, castor and resorcinol adhesives showed higher shear strength in the glue line in dry condition. Castor and phenol formaldehyde adhesives showed higher failure percentage in wood in dry condition.
The expansion of short rotation eucalypt plantations in low soil organic matter (SOM) sandy soils may offer an alternative to improve soil C sequestration. The goal of this study was to estimate the changes in C stocks and emissions in different SOM fractions following conversion of the native Cerrado to pasture and then to eucalypt plantation. Therefore, we studied soils under native Cerrado, planted pasture (cultivated for 34years following the clearing of the Cerrado) and eucalypt plantation (4years). The C and N stocks in particulate organic matter and mineral‐associated organic matter (MAOM) were determined 4years after eucalypt planting. Soil CO2‐C, CH4‐C fluxes and CO2‐C concentrations in soil profile were measured in different seasons over 4years. Variation in the natural abundance of 13C was used to partition the SOM‐C. The soil CO2‐C and CH4‐C fluxes were influenced by soil surface moisture (r= 0.185o and r= 0.430**, respectively), whereas only the soil CH4‐C fluxes correlated with soil surface temperature (r= 0.355**). The highest soil CO2‐C flux in soil under eucalypt occurred after 4years of eucalypt planting (2.5 kg ha−1h−1, approximately 70%). The pasture soil acted as a CH4‐C source to the atmosphere. The pasture MAOM‐C losses in the 0.0–1.0‐m soil layers were not compensated by the new eucalypt C inputs (MAOM‐C lost ~9.6 Mg ha−1). In summary, the recent worldwide expansion of short rotation eucalypt plantations should be carefully considered, particularly under pasture degraded soil sandy soils, because land uses able to increase SOM are priorities.
Eucalyptus forests stand out for their potential to sequestrate atmospheric CO 2 in soil organic matter throughout their growth. Our study evaluated the harvesting and tillage effect in eucalyptus plantations to the soil CO 2 , 13 C-CO 2 , and CH 4 fluxes. This study was carried out in a eucalyptus plantation, on Typic Haplustox soil. The study used stands cultivated with eucalyptus at the end of the first rotation (7 years), established over degraded pastures. The effect of harvesting was assessed through comparisons of samples taken before and after harvesting with Feller + Skidder (F + S) and Harvester + Forwarder (H + F) methods and separate samples of plant rows (R) and plant interrows (IR). The effect of tillage was assessed through comparisons of R and IR samples taken before and after subsoiling tillage in areas harvested with F + S and H + F methods. A nested experimental design was used with eight replicates. The harvest operation (F + S and H + F methods) in eucalyptus plantationsincreased soil CO 2 fluxes, which were primarily derived from eucalyptus materials ('new C'). The F + S harvesting method resulted in the highest soil density and soil moisture reduction in the IR. The tillage operation (subsoiling) resulted in higher soil CO 2 fluxes in eucalyptus plantations harvest with F + S and H + F methods. However, the H + F method preserved the older soil organic carbon (40.8% in R and 50.4% IR of C 4 -CO 2 ). The soil in the eucalyptus plantations showed soil CH 4 influxes, and the harvest and tillage (subsoiling) operations did not negatively affect the net soil CH 4 influx in the studied eucalyptus plantations.
-To evaluate the adhesive efficiency on the union of glued joints in a particular temperature and humidity conditions for a specified time the adhesive must be submitted to specific load tests, such as shear in the glue line. The objective of this study was to evaluate the shear strength in the glue line of Eucalyptus sp and Pinus sp.woods. Five adhesives (castor oil, sodium silicate, modified silicate, , PVA and resorcinolformaldehyde), three weights (150 g/m 2 , 200 g/m 2 , and 250 g/m 2 ) and two species (Eucalyptus sp. and Pinus sp.) of wood were used. Twelve specimens were obtained from each repetition per treatment, corresponding to 108 specimens that were conditioned at a temperature of 23 ± 1°C and relative humidity of 50 ± 2%. The interaction between the weight and type of adhesive was significant for the shear strength in the glue line of eucalyptus wood. However, no interaction between the weight and the adhesive was found for pinus, only the isolated from the adhesive effect. Chemical bonds originated in the polymerization of resorcinolformaldehyde adhesives and castor bi-component conferred upon these adhesives the greatest resistance in the glue line. Castor and resorcinol-formaldehyde adhesives showed the highest shear strength values in the line of glue and wood failure. Castor adhesive presented satisfactory performance for bonding of eucalyptus and pine woods.Keywords: Adhesives; Collage; Weight. RESISTÊNCIA AO CISALHAMENTO NA LINHA DE COLA DAS MADEIRAS DE Eucalyptus sp. E Pinus sp.RESUMO -Para avaliar a eficiência do adesivo na união das juntas coladas, sob uma determinada temperatura e condições de umidade, durante um tempo específico o adesivo deve ser submetido a testes de carregamento, como, por exemplo, o teste de cisalhamento na linha de cola. Portanto, o objetivo deste trabalho foi avaliar a resistência ao cisalhamento na linha de cola de amostras de madeiras de Eucalyptus sp. e Pinus sp. coladas com cinco diferentes adesivos (Bicomponente de mamona, silicato de sódio, silicato modificado, PVA e resorcinolformaldeído) e três gramaturas (150 g/m 2 , 200 g/m 2 e 250 g/m 2 ) . Foram obtidos 12 corpos de prova para cada repetição por tratamento, correspondendo a 108 corpos de prova por tratamento, totalizando 3240 corpos de prova, que foram condicionados a temperatura de 23+1º C e umidade relativa de 50 + 2%. Após atingirem a umidade de equilíbrio higroscópico, a resistência ao cisalhamento e a falha na madeira foram determinadas, nas condições seca e úmida. Foram ensaiados doze corpos-de-prova, sendo nove na condição seca e três na 1110Revista Árvore, Viçosa-MG, v.40, n.6, p.1109-1117, 2016 BIANCHE, J.J. et al.condição úmida. As ligações químicas originadas na polimerização dos adesivos de resorcinol-formaldeído e bicomponente de mamona conferiram a estes adesivos maiores resistências ao cisalhamento na linha de cola e falha na madeira.
Background:The aim of this research is to optimize the routing of Brazil nut harvesting in order to reduce labor costs and promote an equitable redistribution of placements among extractive interests. The study area was located in the Tahuamanu province, designated a Biosphere Reserve by UNESCO, in the Madre de Dios region of Peru. Planning for harvesting activities is vital to support sustainable use of the tropical forest by extractive communities, generating profit while minimizing adverse impacts on the forest. A location-allocation model was used to redistribute extraction placement areas, taking into account the number of trees and productivity for analysis. To optimize the order of nut load pickups at the placement areas, the vehicle routing problem (VRP) was used to minimize real distance and reduce traversal time. Results:The time taken to cover the route without delays was 08:46', which is superior to the time taken to minimize the distance. However, the total delay time was 05:10'. Conclusion:Network analyses were effective in achieving the reallocation of placement areas and optimizing Brazil nut harvest routes.
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