Papers by Keyword: Larch

Abstract: This paper studies on the compression properties of larch glum columns by building a finite element modeling. A three-dimension solid element SOLID 95 (Fig.1) of ANSYS is elected to simulate the test specimens firstly. The numerical simulation result (stress-strain curve) agrees with the experimental result. The highest stress value on the cross section is 12% of that along the grain, which is approximate with the result (10%) carried out from test. For the strain profile under the ultimate load, the strain distributes homogenous along the grain while the values of strain are almost the same at the corn of cross section. The modeling built in this paper can verify the compression test of the larch glum columns. It is reasonable to simplify the glum columns as transverse isotropy material.

Abstract: In this paper, the ultimate, proximate and component analyses of the Daxinganling larch bark and xylem were performed and intercompared respectively. The pyrolysis features of the bark and xylem were analyzed by using the differential thermal thermo-gravimetric analyzer (TG). The influences of heating rate on pyrolysis features were discussed. The results show: (i) the content of H is a little more in the xylem than the bark and the content of ash in the bark is two times of the xylem and the content of fixed carbon in the xylem is two times of the bark. The content of alcohol-benzene extract is significantly more in the bark than the xylem and the glarson lignin in the bark is two times of the xylem but the hemicellulose in the xylem is three times of the bark; (ii) the process of the bark pyrolysis has two pyrolysis areas, but the xylem has a only pyrolysis area, however, the main pyrolysis interval of temperature of the bark and xylem are between 420K to 720K, in which the weight-loss of bark is 87-91% of the full weight-loss and the xylem weight-loss is 91-95% of the full weight-loss. (iii) the DTG peak of the xylem is behind 25 K of bark, and the DTG peak of the bark is-0.47 but the xylem-0.93. (iv) the curves of the TG and DTG move to the side of the higher temperature a bit following the heating rate increased, while the main pyrolysis areas are wider.

Abstract: China has the largest plywood production in the world. With the fast development of timber construction in China, plywood has been used as an important structural material for sheathing. It is needed to evaluate some performances for structural use, such as uniform load test. Plywood of different thickness is manufactured according to independent developed technology on a production line. The uniform load capacity was evaluated for wall sheathing. The results showed that those two types met requirements on structural performances of wall sheathings of PS2. It was suggested that the unnecessary high performance should be intentionally lowered by veneer combination of larch or other soft species.

Abstract: The dynamics of the litter and soil organic matter content of four densities (A: 2500/hm²，B:3300/hm²，C:4400/hm²，D:6600/hm²) of hybrid Larch plantations were studied in Jiangshanjiao forest farm of Heilongjiang province of China. (1) The annual litter stock under the hybrid Larch plantation was 4634.6 ~ 5453.4 kg/hm², and the decreased order of the annual litter stock was under density of 4400, 3300 2500and 6600 trees per hectare. The decrease order of the litter stock no matter undecomposition and decomposition litter was under density of 3300, 4400, 2500 and 6600 trees per hectare, and the rate of the undecomposition litter stock to total litter stock was bigger than 50 %. (2) The seasonal dynamic of the soil organic matter under different densities of plantations basically had the same principle. In 0~10 cm soil layer, the soil organic matter was higher in June and August, was lower in May and July, and was flat or increased slightly in September, but was decreased in September under the plantations with density 4400 and 3300 trees per hectare. The soil organic matter in 10~20 cm and 20~40 cm layer had the same change principle, but the change range was flat and smooth. For the same density of plantation, the difference of the organic matter in the same soil layer between the different months was significantly (P < 0.05). (3) The difference of the soil organic matter content in the same soil layer under different densities of hybrid Larch plantation was significantly, and the decreased order of the soil organic matter in average was under density 4400, 3300, 6600 and 2500 trees per hectare. The results would provide the theories basis for manage the hybrid Larch plantations.

Abstract: The soil physical and chemical properties of four densities (A:2500/hm²，B:3300/hm²，C:4400/hm²，D:6600/hm2) of hybrid Larch plantations, Larix olgensis plantation(E) and Quercus mandsurica forest(F) were studied in Jiangshanjiao forest farm of Heilongjiang province of China. Soil bulk density, soil porosity, total N, total P, available N and available P were affected significantly by plantation density in hybrid Larch plantations. The lowest surface soil bulk density was in density 2500/hm². Soil porosity of density 2500/hm² and 3300/hm² was bigger than that of density 4400/hm² and density 6600/hm². Total N, total P and available N of density 4400/hm² and 3300/hm² were higher than that of density 6600/hm² and density 2500/hm². Total N, total P, available N and available P of hybrid Larch plantations were not lower than that of Larix olgensis plantation. The results of the soil physical and chemical properties under different densities of hybrid Larch plantations and different types of forest seems to confirm that hybrid Larch plantation did not decreased the soil fertility, and the hybrid Larch plantation with densities of 3300/hm² and 4400/hm² could be conductive to improving the soil quality. The results would provide the theories basis for manage the hybrid Larch plantations.

Abstract: The testing experiments to healthy larch logs samplings whose diameter scopes are in 5-12cm and the length respectively are 10cm and 30cm were conducted by using Arbotom stress wave testing instrument and universal mechanics testing machine. The relationships between dynamic modulus of elasticity of stress wave and MOE, between MOR and MOE were all studied in the larch logs samplings. The results indicated that, in the two larch logs samplings, the dynamic modulus of elasticity of stress wave had positive linear correlation with MOE. Moreover, MOR also had a good linear correlation with MOE.

Abstract: The testing experiments to healthy poplar and larch logs samplings were conducted by using hydraulic machine. The relationships among compression and bending strength, modulus of elasticity in compression and bending were studied in the two logs samplings. The results indicated that, in the both species, the compression strength had certain linear correlation with bending strength, and so did the modulus of elasticity in compression and bending. Meanwhile there were remarkable linear correlations with the compression strength and the modulus of elasticity in compression as well as the bending strength and the modulus of elasticity in bending.

Abstract: Model for predicting wood density of Larch was established using near-infrared spectroscopy (NIR) combined with support vector machine (SVM). A hundred and seventeen Larch samples were used in the study. Wood density of samples was measured according to standard test methods for physical and mechanical properties of wood. Support vector machines for regression (SVR) was used for model building. Radial basis function (RBF) was used as kernel function to establish a model for predicting wood density. For the train set, the coefficient of determination (R²) and the mean square error (MSE) were 0.8504 and 0.6460×10^-3, while the R² and MSE was 0.8520 and 0.4451×10^-3, respectively, for the test set. Results showed that using SVM in near-infrared spectroscopy calibration could significantly improve the model performance in order to rapidly and accurately predict wood density.

Abstract: In this paper, Chinese larch bark and different areas of Korean larch bark chemical composition and quantitative analysis of active ingredients, and with several plant resources in the total flavonoids were compared and evaluated. The results showed that: Korean larch bark of ash content (1.34%) lower, phenethyl alcohol extract (16.17%), proanthocyanidins (3.84%), total flavonoids(16.59%) and dihydro-quercetin (4.87% ) the highest. The total flavonoid content is more higher than the development of herbal extracts of total flavonoids. Therefore, the bark is a great potential for development of renewable resources.