The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultras...The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.展开更多
The growth characteristics of petroleum-degrader BS-8（Bacillus sp.） and the factors influencing its biosurfactant production were tested; the biosurfactant releasing mode of BS-8 was speculated by measuring OD600, s...The growth characteristics of petroleum-degrader BS-8（Bacillus sp.） and the factors influencing its biosurfactant production were tested; the biosurfactant releasing mode of BS-8 was speculated by measuring OD600, surface tension and oil displacement of fermentation broth; and the effects of carbon source, nitrogen source, temperature, p H, and Na Cl concentration on biosurfactant production by BS-8 were observed in this study. The results showed that the biosurfactant releasing mode of BS-8 was growth-correlated, the surface tension of BS-8 fermentation broth declined with the total bacteria increasing, and the oil displacement was positive correlated with biosurfactant content in fermentation broth; and the optimal culture conditions for effective biosurfactant production included： glucose as carbon source,yeast extract as nitrogen source, Na Cl concentration of 2%, p H of 7.0 and temperature at 30 ℃.展开更多
Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relati...Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.展开更多
A two-dimensional numerical model of vertical jet scour was developed based on the turbulent flow theory and jet scour mechanism. In this model, drag force acts as the main reference variable and the critical Shields ...A two-dimensional numerical model of vertical jet scour was developed based on the turbulent flow theory and jet scour mechanism. In this model, drag force acts as the main reference variable and the critical Shields number acts as the incipient motion criteria of sediment. The morphological change in the bed caused by bed-load transport is simulated using the moving mesh method and the suspended-load is not considered. An experiment investigating vertical clear water jet scour was conducted in the laboratory, and some effective experimental results, such as flow pattems and distribution characteristics of scour pits, were obtained. Numerical simulation of the 2D jet scour was conducted using the same parameters as were used in the flume experiment. The evolution process of the jet scour observed in the experiment was simulated by the new model; validation of the numerical model and the algorithm was conducted. Semi-empirical formulas of the characteristic length of the equi-librium scour hole were deduced based on the results of the experiment and simulation.展开更多
Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of mu...Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.展开更多
We report a fossil specimen referable to Sinomastodontinae gen. et sp. indet, from the Neogene strata at Yanghecun locality, Xihe County, Gansu Province, China. The specimen is characterized by a brevirostrine mandibl...We report a fossil specimen referable to Sinomastodontinae gen. et sp. indet, from the Neogene strata at Yanghecun locality, Xihe County, Gansu Province, China. The specimen is characterized by a brevirostrine mandible, complete pretrite trefoils, and relatively simple posttfite half lophids, showing typical features of Sinomastodon. It differs from the other known species of Sinomastodon by the following features： relatively short and wide m3 due to fewer lophid numbers, less inflated pretrite ac- cessory central conules, poorly developed secondary trefoils and cementum, and relatively strong cingulid. All of these fea- tures indicate a bias towards pleisiomorphies of Sinomastodon, implying that this specimen is more ancestral than any known species of Sinomastodon. The symphysis of the new specimen is relatively long, which differs from the typical brevirostrine Sinomastodon, and thus we consider it a gen. et sp. indet, in the Subfamily Sinomastodontinae. In addition, the horizon in which the present specimen was found probably represents the Upper Miocene because it is lower than Pliocene strata yielding Hipparion （Proboscidipparon） pater. Generally, Sinomastodon is considered to have migrated from North America at about the time of the Miocene/Pliocene boundary, and to have been derived from a certain clade of American gomphotheres. However, the discovery of the Yanghecun specimen verifies that Sinomastodon lived in East Asia during the Late Miocene, and probably derived from Old World gomphotheres （e.g., G. wimani）. The similarity between the members of the Subfamilies Sinomastodontinae and those of Cuvieroniinae is suggested to have been the result of parallel evolution.展开更多
基金This paper was supported by "Wood-inorganic Res-toration Material" in "Technique Introduction and Innovation of Bio-macromolecule New Material" of Introducing Overseas Advanced Forest Technology Innovation Program of China ("948" Innovation Pro-ject, Number: 2006-4-C03)
文摘The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.
基金Supported by Basic and Cutting-edge Technique Research of Henan Province(152300410092)Key Program in Science and Technology of Education Department of Henan Province(15A210020,15B180002,15B180016)~~
文摘The growth characteristics of petroleum-degrader BS-8（Bacillus sp.） and the factors influencing its biosurfactant production were tested; the biosurfactant releasing mode of BS-8 was speculated by measuring OD600, surface tension and oil displacement of fermentation broth; and the effects of carbon source, nitrogen source, temperature, p H, and Na Cl concentration on biosurfactant production by BS-8 were observed in this study. The results showed that the biosurfactant releasing mode of BS-8 was growth-correlated, the surface tension of BS-8 fermentation broth declined with the total bacteria increasing, and the oil displacement was positive correlated with biosurfactant content in fermentation broth; and the optimal culture conditions for effective biosurfactant production included： glucose as carbon source,yeast extract as nitrogen source, Na Cl concentration of 2%, p H of 7.0 and temperature at 30 ℃.
基金the National Natural Science Foundation Committee (Grant No.40971168)the National 973 Program(2007CB407206)
文摘Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.
基金supported by the National Natural Science Foundation of China (Grant Nos.10972163,51079106))the Fundamental Research Funds for the Central Universities (Grant Nos.2104001,2103002)
文摘A two-dimensional numerical model of vertical jet scour was developed based on the turbulent flow theory and jet scour mechanism. In this model, drag force acts as the main reference variable and the critical Shields number acts as the incipient motion criteria of sediment. The morphological change in the bed caused by bed-load transport is simulated using the moving mesh method and the suspended-load is not considered. An experiment investigating vertical clear water jet scour was conducted in the laboratory, and some effective experimental results, such as flow pattems and distribution characteristics of scour pits, were obtained. Numerical simulation of the 2D jet scour was conducted using the same parameters as were used in the flume experiment. The evolution process of the jet scour observed in the experiment was simulated by the new model; validation of the numerical model and the algorithm was conducted. Semi-empirical formulas of the characteristic length of the equi-librium scour hole were deduced based on the results of the experiment and simulation.
基金supported by the National Basic Research Program of China("973"Project)(Grant No.2015CB250903)the CAS Strategic Priority Research Program(B)(Grant No.XDB10030303)+1 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(Grant No.2012BAK10B01)the Youth Science Fund of the National Natural Science Foundation of China(Grant No.11302230)
文摘Contact detection between interacting blocks is of great importance to discontinuity-based numerical methods, such as DDA, DEM, and NMM. A rigorous contact theory is a prerequisite to describing the interactions of multiple blocks. Currently, the penalty method, in which mathematical springs with high stiffness values are employed, is always used to calculate the contact forces. High stiffness values may cause numerical oscillations and limit the time step. Furthermore, their values are difficult to identify. The intention of this study is to present a two-scale contact model for the calculation of forces between colliding blocks. In this new model, a calculation step taken from the moment of contact will be divided into two time stages: the free motion time stage and the contact time stage. Actually, these two time stages correspond to two real physical processes. Based on this, we present a new numerical model that is intended to be more precise and useful in calculating the contact forces without mathematical springs. The propagation of the elastic wave during collision is of a characteristic length, which determines the volume of material involved in the contact force calculation. In conventional contact models, this range is always regarded as the length of one element, which may lead to an inaccurate calculation of contact forces. In fact, the real scale of this range is smaller than the length of a single element, and subdivided elements, which are refined according to the characteristic length and are presented in the new contact model.
基金supported by Chinese Academy of Sciences(Grant No.XDB03020104)National Basic Research Program of China(GrantNo.2012CB821900)+1 种基金National Natural Science Foundation of China(Grant Nos.41372001,41002010,40730210)the Important Research Plan of IVPP
文摘We report a fossil specimen referable to Sinomastodontinae gen. et sp. indet, from the Neogene strata at Yanghecun locality, Xihe County, Gansu Province, China. The specimen is characterized by a brevirostrine mandible, complete pretrite trefoils, and relatively simple posttfite half lophids, showing typical features of Sinomastodon. It differs from the other known species of Sinomastodon by the following features： relatively short and wide m3 due to fewer lophid numbers, less inflated pretrite ac- cessory central conules, poorly developed secondary trefoils and cementum, and relatively strong cingulid. All of these fea- tures indicate a bias towards pleisiomorphies of Sinomastodon, implying that this specimen is more ancestral than any known species of Sinomastodon. The symphysis of the new specimen is relatively long, which differs from the typical brevirostrine Sinomastodon, and thus we consider it a gen. et sp. indet, in the Subfamily Sinomastodontinae. In addition, the horizon in which the present specimen was found probably represents the Upper Miocene because it is lower than Pliocene strata yielding Hipparion （Proboscidipparon） pater. Generally, Sinomastodon is considered to have migrated from North America at about the time of the Miocene/Pliocene boundary, and to have been derived from a certain clade of American gomphotheres. However, the discovery of the Yanghecun specimen verifies that Sinomastodon lived in East Asia during the Late Miocene, and probably derived from Old World gomphotheres （e.g., G. wimani）. The similarity between the members of the Subfamilies Sinomastodontinae and those of Cuvieroniinae is suggested to have been the result of parallel evolution.
