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991.
中国土壤动物生态地理研究进展(英文) 总被引:7,自引:0,他引:7
This review summarizes main research findings in soil fauna eco-geography in China in the past 30 years.The subject areas and main results were overviewed including biodiversity and eco-geological distribution of soil fauna communities.Studies of ecological distributions of soil fauna and dynamic ranges in space from tropical,subtropical to temperate regions,and in categories from forest,grassland,desert,wetland,farmland to urban ecosystems,the responses and indications of soil fauna to soil environments.Ef... 相似文献
992.
993.
Residual curvature migration velocity analysis for angle domain common imaging gathers 总被引:2,自引:0,他引:2
Pre-stack depth migration velocity analysis is one of the keys to influencing the imaging quality of pre-stack migration.
In this paper we cover a residual curvature velocity analysis method on angle-domain common image gathers (ADCIGs) which can
depict the relationship between incident angle and migration depth at imaging points and update the migration velocity. Differing
from offset-domain common image gathers (ODCIGs), ADCIGs are not disturbed by the multi-path problem which contributes to
imaging artifacts, thus influencing the velocity analysis. On the basis of horizontal layers, we derive the residual depth
equation and also propose a velocity analysis workflow for velocity scanning. The tests to synthetic and field data prove
the velocity analysis methods adopted in this paper are robust and valid. 相似文献
994.
995.
In this study, we evaluated the anti-proliferative activity of phlorotannins derived from brown algae Laminaria japonica Aresch extracts on the human hepatocellular carcinoma cell (BEL-7402) and on murine leukemic cells (P388) by MTT assay. Cells
were incubated with 100 μg/mL of the phlorotannin extract (PE) for 48 h. The inhibitory rate of PE on BEL-7402 and P388 cells
was 30.20±1.16% and 43.44±1.86%, respectively, and the half-inhibitory concentration of PE (IC50) on P388 and BEL-7402 cells was 120 μg/mL and >200 μg/mL, respectively. Microscopic observation shows that the morphologic
features of tumor cells treated with PE and 5-fluorouracil are markedly different from the normal control group. The inhibitory
rate of fraction A2 isolated from PE by sephadex LH-20 for BEL-7402 and P388 cells at the sample concentration of 70.42 μg/mL was 61.96±7.02%
and 40.47±8.70%, respectively. The apoptosis peak for fraction A2 was the most profound of all fractions used in the flow cytometry assay. The results indicate that the anti-proliferative
of this algal extract is associated with the total phlorotannin content. 相似文献
996.
Chemical characteristics and environmental significance of fresh snow deposition on Urumqi Glacier No. 1 of Tianshan Mountains, China 总被引:2,自引:0,他引:2
Ice and snow chemistry of alpine glaciers is crucial for the research of regional atmospheric environment change. Fresh snow samples were weekly collected from Urumqi Glacier No.1 in the Tianshan Mountains, Xin- jiang, China, and the chemical characteristics and seasonal variations of major ions, mineral dust, δ18O and trace metals were measured. Results show that the concentrations of major ions in the snow are Ca2+ SO42- NH4+ NO3- Cl- Na+ Mg2+ K+, in which Ca2+ is the dominant cation, and SO42-is the dominant anion. All major ions have close positive correlations with each other except NO3-. δ18O shows positive correlation with air temperature change during the study period. Mineral dust particle and major ionic concentrations in fresh snow have obvious seasonal change, with high concentration in spring but low concentration in summer and autumn, which indicates that the chemical mass input from Asian dust activity to snow is very significant. Temporal changes of trace metals in fresh snow, e.g., Cd, Pb, Zn, Al, Fe, have shown that human-induced pollution of central Asian region also has large contribution to the snow chemistry on alpine glaciers of the Tianshan Mountains. 相似文献
997.
998.
文中研究在粒状铁化学还原三氯乙烯渗透反应格栅和生物降解苯和甲苯渗透反应格栅的联合格栅技术中,下游生物降解格栅中铁还原环境下微生物对苯和甲苯的生物降解。通过模拟粒状铁渗透反应格栅下游铁还原环境,主要研究微生物以苯、甲苯作为碳源时,对碳源的专一性。通过批实验发现,对于分别用苯和甲苯培养驯化的微生物,互换碳源后,微生物对2 000.00μg/L苯和甲苯的生物降解半衰期分别由之前的1.0和1.5 d减少到0.7和1.0 d,互换碳源后苯和甲苯的去除率分别增加38%和32%。在粒状铁渗透反应格栅下游生物降解渗透反应格栅中,微生物在铁还原环境下以苯、甲苯作为碳源时对碳源没有专一性,苯和甲苯可以同时被生物降解去除。 相似文献
999.
1000.
Nonlinear inversion of electrical resistivity imaging using pruning Bayesian neural networks 总被引:1,自引:0,他引:1
Conventional artificial neural networks used to solve electrical resistivity imaging (ERI) inversion problem suffer from overfitting and local minima. To solve these problems, we propose to use a pruning Bayesian neural network (PBNN) nonlinear inversion method and a sample design method based on the K-medoids clustering algorithm. In the sample design method, the training samples of the neural network are designed according to the prior information provided by the K-medoids clustering results; thus, the training process of the neural network is well guided. The proposed PBNN, based on Bayesian regularization, is used to select the hidden layer structure by assessing the effect of each hidden neuron to the inversion results. Then, the hyperparameter α k , which is based on the generalized mean, is chosen to guide the pruning process according to the prior distribution of the training samples under the small-sample condition. The proposed algorithm is more efficient than other common adaptive regularization methods in geophysics. The inversion of synthetic data and field data suggests that the proposed method suppresses the noise in the neural network training stage and enhances the generalization. The inversion results with the proposed method are better than those of the BPNN, RBFNN, and RRBFNN inversion methods as well as the conventional least squares inversion. 相似文献