Effects of rubber content and temperature on dynamic fracture toughness of ABS materials

The effects of rubber content and temperature on dynamic fracture toughness of ABS materials have been investigated based on the J-integral and crack opening displacement (COD, delta) concepts by an instrumented Charpy impact test. A multiple specimens R-curve method and stop block technique are used. It is shown that the materials exhibit a different toughness behavior, depending on rubber content and temperature. The resistance against stable crack initiation (J(0.2) or delta(0.2)) increases with increasing rubber content. However, J(0.2) first increased with increasing temperature until reaching the maximum value; after that, it decreases with further increasing the temperature. (C) 2000 John Wiley & Sons, Inc.

Theoretical study on the unimolecular fragmentation of ionized tetrahydroimidazole-substituted methylene beta-diketones

Semiempirical molecular orbital calculations on the unimolecular mass spectrometric fragmentation of tetrahydroimidazole-substituted methylene beta-diketones are carried out by Austin Model 1 method, and the calculated results give a strong support to our experimental results reported previously. The optimum of the investigated molecular configuration indicates that the two hydrogen atoms attached to nitrogen atom have different activities due to their chemical environment; the relative energies of the ions in fragmentation pathway of ionized tetrahydroimidazole-substituted methylene beta-diketones provide indirectly an evidence for both the existence of ion/neutral complex and the stabilities of these ions.

Amorphane sesquiterpenes from a marine Streptomyces sp.

The chemical investigation of the crude extract of the marine-derived Streptomyces sp. M491 yielded three new sesquiterpenes, namely, 10 alpha,11-dihydroxyamorph-4-ene (4), 10 alpha,15-dihydroxyamorph-4-en-3-one (6), and 5 alpha,10 alpha,11-trihydroxyamorphan-3-one (7). In addition, the known compounds 10 alpha-hydroxyamorph-4-en-3-one (2), o-hydroxyacetanilide, genistein, prunetin, and indole-3-carbaldehyde and the macrolide antibiotic chalcomycin A were identified. The structures were determined on the basis of spectroscopic analysis, especially 1D and 2D NMR data. This is the first report of these sesquiterpenes from bacteria.

New antibiotic with typical plant anthraquinone structure obtained studying terrestrial and marine Streptomycetes

In our screening for new antibiotics from bacteria, the streptomycete isolate M097 from Jiaozhou Bay in China was found to produce aloesaponarin II (1a) and 1,6-dihydroxy-8-hydroxymethyl-anthraquinone (2). Similarly, a terrestrial streptomycete GW24/1694 produced 1a and its methyl ether, the new compound 1-hydroxy-6-methoxy-8-methyl-anthraquinone (1b). All structures were derived by spectrochemical analysis and by comparison with reference data. The results showed that the marine streptomycete isolate M097 and the terrestrial streptomycete GW24/1694 could be a promising material for studying the biosynthetic pathway of polyketides.

Relationship between differential retention of Escherichia coli and Enterococcus faecalis and variations in enzyme activity in the scallop Patinopecten yessoensis

Uptake of Escherichia coli and Enterococcus faecalis and variations of trypsin amylase activity acid phosphatase and superoxide dismutase in tissue of the scallop Patinopecten yessoensis were detected. The results showed that P. yessoensis accumulated E. faecalis in larger numbers and more rapidly than E. coli, both with the highest concentration in the digestive tract and lowest in hemolymph. Compared to E. coil, all scallops exposed to E. faecalis showed significantly higher trypsin and AMS activity. SOD activity in hemocytes and ACP activity in hemolymph was significantly higher in the treatments with 5 log(10)CFU/ml E. colt than with E. faecalis. But no significant differences in ACP activity of P. yessoensis exposed to a 3 log(10)CFU/ml inoculum of both bacteria were recorded. In conclusion, the mass retention of gut microflora in P. yessoensis is positively correlated with digestive enzymes activity and negatively correlated with ACP activity in the hemocyte. (C) 2010 Published by Elsevier Ltd.

Role of snow depth in spring of Tibetan Plateau in onset of South China Sea summer monsoon

The role of snow depth of Tibetan Plateau in the onset of South China Sea summer monsoon and the influence of ENSO on snow depth of Tibetan Plateau are investigated with use of data from ECMWF reanalysis and NCEP/NCAR reanalysis. The results are as follows: (1) The snow depth data from ECMWF reanalysis are tested and reliable, and can be used to study the influence of snow depth of Tibetan Plateau on the onset of South China Sea summer monsoon; (2) Anomaly of snow depth of Tibetan Plateau causes anomaly in air temperature and its contrast between the Indian Ocean and the continent resulting in easterly wind anomaly over 500 hPa and hence as well as in the atmospheric circulation in the lower layer. For the year of negative anomaly of snow depth a westerly wind anomaly with a cyclone pair takes place, while for positive anomaly of snow depth an easterly anomaly occurs with an anticyclone pair; (3) While positive anomaly of SST occurs in the eastern Pacific Ocean, positive anomaly of air pressure also takes place over the eastern Indian Ocean and the South China Sea, causing stronger meridional pressure gradient between the ocean and continent and then westerly wind anomaly. At the same time, the atmospheric pressure increases in the northern Tibetan Plateau, northerly wind gets stronger, and subtropical front strengthens. All of these are favorable for snowfall over Tibetan Plateau.

青藏高原5种牧草木质素含量及其体外消化率研究

在海拔高度3200 m的中国科学院海北高寒草甸生态系统定位站选取羊茅（Festuca ovina）、早熟禾（Poa annua）、（上艹下洽）草（Koeoeriacristata）以及莎草科的矮蒿草（Kobresia humilis）、黑褐苔草（Carex alrofusca)5种青藏高原重要牧草品种，分别测定羊茅、早熟禾、（上艹下洽）草、矮蒿草茎、矮蒿草叶、黑褐苔草茎和黑褐苔草叶的木质素含量，并采用二级离体培养法测定其体外消化率，比较不同牧草间木质素含量及消化率差异。1999和2000年两年的实验结果表明，牧草木质素含量与其体外消化率之间为极显著负相关（P<0.01）；就同种牧草不同器官而言，牧草茎的木质素含量明显高于叶，其降解率较低；3种禾本科牧草及2种莎草科牧草不同牧草品种间木质素含量和体外消化率差异不显著。

高寒草甸不同土地利用格局土壤CO_2的释放量

分析高寒草甸不同土地利用格局下土壤CO2的释放量大小表明,在植物生长季的5～9 月,土壤CO2 释放量大小排序为:金露梅灌丛草甸(1871.40g/ m2) > 矮嵩草草甸(1769.63g/ m2) > 退化金露梅灌丛草甸(1495.60g/m2) > 退化矮嵩草草甸(1191.26g/ m2) ；而在植物非生长季的10月到翌年4月,其土壤CO2 释放量大小与植物生长季略有差异, 表现出矮嵩草草甸(661.46g/ m2 ) > 金露梅灌丛草甸( 550.90g/ m2 ) > 退化矮嵩草草甸(502.50g/ m2) > 退化金露梅灌丛草甸(384.50g/ m2) 的特点;全年内表现为矮嵩草草甸(2431.09g/ m2 ) > 金露梅灌丛草甸(2422.30g/ m2) > 退化金露梅灌丛草甸(1880.10g/ m2 ) > 退化矮嵩草草甸(1694.06g/ m2 ) . 高寒草甸地区不同土地利用格局土壤CO2 释放数量的差异及季节变化,不仅与各利用格局的土壤生物活性及土壤物理化学性状有关,而且与气象条件(特别是温度) 及其土壤冬季冻结期长短关系极为密切。

海洋机器人变参数大时延控制系统补偿方法的研究

本文提出一种变参数大时延系统的补偿方法，具有传输滞后系统的幅相频率特性和时域特性，流体动力学变参数的修正方法和具有传输滞后和零阶保持器滞后的补偿仿真。

波动方程偏移速度分析

On the subject of oil and gas exploration, migration is an efficacious technique for imagining structures underground. Wave-equation migration (WEM) dominates over other migration methods in accuracy, despite of higher computational cost. However, the advantages of WEM will emerge as the progress of computer technology. WEM is sensitive to velocity model more than others. Small velocity perturbations result in grate divergence in the image pad. Currently, Kirrchhoff method is still very popular in the exploration industry for the reason of difficult to provide precise velocity model. It is very urgent to figure out a way to migration velocity modeling. This dissertation is mainly devoted to migration velocity analysis method for WEM: 1. In this dissertation, we cataloged wave equation prestack depth migration. The concept of migration is introduced. Then, the analysis is applied to different kinds of extrapolate operator to demonstrate their accuracy and applicability. We derived the DSR and SSR migration method and apply both to 2D model. 2. The output of prestack WEM is in form of common image gathers (CIGs). Angle domain common image gathers (ADCIGs) gained by wave equation are proved to be free of artifacts. They are also the most potential candidates for migration velocity analysis. We discussed how to get ADCIGs by DSR and SSR, and obtained ADCIGs before and after imaging separately. The quality of post stack image is affected by CIGs, only the focused or flattened CIGs generate the correct image. Based on wave equation migration, image could be enhanced by special measures. In this dissertation we use both prestack depth residual migration and time shift imaging condition to improve the image quality. 3. Inaccurate velocities lead to errors of imaging depth and curvature of coherent events in CIGs. The ultimate goal of migration velocity analysis (MVA) is to focus scattered event to correct depth and flatten curving event by updating velocities. The kinematic figures are implicitly presented by focus depth aberration and kinetic figure by amplitude. The initial model of Wave-equation migration velocity analysis (WEMVA) is the output of RMO velocity analysis. For integrity of MVA, we review RMO method in this dissertation. The dissertation discusses the general ideal of RMO velocity analysis for flat and dipping events and the corresponding velocity update formula. Migration velocity analysis is a very time consuming work. Respect to computational convenience, we discus how RMO works for synthetic source record migration. In some extremely situation, RMO method fails. Especially in the areas of poorly illuminated or steep structure, it is very difficult to obtain enough angle information for RMO. WEMVA based on wave extrapolate theory, which successfully overcome the drawback of ray based methods. WEMVA inverses residual velocities with residual images. Based on migration regression, we studied the linearized scattering operator and linearized residual image. The key to WEMVA is the linearized residual image. Residual image obtained by Prestack residual migration, which based on DSR is very inefficient. In this dissertation, we proposed obtaining residual migration by time shift image condition, so that, WEMVA could be implemented by SSR. It evidently reduce the computational cost for this method.

喀斯特石漠化与地质-生态环境背景的空间相关性分析——以广西都安瑶族自治县为例

分析都安瑶族自治县喀斯特石漠化分布特征,依托GIS 和RS 技术,采用定性和定量相结合的分析方法,选出分析喀斯特石漠化的地质- 生态环境背景因素。运用主成分分析法,得出喀斯特石漠化的地质生态环境指数,并绘制都安县地质- 生态环境指数图,揭示石漠化与其地质- 生态环境背景因素的空间相关性。利用多元回归方法,通过检验其显著度选出最佳的回归模型,为喀斯特石漠化生态重建提供依据。

RECOMENDAÇÕES técnicas para a cultura do milho.

Preparo do solo; Semeadura; Controle de plantas daninhas; Calagem e adubação; Recomendação de cultivares; Pragas de importância econômica; Principais doenças; Manejo de água; Colheita; Armazenamento; Comercialização; Coeficientes técnicos.