Prebuckling Deformation Theory of Filament-Wound Cylindrical Shells

Based on the theory of composite,the analysis of prebuckling deformation of filament-wound cylindrical shells is performed. The prebuckling deformation theory under axial pressure,lateral pressure or liquid pressure is presented.The emphases are placed on the boundary conditions and coupling effect.     

Research on Independent Product Development for Concurrent Collaborative Environment & Supporting Technologies

This article deals with the research on the features and collaborative process of independent development of key automobile parts. It generally employed concurrent engineering theory and technologies of Internet & Intranet, computer aided design (CAD), computer aided manufacturing (CAM) and product data management (PDM). Field knowledge on independent development of key automobile parts was concluded and a set of concurrent collaborative environment and key enabling supporting technologies that face the independent development of automobile body panel dies were also built up. Meanwhile it introduced the secondary development methods of knowledge based engineering (KBE) to implement the knowledge transformation of designing and manufacturing experiences for an enterprise. The results was applied for the development & production of one of this enterprise's new automobile styles and work well.     

Natural Abundance of 15N in Main N-Containing Chemical Fertilizers of China

As early as the 1950s, there had already been reports on the δ 15N value of some chemical fertilizers (Hoering, 1955). Since Kohl and his co-workers (1971) published the report that attempt was made to distinguish the respective contribution of soil nitrogen and fertilizer nitrogen to the source of nitrates in surface water according to the different.     

Effect of Incorporation of Wheat Straw and Urea into Soil on Biomass Nitrogen and Nitrogen-Supplying Characteristics of Paddy Soil

Pot experiments were carried out to study the effect of incorporation of wheat straw and/ or urea into soil on biomass nitrogen and mineral nitrogen and its relation to the growth and yield of rice.The combined appliation of wheat straw and urea increased much more biomass nitrogen in soil than the application of wheat straw or urea alone and consequently increased the immobilization of urea nitrogen added and reduced the loss of urea nitrogen.An adequate nitrogen-supplying process to rice plant could be obtained if C/ N ratio of the material added was about 20.The three yield components of rice were affected significantly by the status of nitrogen supplying.More than 30mg N/ kg soil of mineral nitrogen at effective tillering stage,panicle initiation stage and filling stage should be maintained in order to get high rice yield,though the criteria varied with the different experimental conditions.     

土壤污染物优势流的数学模拟

A simple modeling approach was suggested to simulate preferential transport of water and contaminants in soil.After saturated hydraulic conductivity was interpolated by means of Krige interpolation method or scaling method,and then zoned,the locations where saturated hydraulic conductivity was larger represented regions where preferential flow occurred ,because heterogeneity of soil,one of the mechanisms resulting in prefeential flow,could be reflected through the difference in saturated hydraulic conductivity,The modeling approach was validatd through numerical simulation of contaminant tansport in a two-dimensional hypothetical soil profle.The results of the numerical simulation showed that the approach suggested in this study was feasible.     

氯离子在土壤中的扩散: Ⅱ.动力学及热力学性质

The amounts of chloride ions diffused in four soils of different textures at the same water content under different temperature and at varied time were measured by the diffusion cell method using ³⁶Cl-labelled CaCl₂ solution. Five kinetic models were used to fit the dynamic process of the diffusion of chloride ions in the soils. It was found that Elovich equation or power function equation was the best model to describe the process. The pseudothermodynamic parameters, i.e. the net reaction energy, the activation entropy, activation enthalpy and activation free energy of the diffusion, were derived from the absolute reaction-rate theory. The results showed that these parameters decreased in the order of loessal soil > black lu soil > lou soil > yellow cinnamon soil, which indicated that the force and the heat-energy barrier to be overcome for diffusion decreased, the diffusion rate increased and the disorder of the soil-solution-ion system due to diffusion decreased successively with the texture becoming heavier in the four soils.     

三峡库区坡地表层风化特征研究

Extractability and mobility of Cu and Zn and their relationships with 1） accumulation of Cu and Zn and 2） soil pH were studied in three sandy soils （Wabasso, Ankona, and Winder） from commercial citrus groves in Florida, USA. The soils, with a broad range of Cu and Zn concentrations, were fractionated by a modified procedure of Amacher, while Cu and Zn mobility were evaluated using column leaching. The extractability of Cu and Zn increased with decreasing soil pH. Also with increasing total soil Cu and Zn for extractable Cu in the Wabasso sand a threshold level, where the metal extraction rate increased, was noted at 100 mg kg^-1, whereas for extractable Zn in the Wabasso sand the threshold level was found at 60 mg kg^-1 and in the Ankona sand at 120 mg kg^-1. These results suggested that the release potential of Cu and Zn was greater in the Wabasso sand than in the Ankona sand. The column leaching experiment showed that at total soil Cu or Zn concentrations 〈 100 mg kg^-1 all leachates had low Cu and Zn concentrations. However at total concentrations 〉 200 mg kg^-1 for Cu and 〉 150 mg kg^-1 for Zn with decreasing soil pH, the concentrations of both Cu and Zn in the leachates increased exponentially. Also in these sandy soils soluble Cu and Zn mainly originated from the exchangeable fractions, and pH was a key factor controlling Cu and Zn extractability and mobility.     

植物汁液化学组成及其与菜心抗性和Cd累积的关系

Sap mixtures of the xylem, phloem, and vacuoles from low and high Cd accumulator varieties of Brassica parachinensis L. H. Bailey were analyzed under Cd stress to understand the biochemical mechanisms of Cd accumulation in plants. Low Cd accumulator （‘Teqing-60＇） and high Cd accumulator （‘Chixin-2＇） plants were grown in Cd-treated soil in pots in a greenhouse. Percentage of cell wall-bound Cd was estimated, pH level and the concentrations of amino acids, organic acids, anions, and cations in both stem and root saps were determined for the calculation of Cd speciations using the computer program GEOCHEM. The results showed that ‘Teqing-60＇ had a significantly higher （P ≤ 0.05） percentage of Cd bound to cell walls in roots and a significantly higher （P ≤ 0.05） pH in the root sap. ‘Teqing-60＇ also contained a higher concentration of total amino acids in both roots and stems compared with the high Cd accumulator variety ‘Chixin- 2＇. However, between the two accumulators, for stems and for roots, there were no significant differences in non-amino organic acids. GEOCHEM calculations showed that Cd in the root sap of ‘Teqing-60＇ mainly combined with amino acids, especially alanine. Compared with ‘Chixin-2＇, in the root sap of ‘Teqing-60＇, much lower levels of Cd as free ions or bound to simple ligands were found, indicating that less ‘Teqing-60＇ is transferred to stems and leaves. Cadmium activity in the shoot sap of ‘Teqing-60＇ was much lower than that in ‘Chixin-2＇; therefore, ‘Teqing-60＇ exhibited higher Cd resistance. However, direct determination of the Cd complexes from xylem and phloem sap is needed to verify these results.     

温度和水分对长白山不同海拔梯度土壤有机质分解的影响

Decomposition of soil organic matter(SOM) is of importance for CO_2 exchange between soil and atmosphere and soil temperature and moisture are considered as two important factors controlling SOM decomposition. In this study, soil samples were collected at 5 elevations ranging from 753 to 2 357 m on the Changbai Mountains in Northeast China, and incubated under different temperatures(5, 10, 15, 20, 25, and 30?C) and soil moisture levels(30%, 60%, and 90% of saturated soil moisture) to investigate the effects of both on SOM decomposition and its temperature sensitivity at different elevations. The results showed that incubation temperature(F = 1 425.10, P 0.001), soil moisture(F = 1 327.65, P 0.001), and elevation(F = 1 937.54, P 0.001) all had significant influences on the decomposition rate of SOM. The significant effect of the interaction of incubation temperature and soil moisture on the SOM decomposition rate was observed at all the 5 sampling elevations(P 0.001). A two-factor model that used temperature and moisture as variables fitted the SOM decomposition rate well(P 0.001) and could explain 80%–93% of the variation of SOM decomposition rate at the 5 elevations. Temperature sensitivity of SOM decomposition, expressed as the change of SOM decomposition rate in response to a 10?C increase in temperature(Q_(10)), was significantly different among the different elevations(P 0.01), but no apparent trend with elevation was discernible. In addition, soil moisture and incubation temperature both had great impacts on the Q_(10) value(P 0.01), which increased significantly with increasing soil moisture or incubation temperature. Furthermore, the SOM decomposition rate was significantly related to soil total Gram-positive bacteria(R~2= 0.33, P 0.01) and total Gram-negative bacteria(R~2= 0.58, P 0.001). These findings highlight the importance of soil moisture to SOM decomposition and its Q_(10) value,which needs to be emphasized under warming climate scenarios.