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171.
172.
为了提高Excel软件的数据处理效率,需建立一个能满足高精确度、高效率、易使用的计算环境。论文建立圆柱螺线优化插值模型,在Excel中通过五组测斜数据计算井眼曲率,再根据云计算可弹性增加计算节点的特点,将Sympho‐ny DE并行软件搭建在本地私有云环境下,通过增加计算节点数目对比运算效率与计算精度。结果表明:随着计算节点数的增加,运算效率大大提高,计算结果更加精确。 相似文献
173.
CaB6陶瓷研究的进展 总被引:8,自引:0,他引:8
综合介绍了CaB6陶瓷粉末、多晶体和单晶体的制备方法。评述了各种方法的基本原理和特点。合成CaB6粉末最常用的方法为碳化硼法,此方法能够以低成本制备较纯的CaB6粉末。但是得到的粉末具有硬团聚现象,使CaB6粉末的烧结有一定的难度。由于CaB6在高温下具有高的化学活性和低的塑性,CaB6多晶多采用热压烧结的方法在高温高压下制备。单晶的制备主要采用区熔法和熔剂法。区熔法适合于生产大尺寸的CaB6单晶,而铝熔剂法制备的CaB6单晶尺寸最大为5mm,对测定其某些物理性能有一定的局限。对CaB6陶瓷的应用及国内外研究现状作了简要的概括,并对其今后的发展趋势作了展望。 相似文献
174.
Summary: Blends of single‐site catalysed ethylene‐α‐butene (C4VLDPE) and ethylene‐α‐octene (C8VLDPE) copolymers were prepared by melt extrusion. The phase morphology, thermal and mechanical properties of the blends have been investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile test and dynamic mechanical analysis (DMA). Depending on the composition and thermal history, significant differences in structure and behaviour were found. It was also found that some degree of co‐crystallization occurred for quenched blends; whereas most of the oven slowly cooled blends showed two well‐defined melting peaks, indicating that the slow cooling favoured partial segregation of the fractions with different degrees of branching to form two morphologies. Moreover, SEM revealed morphology of the thinner crystals distributed in‐between the thicker sheaf‐like crystals for the slowly cooled blends with 20–50% C8VLDPE. Therefore, the synergism in mechanical properties for the blends with 20–50% C8VLDPE is due to a combination of larger crystal size, more complete phase separation and interfacial interaction produced by the segregation effect of the slow cooling treatment. DMA studies showed that the storage modulus increased as the addition of C8VLDPE and modulus for the slowly cooled blends are about twice those measured for the quenched ones, indicating higher stiffness of the blends. The smooth shift of β relaxation temperature with addition of C8VLDPE for both sets of blends confirmed the miscibility in the amorphous phase.
175.
176.
The oxidation and reforming kinetics of methane by O2, CO2 and H2O were studied on a stepped Pt(5 5 7) single crystal from 623 to 1050 K under methane rich conditions. The rate of carbon deposition was followed by ex-situ Auger electron spectroscopy under non-oxidative conditions. The apparent activation energy for methane decomposition was significantly lower than the apparent barriers measured for both total oxidation, CO2 and H2O reforming. Total oxidation of methane to CO2 and H2O followed by combined dry and steam reforming (combined combustion-reforming) led to CO production rates which were higher than direct CO2 or H2O reforming rates. The enhanced rates are most likely due to the ability of adsorbed oxygen to prevent carbon nucleation and/or scavenge carbon enabling the reforming reaction to turnover on a larger fraction of sites. Comparable amounts of carbon were found by Auger electron spectroscopy measurements after both direct dry or steam reforming, while combined oxidation-reforming had considerable less carbon. During direct dry or steam reforming, CO2 and H2O serve only to scavenge adsorbed atomic carbon, while in the presence of oxygen, carbon is removed by both combustion and reforming routes. 相似文献
177.
P. E. H. Gregg A. D. Mackay L. D. Currie J. K. Syers 《Nutrient Cycling in Agroecosystems》1988,17(3):219-234
At two phosphate (P) responsive sites in hill country the effectiveness of Sechura phosphate rock (SPR) as a direct application P fertilizer for permanent pasture was evaluated. Sechura was applied at two rates, in three different application strategies. The treatments were 16.7 and 50 kgP ha–1 annually, 25 and 75 kgP ha–1 biennially, and 50 and 150 kgP ha–1 triennially giving a total of 50 and 150 kgP ha–1, respectively, over three years. Single superphosphate (SSP) served as the standard P fertilizer. A comparison was also made between SPR and Chatham Rise phosphorite (CRP), another reactive PR. Total pasture and legume production and P uptake by pasture was measured with all fertilizer treatments over a three year period.In the year of application, SPR was as effective as SSP in stimulating total pasture and legume production and P uptake by pasture. This reflects the very reactive nature of this PR. In the second and third years of measurement, SPR did not show superior residual efffects to SSP. The ability of CRP to stimulate legume growth more than SPR in the second year following application demonstrates the danger of generalizing about the residual effects of reactive PR materials. Of the application strategies evaluated, a biennial appplication of 25 kgP ha–1 as SPR maintained legume growth at a higher level than a smaller (16.7 kgP ha–1) annual dressing. The biennial strategy also increased total pasture yield, in addition to legume production to a greater extent in the second and third years than a single (50 kgP ha–1) triennial application. 相似文献
178.
179.
Emulsion polymer isocyanate (
), polyvinyl acetate (
) and resorcinol-formaldehyde (
) adhesives were used to produce single lap shear specimens using resinous and non-resinous apitong (Dipterocarpus spp.) timbers. Tests showed that joints made with highly resinous apitong were about 40% weaker than similar joints made with non-resinous apitong. The resinous apitong was treated with different solvents to yield five different extractives which were characterized by infra-red analysis. Apitong extractives were then added to
and
adhesives and joints made with buna (Fagus crenata), a timber known to be low in extractives and easy to bond. Joints prepared using extractive-containing adhesives were generally weaker than those made with the unmodified adhesives. RF adhesives containing extractives cured more slowly than unmodified
. It is thought that the acidic nature of the extractives changes the pH of the system sufficiently to affect the curing mechanism 相似文献
180.
重庆朝天门大桥是当今世界第一大跨度拱桥,其下弦节点直接承受公路荷载与轻轨荷载的双重作用,下弦节点连接处应力幅大,目前大跨度钢桥中未曾有类似的设计及试验,因此,该文对其下弦节点连接进行了高周疲劳试验以确定其连接的可靠性。首先通过相关规范及朝天门大桥的交通量确定出模型的试验荷载,并完成从实桥节点到模型的转换,然后对模型进行正常设计荷载下的200万次疲劳试验,该试验验证了设计寿命期内朝天门大桥节点连接的安全性,并用空间有限元分析结果验证了试验数据的真实性。最后进行了该模型的疲劳破坏试验,得出了这类节点的疲劳破坏规律,为该类桥梁以后的设计及监测提供了数据及参考意见。 相似文献