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961.
962.
才满瑞 《导弹与航天运载技术》1996,(4):18-30
整体模块发动机(IME)系统是一种与传统多发动机系统不同的推进系统,它使用共用集流管将所有涡轮泵组件和推力室组件连接在一起,具有允许件发生故障(而不是允许发动机发生故障)的能力,IME系统可以潜在提高可靠性,改善操作性,提高性能以降低成本,主要对整体模块发动机技术的应用及效益进行了分析和探讨,并对IME系统与传统多发动机系统进行了分析与比较。 相似文献
963.
964.
965.
Jin Zhang Tonglai Zhang Li Yang Jianguo Zhang Yan Cui Xiaochun Hu Zhenhua Liu 《Propellants, Explosives, Pyrotechnics》2009,34(1):24-31
A new coordination compound, [Mn(CHZ)3][C(NO2)3]2, was synthesized and characterized by elemental analysis, IR and UV spectra, and its crystal structure was determined by X‐ray single crystal diffraction. The crystal belongs to the triclinic system and space group with a=0.88737(18) nm, b=1.1804(2) nm, c=1.1936(2) nm, β=83.73(3)°, V=1.1121(4) nm3, Z=2, Dc=1.867 g cm−3. Every Mn(II) ion is six‐coordinated to three CHZ molecules through three carbonyl oxygen atoms and three terminal nitrogen atoms to form a distorted octahedral structure. Mn(II) ions, carbohydrazide ligand molecules, and trinitromethanide anions are jointed to a complicated three‐dimensional netted structure through coordination bonds, electrostatic forces, and extensive hydrogen bonds. The thermal decomposition character and mechanism was studied by DSC, TG‐DTG, and FTIR techniques. The non‐isothermal kinetics has also been studied on the exothermic decomposition by using Kissinger's method and Ozawa–Doyle's method. In addition, the impact, friction, and flame sensitivity data were determined. All properties data observed show that the title complex has high energy, good thermal stability, and moderately friction sensitivity. 相似文献
966.
The effect of functionalized graphene (FG) on the mechanical properties, especially toughness, of nylon12 was investigated. The results revealed that the incorporation of a very small amount (about 0.6 wt%) of the FG caused a significant improvement in ultimate tensile strength, elongation, impact strength and toughness. With 0.6 wt% FG ultimate tensile strength and elongation at break of the nylon 12 are improved by ∼35% and ∼200%, respectively. The KIc of the nylon 12 is ∼1.28 MPa m0.5 and the incorporation of 0.6 wt% FG causes a significant increase of 72% (∼2.2 MPa m0.5). 0.6 wt% FG also causes a significant improvement of 175% in impact failure energy of the nylon 12. The incorporation of FG resulted in an increase in amount of γ-phase of nylon12 which could be the direct reason for the increase of toughness. 相似文献
967.
Ali Nabipour Chakoli Jiehe Sui Maryam Amirian Wei Cai 《Journal of Polymer Research》2011,18(6):1249-1259
Well-dispersed multiwall carbon nanotubes (MWCNTs) were prepared by grafting poly(L-lactide-co-ε-caprolactone) (PLACL) biodegradable copolymer onto the sidewall of hydroxylated MWCNTs using oligomeric L-lactide (LA) and ε-caprolactone (CL). After preparation of MWCNT/PLACL composites, the effect of functionalized MWCNTs on
crystallinity of PLACL was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning
calorimetry (DSC), dynamic mechanical analysis (DMA), and polarized light optical microscopy (POM). The surface functionalization
effectively improved the dispersion and adhesion of MWCNTs which acted as reinforcing filler in the PLACL polymer matrix and
hence improved the physical and thermomechanical properties of the nanocomposites. The glass transition temperature (T
g) and the crystallinity of nanocomposites decreased in comparison with those of neat PLACL when the concentration of functionalized
MWCNTs in nanocomposites was 0.5 wt%. With further increment in concentration of functionalized MWCNTs, the T
g of composites increased until the T
g of neat PLACL, and also the crystallinity of composites increased. The functionalized MWCNTs have no significant effect on
the melting point of nanocomposites. The MWCNTs acted as heterogeneous nucleation points and increased the lamella size and
therefore the crystallinity of PLACL. Furthermore, the larger agglomerated clusters of both kinds of MWCNTs (i.e., MWCNT-grafted-PLACL
and pristine MWCNTs) are more effective than small clusters as nucleation points for growing the spherulites. 相似文献
968.
Assessment of vitrified CBN wheels for precision grinding 总被引:3,自引:0,他引:3
Methods of measuring topographical features of grinding wheels are reviewed. Each technique has advantages and limitations for resolution, measuring depth, ease of application, data analysis and interpretation. Results obtained vary according to the method and instrument employed. Advantages and difficulties experienced with different techniques are discussed. Different replication techniques and materials are compared and suggestions made. A set of parameters that describe the wheel and grain characteristics is defined. Experimental studies with grinding wheels having different structures are carried out in terms of observations and measurements of changes in wheel topography. Experimental results are analysed and discussed in relation to theoretical understanding of abrasive wear and loading. 相似文献
969.
The microstructure, mechanical properties and corrosion behavior of Mg–2 Zn–0.6 Zr alloy under the as-cast and asextruded conditions were investigated. Microstructure analysis indicated the remarkable grain refinement by extrusion, as well as notable reductions in volume fraction and size of precipitate phases. As compared with the as-cast alloy, the asextruded alloy exhibited better mechanical performance, especially in yield strength which was promoted from 51 to 194 MPa. Refined grains, dispersive precipitate phases and texture were thought to be the main factors affecting the improved performance in strength. The electrochemical measurement and immersion test revealed the corrosion rate of Mg–2 Zn–0.6 Zr alloy by extrusion decreased from 1.68 to 0.32 mm/year. The reasons for the enhanced corrosion resistance were mainly attributed to the decreased volume fraction and Volta potential of the precipitate phases, the refinement of the grain size, as well as the formation of more protective corrosion film. 相似文献
970.
对焦化苯酚外观颜色影响因素进行了分析。结合生产中出现的苯酚产品外观颜色变红的情况。提出了加强原料质量控制、优化苯酚蒸馏工序、加强物流控制等措施,减轻变色问题。在焦化苯酚产品中添加变色抑制剂也有一定的作用。 相似文献