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为研究药型对层状变燃速发射药内弹道性能的影响,基于经典内弹道理论建立了多种药型的层状变燃速发射药物理燃烧模型,并推导计算了对应的形状函数与燃气生成猛度表达式,通过VC++软件对在定容条件下的不同药型的层状变燃速发射药内弹道性能进行了数值计算。结果表明:圆饼与方片层状变燃速发射药的燃烧性能相似,且比两面包覆的矩形变燃速发射药燃烧性能好;对于长方体变燃速发射药四面包覆比两面包覆的燃气生成猛度有明显的提高。在12.7mm枪装填条件下,长方体四面包覆比两面包覆膛内最大压力和弹丸初速分别降低11.94%和2.39%。 相似文献
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多层核壳丙烯酸酯乳液的合成及其性能的研究 总被引:8,自引:0,他引:8
以多步种子聚合法合成多层核壳共聚物复合乳液,以MAA和EA二元共聚物为种子乳液,在其外部依次包覆丙烯酸酯聚合物,获得了以交联网络型吸水膨胀性聚合物为核的多层核壳乳液。对不同阶段聚合物的吸水性能的研究表明,种子聚合物吸水性能最强,MAA中和度,交联剂,引发剂用量等因素均对吸水性有影响。随包覆层数的增加,吸水性能降低,核壳聚合物的吸水性能随温度的提高而增加,说明温度影响水对壳层聚合物的渗透,该核壳乳液成膜后得到的聚合物膜具有良好的遮光性能,且聚合物的遮光性随核聚合物吸水性能的提高而提高,同时壳层聚合物的Tg越高,膜的遮光性能越大。 相似文献
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为制备力学性能优异的涂料用有机/无机复合乳液,以硅溶胶、丙烯酸酯类为单体制备壳层乳液和核层乳液,以阴离子型与非阴离子型复配乳化剂,通过半连续种子乳液聚合法制得力学性能良好的聚丙烯酸酯包覆纳米Si O2粒子的壳/核型有机/无机复合乳液,系统地研究了乳化剂配比、核/壳单体质量比及硅溶胶含量对乳液及涂膜性能的影响,并采用透射电镜、红外光谱、粒度仪等测试手段,对乳液的粒径分布及微观结构进行表征。结果表明:在反应温度80℃、乳液滴加时间2~3 h、复合乳化剂SDS/OP-10质量为1∶1、核/壳单体质量比为3∶4(或1∶1)时,制得的乳液及涂膜综合性能最好,乳液为壳/核型包覆的乳胶粒结构,可制备硅溶胶含量高达12%的高性能复合乳液,其涂膜力学性能较纯丙乳液涂膜明显提高。 相似文献
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为有效提高Mg(OH)_2纳米粒子在硅丙乳液中的相容性与分散稳定性,在油酸修饰Mg(OH)_2纳米粒子的基础上,以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸与乙烯基三乙氧基硅烷为共聚单体,通过乳液聚合法制备出具有核壳结构的硅丙乳液包覆Mg(OH)_2复合材料。利用傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对样品结构、形貌进行了表征。通过燃烧实验,研究了硅丙乳液包覆Mg(OH)_2纳米粒子对水性防火涂料阻燃性能的影响。结果表明,油酸通过酯化作用修饰在Mg(OH)_2纳米粒子表面,借助油酸分子中双键结构,丙烯酸类混合单体在纳米Mg(OH)_2表面完成聚合过程,形成以Mg(OH)_2纳米粒子为核、硅丙乳液为壳的复合材料。XRD与热分析表明经硅丙乳液包覆的纳米Mg(OH)_2晶体结构与热稳定性能未受影响。此外,掺杂0.1%(质量分数)的硅丙乳液包覆Mg(OH)_2可使水性防火涂料阻燃时间延长至113 min,较未掺杂水性涂料阻燃时间(91min)提高约23%。 相似文献
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黄婵娟张丹郑磊郑君红龙柱 《高分子材料科学与工程》2018,(11):151-156
对比研究了棕榈蜡与聚乙烯蜡的乳化性能,确定了最佳的乳化方案并将其应用于棉织物上以改善棉织物的微观结构,从而实现棉织物表面的超疏水化,研究了其对于棉织物多方面性能的影响。结果表明,当棕榈蜡质量分数为10%,乳化剂质量分数为1.5%,转速为500 r/min时可以制得乳化效果最佳且粒径最小的棕榈蜡乳液。将正硅酸四乙酯(TEOS)处理后的棉织物在棕榈蜡乳液和聚乙烯蜡乳液复配液中浸渍处理后,棉织物表面可形成一层包覆层,疏水角可达到155.89°,实现对棉织物的超疏水效果。经过整理的棉织物透气率略有下降,耐静水压性能稍有增加,热稳定性能测试中整理布样质量减少最多,经向断裂强力由未整理前的252 N升高到397 N,整理后棉织物经500次摩擦之后接触角下降1.9%左右,比原棉织物摩擦耐久性有所增强。 相似文献
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A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling. 相似文献
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Liebert A Wabnitz H Grosenick D Möller M Macdonald R Rinneberg H 《Applied optics》2003,42(28):5785-5792
A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue. 相似文献
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Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995. 相似文献
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由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。 相似文献
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M. M. Gadenin 《Inorganic Materials》2013,49(15):1352-1356
It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle. 相似文献
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V. T. Kornienko 《Strength of Materials》1991,23(7):760-765
The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991. 相似文献
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An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a
rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate
agreement is demonstrated between the derived relations and experimental data. 相似文献
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水三相点是开尔文热力学温度的唯一基准点,也是ITS-90国际温标重要的定义固定点。因此,水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来,中国计量科学研究院研制出一系列高质量的水三相点容器,加强了水三相点的研究,为不确定度的分析提供了更为可靠的实验依据。同时,不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此,根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明,其扩展不确定度为0.16mK(k=2.69,P=0.99)。 相似文献