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111.
研究一类具有吸收效应的HIV-1病毒感染动力学模型.通过构造适当的Lyapunov函数证明当基本再生数〈1时,未感染平衡点是全局渐近稳定的;当基本再生数〉1时,给出病毒感染平衡点全局渐近稳定的充分条件. 相似文献
112.
The Akko 1 shipwreck is the remains of a 26-metre-long Egyptian armed vessel or auxiliary naval brig built at the beginning of the 19th century. Remains of six flintlock muskets were retrieved from the shipwreck, and characterised by various metallurgical methods. The research aimed to study the composition and microstructure of the musket fittings and their manufacturing processes, and if possible, to determine the date and origin of the raw materials. The lead isotope analysis of the fittings suggests that their raw material originated in Great Britain. Based on their typology and composition, the fittings were made in Great Britain of brass alloy and manufactured by casting, probably at the same workshop; and the staple was manufactured by casting and drawing. Considering the zinc content, combined with the manufacturing techniques, the fittings were manufactured between the latter part of the 18th and the early 19th centuries, which might indicate that they were purchased in the course of 19th century weapons trade to be used on board the Egyptian ship. 相似文献
113.
Yue Yang Xiao-dong Li Yan-tao Sun Jian-an Tian Hui-min Liu Bi-dong Wu Jing-yu Wang 《防务技术》2021,17(2):650-656
Hexagonal boron nitride nanosheets(HBNNSs)have huge potential in the field of coating materials owing to their remarkable chemical stability,mechanical strength and thermal conductivity.Thin-layer hBNNSs were obtained by a liquid-phase exfoliation of h-BN powders and incorporated into EVA coatings for improving the safety performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX).HBNNSs and ethylene-vinyl acetate copolymer(EVA)were introduced to HMX by a solvent-slurry process.For com-parison,the HMX/EVA and HMX/EVA/graphene(HMX/EVA/G)composites were also prepared by a similar process.The morphology,crystal form,surface element distribution,thermal decomposition property and impact sensitivity of HMX/EVA/hBNNSs composites were contrastively investigated.Results showed that as prepared HMX/EVA/hBNNSs composites were well coated with hBNNSs and EVA,and exhibited better thermal stability and lower impact sensitivity than that of HMX/EVA and HMX/EVA/G composites,suggesting superior performance of desensitization of hBNNSs in explosives. 相似文献
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115.
Additive convolution of unimodal and α‐unimodal random variables are known as an old classic problem which has attracted the attention of many authors in theory and applied fields. Another type of convolution, called multiplicative convolution, is rather younger. In this article, we first focus on this newer concept and obtain several useful results in which the most important ones is that if is logconcave then so are and for some suitable increasing functions ?. This result contains and as two more important special cases. Furthermore, one table including more applied distributions comparing logconcavity of f(x) and and two comprehensive implications charts are provided. Then, these fundamental results are applied to aging properties, existence of moments and several kinds of ordered random variables. Multiplicative strong unimodality in the discrete case is also introduced and its properties are investigated. In the second part of the article, some refinements are made for additive convolutions. A remaining open problem is completed and a conjecture concerning convolution of discrete α‐unimodal distributions is settled. Then, we shall show that an existing result regarding convolution of symmetric discrete unimodal distributions is not correct and an easy alternative proof is presented. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 109–123, 2016 相似文献
116.
A polling system comprising n queues and a single server is considered. Service is performed according to an elevator scheme under the globally gated regime. The problem of arranging the channels to minimize a measure of the variability of the waiting times is addressed. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 605–611, 1997 相似文献
117.
提出了随机服务系统的服务能力问题,给出有限服务能力的损失制M/M/1模型的描述和其稳态解,并求出了评价系统运行的几个主要数量指标。 相似文献
118.
文中利用自由电子气体近似(HFEGE)定域交换势和修正的半经典近似(MSCE)定域交换势,加上正交化方法(Orthogonalization technique),对能量在0.1~20eV的低能电子被He,Ne和Ar原子的弹性散射过程进行了计算。其中靶原子的电荷分布以及入射电子和靶原子的静电作用利用原子的Roothaan-Hartree Fock渡函数求出;相关和极化作用则用一个无参数的相关极化势近似表示。通过本文计算结果和严格计及交换作用的结果及实验数据相比较,对HFEGEE和MSCE交换势的准确性以及正交化过程对计算结果的影响进行了分析。 相似文献
119.
利用自主研制的仪器化压入仪,采用Vickers压头对氮化硅和氧化锆2种结构陶瓷进行了仪器化压入试验,通过压入载荷-深度曲线可识别材料的弹性模量E,通过测量压痕对角线直径可确定材料的维氏硬度HV,再通过测量压痕裂纹扩展长度即可得到材料的断裂韧性KIC,实现了在单一压入仪上基于Vickers压头对结构陶瓷材料断裂韧性的测试。与传统压痕法利用硬度计或纳米压入仪测试陶瓷材料断裂韧性相比,试验更简单快捷,可靠性高,同时测得信息量也更为丰富。试验测得2种结构陶瓷的断裂韧性分别为4.77~5.82 MPa.m1/2和7.22~8.94 MPa.m1/2。 相似文献
120.
借助椭圆坐标变换,并利用微分算子分解给出了弹性地基上椭圆薄板的自由振动解.根据马休函数特性,并考虑模态的正交性,针对周边固定和周边滑动固定2种边界条件,求得了弹性地基上椭圆薄板固有频率和相应振型的解析表达式. 相似文献