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141.
In this study, 40CrMnSiB steel cylindrical shells were tempered at 350, 500 and 600 ℃ to study the effect of tempering temperature on the dynamic process of expansion and fracture of the metal shell. A mid-explosion recovery experiment for the metal cylinder under internal explosive loading was designed, and the wreckage of the casings at the intermediate phase was obtained. The effects of different tempering temperatures on the macroscopic and microscopic fracture characteristics of 40CrMnSiB steel were studied. The influence of tempering temperatures on the fracture characteristic parameters of the recovered wreckage were measured and analyzed, including the circumferential divide size, the thick-ness and the number of the circumferential divisions. The results show that as the tempering temper-ature was increased from 350 to 600 ℃, at first, the degree of fragmentation and the fracture characteristic parameters of the recovered wreckage changed significantly and then became essentially consistent. Scanning electron microscopy analysis revealed flow-like structure characteristics caused by adiabatic shear on different fracture surfaces. At the detonation initiation end of the casing, fracturing was formed by tearing along the crack, which existed a distance from the initiation end and propagated along the axis direction. In contrast, the fracturing near the middle position consists of a plurality of radial shear fracture units. The amount of alloy carbide that was precipitated during the tempering process increased continuously with tempering temperature, leading to an increasing number of spherical carbide particles scattered around the fracture surface. 相似文献
142.
分析了多制式调制的原理 ,提出并实现了一种基于PCI总线的多制式调制模块的设计方案。它采用正交调制与数字上变频方法 ,可以生成多种中频调制信号。它的另一个特点是将基带处理单元用PCI总线隔离开来 ,可以结合通用计算机或商用DSP处理模块 ,构成一结构灵活而又具有实时处理能力的多制式调制系统。 相似文献
143.
刘恩博 《兵团教育学院学报》2004,14(2):41-42
本文介绍利用ElectronicsWorkbench(简称EWB)专业电路设计软件,建立数字电路仿真实验教学系统的方法,以此作为数字电路实验教学的重要补充,符合"以虚代实"、"以软代硬"的当代实验技术的发展潮流。 相似文献
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分析预估信道长度对信道估计算法的影响规律,提出利用水声通信均衡恢复信号统计量对信道估计质量评估的方法。通过信道长度自适应修正机制,实现对未知水声信道的高精度估计。针对水声信道造成的正交频分复用子载波特性差异,基于信道估计结果,提出在码元总速率、能量约束条件下,各个正交频分复用子载波速率、功率优化分配的自适应调制算法。与传统的等功率、速率分配算法相比,新算法能够显著提升水声通信系统的误码率性能,通过仿真和实地试验,验证了研究内容的有效性。 相似文献
146.
The cultural and creative industries (CCIs) in Taiwan have gradually contributed to the national economy under the impetus of government policies. We employ a two‐stage data envelopment analysis model with an additive efficiency decomposition approach to measure the profitability and marketability of 22 Taiwanese cultural and creative companies. Furthermore, we employ the network‐based ranking approach to identify benchmark inputs/outputs, and the strengths and weakness of each company. Our empirical results show that the profitability of the cultural and creative companies is better than their marketability. Companies in the industries of publishing, creative life, popular music, and cultural content averagely perform better than those in the other three types of CCIs in terms of profitability. Companies in the creative life industry are on average more efficient than those in the other five types of CCIs in terms of marketability. The profitability/marketability matrix of cultural and creative companies is also presented. 相似文献
147.
Sukanya Podder 《Small Wars & Insurgencies》2017,28(4-5):686-708
AbstractThis paper analyses the multiple pathways through which legitimacy of armed groups is constructed in conflict-affected states. It adopts a political sociological approach to the study of armed group legitimacy. Such a strategy assists in identifying whether armed groups enjoy legitimacy in a given empirical context and avoids applying pre-determined normative criteria. The focus is on three types of relationships: civilian communities, the state or regime in power and external actors including regional and international sponsors, to discern which types of legitimacy matter for armed groups in different relationships. 相似文献
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149.
本文介绍了以过氯乙烯为成膜物质,添加成炭剂、脱水催化剂、发泡剂制备膨胀型防火涂料的组成、工艺、性能和防火效果。并用正交试验法讨论了主要组成成分对涂料防火性能的影响。 相似文献
150.