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41.
针对预警机的地空量子通信问题,首先对影响其传输信道的主要因素进行了分析。基于分析结果,构建一地空量子通信流程,可使地面站与预警机在双向对准和跟踪后进行量子态的无线传输;基于该通信流程搭建一地空量子广域网,网络由空中平台和地面通信端等设备组成,根据不同的通信节点剖析3种路由策略,验证其可行性;最后对量子比特传输错误率进行分析,仿真结果表明通过提高信道系数,缩小测量基的偏差角度以及减少纠缠交换、经典信息引起的差错率,可有效减小传输的误码率。 相似文献
42.
王泽 《达县师范高等专科学校学报》1998,(4)
以王宏建、袁宝林二教授主编的《美术概论》在教学中如何使用,才能体现编者者的意图,才能使教材的理论内容、结构体系及论证特点得到很好贯彻,作者采用“由史入论、由论及史、史论结合”的讲授方法,做了有益探索。 相似文献
43.
为减少四旋翼飞行器姿态跟踪控制中内部计算与通信资源的损耗,提出了基于反步法和多重事件触发机制下的四旋翼飞行器姿态跟踪控制。建立了四旋翼飞行器的动力学模型,并以滚转角系统为例,利用反步法设计连续控制器,实现了飞行器滚转角对参考信号的跟踪控制;通过引入事件触发机制构造了事件触发控制器,基于Lyapunov稳定性理论证明了所设计的事件触发控制器可以使滚转角系统保持稳定,且避免了Zeno现象;同时,在不同的参数作用下,采用相同方法对四旋翼飞行器的其他3个系统分别设计了各自对应的事件触发机制和事件触发控制器;由此构建的4个事件触发机制共同构成了四旋翼飞行器的多重事件触发机制。仿真结果表明,在多重事件触发机制作用下,所提事件触发控制器在3 s内共触发150次即可达到与周期采样控制器连续采样3 000次相同的跟踪效果。 相似文献
44.
现金流优化的网络进度计划问题研究综述 总被引:6,自引:2,他引:4
网络进度计划优化问题的研究主要以最短工期为优化目标,因而进度计划在财务方面对项目的影响被大大忽略略了。A.Russell提出以净现值作为优化目标,首先研究了现金流优化的网络进度计划问题。本文对该领域的研究文献进行了调研,分别概述了支付进度计划问题,资源约束问题以及时间-费用交换问题的研究情况和成果。 相似文献
45.
46.
HUANG Min CAO Jia-heng PENG Zhi-yong ZENG Cheng . School of Computer Wuhan University Wuhan Hubei China . The State Key Laboratory of Software Engineering Wuhan University Wuhan Hubei China 《武汉大学学报:自然科学英文版》2004,(4)
0 IntroductionDatabase’sinformationsecurityisahotpointinrecentre searchandmostofstudiesaboutitconcentrateonDBMS(e.g .securitymodel,useridentificationandaccesscontrol,etc) .Howeverwiththedevelopmentofnetworkanddataminingtech nology ,thedataindatabaseneedsmoreandmoreeffectivecopy rightprotection[1 3] anddigitwatermarktechnologyprovidesaneffectivesolutionfortheproblem .Itbecomesanewissuetoman agethedata’scopyrightthroughdigitwatermark[4] .Digitwatermarktechnologycanconfirmthedata’sowner sh… 相似文献
47.
The Sox genes of allotetraploids and their original maternal red crucian carp (Carassius caassius red var.) and original paternal common carp (Cyprinus carpio L.) were detected by PCR with the designed primers based on the conserved HMG-box sequence in different species. Sequencing of Sox genes indicated that two Sox9 genes (Atsox9a and Atsox9b) existed in allotetraploids, while only one Sox9 gene existed in red crucian carp (Rcsox9a) and common carp (Ccsox9b) . All of the four Sox9 genes contained an intron in the HMG-box. with the sizes of 413 bp, 703 bp, 401 bp and 714 bp, respectively. Moreover, the introns obeyed the rule of "GT-AG" . A high similarity was observed between introns of Atsox9a and Rcsox9a (94.4%), Atsox9b and Ccsox9b (97.8%). Interestingly, the deduced amino acid sequences of their corresponding exons all shared 100% identity. Thus, introns of the HMG-domain of Sox9s in allotetraploids and their original parents have not only the length polymorphism but also intron variability. Our results provide significant molecular evidence for the origin and evolution of allotetraploids. 相似文献
48.
Wang Peirong Zhao Hong Xu Guanjun Zhu Cuishan Xiao Tingrong Zhang Min Zhang Bin 《自然科学进展(英文版)》2007,17(11):1382-1388
An Agilent 6890N GC equipped with both FID and Agilent 5975 MSD analyzer has been employed to analyze C5—C13 hydrocarbon fractions of crude oils. A technical combination of program temperature volatilizer injection, backflush and micro-flow controller afforded a fine separation of C5—C13 compounds on a PONA column with the heavy part of crude oils being cut off before entering the analytical column. Both GC-FID chromatogram and GC-MS mass chromatograms (MID and full scan) could be obtained at the same time. The retension time differences of nC6—nC13 alkanes between GC and TIC were in the range of 0.02—0.58 minutes. Totally 286 peaks have been assigned group compositions. Results on 8 typical oil samples from CNPC Key Laboratory Crude Oil Library showed that the characteristics of C6—C13 hydrocarbon group composition could be used in oil-oil correlation studies. 相似文献
49.
Interface microstructure and formation mechanism of ultrasonic spot welding for Al–Ti dissimilar metals
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Li Zhou Shan Liu Jie Min Zhi-Wei Qin Wen-Xiong He Xiao-Guo Song Hong-Bo Xu Ji-Cai Feng 《矿物冶金与材料学报》2021,28(9):1506-1514
The present study focuses on interface microstructure and joint formation. AA6061 aluminum alloy (Al) and commercial pure ti-tanium (Ti) joints were welded by ultrasonic spot welding (USW). The welding energy was 1100–3200 J. The Al–Ti joint appearance and in-terface microstructure were observed mainly via optical microscopy and field emission scanning electron microscopy. Results indicated that a good joint can be achieved only with proper welding energy of 2150 J. No significant intermetallic compound (IMC) was found under all con-ditions. The high energy barriers of Al–Ti and difficulties in diffusion were the main reasons for the absence of IMC according to kinetic ana-lysis. The heat input is crucial for the material plastic flow and bonding area, which plays an important role in the joint formation. 相似文献
50.
Qiao-kun Du Qing-xia Wu Hong-xun Wang Xiang-juan Meng Ze-kai Ji Shu Zhao Wei-wei Zhu Chuang Liu Min Ling Cheng-du Liang 《矿物冶金与材料学报》2021,28(10):1603-1610
Silicon (Si) particles were functionalized using carbon dots (CDs) to enhance the interaction between the Si particles and the binders. First, CDs rich in polar groups were synthesized using a simple hydrothermal method. Then, CDs were loaded on the Si surface by impregnation to obtain the functionalized Si particles (Si/CDs). The phases and microstructures of the Si/CDs were observed using Fourier-transform infrared reflection, X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy. Si/CDs were used as the active material of the anode for electrochemical performance experiments. The electrochemical performance of the Si/CD electrode was assessed using cyclic voltammetry, electrochemical impedance spectroscopy, and constant current charge and discharge experiment. The electrodes prepared with Si/CDs showed good mechanical structure stability and electrochemical performance. After 150 cycles at 0.2 C, the capacity retention rate of the Si/CD electrode was 64.0%, which is twice as much as that of pure Si electrode under the same test conditions. 相似文献