Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-20 Cooperative journals: 《计算机应用研究》
Abstract： The iterative closest point (ICP) algorithm is usually used in the fine registration of point cloud because of its high registration accuracy, but its registration accuracy and iteration convergence depend on the initial registration position of the point cloud to be registered. This paper proposed an algorithm of spatial optimization transformation matrix combining genetic algorithm with spatial distribution entropy, in which used a new point cloud spatial position evaluation method as the objective function of genetic algorithm, used and genetic operator to guide the solution of search direction. The algorithm achieves the minimum spatial distribution entropy through the new population of iterations, after which the coarse registration of point cloud is achieved by decoding the optimal individuals. The experimental results show that the algorithm is effective and feasible, and it can overcome the problem that traditional method can’t provide a good initial position when the defects and noise exist in the point cloud. The algorithm can directly realize point cloud registration within the acceptable error range.
Subjects: Astronomy >> Astrophysical processes submitted time 2020-01-06 Cooperative journals: 《天文研究与技术》
Abstract：氢原子钟作为一种精密的授时守时仪器，在科学研究与工程应用中发挥着重要作用，但目前我国原子钟还存在设备故障、可靠性差等问题。为了简化技术人员排查流程、提升维修效率，文章提出了一种采用机器学习方法，将氢钟历史运行数据作为训练样本，结合DBSCAN及人工神经网络算法得到氢钟诊断模型，从而大幅简化故障排查过程的方法。实验中将训练好的模型部署到嵌入式设备上，并把实时预判结果给技术人员作为参考，证实了这种方法的可行性及有效性。
Subjects: Astronomy >> Astrophysical processes submitted time 2022-10-17 Cooperative journals: 《天文研究与技术》
Abstract： In order to reduce the relative change rate of the transition frequency of the hydrogen masers caused by the inhomogeneous C field, two designs of C field components, three-segment solenoids and four sets of coils, are proposed. Using the high-order expansion of the magnetic field on the axis, the ampere-turn ratio and the solenoid spacing were calculated when the three-segment solenoid with L=0.05-0.5 constructed a uniform magnetic field. The finite element analysis of the magnetic field is carried out with L=0.2-0.45, and the magnetic field non-uniformity distribution with different widths is given. Among them, the maximum non-uniformity with L=0.45 in the storage bubble area is 0.105%, and the corresponding relative change rate of transition frequency is1.02×10-13 . Using the same method, the ampere-turn ratio and spacing between coils when four or five sets of coils construct a uniform magnetic field are calculated, and the finite element simulation of the magnetic field in the coil is carried out, and the non-uniformity distribution is given. The maximum non-uniformity of the magnetic field in the storage bubble region in the four sets of coils is 0.066%, and the corresponding transition frequency relative change rate is 6.42×10-14
Subjects: Materials Science >> Nanoscience and Nanotechnology submitted time 2016-12-22
Abstract：以 AlGaN/GaN HEMT为代表的 GaN基功率晶体管由于具有宽带隙、高工作结温、高摘要：以 AlGaN/GaN HEMT为代表的 GaN基功率晶体管由于具有宽带隙、高工作结温、高击穿场强和高电子迁移率等优点，成为当前功率器件研究的热点。当 GaN 基功率晶体管应用到大功率开关电路中时，为了电路的设计简单和安全方面考虑，一般要求开关器件具有常关特性即需要器件为增强型器件。通过 Ar离子注入实现具有工艺简单、重复性好、稳定可控的优点。本实验通过调整 Ar 离子注入能量、剂量来研究 Ar 离子注入能否实现增强型HEMT器件，同时研究了 LP-SiNx作为能量阻挡层的效果。实验发现 Ar离子注入能实现增强型，但存在着饱和电流小的问题，退火能够修复损伤，一定程度上提高饱和电流。而采用LP-SiNx作为能量阻挡层，可以减小损伤，饱和电流相对提高，但存在着回滞的问题。作为增强型实现方法，Ar离子注入尚需进一步研究并改进。
Peer Review Status:
Awaiting Review
Subjects: Materials Science >> Nanoscience and Nanotechnology submitted time 2016-12-23
Abstract：AlGaN/GaN HEMT适合应用于高压大功率器件，但在高电压动态使用时，存在导通电阻增加的现象[1,2]。目前可以有效降低动态导通电阻的方法有：场板结构[3,4]和AlN介质层[5]等。本论文采用叠层双栅结构AlGaN/GaN HEMT器件，该器件在栅电极之上新增加了一个通过介质层（Si3N4）与栅电极相隔离并可以单独加信号控制的顶栅。在动态下工作时,顶栅电极的脉冲输入信号与栅电极的脉冲输入信号同步。在器件关态时，顶栅电极加0V偏置；在器件开态时，顶栅电极加正电压。顶栅在器件开态下所加正电压越大，器件的动态导通电阻越小。
Peer Review Status:Awaiting Review
Hits
Hits
Downloads
Comment