Subjects: Astronomy >> Astrophysical processes submitted time 2021-11-12 Cooperative journals: 《天文研究与技术》
Abstract：本文利用SDO(Solar Dynamic Observatory)/HMI(Helioseismic and Magnetic Imager)观测到的矢量磁图，运用Ampere定律的积分形式计算出了2014年11月7日活动区AR12205上发生X1.6级耀斑期间的垂直电流密度，通过分析光球层上垂直电流密度的时间演化，发现它会在耀斑爆发期间表现出突然的增加，增加的区域对应于耀斑双带的辐射增强位置，然后将强电流密度轮廓叠加在SDO/AIA1600 Å波段的观测图像上，发现电流密度的形态与分布和耀斑带有强相互关系。这些观测结果与三维标准耀斑模型的理论预测一致，我们的研究为三维磁准分界面（Quasi-Separatrix Layer，QSL）重联模型提供了有力的观测证据。
Subjects: Astronomy >> Astrophysical processes submitted time 2020-11-19 Cooperative journals: 《天文研究与技术》
Abstract：太阳高能活动爆发与活动区内的电流结构有着密切的联系，安培（Ampere）定律j_z=〖1/μ_0 (∇×B)〗_z是测量活动区内视向电流密度的理论基础。由于实测的矢量磁场中不可避免地存在随机噪声，因此，应用安培定律的不同形式计算的电流密度存在显著的差异。为了比较不同形式计算结果的差异并从中探索一种实用的电流计算方法，基于太阳动力学天文台(Solar Dynamic Observatory,SDO)/HMI(Helioseismic and Magnetic Imager)在2011年2月15日测量的活动区AR11158的矢量磁图，运用安培定律的微分算法和积分算法分别计算了活动区内视向电流密度的分布图。结果显示，微分算法获得的视向电流密度j_z分布图受随机噪声的影响要远比积分算法获得的结果大，电流分布图中的电流结构没有积分算法获得的结果清晰。另外，在扩大积分环路半径的情况下，所计算的电流分布图里的噪声信号快速降低，从而使计算的视向电流分布图中的电流结构更清晰。但是当继续扩大积分环路半径时，在获得清晰电流分布图的同时，电流分布图的部分精细结构也随之失真。该研究结果论证了适当扩大积分环路计算视向电流分布图可以降低计算结果受随机噪声的影响，从而获得清晰真实的视向电流分布图，但是积分路径的半径过大在消除噪声影响的同时会丢失电流分布中的一些精细结构。因此在实际计算电流的过程中，应该利用高分辨率的矢量磁图，选定合适的积分路径运用安培定律的积分算法来计算活动区的视向电流，从而帮助我们探索耀斑爆发与活动区内电流结构的关系。
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-06-19 Cooperative journals: 《计算机应用研究》
Abstract： This paper developed a method about 3D complex models deformation based on semantic parameters to quickly design the 3D complex models, which could solve the problem that 3D models including free-form surfaces have difficult in deformation. This method regarded deformation handles as basic elements, then, by setting the semantic parameters realized the hierarchical deformation: the deformation of components by configuring the deformation handle can make the 3D models redesigned. First, the quadric surfaces replaced the freeform surfaces of each component with Hausdorff distance and the cluster analysis method. Then, the relationship between deformation handles and vertices of each component helped to calculate the constraints of the internal and external components. Finally, editing and modifying the semantic parameters of the deformation handles deformed 3D models. Experimental results which use 3D electrombile as an example show that the above method support users achieve the deformation of 3D models with a few parameters and keep better efficiency of personalized design.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-06-19 Cooperative journals: 《计算机应用研究》
Abstract： To increase the performance of throughput for 802.15.4 network, this paper designed an improved process of node state transition. Movever, it proposed a model of node access channel considering the hidden terminal problem and retransmission, and it carried out the analysis and calculation of model. Based on the calculation results and the analysis of channel state model, Then, it gave out the derivations of the data collisions probability、packet lost rate and throughput channel considering the hidden terminal problem. Finally, it studied the impact of packet arrival rate、backoff exponent and hidden terminal on the performance of network throughput. Experimental results show that, compare with 802.15.4 network without retransmission mechanism, the network throughput is increased by 83.9% or so. Compare with the sleep methods under some conditions, the network throughput is increased by 13.3% on average, the proposed model can effectively improve network throughput performance.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-05-18 Cooperative journals: 《计算机应用研究》
Abstract： In order to reduce the packet lost rate in 802.15.4MAC layer, this paper raised a model of channel competition mechanism based on Markov chain by analyzing the reason of packet loss rate. Then, throught the mathematical derivations of the steady-state probability on the network transmission, backoff and the channel detection state based on the model of channel access, this paper燿iscussed the formulas of channel collision and the frame packet lost rate. Finally, this paper studied the impact of protocol parameters such as packet arrival rate, the number of nodes, bit error rate, backoff exponent, and number of backoffs on the collision probability and the packet lost rate. Experimental results show that, compared with 802.15.4 network without node sleep state, the packet lost rate was reduced by 23.7%. And the model describes the MAC layer channel access mechanism very well, and reasonable settings for parameters could optimize the frame packet lost rate. The research outcome could provide reference for the reliable transmission optimization in the practical application of wireless sensor network.
Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2018-04-24 Cooperative journals: 《计算机应用研究》
Abstract： In order to achieve the goal of green energy-saving communication in 5G, a Femtocell energy-saving sleep strategy based on load prediction is proposed under the Femtocell network. Firstly, the throughput data of FBS (Femtocell Base Station) is collected and chaotic characteristic of the data is verified according to the small-data method. In addition, the load of FBS is learned and predicted. Secondly, the throughput rate is defined on the basis of load prediction and user equipment switching process is designed according to the throughput rate to ensure the communication service quality and energy efficiency. Finally, the real-time transmit power of FBS is calculated and the transmit power of FBS is predicted and controlled. The simulation results show that our scheme can predict the throughput changing trend of FBS accurately, and the energy-saving sleep strategy can also improve the energy efficiency of the system and reduce the overall energy consumption.
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