As a platform for Near space-based Earth-observation network, stratospheric airship has attracted a lot of attention in recent years, because of its advantages in endurance, coverage, cost, and ...durability. However, the airship has low conversion speed and large vehicle inertia, so it is significant to deploy Multi-airship Earth-observation Coverage Network (MAEON) collaboratively. To this end, this paper proposes an Earth-observation model with considerations of loading devices side-swing characteristics and field of view (FOV), and establishes a collaborative deployment model of MAEON to realize objectives of observation coverage, target point statistics, observation resolution, multi-airship community profit. To obtain the solution set of cooperative deployment problem efficiently and widely, a multi-objective evolutionary optimization algorithm (MOEA) with associated bi-criterion is proposed. Then, weight vector distribution control with dynamic adjustment is introduced to ensure that the solution set spreads more uniform and extensive. By embedding improved evolution factors, Non-Pareto criterion (NPC) and Pareto criterion (PC) based parts co-evolve and exchange information, which is effective in diversity and convergence. The normalized weight sum method is modified by adding the moderators, which are controlled by the population outcome in the iterative process. The experiment is repeated in 8 groups of data, and compared with 4 popular MOEAs. Through simulation experiments, it can be seen that the proposed algorithm has advantages in performance, universality, and stability.
The contribution of this paper is the proposal of a new receding horizon trajectory generation method for stratospheric airships’ return phase. Since the energy consumption, wind field and path ...constraints are restrictions during the return phase of airships at low altitude, it is crucial to develop novel trajectory optimization methods to ensure that the airship returns to the landing site. In this article, optimization objects and conditions of the return trajectory were constructed, considering the energy consumption and wind field. Then, a modified interior point method (MIP) was used to transform the inequality constraint, which is a simple and adaptable method used to improve the solving efficiency on the basis of a modified multiple shooting method (MMS). In addition, an adaptive gradient descent regulator was improved to reduce the influence on the optimization result due to different selections of the initial search point, and the convergence was made faster and more stable. Finally, considering the performance and path constraints of the airship, the effectiveness of the scheme was verified by numerical experiments under wind effects and a comparison of different methods.
Particular waveguide structures and refractive index distribution can lead to specified degeneracy of eigenmodes. To obtain an accurate understanding of this phenomenon, we propose a simple yet ...effective approach, i.e., generalized eigenvalue approach based on Maxwell’s equations, for the analysis of waveguide mode symmetry. In this method, Maxwell’s equations are reformulated into generalized eigenvalue problems. The waveguide eigenmodes are completely determined by the generalized eigenvalue problem given by two matrices ( M , N ), where M is 6 × 6 waveguide Hamiltonian and N is a constant singular matrix. Close examination shows that N usually commute with the corresponding matrix of a certain symmetry operation, thus the waveguide eigenmode symmetry is essentially determined by M , in contrast to the tedious and complex procedure given in the previous work Opt. Express 25 , 29822 ( 2017 ) 10.1364/OE.25.029822 . Based on this new approach, we discuss several symmetry operations and the corresponding symmetries including chiral, parity-time reversal, rotation symmetry, wherein the constraints of symmetry requirements on material parameters are derived in a much simpler way. In several waveguides with balanced gain and loss, anisotropy, and geometrical symmetry, the analysis of waveguide mode symmetry based on our simple yet effective approach is consistent with previous results, and shows perfect agreement with full-wave simulations.
Beam combination with high efficiency is desirable to overcome the power limit of single electromagnetic sources, enabling long-distance optical communication and high-power laser. The efficiency of ...coherent beam combination is severely limited by the phase correlation between different input light beams. Here, we theoretically proposed and experimentally demonstrated a new mechanism for beam combining, the topology-enabled beam combination (TEBC), from multiple spatial channels with high efficiency based on a unidirectional topological edge state. We show that the topologically protected power orthogonal excitation arising from both the unidirectional edge states and the energy conservation ensures -0.31dB (93%) efficiency experimentally for a multi-channel combination of coherent microwaves at 9.1-9.3 GHz. Moreover, we demonstrate broadband, phase insensitive, and high-efficiency beam combination using the TEBC mechanism with one single topological photonic crystal device, which significantly reduces the device footprint and design complexity. Our scheme transcends the limits of the required phase correlations in the scenario of coherent beam combination and the number of combined channels in the scenario of incoherent beam combination.
Prolonging the network life of WSN is the purpose of the study in this paper, when the application of the WSN is restricted by the limited power. This paper used Immune Optimization Algorithms to ...reduce the total transmission distance of the whole network by choosing the appropriate nodes as cluster heads in WSN. At the same time, this method considered the residual energy of the nodes, when the cluster heads were chosen. Only when the residual energy of the node is larger than the average energy of the whole network, the nodes can be selected as cluster heads. The simulations show that this method can prolong the lifetime of the network effectively by reducing the total transmission distance of the whole network.
Objective To evaluate the impact of ultra-high-molecular-weight polyethylene (UHMWPE)-Ribbond fibers, when combined with different restorative materials, on fracture resistance and marginal ...adaptation of isolated primary molar defects, to provide a reference for clinical practice. Methods This study was approved by the Ethics Review Committee. A total of 72 extracted primary molars with complete crowns were collected, and 66 primary molars were randomly assigned as experimental groups for the fracture resistance and microleakage tests. The molars were divided into six groups (n = 11) based on the type of restorative materials and the application of Ribbond fibers: Group A1, 3M Filtek Z250 + Ribbond; Group A2, 3M Filtek Z250; Group B1, Beautifil II LS + Ribbond; Group B2, Beautifil II LS; Group C1, 3M Filtek Bulk Fill + Ribbond; and Group C2, 3M Filtek Bulk Fill. Groups A1, B1 and C1 received the fiber-reinforcing technique, whereas Groups A2, B2 and C2 received the direct restorative technique; the remainings
Abnormal Refraction THz Metasurface Li, Meize; Jing, Yuhao; Liu, Yahong
2019 International Symposium on Antennas and Propagation (ISAP),
2019-Oct.
Conference Proceeding
Metasurface is an artificial layered material with a thickness less than the wavelength. It can flexibly and effectively manipulate electromagnetic wave, such as polarization, amplitude, phase, and ...propagation mode. In this paper, we proposed an abnormal refraction THz metasurface consisting of the silicon cubic resonator. By adjusting the geometry of cubic silicon resonator, the transmission phase coverage rang from -3π/4 to π is obtained. It is shown that the proposed metasurface can achieve the anomalous refraction at the THz band.
Research on a library seat management system Jing, Yuhao; Mao, Limin; Xu, Jiaqi
2019 2nd International Conference on Information Systems and Computer Aided Education (ICISCAE),
2019-Sept.
Conference Proceeding
This paper proposes a library seat management system for the phenomenon of seat occupancy. This system takes Arduino single chip microcomputer as the core of data processing, equipped with ...information reading system, lock/unlock system, information transmission system and display system, realized the information collection and transmission function for the use of the library seats. Through the serial port, the information acquired by each system is integrated. Seat position information, Card swiping information and Seat status information, which are transmitted to the upper computer and fed back to the administrator in real time to realize seat management. The test result shows that the system can run stably, manage the vacancy effectively, solve the problem of unreasonable seat reservation, and improve the utilization rate of seats.
Octave-spanning frequency comb generation in microresonators is promising, but strong spectral losses caused by material absorption and mode coupling between two polarizations or mode families can be ...detrimental. We examine the impact of the spectral loss and propose robust comb generation with a loss of even 300 dB/cm.Cavity nonlinear dynamics show that a phase change associated with spectral losses can facilitate phase matching and Kerr comb generation. Given this unique capability, we propose a novel architecture of on-chip spectroscopy systems.
