摘要：Cognitive radio is considered as an efficient way to improve the spectrum efficiency. As one of its key technologies,spectrum handoff can guarantee the transmission continuity of secondary users(SUs). In this paper,we address a new and more generalized spectrum handoff problem in cognitive radio networks(CRNs),by considering simultaneously energy efficiency,multiple spectrum handoffs and multiple channels. Furthermore,effects of the primary users'(PUs')arrival and service rate on the target channel sequence selection are also considered. In order to obtain the energy-efficient target channel sequence,we firstly analyze the energy consumption and the number of delivered bits per hertz in the spectrum handoff process,and formulate a ratio-type energy efficiency optimization problem,which can be transformed into a parametric problem by utilizing fractional programming. Then,we propose an algorithm combining dynamic programming with bisection(DPB)algorithm to solve the energy efficiency optimization problem. Our simulation results verify that the designed target channel sequence has better performance than the existing algorithms in terms of energy efficiency.

摘要：We have theoretically investigated two series of cyclometalated Pt（II） complexes, a series [Pt （C, N, N） Cl] and b series [Pt （C, N, Npyrazolyl） Cl]. The geometrical and electronic structures are calculated at the ECP60MWB//6-31G＊（H, C, Cl, N, S） basis set level using DFT method; one-photon absorption （OPA） properties are calculated by using both TDDFT and ZINDO methods and two-photon absorption （TPA） properties are obtained with the ZINDO/SOS method. The resonance integrals parameters （βsp and βd） for Pt are adjusted to -1 and -28.5 eV, respectively, to make max OPA wavelength calculated by ZINDO closest to the experimental data and TDDFT results. The calculated results indicate the molecule 2b （[Pt （Cnaphthyl, N, Npyrazolyl） Cl]） has the biggest potential as outstanding TPA materials because （i） the TPA properties of b series are more outstanding in IR wavelength range, the molecules in b series have good transparencies and possess 1-pyrazolyl-NH that is also available for another metal coordination （e.g., dimerization） and chemical interactions; （ii） when C is CnaphthyI in the C, N, N ligand of cyclometalated Pt（II） complexes, the molecules have the best conjugation effect and the best TPA properties.

摘要：This paper proposes an intelligent low-thrust orbit phasing control method for multiple spacecraft by simultaneously considering fuel optimization and collision avoidance. Firstly,the minimum-fuel orbit phasing control database is generated by the indirect method associated with the homotopy technique. Then,a deep network representing the minimum-fuel solution is trained. To avoid collision for multiple spacecraft,an artificial potential function is introduced in the collision-avoidance controller. Finally,an intelligent orbit phasing control method by combining the minimum-fuel neural network controller and the collision-avoidance controller is proposed. Numerical results show that the proposed intelligent orbit phasing control is valid for the multi-satellite constellation initialization without collision.

摘要：In this paper,the mechatronic design and maneuverability analysis of a novel robotic shark are *** obtain good maneuverability,a barycenter regulating device is designed to assist the posture adjustment at low *** on the Newton-Euler approach,an analytical dynamic model is established with particular consideration of pectoral fins for threedimensional *** hydrodynamic coefficients are computed using computational fluid dynamics(CFD)*** amplitudes and phases are determined by fitting an optimized fish body *** performance of the robotic shark is estimated by varying the oscillation frequency and offset *** results show that with oscillation frequency increasing,the swimming speed increases *** robotic shark reaches the maximum swimming speed of 1.05 m/s with an oscillation frequency of 1.2 ***,the turning radius decreases nonlinearly as the offset angle *** robotic shark reaches the minimum turning radius of 1.4 times the body length with 0.2 Hz frequency and 12°offset *** the vertical plane,as the pectoral fin angle increases,the diving velocity increases nonlinearly with increase rate slowing down.

摘要：This paper is concerned with the free vibration analysis of open circular cylindrical shells with either the two straight edges or the two curved edges simply supported and the remaining two edges supported by arbitrary classical boundary conditions. Based on the Donnell-Mushtari-Vlasov thin shell theory, an analytical solution of the traveling wave form along the simply supported edges and the modal wave form along the remaining two edges is obtained. With such a unidirectional traveling wave form solution, the method of the reverberation-ray matrix is introduced to derive the equation of natural frequencies of the shell with different classical boundary conditions. The exact solutions for natural frequencies of the open circular cylindrical shell are obtained with the employment of a golden section search algorithm. The calculation results are compared with those obtained by the finite element method and the methods in the available literature. The influence of length, thickness, radius, included angle, and the boundary conditions of the open circular cylindrical shell on the natural frequencies is investigated. The exact calculation results can be used as benchmark values for researchers to check their numerical methods and for engineers to design structures with thin shell components.

摘要：It is highly desired to improve the photoelectric property of nanosized BiOBr by promoting the photogenerated charge transfer and separation. Herein, SnO2 and Ag comodified BiOBr nanocomposites(Ag-SO-BOB) have been prepared through a simple one-pot hydrothermal *** photovoltage response of BiOBr nanoplates has 4.1-time enhancement after being modified with SnO2 nanoparticles. Transient-state surface photovoltage(TS-SPV) and the atmosphere-controlled steady-state surface photovoltage spectroscopy(AC-SPS) confirmed that this exceptional enhancement of the photovoltage response can be ascribed to the coupled SnO2 acting as platform for accepting the photoelectrons from BiOBr so as to prolong the lifetime and enhance charge separation. Remarkably, the surface photovoltage response can be further enhanced by synchronously introducing Ag nanoparticles, which is up to 15.4-times enhancement compared with bulk BiOBr nanoplates. The enhancement can be attributed to the improved O2 adsorption by introducing Ag to further enhance charge separation. Finally, the synergistic effect of SnO2 and Ag co-modification enhances the surface photovoltage response due to the enhanced charge separation and promoted O2 adsorption, which is also confirmed through photoelectrochemistry and photocatalytic experiment.

摘要：利用溶胶-凝胶和溶剂热联合技术制备了Pr-N-P三元掺杂锐钛矿TiO2(PrNPTO)纳米片,并采用X射线衍射、透射电镜、N2吸附、X射线光电子能谱、UV-vis吸收谱和光致荧光光谱分析技术对其进行了表征.当Pr掺杂量为1.75 wt%,焙烧温度为550°C时,制得的PrNPTO在可见和紫外光下光催化降解亚甲基蓝(MB)活性最佳.在模拟太阳光照射下,PrNPTO也表现出优越的光催化降解4-氯酚性能(kapp=3.90×10-2 min-1),优于未掺杂、单掺杂和双掺杂TiO2样品,其光活性是P25 TiO2的3.33倍(kapp=1.17×10-2min-1).PrNPTO光活性的提高归因于Pr-N-P三元掺杂增强了紫外和可见光吸收,降低了光生载流子复合,增加了表面羟基以及改善了表面织构特性.在模拟太阳光照射下,PrNPTO光催化效率高且光催化性能稳定,适合于环境净化领域的实际应用..

摘要：In this paper, for the tool wear problem of the cutting process, the study on improving tool life has been done through the analysis of the Seebeck effect in the efficient turning process. The generation principle of the self-excited electric current in the cutting process is studied, and also its effect on the life of the turning cutter is studied, so as to reveal the mechanism of the self-excited electric current accelerating the wear of cutting tools. The study results show that the self-excited electric current which is generated during the cutting process is one of the main reasons that cause both the accelerated hardening and the low life of cutting tools to happen. Thus, if the generation of self-excited current is avoided and reduced, the cutting performance of cutting tools can be effectively improved, so to improve the tool life. The study can provide the anti-friction and anti-wear theory basis for the design of the efficient cutting tools.

摘要：应用经典稳态Kalman滤波理论提出了设计Wiener状态估值器的新方法,其原理是:基于在Wiener滤波器形式下的稳态Kalman滤波器和预报器及ARMA新息模型,由稳态最优非递推状态估值器的递推变形引出Wiener状态估值器.所提出的Wiener状态估值器可统一处理状态滤波、预报和平滑问题.它们具有ARMA递推形式,且具有渐近稳定性和最优性,仿真例子说明了它们的有效性.

摘要：利用太阳能将CO_(2)转化为增值燃料,对于实现全球碳中和的目标具有重要意义,而光生电荷的有效分离是提高光催化CO_(2)还原效率的重要影响因素.在此,我们报道了一种简易的原位剥离和转化策略,将CeO_(2)纳米颗粒均匀分布在超薄多孔C_(3)N_(4)纳米片上,合成了新型的CeO_(2)/C_(3)N_(4)异质结构.C_(3)N_(4)的超薄多孔结构不仅可以增加比表面积以提供更多的活性位点,还可以有效缩短光生电子空穴的迁移距离以避免复合.此外,高度分散的CeO_(2)与C_(3)N_(4)之间具有紧密的界面接触,使更多的电荷通过界面进行转移.合成的CeO_(2)/C_(3)N_(4)异质结构具有带隙匹配的Z型结构,可以有效延长光诱导电荷载流子的寿命并提升光催化剂的氧化还原能力.与传统块状C_(3)N_(4)相比,合成的CeO_(2)/C_(3)N_(4)异质结在没有贵金属作为助催化剂和没有牺牲剂条件下显示出约5倍的CO_(2)光还原性能的提升.这项工作为用于可持续能源转换的直接Z型光催化剂的设计和实际应用提供了一种新策略.