铁磁性纳米片间相互作用对其微波磁性的影响

在铁磁性元素中,交换能、偶极能和各向异性能之间存在复杂的竞争,因此,这种结构化介质的静态和动态性能与构成材料的固有磁特性,各个元素的形状和尺寸等有着密切的关系.这些多个自由度提供了对于通常未构图的磁性薄膜不可达到的新性能.本文通过将所研究的系统划分成立方体网格的三维阵列来对其进行建模,研究具有不同相对位置、纳米片间距、磁各向异性方向的两矩形铁磁性纳米片的微波磁性能.研究发现:与单个矩形铁磁性纳米片相比,具有不同相对位置、纳米片间距的两矩形铁磁性纳米片共振峰频率分布发生变化;当两矩形纳米片磁各向异性方向所呈角度由0°增加到30°时,其磁性质没有明显变化,而从30°到90°时,其磁性质对磁各向异性方向变化比较敏感.通过调控纳米片的相对位置、纳米片间距以及磁各向异性方向可以制备具有良好性能的吸收材料.     

基于信号博弈的包装企业品牌策略决策研究

为解决向食品制造商提供包装的包装企业面临的品牌策略决策问题,将消费者观察到的包装企业生产外包装的材质以及设计水平作为传递产品质量的信号,运用信号博弈理论,以包装企业与产品制造商得益最大为目标,研究并分析了合并均衡、分离均衡和混合均衡下的包装企业品牌策略结果。结果表明,不完全信息博弈下包装企业的最优品牌策略决策为：对高质量产品的制造商提供并实施混合均衡下的高档次品牌策略,对于低质量产品的制造商提供并实施分离均衡下的低档次品牌策略。对比完全信息博弈结果,包装企业的品牌策略能作为信号,传递且有效区分产品制造商的产品质量。虽然高档次的品牌策略能帮助制造商将低质量产品伪装成高质量产品进入市场,但这种情况下消费者买到高质量产品的可能性反而有所提高。     

Recovering local equilibrium from three-dimensional compatible finite element solutions

We study the application to compressible and incompressible three-dimensional elasticity problems of the technique that we proposed in 2009 for the recovery of equilibrated stresses from compatible finite element solutions. The case of finite elements with linear displacement approximations, for which the partitioned systems of loads are not initially balanced in terms of rotational equilibrium, addressed in 2012, is also considered. The article includes a presentation of the implementation details, a study of the convergence in terms of the energy of the error, and a characterization of the solutions obtained.     

Effect of particle size and adsorption equilibrium time on pore structure characterization in low pressure N2 adsorption of coal: An experimental study

This study examined the influence of particle sizes and adsorption equilibrium time (AET) on pore structure characterization using low pressure N₂ adsorption (LPGA-N₂) method. The results demonstrate that pore structures change with progressive crushing. The increase in pore volume in the minipore and mesopore with decreasing coal particle sizes was caused by creating additional large pores during the crushing. The tendency of decreasing at first and then increasing was observed for both the specific surface area (SSA) and micropore volume, demonstrating that the micropore structure was primarily damaged and then followed by additional micropores being created when the sample was broken down smaller than 80 mesh. It is difficult to choose a suitable coal particle size for LPGA-N₂ measurement to yield pore structure parameters closest to the “real” values due to the difficulty in evaluating the compound effect of crushing on pore structures. To make testing results closer to the coal structure under in situ conditions, we propose 1∼3 mm as the preferred coal particle size. Additionally, many replicate experiments were performed by adjusting the AET to ensure LPGA-N₂ isotherms in equilibrium states. The results indicate that a decrease in particle size did not reduce the time for reaching N₂ adsorption equilibrium. Comparison of pore size distributions under different AETs shows that the AETs' increase has a little influence on the measurement of minipore and mesopore but has a positive correlation with micropore, revealing that N₂ adsorption equilibrium is mainly influenced by the micropore whose volume is underestimated at small AETs. The optimal AET for LPGA-N₂ measurement was 8 min and its yielded data can more accurately characterize the pore structure parameters.     

Alternating Current Photovoltaic Effect

It is well known that the photovoltaic effect produces a direct current (DC) under solar illumination owing to the directional separation of light-excited charge carriers at the p–n junction, with holes flowing to the p-side and electrons flowing to the n-side. Here, it is found that apart from the DC generated by the conventional p–n photovoltaic effect, there is another new type of photovoltaic effect that generates alternating current (AC) in the nonequilibrium states when the illumination light periodically shines at the junction/interface of materials. The peak current of AC at high switching frequency can be much higher than that from DC. The AC cannot be explained by the established mechanisms for conventional photovoltaics; instead, it is suggested to be a result of the relative shift and realignment between the quasi-Fermi levels of the semiconductors adjacent to the junction/interface under the nonequilibrium conditions, which results in electron flow in the external circuit back and forth to balance the potential difference between two electrodes. By virtue of this effect, the device can work as a high-performance broadband photodetector with extremely high sensitivity under zero bias; it can also work as a remote power source providing extra power output in addition to the conventional photovoltaic effect.     

Dynamic Resource Pricing and Allocation in Multilayer Satellite Network

The goal of delivering high-quality service has spurred research of 6G satellite communication networks. The limited resource-allocation problem has been addressed by next-generation satellite communication networks, especially multilayer networks with multiple low-Earth-orbit (LEO) and non-low-Earth-orbit (NLEO) satellites. In this study, the resource-allocation problem of a multilayer satellite network consisting of one NLEO and multiple LEO satellites is solved. The NLEO satellite is the authorized user of spectrum resources and the LEO satellites are unauthorized users. The resource allocation and dynamic pricing problems are combined, and a dynamic game-based resource pricing and allocation model is proposed to maximize the market advantage of LEO satellites and reduce interference between LEO and NLEO satellites. In the proposed model, the resource price is formulated as the dynamic state of the LEO satellites, using the resource allocation strategy as the control variable. Based on the proposed dynamic game model, an open-loop Nash equilibrium is analyzed, and an algorithm is proposed for the resource pricing and allocation problem. Numerical simulations validate the model and algorithm.     

随机潜蚤病模型的动力学行为分析

潜蚤病是贫困地区的一种人畜共患病,其发病过程极易受到随机波动环境因素的影响。因此,建立并讨论了一类以正确卫生习惯为控制策略的随机潜蚤病模型。首先,通过构造恰当的Lyapunov函数并利用It$\hat{\rm o}$公式证明了随机系统全局正解的存在唯一性。其次,在一定的条件下证明了随机系统的正解围绕在确定性系统平衡点附近的振荡行为。最后,通过数值模拟验证了理论结果的正确性。数值结果表明,当随机干扰强度足够大时将会导致疾病灭绝。     

机会网络自私节点的Bertrand博弈与激励机制研究

在真实的网络环境中,很多节点可能是自私的,它们不愿意牺牲自己的资源为其他节点转发消息。针对这种情况,提出一种基于博弈论的激励机制,可以激励节点与其他节点相互合作。该机制为二阶段激励,激励节点接收消息以协助其他节点转发,同时激励节点转发更多的消息。把源节点与中继节点之间的竞争与合作模型化为Bertrand（伯特兰德）博弈,定义了源节点和中继节点的效用函数。求解了源节点的最佳定价策略和中继节点最佳的转发计划,验证了源节点与中继节点之间存在唯一的纳什均衡。模拟仿真结果表明提出的激励机制能够鼓励自私节点参与合作,能提高路由算法的传递率,同时降低了消息传递延迟。与基于声誉的激励机制相比,所提激励机制能使消息传递成功率提高31.4%、平均时延降低9.7%。