Electric vehicles (EVs) are one important enabler for the evolution of sustainable transportation sector. However, one major barrier to the widespread adoption of EVs is their limited battery capacity and the excessive time required to fully charge depleted batteries. Although techniques such as charging with a rapid charger and battery swapping may partially alleviate such concerns, the corresponding high capital investment may not be profitable for areas with low EV adoption rates. Moreover, the diversified charging demands of randomly distributed EVs, both spatially and temporally, restrict high-quality services from current fixed charging stations (FCSs). To resolve such challenges, mobile charging services (MCSs) have been investigated as a supplemental charging method for EVs, wherein energy replenishment is provided by mobile charging vehicles (MCVs). Under the framework of the Internet of EVs (IoEV), this article describes the concept of MCSs and investigates their charging merits under some distinct charging scenarios, e.g., real-time response service and emergency rescue service. A case study concerning real-time response services is investigated to illustrate the influence of MCSs on the current charging system. Simulation results demonstrate the ability of MCSs to improve the quality of charging service by reducing the average service time and service acceptance ratio. Finally, technical challenges, future research issues, and possible methodologies regarding the MCSs for EVs are discussed.

Based on the special structure of variable-boostable chaotic system VB24, a quadratic flux-controlled memristor is embedded for the construction of a 3D memristive chaotic system with conditional symmetry. Coexisting oscillations with conditional symmetry are confirmed systematically based on the bifurcation analysis and circuit verification. Two constants in the absolute value functions play the role of offset boosting, which modifies the distance between pairs of coexisting attractors separately in external and internal state space. Interestingly, any of two coexisting attractors with conditional symmetry could be symmetric or asymmetric. An analog circuit is designed to verify the coexisting oscillations as predicted.

我国自上世纪70年代末开始改革开放以来,经济保持快速增长,伴随而来的是对生态环境的负面影响,经济增长与生态环境保护之间的矛盾日趋严峻.尤其近20年以来,粗放式经济发展模式,使得我们出现了资源短缺、河流污染、雾霾、生态遭到破坏等经济、社会问题,这与人民群众的幸福生活诉求出现背离.生态环境治理问题、高质量可持续发展问题成为我国经济的关键议题之一.

伴随经济的发展,经济、社会、环境的协调发展成为全球各国关注的焦点,人类可持续发展成为经济发展的目标,本文在可持续发展背景下探索了中国装备制造业的发展问题,主要分析了环境规制影响中国装备制造业的产业结构升级现状问题,从直接和间接的角度分析了其影响路径,期望为中国装备制造业的产业结构升级提供理论借鉴.

Mobile charging services (MCSs) have been developed as a supplement charging method for electric vehicles (EVs), wherein energy replenishment is provided by mobile charging vehicles (MCVs). An MCV has an internal storage system employed to replenish the energy of a certain number of EVs. Charging scheduling of MCV is one of the key issues on the Internet of EVs for providing efficient and convenient charging services, which requires determining the charging sequence and the amount of energy when serving multiple EVs by one MCV. In this paper, a multi-objective MCV scheduling problem is investigated. By optimizing the charging sequence and the actual amount of energy being charged, the proposed framework aims to minimize the EV waiting time while simultaneously to maximize the charging benefits of all EVs. To solve the multi-objective optimization problem (MOP), a deep reinforcement learning (DRL) based framework is further explored. The MOP is first decomposed into a set of subproblems. Each subproblem is modelled as a neural network, wherein an actor-critic algorithm and a modified pointer network are adopted to solve each subproblem. Pareto optimal solutions can be directly obtained through the trained models. The experimental results demonstrate that the proposed method can efficiently and effectively solve the MCV scheduling problem and outperform NSGA-II and MOEA/D in terms of solution convergence, solution diversity, and computing time. In addition, the trained model can be applied to newly encountered problems without retraining.

迎角、侧滑角是飞机重要的飞行状态参数,而大气数据系统在恶劣天气、大迎角或机动飞行情况下是难以准确测量出气流角等数据的.基于飞行数据,研究了一种飞机气流角的估计方法.考虑到飞行数据可能受到外部干扰发生数据突变、各数据采样频率不同以及飞行数据之间的噪声统计特性均未知等情况,建立飞机系统状态方程和量测方程,将非等间隔理论与基于极大似然准则的自适应卡尔曼滤波算法进行融合,以飞机转弯和爬升飞行为实例,施加外部干扰,对飞机迎角、侧滑角进行估计.实验结果表明,该算法的估计精度和抗外部干扰的鲁棒性能均优于扩展卡尔曼滤波算法和无迹卡尔曼滤波算法.

以中国装备制造业为例,分析其产业结构升级的对策建议,主要从绿色发展、完善环境规制体系、将环境保护纳入地方政府官员晋升考核体系、完善正式环境规制体系建设、倡导大众绿色生活和消费及因地制宜环境规制等方面出发,实现环境与经济的双赢,为中国装备制造业产业结构升级提供理论借鉴.

In a PoW-based blockchain network, miners participate in a block-discovery racing game for financial incentives. As the total computing power becomes overwhelming, miners join in the mining pool which combines the scattered computing power to win a stable profit. Miners in the same mining pool work as a team and once they successfully mine a valid block, mining pool plays a role in distributing the payoff to miners according to its reward sharing mechanism. Specifically, two main reward sharing strategies: Pay-Per-Share (PPS) and Pay-Per-Last-NShare (PPLNS) are considered. In the mining system model, a miner can choose to join a pool and adapt the selection for improving the expected reward. And we formulate the dynamic pool selection problem as an evolutionary game. We consider the required hash rate, network delay and reward sharing strategy as the main factors which affect the choice of miners. Evolutionary stable equilibrium (ESS) is considered to be the solution, and we conduct theoretical analysis on the existence and stability of the ESS for a case of two mining pools. A low complexity distributed algorithm is proposed for miners to reach the equilibrium. Numerical results show the evolution of miners and demonstrate the theoretical findings of our study.

With the exponential growth of data traffic, the use of caching and device-to-device (D2D) communications has been regarded as an efficient approach for alleviating the backhaul congestion in unmanned aerial vehicle (UAV) assisted networks. In this paper, we investigate the security issue of a cache-enabled UAV-relaying network with D2D communications in the presence of eavesdropper. Specifically, a UAV and multiple D2D users are equipped with cache memory, which can pre-store some popular contents to cooperatively provide content transfer services for users. To achieve secure and fair transmission, an optimization problem is formulated with the aim of maximizing the minimum secrecy rate among receivers, by jointly optimizing the cache placement and UAV flight trajectory in a finite flight period. The joint design problem is a non-convex mixed-integer programming problem. To facilitate solving this problem, we propose an alternating iterative algorithm based on the block alternating descend and successive convex approximation methods. Numerical results show that the joint design scheme significantly outperforms other benchmark schemes in terms of the secrecy rate.

文章以江苏省10个城市为例,通过超效率DEA模型和Tobit回归分析评价了2013-2017年江苏10个城市的生态效率及其影响因素.研究表明:各城市生态效率处于中上水平,各城市由于资源类型、生产技术、科技创新等原因,生态效率存在明显差异.经济发展水平、环境政策和科技水平对生态效率有不同程度的促进作用,产业结构、城镇化率和人口密度对生态效率有负面影响.

User association is indispensable for the operation of wireless network and has critical impacts on system performance. For most existing work, user associations are typically coupled, which require a user equipment (UE) to associate with the same base station (BS) in uplink (UL) and downlink (DL). However, wireless networks are becoming heterogeneous and densifying, which generates intrinsic distinctions (transmission power, data traffic and backhaul capacity etc.) between UL and DL. Accordingly, coupled association may no longer be optimal. In this work, we explore decoupled user association in full-duplex ultra-dense networks (UDNs), which allows a UE to associate with different BSs in UL and DL respectively. Furthermore, to fully exploit the benefits of UDNs, multiple association, referring to associating a UE with multiple BSs, is jointly adopted in UL and DL. Considering the dynamic and complicated association process, an evolutionary game (EG) is formulated, where UEs are players, and their strategies are association selections in UL/DL. Particularly, evolutionary equilibrium is viewed as the stable solution to the formulated problem. Moreover, an EG-based algorithm with low complexity is proposed for decoupled multiple association. Numerical results validate the convergence of the proposed algorithm for strategy adoption. Besides, the impacts of information exchange delay and learning rate are investigated for providing a better association decision.

飞机进场着陆阶段是飞行任务中的事故多发阶段,长着陆和重着陆是该阶段发生最为频繁的不安全事件.为探索诱发长着陆和重着陆的影响因素,考虑飞行数据的时间序列信息,结合实际飞行阶段对着陆因参数进行分段,并通过着陆阶段动力学分析,建立标准着陆模型;采用基于时间序列的灰色接近关联分析进行模型和方法验证,并找到影响长着陆和重着陆事件细节分段后的关键阶段飞行状态参数,再进一步通过灰典型相关分析方法寻找关键阶段的飞行状态参数与长着陆和中重着陆之间定量的关联性.灰色接近关联分析表明,跑道入口至接地段对2个不安全事件的影响最大;进一步的灰典型相关分析结果表明,载荷量达0.9691的下降率对长着陆影响最大,载荷量达0.7670的地速对重着陆影响最大.所得结论与飞行实际情况相符,能够为长着陆和重着陆的预防和风险控制提供参考.

保险协同治理可以充分发挥保险治理的功能与价值,通过与政府部门主体的协同合作降低或者消除社会公众风险,使社会无限经济责任向有限经济责任转变,表现出更高的社会保障职能.但当前我国保险协同治理存在一系列问题:协同动力不足,过分依赖政府政策;保险资源分布不均,协同模式有待丰富;服务创新性匮乏,公共风险治理的广度与深度不足等.本文基于保险产业可以作为公共事业治理主体的理念,以系统理论为出发点,探究保险产业在公共事业领域内的协同治理可行性.通过对我国保险产业协同治理实践的研究,总结出保险协同治理发展的问题及阻碍,并从内部机制改革、升级与创新的角度提出了我国保险业进行创新协同治理发展的策略选择.

作为扩大国民经济再生产的重要依托型产业,装备制造业为满足我国国民经济的发展以及国家安全的需要提供了大量的技术装备.以我国装备制造业比较发达的区域-江苏为例,对其装备制造业的发展概况进行分析,期望为江苏装备制造业的健康发展提供借鉴.

装备制造业对我国经济发展具有重要影响,为制造业的发展提供基础支持,装备制造业技术创新能力的提高是带动我国经济从投资导向转变创新导向的关键因素.本文对江苏省装备制造业的技术创新能力发展现状进行分析,搜集相关文献为本文研究提供理论支持,对江苏省装备制造业的创新模式进行探讨,为其以后的发展提供借鉴.

User association is a crucial factor that affects the performance of wireless networks. In current cellular networks, user association is typically coupled, which means an user equipment (UE) must associate with the same base station (BS) in uplink (UL) and downlink (DL). For single-tier wireless networks, such mechanism is simple and effective. However, in heterogeneous ultra-dense networks (UDNs), there are distinct differences in transmission power, data traffic and channel quality etc., for which coupled association could restrict the performance of system. To cope with it, the concept of decoupled UL-DL (DUDe) association has been introduced recently, which enables a UE to associate with different BSs in UL and DL. In this paper, we investigate decoupled UL-DL user association in UDNs. Considering the existence of asymmetric information (i.e., channel gains and intercell interferences), which can be seen as the private information for UE, we propose a contract-theoretic user association approach. Particularly, we model the decoupled association process as a monopoly labor market, where BSs act as employers and offer contracts to employees (i.e., UEs). The contract items cover the available associated bandwidths, transmitted powers and corresponding prices. Then BS broadcasts these drafted contract information, and UE selects to sign the optimal contract by considering her own demands. Numerical results show significant superiorities of DUDe than coupled UL-DL association in perspective of nodes utilities and social surplus, and compared with the existing user association methods, contract-theoretic approach shows a certain improvement in performance.

The opportunistic mobile sensor network has been extensively used in various public safety applications such as the fire-rescue scenario, since it can provide a surveillance range with an inexpensive cost and avoid the dangers of staying in the risk zones to humans. However, the sensor nodes thrown by firefighters in the fire-rescue scenario are easy to move away from current positions due to many environmental factors such as the building structure damages, airflow push or even some explosions. Consequently, the contacts between nodes become scarce and momentary, thereby making the gathered data packets difficult to be forwarded along stable communication paths. Firstly, the mobility patterns of nodes in the fire-rescue scenario are classified into three types: small-range mobile nodes, large-range mobile nodes and firefighter nodes. Then, the optimal proportions of different types of nodes in the data holders are specially investigated mathematically to maximize the delivery ratio. Thus, a data forwarding approach for fire-rescue scenario (DFAFR) is proposed. In DFAFR, each data holder forwards the held data packets to neighbouring nodes independently, and the optimal proportions of data holders are maintained approximatively. Finally, the performance of DFAFR is analyzed through simulation experiments that produce preferable results in the fire-rescue scenario, indicating that DFAFR can improve the delivery ratio and shorten the delivery delay, so that the fire behavior can be reported and processed timely.

Integrating ambient backscatter communications into RF-powered cognitive radio networks has been shown to be a promising method for achieving energy and spectrum efficient communications, which is very attractive for low-power or no-power communications. In such scenarios, a secondary user (SU) can operate in either transmission mode or backscatter mode. Specifically, an SU can directly transmit data if sufficient energy has been harvested (i.e., transmission mode). Or an SU can backscatter ambient signals to transmit data (i.e., backscatter mode). In this paper, we investigate the performance of such systems. Specifically, channel inversion power control and an energy store-and-reusemechanism for secondary users are adopted for efficient use of harvested energy. We apply stochastic geometry to analyze coverage probability and achievable rates for both primary and secondary users considering both communication modes. Analytical tractable expressions are obtained. Extensive simulations are performed and the numerical results show the validity of our analysis. Furthermore, the results indicate that the performance of secondary systems can be improved with the integration of both communication modes with only limited impact on the performance of primary systems.

格子铺作为一种新型低成本的创业模式,对大学生这个追逐时尚的年轻群体有着巨大的吸引力,有助于大学生进行创业尝试.因此在调查南京市格子铺发展现状的基础上,运用SWOT分析法,从优势、劣势、机会、威胁四个方面分析,并提出格子铺运营发展策略.

当下,随着我国社会主义市场经济的不断完善和迅猛发展,新媒体信息技术以其得天独厚的优势"闯"入了现代人们的视野,参与并影响着人们的生活方式、行为习惯和社会运行,切实将人类社会发展带入了一个全新的阶段即新媒体时代.在新媒体信息技术影响并渗透到高校方方面面之时,高校里,也出现越来越多的大学生低头族现象.该文分析了大学生"低头族"行为及心理,期望为大学生健康发展提供建议.