无线多跳传感器网络中能量消耗均衡分簇策略

针对在无线多跳传感器网络中节点间能量消耗不均衡、中继节点容易过早失效的问题,基于几何规划提出一种自适应的分簇算法.该算法通过节点的能量水平和位置来调节其竞争簇头的概率,同时通过簇头的能量水平和离汇聚点的距离调节簇头"管辖"范围.仿真表明:本算法很好地均衡了网络能量开销,使得网络的生命周期延长了25%,稳定周期延长了50%.     

Highly stretchable and sensitive strain sensor based on silver nanowires/carbon nanotubes on hair band for human motion detection

In this work, a highly stretchable and sensitive strain sensor using silver nanowires(Ag NWs)/multi-walled carbon nanotubes(MWCNTs) on hair band is proposed. The fabrication process of such sensors enabled scalable and facile production with low cost by dipping hair band into Ag NWs/MWCNTs composites suspension. The sensing performance of the sensors was optimized by tuning the Ag NWs/MWCNTs mass ratio. The hair band based strain sensor with Ag NWs/MWCNTs mass ratio of 30 exhibited the best perf...     

The role of jumps in the agricultural futures market on forecasting stock market volatility: New evidence

In this study, we explore the effect of cojumps within the agricultural futures market, and cojumps between the agricultural futures market and the stock market, on stock volatility forecasting. Also, we take into account large and small components of cojumps. We have several noteworthy findings. First, large jumps may lead to more substantial fluctuations and are more powerful than small jumps. The effect of cojumps and their decompositions on future volatility are mixed. Second, a model including large and small cojumps between the agricultural futures market and the stock market can achieve a higher forecasting accuracy, implying that large and small cojumps contain more useful predictive information than cojumps themselves. Third, our conclusions are robust based on various robustness tests such as the realized kernel, expanding forecasts, different forecasting windows, different jump tests, and different threshold values.     

融合视惯传感数据的非接触式物体尺寸获取方法

从视觉数据和惯性测量单元(Inertial Measurement Unit, IMU)数据各自的特点出发,利用计算机视觉三维重建技术从视觉数据中恢复视觉传感器的六维位姿信息,分析计算惯性测量数据和视觉位姿数据的时空关系,实现融合视惯传感数据的场景重建及尺度估计,进而获取待测对象的绝对物理尺寸数据。上述方法在实验数据上取得了相对误差约为3%的非接触式物体尺寸估计结果,由于该方法无需在待测场景中嵌入额外标定物或辅助定位装置,具有较好的灵活性和适用范围。     

Resource Allocation in Public Healthcare: A Team-DEA Model

This paper combines the theory of teams and data envelopment analysis (DEA) to design a mechanism to optimally allocate resources in public healthcare. A statutory authority and the public hospitals under its governance are interpreted as a team, the members of which seek to operate efficiently under the shared institutional constraint that public healthcare is a public good. The individual public hospital exploits DEA to maximize own-payoff, subject to the team-condition that the payoff of each other public hospital does not fall and thereby subtract from the external effects created by the public supply of healthcare. The resulting team-DEA solution, which is shown to be both an individually-efficient and team-satisficing equilibrium and to be computable in terms of a convergent algorithm, can then be applied by the authority to determine the optimal allocation of resources in public healthcare. A case based on Chinese data is presented to illustrate the team-DEA model’s ready operationalization and computation.     

淬火分配处理对高碳钢组织、力学性能和磨损性能的影响

The present work employed the X-ray diffraction, scanning electron microscopy, electron backscattered diffraction, and electron probe microanalysis techniques to identify the microstructural evolution and mechanical and abrasive behavior of high carbon steel during quenching-partitioning treatment with an aim to enhance the toughness and wear resistance of high carbon steel. Results showed that, with the increase in partitioning temperature from 250 to 400°C, the amount of retained austenite (RA) decreased resulting from the carbide precipitation effect after longer partitioning times. Moreover, the stability of RA generally increased because of the enhanced degree of carbon enrichment in RA. Given the factors affecting the toughness of high carbon steel, the stability of RA associated with size, carbon content, and morphology plays a significant role in determining the toughness of high carbon steel. The analysis of the wear resistance of samples with different mechanical properties shows that hardness is the primary factor affecting the wear resistance of high carbon steel, and the toughness is the secondary one.     

偏心搅拌槽内高浓度浆液颗粒的悬浮特性

以直径为0.34 m的无挡板平底圆筒形搅拌槽为研究对象,对偏心搅拌槽内高浓度浆液中颗粒的悬浮特性进行了数值研究,分析了45°的4斜叶开启涡轮式搅拌桨(PBT)和3窄叶整体板式螺旋桨(ZHX)2种桨型在不同偏心率和转速时,搅拌槽内的流型分布、颗粒体积分数分布、完全离底临界悬浮转速以及功率消耗,并与试验结果进行了对比.结果表明:对于高浓度浆液,偏心搅拌打破了中心搅拌时流场结构的对称性,提高了流体的轴向循环能力,颗粒悬浮效果优于中心搅拌;固体颗粒的悬浮效果与搅拌桨在槽内的偏心位置有关,当偏心率E=0.4时颗粒悬浮效果最佳,但偏心搅拌会增大颗粒的完全离底临界悬浮转速和设备的功率消耗,不利于节能降耗.     

Opposite effects of fear conditioning and extinction on dendritic spine remodelling

It is generally believed that fear extinction is a form of new learning that inhibits rather than erases previously acquired fear memories. Although this view has gained much support from behavioural and electrophysiological studies, the hypothesis that extinction causes the partial erasure of fear memories remains viable. Using transcranial two-photon microscopy, we investigated how neural circuits are modified by fear learning and extinction by examining the formation and elimination of postsynaptic dendritic spines of layer-V pyramidal neurons in the mouse frontal association cortex. Here we show that fear conditioning by pairing an auditory cue with a footshock increases the rate of spine elimination. By contrast, fear extinction by repeated presentation of the same auditory cue without a footshock increases the rate of spine formation. The degrees of spine remodelling induced by fear conditioning and extinction strongly correlate with the expression and extinction of conditioned fear responses, respectively. Notably, spine elimination and formation induced by fear conditioning and extinction occur on the same dendritic branches in a cue- and location-specific manner: cue-specific extinction causes formation of dendritic spines within a distance of two micrometres from spines that were eliminated after fear conditioning. Furthermore, reconditioning preferentially induces elimination of dendritic spines that were formed after extinction. Thus, within vastly complex neuronal networks, fear conditioning, extinction and reconditioning lead to opposing changes at the level of individual synapses. These findings also suggest that fear memory traces are partially erased after extinction.