High-frequency nanometre-scale vibration in 'quiescent' flagellar axonemes

The movement of cilia and flagella is based on the interaction between dynein arms and microtubules coupled with ATP hydrolysis. Although it is established that dynein arms cause adjacent microtubules to slide, little is known about the elementary process underlying the force production. To look more closely at the mechano-chemical conversion mechanism, we recently developed an optical method for measuring a nanometre-scale displacement with a time-resolution better than 1 ms. We now report the detection of high frequency (approximately 300 Hz) vibration of sub-nanometre amplitude in non-beating flagellar axonemes. This vibration could reflect the movement of individual activated dynein arms.     

Electronic transport in nanometre-scale silicon-on-insulator membranes

The widely used 'silicon-on-insulator' (SOI) system consists of a layer of single-crystalline silicon supported on a silicon dioxide substrate. When this silicon layer (the template layer) is very thin, the assumption that an effectively infinite number of atoms contributes to its physical properties no longer applies, and new electronic, mechanical and thermodynamic phenomena arise, distinct from those of bulk silicon. The development of unusual electronic properties with decreasing layer thickness is particularly important for silicon microelectronic devices, in which (001)-oriented SOI is often used. Here we show--using scanning tunnelling microscopy, electronic transport measurements, and theory--that electronic conduction in thin SOI(001) is determined not by bulk dopants but by the interaction of surface or interface electronic energy levels with the 'bulk' band structure of the thin silicon template layer. This interaction enables high-mobility carrier conduction in nanometre-scale SOI; conduction in even the thinnest membranes or layers of Si(001) is therefore possible, independent of any considerations of bulk doping, provided that the proper surface or interface states are available to enable the thermal excitation of 'bulk' carriers in the silicon layer.     

Tracking apex marine predator movements in a dynamic ocean

Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.     

Mesoscopic fast ion conduction in nanometre-scale planar heterostructures

Ion conduction is of prime importance for solid-state reactions in ionic systems, and for devices such as high-temperature batteries and fuel cells, chemical filters and sensors. Ionic conductivity in solid electrolytes can be improved by dissolving appropriate impurities into the structure or by introducing interfaces that cause the redistribution of ions in the space-charge regions. Heterojunctions in two-phase systems should be particularly efficient at improving ionic conduction, and a qualitatively different conductivity behaviour is expected when interface spacing is comparable to or smaller than the width of the space-charge regions in comparatively large crystals. Here we report the preparation, by molecular-beam epitaxy, of defined heterolayered films composed of CaF2 and BaF2 that exhibit ionic conductivity (parallel to the interfaces) increasing proportionally with interface density--for interfacial spacing greater than 50 nanometres. The results are in excellent agreement with semi-infinite space-charge calculations, assuming a redistribution of fluoride ions at the interfaces. If the spacing is reduced further, the boundary zones overlap and the predicted mesoscopic size effect is observed. At this point, the single layers lose their individuality and an artificial ionically conducting material with anomalous transport properties is generated. Our results should lead to fundamental insight into ionic contact processes and to tailored ionic conductors of potential relevance for medium-temperature applications.     

Controlled multiple quantum coherences of nuclear spins in a nanometre-scale device

The analytical technique of nuclear magnetic resonance (NMR) is based on coherent quantum mechanical superposition of nuclear spin states. Recently, NMR has received considerable renewed interest in the context of quantum computation and information processing, which require controlled coherent qubit operations. However, standard NMR is not suitable for the implementation of realistic scalable devices, which would require all-electrical control and the means to detect microscopic quantities of coherent nuclear spins. Here we present a self-contained NMR semiconductor device that can control nuclear spins in a nanometre-scale region. Our approach enables the direct detection of (otherwise invisible) multiple quantum coherences between levels separated by more than one quantum of spin angular momentum. This microscopic high sensitivity NMR technique is especially suitable for probing materials whose nuclei contain multiple spin levels, and may form the basis of a versatile multiple qubit device.     

A nanometre-scale electronic switch consisting of a metal cluster and redox-addressable groups

So-called bottom-up fabrication methods aim to assemble and integrate molecular components exhibiting specific functions into electronic devices that are orders of magnitude smaller than can be fabricated by lithographic techniques. Fundamental to the success of the bottom-up approach is the ability to control electron transport across molecular components. Organic molecules containing redox centres-chemical species whose oxidation number, and hence electronic structure, can be changed reversibly-support resonant tunnelling and display promising functional behaviour when sandwiched as molecular layers between electrical contacts, but their integration into more complex assemblies remains challenging. For this reason, functionalized metal nanoparticles have attracted much interest: they exhibit single-electron characteristics (such as quantized capacitance charging) and can be organized through simple self-assembly methods into well ordered structures, with the nanoparticles at controlled locations. Here we report scanning tunnelling microscopy measurements showing that organic molecules containing redox centres can be used to attach metal nanoparticles to electrode surfaces and so control the electron transport between them. Our system consists of gold nanoclusters a few nanometres across and functionalized with polymethylene chains that carry a central, reversibly reducible bipyridinium moiety. We expect that the ability to electronically contact metal nanoparticles via redox-active molecules, and to alter profoundly their tunnelling properties by charge injection into these molecules, can form the basis for a range of nanoscale electronic switches.     

高精度空间磁通门磁力计

基于软磁材料磁化饱和时的非线性特性研制了空间磁通门磁力计,用以精确测量大小为1n1T以下的稳定或者低频交变的磁场,其应用范围涉及深空探测和地球物理学等许多领域．磁通门磁力计信号处理系统应用了相关检测原理,完成了一维空间磁通门磁力计原理样机研制．对样机进行了灵敏度、线性度、噪声和分辨率的测试．实验结果表明,该原理样机的分辨率优于5．2nT,线性动态范围达到12μT．其关键指标达到空间应用的要求．     

Active Tracking with Pan—Tilt—Zoom Camera

This paper intends to introduce the active vision system with autonomous robot competition in the background.It presents some characteristics of the human oculomotor system in active machine vision system:smooth pursuit and saccade.Besides,zoom tracking is used to continuous adjustment of a camera′s focal length to keep a constant sized image of an object moving along the camera′s optical axis.Experiments indicate the technology to be efficient for tracking the ball in the robot competition.     

基于有源辅助的被动跟踪系统

提出了一种有源雷达间歇辅助红外工作的雷达／红外协同跟踪系统,该系统通过减少雷达开机时间降低被敌方ESM（电子支持措施）锁定的可能性．为了改善纯角度跟踪的滤波发散问题,一方面,在滤波处理时采用了非线性逼近能力更强的Unscented卡尔曼滤波算法;另一方面,充分利用雷达、红外同时开机时的量测信息,构造出一组时间多项式,在雷达关机期间,利用该组时间多项式估计目标的运动状态,辅助红外传感器进行跟踪．计算机仿真结果表明,该方法不仅能保证跟踪精度,同时也能有效地降低雷达被敌方ESM锁定的可能性．     

带微分观测器的双环姿态跟踪控制

针对捕获非合作目标航天器的姿态跟踪控制问题,给出了一种双环姿态跟踪控制器。通过引入虚拟角速度将二阶姿态运动方程分解为内外环独立的子系统。外环预设有界虚拟角速度使航天器姿态渐近收敛于期望姿态;内环采用二阶微分观测器精确估计由转动惯量摄动、外部干扰和饱和超幅部分组成的不确定项,基于观测值的鲁棒姿态控制器使内环角速度指数收敛于外环虚拟角速度。双环姿态跟踪控制能够满足控制饱和及角速度有界约束下的跟踪精度和闭环系统的全局渐近稳定性。数值仿真验证了该控制器的鲁棒性和有效性。      

基于目标背景加权的核跟踪

在核跟踪(Mean Shift跟踪)算法中,目标的表示方法对跟踪性能有很重要的影响.传统的核跟踪算法只是通过计算目标模型和候选目标模型,对目标进行跟踪,没有消除背景的影响,特别是目标与背景相近的情况.对此,提出了一种目标背景加权的核跟踪算法,该算法是在跟踪过程中对目标模型进行背景加权,并且在目标的表示中采用颜色纹理联合直方图.为了验证跟踪的可靠性,利用跟踪位置与目标位置之间偏移量的均值和方差进行衡量.实验结果表明,与传统的跟踪算法相比,该算法在目标的表示和跟踪性能上有很大的提高.     

仅有角度信息的红外多传感器异步目标跟踪

跟踪机动目标,红外单站有不少缺陷,多站可以提供比单站多的信息。然而,多站存在同步的问题。通过对状态更新过程的分析,发现跟踪可以异步实现。多站采用异步的处理方式极大的灵活了数据的处理,而且可以通过多站组网扩大跟踪范围。为解决系统方程的非线性,采用伪线性观测方程。仿真结果表明本方法可以实现对空中目标的稳定跟踪,且观测站增加可以提高精度。     

Indoor Pedestrian Tracking with Sparse RSS Fingerprints

Indoor pedestrian localization is of great importance for diverse mobile applications.Many indoor localization approaches have been proposed:among them,Radio Signal Strength(RSS)-based approaches have the advantage of existing infrastructures and avoid the cost of infrastructure deployment.However,the RSS-based localization approaches suffer from poor localization accuracy when the RSS fingerprints are sparse,as illustrated by actual experiments in this study.Here,we propose a novel indoor pedestrian tracking approach for smartphone users:this approach provides a high localization accuracy when the RSS fingerprints are sparse.Besides using the RSS fingerprints,this approach also utilizes the inertial sensor readings on smartphones.This approach has two components:(i) dead-reckoning subsystem that counts the number of walking steps with off-the-shelf inertial sensor readings on smartphones and(ii) particle filtering that computes the locations with only sparse RSS readings.The proposed approach is implemented on Android-based smartphones.Extensive experiments are carried out in both small and large testbeds.The evaluation results show that the tracking approach can achieve a high accuracy of5 m(up to 95%) in indoor environments with only sparse RSS fingerprints.     

高精度高性能晶体振荡器电路

设计了一种用于实时时钟的高精度高性能晶体振荡器.采用振幅控制机理以达到高频率稳定性和低功耗的要求,基于外部电容调谐的原理来进一步提高实时时钟精度.电路在0.6μm CMOS工艺上实现,测试结果表明在工作电压为3 V的条件下,振荡器的工作电流小于240 nA,振荡器能够稳定工作在1.5~5.5 V的电压范围,时钟精度可达5.8×10-6.     

一种高精度Fuzzy控制器的设计

提出了一种基于基本Fuzzy控制器基础上更好地模拟人的操作经验来改善控制性能的一种高精度Fuzzy控制器的设计方法 ,针对将语言变量量化出相应的等级引起的误差 ,采用了加权方法进行处理 ,提高了控制器的精度 ,有一定的实用价值     

二次精度参数插值曲线的构造

提出了一种构造三次参数曲线对给定数据点插值的新方法。该方法不同于现有的许多参数曲线构造方法,其构造参数曲线没有选择节点的过程,而是在每2个数据点之间构造一条单位区间上的三次埃尔米特插值曲线段,所有曲线段拼合在一起形成整体的插值曲线,该方法的关键是计算每个数据点处的导矢。对每个数据点,该方法使用5或4个数据点构造一条二次多项式曲线,数据点处的导矢由二次多项式曲线的导矢近似。该方法构造的三次参数曲线具有二次多项式精度。并以以实例对新方法与其它方法构造的插值曲线的精度进行了比较,结果表明,新方法构造的插值曲线的精度较高。