血管介入手术中的柔性虚拟力触觉系统研究

随着微创手术的发展,虚拟手术的应用前景越来越广阔.力反馈作为虚拟手术的核心技术,其实现的效果直接影响了虚拟手术的沉浸感.通过对经典包围盒碰撞检测算法进行研究比对,选择了球包围盒的碰撞检测算法,并建立了精确的反馈力计算模型,实现了介入血管中的柔性碰撞仿真.该仿真具有很高的实时性和精度.     

基于力反馈手柄的移动载人月球车操作控制系统

移动载人月球车相关技术的研究是我国未来载人登月探测的重要任务.根据载人月球车的需求,本文从航天员操作舒适度和操作工作空间出发,设计了一种面向载人月球车操作的力反馈手柄,在具体的场景设计下可以带给航天员力触觉感受,辅助航天员进行安全、有效的驾驶行为.基于力反馈手柄的移动载人月球车操作控制系统包含力反馈手柄、硬件系统、软件系统.力反馈手柄主要由二自由度旋转机构、手杆、带光编码器的直流电机组成;硬件系统为STM32单片机及相关接口电路,STM32作为下位机接收来自上位机的指令信号和力反馈信息,并且向上位机反馈手柄位置信息;为完成移动载人月球车操作控制系统的仿真测试,软件系统是基于unity3D所开发的月球车驾驶场景,搭载使用虚拟传感器,做出驾驶行为决策解算出相应的力反馈信息.实验结果表明,力反馈手柄能较好地辅助航天员操纵载人月球车,有效提升了载人月球车的驾驶效率和安全性.     

智能肌电控制假手研究进展

智能肌电假手研究作为康复医疗领域中的重要研究内容,始终是国内外研究的热点.随着机器人技术的进步,假手正往仿人型、灵巧性、直觉控制、智能感知方向发展.智能肌电假手应当具有与人手相近的功能,其不仅能通过运动功能重建辅助残疾人进行日常生活,而且还应通过感知反馈功能重建让残疾人产生人机共融的本体感.本文通过对国内外多年的肌电假手研究成果进行分析比较,从质量、灵巧程度、抓取性能、设计原理等多角度分析了假手的机械结构设计要素;另外,本文还较系统地对基于肌电信号的手势识别研究现状进行概述,介绍了目前基于残肢生物信号识别的多种研究思路,并分析了多种基于不同原理的假手信息感知技术,介绍了利用指尖力触觉传感器实现对假手的自适应控制和用户的感知反馈.最后总结了未来假手的研究发展过程中面临的问题与挑战,提出了肌电假手的未来研究方向.     

基于Kinect的机器人辅助上肢被动康复训练控制方法

现有基于Kinect构建的康复训练系统,大多以患者自行开展主动康复训练为主,未能充分利用康复医师的临床经验且很少用于机器人辅助康复训练系统,具有一定的局限.针对此问题,提出一种基于Kinect的机器人辅助上肢被动康复训练方法.首先,开展基于Kinect的上肢骨骼点跟踪与逆运动学计算;其次,基于Linux/QT及Kinect设计三维虚拟康复训练环境;再次,在康复医师示教训练任务并通过Kinect获取示教任务参考轨迹基础上,根据训练过程中Kinect实时捕获的患肢运动位置反馈,设计基于模糊推理的机器人辅助被动康复训练控制器;最后,基于Kinect及Barrett公司4自由度WAM^TM康复机器人构建试验统平台,对方法有效性进行试验验证.实验结果表明,所提方法能有效利用医师的临床康复经验,并使机器人较平稳地牵引受试者上肢沿示教任务轨迹进行训练,较好地实现了"医师-机器人-患者"之间的人机协同康复训练.     

基于Householder矩阵和Butterworth滤波器组的反馈延迟网络人工混响

针对现有人工混响方法中反馈延迟网络方法存在延迟线的个数选择受限和无法设定子带混响时间的不足,本文设计了一种基于Householder反馈矩阵和Butterworth滤波器组的反馈延迟网络人工混响器.Householder反馈矩阵有助于最大化回声密度,延迟线个数的选择相对自由,Butterworth滤波器组便于设定子带混响时间.仿真实验中分别利用语谱图、语音质量感知评价和主观评价验证了本文方法的有效性.     

一类具有随机时滞的受扰马尔科夫跳变系统有限时间稳定性

本文研究了一类具有随机时滞的受扰马尔科夫跳变线性系统的有限时间稳定性问题.通过引入服从伯努利分布的随机变量刻画了时滞变化的随机特性.本文首先分析了系统的随机有限时间稳定性,基于分析结果设计了反馈控制器,使得系统状态在马尔科夫跳变、随机时滞和外界扰动等并存时,在给定时间内收敛于某一区域而不超过指定的上界值,并可获得该上界的具体值.最后通过数值仿真验证了所提算法的有效性.     

基于输出反馈的分数阶奇异线性多智能体系统领导者-跟随一致性

本文主要开展多智能系统领导者-跟随一致性分析,其中每个智能体的动态性能描述为分数阶奇异线性系统.基于系统的输出信息,设计一个输出反馈的控制协议.通过有效的证明,推导出多智能体系统领导者-跟随一致性的充分条件.采用奇异值分解（SVD）技巧,可将一致性条件进一步转换为易于求解的线性矩阵不等式.当通信拓扑图假设为无向连通图时,一致性条件可以简化为相对简单的多个线性矩阵不等式.最后给出一个实例,演示如何求取反馈增益,通过仿真图可以发现本文结果正确、有效.     

一种领队车输入未知的多车辆纵向协作控制方法

本文考虑了领队车控制输入未知的情况,提出一种多车辆纵向协作控制方法.首先,通过采用精确反馈线性化技术,得到了线性的车辆的动力学模型.然后,采用双向领队跟随通信策略,基于邻居车辆的状态信息,为每辆跟随车设计分布式控制律.考虑在领队车输入有界的情况下,提出了一种有效的多车辆协作控制算法,能够保证多车辆系统以最大的收敛速率达到内部稳定.最后,仿真结果展示了所提出控制器设计算法的有效性和优越性.     

基于模糊干扰观测器的抗饱和自适应反步控制

针对一类输入受限的非匹配不确定非线性系统,提出了一种抗饱和自适应反步控制方法.利用模糊干扰观测器在线逼近系统的未知非匹配不确定及干扰,采用反步控制方法设计自适应控制器.控制系统设计中引入限幅滤波器,有效降低了控制输入饱和对系统稳定性的影响,并且控制器设计无需对虚拟控制律进行重复求导.利用李亚普诺夫稳定性定理,证明了闭环系统渐近稳定.仿真结果表明了该方法的有效性.     

基于位置信息的多用户MIMO下行调度算法

基于移动台的位置信息,提出了基于移动台与基站之间的距离信息的多用户调度算法.针对特定的信道模型,分析了所提出的调度方法所需的吞吐量、反馈开销以及计算复杂度.理论和仿真结果表明:该调度方法所需反馈量明显降低且其所需计算量明显小于基于最大信干噪比的调度方法.     

CHARACTERISTICS AND TRENDS OF CLIMATIC EXTREMES IN CHINA DURING 1959–2014

The spatial and temporal variations of daily maximum temperature(Tmax), daily minimum temperature(Tmin), daily maximum precipitation(Pmax) and daily maximum wind speed(WSmax) were examined in China using Mann-Kendall test and linear regression method. The results indicated that for China as a whole, Tmax, Tmin and Pmax had significant increasing trends at rates of 0.15℃ per decade, 0.45℃ per decade and 0.58 mm per decade,respectively, while WSmax had decreased significantly at 1.18 m·s~(-1) per decade during 1959—2014. In all regions of China, Tmin increased and WSmax decreased significantly. Spatially, Tmax increased significantly at most of the stations in South China(SC), northwestern North China(NC), northeastern Northeast China(NEC), eastern Northwest China(NWC) and eastern Southwest China(SWC), and the increasing trends were significant in NC, SC, NWC and SWC on the regional average. Tmin increased significantly at most of the stations in China, with notable increase in NEC, northern and southeastern NC and northwestern and eastern NWC. Pmax showed no significant trend at most of the stations in China, and on the regional average it decreased significantly in NC but increased in SC, NWC and the mid-lower Yangtze River valley(YR). WSmax decreased significantly at the vast majority of stations in China, with remarkable decrease in northern NC, northern and central YR, central and southern SC and in parts of central NEC and western NWC. With global climate change and rapidly economic development, China has become more vulnerable to climatic extremes and meteorological disasters, so more strategies of mitigation and/or adaptation of climatic extremes,such as environmentally-friendly and low-cost energy production systems and the enhancement of engineering defense measures are necessary for government and social publics.     

ANALYSIS OF “BIMODAL PATTERN” STORM ACTIVITY CHARACTERISTICS OF THE BAY OF BENGAL

Storms that occur at the Bay of Bengal (BoB) are of a bimodal pattern, which is different from that of the other sea areas. By using the NCEP, SST and JTWC data, the causes of the bimodal pattern storm activity of the BoB are diagnosed and analyzed in this paper. The result shows that the seasonal variation of general atmosphere circulation in East Asia has a regulating and controlling impact on the BoB storm activity, and the “bimodal period” of the storm activity corresponds exactly to the seasonal conversion period of atmospheric circulation. The minor wind speed of shear spring and autumn contributed to the storm, which was a crucial factor for the generation and occurrence of the “bimodal pattern” storm activity in the BoB. The analysis on sea surface temperature (SST) shows that the SSTs of all the year around in the BoB area meet the conditions required for the generation of tropical cyclones (TCs). However, the SSTs in the central area of the bay are higher than that of the surrounding areas in spring and autumn, which facilitates the occurrence of a “two-peak” storm activity pattern. The genesis potential index (GPI) quantifies and reflects the environmental conditions for the generation of the BoB storms. For GPI, the intense low-level vortex disturbance in the troposphere and high-humidity atmosphere are the sufficient conditions for storms, while large maximum wind velocity of the ground vortex radius and small vertical wind shear are the necessary conditions of storms.     

LOW-FREQUENCY CIRCULATION AND EXTENDED-RANGE FORECAST IN CONNECTION WITH AUTUMN EXTREME HEAVY RAINFALL PROCESS IN HAINAN

Observed daily precipitation data from the National Meteorological Observatory in Hainan province and daily data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis-2 dataset from 1981 to 2014 are used to analyze the relationship between Hainan extreme heavy rainfall processes in autumn (referred to as EHRPs) and 10–30 d low-frequency circulation. Based on the key low-frequency signals and the NCEP Climate Forecast System Version 2 (CFSv2) model forecasting products, a dynamical-statistical method is established for the extended-range forecast of EHRPs. The results suggest that EHRPs have a close relationship with the 10–30 d low-frequency oscillation of 850 hPa zonal wind over Hainan Island and to its north, and that they basically occur during the trough phase of the low-frequency oscillation of zonal wind. The latitudinal propagation of the low-frequency wave train in the middle-high latitudes and the meridional propagation of the low-frequency wave train along the coast of East Asia contribute to the ‘north high (cold), south low (warm)’ pattern near Hainan Island, which results in the zonal wind over Hainan Island and to its north reaching its trough, consequently leading to EHRPs. Considering the link between low-frequency circulation and EHRPs, a low-frequency wave train index (LWTI) is defined and adopted to forecast EHRPs by using NCEP CFSv2 forecasting products. EHRPs are predicted to occur during peak phases of LWTI with value larger than 1 for three or more consecutive forecast days. Hindcast experiments for EHRPs in 2015–2016 indicate that EHRPs can be predicted 8–24 d in advance, with an average period of validity of 16.7 d.     

AN ATTRIBUTION ANALYSIS OF CHANGES IN POTENTIAL EVAPOTRANSPIRATION IN THE BEIJING–TIANJIN–HEBEI REGION UNDER CLIMATE CHANGE

Based on the measurements obtained at 64 national meteorological stations in the Beijing–Tianjin–Hebei (BTH) region between 1970 and 2013, the potential evapotranspiration (ET0) in this region was estimated using the Penman–Monteith equation and its sensitivity to maximum temperature (Tmax), minimum temperature (Tmin), wind speed (Vw), net radiation (Rn) and water vapor pressure (Pwv) was analyzed, respectively. The results are shown as follows. (1) The climatic elements in the BTH region underwent significant changes in the study period. Vw and Rn decreased significantly, whereas Tmin, Tmax and Pwv increased considerably. (2) In the BTH region, ET0 also exhibited a significant decreasing trend, and the sensitivity of ET0 to the climatic elements exhibited seasonal characteristics. Of all the climatic elements, ET0 was most sensitive to Pwv in the fall and winter and Rn in the spring and summer. On the annual scale, ET0 was most sensitive to Pwv, followed by Rn, Vw, Tmax and Tmin. In addition, the sensitivity coefficient of ET0 with respect to Pwv had a negative value for all the areas, indicating that increases in Pwv can prevent ET0 from increasing. (3) The sensitivity of ET0 to Tmin and Tmax was significantly lower than its sensitivity to other climatic elements. However, increases in temperature can lead to changes in Pwv and Rn. The temperature should be considered the key intrinsic climatic element that has caused the "evaporation paradox" phenomenon in the BTH region.     

Could the Recent Taal Volcano Eruption Trigger an El Ni?o and Lead to Eurasian Warming?

正The Taal Volcano in Luzon is one of the most active and dangerous volcanoes of the Philippines. A recent eruption occurred on 12 January 2020(Fig. 1a), and this volcano is still active with the occurrence of volcanic earthquakes. The eruption has become a deep concern worldwide, not only for its damage on local society, but also for potential hazardous consequences on the Earth's climate and environment.     

VARIABILITY OF INTER-ANNUAL RELATIONSHIP BETWEEN INDIAN OCEAN DIPOLE AND HUAXI REGION’S AUTUMN PRECIPITATION

The moving-window correlation analysis was applied to investigate the relationship between autumn Indian Ocean Dipole (IOD) events and the synchronous autumn precipitation in Huaxi region, based on the daily precipitation, sea surface temperature (SST) and atmospheric circulation data from 1960 to 2012. The correlation curves of IOD and the early modulation of Huaxi region’s autumn precipitation indicated a mutational site appeared in the 1970s. During 1960 to 1979, when the IOD was in positive phase in autumn, the circulations changed from a “W” shape to an ”M” shape at 500 hPa in Asia middle-high latitude region. Cold flux got into the Sichuan province with Northwest flow, the positive anomaly of the water vapor flux transported from Western Pacific to Huaxi region strengthened, caused precipitation increase in east Huaxi region. During 1980 to 1999, when the IOD in autumn was positive phase, the atmospheric circulation presented a “W” shape at 500 hPa, the positive anomaly of the water vapor flux transported from Bay of Bengal to Huaxi region strengthened, caused precipitation ascend in west Huaxi region. In summary, the Indian Ocean changed from cold phase to warm phase since the 1970s, caused the instability of the inter-annual relationship between the IOD and the autumn rainfall in Huaxi region.     

Revisiting the Concentration Observations and Source Apportionment of Atmospheric Ammonia

正While China’s Air Pollution Prevention and Control Action Plan on particulate matter since 2013 has reduced sulfate significantly, aerosol ammonium nitrate remains high in East China. As the high nitrate abundances are strongly linked with ammonia, reducing ammonia emissions is becoming increasingly important to improve the air quality of China. Although satellite data provide evidence of substantial increases in atmospheric ammonia concentrations over major agricultural regions, long-term surface observation of ammonia concentrations are sparse. In addition, there is still no consensus on     

全球贸易隐含碳变化及其影响分析

基于最新的GTAP8 (Global Trade Analysis Project）数据库,使用投入产出法,分析了2004年到2007年全球贸易变化下南北集团贸易隐含碳变化及对全球碳排放的影响。结果显示,随着发展中国家进出口规模扩张,全球贸易隐含碳流向的重心逐渐向发展中国家转移。2004年到2007年,发达国家高端设备制造业和服务业出口以及发展中国家资源、能源密集型行业及中低端制造业出口的趋势加强,该过程的生产转移导致全球碳排放增长4.15亿t,占研究时段全球贸易隐含碳增量的63%。未来发展中国家的出口隐含碳比重还将进一步提高。贸易变化带来的南北集团隐含碳流动变化对全球应对气候变化行动的影响日益突出,发达国家对此负有重要责任。     

COMPARATIVE ANALYSIS OF VARIOUS DATA OF AIR–SEA TEMPERATURE DIFFERENCE AND ITS VARIATION ACROSS SOUTH CHINA SEA IN THE PAST 35 YEARS

Using the International Comprehensive Ocean-Atmosphere Data Set(ICOADS) and ERA-Interim data, spatial distributions of air-sea temperature difference(ASTD) in the South China Sea(SCS) for the past 35 years are compared,and variations of spatial and temporal distributions of ASTD in this region are addressed using empirical orthogonal function decomposition and wavelet analysis methods. The results indicate that both ICOADS and ERA-Interim data can reflect actual distribution characteristics of ASTD in the SCS, but values of ASTD from the ERA-Interim data are smaller than those of the ICOADS data in the same region. In addition, the ASTD characteristics from the ERA-Interim data are not obvious inshore. A seesaw-type, north-south distribution of ASTD is dominant in the SCS; i.e., a positive peak in the south is associated with a negative peak in the north in November, and a negative peak in the south is accompanied by a positive peak in the north during April and May. Interannual ASTD variations in summer or autumn are decreasing. There is a seesaw-type distribution of ASTD between Beibu Bay and most of the SCS in summer, and the center of large values is in the Nansha Islands area in autumn. The ASTD in the SCS has a strong quasi-3a oscillation period in all seasons, and a quasi-11 a period in winter and spring. The ASTD is positively correlated with the Nio3.4 index in summer and autumn but negatively correlated in spring and winter.     

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正AIMS AND SCOPE Atmospheric and Oceanic Science Letters (AOSL) publishes short research letters on all disciplines of the atmosphere sciences and physical oceanography. Contributions from all over the world are welcome.SUBMISSIONAll submitted