中国科学院空间科学与应用研究中心空间天气学国家重点实验室

2006年科技部批准我院4个院重点实验室新组建为国家重点实验室,同时,为加强我院重点实验室的建设,促进基础研究和高技术前沿探索工作的持续稳定发展,我院又批准成立了6个重点实验室,本刊将分期介绍这些机构。     

北京城市绿地群落结构对降温增湿功能的影响

清晰揭示城市绿地的空间布局与景观结构特征对其生态服务功能的影响对指导城市规划设计具有重要参考价值。目前国内外已有较多城市绿地降温增湿及其影响因素的实证研究,但是定量解析绿地群落结构与降温增湿功能关系的研究并不多见。本文基于北京市24个典型绿地群落夏季降温增湿效果的实测,重点解析了绿地郁闭度和绿量对降温增湿功能的影响,并提出了绿地结构优化配置的最优阈值。研究结果表明：北京城市绿地夏季日均降温幅度0.2~2.0℃,日均增湿幅度0.20%~8.26%;不同群落结构绿地降温效果上,乔灌草型>乔草或乔木型>灌草型>草地型;在绿地增湿效果上,乔木型>乔灌草>乔草型>灌草型>草地型;郁闭度和绿量对绿地降温增湿功能均有明显影响,但郁闭度影响更大,冠层郁闭度介于0.60~0.85、三维绿量密度≥5m³/ m²的乔灌草或乔草型绿地具有最大降温增湿功能。     

Neuromorphic-computing-based adaptive learning using ion dynamics in flexible energy storage devices

High-accuracy neuromorphic devices with adaptive weight adjustment are crucial for high-performance computing. However, limited studies have been conducted on achieving selective and linear synaptic weight updates without changing electrical pulses. Herein, we propose high-accuracy and self-adaptive artificial synapses based on tunable and flexible MXene energy storage devices. These synapses can be adjusted adaptively depending on the stored weight value to mitigate time and energy loss resulting from recalculation. The resistance can be used to effectively regulate the accumulation and dissipation of ions in single devices, without changing the external pulse stimulation or preprogramming, to ensure selective and linear synaptic weight updates. The feasibility of the proposed neural network based on the synapses of flexible energy devices was investigated through training and machine learning. The results indicated that the device achieved a recognition accuracy of ∼95% for various neural network calculation tasks such as numeric classification.     

State space theory of nonlinear two- terminal higher-order elements

Higher-order elements are introduced to provide a logically complete formulation for nonlinear circuit theory. A distinctive feature of higher-order elements is that they possess internal dynamics that are more complicated than those of conventional circuit elements (namely, the resistor, inductor, capacitor and memristor). In this paper, we provide a state space formulation for studying two-terminal higher-order elements. State-space properties such as local controllability, input-observability, passivity and losslessness are investigated in detail.     

集群内知识流动的空间不均衡性

知识已成为创新的核心资源,集群作为自主创新的重要载体,是企业创新活动发生的外在的客观情景。研究集群内知识流动的特征,及其整个知识网络的结构特征对于深刻把握集群创新的微观机制至关重要,也有利于地方产业集群的有效治理。本文利用社会网络分析方法并从吸收能力角度,以苏州电子信息制造业集群为例,实证发现知识在集群网络里的流动、扩散呈现不均衡性、具有选择性,知识网络结构具有派系结构特征。     

在均匀纳木错湖中水流动力的数值研究

通过σ-坐标系的非流体静力学数值海洋模型,即卑尔根海洋模型(Bergen Ocean Model)对纳木错湖入水河口附近的水流动力进行研究,其中重点研究了河水烟羽动力情况,所有模拟实验应用流体静力和非流体静力模型,水平分辨率分别为5m、2.5m及1.25m,并提供均匀纳木错湖中进行模拟实验的结果.     

空间反射式闪耀光栅支撑结构设计

本文基于有限元分析方法,采用适合中、小型光学元件的周边支撑结构形式,进行了某星载温室气体探测仪大平面反射式闪耀光栅支撑结构的设计。通过对光栅组件进行有限元建模,以及固有模态、静力学、动力学、光机热集成分析,优化了支撑结构设计,使得光栅组件基频〉300Hz,在±5℃均匀温度变化和1g重力耦合作用下,光栅刻划表面波前面形精度仍符合光学设计要求。最终工程分析结果表明：大平面反射式闪耀光栅的支撑结构设计是合理的,光栅组件固有一阶频率高,抗重力变形能力、抗震性能均能满足仪器总体设计指标要求,通过选用不同热膨胀系数的结构材料及合理设计零件配合尺寸等消热设计手段有效抑制了光栅支撑结构的变形对光栅结构的扭曲作用。     

State space model identification of multirate processes with time-delay using the expectation maximization

This paper presents the problems of state space model identification of multirate processes with unknown time delay. The aim is to identify a multirate state space model to approximate the parameter-varying time-delay system. The identification problems are formulated under the framework of the expectation maximization algorithm. Through introducing two hidden variables, a new expectation maximization algorithm is derived to estimate the unknown model parameters and the time-delays simultaneously. The effectiveness of the proposed algorithm is validated by a simulation example.     

城市化地区实体与流空间演变及高质量发展路径分析

生态文明和美丽中国建设进入关键期,城市化地区是美丽中国地理图景的重要空间载体,人地关系矛盾最为突出,也是美丽中国建设难点。聚焦城市化地区的实体地域,基于大数据技术方法,厘清中国城市不透水面的时空分布与分组演化特征,分析流空间视角下城市体系流动网络的结构特征,提出对新时期促进城市化地区高质量发展途径的初步思考与政策建议。以人为核心建设人民城市、分级分类引导城市多样化发展、绿色韧性健康的城市可持续模式、科技创新功能与智慧城市建设、常态化开展城市体检工作等,支撑中国式城市化现代化与美丽中国目标实现。     

Capture zone of linear strategies in interception problems with variable structure dynamics

The paper considers planar interception engagements against maneuverable targets using a linearized kinematic model with constant velocities. Both the interceptor and the target have bounded controls and first-order linear dynamics. Due to the linearization, the duration of the interception is prescribed. The target dynamics is fixed, but the interceptor has variable structure dynamics, switching from one mode to another once during the engagement. For such engagements the capture zone of a given linear feedback control is constructed. Numerical examples demonstrate that proper change of the interceptor dynamic mode leads to an enlarged capture zone.     

Why space matters in technological innovation systems—Mapping global knowledge dynamics of membrane bioreactor technology

Studies on technological innovation systems (TISs) often set spatial boundaries at the national level and treat supranational levels as a geographically undifferentiated and freely accessible global technological opportunity set. This article criticizes this conceptualization and proposes instead to analyze relevant actors, networks and processes in TIS from a relational perspective on space. It develops an analytical framework which allows investigating innovation processes (or ‘functions’) of a TIS at and across different spatial scales. Based on social network analysis of a co-publication dataset from membrane bioreactor technology, we illustrate how the spatial characteristics of collaborations in knowledge creation vary greatly over relatively short periods of time. This finding suggests that TIS studies should be more reflexive on system boundary setting both regarding the identification and analysis of core processes as well as in the formulation of policy advice.     

中国核心生态空间的现状、变化及其保护研究

本文综合中国目前的国土区划和生态工程,提取包括水源涵养区、土壤保持区、防风固沙带、洪水调蓄区、河岸防护带和生物多样性保护区等6类国家核心生态空间,划定维护国土安全的生态红线。结果表明,中国核心生态空间面积为339.77万km2,主要分布在中西部地区。核心生态空间内的土地利用构成以林地、草地和湿地为主,耕地和城乡工矿建设用地等比重较低。1980-2008年近30年间,发挥重要生态功能的用地呈减少趋势,而以生产、生活功能为主的用地呈增加态势,区域生态调节、防护和屏障功能削弱。因此,核心生态空间内应严格控制耕地、建设用地的增长,采取有效措施使其"零增长"乃至"负增长",强调生态红线内林地、草地和湿地的绝对保护。     

Decentralized asymptotic fault tolerant control of near space vehicle with high order actuator dynamics

In this paper, a decentralized asymptotic fault tolerant control system is proposed for near space vehicle (NSV) attitude dynamics. First, NSV reentry mode is described, and the actuator failure model is developed whose behavior is described by high-order dynamics. Next, the multi-model based fault diagnosis and identification (FDI) algorithm is proposed for high order actuator dynamics, which can accurately diagnose and identify the fault in short time. Based on sliding mode, command filter, and backstepping technique, using information of FDI, a constrained fault tolerant control (FTC) is designed for reentry NSV. Finally, simulation results are given to demonstrate the effectiveness and potential of the proposed FTC scheme.     

Adaptive vibration control of a flexible structure based on hybrid learning controlled active mass damping

Natural disasters such as earthquakes and strong winds will lead to vibrations in ultra-high or high-rise buildings and even the damages of the structures. The traditional approaches resist the destructive effects of natural disasters through enhancing the performance of the structure itself. However, due to the unpredictability of the disaster strength, the traditional approaches are no longer appropriate for earthquake mitigation in building structures. Therefore, designing an effective intelligent control method for suppressing vibrations of the flexible buildings is significant in practice. This paper focuses on a single-floor building-like structure with an active mass damper (AMD) and proposes a hybrid learning control strategy to suppress vibrations caused by unknown time-varying disturbances (earthquake, strong wind, etc.). As the flexible building structure is a distributed parameter system, a novel finite dimension dynamic model is firstly constructed by assumed mode method (AMM) to effectively analyze the complex dynamics of the flexible building stucture. Secondly, an adaptive hybrid learning control based on full-order state observer is designed through back-stepping method for dealing with system uncertainties, unknown disturbances and immeasurable states. Thirdly, semi-globally uniformly ultimate boundedness (SGUUB) of the closed-loop system is guaranteed via Lyapunov’s stability theory. Finally, the experimental investigation on Quanser Active Mass Damper demonstrates the effectiveness of the presented control approach in the field of vibration suppression. The research results will bring new ideas and methods to the field of disaster reduction for the engineering development.     

电子商务企业的信息流模式及组织架构

企业核心技术的改变将会导致组织结构的更新,而新的组织结构必将具有新的信息流模式。本文在研究企业纵向及横向信息流性质与作用的基础上,分析了电子商务对传统企业信息流模式的冲击,由此总结出电子商务企业组织中信息流的双回路模式及其存在的必然性。文章期望从信息流的角度构建电子商务企业的组织架构,以满足现代企业管理的要求。     

On the exponential stabilization of a flexible structure with dynamic delayed boundary conditions via one boundary control only

This study deals with the stability analysis of a flexible structure with one and only one boundary control. The system is composed of three parts: a cart (motorized platform), a flexible cable, and a load mass attached to the lower part of the cable. This situation leads to a hybrid system as a mathematical model for the cable dynamics: one partial differential equation coupled to two ordinary differential equations. Despite the presence of a time-delay in the top-end of the cable, we are able to prove that the hybrid system is well-posed in the sense of semigroups theory and more importantly, only one boundary control can guarantee the exponentially decay of the energy of the system under reasonable conditions on the parameters of the system. This outcome considerably improves the result recently established in [17], where two more controls are required: one interior (Kelvin–Voigt) damping which acts over the entire cable and another boundary control which is exerted on the lower-end of the cable. Furthermore, we provide an estimate of the exponential decay of the system by means an appropriate Lyapunov functional. Lastly, numerical examples are presented in order to ascertain and highlight our theoretical outcomes.     

The representation of radiation reaction in wave mechanics

It is well known that the wave mechanical ψ equation leads to the conclusion that the centroid of the wave mechanical electron should move according to the classical electrodynamic equation of motion in which, however, the terms representing what is commonly called radiation reaction are absent. If v is the velocity of the electron, the classical rate of change of momentum is $\text{md}\text{dt}\text{{}\text{v}\text{(}\text{I}\text{?}\text{v}{}^2\text{c}{}^2\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{}}$. The equation of motion including radiation reaction terms may be regarded as obtainable by replacing this quantity by one obtained by operating upon it with the operator P^?1

$\text{P={I?}\text{α}{}_1\text{kd}\text{dt}\text{+}\text{α}{}_2\text{d}\text{dt}\text{(}\text{kd}\text{dt}\text{)?·}}{}^{\mathrm{?}}$

where α₁, α₂, etc., are constants and $\text{k = (}\text{I}\text{?}\text{v}{}^2\text{c}{}^2\text{)}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$. The main purpose of the paper is to show that if there be any relativistically invariant ψ equation which leads to the classical equation of motion without radiation reaction terms, then by replacing the vector and scalar potentials U and ? in that equation by P(U) and P(?), a relativistically invariant equation of motion will be obtained including the radiation reaction terms, provided that the $\text{d}\text{dt}$ in P be now regarded as $\text{?}\text{?t}$ + u · grad, where u is the velocity of the wave mechanical density distribution at a point. The purpose is to use the power to produce the equation of motion as a criterion for suggesting the proper modification of the ψ equation to apply in those cases where, on the classical theory, the electron would suffer great acceleration, as in ionization by rapidly moving corpuscles.     

环境规制、要素区际流动与城市群产业结构调整

基于城市群视角,聚焦要素区际流动机制,探讨环境规制对产业结构调整的影响具有重要的理论和现实意义。本文在阐述环境规制、要素区际流动与产业结构调整理论机制的基础上,构建环境规制综合指数、要素区际流动指数等,并基于中国十大代表性城市群2003—2018年的数据进行实证检验。结果显示：①各类样本检验均表明环境规制能够显著促进产业结构调整;②整体样本下环境规制能够分别通过劳动区际流动、资本区际流动和技术区际流动促进产业结构调整;③分区域及不同环境规制水平样本下中介效应存在异质性：东部城市群和中环境规制组的3类要素区际流动在环境规制与产业结构调整之间均存在显著的中介效应;中西部城市群仅劳动要素区际流动呈现显著的中介效应,高规制组3类要素区际流动中介效应均不显著。针对分析结果,本文提出了相应政策建议,以期破解城市群资源环境难题,探寻城市群要素优化配置和产业结构调整路径,推动中国城市群高质量发展。     

上市公司自由现金流与资本结构动态调整研究

本文采用我国沪深两市A股非金融上市公司2004–2012年的财务数据,首先通过动态面板系统GMM模型,估算出我国上市公司的最优资本结构,并计算出资本结构调整速度为0.186;然后建立了反映自由现金流盈亏程度和资本结构偏离程度如何影响资本结构调整的固定效应模型,分析得出与单独调整资本结构的情况相比,企业同时调整资本结构和自由现金流时,调整成本降低,调整速度加快;当资本结构调整至(或接近)最优状态后,企业会保持资本结构在最优水平,不受自由现金流调整的影响。上述结论对企业是否存在融资约束具有稳健性,但受融资约束的企业调整成本相对较高,调整速度相对较慢。