试论可持续发展在全面建设小康社会中的地位及对策

实施可持续发展战略是全面建设小康社会的重要保证.可持续发展原则在全面建设小康社会目标中得到了充分体现,但在实施可持续发展战略中仍存在许多问题.因此,应从舆论宣传、制度建设、民主建设、大力发展教育等方面入手,切实解决实施可持续发展战略中存在的问题.     

1949-1956年中国民族资产阶级心理之变迁

1949至1956年,随着中国社会的剧烈变动,中国民族资产阶级心理也发生着变化:从新中国成立初期的疑惧,到了解党的政策后的兴奋;从"五反"开始后的恐慌,到"五反"结束后对共产党的服从;从过渡时期总路线公布后的犹豫彷徨,到最后接受社会主义改造,走上社会主义道路.     

顿顶螺旋藻完整藻胆体与解离藻胆体光谱特性的比较研究

对钝项螺旋藻完整藻胆体与解离藻胆体吸收光谱进行了比较研究.随着藻胆体的逐渐解离,其吸收光谱表现出如下变化特点:在紫外光区,吸收峰始终位于355nm,尖形峰逐渐变成钝形峰;在红光区,都有很强的吸收,吸收峰呈平顶状,其半带宽逐渐变小;紫外光区与红光区相对吸收强度的比值逐渐变小;四级导数吸收光谱的小峰数目越来越少.室温荧光发射光谱表明,藻胆体在低于0.9mol/L的磷酸缓冲液中变得不稳定,并开始逐渐解离,解离的藻胆体与完整的藻胆体相比,其荧光发射峰波长逐渐变短.     

国内外医学期刊网站现状及分析

通过互联网了解国内外不同医学期刊网站建设的现状,对比发现国内与国外医学期刊的网站建设差距明显.对差距产生的原因做一分析并提出改进建议.     

Formation control and collision avoidance for a class of multi-agent systems

In this paper, a control scheme is proposed for a group of elliptical agents to achieve a predefined formation. The agents are assumed to have the same dynamics, and communication among the agents are limited. The desired formation is realized based on the reference formation and the mapping decision. In the control design, searching algorithms for both cases of minimum distance and tangents are established for each agent and its neighbors. In order to avoid collision, an optimal path planning algorithm based on collision angles, and a self-center-based rotation algorithm are also proposed. Moreover, randomized method is used to provide the optimal mapping decision for the underlying system. Two examples and analyses are presented to demonstrate the effectiveness and potential of the new control scheme.     

Fractional order sliding mode control of a pneumatic position servo system

Gas flow has fractional order dynamics; therefore, it is reasonable to assume that the pneumatic systems with a proportional valve to regulate gas flow have fractional order dynamics as well. There is a hypothesis that the fractional order control has better control performance for this inherent fractional order system, although the model used for fractional controller design is integer order. To test this hypothesis, a fractional order sliding mode controller is proposed to control the pneumatic position servo system, which is based on the exponential reaching law. In this method, the fractional order derivative is introduced into the sliding mode surface. The stability of the controller is proven using Lyapunov theorem. Since the pressure sensor is not required, the control system configuration is simple and inexpensive. The experimental results presented indicate the proposed method has better control performance than the fractional order proportional integral derivative (FPID) controller and some conventional integral order control methods. Points to be noticed here are that the fractional order sliding mode control is superior to the integral order sliding mode counterpart, and the FPID is superior to the corresponding integral order PID, both with optimal parameters. Among all the methods compared, the proposed method achieves the highest tracking accuracy. Moreover, the proposed controller has less chattering in the manipulated variable, the energy consumption of the controller is therefore substantially reduced.     

Non-weighted H∞ performance for 2-D FMLSS switched system with maximum and minimum dwell time

This paper investigates the H_∞ performance of two-dimensional (2-D) switched system represented by Fornasini–Marchesini local state-space (FMLSS) model with maximum and minimum dwell time approach. By using the multiple Lyapunov function approach, and designing a set of switching signals subject to maximum and minimum dwell time characteristic, respectively, for all stable subsystems or both stable and unstable subsystems exist, we give the sufficient condition on exponential stability of the given switched system, and propose the sufficient condition which can guarantee that the given switched system is exponentially stable and has a specified H_∞ disturbance attenuation level γ. All the results obtained are on normal noise attenuation index of strictly non-weighted form, which are better than the existing results on weak one of weighted form from the physical point of view. Finally, numerical examples are presented to display the effectiveness of the proposed results.     

Stabilization of artificial gas-lift process using nonlinear predictive generalized minimum variance control

Artificial gas-lift (AGL) is one of the most widely used methods in oil production to maintain acceptable oil flow to the processing equipment and sales when the reservoir pressure is not high enough. In spite of its popularity, the AGL process is prone to casing-heading instability, which is revealed as significant flow oscillation. This is undesirable as it results in production losses and unstable behavior that has negative impact on the downstream equipment. Controller design for such a process is very challenging as it exhibits highly nonlinear dynamics. In this work, the predictive generalized minimum variance control (NPGMV) is employed to derive a robust controller based on the state estimation to stabilize AGL process when casing-heading phenomenon occurs. A closed-form optimal control law is obtained based on the Taylor series approximation. Further, a nonlinear state observer is produced and combined with the controller to ensure closed-loop control through variables that are most beneficial to the system performance, which are unmeasurable and can be obtained only via estimation. Through simulation studies, the effectiveness of the proposed controller is demonstrated.     

Output reachable set estimation for discrete-time switched systems with persistent dwell-time

This paper is concerned with the output reachable set estimation for discrete-time switched systems. The switching signal is considered as persistent dwell-time (PDT), which is more general and flexible compared with the common dwell-time and average dwell-time switching. The estimation of output reachable set is determined by a collection of bounding ellipsoids based on a family of quasi-time-dependent (QTD) Lyapunov functions. Furthermore, a set of non-fragile QTD controllers is designed. Finally, two examples are employed to illustrate the potentials of proposed methods.     

复杂工程机械制造企业技术能力序贯性演进——三一重工和中联重科的纵向案例分析

通过对两家后发工程机械制造企业创新追赶历程的探索性案例分析,得到以下研究发现。一是发现工程机械制造企业的技术能力提升呈现“序贯性”特征,企业创新追赶过程中需要科学依循技术能力的序贯性。二是发现组织学习和资源治理作为技术能力提升的重要支撑行动,随着追赶过程的深入也呈现序贯性的演进。三是发现技术(工程)科学知识的掌控是复杂工程机械制造企业技术能力向高端演进的关键因素,对其的关注应贯穿技术能力提升的整个过程。