表频率副词“时不时”和“动不动”

现代汉语中"时不时"和"动不动"都是表中等频率义副词,两词在句法功能上有很多共同点,但在语义、句法、语用方面也有很大差异。句法上,二者在谓语的词性、后加"地"、在句中的位置、主语的人称、否定式的意义、可进入的祈使句的类型等方面都有差别。"动不动"可以提示"反预期事件"或"反预期频率",而"时不时"没有这样的功能。另外,"动不动"常含有"轻易"、"随意"、"轻率"的意味,有明显的主观性,口语色彩明显,"时不时"没有明显的主观性,口语色彩也不明显。

三音节频率副词“时不时”的语法分析

在现代汉语中,“时不时”是一个表示中等频率义的副词,同时,它也属于描写性频率副词,“时不时”在权威字典中解释多为“时常,时时”之义,但“时不时”并不完全等同于“时常,时时”,与之有细微的差别;“时不时”在句法功能上有很多自己的特点;它主要用于说话者想要表达不是非常明确的时间段,但表示动作行为每次发生的时长相对较短、事件发生频率较适中的语境中,主要出现在书面语中。

频率副词“时不时”的生成机制与动因——兼论频率副词“时时”“不时”的来源

频率副词"时时"早在西汉时期由频率副词"时"重叠而成,"不时"大概在宋元时期由跨层结构"不时"词汇化而来。频率副词"时不时"可能始见于民国时期,并不是在频率副词"时时"中间插入否定副词"不"而成的,也不是由"X不X"三字格类推而来的。频率副词"时不时"的生成机制是糅合。从表层来看,"时不时"是由语义相近的频率副词"时时"与"不时"糅合而成的。从深层来看,"时不时"是在句式"S时时VP"与"S不时VP"糅合过程中生成的。频率副词"时不时"的生成动因是凸显言者的主观性。

频率副词“时时”“时不时”在国际中文教学中的应用研究

“时时”和“时不时”是现代汉语中常见的两个频率副词,意义仅有微妙的差别,汉语二语学习者很难掌握。本文以频率副词“时时”和“时不时”为研究对象,通过结合历年学者们的研究,分析二者在语义特征和语用功能方面的相似与不同之处,从而展开对频率副词“时时”和“时不时”的多角度剖析。

“无时无刻不”和“时时刻刻都”

“无时无刻不”和“时时刻刻都”在句法、语义、认知、语用方面都存在着一定的差异。在句法上,当搭配对象为领有动词、能愿动词、形容词和否定词语时,一般只能用“时时刻刻都”,当前面为副词“都”时,只能用“无时无刻不”。在语义上,“无时无刻不”比“时时刻刻都”要丰富、复杂一些。在认知上,人们对“无时无刻不”的理解难于对“时时刻刻都”的理解。在语用上,“无时无刻不”比“时时刻刻都”语气更强烈,“无时无刻不”经常进行主观陈述,“时时刻刻都”则经常进行客观描写。从规范化的角度看,只有“无时无刻不”的用法,不存在“无时无刻都”的用法。

Low-Storage Runge-Kutta Method for Simulating Time-Dependent Quantum Dynamics

A wide range of quantum systems are time-invariant and the corresponding dynamics is dic- tated by linear differential equations with constant coefficients. Although simple in math- ematical concept, the integration of these equations is usually complicated in practice for complex systems, where both the computational time and the memory storage become limit- ing factors. For this reason, low-storage Runge-Kutta methods become increasingly popular for the time integration. This work suggests a series of s-stage sth-order explicit Runge- Kutta methods specific for autonomous linear equations, which only requires two times of the memory storage for the state vector. We also introduce a 13-stage eighth-order scheme for autonomous linear equations, which has optimized stability region and is reduced to a fifth-order method for general equations. These methods exhibit significant performance improvements over the previous general-purpose low-stage schemes. As an example, we ap- ply the integrator to simulate the non-Markovian exciton dynamics in a 15-site linear chain consisting of perylene-bisimide derivatives.

Alpha-reliable combined mean traffic equilibrium model with stochastic travel times

Based on the reliability budget and percentile travel time(PTT) concept, a new travel time index named combined mean travel time(CMTT) under stochastic traffic network was proposed. CMTT here was defined as the convex combination of the conditional expectations of PTT-below and PTT-excess travel times. The former was designed as a risk-optimistic travel time index, and the latter was a risk-pessimistic one. Hence, CMTT was able to describe various routing risk-attitudes. The central idea of CMTT was comprehensively illustrated and the difference among the existing travel time indices was analyzed. The Wardropian combined mean traffic equilibrium(CMTE) model was formulated as a variational inequality and solved via an alternating direction algorithm nesting extra-gradient projection process. Some mathematical properties of CMTT and CMTE model were rigorously proved. Finally, a numerical example was performed to characterize the CMTE network. It is founded that that risk-pessimism is of more benefit to a modest(or low) congestion and risk network, however, it changes to be risk-optimism for a high congestion and risk network.

Total ischemic time and outcomes for patients with ST-elevation myocardial infarction： does time of admission make a difference？

Objective To investigate whether admission time was associated with the delay of reperfusion therapy and in-hospital death in patients with ST-elevation myocardial infarction （STEMI）. Methods All patients with STEMI who were admitted to the emergency depart- ment and underwent primary percutaneous coronary intervention at Peking University People＇s Hospital between April 2012 and March 2015 were included. We examined differences in clinical characteristics, total ischemic time, and in-hospital death between patients admitted during off-hours and those admitted during regular hours. Multivariate logistic regression was used to estimate the relationship between off-hours admission and clinical outcome. Results The sample comprised 184 and 105 patients with STEMI admitted to hospital during off-hours and regular hours, respectively. Total ischemic and onset-to-door times were significantly shorter in patients admitted during off-hours than among those admitted during regular hours （all P 〈 0.05）. Door-to-balloon （DTB） time, the rate of DTB time 〈 90 min, and in-hospital death were comparable between groups. Multivariate logistic regression showed that age and creatinine level, but not off-hours admission, were associated independently with increased in-hospital death. Conclusions Off-hours admission did not result in delayed reperfusion therapy or increased in-hospital mortality in patients with STEMI. Further efforts should focus on identifying pivotal factors associated with the pre-hospital and in-hospital delay of reperfusion therapy, and implementing quality improvement initiatives for reperfusion programs.

A novel stabilization approach for small signal disturbance of power system with time-varying delay

Small signal instability may cause severe accidents for power system if it can not be dear correctly and timely. How to maintain power system stable under small signal disturbance is a big challenge for power system operators and dispatchers. Time delay existing in signal transmission process makes the problem more complex. Conventional eigenvalue analysis method neglects time delay influence and can not precisely describe power system dynamic behaviors. In this work, a modified small signal stability model considering time varying delay influence was constructed and a new time delay controller was proposed to stabilize power system under disturbance. By Lyapunov-Krasovskii function, the control law in the form of nonlinear matrix inequality （NLMI） was derived. Considering synthesis method limitation for time delay controller at present, both parameter adjustment method by using linear matrix inequality （LMI） solver and iteration searching method by solving nonlinear minimization problem were suggested to design the controller. Simulation tests were carried out on synchronous-machine infinite-bus power system. Satisfactory test results verify the correctness of the proposed model and the feasibility of the stabilization approach.

Robust user equilibrium model based on cumulative prospect theory under distribution-free travel time

The assumption widely used in the user equilibrium model for stochastic network was that the probability distributions of the travel time were known explicitly by travelers. However, this distribution may be unavailable in reality. By relaxing the restrictive assumption, a robust user equilibrium model based on cumulative prospect theory under distribution-free travel time was presented. In the absence of the cumulative distribution function of the travel time, the exact cumulative prospect value(CPV) for each route cannot be obtained. However, the upper and lower bounds on the CPV can be calculated by probability inequalities.Travelers were assumed to choose the routes with the best worst-case CPVs. The proposed model was formulated as a variational inequality problem and solved via a heuristic solution algorithm. A numerical example was also provided to illustrate the application of the proposed model and the efficiency of the solution algorithm.

Robust synchronization of uncertain complex systems with time-varying delays

Synchronization analysis and design problems for uncertain time-delayed high-order complex systems with dynamic output feedback synchronization protocols are investigated. By stating projection on the synchronization subspace and the complement synchronization subspace, synchronization problems are transformed into simultaneous stabilization problems of multiple subsystems related to eigenvalues of the Laplacian matrix of the interaction topology of a complex system. In terms of linear matrix inequalities(LMIs), sufficient conditions for robust synchronization are presented, which include only five LMI constraints.By the changing variable method, sufficient conditions for robust synchronization in terms of LMIs and matrix equalities are given,which can be checked by the cone complementarily linearization approach. The effectiveness of theoretical results is shown by numerical examples.

Robust H_∞ filtering for neutral jump system with time-delays and uncertainties

The problem of robust H∞ filtering for a class of neutral jump systems with time-delay and norm- bounded uncertainties is considered. By re-constructing the system, the dynamics of overall augmented error systems is obtained which involves unknown inputs represented by disturbances, model uncertainties and time-delays. As to the nominal system, sufficient conditions are provided for the existence of the mode-dependent H∞ filter by selecting the appropriate Lyapunov-Krasovskii function and the robust H∞ filter is proposed for the jump system while considering the time-delays and uncertainties. Both of above conditions for the existence of the H∞ filter and roust H∞ filter are presented in terms of linear matrix inequalities, and convex optimization problems are formulated to design the desired filters. By employing the proposed mode-dependent H∞ filter, the systems have the stochastic stability and better ability of restraining disturbances stochastically, and the given prescribed H∞ performance is guaranteed. Simulation resuhs illustrate the effectiveness of developed techniques.

Guaranteed cost sampled-data control for uncertain nonlinear time-varying delay system

The robust guaranteed cost sampled-data control was studied for a class of uncertain nonlinear systems with time-varying delay. The parameter uncertainties are time-varying norm-bounded and appear in both the state and the input control matrices. By applying an input delay approach, the system was transformed into a continuous time-delay system. Attention was focused on the design of a robust guaranteed cost sampled-data control law which guarantees that the closed-loop system is asymptotically stable and the quadratic performance index is less than a certain bound for all admissible uncertainties. By applying Lyapunov stability theory, the theorems were derived to provide sufficient conditions for the existence of robust guaranteed cost sampled-data control law in the form of linear matrix inequalities (LMIs), especially an optimal state-feedback guaranteed cost sampled-data control law which ensures the minimization of the guaranteed cost was given. The effectiveness of the proposed method was illustrated by a simulation example with the asymptotically stable curves of system state under the initial condition of x(0)=[0.679 6 0].

Some Open Problems on Simultaneous Stabilization of Linear Systems

Simultaneous stabilization of linear systems is a fundamental issue in the system and control theory, and is of theoretical and practical significance. In this paper, the authors review the recent research progress and the state-of-art results on simultaneous stabilization of single-input single-output linear time-invariant systems. Especially, the authors list the ever best results on the parameters involved in the well known ＂French Champagne Problem＂ and ＂Belgian Chocolate Problem＂ from the point of view of mathematical theoretical analysis and numerical calculation. And the authors observed that Boston claimed the lower bound of 5 can be enlarged to 0.976461 in 2012 is not accurate. The authors hope it will inspire further study on simultaneous stabilization of several linear systems.

Synchronization and bursting transition of the coupled Hindmarsh-Rose systems with asymmetrical time-delays

The study of synchronization and bursting transition is very important and valuable in cognitive activities and action control of brain as well as enhancement for the reliability of the cortex synapses. However, we wonder how the synaptic strength and synaptic delay, especially the asymmetrical time-delays between different neurons can collectively influence their synchronous firing behaviors. In this paper, based on the Hindmarsh-Rose neuronal systems with asymmetrical time-delays, we investigate the collective effects of various delays and coupling strengths on the synchronization and bursting transition. It is shown that the interplay between delay and coupling strength can not only enhance or destroy the synchronizations but also can induce the regular transitions of bursting firing patterns. Specifically, as the coupling strength or time-delay increasing, the firing patterns of the time-delayed coupling neuronal systems consistently present a regular transition, that is, the periods of spikes during the bursting firings increase firstly and then decrease slowly. In particular, in contrast to the case of symmetrical time-delays,asymmetrical time-delays can lead to the paroxysmal synchronizations of coupling neuronal systems, as well as the concentration level of synchronization for the non-identically coupled system is superior to the one of identical coupling. These results more comprehensively reveal the rich nonlinear dynamical behaviors of neuronal systems and may be helpful for us to have a better understanding of the neural coding.

Singularly Perturbed Differential-Difference Reaction Diffusion Equations with Time Delay

A class of differential-difference reaction diffusion equations with a small time delay is considered.Under suitable conditions and by using the method of the stretched variable,the formal asymptotic solution is constructed.And then,by using the theory of differential inequalities the uniformly validity of solution is proved.

IMPROVED STABILITY CRITERIA FOR UNCERTAIN LINEAR SYSTEMS WITH INTERVAL TIME-VARYING DELAY

This paper deals with the robust stability analysis of dynamic systems with interval time- varying delay and uncertainties. The innovation of the method includes employment of a tighter integral inequality and construction of an appropriate type of Lyapunov functional. The stability criteria derived from this method have less conservatism than some existing ones. Numerical examples are given to illustrate the effectiveness of the orooosed method.

ON FORMABILITY OF LINEAR CONTINUOUS-TIME MULTI-AGENT SYSTEMS

This paper is focused on formability of multi-agent systems （MASs）. The problem is concerned with the existence of a protocol that has the ability to drive the MAS involved to the desired formation, and thus, is of essential importance in designing formation protocols. Formability of an MAS depends on several key factors： agents＇ dynamic structures, connectivity topology, properties of the desired formation and the admissible control set. Agents of the MASs considered here are described by a general continuous linear time-invariant （LTI） model. By using the matrix analysis and algebraic graph theory, some necessary and sufficient conditions on formability of LTI-MASs are obtained. These conditions characterize in some sense the relationship of formability, connectivity topology, formation properties and agent dynamics with respect to some typical and widely used admissible protocol sets.

Subspace-based identification of discrete time-delay system

We investigate the identification problems of a class of linear stochastic time-delay systems with unknown delayed states in this study. A time-delay system is expressed as a delay differential equation with a single delay in the state vector. We first derive an equivalent linear time-invariant(LTI) system for the time-delay system using a state augmentation technique. Then a conventional subspace identification method is used to estimate augmented system matrices and Kalman state sequences up to a similarity transformation. To obtain a state-space model for the time-delay system, an alternate convex search(ACS) algorithm is presented to find a similarity transformation that takes the identified augmented system back to a form so that the time-delay system can be recovered. Finally, we reconstruct the Kalman state sequences based on the similarity transformation. The time-delay system matrices under the same state-space basis can be recovered from the Kalman state sequences and input-output data by solving two least squares problems. Numerical examples are to show the effectiveness of the proposed method.

ON NEARLY-CONTROLLABLE SUBSPACES OF A CLASS OF DISCRETE-TIME BILINEAR SYSTEMS

If a linear time-invariant system is uncontrollable,then the state space can be decomposed as a direct sum of a controllable subspace and an uncontrollable subspace.In this paper,for a class of discrete-time bilinear systems which are uncontrollable but can be nearly controllable,by studying the nearly-controllable subspaces and defining the near-controllability index,the controllability properties of the systems are fully characterized.Examples are provided to illustrate the conceptions and results of the paper.