期刊文献+
共找到9篇文章
< 1 >
每页显示 20 50 100
基于行为的访问控制模型及其行为管理 被引量:46
1
作者 李凤华 王巍 +1 位作者 马建峰 梁晓艳 《电子学报》 EI CAS CSCD 北大核心 2008年第10期1881-1890,共10页
访问控制模型是对信息资源进行授权决策的重要方法之一.首先给出了环境的定义,结合角色、时态和环境的概念,给出了行为的定义.在不同的信息系统中,行为可以用来综合角色、时态状态和环境状态的相关安全信息.然后介绍了行为、时态状态和... 访问控制模型是对信息资源进行授权决策的重要方法之一.首先给出了环境的定义,结合角色、时态和环境的概念,给出了行为的定义.在不同的信息系统中,行为可以用来综合角色、时态状态和环境状态的相关安全信息.然后介绍了行为、时态状态和环境状态的层次结构,提出了基于行为的访问控制模型ABAC(Action-Based AccessControl Model),并讨论了在ABAC模型中角色、时态状态和环境状态之间的相互关系.在此基础上,通过引入受限的时态状态和环境状态,给出了管理行为的定义和ABAC管理模型的结构;描述了ABAC管理模型下用户-管理行为、管理行为-管理权限的控制关系,使用Z-符号形式化地描述了行为状态管理中使用的管理函数AddAction、ModifyAction和DeleteAction,以及和ABAC管理模型相关的管理方法.与已有其他模型相比,ABAC模型更加适用于解决网络环境下支持移动计算的信息系统中的访问控制问题. 展开更多
关键词 访问控制 行为 环境状态 时态状态 管理行为
在线阅读 下载PDF
State Space-Time and Four States of Universe 被引量:5
2
作者 Jinzhong Yan 《Journal of Physical Science and Application》 2013年第2期127-134,共8页
All things in the universe possess a state and characteristics of state, resultantly in presence of space-time, which is perceived by human beings. An outlook of space-time is shaped in human by perceiving the existen... All things in the universe possess a state and characteristics of state, resultantly in presence of space-time, which is perceived by human beings. An outlook of space-time is shaped in human by perceiving the existence and change of objects. The state space is all state characteristics exhibited in objects whilst the state time refers to the duration of an object's state. The time is a spatial property and not an independent dimension. The state space-time is a unity of internal and external space-time. The internal space-time is stemmed from the overall internal forces and internal energies and is a covert space-time. The external space-time refers to a space-time manifested by the external characteristics and movement of an object and is an overt space-time. In physics, there are four kinds of forces and four state space-times: bonding force and three-dimensional space-time; strong interaction of exchangeable n meson and two-dimensional space-time; quark confinement and one-dimensional space-time; and weak interaction and zero-dimensional space-time. The universe is constituted by dissimilar state space-times. Newton space-time is a three-dimensional state space-time; Einstein's theory of relativity is a two-dimensional state space-time. Newton and Einstein were different observers. Temporal and spatial perception of human is dependent upon human's intemal energy and quality. Through Qigong exercises, the human is able to enter the three-dimensional, two-dimensional, one-dimensional and zero-dimensional space-times. The relativity theory of human body will solve the time problems at the interplanetary voyage of astronauts. 展开更多
关键词 State space-time UNIVERSE four states.
在线阅读 下载PDF
Some Dynamic and Combinatorial Properties of One Parameter Families of Unimodal Maps with Monotonicity
3
作者 John Taylor 《Journal of Mathematics and System Science》 2013年第6期301-308,共8页
It is known that certain one parameter families of unimodal maps of the interval have a topological universality with regard to their dynamic behavior [ 1, 2]. As a parameter is smoothly increased, a fascinating varie... It is known that certain one parameter families of unimodal maps of the interval have a topological universality with regard to their dynamic behavior [ 1, 2]. As a parameter is smoothly increased, a fascinating variety of dynamic behaviors are produced. For some families the behaviors are monotonic in the parameter, while in others they are not [3]. The question is what sort of conditions on a one parameter family will ensure this monotonicity of the behavior with the parameter? The answer is unknown and will not be given here. What we do instead is to investigate certain geometric-dynamic-combinatorial consequences of assuming that the family has this monotonicity. Specifically, using tools of symbolic dynamics, state space is "course grained" with a finite alphabet. We decompose a non-invertible map into nonlinear but invertible pieces. From these invertible pieces, we form inverse maps via composition along words. Equations of motion are developed for both forward and inverse orbits (in both the variables of state space and the parameter), and an equation relating forward and inverse motions at fix-points is exhibited. Finally, we deduce a list of conditions, each of which is equivalent to monotone behavior. One of these conditions states that simple parity characteristics of words correspond to definite dynamics near fixed-points and vice versa. 展开更多
关键词 One parameter family unimodal map kneading theory connection equation.
在线阅读 下载PDF
Temporal dynamics of mental impasses underlying insight-like problem solving 被引量:1
4
作者 SHEN WangBing LIU Chang +2 位作者 YUAN Yuan ZHANG XiaoJiang LUO Jin 《Science China(Life Sciences)》 SCIE CAS 2013年第3期284-290,共7页
Insight problem solving is characterized by mental impasses,states of mind in which the problem solver does not know what to do next.Although many studies have investigated the neural correlates of insight problem sol... Insight problem solving is characterized by mental impasses,states of mind in which the problem solver does not know what to do next.Although many studies have investigated the neural correlates of insight problem solving,however,the question when mental impasses occur during insight problem solving has been rarely studied.The present study adopted high temporal resolution ERPs to investigate the temporal dynamics of an impasse underlying insight problem solving.Time locked ERPs were recorded associated with problems with impasses(PWI) and problems without impasses(POI).The problem types were determined by participants' subjective responses.The results revealed an early frontocentral P2 was linked with the preconscious awareness of mental impasses and a P3a was associated with fixed attention when the impasse formed.These findings suggest the impasse may occur initially at a relatively early stage and metacognition plays an important role in insight problem solving. 展开更多
关键词 insight problem solving METACOGNITION mental impasse event-related potential (ERP) P200
原文传递
Quantitative conditions for time evolution in terms of the von Neumann equation
5
作者 WenHua Wang HuaiXin Cao +1 位作者 ZhengLi Chen Lie Wang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS CSCD 2018年第7期54-60,共7页
The adiabatic theorem describes the time evolution of the pure state and gives an adiabatic approximate solution to the Schrrdinger equation by choosing a single eigenstate of the Hamiltonian as the initial state. In ... The adiabatic theorem describes the time evolution of the pure state and gives an adiabatic approximate solution to the Schrrdinger equation by choosing a single eigenstate of the Hamiltonian as the initial state. In quantum systems, states are divided into pure states (unite vectors) and mixed states (density matrices, i.e., positive operators with trace one). Accordingly, mixed states have their own corresponding time evolution, which is described by the von Neumann equation. In this paper, we discuss the quantitative conditions for the time evolution of mixed states in terms of the von Neumann equation. First, we introduce the definitions for uniformly slowly evolving and δ-uniformly slowly evolving with respect to mixed states, then we present a necessary and sufficient condition for the Hamiltonian of the system to be uniformly slowly evolving and we obtain some upper bounds for the adiabatic approximate error. Lastly, we illustrate our results in an example. 展开更多
关键词 quantitative condition time evolution uniformly slowly evolving δ-uniformly slowly evolving upper bound
原文传递
The effect of finite duration inputs on the dynamics of a system: Proposing a new approach for cancer treatment 被引量:1
6
作者 Mostafa Nazari Ali Ghaffari 《International Journal of Biomathematics》 2015年第3期155-173,共19页
In this paper, a principal question regarding the effect of inputs on the characteristics of dynamic systems is discussed. Whether an input implemented only for a limited duration, can change the characteristics of a ... In this paper, a principal question regarding the effect of inputs on the characteristics of dynamic systems is discussed. Whether an input implemented only for a limited duration, can change the characteristics of a dynamic system such that the behavior of the free system, after eliminating the input, differs from that before acting the input? In this paper, it is shown that a limited time acted input is not able to change the dynamical properties of a system after its elimination. Regarding the proposed approach, a novel finite duration treatment method is developed for a tumor-immune system. The vaccine therapy is used to change the parameters of the system and the chemotherapy is applied for pushing the system to the domain of attraction of the healthy state. For optimal chemotherapy, an optimal control is used based on state-dependent Riccati equation (SDRE). It is shown that, in spite of eliminating the treatment (therapeutic inputs), the system approaches to healthy state conditions. The present analysis suggests that a proper treatment method must change the dynamics of the cancer instead of only reducing the population of cancer cells. 展开更多
关键词 CANCER stability changeable dynamic properties system.
原文传递
Experimental Study and Heat Transfer Analysis on the Boiling of Saturated Liquid Nitrogen under Transient Pulsed Laser Irradiation
7
作者 ZhaoyiDONG XiulanHUAI 《Journal of Thermal Science》 SCIE EI CAS CSCD 2005年第1期62-68,共7页
The boiling behavior of the liquid nitrogen (LN2) under the transient high heat flux urgently needs to be researched systematically. In this paper, the high power short pulse duration laser was used to heat the satura... The boiling behavior of the liquid nitrogen (LN2) under the transient high heat flux urgently needs to be researched systematically. In this paper, the high power short pulse duration laser was used to heat the saturated LN2 rapidly, and the high-speed photography aided by the spark light system was employed to take series of photos which displayed the process of LN2's boiling behavior under such conditions. Also, a special temperature measuring system was applied to record the temperature variation of the heating surface. The experiments indicated that an explosive boiling happened within LN2 by the laser heating, and a conventional boiling followed up after the newly-defined changeover time. By analyzing the temperature variation of the heating surface, it is found that the latent heat released by the crack of the bubbles in the bubble cluster induced by the explosive boiling is an important factor that greatly influences the boiling heat transfer mechanism. 展开更多
关键词 explosive boiling pulsed laser heating liquid nitrogen changeover time.
原文传递
Geometric measure of quantum discord and the geometry of a class of two-qubit states
8
作者 SONG Wei YU LongBao +3 位作者 DONG Ping LI DaChuang YANG Ming CAO ZhuoLiang 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2013年第4期737-744,共8页
We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct unde... We investigate the geometric picture of the level surfaces of quantum entanglement and geometric measure of quantum discord(GMQD) of a class of X-states, respectively. This pictorial approach provides us a direct understanding of the structure of entanglement and GMQD. The dynamic evolution of GMQD under two typical kinds of quantum decoherence channels is also investigated. It is shown that there exists a class of initial states for which the GMQD is not destroyed by decoherence in a finite time interval. Furthermore, we establish a factorization law between the initial and final GMQD, which allows us to infer the evolution of entanglement under the influences of the environment. 展开更多
关键词 geometric measure of quantum discord geometric picture two-qubit states
原文传递
Subspace-based identification of discrete time-delay system
9
作者 Qiang LIU Jia-chen MA 《Frontiers of Information Technology & Electronic Engineering》 SCIE EI CSCD 2016年第6期566-575,共10页
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 ... 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. 展开更多
关键词 Identification problems Time-delay systems Subspace identification method Alternate convex search Least squares
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部