面向手机短信的隐私保护方案

针对手机短信存在的用户隐私泄露问题,设计一种面向手机短信的隐私保护方案.本方案结合非对称加密技术,通过使用信息接收者的公钥对原始短信进行加密获得短信密文,并结合预设的生命周期信息封装成短信自毁对象(Message Self-destructing Object,MSO)并通过运营商发送给接收者,接收者接收到MSO后对其生命周期进行验证,只有当前时间处于其生命周期内时,才能进一步使用其私钥对短信密文进行解密获取原始短信内容,一旦超过MSO的生命周期,则MSO将被自动删除以保护用户隐私安全.实验分析表明,本方案能够有效保护用户手机短信的隐私安全,实现生命周期控制并自动删除过期短信,并且对硬件系统要求低,开销合理,适合在人们日常生活中进行推广使用.     

基于区域密度的交通拥堵判别方法

本文通过对交通流进行特征提取和状态的划分,建立了交通流判别准则.同时提出一种交通拥堵程度的智能判断方法,该方法以区域密度作为判别交通流状态的主要特征值,辅以时间占有率,结合空间和时间维度来判断当前道路的拥挤程度.仿真实验说明该方法具有较好的准确性和客观性.     

石油类危化品实时巡检系统

提出了基于GIS、GPS、GPRS和无线传感网络技术的石油类危险化学品油气管道监控系统结构及该系统的软件架构和功能设计.该系统利用无线传感网络、GPS和GPRS技术对油气管道进行实时跟踪巡检预警,利用地理信息系统实现对石油类危险化学品查询、综合分析、动态管理等功能,从而为石油类危险化学品安全监测提供科学依据,对减少事故发生或伤亡损失具有重要的现实意义.     

基于时间和影响力因子的Github Pull Request评审人推荐

开源社区github提供了pull request的机制让开发者可以把自己的代码集成到github的开源项目中从而为项目做出贡献.Pull request的代码评审是github这类分布式软件开发社区维护开源项目代码质量的非常重要的方式.为一个新到来的pull request指派合适的代码评审人可以有效减少pull request从提交到开始审核的延迟.目前github是由项目核心成员人工来完成评审人的指派,为了减少这种人力损耗,我们提出代码评审人的推荐系统,该系统基于信息检索的方法,并考虑了评审人的影响力因子以及评审的时间衰减的因素,对新到来的pull request,自动推荐最相关的评审人.我们的方法对top 1的准确度达到了68%,对top 10的召回率达到了78%.     

Output feedback regulation of upper triangular nonlinear systems with uncertain time‐varying delays in states and input

In this paper, an output feedback controller is studied to regulate a class of upper triangular nonlinear systems with uncertain time‐varying delays. The key features of our considered system are that there are uncertain time‐varying delays in both states and input and the high‐order nonlinearity is in a more relaxed form over the previous results. Theoretical analysis and numerical example are presented to show the benefits of our controller. Copyright © 2017 John Wiley & Sons, Ltd.     

Command governor for constrained switched systems with scheduled model transition dwell times

In this paper, a switched control architecture for constrained control systems is presented. The strategy is based on command governor ideas that are here specialized to ‘optimally’ schedule switching events on the plant dynamics for improving control performance at the expense of low computational burdens. The significance of the method mainly lies in its capability to avoid constraints violation and loss of stability regardless of any configuration change occurrence in the plant/constraint structure. To this end, the concept of model transition dwell time is used within the proposed control framework to formally define the minimum time necessary to enable a switching event under guaranteed conditions on the overall stability and constraint fulfilment. Simulation results on a simple linear system and on a Cessna 182 aircraft model show the effectiveness of the proposed strategy. Copyright © 2017 John Wiley & Sons, Ltd.     

Distributed consensus and tracking control of second‐order time‐varying nonlinear multi‐agent systems

In this paper, the distributed consensus and tracking protocols are developed for the second‐order time‐varying nonlinear multi‐agent systems under general directed graph. Firstly, the consensus and tracking problems can be converted into a conventional stabilization control problem. Then a state transformation is employed to deal with the time‐varying nonlinearities. By choosing an appropriate time‐varying parameter and coupling strengths, exponential consensus and tracking of second‐order nonlinear multi‐agent systems can be achieved. Finally, a simulation is given to illustrate the effectiveness of the proposed consensus and tracking protocols. Copyright © 2017 John Wiley & Sons, Ltd.     

Second‐order sliding mode controller design subject to mismatched unbounded perturbations

The dynamics of the second‐order sliding mode (SOSM) can be obtained by directly taking the second derivative on the sliding variable when it has a relative degree of 2 with respect to the control input. However, there will always appear some state‐dependent certain or uncertain terms in the first derivative of the sliding variable, and the derivative directly imposed on these terms could enlarge the uncertainties in the control channel. One method to reduce the uncertainties in the control channel is to hold this information in the dynamics of the first derivative of the sliding variable, while the original SOSM dynamics could be transformed to be a SOSM system with a mismatched unbounded perturbation. This paper focuses on the controller design problem for SOSM dynamics subject to mismatched unbounded perturbation. By using Lyapunov analysis, a novel backstepping‐like design methodology will be proposed. The rigorous mathematical proof will show that under the derived SOSM controller, the closed‐loop sliding mode dynamics is globally finite‐time stable. Meanwhile, the frequently used constant upper bound assumptions for the standard SOSM system can also be extended to the state‐dependent hypotheses in this paper. An academic example is illustrated to verify the effectiveness of the proposed method. Copyright © 2017 John Wiley & Sons, Ltd.     

Continuous output‐feedback control for a class of switched high‐order planar systems and its application

This paper deals with the problem of continuous output‐feedback stabilization for a class of switched high‐order planar systems under arbitrary switchings. Based on the common Lyapunov function design method, by using the adding a power integrator technique and designing an implementable observer, a continuous output‐feedback controller is constructed such that the closed‐loop system is global stabilization and the output can be regulated to the origin. As an application, the developed strategy is utilized to the control design for the continuous stirred tank reactor with two modes feed stream. The simulation results verify the efficiency of the proposed design scheme. Copyright © 2017 John Wiley & Sons, Ltd.     

Robust adaptive DSC of directly input‐coupled nonlinear systems with input unmodeled dynamics and time‐varying output constraints

In this paper, an adaptive robust dynamic surface control is proposed for a class of uncertain nonlinear interconnected systems with time‐varying output constraints and dynamic input and output coupling. The directly coupled inputs and control inputs are both of nonlinear input unmodeled dynamics. To counteract the instable impact of the nonlinear input unmodeled dynamics, normalization signals are designed on the basis of the convergence rates of their Lyapunov functions. With new state variables and control variables being defined, the real control inputs are obtained through solving the equations of intermediate control laws. The time‐varying constraints on output signals are implemented by introducing asymmetric barrier Lyapunov functions. In addition, dynamic signals and decentralized K‐filters are used to deal with the state unmodeled dynamics and to estimate the unmeasurable states, respectively. By the theoretical analysis, the signals in the closed‐loop system are proved to be semi‐globally uniformly ultimately bounded, and the output constraints are guaranteed simultaneously. A numerical example is provided to show the effectiveness of the proposed approach. Copyright © 2017 John Wiley & Sons, Ltd.