共查询到20条相似文献,搜索用时 15 毫秒
1.
Ensuring that service-oriented systems can adapt quickly and effectively to changes in service quality, business needs and their runtime environment is an increasingly important research problem. However, while considerable research has focused on developing runtime adaptation frameworks for service-oriented systems, there has been little work on assessing how effective the adaptations are. Effective adaptation ensures the system remains relevant in a changing environment and is an accurate reflection of user expectations. One way to address the problem is through validation. Validation allows us to assess how well a recommended adaptation addresses the concerns for which the system is reconfigured and provides us with insights into the nature of problems for which different adaptations are suited. However, the dynamic nature of runtime adaptation and the changeable contexts in which service-oriented systems operate make it difficult to specify appropriate validation mechanisms in advance. This paper describes a novel consumer-centered approach that uses machine learning to continuously validate and refine runtime adaptation in service-oriented systems, through model-based clustering and deep learning. 相似文献
2.
For a synchronous distributed system of n processes with up to t potential and f actual crash failures, where (t<n-1,f≤t), the time lower bound for a protocol to achieve consensus is min(t+1,f+2) rounds. Currently, most researches in this field focus on the time efficiency of consensus protocols. This paper proposes consensus protocols for synchronous distributed systems that achieve both message and time efficiency. Based on an early stopping consensus protocol for synchronous distributed system with crash failures, we propose a rotating coordinator scheme that significantly reduces message complexity. However, this protocol is not time efficient because it requires min(t+1,f+3) rounds to reach consensus. Thus, to achieve both time and message efficiency, we propose another protocol in which (t+1) coordinators are used to send messages in each round. Furthermore, we show that the proposed consensus protocol with crash failures can be revised to be more message-efficient with orderly crash failures. When a process is able to send more than one message to another in a round, we propose an optimal message efficient early stopping consensus protocol for synchronous distributed systems with orderly crash failures. 相似文献
3.
In this paper, we introduce a control synthesis method for discrete event systems whose behavior is dependent on explicit values of time. Our goal is to control the occurrence dates of the controllable events so that the functioning of the system respects given specifications. The system to be controlled is modeled by a time Petri net. In a previous work we proposed a systematic method to build the timed automaton which models the exact behavior of a time Petri net. Furthermore, the forbidden behaviors of the system are modeled by forbidden timed automaton locations. This paper focuses on the control synthesis method, which consists in computing new firing conditions for the timed automaton transitions so that the forbidden locations are no longer reachable. 相似文献
4.
Bucci G. Vicario E. 《IEEE transactions on pattern analysis and machine intelligence》1995,21(12):969-992
An extended Petri net model which considers modular partitioning along with timing restrictions and environment models is presented. Module constructs permit the specification of a complex system as a set of message passing modules with the timing semantics of time Petri nets. The state space of each individual module can be separately enumerated and assessed under the assumption of a partial specification of the intended module operation environment. State spaces of individual modules can be recursively integrated, to permit the assessment of module clusters and of the overall model, and to check the satisfaction of the assumptions made in the separate analysis of elementary component modules. In the intermediate stages between subsequent integration steps, the state spaces of module and module clusters can be projected onto reduced representations concealing local events that are not essential to the purposes of the analysis. The joint use of incremental enumeration and intermediate concealment of local events allows for a flexible management of state explosion, and permits a scalable approach to the validation of complex systems 相似文献
5.
N identical agents with bounded inputs aim to reach a common target state (consensus) in the minimum possible time. Algorithms for computing this time-optimal consensus point, the control law to be used by each agent and the time taken for the consensus to occur, are proposed. Two types of multi-agent systems are considered, namely (1) coupled single-integrator agents on a plane and, (2) double-integrator agents on a line. At the initial time instant, each agent is assumed to have access to the state information of all the other agents. An algorithm, using convexity of attainable sets and Helly's theorem, is proposed, to compute the final consensus target state and the minimum time to achieve this consensus. Further, parts of the computation are parallelised amongst the agents such that each agent has to perform computations of O(N2) run time complexity. Finally, local feedback time-optimal control laws are synthesised to drive each agent to the target point in minimum time. During this part of the operation, the controller for each agent uses measurements of only its own states and does not need to communicate with any neighbouring agents. 相似文献
6.
Hong Jun Choi Dong Oh Son Seung Gu Kang Jong Myon Kim Hsien-Hsin Lee Cheol Hong Kim 《The Journal of supercomputing》2013,65(2):886-902
Computing systems should be designed to exploit parallelism in order to improve performance. In general, a GPU (Graphics Processing Unit) can provide more parallelism than a CPU (Central Processing Unit), resulting in the wide usage of heterogeneous computing systems that utilize both the CPU and the GPU together. In the heterogeneous computing systems, the efficiency of the scheduling scheme, which selects the device to execute the application between the CPU and the GPU, is one of the most critical factors in determining the performance. This paper proposes a dynamic scheduling scheme for the selection of the device between the CPU and the GPU to execute the application based on the estimated-execution-time information. The proposed scheduling scheme enables the selection between the CPU and the GPU to minimize the completion time, resulting in a better system performance, even though it requires the training period to collect the execution history. According to our simulations, the proposed estimated-execution-time scheduling can improve the utilization of the CPU and the GPU compared to existing scheduling schemes, resulting in reduced execution time and enhanced energy efficiency of heterogeneous computing systems. 相似文献
7.
An efficient direct differentiation approach for sensitivity analysis of flexible multibody systems 总被引:1,自引:0,他引:1
This paper presents a recursive direct differentiation method for sensitivity analysis of flexible multibody systems. Large
rotations and translations in the system are modeled as rigid body degrees of freedom while the deformation field within each
body is approximated by superposition of modal shape functions. The equations of motion for the flexible members are differentiated
at body level and the sensitivity information is generated via a recursive divide and conquer scheme. The number of differentiations
required in this method is minimal. The method works concurrently with the forward dynamics simulation of the system and requires
minimum data storage. The use of divide and conquer framework makes the method linear and logarithmic in complexity for serial
and parallel implementation, respectively, and ideally suited for general topologies. The method is applied to a flexible
two arm robotic manipulator to calculate sensitivity information and the results are compared with the finite difference approach. 相似文献
8.
Claesson V. Lonn H. Suri N. 《Parallel and Distributed Systems, IEEE Transactions on》2004,15(8):725-739
A desired attribute in safety-critical embedded real-time systems is a system time and event synchronization capability on which predictable communication can be established. Focusing on bus-based communication protocols, we present a novel, efficient, and low-cost start-up and restart synchronization approach for TDMA environments. This approach utilizes information about a node's message length that forms a unique sequence to achieve synchronization such that communication overhead can be avoided. We present a fault-tolerant initial synchronization protocol with a bounded start-up time. The protocol avoids start-up collisions by deterministically postponing retries after a collision. We also present a resynchronization strategy that incorporates recovering nodes into synchronization. 相似文献
9.
This paper proposes a computationally efficient iterative learning control (ILC) approach termed non-lifted norm optimal ILC (N-NOILC). The objective is to remove the computational complexity issues of previous 2-norm optimal ILC approaches, which are based on lifted system techniques, while retaining the iteration domain convergence properties. The computational complexity needed to implement the proposed method scales linearly with the trial length. Therefore, the approach can be implemented on controlled processes having long trial durations and high sampling rates. Robustness is accomplished by adding a penalty term on the control input in the cost function. Simulations are presented to verify and validate the features of the proposed method. 相似文献
10.
This paper proposes a new differential dynamic programming algorithm for solving discrete time optimal control problems with equality and inequality constraints on both control and state variables and proves its convergence. The present algorithm is different from differential dynamic programming algorithms developed in [10]-[15], which can hardly solve optimal control problems with inequality constraints on state variables and whose convergence has not been proved. Composed of iterative methods for solving systems of nonlinear equations, it is based upon Kuhn-Tucker conditions for recurrence relations of dynamic programming. Numerical examples show file efficiency of the present algorithm. 相似文献
11.
Future generations wireless systems, which integrate different wireless access networks together, will support a secured seamless mobility and a wide variety of applications and services with different quality of service (QoS) requirements. Most of the existing re-authentication protocols during vertical handover still have certain limitations such as man in the middle, eavesdropping and session hijacking attacks, and unacceptable delay for real time applications. In this article, we propose two re-authentication schemes to secure handover between 3GPP LTE and WLANs systems: Initial Handover Re-authentication Protocol, and Local Re-authentication Protocol. The second proposed protocol is executed locally in a WLAN network without contacting the authentication server of the home network for credentials verification. In fact, after a successful execution of the Initial Handover Re-authentication Protocol, the local key (LK) is shared between USIM and the authentication server of the WLAN. It is then used for securing handover and traffic in WLAN networks. Performance evaluation results obtained using simulation analysis show that the proposed re-authentication protocol enhances handover parameters such as handover latency, handover blocking rate and packet loss rate. Additionally, the proposed enhanced fast re-authentication protocol has been modeled and verified using the software AVISPA and is found to be safe. 相似文献
12.
World Wide Web - In recent years, time series classification with shapelets, due to the high accuracy and good interpretability, has attracted considerable interests. These approaches extract or... 相似文献
13.
Singular systems: A new approach in the time domain 总被引:1,自引:0,他引:1
A new approach in the time domain is developed for the study of singular linear systems of the formEdot{x} = Ax + Bu, y = Cx withE singular. Central to the approach is the fundamental triple((alpha E - A)^{-1}E, (alphaE - A)^{-1}B, C) with α a real number satisfying det(alpha E - A) neq 0 . Controllability and observability matrices are expressed in terms of the fundamental triple. New tests for impulse controllability and impulse observability are also established. Feedback control problems including pole placement, decoupling, and disturbance localization are studied by use of a modified proportional and derivative feedback of the state in the form ofu = F(alpha x - dot{x})+ v . 相似文献
14.
Microsystem Technologies - This study presents a new approach for system simplification and control. This approach is based on the behaviour of growth and reproduction of weed plants namely... 相似文献
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17.
FRANCO BLANCHINI 《International journal of systems science》2013,44(2):407-414
A method for the computation of the transfer function for linear time-invariant singular SISO systems is presented. The system must be reduced to the Hessen-berg/triangular form, then the transfer function denominator and numerator are obtained by two simple formulae derived from the expression of the determinant of a Hessenberg matrix. The problem of computing a minimal representation by removing the input and output decoupling zeros via Hessenberg/triangular form is also considered. Unitary transformations are used and so the numerical stability is preserved. An extension to multivariable systems is proposed. 相似文献
18.
De Santis E. Di Benedetto M.D. Berardi L. 《Automatic Control, IEEE Transactions on》2004,49(2):184-195
The problem of determining maximal safe sets and hybrid controllers is computationally intractable because of the mathematical generality of hybrid system models. Given the practical and theoretical relevance of the problem, finding implementable procedures that could at least approximate the maximal safe set is important. To this end, we begin by restricting our attention to a special class of hybrid systems: switching systems. We exploit the structural properties of the graph describing the discrete part of a switching system to develop an efficient procedure for the computation of the safe set. This procedure requires the computation of a maximal controlled invariant set. We then restrict our attention to linear discrete-time systems for which there is a wealth of results available in the literature for the determination of maximal controlled invariant sets. However, even for this class of systems, the computation may not converge in a finite number of steps. We then propose to compute inner approximations that are controlled invariant and for which a procedure that terminates in a finite number of steps can be obtained. A tight bound on the error can be given by comparing the inner approximation with the classical outer approximation of the maximal controlled invariant set. Our procedure is applied to the idle-speed regulation problem in engine control to demonstrate its efficiency. 相似文献
19.
针对无线传感器网络时间同步能耗问题,提出一种能量有效的时间同步算法。该算法结合了TPSN协议和RBS协议的特点,利用无线信道的广播特性,在两个参考节点广播域里的所有节点通过监听参考节点之间的数据包交换而达到同步。并提出一种同步节点选择方法,将该同步算法扩展到多跳网络。实验结果表明,该算法在保持同步精度的同时降低了能量消耗。 相似文献
20.
This paper presents a probabilistic model validation methodology for nonlinear systems in time-domain. The proposed formulation is simple, intuitive, and accounts both deterministic and stochastic nonlinear systems with parametric and nonparametric uncertainties. Instead of hard invalidation methods available in the literature, a relaxed notion of validation in probability is introduced. To guarantee provably correct inference, algorithm for constructing probabilistically robust validation certificate is given along with computational complexities. Several examples are worked out to illustrate its use. 相似文献