The Experts below are selected from a list of 34254 Experts worldwide ranked by ideXlab platform
Jinjun Chen - One of the best experts on this subject based on the ideXlab platform.
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A privacy leakage upper Bound Constraint-based approach for cost-effective privacy preserving of intermediate data sets in cloud
IEEE Transactions on Parallel and Distributed Systems, 2013Co-Authors: Xuyun Zhang, Suraj Pandey, Surya Nepal, Chang Liu, Jinjun ChenAbstract:Cloud computing provides massive computation power and storage capacity which enable users to deploy computation and data-intensive applications without infrastructure investment. Along the processing of such applications, a large volume of intermediate data sets will be generated, and often stored to save the cost of recomputing them. However, preserving the privacy of intermediate data sets becomes a challenging problem because adversaries may recover privacy-sensitive information by analyzing multiple intermediate data sets. Encrypting ALL data sets in cloud is widely adopted in existing approaches to address this challenge. But we argue that encrypting all intermediate data sets are neither efficient nor cost-effective because it is very time consuming and costly for data-intensive applications to en/decrypt data sets frequently while performing any operation on them. In this paper, we propose a novel upper Bound privacy leakage Constraint-based approach to identify which intermediate data sets need to be encrypted and which do not, so that privacy-preserving cost can be saved while the privacy requirements of data holders can still be satisfied. Evaluation results demonstrate that the privacy-preserving cost of intermediate data sets can be significantly reduced with our approach over existing ones where all data sets are encrypted.
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Dynamic Setting, Verification and Adjustment of Upper Bound Constraints in Grid Workflow Systems
2006 Semantics Knowledge and Grid Second International Conference on, 2006Co-Authors: Jinjun Chen, Yun YangAbstract:Upper Bound Constraints are often set when complex scientific or business processes are modelled as grid workflow specifications. However, many existing processes such as climate modelling or international stock market analysis often have only one end-to-end upper Bound Constraint. This is not sufficient to control overall temporal correctness as we may not find temporal violations until the last activity. Then, it is too late to take any handling actions. Consequently, the execution results may not be useful and overall cost-effectiveness would be impacted. Therefore, in this paper, we systematically investigate how to set, verify and adjust sub-upper Bound Constraints within the timeframe of one end-to-end upper Bound Constraint so that we can control grid workflow execution locally. We develop corresponding setting, verification and adjustment methods and algorithms. The quantitative evaluation demonstrates that with sub-upper Bound Constraints, we can achieve better cost-effectiveness than only based on one end-to-end upper Bound Constraint.
Biao Huang - One of the best experts on this subject based on the ideXlab platform.
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monitoring control performance via structured closed loop response subject to output variance covariance upper Bound
Journal of Process Control, 2006Co-Authors: Fangwei Xu, Biao HuangAbstract:Abstract Owing to the process time delays, the closed-loop response can be divided into feedback control invariant part and feedback controller dependent part. If the latter part is replaced by a user specified response trajectory, we refer to the resultant closed-loop response as structured closed-loop response. The user specified structured closed-loop response has been used as an achievable control against which one can assess performance of control loops. In the control performance monitoring literature, the user specified response is often given as a first-order transfer function with some specified performance requirement, such as time constant. In this paper, we solve this problem from a systematic approach, i.e., in viewpoint of a variance/covariance upper Bound on the outputs. With available closed-loop routine operating output data and process time delay/interactor matrix, the desired structured closed-loop response can be obtained directly via estimated closed-loop time series model. A significant feature is that the output variance/covariance upper Bound Constraint can be explicitly specified according to the product specifications and is always satisfied when the problem is feasible. This desired structured closed-loop response can thus be served as a benchmark against which the existing controller performance can be compared. We also show that two approaches, linearizing change of variables and Frank and Wolfe algorithm, are suitable for solving this problem, which result in a full order and a reduced order structured closed-loop response, respectively. Both approaches are illustrated by two case studies.
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robust h observer design of linear time delay systems with parametric uncertainty
Systems & Control Letters, 2001Co-Authors: Zidong Wang, Biao Huang, Heinz UnbehauenAbstract:Abstract This paper deals with the problem of H∞ observer design for a class of uncertain linear systems with delayed state and parameter uncertainties. This problem aims at designing the linear state observers such that, for all admissible parameter uncertainties, the observation process remains robustly stable and the transfer function from exogenous disturbances to error state outputs meets the prespecified H∞ norm upper Bound Constraint, independently of the time delay. The time delay is assumed to be unknown, and the parameter uncertainties are allowed to be norm-Bounded and appear in all the matrices of the state-space model. An effective matrix inequality methodology is developed to solve the proposed problem. We derive the conditions for the existence of the desired robust H∞ observers, and then characterize the analytical expression of these observers in terms of some free parameters. A numerical example demonstrates the validity and applicability of the present approach.
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Robust H/sub 2//H/sub /spl infin// filtering for linear systems with error variance Constraints
IEEE Transactions on Signal Processing, 2000Co-Authors: Biao HuangAbstract:In this correspondence, we consider the robust H/sub 2//H/sub /spl infin// filtering problem for linear perturbed systems with steady-state error variance Constraints. The purpose of this multiobjective problem is to design a linear filter that does not depend on the parameter perturbations such that the following three performance requirements are simultaneously satisfied. (1) The filtering process is asymptotically stable. (2) The steady-state variance of the estimation error of each state is not more than the individual prespecified value. (3) The transfer function from exogenous noise inputs to error state outputs meets the prespecified H/sub /spl infin// norm upper Bound Constraint. We show that in both continuous and discrete-time cases, the addressed filtering problem can effectively be solved in terms of the solutions of a couple of algebraic Riccati-like equations/inequalities. We present both the existence conditions and the explicit expression of desired robust filters. An illustrative numerical example is provided to demonstrate the flexibility of the proposed design approach.
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technical communique robust h observer design of linear state delayed systems with parametric uncertainty the discrete time case
Automatica, 1999Co-Authors: Biao Huang, Heinz UnbehauenAbstract:In this note we consider the problem of H"~ observer design for a class of uncertain linear discrete-time systems with delayed state and parameter uncertainties. The goal of this problem is to design a linear state observer such that, for the positive integer state time-delay and all admissible norm-Bounded parameter uncertainties, the observation process remains robustly stable and the transfer function from exogenous disturbances to error state outputs meets the prespecified H"~-norm upper-Bound Constraint. The observer structure does not depend on the parameter uncertainties. A simple, effective algebraic methodology is developed to derive the conditions for the existence of the desired robust H"~ observers, and the analytical expression of these observers is then characterized in terms of the matrix Riccati-like equations/inequalities. We provide a numerical example to demonstrate the validity and the applicability of the proposed approach.
Heinz Unbehauen - One of the best experts on this subject based on the ideXlab platform.
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robust h observer design of linear time delay systems with parametric uncertainty
Systems & Control Letters, 2001Co-Authors: Zidong Wang, Biao Huang, Heinz UnbehauenAbstract:Abstract This paper deals with the problem of H∞ observer design for a class of uncertain linear systems with delayed state and parameter uncertainties. This problem aims at designing the linear state observers such that, for all admissible parameter uncertainties, the observation process remains robustly stable and the transfer function from exogenous disturbances to error state outputs meets the prespecified H∞ norm upper Bound Constraint, independently of the time delay. The time delay is assumed to be unknown, and the parameter uncertainties are allowed to be norm-Bounded and appear in all the matrices of the state-space model. An effective matrix inequality methodology is developed to solve the proposed problem. We derive the conditions for the existence of the desired robust H∞ observers, and then characterize the analytical expression of these observers in terms of some free parameters. A numerical example demonstrates the validity and applicability of the present approach.
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technical communique robust h observer design of linear state delayed systems with parametric uncertainty the discrete time case
Automatica, 1999Co-Authors: Biao Huang, Heinz UnbehauenAbstract:In this note we consider the problem of H"~ observer design for a class of uncertain linear discrete-time systems with delayed state and parameter uncertainties. The goal of this problem is to design a linear state observer such that, for the positive integer state time-delay and all admissible norm-Bounded parameter uncertainties, the observation process remains robustly stable and the transfer function from exogenous disturbances to error state outputs meets the prespecified H"~-norm upper-Bound Constraint. The observer structure does not depend on the parameter uncertainties. A simple, effective algebraic methodology is developed to derive the conditions for the existence of the desired robust H"~ observers, and the analytical expression of these observers is then characterized in terms of the matrix Riccati-like equations/inequalities. We provide a numerical example to demonstrate the validity and the applicability of the proposed approach.
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Robust H/sub 2//H/sub /spl infin//-state estimation for systems with error variance Constraints: the continuous-time case
IEEE Transactions on Automatic Control, 1999Co-Authors: Heinz UnbehauenAbstract:The paper is concerned with the state estimator design problem for perturbed linear continuous-time systems with H/sub /spl infin// norm and variance Constraints. The perturbation is assumed to be time-invariant and norm-Bounded and enters into both the state and measurement matrices. The problem we address is to design a linear state estimator such that, for all admissible measurable perturbations, the variance of the estimation error of each state is not more than the individual prespecified value, and the transfer function from disturbances to error state outputs satisfies the prespecified H/sub /spl infin// norm upper Bound Constraint, simultaneously. Existence conditions of the desired estimators are derived in terms of Riccati-type matrix inequalities, and the analytical expression of these estimators is also presented. A numerical example is provided to show the directness and effectiveness of the proposed design approach.
Xuyun Zhang - One of the best experts on this subject based on the ideXlab platform.
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A privacy leakage upper Bound Constraint-based approach for cost-effective privacy preserving of intermediate data sets in cloud
IEEE Transactions on Parallel and Distributed Systems, 2013Co-Authors: Xuyun Zhang, Suraj Pandey, Surya Nepal, Chang Liu, Jinjun ChenAbstract:Cloud computing provides massive computation power and storage capacity which enable users to deploy computation and data-intensive applications without infrastructure investment. Along the processing of such applications, a large volume of intermediate data sets will be generated, and often stored to save the cost of recomputing them. However, preserving the privacy of intermediate data sets becomes a challenging problem because adversaries may recover privacy-sensitive information by analyzing multiple intermediate data sets. Encrypting ALL data sets in cloud is widely adopted in existing approaches to address this challenge. But we argue that encrypting all intermediate data sets are neither efficient nor cost-effective because it is very time consuming and costly for data-intensive applications to en/decrypt data sets frequently while performing any operation on them. In this paper, we propose a novel upper Bound privacy leakage Constraint-based approach to identify which intermediate data sets need to be encrypted and which do not, so that privacy-preserving cost can be saved while the privacy requirements of data holders can still be satisfied. Evaluation results demonstrate that the privacy-preserving cost of intermediate data sets can be significantly reduced with our approach over existing ones where all data sets are encrypted.
Luca Gambetti - One of the best experts on this subject based on the ideXlab platform.
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on the empirical ir relevance of the zero lower Bound Constraint
Nber Macroeconomics Annual, 2020Co-Authors: Davide Debortoli, Jordi Gali, Luca GambettiAbstract:We evaluate the hypothesis that the zero lower Bound (ZLB) Constraint was, in practice, irrelevant during the recent ZLB episode experienced by the US economy (the 2009Q1–2015Q4 period). We focus o...
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on the empirical ir relevance of the zero lower Bound Constraint
Social Science Research Network, 2018Co-Authors: Davide Debortoli, Jordi Gali, Luca GambettiAbstract:The zero lower Bound (ZLB) irrelevance hypothesis implies that the economy's performance is not affected by a binding ZLB Constraint. We evaluate that hypothesis for the recent ZLB episode experienced by the U.S. economy (2009Q1-2015Q4). We focus on two dimensions of performance that were likely to have experienced the impact of a binding ZLB: (i) the volatility of macro variables and (ii) the economy's response to shocks. Using a variety of empirical methods, we find little evidence against the irrelevance hypothesis, with our estimates suggesting that the responses of output, inflation and the long-term interest rate were hardly affected by the binding ZLB Constraint, possibly as a result of the adoption and fine-tuning of unconventional monetary policies. We can reconcile our empirical findings with the predictions of a simple New Keynesian model under the assumption of a shadow interest rate rule.
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on the empirical ir relevance of the zero lower Bound Constraint
Research Papers in Economics, 2018Co-Authors: Davide Debortoli, Jordi Gali, Luca GambettiAbstract:We evaluate the hypothesis that the zero lower Bound (ZLB) Constraint was, in practice, irrelevant during the recent ZLB episode experienced by the U.S. economy (2009Q1-2015Q4). We focus on two dimensions of economic performance that were ex-ante likely to have been affected by a binding ZLB: (i) the volatility of macro variables and (ii) the economy’s response to shocks. Using a variety of empirical methods, we find little evidence against the irrelevance hypothesis, with our estimates suggesting that the responses of output, inflation and the long-term interest rate were hardly affected by the binding ZLB Constraint. We show how a shadow interest rate rule (which we take as a proxy for forward guidance) can reconcile our empirical findings with the predictions of a simple New Keynesian model with a ZLB Constraint.