507 research outputs found
Privacy preserving distributed optimization using homomorphic encryption
This paper studies how a system operator and a set of agents securely execute
a distributed projected gradient-based algorithm. In particular, each
participant holds a set of problem coefficients and/or states whose values are
private to the data owner. The concerned problem raises two questions: how to
securely compute given functions; and which functions should be computed in the
first place. For the first question, by using the techniques of homomorphic
encryption, we propose novel algorithms which can achieve secure multiparty
computation with perfect correctness. For the second question, we identify a
class of functions which can be securely computed. The correctness and
computational efficiency of the proposed algorithms are verified by two case
studies of power systems, one on a demand response problem and the other on an
optimal power flow problem.Comment: 24 pages, 5 figures, journa
On privacy preserving data release of linear dynamic networks
Distributed data sharing in dynamic networks is ubiquitous. It raises the
concern that the private information of dynamic networks could be leaked when
data receivers are malicious or communication channels are insecure. In this
paper, we propose to intentionally perturb the inputs and outputs of a linear
dynamic system to protect the privacy of target initial states and inputs from
released outputs. We formulate the problem of perturbation design as an
optimization problem which minimizes the cost caused by the added perturbations
while maintaining system controllability and ensuring the privacy. We analyze
the computational complexity of the formulated optimization problem. To
minimize the and norms of the added perturbations, we derive
their convex relaxations which can be efficiently solved. The efficacy of the
proposed techniques is verified by a case study on a heating, ventilation, and
air conditioning system.Comment: 18 pages, 5 figures, journa
Teacher Efficacy, Work Engagement, and Social Support Among Chinese Special Education School Teachers
This paper investigates the relationship between teacher efficacy and sociodemographic
factors, work engagement, and social support among Chinese
special education school teachers. The sample comprised 1,027 special education
school teachers in mainland China. The Teachers’ Sense of Efficacy Scale,
the Multi-Dimensional Scale of Perceived Social Support, and the Utrecht Work
Engagement Scale were used for data collection. Correlation analysis revealed that
social support, work engagement, and teacher efficacy were significantly correlated
with each other. Additionally, gender, years of experience, and monthly salary were
significant predictors of teacher efficacy. Furthermore, structural equation modeling
analysis showed that social support exerted its indirect effect on teacher efficacy
through the mediation of work engagement. The findings of this study provide a new
perspective on the complex association between social support and teacher efficacy.
The explanations and limitations of these findings are discussed
Unified Equivalent-circuit Models for Voltage-source Inverters that Capture Averaged Dynamics and Power-flow Solutions in Distribution Networks
This paper demonstrates how three-phase distribution networks composed of voltage-source inverters can be modeled as a single unified equivalent-circuit network realized with familiar circuit elements. Such a model is derived by representing all physical- and control-subsystem dynamics as equivalent circuits. Two versions are put forth: the first captures averaged dynamics; while the second is a steady-state version of the first and it captures the power-flow solution in sinusoidal steady state. The main challenge in undertaking such an effort is presented by the fact that inverters are composed of subsystems (filters, pulse width modulators, phase-locked loops, controllers, direct-quadrature reference-frame transformations) that belong to multiple domains (physical and control). We demonstrate how all these constituent subsystems can be transcribed as equivalent circuits which then promote a single and unified circuit model that captures network physical- and control-layer dynamics. Numerical simulations for a representative distribution network compare results from the averaged model and the steady-state model with high-fidelity switch-level simulations. The results establish the validity of the circuit-based models and the computational benefits of the proposed approach
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