12,740 research outputs found
Unifying approach for fluctuation theorems from joint probability distributions
Any decomposition of the total trajectory entropy production for Markovian
systems has a joint probability distribution satisfying a generalized detailed
fluctuation theorem, when all the contributing terms are odd with respect to
time reversal. The expression of the result does not bring into play dual
probability distributions, hence easing potential applications. We show that
several fluctuation theorems for perturbed non-equilibrium steady states are
unified and arise as particular cases of this general result. In particular, we
show that the joint probability distribution of the system and reservoir
trajectory entropies satisfy a detailed fluctuation theorem valid for all times
although each contribution does not do it separately
Density functional approaches for the interaction of metal oxides with small molecules
The density functional tight-binding (DFTB) and time-dependent DFTB (TD-DFTB) methods are here extended. The incorporation of one-center exchange-like terms in the expansion of multicenter integrals leads to a DFTB scheme in which the fluctuation of the dual density matrix is treated self-consistently. This formalism improves upon hydrogen bond energies of neutral, protonated and hydroxide water clusters as well as of methylimidazole-water complexes. An analogous correction for TD-DFTB leads to marked qualitative and quantitative improvements over the original method. These formalisms are employed to investigate the structural and optical properties of titanium dioxide complexed with nitric oxide and acetaldehyde. Additionally, density functional theory (DFT) and DFTB are employed to investigate the structural and electronic properties of the interfaces between zinc oxide and several organic molecules
Differentially Private Distributed Optimization
In distributed optimization and iterative consensus literature, a standard
problem is for agents to minimize a function over a subset of Euclidean
space, where the cost function is expressed as a sum . In this paper,
we study the private distributed optimization (PDOP) problem with the
additional requirement that the cost function of the individual agents should
remain differentially private. The adversary attempts to infer information
about the private cost functions from the messages that the agents exchange.
Achieving differential privacy requires that any change of an individual's cost
function only results in unsubstantial changes in the statistics of the
messages. We propose a class of iterative algorithms for solving PDOP, which
achieves differential privacy and convergence to the optimal value. Our
analysis reveals the dependence of the achieved accuracy and the privacy levels
on the the parameters of the algorithm. We observe that to achieve
-differential privacy the accuracy of the algorithm has the order of
An Optimal and Distributed Method for Voltage Regulation in Power Distribution Systems
This paper addresses the problem of voltage regulation in power distribution
networks with deep-penetration of distributed energy resources, e.g.,
renewable-based generation, and storage-capable loads such as plug-in hybrid
electric vehicles. We cast the problem as an optimization program, where the
objective is to minimize the losses in the network subject to constraints on
bus voltage magnitudes, limits on active and reactive power injections,
transmission line thermal limits and losses. We provide sufficient conditions
under which the optimization problem can be solved via its convex relaxation.
Using data from existing networks, we show that these sufficient conditions are
expected to be satisfied by most networks. We also provide an efficient
distributed algorithm to solve the problem. The algorithm adheres to a
communication topology described by a graph that is the same as the graph that
describes the electrical network topology. We illustrate the operation of the
algorithm, including its robustness against communication link failures,
through several case studies involving 5-, 34-, and 123-bus power distribution
systems.Comment: To Appear in IEEE Transaction on Power System
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