Engineering topics

Aggarwal, Rachit

Publications and source records attributed to Aggarwal, Rachit.

3 records

DOE OSTI2017

Task allocation in geo-distributed cyber-physical systems - 256

This paper studies the task allocation algorithm for a distributed test facility (DTF), which aims to assemble geo-distributed cyber (software) and physical (hardware in the loop) components into a prototype cyber-physical system (CPS). This allows low cost testing on an early conceptual prototype (ECP) of the ultimate CPS (UCPS) to be developed. The DTF provides an instrumentation interface for carrying out reliability experiments remotely such as fault propagation analysis and in-situ testing of hardware and software components in a simulated environment. Unfortunately, the geo-distribution introduces an overhead that is not inherent to the UCPS, i.e. a significant time delay in communication that threatens the stability of the ECP and is not an appropriate representation of the behavior of the UCPS. This can be mitigated by implementing a task allocation algorithm to find a suitable configuration and assign the software components to appropriate computational locations, dynamically. This would allow the ECP to operate more efficiently with less probability of being unstable due to the delays introduced by geo-distribution. The task allocation algorithm proposed in this work uses a Monte Carlo approach along with Dynamic Programming to identify the optimal network configuration to keep the time delays to a minimum. (authors)

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2017

TASK ALLOCATION IN GEO-DISTRIBUTED CYBER-PHYSICAL SYSTEMS

This paper studies the task allocation algorithm for a distributed test facility (DTF), which aims to assemble geo-distributed cyber (software) and physical (hardware in the loop components into a prototype cyber-physical system (CPS). This allows low cost testing on an early conceptual prototype (ECP) of the ultimate CPS (UCPS) to be developed. The DTF provides an instrumentation interface for carrying out reliability experiments remotely such as fault propagation analysis and in-situ testing of hardware and software components in a simulated environment. Unfortunately, the geo-distribution introduces an overhead that is not inherent to the UCPS, i.e. a significant time delay in communication that threatens the stability of the ECP and is not an appropriate representation of the behavior of the UCPS. This can be mitigated by implementing a task allocation algorithm to find a suitable configuration and assign the software components to appropriate computational locations, dynamically. This would allow the ECP to operate more efficiently with less probability of being unstable due to the delays introduced by geo-distribution. The task allocation algorithm proposed in this work uses a Monte Carlo approach along with Dynamic Programming to identify the optimal network configuration to keep the time delays to a minimum.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2016

Effect of Aging and Demand for Reliability Analysis of Degrading Components

According to the U.S Energy Information Administration (EIA), the U.S fossil fuel share of energy consumption in 2015 was 67%. Furthermore, the Ecotricity UK report based on the CIA World Factbook states that with the current rate of consumption of fossil fuels, petroleum would run out by 2052, natural gas by 2060, and coal by 2088. No fossil fuel will remain by the next century. Besides the limited reserves of fossil fuel, massive consumption of fossil fuel also raises concerns about global warming and pollution. Therefore, there has been a growing interest in reducing fossil fuel consumption in the energy structure and in increasing the proportion of clean energy. Renewable energy (e.g. wind, solar) has the potential for distributed generation. However, the availability for renewable energy fluctuates and is uncontrollable. Therefore, additional energy sources need to be coupled with renewable energy to produce a stable electricity generation profile. Nuclear energy can serve this purpose as it is a clean energy source, has low greenhouse gas emission and possesses high power density and baseload power supply with low fuel cost. It is desirable to develop a hybrid energy system that combines both renewable energy and nuclear energy to meet low carbon emission goals and to utilize renewable energy. Such a nuclear hybrid energy system, consisting of different energy subsystems such as nuclear, solar, and wind, involves frequent switching between different energy subsystems. Since the primary loop in a nuclear power plant generates constant heat, the turbine bypass line in the secondary loop is required to switch frequently to meet the gap in the energy demand and that generated by the renewables. The increased usage of the turbine bypass system is considered to be the major difference between a nuclear hybrid energy system and a traditional nuclear power plant. Reliability analysis for designing such a complex system involves both high level fault propagation analysis at the conceptual design stage and low level failure prediction for specific components. The main focus of this summary to derive a degradation model of hardware components which can later help in the high level fault propagation analysis. The degradation model is a low level failure mode model that combines the effects of natural aging and frequent switching. The model can be used for predicting components' failure due to specific failure modes. The results can serve as indicators for conducting repair actions and maintenance to minimize Operation and Maintenance (O and M) costs. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗