scholarly journals Simulating and Evaluating a Real-World ElasticSearch System Using the RECAP DES Simulator

2021 ◽  
Vol 13 (4) ◽  
pp. 83
Author(s):  
Malika Bendechache ◽  
Sergej Svorobej ◽  
Patricia Takako Endo ◽  
Adrian Mihai ◽  
Theo Lynn
Keyword(s):  
Real World ◽  
Large Scale ◽  
Low Cost ◽  
Discrete Event ◽  
Distributed Data ◽  
Simulation Experiments ◽  
Large Scale Systems ◽  
Data Indexing ◽  
Simulation Results ◽  
Discrete Event Simulator

Simulation has become an indispensable technique for modelling and evaluating the performance of large-scale systems efficiently and at a relatively low cost. ElasticSearch (ES) is one of the most popular open source large-scale distributed data indexing systems worldwide. In this paper, we use the RECAP Discrete Event Simulator (DES) simulator, an extension of CloudSimPlus, to model and evaluate the performance of a real-world cloud-based ES deployment by an Irish small and medium-sized enterprise (SME), Opening.io. Following simulation experiments that explored how much query traffic the existing Opening.io architecture could cater for before performance degradation, a revised architecture was proposed, adding a new virtual machine in order to dissolve the bottleneck. The simulation results suggest that the proposed improved architecture can handle significantly larger query traffic (about 71% more) than the current architecture used by Opening.io. The results also suggest that the RECAP DES simulator is suitable for simulating ES systems and can help companies to understand their infrastructure bottlenecks under various traffic scenarios and inform optimisation and scalability decisions.

Traffic Fuzzy Controller's Improvement Based on Self-Adaptive Optimal Algorithm

2012 ◽  
Vol 562-564 ◽  
pp. 1414-1417
Author(s):  
Zhi Yi Xu ◽  
Da Lu Guan ◽  
Ai Long Fan
Keyword(s):  
Mathematical Model ◽  
Large Scale ◽  
Fuzzy Controller ◽  
Optimal Algorithm ◽  
Signal Control ◽  
Traffic Signal Control ◽  
Time Varying ◽  
Large Scale Systems ◽  
Simulation Results ◽  
Self Adaptive

The transport system is a nonlinear, time-varying, lagging large-scale systems. Fuzzy control does not need to build a precise mathematical model, can be easily integrated people's thinking and experience, and is suitable for applications in the traffic signal control system. Here,a self-adaptive optimal algorithm was used to improve the traditional fuzzy controller. Simulation results show that the improved system has higher availability.

scholarly journals Experimental Methods for Investigation of Drilling Fluid Displacement in Irregular Annuli

Energies ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 5201
Author(s):  
Bjørnar Lund ◽  
Ali Taghipour ◽  
Jan David Ytrehus ◽  
Arild Saasen
Keyword(s):  
Electrical Conductivity ◽  
Large Scale ◽  
Drilling Fluid ◽  
Low Cost ◽  
Relevant Information ◽  
Experimental Methods ◽  
Optical Measurements ◽  
Complex Flow ◽  
Large Scale Systems ◽  
Fluid Displacement

Experimental methods are still indispensable for fluid mechanics research, despite advancements in the modelling and computer simulation field. Experimental data are vital for validating simulations of complex flow systems. However, measuring the flow in industrially relevant systems can be difficult for several reasons. Here we address flow measurement challenges related to cementing of oil wells, where main experimental issues are related to opacity of the fluids and the sheer size of the system. The main objective is to track the propagation of a fluid-fluid interface during a two-fluid displacement process, and thereby to characterize the efficiency of the displacement process. We describe the implementation and use of an array of electrical conductivity probes, and demonstrate with examples how the signals can be used to recover relevant information about the displacement process. To our knowledge this is the most extensive use of this measurement method for studying displacement in a large-scale laboratory setup. Optical measurements and visual observations are challenging and/or costly in such large-scale systems, but can still provide qualitative information as shown in this article. Using electrical conductivity probes is a robust and fairly low-cost experimental method for characterizing fluid-fluid displacement in large-scale systems.

The inverse modeling problem

SIMULATION ◽  
1970 ◽  
Vol 15 (6) ◽  
pp. 264-268 ◽  
Author(s):  
Bernard C. Patten
Keyword(s):  
Real World ◽  
Inverse Modeling ◽  
Simulation Modeling ◽  
Large Scale ◽  
State Variables ◽  
Large Scale Systems ◽  
Natural Systems ◽  
Valid Model ◽  
The Relationship ◽  
Definite Solution

In simulation modeling of very large-scale systems, such as social and natural systems, reductions in scale must be so severe that state variables of the abstraction (model) often cannot be translated back to variables that have real-world significance. Model behavior may not much resemble anything that occurs naturally. If y is a real system and x a model of it, the two can be viewed as related by a set of homomorphic corres pondences M. Then, xMy means x "is a model of" y. Behavior of x pertains to that of y only as M is a valid model, and the relationship is implicit in an inverse model M-1, defined from the fact that xMy implies yM-1x (y "is modeled by" x). To make it explicit, that is to interpret model behavior in terms of real-world variables, means in some sense to be able to identify M-1. One approach to estimating it is suggested, but a definite solution is not reached.

Decentralized Semi-Global Stabilization of Large-Scale Nonlinear Systems with Mixed-Order Nonlinearities

2011 ◽  
Vol 291-294 ◽  
pp. 1555-1558
Author(s):  
Hui Ye ◽  
Jun Yong Zhai
Keyword(s):  
Nonlinear Systems ◽  
Lower Order ◽  
Output Feedback ◽  
Large Scale ◽  
Output Feedback Control ◽  
Global Stabilization ◽  
Large Scale Systems ◽  
Mixed Order ◽  
Simulation Results ◽  
Lower Order Terms

This paper considers the problem of semi-global decentralized output feedback control of large-scale systems with subsystems interconnected by nonlinearities which are functions of the measurable and immeasurable. The distinguishing factor of this paper is that the nonlinearities are allowed to have both higher-order and lower-order terms, to which the existing design schemes are inapplicable. Simulation results are given to demonstrate the validity of the proposed method.

scholarly journals Use cases for COVID-19 screening and surveillance with rapid antigen-detecting tests: a systematic review

2021 ◽  
Author(s):  
Apoorva Anand ◽  
Jacob Bigio ◽  
Emily MacLean ◽  
Talya Underwood ◽  
Nitika Pant Pai ◽  
...  
Keyword(s):  
Systematic Review ◽  
Real World ◽  
Large Scale ◽  
Low Cost ◽  
Risk Of Bias ◽  
Use Cases ◽  
Global Alliance ◽  
Prevalence Survey ◽  
Screening And Surveillance ◽  
Wide Range

Introduction: Testing is critical to controlling the COVID-19 pandemic. Antigen-detecting rapid diagnostic tests (Ag-RDTs) that can be used at the point of care have the potential to increase access to COVID 19 testing, particularly in settings with limited laboratory capacity. This systematic review synthesized literature on specific use cases and performance of Ag RDTs for detecting SARS-CoV-2, for the first comprehensive assessment of Ag RDT use in real-world settings. Methods: We searched three databases (PubMed, EMBASE and medRxiv) up to 12 April 2021 for publications on Ag-RDT use for large-scale screening, irrespective of symptoms, and surveillance of COVID-19, excluding studies of only presumptive COVID-19 patients. We tabulated data on the study setting, populations, type of test, diagnostic performance and operational findings. We assessed risk of bias using QUADAS-2 and an adapted tool for prevalence studies. Results: From 4313 citations, 39 studies conducted in asymptomatic and symptomatic adults were included. Study sample sizes varied from 40 to >5 million. Of 39 studies, 37 (94.9%) investigated lateral flow Ag-RDTs and two (5.1%) investigated multiplex sandwich chemiluminescent enzyme immunoassay Ag-RDTs. Six categories of testing (screening/surveillance) initiatives were identified: mass screening (n=13), targeted screening (n=11), healthcare entry testing (n=6), at-home testing (n=4), surveillance (n=4) and prevalence survey (n=1). Across studies, Ag-RDT sensitivity varied from 40% to 100%. Ag-RDTs were noted as convenient, easy-to-use and low cost, with a rapid turnaround time and high user acceptability. Risk of bias was generally low or unclear across the studies. Conclusion: This systematic review demonstrates the use of Ag-RDTs across a wide range of real-world settings for screening and surveillance of COVID-19 in both symptomatic and asymptomatic individuals. Ag-RDTs were overall found to be easy-to-use, low cost and rapid tools, when consideration is given to their implementation and interpretation. The review was funded by FIND, the global alliance for diagnostics.

scholarly journals H∞Filter Design for Large-Scale Systems with Missing Measurements

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Ying Zhou ◽  
Shuming Yang ◽  
Qiang Zang
Keyword(s):  
Large Scale ◽  
Filter Design ◽  
Sufficient Conditions ◽  
Linear Matrix ◽  
Matrix Inequality ◽  
Mean Square ◽  
Missing Measurements ◽  
Large Scale Systems ◽  
Error System ◽  
Simulation Results

This paper is concerned withH∞filter design problem for large-scale systems with missing measurements. The occurrence of missing measurements is assumed to be a Bernoulli distributed sequence with known probability. The new full-dimensional filter is designed to make the filter error system exponentially mean-square stable and achieve a prescribedH∞performance. Sufficient conditions are derived in terms of linear matrix inequality (LMI) for the existence of the filter, and the parameters of filter are obtained by solving the LMI. Finally, the numerical simulation results illustrate the effectiveness of the proposed scheme.

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