Multiscale entropy-based methods have made great progress in the field of health condition monitoring and fault diagnosis of machines due to their powerful feature representation capabilities. ...However, existing multiscale entropy methods suffer from three major obstacles: high fluctuation under large scale-factor, loss of high-frequency information, and poor robustness to noises. Thus, this work proposes a symbol-scale analysis method to deal with the above problems. In one aspect, to capture fault features from the time series over multiple time scales, time-delay process of different intervals is utilized to obtain long-term features and short-term features. In the other aspect, symbol-scale analysis introduces a symbolization procedure and maps time series into a corresponding sequence of symbols to overcome the limitation of weak fault extraction under a low-signal-to-noise ratio environment. Moreover, the symbol-scale entropy approach is developed by integrating with diversity entropy, called symbol-scale diversity entropy. The effectiveness of the proposed strategy is intensively validated using two simulated signals and experimental cases. Results demonstrate its advantages in dynamic change tracking ability and calculation efficiency by comparing it with other state-of-the-art entropy methods. Apart from diversity entropy, the versatility of incorporating the proposed symbol-scale analysis and other entropy methods is also verified using experimental data.
This paper analyzes the information delivery delay for the purpose of roadside unit (RSU) deployment in a vehicular ad hoc network (VANET) with intermittent connectivity. A mathematical model is ...developed to describe the relationship between the average delay for delivering road condition information and the deployment distance between two neighbor RSUs. The derived mathematical model considers a sparse highway scenario where two neighbor RSUs are deployed at a distance without a direct connection, and vehicles are sparsely distributed on the road with road condition information randomly generated between the two neighbor RSUs. Moreover, the model takes into account the vehicle speed, the vehicle density, the likelihood of an incident, and the deployment distance between two neighbor RSUs. The correctness and accuracy of the derived mathematical model is verified, and the impacts of different parameters on the average information delivery delay are investigated through simulation results. Given an information delivery delay constraint for time-critical applications, this model can be used to estimate the maximum deployment distance allowed between two neighbor RSUs, which can provide a reference for the deployment of RSUs in such scenarios.
Airport operators need good capacity estimates for many purposes, including to bolster applications for funding support for capacity improvements. Based on a recognized need to enhance models for ...estimating the operating capacity of airports serving a user base of smaller aircraft, such as small general aviation airports, this paper describes research conducted to leverage automated dependent surveillance-broadcast (ADS-B) data to develop aircraft performance characteristics for use as inputs to future small airport capacity models. The research addresses this challenge by constructing home-built ADS-B data collection units using a Raspberry Pi-based hardware platform and an Amazon Web Services-based cloud architecture housing the study’s PostGreSQL database, and python-based codebase. The work was focused at three participating airports: The Ohio State University Airport in Columbus, OH (KOSU); College Park, MD (KCGS); and Republic Airport in Farmingdale, NY (KFRG). The hardware units were deployed at three study airports, collecting more than 90 million individual ADS-B messages transmitted by aircraft operating within the vicinity of the study airport. Models were developed to clean, process, and assess the data, and leveraged to determine aircraft performance characteristics within these environments. Initial work focusing on assessing the fleet mix, approach speeds, aircraft separation in arrival streams, and runway occupancy times was performed. Findings from this research revealed a very high accuracy and richness of collected and processed data, and performance metrics that were reasonable, valid, and applicable for use as inputs to future airport capacity models.
In this paper, we report the development of time‐delay analysis method of inductance and capacitance for microfluidic circuit. The sensor used in this method is composed of the sensing inductor (SI) ...and the sensing capacitor (SC) with a microfluidic circuit. This sensor measures inductance and capacitance in a time difference by delaying with microfluidic circuit. We confirmed that SI and SC have different responses to conductive and dielectric solution. This research is expected to be applied to the combined analysis of liquid samples.
We first investigate the accumulated loopback self-interference (ALSI) under amplify-and-forward (AF) protocol in two-way full-duplex (TWFD) relaying systems with simultaneous wireless information ...and power transfer (SWIPT). We analyze how SWIPT affects ALSI and establish the condition for ALSI to converge when there is no energy buffer. Unlike ALSI in TWFD relaying without SWIPT (Chang et al. , 2019), ALSI in TWFD relaying with SWIPT always converges and does not grow unbounded. In addition, we study the delay performance in such a system under AF and decode-and-forward (DF) protocols. In AF protocol, the condition for successful signal transmissions is provided. When that condition is met, the received signals at the relay can always get through the channels but experience delays. Otherwise, the outage event occurs. In DF protocol, the best-effort scenario (having no energy buffer) and the QoS scenario (having energy buffer) are discussed. The probability of successful transmissions and the distribution of the delay in both scenarios are derived. Simulation results of DF protocol show that the best-effort scenario is suitable for the delay-tolerant service and the QoS scenario is suitable for the delay-sensitive service. Furthermore, AF protocol is more suitable for the service with less QoS demanding.
The use of a data network in a control loop has gained increasing attentions in recent years due to its cost effective and flexible applications. One of the major challenges in this so-called ...networked control system (NCS) is the network-induced delay effect in the control loop. Network delays degrade the NCS control performance and destabilize the system. A significant emphasis has been on developing control methodologies to handle the network delay effect in NCS. This survey paper presents recent NCS control methodologies. The overview on NCS structures and description of network delays including characteristics and effects are also covered.
Many construction projects suffer delays. Their delay risk exacerbates as projects become larger with more complex schedules, because of the ‘ripple effect’, the phenomenon that an individual ...activity delay can spread, accumulate, and quantifiably impact the project finish. Its magnitude depends on the intricate network schedule structure. Yet criticality is currently assessed based on static durations. And the criticality index merely counts occurrences in probabilistic simulation runs without considering an underlying dependency structure. This research therefore establishes a methodology to systematically study and track the dynamic phenomenon of the ripple effect. Its contribution to the body of knowledge is threefold: First, it develops measures that connect the activity and project levels within the structure to quantify the aforementioned ripple effect. Second, it explores cruciality in a variety of schedule structures and concludes that the cruciality is additive on sequential paths and in proportion to their variances on merges of parallel paths. Links other than the default finish-to-start links may cause an activity directionality to change or even be bypassed, which its cruciality will reflect correctly. Third, it substantiates results by simulating a benchmark schedule to give practical suggestions for delay avoidance that consider how the network structure shapes schedule behavior.
•Local delays of activities can impact global timeliness performance of network schedules.•Structure of networks with four link types is captured through binary reachability matrix.•Scaled covariance matrix captures additive delay contribution of activities to their paths.•Activity cruciality is newly defined as the product of reachability and scaled covariance.•Results show that the contribution of crucial activities to the ripple effect is quantifiable.
We employed discrete-event simulation with embedded multivariate statistical models for time and situation-dependent parameters to study the potential impact of regulating the release of planes from ...their terminal gates in peak periods to reduce congestion on ramps and taxiways at Charlotte Douglas International Airport, a major U.S. hub for of the world’s largest airline, American Airlines. Gate-holding strategies are one of several operational strategies to reduce aviation’s carbon footprint. They have been shown to reduce fuel consumption, air pollution, and greenhouse gas emissions, but past studies have concentrated on taxi times and fuel consumption of outbound aircraft without considering the potential disruptions on inbound traffic, which may be blocked from reaching their intended gates. We verified that reductions in outbound taxi times could be achieved without delaying the times when planes lifted off for departure but, depending on the gate-hold rules employed and the intensity of flight operations, more delays and gate changes occurred for arriving aircraft. Our models allow intensive examination of the tradeoffs involved in improving system performance with various strategies.
Performances analysis of resource management techniques and algorithms for edge computing is a crucial step that reveals the effectiveness of edge service placement and migration strategies in terms ...of delay and usage. To be able to gauge how different optimisations affect the end user quality of experience a holistic approach is needed, so that the end-to-end delay can be measured in a combined setup where the edge infrastructure is integrated in the 5G system architecture. For these purposes we put forward an open source workflow based on the integration of proven simulators as SUMO, OMNeT++ and CloudSim, that will provide the means to create large scale urban mobile simulation environments. This paper discusses the benefits and challenges of such an approach, and provides example results that showcase a few aspects of the potential end-to-end delay analysis by processing the gathered simulation output.
The satellite data relay networks (SDRNs) hold great promise in 6G communications for the timely offloading of the global traffic. Since the delay performance is regarded as one of the most important ...metrics reflecting the offloading efficiency, studying its relationship with network parameters becomes really essential to the development and application of the SDRN. However, the complex data offloading process and heterogeneity of traffic arrivals and transmission links pose many challenges to the stochastic delay analysis. To accurately model the data offloading process in SDRNs, we build a series-parallel queuing model with through and cross traffic while considering the propagation delay. On this basis, we respectively propose a propagation delay embedded min-plus convolution method based on stochastic network calculus and a Markov chain method based on Monte Carlo to depict the leftover services of the heterogeneous links received by the per-flow traffic in an aggregate. To eliminate the impacts of the heterogeneity, we uniformly characterize the arrivals and leftover services by their moment generating functions (MGFs) which contain the full moment information, and shield the heterogeneity by deriving the envelopes of the arrivals and leftover services with the help of MGFs, Chernoff bound and union bound. Then, in the light of the geometric relationship between the envelopes of the arrivals and leftover services, we analyze the upper bounds of the stochastic delay, which provides the guidance to the network configuration. Eventually, simulation results verify the effectiveness of the theoretical analysis and further reveal maximum four times the delay difference between the heterogeneous links influenced by traffic type, burstiness, and access number.
PDF
