Performance In Real Environment Research Articles

Analysis of the sensitivity of the identification method of inability states of rotating systems to the conditions of the experiment

One of the most important subsystems of the vehicles and machines operating currently in industry and transportation are the rotating subsystems. Monitoring of its technical state is an important issue of the engineering and academic research. As a result of the research a lot of new diagnostic methods have been formulated but one of the most important characteristic of them is the ability to industrial implementation. It depends on the insensitivity to disturbance which can arise in real operational environment. In the paper the method formulated by the authors is analysed. This is the method of the identification of inability states of rotating subsystems based on the vibrations analyses in the time domain. It constitutes the system approach to the considered issue. There are three applications of the method described - research on simulation laboratory stand, research on a real technical object conducted in the laboratory and research carried out on a real technical object under the real operation conditions. In each case different accuracy of the ability and inability states identification is achieved. Analysing the differences in accuracy of the method applications the conclusion of its sensitivity to the conditions of the experiment were formulated which are presented in the end of the paper.

Load assumption process for durability design using new data sources and data analytics

Durability engineering for vehicles is about relating the real operational loading and fatigue environment to the actual capability and strength capacity of the product and its parts. The statistical modelling of the usage loading distribution has always been a big challenge; the latter is necessary to derive statistically validated design targets. In the past, dedicated durability measurement campaigns were the only available data source to obtain durability loads. Nowadays, this has changed due to the increasing availability of new complementary data sources. We show how such data like field monitoring data and geographic data, along with the usage of new data analytics and simulation methods can be used to derive customer and usage related durability loads and targets.

A nonlinear Wiener degradation model integrating degradation data under accelerated stresses and real operating environment

Remaining useful life (RUL) prediction in real operating environment (ROE) plays an important role in condition-based maintenance. However, the life information in ROE is limited, especially for some long-life products. In such cases, accelerated degradation test (ADT) is an effective method to collect data and then the accelerated degradation data are converted to normal level of accelerated stresses through acceleration factors. However, the stresses in ROE are different from normal stresses since there are some other stresses except normal stresses, which cannot be accelerated, but still have impact on the degradation. To predict the RUL in ROE, a nonlinear Wiener degradation model is proposed based on failure mechanism invariant principle which is the precondition and requirement of an ADT and a calibration factor is introduced to calibrate the difference between ROE and normal stresses. Moreover, the unit-to-unit variability is considered in the concern model. Based upon the proposed approach, the RUL distribution is derived in closed form. The unknown parameters in the model are obtained by a new two-step method through fuzing converted degradation data in normal stresses and degradation data in ROE. Finally, the validity of the proposed model is demonstrated through several simulation data and a case study.

Modeling of CO2 Capture with Water Bubble Column Reactor

The demand for carbon capture is increasing over time due to rising CO2 levels in the atmosphere. Even though fossil emission could be decreased or even eliminated, there is a need to start removing CO2 from the atmosphere. The removed CO2 could be either stored permanently to a reservoir (CCS, Carbon Capture and Storage) or utilized as a raw material in a long-lasting product (CCU, Carbon Capture and Utilization). The capture of CO2 could be done by direct air capture, or capturing CO2 from biogenic sources. Amine absorption is the state-of-the-art method to capture CO2, but it has some drawbacks: toxicity, high heat demand, and sorbent sensitivity towards impurities such as sulfur compounds and degradation in cyclic operation. Another potential solvent for CO2 could be water, which is easily available and safe to use in many applications. The problem with water is the poorer solubility of CO2, compared with amines, which leads to larger required flow rates. This study analyzed the technical feasibility of water absorption in a counterflow bubble column reactor. A dynamic, one-dimensional multiphase model was developed. The gas phase was modeled with plug flow assumption, and the liquid phase was treated as axially dispersed plug flow. CO2 capture efficiency, produced CO2 mass flow rate, and the product gas CO2 content were estimated as a function of inlet gas and liquid flow rate. In addition, the energy consumption per produced CO2-tonne was calculated. The CO2 capture efficiency was improved by increasing the liquid flow rate, while the CO2 content in product gas was decreased. For some of the studied liquid flow rates, an optimum gas flow rate was found to minimize the specific energy consumption. Further research is required to study the integration and dynamical operation of the system in a realistic operation environment.

Sparse DOA Estimation for Directional Antenna Arrays: An Experimental Validation

In the literature, antenna arrays for direction of arrival (DOA) estimation are being theoretically optimized to maximize the number of sources that can be estimated for a given number of isotropic elements. In this work, coprime arrays with monopole and patch elements are designed and fabricated to evaluate the impact of antenna directivity and realistic antenna behavior on DOA estimation accuracy. Two DOA estimation algorithms, namely: MUSIC and Lasso are applied where the complex radiation patterns are incorporated within the steering matrix and then the received signal is modified accordingly. With four sources, a root mean square error (RMSE) of around 4 and 1 degrees is achieved at 5 dB with monopole and patch elements, respectively. Furthermore, a software-defined radio (SDR) platform is utilized to experimentally evaluate the real-time performance in realistic environments. It is shown that when the DOA deviates from the boresight, the estimation error increases due to antenna directivity. The performance of the patch array is better than its monopole counterpart due to the inherent multipath mitigation in the directive antennas and polarization purity of the two radiated electric filed components. Experimental results show that the RMSE in the DOA estimation of two sources using coprime array with monopole and patch elements is around 4 and 1 degrees, respectively.

SimLife model: introducing a new teaching device in endocrine surgery simulation

To evaluate the validity and reliability of an innovative training model for endocrine surgical procedures. A simulator training model for endocrine procedures (SimLife) was developed at an academic center. The model consisted of a realistic operating environment with a coherent simulated patient dynamized by pulsatile vascularization with simulated blood warmed to 37 °C, and ventilation. Training sessions were designed for adrenal and thyroid surgery, as well as neck dissection. The primary outcome of interest was to evaluate learners’ performance and satisfaction. Learners’ performance was evaluated based on a scoring scale that followed the Downing method for the assessment of competency. While learners’ satisfaction was evaluated using a Likert scale of 1 to 10 on four items (ease of learning, anatomic correspondence of landmarks, realism, and overall satisfaction). Participants were engaged in 32 training sessions. These included 24 adrenalectomies (conventional and laparoscopic both transabdominal and posterior), and 4 thyroid lobectomies with concomitant functional lateral compartment neck dissection. competency scores were procedure-specific addressing specific core components of a given procedure. Learners’ performance scored above average in all procedures evaluated. Satisfaction scores for the specified four items ranged between 8.43 (SD 0.87) and 8.89 (SD 0.96). No major events were reported for the adrenalectomies, while only one jugular vein injury occurred during neck dissection. SimLife is a hyper-realistic training model that allows for satisfactory acquisition of skills and the evaluation of performance progression. It has the potential to become a cornerstone in specialized surgical training.Electronic supplementary materialThe online version of this article (10.1007/s13304-020-00871-x) contains supplementary material, which is available to authorized users.

Benchmark-Based Reference Model for Evaluating Botnet Detection Tools Driven by Traffic-Flow Analytics.

Botnets are some of the most recurrent cyber-threats, which take advantage of the wide heterogeneity of endpoint devices at the Edge of the emerging communication environments for enabling the malicious enforcement of fraud and other adversarial tactics, including malware, data leaks or denial of service. There have been significant research advances in the development of accurate botnet detection methods underpinned on supervised analysis but assessing the accuracy and performance of such detection methods requires a clear evaluation model in the pursuit of enforcing proper defensive strategies. In order to contribute to the mitigation of botnets, this paper introduces a novel evaluation scheme grounded on supervised machine learning algorithms that enable the detection and discrimination of different botnets families on real operational environments. The proposal relies on observing, understanding and inferring the behavior of each botnet family based on network indicators measured at flow-level. The assumed evaluation methodology contemplates six phases that allow building a detection model against botnet-related malware distributed through the network, for which five supervised classifiers were instantiated were instantiated for further comparisons—Decision Tree, Random Forest, Naive Bayes Gaussian, Support Vector Machine and K-Neighbors. The experimental validation was performed on two public datasets of real botnet traffic—CIC-AWS-2018 and ISOT HTTP Botnet. Bearing the heterogeneity of the datasets, optimizing the analysis with the Grid Search algorithm led to improve the classification results of the instantiated algorithms. An exhaustive evaluation was carried out demonstrating the adequateness of our proposal which prompted that Random Forest and Decision Tree models are the most suitable for detecting different botnet specimens among the chosen algorithms. They exhibited higher precision rates whilst analyzing a large number of samples with less processing time. The variety of testing scenarios were deeply assessed and reported to set baseline results for future benchmark analysis targeted on flow-based behavioral patterns.

Electrically Small Platform-Based Antennas for an Unmanned Ground Vehicle

We present a design strategy for platform-based antennas operating on electrically small platforms such as unmanned ground vehicles (UGVs). Specifically, we report the design of a platform-based antenna operating at the lower end of the very-high-frequency (VHF) band for a small UGV with physical dimensions of 99 cm × 67 cm × 39 cm. The antenna is mounted on the bottom of the platform resulting in an extremely low-profile design and generating vertically polarized, monopole-like radiation patterns. Using characteristic-mode theory (CMT), performance metrics of the antenna including its maximum potential bandwidth and radiation patterns are investigated. The performance of the antenna when operating in a realistic operational environment is analyzed using full-wave electromagnetic simulations. A full-scale prototype of the antenna mounted on the bottom of the vehicle was fabricated and experimentally characterized. Finally, the design of this low-profile antenna is extended to a two-element antenna array mounted on the same platform and a prototype of this two-element array was fabricated. Basic experiments were conducted to study impedance matching and mutual coupling effects in this electrically small antenna array. The performance of this array as part of a two-element direction-finding system was investigated through computer simulations.

CORA hand: a 3D printed robotic hand designed for robustness and compliance

This work presents design and experimental evaluation of CORA (COmpliant Robotic hAnd), a robotic hand designed for easy manufacturing and maintenance, and for robustness and compliance in real operational environments. It takes advantage of recent soft-polymer printable filaments to obtain intrinsic compliance during grasping and accidental contacts. All parts are designed and optimized for manufacturing with conventional fused deposition modeling 3D printers, in order to allow simple fabrication and replacement of parts. In this paper design of the CORA hand is presented, focusing on specific design solutions adopted for improving robustness of the final 3D printed parts and for obtaining compliance in interaction with the environment. A prototype of the CORA hand was built and experimentally tested in terms of grasping capabilities, measuring contact forces and the distributed grasping pressure. Compliance introduced by soft polymer links was evaluated with finite element method simulation and experimental bending tests. A collision test evidenced robustness of the finger mechanism and transmission to pronounced passive deformations, induced by lateral contacts possibly occurring in common manipulation tasks.

On the oxygen vacancies optimization through Pr co-doping of ceria-based electrolytes for electrolyte-supported solid oxide fuel cells

Praseodymium-doped ceria electrolyte powders are synthesized by a co-precipitation method using ammonium carbonate in little excess to fabricate a stable electrolyte-supported solid oxide fuel cell able to operate in hydrogen conditions. Raman and X-ray Photoelectron Spectroscopy are employed for the electrolyte characterization to check the distribution of vacancies and the initial oxidation state of Pr that influences the transport mechanism under the real operation of SOFCs. The optimum Pr concentration in the electrolyte is found to be 6 mol% of Pr and 14 mol% of Gd (sample 6Pr). The electrolyte-supported cells fabricated with this composition are sintered at 1250 °C for 3 h and tested in different gas conditions and operating temperatures, showing a maximum power density of 305.31 mW·cm-2 at 530.36 mA·cm-2 (750 °C) in wet hydrogen conditions. Compared to standard cells fabricated with a gadolinium-doped ceria electrolyte sintered at 1500 °C, the 6Pr has long term stability performances with a power density loss of 17% after 100 h of operation. The results demonstrate the eligible use of this electrolyte under real operating environments.

Practical Quick File Server Migration

Regular file server upgrades are indispensable to improve performance, robustness, and power consumption. In upgrading file servers, it is crucial to quickly migrate file-sharing services between heterogeneous servers with little downtime while minimizing performance interference. We present a practical quick file server migration scheme based on the postcopy approach that defers file copy until after switching servers. This scheme can (1) reduce downtime with on-demand file migration, (2) avoid performance interference using background migration, and (3) support heterogeneous servers with stub-based file management. We discuss several practical issues, such as intermittent crawling and traversal strategy, and present the solutions in our scheme. We also address several protocol-specific issues to achieve a smooth migration. This scheme is good enough to be adopted in production systems, as it has been demonstrated for several years in real operational environments. The performance evaluation demonstrates that the downtime is less than 3 seconds, and the first file access after switching servers does not cause a timeout in the default timeout settings; it takes less than 10 seconds in most cases and up to 84.55 seconds even in a large directory tree with a depth of 16 and a width of 1,000. Although the total migration time is approximately 3 times longer than the traditional precopy approach that copies all files in advance, our scheme allows the clients to keep accessing files with acceptable overhead. We also show that appropriate selection of traversal strategy reduces tail latency by 88%, and the overhead after the migration is negligible.

Dynamic behaviour of piezoelectric nanoribbons with wavy configurations on an elastomeric substrate

To meet the great needs for high-performance of piezoelectric nano-scaled structures, the study of their dynamic behaviour is essential in the design of stable and controllable nano-devices, such as energy harvesters, actuators and so on. Brittle wrinkled thin nanoribbons of lead zirconate titanate (Pb(Zr1−xTix)O3, abbreviated as PZT) bound to an elastomeric substrate form a wavy configuration, whose amplitude and wavelength can be designed to accommodate different deformation ranges that would suit real operating environments, including vibration. In this paper, the PZT nanoribbon is modelled as an elastic nonlinear beam with von Karman approximation, and the elastomeric substrate is modelled as a semi-infinite linear elastic medium. Electrical-mechanical coupling is considered in the constitutive relation of the PZT nanoribbon. By utilizing the extended Lagrangian principle, the equation of motion of the PZT nanoribbon-substrate structure with damping, which can more accurately characterise the electromechanical dynamic behaviour of the structure, is derived. To evaluate the dynamic performance of the partly buckled structure, the symplectic Runge–Kutta method (SRK), which has been developed to solve linear damped ordinary differential equations, is adopted to solve the corresponding equations. Bifurcation diagrams are depicted, and the effects of the applied voltage and pre-strain to the elastomeric substrate on the static bifurcation are analysed, indicating that the pre-strain can easily induce surface wrinkling and the applied voltage can be used to more precisely control surface wrinkling. Moreover, the effect of damping on the dynamic behaviour is discussed through the results of time histories and phase portraits for different values of the applied voltage and pre-strain, confirming that as time progresses, the motion gradually vanishes around the static buckling amplitude. The conclusions of this study are useful for the wavy-design strategy of the PZT nanostructure-based stretchable electronics devices, and for the prediction and passive control of the dynamic behaviour of these devices.

Morphology and mechanisms of cavitation damage on lamellar gray iron surfaces

Engine parts in contact with liquids may suffer cavitation erosion damage. Understanding its mechanisms in realistic operating environments is necessary for improvements in the service life and durability of materials for heavy-duty diesel engines. This work illustrates the cavitation erosion behavior of a cylinder liner material with a follow-up of detailed, high-magnification SEM images of damaged sites on the surface. The cylinder liner encloses the piston and combustion chamber in the engine of large trucks and its material of choice is usually a lamellar gray cast iron, its microstructure consisting of flake-shaped graphite, a pearlitic matrix and some steadite. Testing was carried out using an ultrasonic vibratory apparatus, and the liquid of choice was a commercial engine coolant composed of water, glycol and inhibitors. Based on observations of tested surfaces, a sequence of damage patterns is proposed as an explanation of the material’s cavitation erosion behavior. Initiation consists of: chipping at graphite cluster centers, graphite flake removal, pitting along graphite flakes and direct matrix pitting. Development consists of: evolution of chipped spots into matrix-damaging pits, radial pit expansion, pit merging and surface roughening. It can be concluded that presence and morphology of graphite are critical to the cavitation erosion behavior of LGI.

Implementing The Abstract MAC Layer in Dynamic Networks

Dynamicity is one of the most challenging, yet, key aspects of wireless networks. It can come in many guises, such as churn (node insertion/deletion) and node mobility. Although the study of dynamic networks has been popular in distributed computing domain, previous works considered only partial factors causing dynamicity. In this work, we propose a dynamic model that is comprehensive to include crucial dynamic factors on nodes and links. Our model defines dynamicity in terms of localized topological changes in the vicinity of each node, rather than a global view of the whole network. Obviously, a localized dynamic model suits distributed algorithm studies better than a global one. The proposed dynamic model makes use of the more realistic SINR model to describe wireless interference, instead of the oversimplified graph-based models adopted by most existing research. Under the proposed dynamic model, we develop an efficient distributed algorithm accomplishing local broadcast services in the abstract MAC layer that was first presented by Kuhn <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> <xref ref-type="bibr" rid="ref24" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[24]</xref> . Our solution paves the way for many new fast algorithms to solve high-level problems in dynamic networks, such as consensus, single-message broadcast, and multiple-message broadcast. Extensive simulation studies indicate that our algorithm exhibits good performance in realistic environments with dynamic network behaviors.

Aggregate Impact of Anomalous Noise Events on the WASN-Based Computation of Road Traffic Noise Levels in Urban and Suburban Environments.

Environmental noise can be defined as the accumulation of noise pollution caused by sounds generated by outdoor human activities, Road Traffic Noise (RTN) being the main source in urban and suburban areas. To address the negative effects of environmental noise on public health, the European Environmental Noise Directive requires EU member states to tailor noise maps and define the corresponding action plans every five years for major agglomerations and key infrastructures. Noise maps have been hitherto created from expert-based measurements, after cleaning the recorded acoustic data of undesired acoustic events, or Anomalous Noise Events (ANEs). In recent years, Wireless Acoustic Sensor Networks (WASNs) have become an alternative. However, most of the proposals focus on measuring global noise levels without taking into account the presence of ANEs. The LIFE DYNAMAP project has developed a WASN-based dynamic noise mapping system to analyze the acoustic impact of road infrastructures in real time based solely on RTN levels. After studying the bias caused by individual ANEs on the computation of the A-weighted equivalent noise levels through an expert-based dataset obtained before installing the sensor networks, this work evaluates the aggregate impact of the ANEs on the RTN measurements in a real-operation environment. To that effect, 304 h and 20 min of labeled acoustic data collected through the two WASNs deployed in both pilot areas have been analyzed, computing the individual and aggregate impacts of ANEs for each sensor location and impact range (low, medium and high) for a 5 min integration time. The study shows the regular occurrence of ANEs when monitoring RTN levels in both acoustic environments, which are especially common in the urban area. Moreover, the results reveal that the aggregate contribution of low- and medium-impact ANEs can become as critical as the presence of high-impact individual ANEs, thus highlighting the importance of their automatic removal to obtain reliable WASN-based RTN maps in real-operation environments.

A Prognostic Framework for Wheel Treads Integrating Parameter Correlation and Multiple Uncertainties

As crucial rotary components of high-speed trains, wheel treads in realistic operation environment usually suffer severe cyclic shocks, which damage the health status and ultimately cause safety risks. Timely and precise health prognosis based on vibration signals is an effective technology to mitigate such risks. In this work, a new parameter-related Wiener process model is proposed to capture multiple uncertainties existed in on-site prognosis of wheel treads. The proposed model establishes a quantitative relationship between degradation rate and variations, and integrates uncertainties via heterogeneity analysis of both criterions. A maximum-likelihood-based method is presented to initialize the unknown model parameters, followed by a recursive update algorithm with fully utilization of historical lifetime information. An investigation of real-world wheel tread signals demonstrates the superiority of the proposed model in accuracy improvement.

Standing Passenger Comfort: A New Scale for Evaluating the Real-Time Driving Style of Bus Transit Services

On-board bus comfort is a key factor affecting the quality of transit service. Thus, its assessment is crucial for public transport companies, as it can support the monitoring, evaluation and implementation of specific actions to improve their services. Previous research mainly focused on separate subjective and objective measurements of on-board comfort. Furthermore, even if concurrent measurements of objective and subjective on-board comfort have been collected, no study has built a gradual scale for the real-time measurement of comfort. This paper covers this gap by integrating subjective measurements of driving style with objective measurements of longitudinal and transversal accelerations collected by intelligent transportation system tools. These findings are very useful because they represent the first contribution for establishing a comfort scale in a real operational environment as a tool to regulate driver behavior, i.e., each driver will be able to recognize when passengers experience conditions of discomfort and acts to improve comfort.

Effect of heat flux on boundary layer flow under rotating conditions

The boundary layer flow behaviour in a smooth rotating channel with heated walls is measured by particle image velocimetry (PIV). To simulate the real operation environment of an internal coolant channel in a turbine blade, airflow is analysed in a rotating channel, whose four walls are uniformly heated by Indium Tin Oxide (ITO) glass. The flow is measured in the middle plane of the rotating channel with a Reynolds number equal to 10000 and rotation numbers ranging from 0 to 0.52. The results are presented for the boundary layer flow behaviour with and without heated thermal boundary conditions. The buoyancy force generated by the heated walls influences the flow behaviour under rotating conditions. Separated flow occurs, which substantially influences the turbulent flow behaviours. Sometimes, this buoyancy force can determine the flow behaviours. The results also showed that the displacement thickness and the momentum loss thickness present new changes at different radius positions due to the heated thermal boundary conditions. The displacement thicknesses of both the leading and trailing sides with heated walls are both thicker than those of the leading and trailing sides without heated walls. Then, the difference of the boundary layer thickness between these two cases increases with the increase of rotation number. For momentum loss thickness, a sharp drop happens when the rotation number increases to a certain value. At the large radius position, the drop in momentum loss thickness is much greater than that in the small radius position.

Dual-Probe Near-Field Phaseless Antenna Measurement System on Board a UAV.

On-site antenna measurement has been recently attracting an increasing interest in order to assess the antenna performance in real operational environments. The complexity and cost of these kind of measurements have been significantly cut down due to recent developments in unmanned aerial vehicles’ (UAVs) hardware and antenna measurement post-processing techniques. In particular, the introduction of positioning and geo-referring subsystems capable of providing centimeter-level accuracy together with the use of phase retrieval techniques and near-field to far-field transformation algorithms, have enabled near field measurements using UAVs. This contribution presents an improved UAV-based on-site antenna measurement system. On the one hand, the simultaneous acquisition on two measurement surfaces has been introduced and calibrated properly, thus reducing geo-referring uncertainties and flight time. On the other hand, the positioning and geo-referring subsystem has been enhanced by means of a dual-band real time kinematics (RTK) unit. The system capabilities were validated by measuring an offset reflector antenna, and the results were compared with the measurements at the spherical range in the anechoic chamber and with the measurements collected with a previous version of the implemented system.

Biological nutrient removal from slaughterhouse wastewater via nitritation/denitritation using granular sludge: an onsite pilot demonstration

AbstractBACKGROUNDIn this study, an onsite pilot sequencing batch reactor (SBR) of 450 L was operated at a local Flemish slaughterhouse in two consecutive periods. During period I, nitrogen removal via nitritation/denitritation (Nit/DNit) was achieved by the use of an innovative startup strategy without seed sludge and subsequently maintained by the use of aeration phase length control based on the oxygen uptake rate (OUR). In period II, the operational strategy was modified. In order to obtain Nit/DNit granular sludge (GS), an anaerobic (feast) feeding was introduced followed by a dynamic controlled (OUR‐based) aerobic (famine) reaction step.RESULTSAfter 74 days, the local (Flemish) legislation standards for COD (125 mg O2 L−1) and T‐N (15 mg N L−1) were fulfilled. During period II, floccular sludge was partially transformed into GS, which resulted in increased COD and NH4‐N conversion rates of 50 and 60% respectively. Average removal efficiencies for SCOD, N and P during period II were 89.5 ± 4.2, 88.8 ± 9.8 and 84.4 ± 9.3% respectively. Despite the relatively low biomass concentrations (2.5 g L−1), excellent sludge settling was reported, with SVI30 &lt; 100 mL g−1 from day 167 onwards. Moreover, it was found that the operational strategy and temperature variability had a crucial impact on the microbial community dynamics and granule growth.CONCLUSIONThis study demonstrated the Nit/DNit BNR‐GS system in a real operational environment through the operation of an onsite pilot plant. © 2019 Society of Chemical Industry