bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Analysis of Nitinol Peripheral Artery Stents Under Complex Loads
Authors: Chen Yanlong , Feng Haiquan , Zhang Hailu , Su Juan , Wang Lin
Published: September 2024

The complex deformation of a peripheral arterial stent during limb movements is the main reason for its fatigue fracture. The aim of this study is to explore the impact of complex loads on the fatigue behavior and life of lower limb arterial stents. Specifically, the finite element simulation was adopted to compare and analyze the fatigue performance of three stents under five superimposed loads. Besides, the life and the fatigue crack growth life of these stents were predicted. It demonstrated that the bending load superimposed on other loads exerted a significant impact on the fatigue performance of these stents. The “spiral” structure design of the stent helped to improve the fatigue durability under complex deformations. Moreover, the prediction method for fatigue crack growth life is relatively conservative, which accounted for approximately 65–97% of the full life. The work provides important references for the fracture assessment and the optimization design of structure of stents.
A Comparative Evaluation of New and Used Dental Explorer Working Tips
Authors: Valeri Arthur S. , Cage Charlie E. , Donovan Terrence E.
Published: September 2024

The dental explorer medical device assists multiple functions, including marginal assessment. The working tip quality of this instrument has been previously established as a factor affecting operator judgment. However, little data exists to demonstrate the actual quality of working tips in clinical practice. The purpose of this study is to investigate and quantify if any real, measurable differences of the explorer working tip dimension exist among such instruments currently in service and compare to published medical device industry standards. Twenty new #23 dental explorer instruments from two manufacturers served as controls and sixty-three instruments in circulation at a dental school clinic were observed using light microscopy. The instruments were measured 50 micrometers from the terminus. A one-way analysis of variance (ANOVA) was performed to analyze values among groups. No statistically significant difference between the mean working tip dimension of new instruments was detected between brands. However, statistically significant differences between new and used instruments were detected regardless of brand. The range of values was 92.5–227.5 micrometers with average used instrument tip estimated over 50% wider than the average new instrument. These findings imply that other studies employing a dental explorer may be confounded if the instrument is not measured. Furthermore, the results of this study should serve as a motivating factor toward future research to update quality standards regarding the medical device with a goal of defining acceptable dimensions of the instrument working tip for certain applications in relation to clinical performance and expected outcomes.
Numerical Investigation of CO and NO Production From Premixed Hydrogen/Methane Fuel Blends
Authors: Singh Sanjana , Rajagopalan Haripriya , Emerson Benjamin , Noble David , Steele Robert , Lieuwen Tim C.
Published: September 2024

There is significant interest in utilizing hydrogen as an energy carrier in a net-zero carbon energy economy. A variety of fundamental and practical issues associated with premixed hydrogen/methane combustion must be addressed, particularly flame flashback, combustion instabilities, and NOx emissions. Significantly less attention has been given to CO emissions from hydrogen blending. However, recent H2 blending engine tests have clearly noted major reductions in CO emissions, reductions which substantially exceed what would be expected based upon C atom mass balances in the fuel. Moreover, NOx, CO, and combustor operability always tradeoff with each other, and so, for example, these CO reductions can also enable operational or design modifications to reduce NOx emissions and/or wider operability windows. This paper addresses H2 blending effects on CO emissions, addressing both the direct influences on CO emissions, as well as how it influences NOx–CO tradeoffs. The paper presents computations that differentiate between the kinetic and equilibrium effects of H2 blending, as well as how H2 blending can lead to reductions in both NOx and CO by moving the Pareto front downward. Finally, this work suggests that H2 blending, in addition to its CO2 reductions, can also increase plant operational flexibility and so provide additional value propositions to an evolving electricity market.
Performance Improvement of a Heat Sink for Battery Thermal Management System
Authors: Rasimarzabadi Faezeh , Azarkish Hassan , Crain Alexander , Recoskie Steven , Bordatchev Evgueni , Shirazy Mahmood
Published: September 2024

Dissipating heat generated by onboard battery systems is a key thermal management challenge for hybrid/electric aircraft. The National Research Council Canada is collaborating with Calogy Solutions, Ltd. (Sherbrooke, Quebec, Canada) to support their development of a novel aviation battery module. The goal of the project is to optimize the heat sink design for battery thermal management system by minimizing thermal resistance as well as reducing overall weight, considering fabrication cost to be used by the industry. In this research, the original heat sink used by Calogy (plate-fin type) was numerically simulated using commercial software and the results were compared with the experiment. This was done to validate the numerical simulation was accurate enough to be used for future simulations. The heat transfer of the heat sink was enhanced by optimizing fin dimensions and spacing, and fin design modification (a first in this application), based on system analysis of a kW scale hybrid/electric aircraft. The selected model as the optimized heat sink resulted in about 34% improvement in heat transfer coefficient, and about 24% reduction in weight comparing with the original plate-fin type heat sink.
Investigation of an Ammonia-Fueled SOFC-mGT Hybrid System: Performances Analysis and Comparison With Natural Gas-Based System
Authors: Anfosso Chiara , Crosa Silvia , Iester Federico , Bellotti Daria , Magistri Loredana
Published: September 2024

Hybrid systems (HS) are highly attractive in power generation due to their potential for higher power outputs and efficiencies by integrating different technologies. Among solid oxide fuel cell (SOFC) plants, the SOFC-Micro-Gas Turbine (mGT) system is particularly innovative. In this setup, the SOFC replaces the mGT combustion chamber, with an afterburner completing fuel combustion before the expander. Various configurations and control systems have been explored over the years, and prototypes have demonstrated satisfactory efficiency. However, these systems have predominantly used NG and Biogas, which do not achieve zero carbon emissions. The growing global demand for carbon-free energy production is increasing, highlighting the importance of alternative fuels in the power generation sector: among them, thanks to its chemical and physical properties, ammonia is gaining more and more interest. This work investigates an innovative ammonia-to-power system based on an SOFC-mGT HS, focusing on thermodynamic parameters, system features, and technical and environmental challenges. A MATLAB/Simulink model, built on a validated HS model fueled by NG, was developed to analyze the new system configuration. This configuration replaces the SOFC prereformer with an ammonia cracker, allowing for the exploration of anode gas recirculation effects and optimal system design. Key operating parameters such as anodic recirculation factor, fuel utilization, performance, and gas turbine characteristics are discussed. Finally, a comparison is made between hybrid systems and mGTs powered by methane, biogas, and ammonia.
Thermal Load Control in High-Temperature Heat Pumps: A Comparative Study
Authors: Pettinari Matteo , Frate Guido Francesco , Ferrari Lorenzo , Yücel Fatma Cansu , Tran A. Phong , Stathopoulos Panagiotis , Kyprianidis Konstantinos
Published: September 2024

High-temperature heat pumps (HTHPs) are becoming increasingly relevant in the industry as they represent a promising solution for decarbonizing industrial heat. These technologies can enable the electrification of industrial processes by exploiting electricity from renewables to provide process heat at temperatures above 250 °C, as in the case of emerging Brayton-based HTHPs. To succeed in this purpose, HTHPs must also ensure operational flexibility, which entails the ability to operate safely under varying loads and promptly respond to fluctuations in demand, while maintaining high efficiencies. Moreover, the ability to provide large flexible electric loads to transmission system operators has the potential to unlock innovative business cases and further promote the use of these systems. Common control strategies for achieving this include employing bypass mechanisms, fluid inventory control, and adjusting turbomachinery rotational speeds. Despite their variety, the simultaneous use of such control strategies is often limited as they may lead to significantly different system behaviors, both in terms of transient and steady performance. In this paper, rotational speed and fluid inventory control are examined from a transient perspective to maintain the desired sink temperature while regulating the thermal load of a novel Brayton-based HTHP. A comprehensive dynamic model of the system is proposed and leveraged to numerically test the two control approaches, aiming to provide insights for forthcoming experimental investigation. Results indicate that rotational speed control leads to negligible sink temperature residuals, while fluid inventory control better preserves the HTHP performances for varying temperature glides.
Assessment of the Wilshire-Cano-Stewart Model Using Strain Energy Density Dissipation
Authors: Pellicotte Jacob , Hossain Md Abir , Cano Jaime , Stewart Calvin M.
Published: September 2024

In this study, strain energy density (SED) is employed as a creep damage parameter to calibrate the Wilshire-Cano-Stewart (WCS) model. The WCS model is an adaptation of the Wilshire equations combined with continuum damage mechanics to enable predictions of creep deformation and damage. In WCS, the analytical calibration methods for the Wilshire equations remain unchanged and the additional damage parameters are found using numerical optimization. Though the WCS model can accurately predict progressive creep deformation, the damage remains phenomenological. Herein, damage is represented as SED. In SED, it is assumed that a material system has a finite amount of energy per unit volume that can be dissipated before failure. Assuming that SED is caused by the accumulation of microstructural defects, the damage process is represented as a scalar value from zero (undamaged) to unity (rupture). By combining the WCS model with SED, damage evolution is pinned physically and can be measured experimentally. Stress rupture, minimum-creep-strain-rate, and creep deformation data are gathered for alloy P91 at 600 °C and stresses from 100 to 200 MPa. The Wilshire constants are analytically determined and compared with the literature. The damage-trajectory constant is calibrated using SED measurements. The new calibration accurately predicts the material response across the range of stresses and temperatures. A comparison between numerical optimization and measured damage-trajectory constants is performed. Parametric simulations verify the interpolation and extrapolation capabilities of this new approach.
Vaneless Diffuser Modeling for Real Gas Supercritical Carbon Dioxide Flows: Need for a Data-Driven Approach
Authors: Seshadri Lakshminarayanan , Kumar Pramod
Published: September 2024

In this work, a real gas-based vaneless diffuser (VLD) differential equation model is presented. The model requires the specification of the skin friction coefficient as input. However, the use of standard VLD friction coefficient estimation expressions require a reexamination for supercritical CO2 (sCO2) flows. To establish the skin friction coefficient for real gas sCO2 flows, computational fluid dynamics (CFD) data are generated using Latin hypercube sampling (LHS), with boundary conditions spanning the typical operating conditions of sCO2 centrifugal compressors in the kW to MW scale of power generation. The CFD computations are carried out using ansys® cfx. The corresponding VLD friction coefficient for which the VLD stagnation pressure loss predicted by the one-dimensional (1D) differential equation model matches with the three-dimensional (3D) CFD result is back calculated for the LHS designs. This is carried out using a root finding function in MATLAB® software. The existing empirical relation that characterizes the VLD skin friction coefficient using the inlet Reynolds number alone shows a poor correlation (R2 = 0.26), when compared to the CFD data. It is evident that a data driven approach is required to model the sCO2 VLD real gas flow for accurate results. Using the LHS data, the efficacy of an artificial neural network (ANN)-based model is demonstrated. A two hidden layer ANN is developed, which accurately predicts the skin friction coefficient for sCO2 real gas flows (R2 = 0.87). This proposed ANN-based VLD model can be easily integrated into existing 1D codes for real gas sCO2 centrifugal compressor rating and sizing.
Modeling of Casing Containment in an Overspeeding Turbine Stage
Authors: Eryilmaz Ibrahim
Published: September 2024

This paper is on the structural characterization of a turbine casing in terms of blade containment. Gas turbines experience unintentional blade loss events in service for various reasons such as fatigue and the engines are certified on the basis that these events do not cause hazardous outcomes. In certain conditions, such as permanent loss of load after a shaft or transmission failure, the turbine stage(s) may accelerate to excessively high speeds creating the possibility of disk burst. An ls-dyna explicit finite element model of a bullet to plate experiment has been prepared with flat nose projectiles. Following the method verification, the procedure was applied for a turbine stage with a single layer and a multilayer casing to assess the performance of those in a blade-off at overspeed conditions when turbine experiences permanent loss of load. The intention with the multilayer casing is to allow penetration within the first layer to dissipate the energy of the fragments and to contain them within the second layer.
Rotordynamics of a Single-Stage Brush Seal in Isolation: The Effects of Variable Stiffness and Back Plate Geometry
Authors: Bird Joshua , Keogh Patrick S. , Sangan Carl M. , Bowsher Aaron A. , Crudgington Peter F. , Scobie James A.
Published: September 2024

Brush seals control leakage around rotating components from areas of high to low pressure inside turbomachinery. They are known to contribute to the overall stability of gas turbines, therefore their dynamic behavior is of particular importance to engine designers. Despite this, limited research exists in the literature on the rotordynamic behavior of brush seals. This paper aims to experimentally characterize the leakage and rotordynamic performance of two seals with different bristle diameters tested with both conventional and pressure-relieved back plates with a slight interference. A dynamic test facility was utilized to study the dynamic characteristics of an isolated seal with changes in excitation frequency, rotational speed, and pressure drop. Seal leakage increased with bristle diameter and with the use of the pressure-relieved back plate but reduced with increasing rotational speed for all tests. The direct dynamic coefficients were shown to increase with pressure difference. The back plate geometry influenced the change in stiffness coefficient with rotational speed. The larger bristle diameter resulted in a stiffer seal, however, the damping coefficient reduced with the reduction in packing density. The insight provided by these results will help inform engine manufacturers on the suitability of implementing brush seals in future gas turbine designs.
Nonlinear Normal Modes-Related Isolated Branches of Subharmonic Solutions for Forced Response Blade-Tip/Casing Contact Problems
Authors: Vadcard Thibaut , Thouverez Fabrice , Batailly Alain
Published: September 2024

This article investigates the emergence of isolated branches of solutions for blade-tip/casing structural contact configurations by means of a numerical procedure relying on Melnikov's energy principle. This study is carried out on the open fan blade model NASA rotor 67 in order to promote the reproducibility of the results. The blade is subjected to an harmonic forcing so as to initiate rubbing interactions. Contact is modeled in the frequency domain by the dynamic Lagrangian frequency-time harmonic balance method (DLFT-HBM) that accounts for vibro-impact as well as dry friction. This paper employs an isola detection procedure that was shown to give accurate results on such highly nonlinear applications. Several types of harmonic forcing are applied to the blade in order to observe subharmonic (i.e., with a fundamental frequency expressed as a fraction of the excitation frequency) isolated solutions. The existence of these solutions is shown to be related to nonlinear normal modes that feature lower periodicities than the excitation. The periodicity of the solutions is assumed to be linked to the periodicity of the nonlinear normal modes from which these solutions emerge. In some configurations, it is shown that nonlinear periodic solutions exist in the form of isolated branches while the main predicted response remains within the linear domain. This behavior is particularly detrimental since numerical strategies tackling nonlinear problems are usually not put to use when the response of the system is expected to be linear. The existence of such solutions is cross-checked by means of reference time integration simulations. Finally, an excitation of random shape is applied to show that this complex phenomenon persists for nonsimplified excitation shapes.
Probabilistic Modeling Geometric Tolerance and Low Cycle Fatigue Life of Gas Turbine Compressor Blade
Authors: Meng Zhiqiang (David) , Bluck Richard , Sjödin Björn
Published: September 2024

This paper presents a probabilistic low cycle fatigue (LCF) assessment for geometric tolerances on high load contact surfaces of gas turbine compressor blades. The typical patterns of the geometric deviations for the root contact flank of the compressor blades are identified and characterized according to coordinate measurement machine (CMM) measurements of the blade root. These typical patterns are closely related to the root form manufacture tools and process. Finite element (FE) models for the typical geometric deviation patterns are created based on nodal coordinates transformation of the surface nodes on the blade root contact flanks and radius. An optimized blade root profile tolerance is established, which enables significant cost saving. The elastic-plastic FE analysis with nonlinear contact model, material strain-life test, response surface, and constrained Monte Carlo simulation are used to create a probabilistic LCF life model for the optimized tolerance. The model quantifies the effect of the geometric deviations, blade mass, and material property on the blade LCF life. The result shows that with the optimized tolerance, the probability of blade LCF failure is very low and acceptable. It is also shown that the strain life material property is the most critical factor for the LCF failure. The root profile tolerance and blade mass are seen to have a much weaker effect on the blade LCF life.
A Review of Numerical Methodologies for Predicting Rotating Stall and Surge in High-Speed Centrifugal Compressors
Authors: Neri Francesco , Hickel Stefan , Pini Matteo
Published: September 2024

High-speed supersonic radial compressors are a critical enabling technology for meeting the requirements of future aviation-propulsion and thermal-management systems. These turbomachines must be designed to be both efficient and robust on the widest possible operating range. Flow instabilities in the form of rotating stall and surge are therefore phenomena that must be accurately predicted early in the design process. Unsteady full-annulus computational fluid dynamics (CFD) can be used to get accurate information about the onset of instabilities, but at the expense of costly simulations. As a result, the design of new compressors continues to rely on existing correlations for the prediction of the critical mass flowrate. This approach, however, leads to suboptimal compressor designs. This article provides a review of the numerical methodologies that can be used for the accurate prediction of the critical mass flowrate in high-speed centrifugal compressors. Methods of different fidelity level and computational cost are described. Two particularly promising models, namely, those proposed by Spakovszky and Sun, are subsequently examined in more detail. Exemplary applications of these two models are finally discussed.
The Effect of Air–Water Mixture on the Dynamic Response of a Hydrodynamic Journal Bearing With Inclined Grooves
Authors: Voitus Anthony , Arghir Mihai , Hassini Mohamed-Amine
Published: September 2024

Water-lubricated hydrodynamic journal bearings with deep inclined grooves are often used to support radial loads and dampen pump vibrations in nuclear power plants. The inclined grooves increase the pumping effect of the lubricant thus reducing wear and friction during rotor startup and coast-down. The deep grooves also facilitate the removal of debris without damaging the bearing. The load capacity and the stability of this type of bearing are studied in the present work. A sensitivity study of the impact of the number of grooves on bearing performance underlined the superiority of the journal bearing with two inclined grooves. Moreover, these journal bearings may operate with a mixture of water and air. This compressible two-phase lubricant will modify the load capacity and the stability of the journal bearing. The impact of the ingested volume fraction of air is therefore investigated. A physical model of the homogeneous air–water mixture linking the local air volume fraction with the pressure was used in conjunction with the numerical solution of the compressible Reynolds equation on an unstructured grid. It was found that the air ingestion in the two-inclined grooves journal bearing decreases the load capacity but improves the stability for mild and low loads.
Interplay Between Unburned Emissions and NOx Emissions From a Dual Swirl Hydrogen Air Injector
Authors: Magnes Hervé , Vilespy Martin , Selle Laurent , Poinsot Thierry , Schuller Thierry
Published: September 2024

OH planar laser induced fluorescence (OH-PLIF) and particle image velocimetry (PIV) are employed to analyze the structure of hydrogen/air flames stabilized by a dual swirl injection system under globally lean and atmospheric conditions with preheat air temperature varied from ambient up to 673 K. The flames exhibit two distinct reaction branches. The first, located in the central recirculation zone (CRZ), is a diffusion-controlled reaction layer characterized by a relatively large thickness associated with low strain rates. The second branch, stabilized in the shear layer of the swirling jet, is strongly influenced by large coherent structures. Depending on operating conditions, this front may adopt either the form of a fully diffusive strained reaction layer anchored to the hydrogen injector lip or a lifted diffusion front with a leading-edge flame evolving into a partially premixed flame at high air injection velocities. Flue gas analysis indicates NOx emission levels, typically below 10 ppm at 15% O2, for sufficiently large air injection velocities. Air preheating barely increases NOx emissions at lean operating conditions. The injector operational range is constrained only by the ultralean blowout limit reached for global equivalence ratios below 0.02. Furthermore, it demonstrates remarkable resilience to large and rapid drop in fuel flow rate. However, combustion efficiency drops close to the lean blowout (LBO) limit due to intermittent fragmentation of the flame wings that progresses further upstream as the equivalence ratio drops. The results demonstrate that fragmentation arises from the combined effects of a temperature drop in the central recirculation zone and the flame wings being exposed to high shear stress. Additionally, it is shown that combustion efficiency under ultralean conditions improves significantly with an increase in air preheat temperature.
Transesterification catalyst strength as observed by solution-based oxygen-17 nuclear magnetic resonance spectroscopy
Authors: Purdy S.K. , Shen J. , Zhu J. , Tse T.J. , Reaney M.J.T.
Published: September 2024

Natural abundance oxygen-17 nuclear magnetic resonance spectroscopy (17O-NMR) was applied to study homogeneous transesterification catalysts for fatty acid methyl ester production. Alkoxide catalysts were made with selected permutations of lithium, sodium, magnesium, and potassium hydroxides with ethanol, methanol, isopropanol, and glycerol. Pilot scale transesterification reactions of Canola oil were completed and the 17O-NMR spectra were collected from the reaction products. The alkoxide solutions showed the downfield shifts relative to the reagent alcohol, in a linear relationship with the concentration of catalyst ion. The electron deshielding of the oxygen of the alkoxide catalyst is observed directly by 17O-NMR, and the fastest catalyst has the largest downfield (high frequency) shift. This effect is most pronounced in potassium methoxide and less pronounced for less polar solvents such as isopropanol.
Enhancing Reliability of Folded Petersen Networks Based on Edge Partition
Authors: Lin Wanling , Lin Zhaoding , Zhuang Hongbin , Li Xiao-Yan
Published: September 2024

The rapid expansion of infrastructure topology, especially noticeable in high-performance computing systems and data center networks, significantly increases the likelihood of failures in network components. While traditional (edge) connectivity has long been the standard for measuring the reliability of interconnection networks, this approach becomes less effective as networks grow more complex. To address this, two innovative metrics, named matroidal connectivity and conditional matroidal connectivity, have emerged. These metrics provide the flexibility to impose constraints on faulty edges across different dimensions and have shown promise in enhancing the edge fault tolerance of interconnection networks. In this paper, we explore (conditional) matroidal connectivity of the [Formula: see text]-dimensional folded Petersen network [Formula: see text], which is constructed by iteratively applying the Cartesian product operation on the well-known Petersen graph and possesses a regular, vertex- and edge-symmetric architecture with optimal connectivity and logarithmic diameter. Specifically, the faulty edge set [Formula: see text] is partitioned into [Formula: see text] subsets according to the dimensions of [Formula: see text]. We then arrange these subsets by their cardinality, imposing the restriction whereby the cardinality of the [Formula: see text]th largest subset dose not exceed [Formula: see text] for [Formula: see text]. Subsequently, we show that [Formula: see text] is connected with [Formula: see text] and determine the exact value of matroidal connectivity and conditional matroidal connectivity.
Anti-Inflammatory Effects of Lupeol as a Candidate for New Drug Development
Authors: Park Yun Jin , Park Dong Ho , Bae Jong-Sup
Published: September 2024

This study explores the anti-inflammatory properties of lupeol, a notable phytosterol found in various medicinal plants, highlighting its potential as a candidate for new drug development. We examined the effects of lupeol on heme oxygenase (HO)-1, cyclooxygenase (COX)-2, and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cells (HUVECs), as well as its impact on inflammatory markers in the lung tissues of LPS-challenged mice. Lupeol treatment enhanced HO-1 production, inhibited nuclear factor (NF)-κB activity, and reduced levels of COX-2/prostaglandin E2 (PGE2) and iNOS/nitric oxide (NO). In addition, lupeol decreased the phosphorylation of signal transducer and activator of transcription 1 (STAT-1) and promoted the nuclear translocation of nuclear factor erythroid 2-related factor 2 (Nrf2), enhancing its binding to the anti-oxidant response element (ARE) and subsequently reducing interleukin (IL)-1β expression. In vivo, lupeol significantly lowered iNOS expression and tumor necrosis factor (TNF)-α levels in bronchoalveolar lavage fluid from LPS-treated mice. These findings suggest that lupeol exerts its anti-inflammatory effects by modulating key signaling pathways, positioning it as a promising candidate for the development of novel therapeutics targeting pathological inflammation.
Planar Insert Loaded Triple Band Waveguide Bandpass Filter for X-Band Applications
Authors: Bage Amit
Published: September 2024

This paper presents a novel design of second-order triple band waveguide bandpass filter using planar insert technology. A conventional WR-90 rectangular waveguide has two identical inserts inserted into its transverse plane at an optimal spacing of 8.41[Formula: see text]mm. The insert consists of a combination of a double-split square resonator and a single split square resonator with stub. These resonators are used to achieve triple-band bandpass characteristics. The structure allows independent control of three center frequencies, insertion loss, return loss and 3-dB bandwidth. The simulation analysis of the proposed filter is carried out using the CST microwave studio, and its frequency response is compared with its equivalent circuit response. To validate the numerical analysis, the WR-90 waveguide and planar insert are fabricated independently and inserted manually. The dual-pole triple band bandpass characteristic of the manufactured filter, with center frequencies of 8.19, 9.39 and 11.09[Formula: see text]GHz, is shown by the measured data. The complete design process has also been provided, along with a corresponding circuit diagram. The suggested waveguide filter’s performance is evaluated against those found in the literature already.
Dynamical Phenomena Based on Chaotic Systems Without Equilibria
Authors: Zhao Boyu , Ye Xiaolin
Published: September 2024

A chaotic system without equilibrium points is a focal subject in recent years, and its unique dynamic characteristics have attracted extensive research. In this paper, different chaotic systems with no equilibrium points are constructed by modifying the Sprott-A system. The test results show that the first system is conservative. After investigating the hidden dynamical behavior of the first system, the rotation attractor phenomenon is revealed by the rotation factor. Next, we make a second transformation of the Sprott-A system. By introducing a trigonometric function, we get a new system that can generate infinitely many coexisting grid attractors. After calculation, we find that the new system still belongs to the chaotic system without equilibrium points and the coexistence phenomenon of attractors is created by adjusting the initial value continuously. The chaotic system without equilibrium points which can realize the coexistence of attractors has potential applications in some related fields, which is worthy of further study.
Pushing Yourself to the Limit - Influence of Emotional Virtual Environment Design on Physical Training in VR
Authors: Oberdörfer Sebastian , Steinhaeusser Sophia C. , Najjar Amiin , Tümmers Clemens , Latoschik Marc Erich
Published: September 2024

The design of virtual environments (VEs) can strongly influence users’ emotions. These VEs are also an important aspect of immersive Virtual Reality (VR) exergames – training system that can inspire athletes to train in a highly motivated way and achieve a higher training intensity. VR-based training and rehabilitation systems can increase a user’s motivation to train and to repeat physical exercises. The surrounding VE can potentially predominantly influence users’ motivation and hence potentially even physical performance. Besides providing potentially motivating environments, physical training can be enhanced by gamification. However, it is unclear whether the surrounding VE of a VR-based physical training system influences the effectiveness of gamification. We investigate whether an emotional positive or emotional negative design influences the sport performance and interacts with the positive effects of gamification. In a user study, we immerse participants in VEs following either an emotional positive, neutral, or negative design and measure the duration the participants can hold a static strength-endurance exercise. The study targeted the investigation of the effects of (1) emotional VE design as well as the (2) presence and absence of gamification. We did not observe significant differences in the performance of the participants independent of the conditions of VE design or gamification. Gamification caused a dominating effect on emotion and motivation over the emotional design of the VEs, thus indicating an overall positive impact. The emotional design influenced the participants’ intrinsic motivation but caused mixed results with respect to emotion. Overall, our results indicate the importance of using gamification and support the commonly used emotional positive VEs for physical training. They further indicate that the design space could also include other emotional directions of VE design.
Cross Project Defect Prediction using Dropout Regularized Deep Learning and Unique Matched Metrics
Authors: Bal Pravas , Kumar Sandeep
Published: September 2024

The primary goal of software defect prediction (SDP) is to predict the software defects for a specific software using historical data or data from past releases of software projects. The existing state of arts on SDP primarily discusses two prediction scenarios: Within Project Defect Prediction (WPDP) and Cross Project Defect Prediction (CPDP). The prediction model belongs to the WPDP scenario, which means that the model is trained and tested on different parts of the same dataset or trained on the dataset belonging to the previous version of the same project. While in the CPDP scenario, training and testing occur on different software project datasets. Due to the unavailability of historical datasets or prior releases of software defect datasets, CPDP is more useful in real-life scenarios. So, CPDP analysis is a very challenging issue in the SDP domain. Sometimes, machine learning (ML) models perform poorly due to inadequate training in the CPDP scenario. To support better CPDP performance, we must carefully build an ML model focusing on lower training error and overfitting issues. To address these issues, we have proposed a cross-project data preprocessing method to correlate the metrics of different project datasets, namely Unique Selection of Matched Metrics (USMM), using the KS test and Hungarian method. To further improve the CPDP performance, we have also used the dropout regularized deep learning (DRDL) model. We have deployed 34 software defect datasets to validate the DRDL model and USMM method. The experimental results demonstrate that the DRDL model using the USMM method (DRDL-USMM) is a promising model to enhance the prediction accuracy, and an improvement in the range of 3.3% to 8.5% as compared to the existing works in the CPDP scenario has been found.
Category-Based Administrative Access Control Policies
Authors: Bertolissi Clara , Fernandez Maribel , Thuraisingham Bhavani
Published: September 2024

As systems evolve, security administrators need to review and update access control policies. Such updates must be carefully controlled due to the risks associated with erroneous or malicious policy changes. We propose a category-based access control (CBAC) model, called
Admin-CBAC
, to control administrative actions. Since most of the access control models in use nowadays (including the popular RBAC and ABAC models) are instances of CBAC, from
Admin-CBAC
, we derive administrative models for RBAC and ABAC, too. We present a graph-based representation of
Admin-CBAC
policies and a formal operational semantics for administrative actions via graph rewriting. We also discuss implementations of
Admin-CBAC
exploiting the graph-based representation. Using the formal semantics, we show how properties (such as safety, liveness, and effectiveness of policies) and constraints (such as separation of duties) can be checked, and discuss the impact of policy changes. Although the most interesting properties of policies are generally undecidable in dynamic access control models, we identify particular cases where reachability properties are decidable and can be checked using our operational semantics, generalising previous results for RBAC and
ABAC
α
.
Enhancing Alexa Skill Testing Through Improved Utterance Discovery
Authors: Shafei Hassan A. , Tan Chiu C.
Published: September 2024

Extracting skill utterances is a crucial step in testing and evaluating smart speaker skills. Previous works have proposed various techniques for extracting utterances from the skill web page to test and evaluate smart speaker skills. In this article, we evaluate the effectiveness and correctness of different utterance-extracting techniques proposed in previous works. Our evaluation reveals that some techniques can capture incorrect utterances that the skill will not accept as spoken utterances. We also find that all of the proposed techniques would never capture the total utterances supported by skills, and combining these techniques yields the best results in terms of text parsing. To address these limitations, we propose a new technique that combines the strengths of previous techniques and leverages human to interact with a small set of skills to expand the coverage for testing other skills. We evaluate the effectiveness of our technique and demonstrate that it can capture a higher number of utterances supported by skills. We delved into the impact assessment of utterance extraction, aiming to enhance the thoroughness and effectiveness of skill testing. We conducted an impact study on 11 skills to assess the importance of utterance extraction in the context of skills testing. Our findings demonstrate that our technique captures a higher number of utterances compared to previous techniques. Through our evaluation, we provide insights into the significance of discovering more utterances in the testing context, and demonstrate the effectiveness of our proposed technique in capturing more utterances for skill testing and evaluation.
Optimizing Urban Traffic Management: Investigating the Impact of Probe Vehicle Road Coverage, Penetration Rates, and Speed Data Quality in Macroscopic Fundamental Diagram Estimation
Authors: Rizvi Syed Muzammil Abbas , Friedrich Bernhard
Published: September 2024

Probe vehicles and loop detectors collect traffic data for empirical MFD estimation. The accuracy of MFD estimation is contingent upon the percentage of road network links covered (road coverage) and the extent of information (penetration rate) from each link. While the previous research has explored the effects of loop detector road coverage and probe vehicle penetration rates, the impact of probe vehicle road coverage remains unaddressed. Furthermore, the unequal distribution and low penetration rates of probe vehicles undermine the reliability of the data obtained from them. Therefore, this study aimed to (i) examine the impact of probe vehicle road coverage on MFD estimation, (ii) enhance the reliability of the spatial data by using speed data reconstruction, (iii) highlight the increased role of spatial data in the accuracy of MFD estimation, and (iv) develop a performance factor of speed data quality to demonstrate that the quality of spatial data is more susceptible to the penetration rate than road coverage. The results underlined the role of FCD road coverage in MFD estimation, and the proposed methodology significantly improves spatial data quality. The study concluded that spatial and temporal data affect the MFD estimation differently, and the proposed performance factor increases the role of spatial data in MFD estimation.
Machines’ Intelligent Fault Diagnosis Based on Hierarchical Refined Composite Generalized Multiscale Fluctuation Dispersion Entropy
Authors: Chen Biwen , Chen Changsheng , Ma Zhenlai , Li Guoping , Zhang Yi , Li Baoyue
Published: September 2024

Vibration data from mechanical equipment contain extensive information distributed across multiple dimensions. Single‐scale analysis fails to comprehensively reflect its damage characteristics, thereby reducing fault diagnosis accuracy. This study proposes a novel signal vibration feature extraction method called hierarchical refined composite generalized multiscale fluctuation dispersion entropy (HRCGMFDE). This method simultaneously extracts fault information from both low‐frequency and high‐frequency components of the data, addressing the drawback of high‐frequency information loss in refined composite generalized multiscale fluctuation dispersion entropy (RCMFDE). Comparative results on two simulated signals demonstrate the method’s advantages of high stability and more accurate complexity measurement. Furthermore, low‐frequency and high‐frequency components of the data are comprehensively extracted using dual‐tree complex wavelet packet transform (DTCWPT), and high‐dimensional features are downscaled using t‐distributed stochastic neighbor embedding (t‐SNE) to obtain low‐dimensional sensitive fault features. Subsequently, a Random Forest (RF) classifier is employed for fault identification. Finally, the effectiveness of the proposed method is validated using three typical mechanical datasets. Results confirm the method’s capability to effectively determine the fault states of bearings, gearboxes, and centrifugal pumps, showcasing significant advantages over comparative methods.
CPR‐Induced Consciousness during Ventricular Fibrillation: Case Report and Literature Review
Authors: Zhou Xiaoqing , Sun Boru
Published: September 2024

Introduction. Over the years, numerous studies have suggested the occurrence of a peculiar phenomenon known as “CPRIC” during the revival process. The revelation of this phenomenon has ignited widespread discussion and investigation, yet many enigmas remain unsolved. This study describes the case of a 52‐year‐old man diagnosed with acute anterior myocardial infarction, who experienced ventricular fibrillation while awaiting further treatment. Despite ultimately not regaining spontaneous circulation, he remained conscious for a period during chest compressions and showed signs of resistance. Methods. PubMed and Web of Science were searched until July 11, 2024. We included original studies and case reports relevant to CPRIC. For case reports, we extracted information on the author (year), country, patients, location, compression, signs of CPRIC, treatment of CPRIC, and patient outcomes. For other studies, we included the author (year), country, participants, and results. The extracted data were synthesized using a narrative approach. Results. Of 3038 articles, 32 were included, i.e., 18 case reports (24 cases), 9 cross‐sectional surveys, and 5 cohort studies. In CPRIC cases, patients exhibited various manifestations including opening their eyes, speaking, and moving. Other included studies explored healthcare workers’ awareness and experiences of CPRIC, the incidence and manifestations of CPRIC, the impact of CPRIC on patient outcomes, memories and perceptions of cardiac arrest indicating consciousness, the effects of CPRIC on rescuers, and the management of CPRIC. Conclusions. There is an urgent need to establish a globally recognized definition of CPRIC. It is crucial to develop clear algorithms that focus not only on identifying this phenomenon but also on determining the best approaches to manage it. Furthermore, CPRIC can cause multiple interruptions during CPR, making it essential to differentiate whether these interruptions are due to CPRIC or indicative of a return of spontaneous circulation.
A Novel Terminal Sliding Mode Variable Structure Model Reference Adaptive System Observer for Permanent Magnet Synchronous Motors
Authors: Bai Yan , Zhang Lei , Meng Xiang-Min , Bai Jing , Han Guang
Published: September 2024

This paper introduces a model reference adaptive system observer based on the non‐singular fast terminal sliding mode (NFSM‐MRASO) for the purpose of sensorless control of permanent magnet synchronous motors (PMSMs) in electric vehicle applications. Firstly, a non‐singular fast terminal sliding surface is constructed based on the output errors of the reference model and the adjustable model. This ensures that the output errors between the two models converge to zero in a finite time and effectively avoids the singularity problem in the terminal sliding mode control. In addition, a novel reaching law (NRL) is designed to replace the traditional exponential reaching law (TRL) to suppress the chattering phenomenon in the sliding mode control. Finally, the feasibility and effectiveness of the NFSM‐MRASO strategy are demonstrated through simulation results.
CDC25B Is a Prognostic Biomarker Associated With Immune Infiltration and Drug Sensitivity in Hepatocellular Carcinoma
Authors: Huang Zixiang , Xu Liangzhi , Wu Zhengqiang , Xiong Xiaofeng , Luo Linfei , Wen Zhili
Published: September 2024

Cell division cycle 25B (CDC25B), a member of the CDC25 phosphatase family, plays a key role in cell cycle regulation. Studies have suggested its carcinogenic potential in various cancers, but the role of CDC25B in the development of hepatocellular carcinoma (HCC) remains poorly understood. The aim of this study was to clarify the role of CDC25B in HCC using bioinformatics and experiments. CDC25B expression data of HCC cancer tissues and paracancerous normal samples were obtained from The Cancer Gene Atlas (TCGA) and Gene Expression Omnibus (GEO) databases, and the relationship between CDC25B expression and the prognosis and degree of tumor differentiation of HCC patients was analyzed. CDC25B expression was verified in clinical HCC tissue samples using fluorescence quantitative polymerase chain reaction (q‐PCR) and protein immunoblotting (Western blot). Gene set enrichment analysis (GSEA) was used to identify signaling pathways enriched in CDC25B expression, and differential genes (DEGs) were used to screen out coexpressed hub genes and construct protein‐protein interaction (PPI) networks. 5‐Ethynyl‐2 ′‐deoxyuridine (EDU) staining was used to compare the proliferation and differentiation ability of the HCC cell line (HCC‐LM3) after knockdown of CDC25B. Finally, we investigated the mutation of CDC25B in HCC and the relationship between CDC25B expression and tumor cell infiltration of lymphocytes and some immune checkpoints as well as drug sensitivity. CDC25B was overexpressed in HCC tissues and correlated with poor prognosis and the degree of tumor differentiation in patients with HCC. The GSEA and PPI networks together revealed significantly upregulated signaling pathways, as well as functions, associated with the development of HCC when CDC25B was overexpressed. The EDU assay demonstrated that the ability of cells to differentiate value addedly was markedly reduced following the downregulation of CDC25B expression in HCC‐LM3s. CDC25B was also involved in the formation of the tumor microenvironment (TME) and immune processes in HCC, and the high expression of CDC25B made patients less sensitive to some drugs. CDC25B can be used as a biomarker and immunotherapeutic target for poor prognosis and partial drug sensitivity in HCC, providing new ideas for HCC treatment.