Velocity Analysis Research Articles

Influence of Grip Width on the Load-Velocity Relationship and 1 Repetition Maximum Value in the Bench Press Exercise: A Comparative and Reliability Analysis of Mean Velocity Vs. Mean Propulsive Velocity Vs. Peak Velocity.

Herrera-Bermudo, JC, Puente-Alcaraz, C, Díaz-Sánchez, P, González-Badillo, JJ, and Rodríguez-Rosell, D. Influence of grip width on the load-velocity relationship and 1 repetition maximum value in the bench press exercise: a comparative and reliability analysis of mean velocity vs. mean propulsive velocity vs. peak velocity. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to analyze the reliability and compare the load (percentage of 1 repetition maximum [%1RM])-velocity relationship, bar displacement (DIS), the 1RM, and the velocity attained against the 1RM value (V1RM) in the bench press exercise using 3 different bar grip widths: narrow (120% of the biacromial distance [BD]), medium (160%), and wide (200%). A group of 54 healthy, physically active men randomly performed a total of 6 incremental tests (1 week apart) up to 1RM (2 with each bar grip width) on a Smith machine. The mean velocity (MV), mean propulsive velocity (MPV), peak velocity, and DIS were recorded for the subsequent analysis. The 3 velocity variables showed high relative (intraclass correlation coefficient: 0.90-0.97) and absolute (coefficient of variation: 2.21-9.38%) reliability in all grip widths against all relative loads. The 1RM value and the V1RM present high absolute and relative reliability in all grip widths. There are no significant differences in the value of 1RM and V1RM between grip widths. High relationships were observed between the relative load (%1RM) and velocity variables, with MPV showing the best fit. Significant greater values in MPV, MV, and DIS associated with each %1RM were observed for narrow and medium compared with wide grip width. In conclusion, our results suggest that the 3 velocity variables were highly reliable at the different grip widths used against all relative loads. In addition, there was a tendency to reach higher MV, MPV, and DIS values as the grip width decreased. Therefore, this factor should be considered for the assessment and design of training.

Combined light curve and radial velocity analysis of the neglected contact binary S Ant

We present the first combined photometric and spectroscopic solution of the bright southern contact binary S Ant based on the Transiting Exoplanet Survey Satellite (TESS) light curve and the radial velocities from the David Dunlap Observatory survey. S Ant is a W UMa type binary in deep contact, with a mass ratio of 0.34 and a relatively massive and hot F-type primary. Beside the standard modeling of the phase-binned light curve, we also perform “seasonal modeling” where we treat each of the 83 orbital cycles present in the TESS data as a separate light curve. The resulting ensemble of solutions shows evidence of quasi-periodic migration of a long-lived, dark, polar spot. The migration is confirmed independently by eclipse time variations which display remarkably strong correlation with the spot location.

Study of oblique granular impingement flow through CFD-DEM simulations and energy consumption statistics

This paper investigates an experimental granular impingement flow system through simulations and energy consumption statistics. With the increase of solid concentration, flow patterns undergo cross flow (dense edge and dilute center), dispersed flow, and mixed-jet flow (dilute edge and dense center) in turn. The influence of gas phase on the flow pattern was investigated. According to the analysis of force and time-averaged velocity, it is revealed that gas-solid interaction will cause energy dissipation of granular flow, which cannot be ignored in specific cases. Then, a flow map is proposed according to both the Archimedes number and solid concentration. In addition, the flow pattern transition and local structure variations can be reflected by energy consumption statistics. Based on the simulations and methods developed in this work, it is promising to deepen the understanding and study of granular impingement flow from the viewpoints of energy consumption and new-type flow map.

Transport Effects in Electrochemical Biochip Sensors with Redox Cycling Amplification: Computational and Experimental Analysis

In the last few decades, and especially after the COVID-19 pandemic, point-of-care diagnostics and field-deployable biosensors have attracted significant attention. Key components of these instruments are microchips that integrate microfluidics with a sensor (e.g., optical or electrochemical) to provide rapid, low-cost, real-time detection of analyte molecules in very small volumes. Next-generation electrochemical sensors have been miniaturized on solid-state platforms (e.g., arrays and vectors) where the area is limited. However, as the active surface area of the sensors decreases from a few square microns to sub-micron and nanometric scales, the measured currents drop, hence affecting the limit of detection. As the concentration of many analytes in the physiological environment is low, low signal-to-noise ratios have limited the miniaturization of standard electrochemical sensors. One way to increase signal at the sensor output is by redox amplification. To achieve amplification, a second working electrode must be incorporated close to the first working electrode and proper bias must be applied to both. Micrometer-sized interdigitated electrode arrays have been fabricated using robust and scalable processes based on optical lithography and reactive ion-etching techniques. In some cases, IDAs have been integrated into microfluidics devices. The physical and electrochemical phenomena that occur in microfluidic channels under flow have been previously evaluated and showed an increase of current under flow. The effect of redox cycling in microfluidic and nanofluidic systems has also been qualitatively demonstrated. Some studies measured the amplification in the cases with and without flow and showed that the flow itself amplifies the measured electrochemical current, though in most cases, it reduces the amplification factor.Towards a more quantitative investigation, analytical and computational modeling were used, providing meaningful insights into the physics of IDAs without requiring numerous device fabrications. In this work, we used COMSOL Multiphysics to create a full three-dimensional simulation-based model of a real device in order to study the effect of laminar flow on redox cycling, as well as a simplified one-dimensional model for the analysis of transition velocity between different amplification regimes. IDAs with 5-10 mm for both electrodes width and gap were studied numerically and experimentally. The results of the 3D and 1D simulations were consistent between themselves, and also with those of the physical experiments. The relationship between the two mass transfer methods — diffusion and convection — were analyzed at different flow velocities and for different electrode geometries.Here we report a study of transport effects on a microfluidic sensor-chip in which electrochemical sensing is amplified by redox cycling using an interdigitated electrode array (IDA). Our models indicate that there exist two dominant regimes: one which is limited by redox cycling diffusion—a unique feature of IDAs— which is dominant at relatively low flow rates, and another which is limited by convection and has dominant flow effects which are effective at high flow rates (see Figure). The transition velocity between the two sensing regimes depends on the width of the electrode and spacing. It was found to be Vflow [mm/sec]=0.335/L[μm] + 0.04 which is similar to the prediction of Vflow∝1/L obtained from the one-dimensional model.An understanding of the combined effects of redox cycling and convection flow is critical as microfluidic chips with electrochemical sensing amplified by redox cycling using IDAs are becoming widely used in diagnostic assays. The method for prediction of current under any flow rate described here will support technological development of more efficient and accurate devices. Figure 1

Comparative Analysis of Diabetic Neuropathy Examination Scores and Nerve Conduction Velocity in Patients with Diabetic Neuropathy

Background: Diabetic neuropathy is a prevalent consequence of diabetes, resulting in substantial morbidity. Precise evaluation is essential for prompt intervention and control. The study assessed the correlation and effectiveness of the Diabetic Neuropathy Examination (DNE) scores and Nerve Conduction Velocity (NCV) as diagnostic tools in individuals with diabetic neuropathy. Methods: An observational research was done, comprising 200 diabetic patients who were diagnosed with diabetic sensory-motor polyneuropathy. Participants completed Dynamic Neuromuscular Examination (DNE) grading and Nerve Conduction Velocity (NCV) testing. The data were analysed using SPSS version 20.0. Results: The study found a considerable negative correlation (r = -0.68, p < 0.001) between DNE scores and NCV results. Higher DNE scores were associated with lower NCV values. Specifically, 20% of participants had mild neuropathy, 40% had moderate neuropathy, and 40% had severe neuropathy according to DNE scores. NCV testing revealed that 65% of participants had abnormal nerve conduction, with 25% showing mild reduction, 25% moderate reduction, and 15% severe reduction. Multivariate regression confirmed that DNE scores are significant predictors of NCV outcomes (Beta = -0.52, p < 0.001), even after adjusting for confounding variables such as gender, age, diabetes duration, and HbA1C levels. Conclusion: DNE scoring is a reliable tool for assessing neuropathy severity in diabetic patients, correlating well with NCV results. Integrating DNE scoring in routine clinical practice can enhance the early detection and management of diabetic neuropathy. Recommendations: Routine use of DNE scoring along with NCV testing is recommended for comprehensive evaluation of diabetic neuropathy. Further research should explore additional diagnostic tools to improve early detection and intervention. Keywords: Diabetic Neuropathy, Diabetic Neuropathy Examination Score, Nerve Conduction Velocity Testing, Diabetic Polyneuropathy, Neuropathy Assessment..

An experimental and numerical study of propyl acetate laminar combustion characteristics

The laminar burning characteristics of propyl acetate were investigated using the constant volume combustion experimental unit at the working conditions of 1, 2, and 4 bar and 390, 420, and 450 K over a wide range of equivalence ratios (0.7–1.4). Both experimental and numerical investigations were used to study the laminar combustion characteristics of propyl acetate. Also, a chemical mechanism was proposed in this work to numerically investigate the laminar combustion of propyl acetate. A comparison of this study and literature experimental burning velocity data with the proposed mechanism laminar burning velocity showed satisfactory agreement. Sensitivity investigations of the burning velocity and production rate analysis of the reactions revealed that the reaction that mostly produces OH, H, and O radicals significantly drives the combustion of propyl acetate and increases the laminar burning velocity. Moreover, fuel-related reaction R1086: H + PA ⇔ H2 + PA2J increased the laminar burning velocity but fuel-related reaction R1098: OH + PA ⇔ H2O + PAMJ decreased the burning velocity. The reaction pathway study showed that propyl acetate mainly decomposes to PAMJ radical, PA2J radical, PAEJ radical, propene, and acetic acid before it converts into other radicals. Also, it was shown that ally radicals and ketene are essential intermediates in the fuel conversion process of propyl acetate.

Abstract We083: A new mouse model for the study of cardiogenic TFs Tbx5 , Gata4 , and Mef2c during cardiogenesis

Congenital heart defects (CHDs) are be caused by mutations in genes that drive cardiac development, such as Tbx5 , Gata4 , and Mef2c . Cardiac development, and its transcriptional regulators are also regulated by microRNAs (miRs). These small RNAs target the transcripts of genes in numerous cardiac cell types during embryonic development. We and others have shown that the miR-200 family modulates the transcripts of cardiogenic transcription factors (TFs) Tbx5 , Gata4 , and Mef3c. However, the relationship between these miRs and cardiogenic TFs during in vivo cardiac development is poorly understood. During cardiogenesis, miR-200 family members are highly expressed (E14.5) but reduced in adults (3mo) (Ct Value: miR-200a : 24.3 ± 0.59 v 38.3 ± 0.21; miR-200c : 25.0 ± 0.64 v 32.5 ± 0.16). Using our miR-200 family inhibitor mice models (PMIS), we have found these miRs are required for cardiac development. PMIS-miR-200 embryos are found with a ventral septal defect and poor ventricle wall development, which is lethal by e16.5. At e14.5, PMIS-miR-200 hearts have a significant increase in expression of Tbx5, Gata4, and Mef2c compared to Wild-Type. This induced expression of these TFs is seen within CMs of the ventricle at E14.5. snMulti-Omics of WT and PMIS-miR-200 hearts found a population of CMs enriched in the PMIS-miR-200 hearts. These CMs are marked by expression of Tbx5 , Nppa , and Sox5 . RNA velocity analysis found these CMs to be “progenitor-like” and associated with an early pseudotime. Expression of Tbx5 , Nppa , and Sox5 correlated along the pseudotime with the “progenitor-like” CMs. ATAC-seq showed enrichment of Tbx5 and Mef2c motifs within this new CM cell state. Conclusions: The miR-200 family is a modulator of cardiogenic TFs expression and activity during development. Inhibition of miR-200 induces a CM cell state with “progenitor-like” qualities. Future directions will determine the role of miR- 200 in adult cardiac disease, such as ischemic injury. Our work provides new insights into gene dosage, modulated by miRs, that is required and necessary during cardiac development.

Experimental Investigation of Threshold Velocities for Air-Water Two-Phase Flow in a Vertical Tube and Annular Channels

This work presents an experimental study of five threshold velocities for air-water flow in three different vertical channels. The measured threshold velocities included onset flooding (OF), end flooding (EF), onset deflooding (OD), end deflooding (ED), and minimum pressure (MP) velocities. The experimental system includes a transparent vertical tube of 52.5 mm inner diameter and 1500 mm length. The test channel can be easily changed from a tube to an annular shape by inserting a cylindrical test element. A counter-current or concurrent upward flow was achieved by blowing air upward from the channel’s bottom and flowing water from its top. The threshold velocities were determined by analyzing the pressure drop versus air superficial velocity. Findings revealed evident hysteresis between the end flooding and onset deflooding velocities. In contrast, the end deflooding and onset flooding velocities were found to be identical. The end flooding velocity was indifferent to the water’s superficial velocity for all three channel geometries. A generalized gas-liquid flow state diagram for vertical channels is developed based on the present empirical analysis for different threshold velocities.

Development and study of ultrasonic pulse velocity measurement system using wave analysis and two-point detection approach

Abstract This article focuses on the development and analysis of an Ultrasonic Pulse Velocity (UPV) measurement system used for the evaluation of concrete and Reinforced Cement Concrete (RCC) in civil construction. The UPV tester is essential for on-site assessments of structures, as it is used to measure the velocity of ultrasonic waves within the material, directly correlating with its strength. UPV testing is affected by the attenuation of ultrasonic waves in concrete, particularly due to the interfacial transition zone. Excess ultrasonic attenuation results in the reduction in the received signal amplitude which may also results in the omission of the initial pulses due to threshold comparison at the receiver. The study highlights the impact of receiver gain on threshold error and discusses the limitations associated with ADC sampling rate and amplitude resolution. UPV measurement, including counter or data acquisition approach, have error contributions associated with threshold voltage comparison. The error due to threshold amplitude selection is quantified, emphasizing the importance of accurate signal analysis, particularly in highly attenuating medium. The article presents the design and development of a PC-based UPV tester with automatic threshold error compensation. The system includes a transmitter, receiver, 32-bit microcontroller, and a Graphical User Interface (GUI) for data analysis. The article introduces a two-point linear detection logic to minimize errors caused by selected signal amplitude and omission of initial pulses in transit time measurements. The proposed method provides effective resolution of 10 ns through software, even at low sampling rate of 2 MS/s. The experimental results demonstrate the effectiveness of the developed UPV tester, with comparisons to a reference calibration facility at CSIR-NPL. The standard deviation in the ultrasonic transit time measurement by the developed UPV device, with threshold error correction, was ±70 ns.

Collapse Pattern in Gypseous Soil using Particle Image Velocimetry

Abstract Gypseous soil is prevalent in arid and semi-arid areas, is from collapsible soil, which contains the mineral gypsum, and has variable properties, including moisture-induced volume changes and solubility. Construction on these soils necessitates meticulous assessment and unique designs due to the possibility of foundation damage from soil collapse. The stability and durability of structures situated on gypseous soils necessitate close collaboration with specialists and careful, methodical preparation. It had not been done to find the pattern of failure in the micromechanical behavior of gypseous sandy soil through particle image velocity (PIV) analysis. This adopted recently in geotechnical engineering to track the motion of soil grains and using tracer particles by applying digital particle image analysis. It has also been used to study the displacement distribution in some cases of granular materials. Therefore, the goal of this study is to find out how gypseous sand medium moves when in contact with a rigid strip foundation that is under static stress and plane strain conditions. The experimental model would focus on two common types of wetting, namely water table rise and dry conditions. The PIV showed that the collapse pattern under the footing is of the type of punching shear failure. The predominant mechanism of soil deformation was the vertical compression of the gypseous granular soil. The results showed that understanding gypseous sandy grain displacement and failure patterns at the local scale is crucial for enhancing the design of foundations under static stress conditions.

Photo-dynamical characterisation of the TOI-178 resonant chain

Context. The TOI-178 system consists of a nearby, late-K-dwarf with six transiting planets in the super-Earth to mini-Neptune regime, with radii ranging from to 2.9 R⊕ and orbital periods between 1.9 and 20.7 days. All the planets, but the innermost one, form a chain of Laplace resonances. The fine-tuning and fragility of such orbital configurations ensure that no significant scattering or collision event has taken place since the formation and migration of the planets in the protoplanetary disc, thereby providing important anchors for planet formation models. Aims. We aim to improve the characterisation of the architecture of this key system and, in particular, the masses and radii of its planets. In addition, since this system is one of the few resonant chains that can be characterised by both photometry and radial velocities, we propose to use it as a test bench for the robustness of the planetary mass determination with each technique. Methods. We performed a global analysis of all the available photometry from CHEOPS, TESS and NGTS, and radial velocity from ESPRESSO, using a photo-dynamical modelling of the light curve. We also tried different sets of priors on the masses and eccentricity, as well as different stellar activity models, to study their effects on the masses estimated by transit-timing variations (TTVs) and radial velocities (RVs). Results. We demonstrate how stellar activity prevents a robust mass estimation for the three outer planets using radial velocity data alone. We also show that our joint photo-dynamical and radial velocity analysis has resulted in a robust mass determination for planets c to 𝑔, with precision of ~ 12% for the mass of planet c, and better than 10% for planets d to 𝑔. The new precisions on the radii range from 2 to 3%. The understanding of this synergy between photometric and radial velocity measurements will be valuable for the PLATO mission. We also show that TOI-178 is indeed currently locked in the resonant configuration, librating around an equilibrium of the chain.

Atmospheric Pressure Plasma Functionalization of Sealed PDMS Microfluidics: Application to Capillary Pumping and Enhanced Cell Growth.

Microfluidic devices serve as essential tools across diverse fields like medicine, biotechnology, and chemistry, enabling advancements in analytical techniques, point-of-care diagnostics, microfluidic cell cultures, and organ-on-chip models. While polymeric microfluidics are favoured for their cost-effectiveness and ease of fabrication, their inherent hydrophobic properties necessitate surface functionalization, often post-sealing. Here, we introduce a versatile apparatus for functionalizing sealed microfluidic devices using atmospheric plasma processing, with a focus on PDMS (polydimethylsiloxane) microfluidics. Through meticulous analysis of surface properties and capillary speed, before and after plasma treatment, along with a comparison between vacuum and atmospheric plasma functionalization methods, we demonstrate the efficacy of our approach. Subsequent experimentation within 3D PDMS microfluidic chambers, combining atmospheric pressure plasma treatment with collagen coating to facilitate mesenchymal stem cells (MSCs) growth over five days, reveals enhanced initial cell adhesion and proliferation, highlighting the potential of our method for improving cell-based applications within microfluidic systems.

Анализ течений при лазерно-акустической обработке нержавеющей стали AISI 316L

The influence of ultrasonic vibrations on the flow of molten metal during laser processing is investigated. This problem is of interest within the context of modernization of existing technological processes, such as laser welding and cladding, for the production of structures with improved physical and mechanical properties. The introduction of additional ultrasonic energy into the liquid metal bath intensifies the metal flow via forced stirring, which provides its homogenization and leads to an increase in the mechanical properties of the processed material due to the growth of the number of crystallization centers during its solidification. In order to get a better understanding of this combined process and to control it, a method for synthesizing hydrodynamic and strength solvers used in the ANSYS software package is proposed. Setting up the coupling between two corresponding ANSYS Transient Structural and ANSYS CFX modules is executed through the additional ANSYS System Coupling module. Under this numerical implementation of the problem, it is possible to calculate the displacements at the solid metal boundary and their transfer to the liquid metal boundary and vice versa at each moment of time. The impact of laser radiation on the liquid metal is considered taking into account Marangoni convection, and convection and radiation heat transfer. The results of numerical experiments make it possible to conduct a qualitative and quantitative comparison between the liquid AISI 316L stainless steel flows formed without and with ultrasonic vibration. It is shown that the intensification and deceleration of the flows is observed at the average values of the ultrasonic amplitude. This fact correlates with the moments of time at which the deformed surface of the metal in the bath moves down and up. A comparative analysis of the maximum axial velocities inside the liquid metal bath was conducted. The absence of ultrasonic action on the liquid metal motion was observed at the maximum values of the vibration amplitude, which correspond to the maximum displacement and deformation of the surface at the interface between liquid and solid.

Hear Wave Velocity Analysis Based on Two Rock Layers Modeling Using Microtremor Data of Gresik and Surrounding Areas

The lithology on the surface in the current condition is often found to be not a fresh rocks, but all materials, be it alluvial, soil, backfill soil, or rocks with a very high degree of weathering. Therefore, this study was conducted to estimate the type of layer on the surface and its underlying layer based on the analysis of Vs (shear wave velocity) values in the surface lithological media and the underlying layer through the modeling of two rock layers. To complete this research, microtremor array data was collected by the Geological Survey Center in the Gresik area which was then processed using the SPAC (Spatial Autocorrelation) method. Based on the results of the study, the Gresik area has a surface Vs value that still shows soft soil values in the range of 65 - 170 m/s and its basement Vs already shows fresh rocks to older lithologies in the alluvial area in the range of 150 - 435 m/s, so it can be seen that some areas that should consist of a fairly hard lithology in the Gresik area have changed with a fairly high level of weathering.

Swimming Velocity Analysis Using Wearable Inertial Sensors and Speedometer: A Comparative Study.

The speedometer is widely used to evaluate swimming velocity but has some constraints. With the constant development of inertial units (IMUs), it is expected that they will become a good alternative to the speedometer. This study aimed to compare the data retrieved by an IMU and a speedometer when breaststroke is performed at maximum speed. Sixteen swimmers, nine males and seven females (20.3 ± 3.3 vs. 18.7 ± 1.1 years old, 65.8 ± 11.2 vs. 57.7 ± 9.1 kg of body mass and 1.75 ± 0.07 vs. 1.61 ± 0.10 m of height, respectively), performed 4 × 25 m of breaststroke sprint. They were equipped with an IMU fixed to the sacrum and with the line of an electromechanical speedometer (acquisition frequency of 50 Hz) fixed at the central point in the lumbar region. Statistical parametric mapping was used to compare the velocity curves, IBM SPSS was used for descriptive statistics and Bland-Altman plots were used for agreement of measurements. The results show that the IMU and speedometer do not show similar patterns, and the velocity values measured by the IMU are lower (p < 0.001). Bland-Altman plots presented a larger bias in terms of coefficient of variation and intracycle velocity variation. It can be concluded that IMUs and speedometers are not substitutes for each other as methods for evaluating intracycle velocity variations.

Effects of equivalent ratio and initial temperature on the explosion characteristics of ethanol, acetone, and ethyl acetate

In this paper, the effects of equivalence ratio (0.8–2.0) and temperature (30°C–120°C) on ethanol, acetone, and, ethyl acetate vapors explosion characteristics through experimental and numerical studies were investigated. The explosion overpressure and flame propagation velocity were recorded through the pressure transducer and high-speed camera. The results showed that the flame propagation velocity, peak explosion overpressure, and peak growth rate of explosion overpressure increased first and then decreased with the increase of equivalence ratio. The cracks on the flame surface enhanced with the increase of the equivalence ratio. As the initial temperature increased, peak explosion overpressure, the flame propagation velocity, and peak growth rate of explosion overpressure gradually increased. The sensitivity analysis of laminar burning velocity indicated that with the change of equivalence ratio and initial temperature, the shared elementary reactions that increased the reactivity were H + O2 &amp;lt;=&amp;gt; O + OH, HCO + M &amp;lt;=&amp;gt; H + CO + M, and CO + OH &amp;lt;=&amp;gt; CO2 + H, and the shared elementary reaction that reduced the reactivity was H + OH + M &amp;lt;=&amp;gt; H2O + M. The main factor affecting laminar burning velocity was the mole fraction of H and OH radicals.

Spatial Distribution and Variation in Debris Cover and Flow Velocities of Glaciers during 1989–2022 in Tomur Peak Region, Tianshan Mountains

In this study, we utilized a feature optimization method combining texture and topographical factors with the random forest (RF) approach to identify changes in the extent of the debris cover around the Tianshan Tomur Peak between 1989 and 2022. Based on Sentinel-1 image data, we extracted glacier flow velocities using an offset tracking method and conducted a long-term analysis of flow velocities in combination with existing datasets. The debris identification results for 2022 showed that the debris-covered area in the study region was 409.2 km2, constituting 22.8% of the total glacier area. Over 34 years, the area of debris cover expanded by 69.4 km2, reflecting a growth rate of 20.0%. Analysis revealed that glaciers in the Tomur Peak area have been decelerating at an overall rate of −4.0% per decade, with the complexity of the glacier bed environment and the instability of the glacier’s internal structure contributing to significant seasonal and interannual variability in the movement speeds of individual glaciers.

Congestions and spectral transitions in time-lagged correlations of motorway traffic

The understanding of congestions contributes to the development of effective traffic management strategies. The propagation of congestions from a motorway section to the neighboring ones results in correlations. Here, we study symmetrized time-lagged correlation matrices and show how their spectral properties reveal congestion durations. We first carry out an empirical analysis of velocities for two local motorway networks, then set up a numerical simulation for indicator time series of traffic phases, and further propose a simplified, analytical model capturing various scenarios of congestion durations. Our empirical analysis reveals a transition behavior for the dominant eigenvalue as function of time lags, reflecting changes in traffic dynamics. Furthermore, both the numerical simulations and the analytical model disclose a nonlinear relation between the spectral transition and the congestion duration.

Experimental study on flow characteristics of gas–solid two-phase flow in inclined pipes

In a fluid catalytic cracking unit, inclined pipes are mainly used for particle transportation and to maintain the pressure balance between the reactor and regenerator. In this experimental inclined pipe device, the characteristics of gas–solid two-phase flow were studied by measuring and analyzing the dynamic pressure and particle concentration parameters in different flow states. Corresponding relationships between pressure fluctuation and particle concentration on the one hand and flow patterns on the other were discovered. These were used for the quantitative identification of flow patterns. Measurement data from an analysis of bubble and particle velocities in an inclined pipe revealed a critical mass flow rate, Gs, in the mutual transformation of different particle flow patterns. The critical mass flow rate Gsc1 of lean-phase and dense-phase flows was 149 kg/(m2·s). The critical mass flow rate Gsc2 of packed-bed and dense-phase flows was 240 kg/(m2·s). This study enriches the basic theoretical knowledge on flow patterns in inclined pipes and provides a theoretical basis for the adjustment of inclined pipe operation in industrial fluid catalytic cracking units.

Plasma plume enhancement of a dual-anode vacuum arc thruster with magnetic nozzle

Vacuum arc thruster (VAT) is a type of pulsed electric propulsion device that generates thrust based on vacuum arc discharges, it has great candidate for micro-newton force applications in orbit. To improve both the thrust and longevity of the VAT, a novel dual-anode structure, comprising a central anode and a ring anode, was developed. We conducted an investigation into the plasma discharge and acceleration process within the influence of a magnetic nozzle. The dual-anode architecture resulted in a reduction in the initial plasma impedance, thereby enhancing ion current and velocity. Analysis of surface parameters during discharge revealed a synergistic mechanism between the two insulator-conducting films, enabling a co-cyclic distribution of energy and resistance fluctuations within the discharge. Consequently, the dual-anode setup demonstrated a lifespan extension of at least twofold. Comparative analyses of arc energy, plasma velocity, ion current, and thrust variations with magnetic field strength were conducted between the dual-anode and single-anode configurations under magnetic nozzle influence. Results showed that the dual-anode structure increased ion current and velocity when subjected to magnetic nozzle influence, resulting in a thrust increase of up to 303%. Additionally, we developed a theoretical model for the diffusion coefficient to elucidate the adaptive splitting phenomenon of the arc within the dual-anode structure under magnetic field influence. This model suggests that the dual-anode structure can achieve a more significant enhancement in beam current from the magnetic nozzle compared to the single-anode configuration.