Velocity Difference Research Articles

Water Droplet Collison and Erosion on High-Speed Spinning Wheels

<div>The water droplet erosion (WDE) on high-speed rotating wheels appears in several engineering fields such as wind turbines, stationary steam turbines, fuel cell turbines, and turbochargers. The main reasons for this phenomenon are the high relative velocity difference between the colliding particles and the rotor, as well as the presence of inadequate material structure and surface parameters. One of the latest challenges in this area is the compressor wheels used in turbochargers, which has a speed up to 300,000 rpm and have typically been made of aluminum alloy for decades, to achieve the lowest possible rotor inertia. However, while in the past this component was only encountered with filtered air, nowadays, due to developments in compliance with tightening emission standards, various fluids also collide with the spinning blades, which can cause mechanical damage. One such fluid is the condensed water in the low-pressure exhaust gas recirculation channel (LP-EGR) formulated at cold starts and low-speed high load conditions. This kind of design has been developed to reduce nitrogen oxide emissions and is used in both gasoline and diesel engines. This article presents a state-of-the-art review of this WDE process, focusing on the formation of the condensed water before the compressor wheel, summarizing the influencing factors of WDE and the effects of the damage including using component testbench experiences and simulation methodologies. Inspection possibilities such as high-speed camera measurement and vibration analysis are also an important part of the document.</div>

Study on Driver Behavior Pattern in Merging Area under Naturalistic Driving Conditions

To reduce the risk of traffic conflicts in merging area, driver’s behavior pattern was analyzed to provide a theoretical basis for traffic control and conflict risk warning. The unmanned aerial vehicle (UAV) was used to collect the videos in two different types of merging zones: freeway interchange and service area. A vehicle tracking detection model based on YOLOv5 (the fifth version of You Only Look Once) and Deep SORT was constructed to extract traffic flow, speed, vehicle type, and driving trajectory. Acceleration/deceleration distribution and vehicle lane-changing behavior were analyzed. The influence of different vehicle models on vehicle speed and lane-changing behavior was summarized. Based on this data, the mean and standard deviation of velocity, acceleration, and variable acceleration were selected as the characteristic variables for driving style clustering. To avoid redundant information between features, principal component dimensionality reduction was performed, and the dimensionality reduction data was used for K-means and K-means++ clustering to obtain three driving styles. The results show that there are obvious differences in the driving behaviors of vehicles in different types of merging areas, and the characteristics of different areas should be fully considered when conducting traffic conflict warnings.

Can cerebellar theta-burst stimulation improve balance function and gait in stroke patients? A randomized controlled trial.

The cerebellum is a key structure involved in balance and motor control, and has become a new stimulation target in brain regulation technology. Interference theta-burst simulation (iTBS) is a novel simulation mode of repetitive transcranial magnetic simulation. However, the impact of cerebellar iTBS on balance function and gait in stroke patients is still unknown. The aim of this study was to determine whether cerebellar iTBS can improve function, particularly balance and gait, in patients with post-stroke hemiplegia. This study is a randomized, double-blind, sham controlled clinical trial. The study was carried out at the Department of Rehabilitation Medicine in a general hospital. Patients with stroke with first unilateral lesions were enrolled in the study. Thirty-six patients were randomly assigned to the cerebellar iTBS group or sham stimulation group. The cerebellar iTBS or pseudo stimulation site is the ipsilateral cerebellum on the paralyzed side, which is completed just before daily physical therapy. The study was conducted five times a week for two consecutive weeks. All patients were assessed before the intervention (T0) and at the end of 2 weeks of treatment (T1), respectively. The primary outcome was the Berg Balance Scale (BBS), while secondary outcome measures included the Fugl Meyer Lower Limb Assessment Scale (FMA-LE), timed up and go (TUG), Barthel Index (BI), and gait analysis. After 2 weeks of intervention, the BBS, FMA-LE, TUG, and BI score in both the iTBS group and the sham group were significantly improved compared to the baseline (all P<0.05). Also, there was a significant gait parameter improvement including the cadence, stride length, velocity, step length compared to the baseline (P<0.05) in the iTBS group, but only significant improvement in cadence was identified in the sham group (P<0.05). Intergroup comparison showed that the BBS (P<0.001), FMA-LE (P<0.001), and BI (P=0.002) in the iTBS group were significantly higher than those in the sham group, and the TUG in the iTBS was significantly lower than that in the sham group (P=0.002). In addition, there were significant differences in cadence (P=0.029), strip length (P=0.046), gain velocity (P=0.002), and step length of affected lower limb (P=0.024) between the iTBS group and the sham iTBS group. Physical therapy is able to improve the functional recovery in hemiplegic patients after stroke, but the cerebellar iTBS can facilitate and accelerate the recovery, particularly the balance function and gait. Cerebellar iTBS could be an efficient and facilitative treatment for patients with stroke. Cerebellar iTBS provides a convenient and efficient treatment modality for functional recovery of patients with stroke, especially balance function and gait.

1 Sex Differences in Middle Cerebral Artery Velocity in Patients with Persistent Post-Concussion Convergence Insufficiency (PPCS-CI)

OBJECTIVES/GOALS: The objective of this study is to investigate the neurophysiological mechanism of vision therapy in male and female adolescents with persistent post-concussion convergence insufficiency (PPCS-CI). This study may improve diagnostics and inform more effective personalized point of care treatment strategies to remediate symptoms. METHODS/STUDY POPULATION: Participants (ages 11-25) were diagnosed with PPCS by a physician, CI was diagnosed by an optometrist and OBVAT was performed by certified therapists. Patients with PPCS-CI were randomly assigned to a therapy type (immediate therapy or natural recovery). Hemodynamic measures were examined in patients with PPCS-CI at baseline (1-3 months post-concussion), and post OBVAT to evaluate recovery outcomes. Non-invasive techniques were used to measure middle cerebral artery velocity (MCAv), blood pressure, heart rate, and end-tidal CO2 at rest and during objective symmetrical convergence step eye movements. Functional magnetic resonance imaging (fMRI) was acquired during convergence step eye movement experiments contrasted to sustained fixation and resting state data collection. RESULTS/ANTICIPATED RESULTS: To investigate the neural mechanism of OBVAT, eye movements, fMRI and physiological measures were collected in 8 patients with PPCS-CI (4 men and 4 women). Results show an 10% decrease in the MCA during 4-degree symmetrical convergent eye movement responses in males post-OBVAT and a 19% increase in MCA during convergent eye movement responses in females. Furthermore, there was a group level activation of the frontal eye fields, which improves post-OBVAT. The beta weights in the left frontal eye fields show a trending decrease in male patients post-OBVAT and trending increase in females. Males had a decrease in MCAv post OBVAT (baseline 83.6 ± 7.5 cm/sec &amp; 75.7 ± 12.5 cm/sec post-OBVAT), while females show a significant increase post-OBVAT (baseline 53.77 ± 5.2 cm/sec &amp; post-OBVAT 65.13 cm/sec ± 12.5). DISCUSSION/SIGNIFICANCE: This initial pilot demonstrates there may be different underlying pathophysiological outcomes associated with a concussion dependent on sex. This work may have direct implications on treatment strategies for male and female adolescent patients with PPCS-CI.

An enhancement in the petrophysical evaluation in a vuggy carbonate gas reservoir by integrating the core data and empirical methods, Zagros basin, south of Iran

The presence of vuggy pore types poses challenges in accurately assessing effective porosity. This study focuses on the significant scientific issue of improving petrophysical evaluation in vuggy carbonate gas reservoirs. The Kangan Formation is one of the main gas reservoir formations in the southern Zagros region, Iran. The main objective of the current research is to distinguish and exclude the influence of vuggy pore types from effective porosity in the reservoir pay zones of the Kangan reservoir.In the current research, a combination of full suite logs, image logs, core analysis, and thin section studies was employed. The image logs illustrate that vuggy porosity is abundant in the Kangan Formation and these results are confirmed by the available core thin sections, specifically in Zone Kangan_B; Additionally, the cross plots of compressional velocity versus bulk density and total porosity, as a part of rock physics study, indicate the characteristics of the vuggy reservoir. Two methods are utilized to quantify vuggy porosity. The first method, the Velocity Deviation Log (VDL) approach, identifies various available pore types, especially vugs. The second method is a newly proposed approach that can exclude vuggy porosity from the computed effective porosity. In this novel approach, a variable porosity exponent (m) is derived by adopting the Lucia equation to exclude vuggy porosity from the effective porosity computations. Thus, petrophysical evaluation can be implemented based on the constant and variable “m”. Comparing both petrophysical results, it is evident that the amounts of effective porosity and water saturation are modified in the vuggy-bearing intervals. Applying the proposed approach will improve the accuracy of petrophysical properties and lead to the proper calculation of the hydrocarbon volume in the carbonate reservoir rocks containing isolated vugs, particularly in gas-bearing reservoirs where conventional logs are affected by gas contents.

Addition of the Local Volume sample of galaxies from the FAST HI survey

We report the discovery of 20 new dwarf galaxies in the Local Volume identified as optical counterparts to the Five-hundred-meter Aperture Spherical radio Telescope (FAST) All Sky HI Survey (FASHI) sources. The galaxies have a median stellar mass of 7.8 × 106 M⊙ and a median HI mass of 1.0 × 107 M⊙. Most of them are field galaxies, while three are probable members of the M 101 and M 106 groups. We also found seven FASHI radio sources to be probable dark HI clouds in nearby groups. Together with four other known HI clouds in the local groups, their mean-square radial velocity difference of 49 km s−1 with respect to the host galaxies yields an average total mass of (2.7 ± 1.0)×1011 M⊙ for these groups on the projected scale of 90 kpc.

A method for locating lightning strikes in distribution lines with multiple branches

A lightning strike fault location (FT) method for multi-terminal overhead lines based on 0-mode 1-mode wave velocity difference is proposed to address the shortcomings of current multi-terminal overhead line positioning methods that are difficult to identify due to multi-terminal GPS time synchronization and reflected traveling waves. Based on the wave velocity difference between 0-mode and 1-mode, single-end ranging is performed, and an FT judgment vector is formed based on the ratio of the ranging results of each monitoring terminal to the inherent length of the line. By analyzing the element features in the FT judgment vector, an FT criterion is proposed, and the FT results of the appropriate monitoring terminal are selected as the final FT. After PSCAD/EMTDC simulation verification, this method is suitable for complex multi-branch overhead lines, and can accurately locate the FT without being affected by time synchronization.

Temperature Dependent Behavior of Elastic and Ultrasonic Proprieties of Transition Metal Carbide Mo2C Superconductor

Abstract: Transition metal carbides exhibit peculiar chemical and physical properties, making them integral to industrial applications that demand performance under high temperatures In the case of the hexagonal transition metal carbide Mo2C superconductor, higher-order elastic constants were calculated to be temperature-dependent using an interactional potential model. Second-order elastic constants are used to determine other allied ultrasonic variables. Second-order coefficients are used to analyze the temperature variation of ultrasonic velocities along the z-direction of the superconductor. Furthermore, the temperature difference of Debye average velocity and thermal relaxation time are considered along the same direction. The temperature dependence of ultrasonic properties is explored in relation to thermal, elastic, and mechanical properties. Ultrasonic attenuation , resulting from phonon–phonon (p–p) interactions, is calculated at different temperatures .The study establishes that thermal conductivity is a core provider of the observed ultrasonic attenuation, particularly at higher temperatures. The mechanical and thermal properties of the Mo2C superconductor are superior at lower temperatures. Keywords:Transition metal carbide superconductor, Thermal conductivity, Ultrasonic properties, Elastic properties, Mechanical properties. PACS numbers: 43. 35. Cg; 62.20.Dc; 63.20.Kr.

Study on the characteristics of compound dust source pollution and foam dust suppression technology in coal mine anchor excavation production

To guard against the damage caused by the dust pollution of the shuttle driver in the anchor excavation production, the Discrete Phase Model(DPM)-Discrete Element Model(DEM) was constructed based on the gas-solid two-phase flow theory, the dust pollution characteristics of the shuttle transfer stage were numerically simulated, and a dual carborne combined foam dust suppression system was developed. The results showed that at the rear of the transfer machine, due to the reduction of the roadway section space during transferring made the wind velocity relatively maximum, and the space after transferring dispersed many cutting dust and transferring dust, resulting in the wind velocity after transferring was slightly smaller than before transferring, and the wind velocity difference was 0.18 m/s on average. The dust pollution in the operating environment of the shuttle driver before, during and after transferring was more serious, with 162.1 mg/m³, 340.7 mg/m³ and 540.8 mg/m³. There was variability in the particle diameter of dust generated by different processes, and smaller micron-sized dust particles were generated during transferring, of which respiratory dust below 7.07 μm accounted for up to 21% of the total. To reduce the high concentration of respiratory dust clusters, a strong wettability high-fold foam dust suppressant was prepared and applied to a dual carborne combined foam dust suppression system, and the average dust reduction rates of total dust and respiratory dust reached 91.9% and 93.6%, respectively.

Reversal of particle Migration for viscoelastic solution at high solvent viscosity

The imbalance of normal stress around a particle induces its transverse migration in pressure-driven viscoelastic flow, offering possibilities for particle manipulation in microfluidic devices. Theoretical predictions align with experimental evidence of particles migrating towards the center-line of the flow. However, these arguments have been challenged by both experimental and numerical investigations, revealing the potential for a reversal in the direction of migration for viscoelastic shear-thinning fluids. Yet, a significant property of viscoelastic liquids that remains largely unexplored is the ratio of solvent viscosity to the sum of solvent and polymer viscosities, denoted as β. We computed the lift coefficients of a freely flowing cylinder in a bi-dimensional Poiseuille flow with Oldroyd-B constitutive equations. A transition from a negative (center-line migration) to a positive (wall migration) lift coefficient was demonstrated with increasing β values. Analogous to inertial lift, the changes in the sign of the lift coefficient were strongly correlated with abrupt (albeit small) variations in the rotation velocity of the particle. We established a scaling law for the lift coefficient that is proportional, as expected, to the Weissenberg number, but also to the difference in rotation velocity between the viscoelastic and Newtonian cases. If the particle rotates more rapidly than in the Newtonian case, it migrates towards the wall; conversely, if the particle rotates more slowly than in the Newtonian case, it migrates towards the center-line of the channel. Finally, experiments in microfluidic slits confirmed migration towards the wall for viscoelastic fluids with high viscosity ratio.

The Utilization of LiCSBAS for Deformation Monitoring in Geresa Segment of Matano Fault, Central Sulawesi, Indonesia

Sulawesi is situated between the confluence of three plates, resulting in a very complex tectonic setting on the island. This has an impact on the occurrence of geological structures, including faults. One of them is the Matano Fault which consists of 6 segments (Kuleana Segment, Pewusai Segment, Matano Segment, Pamsoa Segment, Ballawai Segment, and Geresa Segment). The research area is located in Morowali Regency, covering the Geresa Segment. Morowali Regency recorded an earthquake with a magnitude of 5.7 in 2012. This indicates that deformation has occurred. Therefore, this study aims to identify the deformation velocity around the Geresa Segment area. The methods used are geological observation and satellite image data processing to obtain information on deformation rates. The geological field study includes aspects of geomorphology, geological structure, and the rock types distribution. Meanwhile, the processing of satellite image data in the form of InSAR is carried out through the LiCSBAS package tools that has been integrated with LiCSAR. The analysis results illustrate the difference in deformation velocity around the Geresa Segment area. The area which is composed of Tolaka formation and Ultramafic complex tends to uplift with a deformation rate of up to 17 mm/year. In addition, alluvium that covers the southeastarn part has a land subsidence of up to 7 mm/year.

Low temperature and excess moisture affect seed germination of soybean (Glycine max L.) under controlled environments

Cold and excess moisture pose a serious threat to soybean production especially during seed germination in short-season environments. In this study, the effects of low temperature and excess moisture stress on seed germination were investigated in 187 soybean accessions originating from 18 countries. The experiment used a combination of three temperature conditions (i.e., 20 °C/14 °C, 14 °C/10 °C, and 10 °C/10 °C day/night) and two moisture levels (i.e., normal and excess). The seed germinability traits measured included germination rate (GR), germination index, germination time, germination uniformity, and coefficient of velocity of germination. Overall, GR was lowest in the 20 °C/14 °C + excess moisture and germination time was longest in the 10 °C/10 °C + excess moisture. When compared with 20 °C/14 °C + normal moisture treatment, GR at 10 °C/10 °C + excess moisture decreased by 38%; germination time increased by 20 days; seed viability decreased by 83%; germination uniformity decreased by 70%; germination speed decreased by 73%. Differences in GR, germination index, and germination velocity under different treatments were affected by temperature, moisture, and their interaction. Variation in germination time uniformity was determined by temperature, with no significant effects of moisture conditions and the interaction of temperature and moisture. It was shown that the temperature–excess moisture interaction led to a sharp decrease in seed germination. Two genotypes including PI 603147 and PI 507702 were identified with a GR over 90% at 10 °C/10 °C + excess moisture. This study generated new knowledge and data to further the understanding of genetic resistance to cold and excess moisture stress in soybean.

Single-nucleus RNA velocity reveals critical synaptic and cell-cycle dysregulations in neuropathologically confirmed Alzheimer’s disease

Typical differential single-nucleus gene expression (snRNA-seq) analyses in Alzheimer’s disease (AD) provide fixed snapshots of cellular alterations, making the accurate detection of temporal cell changes challenging. To characterize the dynamic cellular and transcriptomic differences in AD neuropathology, we apply the novel concept of RNA velocity to the study of single-nucleus RNA from the cortex of 60 subjects with varied levels of AD pathology. RNA velocity captures the rate of change of gene expression by comparing intronic and exonic sequence counts. We performed differential analyses to find the significant genes driving both cell type-specific RNA velocity and expression differences in AD, extensively compared these two transcriptomic metrics, and clarified their associations with multiple neuropathologic traits. The results were cross-validated in an independent dataset. Comparison of AD pathology-associated RNA velocity with parallel gene expression differences reveals sets of genes and molecular pathways that underlie the dynamic and static regimes of cell type-specific dysregulations underlying the disease. Differential RNA velocity and its linked progressive neuropathology point to significant dysregulations in synaptic organization and cell development across cell types. Notably, most of the genes underlying this synaptic dysregulation showed increased RNA velocity in AD subjects compared to controls. Accelerated cell changes were also observed in the AD subjects, suggesting that the precocious depletion of precursor cell pools might be associated with neurodegeneration. Overall, this study uncovers active molecular drivers of the spatiotemporal alterations in AD and offers novel insights towards gene- and cell-centric therapeutic strategies accounting for dynamic cell perturbations and synaptic disruptions.

Quantitative Analysis of Diagenesis Control on the Spatial Heterogeneity of Sarvak Carbonate Formation, the Dezful Embayment of Zagros Basin, Western Iran

Summary The heterogeneity indices in conventional carbonate reservoirs are usually influenced by various diagenetic processes. The main aim of this study is to build 3D geological models of the diagenetic and heterogeneity indices addressing the role of diagenesis on spatial heterogeneity variations in the Sarvak carbonate reservoir of an Iranian oil field situated in the Dezful Embayment in the Zagros Basin. Vertical heterogeneity has been discussed in many studies, but the literature is limited on the 3D geological modeling of heterogeneity and providing spatial heterogeneity maps. In this study, we determined the main diagenetic parameters influencing the reservoir heterogeneity and constructed 3D geological models for evaluating the spatial heterogeneity. A couple of heterogeneity indices including the coefficients of variation (CVs) of porosity and permeability, Lorenz coefficient, and Dykstra-Parsons coefficient in cored intervals along with some diagenetic parameters were calculated and modeled. This study shows that lateral heterogeneity is mappable and correlatable with different diagenetic overprints along with shale volume, which controls the reservoir quality and spatial heterogeneity. It also indicates that lateral trends of the heterogeneity indices in different zones of the studied reservoir are influenced by other diagenetic parameters such as secondary porosity (SPI), dolomitization, cementation, and velocity deviation log (VDL, as a diagenetic index). Different diagenetic parameters control reservoir heterogeneity in each zone by decreasing or increasing the degree of the heterogeneity, some of which have dual constructive or destructive effects on heterogeneity indices. Moreover, the results show that the effect of shale volume on reservoir heterogeneity is significant, especially when the amount of the shale volume is notable.

A 3D-Sparse A* autonomous recovery path planning algorithm for Unmanned Surface Vehicle

Thanks to the development of marine intelligent technology and equipment, the Unmanned Surface Vehicle (USV) has been brought into focus for its exceptional application. To overcome the challenge of the stern ramp recovery for USVs, an advanced 3D-Sparse A* path planning algorithm has been proposed. This algorithm incorporated sparse sampling and the time dimension to optimize the generation of waypoints, resulting in a smaller computation load. Dynamic constraints and evaluation functions were integrated to reconstruct the algorithm’s framework. Simulations suggest that planning speed can be increased by a factor of 20, improving recovery efficiency. The path’s smoothness was elevated, with a maximum curvature 50% lower than the original version. Furthermore, the malposition was reduced to 54.78% of the original, meeting the requirements for particular attitude adjustment during stern ramp recovery. Field experiment indicates that the actual results have a maximum velocity deviation of 0.61 m/s and a maximum course deviation of 1.61 m compared to the planning results. The 3D-Sparse A* algorithm can complete the recovery within a distance of 100 m in 60 s, assuming an unobstructed trajectory. This verifies the feasibility and planning efficiency of the algorithm.

Research on Radial Double Velocity Measurement Method of Laser Tracker

For the dynamic problem that the low-speed sliding table is unable to meet the radial measuring speed of the laser tracker, this paper takes the sliding table of the indoor large-length standard device as the moving object to double the measuring distance by adding a pyramid prism, thereby doubling the radial speed of the laser tracker. In this paper, the measurement data are analyzed through equal interval measurement experiments, equal sampling frequency experiments and repeatability measurement experiments using a pyramid prism to obtain the following conclusions, respectively: Firstly, the stability of the actual interval of the laser tracker is optimal when the rated speed of the sliding table is 50 mm/s. When the pyramid prism is not used, the minimum standard deviation obtained by the laser tracker at a sampling interval of 5 mm is 0.0158 mm. Secondly, during the equal sampling frequency measurement, the stability of the laser interferometer is better than that of the laser tracker when the pyramid prism is not used. With two instruments at a sampling frequency of 10 Hz, the standard deviations of the local velocity of the laser interferometer are 0.1466 mm/s, 0.0693 mm/s and 0.1106 mm/s, respectively. The standard deviations of the laser tracker are 0.1582 mm/s, 0.1033 mm/s and 0.2008 mm/s, respectively. The same conclusion is obtained at a sampling frequency of 20 Hz. The stability of the laser tracker is better than that of the laser interferometer when the pyramid prism is used. Thirdly, the stability and reliability of the local velocity of the laser tracker are better than that of the laser interferometer. For example, at 10 Hz, the standard deviations of the local velocity of the laser tracker are 0.2745 mm/s and 0.2097 mm/s, respectively, and the repeatability of the local velocity is 0.9140 mm/s. The standard deviations of the local velocity of the interferometer are 0.6141 mm/s and 0.6368 mm/s, respectively, and the repeatability of the local velocity is 1.4886 mm/s. And the local velocity of the two measuring instruments is more reliable and stable at a low frequency (10 Hz). This experimental scheme provides a way to measure the high speed of a laser tracker using a sliding table at low speed.

Estimating crash risk and injury severity considering multiple traffic conflict and crash types: A bivariate extreme value approach

Traffic conflicts are generally considered independent events in existing extreme value theory models to estimate the risk of total or single types of crashes. However, traffic events at a road entity are not necessarily independent interactions and can lead to multiple traffic conflicts with shared common unobserved factors. A comprehensive estimation of crash risks in a road entity needs to consider the correlation of potential traffic conflicts to avoid possible bias in prediction performance and the problem of undetected deficiencies. This study proposes a Bayesian non-stationary bivariate generalised extreme value modelling framework to estimate the severe and non-severe crash risks accounting for the correlation between right-turn and rear-end conflicts at signalised intersections. A deep neural network-based computer vision technique was applied to extract the traffic conflicts from 77 h of video recordings over two right-turn approaches at two signalised intersections in Cairns, Australia. Post encroachment time and modified time to collision were used to characterise right-turn and rear-end conflicts, respectively, while an expected post-collision velocity difference was combined with post encroachment time and modified time to collision for crash risk estimation by injury severity levels. Several covariates were used to address the time-varying heterogeneity of traffic conflict extremes and to estimate the differential crash risks at signal cycles. Results showed a significant correlation between right-turn and rear-end crashes at signal cycle levels, indicating the importance of accounting for the dependency among traffic conflict types. Overall, the bivariate models considering the correlation among traffic conflict types were found to understandably perform better than their univariate counterparts. This study provides a demonstration of a correlated crash risk modelling framework that addresses issues related to the suitable traffic conflict measures, time varying risks (non-stationarity), heterogeneity, and injury severity levels of different crash types.

Design of air-ground cooperative landing platform and autonomous landing strategy

This paper studies innovative design for landing platform design and autonomous landing strategies for unmanned aerial vehicles (UAVs). First, a self-leveling landing platform on a mobile unmanned ground vehicle (UGV) is designed, which can be maintained even when the UGV moves on uneven terrain. Then, with the cooperation of the UAV and the UGV, they are controlled to reach the same velocity in the horizontal direction, which helps avoid the UAV’s rollover caused by horizontal velocity difference. Meanwhile, a buffering strategy is designed to reduce the vertical velocity difference, which helps avoid a hard landing. Finally, a combined landing code is designed to improve the accuracy and success rate of UAV landing. Experiments are carried out to demonstrate the effectiveness of the proposed design of a self-leveling platform and autonomous landing strategies.

Multi-scale invariant solutions in plane Couette flow: a reduced-order model approach

Plane Couette flow at Reynolds number $Re=1200$ (based on the channel half-height and half the velocity difference between the top and bottom plates) is investigated with a spatial domain designed to retain only two spanwise integral length scales. In this system, the computation of invariant solutions that are physically representative of the turbulent state has been understood to be challenging. To address this challenge, our approach is to employ an accurate reduced-order model with 600 degrees of freedom (Cavalieri &amp; Nogueira, Phys. Rev. Fluids, vol. 7, 2022, L102601). Using the two-scale energy budget and the temporal cross-correlation of key observables, it is first demonstrated that the model contains most of the multi-scale physical processes identified recently (Doohan et al., J. Fluid Mech., vol. 913, 2021, A8); i.e. the large- and small-scale self-sustaining processes, the energy cascade for turbulent dissipation, and an energy-cascade mediated small-scale production mechanism. Invariant solutions of the reduced-order model are subsequently computed, including 96 equilibria and 43 periodic orbits. It is found that none of the computed equilibrium solutions are able to reproduce an accurate energy balance associated with the multi-scale dynamics of the turbulent state. Incorporation of unsteadiness into invariant solutions is seen to be essential for a sensible description of the multi-scale turbulent dynamics and the related energetics, at least in this type of flow, as periodic orbits with a sufficiently long period are mainly able to describe the complex spatio-temporal dynamics associated with the known multi-scale phenomena.

Abstract P531: Contralateral Differences in Ankle Systolic Blood Pressure and Pulse Wave Velocity: Associations With Incident Heart Failure and Mortality

Introduction: Contralateral differences in systolic blood pressure (SBP) are a risk assessment tool and indicative of underlying cardiovascular issues. Most of the available studies focused on brachial blood pressure and its clinical impact. This study evaluated whether interankle SBP differences and contralateral differences in pulse wave velocity (PWV) are associated with incident heart failure (HF) and all-cause and cardiovascular mortality in a community-dwelling sample of older adults. Methods: Sample included 5,077 participants (75.2 ± 5.1 years old) of the Atherosclerosis Risk in Communities (ARIC) study. The OMRON VP-1000 plus was used to measure PWV and blood pressure in the ankles. PWV was assessed between the brachial artery and ankle (baPWV) and heart and ankle (haPWV) on the right and left sides. Cut points for contralateral differences in PWV were set at the 90th percentile in our sample. Outcomes included incident HF (first definite or probable hospitalization for acute decompensated HF), all-cause and cardiovascular mortality (until December 31, 2020). Cox proportional hazards regression models were used to calculate hazard ratios (HR) and 95% confidence intervals (CI). Results: Over a mean follow-up of 7.5 ± 2.1 years, incident HF was diagnosed in 457 participants, and 1,275 all-cause and 363 cardiovascular deaths occurred. The prevalence of interankle SBP difference ≥10 and ≥15 mmHg was 24.9% (1,268) and 12.0% (605), respectively. The prevalence of contralateral differences in baPWV (&gt;240 cm/s) and haPWV (&gt;80 cm/s) was 10.1% (513) and 9.1% (464), respectively. Interankle SBP difference ≥10 mmHg (HR 1.13; 95% CI 1.00-1.29), ≥15 mmHg (HR 1.25; 95% CI 1.06-1.48), contralateral difference in baPWV &gt;240 cm/s (HR 1.18; 95% CI 1.00-1.41), and haPWV &gt;80 cm/s (HR 1.21; 95% CI 1.01-1.44) were each independently associated with all-cause mortality after adjustment for demographics, traditional cardiovascular risk factors, and extreme values of ankle-brachial index ≤0.9 or &gt;1.40. Contralateral differences in ankle SBP ≥15 mmHg (HR 1.55; 95% CI 1.16-2.06), and haPWV &gt;80 cm/s (HR 1.40; 95% CI 1.02-1.91) were both independently associated with cardiovascular mortality. Crude analysis revealed that those with contralateral differences in ankle SBP ≥10 and ≥15 mmHg, baPWV &gt;240 cm/s, and haPWV &gt;80 cm/s had a significantly higher risk of HF (p&lt;0.05 for all). However, these HF relationships were no longer statistically significant after adjustment for confounders. Conclusions: Contralateral differences in ankle SBP and PWV were independently associated with all-cause and cardiovascular mortality risk even after accounting for traditional cardiovascular risk factors and the ankle-brachial index. These results underscore the significance of evaluating contralateral differences in ankle SBP and PWV as potential markers of increased mortality risk among older adults.