Velocity Difference Research Articles

Response Plasticity of Drosophila Olfactory Sensory Neurons.

In insect olfaction, sensitization refers to the amplification of a weak olfactory signal when the stimulus is repeated within a specific time window. In the vinegar fly, Drosophila melanogaster, this occurs already at the periphery, at the level of olfactory sensory neurons (OSNs) located in the antenna. In our study, we investigate whether sensitization is a widespread property in a set of seven types of OSNs, as well as the mechanisms involved. First, we characterize and compare the differences in spontaneous activity, response velocity and response dynamics, among the selected OSN types. These express different receptors with distinct tuning properties and behavioral relevance. Second, we show that sensitization is not a general property. Among our selected OSN types, it occurs in those responding to more general food odors, while OSNs involved in very specific detection of highly specific ecological cues like pheromones and warning signals show no sensitization. Moreover, we show that mitochondria play an active role in sensitization by contributing to the increase in intracellular Ca2+ upon weak receptor activation. Thus, by using a combination of single sensillum recordings (SSRs), calcium imaging and pharmacology, we widen the understanding of how the olfactory signal is processed at the periphery.

Comparison of the environmental, energy, and thermal comfort performance of air and radiant cooling systems in a zero-energy office building in Singapore

In an experimental study set in Singapore’s tropical climate, we evaluated the thermal environmental performance, energy consumption, and thermal comfort of air and radiant cooling systems, operating at an operative and air temperature of 26 °C. 78 participants across five groups answered thermal comfort surveys in a crossover study design. Environmental performance metrics indicated that both systems produced similar conditions, with a noticeable difference in air velocity. The mean radiant temperature to air temperature difference was less than 0.5 °C in both systems. The radiant system exhibited a 33 % higher heat flux extraction than the air system and required less electrical power for the transportation of the cooling medium and ventilation air. Overall, the radiant system used 4 % less energy than the air system when controlled at 26 °C and 34 % when operated at 23 °C. Results show that radiant and air systems provided equal thermal comfort in cooling, with over 60 % of participants expressing satisfaction and ∼ 20 % voted neutral thermal satisfaction. ∼ 40 % of participants preferred cooler conditions, and ∼ 30 % desired increased air movement.

How Switchbacks Can Maintain a Longer Time in the Interplanetary Space

Parker Solar Probe, the closest spacecraft to the Sun, has renewed our understanding of the solar corona and the interplanetary space. One of its important findings is the prevalence of switchbacks, which display localized magnetic reversals along the otherwise Parker spirals. While some switchbacks might disappear quickly, others can maintain for a long period of time, and there are indications that many switchbacks strengthen from the solar corona to the interplanetary space despite their magnetic tension force, which tends to straighten the magnetic field lines. Therefore, how these switchbacks could be maintained for a long period of time remains a mystery. In this paper, we employed a 3D data-driven global full magnetohydrodynamics numerical model to explore the evolution of switchbacks formed in the dynamic corona. Our simulations indicate that two factors can affect the lifetime of a switchback. One factor is the combination of angle and leg length ensures that the switchback with greater curvature after reconnection can last longer, and the greater the angle, the more magnetic field lines that can be reconnected, and thus the longer the duration. We call this influencing factor flux tube shape factor. The other factor is the velocity shear, i.e., when the solar wind at the convex-outward turning of a switchback is faster than that at the concave-outward turning, the switchback becomes enhanced during propagation, and it weakens when the velocity difference is opposite.

Effect of maternal postnatal balanced energy protein supplementation and infant azithromycin on infant growth outcomes: an open-label randomized controlled trial

BackgroundMaternal undernutrition is a direct risk factor for infant growth faltering. ObjectivesWe evaluated the effect of postnatal balanced energy protein (BEP) supplementation in lactating women and azithromycin (AZ) in infants on infant growth outcomes. MethodsA randomized controlled superiority trial of lactating mother–newborn dyads was conducted in Karachi, Pakistan. Mothers intending to breastfeed their newborns with mid-upper arm circumference of <23 cm and live infants between 0 and 6 d of life were randomly assigned to 1 of 3 arms in a 1:1:1 ratio. Lactating mothers in the control arm received standard-of-care counseling on exclusive breastfeeding, nutrition, infant immunization, and health promotion plus iron-folate supplementation until the infant was 6 mo old. In intervention arm 1, mothers additionally received two 75-g sachets of BEP per day. In intervention arm 2, along with the standard-of-care and BEP to the mother, the infant also received 1 dose of azithromycin (20 mg/kg) at the age of 42 d . The primary outcome was infant length velocity at 6 mo. The total sample size was 957 (319 in each arm). ResultsFrom 1 August, 2018 to 19 May, 2020, 319 lactating mother–newborn dyads were randomly assigned in each arm, and the last follow-up was completed on 20 November, 2020. The mean difference in length velocity (cm/mo) between BEP alone and control was 0.01 (95% confidence interval [CI]: −0.03, 0.06), BEP plus AZ and control was 0.08 (95% CI: 0.03, 0.13), and between BEP + AZ and BEP alone was 0.06 (95% CI: 0.01, 0.11). There were 1.46% (14/957) infant deaths in the trial, and 17.9% (171/957) nonfatal events (injectable treatment and/or hospitalizations) were recorded. ConclusionsPostnatal maternal BEP supplementation and infant AZ administration could modestly improve infant growth outcomes at 6 mo, suggesting potential benefits in simultaneously addressing maternal and infant undernutrition.This trial was registered at clinicaltrials.gov as NCT03564652.

Elevated Smooth Pursuit Gain in Collegiate Athletes with Sport-related Concussion Immediately Following Injury.

Although there is evidence that sport-related concussion (SRC) affects oculomotor function and perceptual ability, experiments are often poorly controlled and are not replicable. This study aims to test the hypothesis that there are decreased values when assessing oculomotor impairment indicating poorer performance in SRC patients. Fifteen DI athletes presenting with SRC (7 females, 8 males) and 15 student volunteers (CON) (12 females, 3 males) completed a dynamic visual acuity (DVA) task that involved answering the direction of a moving stimulus (Landolt C) while wearing a head-mounted binocular eye tracker. There were 120 trials total with 60 trials presenting at 30º per second and 60 presenting at 90º per second. Various eye movement measurements, including horizontal smooth pursuit eye movements (SPEM) gain and saccadic peak velocity, were analyzed between groups using univariate ANOVAs. Saccade count in SPEM trials, accuracy, and vision were analyzed using Kruskal-Wallis tests. There was no statistical difference in saccadic peak velocity: SRC = 414.7 42º/s, CON = 406.6 40.6º/s. A significant difference was found between SRC patients and healthy controls in horizontal SPEM gain (SRC = 0.9 0.04, CON = 0.86 0.03, F(1,28) = 7.243, P = 0.012) indicating that patients demonstrated compensatory eye movements when tracking the target. There were significantly more saccades in all SPEM trials (P = 0.001). SRCoculomotor deficits manifest as elevated horizontal SPEM gain when assessed within 48 hours of injury and compared to healthy controls within the same age range. SRC demonstrates altered oculomotor ability. While accurate in tracking a stimulus, SRC patients may conduct less controlled eye movements.

An extended stochastic car‐following model and its feedback control

Real‐world traffic flow is influenced by various random factors. Gaussian white noise is employed to describe the inherent randomness of traffic flow. A stochastic optimization velocity model is established for dynamic analysis. To enhance the traffic flow stability, the velocity difference of two successive vehicles ahead is considered. The velocity difference feedback control strategy is proposed, utilizing the velocity differences between the vehicle and the two targeted vehicles as control signals. Stability conditions for both the stochastic optimization velocity model and the feedback control model are derived by using the moment stability theory. The study demonstrates that the random factors can destabilize traffic flow, while the proposed feedback control strategy effectively stabilizes traffic flow. Additionally, the influences of random factors on the stability of traffic flow are discussed extensively, aiding in understanding actual traffic congestion mechanisms and offering insights for traffic control strategies.

Influence of Instantaneous Shut‐In on the Safety of Tubing String in Ultra‐Deep High‐Temperature and High‐Pressure Gas Well

In this article, considering the factors such as well trajectory and tubing string structures, the transient shut‐in tubing string pressure fluctuation model of ultra‐deep high‐temperature and high‐pressure (hereinafter referred to as HTHP) gas well is established, the propagation of pressure wave along the well depth is obtained, and the effects of different production and shut‐in time on the fluctuating pressure and its variation range are analyzed. Through calculation and analysis, it can be seen that there are differences in pressure waveforms at different well depths. The closer to the bottom of the well, the more delayed the occurrence of water hammer, and the smaller the water hammer pressure value. The larger the production, the greater the pressure wave velocity, and the closer to the wellhead, the more obvious the change. For well X, the pressure wave velocity in the well section below 6500 m varies greatly with the increase of production. When the production is 140 × 104 m3 D−1, the difference of pressure wave velocity between the bottom hole and the wellhead is 105.19 m s−1. After instantaneous shut‐in, the wellhead pressure increases by 3.2% compared with the initial pressure and the bottom hole pressure increases by 0.6%.

Lithological control of the active Mejillones fault from Triassic to Quaternary, northern Chile

Understanding the lithological control of crustal faults near cities is important for assessing the seismic hazard and characterising complex fault systems. We studied the Mejillones Fault (MF), located near one of the strategic ports in northern Chile. The MF is an active geological fault that extends 40 km in the N-S direction and is part of an extensive complex system of structures known as the Atacama Fault System (AFS). We built an S-wave tomography model using seismic ambient noise data that was recorded continuously in a dense network of stations from 2013 to 2015. The tomographic maps exhibited velocity anomalies that correlate with surface geology. We found lower velocities in the western part of the MF than in the eastern zone, with a shear wave velocity (Vs) of about 2.4 km/s, associated to fractured metamorphic rocks (Triassic) and marine sediments (Neogene-Quaternary). Higher velocities (Vs > 3.0 km/s) in the eastern part of the fault are related to igneous rocks from the Upper Jurassic. The difference in velocities between the western and eastern zones of the MF remained persistent in depth. The potential depth of the MF could be >5 km and delimits the boundary between 2 different geological zones. Intermediate Vs (∼2.8 km/s) at −23.25°, observed up to 4 km depth, can be associated with andesitic rocks deposited in an intra-arc basin (Upper Triassic) and accommodated by the MF over the last ∼200 Myr, evidencing the activity of this fault from Triassic to Quaternary.

Investigation of the Effect of Mutual Diffusion on Hydrodynamic Parameters under Fluid Displacement

Formation of stagnant zones in a reservoir is mainly determined by differences in the flow velocity of fluids in heterogeneous micro and macro porous media. Additional resistance forces to fluid flow, which are of a different nature, result in a decrease in flow velocity. Forces arising from the diffusion of fluids with different physical-chemical characteristics and acting in different directions are one such class of the above-mentioned drag forces. An increase in the degree of fluid mineralization is capable of causing changes in the flow of a continuous diffusion layer. The mathematical solution of the problems considered in the study was solved using the "Matlab" program using the Finite Difference Method. The paper presents the results of displacement studies in porous media under the assumption that the flow characteristics of displacing and displaced fluids can be controlled. Theoretical and experimental substantiations showing the effect of diffusion process in fluids on flow properties have been carried out in the displacement process. The theoretical solution and modelling of concentration change in flow of mutually soluble dispersed solutions were presented. The effect of diffusion on the flow velocity in the process of displacement of mutually soluble liquid mixtures has been evaluated.

Contralateral differences in ankle SBP and pulse wave velocity: associations with incident heart failure and mortality.

Contralateral differences in brachial SBP are indicative of underlaying cardiovascular issues. To examine the association of contralateral differences in ankle SBP, brachial-ankle pulse wave velocity (baPWV), and heart-ankle pulse wave velocity (haPWV) with incident heart failure and all-cause and cardiovascular mortality. Cox proportional-hazards models were used to calculate hazard ratios and 95% confidence intervals (95% CIs) in 5077 participants (75 ± 5 years) of the Atherosclerosis Risk in Communities study. Over a mean follow-up of 7.5 ± 2.2 years, there were 457 heart failure events, 1275 all-cause and 363 cardiovascular deaths. Interankle SBP difference of at least 10 mmHg [hazard ratio = 1.12; confidence interval (CI) 1.00-1.28], at least 15 mmHg (hazard ratio = 1.21; CI 1.03-1.43), contralateral difference in baPWV more than 240 cm/s (hazard ratio = 1.22; CI 1.02-1.46), and haPWV more than 80 cm/s (hazard ratio = 1.24; CI 1.04-1.48) were each independently associated with all-cause mortality after adjustment for confounders. Contralateral differences in ankle SBP of at least 15 mmHg (hazard ratio = 1.56; CI 1.17-2.09), and haPWV more than 80 cm/s (hazard ratio = 1.42; CI 1.03-1.96) were both independently associated with cardiovascular mortality. Unadjusted analysis revealed that those with contralateral differences in ankle SBP of at least 10 and at least 15 mmHg, baPWV more than 240, and haPWV more than 80 cm/s had higher risks of heart failure (all P < 0.05). These results underscore the significance of evaluating contralateral differences in ankle SBP and PWV as potential markers of increased mortality risk among older adults.

Verification of Delayed Equilibrium Model for the R134a critical flow in a slit

R134a has the advantage of conducting visible critical flow experiments because of the lower temperature and pressure at the critical point than water. Whether the water critical flow model is suitable for predicting the flow rate and the pressure profile of R134a critical flow is unknown. An experiment on the critical flow rate and the pressure profile of R134a critical flow in a slit, mimicking the shape of a crack in the pipe, has been conducted. The dimension of the slit and the subcooling degree at the entrance are changed in the experiment. The Delayed Equilibrium Model (DEM), which is accurate for the water critical flow mass flux in a slit, is verified based on the experiment results. The empirical coefficients in the original DEM are adjusted according to the approximate saturated curve of R134a. The conservative and aggressive approaches to changing empirical coefficients are verified, respectively. For R134a, the ratio of boiling pressure to saturated inlet pressure is determined to minimize the relative error of volume flow rate and pressure profile in the slit with 0.3 mm width. It proves that the aggressive approach is lower in relative errors and differences in relative errors among different slit widths and different subcooling degrees. For the aggressive approach, the abstract value of the relative error of volume flow rate is lower than 20% in most cases. The abstract value of the mean relative error of pressure is lower than 15% in most cases. Besides, the differences in relative errors among different slit widths are not significant, and the differences in relative errors tend to be zero as the subcooling degree increases. DEM is adequate for predicting the volume flow rate and pressure profile for the R134a critical flow in a slit. Nevertheless, the relative error of the volume flow rate should disperse around zero at low subcooling degree, which is not achieved in this research. Further optimization requires more rigorous analytical methods and experiment data to find the best set of empirical coefficients, and the effect of velocity difference may be introduced.

GNSS spoofing detection for UAVs using Doppler frequency and Carrier-to-Noise Density Ratio

Unmanned Aerial Vehicles (UAVs) are typical real-time embedded systems, which require precise locations for completing flight missions. The Global Navigation Satellite System (GNSS) plays a crucial role in navigation and positioning for UAVs. However, GNSS spoofing attacks pose an increasing threat to GNSS-dependent UAVs. Existing spoofing detection methods primarily rely on simulated data, perception data from multiple UAVs, or various control parameters. This paper proposes SigFeaDet, a signal feature-based GNSS spoofing detection approach for UAVs utilizing machine learning techniques. The core concept revolves around identifying anomalies in signal features arising from differences between authentic and spoofing signals. Key signal features, including Carrier-to-Noise Density Ratio (CN0) and Doppler frequency crucial for GNSS positioning, are employed to discern spoofing signals. Various machine learning algorithms are leveraged to train on GNSS signal data, determining the most effective classifier. TEXBAT GNSS dataset is processed to extract spoofing signal data, and flight experiments are conducted to gather GNSS data, augmenting the authentic GNSS signal dataset. The detection accuracy exceeds 95%. Equal Error Rate (EER) is approximately 5%. We evaluate various impact factors on SigFeaDet to show its robustness, including differences in velocities, altitudes, and experimental locations (10 kilometers apart), and the accuracy consistently surpasses 99%.

Research on dynamic target steady and quasi-grasping method of coal gangue sorting robot based on global planning and local vision

ABSTRACT Using robots instead of manual sorting of coal gangue can significantly improve the sorting rate. However, the stable grasping of the target gangue by the manipulator is the key to the efficient sorting of robot. The coal gangue on the belt conveyor has the characteristics of high speed and high quality. In the process of grasping, the velocity difference between the end of the manipulator and the coal gangue will cause impact load. In addition, the belt speed fluctuation and deviation also lead to the inaccurate location of the gangue, resulting in excessive position error of the manipulator during grasping, leading to grasping failure. For this reason, a synchronous tracking trajectory planning method of manipulator based on global planning and local visual servo is proposed in this paper. In this method, the manipulator is controlled by the BPNG method to reach the top of the target gangue quickly, and the accurate location of the target gangue is completed by the extended FDSST tracking algorithm. The manipulator uses the “position-velocity-acceleration” three-loop PID square method to realize the synchronous tracking trajectory planning of the target gangue. The experimental results show that this method can achieve stable and accurate grasping of target gangue by manipulator.

The exploration of the upper body kinematics and kinematic asymmetries during forwards and backwards wheelchair propulsion

The current literature available on the kinematic asymmetries in the upper body during wheelchair propulsion remains limited (Slowick, Requejo, Mulro. &amp; Neptune, 2015, Front Bioeng Biotech, 3, 86-86). This research provides an opportunity to add to this limited area and help provide an understanding of the how the upper body movements change when faced with a change in speed and direction. The present cross-sectional laboratory study aimed to explore the kinematics and kinematic asymmetries during forwards and backwards wheelchair propulsion in able bodied individuals. This study investigated the effect of changes in speed and quantified the upper body kinematics of forwards and backwards wheelchair propulsion. Upon ethical approval, five able bodied participants, 3 male and 2 female (age = 21 ± 1 years, stature = 173 ± 8 cm, mass = 73 ± 7 kg) provided written informed consent and participated in this study. Participants took part in exercise regularly but had no prior wheelchair experience. Individual measurements (Height, weight, weekly exercise levels, injury history, dominant hand and upper body pain via the musculoskeletal pain questionnaire) were taken then participants took part in a series of trials in a wheelchair. Four Inertial Measurement Units (IMeasureU, Blue Trident, VICON, Oxford, UK) were placed on the participant's 7th cervical vertebrae, underneath the wheelchair seat and on the lateral side of each humerus above the elbow joint. Before testing began, participants were given a five-minute familiarisation period on the wheelchair. The testing consisted of ten forwards and ten backwards self-paced wheelchair propulsions on an Invictus Active Trainer (Invictus Active, Wolverhampton, UK), a 20 metre sprint overground on a track (with verbal encouragement throughout the sprint) and a single arm 3 kg medicine ball throw. All tests were performed from a stationary start and shoulder angles were measured to 180° before each test began. This research expects to see a difference in angular velocity between each participant's arms, with a greater level of asymmetry as speed increases. Participants are required to work harder in order to gain speed and as a result their propulsion technique will change to meet the new demands. The other expectation is to see the same side as the participants dominant hand have a higher level of force production during propulsion compared to their arm with the non-dominant hand.

Nonequilibrium molecular dynamics investigation on friction behavior of organic friction modifiers under dynamic load

The evolution of lubricating oil containing additives under dynamic conditions is very significant, since its oil film structure, velocity distribution, and adsorption characteristic have an obvious impact on friction and wear. In this work, a boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) models under sinusoidal load were carried out by nonequilibrium molecular dynamics (NEMD), using iron oxide as the substrate, hexadecane, and stearic acid molecules as lubricants. It was discovered that the friction in the BL regime is positively correlated with the degree of additive’s solidification. The greater the solidification degree of additive layers, the less the interlacing between them, making the relative motion between them easier and reducing compression oscillation within them, thus diminishing friction in the BL regime. The degree of liquefaction of base oil and additive regions, as well as the velocity difference within their interlacing zones, are connected to the friction force in the EHL regime. At high frequencies as well as large amplitudes, the oil film has a very high degree of liquefaction, which facilitates internal shear in it, and there is essentially no relative motion between the base oil and additives, resulting in low friction.

The SAMI Galaxy Survey: impact of star formation and AGN feedback processes on the ionized gas velocity dispersion

ABSTRACT We investigate the influence of star formation and instantaneous active galactic nuclei (AGN) feedback processes on the ionized gas velocity dispersion in a sample of 1285 emission-line galaxies with stellar masses $\log \, (M_*/\mathrm{ M}_{\odot }) \ge 9$ from the integral-field spectroscopy Sydney-AAO Multi-object Integral-field Galaxy Survey. We fit both narrow- and broad-emission-line components using aperture spectra integrated within one effective radius, while ensuring the elimination of velocity differences between the spectra of individual spaxels. Our analysis reveals that 386 (30 per cent) galaxies can be adequately described using a single-emission component while 356 (28 per cent) galaxies require two (broad and narrow) components. Galaxies characterized by high-mass, elevated star formation rate surface density, or type-2 AGN-like emissions tend to feature an additional broad-emission-line component, leading to their classification as double-component galaxies. We explore the correlations between M* and gas velocity dispersions, highlighting that the prominence of the broad component significantly contributes to elevating the gas velocity dispersion. Galaxies displaying AGN-like emission based on optical definitions show enhanced gas velocity dispersions. In star-forming galaxies, both stellar mass and star-formation rate surface density substantially contribute to the velocity dispersion of the narrow component. Increased star-forming activity appears to elevate the velocity dispersion of the narrow component. The broad component exhibits a weaker dependence on stellar mass and is primarily driven by galactic outflows. We suggest that strong star-forming activity leads to the formation of a broad-emission-line component, but the impact on inflating gas velocity dispersion is moderate. On the other hand, AGN-driven outflows appear to be a more important contributor to the elevated velocity dispersion of the ionized gas.

Evaluation of wind farm performance over heterogeneously rough terrain using large eddy simulation

We evaluate the effect of an abrupt change in the surface aerodynamic roughness height on a wind farm sited on it using the large eddy simulation (LES). Compared to a wind farm sited on a uniformly rough surface, the alteration in aerodynamic surface roughness from a rough to smooth value leads to substantial changes in the first-order and second-order turbulent statistics. Specifically, the rough-to-smooth surface roughness transition leads to an acceleration of the flow downstream of it, which affects the wake recovery and wind farm power production. Different velocity deficits are formulated considering different definitions of “upstream” velocity. The usual deficit, i.e., the difference between the overall wind farm upstream velocities and downstream of a turbine, attains negative values near the ground, rendering it difficult to model within the usual Gaussian radial-shape framework. An alternative definition, i.e., the difference in velocity at the same location with and without turbines on a heterogeneous surface, consistently yields positive values and is amenable to Gaussian shape-based modelling. The power generation decreases as the step change in surface roughness progressively moves into the wind farm. Maximum power is produced when all turbines are placed downstream of the surface roughness jump and minimum power is generated for a homogeneously rough surface when the entire wind farm is placed on the rough surface.

PIV experimental study on water-sediment two-phase flow in NACA0012 cascade

Abstract Sediment wear is one of the important reasons for the damage of hydraulic machinery components, and the motion characteristics of sediment are the key factors to determine the degree of wear damage. In order to reveal the mechanism of sediment wear of turbine guide vane, motion characteristics of sediment near the wall of NACA0012 cascade were studied by PIV test method. In this research, fluorescent and sediment particles were used as tracer particles respectively, and the particle images of solid and liquid phases were recorded by double-camera synchronous imaging method. Finally, the synchronous velocity field of solid and liquid phases was determined by correlation analysis of particle images. The experimental results show that the PIV test method can accurately determine the motion characteristics of the solid phase. There is velocity slip between the solid phase and the liquid phase, and the velocity deviation is related to the factors of particle characteristics and Reynolds number.

Hydraulic transient calculation by wave tracking method for pumped storage power plant with four units in a diversion system

Abstract Hydraulic transient calculations are a key issue related to the operational safety of pumped storage power plants. Based on the new calculation method, wave tracking method, this paper establishes a calculation model for the hydraulic transient of pumped storage power plant, verifies the accuracy of the calculation model through hydraulic model experiments, and calculates the transient process of Guangdong Qingyuan pumped storage power plant. The results show that the calculation error is reduced by considering the difference of wave velocity of different branch pipes by wave tracking method. The wave tracking method is convenient to establish a calculation model of pumped storage power plant with four units in a diversion system, which is suitable for the load shedding transient regime of the turbine mode and the pump outage condition, and the accuracy is good. Wave parameters visually show the connection between flow rate, pressure changes within the water transmission system, and surge fluctuations in the regulator well throughout the hydraulic transition.

Evolution of some flow-related properties of diffusive aerosols along a tube

This is the third of a series of papers dealing with the behavior of Brownian aerosol particles immersed in a laminar fluid flow. The evolution along the tube of the distributions of particle radial positions (RPD), particle residence time (RTD), and particle mean axial velocity (MAVD) were determined by Monte Carlo (MC) simulation of particles trajectories. The RPD and particle penetration was also determined by numerical solution of the advection-diffusion equation (ADE) with negligible particle axial diffusion. The fairly good agreement shown between the results obtained by these two methods justifies our confidence on the use of the MC technique to determine other particle properties, as MAVD and RTD, for which the corresponding differential equation is yet unknown. Flow-related properties of the aerosol, such as penetration and residence time, are mainly determined by its MAVD. The MAVD is intimately related to the RPD; the latter evolves in such a manner that the surviving particles tend to accumulate nearer the tube axis and farther from the wall. When the fluid local velocity depends on the spatial location, the mean particle axial velocity increases as the aerosol flows downstream the tube, and its value can be considerably larger than the mean fluid velocity, in spite that no external force is acting on the particle. A direct consequence of this counterintuitive fact is that the mean aerosol residence time in the tube can be much smaller, by a factor of ∼0.65, than that of the fluid for even moderate values of the particle diffusion coefficient. This asymptotic value of the aerosol mean residence time can be predicted using the ADE in conjunction with a simple estimation model proposed here. If the fluid velocity is constant within the tube (uniform or plug flow), the mean particle axial velocity is everywhere equal to the fluid velocity, and particles and fluid spend the same time to traverse the tube. The larger the departure of the fluid velocity profile from uniformity, the larger the difference of mean axial velocity and mean residence time between particles and fluid.