Average Velocity Research Articles

Neutron activation of stable isotopes in soil and groundwater from a radionuclide production facility, South Africa

ABSTRACT The neutron activation of stable isotopes in environmental matrices, such as soil and groundwater, is a critical aspect of assessing the impact of radionuclide production facilities on the surrounding ecosystem. The envisioned Low-Energy Radioactive Ion Beams (LERIB) facility at the iThemba LABS, South Africa is anticipated to generate significant sources of ionising radiation. The study investigated the possible repercussions of neutron irradiation stemming from the facility, focusing on the activation of stable isotopic compositions in the environment. The investigation employed a combination of experimental and analytical techniques to characterize the neutron activation products in soil and groundwater samples collected from the vicinity. Samples were collected from designated areas for background radiological measurements and were irradiated with neutrons for a period of 1 h. The induced radioactivity measured by the High Purity Germanium detector included 24Na, 22Na, 54Mn, 52Mn, and 46Sc. The application of Darcy's law for groundwater velocity suggests that radionuclides in groundwater will migrate at an average flow velocity of 0.8 m/day. The isotopes with longer half-lives have count rates at background concentrations; therefore, environmental impacts on the site and surrounding communities might be minimal.

Shear-Wave Elastography Gradient Analysis of Newly Diagnosed Breast Tumours: A Critical Analysis

Background: A better understanding of the peritumoral stroma changes due to tumour invasion using non-invasive diagnostic methods may improve the differentiation between benign and malignant breast lesions. This study aimed to assess the correlation between breast lesion differentiation and intra- and peritumoral shear-wave elastography (SWE) gradients. Methods: A total of 135 patients with newly diagnosed breast lesions were included. Intratumoral, subsurface, and three consecutive peritumoral SWE value measurements (with three repetitions) were performed. Intratumoral, interface, and peritumoral gradients (Gradient 1 and Gradient 2) were calculated using averaged SWE values. Statistical analysis included descriptive statistics and an ordinary one-way ANOVA to compare overall and individual gradients among Breast Imaging-Reporting and Data System (BI-RADS) 2, 3, and 5 groups. Results: Malignant tumours showed higher average SWE velocity values at the tumour centre (BI-RADS 2/3: 4.1 ± 1.8 m/s vs. BI-RADS 5: 4.9 ± 2.0 m/s, p = 0.04) and the first peritumoral area (BI-RADS 2/3: 3.4 ± 1.8 m/s vs. BI-RADS 5: 4.3 ± 1.8 m/s, p = 0.003). No significant difference was found between intratumoral gradients (0.03 ± 0.32 m/s vs. 0.0 ± 0.28 m/s; p > 0.999) or gradients across the tumour–tissue interface (−0.17 ± 0.18 m/s vs. −0.13 ± 0.35 m/s; p = 0.202). However, the first peritumoral gradient (−0.16 ± 0.24 m/s vs. −0.35 ± 0.31 m/s; p < 0.0001) and the second peritumoral gradient (−0.11 ± 0.18 m/s vs. −0.22 ± 0.28 m/s; p = 0.037) were significantly steeper in malignant tumours. The AUC was best for PTG1 (0.7358) and PTG2 (0.7039). A threshold value for peritumoral SWI PT1 above 3.76 m/s and for PTG1 below −0.238 m/s·mm−1 indicated malignancy in 90.6% of cases. Conclusions: Evaluating the peritumoral SWE gradient may improve the diagnostic pre-test probability, as malignant tumours showed a significantly steeper curve of the elasticity values in the peritumoral stroma compared to the linear regression with a relatively flat curve of benign lesions.

Fast lipid vesicles and dielectric particles migration using thermal-gradient-induced forces

Abstract Lipid vesicles represent small biological particles that can be used for both targeted drug delivery systems and clinical studies. However, their optical manipulation is hindered by the small difference in the refractive indices with the surrounding medium and the high trapping laser powers that are required. In this work, we combine gradient force, thermophoresis, and diffusiophoresis to deliver and trap individual lipid vesicles with low trapping laser powers. The total optothermal force exerted on liposomes causes them to migrate rapidly toward the laser focus with a high average migration velocity of 1.77 µm under 7.3% w/v PEG concentration and low trapping laser power of 1 mW. A high normalized experimental trap stiffness of 0.88 (pN/µm)/mW was obtained at 7.3% w/v PEG/water solution. This work opens new ways for bioparticle sorting and manipulation with potential applications in cellular studies, drug delivery, biosensing, and medicine

Firefighter Hose Rolling Method: Low Back Pain Risks Analysis with Full-Factorial Approach

Firefighters frequently face the risk of Low back pain (LBP) due to the strenuous nature of their duties, especially during hose rolling tasks. Prioritizing their safety and health is vital. This study aimed to evaluate and compare various hose rolling techniques to lower the LBP risk in firefighters. A full-factorial approach was employed to exhaustively examine every possible combination of three key factors: the hose rolling method (conventional, mechanical, motorized), hose condition (dry, wet, dirty), and hose length (10, 20, 30 meters). Across 27 different trials, an Industrial Lumbar Motion Monitor (iLMM) was used to assess the LBP risk, which is lift rate, average twisting velocity, maximum moment, maximum sagittal flexion, and maximum lateral velocity. The study's results indicated that conventional method had the highest LBP risk at 58.22%, with mechanical rolling at 34.33%. In contrast, the motorized hose rolling method showed a significantly lower risk, averaging at 17.44%. This denotes a 40.78% reduction in LBP risk compared to conventional hose rolling method, positioning the motorized roller as the most effective and safest option among those tested. This method's efficacy underscores its potential as a viable solution for improving firefighter safety. These findings offer important insights into occupational health and safety in firefighting. The data suggests that adopting motorized hose rolling tools could significantly alleviate the physical burdens and associated health hazards firefighters face. This advancement is a critical step towards enhancing their overall safety and well-being in the field.

Diffusion dynamics of an overdamped active ellipsoidal Brownian particle in two dimensions

Shape asymmetry is the most abundant in nature and has attracted considerable interest in recent research. The phenomenon is widely recognized: a free ellipsoidal Brownian particle displays anisotropic diffusion during short time intervals, which subsequently transitions to an isotropic diffusion pattern over longer timescales. We have further expanded this concept to incorporate active ellipsoidal particles characterized by an initial self-propelled velocity. This paper provides analytical and simulation results of diffusion dynamics of an active ellipsoidal particle. The active ellipsoidal particle manifests three distinct regimes in its diffusion dynamics over time. In the transient regime, it displays diffusive behavior followed by a super-diffusive phase, and in the longer time duration, it transitions to purely diffusive dynamics. We investigated the diffusion dynamics of a free particle as well as a particle in a harmonic trap, and a particle subject to a constant field force. Moreover, we have studied the rotational diffusion dynamics and torque production resulting from an external constant force field. Furthermore, our investigation extends to the examination of the scaled average velocity of an ellipsoidal active particle, considering both a constant force field and a one-dimensional ratchet.

The volumetric ultrasound imaging strategy for quantification of the defects in concrete based on the optimized cumulative kurtosis method

Currently, ultrasonic tomography is widely used for quantifying the status of damage/flaw in various materials including metal, concrete, and composite. It is capable of visualizing the internal damage or flaws by reconstructing the velocity of ultrasound. For most cases, the conventional ultrasonic tomography is adapted for slice-based investigations. Though 3D image can be generated by slice-based method, the involvement of multi-scan interpolation caused high computational cost and unexpected errors. Moreover, for 3D imaging, two essential factors are dominant: (i) reconstructing the velocity; and (ii) scheme of forming up the 3D image. To this end, this study proposed to develop a novel volumetric ultrasound imaging strategy with high accuracy. To obtain more accurate Time-of-Flight (TOF) for ultrasonic velocity, an improved method based on cumulative kurtosis is proposed. With the proposed method, the adverse influence of internal complexity within samples on ultrasound was reduced. The proposed novel volumetric ultrasound imaging strategy was verified numerically and experimentally. Finally, the performance of the proposed method has been evaluated by the comparison of three-dimensional imaging results with different inclusion. Additionally, the parametric study was conducted using path average velocity, voxel velocity, and image accuracy. The results show a positive correlation between the number of voxels and imaging accuracy. However, as the number of voxels increases, the errors introduced by the Simultaneous Algebraic Reconstruction Technique (SART) increase. The influential factors on the imaging accuracy were discussed, such as inclusion eccentricity, the relationship among the reduced volume imaging quantity, and accuracy in voxel inversion result. For further application, the recommendations were also provided.

The Normal/Umklapp/Intervally/Intravally transport property of 2D SnSe

Based on the Boltzmann transport equation, both the electrical and thermal transport properties of 2D SnSe have been accurately calculated. The mobility of n-type SnSe is higher than that of p type due to the greater average velocity and smaller electron-phonon coupling matrix. For both n-type and p-type electron-phonon scattering, the LA phonon mode primarily governs the total, Normal, Umklapp, Intervally, and Intravally scattering processes. As the temperature increases from 300K to 800K, the LA phonon remains the dominant scattering mode. Compared to the Umklapp and Intervally scattering process, both Normal and Intravally scattering processes mainly govern electrical transport. In terms of phonon-electron scattering, the Normal/Intravalley processes dominate initially, followed by the Umklapp/Intervalley processes governing thermal transport as the temperature increases, governing thermal transport. The critical carrier concentration changes from 1018 cm−3 to 1019 cm−3, as the temperature rises from 300K to 800K, indicating a shift in the competitive relationship between Normal/Intravalley and Umklapp/Intervalley processes with temperature. Using the iteration method, the optimal power factor for n type@300K, p type@300K, n type@800K, p type@800K are 1.63 μW/cmK, 5.62 μW/cmK, 2.30 μW/cmK, 4.04 μW/cmK, respectively. After considering phonon-electron scattering, the lattice thermal conductivity of n type (p type) is 0.70 W/mK (0.64 W/mK) at 300K and 0.31 W/mK (0.30 W/mK) at 800K. The optimal ZT of n type is 1.17 at 800K, originating from the Normal scattering process, while the optimal ZT of p type is 0.86, stemming from the Intravally scattering process. Our results provide a deeper understanding of the transport processes in SnSe and offer insights for tuning the thermoelectric properties of two-dimensional materials through electron-phonon and phonon-electron scattering processes.

Kinetic Predictors of Weightlifting Performance in Young Weightlifters.

Morris, SJ, Oliver, JL, Pedley, JS, Radnor, JM, Haff, GG, Cooper, S-M, and Lloyd, RS. Kinetic predictors of weightlifting performance in young weightlifters. J Strength Cond Res XX(X): 000-000, 2024-Relationships between force-generating capabilities and weightlifting performance (e.g., snatch, clean and jerk [C&J], and combined total) have previously been explored in adult weightlifters; however, associations in young athletes are unknown. The purpose of this study was twofold: (a) to examine the relationships between countermovement jump (CMJ) and isometric midthigh pull (IMTP) kinetics and weightlifting performance in young weightlifters and (b) to determine the proportion of weightlifting performance that could be accounted for by CMJ and IMTP kinetics using principal component analysis (PCA). Thirty-seven young weightlifters (12-18 years of age) completed 3 trials of CMJ and 2 trials of the IMTP assessments on dual force plates. Recent competition maximum loads, obtained within 2 weeks of the data collection, for the C&J and snatch were also recorded. Pearson's zero-order correlation coefficients demonstrated moderate to very high correlations (r = 0.359-0.801; all p ≤ Benjamini-Hochberg critical values [B-Hα]) between CMJ kinetic variables, including jump height, average braking force, average braking velocity, absolute and relative braking net impulse, absolute and relative force at minimum displacement, absolute and relative propulsive force, absolute and relative propulsive net impulse and average propulsive velocity, and weightlifting performance. High to very high correlations were evident between IMTP peak force and relative peak force and all weightlifting performance metrics (snatch, C&J, combined total, combined total [kg]/body mass [kg-0.67], and Sinclair's total; r = 0.538-0.796; p ≤ B-Hα). Components from the PCA were used to conduct stepwise, multiple, linear regression analyses. Moderate (45.8-52.9%) and large percentages (79.1-81.3%) of variance in absolute measures of weightlifting performance were explained by IMTP peak force variables and CMJ propulsive variables, respectively. These novel findings indicate that IMTP peak force variables and CMJ propulsive variables could provide valuable insight for talent identification and long-term athletic development in junior weightlifting pathways.

Enhancing pure NH3 combustion: Impacts of O2 enrichment under MILD conditions in a 20-kW semi-industrial scale furnace

This experimental work provides insights into the effects of oxygen (O2) enrichment on pure ammonia (NH3) combustion in a 20-kW semi-industrial scale furnace featuring an industrial-grade burner operated under MILD/Flameless conditions. The impact of O2 enrichment on the NH3 combustion stabilization, the flame and furnace temperature, the exhaust emissions, and the OH* chemiluminescence were explored. The tests were conducted by varying O2 concentration in the oxidizer stream from 21 % to 50 % and using two different oxidizer injectors to achieve average inlet velocities of 80 m/s and 150 m/s while keeping the inlet power and the total oxidizer mass flow rate constant. Stable flameless combustion with a distributed reaction zone and a consistent and uniform temperature profile throughout the combustion chamber was achieved with O2 enrichments higher than 34 %. Nevertheless, high levels of NH3 slips were observed, which were drastically reduced to negligible concentrations at higher O2 enrichments. On the contrary, NO emissions increased with the O2 fraction with an opposite non-linear trend compared to that of NH3 slip. An optimum trade-off between NOx emissions and NH3 slip was achieved by co-firing NH3 with O2=37 % with ID16 and 36 % with ID20 injector. This study also compares the behavior of pure O2-enriched NH3 combustion under flame and MILD combustion conditions to highlight the advantages of oxygen-enhanced NH3 flameless combustion. While operating in flame mode ensured a stable ammonia oxidation process already at low O2 enrichment=30 %, NO emissions and NH3 slips were significantly higher than those measured under MILD conditions. Finally, the impact of varying industrial load and the related heat balance on the NH3 slip was assessed at different levels of O2 enrichments at a fixed equivalence ratio. The overall results show that O2-enriched flameless ammonia combustion can simultaneously expand the range of stable combustion and reduce NO and NH3 emissions.

An Experimental Study of the Morphological Evolution of Rills on Slopes under Rainfall Action

Accurately monitoring the morphology and spatiotemporal evolution characteristics of the entire process of slope erosion rill development is essential to circumvent the limitations inherent in traditional methods that rely on average flow velocity for hydrodynamic parameter calculations. This study employs an environmental chamber and a self-developed slope erosion test device to perform erosion tests on slopes with varying gradients and rainfall intensities. By integrating the structure-from-motion (SfM) method, fixed grid coordinate method, and continuous camera combined with the dye tracer technique, the morphological indexes and hydrodynamic parameters of the entire rill development process are precisely computed. The main conclusions are as follows: The entire process of slope rill development can be divided into three distinct stages. The initial stage is characterized by the appearance of tiny rills with mild erosion. The middle stage involves severe transverse spreading erosion and longitudinal undercutting, resulting in diverse rill morphologies. The final stage is marked by the stabilization of morphological characteristics. The peak slope soil loss is observed during the middle stage of rill development. The most effective parameters for characterizing slope soil loss from the beginning to the end are the Reynolds number and flow shear stress, the Froude number and flow shear stress, and the Froude number during different periods. Throughout the development of rills, the flow velocity initially decreases and then gradually increases until it stabilizes. The morphological indexes, including rill density, dissected degree, inclination, and complexity, generally show an increasing trend. However, in the middle stage, the rate of increase slows down, followed by a sharp rise at certain points. The optimal hydraulic parameters for evaluating rill density across different slope gradients, which were found to be the Darcy–Weisbach drag coefficient and real-time flow velocity, for assessing rill dissected degree, complexity, and inclination, were the Reynolds number and flow power. Under varying rainfall intensities, the most effective hydraulic and kinetic parameters for evaluating rill density, dissected degree, and inclination were flow shear stress and Reynolds number; for assessing rill complexity, the Reynolds number and flow power were used. The findings of this research enhance the accuracy of hydrodynamic parameter calculations in rill erosion tests, enable precise prediction of rill development trends on slopes, and offer innovative approaches for real-time dynamic monitoring of rill morphology and characteristics. These advancements are of significant importance for soil and water conservation and sustainability.

The impact of V-flow on preoperative diagnosis of thyroid tumors: individually and as part of multimodal sonographic imaging.

V-flow is a dynamic ultrasound technique that visualizes perfusion patterns by displaying dynamic arrows that change in response to the flow of erythrocytes. Furthermore, it provides quantitative values for the maximum and mean velocity of blood flow as well as a percentage value for turbulence. The aim was to enhance the preoperative diagnostic accuracy of thyroid lesions by combining V-flow with established ultrasound modes.B-mode, CCDS, elastography, CEUS, and V-flow were performed on 101 patients. After the ultrasound examination, every nodule was confirmed as benign or malignant via histopathology. The Kruskal-Wallis test, ROC curve, and binary logistic regression were used for the statistical analysis.93 benign regressive thyroid nodules and 8 carcinomas were included in this study. The average mean velocity value for benign lesions was measured at 19.5 cm/s and at 10.7 cm/s for malignant lesions (p = 0.039). The average turbulence percentage was 26.1% for benign nodules and 46.7% for carcinomas (p = 0.016). Carcinomas exhibited a slower and more turbulent perfusion pattern compared to benign tumors. A V-flow-centered system achieves a sensitivity of 100.0% and a specificity of 84.9% in predicting malignancy. This system could have reduced the number of unnecessary thyroid surgeries for benign lesions in our patient group by 70%.The capillary perfusion of thyroid nodules represents a significant indicator of its status. By analyzing the velocity and turbulence level of microvascular blood flow, V-flow offers promising prospects for accurately distinguishing between benign and malignant thyroid lesions. When integrated into a comprehensive multimodal sonographic imaging approach, V-flow further enhances diagnostic accuracy. · V-flow allows for qualitative and quantitative analysis of microvascular perfusion. · Malignant tumors are associated with slower and more turbulent microvascular hemodynamics. · Combining V-flow with other ultrasound modes eases the diagnosis of thyroid carcinomas. · Brandenstein MK, Zhang L, Scharf G et al. The impact of V-flow on preoperative diagnosis of thyroid tumors: individually and as part of multimodal sonographic imaging. Fortschr Röntgenstr 2024; DOI 10.1055/a-2350-0107.

Analytical and Computational Modeling of Relaxation Times for Non-Newtonian Fluids

With the availability of efficient and sophisticated finite element analysis (FEA) and computational fluid dynamics (CFD) tools, engineering designs are becoming more software-driven and simulation-based. However, the insights relevant to engineering designs tend to be hidden within massive temporal and spatial data produced with full-fledged three-dimensional simulations. In this paper, we present a preliminary study of the controlled intermittent dispensing of a typical non-Newtonian glue employed in the manufacturing of electric vehicles (EVs). The focus of the study is on the scaling issues derived from different computational and analytical models of interest and importance to the precision control of this non-Newtonian fluid, the lowest dynamic viscosity of which at extremely high shear rates is nearly four million times that of water. More specifically, the abrupt change of the inlet pressure with a constant outlet or ambient pressure and various modeling strategies for transient viscous internal flow with both Newtonian and non-Newtonian fluids are modeled and compared. The analytical and computational results of the developing Newtonian fluid, i.e., water, are derived and computed for validation and verification purposes before the actual applications to the developing non-Newtonian fluid. The concept of a well-established relaxation time before the onset of the steady solution for Newtonian fluids has been validated with both analytical and computational approaches before its expansion and adoption to non-Newtonian fluids with complex rheological behaviors. Other issues attributed to transient operations and precision controls of non-Newtonian fluid delivery involve the pressure pulse and pressure wave propagation within the flexible pipe with compressible or almost incompressible non-Newtonian fluids with a constant pressure at the outlet and a constant mass flow rate or average axial velocity at the inlet, which will be addressed in a separate paper.

Comparison between Liquid Immersion, Laser Diffraction, PDPA, and Shadowgraphy in Assessing Droplet Size from Agricultural Nozzles

Spray droplet diameters play a key role in the field of liquid plant protection product (PPP) application technology. However, the availability of various measurement techniques, each with its unique operating principles for evaluating droplet size spectra, can lead to different interpretations of spray characteristics. Therefore, in this study, four measurement techniques—Liquid Immersion (LI), Laser Diffraction (LD), Phase Doppler Particle Analysis (PDPA), and Shadowgraphy (SG)—were utilized to evaluate the droplet size distribution of agricultural spray nozzles. Additionally, PDPA and SG were used to assess the average velocity of spray droplets. Experiments were conducted in three different laboratories with the main aim of comparing results obtained with various types of equipment utilized under ordinary practical conditions. Spraying tests were carried out using three flat fan nozzles and an air-induction flat fan nozzle. As a general trend, the lowest values for droplet diameters were measured using the Laser Diffraction technique, followed by Shadowgraphy. The PDPA technique provided the highest values for mean diameters (D10, D20, and D30) and the numeric median diameter (Dn0.5), whereas the Liquid Immersion method yielded the highest values for the Sauter mean diameter (D32) and volumetric diameters (Dv0.1, Dv0.5, and Dv0.9). Importantly, all measurement techniques were able to discriminate the four nozzles based on their Dv0.5 diameter. Average droplet velocities showed a similar pattern across the four nozzles with the PDPA and the SG measurement techniques. The differences in diameter values observed with the four measurement techniques underline the necessity of always including reference nozzles in spray quality assessments to base classifications on relative rather than absolute values.

Vibrational Characteristics of a Submerged Double-Shell Structure with Acoustic-Structure Coupling: An Analytical Model and Analysis

The vibrational characteristics in a submerged double-shell structure, which consists of two concentric cylindrical shells coupled by the entrained fluid, are investigated in this paper considering the acoustic-structure coupling. An analytical model is proposed based on the wave propagation approach and the Flügge thin-shell theory, and then a detailed analysis is conducted. The spectrum of the averaged quadratic velocity of total modal superposition is calculated to elucidate the vibrational transmission between inner and outer shells, while that of typical modes are separated to further clarifies the strong and weak coupling. Furthermore, the natural frequencies of the inner and outer shell are determined by the location of the resonance peak in the separated spectrum. The impact of variation of the governing parameters such as the length, the radius and the thickness on the natural frequencies of double-shell structure are investigated and some conclusions are outlined.

Persons with Unilateral Transtibial Amputations Modulate Ipsilateral Hip and Contralateral Ankle Joint Work to Accelerate and Decelerate Walking

ABSTRACT Introduction Loss of power production at the ankle joint contributes to many problems people with unilateral transtibial (UTT) amputation experience during walking. Little is known about walking acceleration and deceleration, which is common in daily living and may require substantial compensatory behaviors from the residual lower-limb joints. Objective The aim of this study was to quantify individual lower-limb joint contributions to walking acceleration and deceleration in people with UTT amputations. We hypothesized that joint work on the prosthetic limb would be primarily modulated at the hip, and joint work on the sound limb would be primarily modulated at the ankle. Study Design The study is a repeated-measures design. Methods Six K3 level ambulators with UTT amputations participated. Participants performed a total of 40 walking trials while wearing their own nonarticulated dynamic prosthetic foot and socket. Each trial consisted of walking along a straight walkway. After walking approximately 2 m, participants received a cue instructing them to perform one of three walking conditions: continue walking at a constant average velocity, rapidly accelerate, or rapidly decelerate. We used ground reaction forces and motion capture data to derive joint kinematics and kinetics during the three walking conditions. We used one-way repeated-measures analyses of variance (ANOVAs) to identify significant differences between conditions. Results For the sound limb, positive hip and ankle work was significantly greater during acceleration compared with constant average velocity or deceleration conditions, and negative knee work was significantly greater during acceleration compared with deceleration. For the prosthetic limb, negative ankle work was significantly greater during acceleration compared with deceleration. Conclusions People with UTT amputation who use nonarticulated prostheses primarily modulated joint work on their sound limb to accelerate or decelerate walking speed. Clinical Relevance Characterizing compensatory behaviors of people with a UTT amputation is important for understanding injury mechanisms, informing clinical guidelines, and improving future ankle-foot prosthesis designs.

Renormalization group model of turbulent bioconvection of gyrotactic microorganisms

The problems connected with processes of turbulent bioconvection are considered. These processes are typical for technologies of microbiological and other industries. The concept of using renormalization groups in the theory of turbulence is shown. A step-by-step algorithm for applying the renormalization methodology to deriving the equation for mass transfer in bioconvective processes, which includes renormalization of the turbulent diffusion coefficient, is presented. The dependence for the turbulent Schmidt number was obtained. It has been shown that turbulent Schmidt number is function of six parameters: molecular Schmidt number, turbulent viscosity, molecular viscosity, parameter of geometric shape of microorganisms, average velocity of motion of microorganisms relative to the fluid, orientation parameter. The turbulent Schmidt number enables closing the diffusion equation. The effect of the geometric shape of microorganisms on the development of turbulence in a bioconvective flow in the presence of gyrotactic microorganisms is analyzed. Analysis shows that microorganisms with spherical symmetry make a small contribution to the formation of turbulent mass transfer processes. The results of the analysis are in a good agreement with data from studies of the nonlinear hydrodynamic stability of bioconvective processes based on the Lorentz model.

ANALYSIS OF THE SPATIO-TEMPORAL CHARACTERISTICS OF THE TECHNIQUE OF KICKING WITH THE LEFT FOOT TO THE SIDE FROM THE LEFT-HANDED STANCE OF HIGHLY SKILLED ATHLETES SPECIALISING IN HAND-TO-HAND COMBAT

The relevance of the research topic. A wide arsenal of technical actions and a wide range of potential conflict situations that regularly occur in the course of martial arts determine the peculiarities of operations, actions and mechanisms for their improvement. The aim of the research was to analyse the indicators of the spatial-temporal structure of the technique of a kick with the left foot to the side from the left- handed stand performed by highly skilled sportsmen. Research methods: analysis of literature sources, video recording and biomechanical video computer analysis using the optoelectronic system "Qualisys", methods of mathematical statistics. Results. The movement of the biolinks of the athletes' body during the phase of preparing for the impact is from 0.03 m to 0.25 m. During the kicking phase, the values of the average velocities of the right ankle and right knee joints are 4.23 m·s-1 and 2.26 m·s -1 respectively. Conclusions. The execution of a blow is effective from the point of view of biomechanical analysis, and the indicators of the kinematic structure of movements during the execution of this blow can be used both as a reference sample of sports technique and for the development of model characteristics of movements based on them. The values of the average velocities of the shoulder, elbow, and carpal joints of the right hand during the walking phase are 0.50 m·s-1, 1.10 m·s-1, and 0.95 m·s-1, respectively. The average speed of the shoulder joint of the left hand is 0.69 m·s-1, the left elbow joint - 0.97 m·s-1, and the left carpal joint - 2.03 m·s-1. Such high indicators of the average speeds of the hand joints during the walking phase indicate swinging movements to increase the force of the impact due to the use of inertial forces. The movement of the biolinks of the athletes' body during the walking phase ranges from 0.08 m to 0.63 m. The values of the indicators of the joints of the upper limbs during the two support phases when performing a left leg kick to the side from the left stance are: right shoulder joint - 0.65 m·s-1, left shoulder joint -0.52 m·s-1, right elbow joint – 2.73 m·s-1, left elbow joint – 1.71 m·s-1, right and left carpal joints – 1.84 m·s-1. In the two-support phase, the movement of the studied body points of the athletes is in the range from 0.08 m to 0.56 m. The values of the average velocities of the studied body points of the athletes during the contact phase when performing a left leg kick to the side from the left stance range from 0.23 m s- 1 to 2.53 m·s-1, and the displacement of the same points during this phase is from 0.02 m to 0.20 m

Simulation Studies of Pollutant Emission from Passenger Cars

<div>The article presents the results of simulation studies of pollutant emissions from passenger cars. The characteristics of emissions were determined using the vehicle driving test procedures, in consideration of differentiated average velocities as well as model traffic conditions: urban traffic jam, urban traffic with no congestion, rural, motorways, and highways. This article also presented the possibility of determining the characteristics of pollutant emission based on a singular realization of the vehicle velocities processes, as well as the intensity of pollutant emission, with the use of the Monte Carlo method. The pollutant emission characteristics enable specification of pollutant emission intensity, which can be used for the inventory of pollutant emissions from road transport (COPERT software applied as standard) and can be useful in the assessment of a degree of environmental hazard by modeling pollutant dispersion. In this article, the results related to pollutant emission characteristics were obtained with the use of the software HBEFA INFRAS AG for the cumulative category of passenger cars, in terms of their representative structure in Europe in 2020. The simulation driving tests were carried out separately for cars with spark ignition engines and for those with compression ignition engines. It was concluded that using specialized software to simulate emissions from road vehicles is an effective way to determine the characteristics of emissions from road transport.</div>

Pickleball sounds: impact induced vibration and radiated sound

The rapid growth in popularity of pickleball and the ever-increasing number of pickleball courts has resulted in growing concerns about the effect of pickleball sounds on nearby neighbors. The vibration of the ball and paddle that is generated at impact, and which is the source of the radiated sound, was measured for different paddles as a function of frequency using an impact hammer instrumented with a force gage. Average vibration velocities over the paddle surface were generated that scale the radiated sound. Animations of paddle vibration were also generated. A paddles vibration level depends on its internal mechanical damping which was also measured. A performance metric is proposed where the paddles' sound levels are compared at the same "power" in terms of the change in momentum (velocity) of the pickleball on impact. Outdoor directivity measurements of the sound for a paddle were "dipole-like" in character with lower levels, by 10 dB or more, in the plane of the paddle compared to levels perpendicular to its face. The orientation of the courts may be important if the sound levels during play are quieter in the general direction along the nets.

The Importance of Preconditioning for the Sonographic Assessment of Plantar Fascia Thickness and Shear Wave Velocity.

Plantar fasciopathy is a very common musculoskeletal complaint that leads to reduced physical activity and undermines the quality of life of patients. It is associated with changes in plantar fascia structure and biomechanics which are most often observed between the tissue's middle portion and the calcaneal insertion. Sonographic measurements of thickness and shear wave (SW) elastography are useful tools for detecting such changes and guide clinical decision making. However, their accuracy can be compromised by variability in the tissue's loading history. This study investigates the effect of loading history on plantar fascia measurements to conclude whether mitigation measures are needed for more accurate diagnosis. The plantar fasciae of 29 healthy participants were imaged at baseline and after different clinically relevant loading scenarios. The average (±standard deviation) SW velocity was 6.5 m/s (±1.5 m/s) and it significantly increased with loading. Indicatively, five minutes walking increased SW velocity by 14% (95% CI: -1.192, -0.298, t(27), p = 0.005). Thickness between the calcaneal insertion and the middle of the plantar fascia did not change with the tissues' loading history. These findings suggest that preconditioning protocols are crucial for accurate SW elastography assessments of plantar fasciae and have wider implications for the diagnosis and management of plantar fasciopathy.