Velocity Research Articles

Identification and Quantification of Polycyclic Aromatic Hydrocarbons in Otamiri River Owerri Southeast Nigeria

The present study evaluates the Identification and Quantification of polycyclic aromatic Hydrocarbons in Otamiri River. Water samples were collected from Otamiri River and analyzed for polycyclic aromatic hydrocarbons (PAHs). Samples were collected from various strategic sampling points from Otamiri River: Abattoir/Shoprite Residence Point 1 (sampling point 1), Abattoir/Shoprite Residence 2 (sampling point 2), Nekede/Ihiagwa Bridge 1 (sampling point 3), and Nekede/Ihiagwa Bridge 2 (sampling point 4). The Global Positioning System (GPS) was utilized to locate the coordinates of the sampling points. The analysis of polycyclic aromatic hydrocarbons (PAHs) was performed using a BUCK M910 Gas Chromatograph equipped with an Electron Capture Detector (ECD). A RESTEK MXT-1 column (15 m × 250 µm × 0.15 µm) was employed for the separation. The injector temperature was set to 280°C, with a splitless injection of 2 µL of sample, and a linear velocity of 30 cm/s. Helium 5.0 served as the carrier gas, flowing at a rate of 40 ml/min. The oven was initially maintained at 200°C, then ramped to 330°C at a rate of 30°C per minute, and held at that temperature for 5 minutes. The detector operated at 320°C. PAHs were quantified by calculating the ratio of the area-to-mass of the internal standard to the area of the identified compounds. Abattoir/Shoprite Residence sampling point 1 recorded 3.920 mg/ml, Abattoir/Shoprite Residence 2 sampling point 2 recorded 7.749 mg/ml, Nekede/Ihiagwa Bridge 1 sampling point 3 recorded 3.841 mg/mL, and Nekede/Ihiagwa Bridge 2 sampling point 4 recorded 5.422 mg/ml. The total PAH concentrations in the Otamiri River are consistently above the Federal Ministry of Environment (FMEnv) standard of 1.845 mg/mL which suggests a high level of PAH pollution in the Otamiri water, which should be a serious public health concern. High PAH concentrations can harm on aquatic ecosystems, other animals and humans consuming the water.

Tribochemistry of Glycerol-Water Mixtures Confined between Ferrous Substrates: An Atomic-Scale Concept by Reactive Molecular Dynamics Simulation

In this study, non-equilibrium molecular dynamics (NEMD) simulations with a reactive force field were used to investigate the tribochemical properties of glycerol, with and without water, confined between two ferrous surfaces. The results demonstrated that glycerol significantly reduced friction on α-Fe slabs more effectively than on functionalized amorphous magnetite. A numerical method was introduced to identify the interface region and evaluate the dissociated surface atoms. It was found that the dissociation rate of glycerol molecules increased with applied normal pressure and shear stress. Additionally, the production rate of water molecules from glycerol dissociation was consistently positive for all solutions above 80% wt. The assumption of linear velocity distribution across the film thickness was validated for all systems studied.

Utilizing linear and nonlinear ultrasound for improved estimation of concrete strength

ABSTRACT This study investigated non-destructive concrete strength evaluation using in-situ cored samples. Data from various mix proportions and design strengths revealed inconsistent correlations between compressive strength and linear ultrasonic wave velocity (V p). This inconsistency arises because V p captures only linear elastic behaviour, whereas concrete strength reflects both linear and nonlinear behaviours. In contrast, the acoustic nonlinearity parameter (β re) exhibits superior sensitivity to microstructural conditions owing to its direct link to material nonlinearity. We proposed a new integrity index (M/β*) by combining the constrained modulus (M) derived from V p with β re to capture the entire elastic behaviour. This index demonstrated statistically significant correlation with the factor of safety (FS) across different design strengths and mix proportions. Next, we developed a risk stratification system based on M/β* using fuzzy c-means clustering, categorising concrete into three risk zones: critical (M/β* <40), moderate (40 < M/β* <75) and low (M/β* >75), providing a quantitative tool for assessing concrete quality. The results highlight the importance of integrating linear and nonlinear ultrasonic parameters for accurate strength prediction, particularly in field conditions where traditional V p–strength correlations are unreliable. This approach offers a new method for non-destructive concrete strength detection, thereby enhancing structural safety assessments.

Comparative analysis of different catalytic baskets for dual-bed catalytic reactor based on CFD simulations

Catalytic baskets used to support catalyst beds can have different designs. For industrial practice, reactors with axial and radial gas flow direction through the catalyst bed are commonly used. Based on CFD simulations, the influence of the tail gas distribution in a dual-bed catalytic reactor on the linear gas flow velocity and pressure drop across the catalyst bed was analysed. CFD simulations were performed for the reactor's use in a pilot nitric acid plant for axial-radial and radial catalytic basket designs. The calculation results indicated a significant influence of the basket design on the linear gas flow velocity profile and pressure drop distribution in a dual-bed catalytic reactor. The most advantageous solution was the coaxial arrangement of the catalyst beds without separating them with a space, which can affect the reliability of the reactor. The lowest linear flow velocity and gas flow resistance values in a dual-bed catalytic reactor were obtained for the mixed axial and radial gas flow through the catalysts beds, separated only with a porous baffle.

Exploring the Feasibility of Head-Tracking Data for Cybersickness Prediction in Virtual Reality

Cybersickness remains a significant barrier to the widespread adoption of virtual reality (VR) technology. Traditional methods for predicting cybersickness rely on self-reported questionnaires or physiological signals from specialized sensors, which have their limitations. This study explores the potential of using real-time, easily acquired head-tracking data (HTD) from standard VR headsets as a scalable alternative for estimating cybersickness. Twelve participants engaged in a VR session using an Oculus Quest 2 headset while their HTD were recorded. Kinematic metrics such as linear and angular velocity, acceleration, and jerk were computed from the HTD, including positional and angular parameters. Participants’ cybersickness levels were assessed using the Virtual Reality Sickness Questionnaire. While exploratory data analysis revealed no significant direct correlation between individual kinematic variables and cybersickness scores, machine learning models were employed to identify predictive patterns. Subsequently, four regression models, including Random Forest, Gradient Boosting, K-Nearest Neighbors, and Support Vector Machines, were trained and evaluated using the computed kinematic features to predict the cybersickness score. Among these, the Gradient Boosting model demonstrated superior performance, accurately predicting cybersickness scores with normalized differences less than 3.08% on unseen data. This approach offers a scalable and practical solution for real-time cybersickness prediction in VR applications and compliments other techniques that rely on physiological sensors, hardware, or user profiles.

Enhanced Pure Pursuit Path Tracking Algorithm for Mobile Robots Optimized by NSGA-II with High-Precision GNSS Navigation

With the rapid development of automation and intelligent technology, mobile robots have shown wide application potential in many fields, and accurate navigation systems are the key to robots completing tasks. This paper proposes an enhanced pure pursuit path tracking algorithm for mobile robots, which is optimized using NSGA-II, with high-precision GNSS navigation for accurate positioning. The improved algorithm considers the dynamic characteristics and real–world operating conditions of the robot, optimizing steering decisions to enhance path tracking accuracy. Experimental results demonstrate the effectiveness of the algorithm: with a look–ahead distance of 0.5 and a maximum linear velocity of 3, the average absolute pose error (APE) is reduced by 14.63%, while a velocity of 4 reduces the APE by 55.94%. The enhanced algorithm significantly reduces path deviation and improves navigation performance.

Regional blood flow in dental patients with reduced interalveolar distance and auditory disorders (Part 2)

Relevance. Reduced interalveolar distance, resulting from increased wear of dental hard tissues, generalized periodontitis, and tooth loss, leads to morphofunctional changes not only in the masticatory muscles and temporomandibular joint (TMJ) but also in other structures of the maxillofacial region. These changes affect hemodynamics in the vascular regions of the face, neck, brain, TMJ, and upper cervical spine. Objective. To evaluate regional blood flow in dental patients with reduced interalveolar distance and auditory disorders.Materials and methods. The study was conducted on a group of patients with signs of reduced interalveolar distance (n = 50), aged 34 to 73 years, with a mean age of 53.5 ± 2.4 years. The group comprised 22 men (44.0%) and 28 women (56.0%). The examination included the functional-physiological method for determining the central relationship of the jaws using the Apparatus for Determining Central Occlusion (AOTSO) and duplex ultrasound scanning of the head, neck, and TMJ vessels.Results. In patients with reduced interalveolar distance in habitual occlusion, a high asymmetry coefficient of linear blood flow velocity was observed in the examined arteries, reaching up to 40%, along with signs of venous dysgemia. Using loading tests during the functional-physiological method achieved optimal positioning of the mandibular condyles in the mandibular fossa and optimized occlusion. This significantly reduced the blood flow asymmetry coefficient to 4%, with no signs of venous outflow disorders. These improvements indirectly influenced the hemodynamics of the peripheral auditory system, enhancing its function. Conclusion. reduced interalveolar distance, temporomandibular joint, auditory disorders.

FRT*: fast reactive tree for mobile robot replanning in unknown dynamic environments

Purpose This study aims to introduce the fast reactive tree (FRT*) algorithm for enhancing replanning speed and reducing the overall cost of navigation in unknown dynamic environments. Design/methodology/approach FRT* comprises four key components: inverted tree build, convex hull construction, dead nodes inform activation and lazy-rewiring replanning. First, an initial path is found from the inverted tree where the valid structure is preserved to minimise re-exploration areas during the replanning phase. As the robot encounters environment changes, convex hulls are extracted to sparsely describe impacted areas. Next, the growth direction of the modified tree is biased by the inform activation of dead nodes to avoid unnecessary exploration. In the replanning phase, the tree structure is optimized using the proposed lazy-rewiring replanning to find a high-quality path with low computation burden. Findings A series of comprehensive simulation experiments demonstrate that the proposed FRT* algorithm can efficiently replan short-cost feasible paths in unknown dynamic environments. The differential wheeled mobile robot with varying reference linear velocities is used to validate the effectiveness and adaptability of the proposed strategy in real word scenarios. Furthermore, ablation studies are conducted to analyze the significance of the key components of FRT*. Originality/value The proposed FRT* algorithm introduces a novel approach to addressing the challenges of navigation in unknown dynamic environments. This capability allows mobile robots to safely and efficiently navigate through unknown and dynamic environments, making the method highly applicable to real-world scenarios.

Human fallopian tube organoids provide a favourable environment for sperm motility.

Does a human fallopian tube (HFT) organoid model offer a favourable apical environment for human sperm survival and motility? After differentiation, the apical compartment of a new HFT organoid model provides a favourable environment for sperm motility, which is better than commercial media. HFTs are the site of major events that are crucial for achieving an ongoing pregnancy, such as gamete survival and competence, fertilization steps, and preimplantation embryo development. In order to better understand the tubal physiology and tubal factors involved in these reproductive functions, and to improve still suboptimal in vitro conditions for gamete preparation and embryo culture during IVF, we sought to develop an HFT organoid model from isolated adult stem cells to allow spermatozoa co-culture in the apical compartment. Over a 2-year period, fallopian tube tissues were collected for organoid culture purposes from 10 'donor' patients undergoing bilateral salpingectomy by laparoscopy for definitive sterilization. After tissue digestion, isolated cells from the isthmus and ampulla regions were separately seeded in 3D Matrigel and cultured with conventional growth factors for organoid culture and specific factors for differentiation of the female genital tract. HFT organoids were characterized by light microscopy, scanning and transmission electron microscopy, immunofluorescence, and transcriptome analysis. Following simultaneous organoid culture on specific inserts, spermatozoa from five donors were placed either in control media or in the apical compartment of colon or HFT organoids (isthmus and ampulla separately) for 96 h. Vitality and motility and kinematic parameters were assessed at 0, 48, and 96 h on 200 spermatozoa in each condition and in duplicate and compared using the Wilcoxon test. Specific fallopian tube differentiation of our model was confirmed by immunofluorescence, transcriptome analysis, and electron microscopy observations that exhibited ciliated and secretory cells. We succeeded in releasing spermatozoa in the apical compartment of HFT organoids and in recovering them for sperm analysis. Sperm vitality values were similar in HFT organoids and in commercial sperm media. We demonstrated a superiority of the HFT organoid apical compartment for sperm motility compared with other controls (colon organoids, organoid culture media, and conventional commercial sperm fertilization media). At 48 h of incubation, progressive sperm motility was higher in the apical compartment of HFT organoids (ampulla 31% ± 17, isthmus 29% ± 15) than in commercial fertilization media (15% ± 15) (P < 0.05) and compared with all other conditions. At 96 h, progressive sperm motility was almost nil (<1%) in all conditions except for spermatozoa in HFT organoids (P < 0.05): 12% ± 15 and 13% ± 17 in ampulla and isthmus organoids, respectively. Computer-assisted sperm analysis (CASA) analysis also showed that the organoids were able to maintain significantly higher levels of kinematic parameters (curvilinear velocity, average path velocity, straight linear velocity, and amplitude of lateral movement of the head) and therefore more efficient mobility compared with commercial IVF media. N/A. This was an in vitro study in which conditions of organoid culture could not exactly mimic the in vivo environment of the extracellular matrix and vascularization of fallopian tubes. This work opens up perspectives for better understanding of HFT physiology. For the first time, it highlights the possibility of developing HFT organoids for reproductive purposes. In the future, it could help us to improve gamete fertilizing abilities and embryo culture conditions during human ARTs. This study was funded by a grant from the Occitanie region, and by financial allocations from the DEFE and IRSD research teams. The authors have no conflicts of interest to report.

Upper Leg Muscular Co-Contraction During Maximal-Speed Sprinting in Male Club Ice Hockey Athletes

BackgroundLittle is known about the lower extremity muscle co-contraction patterns during sprinting and its relation to running velocity (i.e., performance). Therefore, we compared lower extremity muscular activation patterns during sprinting between slower and faster collegiate club hockey athletes. We hypothesized that faster athletes would have lower EMG-assessed co-contraction index (CCI) values in the lower extremities during over-ground sprinting.MethodsTwenty-two males (age = 21 [1] yrs (median[IQR]); body mass = 77.1 ± 8.6 kg (mean ± SD)) completed two 20-m over-ground sprints with concomitant EMG and asynchronous force plate testing over four days in Tallahassee, Florida, USA. We split participants using median running velocity (FAST: 8.5 ± 0.3 vs. SLOW: 7.7 ± 0.3 m/s, p < 0.001).ResultsFaster athletes had lower CCI between the rectus femoris and biceps femoris (group: p = 0.05), particularly during the late swing phase of the gait cycle (post hoc p = 0.02). Early swing phase duration was moderately inversely related to Hip CCI in the stance phase (ρ=-0.58, p < 0.01) and weakly related to Knee CCI in the swing phase (ρ = 0.44, p = 0.046). Finally, swing phase duration was moderately inversely related to Hip CCI in the stance phase (ρ=-0.50, p = 0.02).ConclusionsIn agreement with our hypothesis, we found lower CCI values in the upper leg musculature during maximal-speed over-ground sprinting. These data from collegiate club hockey athletes corroborate other reports in clinical populations that the coordination between the rectus femoris and biceps femoris is associated with linear over-ground sprinting velocity.

An approach towards mobile robot recovery due to vision sensor failure in vSLAM systems using ROS

Abstract This paper proposes a mobile robot recovery mechanism for low-cost robotic systems due to vision sensor failure in vSLAM systems. The approach takes advantage of ROS architecture and adopts the Shannon Nyquist sampling theory to selectively sample path parameters that will be used for back travel in case of vision sensor failure. As opposed to point clouds normally used to store vSLAM data, this paper proposes to store and use lightweight variables namely distance between sampled points, velocity combinations, i.e., linear and angular velocity, sampled period, and yaw angle values to describe the robot path and reduce the memory space required to store these variables. In this study, low-cost robotic systems typically using cameras aided by proprioceptive sensors such as IMU during vSLAM activities are investigated. A demonstration is made on how the ROS architecture can be used in a scenario where vision sensing is adversely affected, resulting in mapping failure. Additionally, a recommendation is made for adoption of the approach for vSLAM platforms implemented on both ROS1 and ROS2. Furthermore, a proposal is made to add an additional layer to vSLAM systems that will be exclusively used for back travel in case of vision loss during vSLAM activities resulting in mapping failure.

Identifying the most notable events at the first stage of the solar cycle 25

This study documented 359 occurrences during the initial phase of solar cycle 25, spanning from December 2019 to April 2023. These events were the most powerful coronal mass ejections (CMEs). Out of the total of 359 events, four of them did not have any solar flares, whereas the remaining 355 events were linked to solar flares. This study involved the observation and analysis of solar events, which led to the identification of two significant coronal mass ejections that displayed robust shock waves. Both of these events displayed rapid linear velocities and significant angular widths. The coronal mass ejections were accompanied by solar flares that displayed exceptional intensity in the form of X-rays. The shock waves generated during these events provided valuable insights into the dynamics and transmission of coronal mass ejections. These findings enhance our comprehension of the impact of powerful events on the space environment by analyzing the attributes of shock waves.

A variable diameter spiral path planning strategy for large eccentricity variable curvature rotating parts with focus on thickness and performance control in cladding

When laser cladding rotating parts that have large eccentricity and variable curvature, first-order discontinuities in the cladding path and fluctuations in the real-time scanning speed are common problems. These issues cause significant inhomogeneities in the cladding thickness and localized excessive material accumulation. This not only leads to unstable mechanical properties of the cladding layer but also results in a significant waste of cladding materials during subsequent precision machining. In response, this paper introduces a cladding method that employs a variable diameter constant linear velocity spiral path and establishes models for dynamic vector and angle conversion, constant linear velocity optimization, and cladding path data conversion. This approach enables consistent control over the real-time scanning speed and defocus distance during laser cladding of parts with large eccentricity and variable curvature. A comparison of the experimental results from spiral path cladding, variable linear velocity and variable diameter spiral cladding, and constant linear velocity variable diameter spiral cladding revealed that the latter method achieves a more uniform cladding layer thickness, with a maximum deviation of only 0.036 mm. The microstructure primarily consists of cellular structures, demonstrating improved consistency. Samples were taken from three different cladding methods, and hardness tests were performed on the cross-sections of the cladding layers.

RENAL HEMODYNAMICS IN PATIENTS WITH HYPERTENSION AND STAGE II–III CHRONIC OBSTRUCTIVE PULMONARY DISEASE

The purpose of the study is to assess the changes in renal blood flow during the combined course of essential hypertension and stage II-III chronic obstructive pulmonary disease. Participants and methods. The study included 60 patients, divided into three clinical groups: Group 1 involved 15 patients with stage II essential hypertension (mean age 52.87 ± 1.36 years; male-to-female ratio 73.33%/26.67%); Group 2 included 15 patients with stage II–III chronic obstructive pulmonary disease (COPD) (mean age 48.01 ± 2.75 years; male-to-female ratio 86.67%/13.33%); Group 3 included 30 patients with stage II–III COPD combined with stage II essential hypertension and stage I–III arterial hypertension (23 men and 7 women; mean age 57.49 ± 2.39 years). These patients had no other clinically significant concomitant pathologies and had not received systematic antihypertensive therapy. A control group of 20 healthy donors was also examined. Results. The study of renal blood flow dynamics at the levels of the common trunk, segmental, and interlobar branches of the renal artery revealed statistically significant changes, particularly in the presence of comorbidity. A notable increase in the parameters Vmax, Vmin, and Vaverage, as well as the resistive index (RI) and pulsatility index (PI), was observed in patients with chronic obstructive pulmonary disease (COPD) combined with essential hypertension. These changes indicate impaired renal hemodynamics, characterized by increased microvascular resistance in the interlobar branches. The severity of disturbances in key Doppler parameters of renal blood flow at the levels of the common trunk, segmental, and interlobar branches was associated with elevated RI and PI values in patients with the comorbidity of essential hypertension and COPD (p&lt;0.05), as well as in those with essential hypertension alone (p&lt;0.05). In contrast, patients with COPD alone exhibited higher values of Vmax, Vmin, and Vaverage at these levels of the renal artery. Conclusions. The evolution of linear velocity and vascular resistance indices in the renal vessels across the studied patient groups showed a consistent, proportional pattern, with more pronounced renal blood flow impairment observed in patients with the comorbidity of essential hypertension and chronic obstructive pulmonary disease, based on key Doppler criteria.

Heat and mass transfer in anisotropic heat-protective composite materials under aerodynamic heating

This article presents a mathematical model of heat and mass transfer in anisotropic heat-protective composite materials (HPCM) during phase transformations of HPCM binders with the formation of a porous coke residue and pyrolysis gases filtering through the residue to the outer boundary. Using known binder decomposition and nonlinear filtration laws for random HPCMs, the model determines the velocity and coordinates of the two-dimensional HPCM binder decomposition zone, as well as the two-dimensional regions of the porous-gas residue and the initial phase, which are unsteadily separated by a moving zone of binder decomposition. In the newly formed porous-gas region, a two-dimensional unsteady problem of anisotropic heat conduction was solved taking into account nonlinear anisotropic gas filtering. In the initial region unaffected by the binder decomposition, a two-dimensional unsteady problem of anisotropic heat conduction was solved. The mass and linear velocities of the binder decomposition (pyrolysis) zone were calculated from Stefan conditions for heat flow and temperature continuity. The complex model was solved by the previously developed effective and absolutely stable method of alternating directions with extrapolation. New results wereobtained and discussed.

Association between birth length, linear growth velocities, and primary school achievement at age 10 years: evidence from the Ethiopian iABC birth cohort

BackgroundChildhood is a period marked by dynamic growth. Evidence of the association between childhood linear growth and school achievement comes mostly from cross-sectional data. We assessed associations between birth length, childhood linear growth velocities, and stunting with school achievement.MethodsNewborns were recruited into the Ethiopian infant Anthropometry and Body Composition (iABC) birth cohort and followed from birth to 10 years. Velocities from 0 to 6 years were computed using linear spline mixed effect modelling. Stunting (height-for-age < -2 z-scores) was assessed at the ages of 1, 2, 4, 5, and 6 years. School achievement was measured by having a high (≥ 80%) combined high math, English, and science (MES) score and being at appropriate grade-for-age. Logistic regression models assessed associations between birth length, linear growth velocities and stunting with school achievement.ResultsChildren’s mean age was 9.8 years (standard deviation, SD 1.0, range 7–12 years). A 1 SD greater birth length increased the odds of achieving a high MES combined score by 1.42 (95% CI: 0.99, 2.03). A 1 SD increase in linear growth velocity from 6 to 24 months increased the odds of being in the appropriate grade-for-age by 1.66 (95% CI: 1.14, 2.43). Stunting at ages 4 and 6 years was associated with lower odds of achieving a high MES combined score: 0.43 (95% CI: 0.20, 0.93) and 0.31 (95% CI: 0.11, 0.89), respectively. Faster post-natal linear growth was not associated with school achievement.ConclusionGreater birth length and higher growth velocity from 6 to 24 months were associated with higher school achievement and being in the appropriate grade-for-age, respectively. Children who experienced growth failure were less likely to achieve a high MES score. Interventions aimed at improving school achievement should address maternal and fetal nutrition and health, and monitor post-natal growth.

Influence of oil-water mixing conditions on the friction and wear performance of ship tail-bearing materials

This study addresses the lubrication challenges posed by oil-water mixtures that arise when vessels encounter adverse maritime conditions, including collisions, grounding, and reefing, which can lead to failures in lubrication systems during navigation. The research focuses on three representative ship tail-bearing composites: polymer material(K4), thordon material(SR), and tenmat material(FR). Various volume fractions of oil-water mixtures were prepared, and the rheological properties of these mixtures were examined using a rotational rheometer (MCR102). Additionally, the variation of friction coefficients of the composites about load and linear velocity under different oil-water mixtures was analyzed using a Ring-Block Friction and Wear Testing Machine. Following the experiments, the surface morphology of the composites was assessed, and the wear mechanisms were analyzed using a laser interferometric surface profiler (LI-type), a confocal laser microscope (CLSM), and a scanning electron microscope (SEM). The findings indicate that, under all lubrication conditions, the friction coefficients of the three materials exhibit a gradual decrease with increasing load and linear velocity.Furthermore, the wear of the materials initially increases and then decreases with rising oil content, with higher oil concentrations in the oil-water mixture correlating with reduced wear. The study reveals that the three materials experience significant abrasive and adhesive wear under adverse oil-water mixing conditions. This research offers valuable insights for developing friction substitutes for oil-water mixing bearings in specialized operational environments and guides the design of friction components in such bearings.

Thermo-mechanical simulation of the effect of tool welding speed on butt-joint friction stir welding (FSW) of AA6061

FSW is a welding method that joins pieces of material by rotating a non-consumable pin at high speeds (RPM) while moving it along the weld joint. The combination of this rotation and movement generates heat through friction between the tool and the sheets, facilitating the welding process without the requirement for filler metal. Developed by the British Welding Institute (TWI) in 1991, FSW is celebrated for producing strong, reliable welds and is extensively used in industries such as automotive and aerospace. In these sectors, aluminum alloys are essential due to their unique set of properties, making them highly suitable for FSW applications. In FSW, welding speed refers to the linear velocity at which the tool progresses along the joint line during the welding process. This parameter plays a pivotal role in controlling heat generation, material flow, and ultimately, the quality of the weld. The quantity of heat introduced to the plates directly influences the final weld quality, as well as the residual stresses and deformation observed in the workpieces. This research examines how different welding speeds affect temperature distribution, the width of the heat-affected zone, and the Von Mises stress distribution in welded aluminum alloy 6061 sheets. The aim of this study is to gain a comprehensive understanding of how these factors interact, with the ultimate goal of contributing to the optimization of FSW parameters and improving weld quality. The analysis was performed using finite element method and ALTAIR software, providing valuable insight into the effects of welding speed variations.

Linear Growth During Treatment With a Simplified, Combined Protocol: Secondary Analyses of Severely Wasted Children 6-59 Months in the ComPAS Cluster Randomized Controlled Trial.

A simplified, combined protocol treats children with moderate acute malnutrition (MAM), defined by mid-upper arm circumference (MUAC) of < 125 and ≥ 115 mm and no oedema, with 1 daily sachet of ready-to-use therapeutic food (RUTF) and those with severe acute malnutrition (SAM), defined by MUAC < 115 mm and/or oedema, with two daily sachets of RUTF. This protocol was previously shown to result in non-inferior recovery compared to standard treatment that used higher, weight-based RUTF dosing among children with SAM and ready-to-use supplementary food (RUSF) for MAM in a cluster-based randomised controlled trial in Kenya and South Sudan. We conducted a secondary analysis of this trial to compare linear growth among children admitted with MUAC < 115 mm. Linear and ponderal growth were calculated from admission to discharge and visualised using aggregate growth curves. HAZ change adjusted for admission characteristics was negative across the course of treatment but similar across arms [-0.21 ± 0.18 SE in the standard arm, -0.24 ± 0.18 SE in simplified; difference (95% confidence interval) 0.03 (-0.12, 0.18)]. The unadjusted mean ± SE linear growth velocity from admission to discharge was 1.8 ± 0.7 mm/week in the standard arm compared to 1.7 ± 0.7 mm/week in the simplified arm [difference = 0.09 (-0.36, 0.53)] and similar in adjusted analysis. MUAC and weight gain velocities were not significantly different by treatment arm. Reducing the RUTF dose prescribed to children during SAM treatment does not appear to affect linear growth or other growth velocities during treatment.

Kalkayotl 2.0. Bayesian phase-space modelling of star-forming regions, stellar associations, and open clusters

Star-forming regions, stellar associations, and open clusters are fundamental stellar systems where predictions from star-formation theories can be robustly contrasted with observations. We aim to provide the astrophysical community with a free and open-source code to infer the phase-space (i.e. positions and velocities) parameters of stellar systems with lesssim 1000 stars based on Gaia astrometry and possibly observed radial velocities. We upgrade an existing Bayesian hierarchical model and extend it to model 3D (positions) and 6D (positions and velocities) stellar coordinates and system parameters with a flexible variety of statistical models, including a linear velocity field. This velocity field allows for the inference of internal kinematics, including expansion, contraction, and rotation. We extensively validated our statistical models using realistic simulations that mimic the properties of the Gaia Data Release 3. We applied Kalkayotl to beta -Pictoris, the Hyades, and Praesepe, recovering parameter values compatible with those from the literature. In particular, we found an expansion age of $19.1 Myr for beta -Pictoris and rotational signal of $32\! $ for the Hyades and that Praesepe's rotation reported in the literature comes from its periphery. The robust and flexible Bayesian hierarchical model that we make publicly available here represents a step forward in the statistical modelling of stellar systems. The products it delivers, such as expansion, contraction, rotation, and velocity dispersions, can be directly contrasted with predictions from star-formation theories.