Exit Speed Research Articles

Efecto del sexo y variación individual sobre respuestas de comportamiento y desempeño de bovinos Simbrah

The aim of this study was to evaluate the effect of sex and individual variation on the behavioural responses and performance of Simbrah bovines subjected to a habituation process to human interaction and exposure training. Nineteen animals were used (8 females and 11 males). Reactivity was assessed through points in the restraint cage (1-5), a score for cage exit speed (1-2), and body weight in five assessments over 86 days. Linear mixed models and the effect of individual variations were adopted through a linear regression for each animal, using the b coefficients to classify the animals as habituated, neutral and sensitized. The sex of the animal did not affect the reactivity in the restraint cage, or the cage exit speed (p>0.05); however, reactivity decreased from day 16 (p<0.05) in relation to day 0 in both reactivity scores. There were individual differences in reactivity in the restraint cage and in body weight. On this, 74% of the animals became accustomed to the handling procedure, 21% showed neutral responses in the restraint challenge and 5% were sensitized. In turn, all animals gained weight at different levels, with positive, significant b coefficients (p<0.05) and R2 >0.70. In conclusion, the process of habituation to human interaction and exposure training consistently reduced the reactivity of the animals, without altering their productive performance; however, individual differences must be considered during handling procedures.

Caffeinated chewing gum improves the batting and pitching performance of female softball players: a randomized crossover study.

The purpose of this study was to investigate the effects of caffeinated chewing gum on female softball pitching and hitting performance in trained female softball fielders and pitchers. Twenty-four trained female softball players (10 pitchers and 14 fielders) were divided into a caffeine chewing gum trial (CAF) or a placebo trial (PLA) in a single-blind, randomized, crossover experimental design. Two pieces of gum containing 100 mg of caffeine (CAF) or without caffeine (PLA) were chewed for 10 minutes and then spit out, followed by a 15-minute warm-up. The physical tests included grip strength and countermovement jump (CMJ). The softball-specific tests included pitching or hitting. The two trials were separated by seven days. The CAF trial had significantly higher grip strength than the PAL trial in fielder (P=0.032, Cohen's d=0.29) and pitcher (P=0.016, Cohen's d=0.33). The height of CMJ in fielders was significantly higher in the CAF trial than in the PLA trial (P=0.015, Cohen's d=0.65) but not in pitchers (P=0.596, Cohen's d=0.15). The fielder's average and maximum batting exit speeds were significantly higher in the CAF trial than in the PLA trial (P<0.05). The average and max fastball speeds of the CAF trial were significantly higher than that of the PLA trial in pitchers (P<0.05). The study showed that chewing gum containing two pieces of gum containing 100 mg of caffeine effectively improved female softball fielder's batting performance and pitcher's pitching performance.

The effect of baseball bat properties and participant ability on youth hit ball speed

The following describes the results of a batting cage study involving youth batters hitting with three types of baseball bats in two weight classes. Participants were allowed to select a bat length from within each type and weight according to their preference. The bats were then swung in random order. Reflective markers were placed on the bats and balls, allowing infrared cameras to track their motion from which speed was obtained. Given the differing ability of the participants, the study outcomes were normalized to the swing speed of each batter. Bat performance was quantified from the bat-ball coefficient of restitution. Laboratory measures of bat performance were shown to strongly correspond with the peak batting cage results. The ball exit speed of hollow bats exceeded that of traditional solid wood bats by as much as 5%. The ball exit speed was also found to be affected more by players’ ability than the bat type. Batter swing speed correlated strongly with bat inertia and was relatively insensitive to the bat-ball impact location, showing that participant effort was not biased by impact quality. Batter swing speed tended to depend more strongly on bat inertia than has been found in adult studies, which may be due to the smaller size of youth participants.

Cyclone Shapes for Sand and Microplastic Separation: Efficiency and Reynolds Number Relationships

In this study, three geometries were analyzed for sand and microplastic separation to confirm the applicability of cyclones. This research aimed to apply plastic-based samples such as Styrofoam, PET, PP, and PU to an analytical model, characterized by separating sand spread on Korean beaches into different outlets using a cyclone model. Regarding the numerical analysis, the results of sand particle separation were analyzed by designing a general cyclone (Type A), a cone-shaped cyclone (Type B), and a cone-shaped cyclone (Type C) with double the cone length, for four microplastics in three shapes. The results of the analysis of the characteristics showed that Type B, which has a conical shape, achieved an efficiency of 99.3–100% for sand, 72.7% for Styrofoam, and 95.7–100% for other plastics at an exit speed of 5–7 m/s, after which the efficiency decreased as the speed increased. Type C showed an efficiency of 92.2–100% for sand, 66.6–70.8% for Styrofoam, and 61% for PET at 5–10 m/s. Type C showed a maximum efficiency of 95.5% for PP and 73.4% for PU at 11 m/s. As the speed increased, the efficiency decreased. This is believed to be due to differences in the Reynolds number range, which helps separate particles depending on their shape; therefore, the applicability of the cone-shaped cyclone separator for sand and microplastic separation was confirmed, and it was found that an optimal speed condition exists in relation to the Reynolds number.

Classifying batted ball outcomes from Division I collegiate baseball players

ABSTRACT Modern technology challenges anecdotal beliefs on baseball performance. The study’s purpose examines these beliefs by classifying batted ball outcomes. Three categories of independent variables (anthropometry, in-game situation, technique-based), from 1,922 batted ball outcomes produced by 230 players, were used to classify the likelihood of hits during 2021 college baseball games. Anthropometry included player’s heights and weights. In-game situation entailed batter side, same side, ahead count, and pitch type. Technique-based variables measured by TrackMan radar included exit speed (ExSp), launch angle (LA), batted ball distance (BBD), and hang time (HT). Binary logistic regression analysis was performed with batted ball outcome as the dependent variable. Independent variables provided a good fit (χ2 (10) = 522.358, p < 0.01) and correctly classified nearly three-fourths of outcomes. Height (β = 0.030, p < 0.05), ExSp (β = 0.023, p < 0.05), LA (β = 0.028, p < 0.01), and BBD (β = 0.067, p < 0.01) each had significant positive associations, yet HT (β = –1.661, p < 0.01) had a significant negative association, with batted ball outcomes. TrackMan provided four significant independent variables. Anthropometry’s contribution to batting outcome was modest, while in-game situation’s impact was non-significant; results contradict anecdotal beliefs of their importance.

Optimization of Fuel Injection Process and Structural Analysis

In order to solve the problem of precise and controllable ignition fuel injection point in the process of UCG, this paper proposes a process method of presetting the ignition agent. The method achieves the purpose of improving the ignition success rate by increasing the downhole ambient temperature and reducing the ignition threshold. By simulating and analyzing the fluid properties of the fuel in the pipeline, the velocity and dynamic pressure at the outlet of the pipeline under different initial velocities are obtained. The results show that the outlet velocity, dynamic pressure and initial velocity have an irregular curvature relationship. As the initial velocity increases, the outlet velocity and dynamic pressure continue to increase. After calculation, the relationship between the exit speed (Y) and the initial speed (X) is Y=-0.5069X2+2.0909X+5.0624. Therefore, long-distance injection is not conducive to the successful ignition of the fuel downhole.

Improved mechanical properties of high-speed extruded BA53 alloy through long-range water-cooling system

A recently developed Mg–5Bi–3Al (BA53, wt%) alloy exhibited remarkable extrudability despite its high alloying content. However, when subjected to high-speed extrusion with a die exit speed of 67 m/min, grain coarsening of recrystallized grains occurs, increasing their size from 12.1 to 26.4 μm due to excessive heat generation during extrusion. Herein, a long-range water-cooling system is installed immediately after the extrusion die to mitigate grain coarsening and attain finer grains in the high-speed extruded alloy. The results demonstrate that the use of the cooling system leads to a significant reduction in the average grain size (from 26.4 to 15.7 μm) of the BA53 alloy extruded at high speed. Furthermore, grain refinement led to notable increases in the ultimate tensile strength (from 255 to 276 MPa) and elongation (from 7.5% to 8.6%) of the alloy. These enhancements in strength and elongation are primarily attributed to the enhanced grain-boundary hardening effect and suppression of twinning during tension, both of which are consequences of grain refinement. This study underscores the effectiveness of a long-range water-cooling system, comprising water spraying over a length of 2 m, in achieving grain refinement during high-speed extrusion of the BA53 alloy and improving both the strength and ductility of the alloy after high-speed extrusion.

The Use of Transition Curves in Airport Runway Rapid Exit Taxiways (RETs)

This paper describes a study result focused on the transition curves used in airport rapid exit taxiways (RETs). Such geometric elements are not currently made explicit by standards, and major international government agencies, such as the International Civil Aviation Organization and the Federal Aviation Administration, are limited to providing some layouts consisting of only constant curvature elements, although the aircrafts speed in RETs is variable. In addition to the clothoid that has unitary shape parameter “n” and the multiparameter clothoids (generalized Cornu spirals), the study analyzes the Bloss curve employment. Regarding the multiparameter clothoids, four schemes with shape parameter equal to 1.25, 1.50, 1.75, and 2.00 were considered, respectively. The proposed curves’ effectiveness was evaluated by analyzing the main geometric and kinematic variables trend, that is, curvature, transversal acceleration, lateral jerk, speed, travel time, longitudinal deceleration, and centrifugal force. To ensure the analysis effectiveness, the study layouts were designed from those used for runways codes 1‐2 and 3‐4 maintaining the main geometric elements dimensions unchanged (length of straight lines, radii of circular curves, exit angles, etc.). The kinematic variables values along the design RETs were calculated “point by point” by MATLAB software to take into account nonuniform motion regimen. The obtained results show that both the Bloss curve and the multiparameter clothoid having a shape factor equal to 2 are capable of better contribution in terms of safety and comfort. Implications in the airport construction field are related to the possibility of using lower deceleration values compared to current standards, that is, allowing higher exit speed for the same deceleration. This allows aircrafts to vacate the runway more quickly and, therefore, to increase runway capacity without taking expensive RETs repositioning.

Multi-parameters study on underwater coil launch

The projectile launched by electromagnetic weapon has strong kinetic energy. In order to study the laws and characteristics of electromagnetic induction coilgun launching underwater, a multi-stage coilgun model was established in this paper. Based on the control variates method, the effects of trigger position, coil turns, capacitance value and other parameters on the launching process were studied, then the effects of above factors on the launching efficiency and exit speed were analyzed. The results show that the optimal trigger position offsets to the direction of the breech with the increase of the projectile speed; the optimal coil turns for a certain projectile and launching occurs when the trigger position is determined; the increase of the capacitance value can increase the exit speed of projectile, and the capacitance value should be selected according to the efficiency-speed curve when the launch efficiency is considered; the seawater resistance has little influence on the acceleration of the projectile, and comparatively large influence when there is no driving force. The research results of this paper can provide theoretical support for the manufacture of underwater coilgun prototype.

Three-Dimensional Printing of Large Ceramic Products and Process Simulation.

Ceramic 3D printing is a promising technology that overcomes the limitations of traditional ceramic molding. It offers advantages such as refined models, reduced mold manufacturing costs, simplified processes, and automatic operation, which have attracted a growing number of researchers. However, current research tends to focus more on the molding process and print molding quality rather than exploring printing parameters in detail. In this study, we successfully prepared a large-size ceramic blank using screw extrusion stacking printing technology. Subsequent glazing and sintering processes were used to create complex ceramic handicrafts. Additionally, we used modeling and simulation technology to explore the fluid model printed by the printing nozzle at different flow rates. We adjusted two core parameters that affect the printing speed separately: three feed rates were set to be 0.001 m/s, 0.005 m/s, and 0.010 m/s, and three screw speeds were set to be 0.5 r/s, 1.5 r/s, and 2.5 r/s. Through a comparative analysis, we were able to simulate the printing exit speed, which ranged from 0.0751 m/s to 0.6828 m/s. It is evident that these two parameters have a significant impact on the printing exit speed. Our findings show that the extrusion velocity of clay is approximately 700 times faster than the inlet velocity at an inlet velocity of 0.001-0.010 m/s. Furthermore, the screw speed is influenced by the inlet velocity. Overall, our study sheds light on the importance of exploring printing parameters in ceramic 3D printing. By gaining a deeper understanding of the printing process, we can optimize printing parameters and further improve the quality of ceramic 3D printing.

Comparative study of extrudability, microstructure, and mechanical properties of AZ80 and BA53 alloys

The extrudability, microstructural characteristics, and tensile properties of the Mg–5Bi–3Al (BA53) alloy are investigated herein by comparing them with those of a commercial Mg–8Al–0.5 Zn (AZ80) alloy. When AZ80 is extruded at 400 °C, severe hot cracking occurs at exit speeds of 4.5 m/min or more. In contrast, BA53 is successfully extruded without any surface cracking at 400 °C and at high exit speeds of 21–40 m/min. When extruded at 3 m/min (AZ80–3) and 40 m/min (BA53–40), both AZ80 and BA53 exhibited completely recrystallized microstructures with a 〈10–10〉 basal texture. However, BA53–40 has a coarser grain structure owing to grain growth promoted by the high temperature in the deformation zone. AZ80–3 contains a continuous network of Mg 17 Al 12 particles along the grain boundaries, which form via static precipitation during natural air-cooling after the material exits the extrusion die. BA53–40 contains coarse Mg 3 Bi 2 particles aligned parallel to the extrusion direction along with numerous uniformly distributed fine Mg 3 Bi 2 particles. AZ80–3 has higher tensile strength than BA53–40 because the relatively finer grains and larger number of solute atoms in AZ80–3 result in stronger grain-boundary and solid-solution hardening effects, respectively. Although BA53 is extruded at a high temperature and extrusion speed of 400 °C and 40 m/min, respectively, the extruded material has a high tensile yield strength of 188 MPa. This can be primarily attributed to the large particle hardening effect resulting from the numerous fine Mg 3 Bi 2 particles.

Research on Spiral Tunnel Exit Speed Prediction Model Based on Driver Characteristics

The “white hole effect” alters the driving environment during a tunnel’s exit phase, making it more difficult and uncertain for drivers to access information and control their behavior, thereby endangering traffic safety. Consequently, the driving risk at the exit of a long spiral tunnel served as the subject of this study, and the Jinjiazhuang spiral tunnel served as the object of the natural vehicle driving experiment. Following the theory of a non-linear autoregressive dynamic neural network, a vehicle speed prediction model based on driver characteristics was developed for the exit phase of the tunnel, taking driver expectations and behavioral changes into account. It also classifies the driver’s behavior during the tunnel’s exit phase to assess the risk posed by the driver’s behavior during the tunnel’s exit phase and determine a dynamic and safe comfort speed. The study’s results indicate that the driver’s behavioral load changed significantly as the vehicle approached the tunnel exit. At the exit of the spiral tunnel, the vehicle’s actual speed was 71 km/h, which is below the speed limit of 80 km/h. This demonstrates that the expected change in the driver’s behavior in the tunnel exit phase was substantial. Therefore, setting the emotional safety and comfort speed so that the driver maintains a smooth comfort level in the tunnel exit phase can reduce the tunnel exit driving risk. The results of this study provide a benchmark for tunnel traffic safety and lay the groundwork for further development of vehicle risk warning settings for the tunnel’s exit phase.

Analytical Study of the Stagnation Point Properties and Impact Forces for Non-Continuum Flow Out of Planar Exit Impinge on Inclined Flat Plate Surface

This paper investigated the stagnation point properties and the impact forces acting on the flat plate exposed to rarefied flow with arbitrary inclination angle issuing from planner nozzle. The gaskinetic method was used to investigate this problem. The analytical solutions for the drag and the shear forces were derived. The parameters that effect on drag, shear forces and their coefficients and the stagnation point properties were studied, focusing on the effect of plate inclination angle. The results were as follows: the drag and shear forces increased with the increasing the plate inclination angle, area of the plate, the temperature of issuing gas, and the temperature of the plate. The drag and the shear forces decreased with increasing the distance between the nozzle and the center of the plate and the exit speed ratio. The stagnation pressure and the heat flux coefficients increased with increasing the plate inclination angle, the exit speed ratio, and by decreasing the distance between the nozzle exit and the center of plate and the gas temperature. The direct simulation Monte Carlo method was used to validate the analytical results of this study. The comparisons between the numerical results that obtained from the direct simulation Monte Carlo method and the analytical solutions were in good agreement.

Global shockwaves of the Hunga Tonga-Hunga Ha’apai volcano eruption measured at ground stations

The eruption of the Tonga volcano created globally propagating spherical shockwaves in the atmosphere. Analyses are done to data from two southern U.S. stations of the author sampling at 3-21s intervals and 189 weather stations at 1-5min intervals. The shockwaves arrived from two routes in the atmosphere: the shortest spherical arc and the longer spherical arc through the antipole. In most stations, signals up to the 6th path of shockwaves were recorded as the waves traveled around the globe multiple times. The speed of shockwaves is estimated to be 309.5± 2.9m/s, consistent with the speed of sound at the top of the troposphere where a waveguide exists. Discussion is made on the post-shockwave ringing of 4-8min as higher amplitude oscillations above the level of pre-shockwaves background noise. A theoretical wave dispersion is derived which verifies that the spherical shockwave's phase speed is the same as the speed of sound.

Do You Feel What I Feel? Shared Cognition, Shared Affect and Co-Founder Exits

Extant research on co-founder exits presents contradicting results: exits can either lead to venture failure or enhance the effectiveness of the remaining team. Using in-depth, qualitative case studies of dynamic affective interactions and follow-up interviews from nine founding teams over twenty months, we examine how differences in team shared affect and cognition before a co-founder exit subsequently impacts how cofounders exit, and the impact of their exit. We develop a model of affective and cognitive dynamics in the co-founder exit process and identify how patterns of shared affect and cognition cause different team vulnerabilities leading to differing team behaviours which in turn influences team conflict, exit speed, co-founder commitment and co-founder relationships. Our findings have important implications for co-founder exit literature, we propose why some exits lead to failure while others improve the venture overall.

Extrusion of Lightweight Aluminum and Magnesium Alloys Structures for Aviation Applications

The development of light-weight materials and fabricating parts/sub-assemblies of substantially large dimensions has become a major issue for the aerospace industry, which has boosted the development of more advanced materials with high specification properties. Recent aluminum and magnesium alloys developments are based on achieving superior fatigue crack growth resistance, better corrosion resistance, lower density, etc. Standard manufacturing techniques, such as extrusion, ought to be developed in order to find a beneficial solution allowing for structural weight reduction, which is a very efficient means of improving aircraft performance. It is associated with the problem of extrusion profiles with a complex cross-section shape. In this work the formability of aluminum and magnesium alloys in the extrusion process was determined by the upsetting test through specification of the flow stress in relationship to the deformation size and rate. The results of the upsetting test of Al (7075, 2024, 8090, 2099) and Mg ( AZ31, AZ61, AZ80, WE 43) alloys were used in determining the conditions of the extrusion of profiles of various cross section shape and extrusion ratio. The analysis of macro and microstructure of extruded products and their mechanical properties demonstrates strong influence of the shape of extrudate cross section on metal exit speed and extrusion force value. Macro-and microstructure of all the investigated alloys after extrusion are highly homogeneous in terms of the grain size and morphology of the phase components, compared to the macro- and microstructure in the initial state, which justifies the use of them in production of aviation profiles.

THE EFFECT OF SLIVER DELIVERY SPEED ON THE UNEVENNES OF CARDED AND COMBED COTTON YARNS

The purpose of this study is to determine the effect of five different sliver delivery speeds on the yarn unevenness CVm (%). For this purpose, 100% cotton raw material was used, and card sliver samples were produced at five different card sliver delivery speeds (60 m/min, 120 m/min, 180 m/min, 240 m/min and 300 m/min). A total of 600 sample cops were produced in the ring spinning machine, each of which is 10 pieces of knitting and weaving yarn types in the carded and combed machine line, with the yarn counts Ne 20/1, Ne 30/1 and Ne 40/1 from these reed strips produced. The quality characteristics of the raw material used and the produced carded sliver samples were measured using the Uster HVI 1000 and Uster AFIS test equipment. The quality characteristics of the ring yarn cops samples produced on the ring spinning machine were measured with the help of Uster Tester 4 and Uster Tensojet Test devices. The results were analyzed by inferential and descriptive analysis methods. ANOVA analysis method was used for statistical analysis. According to the research findings, in both carded and combed Ne 40/1 yarn samples, an increase in yarn unevenness was observed with the increase in card sliver exit speed, and this increase created a statistically significant difference. The results revealed that the yarn unevenness is directly proportional to the card sliver exit speed and the increase of the card sliver exit speed causes the production of card sliver samples with higher unevenness values (Cvm (%).

Collisionless jet expanding into vacuum from a circular aperture

Collisionless flows expanding into a vacuum from a circular slit are investigated using the gaskinetic theory. Both accurate and approximate expressions to the plume fields along a centerline and a constant radius are obtained, including the density, velocity components, and translational temperature. Special non-dimensional parameters such as the exit semi-opening angle, gas speed ratio at the exit, and positions are included in these expressions. Particle simulations with the direct simulation Monte Carlo method are performed to validate the above results. These expressions are complex and may need computers for evaluations; however, the cost is minor when compared to particle simulations. With the assumptions of a high or low exit speed ratio and small exit angle, simple explicit expressions for properties along the centerline and a constant radius are obtained. The investigations also find out that the cosine law relations can provide fast and crude estimations, but it is not recommended to use the cosine law relation to compute collisionless plume flowfields with a large exit speed.

Hydrogen gas dispersion studies for hydrogen fuel cell vessels I: Vent Mast releases

We report modeling results for hydrogen releases associated with deploying hydrogen fuel cell technology on vessels. This first paper (I) considers hydrogen releases through the vessel Vent Mast from 250-bar hydrogen gas storage tanks, the type of tanks being used for the first hydrogen vessels. A manifolded 10-tank hydrogen storage system, holding 278 kg of hydrogen, can be emptied in ∼10 min for maintenance purposes, with a pressure reduction to half the original pressure (125 bar) realized in 2 min if a rapid pressure reduction is needed, for example in the event of a fire. The time profile for filling a tank is also of interest so as not to exceed the tank thermal limits. The calculations show that a manifolded 10-tank array can be filled with hydrogen to 250-bar pressure in ∼2 h from a 350-bar hydrogen refueling trailer without exceeding the 85 °C temperature limit typical of Type IV hydrogen tanks.Computational fluid dynamic (CFD) modeling shows that when the hydrogen is released out of the 10-tank array and into the Vent Mast in a 5-mph wind blowing horizontally, the effect of the wind on the hydrogen dispersion strongly depends on the hydrogen exit speed. For high release speeds (∼800–900 m/s), the hydrogen flow is strongly momentum-driven, and there is modest cross-wind influence. For low hydrogen exit speeds (∼10 m/s), the hydrogen is readily entrained in the wind flow and blown sideways, with the downstream flammable envelope rising at a positive angle to the horizontal due to buoyancy. To capture the influence of a wind with a downward component (e.g., created by a downdraft near a building), a calculation of a low-velocity (8.6 m/s) hydrogen release was performed with a 5-mph wind pointed downward at a 45° angle. The results show that despite the buoyancy of hydrogen, the wind blows the hydrogen substantially downward for low hydrogen speeds exiting the Vent Mast.

Quantifying Strombolian Activity at Etna Volcano

Understanding the dynamics of mild explosive activity is a fundamental tool for hazard assessment at open conduit volcanoes. This is a particularly critical task for Etna volcano. Etna is in fact characterized by frequent, mild explosive activity, punctuated by lava flows and paroxysmal events (‘lava fountains’), which, because of their greater impact, have been the main target for hazard studies, whereas more frequent Strombolian activity has been overlooked. As a result, their impact and associated hazards have been never quantified, despite the extensive monitoring and surveillance activities carried out on this volcano. In this paper, we analyze video recordings of a sequence of Strombolian explosions occurring at the summit craters of Mt. Etna, in Italy, in February 2020. Data were also integrated with a petrographic analysis of collected samples, and drone surveys were performed at the same time as the video recordings. We estimate the frequency of explosions (20–12 per min); particle exit speeds (1–50 m/s), and erupted mass (100–102 kg) of those explosions. A very regular, small-scale activity (marked by a single burst of gas breaking the magma free surface into bombs and lapilli fragments) was occasionally punctuated by larger explosions, (at least one every 5 min), with a longer duration, fed by larger magma volumes, and consisting of two to three distinct pulses followed by a stationary phase. We found that the repose times between explosions follows a log logistic distribution, which is in agreement with the behavior of open vent explosive activity. The four largest explosions of the sequence were analyzed in detail: they emitted particles with median diameters (Mdphi) ranging from −10.1 to −8.8 phi, with bimodal distributions.