Maximum Speed Research Articles

Biceps femoris muscle-tendon strain during an entire overground sprint acceleration: a biomechanical explanation for hamstring injuries in the acceleration phase.

The objectives of this study were to analyse the peak muscle-tendon (MT) strain of the hamstring during an entire acceleration sprint overground and examine their relationship with relative joint angles and segment orientation in the sagittal plane, which are the direct causes of MT strain. Kinematic data were recorded using a 3D inertial motion capture system in 21 male semi-professional soccer players during 40-metre overground sprint. Scaled musculoskeletal models were used to estimate peak MT strain in the hamstring over 16 steps. Biceps femoris long head (BFLH) exhibited the largest peaks in MT strain compared to semitendinosus (ST) and semimembranosus (SM) muscles across all the steps, with its overall strain decreased as the number of steps and maximum speed increased. Hip flexion angle was found to be a strong predictor (p < 0.001) of joint angles, being the orientation of the pelvis in the sagittal plane of the segment with the greatest influence (p < 0.001) on the peak MT strain of BFLH during sprinting. The current study provides a biomechanical explanation for the high proportion of hamstring injuries in the acceleration phase of sprinting.

Simulation and electrification of a conventional vehicle into a battery electric vehicle for sustainability mobility

ABSTRACT This work explores converting a conventional 1996 Honda Civic Coupe into a battery-electric vehicle (BEV). A simulation model is developed to analyze the vehicle’s dynamic behavior under various conditions, including changes in vehicle mass and road slope. The system specifications are detailed based on a 50 kW AC induction motor, controller, battery, and battery management system. The battery comprises 2,376 NCR18650B cells with a capacity of 23 kWh based on inverter requirements. Energy consumption is simulated using the New European Driving Cycle (NEDC), resulting in 1.69 kWh to travel 10.8 km. Autonomy is estimated at 147 km. The environmental impact of 19.2 g CO2/km is calculated. The results illustrate the change in maximum speed, acceleration, and distance traveled based on changes in mass and slope. It is concluded that mass variation has a lesser impact on performance than road slope. The work demonstrates the feasibility of converting a conventional vehicle to a BEV with comparable dynamic capabilities using currently available technology. Future development plans include constructing a battery prototype, electrifying the vehicle, and incorporating instrumentation for validation.

Maximum speed of dissipation

Maximum speed of dissipation

Critical speed models of high-resolution speed-duration profiles describe peak running demands in soccer

The purpose of this study was to characterize critical speed (CS) models for summarizing high-resolution speed-duration profiles from GPS tracking data obtained from soccer players. GPS data from 15 male NCAA Division I soccer players were collected during practices and games over a 6-week period. Moving averages of the speed data were computed for each file for duration windows spanning 0.1 to 600 seconds at 0.1-second resolution. Speed-duration profiles for each session and for the entire sampling period (“global”) were generated for each player by selecting the maximal mean speeds for each duration. Four models were fit to the profiles: the two-parameter CS (CS2) model, the three-parameter CS (CS3) model, the omni-domain speed-duration (OmSD) model, and the five-parameter logistic (5PL) model. The 5PL, CS3, and OmSD models exhibited similar goodness of fits, and all outperformed the CS2 model. Similar CS estimates were obtained for each model, whereas maximum speed ( Smax) estimates were lower for OmSD compared to the 5PL. Players exhibited a range of parameter values for CS, D′, and Smax. Smax and CS estimated from session-specific speed-duration profiles were on average higher for games compared to practices. We conclude that CS models are useful for empirically describing speed-duration profiles and for assessing peak running demands for soccer practices and games. The proposed approach could help coaches design practice activities to better mimic game demands.

Effect of Obstacle Gradient on the Deflagration Characteristics of Hydrogen/Air Premixed Flame in a Closed Chamber

In this paper, computational fluid dynamics (CFD) numerical simulation is employed to analyze and discuss the effect of obstacle gradient on the flame propagation characteristics of premixed hydrogen/air in a closed chamber. With a constant overall volume of obstacles, the obstacle blocking rate gradient is set at +0.125, 0, and −0.125, respectively. The study focuses on the evolution of the flame structure, propagation speed, the dynamic process of overpressure, and the coupled flame–flow field. The results demonstrate that the flame front consistently maintains a jet flame as the obstacle gradient increases, with the wrinkles on the flame front becoming increasingly pronounced. When the blocking rate gradients are +0.125, 0, and −0.125, the corresponding maximum flame propagation speeds are measured at 412 m/s, 344 m/s, and 372 m/s, respectively, indicating that the obstacle gradient indeed increases the flame propagation speed. Moreover, the distribution of pressure is closely related to changes in the flame structure, with the overpressure decreasing in the obstacle channel as the obstacle gradient increases. Furthermore, the velocity vector and vortex distribution in the flow field are revealed and compared. It is found that the obstacle tail vortex is the main factor inducing flame evolution and flow field changes in a closed chamber. The effect of the blocking rate gradient on flow velocity is also quantified, with instances of deceleration occurring when the blocking rate gradient is −0.125.

Stent Ablation by Rotational Atherectomy for Management of Resistant Lesions within and across the Stent Struts in Coronary Arteries

Background: Non-dilatable stent underexpansion has limited treatment options. Stent ablation by rotational atherectomy (RA) for the management of non-dilatable coronary stents is an off-label strategy. The principle of stent ablation by RA of underexpanded stent relies on modification of both stent and underlying calcium. This study aims to describe and compare the use of RA for non-dilatable lesions in two anatomical categories: group 1 (within the stent struts) and group 2 (across the stent struts). Methods: A total of seven patients who had undergone stent ablation by RA were analysed. Indications for revascularisation were acute coronary syndrome or chronic stable angina. Two groups are described: RA within underexpanded stents (group 1) and across the stent struts (across stented bifurcation; group 2). Results: The burr:artery ratio was 0.6 ± 0.1 in group 1 and 0.5 in group 2 (p=0.24). The maximum rotational speed was 154,400 ± 2,500 and 155,000 rpm in the two groups. The total number of RA runs was 3.6 ± 0.90 in group 1 and 7.0 ± 2.8 in group 2, respectively, p=0.04. Procedural success was achieved in all cases with no complications. Conclusion: RA is a feasible bailout option for resistant non-dilatable lesions within and across the stent struts.

Study on Non-Stationary Wind Speed Models and Wind Load Design Parameters Based on Data from the Beijing 325 m Meteorological Tower, 1991–2020

As the capital of China and a densely populated major city, the characteristics of Beijing’s near-surface wind field change significantly with the increase in the density of underlying urban structures. The high randomness of natural wind makes it extremely difficult to develop a universally applicable wind-resistant load design code based on topographic factors and architectural features. This article takes the wind speeds recorded at 15 different height levels within the urban area by the 325 m meteorological tower in Beijing from 1991 to 2020 as the research subject. It quantifies the wind speed trends at different heights and introduces time-varying functions to establish a non-stationary wind speed model based on the optimal model. Additionally, it compares the basic wind speeds and wind pressure height variation coefficients obtained from measurements with the standards. The results show that, during the past 30 years of urbanization, the near-surface wind speed in the Beijing area has shown a decreasing trend. The model incorporating time-varying functions exhibited the best fit and demonstrated good predictive capabilities, with its calculated basic wind speeds being relatively high. The wind pressure height variation coefficient values in Beijing are between Class C and Class D terrains, being closer to Class C at lower altitudes. The conclusion reveals that urbanization has a significant impact on wind speeds, primarily concentrated at lower height levels, and that the basic wind speeds calculated based on standards underestimate the actual conditions when this impact is not considered. Although the average wind speed’s wind profile index across the entire time series is mostly greater than the fixed value of 0.3 given by Class D, this represents an overestimated wind profile index for maximum wind speeds.

Accelerometer-based swimming metabolism of smallmouth bass (Micropterus dolomieu).

Bioenergetics is informative for a range of fundamental and applied resource management questions, but findings are often constrained by a lack of ecological realism due to the challenges of remotely estimating key parameters such as metabolic rate. To enable field applications, we conducted a calibration study with smallmouth bass (Micropterus dolomieu, 0.7-2 kg) surgically implanted with accelerometer transmitters and exposed to a ramp-Ucrit swimming protocol in a swim tunnel respirometer across a range of water temperatures (6, 12, 18, and 24°C). There was an exponential increase in fish acceleration with swimming speed, and acceleration per speed was higher in smaller fish and female fish, and at colder temperatures. Mass-specific fish metabolic rate (MO2; mg O2 kg-1 h-1) increased with swimming speed, acceleration, and temperature, and decreased with fish mass, which when combined were strong predictors of MO2. Maximum metabolic rate (MMR) was estimated to peak at 22°C, but maximum sustained swimming speed (Ucrit) remained high at c. 90-100 m s-1 above 20°C, based on second-order polynomial functions. Aerobic scope (AS) estimates peaked at 20°C (>90% AS at 17-24°C; >50% AS at 11-28°C). Males exhibited marginally higher MMR, AS, and Ucrit than females at higher temperatures. Larger fish generally exhibited higher Ucrit, but smaller fish had a marginally broader performance range (AS, Ucrit) among temperatures, benefiting from higher MMR despite a steeper increase in resting metabolic rate with temperature. These findings enable field studies to estimate metabolic metrics of smallmouth bass in situ to characterize their ecological energetics and inform bioenergetics models.

Space and time joint optimization for vertical takeoff and landing aircraft in dense obstacles and interference environments

ABSTRACT The Vertical Takeoff and Landing Aircraft (VTOL) is capable of both low-speed hovering and high-speed flight. This paper proposes an autonomous motion planning and anti-wind disturbance control algorithm for the VTOL, implemented spatial and temporal joint motion planning for VTOL, under the limitation of maximum flight speed of the aircraft, VTOL can achieve fully autonomous flight in complex environments, which can realize the autonomous flight of a single aircraft in a complex and dense environment, achieve real-time perception and avoidance of static and dynamic obstacles. The information generated by motion planning includes the position, velocity, and acceleration information of the aircraft, and proposes a wind disturbance estimation and active control strategy in a wind disturbance environment, accurate estimation of wind disturbance is achieved through a state observer, and the wind disturbance was suppressed through nonlinear error feedback control law, implemented wind disturbance estimation and suppression for aircraft in wind disturbance environments, and achieved complete autonomous motion planning and trajectory tracking of VTOL in a complex and wind disturbance environment. Our work can provide a basis for the collaborative control of multiple UAVs.

Efficiency assessment of follow-up methodology of patients with knee replacement to predict post-surgical functionality: a protocol for randomised control PROKnee trial

IntroductionEven when total knee arthroplasty (TKA) is an extended treatment, most patients experience a suboptimal evolution after TKA. The objectives of this study are the following: (1) to determine the...

Investigating the Forming Characteristics of 316 Stainless Steel Fabricated through Cold Metal Transfer (CMT) Wire and Arc Additive Manufacturing

Wire and arc additive manufacturing (WAAM), recognized for its capability to fabricate large-scale, complex parts, stands out due to its significant deposition rates and cost-effectiveness, positioning it as a forward-looking manufacturing method. In this research, we employed two welding currents to produce samples of 316 austenitic stainless steel utilizing the Cold Metal Transfer wire arc additive manufacturing process (CMT-WAAM). This study initially evaluated the maximum allowable arc travel speed (MAWFS) and the formation characteristics of the deposition bead, considering deposition currents that vary between 100 A and175 A in both CMT and CMT pulse(CMT+P) modes. Thereafter, the effect of the CMT+P mode arc on the microstructure evolution was analyzed using the EBSD technique. The findings indicate that the arc travel speed and deposition current significantly affect the deposition bead’s dimensions. Specifically, an increase in travel speed or a reduction in current results in reduced bead width and height. Moreover, the employment of the CMT+P arc mode led to a reduction in the average grain size in the mid-section of the sample fabricated by CMT arc and wire additive manufacturing, from 13.426 μm to 9.429 μm. Therefore, the components of 316 stainless steel produced through the CMT+P-WAAM method are considered fit for industrial applications.

Match-play running demands in a female soccer professional club: From academy to professional team

The objective of the study was to examine the match-running load of female soccer players competing at distinct age groups (U15, U18 and senior cohorts) belonging to the same professional club, over a competitive season. The external load variables of the official matches were monitored with Global Positioning System (GPS) technology: total distance (TD), at &gt;18 km·h−1 (running), at &gt;21 km·h−1 (high-speed running, HSR) and at &gt;24 km·h−1 (sprint, SPR) distances, efforts at &gt;85% of the maximal sprint speed (&gt;85% MSS), acceleration load (aLoaD), accelerations (ACC2 and ACC3, &gt;2 and &gt;3 m·s−2) and decelerations (DEC2 and DEC3 &lt;−2 and &lt;−3 m·s−2). Overall, distances covered at running, HSR and sprinting were greater for senior players than their younger peers (U15 and U18; p &lt; 0.05). Regarding HSR and sprints, no difference was found for sprints accumulated by central defender (CD) players in comparison to U18 and U15 ( p &gt; 0.05). In addition, U18 and senior players engaged more often in ACC and DEC, &gt;2 and &gt;3 m·s−2, respectively, than U15 players ( p &lt; 0.05). In conclusion, older female soccer players are exposed to higher match load than their younger peers. These findings could be useful for soccer coaches to design specific speed development programmes across the long-term athletic development pathway.

The association of interlimb coordination and temporal symmetry with walking function and motor impairment after stroke.

Interlimb coordination during walking is impaired after stroke, with unknown effects on walking function. This cross-sectional study determined associations of interlimb coordination and temporal symmetry with walking function and motor impairment. During walking, participants wore wireless sensors to detect heel strikes. We calculated interlimb coordination as the phase coordination index and temporal symmetry as the ratio of contralesional (i.e., paretic) to ipsilesional (i.e., non-paretic) stance times. Associations with walking speed (10-meter walk test), walking endurance (6-minute walk test), dynamic balance (Mini Balance Evaluation Systems Test), and motor impairment (Fugl Meyer Lower Extremity assessment) were assessed. 56 individuals with chronic stroke were tested. Worse interlimb coordination was correlated with slower comfortable (R = -0.38, p = 0.004) and maximal (R = -0.36, p = 0.006) walking speed and worse motor function (R = -0.45, p = 0.001). Worse temporal symmetry was correlated with worse motor function (R = 0.39, p = 0.004). Interlimb coordination had stronger associations than temporal symmetry with comfortable (R: -0.38 vs. 0.08) and maximal walking speeds (R: -0.36 vs. 0.12). Poor interlimb coordination was associated with slow walking and motor impairment and had stronger associations with walking speeds than temporal symmetry did. Interlimb coordination may provide unique insights into walking function and a target for walking rehabilitation after stroke.

The Effect of Insulation Thickness on Heat Transfer Characteristics and Flammability in Tube Mesoscale Combustors

The Effect of Insulation Thickness on Heat Transfer Characteristics and Flammability in Tube Mesoscale Combustors

Development of an Integrated Computing Platform for Measuring, Predicting, and Analyzing the Profile-Specific Fixity of Railway Tracks

The current measures for railway track fixity in the UK’s railway remain at a relatively low level of granularity. This paper presents a pilot proof-of-concept study on the development of an integrated computing framework for improving the measurement, prediction, and analysis of profile-specific track fixity in the context of the UK’s rail network. The framework is aimed to produce a data integration and mining tool, which can determine track fixity parameters for any given section of track. In this study, we propose to measure track movement based on point cloud data and assess the track fixity by a set of parameters, such as the direction and rate of the track movement relative to the plane of the rail within a certain period. We seek to integrate a data mining algorithm into the framework to predict these parameters, given vast amounts of disparate and heterogeneous data of potential influencing factors in the area. From the study, we have developed a prototype framework, which allows the rapid implementation of data workflows with the necessary functionality. The feasibility of the prototype was demonstrated by training a random forest model on real data from an approximately 80-km section of the East Coast Main Line, southeast of Edinburgh, Scotland. The modeling results indicate that the curvature, cant, and maximum speed of trains are among the key factors that impact on, and are critical for predicting and analyzing, the profile-specific track fixity.

Global Climatology of Low‐Level‐Jets: Occurrence, Characteristics, and Meteorological Drivers

AbstractLow‐level jets (LLJs), vertical profiles with a wind speed maxima in the lowest hundred meters of the troposphere, have multiple impacts in the Earth system, but a global present‐day climatology based on contemporary data does not exist. We use the spatially and temporally complete data set from ERA5 reanalysis to compile a global climatology of LLJs for studying the formation mechanisms, characteristics, and trends during the period of 1992–2021. In the global mean, LLJs are detected 21% of the time with more cases over land (32%) than over the ocean (15%). We classified the LLJs into three categories: non‐polar land (LLLJ), polar land (PLLJ), and coastal (CLLJ) LLJs. For LLLJ, the averaged frequency of occurrence is 20% and 75% of them are associated with a near‐surface temperature inversion as a prerequisite for an inertial oscillation. PLLJs are also associated with a temperature inversion and occur even more frequently with 59% of the time. These are also the lowest and the strongest LLJs among the three categories. CLLJs are particularly frequent in some marine hotspots, situated along the west coast of continents, with neutral to unstable stratification close to the surfaces and a stably stratified layer aloft. We found distinct regional trends in both the frequency and intensity of LLJs over the past decades, which can have implications for the emission and transport of aerosols, and the transport of atmospheric moisture. Future studies could address changes in LLJs and the associated implications in more detail, based on the here released ERA5‐based LLJ data.

A Time Headway Control Scheme for Virtually Coupled Heavy Haul Freight Trains

Abstract Virtual coupling of railway trains is an emerging technology that has the potential to significantly increase railway operational efficiency by reducing the train following distance from absolute braking distances to relative braking distances. Current research in this topic is mainly focused on passenger trains and uses distance-based headways. This paper studied virtual coupling for heavy haul freight trains and demonstrated that the distance headway scheme was challenging and sometimes impractical for heavy haul trains to achieve virtual coupling. A time-based headway scheme was then proposed to set the follower train to be a certain time behind the schedule of the leader train rather than a distance headway. The time-based headway required the follower train to reproduce the leader train's operational status at the same track location. This also allowed the follower train to copy any optimized train driving strategies from the leader train. Demonstrative simulations were carried out without the consideration of communication errors and train localization errors. The results show that a conventional distance headway simulation had maximum distance and speed errors of 716 m (36%, reference 2 km) and 24 km/h (66%, reference 36 km/h), respectively. A time-based headway simulation reduced the maximum distance and speed errors to 0.07 m (0%, reference 2 km) and 0.1 km/h (9%, reference 1.18 km/h), respectively.

Cooling performance improvement for two hot elastic plates by using double channels with rotating cylinders

Abstract Alternative cooling systems that can be used for thermal management in different technological applications such as in batteries, solar panels, electronic systems and in diverse heat transfer equipments are needed. This study uses a hybrid channel system with rotating circular cylinders to explore the cooling of two heated elastic plates. The numerical analysis of a coupled fluid-structure-thermal system with rotating cylinders is done using the finite element technique with ALE. The study is carried out for different values of the Reynolds number (Re) in the upper channel flow (between 200 and 1000), the non-dimensional rotational speeds of the cylinders (Ω in the range between -1000 and 1000), and the non-dimensional location of the cylinders (between 0.4 and 1) taking into account the cooling of both the rigid and elastic plates. Rigid plates have better cooling performance than elastic ones. The cooling performance increases for both rigid and elastic plates reach up to 26.1% and 31.7% at the maximum upper channel flow Re. For elastic and rigid plates, CCW rotation at maximum speed increases cooling performance by 18.5% and 19%, respectively, but CW rotation increments cooling performance by only 7%. By using optimization, the cooling performance increase with rotatingcylinders at Re=200 is determined to be 73.6% more than that of the case without cylinders. Optimization results in an extra 11.2% increase in cooling performance at Re=1000 when compared to the parametric CFD scenario

Harnessing the power of wind: a comprehensive analysis of wind energy potential in Dhaka city

This study gives a thorough analysis on the wind energy potential in Dhaka, Bangladesh, utilizing data from NASA Power's remote sensing tools and weather data from the Bangladesh Meteorological Department (BMD). The wind speed data collected over a 22 year period at an altitude of 10 m. The results indicate that 3.07 m per second (ms−1) is Dhaka city's typical wind speed, while the maximum wind speeds were recorded in June and July. A Weibull distribution is used to observe the wind data, as well as to calculate the Weibull form parameter of 2.65 and the scale parameter of 3.43 ms−1. Based on these parameters, the most probable wind speed along with the wind speed carrying maximum energy were calculated 2.83 ms−1 and 4.28 ms−1, respectively. The highest density of energy has been found in the month of July with a value of 52.11 W/m2. According to the study, the south is the most prominent wind direction for Dhaka city. Moreover, the study analyzes the relations between energy density and other variables, like wind speed, humidity, dry bulb temperature, etc. Positive correlations between energy density, wind speed, and dry bulb temperature imply that the higher wind speeds and dry bulb temperatures result in greater energies. The study's conclusions offer intuitive information about Dhaka City's potential for wind energy and can support direct future efforts to pursue this green resource in alignment with the Sustainable Development Goals (SDGs) of Bangladesh.

THE EFFECTIVENESS OF PROGRESSIVE RESISTANCE TRAINING IN MANAGING PROGRESSIVE SUPRANUCLEAR PALSY: A CASE STUDY

SETTING The Centre for STRONG Medicine is an outpatient multidisciplinary geriatric service at Concord Hospital, Sydney. An 82-year-old male with a primary diagnosis of Progressive Supranuclear Palsy (PSP) with cardiac and metabolic comorbidities was referred in March 2023. PSP is a rare neurological disorder that affects gait, balance, vision, and cognition. The participant mobilised with a rollator and had previously sustained vertebral and wrist fractures secondary to falls. MANAGEMENT Management was to use progressive resistance training (PRT) to combat mobility decline, prevent falls and provide education to encourage independent exercise. Initial assessment determined current health status using Falls Self Efficacy Scale (FSE-I) and Fried Frailty Phenotype (FFP) questionnaires, and measured function and strength using maximal gait speed, five times sit-to-stand (5xSTS) and one repetition maximum (1RM), respectively. FSE-I determined a high fear of falling and FFP determined frail classification. Outcomes informed the PRT exercise prescription targeting the major muscle groups for 2-3 sets of 7-9 repetitions at 70-85% 1RM progressed gradually and preformed twice weekly in a supervised group. Education regarding breathing, exercise tempo, rest, progression, and risk mitigation were provided. All outcomes were reassessed after 12-weeks of training. RESULTS Attendance was 100% (23 sessions) with improvement in all outcomes. Functional improvements included 0.25metres/second increase in maximal gait speed, 2.5 second reduction in 5xSTS, and safe mobilisation without a rollator. Strength improvements included 101% increase in 1RM leg press, 100% increase in 1RM triceps extension and 72% increase in 1RM seated row. Frailty status improved to pre-frail and fear of falling reduced. Self-reported improvements included increased steadiness and confidence exercising unsupervised. DISCUSSION Although PSP is progressive, PRT resulted in meaningful benefits in strength and function that improved daily task performance and confidence. Further research is needed to investigate the effects of PRT on PSP management in a larger cohort.