Experimental Study on the Mechanical Properties of Friction, Collision and Compression of Tiger Nut Tubers

The mechanical properties of agricultural materials can provide the basis for the design and optimisation of agricultural machinery. There are currently very few studies on the mechanical properties of tiger nut tubers, which is not conducive to the design and development of machinery for their harvesting and processing. To obtain the mechanical parameters of tiger nut tubers, this study investigated the effects of variety (Zhong Yousha 1 and Zhong Yousha 2), moisture content (8%, 16%, 24%, 32% and 40%), contact material (steel, aluminium, plexiglass and polyurethane), release height (170 mm, 220 mm, 270 mm and 320 mm), loading speed (5 mm/min, 10 mm/min, 15 mm/min and 20 mm/min), compression direction (vertical and horizontal) on the friction, collision and compression mechanical properties of the tubers. The results were as follows: Both moisture content and contact material had a significant effect (p < 0.01) on the sliding friction coefficient (0.405–0.652) of the tubers; both variety and moisture content had a significant effect (p < 0.01) on the angle of repose (27.96–36.09°); contact material, moisture content, release height and variety all had a significant effect (p < 0.01) on the collision recovery coefficient (0.376–0.672) of tubers; variety, loading speed, moisture content and compression direction all had significant effects (p < 0.01) on the damage force (87.54–214.48 N), deformation (1.25–6.12 mm) and damage energy (82.38–351.08 mJ) of the tubers; only moisture content and compression direction had significant effects (p < 0.01) on the apparent elastic modulus (12.17–120.88 MPa) of the tubers. The results of this study can provide a reference for the design and optimisation of machinery for the harvesting and processing of tiger nut tubers.

Pollutant dispersion over Industrial Sub-urban area (Helwan)

The concentration of pollutants released from one chimney of the National Company for cement production in Helwan industrial area has been calculated; The calculations are based on the Gaussian plume model covering the period June 1988-May .1989. A method has been presented to calculate the dispersion parameters ay and az in horizontal and vertical directions respectively. The method rely on two-level observation of both wind velocity and temperature. The plume rise correction recommended by Briggs has been adopted to calculate the effective release height (stack height~ plus the plume rise).. The maximum concentration values for different heights and their1otations have been calculated.

Crosswind integrated concentration for various dispersion parameter systems

LFkkuh; Lrj izdh.kZu ds fy, xkSlh;u fiPNd ekWMy ¼Gaussian Plume Model½ dk O;kid :i ls iz;ksx fd;k tkrk gSA vuqizLFk iou dh dqy lkanzrk Kkr djus ds fy, xkSlh;u lw= ¼QkWewyk½ dks laxfBr fd;k gSA vuqizLFk iou dh dqy lkanzrk dh x.kuk djus ds fy, izdh.kZu izkpyksa dh fHkUu&fHkUu iz.kkfy;ksa dk mi;ksx fd;k x;k gSA lrg Lrj esa Å¡pkbZ ds vuqlkj iou xfr dh fHkUurk dk o.kZu djus ds fy, ykxfjFehd foaM izksQkby dk mi;ksx fd;k x;k gSA blesa NksM+h tkus okyh izHkkoh Å¡pkbZ dks /;ku esa j[kk x;k gSA fHkUu fHkUu izdh.kZu izkpy iz.kkfy;ksa ds fy, iwokZuqekfur lkanzrkvksa vkSj dksisugsxu ds folj.k iz;ksx ls izkIr fd, x, izsf{kr vk¡dM+ksa dh rqyuk djus ds fy, lkaf[;dh; ifjekiksa dk mi;ksx fd;k x;k gSA The Gaussian plume model is the most widely used model for local scale dispersion. The Gaussian formula has been integrated to obtain the crosswind-integrated concentration. Different systems of dispersion parameters are used to calculate the crosswind integrated concentration. A logarithmic wind profile is used to describe the variation of wind speed with height in the surface layer. The effective release height was taken into consideration. Statistical measures are utilized in the comparison between the predicted concentrations for different dispersion parameter systems and the observed concentrations data obtained from Copenhagen diffusion experiment.

A simple mechanistic model of the invasive species Heracleum sosnowskyi propagule dispersal by wind

Background Invasive species are one of the key elements of human-mediated ecosystem degradation and ecosystem services impairment worldwide. Dispersal of propagules is the first stage of plant species spread and strongly influences the dynamics of biological invasion. Therefore, distance prediction for invasive species spread is critical for invasion management. Heracleum sosnowskyi is one of the most dangerous invasive species with wind-dispersed propagules (seeds) across Eastern Europe. This study developed a simple mechanistic model for H. sosnowskyi propagule dispersal and their distances with an accuracy comparable to that of empirical measurements. Methods We measured and compared the propagule traits (terminal velocity, mass, area, and wing loading) and release height for H. sosnowskyi populations from two geographically distant regions of European Russia. We tested two simple mechanistic models: a ballistic model and a wind gradient model using identical artificial propagules. The artificial propagules were made of colored paper with a mass, area, wing loading, and terminal velocity close to those of natural H. sosnowskyi mericarps. Results The wind gradient model produced the best results. The first calculations of maximum possible propagule transfer distance by wind using the model and data from weather stations showed that the role of wind as a vector of long-distance dispersal for invasive Heracleum species was strongly underestimated. The published dataset with H. sosnowskyi propagule traits and release heights allows for modeling of the propagules’ dispersal distances by wind at any geographical point within their entire invasion range using data from the closest weather stations. The proposed simple model for the prediction of H. sosnowskyi propagule dispersal by wind may be included in planning processes for managing invasion of this species.

KINEMATIC DIFFERENCES BETWEEN PROFICIENT AND NON-PROFICIENT FREE THROW SHOOTERS – VIDEO ANALYSIS

Despite its importance and significant contribution to the final game outcome, the free throw shooting motion is greatly understudied. The purpose of this study was to examine kinematic differences between proficient and non-proficient free throw shooters and to determine which variables have the greatest impact on successful free throw shooting performance. Thirteen healthy recreationally active males volunteered to participate in this study. Each participant shot three sets of ten consecutive free throws from the regulation distance from the basket. Each set was performed under 3 minutes with 1-2-minute rest between each set. A high-definition camera recording at 30 fps captured the free throw shooting motion from a sagittal point of view. Video analysis software was used to analyze the following kinematic variables: knee angle, elbow angle, hip flexion, ankle flexion, release angle, shoulder angle, hand release height, and elbow height. The findings of this study suggest that lower elbow positioning influenced by greater knee, ankle, and hip flexion during the preparatory phase of the shooting motion may lead to improvements in free throw shooting accuracy. Moreover, greater ball release height and release angle, as previously suggested, could decrease the margin of error and enhance free throw shooting performance. By using these kinematic variables to create the discriminant function projection model, it is plausible that proficient free throw shooters can be accurately classified in 94% of cases.

Effects of a self-training program on shooting performance and kinematics in young basketball players: a case study (Efectos de un programa de autoentrenamiento sobre el rendimiento y cinemática de tiro en jóvenes jugadores de baloncesto: un caso de estu

The current study intended to investigate the effects of a self-training program on shooting performance and kinematics of young basketball players. Fourteen male basketball players aged 16.64±.50 years, divided in control group (n=7) and experimental group (n=7), were assessed on free-throw, two-point and three-point shooting performance and on four kinematic parameters (release height, release angle, release speed and trajectory variability), before and after a five-week training program. During the five-week period, the experimental group accomplished a shooting training program that included 600 shots per week. Both groups maintained their regular basketball practice. The results show that the experimental group significantly increased their shooting performance on three-point (p<.05) and on free-throw (p<.05). Moreover, a significant decrease in three-point ball release angle (p<.05) and a significant increase in free-throw ball release height (p<.05) were observed in the experimental group, while the control group significantly increased the two-point ball release speed (p<.05). In conclusion, self-shooting basketball practice, in addition to formal practice, significantly improves shooting performance of young basketball players. In contrast, the reduced changes on the analysed kinematic parameters caused by the self-training program are most likely a consequence of the absence of external feedback during training process. Resumen. El propósito del presente estudio fue investigar los efectos de un programa de autoentrenamiento en el rendimiento y cinemática de tiro de jóvenes jugadores de baloncesto. Catorce jugadores de baloncesto masculinos, de 16.64±0.50 años, divididos en grupo de control (n=7) y grupo experimental (n=7), fueron evaluados en el rendimiento de tiro libre, de dos puntos y de tres puntos y en cuatro parámetros cinemáticos (altura de liberación, ángulo de liberación, velocidad de liberación y variabilidad de la trayectoria), antes y después de un programa de entrenamiento de cinco semanas. Durante el período de cinco semanas, el grupo experimental realizó un programa de entrenamiento de tiro que incluía 600 tiros por semana. Ambos grupos mantuvieron su práctica regular de baloncesto. Los resultados muestran que el grupo experimental aumentó significativamente su rendimiento en el tiro de tres puntos (p<.05) y en el tiro libre (p<.05). Además, se observó, en el grupo experimental, una disminución significativa del ángulo de liberación en el tiro de tres puntos (p<.05) y un aumento significativo de la altura de liberación en el tiro libre (p<.05), mientras que el grupo de control aumentó significativamente la velocidad de liberación en el tiro de dos pontos (p<.05). En conclusión, la autopráctica de tiro en baloncesto, además de la práctica formal, mejora significativamente el rendimiento de tiro de los jugadores jóvenes. Por el contrario, los cambios reducidos en los parámetros cinemáticos analizados son probablemente una consecuencia de la ausencia de corrección externa durante el proceso de autoentrenamiento.

A Simulation of the Effects of Badminton Serve Release Height

In this work, we develop and calibrate a model to represent the trajectory of a badminton shuttlecock and use it to investigate the influence of serve height in view of a new serve rule instated by the Badminton World Federation. The new rule means that all players must launch the shuttlecock below a height of 1.15 m, as opposed to the old rule whereby the required launch height was under the rib cage of the server. The model is based on a forward dynamics model of ballistic trajectory with drag, and it is calibrated with experimental data. The experiments also served to determine the actual influence of the new rule on the shuttlecock launch position. The model is used in a Monte Carlo simulation to determine the statistical influence of the new serve rules on the player’s ability to perform good serves; i.e., serves with little opportunity for the receiver to attack. We conclude that, for the female player in question, serving below a height of 1.15 m makes it marginally more difficult to perform excellent serves. We also conclude that there might be alternative launch positions that would be less likely to produce the best serves but could be exploited as a tactical option.

Using sport science to improve coaching: A case study of Felisha Johnson’s Road to Rio

During a shot put, there are different finite variables that can be controlled by the thrower, including release angle, release height, release direction, and release velocity. Previous studies have determined thresholds of release velocity necessary for achieving certain distances, and this case study sought to expand upon that concept. Conclusions from key biomechanical data can make a significant difference in the performance of athletes in the shot put if properly understood by coaches. By utilizing this scientific approach to the shot put event, the throws coach will be able to determine more accurate adjustments and devise training stimuli to better accommodate the athlete. In this case study, researchers and the coach attempted to bridge the gap in the approach to teaching and coaching the glide shot put by using a physics-based equation regarding projectile motion in tandem with biomechanical analyses. The use of immediate feedback via video analysis was an essential part the coaching and teaching system. The athlete’s release angles decreased, and her maximum release velocities increased from 12.5 m/s in 2015 to 13.1 m/s in 2016. This USATF coaching education shot put project is an example in which the cooperation between sport science and coaching helped to produce an Olympic berth (19.24 m) by Felisha Johnson in the women’s shot put in 2016.

Physical Model Study on Discharge over a Dam Due to Landslide Generated Waves

Impulse waves generated by landslides falling into reservoirs may lead to overtopping of a dam and, in turn, to flooding of the downstream area. In the case of an embankment dam, the overtopping may lead to erosion of the downstream slope, ultimately resulting in breaching and complete failure with consequent further hazardous release of water to the downstream area. This research deals with the overtopping process of a dam due to landslide generated waves in a three-dimensional (3D) physical scale model setup. Experiments have been conducted with varying the slide, reservoir, and dam parameters. The primary focus is on investigating the feasibility of employing the steady state weir equation in order to predict the overtopping discharge over a dam crest due to landslide generated waves. Calibration and validation of the coefficient of discharge values for the different dam section are conducted for the specified model setup. Accordingly, a two-step calculation procedure is presented for predicting the overtopping discharge based on the maximum overtopping depth values. Hence, for the fixed setup, which includes a constant slope angle of the landslide surface, a predictive equation for maximum overtopping depth is proposed, based on slide volume, slide release height, still water depth, upstream dam slope angle, and dam height. The relative slide volume and relative still water depth both seem to have a significant effect on the relative overtopping depth.