A Concise Method to Predict the Mean Dynamic Pressure on a Plunge Pool Slab

Hydrodynamic pressure exerted on a plunge pool slab by jet impingement is of high interest in high dam projects. The present study experimentally investigated the characteristics of pressure induced by a jet through a constant width flip bucket (CFB) and a slit flip bucket (SFB). A pressurized plane pipe was employed in the flume experiments to control the inlet velocities in the flip buckets. A concise method is proposed to predict the mean dynamic pressure field. Its implementation is summarized as follows: First, the position of the pressure field is determined by the trajectories of free jets, and to calculate its trajectories, an equation based on parabolic trajectory theory is used; second, the maximum mean dynamic pressure is obtained through dimensional analysis, and then the pressure field is established by applying the law of Gaussian distribution. Those steps are integrated into a concise computing procedure by using some easy-to-obtain parameters. Some key parameters, such as takeoff velocity coefficient, takeoff angle coefficient, and the parameter k2, are also investigated in this paper. The formulas of these coefficients are obtained by fitting the experimental data. Using the proposed method, the easy-to-obtain geometric parameters and initial hydraulic conditions can be used to calculate the maximum mean dynamic pressure on the slab. A comparison between experimental data and calculated results confirmed the practicability of this model. These research results provide a reference for hydraulic applications.

Key Parameters Affecting Kick Start Performance in Competitive Swimming

The study aims to determine the contribution of kinematic parameters to time to 5 m without underwater undulating and kicking. Eighteen male competitive swimmers started from three weighted positions and set the kick plate to positions 1–5. We used SwimPro cameras and the Dartfish© software. In the on-block phase, we found significant correlations (p < 0.01) between the front ankle angle and block time. The correlations between start phases were statistically significant (p < 0.01) between block time and rear ankle angle, respectively, to time to 2 m; rear knee angle and glide time; block time and time to 5 m; time to 2 m and time to 5 m; and flight distance and glide distance. The multiple regression analysis showed that the on-block phase and flight phase parameters, respectively, contributed 64% and 65% to the time to 5 m. The key block phase parameters included block time and rear knee angle. The key flight phase parameters determining time to 5 m included take-off angle and time to 2 m. The key parameters determining the performance to 5 m during the above-water phase include rear knee angle, block time, takeoff angle, and time to 2 m.

Kinematics Study of Depth Jump on Male Triple Jumpers with Slope Run-Up

Objective. To explore the training methods of developing the special strength of Chinese male triple jumpers through the experimental study of nine male triple-jumpers who performed step takeoff and depth long jump on the force platform. Methods. Through the combination of high-velocity shooting and a three-dimensional force measuring platform, the data of the athletes’ full run-up and depth jump landing, horizontal velocity, vertical velocity, takeoff time, landing angle, takeoff angle, and strength were obtained. In this study, the kinematics characteristics of four slopes with different slopes of 25 cm and 35 cm were studied. Kinematics’ data was measured by a high-velocity video camera. Results. The vertical velocity of the 35 cm platform is obviously less than that of the 25 cm platform p < 0.01 . The 25 cm platform is better at developing vertical, rapid takeoff ability, especially the fourth slope of this height, which is the fastest from horizontal velocity and vertical speed. All the depth jump practice ground angles are larger than the whole step jump, and the off-ground angle is smaller than the step jump, the takeoff time is larger than the step jump, which indicates that the athletes takeoff range is larger and the takeoff time is longer, and the results are in greater stimulation intensity of lower limb muscles. Conclusion. The 25 cm high platform depth jump exercise has achieved a better takeoff effect. Among the four slope depth jump exercises on this high platform, the 6.84 slope takeoff effect is the best.

Usefulness of the angiographic anatomy of the vein of marshall for ablation procedures for persistant atrial fibrillation

Funding Acknowledgements Type of funding sources: None. Background Ethanol Infusion in the Vein of Marshall (EIVOM) was recently proposed as an efficient adjunctive technique for obtaining mitral isthmus block during catheter ablation for persistent atrial fibrillation. Purpose Given these considerations the objective of this research was to delineate the angiographic anatomy of the Vein of Marshall (VOM). Methods Fluoroscopy images were obtained retrospectively in 124 patients with persistent atrial fibrillation who underwent coronary sinus angiography for EIVOM (96 patients) or cardiac resynchronization implant (18 patients). The measurements were performed using Osirix DICOM reader using the known diameter of the angiographic catheter for calibration. The distance between the ostium of the coronary sinus (CS) and the ostium of the VOM was measured in the anteroposterior view. Additionally, the angle at which the ostium of VOM opens in the CS was obtained. Results The diameter of the VOM ostium was 1.8 ± 0.6mm. The length of the VOM was 18.6 ± 9.1mm. The distancebetween the CS ostium and VOM ostium was as follows: less than 10mm for 1 patient (1%), between 11-20mm for 10 patients (10.41%), between 21-30mm for 38 patients (39.58%), 31-40mm for 31 patients (32.29%), between 41-50mm for 15 patients (15.62%) and &gt;50mm for 1 patients (1%) (53mm). The average takeoff angleof the VOM from the CS between the main branch of the VOM and the CS was measured at 140 degrees (range 90-175 degrees). No correlation could be made between the takeoff angle and the distance between CS ostium and VOM ostium. In the group of patients undergoing cardiac resynchronization the takeoff angle from the CS was 153°±17° and it correlated significantly with the left ventricular systolic diameter and the left ventricular ejection fraction determined by echocardiography(r = 0.52; p = 0.008 and respectively r = 0.50; p = 0.009). Conclusions Understanding the anatomy of the Vein of Marshall (VOM) is crucial in helping operators efficiently exploit the therapeutic potential of ethanol injection after accurate localization of such an important branch of the left atrial venous system. Abstract Figure. 1 Fig 1 Angle CS-VOM

Anatomical aspects of the use of the thoracodorsal nerve as a donor in musculocutaneous nerve ­injury

Aim. To assess the anatomical possibility of the use of the thoracodorsal nerve as a donor for nerve transfer to the musculocutaneous nerve. Methods. Anatomical dissection of the brachial plexus with layer-by-layer dissection of secondary bundles, short and long branches was performed in 121 male and female corpses. The localization of the origin of thoracodorsal and musculocutaneous nerves relative to the clavicle, the takeoff angle (degrees) from the secondary bundle, the length (in centimeters) of the nerves from the site of origin to the latissimus dorsi muscle entry point and the perforation of the coracobrachialis muscle, respectively, were investigated. The length of the thoracodorsal nerve with and without extramuscular branches was studied separately. Results. It was revealed that, in 58.7% of cases, the thoracodorsal nerve has the optimal length required for transposition to the musculocutaneous nerve. The excess length of the thoracodorsal nerve was between 0.1 and 9.1 cm. In 41.3% of cases, the length of the thoracodorsal nerve is not enough for transposition. Of these, in 17.4% of cases, the shortage of the length of the thoracodorsal nerve was 2 cm or less, which categorically does not allow its transfer to the musculocutaneous nerve. Only in 5% of cases, the length of the nerve was not enough for transposition in the use of the thoracodorsal nerve with extramuscular branches. Conclusion. Due to tension in many cases, the thoracodorsal nerve transfer to the musculocutaneous nerve can be performed with difficulty, and in some cases it is impossible, solving the problem in this category of people dictates the development of new surgical techniques with the thoracodorsal nerve or the use of another nerve as a donor.

Kinematic analysis of the kick start from OSB12

Introduction: Start performance in swimming plays a major role in determining the final standings, especially in sprint races. The purpose of the study was to determine kinematic parameters underlying the kick start from OSB12 in terms of the kick plate position and shoulder positioning at the start. Material and methods: The sample included 8 non-randomly recruited performance-level swimmers whose average age, body height, and body weight was 17.4 ± 1.8 years, 182.2 ± 3.4 cm and 81.00 ± 3.9 kg, respectively. To measure the kinematic parameters, we used the SwimPro camera system. The parameter rs measured included angular parameters and kinematic parameters for each of the start phases: block phase, flight phase, and water phase. We processed the collected biomechanical data using the Statistica 12.0 software. To determine significant differences between the kick plate positions in three types of start, we applied the Mann-Whitney U test. Results: We found significant differences (p<0.05) in the selected kinematic parameters in all phases, which depended on the OSB12 kick plate position and basic starting position (front-, neutral-, and rear-weighted). The greatest differences in the parameters measured were found between the front-weighted start and rear-weighted start. We may conclude that performance-level swimmers should adjust the rear kick plate to positions 3 and 4 and assume the following starting position: front knee angle between 131° and 133°, rear knee angle around 80°, and trunk angle between 40° and 41°. This starting position affects the flight phase, namely takeoff angle (40⁰-41⁰), head position at takeoff (1.33-1.38 m), flight time and distance (0.346-0.368 s; 2.74-2.79 m), entry angle (38⁰). The starting position also affects the glide phase, namely the glide time and distance (0.532-0.536 s; 2.22-2.26 m) and maximum depth (-0.91-0.92 m). Conclusions: The results of the study show that swimmers produced shorter times to 5 meters and higher velocity at 5 meters compared with other starting positions and OSB12 kick plate positions.

Quantitative Measurement of Iron-Silicides by EPMA Using the Fe Lα and Lβ X-ray Lines: A New Twist to an Old Approach

The recent availability of Schottky-type field emission electron microprobes provides incentive to consider analyzing micrometer-sized features. Yet, to quantify sub-micrometer-sized features, the electron interaction volume must be reduced by decreasing accelerating voltage. However, the K lines of the transition elements (e.g., Fe) then cannot be excited, and the L lines must be used. The Fe Lα1,2 line is the most intense of the L series but bonding effects change its atomic parameters because it involves a valence band electron transition. For successful traditional electron probe microanalysis, the mass absorption coefficient (MAC) must be accurately known, but the MAC of Fe Lα1,2 radiation by Fe atoms varies from one Fe-compound to another and is not well known. We show that the conventional method of measuring the MAC by an electron probe cannot be used in close proximity to absorption edges, making its accurate determination impossible. Fortunately, we demonstrate, using a set of Fe–silicide compounds, that it is possible to derive an accurate calibration curve, for a given accelerating voltage and takeoff angle, which can be used to quantify Fe in Fe–silicide compounds. The calibration curve can be applied to any spectrometer without calibration and gives accurate quantification results.

High-speed video analysis of jumping in Locusta migratoria

Among insects, locusts are widely recognized for their excellent jumping performances. Indeed, jumping helps locusts to avoid predators as well as to initiate flight. In the present contribution, we employed high-speed videos to analyze the jumping performance of Locusta migratoria L. from ground with different toughness. Results outlined that L. migratoria can prolong their takeoff time to get bigger takeoff velocity to adapt to different terrains, and takeoff velocity has no connection with takeoff angle.

High-speed video analysis of jumping in Locusta migratoria

Among insects, locusts are widely recognized for their excellent jumping performances. Indeed, jumping helps locusts to avoid predators as well as to initiate flight. In the present contribution, we employed high-speed videos to analyze the jumping performance of Locusta migratoria L. from ground with different toughness. Results outlined that L. migratoria can prolong their takeoff time to get bigger takeoff velocity to adapt to different terrains, and takeoff velocity has no connection with takeoff angle.