Slow-motion Camera Research Articles

The Sprint Mechanics Assessment Score: A Qualitative Screening Tool for the In-field Assessment of Sprint Running Mechanics

Background: Qualitative movement screening tools provide a practical method of assessing mechanical patterns associated with potential injury development. Biomechanics play a role in hamstring strain injury and are recommended as a consideration within injury screening and rehabilitation programs. However, no methods are available for the in-field assessment of sprint running mechanics associated with hamstring strain injuries. Purpose: To investigate the intra- and interrater reliability of a novel screening tool assessing in-field sprint running mechanics titled the Sprint Mechanics Assessment Score (S-MAS) and present normative S-MAS data to facilitate the interpretation of performance standards for future assessment uses. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Maximal sprint running trials (35 m) were recorded from 136 elite soccer players using a slow-motion camera. All videos were scored using the S-MAS by a single assessor. Videos from 36 players (18 men and 18 women) were rated by 2 independent assessors blinded to each other's results to establish interrater reliability. One assessor scored all videos in a randomized order 1 week later to establish intrarater reliability. Intraclass correlation coefficients (ICCs) based on single measures using a 2-way mixed-effects model, with absolute agreement with 95% CI and kappa coefficients with percentage agreements, were used to assess the reliability of the overall score and individual score items, respectively. T-scores were calculated from the means and standard deviations of the male and female groups to present normative data values. The Mann-Whitney U test and the Wilcoxon signed-rank test were used to assess between-sex differences and between-limb differences, respectively. Results: The S-MAS showed good intrarater (ICC, 0.828 [95% CI, 0.688-0.908]) and interrater (ICC, 0.799 [95% CI, 0.642-0.892]) reliability, with a standard error of measurement of 1 point. Kappa coefficients for individual score items demonstrated moderate to substantial intra- and interrater agreement for most parameters, with percentage agreements ranging from 75% to 88.8% for intrarater and 66.6% to 88.8% for interrater reliability. No significant sex differences were observed for overall scores, with mean values of 4.2 and 3.8 for men and women, respectively (P = .27). Conclusion: The S-MAS is a new tool developed for assessing sprint running mechanics associated with lower limb injuries in male and female soccer players. The reliable and easy-to-use nature of the S-MAS means that this method can be integrated into practice, potentially aiding future injury screening and research looking to identify athletes who may demonstrate mechanical patterns potentially associated with hamstring strain injuries.

Mzansi Magic

Mzansi Magic

Evidence of validity and reliability of Jumpo 2 and MyJump 2 for estimating vertical jump variables.

We investigated the concurrent validity and test-retest reliability of the Jumpo 2 and MyJump 2 apps for estimating jump height, and the mean values of force, velocity, and power produced during countermovement (CMJ) and squat jumps (SJ). Physically active university aged men (n=10, 20±3 years, 176±6 cm, 68±9 kg) jumped on a force plate (i.e., criterion) while being recorded by a smartphone slow-motion camera. The videos were analyzed using Jumpo 2 and MyJump 2 using a Samsung Galaxy S7 powered by the Android system. Validity and reliability were determined by regression analysis, typical error of estimates and measurements, and intraclass correlation coefficients. Both apps provided a reliable estimate of jump height and the mean values of force, velocity, and power. Furthermore, estimates of jump height for CMJ and SJ and the mean force of the CMJ were valid. However, the apps presented impractical or poor validity correlations for velocity and power. Compared with criterion, the apps underestimated the velocity of the CMJ. Therefore, Jumpo 2 and MyJump 2 both provide a valid measure of jump height, but the remaining variables provided by these apps must be viewed with caution since the validity of force depends on jump type, while velocity (and as consequence power) could not be well estimated from the apps.

Fatigue crack growth rate of AISI 4140 low alloy steel treated via shot peening and plasma nitriding

In this study, the effects of conventional shot peening (CSP), severe shot peening (SSP), and plasma nitriding (PN) on the fatigue crack growth (FCGR) of AISI 4140 low alloy steel were investigated. FCGR tests were performed on axial fatigue equipment, associated with slow-motion camera and COD gauge. As a result of the experiments, an improvement of 8% in CSP, 15% in SSP, and 5,5% in the PN operations were observed on the number of cycles of all specimens at 30 mm crack length. Particularly for SSP treatments, hardness, compressive stresses, and the creation of nano-crystallization on the surface provide the most effective improvement in FCGR behavior. Additionally, for PN, formation of nitrogen diffusion and effective hardness improvement showed positive results in FCGR behavior. CSP and SSP (particularly SSP) behaved dominant on the improvement of FCGR performance compared to PN treatment. The formation of two-phase brittle structural white layer on the surface prevented the effective FCGR improvement.

Rancang Bangun Smoke Generator pada Kecepatan Angin Rendah dengan Wind Tunnel Rangkaian Terbuka

Flow Visualization is the process of making the physical flow of a fluid visible. The air fluid used is transparent, so the flow pattern must be shown by several special methods. There are three methods for visualizing flow: surface flow visualization, particle tracking method, and optical method. Turbulence is one of the most important subjects related to testing the test section in a wind tunnel, at different wind speeds turbulence levels and other flow quality parameters must be kept as close as possible to free flow conditions. The flow visualization test is carried out using a slow motion camera at speeds of 1 m/s, 2 m/s, 3 m/s, 4 m/s and 5m/s which will form a fluid flow in the form of lines of smoke coming out of the nozzle holes inside. Test section. From the research results, the authors can conclude that the flow obtained forms a laminar flow and good suction power from various wind speed variables.

Preliminary investigation of flapping paper inside a file

The present paper is about the flapping mechanism of a paper locked inside a file. The investigation consists of visualization of flapping phenomenon and acoustic measurements resulting from the flapping. The normal ceiling fan is used as a source for the flow. The axial flow is converted to wall jet flow by using a surface perpendicular to the axis of the fan. The file placed with an offset from the fan which produces instabilities and in turn triggers the flapping mechanism. A super slow-motion camera is used to record the phenomenon and a microphone is used for acoustic measurements. The time-series results reveal the intermittent nature of the flow. The acoustic measurements reveal the noise sources and their frequencies via Fast Fourier Transformation.

Design and Testing of a Helix Antenna Deployment System for a 1U CubeSat

CubeSats have revolutionized Earth Observation and space science, although their small size severely restricts satellite performance and payload. Antenna deployment from a stowed configuration in these small-satellites remains a great challenge. This paper presents the design, optimization, and testing of an L-band helix antenna deployment system for the 3Cat-4, a 1U CubeSat developed at the NanoSat Lab (UPC). The 506-mm-long antenna is packed into a 26.8 mm gap together with a tip mass that provides a gravity gradient for nadir-pointing. The 3Cat-4 Nadir Antenna Deployment Subsystem (NADS) melts dyneema strings to release the antenna in successive steps. PTFE coated fiberglass ensures the helix’s nominal diameter and pitch while a security locking mechanism serves as a redundant system for holding it in place before deploying. Our novel methodology optimizes the number and length of the NADS deployment steps. A slow-motion camera and image recognition software track the velocity and acceleration of the antenna sections by means of tracking dots. Kinematic analysis of the antenna resulted in a final design of four length steps: 90, 300, 420 and 506 mm. Our methodology for calculating these values can be widely applied for measuring many deployment system’s kinematic properties. The NADS performance is tested by characterizing antenna rigidity, analyzing helix behavior after one year in stowed configuration, and by testing the deployment mechanism in a thermal vacuum chamber at −35°C, the most critical temperature stress scenario. All test results are satisfactory. The final design of the NADS deployment mechanism is light, stable, reliable, affordable, highly scalable, and can be used in many antenna configurations and geometries. The 3Cat-4 mission was selected by the ESA Academy to be launched in Q4 2021.

Video analysis of response of reinforced concrete beam to impact loading during drop test

A response of concrete and reinforced concrete structures to very rapid dynamic loading shows an increase of both tensile and compressive strength. This behaviour is also accompanied by an increase of stiffness of the structure. Described response can be numerically simulated only with adequate viscous nonlinear material model of concrete. The problem of these simulations is based not only on a necessity of a derivation of the right material model but also on viscous parameters whose values are not known in advance. The proposed article deals with experimental research of the response of the reinforced concrete beam exposed to impact loading during drop test. The beam response was measured with conventional strain gauges and accelerometers and whole experiment was recorded with 1000 frames per second by slow motion camera. Measured values of vertical acceleration were then compared with results of software analysis of slow-motion video footage. The paper contains the description of the experimental research, the comparison of conventional measurements with video analysis and the simulated response of the specimen in the software based on the finite element method using the viscous material model of concrete.

Scalable visible light communications with a micro-LED array projector and high-speed smartphone camera.

Solid-state camera systems are now widely available in portable consumer electronics, providing potential receivers for visible light communications in every device. Typically, data rates with camera receivers are limited by the 60 fps frame rate of both the image sensor and projector systems. Recent developments in high-frame rate microdisplays and slow-motion cameras for smartphones now permit high-speed, spatially structured signals to be transmitted and captured. Here, we present a method for transmitting data to a smartphone using a CMOS-controlled micro-LED projector system. Spatial patterns are projected onto a wall at a refresh rate of 480 Hz, which can be captured by the smartphone's 960 fps camera. Data transfer is performed over meter scale distances, and the use of an alignment frame gives the system a level of tolerance to motion and misalignment. The current system allows data transmission at a peak rate of 122.88 kb/s using a 16 × 16 micro-LED array, which can be readily scaled to Mb/s rates with a higher resolution transmitter.

Determination of time dependent stress distribution on a potato tuber during drop case

AbstractRealistic representation of time‐dependent internal stress progression and deformation behavior of a potato tuber during a sample drop case has been studied in this article. A reverse engineering approach, compressive tests, slow motion camera records and finite element analysis (FEA) were employed to analyze the drop case deformation behavior of a sample potato tuber. Simulation results provided useful numerical data and stress distribution visuals. The numerical results are presented in a format that can be used for the determination of bruise susceptibility magnitude on solid‐like agricultural products during drop case. The visual observations revealed that slow motion camera images and simulation printouts were in good correlation. The modulus of elasticity of the potato specimens was calculated from experimental data to be 3.12 MPa and simulation results showed that the maximum equivalent stress was 0.526 MPa on the tuber. This value for stress indicates that bruising is not likely on the tuber under a pre‐defined drop height. In order to test the simulation accuracy, empirical, and simulation‐based estimates for total energy in this drop case were compared. The relative difference between empirical and simulation results was 1.27%. This study provide a good “how to do” guide to further research on the utilization of (FEM)‐based time‐dependent simulation approach in complex mechanical impact based damaging analyses and industry focused applications related to solid‐like agricultural products such as potato.Practical applicationsThe engineering simulation based “how to do” pathway presented in this study is a scientific novelty because the explicit dynamics simulation technique for potato tuber damage under drop case and its visual verification has been limitedly introduced in the literature. This study present deeper analysis on material model description, slow motion camera records, time dependent non‐linear stress analysis and FEM based Explicit Dynamics Simulation procedures. This study aims to represent a realistic non‐linear deformation case of the tuber which is very complicated to obtain through physical and/or empirical expressions. As a further step from other literature studies, this research has presented a novel realistic time‐dependent non‐linear drop test simulation based on physical compressive material test data. The findings have been prepared in a form which may be used as input parameters in design studies for solid‐like agricultural products (such as potato tubers) processing machinery systems used in food/agricultural industries.

Enhancing physics demos using iPhone slow motion

Slow motion video enhances our ability to perceive and experience the physical world. This can help students and teachers especially in cases of fast moving objects or detailed events that happen too quickly for the eye to follow. As often as possible, demonstrations should be performed by the students themselves and luckily many of them will already have this technology in their pockets. The “S” series of iPhone has the slow motion video feature standard, which also includes simultaneous sound recording (somewhat unusual among slow motion cameras). In this article I share some of my experiences using this feature and provide advice on how to successfully use this technology in the classroom.

CSM 2017 Sports Physical Therapy Section Poster Presentations (Abstracts SPO1–SPO152)

CSM 2017 Sports Physical Therapy Section Poster Presentations (Abstracts SPO1–SPO152)

Influence of different movement kinematics on cyclic fatigue resistance of nickel-titanium instruments designed for retreatment

Aim: The objective of this study was to investigate the effect of different types of movement kinematics on the resistance of the ProTaper D3 retreatment file to cyclic fatigue. Materials and Methods: Eighty ProTaper Universal D3 (20.07) files were utilized in this study. The cyclic fatigue tests were performed using a specially manufactured dynamic cyclic fatigue testing device, which has an artificial stainless steel canal having 60° of curvature angle and 5 mm of curvature radius. The files were randomly divided into four groups (Group 1: Rotary motion [RM]; Group 2: Adaptive motion [AM]; Group 3: Reciprocating motion [RCM]; Group 4: WaveOne motion [WM]). The movements of files until the files broke were recorded in “MOV” format using a device employing a slow-motion camera. The number of cycles to failure was calculated for each group. The data were analyzed statistically using one-way ANOVA and Tukey's honestly significant difference test (P Results: The cyclic fatigue resistance of the AM group (3357.9 ± 88.5) was significantly higher than that of the other groups (P Conclusion: Within the limitations of the present study, resistance of ProTaper Universal D3 file to the cyclic fatigue significantly increased in the AM group when compared to the RCM and WM groups.

Stone Retropulsion with Ho: YAG and Tm: YAG Lasers: A Clinical Practice-Oriented Experimental Study.

To compare the retropulsion of stones with the use of holmium: yttrium aluminum garnet (Ho: YAG) laser and thulium: yttrium aluminum garnet (Tm: YAG) laser in settings that could be used in clinical practice. The experimental configuration included a glass tube set in a water bath filled with physiologic saline. Plaster of Paris stones were inserted in the tube. Tm: YAG and Ho: YAG laser systems were used along with a high-speed slow-motion camera. The lasers were activated with different settings. The displacement of the stone was measured according to a custom-made algorithm. Ho: YAG: the retropulsion of stones was the lowest with the energy setting of 0.5 J and the frequency of 20 Hz with long pulse duration. The highest retropulsion was observed in the case of 3 J, 5 Hz, and short pulse. Tm: YAG: the retropulsion of stones was the lowest with the energy setting of 1 J and the frequency of 10 Hz with either long or short pulse duration. Practically, there was no retropulsion at all. The highest retropulsion was observed in the case of 8 J, 5 Hz, and short pulse. Ho: YAG laser has a linear increase in stone retropulsion with increased pulse energy. On the other hand, the retropulsion rate was kept to the minimum with Tm: YAG as much as the energy level of 8 J. The activation of lasers with short pulse resulted in further displacement of the stone. Lower frequency with the same power setting seemed to result in further stone retropulsion. Higher power with the same frequency setting resulted in further displacement of the stone.

Factors Influencing Performance of a Model Steam Engine (Putt-Putt Boat)

In this paper, thermal oscillatory approach is used to investigate the undocumented factors that influence performance of a putt-putt boat. The engine was designed and fabricated with all the required components including the boat according to the calculations. Setting up a test rig, the engine was tested against thrust and readings were noted down at regular intervals from the first propulsion. Fluctuations of frequencies for different factors are also recorded using a slow-motion camera. Factors such as the tube number, length, diameter, power, etc. were tested and compared to a standard test and were repeated where necessary in order to achieve maximum accuracy. The results of this research are com-pared to the varying factors tested in this experiment, and are not compared to any external research due to varying designs of engine.

Carmilla, Camilla: The Influence of the Gothic on David Lynch's Mulholland Drive.

Carmilla, Camilla: The Influence of the Gothic on David Lynch's Mulholland Drive.

Analysis of the detachment of citrus fruits by vibration using artificial vision

The vibratory behaviour of citrus fruits is studied using slow-motion cameras in order to gain a better understanding of the parameters involved in fruit detachment when mechanical harvesting is done using shakers. Single citrus fruits with a small portion of stem were vibrated using strokes from 60 mm to 180 mm and frequencies from 3 Hz to 18 Hz. The movement was recorded at 300 fps and the main parameters considered for fruit detachment were determined through the analysis of the video sequences. Image-processing algorithms created for this purpose were applied to the automated estimation of the centroid of the fruit, the angle of the stem–pistil axis, and the position of some selected points in the fruit in each frame of the video sequences to obtain dynamic parameters such as the position, speed and acceleration of the fruit during the movement until it is detached. The signals obtained from the image processing were filtered, providing results in accordance with the calibration systems. In general, results suggest that the inertial forces transmitted to the fruit were lower than the tensile forces required to detach the fruit by pulling it in the stem–pistil direction. The largest peaks were observed using long strokes that required fewer cycles for detachment. On the other hand, short strokes combined with high frequencies needed more cycles, and thus a fatigue phenomenon was present. Short strokes and low frequencies were unable to detach some fruit.

Non-invasive damage detection in beams using marker extraction and wavelets

For structural health monitoring applications there is a need for simple and contact-less methods of Non-Destructive Evaluation (NDE). A number of damage detection techniques have been developed, such as frequency shift, generalised fractal dimension and wavelet transforms with the aim to identify, locate and determine the severity of damage in a material or structure. These techniques are often tailored for factors such as (i) type of material, (ii) damage pattern (crack, delamination), and (iii) the nature of any input signals (space and time). This paper describes and evaluates a wavelet-based damage detection framework that locates damage on cantilevered beams via NDE using computer vision technologies. The novelty of the approach is the use of computer vision algorithms for the contact-less acquisition of modal shapes. Using the proposed method, the modal shapes of cantilever beams are reconstructed by extracting markers using sub-pixel Hough Transforms from images captured using conventional slow motion cameras. The extracted modal shapes are then used as an input for wavelet transform damage detection, exploiting both discrete and continuous variants. The experimental results are verified and compared against finite element analysis. The methodology enables a non-invasive damage detection system that avoids the need for expensive equipment or the attachment of sensors to the structure. Two types of damage are investigated in our experiments: (i) defects induced by removing material to reduce the stiffness of a steel beam and (ii) delaminations in a (0/90/0/90/0)s composite laminate. Results show successful detection of notch depths of 5%, 28% and 50% for the steel beam and of 30mm delaminations in central and outer layers for the composite laminate.

Influence of the opposition in throwing accuracy in elite and amateur handball players

The success of goal shooting in handball depends mostly on accuracy and throwing velocity. Several researchers have investigated the relationship between ball velocity and accuracy, but few investigations have included opposition, and there is no evidence on how opposition affects throwing accuracy. The present study analysed differences in throwing accuracy according to the opposition in handball players. Forty-three elite (E) and amateur (A) handball players (24±3 years; 187±3 cm; 91.8±9.1 kg) were assessed in two throwing tests: without (T1) and with opposition (T2). The instructions were: throw the ball at the highest possible speed, using the technique appropriate in handball, with three steps before throwing, from behind the free-throw line, at 9 m from the goal. The players were instructed to make precise shots following the goalkeeper intervention difficulty criterion1 2: throws had to target the corner of the goal. The goalkeeper (T2) was situated on the goal line. An observer assessed the impact location of the ball in the goal or goalkeeper using a slow motion camera. Each release was scored according to its precision: 0 (minimum) to 5 (maximum accuracy). E players (T1=4.46±0.66, T2=4.31±0.75) achieved better precision values than As (T1=3.63±1.09, T2=3.37±1.18) in T1 (p=0.016, t=2.519, df=41) and T2 (p<0.01, t=2.809, df=41). The analysis of mean differences showed that accuracy was lower with than without opposition (T1-T2=0.651±0.376; p<0.01; t=3.267; gl=42). The greatest difference between T1 and T2 was found in the A group (T1-T2=0.867±1.5, p<0.01, t=3.159, df=29) while in the E group there was no significant effect (T1-T2=0.154, p=0.165; t=1.477, df=12). The competitive level determines throwing accuracy, with and without opposition. The opposition has a negative effect on throwing accuracy, especially in A players.

PREY CAPTURE FLIGHT OF CALOPTERYX HAEMORRHOIDALIS (VANDER LINDEN) (ZYGOPTERA: CALOPTERYGIDAE)

This paper is dedicated to Philip S. Corbet on the occasion of his 70th birthday. Abstract Calopteryx haemorrhoidalis females (mainly) and males were filmed with a slow-motion camera to analyse, frame by frame, manoeuvres during prey capture flight. Acceleration immediately after take-off was very high, although no high maximum speed resulted. The legs did not assist acceleration but at take-off were already spread in a capture position and remained so until landing. Most successful approaches were frontal but prey often escaped by rapid flight. Approach flights were short and often several odonates pursued the same prey individual. The kinematics of prey capture flight are discussed in relation to calopterygid evolution.