Landing Phase Research Articles

Dynamic simulation model for three-wheel air-cycle refrigeration systems in civil aircrafts

Dynamic simulation model of air-cycle refrigeration systems in civil aircrafts is essential for revealing the operation mechanism during flight process. In the present study, a dynamic model of three-wheel air-cycle refrigeration system was developed. A near-logarithm heat transfer temperature difference function is utilized to improve the stability of the heat transfer solution. A dynamic solution method based on continuity equation and theorem of momentum was presented as the framework of the dynamic mass transfer solution. A pressure-flow decoupling method is presented to solve the dynamic pressure in the high-pressure zone, resolving the absence of key pressure parameters. The model has been validated based on experimental data, with a pack discharge temperature deviation of 0.05K. Dynamic simulations have been conducted with actual flight data to obtain transient performance under airborne condition. In the takeoff and landing phase, the drastic change in the environment results in low discharge temperature, endangering the condenser with icing risk, which can be avoided by enabling the TCV. In the cruise phase, the discharge temperature slightly exceeds the upper limit for a couple of minutes. The optimization by slightly extending the length of heat exchanger channels succeeded in eliminating the excessive discharge temperature with minimal side effects.

Kinematic Differences Between Landing Phase During Double And Single Leg Jumping Tasks

Anterior cruciate ligament (ACL) injury risk is often examined using the initial landing/takeoff phase following a drop off a box during a drop vertical jump (DVJ) task, while the second landing after maximum jump is not typically examined. As ACL injuries are frequently sustained during similar rapid deceleration maneuvers, the second landing during a DVJ and a single leg countermovement (SLC) jump may better simulate injury risk mechanics. PURPOSE: To investigate differences between landing phases during double and single leg jumping tasks. METHODS: 15 collegiate basketball players (height: 180.8 ± 14.0 cm, mass: 80.8 ± 19.0 kg) completed 3 DVJ and 3 maximum SLC jumps on each limb. Takeoff phase (TO) was defined as the first jump/landing and the landing phase (LN) was defined as the second landing for each task. High performance (HP) side was determined as the limb with the highest SLC jump compared to the low performance (LP) side. Standard 3D motion analysis was used to determine joint kinematics at peak knee flexion during each phase. A two-factor repeated measures ANOVA (p < 0.05) was used to determine differences between phase (TO, LN) and side (HP, LP). RESULTS: A main effect of phase during the DVJ was found for knee flexion (p < 0.001, TO: -83.1 ± 10.6°, LN: -68.6 ± 10.8°), knee abduction (p = 0.004, TO: -7.4 ± 5.2°, LN: -4.7 ± 4.9°), and hip flexion (p < 0.001, TO: 60.5 ± 11.7°, LN: 37.3 ± 13.1°) with a significant interaction between phase and side for hip adduction (p = 0.015). During the SLC jump, a main effect of phase was found for knee (p = 0.002, TO: -66.2 ± 8.7°, LN: -58.3 ± 10.8°) and hip (p = 0.005, TO: 48.7 ± 15.1°, LN: 35.4 ± 10.0°) flexion. A main effect of side was found for hip adduction (p = 0.029, HP: 5.3 ± 6.5°, LP: 8.4 ± 6.7°). No significant main effects were present for knee abduction during the SLC (p > 0.05). CONCLUSIONS: Collegiate basketball players exhibit greater knee and hip flexion and knee abduction during the initial land of the DVJ compared to the landing following maximum jump. Similarly, players also exhibit greater knee and hip flexion during the takeoff phase of a single leg task compared to the landing. However, they exhibit lower hip adduction on their higher performing limb. Between phase differences of each task outline the importance of identifying high-risk mechanics during both takeoff and landing.

Comparison Of Lower Extremity Joint Coordination Between Limbs In Individuals With ACL Reconstruction During Landing

Individuals with anterior cruciate ligament reconstruction (ACLR) display smaller dorsiflexion angles (DFA) and knee flexion angles (KFA) during the landing and propulsive phases of jumping in their injured compared with their uninjured limb. Kinematic differences may be due to different sagittal plane ankle and knee joint coordination strategies that influence force attenuation and propulsion. PURPOSE: To compare peak DFA and KFA during landing and coordination pattern frequencies during the landing and propulsion phases of a drop vertical jump between the injured and uninjured limb of individuals with ACLR. METHODS: 15 females and 14 males with unilateral ACLR performed a drop vertical jump from a 30 cm box. Peak DFA and KFA were compared using paired t-tests. A modified vector coding technique and binning analysis were used to compare coordination patterns between sagittal plane DFA and KFA using Wilcoxon signed rank tests. RESULTS: The peak DFA was lower in the injured (121.07 ± 5.27°) compared with the uninjured (123.44 ± 4.70°) limb (Mean Difference: -2.37 [95%CI: -3.81, -.94], p = .002). The peak KFA was not different between the injured (-102.69 ± 14.78°) and uninjured (-103.77 ± 13.59°) limbs (Mean Difference: 1.08 [95%CI: -.66, 2.81], p = .215). The injured limb had more anti-phase (Z = -2.30, p = .022) and less exclusive knee flexion (KF) (Z = -2.11, p = .035) motion during landing than the uninjured limb. In-phase (Z = -.42, p = .676) and exclusive dorsiflexion (DF) (Z = -1.42, p = .157) motion were not different between the injured and uninjured limbs during landing. Anti-phase (Z = -1.32, p = .188), in-phase (z = -.69, p = .49), exclusive knee extension (Z = -1.85, p = .064), and exclusive plantarflexion (Z = -1.95, p = .052) motion were not different between limbs during propulsion. CONCLUSIONS: The injured limb had a smaller peak DFA, more simultaneous DF and KF, and less exclusive KF compared with the uninjured limb during landing. Individuals with ACLR may restrict peak DF in their injured limb during landing to limit isolated knee flexion as a protective mechanism to prevent anterior knee motion. More simultaneous DF and KF may be utilized to reduce the amount of force attenuation required from isolated KF. However, utilizing such a strategy for force attenuation may be perilous since the injured limb lands with less peak DF.

Asymmetry In Single Leg Vertical Countermovement Hop Kinematics In Collegiate Female Soccer Players

Multidirectional sports such as soccer have a high incidence rate of anterior cruciate ligament injury. Asymmetries between limb have been linked to such non-contact injuries, thereby outlining the importance of screening measures that may identify at-risk groups. Specifically, tasks such as a vertical single leg countermovement (SLC) jump can provide an objective measure of frontal and sagittal plane asymmetries. PURPOSE: To identify lower limb asymmetries during a SLC jump. METHODS: 25 collegiate female soccer players (height: 167.4 ± 6.0 cm, mass: 67.16 ± 6.6 kg) completed 3 maximum SLC jumps on each limb. The side with the highest average jump height was defined as the high performance (HP) side and compared to the low performance side (LP). An 8 camera markerless motion capture system was utilized to analyze kinematic data at peak knee flexion during both the takeoff (TO) and landing (LN) phase using advanced machine learning. Force platforms measured the peak takeoff and landing vertical ground reaction force (GRF). A two-factor repeated measures ANOVA (p < 0.05) was used to determine differences between side (HP, LP) and phase (TO, LN) during the SLC task. RESULTS: 52% of the players had greater jump performance on their preferred kicking side. A main effect of side (p = 0.035) and phase (p < 0.001) was found for knee flexion (HP: TO 67.2 ± 7.2°, LN 60.5 ± 10.8°; LP: TO 65.0 ± 6.5°, LN 58.8 ± 7.2°). Likewise, a main effect of side (p < 0.001) and phase (p < 0.001) was found for GRF (HP: TO 1373 ± 236 N, LN 2238 ± 435 N; LP: TO 1341 ± 224 N, LN 2088 ± 280 N). A phase main effect was found for both hip flexion (p = 0.002) (HP: TO 49.8 ± 10.9°, LN 42.5 ± 11.9°; LP: TO 50.8 ± 10.1°, LN 41.0 ± 12.8°) and adduction (p = <0.001) (HP: TO 8.1 ± 4.4°, LN 5.5 ± 4.9°; LP: TO 8.7 ± 3.8°, LN 5.1 ± 5.7°). Significant main effects were not present for knee abduction (p > 0.05). CONCLUSIONS: Collegiate female soccer players demonstrate greater knee and hip flexion and hip adduction occur during the take-off phase of the single leg vertical jump compared to the landing phase. Additionally, the leg with greater performance has increased knee flexion during both take-off and landing which corresponds to greater peak force. These identified asymmetries between phase and limb could be considered important factors in monitoring potentially at-risk populations.

Impact Of Limb And Total Body Composition On Drop Vertical Jump Landing Kinematics

Lower limbs containing elevated levels of adipose tissue exhibit diminished quadricep strength and power. Deficits in quadriceps function negatively influence sagittal knee mechanics during drop vertical jumping (DVJ) maneuvers. It is poorly understood how measures of limb and systemic composition impact landing performance and injury risk. PURPOSE: Determine the relationship between composition and sagittal knee kinematics during landing from a DVJ. METHODS: Thirty-six female (171.0 ± 7.6 cm; 66.5 ± 7.6 kg; 22.7 ± 1.8BMI) collegiate volleyball and soccer athletes participated in this study. Biomechanical variables of interest include sagittal knee angle (KA) obtained at two different points during landing using 3-dimensional marker-less motion capture during DVJ maneuvers. These two points were initial contact (IC) and the ending of the landing phase, defined where the center of gravity was at its lowest point (MIN). Higher negative sagittal angle values are indicative of greater knee flexion. Dual x-ray absorptiometry (DXA) was used to compute total body fat percentage (BF%) and bilateral limb lean mass (LLM). LLM was normalized to the total mass of the limb. Associations between landing biomechanics and compositional measures were analyzed via Pearson Product Moment correlations. RESULTS: KA at MIN in the left (-92.8 ± 8.9°) and right leg (-92.4 ± 9.5°) were associated with BF% (27.5 ± 4.3%) (Right: r = 0.430, p = 0.009; Left: r = 0.432, p = 0.008) and LLM (Right: 64.3 ± 4.3% limb mass; Left: 64.0 ± 4.6% limb mass) (Right: r = -0.416, p = 0.012; Left: r = -0.410, p = 0.013). At IC, right leg (-23.7 ± 8.4°) KA had a weak relationship to BF% (r = 0.390, p = 0.019) and LLM (r = -0.364, p = 0.029). Relationships between KA at IC in the left leg (-26.5 ± 8.3°) and BF% (r = 0.289, p = 0.088) and LLM (r = -0.311, p = 0.065) were not significant. CONCLUSIONS: The relationship between BF% and LLM and sagittal KA during DVJ landing indicate that greater LLM and lower BF% may be better for injury risk and performance. Lesser knee flexion range of motion during landing may be caused by inhibited capacity to attenuate landing forces during sport performance. Greater adipose tissue within the limb and systemically may negatively influence injury risk by reducing the ability to adequately absorb forces when landing during an athletic task.

Hydrodynamic analysis of the water landing phase of aircraft fuselages at constant speed and fixed attitude

In this paper the hydrodynamics of fuselage models representing the main body of three different types of aircraft, moving in water at constant speed and fixed attitude is investigated using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) level-set flow solver χnavis. The objective of the CFD study is to give insight into the water landing phase of the aircraft emergency ditching. The pressure variations over the wetted surface and the features of the free surface are analysed in detail, showing a marked difference among the three shapes in terms of the configuration of the thin spray generated at the front. Such a difference is a consequence of the different transverse curvature of the fuselage bodies. Furthermore, it is observed that at the rear, where a change of longitudinal curvature occurs, a region of negative pressure (i.e. below the atmospheric value) develops. This generates a suction (downward) force of pure hydrodynamic origin. In order to better understand the role played by the longitudinal curvature change on the loads, a fourth fuselage shape truncated at the rear is also considered in the study. The forces acting on the fuselage models are considered as composed of three terms: the viscous, the hydrodynamic and the buoyancy contributions. For validation purposes the forces derived from the numerical simulations are compared with experimental data.

An Analysis on Serious Incidents and Accidents in Aviation Using Shell Model

A thorough investigation must be conducted in every aviation incident or accident to find the root cause so that recommendations can be drawn to prevent the same incident or accident from occurring again. This research is a descriptive analysis with quantitative methods. Data were collected from the final reports released by the KNKT from 2015 until 2019. The main causes were grouped using the SHELL Model analysis. The results showed that the most prevalent cause of aviation incidents/accidents in Indonesia was the mismatch between liveware-liveware of which the percentage reached 64%. Furthermore, this mismatch was caused by lack of supervision from management as many as 17 events or 74%; 5 events or 22% were caused by unavailability of rules; and lack of coordination with as many as 1 event or 4%. Within 17 events caused by lack of supervision from management, there were 3 phases of which the events occurred namely the landing phase comprising 59% or 10 events, the cruising phase comprising 18% or 3 events, and the approaching phase consisting of 24% or 4 events. Accidents and serious incidents may occur if latent causes such as lack of supervision from management, unavailability of rules and lack of coordination are not mitigated.

Numerical Simulation of Ground Effect on Circulation Control Airfoil

Circulation control (CC) is used extensively to control the attitude of rudderless aircraft experiencing ground effect in take-off and landing phases. The investigation of ground effect on airfoil CC is necessary to improve flight performance and quality in proximity to the ground. The aerodynamics and flow field of a modified NACA0012 airfoil with CC in ground effect are investigated with numerical simulations. The compressible Reynolds-averaged Navier–Stokes equations with the shear-stress transport k − ω turbulence model equations are solved using the Finite Volume Method (FVM). Simulation results show that the ground effect changes the lift increment per unit jet momentum coefficient, and CC can reverse the polarity ground effect. The effective angle of attack α E and the downwash space downstream airfoil are altered by the ground effect resulting in variations of airfoil surface pressure and lift. Unlike the unbounded flow field, the jet attachment distance is not only determined by the jet momentum coefficient but it can change with the ride height, which is the distance from the ground to the center of the semicircular Coanda surface, for the same jet momentum coefficient.

Persistent Charging System for Crazyflie Platform

Nowadays, quadcopters are used widely in different applications, but their flight time is limited during operation. In this paper, a precision landing method based on a Kalman filter is proposed for an autonomous indoor persistent drone system that aims to increase the flight time of quadcopters. First, a local positioning system is used for tracking performance. Second, instead of using this local positioning system during the landing phase, a multi-ranger sensor is proposed to increase the accuracy of horizontal errors. Next, based on the relative position provided by the multi-ranger sensor, a Kalman filter technique is applied to estimate the relative velocity of the system, which is then applied to control the position of the quadcopter during the landing phase. Finally, a charging state machine law is proposed to charge the battery of three quadcopters sequentially. The experimental results demonstrate that the proposed concept based on a multi-ranger sensor can enhance the accuracy of the landing phase in comparison with the conventional method.

Sensing Requirements and Vision-Aided Navigation Algorithms for Vertical Landing in Good and Low Visibility UAM Scenarios

To support the rapid development of the Urban Air Mobility framework, safe navigation must be ensured to Vertical Take-Off and Landing aircraft, especially in the approach and landing phases. Visual sensors have the potential of providing accurate measurements with reduced budgets, although integrity issues, as well as performance degradation in low visibility and highly dynamic environments, may pose challenges. In this context, this paper focuses on autonomous navigation during vertical approach and landing procedures and provides three main contributions. First, visual sensing requirements relevant to Urban Air Mobility scenarios are defined considering realistic landing trajectories, landing pad dimensions, and wind effects. Second, a multi-sensor-based navigation architecture based on an Extended Kalman Filter is presented which integrates visual estimates with inertial and GNSS measurements and includes different operating modes and ad hoc integrity checks. The presented processing pipeline is built to provide the required navigation performance in different conditions including day/night flight, atmospheric disturbances, low visibility, and can support the autonomous initialization of a missed approach procedure. Third, performance assessment of the proposed architecture is conducted within a highly realistic simulation environment which reproduces real world scenarios and includes variable weather and illumination conditions. Results show that the proposed architecture is robust with respect to dynamic and environmental challenges, providing cm-level positioning uncertainty in the final landing phase. Furthermore, autonomous initialization of a Missed Approach Procedure is demonstrated in case of loss of visual contact with the landing pad and consequent increase of the self-estimated navigation uncertainty.

Robust control of aircraft flight in conditions of disturbances

One of the most dangerous parts of the flight is the landing phase, as most accidents occur at this stage. In order to reduce the effect of the low-level wind shear on the longitudinal motion of the aircraft in the glide path landing mode (task) a robust H- control is proposed. Dynamic models of the plane and wind shear are built. H&lt;sub&gt;2&lt;/sub&gt; and H&lt;sub&gt;∞&lt;/sub&gt; synthesis methods are investigated for the task of aircraft flight control in a vertical plane during landing under conditions of undefined disturbances. Both control methods allow to reduce height deviation significantly. However, suboptimal control H&lt;sub&gt;∞&lt;/sub&gt; provides better quality of transition processes both in height and speed than optimal control H&lt;sub&gt;2&lt;/sub&gt;. The results of simulation of the synthesized system confirm the effectiveness of H&lt;sub&gt;∞&lt;/sub&gt; - control for increasing robust stability to uncertainties caused by wind disturbances.

Peak Loads Associated With High-Impact Physical Activities in Children.

Examine the magnitude of peak ground reaction forces (pGRF) across different jumping activities in children. Eight children between 8 and 12 years (9.63 [1.49]y; 1.42 [0.08]m; 33.69 [4.81]kg), performed 5 trials of a broad jump, countermovement jump, jumping jack, leap jump, and drop jump on a force plate. The pGRF were determined during the landing phase of each activity and expressed in units of body weight (BW). A repeated-measures analysis of variance was employed to assess differences in pGRF across activities. Drop jump exhibited the greatest pGRF (3.09 [0.46]BW) in comparison with the vertical jumping jack (2.56 [0.21]BW; P < .001) and countermovement jump (2.45 [0.22]BW; P = .001), as well as the horizontal broad jump (2.25 [0.2]BW; P = .003), and leap jump (2.01 [0.1]BW; P = .002). Peak loads between 2 and 3.1BW were exhibited across each jump activity, which is moderate compared with magnitudes in most jump interventions seeking to improve bone health. All conditions except drop jump exhibited loading <3BW, suggesting these activities may not produce sufficient loads to improve bone outcomes.

On springtails (Hexapoda: Collembola): a morphofunctional study of the jumping apparatus

BackgroundSpringtails (Hexapoda: Collembola) are tiny organisms that lead a hidden life, mostly occuring deep in the soil and on leaf litter. They have a variety of interesting body morphology patterns, the most famous of which is the catapult-like structure that enables them to jump and flee from predators. This highly specialized jumping apparatus consists of a mobile furca, which when at rest fits into a trigger, "the retinaculum" on the ventral side of the abdomen. Despite the many studies that have attempted to investigate the jumping apparatus, the actual mechanisms involved in the jump, for example the way in which the furca is released by the retinaculum, how and where the mechanisms of spring and hydrostatic pressure originate, are still not properly understood. The morphology of the jumping apparatus of Orchesella cincta was investigated in detail using confocal laser scanning microscopy and MicroCT techniques for 3D reconstruction.ResultsThe morphology of O. cincta with both flexed and extended furca is analysed and described. The abdominal musculature involved in the jumping mechanism and relevant structures of the exoskeleton of retinaculum and furca are described in detail. With the data obtained in this study, hypotheses can be made about (1) where and how the spring and hydrostatic pressure mechanisms originate; (2) which muscles act on the extension and flexion of the furca; (3) which muscles act on the retinaculum and (4) how the retinaculum is released from the furca.ConclusionsThe comparative morphological study proved informative, and shows how springtail jumping involves mechanisms unique to this taxon. Hydrostatic pressure regulation possibly varies between animals with distinct segmentation, and those with fused segmentation. Interesting cuticular characters were revealed, such as basal plates and sclerites related to the construction of the spring mechanism. The present study establishes itself as a model option for future morphofunctional studies on springtail’s jumping. Analysis of videos and images using a high speed camera will be useful for understanding how the jump develops through take-off, aerial and landing phases.

Lower Limb Biomechanics during the Topspin Forehand in Table Tennis: A Systemic Review.

The aim of this study is to review the valuable lower limb biomechanical contribution to table tennis topspin forehand. Databases included Scopus, PubMed, and Web of science. In this case, 19 articles were selected for the systematic review. The mechanics of the plantar, lower limb joints kinematics and kinetics, muscle activity, and racket-joint relationship are described through gender, performance level, and footwork. The study found that the hip movement characteristics and the hip muscle group activity following a proximal-to-distal sequence strategy significantly contributed to the maximum acceleration of the racket. Optimizing the motion strategy of the ankle and plantar as well as the ankle muscle group activity is beneficial for the transmission of energy in the kinetic chain. Muscle groups around the ankle and subtalar joints are heavily activated during landing to maintain foot stability during the landing phase. Lower limb muscle development plays an important role in movement control and stability as well as sports injury prevention in table tennis footwork during the performance of the topspin forehand. Furthermore, physical development levels and anatomical differences (such as hip and lower trunk muscle strength differences), maybe the main reasons for gender differences observed during the topspin forehand. Systematically summarizing this valuable information can contribute to athletes’ and coaches’ knowledge to enhance topspin forehand performance and training regimes. We suggest that future research could consider the joint contact forces, ball movement, and ball-racket impact during a performance of topspin forehand.

Is there a correlation between isometric muscle strength and the kinematics of the pelvis, hip and knee during functional tasks in women with patellofemoral pain?

ObjectivesTo evaluate the correlation between isometric muscle strength of the hip abductors (HABD) and lateral rotators (HLR) with the range of motion (ROM) of the pelvis/hip in the frontal/transverse planes, respectively, and between the strength of the knee extensors (KExt) with the ROM of the knee in the sagittal plane during seven tasks. DesignCross-sectional study. SettingLaboratory. ParticipantsThirty-five women with patellofemoral pain. Main outcome measuresMaximum isometric muscle strength of the HABD, HLR, and KExt was measured using a manual dynamometer, and pelvis and lower limbs kinematics were evaluated using 3D optical system during gait, ascending and descending stairs, the forward and lateral step down tests, and the propulsion and landing phases of the single leg hop test (SLHT). ResultsA weak correlation was found between KExt strength and knee ROM in the sagittal plane (p = 0.05; r = −0.33) during SLHT landing, and a moderate correlation between HABD strength and ROM of pelvic obliquity (p < 0.01; r = 0.50) during ascending stairs. ConclusionsThe lower strength of KExt has a weak correlation with higher knee flexion during the landing phase of the SLHT, and the lower strength of HABD has a moderate correlation with lower pelvis ROM in the frontal plane when ascending stairs.

Push-Off Dynamics Reveal Task-Independent Alterations in Athletes Returning to Sport after ACL Reconstruction.

Athletes with an anterior cruciate ligament (ACL) reconstruction (ACLR) show persisting biomechanical and neuromuscular landing alterations. So far, most research focused on the landing phase of dynamic tasks where most ACL injuries occur. This study will assess whether these landing alterations are also present in the propulsion phase, in an attempt to identify generalized movement alterations. Twenty-one athletes with ACLR (cleared by their surgeon and/or physiotherapist for return-to-sport) and twenty-one controls performed five single-leg hop tasks. Propulsion kinematics, kinetics, and muscle activations were compared between legs and between groups. Increased hamstrings activation was found during propulsion when comparing the ACLR limb with both the uninjured limb and the controls. In addition, decreased internal knee extension moments were found in the ACLR limb compared with the uninjured limb. Athletes with ACLR show task-independent alterations that unload the knee during the propulsion phase of single-leg hopping tasks. If longitudinal data deem these alterations to be maladaptive, more emphasis must be placed on their normalization during the propulsion phase, assuming beneficial carryover effects into the landing phase. Normalizing these patterns during rehabilitation may potentially reduce the risk of long-term complications such as reinjuries and posttraumatic osteoarthritis.

Knee Movement Characteristics of Basketball Players in Landing Tasks Before Onset of Patellar Tendinopathy: A Prospective Study.

BackgroundPatellar tendinopathy is one of the most common injuries for basketball players. Jumping and landing movement patterns are potential risk factors for patellar tendinopathy.HypothesisMale college basketball players who developed patellar tendinopathy would demonstrate greater peak vertical ground reaction force and knee flexion angular velocity, and smaller knee flexion range of motion and knee flexion angles at initial contact compared to players who did not develop the injury when performing a stop-jump task within a year prior to the onset of the injury.Study DesignProspective study.MethodsFreshmen college basketball male players (n = 181) were recruited for three consecutive years and followed to the end of the third year of the study. Three-dimensional kinematic and kinetic data during a stop-jump task were collected for all participants at the beginning of each school year. Peak vertical ground reaction force, knee flexion angle at initial foot contact with the ground, range of motion for knee flexion and maximal knee flexion angular velocity during the landing phases of the stop-jump task were collected and calculated. Development of patellar tendinopathy was monitored in follow-up. Independent t-tests and Cohen's d effect sizes (ES) were used to compare movement patterns between injury and no injury groups for each school year.ResultsA total of 60 knees developed patellar tendinopathy. The injury groups had a significantly greater peak vertical ground reaction force in freshmen and junior years (P = 0.020, ES = 0.13; P = 0.046, ES = 0.17), smaller knee flexion ROM in freshmen year (P = 0.002, ES = 0.10), and greater maximum knee flexion angular velocity in freshmen and junior year (P = 0.012, ES = 0.10; P = 0.001, ES = 0.35) during the horizontal landing phase before the takeoff of the jump compared to the no injury groups. The injury groups also had a significantly smaller knee flexion angle at initial contact during vertical landing phase after the takeoff of the jump in freshmen and junior years (P = 0.001, ES = 0.36; P = 0.001; ES = 0.37) during vertical landing phase.ConclusionPeak vertical ground reaction force, knee flexion angle at initial foot contact, knee flexion range of motion, and maximum knee flexion angular velocity are associated with patellar tendinopathy among male college basketball players in different school years.

Integrated visual navigation based on angles-only measurements for asteroid final landing phase

Integrated visual navigation based on angles-only measurements for asteroid final landing phase

THE INFLUENCE OF STRENGTH ON THE GYMNASTS’ SUCCESS IN PERFORMING VAULT

The aim of the study was to determine the influence of absolute and relative strength of the muscles of the legs, upper arms and shoulder girdle on the success of performing vault with gymnasts aged 13 to 16 who have been training gymnastics from five to 12 years. The Japanese digital dynamometer IMADAZ2H-1100 with WinWedge 3.4 software was used to estimate the absolute strength of the leg, upper arm and shoulder girdle muscles. The values shown on the digital meter represented the absolute value of the maximum force, and when the absolute value of the force was divided by the weight of the participant, the value of the relative force was obtained. Regression analysis was used to determine the influence of absolute and relative strength of leg muscles, upper arm and shoulder girdle on the success of performing vault. The results showed that although there is an influence of the above muscles, it is not statistically significant. Specifically, for a successful performance on the vault, the muscles of the shoulder girdle have the greatest influence (without statistical significance). The reason for the results obtained in this way lies in the fact that the phase of flight and landing depends on the support phase and the repulsion from the vault. As there are few research studies on the subject of this paper, regardless of the obtained results, this research represents a good foundation and basis for some future research of absolute and relative strength in artistic gymnastics.

Analysis of pilots' EEG map in take-off and landing tasks.

The take-off and landing phases are considered the critical stages of aircraft flight. To ensure flight efficiency and safety in the critical stages, this research proposes a method for analyzing and monitoring pilot flight status by β-wave. The focus of the study is β potential changes on the EEG map. First, the proportion of β-wave in the electroencephalogram (EEG) of pilots during take-off and landing increases significantly. Second, the EEG map accurately and intuitively reflects the spatial distribution of potential changes in brain regions. Finally, correlation and machine learning are used for further research of β-wave. The conclusions show that the significant changes in the β-wave caused by take-off and landing can be seen in the EEG map to identify and adjust the pilot's state. Therefore, this research provides more accurate and effective reference information (like the EEG map, correlation and machine learning) for efficient and safe flight training in the critical stages.