Recoil Movements Research Articles

Identifying Gravity-Related Artifacts on Ballistocardiography Signals by Comparing Weightlessness and Normal Gravity Recordings (ARTIFACTS): Protocol for an Observational Study.

Modern ballistocardiography (BCG) and seismocardiography (SCG) use acceleration sensors to measure oscillating recoil movements of the body caused by the heartbeat and blood flow, which are transmitted to the body surface. Acceleration artifacts occur through intrinsic sensor roll, pitch, and yaw movements, assessed by the angular velocities of the respective sensor, during measurements that bias the signal interpretation. This observational study aims to generate hypotheses on the detection and elimination of acceleration artifacts due to the intrinsic rotation of accelerometers and their differentiation from heart-induced sensor accelerations. Multimodal data from 4 healthy participants (3 male and 1 female) using BCG-SCG and an electrocardiogram will be collected and serve as a basis for signal characterization, model modulation, and location vector derivation under parabolic flight conditions from µg to 1.8g. The data will be obtained during a parabolic flight campaign (3 times 30 parabolas) between September 24 and July 25 (depending on the flight schedule). To detect the described acceleration artifacts, accelerometers and gyroscopes (6-degree-of-freedom sensors) will be used for measuring acceleration and angular velocities attributed to intrinsic sensor rotation. Changes in acceleration and angular velocities will be explored by conducting descriptive data analysis of resting participants sitting upright in varying gravitational states. A multimodal data set will serve as a basis for research into a noninvasive and gentle method of BCG-SCG with the aid of low-noise and synchronous 3D gyroscopes and 3D acceleration sensors. Hypotheses will be generated related to detecting and eliminating acceleration artifacts due to the intrinsic rotation of accelerometers and gyroscopes (6-degree-of-freedom sensors) and their differentiation from heart-induced sensor accelerations. Data will be collected entirely and exclusively during the parabolic flights, taking place between September 2024 and July 2025. Thus, as of June 2024, no data have been collected yet. The data will be analyzed until December 2025. The results are expected to be published by June 2026. The study will contribute to understanding artificial acceleration bias to signal readings. It will be a first approach for a detection and elimination method. Deutsches Register Klinische Studien DRKS00034402; https://drks.de/search/en/trial/DRKS00034402. PRR1-10.2196/63306.

Finite time adaptive recoil controller design for deepwater drilling riser systems

In this paper, we propose a finite-time model reference adaptive controller to attenuate the recoil response of deepwater drilling riser systems following an emergency disconnection. Firstly, a coupled model that characterizes the recoil movements of the riser, wave-excited heave motion, and the frictional resistance due to drilling fluid discharge is developed. Secondly, an adaptive control law is presented, with a portion of the adaptive gain determined through linear matrix inequalities. Thirdly, the stability criteria and updating rules that ensure finite settling time for the recoil control system is established. Then, the effectiveness and robustness of the controller against nonlinear systematic perturbations are verified. It is worth pointing out that: (1) The proposed adaptive controller significantly attenuates the recoil responses of the riser in finite time. (2) Compared to other controllers, the finite-time adaptive controller provides faster convergence for both error states and adaptive gains. (3) Perturbation cases involving nonlinear and unmodeled dynamics are examined, demonstrating the controller’s effectiveness and robustness, which ensures the safety of the drilling riser system.

Discrete recoil control system modelling and optimal recoil damping of deepwater drilling riser systems

This study addresses discrete dynamic modelling and the optimal recoil control problem of deepwater drilling riser systems subject to the friction resistance of fluid discharge and platform heave motion. First, a discrete-time exosystem model for friction resistance of drilling fluid discharge is developed; then, a discrete-time dynamic model of platform heave motion is established. Third, a finite-time discrete optimal recoil controller with feedforward compensation mechanisms was designed. The optimal recoil controller gains can be obtained by iteratively solving discrete equations. The simulation results show that under the discrete feedforward and feedback optimal recoil controller and pure feedback optimal recoil controller, the recoil movements of the riser system are significantly restrained. Moreover, the former is more effective than the latter at resisting the riser recoil response.

Performance Study of a Permanent-Magnet Eddy Current Damper for Guns Recoil Control

Eddy current damper (ECD) is a promising device for dissipating kinetic energy in dynamic systems, this study is conducted to analyze the dynamic characterization and structural optimization of linear ECD under guns launch load. The recoil resistance of ECD under guns launch load is highly nonlinear at high recoil velocity, and the recoil resistance curve shows an increase-decrease-increasing shape like a “saddle”, which is not conducive to the stability of ECD during operation. The effects of several structural parameters on the dynamic characterization of ECD were studied in details. Results show that the air-gap size, the thickness of the magnetic conduction tube and conductive tube all have a notable influence on the recoil resistance curve of ECD. Moreover, BP neural network and genetic algorithm were used for structural optimization and the optimal value was verified by FEM. The optimization results indicate that the “saddle” shape of optimized recoil resistance curve is basically invisible. The fullness of the recoil resistance curve is significantly improved from 84.93% to 92.1%, which guaranteeing a smooth recoil movement. Finally, an impact loading test system for eddy current damper was built and the experimental results were basically consistent with the simulation results.

Capillary Property of Entangled Porous Metallic Wire materials and Its Application in Fluid Buffers: Theoretical Analysis and Experimental Study

Strong impact does serious harm to the military industries so it is necessary to choose reasonable cushioning material and design effective buffers to prevent the impact of equipment. Based on the capillary property entangled porous metallic wire materials (EPMWM), this paper designed a composite buffer which uses EPMWM and viscous fluid as cushioning materials under the low-speed impact of the recoil force device of weapon equipment (such as artillery, mortar, etc.). Combined with the capillary model, porosity, hydraulic diameter, maximum pore diameter and pore distribution were used to characterize the pore structure characteristics of EPMWM. The calculation model of the damping force of the composite buffer was established. The low-speed impact test of the composite buffer was conducted. The parameters of the buffer under low-speed impact were identified according to the model, and the nonlinear model of damping force was obtained. The test results show that the composite buffer with EPMWM and viscous fluid can absorb the impact energy from the recoil movement effectively, and provide a new method for the buffer design of weapon equipment (such as artillery, mortar, etc.).

Recoil attenuation for deepwater drilling riser systems via delayed [formula omitted] control

This paper deals with the recoil suppression problem of a deepwater drilling riser system via active H∞ control using both current and delayed states. First, based on the three degrees of freedom spring–mass–damping model of the riser system, an incremental dynamic equation of the system subject to the platform heave motion and the friction force induced by drilling discharge mud and seawater is established. Then, to reject recoil movements of the riser, a delayed state feedback H∞ controller with delayed states as well as current states is designed. The existence conditions and the design method of the delayed H∞ recoil controllers are presented. Third, the effects of the introduced time-delays on the recoil control of the riser are analyzed, and the design of optimal artificial time-delays is formulated as the minimum value problem of a series of quintic algebraic polynomials, which are related to the weights of average response amplitudes, steady-state errors, and the control force. Lastly, simulation results are provided to demonstrate the effectiveness of delay-free and delayed H∞ recoil control schemes for the riser. It is shown that (i) under the delayed H∞ controllers, the recoil responses of the riser can be controlled significantly; (ii) the decay rate of the recoil response under the delay-free H∞ controller is slightly faster than the one under the delayed H∞ controllers. However, the former requires more control cost than the latter; (iii) compared with the delayed H∞ controller with the existing linear quadratic optimal controller, the control cost by the former is larger than that by the latter. However, the steady-state errors of the riser under the latter are slightly smaller than that under the former; (iv) the introduced time-delays with proper size play positive role of suppressing recoil response of the system, and the corresponding delayed H∞ controller series provide more options for recoil control of the riser.

Optimizacija uravnoteženja nagibnog sklopa protivavionskog topa BOFORS 40 mm L/70

The reconstruction of the anti - aircraft gun's loader and the increase in its capacity leads to an elevating mass debarment in relation with the axis of the gun's trunnion which creates a need for balancing gear reconstruction. The elevating mass is completely balanced in all elevations and even throughout the recoil movements by two balancing gears. Elevation balancing gear is on the left side of the gun while recoil and elevation balancing gear is on the right side. The mass increase is happening on the far back side of the gun and leads to translation of center of mass which makes pulling effects of balancing gears negative for the balance of elevating mass. By creating a real 3D model of the gun, new mass and its center of gravity are found. Using that information and knowing characteristics of balancing gears makes it possible to reconstruct them and create an elevating mass equilibrium.

Research on Dynamics of High-Efficiency Recoil-Reducing for Muzzle Brake of Chain Gun

In order to reduce the recoil energy of the chain gun, this paper put forward a high-efficiency recoil-reducing way with new-style high-efficiency muzzle brake and buffer parameter combined by studying the modeling and simulation of low recoil firing of chain gun. This paper studied the variation rules of gun recoil movement and recoil force of muzzle brake on three states. The results show the recoil of chain gun can be reduced significantly by using high-efficiency muzzle brake and selecting suitable parameters for buffer compared with that of only using muzzle brake and buffer. The research results put forward theoretical basis and application reference for studying high power low recoil chain gun.

Design and Analysis of Magneto-Rheological Dampers under Impact Loads

In order to improve recoil mechanism’s buffering function of automatic weapon, using Newton’s second law, its recoil movement is analyzed and design model of magneto-rheological (MR) damper under impact loads is built. Structure parameter and control strategy are defined. Dampers’ characteristic curves at different magnetizing currents and different recoil speeds are tested on a damper indicator test bench. Some weapon’s recoil forces are artificially computed. The research results indicate that MR dampers have a perfect damping plateau effect. Recoil force of automatic weapon will be reduced by a big margin using the property that MR fluid can change at applied magnetic to control damping rules.

Powered control mechanisms contributing to dynamically stable swimming in porcupine puffers (Teleostei: Diodon holocanthus)

Balances of multiple varying forces must be the basis for the unusually great dynamic stability of swimming pufferfishes. We used high-speed digital video recordings to study biomechanics and kinematics of rectilinear swimming at different speeds of five porcupine puffers in a water tunnel. We measured critical swimming speeds (U crit ); fin biomechanics, kinematics, and coordination; recoil movements; and gait changes. Major propulsors were pectoral fins at lower speeds; dorsal, anal, and caudal fins at higher speeds. Precise coordination of fin movements produced small recoil movements at speeds below U crit . The unusual body shape probably contributes to unconscious stability control.

Contact-free measurement of heart rate, respiration rate, and body movements during sleep

We describe a noncontact method for the ambulant measurement of basic sleep physiology parameters in humans, particularly for field studies involving sleep research and sleep disturbances. This method traces the body movements, respiration, and heart action of a person at rest or asleep on a bed, using four high-resolution force sensors installed under the bedposts. The recoil movement of the body at each heartbeat, known as the cardioballistic effect, as well as the lifting and lowering of the thorax, while breathing, causes very small shifts o f the center of gravity of the bed andthe subject. These shifts arereflected in the altering forcedistributions across the four sensors. Cardiac and respiratory parameters and the subject's movement activity can be calculated from the sensor signals. Neither electrodes nor other kinds of transducers are in direct contact with the subject, which is the main advantage of this technique over conventional methods. Laboratory experiments were carried out to estimate validity and practicability. The method has been found to be adequate, especially for automated and unattended sleep-data collection over long periods of time.

Hydrodynamic stability of swimming in ostraciid fishes: role of the carapace in the smooth trunkfish Lactophrys triqueter (Teleostei: Ostraciidae).

The hydrodynamic bases for the stability of locomotory motions in fishes are poorly understood, even for those fishes, such as the rigid-bodied smooth trunkfish Lactophrys triqueter, that exhibit unusually small amplitude recoil movements during rectilinear swimming. We have studied the role played by the bony carapace of the smooth trunkfish in generating trimming forces that self-correct for instabilities. The flow patterns, forces and moments on and around anatomically exact, smooth trunkfish models positioned at both pitching and yawing angles of attack were investigated using three methods: digital particle image velocimetry (DPIV), pressure distribution measurements, and force balance measurements. Models positioned at various pitching angles of attack within a flow tunnel produced well-developed counter-rotating vortices along the ventro-lateral keels. The vortices developed first at the anterior edges of the ventro-lateral keels, grew posteriorly along the carapace, and reached maximum circulation at the posterior edge of the carapace. The vortical flow increased in strength as pitching angles of attack deviated from 0 degrees, and was located above the keels at positive angles of attack and below them at negative angles of attack. Variation of yawing angles of attack resulted in prominent dorsal and ventral vortices developing at far-field locations of the carapace; far-field vortices intensified posteriorly and as angles of attack deviated from 0 degrees. Pressure distribution results were consistent with the DPIV findings, with areas of low pressure correlating well with regions of attached, concentrated vorticity. Lift coefficients of boxfish models were similar to lift coefficients of delta wings, devices that also generate lift through vortex generation. Furthermore, nose-down and nose-up pitching moments about the center of mass were detected at positive and negative pitching angles of attack, respectively. The three complementary experimental approaches all indicate that the carapace of the smooth trunkfish effectively generates self-correcting forces for pitching and yawing motions--a characteristic that is advantageous for the highly variable velocity fields experienced by trunkfish in their complex aquatic environment. All important morphological features of the carapace contribute to producing the hydrodynamic stability of swimming trajectories in this species.

Flow Patterns Around the Carapaces of Rigid-bodied, Multi-propulsor Boxfishes (Teleostei: Ostraciidae)

Boxfishes (Teleostei: Ostraciidae) are rigid-body, multi-propulsor swimmers that exhibit unusually small amplitude recoil movements during rectilinear locomotion. Mechanisms producing the smooth swimming trajectories of these fishes are unknown, however. Therefore, we have studied the roles the bony carapaces of these fishes play in generating this dynamic stability. Features of the carapaces of four morphologically distinct species of boxfishes were measured, and anatomically-exact stereolithographic models of the boxfishes were constructed. Flow patterns around each model were investigated using three methods: 1) digital particle image velocimetry (DPIV), 2) pressure distribution measurements, and 3) force balance measurements. Significant differences in both cross-sectional and longitudinal carapace morphology were detected among the four species. However, results from the three interrelated approaches indicate that flow patterns around the various carapaces are remarkably similar. DPIV results revealed that the keels of all boxfishes generate strong longitudinal vortices that vary in strength and position with angle of attack. In areas where attached, concentrated vorticity was detected using DPIV, low pressure also was detected at the carapace surface using pressure sensors. Predictions of the effects of both observed vortical flow patterns and pressure distributions on the carapace were consistent with actual forces and moments measured using the force balance. Most notably, the three complementary experimental approaches consistently indicate that the ventral keels of all boxfishes, and in some species the dorsal keels as well, effectively generate self-correcting forces for pitching motions-a characteristic that is advantageous for the highly variable velocity fields in which these fishes reside.

U-Th dating of carbonate platform and slope sediments

Absolute chronology of marine sediment beyond the 14C age range provides a test for models of climate change and has many other applications. U-Th techniques have been used for such chronology by dating corals, but extending these techniques to marine sediment is complicated by the presence of significant initial 230Th—both in detrital material and scavenged from seawater. In this study, we investigate four methods of solving the initial 230Th problem for a particular type of marine sediment—the aragonite-rich sediments of carbonate platforms and slopes. Bulk sediment U-Th analyses can be corrected for initial Th to yield ages with ≈2 to 3 kyr precision for highstand periods when sediment aragonite contents are particularly high. Uncertainty on the corrections causes inadequate precision for sediment from other periods, however. Removal of scavenged Th before analysis would enable a dramatic increase in this precision but has not proved successful despite a range of chemical leach approaches. Using heavy liquids to separate the various carbonate minerals found in Bahamas sediment enables an isochron approach to correct for initial Th, but the presence of initial Th from two sources requires correction or removal of one source of initial Th before the other is deconvolved by the isochron. Quantitative removal of detrital material before isochron analysis proves a successful approach. Such isochron data demonstrate that, although sediment remains closed to U-Th on a centimetre scale, nuclides are moved from grain to grain by α-recoil. Such intergrain exchange is expected to be observed in all sediments containing mineral grains with different U concentrations. Measured 234U/238U allows the recoil movement to be corrected and results in isochron ages with precision sometimes as low as 3 kyr. The accuracy of this approach has been proved by dating samples within the 14C age range. Sediments spanning the penultimate deglaciation have also been dated. After a small correction for bioturbation, the age for this event is found to be 135.2 ± 3.5 ka. This date is ≈8 kyr before the peak in northern hemisphere insolation and suggests that deglaciation is initiated by a mechanism in the southern hemisphere or tropics. This isochron approach shows considerable promise for dating of sediments older than this event, which will provide further information about the timing and mechanisms of global climate change.

Theme and Thesis in Le Chevalier de la Charrete

Critics have traditionally treated the narrator's addresses as evidence to assess whether Chrétien promoted the ideal of courtly love in the Charrete . If we consider the use of appropriation and recoil movements in the total text, the operation of the will emerges as the dominant theme of the text. This theme is considered in the context of the parallel but contrasting pacts formed by Lancelot in the service of Guinevere and Chrétien in the service of Marie de Champagne.

Locomotion, fin coordination and body form of the living coelacanth Latimeria chalumnae

Locomotion and fin coordination of the only living crossopterygian fish Latimeria chalumnae were studied with submersibles in the fish's natural habitat at around 200 m depth off Grand Comoro, western Indian Ocean. Latimeria is a highly specialized predatory fish adapted for nocturnal drift hunting with good fast start capability. Twelve different forward movements and manoeuvres were found and described. The movements of the paired and unpaired fins were analysed. Propulsion was accomplished with downstrokes of the pectoral fins and right-left or left-right strokes of the unpaired lobed fins. The paired fins were not used for walking on the bottom. Swimming velocity, stroke amplitudes and stroke duration were analysed from films and videos taken in the wild. Stroke duration of the paired and unpaired lobed fins was similar and varies between 1.9 to 5.8 sec. Paired fins alternated synchronously. The coordination at approximately o = 180° between opposite paired fins is stable and independent of locomotory pattern and velocity. A phase deviation of about 90°–100° exists between paired and unpaired fins. A model is developed that describes the functional implication of this deviation as a method of producing a steady swimming performance which smooths recoil movements and prevents rotation of the body. The novel slow and fast swimming mode of Latimeria is named in accordance with Breder's (1926) descriptive nomenclature as ‘coelacanthiform’. This study indicates a primary swimming function for the primitive sarcopterygian fin and confirms earlier evolutionary assumptions of a more open-water life style of coelacanth fishes. Paleoethological models of the walking habits of Latimeria have to be rejected. Synchronous alternation of paired fins originating from hydrodynamic demands could be a pre-adaptation and a shared derived character in sarcopterygian fishes that facilitated the fish-tetrapod transition.

‘Steady’ Swimming Kinematics of Tiger Musky, an Esociform Accelerator, and Rainbow Trout, a Generalist Cruiser

ABSTRACTLocomotor kinematics of tiger musky (Esox sp.) and rainbow trout (Salmo gairdneri) were measured at ‘steady’ swimming speeds of up to 85 cm s−1. Tail beat frequencies of musky were approximately 2 Hz higher than those of trout at any swimming speed, but tail beat amplitudes were 0·04L (where L is total body length) smaller. The product of these two variables was similar for the two species at any speed. The length of the propulsive wave was independent of speed, and was 0·8L for musky, somewhat smaller than the value for trout, 0·9L. The depth of the caudal fin trailing edge of trout was greater than that of musky, but the greater depth of the posteriorly located median fins of musky also contributed to thrust production. The cosine of the angle of the trailing edge to its beat plane showed the same phase relationship with lateral displacement in both musky and trout. It increased with speed for both species, and values for musky were slightly smaller. Thrust power requirements of musky and trout were similar. Thrust (= drag) coefficients of musky were 1·55 times larger than those for trout: this is roughly as expected on the basis of the larger proportion of the total area of musky located caudally and the higher drag coefficients in this region of the body. Lateral recoil movements of musky were unexpectedly smaller than for trout and were associated with smaller energy wastage from undamped recoil movements. The large recoil expected for the body form of musky was damped to some extent by higher tail beat frequencies, although this entailed some loss in Froude efficiency. Otherwise, no hydrodynamic explanation for the small recoil movements of musky was apparent. It is suggested that the myotomal muscles could be involved in minimizing recoil. The esociform morphology incurs costs in steady swimming, in comparison with generalist cruises, because of reduced sprint speeds for fish of a given length or increased power requirements for fish of a given mass.

Shock absorber for firearms and the like

A shock absorber for automatic weapons of the kind where all the shots in a burst with the exception of the first are fired during the return movement to the initial position of the weapon. The weapon has a recoil member movable with respect to a fixed member to absorb the impact and resilient restoring means for restoring the recoil member to its initial position. Braking means brake the movement of the recoil member during recoil. The braking means are inoperative or of reduced effect during the recoil movements relative to all the shots in the burst other than the first shot.

Mechanics of Escape Responses in Crayfish (Orconectes Virilis)

ABSTRACT Measurements of acceleration performance of crayfish (mean mass 0·018 kg) were made during lateral giant mediated tail flips (LG tail flips) and truncated tail flips at 15°C. The LG tail flip power stroke was composed of a lift-off phase, when crayfish accelerated vertically from the substrate, and a free swimming phase. The total duration of the power stroke was 44 ms, followed by a recovery stroke lasting 173 ms. Truncated tail flips were used in acceleration and swimming by crayfish free of the substrate. Power strokes had a mean duration of 36 ms, and recovery strokes 92 ms. Net velocities, acceleration rates, and distances travelled by the centre of mass were similar for both types of tail flips. Thrust was generated almost entirely by the uropods and telson. Velocities and angles of orientation to the horizontal of abdominal segments were similar for both types of tail flip. Angles of attack were large, varying from 30° to 90°. Pressure (drag) forces were considered negligible compared to inertial forces associated with the acceleration of added water mass. Thrust forces, energy and power were determined for exemplary tail flips. Thrust was 0·92 and 0·42 N for LG tail flip lift-off and swimming phases respectively, and 0·29 N for the swimming truncated tail flip. Rates of working were 0·39, 0·19, and 0·18 W respectively. The efficiency of converting muscle power to backward motion was estimated to be 0·5 for power strokes and o-68 for complete swimming cycles. Comparisons with fish performance suggested fish would be less efficient (0·1–0·2). The low efficiency is attributed to energy lost in lateral recoil movements.

Studies of straingauge kinetocardiogram recording methods and its clinical implication.

1) A new technique of kinetocardiogram (S-KCG) by using straingauge was introduced to measure the absolute precordial movement. 2) The device had constant frequency-response curve within the range lower than 15 Hz, linear relationship between the given displacement and the recorded amplitude and infinite time constant. 3) The influences of intervening soft tissue on the record could be avoided by the pressure (700 gram) on the chest wall applied through the pickup device. 4) The recorded tracings were consisted of 5 main components: atria wave (a), preejection wave and ejection wave (PE and E), midsystolic outward movement (MOM), recoil movement at the time of second heart sound (R), rapid and slow filling wave (rF and sF). A magnitude of wave was expressed as wave ratio to the total maximum deflection (a/TD). 5) Various changes in the configuration of S-KCG in altered hemodynamics which were induced by amyl nitrite inhalation, β-stimulant injection, arrhythmias and various congenital and acquired heart diseases were demonstrated. 6) Absolute amplitude of a wave as well as a/TD increased under the conditions of both pressure, and volume overload in the left atrium. In mitral stenosis, there was significant positive correlation between a/TD and the pulmonary capillary wedge pressure. 7) The direct measurement of isovolumetric contraction time could be possible by measuring the PE-E interval. 8) Several possible mechanism and genesis of MOM wave were discussed. 9) It was concluded that the S-KCG is useful in the evaluation of the synchrony of the contraction.