Amplitude Of Roll Research Articles

Body roll amplitude and timing in backstroke swimming and their differences from front crawl at the same swimming intensities

The current study investigated body roll amplitude and timing of its peak in backstroke and compared them with front crawl swimming. Nineteen anatomical landmarks were digitised using 80 swimming trial videos (ten swimmers × two techniques × four intensities) recorded by two above- and four below-water cameras. One upper-limb cycle was analysed for each trial, and shoulder and hip roll, whole-body roll (WBR), and WBR due to the buoyant torque (WBRBT) were obtained. Main effects of intensity and technique on the amplitude and timing to reach the peak in those variables were assessed by two-way repeated-measures ANOVA. Swimmers decreased their WBRBT amplitude with an increase in the intensity in both techniques (p ≤ 0.005). The same result was observed for the amplitude of WBR, shoulder roll, and hip roll only in front crawl (p ≤ 0.017). Swimmers maintained the timing of peak WBRBT in both techniques, while they shifted the timing of WBR and hip roll peak toward the beginning of the cycle when increasing the intensity in front crawl (p ≤ 0.017). In conclusion, swimmers maintain the amplitude of WBR, shoulder roll, and hip roll in backstroke when the intensity increases, whereas they reduce the amplitude of all rolls in front crawl.

GROUND ROLL NOISE ATTENUATION IN 3D LAND SEISMIC DATA IN PARTS OF NIGER DELTA, NIGERIA

Three-dimensional (3D) land seismic datasets were acquired from Central Depobelt in the Niger Delta region, Nigeria, with with the aim of attenuating ground roll noise from the dataset. The Omega (Schlumberger) software 2018 version was used along with frequency offset coherent noise suppression (FXCNS) and Anomalous Amplitude Attenuation (AAA) algorithms for ground roll attenuation. From the results obtained, Frequency Offset Coherent Noise Suppression (FXCNS) attenuates ground roll while AAA algorithm attenuates the residual high amplitude noise from the seismic data. Average frequency of the ground roll in the seismic data is 10.50Hz which falls within the actual range of ground roll frequency which is within the range of 3.00 – 18.00Hz. The average velocity of the ground roll in the seismic data is 477.36ms-1 while the velocity of ground roll ranges between 347.44 and 677.37ms-1. The wavelength of ground roll in the seismic data is 50.28m. The amplitude of the ground roll of -6.24dB is maximum at 4.2Hz. Frequency of signal ranges between 10.21 and 25.12Hz with an average of 17.67Hz. Signal amplitude of -8.32dB is maximum at 6.30Hz, while its wavelength is 57.12m. The results of this work can be used in the seismic source-receiver design for application in the area of study. Moreover, with ground roll noise attenuated, a better image of the subsurface geology is obtained hence reducing the risk of obtaining a wild cat drilling.

Ship weather routing optimization with dynamic constraints based on reliable synchronous roll prediction

Ship routing process taking into account weather conditions is a constrained multi-objective optimization problem and it should consider various optimization criteria and constraints. Formulation of a stability-related, dynamic route optimization constraint is presented in this paper. One of the key objectives of a cross ocean sailing is finding a compromise between ship safety and economics of operation. This compromise should be taken into account by the planning procedure and proper optimization algorithm. In this research complex stability-related phenomena are adopted as the basis for the constraint set formulation in weather routing. Thus, the synchronous roll, parametric resonance, surf riding and broaching-to are considered according to the IMO MSC.1/Circ.1228 guidance. However, the dangerous resonance motion of the ship depends on her natural period of roll and a degree of tuning to the encounter wave period. This natural period strictly depends on the GZ curve shape and, consequently, on the amplitude of roll. In order to properly model the natural period of roll, a new method utilizing equivalent metacentric height is applied and incorporated into the route optimization. Sample calculations of the cross ocean routes are presented and the effect of the dynamic approach to the constraint set is demonstrated and discussed.

An energy analysis of parametric roll for application to the second generation intact stability criteria

Parametric roll is an amplification of the roll motion due to the periodic variation of the restoring moment in waves. This phenomenon is mostly observed in head and following seas and is the cause of several accidents occurred on container vessels during recent decades. One of the second generation intact stability criteria, currently under finalization and validation by the IMO, requires computing the maximum roll angle with regard to parametric roll. Both proposed methods are relatively complex to implement and require tools that naval architects are not accustomed to. In this paper, we propose an easier alternative method providing the amplitude of parametric roll for any loading condition at any speed, based on energy considerations and assuming a linear GZ. The implementation of this easy method in the corresponding second generation intact stability criterion provides almost the same value of KGmax than the on-degree-of-freedom time simulation proposed by the future regulation.

Influence of yaw-roll coupling on the behavior of a FPSO: An experimental and numerical investigation

An inconvenience in the experimental set-up of a FPSO in regular waves highlighted occurrence of parametric-roll events promoted by yaw-roll coupling and motivated a combined physical and numerical analysis on the relevance of this phenomenon on the roll resonance, as well as on the water shipping. The model tests examine the ship in head- and bow-sea waves in the zone of the first parametric resonance. Numerically, it is adopted a 3D Domain-Decomposition (DD) strategy combining a weakly-nonlinear potential-flow solver based on the weak-scatterer theory with a shallow-water approximation for the shipped liquid and with a bottom-slamming solution. Detailed comparisons against these and other seakeeping experiments validated the numerical method in its different aspects with global success.At first, a 2-dof equivalent linearized yaw-roll coupled system is examined and the measurements are used to estimate hydrodynamic coefficients required to complete the mathematical model of the problem. Then the DD method is applied to verify the instability occurrence and compared against the experiments. From the analysis, the parametric-roll instability does not occur if all nonlinearities in the roll restoring load are not accounted for. However the amplitude of the resonant roll is affected by the coupling with the other degrees of freedom. Especially the coupling with yaw tends to increase the steady-state roll amplitude. It also affects the water shipping with the trend in reducing its severity for the vessel, this is opposite to the influence of the parametric roll in head-sea waves on the water on deck, as documented in Greco et al. (2014) [4].

Navigation Condition Effect on Ship Motion in some Sea State

According to analyzing the identity of ocean wave, theory of wave energy spectrum was applied to compute the curve of wave elevation vs. time in some sea state. Based on ship motion equations, ship motion was acquired by the simulation software of the of ship strip theory in some situation. How different navigation conditions effect on ship motion is researched in some sea state. The results show the change of degree of abaft the beam badly influenced the amplitude and periods of pitch, it also influenced periods of heave and amplitude of roll. The change of ship speed influenced the amplitude and periods of pitch, it also influenced periods of heave and roll.

능동형 횡동요 감쇠장치의 성능에 관한 연구

제주대학교 실습선 아라호에 정착된 능동형 횡동요 감쇠장치의 성능에 관해 연구하기 위하여 33<TEX>$^{\circ}$</TEX>00‘.44”N, 125<TEX>$^{\circ}$</TEX>59’.88 ”E 위치에서 선박을 정지한 후, 횡동요 감쇠장치를 정지 (Passive A.R.T), 작동 (Active A.R.T)을 했을 때 경사계에 의한 횡동요각 및 종동요각, 풍속계에 의한 풍속의 변화와 그리고 선박이 항해 중에 감쇠장치의 작동을 정지(Passive A.R.T), 작동(Active A.R.T) 했을 때 의 능동형 횡동요 감쇠장치의 성능을 분석한 결과에 대해 요약하면 다음과 같다. 1. 선박이 정지했을 때 횡동요 감쇠장치를 정지, 작동한 경우 횡동요각의 평균진폭 (Average Amplitude of Roll) 은 각각 8.30<TEX>$^{\circ}$</TEX>, 4.37<TEX>$^{\circ}$</TEX>, 횡동요각의 유의진폭(Significant Amplitude of Roll <TEX>$_{{\pi}{1/3}}$</TEX>)은 각각 10.10<TEX>$^{\circ}$</TEX>, 5.30<TEX>$^{\circ}$</TEX>으로 나타났다. 2. 선박이 항해 중 일 때에는 횡동요각의 평균진폭 (Average Amplitude of Roll)은 각각 5.01<TEX>$^{\circ}$</TEX>, 4.36<TEX>$^{\circ}$</TEX>, 횡동요각의 유의진폭 (Significant Amplitude of Roll<TEX>$^{\circ}$</TEX>) 은 각각 5.50<TEX>$^{\circ}$</TEX>, 5.10<TEX>$^{\circ}$</TEX>으로 각각 나타났다. 3. 횡동요 감쇠장치는 선박이 정치했을 때에는 47.5%, 선박이 운항 했을 때는 12.7% 정도의 감쇠 효율을 보여서 정지했을 때 그 효율이 높은 것으로 나타났다. 4. 횡동요 감쇠 장치는 종동요(Pitching)에 대해서는 거의 영향을 미치지 않았다. This experimental paper deals with the performance of tanks that are turned the active A.R.T(Anti-Rolling Tank) when the fluid transfers from wing tank to the opposite tank by the power developed by the automatic control system (INTERING Stabilizer), which was installed in the fishery training ship T/S. A - RA (G/T:990 tons) of Cheju National University. In this paper, the author has tested the performance of INTERING Stabilizer for the signals obtained by the inclinometer in irregular waves and compared with the results obtained in passive mode operation at stop and at various ship speeds. The performances of the system were confirmed the results as follows through the tests: 1. The average amplitude and significant roll (<TEX>${\pi}$</TEX>1/3) of the passive and active mode operations in the condition of stoped engine and underway were obtained 8.30<TEX>$^{\circ}$</TEX>, 4.37<TEX>$^{\circ}$</TEX>, 8.30<TEX>$^{\circ}$</TEX>, 4.37<TEX>$^{\circ}$</TEX>, and 5.01<TEX>$^{\circ}$</TEX>, 4.36<TEX>$^{\circ}$</TEX>, 5.50<TEX>$^{\circ}$</TEX>, 5.10<TEX>$^{\circ}$</TEX>, respectively. 2. The rates of performance of active mode operations were carried out during a sea trial in the condition of stop engine and underway resulted in 47.5%, 12.7%, respectively, therefore the active mode operation estimated to be improved more than passive mode operation. 3. Active - A.R.T by INTERING Stabilizer didn't affect the amplitude of pitching.

Age‐dependent variations in the directional sensitivity of balance corrections and compensatory arm movements in man

We investigated the effects of ageing on balance corrections induced by sudden stance perturbations in different directions. Effects were examined in biomechanical and electromyographic (EMG) recordings from a total of 36 healthy subjects divided equally into three age groups (20-34, 35-55 and 60-75 years old). Perturbations consisted of six combinations of support-surface roll (laterally) and pitch (forward-backward) each with 7.5 deg amplitude (2 pure pitch, and 4 roll and pitch) delivered randomly. To reduce stimulus predictability further and to investigate scaling effects, perturbations were at either 30 or 60 deg s(-1). In the legs, trunk and arms we observed age-related changes in balance corrections. The changes that appeared in the lower leg responses included smaller stretch reflexes in soleus and larger reflexes in tibialis anterior of the elderly compared with the young. For all perturbation directions, onsets of balance correcting responses in these ankle muscles were delayed by 20-30 ms and initially had smaller amplitudes (between 120-220 ms) in the elderly. This reduced early activity was compensated by increased lower leg activity after 240 ms. These EMG changes were paralleled by comparable differences in ankle torque responses, which were initially (after 160 ms) smaller in the elderly, but subsequently greater (after 280 ms). Findings in the middle-aged group were generally intermediate between the young and the elderly groups. Comparable results were obtained for the two different stimulus velocities. Stimulus-induced trunk roll, but not trunk pitch, changed dramatically with increasing age. Young subjects responded with early large roll movements of the trunk in the opposite direction to platform roll. A similarly directed but reduced amplitude of trunk roll was observed in the middle-aged. The elderly had very little initial roll modulation and also had smaller stretch reflexes in paraspinals. Balance-correcting responses (over 120-220 ms) in gluteus medius and paraspinals were equally well tuned to roll in the elderly, as in the young, but were reduced in amplitude. Onset latencies were delayed with age in gluteus medius muscles. Following the onset of trunk and hip balance corrections, trunk roll was in the same direction as support-surface motion for all age groups and resulted in overall trunk roll towards the fall side in the elderly, but not in the young. Protective arm movements also changed with age. Initial arm roll movements were largest in the young, smaller in the middle aged, and smallest in the elderly. Initial arm roll movements were in the same direction as initial trunk motion in the young and middle aged. Thus initial roll arm movements in the elderly were directed oppositely to those in the young. Initial pitch motion of the arms was similar across age groups. Subsequent arm movements were related to the amplitude of deltoid muscle responses which commenced at 100 ms in the young and 20-30 ms later in the elderly. These deltoid muscle responses preceded additional arm roll motion which left the arms directed 'downhill' (in the direction of the fall) in the elderly, but 'uphill' (to counterbalance motion of the pelvis) in the young. We conclude that increased trunk roll stiffness is a key biomechanical change with age. This interferes with early compensatory trunk movements and leads to trunk displacements in the direction of the impending fall. The reversal of protective arm movements in the elderly may reflect an adaptive strategy to cushion the fall. The uniform delay and amplitude reduction of balance-correcting responses across many segments (legs, hips and arms) suggests a neurally based alteration in processing times and response modulation with age. Interestingly, the elderly compensated for these 'early abnormalities' with enlarged later responses in the legs, but no similar adaptation was noted in the arms and trunk. These changes with age provide an insight into possible mechanisms underlying falls in the elderly.

Ground roll supression using the Karhunen‐Loeve transform

Ground roll is the main type of coherent noise in land seismic surveys, and is commonly much stronger in amplitude than the reflection signals. Standard methods for suppressing ground roll include 1-D high‐pass filtering and 2-D f-k filtering. High‐pass filtering is based on the low‐frequency nature of ground roll, but has the disadvantage that it also eliminates low‐frequency reflection signals which contribute to the character of reflection events and are very important in inversion for acoustic impedance. When the amplitude of the ground roll is much stronger than the reflection signals, f-k filters cause serious distortion of the signal.

Ocular torsion induced by static visual stimulation and static whole body roll

Objective. This study was aimed to improve the reliability of clinical statolith testing by quantifying the influence of visual orientation and stimulation on the statolith-ocular reflex. Materials and methods. Ocular torsion was induced in 12 healthy adults by visual stimulation and by static whole body roll with and without simultaneous visual orientation. Visual stimulation was achieved by a horizontal grating oscillating sinusoidally in a frontal plane. Visual orientation during whole body roll was established by mounting an illuminated horizontal grating either on a tilting device (head-fixed) or on the wall in the frontal plane (earth-fixed). Results. No eye torsion was observed in static visual tilts of the grating. Dynamic visual stimulation elicited substantial eye torsion. Static whole body roll in the dark induced static ocular counter-rolling. Visual orientation either head- or earth-fixed did not affect the amplitude or gain of the body roll induced ocular counter-rolling. Conclusion. Dynamic visually induced torsional eye movements can be used to test the ability of the oculomotor system to generate torsional eye movements prior to quantifying the statolith-ocular reflex. Simultaneously visual information does not affect the gain of the static statolith-ocular reflex.

Ocular torsion induced by static and dynamic visual stimulation and static whole body roll.

By means of real-time infra-red video-oculography we studied eye torsion in 12 normal healthy subjects. Ocular torsion was induced by visual stimulation or static whole body roll with and without visual orientation ("head-fixed" or "earth-fixed"). Visual stimulation was achieved by a horizontal grating that oscillated sinusoidally in a frontal plane. The oscillation frequency varied from 0 to 0.6 Hz while amplitude varied from 6 degrees to 33 degrees. Visual orientation during whole body roll was established by mounting a 32 lx illuminated horizontal grating either on a tilting device (head-fixed) or on the wall in the frontal plane (earth-fixed). Maximum visual-induced eye torsion gain was reached at about 0.2 Hz. No eye torsion was observed in static (0 Hz) visual tilts of the grating. Maximum gain was about 0.36 at amplitudes between 6 degrees and 10 degrees. Eye torsion gain decreased with increasing amplitude and increasing frequency (> 0.2 Hz). Static whole body roll in the dark up to 180 degrees clockwise and counterclockwise induced static ocular counter rolling with a maximum amplitude of 12 degrees and a maximum gain of 0.22. Gain decreased with increasing roll down to zero at 180 degrees. Visual orientation with either head or earth fixed did not affect the amplitude or gain of the body roll induced ocular counter-rolling. The results are interpreted in terms of improving the reliability of clinical statolith testing and understanding the processes involved in motion sickness.

実船を用いた船体応答計測について-II : 周波数応答関数の推定

Tests with a hull response system on board a fishing vessel were carried out to establish the hull response during cruising and fishing. The records of the wave and ship motions obtained were analysed and the observed values compared with the theoretical values using the New Strip Method. The results confirmed that the wave height and double amplitude of roll and pitch angles followed Rayleigh distribution. The observed values for the response function were almost equal to the theoretical values using the New Strip Method. However, it is necessary to analyse the response function according to the short wave hypothesis.

Mapping a bedrock surface under dry alluvium with shallow seismic reflections

Shallow seismic‐reflection techniques were used to image the bedrock‐alluvial interface, near a chemical evaporation pond in the Texas Panhandle, allowing optimum placement of water‐quality monitor wells. The seismic data showed bedrock valleys as shallow as 4 m and accurate to within 1 m horizontally and vertically. The normal‐moveout velocity within the near‐surface alluvium varies from 225 m/s to 400 m/s. All monitor‐well borings near the evaporation pond penetrated unsaturated alluvial material. On most of the data, the wavelet reflected from the bedrock‐alluvium interface has a dominant frequency of around 170 Hz. Low‐cut filtering at 24 dB/octave below 220 Hz prior to analog‐to‐digital conversion enhanced the amplitude of the desired bedrock reflection relative to the amplitude of the unwanted ground roll. The final bedrock contour map derived from drilling and seismic‐reflection data possesses improved resolution and shows a bedrock valley not interpretable from drill data alone.

Intersegmental interneurons involved in the control of head movements in crickets

1. Seven intersegmental interneurons (INs) were recorded intracellularly in the prothoracic ganglion of crickets (Gryllus campestris). When stimulated electrically each of these INs caused a head movement by activating the motoneurons (MNs) of the dorsoventral neck muscles M55, M56 and M60 (Figs. 1–8). Different INs caused different activity patterns in the muscles, i.e. different head movements, but head roll predominated. During stimulation of these INs only head movements could be detected. Therefore they were called ‘neck muscle INs’ (NMINs). 2. Activity evoked by the NMINs in M60 was measured quantitatively by myogram recordings. NMIN 1, 6 and 7 excited one M60, NMIN 2, 4 and 5 excited both M60 but with different strength and NMIN 3 inhibited the MN of one M60. The parallel activation of M55 and M56 was deduced qualitatively from strength and direction of head movements. Excitation of these muscles, i.e. the amplitude of head roll varied linearly with the activity in the NMINs, at least within a certain frequency range (Figs. 1–8). 3. The participation of NMINs in natural movements was tested by recording from NMIN 1, 2 and 7 during the head roll of eye cleaning behavior (Fig. 9). The experimental animals were minimally dissected and behaved normally during intracellular recordings from the prothoracic ganglion. All three INs were excited during cleaning of the eye contralateral to their axon. During eye cleaning ipsilateral to their axon NMIN 1 was inhibited, NMIN 2 was excited and NMIN 7 was not active. The activity of single NMINs was weak and had only a small influence on the activity of the MNs (Fig. 10), as confirmed by inactivating single NMINs by means of hyperpolarization. 4. A model is proposed to explain how neck muscle MNs are controlled during the head roll of eye cleaning and probably during other head movements: a specific motor pattern comes about by the concerted activity of a number of NMINs, each one controlling an element of the final movement. This model allows maximum plasticity, an important prerequisite for a motor system like that of the neck muscles which is involved in almost every behavioral context.

波浪中における沿岸漁船の動揺について-II : スケグ付き船型の動揺

As a series of experiment for the motions of inshore fishing boat in waves, the seakeeping experiments were carried out varying speeds, heading angles and displacement of a actual boat. And these experiments were repeated for four different sea conditions. From these experiments, we obtained the following results. (1) The wave hights of a record and double amplitude of roll and pitch angles were found to follow nearly Rayleigh distribution. (2) The values of the bandwidth parameter, ε_s, obtained by spectral analysis, lies in the range ε_s=0.30 to ε_s=0.80 for roll angles and in the range ε_s=0.40 to ε_s=0.95 for pitch angles under various boat and sea condition. And the values of ε_s for these motions were found to increase as the speeds increase.

THREE‐DIMENSIONAL SEISMIC MODEL STUDIES

Elastic wave propagation in a two‐layer section has been studied with a solid two‐bed model and records resembling seismograms obtained for the four possible source‐detector configurations. Numerous events are identified. Among these, the shear waves are found to be surprisingly prominent. The amplitude of the ground roll falls off approximately as [Formula: see text] This is the amplitude‐range dependence expected for a surface wave. The ability of two in‐line detectors to reduce surface waves has been demonstrated.