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1

Effects of sway and roll excitations on sloshing loads in a KC-1 membrane LNG tank

An Se-yeol, Jeong Hyeon-won, Kim Ohyoung, Shim W. Jaewoo

Polish Maritime Research

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2023

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nr 4

43--53

EN

This study investigates the effects of sway and roll excitations on sloshing liquid loads in a tank, using Ansys Fluent software. The model considered in the study is a 1:50 scaled membrane-type tank, based on a KC-1 membrane LNG tank designed by Korea Gas Corporation (KOGAS). The volume of fluid (VOF) method is used to track the free surface inside the tank, and the standard k-ε model is applied to express the turbulent flow of the liquid. To explore the motion of the tank under excitation, a user-defined function (UDF) and a dynamic mesh technique are employed to control the external forces exerted on the tank through its motion. The results, in the form of time series data on the sloshing pressures in the tank under pure sway, roll, and coupled sway-roll, are analysed, with specific ranges for the excitation amplitudes and frequencies. We show that variations in excitation frequency and amplitude significantly influence the sloshing loads. Sloshing loads are found to intensify when the excitation frequency matches the tank’s primary natural frequency, 1.0 ω'1. Furthermore, with coupled sway-roll excitations, the sloshing loads are weakened when the sway and roll are in-phase and are intensified when these are out-of-phase. Fast Fourier transform analysis provides insights into the frequency domain, showing that the dominant frequency is 0.88 Hz and it is approximately equal to the tank’s primary natural frequency, 1.0 ω'1.

2

Balance control via tactile biofeedback in children with cerebral palsy

Argunsah Hande, Yalcin Begum

Acta of Bioengineering and Biomechanics

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2023

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Vol. 25, no. 1

161--171

EN

Children with cerebral palsy have limitations in utilizing neural information to perform smooth movement and maintain balance during walking. This study aimed to develop a wearable sensor that tracks balance continuously and provides haptic biofeedback to its user through real-time vibration stimulus to assist patients with balance and postural control impairments such as cerebral palsy. Methods: Twelve children with cerebral palsy and 12 age-matched typically developed children used the sensor during walking at a self- -selected speed. The lower extremity joint kinematics, center of mass, and spatial-temporal parameters were recorded with Xsens MVN during “with” and “without” biofeedback conditions. Results: The sensor did not disturb healthy gait. Pearson correlation coefficient and Root Mean Square Error techniques showed that biofeedback regulated the gait parameters and trunk stability of the CP group. The extended stance percentage (without BF: 73.91% ± 10.42, with BF: 63.53% ± 2.99), step width (without BF: 0.20 m ± 0.05, with BF: 0.18 m ± 0.07), and step time (without BF: 1.55 s ± 1.07, with BF: 0.73 s ± 0.14) parameters decreased. Similarly, cadence and walking speed increased. Conclusions: Obtained results indicated that this wearable sensor can be integrated into the physical therapy and rehabilitation process of children with balance and postural control impairments to improve motor learning and balance control. The present findings contribute to a better understanding of the adaptation of innovative engineering applications with rehabilitation processes, which, in turn, could assist patients with balance impairments and facilitate their integration into society.

3

Statyczne i dynamiczne testy równowagi u osób trenujących Taekwondo

Podbielska M., Senhadri H., Kuczyński M.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2013

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Vol. 19, nr 2

79--84

PL

Równowaga dynamiczna i statyczna oceniania była u osób w wieku 19 do 27 lat, trenujących Taekwondo i w grupie kontrolnej, nieuprawiającej aktywności fizycznej. Równowaga statyczna była mierzona w czasie 20 s spokojnego stania na platformie stabilograficznej. Równowaga dynamiczna oceniana była przez 2,5 s po skoku na platformę i zeskoku z platformy. Nie stwierdzono znaczących różnic w równowadze statycznej pomiędzy grupami. W grupie osób uprawiających Taekwondo zmierzono mniejsze zmiany sił reakcji podłoża po skoku jednonożnym na platformę niż u osób nieuprawiających sportu, co dowodzi lepszej równowagi dynamicznej.

EN

Static and dynamic postural stability was tested on a force plate between recreational Taekwondo athletes (TAE) and subjects who were not involved in any systematic sports activities (CON) aged 18 to 27 years. The static stability was measured in single- and double-leg 20 s quiet stance. The dynamic stability was assessed by the standard deviation of the ground vertical forces during 2.5 s period after landing in two tests: hopping and leaping on the force plate. The results revealed similar postural sway in TAE and in CON groups during a 20-sec quiet stance indicating that the traditional interpretation of stabilographic findings may be sometimes misleading in the assessment of postural performance in athletes. However, the vertical force variability that resulted from a single-leg hopping on the force plate was much lower in athletes than in controls.

4

Effects of Diabetic Neuropathy on Body Sway and Slip Perturbation Detection in Older Population

Kim B. J., Robinson C. J.

International Journal of Occupational Safety and Ergonomics

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2006

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Vol. 12, No. 3

241--254

EN

Postural control is a common mechanism to compensate for unexpected displacements of the body. In the older population, a slip or fall due to a failure of postural control is a common cause of morbidity and mortality. The ability of postural control decreases with aging or neuropathy. In this study, 2 groups, diabetics and non-diabetics in the older population, were compared to determine how patterns of postural sway during quiet standing were related to the detection of perturbation. The SLIP-FALLS system was applied to the measurement of sway and detection of perturbation. In phase 1 of the development of the predictive model, neural network algorithms were applied to find determinant variables for perturbation detection. In phase 2, a fuzzy logic inference system was developed to investigate the relationship between sway and perturbation detection. Results of this study may be applied to the design of floor mats or shoe insoles for preventing fatigue in workplaces.