• The Journal of Korean Physical Therapy
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• v.32 no.4
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• pp.238-244
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• 2020

Purpose: This study compared the effects of the fascial distortion model (FDM), foam rolling (FR), and self-stretching (SS) on the ankle dorsiflexion range of motion (ROM). Methods: Thirty subjects who had no more than 30° of ankle dorsiflexion ROM at the weight-bearing lunge test were recruited in this study. They were divided into three groups: (FDM, FR, and SS), and underwent each intervention for five minutes. Before and after the intervention, the ankle dorsiflexion ROM in the supine (the open-) and standing (the closed-kinetic chain) of the subjects were tested. The changes in the ROM between pre- and post-intervention and among the groups were analyzed. Results: All groups showed increased ankle dorsiflexion ROM after the intervention in both positions. In the position of the open kinetic chain, the changes in the ROM between pre- and post-intervention had significant differences among the groups, and the FDM was higher than the FR and SS. In the position of the closed kinetic chain, the ROM after the interventions and the changes in the ROM had significant differences among the groups, and FDM was higher than the FR (ROM after the intervention, the change in ROM) and SS (the change in ROM). Conclusion: These findings showed that FDM had more efficiency than the FR and SS as FDM had a stronger effect on increasing ankle dorsiflexion in a short, limited time. Clinicians who have limited time to treat their patients, particularly trying to increase ankle dorsiflexion ROM, should consider the application of FDM.

• Physical Therapy Rehabilitation Science
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• v.9 no.1
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• pp.1-9
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• 2020

Objective: This study aimed to investigate the immediate effects of intervention using neuromuscular control, self-stretching (SS), and neck stabilization exercises (NSEs) on neck pain, range of motion (ROM), and proprioception of position sense in adults with neck discomfort. Design: Three-group pretest-posttest design. Methods: Forty-four adults who complained of neck pain participated in the experiment. They were randomly assigned to the following groups: neuromuscular control exercise (NMCE) group (n=15), SS group (n=14) and NSE group (n=15). The NMCE group did rolling with only upper limb pattern on both sides. The SS group performed neck stretching on each side, 3 sets of 30 seconds for each muscle. The NSE group had the pressure biofeedback applied with increases in pressure by 2 mmHg at a time from 20-30 mmHg while in the hook-lying position. All groups performed exercises for 10 minutes. Neck pain, ROM, and proprioception were measured to determine differences between the intervention methods. Results: Intra-group comparisons showed significant improvement after exercise in pain, ROM, and proprioception in the NMC group (p<0.05). In the comparison between groups, the NMC group had a significant decrease in pain compared to the other two groups (p<0.05). There was no difference in ROM between the groups but the NMC group showed significant improvement in left rotation compared to the stabilization exercise group (p<0.05). For proprioception, the NMC group had significantly lower error than the other two groups (p<0.05). Conclusions: NMCEs through upper extremity pattern rolling exercise is effective in improving neck pain, ROM, and proprioception.

• Earthquakes and Structures
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• v.24 no.3
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• pp.217-235
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• 2023

Orthogonal pairs of rollers on concave beds (OPRCB) are a low-cost, low-tech rolling-based isolating system, whose high efficiency has been shown in a previous study. However, seismic performance of OPRCB isolators has only been studied in the two-dimensional (2D) state so far. This is while their performance in the three-dimensional (3D) state differs from that of the 2D state, mainly since the vertical accelerations due to rollers' motion in their beds, simultaneously in two orthogonal horizontal directions, are added up and resulting in bigger vertical inertia forces and higher rolling resistance. In this study, first, Lagrange equations were used to derive the governing equations of motion of the OPRCB-isolated buildings in 3D. Then, some regular shear-type OPRCB-isolated buildings were considered subjected to three-component excitations of far- and near-source earthquakes, and their responses were compared to those of their fixed-base counterparts. Finally, the effects of more realistic modeling and analysis were examined by comparing the responses of isolated buildings in 2D and 3D states. Response histories were obtained by the fourth-order Runge-Kutta-Nystrom method, considering the geometrical nonlinearity of isolators. Results reveal that utilizing the OPRCB isolators effectively reduces the acceleration response, however, depending on the system specifications and earthquake characteristics, the maximum responses of isolated buildings in the 3D state can be up to 40% higher than those in the 2D state.

• Journal of Navigation and Port Research
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• v.37 no.1
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• pp.55-61
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• 2013

In this paper, ship accidents are analyzed briefly and the main objective is to investigate a potential technological approach for risk assessment of vessel stability. Ship nonlinear motion equation and main parameters that induce ship capsizing in beam seas have analyzed, the survival probability of a ferry in random status have estimated and finally find out a risk assessment concept for ship's intact stability estimation by safe basin simulation method. Since a few main parameters are considered in the paper, it is expected to be more accurately for estimating ship survival probability when considering ship rolling initial condition and all other impact parameters in the future research.

• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.5-9
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• 2013

The aim of present study is to evaluate the stability of GM(Metacentric Height) calculation and investigate the damping effect of free rolling test. Moreover, GZ(Righting arm in stability) curve shows that it can provide reasonable design conditions for Fish boat. The roll damping characteristics of the improved model for an 7.9 ton class fishing boat are investigated through the free roll test in towing tank. The safety and boarding sensitivity are evaluated by GM calculation and roll motion period. Therefore, the results in this paper describe that the effect for improved hull is more improved than the original hull.

• Journal of Biosystems Engineering
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• v.21 no.3
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• pp.293-305
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• 1996

Effects on the tractor vibrations of tread, wheelbase and axle load distribution were analyzed by using mathematical models of tractor and random road surface. A 4 degrees of freedom tractor model was developed to predict the bounce, pitch and roll motions of tractor. The front axle which is constrained to roll with respect to tractor body was also included in the model. A random road profile was generated and used as an excitation input to the tractor. Output vibrations of the model were predicted and analyzed by a computer simulation method. In general, longer tread tends to reduce rolling and longer wheelbase does bouncing and pitching motions. Tractor vibrations were minimum when the ratio of front to rear axle loads was in the range of 30:70-35:65. Sensitivity analysis showed that rolling and pitching motions most sensitively varied with changes in tread and wheelbase while bouncing motion did with the location of mass center.

• Journal of Ocean Engineering and Technology
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• v.19 no.3
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• pp.25-30
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• 2005

To predict rolling performance for a barge-type FPSO, the evaluation of correct nonlinear roll damping is critical. The square section of FPSO causes a considerable viscous damping effect. Free roll decay tests were carried out to estimate nonlinear roll damping for a barge-type FPSO, under three different conditions. The roll motion RAO was deduced from model tests in the wave condition of the wideband spectrum. In numerical calculation, the quadratic damping was considered as equivalent linear damping, using the results of free roll decay test. Tested roll performance in the JONSWAP wave spectrum was compared with numerical results. These two results shaw good agreement, in spite of the proximity of peak wave period and roll natural period.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.4
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• pp.420-426
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• 1998

It is the purpose of this paper to make a preliminary study on the use of repetitive control to improve velocity accuracy by eliminating repetitive disturbances caused by machining inaccuracies of the axis of rotation location. If the control system can be intelligent enough to compensate for such machining errors, then one may be able to improve the accuracy of the velocity control, or alternatively, one may maintain the same accuracy and relax the machining tolerances required. This could decrease cost significantly. Experiments are performed testing repetitive control methods on a constant speed rolling operation testbed. The experimental results show very substantial decreases in the tracking error of the system. Spectral data of the output motion are given to demonstrate the attenuation of the disturbance frequencies and harmonics, related to the bandwidth being used. It is seen that the simplest form of repetitive control which is very easily implemented, can produce striking improvement in control system performance in such belt drive rolling operations, and the learning can be accomplished in a short time.

• Journal of the Korean Society of Visualization
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• v.9 no.3
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• pp.51-58
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• 2011

The purpose of the study is to provide a foundation in predicting a maximum wave force when the ocean structure is laid out under breaking wave. Experiments were conducted with a down-scaled cylindrical model installed in a wave generating water channel. Maximum wave slopes were changed in regular wave condition by the wave breaker in the water channel. Cylinder's diameters were changed to 0.1m and 0.05m, respectively. Using the PIV results qualitative analyses were performed based upon the previous knowledge.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.98-103
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• 2006

The hunting is the natural characteristics of the railway wheelset which is originated from the contact between the conical type wheel profile and rail. The critical speed of rolling-stock is called when the hunting is occurred, and it is closely connected with vehicle stability. The parameters which influence the hunting motion are like wheel profile, primary spring property and wheelset dimension, etc. The studies for these parameters are reported diversely. In this study, we aim to analyze the influence of parameters on hunting with the change of wheel profile produced by wheel wear and material property produce by aging of primary spring. For this, we made a dynamic model for wheelset and vehicle. Using these models, we analyzed the critical speed with the variations of the parameters like as wheel profile and primary spring property and we show the results.