• Journal of Ocean Engineering and Technology
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• v.33 no.4
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• pp.313-321
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• 2019

The prediction of the hydrodynamic performance of a planing hull vessel is an important and challenging topic for computational fluid dynamic (CFD) applications to naval hydrodynamics. In this paper, the resistance and planing attitude analysis for a Fridsma hull, which is a prismatic planing hull, in still water are numerically studied using OpenFOAM. OpenFOAM is an open source code package based on C++ libraries and the finite volume method (FVM) for the discretization of the RANS equation. The volume of fluid method (VOF) is used to capture the water-air interface and the SST ${\kappa}-{\omega}$ model is used for the turbulence simulation. The overset mesh method is used to capture the large motion of the hull at higher speeds. Before the extensive analysis, uncertainty analyses using various time steps and grid sizes were performed for one ship speed case of Fn = 1.19. The results of the present study are compared with those of a model test, other CFD research, and Savitsky's empirical formula. The results of the present study, following the trend of other CFD results, slightly over predict the resistance and under predict the sinkage and, more significantly, the trim.

• Journal of the Korean Society of Radiology
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• v.8 no.2
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• pp.89-96
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• 2014

This paper tries to examine whether the application of joint mobilization to subjects who have the forward head posture due to malalignment in the cervical joint has influence on posture changes and functions in the cervical joint. The subjects were 39 students from G University in Gyeongsangbuk-do. The cervical joint mobilization was applied to 20 subjects and not to 19. The students with a cervical lordosis angle of $21^{\circ}C$ or less, an anterior weight bearing (AWB) of 15mm or greater, and a cervical extension ROM of $70^{\circ}C$ or less in terms of radiography were selected as subjects under their voluntary agreement. The patients actively performed the joint mobilization slowly 8 times per session while therapists continuously applied sustained accessory glide to their painful joints 3 times per week for 4 weeks along with the cervical expansion and flexion in SNAGS among other Mulligan's (1995) techniques. The measurement was carried out in terms of radiographic inspection and neck disability indexes. As a result of the experiment, it turned out that the subjects with the forward head posture had changes in the cervical AWB and ARA, the ranges of expansion and flexion, and the NDI(Neck Disability Index) after the intervention for the experimental group by applying cervical joint mobilization. There were no changes observed in the control group. In conclusion, the application of joint mobilization turned out to have influence on the improvement of cervical joint postures, and craniocervical region functions.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.401-414
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• 2018

Planing hull type ships are often equipped with interceptor or trim tab to improve the excessive trim angle which leads to poor resistance and sea keeping performances. The purpose of this study is to design a controller to control the attitude of the ship by controllable stern interceptor and validate the effectiveness of the attitude control by the towing tank test. Embedded controller, servo motor and controllable stern interceptor system were equipped with planing hull type model ship. Prior to designing the control algorithm, a model test was performed to identify the system dynamic model of the planing hull type ship including the stern interceptor. The matrix components of model were optimized by Genetic Algorithm. Using the identified model, PID controller which is a classical controller and sliding mode controller which is a nonlinear robust controller were designed. Gain tuning of the controllers and running simulation was conducted before the towing tank test. Inserting the designed control algorithm into the embedded controller of the model ship, the effectiveness of the active control of the stern interceptor was validated by towing tank test. In still water test with small disturbance, the sliding mode controller showed better performance of canceling the disturbance and the steady-state control performance than the PID controller.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.6
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• pp.674-680
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• 2013

As the range of marine leisure activity gradually expands to ocean-going, a habitable cruise boat has been getting the limelight. Advanced countries in the marine leisure industry in Europe and North America have already secured their competitiveness in designing and building cruise boats by elegant design, ergonomic structure and fuel efficiency through the adoption of light-weight hull materials. In contrast, mostly small power boats are developed and built in Korea, and GFRP take up the most of hull materials. This study inquired into the design and characteristics of a 50ft-class CFRP that ocean-going is possible. The hull-form of the CFRP cruise boast were analyzed to propose a hull form for the designed ship (MMU-C.B), and based on that, the design model of the MMU-C.B was built. Finally, the MMU-C.B's characteristics of the resistance performance and hull-planing were found by comparative reviews with the results of model tests of GFRP pleasure yachts.