• International Journal of Naval Architecture and Ocean Engineering
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• v.12 no.1
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• pp.491-500
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• 2020

The present study proposes a time domain model for the Vortex-induced Vibration (VIV) simulation of a catenary riser under the combination of the current and oscillatory flow induced by vessel motion. In this model, the hydrodynamic force of VIV comprises excitation force, hydrodynamic damping and added mass, which are taken as functions of the non-dimensional frequency and amplitude ratio. The non-dimensional frequency is related with the response frequency, natural frequency, lock-in range and the fluid velocity. The relatively oscillatory flow induced by vessel motion is taken into account in the fluid velocity. Considering that the added mass coefficient and the non-dimensional frequency can affect each other, an iterative analysis is conducted at each time step to update the added mass coefficient and the natural frequency. This model is in detail validated against the published test models. The results show that the model can reasonably reflect the effect of the added mass coefficient on the VIV, and can well predict the riser's VIV under stationary and oscillatory flow induced by vessel motion. Based on the model, this study carries out the VIV simulation of a catenary riser with harmonic vessel motion. By analyzing the bending moment near the touchdown point, it is found that under the combination of the ocean current and oscillatory flow the vessel motion may decrease the VIV response, while increase the excited frequencies. In addition, the decreasing rate of the VIV under vessel surge is larger than that under vessel heave at small vessel motion velocity, while the situation becomes opposite at large vessel motion velocity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.3
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• pp.326-333
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• 2014

This study was conducted to investigate the fishing efficiency of an improved LED fishing lamp for squids. A total of 31 fishing operations were carried out with six-crew commercial fishing vessel Haengbok-Ho (24 tons) on which 43.2kW LED was installed, along with 14 automatic jigging machines, from October 6 to November 16, 2012. The 19 fishing vessels with Haengbok-Ho were compared with a control subject was 24 tons or 29 tons. A total illuminating power of metal halide (MH) fishing lamps in the control fishing vessel was either 84kW or 120kW. The number of automatic jigging machines in the control vessels was 8-18 and the number of crews engaged for fishing operation was 3-13. Average fuel consumption of LED fishing vessels during fishing operation was 505.1l which led to an average fuel consumption of 42.7l per hour. LED fishing vessel and MH fishing vessel caught on an average 1,946 squids and 2,439 squids, respectively, during the study period. Crews (hand line and hand reel) caught about 2.2 times the automatic jigging machines for LED fishing vessel and about 2.1 times for MH fishing vessel. Meanwhile, catches by the fishing vessels with LED in the combined total number per one line of automatic jigging machine and per crew were 86.6% of that of the control fishing vessel with MH. Also, fishing vessels with LED per automatic jigging machine achieved 71.8% of catches of that with MH fishing lamp. The catches of squids per the fishing vessel with 1W LED fishing lamp were higher by more than 135.5% of that in the fishing vessel with MH, which showed a good fishing performance even with only the use of a LED fishing lamp.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.4
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• pp.401-409
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• 2021

In this study, an improvement plan was derived by statistically analyzing the system and current status of tests in Korea and survey of seafarers perception in order to improve the expertise of the Korean fishing vessel officer examination. Recently, about 70% of marine accident occurs from fishing vessels. Therefore, it's necessary to improve the examination to reduce marine accidents. As a result, it was identified that an average of 29,265 applicants have applied over the past four years, and among them, 1,833 people have applied for fishing vessel licenses, accounting for 6.3% of the total. According to the result of explanation and response of 115 people, they responded that practical utilization was low, each operation waters has different requirements and it's necessary to improve the contents of the questions for the specialty subject. In addition, inappropriate questions were found in previous exams. To reduce marine accidents caused by human error and to improve the professionalism of fishing vessel officers, it is necessary to adjust the test criteria and ratio with characteristics of fishing vessels and in the long run, institutional improvements such as the distinction between test subjects and licenses are needed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.4 s.247
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• pp.314-319
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• 2006

To analyze in-vivo blood flow characteristics in a chicken embryo, in-vivo experiment was carried out using micro-PIV technique. Because endothelial cells in blood vessels are subject to shear stress of blood flow, it is important to get velocity field information of the placental blood flow. Instantaneous velocity fields of an extraembryonic blood vessel using a high-speed camera and intravital microscope. The flow images of RBCs were obtained with a spatial resolution of $20\times20{\mu}m$ in the whole blood vessels. The mean velocity field data confirm that the blood flow does show non-Newtonian fluid characteristic. The blood in a branched vessel merged smoothly without any flow separation into the main blood vessel with the presence of a slight bump. This in-vivo micro-PIV measurement technique can be used as a powerful tool in various blood flow researches.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.2
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• pp.153-160
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• 2013

Control allocation is an important part of a system. It implements the function that map the desired command forces from the controller into the commands of the different actuators. In this paper, the authors present an approach for solving constrained control allocation problem in vessel system by using multi-parametric quadratic programming (mp-QP) algorithm. The goal of mp-QP algorithm applied in this study is to compute a solution to minimize a quadratic performance index subject to linear equality and inequality constraints. The solution can be pre-computed off-line in the explicit form of a piecewise linear (PWL) function of the generalized forces and constrains. The efficiency of mp-QP approach is evaluated through a dynamic positioning simulation for a vessel by using four tugboats with constraints about limited pushing forces and found to work well.

• Journal of Biomedical Engineering Research
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• v.41 no.5
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• pp.210-218
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• 2020

Vessel sealing is a medical device that converts electrical or ultrasonic energy into thermal energy and leads to seal, coagulate, and cut the vessel by protein modification within the walls or surrounding connective tissues. As most of surgeries have recently been conducted with minimally invasive surgery, the demand and market for vessel sealing are expected to get bigger. However, there is a problem that electrosurgical or ultrasonic surgical is applied and we have a high risk to evaluate the strength of seal, because the collateral and particular standards currently in force follows have not been establish. Therefore, in this study, we investigated some papers studied on the efficacy and safety of the device, the guidance of FDA and test papers previously conducted from 3 individual subject device made in Korea. We found there is a relationship between burst pressure and the performance of the device, therefore, we propose the vascular bursting pressure test for evaluating the safety and performance of the vessel sealing.

• Journal of Navigation and Port Research
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• v.31 no.2
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• pp.127-132
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• 2007

The primary purpose of this study is to examine empirically the effect of the organizational characteristics in the vessel with foreign crews on their self-efficacy and organization commitment. Currently, the restrictions on the employment of the foreign crews are being eased in the Korean shipping industry and many problems are occurring consequently. However, specific and empirical studies on the relevancy of organizational characteristics to the crew's self-efficacy and organizational commitment on board the vessels with combined crews have not yet been carried out. To solve these problems, we examined how the organizational characteristics such as communication and leadership trust of different language and culture related to vessels with combined crews influence on the self-efficacy, job satisfaction and organizational commitment of the foreign crews through SEM analysis. According to the results, hypothesis 1, 2 and 3 were all supported with statistical significance. That means that communication and leadership trust of the vessel with foreign crew had positive effects on their self-efficacy and that such self-efficacy also had a positive effect on the organizational commitment and job satisfaction. To conclude, this study suggests that foreign crew's self-efficacy should be firstly enhanced in order to improve organizational commitment on the vessel with combined crews. Furthermore, studies on self-efficacy of foreign crew's organization are urgently needed to enhance the effectiveness of an organization in a vessel with combined crews that has special environment - working environment with depression and uneasiness due to the exposure to the different language and culture, and excessive stress from the social and psychological adaptation. Therefore, an attempt of this study is considered to be timely since there has not been a study on this subject so far and result of this study will contribute a lot to the organization management of a vessel with combined crews.

• The Journal of Korean Physical Therapy
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• v.25 no.3
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• pp.126-131
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• 2013

This case report described a single case of adult stoke patient due to Moyamoya disease through long-term follow-up observation, which included his demographics, brain images, and change of motor function and functional activities. The subject was the 54-year-old male diagnosed with left hemiparesis from a stroke due to multifocal encephalomalacia in both hemispheres. At the time of the stroke attack, he took brain surgery intervention including external ventricular drain. Physical and occupational therapy for stroke rehabilitation were admitted including muscle strengthening exercises, functional activity/ADL training, neurofacilitative techniques with bobath or proprioceptive neuromuscular facilitation concepts, and compensatory strategy. Patient's MRI showed that right frontal lobe, right peri-ventricular area, left parietal, and left occipital lobes were damaged, and MRA showed that abnormal collateral vessel was richly developed in both hemispheres by occlusion of proximal internal carotid arteries in both sides. His motor strength was improved from poor to good grade in all of upper and lower limb motions, that MBC was improved from stage 1 to stage 5. In FAC and barthel index, at the initial evaluation, he could not perform any functional movement, but his FAC and barthel index were on 3 and 14 points at present, respectively. During long-term follow-up for approximately 4 years, the subject's functional motor ability was improved, as similar with recovery progression of usual stroke patient. We believe that this single case report will provide clinical information and concern regarding Moyamoya disease with physical therapist, in terms of such as epidemiology, pathogenesis, diagnostic procedures, clinical features, recovery process, and prognosis.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.767-774
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• 2017

Maritime traffic safety audits (MTSA) were enacted in order to ensure marine traffic safety throughout changes or the construction of water facilities, port facilities, etc. After the introduction of MTSA, the scope of subject vessels was restricted to an LOA of more than 100 m or a maximum speed of more than 60 knots as of 2014. In this study, the scope of subject vessels was re-examined in comparison with specific marine traffic safety areas and tanker prohibited areas identified in the maritime safety act. Furthermore, the state of subject vessels and exception cases for MTSA were also analyzed. As a result of these analyses, MTSA were deemed necessary for dangerous goods carriers of more than 1,000 G/T in specific marine traffic safety areas and dangerous goods carriers of more than 794 G/T in tanker prohibited areas. Finally, the necessity of further review was suggested given the present scope of subject vessels.

• Journal of Electrical Engineering and Technology
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• v.12 no.6
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• pp.2365-2377
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• 2017

This paper addresses two interrelated problems concerning the tracking control of pod propulsion unmanned surface vessel (USV), namely, the modeling of pod propulsion USV, and tracking controller design. First, based on MMG modeling theory, the model of pod propulsion USV is derived. Furthermore, a practical adaptive neural tracking controller is proposed by backstepping technique, neural network approximation and adaptive method. Meanwhile, unlike some existing tracking methods for surface vessel whose control algorithms suffer from "explosion of complexity", a novel neural shunting model is introduced to solve the problem. Using a Lyapunov functional, it is proven that all error signals in the system are uniformly ultimately bounded. The advantages of the paper are that first, the underactuated characteristic of pod propulsion USV is proved; second, the neural shunting model is used to solve the problem of "explosion of complexity", and this is a combination of knowledge in the field of biology and engineering; third, the developed controller is able to capture the uncertainties without the exact information of hydrodynamic damping structure and the sea disturbances. Numerical examples have been given to illustrate the performance and effectiveness of the proposed scheme.