• Journal of the Korean Institute of Navigation
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• v.21 no.2
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• pp.11-17
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• 1997

In this paper, we studied to improve Inoue's[1] and Kijima's[2] model used to predict ship's manoeuvrability in initial design stage. To perform this work, we had PMM(Planar Motion Mechanism) test and rudder open water test for 12 Models of low-speed blunt-ship which have horn type rudder and bulb in afterbody. Using MMG(Mathematical Modelling Group) model, we analyzed hydrodynamic and MMG experimetnal coefficidnts used to search sensitivities and to estimate ship's manoeuvrability, adn the results are performed by the regression analysis of principle parameters. We varified them to analyze ship's manoeubbrability , had simulate manoeubrability to check revised MMG model and compared them wiht Inoue's method. the result of PMM test and sea trial. Then it is found that the revised method can predict the maneuverability more accurately even for an unstable ship.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.873-876
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• 1993

A fuzzy controller designed by mini-max-gravity(MMG) method is essentially nonlinear with respect to the controller's input and output relationship, and stability analysis is thus needed to construct a stable control system. This paper deals with a design method of a position-type MMG fuzzy controller stable in a sense of Lyapunov when considered is a single-input-single-output linear, stable plant. We first introduce a method to construct a Laypunov function by using an eigen-value of A matrix of the linear, stable plant dynamics and then we derive an asymtotic stability condition in terms of scale factors for fuzzy state variables and controller gain. The stability condition is found reasonably practical through comparing the theoretical stability region with that obtained from simulations.

• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.5
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• pp.525-536
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• 2017

Course keeping is hard to implement under the condition of the propeller stopping or reversing at slow speed for berthing due to the ship's dynamic motion becoming highly nonlinear. To solve this problem, a practical Maneuvering Modeling Group (MMG) ship mathematic model with propeller reversing transverse forces and low speed correction is first discussed to be applied for the right-handed single-screw ship. Secondly, a novel PID-based nonlinear feedback algorithm driven by bipolar sigmoid function is proposed. The PID parameters are determined by a closed-loop gain shaping algorithm directly, while the closed-loop gain shaping theory was employed for effects analysis of this algorithm. Finally, simulation experiments were carried out on an LPG ship. It is shown that the energy consumption and the smoothness performance of the nonlinear feedback control are reduced by 4.2% and 14.6% with satisfactory control effects; the proposed algorithm has the advantages of robustness, energy saving and safety in berthing practice.

• Journal of Ship and Ocean Technology
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• v.11 no.1
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• pp.11-24
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• 2007

Better prediction of a ship's manouevrabilty in initial design stage is becoming more, important as IMO manoeuvring criteria has been activated in the year of 2004. In the present study, in order to obtain more exact and reliable results for ship manoeuvrability in the initial design stage, numerical simulation is carried out by use of RANS equation based calculation of hydrodynamic forces exerted upon the ship hull. Other forces such as rudder force and propeller force are estimated by one of the empirical models recommended by MMG Group. Calculated hydrodynamic force coefficients are compared with those obtained by empirical models. Standard manoeuvring simulations such as turning circle and zig-zag are also carried out for a medium size Product Carrier and the results are compared with those of pure empirical models and manoeuvring sea trial. Generally good qualitative agreement is obtained in hydrodynamic forces due to steady oblique motion and steady turning motion between the results of CFD calculation and those of MMG model, which is based on empirical formulas. The results of standard manoeuvring simulation also show good agreement with sea trial results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.11a
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• pp.99-101
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• 2011

접이안 조선은 도선사들의 필수 업무에 해당하는 것이며 이에 대한 안전성 확보는 무엇보다 중요하다. 새로운 항만의 개발, 새로운 선형 선박의 등장 등으로 도선사가 접이안 하는 항만은 계속 그리고 빠르게 변화하고 있다. 이런 변화에 능동적으로 대처하여 도선사 개개인의 선박조종 능력을 함양할 수 있는 방법의 하나로서 도선사들이 쉽게 어디서나 접할 수 있도록 랩탑(laptop) 기반의 선박조종 시뮬레이터를 개발하였다. 도선사들이 다루는 선박에서는 통상의 정속의 항행속력이 아닌 저속에서의 선박 조종이 주가 되므로 이에 대하여 특별히 고려하여 선박모델을 개발하였다. 선박 텔러그래프의 해당 속력 및 그 속력에 도달하는 시간 등이 실선에 부합할 수 있도록 하였다. 선박은 일본의 MMG 모델을 기반으로 하였으며 실제 선박의 시운전 데이터를 참고하여 개발하였다. 실선박이 가진 시운전 자료는 공선의 경우가 많으므로 이에 대하여서는 각 도선사들의 자문을 받아 수정 보완하였다.

• Journal of Advanced Research in Ocean Engineering
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• v.4 no.2
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• pp.53-65
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• 2018

The load condition significantly influences ship maneuverability in calm water. In this research, the effect of the load condition on turning performance of a very large crude oil carrier (VLCC) sailing in adverse weather conditions is investigated by an MMG-based maneuvering simulation method. The relative drift direction of the ship in turning to the wave direction is $20^{\circ}-30^{\circ}$ in ballast load condition (NB) and full load condition (DF) with a rudder angle $35^{\circ}$ and almost constant for any wind (wave) directions. The drifting displacement in turning under NB becomes larger than that under DF at the same environmental condition. Advance $A_d$ and tactical diameter $D_t$ become significantly small with an increasing Beaufort scale in head wind and waves when approaching, although $A_d$ and $D_t$ are almost constant in following wind and waves. In beam wind and waves, the tendency depends on the plus and minus of the rudder angle.

• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.461-463
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• 2016

Information security and preservation of customer's data privacy are key factors for further wide spread adoption of microgrid (MG) technology. However, strong coupling between the operation cost of multi-microgrid (MMG) system and privacy of customer data makes it more challenging. A nested energy management system (EMS) has been proposed in this paper. The surplus/shortage information from the inner level MGs is included in processing the optimal operation of outer level MGs. This type of optimization ensures a layered privacy-preservation to customer at each MG level. The proposed EMS architecture is a better trade-off architecture between the operation cost of the MMG system and customer privacy-preservation at each level of MG.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.57-64
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• 2021

Maneuvering motions of a ship in calm water are studied through the concept of MMG model. Governing forces are defined by the use of available empirical formulae that require only main ship particulars as input variables. In order to validate the calculation tool, a full-scale sea experiment was carried out in Osaka Bay using a 17-m twin-screw passenger ferry. Test execution and data measurement were performed through the utilization of an autopilot control unit and satellite compass. The result of a straight running test confirms the acceptable accuracy in addressing the surge motion problem. Reasonable agreement between simulation and experiment is also confirmed for 5°/5° and 10°/10° zig-zag tests despite the strong environmental disturbance. The current model can generally represent the subject ship maneuvering motions and is promising for the application to other ship hulls.

• Journal of Navigation and Port Research
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• v.43 no.6
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• pp.369-376
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• 2019

Ship hydrodynamics in the confined waterways is challenging. When a ship is maneuvering in confined waterways, the hydrodynamic behavior may vary significantly because of the hydrodynamic interaction between the bottom of the ship hull and the seabed, or so-called shallow water effects. Thus, an accurate prediction of shallow water and bank effects is essential to minimizing the risk of the collision and the grounding of the ships. The hydrodynamic derivatives measured by the virtual captive model test provide a path to predicting the change in ship maneuverability. This paper presents a numerical simulation of captive model tests to predict the maneuverability of a ship in confined waterways. Also, straight and zig-zag simulation were conducted to predict the trajectory of a ship maneuvering in confined waterways. The results showed that the asymmetric flow around a ship induced by vicinity of banks causes pressure differences between the port and starboard sides and the trajectory of a ship maneuvering in confined waterways.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.8
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• pp.4137-4141
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• 2016

Background: A recent guideline by the American Cancer Society recommended that mammography (MMG) should be done for women starting in their mid-40s. In Thailand, information on opportunistic mammography screening is limited and data on the total incidence of breast cancer are also lacking. The purpose of this study was to estimate the breast cancer detection, incident and prevalence rates among Thai women. Materials and Methods: We retrospectively reviewed the opportunistic mammography screening of normal women between 30 and 80 years who underwent the procedure between 2001 and 2010. All cases were followed until 2012. The detection rate was calculated for the whole period of observation using 'number of women with positive findings' divided by 'total number of women screened'. The incidence rate was calculated only at the first MMG while the subsequence rate was calculated based on all new cases detected at each subsequent MMG. Results: Among the 47,430 women, there were 152,091 MMGs or approximately 3.2 occasions per person (range, 1-10). The average duration of the interval between each subsequence visit was 1.8 years. Overall, breast cancer was detected in 543 women, with a detection rate of 10.3 per 1,000 persons. The prevalence rate of breast cancer at the first visit was 5.78 per 1,000 persons. The incidence or new cases detected at any follow-up visit was 10.4 per 1,000 persons. The overall interval cancer was 0.91 per 1,000 women, mainly detected before their second and third MMG, with a rate of 0.0.47 and 0.76 per 1,000 women. Conclusions: Opportunistic mammography screening in Thailand detected 10 case of breast cancer from each 1,000 women. This paper indicated a high rate of cancer detection during a two year interval, hence, a screening mammogram should be performed more often.