• 대한조선학회논문집
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• 제55권4호
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• pp.306-312
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• 2018

To navigate in ice-covered waters, the ice-breaking process is required. The ice-breaking mode depends on material properties of sea ice and ice conditions. The ice-breaking mode is classified into ramming and continuous ice-breaking. The ramming is effective on large ice features, such as thick ice ridge and icebergs, and the continuous ice-breaking is on level ice. In general, the impact time duration of crushing or bending on ice sheets is from 0.2 to 1.0 second. However, impact duration in ramming will be increased. The Korean ice-breaking research vessel ARAON conducted her research voyage in the Antarctic sea during the winter of 2012. The IBRV ARAON measured strain in ramming and continuous ice-breaking. Strain gauge signals were recorded during the planned ice-breaking performance and the unplanned ice transits in heavy ice conditions. The aim of this study is to investigate the ice load signals measured in ramming processes under the heavy ice condition. Based on the time history of the signals, a raising time, a half-decaying time and time duration were investigated and compared with the previous study which was suggested the five profiles of the ice load signals.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.667-679
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• 2020

As the LNG carrier operates in ice covered waters, it is key to ensure the overall safety, which is related to the coupling effect of ice-breaking process and internal liquid sloshing. This paper focuses on the sloshing simulation of the ice-breaking LNG carrier, and the numerical method is proposed using Circumferential Crack Method (CCM) and Volume of Vluid (VOF) with two main key factors (velocity νx and force Fx). The ship motion analysis is carried out by CCM when the ship navigates in the ice-covered waters with a constant propulsion power. The velocity νx is gained, which is the initial excitation condition for the calculation of internal sloshing force Fx. Then, the ship motion is modified based on iterative computations under the union action of ice-breaking force and liquid sloshing load. The sloshing simulation under the LNG tank is studied with the modified ship motion. Moreover, an ice-breaking LNG ship with three-leaf type tank is used for case study. The internal LNG sloshing is simulated with three different liquid heights, including free surface shape and sloshing pressure distribution at a given moment, pressure curves at monitoring points on the bulkhead. This present method is effective to solve the sloshing simulation during ice-breaking process, which could be a good reference for the design of the polar ice-breaking LNG carrier.

• 대한조선학회논문집
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• 제57권6호
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• pp.353-364
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• 2020

This paper presents the semi-analytical ice load calculation methods that are useful to simulate the ice-breaking process. Since the semi-analytical methods rely on the previously developed closed form equations or numerical analysis results, the user's exact understanding for the equations must be supported in order to use the methods properly. In this study, various failure modes of ice such as local crushing, in-plane splitting failure, out-of-plane bending failure and radial or circumferential cracking with rotation of the broken ice floe are considered. Based on the presented methods, the fracture modes were evaluated according to the size and thickness of ice. In addition, time series analysis for the ice-breaking process was performed on several ice conditions and the results were analyzed.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.796-808
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• 2019

In this paper, a Smoothed Particle Hydrodynamics (SPH) method is extended to simulate the ice failure process and ice-ship interactions. The softening elastoplastic model integrating Drucker-Prager yield criterion is embedded into the SPH method to simulate the failure progress of ice. To verify the accuracy of the proposed SPH method, two benchmarks are presented, which include the elastic vibration of a cantilever beam and three-point bending failure of the ice beam. The good agreement between the obtained numerical results and experimental data indicates that the presented SPH method can give the reliable and accurate results for simulating the ice failure progress. On this basis, the extended SPH method is employed to simulate level ice interacting with sloping structure and three-dimensional ice-ship interaction in level ice, and the numerical data is validated through comparing with experimental results of a 1:20 scaled Araon icebreaker model. It is shown the proposed SPH model can satisfactorily predict the ice breaking process and ice breaking resistance on ships in ice-ship interaction.

• 대한조선학회논문집
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• 제57권1호
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• pp.23-34
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• 2020

This paper covers the development of prediction techniques for ice load on ice-breakers operating in continuous ice-breaking under level ice conditions using particle-based continuum mechanics. Ice is assumed to be a linear elastic material until the fracture occurs. The maximum normal stress theory is used for the criterion of fracture. The location of the crack can be expressed using a local scalar function consisting of the gradient of the first principal stress and the corresponding eigen-vector. This expression is used to determine the relative position of particle pair to the new crack. The Hertz contact model is introduced to consider the collisions between ice fragments and the collisions between hull and ice fragments. In order to verify the developed technique, the simulation results for the three-point bending problems of ice-specimen and the continuous ice-breaking problem around a wedge-type model ship with bow angle of 20° are compared with the experimental results carrying out at Korea Research Institute of Ships and Ocean Engineering (KRISO).

• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.228-234
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• 2016

Recent icebreaking ships need to be designed to enhance not only icebreaking capability but also turning ability. For the evaluation of ice resistance induced by an icebreaking hull form, HHI (Hyundai Heavy Industries) has developed the hybrid empirical formulas (Park et al., 2015) by considering the geometrical hull shape features, such as waterline and underwater sections. However, the empirical formulas have inherent limits to the precise estimation of the icebreaking and turning ability because the breaking process and the resulting pattern are ignored. For this reason, numerical calculation in time domain is performed to predict the icebreaking process and pattern. In the simulation, varying crushing stress according to velocity vectors and contact areas between hull and ice is newly introduced. Moreover, the simulation results were verified by comparing them with the model test results for three different bow-first icebreaking models.

• 지질공학
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• 제32권1호
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• pp.113-126
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• 2022

북극해 아메라시아 분지(Amerasia Basin)에 속한 척치 해저평원(Chukchi Abyssal Plain)의 지구조 역사(tectonic history)는 혹독한 해빙 조건으로 인한 관측 부족으로 인하여 아직 밝혀지지 않았다. 지구조역사에 대한 여러 경쟁 가설들은 형성 시기로는 중생대에서 신생대까지, 지각 유형으로는 과도하게 확장된 대륙 지각에서 해양 지각까지, 형성 기작으로는 평행/부채꼴 균열에서 평행이동까지의 광범위한 범위를 갖는다. 2018년(ARA09C 항차)과 2021년(ARA12C 항차)에 쇄빙연구선 아라온을 이용해 해저평원의 수심 2,160~2,250 m 범위의 3개 정점에서 해양지각의 연령 결정에 필수적인 역할을 하는 해양지열의 관측이 이루어졌다. 해양지열 정점은 약 40 km에 걸쳐 확장축에 수직으로 위치한다. 퇴적물 코어 시료의 실험실 열전도도로부터 보정된 현장 열전도도를 사용하면, 관찰된 해양지열은 54~60 mW/m² 범위를 보인다. 해양지각을 가정할 때, 해양지열 관측결과는 형성 시기로서 후기 백악기(중생대)에 해당한다. 추정된 연대는 후기 중생대-신생대 동안 마카로프 분지가 열리면서 척치 해저평원 형성이 활성화되었다는 가설을 뒷받침한다. 이 시기는 동쪽으로 해저평원에 인접한 척치 보더랜드(Chukchi Border Land)의 열개 현상 발생과 동시대이다. 본 연구의 해양지열 관측결과로 퇴적물 내 가스하이드레이트 안정영역 하부(the base of the gas hydrate stability zone)의 위치가 추정되었고(332~367 mbsf), 이는 척치 고원(Chukchi Plateau)에서처럼 가스하이드레이트와 연관된 해저면 모사 반사면을 식별하는 데 도움이 될 것이다. 척치 해저평원의 정확한 형성 과정과 맨틀 열구조에 대한 이해를 높이기 위해 해양지열 관측을 포함한 추가적인 지구물리 탐사가 필요하다.

• 현장농수산연구지
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• 제11권1호
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• pp.137-158
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• 2009

This study is to find the causes of the current situations of conflict between generations in regards to succession of their family farm, for the target group of graduates Korea National Agricultural College of the year 2008 and their parents. This study aims at finding a way of controlling and solving the conflicts, and of developing a course of education and training, so that through this process they can come to a rational conclusion to the conflicts that arise regarding succession of the farm, in a climate of harmony and peace. It is found that communication between parents and graduates has normally gone on well, but specific problems related to management of the farm are often present. Furthermore, there is often lack of trust and promise between the parties which often causes difficulties in preparation for the succession of the farm. On the basis of these observation, we have designed and implemented an education workshop and training, as a program in which parents and their successors participated. As a result, we found it to be very effective, but it was also found to be in need of some changes. The workshop is to be implemented in two separate stages. The first stage should focus on communication and trust between family members. Firstly, they are given the opportunity to share the list of concerns withone another, as an ice breaking activity. Secondly, they can present their own hopes or wishes. And lastly, they can communicate with one another in an effort to find resolutions that will be keep both parties satisfied. The second stage should be aimed at establishing agreements concerning succession of the farm in a harmonious and peaceful manor; the second stage is also an opportunity to discuss 'Farm management and succession'. The Korea National Agricultural College (KNAC) is in the pursuit of fostering agricultural CEO's for the future of Korea. KNAC is currently implementing a very unique system of interviews in which parents participate together with students, in order to help them make a plan for rational management of their farm and smooth succession of the farm. Although KNAC now has students present a blueprint of their own unique business plans as a graduation thesis, it is necessary for KNAC to complement this system with education and training regarding the succession of family farms. Furthermore, KNAC should also develop an education and training program that is separate for this purpose, and make it a regular course of study of KNAC in the future.

• 현장농수산연구지
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• 제10권1호
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• pp.3-27
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• 2008

This study is to find the causes of the current situations of conflict between generations in regards to succession of their family farm, for the target group of graduates of the year 2008 and their parents. This study also aims at finding a way of controlling and solving the conflicts, and of developing a course of education and training, so that through this process they can come to a rational conclusion to the conflicts that arise regarding succession of the farm, in a climate of harmony and peace. It is found that communication between parents and graduates has normally gone on well, but specific problems related to management of the farm are often present. Furthermore, there is often lack of trust and promise between the parties which often causes difficulties in preparation for the succession of the farm. On the basis of these observation, we have designed and implemented an education workshop and training, as a program in which parents and their successors participated. As a result, we found it to be very effective, but it was also found to be in need of some changes. The workshop is to be implemented in two separate stages. The first stage should focus on communication and trust between family members. Firstly, they are given the opportunity to share the list of concerns withone another, as an ice breaking activity. Secondly, they can present their own hopes or wishes. And lastly, they can communicate with one another in an effort to find resolutions that will be keep both parties satisfied. The second stage should be aimed at establishing agreements concerning succession of the farm in a harmonious and peaceful manor; the second stage is also an opportunity to discuss 'Farm management and succession'. The Korea National Agricultural College (KNAC), as a state college, is in the pursuit of fostering agricultural CEO's for the future of Korea. KNAC is currently implementing a very unique system of interviews in which parents participate together with students, in order to help them make a plan for rational management of their farm and smooth succession of the farm. Although KNAC now has students present a blueprint of their own unique business plans as a graduation thesis, it is necessary for KNAC to complement this system with education and training regarding the succession of family farms. Furthermore, KNAC should also develop an education and training program that is separate for this purpose, and make it a regular course of study of KNAC in the future.