• International Journal of Naval Architecture and Ocean Engineering
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• 제7권4호
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• pp.708-719
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• 2015

The two most important tasks of icebreakers are first to secure a sailing route by breaking the thick sea ice and second to sail efficiently herself for purposes of exploration and transportation in the polar seas. The resistance of icebreakers is a priority factor at the preliminary design stage; not only must their sailing efficiency be satisfied, but the design of the propulsion system will be directly affected. Therefore, the performance of icebreakers must be accurately calculated and evaluated through the use of model tests in an ice tank before construction starts. In this paper, a new procedure is developed, based on model tests, to estimate a ship's ice breaking resistance during continuous ice-breaking in ice. Some of the factors associated with crushing failures are systematically considered in order to correctly estimate her ice-breaking resistance. This study is intended to contribute to the improvement of the techniques for ice resistance prediction with ice breaking ships.

• 대한조선학회논문집
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• 제58권3호
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• pp.175-181
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• 2021

This study describes the model tests in ice according to the frictional coefficient of an ice-breaking ship and the change in ice resistance by the analysis method for each component of ice resistances. The target vessel is a 90K DWT ice-breaking tanker capable of operating in ARC7 ice conditions in the Arctic Ocean, and twin POD propellers are fitted. The hull was specially painted with four different frictional coefficients on the same ship model. The total ice resistance can be separated by ice breaking, ice buoyancy, ice clearing resistances through the tests in level ice, pre-sawn ice and creep test in pre-sawn ice under sea ice thickness of 1.2 m and 1.7 m. Ice resistance was analyzed by correcting the thickness and bending strength of model ice by the ITTC correction method. As the frictional coefficient between the hull and ice increases, ice buoyancy and clearing resistances increase significantly. When the surface of the hull is rough, it is considered that the broken ice pieces do not slip easily to the side, resulting in an increase in ice buoyancy resistance. Also, the frictional coefficient was found to have a great influence on the ice clearing resistance as the ice thickness became thicker.

• 대한조선학회지
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• 제26권2호
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• pp.1-12
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• 1989

본 논문에서는 선체로부터 멀리 전파해 나아가는 선형파와 선체 가까이에 존재하는 쇄파로 인한 조파저항성분을 최소화시키는 방법을 보여준다. 본 방법은 선형조파저항의 최적화 방법과 시험자료 분석을 통한 쇄파저항의 통계적 최적화방법으로 구성된다. 응용목적으로서, 수선형상이 포물선이고 측면이 수직한 모형을 기본선형으로 택하였고, 선형파를 최적화하는 방법과 경험적인 방법을 통하여서 선체전반부의 횡단면적 곡선을 변화시킨 두척의 수정모형선을 얻었다. 3척의 선형에 대한 시험 및 분석결과로부터 선체전반부의 횡단면적 곡선의 변화에 따른 선형파저항과 쇄파저항과의 상관관계를 살펴보았다. 본 방법으로 선체전반부가 최적화된 선형은 설계속도($F_n=0.26$)에서 기본선형에 비하여 약 47%의 조파저항감소를 보이고 있다.

• 전기학회논문지
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• 제56권9호
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• pp.1566-1570
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• 2007

[ $SF_6$ ] gas circuit breakers are widely used for short circuit current interruption in EHV(Extra High Voltage) or UHV(Ultra High Voltage) power systems. To develop $SF_6$ gas circuit breakers, the arc resistance value is necessary to compare experimental results to numerical ones. The arc resistance value can be obtained from a breaking test with a $SF_6$ gas circuit breaker. The direct testing or synthetic testing facility is widely used to verify the breaking ability for $SF_6$ gas circuit breakers. We employed the simplified synthetic testing facility to test a $SF_6$ gas circuit breaker prototype. The arc resistance characteristic was measured and calculated under the various experimental conditions. This arc resistance value can be used for verifying the numerical results from arc simulation in a circuit breakers.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권6호
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• pp.613-623
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• 2017

A semi-empirical model to predict ship resistance in level ice based on Lindqvist's model is presented. This model assumes that contact between the ship and the ice is a case of symmetrical collision, and two contact cases are considered. Submersion force is calculated via Lindqvist's formula, and the crushing and breaking forces are determined by a concept of energy consideration during ship and ice impact. The effect of the contact coefficient is analyzed in the ice resistance prediction. To validate this model, the predicted results are compared with model test data of USCGC Healy and icebreaker Araon, and full-scale data of the icebreaker KV Svalbard. A relatively good agreement is achieved. As a result, the presented model is recommended for preliminary total resistance prediction in advance of the evaluation of the icebreaking performance of vessels.

• 한국강구조학회 논문집
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• 제8권3호통권28호
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• pp.47-54
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• 1996

Recently Sucessive progress in train technic has enabled us to constructed high-speed railways for ourselves. This caused more rapid train more pressure on a track and speedier track break-down. Especially in the construction of high-speed rails for high-speed traveling and safety accurate breaking distance is essential and not only computation of rolling resistance in theory but also verification through real measurement are important in basic material for breaking and starting load caused during the train running. In this study, we measured traveling resistance and calculated traveling resistance formula in the case of the SAEMA-EUL which consists of main part of current passenger trains and frights in this country.

• The Plant Pathology Journal
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• 제22권3호
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• pp.265-270
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• 2006

Cultivated hot pepper crops showing severe mosaic symptom were found in Korea in 2004 and their causal agent was identified as Cucumber mosaic virus (CMV). These pepper crops was resistant to the virus in the filled, and they belonged to pathotype 0 (P0) resistant pepper. Resistance screening of selected pepper plants showed that a pepper isolate of CMV was the P0 resistance-breaking virus. This P0 resistance-breaking isolate of CMV, named as Ca-P1, was isolated from leaves of the virus-infected Capsicum annuum cv. Manidda that showed systemic severe mosaic symptom. Ca-P1-CMV could induce systemic mosaic symptoms on P0-susceptible (P0-S) and P0-resistant (P0-R) cultivars whereas an ordinary strain (Fny-CMV) could not infect P0-R. This result suggests that Ca-P1-CMV can overcome P0 resistant pepper cultivars. To analyze its genome sequence, the complete nucleotide sequence of RNA3 of Ca-P1-CMV was determined from the infectious full-length cDNA clone of the virus. RNA3 of Ca-P1-CMV consisted of 2,219 nucleotides. Overall sequence homology of RNA3-encoded two viral proteins (movement protein and coat protein) revealed high similarity (75.2-97.2%) with the known CMV strains. By sequence analysis with known representative strains of CMV, Ca-P1-CMV belongs to a typical member of CMV subgroup IB. The resistance and resistance-breaking mechanisms of pepper and counterpart CMV, respectively, remain to be investigated, which will enrich the genetic resources and accelerate CMV-resistant pepper breeding programs.

• 한국의류학회지
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• 제36권6호
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• pp.583-591
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• 2012

This study selected three model designs used for air injection type welding clothes designed for insulation purposes and analyzed the performance of each design. The bending characteristics were analyzed in order to identify the flexibility of the welded areas; subsequently, the seam breaking strength and water pressure resistance were analyzed to identify the bonding strength. In addition, two types of waterproof fabric, polyurethane (PU) coated 2 layer and PU laminated 2 layer fabrics, were used for a performance analysis, according to fabric processing specifications. The circle type showed the highest flexibility in the terms of bending characteristics that influence wearability and were followed by the wave and the straight type. In terms of breaking strength, the straight type showed the highest breaking strength, followed by the wave and the circle type. The water pressure resistance analysis found that the wave type was superior to the straight type in terms of water pressure resistance. The wave type is deemed to be a design type suitable for maximizing performance, provided that the issue of stabilization in the welding production process is addressed. Looking at the bending characteristics of waterproof fabric for each specification, the laminating waterproof cloth outperformed the coated waterproof cloth in terms of flexibility. However, in terms of seam breaking strength, the coated waterproof cloth outperformed the laminated cloth. In contrast, the water pressure resistance of the laminated waterproof fabric was found to be higher than the coated waterproof fabric, leading to the conclusion that the bonding strength of the laminated waterproof fabric is higher than that of the coated waterproof fabric based on the assumption of injecting air.

• 대한토목학회논문집
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• 제31권4B호
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• pp.323-332
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• 2011

하천에서 수목의 관리를 위해서는 수목이 홍수에 미치는 영향이나 생태적 특성을 고려하여 대책을 수립하여야 한다. 수목에 의한 수리학적 영향은 통수능 감소와 유수력에 의한 전도로 인한 하류 하천시설물의 기능 저해이다. 현장 인발시험은 수목이 전도될 때의 최대 저항력을 측정하여, 하천 내의 수목이 외력에 저항하는 정도를 파악하기 위해 시행하였다. 수목의 전도모멘트를 파악하기 위한 인자는 수목의 외형적 특성인 수종, 흉고직경, 수고 등이며, 본 연구에서는 전도모멘트와 흉고 직경의 상관관계를 이용하였다. 수목의 한계 전도모멘트는 흉고직경 4.9-32.8 cm의 관목과 교목 100주를 바탕으로 검토되었다. 교목과 관목을 함께 고려할 경우에는 흉고직경과 한계 전도모멘트의 상관관계를 도출하기 어려웠다. 그러나 교목만을 고려할 경우에는 흉고직경과 한계 전도모멘트 사이에 일정한 상관관계가 있음을 확인하였다.

• 한국해양공학회지
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• 제24권1호
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• pp.116-122
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• 2010

The aim of this study is to examine the effects of shape and plane arrangement of submerged breakwaters on 3-D wave breaking characteristics over them. First, the numerical model, which is able to consider the flow through a porous medium with inertial, laminar, and turbulent resistance terms, i.e. simulate directly WAve Structure Seabed/Sandy beach interaction, and can determine the eddy viscosity with a LES turbulent model in a 3-Dimensional wave field (LES-WASS-3D), has been validated by a comparison with Goda's equation for breaking wave heights. And then, using the numerical results, the wave breaking points over the crest of submerged breakwaters have been examined in relation to the shape and plane arrangement of submerged breakwaters. Moreover, the wave height distribution and upper flow around submerged breakwaters have been also discussed, as well as the distribution of the wave breaking points over the beach.