• Journal of Advanced Marine Engineering and Technology
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• v.40 no.3
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• pp.185-190
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• 2016

Damages of the main engine aftmost bearing and the after stern tube bearing tend to increase due to misalignment. And as the shafting system becomes stiffer due to the large engine power, whereas the hull structure becomes more flexible due to optimization by using high tensile thin steel plates. And this is the reason that more sophisticated shaft alignments are required. In this study, the optimum shafting alignment calculation was carried out, considering the thermal expansion effect, exploiting the sensitivity index, which indicates the reasonable position of forward intermediate shaft bearing for shaft alignment. and as the main subject in this study, the elastic deformation on intermediate shaft and main engine bearings occurred by vertical load of shaft mass were examined thoroughly and analyzed allowable load of bearings, reaction influence numbers of all bearings. As the result, a reliable optimum shafting alignment was derived theoretically. To verify these results, they were referred to the engine maker's technical information of main engine installation and being used shafting alignment programs of both Korean Register of Shipping and Det Norske Veritas, their reliability were reviewed.

• Explosives and Blasting
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• v.31 no.2
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• pp.6-13
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• 2013

Recently, complaints or environmental problems caused by the noise and dust generated from crusher of the mine and quarry are emerging. Therefore mining facilities such as crushers and mills have been installed in an underground. In order to facilitate crusher equipments in the underground, excavation of large space is required and then the stability of the large space underground structure is an important issue. In this study, the blast experiments, which use a block of the limestone, are performed. Based on the blast experiments, the numerical model was prepared and simulated using dynamic fracture process analysis code(DFPA) with considering the rising time of applied borehole pressure and microscopic tensile strength variation. Comparing the non-dimensional crack length and no-dimensional tensile strength obtained from blast experiments and numerical analyses, the input parameters of DFPA code for predicting a radial tensile crack in limestone blasting were determined.

• Journal of Navigation and Port Research
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• v.29 no.6 s.102
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• pp.529-536
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• 2005

Recently the building of ultra large container ship are discussed among ship building companies and ship operating company who have a tendency to pursue the advantage of large scale of economy. These tendency will be continued for the time being, if ship-building skill and economical efficiency are available. As the enlargement of container ship size becomes hot issues in ship-building markets, the needs for re-arrangement of accommodation house in large container ship are proposed carefully in some researches. This study examined economical efficiency of re-arrangement of accommodation house in ultra large container ship. The separation between accommodation and engine room is proposed through out drawing works in initial design stage and we examined the merits and demerits of the separation in the view of economical efficiency. The RFR(Required Freight Rate) is considered as the objective function to evaluate the re-designed vessel. The economical benefits are analyzed in the view of ship operator and shipyard respectively.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.71-76
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• 2005

Many sea accidents such as collisions and groundings of vessels were occurred due to the lack of sufficient manoeuvring capability of vessels. Therefore IMO adopted 'The interim standards of ship manoeuvrability by Resolution A.751(18) and the standards have been applied to vessels of 100m or more in length and all chemical tankers and gas carriers regardless of the length, which were constructed on or after 1 July 1994. The IMO manoeuvrability standards are divided into three kinds as bellows; (1) Turning capability standards : Estimated values in design stage are to be certified by turning circle test of the actual vessel. (2) Course keeping quality standards : Estimated values in design stage are to be certified by $10^\sqsubset\;and\;20^\sqsubset$ Zig-Zag tests of the actual vessel. (3) Shortest stopping distance standards : Estimated values in design stage are to be certified by the shortest stopping distance tested by the actual vessel. In this paper, the authors computed the values of the manoeuvring standards of several vessels from their original design and compared them with those results from experiments of the model ships and also examined the values and concluded about the validity of IMO Manoeuvrability standards.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.325-332
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• 2005

As ship builder companies have a tendency to pursuit the effect of scale economy, recently the ultra-large sized container ship is discussed very actively among them. It is expected that these situation will be continued for the time being. The need of accommodation re-arrangement is carefully proposed according to the tendency of ultra-large sized ship. In this paper, accommodation re-arrangement of ultra-large container ship is examined in the view of economy. We proposed separation of engine room and accommodation part through review and supplementaition of drawing generation in intial design stage. Also we investigated its merits and demerits to find out whether it can be realized or not in the view of economical efficiency. The RFR(Required Freight Rate) is considered as the objective function to evaluate the re-designed vessel. The economical benefits for increasing the number of TEU(Twenty-foot Equivalent Units)'s and the re-arranged space are analyzed in the view of ship owner and shipyards respectively.

• Tribology and Lubricants
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• v.28 no.6
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• pp.265-271
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• 2012

In the preceding Part I study, for improving the unbalance response vibration of a large PRT motor-generator rotor fundamentally by design, a series of design analyses were carried out for bearing improvement by retrofitting from original plain partial journal bearings, applied for operation at a rated speed of 1,800 rpm, to final tilting pad journal bearings. To satisfy evenly key basic lubrication performances such as the minimum lift-off speed and maximum oil-film temperature, a design solution of 5-pad tilting pad journal bearings and maximizing the direct stiffness by about two times has been achieved. In this Part II study, a detailed rotordynamic analysis of the large PRT motor-generator rotor-bearing system will be performed, applying both the original plain partial journal bearings and the retrofitted tilting pad journal bearings, to confirm the effect of rotordynamic vibration improvement after retrofitting. The results show that the rotor unbalance response vibrations with the tilting pad journal bearings are greatly reduced by as much as about one ninth of those with the plain partial journal bearings. In addition, for the tilting pad journal bearings there exist no critical speed up to the rated speed and just one instance of a concerned critical speed around the rated speed, whereas for the plain partial journal bearings there exist one instance of a critical speed up to the rated speed and two instances of concerned critical speeds around the rated speed.

• Journal of the Korean Geotechnical Society
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• v.28 no.11
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• pp.53-67
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• 2012

In this research, stainless steel and heat-shrinkage tube were used for new TDR sensing line to solve the problems of ordinary TDR system. The new TDR line improved the sensitivity of water content and endurance, and reduced the data noise. The saturation degree test and acryl model test were done by revised TDR sensor. From the results, without additional data filtering and quantitative analysis, the raw data were separated into 3 zones; saturated, unsaturated and dried zones easily. In addition, the revised TDR sensor was installed in large-scale embankment model to perform the seepage test. The raw data of the model tests showed the distributed seepage behaviors and separated zones clearly, which were almost the same tendencies as the lab test results.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.154.2-154.2
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• 2011

행성 및 타이탄과 같은 태양계 내의 면천체(extended source)를 관측하기 위해서는 공간분해능이 높은 대형망원경과 파장분해능이 높은 분광기가 필요하다. 특히 분광 관측 자료를 이용하면 행성 및 타이탄의 대기 구성 성분 및 그 성분비, 온도 분포, 구름과 연무 등의 수직 구조 등을 알 수 있다. 최근 연구에서는 구름, 연무, 비 등의 생성 과정에 불포화/초과포화 상태의 메탄, 에탄, 에틸렌 등이 관여하는 것이 새롭게 알려져 보다 활발한 후속 연구가 필요하다. 현재 개발 중인 IGRINS는 적외선 영역의 H band($1.49{\sim}1.8{\mu}m$)와 K band($1.96{\sim}2.46{\mu}m$)를 동시에 관측할 수 있고, McDonald 2.7m 망원경에 부착할 때 R~40,000의 높은 분해능을 가지는 장비로서 태양계 천체를 관측하는 데에 매우 적합하다. 따라서 향후 IGRINS가 본격적으로 가동될 때 얻을 수 있는 자료에 대한 사전 연구가 필요하며, 이는 대형 망원경 및 고분산 분광기를 이용한 관측, 자료 처리 및 분석 등의 경험에 기반을 두어 진행되어야 한다. 이에 NIFS/Gemini에 의해 관측된 타이탄 분광 자료와 TEXES/IRTF에 의해 획득된 목성극지방의 분광 자료를 분석하는 사전 연구를 진행하고 있다. 목성에 대해서는, 극지방에서 관측되는 hotspot, warm, normal 지역의 근적외선 영역 분광선 분석을 통해 기존에 결정되어 있지 않은 극지방 성층권의 고도에 따른 온도분포를 알아본다. 타이탄에 대해서는, 근적외선 영역의 메탄흡수밴드에서 관측된 주연증광(Limb brightening) 현상을 복사전달모델로 구현함으로써 어떤 기작이 이 현상에 가장 큰 영향을 미치는지에 대해 알아본다. 이런 태양계 천체 자료에 대한 연구는 향후 mission 및 rover 작업을 수행함에 있어 기본적인 정보로서 활용될 수 있다.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.88-97
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• 1998

Large aluminium extrusions can be used in rolling stocks and high speed vessels to reduce weight and labor cost. As sandwich plates with corrugated core have enough strength in transverse and longitudinal direction, welding lines to connect members are reduced and transverse members to strength longitudinal members are not required. However, for proper design of aluminium extrusion plates, understanding of structural behaviors of the exclusions are necessary. In this paper, at first, detailed finite element analysis is carried out to understand structural behavior. And then, simple theoretical formulas for design purpose are proposed using the orthotropic plate theory. Shear stresses resulting from end twisting which is characteristics of deep aluminium extrusion plates can also be calculated by the simple theoretical formula. Comparison with the results by detailed finite element analysis shows good accuracy of the proposed simple formulas. The simple formulas can be useful in repetitive analysis in the initial design stage.

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.365-370
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• 2005

Many sea accidents such as collisions and groundings of vessels were occurred due to the lack of sufficient manoeuvring capability of vessels. Therefore IMO adopted 'The interim standards of ship manoeuvrability by Resolution A.751(18)' and the standards have been applied to vessels of 100m or more in length and all chemical tankers and gas carriers regardless qf the length, which were constructed on or after 1 July 1994. The IMO manoeuvrability standards are divided into three kinds as bellows; (1) Turning capability standards : Estimated values in design stage are to be certified by turning circle test of the actual vessel. (2) Course keeping quality standards : Estimated values in design stage are to be certified by $10^{\circ}\;and\;20^{\circ}$ Zig-Zag tests of the actual vessel. (3) Shortest stopping distance standards : Estimated values in design stage are to be certified by the shortest stopping distance tested by the actual vessel. In this paper, the authors computed the values of the manoeuvring standards of several vessels from their original design and compared them with those results from experiments of the model ships and also examined the values and concluded about the validity of IMO manoeuvrability standards.