• International Journal of Naval Architecture and Ocean Engineering
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• 제4권4호
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• pp.386-402
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• 2012

In this paper, a method to estimate ice loads as a function of the buttock angle of an icebreaker is presented with respect to polycrystalline freshwater ice. Ice model tests for different buttock angles and impact velocities are carried out to investigate ice pressure loads and tendencies of ice pressure loads in terms of failure modes. Experimental devices were fabricated with an idealized icebreaker bow shape, and medium-scale ice specimens were used. A dry-drop machine with a freefall system was used, and four pressure sensors were installed at the bottom to estimate ice pressure loads. An estimation equation was suggested on the basis of the test results. We analyzed the estimation equation for design ice loads of the International Association of Classification Societies (IACS) classification rules. We suggest an estimation equation considering the relation between ice load, buttock angle, and velocity by modifying the equations given in the IACS classification rules.

• 소성∙가공
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• 제7권6호
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• pp.554-561
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• 1998

This paper describes a research work of developing a computer-aided design of lead frame semicon-ductor with piercing operation which is very precise for progressive working. An approach to the sys-tem is based on to knowledge-based rules. Knowledge for the system is formulated from plasticity theories experimental results and the empirical knowledge of field experts. This system has been writ-ten using AutoLISP to AutoCAD on a personal computer and is composed of three main modules which are input and shape treatment production feasibility check and strip-layout module. Based on the knowledge-based rules the system is designed by considering several factors such as material and thickness of product complexities of blank geometry and punch profile, and availability of press. Also strip-layout drawing generated by piercing operation according to punch profiles considered V-notch dimple. pad chamfer spank cavity punch camber and cross bow of lead frame is displayed in graphic forms. This system can be used by a novice who may not have any knowledge of tool design and will invrease efficiencies to the designer in this field.

• 대한조선학회지
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• 제27권3호
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• pp.73-88
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• 1990

본 논문에서는 이론적인 방법과 실험적인 방법에 의해서 구와 플레어 형상을 갖는 축대칭 물체와 같이 3차원 물체에 대한 충격력을 검토하였다. 플레어 형상을 갖는 축대칭물체는 선수와 유사한 형상을 갖고 있다. 플레어 형상물체는 연직운동에 대한 것만을 검토한 반면 구에 대해서는 연직운동만이 아니라 사각 충격에 대해서도 검토하였다. 다이폴분포와 등포텐시얼 자유표면문제를 푼 계산결과와 실험결과를 비교하였다. 경계치문제는 알려진 내부유동을 사용함으로써 계산시간을 단축하였다. 이론과 실험의 비교로부터 물체형상에 따라 최대 충격력의 이론추정치는 실험치보다 더 크거나 작을 수 있다는 것을 보여주고 있다. 그러나, 이론치가 실용적으로 사용될 수 있음을 보여주고 있다.

• 천문학회보
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• 제44권2호
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• pp.48.1-48.1
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• 2019

We found a diffuse Hα feature with a large size of ~2' around a Herbig star, MWC 1080. It shows a strong correlation with the elongated outflow cavity centered on the star. To investigate the diffuse Hα source and the molecular cavity in detail, we carried out the high-resolution NIR spectroscopy using IGRINS. We detected six hydrogen Brackett line series, seven H2 lines, and an [Fe II] forbidden line. With the obtained spatial, kinematic, and line ratio results, we discuss the characteristics of the central MWC 1080A, the NE outflow cavity, and the SE molecular cloud regions separately. Most of the bright Brγ sources around MWC 1080A were found to be reflection nebulae, but a point-like Brγ source close to another young star, MWC 1080E, was identified as a distinct source due to MWC 1080E itself. The narrow components of the H2 lines observed around MWC 1080A were found to trace PDRs located on the wall of the main outflow cavity. Based on the shock-excited H2 and [Fe II] lines detected just inside a bow-shock shape Hα feature, we suggest that it represents the actual shock at the head of the NE outflow from MWC 1080A. Also, we newly detected the shock-excited H2 and [Fe II] lines with highly blueshifted velocities in the SE molecular cloud region. They could be related to unrevealed outflows from other young stars existing around MWC 1080A.

• 한국가구학회지
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• 제17권2호
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• pp.57-68
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• 2006

This study understands rockers of today and supplies basic data of design and manufacture studying pattern change of rockers arisen in West, there is the purpose. Also, this study is investigated by dividing theoretical background of rockers, 7 kinds of American traditional rockers and European rockers from 18th century to opening part of 20th century and contemporary rockers since 20th century. The theoretical background and the style of 2 rockers (Windsor rocker, Boston rocker) were investigated to study the stylistic changes of rockers. Originally a rocker was invented by a European farmer around 1700. It developed to a household which equip practicality and comfortablness in the United States than Europe. Early rockers in a primal form appeared in the 1740s in the United States. American early rockers connected skate to established chair bridge. Rockers are deep connection with family's emotion. Rockers can provide playing functions for children and medically treating functions for adults. Windsor Rockers developed by attaching skate is mammy bench and according to shape of back form bow or hoop-back rocker, birdcage rocker, comb-back rocker. Windsor Rockers formed peculiar American tradition of craftsman furniture through structure that have a unique back of a chair and round seat. Boston Rockers were the first chairs made by mass production method. They show a particular shape with S-curve style seat and rectangular crest at the upper part of the back. Often Crests were decorated by stenciled pattern with curled leaves such as rosettes and scrolled designs.

• 대한조선학회논문집
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• 제51권4호
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• pp.334-341
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• 2014

Due to the rise of international oil prices, with the continued increase of vessel operating costs, profitability has gradually deteriorated in the some case of South Korea ferry shipping. Therefore, it is necessary to improve the resistance performance of passenger ship. Goose neck bulb can be one of the methods to improve the resistance performance of passenger ship. Goose neck bulb has been applied to passenger ships operated in Europe and large cruise line. But there is no application example in the passenger ship to be operated on a regular basis in the sea near Korea. It is needed to provide reference data that can be applied efficiently goose neck bulb on the medium-sized passenger ships. This study, intended for the medium-sized passenger ship operated short international routes, presents the design of the hull form that goose neck bulb has been applied. And the resistance performance of the designed hull confirmed by numerical simulation. The numerical simulation is performed while changing the local shape of the goose neck depending on the bulb parameters. This study finds bulb parameters and their range that can affect the resistance performance. Thus, it is possible to provide a foundation to develop the optimal design technique and regression analysis on the resistance performance and goose neck bulb.

• 한국항공우주학회지
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• 제48권2호
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• pp.109-117
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• 2020

기존 정렬 격자의 많은 제약 조건들을 완화할 수 있는 patched-grid 알고리즘을 이용하여 효율적으로 정렬 격자계를 구성하였다. EFD-CFD 워크숍의 case 4: 삼각 날개-원통형 동체 형상에 크게 3가지의 접근 방식을 적용하여 기존의 격자 생성 문제점들을 해결하였고, 실험값과 비교하여 검증하였다. 고 받음각 영역에서 표면 압력 분포가 실험값과 다소 차이를 보였다. 마하수의 증가에 따른 피칭 모멘트의 기울기 변화를 분석하였고 이는 tuck under 현상으로 설명할 수 있었다. 초음속 영역에서는 형상 앞에 궁형 충격파가 발생함으로써 삼각익 뒷전까지 양력을 발생시키는 영역이 확장되었다. 또한, 마하수와 받음각에 따라 압력 중심과 무게 중심의 위치를 비교하여 피칭 모멘트의 경향성을 분석하였다.

• Journal of Advanced Marine Engineering and Technology
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• 제41권4호
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• pp.316-322
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• 2017

본 논문의 주 목적은 수치해석 도구를 활용하여 저항성능 관점에서 우수한 선형을 개발하는 것이다. 최종 개발된 선형의 성능 평가를 위해 수조 모형시험을 수행하였다. 현존선은 도면을 바탕으로 실물과 도면의 타당성 검토를 위해 실태조사를 수행하였다. 실태조사 시에 실제 운항 상태인 주 운항 배수량 및 주 운항 선속을 확인하였다. 수치해석을 바탕으로 현존선의 저항성능을 검토하였다. 개발선은 선수어깨의 파형개선, 배수량 분포의 균형화, 단면형상의 수정 그리고 중앙 스케그의 크기와 형상 변경에 관한 스터디를 통해 도출되었다. 수치해석 결과 개발선은 조파저항 개선에 의해 저항성능 관점에서 주 운항 선속인 11노트에서 약 15% 개선된 양을 보여주었다(Table 4 참조). 개발된 선형의 성능 평가를 위해서 수조 모형시험을 수행하였으며 그 결과 11노트에서 약 17% 개선된 양을 보여주었다(Table 5 참조).

• 한국해양공학회지
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• 제18권6호
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• pp.79-83
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• 2004

The curved blocks which compose the bow and stem of a ship contain many skewed joints that are inclined horizontally and vertically. Most of these joints have a large fitness error and are continuously changing their form and are not easily accessible. The welding position and parameter values should be appropriately set in correspondence to the shape and the inclination of the joints. The welding parameters such as current, voltage, travel speed, and melting rate, are related to each other and their values must be in a specific limited range for the sound welding. These correlations and the ranges are dependent up on the kind and size of wire, shielding gas, joint shape and fitness. To determine these relationships, extensive welding experiments were performed. The experimental data were processed using several information processing technologies. The regression method was used to determine the relationship between current voltage, and deposition rate. When a joint is inclined, the weld bead should be confined to a the limited size, inorder to avoid undercut as well as overlap due to flowing down of molten metal by gravity. The dependency of the limited weld size which is defined as the critical deposited area on various factors such as the horizontally and vertically inclined angle of the joint, skewed angle of the joint, up or down welding direction and weaving was investigated through a number of welding experiments. On the basis of this result, an ANN system was developed to estimate the critical deposited area. The ANN system consists of a 4 layer structure and uses an error back propagation learning algorithm. The estimated values of the ANN were validated using experimental values.

• Steel and Composite Structures
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• 제49권6호
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• pp.615-631
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• 2023

To investigate the seismic behavior of steel slag self-stressing concrete-filled circular steel tubular (SSSCFCST) columns, 14 specimens were designed, namely, 10 SSSCFCST columns and four ordinary steel slag (SS) concrete (SSC)-filled circular steel tubular (SSCFCST) columns. Comparative tests were conducted under low reversed cyclic loading considering various parameters, such as the axial compression ratio, diameter-thickness ratio, shear-span ratio, and expansion ratio of SSC. The failure process of the specimens was observed, and hysteretic and skeleton curves were obtained. Next, the influence of these parameters on the hysteretic behavior of the SSSCFCST columns was analyzed. The self stress of SS considerably increased the bearing capacity and ductility of the specimens. Results indicated that specimens with a shear-span ratio of 1.83 exhibited compression bending failure, whereas those with shear-span ratios of 0.91 or 1.37 exhibited drum-shaped cracking failure. However, shear-bond failure occurred in the nonloading direction. The stiffness of the falling section of the specimens decreased with increasing shear-span ratio. The hysteretic curves exhibited a weak pinch phenomenon, and their shapes evolved from a full shuttle shape to a bow shape during loading. The skeleton curves of the specimens were nearly complete, progressing through elastic, elastoplastic, and plastic stages. Based on the experimental study and considering the effects of the SSC expansion rate, shear-span ratio, diameter-thickness ratio, and axial compression ratio on the seismic behavior, a peak displacement coefficient of 0.91 was introduced through regression analysis. A simplified method for calculating load-displacement skeleton curves was proposed and loading and unloading rules for SSSCFCST columns were provided. The load-displacement restorative force model of the specimens was established. These findings can serve as a guide for further research and practical application of SSSCFCST columns.