• 한국기계가공학회지
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• 제20권1호
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• pp.80-87
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• 2021

Most container ships are currently being constructed as Ultra-Large Container Ships. Hence, the equipment of the ships is also becoming relatively large. In particular, propellers, rudders, and rudder stocks are large in the stern structure, and in relation, efficient design of the hull structures to safely secure these parts is important. The bottom shell plate surface of a stern skeg is a perforated plate from which the rudder stock penetrates, so it is an important component for the stern structure. In this paper, to determine the critical buckling of the shell plate, an interaction curve equation for the two-axis compression of the shell plate was derived using the maximum value of the static structural stress multiplier in a load multiplier mode. This equation predicts the timing of the buckling occurrence. By analyzing this interaction curve equation, the buckling behavior of the plates subjected to a combination load was determined and the usefulness of applying it to ship building was investigated.

• Earthquakes and Structures
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• 제22권6호
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• pp.539-548
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• 2022

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

• Steel and Composite Structures
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• 제49권2호
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• pp.215-230
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• 2023

Cable-girder anchorage joint is the critical part of cable-supported bridges. Tensile-plate anchorage (TPA) is one of the most commonly used types of cable-girder anchorage joints in steel girder cable-supported bridges. In recent years, it has been proposed by bridge designers to apply TPA to concrete girder cable-supported bridges to form composite cable-girder anchorage joint (CCGAJ). In this paper, the mechanical performance of CCGAJ under tensile force is studied through experimental and numerical analyses. Firstly, the effects of the external prestressing (EP) and the bearing plate (BP) on the mechanical performance of CCGAJ were investigated through three tests. Then, finite element model was established for parametrical study, and was verified by the experimental results. Then, the effects of shear connector forms, EP, BP, vertical rebar rate, and perforated rebar rate on the tensile capacity of CCGAJ were investigated through numerical analyses. The results show that the tensile capacity of CCGAJ depends on the first row of PR. The failure mode of CCGAJ using headed stud connectors is to form a shear failure surface at the end of the studs while the failure mode using PBLs is similar to the bending of a deep girder. Finally, based on the strut-and-tie model (STM), a calculation method for CCGAJ tensile capacity was proposed, which has a high accuracy and can be used to calculate the tensile capacity of CCGAJ.

• 대한조선학회논문집
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• 제54권6호
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• pp.476-484
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• 2017

The purpose of this paper is to verify the structural integrity of a region with numerous penetration-holes in offshore structures such as semi-submersible rig and FPSO. In order to effectively check the yielding and buckling strength of plate members with penetration-holes, a screening analysis program was developed with the FE analysis tool to generate fine meshed model using the theoretical and analysis methods. When a hole is appeared in the plate structure members, the flow of stress is altered such that concentrations of stress form near the hole. Stress concentrations are of concern during both preliminary and detail design and need to be addressed from the perspectives of strength. To configure the geometrical shape, very fine meshed FE analysis is needed as the most accurate method. However, this method is practically impossible to apply for the strength verifications for all perforated plates. In this paper, screening analysis method was introduced to reduce analysis tasks prior to detailed FE analysis. This method is applied to not only the peak stress calculation combined stress concentration factor with nominal stress but also nominal equivalent stress calculation considering cutout effects. The areas investigated by very fine meshed analysis were to be chosen through screening analysis without any reinforcements for penetration-holes. If screening analysis results did not satisfy the acceptance criteria, direct FE analysis method as the 2nd step approach were applied with one of the coarse meshed model considering hole or with the very fine meshed model considering the hole shape and size. In order to effectively perform the local fine meshed analysis, automatic model generating program was developed based on the MSC/PATRAN which is pre-post FE analysis program. Buckling strength was also evaluated by Common Structure Rule (CSR) adopted by IACS as the stress obtained from very fine meshed FE analysis. Due to development of the screening analysis program and automatic FE modeling program, it was able to reduce the design periods and structural analysis costs.

• 대한지구과학교육학회지
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• 제15권1호
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• pp.91-102
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• 2022

남해 해상 국립공원의 신수도는 다양한 형태의 지질구조와 화성활동, 화석 등을 관찰할 수 있어 지질학습과 지질관광에 적합한 곳이다. 본 연구에서는 2015개정 과학과 교육과정의 핵심 요소를 분석하여 신수도의 8지점 지질명소를 탐색하고 3D 파노라마 야외학습장을 개발하였다. 신수도의 지질명소 탐색을 통한 3D 파노라마 야외학습장은 3단계 야외학습 모형에 따라 개발하였다. 8차시로 구성된 3D 파노라마 야외학습장은 모둠별 협동 학습으로 구성하여 자율적인 탐구 활동이 이루어지도록 하였다. 석회암 단괴, 박리작용, 염풍화 작용, 천공 조개 구멍, 퇴적구조와 퇴적환경, 공룡의 서식지, 화산활동을 통한 지질학습과 더불어 창의와 인성을 학습할 수 있는 융합 교육이 실현될 수 있도록 구성하였다. 5명의 전문가에 의해 델파이 분석방법을 활용하여 수정 및 보완되었고, 개발 목적과 방향에 대한 타당성을 검증받았다. 3D 파노라마 야외학습장에 대한 전반적인 만족도는 4.52로, 전체적으로 야외학습에 대한 높은 만족도를 나타내었다. 3D 파노라마 야외학습장과 관련한 학생들의 면담 의견을 반영하여 개인의 수준을 고려하고 안전교육을 강화하여 신수도의 야외학습장을 완성하였다. 신수도의 3D 파노라마 야외학습장은 지질학습 및 관광을 하면서 과학적 이해와 더불어 심미적으로 감상하고 추억을 생성할 수 있는 지질학습 및 관광의 좋은 사례가 될 것이다.

• 한국축산시설환경학회지
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• 제10권1호
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• pp.23-28
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• 2004

본 연구는 국내의 있는 무창 분만ㆍ자돈사에 대하여 환기시스템 정립의 기초자료를 수집하고자 수행하였다. 측벽상단입기 지붕굴뚝배기, 천공천장입기 지붕굴뚝배기, 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기의 4종류 무창분만ㆍ자돈사 환기 형태에 대하여 조사하였다. 겨울철 돈사 내 온도, 습도, 공기유속, 암모니아가스 농도의 환경상태를 조사하였다. 겨울철 각 환기 형태별 돈사 내 온도는 환기형태에 따른 온도의 차이는 없었다. 공기유속은 측벽덕트입기 측벽배기가 다른 환기 형태보다 높은 공기 유속이 있었다. 돈사 공간내 각 환기형태별 공기유동은 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기 환기형태가 비교적 다른 환기 시스템에 비교하여 원활한 공기유동이 있는 것으로 나타났다. 암모니아(NH$_3$) 농도도 다른 환기형태보다 측벽덕트입기 측벽배기가 낮은 경향을 보였다. 따라서, 측벽덕트입기 지붕굴뚝배기, 측벽덕트입기 측벽배기가 국내의 무창 분만ㆍ자돈사 환기방식에 적용할 수 있을 것으로 판단되었다.

• 한국식품영양과학회지
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• 제41권3호
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• pp.418-429
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• 2012

현재 시장에서 유통되고 있는 떡 포장은 플라스틱 재료가 주로 사용하며 랩핑 포장 방법을 많이 사용하고 있다. 현재 시장에서 판매되는 떡들은 당일 생산 및 당일 소비(2일내 소비)를 하는 제품으로 포장을 중요성을 많이 고려하고 있지 않지만, 최근 유통기한이 늘어난 떡 제품의 상품화를 위해서 떡 포장의 개발에 관심이 높아지고 있다. 떡의 상품화 증대를 위하여 수도권 지역 소비자 대상 중심으로 포장 개선에 대한 기호도 조사에서 절취선을 손으로 개봉하는 개봉방법, 2~3개의 파티션(홈)이 존재하는 내부 디자인, 제품을 낱개 포장한 포장, 포장에 직접 인쇄하는 인쇄방법, 내용물의 상태가 완전히 보일 수 있는 포장방법을 선호하는 것으로 파악되었다. 본 연구는 국내 떡 제품에 대한 상품성 부여를 위하여 현재 소비자가 떡 제품 포장의 선호하는 트랜드 분석과 포장의 중요성이 인지되고 있다는 점에서 큰 의미를 부여할 수 있다. 따라서 본 연구에서 고려한 국내 주요 떡 제품 포장에 따른 소비자 구입 선호도를 조사 연구를 기반으로 다양한 떡 종류 및 형태에 따른 포장 소비 선호도 그리고 각 포장 방법 변경에 따른 상품화 가능성 및 가격 변화 요인을 고려한 연구가 향후 필요할 것으로 판단된다. 조사 연구 결과로 제시한 떡 포장 설계 구조의 적용과 함께 떡의 품질 개선을 위한 기능성 포장재 적용 연구 및 최적 제품 환경을 조성하는 포장 기법 연구 등을 통하여 떡 제품의 부가가치를 향상 시킬 수 있으리라 기대해 본다.

• Journal of Chest Surgery
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• 제5권1호
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• pp.45-56
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• 1972

Esophageal perforation is one of the most grave prognostic problems among thoracic and general surgical emergencies which necessitate urgent operative measures. In Korea,there are still many persons ingesting lye for suicidal attempt and thoracic surgeons in Korea have more chances to deal with lye burned esophagus with or without instrumental perforation than those in Western countries. Main cause of esophageal perforation in Korea is instrumental perforation in patients with lye stricture of the esophagus during diagnostic endoscopy or therapeutic bouginage. Other causes are corrosion of the esophagus due to ingestion of caustic agents, pathologic perforation, surgical trauma, stab wound and spontaneous rupture of the esophagus in our series. Therapeutic measures are various,and depend on duration of perforation, severity of its complications, pathology of perforated portion of the esophagus and degrees of inflammation at the point of perforation. The most important therapeutic measures are prevention of this grave condition during esophagoscopy, bouginage and surgical procedures on lungs and mediastinal structures and to make early diagnosis with prompt therapeutic measures. During the period of January, 1959, to December, 1971, the authors experienced 65 cases ofesophageal perforation including acquired esophagorespiratory fistula at Dept. of Chest Surgery, the National Medical Center in Seoul, and obtained following results in the series. 1. Female were 35 cases, and peak age incidence was 2nd and 3rd decades of life. 2. Among 65 cases, 43 were corrosive esophagitis or benign stricture of the esophagus due to caustic agents, 7 were patients with esophageal cancer. and there were 5 cases of esophageal perforation developed after pneumonectomy or pleuropneumonectomy. 3. Causes of perforation are instrumental perforation in 45, acute corrosion in 7, pathologic perforation in 7, surgical trauma in 3, stab wound in 2 cases, and one spontaneous rupture of the esophagus. 4. Most frequent sites of esophageal perforation were upper and mid thoracic esophagus, and 8 were cases with cervical esophageal perforation. 5. Complications of esophageal perforation were mediastinitis in 42, empyema or pneumothorax in 35, esophagorespiratory fistula in 12, retroperitoneal fistula or abscess in 5,pneumoperitoneum in 3, and localized peritonitis in 1 case. 6. Cases with malignant esophagorespiratory fistula were only 3 in the series which is predominant cause of acquired esophagorespiratory fistula in Western countries. 7. Various therapeutic measures were applied with mortality rate of 27.7% in the series. 8. In usual cases early treatment gave better prognosis, and least mortality rate in cases with perforation in mid thoracic esophagus. 9. Main causes of death were respiratory complications,acute hemorrhage with asphyxia, and septic complications. 10. Esophageal perforation developed after pneumonectomy gave more difficult therapeutic problems which were solved in only 1 among 5 cases.