• 한국소음진동공학회논문집
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• 제25권5호
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• pp.321-328
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• 2015

최근 극지 선박의 수요가 늘어나고 있고 IACS(국제선급연합)에서는 대빙 선박에 대한 새로운 기준이 적용되고 있다. 이 선박에서는 추진시스템에 대한 대빙 설계 기준으로 빙 충격 토크는 프로펠러 날개 수를 중심으로 한 조화 함수로 규정되어 있다. 그러나 실 상황에서는 이러한 주기적인 기진 토크보다는 불규칙한 빙의 충격 토크가 발생할 수 있는 확률이 오히려 크다. 이 논문에서는 비틀림진동이 비교적 큰 6개의 실린더를 갖는 디젤엔진을 주 기관으로 한 추진시스템의 안정성을 검토하고자 한다. 특히 불규칙한 빙 충격 토크와 디젤엔진에서 발생하는 진동토크를 동시에 고려하여 비틀림진동의 공진점을 통과할 과도 비틀림 진동 응답을 이론적으로 해석하였다. 여기서 빙 충격토크는 빙이 프로펠러에 부딪칠 때를 여러 유형별로 가상하여 선급에서 규정된 방법에 의해서 구하였다. 전체적인 시스템의 과도응답 해석은 직접적분방법의 하나인 뉴마크(Newmark) 법을 이용하였다.

• 대한한의진단학회지
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• 제9권1호
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• pp.59-68
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• 2005

Background and purpose: Cardiovascular disease will undoubtedly rise along with the aging of the 'baby-boom' generation. The purpose of this study is to find the new index of the cardiovascular aging. Methods: The effects of aging on the heart and the arterial system are surveyed in the point of structure and function. Results: Arterial stiffening is due to the fatiguing effects of periodic stress on the arterial wall and is the main reason for increasing pulse wave velocity. The systolic hypertension is caused by the early return of wave reflection. The increased after-load by the arterial change leads to the development of left ventricular hypertrophy. The reduction in left ventricular compliance cause the impairments of the diastolic function. In contrast to the lower limb, aging effect in the upper limb are almost due to the ascending aortic pressure wave and the reflected wave from the lower limb. Conclusion: We have the following points. (1) The change of physiological pulse pattern by age can be explained by the early returning of reflected wave. (2) The atrial pulse in old age are generated by the left ventricular hypertrophy.

• 한국자동차공학회논문집
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• 제22권1호
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• pp.117-125
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• 2014

The temperature distribution of steady state rolling tires with detailed tread blocks is numerically predicted using the three dimensional full patterned tire model. A three dimensional periodic patterned tire model is constructed by copying 1-sector mesh in the circumferential direction. Using the static tire contact analysis, the strain cycles during one revolution are approximated with the strains at Guassian points of the elements which are sector-wise repeated within the same circular ring of elements, by neglecting the tire rolling effect. Based upon the multi-axial fatigue theory, the maximum principal strain is used to represent the combined effect of six strain components on the hysteretic loss. In the following, the deformation due to the inflation and vertical load is calculated using ABAQUS. Then heat generation rate in each element is calculated using an in-house code. Lastly, temperature distribution is calculated using ABAQUS again. Through the numerical experiments, the validity of the proposed prediction method is examined by comparing with the experiment and the temperature distribution of a patterned tire model is compared with those of the main-grooved simple tire model.

• Journal of Korean Neurosurgical Society
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• 제55권5호
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• pp.244-247
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• 2014

Objective : The aim of this study was to evaluate the microanatomy and histological features of the central myelin in the root exit zone of facial nerve. Methods : Forty facial nerves with brain stem were obtained from 20 formalin fixed cadavers. Among them 17 facial nerves were ruined during preparation and 23 root entry zone (REZ) of facial nerves could be examined. The length of medial REZ, from detach point of facial nerve at the brain stem to transitional area, and the thickness of glial membrane of central myelin was measured. We cut brain stem along the facial nerve and made a tissue block of facial nerve REZ. Each tissue block was embedded with paraffin and serially sectioned. Slices were stained with hematoxylin and eosin (H&E), periodic acid-Schiff, and glial fibrillary acid protein. Microscopy was used to measure the extent of central myelin and thickness of outer glial membrane of central myelin. Thickness of glial membrane was examined at two different points, the thickest area of proximal and distal REZ. Results : Special stain with PAS and GFAP could be differentiated the central and peripheral myelin of facial nerve. The length of medial REZ was mean 2.6 mm (1.6-3.5 mm). The glial limiting membrane of brain stem is continued to the end of central myelin. We called it glial sheath of REZ. The thickness of glial sheath was mean $66.5{\mu}m(40-110{\mu}m$) at proximal REZ and $7.4{\mu}m(5-10{\mu}m$) at distal REZ. Conclusion : Medial REZ of facial nerve is mean 2.6 mm in length and covered by glial sheath continued from glial limiting membrane of brain stem. Glial sheath of central myelin tends to become thin toward transitional zone.

• 수산해양기술연구
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• 제40권4호
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• pp.360-366
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• 2004

침하식 가두리 시설의 안정성 평가를 위한 기초 단계로서 일방향 규칙파 중 2점 계류된 원통형 부체를 대상으로 부설 수심의 변화에 따른 부체의 동적 거동 및 계류삭에 작용하는 장력 산정에 관한 수치 계산을 수행하였다. 수치 계산 결과, 수면 상에 설치된 부체를 수면 아래의 약 1/2되는 수층까지 침하 시킨 경우 그것은 동적 거동과 파력은 초기 상태에 비해 각각 최대 50%와 77%까지 감소되어 시설물을 수중으로 침하 시키면 그것의 안정성 유지에 매우 효과적임을 확인할 수 있었다. 또한 부체의 전 후단 변위 및 계류삭에 작용하는 장력의 최대치는 부체의 고유 주기의 영향으로 인해 그것은 길이 d 에 대한 파장 ${\lambda}$의 비 즉, d/${\lambda}$가 약 0.66에서 나타났으며, 이와 같은 현상은 기존 수리 모형실험 결과와 비교적 잘 일치하였다. 그러나 본 수치 계산의 신뢰성 확인을 위해서는 수리 모형실험을 통해 부체의 고유 주기와 작용 파고에 대한 전 후단 변위 등에 대한 충분한 검토가 요구된다.

• 한국측량학회지
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• 제9권1호
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• pp.17-25
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• 1991

토목 구조물의 시공을 위해서는 기초굴착이 필수적이며 변형으로 인한 재해의 위험이 있으므로 주기적인 변형측정이 필요하다. 기존의 굴착측면에 대한 현장계측은 상대변위 밖에 얻을 수 없고 표면 측정이 불가능하므로 이러한 난점을 해결할 수 있는 방법의 개발이 절실하다. 본 연구에서는 대상물로부터 독립적으로 단 시간내에 다량의 측점에 대해 절대변형량의 도출이 가능한 지상사진 측량을 굴착현장에 적용하기 위하여 동일점 촬영기법을 개발, 실내실험을 통해 해석 가능성을 제시하고 현장에 적용, 기간별 절대변형량을 산출하였다. 동일 촬영점 기법을 실내실험에 적용한 결과 해석인 가능하였으며, 인접 사진과의 중복도를 보다 크게하여 해석한다면 다른 기법보다 신속하게 양호한 성과를 얻을 수 있음을 알 수 있었다. 이 기법을 실제 굴착측면에 적용한 결과 기대 정확도 범위내에서 일관성있는 3차원 변형량을 도출할 수 있었으며 보다 신속 정확한 기준점 측량방법을 개발한다면 효율적으로 변형량을 얻을 수 있을 것이다.

• 한국정보과학회논문지:데이타베이스
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• 제33권4호
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• pp.409-422
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• 2006

데이타 스트림에 대한 다중 연속 질의들 사이에는 질의들의 윈도우 중첩 및 주기적 실행 간격으로 인해 재사용이 가능한 중간 결과들이 다수 생길 수 있다. 본 논문은 다중 연속 질의들을 위한 전체 실행 계획을 구성하기 위해, 효율적인 탐욕 기반의 경험적 알고리즘인 GAGPC를 제안한다. 제안한 GAGPC 알고리즘은 질의들의 전체 실행 사이클을 결정하고 관련된 실행 시점들의 최대 집합인 SRP를 찾는다. 다음, 각 SRP에서 실행될 질의들이 가장 높은 이익을 갖는 공통의 조인 부분들을 공유하도록 전체 실행 계획을 구성한다. 본 논문은 공통된 질의 부분의 존재뿐만 아니라 그것과 관련된 중첩된 윈도우 크기에 따라 통일한 연속 질의라 하더라도 최상의 질의 계획아 바뀔 수 있다는 점을 제시한다. 또한 기존 연구와는 달리, 윈도우가 부분 또는 전체적으로 중첩될 수 있으므로 중간 결과의 전체뿐만 아니라 일부도 재 사용할 것을 반영한다. 마지막으로, 본 논문은 GAGPC의 유효성을 위한 시뮬레이션 결과를 제시한다.

• 설비공학논문집
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• 제23권4호
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• pp.303-311
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• 2011

This study presents a new idea of liquid desiccant dehumidifier with extended surface to improve the compactness. Extended surface is inserted between vertical cooling tubes, and the liquid desiccant flows down along the tube walls and the extended surface as well. Though the extended surface contributes to the increase in the mass transfer area, the effect tends to be limited because less conductive non-metallic materials need to be applied due to the high corrosiveness of liquid desiccant. To analyze the effects of the extended surface insertion, mathematical modelling and numerical integration are performed for the heat and mass transfer in the liquid desiccant dehumidifier. The results show that, though the liquid desiccant on the extended surface is heated due to the moisture absorption, the temperature can be maintained by periodic mixing at the contact points between the tube and the extended surface with the liquid desiccant stream from the tube side at a relatively low temperature. This implies the absorption heat from the extended surface side can be removed effectively by mixing, which leads to a substantial improvement of the dehumidification in the liquid desiccant dehumidifier with extended surface. When the interval of the extended surface, $p_e/L$, is less than 0.1, the dehumidification is shown to increase by more than two times compared with that without extended surface.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.453-454
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• 2003

Most research materials (data), which are used for the study of digital mapping and digital elevation model (DEM) in the field of Remote Sensing and Aerial Photogrammetry are aerial photographs and satellite images. Additionally, they are also used for National land mapping, National land management, environment management, military purposes, resource exploration and Earth surface analysis etc. Although aerial photographs have high resolution, the data, which they contain, are not used for environment exploration that requires continuous observation because of problems caused by its coastline, as well as single - spectral and long-term periodic image. In addition to this, they are difficult to interpret precisely because Satellite Images are influenced by atmospheric phenomena at the time of photographing, and have by far much lower resolution than existing aerial photographs, while they have a great practical usability because they are mulitispectral images. The PKNU 2 is an aerial photographing system that is made to compensate with the weak points of existing aerial photograph and satellite images. It is able to take pictures of very high resolution using a color digital camera with 6 million pixels and a color infrared camera, and can take perpendicular photographs because PKNU 2 system has equipment that makes the cameras stay level. Moreover, it is very cheap to take pictures by using super light aircraft as a platform. It has much higher resolution than exiting aerial photographs and satellite images because it flies at a low altitude about 800m. The PKNU 2 can obtain multispectral images of visible to near infrared band so that it is good to manage environment and to make a classified diagram of vegetation.

• Steel and Composite Structures
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• 제52권3호
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• pp.343-356
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• 2024

This paper presents an analytical solution for correctly predicting the Lateral-Torsional Buckling critical moment of simply supported castellated beams, the solution covers uniformly distributed loads combined with compressive loads. For this purpose, the castellated beam section with hexagonal-type perforation is treated as an arrangement of double "T" sections, composed of an upper T section and a lower T section. The castellated beam with regular openings is considered as a periodic repeating structure of unit cells. According to the kinematic model, the energy principle is applied in the context of geometric nonlinearity and the linear elastic behavior of materials. The differential equilibrium equations are established using Galerkin's method and the tangential stiffness matrix is calculated to determine the critical lateral torsional buckling loads. A Finite Element simulation using ABAQUS software is performed to verify the accuracy of the suggested analytical solution, each castellated beam is modelled with appropriate sizes meshes by thin shell elements S8R, the chosen element has 8 nodes and six degrees of freedom per node, including five integration points through the thickness, the Lanczos eigen-solver of ABAQUS was used to conduct elastic buckling analysis. It has been demonstrated that the proposed analytical solution results are in good agreement with those of the finite element method. A parametric study involving geometric and mechanical parameters is carried out, the intensity of the compressive load is also included. In comparison with the linear solution, it has been found that the linear stability underestimates the lateral buckling resistance. It has been confirmed that when high axial loads are applied, an impressive reduction in critical loads has been observed. It can be concluded that the obtained analytical solution is efficient and simple, and offers a rapid and direct method for estimating the lateral torsional buckling critical moment of simply supported castellated beams.