• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.478-492
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• 2021

In this study, hull dimensions of an FPSO were optimized to maximize its operability at Brazil field. In contrast with the previous works which have used simplified models to evaluate some indicators related to stability and hydrodynamic performances of FPSOs for its own optimal design, we developed a generic hull and compartment modeler and sophisticated stability and hydrodynamic calculation modules. With the aid of the developed tools, the hull optimization was performed with initial dimensions of an FPSO originally designed for west Africa field. The optimization results indicated the relative importance of hydrodynamic performances compared with stability performances for the FPSO hull dimensioning by showing that there were 3 active constraints related to them, which were the natural periods of heave and roll and the maximum pitch angle under 1-year return period waves at full load condition. To the author's knowledge, this study is the first attempt to combine altogether the hull and compartment modeling and full set of stability and hydrodynamic calculations precisely to optimize an FPSO's hull dimensions within 30 min. Also, it is worthwhile to mention that the developed methods are generic enough to be applied to all types of ship-shaped offshore platforms.

• Geomechanics and Engineering
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• 제32권1호
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• pp.35-47
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• 2023

Deformability of road pavements in the form of ruts represent a safety risk for road users. In the procedures for dimensioning the pavement structure, the requirement that such deformations do not occur is imperatively included, which results in the appropriate selection of elements (material, geometry) of the pavement structure. Deformability and functionality, will depend of the correct design of pavement structure during exploitation period. Nevertheless, there are many examples where deformations are observed on the pavement structure, in the form of rutting at parts of the road with relatively short length, realised in the same climatic and the same geoenvironmental conditions. The performed analysis of deformability led to the conclusion that the level of deformation is a function of the speed of traffic. This effect is observed on city roads, but also outside of urban areas at roads with speed limits are significant, due to the traffic management, traffic jams (intersections, etc.). Still, the lower speed cause greater deformations. The authors tried to describe the deformability of flexible pavement structures, from the aspects of geotechnical problems, as a function of driving speed. Outcome of the analysis is a traffic load correction coefficient, in terms of using the existing methods of flexible pavement structures design.

• Steel and Composite Structures
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• 제44권5호
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• pp.603-617
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• 2022

Structural design, in general, is developed through trial and error technique which is guided by standards criteria and based on the intuition and experience of the engineer, a context that leads to structural over-dimensioning, with uneconomic solutions. Aiming to find the optimal design, structural optimization methods have been developed to find a balance between cost, structural safety, and material performance. These methods have become a great opportunity in the steel structural engineering domain since they have as their main purpose is weight minimization, a factor directly correlated to the real cost of the structure. Assuming an objective function of minimum weight with stress and displacement constraints provided by Brazilian standards, the present research proposes the sizing optimization and combined approach of sizing and shape optimization, through a software developed to implement the Simulated Annealing metaheuristic algorithm. Therefore, two steel plane frame layouts, each admitting four typical truss geometries, were proposed in order to expose the difference between the optimal solutions. The assessment of the optimal solutions indicates a notable weight reduction, especially in sizing and shape optimization combination, in which the quantity of design variables is increased along with the search space, improving the efficiency of the optimal solutions achieved.

• 한국전산구조공학회논문집
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• 제14권4호
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• pp.515-523
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• 2001

본 논문에서는 고준위 핵폐기물의 지하 처분 시 사용되는 핵폐기물 처분장치의 기본 구조설계에 필요한 처분장치내의 핵 폐기물다발들을 지지하는 내부 삽입물의 구조형상과 재원 또 처분장치의 화학적 부식을 방지하기 위해 외곽에 설치하는 외곽쉘과 위아래 덮개의 두께를 결정하기 위하여 처분장치 구조물에 대한 선형정적 구조해석을 수행하였다. 해석 대상 처분장치는 가압경수로와 중수로의 핵폐기물 처분장치를 사용하였다. 일반적으로 핵폐기물 처분장치는 지하수백 미터에 위치하는 화강암 등의 암반 내에 설치하게 되는데 이 때 지하수의 침수에 의한 지하수압 및 처분장치 외곽에 완충장치로 설치하는 벤토나이트 버퍼의 팽윤압을 견디어 내야 한다. 따라서 이와 같은 압력의 변화에 따른 처분장치 구조물에 발생하는 응력 및 변형 등을 알기 위해서는 처분장치 구조물에 대한 구조해석을 수행해야 된다. 이를 위하여 본 논문에서는 처분장치에 대하여 선형정적 구조해석을 수행하였다.

• 산업경영시스템학회지
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• 제39권4호
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• pp.1-6
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• 2016

As manufacturing industries become globalized, product design affects every area of organization. The design sets the goals for a number of different departments, so if it fails to effectively communicate these goals, the entire organization is less efficient. In addition, To communicate clearly, the design must represent a product that meets its technical specification. GD&T (Geometric Dimensioning and Tolerancing) is one of the most important factors, which has an effect on efficiency of manufacture system, in designing products. However, most of designers in different industries are prone to ignore the importance of GD&T. To analyse the importance of GD&T compliance with international standards for design drawing, a comparison analysis of the difference between two methods, composite profile control and multiple single segment profile control, is performed on three different cases and suggests how it used to be more suitable. Composite profile tolerance is specified by a dual feature control frame that has one profile symbol specified with two lines of tolerance information. Whereas a multiple single segment profile control is when two or more single segment profile callouts are used to define the location and/or orientation and/or size and/or form of a part feature. In this study, the following results will be provided : a clear definition and an obvious difference of the tolerance zone, datums and datums sequence and minimization of tolerances. On this study, composite profile tolerance and multiple single segment profile tolerance were discussed. Next steps of research will consist on reaching more accurate results for profile control. Further research will be focused on dealing with the remaining 14 symbols of GD&T.

• 대한전자공학회논문지
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• 제13권3호
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• pp.11-15
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• 1976

한국산 천연수정은 보석장식용으로서는 그 품질이 이미 알려져 있으나 수정진동자로서의 특성에 관해서는 아직 보고된 바가 없다. 본 연구는 특히 경상도일대에서 채굴되고 있는 천연수정을 채집, 선별, 가공하여 그 수정진동자로서의 사용가능성을 실험을 통하여 검토한 것이다. 필자들은 채굴현장 근처에서 채집한 원석을 특별히 고안제작된 검사경을 이용하여 분석선별하였으며 X-ray를 사용하여 AT-cut로 orientation 한후 시판을 절단하였다. 다음 적용하여 전기적, 광학적 쌍수상태를 검토하고 다시 선별하였다 Dimensioning은 5MHz를 목표로 하였는데 연잠제를 사용하여 5MHz의 조도까지 연마하고 전극으로서 표준형의 은막을 부착하여 시판을 완성하였다. 시판을 대한 측정결과는 모든 등가정수가 대표적인 수입수정판의 것과 대등하였으며 특히 Q는 모두 105를 넘었다. 온도특성도 AT-cut의 이론치와 대차가 없었으며 -20℃-+100℃ 범위에서 최대 20PPM 이내의 편차를 보였다. 즉, 한국산 천연수정은 적절히 선별, 가공 한다면 부유한 수정진동자의 원재로서 사용할수 있음이 증명되었다. Samples of domestic natural quartz were collected and screened optically and chemically, and, after weeding out portions unfit for electrical resonator, were cut into AT-cut wafers, which in turn were dimensioned, trimmed and lapped into 5MHz resonator units. The results of measurements obtained from the specimens indicated excellent electrical characteristics of domestic natural quartz with the average Q quotient of 10s or higher. Temperature characteristics also showed typical AT-cut corves with the frequency deviation of 20PPM at maximum throughout the range of -20 to 100℃. The experiment on the initial batch of samples amply indicates the excellent electrical quality of domestic natural quartz as quartz resonator units.

• 대한공간정보학회지
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• 제15권2호통권40호
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• pp.67-75
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• 2007

터널 구조물 시공시에 수많은 위험요소를 가지고 있다. 이러한 요소들을 미연에 방지하고 안정성 확보를 위해서는 터널 내부의 변위에 대한 정확하고 신속한 관측이 요구된다. 그러나 현재 천단침하, 내공변위, 지표침하 등은 토탈 스테이션. 각종 계측기를 이용하는 보편적인 측량 방법에 의존하고 있는 실정이다. 최근 측량기술의 향상과 개발에 따른 구조물의 유지관리에 대한 자료를 제공하기 위한 방법으로 3차원 레이저 스캐닝을 이용하여 기존 구조물의 변형량 계측방법의 신뢰성 문제를 해결하고, 구조물의 형태 변화를 3차원화 하여 시각적으로 판단할 수 있는 자료를 제시하고 빠른 대책을 강구할 수 있도록 하여 구조물의 유지관리 및 현장계측에 능률적으로 활용할 수 있도록 하였다.

• 대한전기학회논문지:전력기술부문A
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• 제48권2호
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• pp.119-126
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• 1999

Current transformer (CT) saturation may cause a variety of protective relays to malfunction. The conventional CT is designed that it can carry up to 20 times the rated current without exceeding 10% ratio error. However, the possibility of CT saturation still remains if the fault current contains substantial amounts of ac and/or dc components. This paper presents a design method of iron-cored CTs for use with protective relays to prevent CT saturation. The proposed design method determines the core cross section of the CT; it employs the transient dimensioning factor to consider relay's operating time (duty cycle) and dc component as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider the biggest fault current. The method designs the cross section of CTs in cases of reclosure and no reclosure.

• 소성∙가공
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• 제29권4호
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• pp.194-202
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• 2020

In this paper, experimental and numerical study on a combined sheet metal forming and plate forging of a seal part of a passenger car's hub bearing is conducted to develop the new process of which target is to remove machining process by plate forging and to achieve near-net shape manufacturing. The previous process of a sheet metal forming inevitably needed a machining process for making stepped sheet after conventional sheet metal forming in a progressive way. The stepped sheet is intended to be formed by plate forging in this study. Through the systematic way of developing the combined forming process using solid elements based-elastoplastic finite element method (FEM), several conceptual designs are made and an optimized process design in terms of geometric dimensioning and tolerance of straightness of the thin part is found, which is exposed to bending in metal forming of axisymmetric part. The predicted straightness measured by the slope angle of the tilted thin region is compared with the experimental straightness, showing that they are in a good agreement with each other. Through this study, a systematic approach to optimal process design, based on elastoplastic FEM with solid elements, is established, which will contribute to innovating the conventional small-scaled sheet metal forming processes which can be dealt with by solid elements.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 사면안정 학술발표회
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• pp.3-38
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• 2000

Slope draperies in soil and rock are a well known method to avoid rockfalls into the roads or onto housings. Common wire mesh or a combination of wire mesh and wire rope nets are pinned to the slope by the means of fully grouted nails or anchors. Most of these installations have not been designed to stabilize the slope, but simply avoid the rocks from bouncing. The combination of soil- or rocknailing with a designable flexible facing system offers the advantage of a longterm stabilization of slopes and can replace other standard methods for slope stabilization. The capability to transfer axial and shear loads from the flexible facing system to the anchor points is most decisive for the design of the stabilization system. But the transfer of forces by mesh as pure surface protection devices is limited on account of their tensile strength and above all also by the possible force transmission to the anchoring points. Strong wire rope nets increase the performance for slope stabilizations with greater distances between nails and anchors and are widely used in Europe. However, they are comparatively expensive in relation to the protected surface. Today, special processes enable the production of diagonally structured mesh from high-tensile steel wire. These mesh provide tensile strengths comparable to wire rope nets. The interaction of mesh and fastening to nail / anchor has been investigated in comprehensive laboratory tests. This also in an effort to find a suitable fastening plates which allows an optimal utilization of the strength of the mesh in tangential (slope-parallel) as well as in vertical direction (perpendicular to the slope). The trials also confirmed that these new mesh, in combination with suitable plates, enable substantial pretensioning of the system. Such pretensioning increases the efficiency of the protection system. This restricts deformations in the surface section of critical slopes which might otherwise cause slides and movements as a result of dilatation. Suitable dimensioning models permit to correctly dimension such systems. The new mesh with the adapted fastening elements have already been installed in first pilot projects in Switzerland and Germany and provide useful information on handling and effects.