• Journal of Korean Association for Spatial Structures
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• v.12 no.3
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• pp.97-104
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• 2012

In the design procedure of the cooling tower the form-finding of the shell is the most important process, because the shape of the shell determines the sensitivity of dynamic behaviour of the whole tower against wind excitation. In engineering practice, geometric parameters of the shell are generally determined based on natural frequency analysis. 32 cooling tower shell geometries were selected through variation of the geometric parameters of an existing cooling tower shell. They were evaluated based on the first natural frequency. From the result three representative cooling towers are selected for the analysis of the structural behaviour by means of linear FE-method. As a result, a hyperbolic rotational shell with the small radius overall will yield the shell geometry with a higher first natural frequency and thus a wind-insensitive structure.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.28-33
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• 2002

The characteristics of hull-pieces are large quantity, comparatively large piece-size, and different each shape. For the more, in the forming process(including Line-Heating Process) of curved hull pieces, shape checking processes including initial shape measurement and forming shape measurement of the each pieces are needed to achieve a given accuracy. So, the forming process of large curved hull pieces needs efficient measurement and comparison technique to check the shape and ensure the forming-accuracy In this paper, we try to construct integrated S/W, H/W system for efficient measurement and comparison of large curved hull pieces, which can apply to above forming environment.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.42-42
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• 2019

유량조절을 위한 자동수문은 설정된 관리수위 이하에서는 수문이 개방되지 않으며, 유량이 증가하여 관리수위 이상이 되면 수문이 개방되어 방류를 시작하여 일정 수위를 유지하는 것을 의미한다. 자동수문의 운영 중 수문의 거동과 자동 개폐 시점을 예측하는 것은 정밀한 수문 설계를 위해 매우 중요하다. 수문 하단으로 흐름이 발생하면 수문 선단을 포함한 주변에서의 압력 차이로 인한 동수압 하중이 발생하고 진동을 유발, 수문 개방을 억제하는 하향력 등의 효과로 수문 운영에 큰 영향을 미친다. 본 연구에서는 부력식 수문의 모형실험을 통하여 정수압 상태의 부력 이론에 의한 수문 개방률과 측정에 의한 수문 개방률을 비교하였으며, 이론과 측정 수문 개방고의 차이를 하향력에 의한 효과임을 확인하였다. 부력식 수문의 하향력을 검토하기 위해 기존 이론식을 이용한 결과, 이론식은 부력식 수문에 적용하기 어려운 것으로 나타났다. 따라서, 기존 이론식을 이용하여 부력식 수문의 하향계수 산정을 위한 매개변수 관계식을 개방률을 이용하여 제시하였다. 제시된 매개변수 관계식의 결정계수는 0.721, 수정된 결졍계수는 0.690으로 나타났다. 부력식 수문의 형상비에 따른 하향력을 검토하기 위해서 수치모의를 수행하였다. 모형실험에서 측정된 자료와 수치모형 ANSYS-Fluent의 사용성을 검증하였고, 부력식 수문의 형상비를 0.24, 0.49, 0.69, 0.89, 1.09로 총 5가지로 설정하여 하향계수와 하향력을 분석하였다. 부력식 수문의 하향계수와 하향력 검토는 부력체, 스커트로 구분하여 분석을 수행하였다. 하향계수 분석결과, 하향계수는 개방률이 증가함에 따라 감소하였으며 하향계수가 부력체 부분에서는 0.465~1.542, 스커트 부분에서는 0.058~1.148의 범위로 나타났다. 하향력 분석결과, 하향력은 개방률 0.300 이하에서는 개방률이 증가함에 따라 하향력은 증가하였나 개방율 0.300 초과하면서부터 개방률이 증가함에 따라 하향력이 감소하는 것으로 나타났다. 또한 부력체 부분에서는 형상비가 증가함에 따라 하향력이 감소하였으나, 스커트 부분에서는 형상비가 증가함에 따라 하향력이 증가하였다. 이는 형상비가 증가함에 따라 스커트 부분의 면적이 증가하기 때문이다. 부력식 수문의 전체적인 하향력을 계산한 결과, 부력식 수문의 하향력은 0.002~0.015 kN의 범위를 가지며 형상비가 증가함에 따라 부력식 수문에 발생하는 하향력은 증가하는 것으로 나타났다.

• Journal of the Microelectronics and Packaging Society
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• v.10 no.2
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• pp.1-5
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• 2003

In this project, the efficiency of localized heating for micro systems packaging is developed by using a forced potential scheme microheater. Less than 0.2 Mpa contact pressure was used for bonding with a 200 mA current input for $50{\mu}m$ width, $2{\mu}m$ height and $8mm{\times}8mm$, $5mm{\times}5mm$, $3mm{\times}3mm$ sized phosphorus-doped poly-silicon microheater. The temperature can be raised at the bonding region to $800^{\circ}C$, and it was enough to achieve a strong and reliable bonding in 3 minutes. The IR camera test results show improved uniformity in heat distribution compared with conventional microheaters. For performing the gross leak check, IPA (Isopropanol Alcohol) was used. Since IPA has better wetability than water, it can easily penetrate small openings, and is more suitable for conducting a gross leak check. The pass ratio of bonded dies was 67%, for conventional localized heating, and 85% for our newly developed FP scheme. The bonding strength was more than 25Mpa for FP scheme packaging, which shows that FP scheme can be a good candidate for micro-scale hermetic packaging.

• Korean Journal of Optics and Photonics
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• v.34 no.3
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• pp.117-123
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• 2023

The size of an optical surface can significantly affect the performance of an optical system, and high spatial frequency errors have a greater impact. Therefore, it is crucial to measure the surface figure error with high frequency. To address this, a new method called rotational prism stitching interferometer (RPSI) is proposed in this study. The RPSI is a type of stitching interferometer that enhances spatial resolution, but it differs from conventional stitching interferometers in that it does not require the movement of either the mirror tested or the interferometer itself to obtain sub-aperture interferograms. Instead, the RPSI uses a beam expander and a rotating Dove prism to select particular sub-apertures from the entire aperture. These sub-apertures are then stitched together to obtain a full-aperture result proportional to the square of the beam expander's magnification. The RPSI's effectiveness was demonstrated by measuring a 40 mm diameter spherical mirror using a three-magnification beam expander and comparing the results with those obtained from a commercial interferometer. The RPSI achieved surface testing results with nine times higher sampling density than the interferometer alone, with a small difference of approximately 1 nm RMS.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.23-33
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• 2004

MDO framework, which provides multidisciplinary system design and optimization environment, requires integration of the analyses codes developed at various computer languages and operating systems, integration of CAD and DBMS, and development of complex GUI. Emphases must be given to the software modification and upgrades in conjunction with the analysis code addition and MDO method implementation. In this study, techniques about system integration and analysis code interface have been studied extensively, and the database design and communication methods which can handle the MDO methods like MDF and CO have been studied. Using the dedicated MDO framework developed for the air vehicle design, the multidisciplinary fighter aircraft wing design has been performed to demonstrate the efficiency and usefulness of the software. Optimum wing configuration is derived using the gradient-based optimization methods within thirty design iterations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.805-811
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• 2010

When we design a product, we spend a considerable amount of time in designing fasteners and their mating parts. Fasteners have special features because of which they are widely used and well standardized. Although we use some equations to design the fasteners, we should select these fasteners from the standardized table. In order to design them quickly using the CAD system, we proceeded as follows. First, we prepared some standardized shapes of fasteners to design them automatically. Next, we built a database of some fasteners such as a tension bolt, lock wire, thread, pin, and snap ring. Then, we used the design equations to quickly and precisely calculate the various parameters. Finally, we used a configuration design method to generate the shapes automatically using the results of the calculation and the values retrieved from the database. We applied this approach to the design of a propulsion structure, and demonstrated that this approach worked well and saved considerable time.

• Magazine of the Korea Concrete Institute
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• v.20 no.6
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• pp.28-35
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• 2008

The Burj Dubai Project will be the tallest structure ever built by man; when completed the tower will be more than 700 meter tall and more than 160 floors. While the early integration of aerodynamic shaping and wind engineering considerations played a major role in the architectural massing and design of this multi-use/residential tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria, the material selection for the structural systems of the tower was also a major consideration and required detailed evaluation of the material technologies and skilled labor available in the market at the time Concrete was selected for its strength, stiffness, damping, redundancy, moldability, free fireproofing, speed of construction, and cost effectiveness. In addition, the design challenges of using concrete for the design of the structural system components will be addressed. The focus on this paper will also be on the early planning of the concrete works of the Burj Dubai Project.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.532-540
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• 2008

Recently there are growing interests in calculating aerodynamic characteristics of aircraft configurations with structural deformation using the FSI(Fluid-Structure Interaction) system in which CFD(Computational Fluid Dynamics) and CSD(Computational Structure Dynamics) modules are coupled. In this paper the FSI system comprised of CAD, CFD, CSD, VSI(Volume Spline Interpolation) and grid deformation modules was constructed in order to investigate aerodynamic characteristics of the deformed shape. In the process VSI and grid generation modules are developed to combine CSD and CFD routines and to regenerate the aerodynamic grids for the deformed shape, respectively. For the CFD and CSD analysis, commercial programs FLUENT and NASTRAN were used. As a test model, DLR-F4 wing configuration was chosen and its aerodynamic characteristics were calculated by applying the static FSI system. It was shown that lift and drag coefficients of the wing at mach number 0.75 are reduced to 20.26% and 18.5%, respectively, owing to the structural deformation.

• Journal of the Korea Convergence Society
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• v.10 no.7
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• pp.281-287
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• 2019

Application of heat recovery system applying air supply and cexhaust ventilation device essential in energy management system for the optimum ventilation system utilization and energy saving. This is a key element of infrastructure technology for high-efficiency energy buildings, because it can save heating and cooling energy in winter and summer. In this paper, heat transfer efficiency was simulated using paper, plastic, and aluminum materials that was examined to compare heat exchanger performance under uniform flow conditions. We tested heat transfer efficiengy according to the shape of two of that, one is orthogonal and the other is refraction shape. Based on the simulation results, it is expected to contribute to the production of high performance heat exchanger with heat transfer performance and pressure loss.