• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.43-50
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• 2012

Recently, due to the advanced computer technology, momental architectures have been designed and built using features that are very sophisticated. People's interest in free-form structural system has increased steadily not only nationwide, but also worldwide. However, there were many difficulties in the materialization of free-form structural system owing to the lack of technique and research. To solve this problem, this study performs the interface between the 3D modeling program and the optimization program. In the 3D modeling program, it is possible to automatic mesh generation and immediately to information extraction. It performs the shape optimization. Consequently, this research designs the example model and performs optimization in order to verify the developed interface module.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.11
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• pp.1459-1466
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• 2004

The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.9
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• pp.1325-1334
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• 1998

The objectives of the present study are to develop a systematic method rather than a conventional trial-and-error method for an optimal shape design using a mathematical theory, and to apply it to engineering problems. In the present study, an optimal condition for a minimum pressure loss in a two-dimensional curved duct flow is derived and then an optimal shape of the curved duct is designed from the optimal condition. In the design procedure, one needs to solve the adjoint Navier-Stokes equations which are derived from the Navier-Stokes equations and the cost function. Therefore, a computer code of solving both the Navier-Stokes and adjoint Navier-Stokes equations together with an automatic grid generation is developed. In a curved duct flow, flow separation occurs due to an adverse pressure gradient, resulting in an additional pressure loss. Optimal shapes of a curved duct are obtained at three different Reynolds numbers of 100, 300 and 800, respectively. In the optimally shaped curved ducts, the separation region does not exist or is significantly reduced, and thus the pressure loss along the curved duct is significantly reduced.

• Journal of the Korean Solar Energy Society
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• v.31 no.6
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• pp.32-39
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• 2011

This study is about the installation of the solar cell modules. The solar cell modules are built by the tree-mimic structure, and the performance is compared with that of the flat-plate type solar cell module installation. The mathematical tree model, which was suggested by Fisher and Honda, is utilized to determine the location of the solar cell modules for the tree-mimic type. The experiment shows that the generated electric power of the flat-plate type is higher than that of the tree-mimic type by 30% for one month of July. This lower performance for the tree-mimic type comes from the shading effects among the solar cell modules. The theoretical calculation for the absorbed solar radiation on the two types of solar cell installation shows that the tree-mimic type is higher than the flat-plate type by 8.5%. The shading area for the tree-mimic model is calculated with time by using the 3D-CAD, which will be utilized for the optimization of the tree-mimic model in the future.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.1
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• pp.7-10
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• 2002

$TiO_2$ thin films were prepared by coating and subsequent pyrolysis processes using Titanium-naphthenate as a raw material. $TiO_2$ thin films were made by spin-coating technique on the glass substrates, and heat treated at 45$0^{\circ}C$, The transmittance, refractive index, crystallinity and surface morphology of the $TiO_2$ thin films were measured by UV/Vis spec trophotometer, x-ray diffractometer and scanning electron microscope. $TiO_2$thin films on the slide glass showed the trans mittance of 70-90% and refractive index of 2.6 at 420 nm. The results of XRD and SEM showed that the $TiO_2$ thin films exhibited the anatase phase and the thread-like surface morphology.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.445-450
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• 2017

ZPP(Zirconium Potassium Perchlorate) is an igniter composed of potassium perchlorate as oxidizing agent and zirconium as fuel with a Viton binder. ZPP is used to provide ignition in the aerospace, propulsion, automotive industries. This research is investigated for the manufacturing process and characteristics analysis of the ZPP such as the performance and shape/calorimetry/pressure characteristics of the ZPP on PMD(Pyrotechnic Mechanical Device). During the production of ZPP, the mixing process was designed so that the ZPP could be produced in uniform particle size and shape by mixing the raw materials at high speed.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.46-57
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• 1998

Even though there are some studies on the deep drawing process and process planning, little study has been done on the methodology of process planning of secondary operations of deep drawing such as 'piercins'. In this paper, first, we systematized the methodology of the process planning of secondary operations on axisymmetric cup. Second we described the development of the expert system for their CAPP For these studies, we extracted the knowledge of their process planning from experts and analysed and systemized them. To develop the expert system, rule-based reasoning paradigm is used. The shape information of manufacturing features of secondary operations are manually input to the system through SUI. The process planning results are automatically connected to AutoCAD. We believe that the systematized process knowledge and the development of the expert system for its CAPP could give lots of aids to the associated field.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.888-890
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• 2015

많은 개발자가 참여하는 대형 소프트웨어 시스템 개발의 효율성 증대를 위해서는 컴포넌트 간 인터페이스의 효과적인 관리가 필수적이다. MDMS는 컴포넌트간의 인터페이스 정의 및 변경 이력 관리, 인터페이스 기술서 자동 생성, 소스 코드 자동 생성 등의 기능을 제공하는 도구이다. 한화탈레스는 1998년 MDMS를 처음 개발하여 적용한 이후 다양한 국방 소프트웨어 시스템 개발에 적용하여 소프트웨어 개발 생산성 향상에 효과를 보았다. 하지만, MDMS를 다양한 프로젝트에 적용하는 과정에서 최초 개발시 고려하지 못했던 여러 문제점 및 한계를 발견하였다. 이러한 문제점 및 한계는 다양한 프로젝트의 특성 지원 미흡, 형상관리 및 유지보수 문제, 프로젝트 간 메시지 재사용 미지원, 취약한 보안 등 이다. 본 논문에서는 이를 해결하기 위하여 네가지 개선방안을 제시한다. 첫 번째, 다양한 프로젝트에 적용이 가능한 유연한 SW 구조로 개선해야 한다. 두 번째, 통일되고 일관된 형상관리와 함께 전담 개발 및 유지보수 조직이 필요하다. 세 번째, 프로젝트간 메시지의 재사용 지원을 위한 방안으로 프로젝트 별 MDMS 운용이 아닌 통합된 MDMS의 운용이 필요하며, 그를 통하여 다른 프로젝트의 인터페이스 정의를 상호 참조할 수 있는 구조를 적용해야 한다. 마지막으로, 외부 협력업체와의 협업을 위한 보안 대책을 수립하고, 관련 보안 기능을 지원하여 사외의 협력업체의 개발자가 직접 MDMS에 접속하여 개발할 수 있도록 개선해야 한다.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.5
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• pp.3-11
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• 2018

Since the tensegrity structure is flexible and variable, the study on the mobility to the tensegrity has been conducted. However, it is difficult to apply the tensegrity to the architecture field due to several limits. This paper describes the methodology for the analysis of the shape change process of single prism tensegrity structure as an initial study. To apply the tensegrity structure to the architectural field, the assemblage and mathematical formulation procedures of the single prism tensegrity structures are carried out. And single prism tensegrity are presented to the computational strategies for simulate the shape change of those structures. Next, the investigation of structural behaviors through various cases of target displacements is described. Also, the summary of these methods in algorithms is illustrated. As a result it is confirmed that the single prism tensegrity structure model converges 99% on average to a given target node by using the proposed algorithm. Therefore, it is confirmed that the proposed algorithm and program are suitable for shape change analysis of single prism tensegrity structure model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.448-454
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• 2020

This study aims to determine the cause of structural defects occurring during aircraft operations and to verify the structural integrity of the improved features. The fracture plane was analyzed to verify the characteristics of the cracks and the fatigue failure leading to the final fracture was determined by the progress of the cracks by the repeated load. During aircraft operations, the comparative analysis of the load measurement data at the cracks with the aircraft design load determined that the measured load was not at the level of 30% of the design to be capable of being damaged. A gap analysis resulted in a significant stress of approximately 32 ksi at the crack site. Pre-Load testing also confirmed that the M.S. was reduced by more than 50% from +0.71 to +0.43, resulting in a sharp increase in aircraft load and the possibility of cracking when combined. Thus, structural reinforcement and the removal of the gap for aircraft cracking sites improved the defect. Based on the structural strength analysis of the improvement features, the bulkhead has a margin of about +0.88 and the fitting feature is about +0.48 versus allowable stress. In addition, the life analysis results revealed an improvement of approximately 84000 hours.