• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.192-197
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• 2017

Typical materials including concrete behaves with positive poisson's ratio when external force is applied. However, it is also available to manufacture a grating system which has negative poisson's ratio(Auxetic). In this study, double arrow type 2-D auxetic mesh was manufactured and mechanical behaviors were observed. Also, direct tensile tests of cementitious composites reinforced by auxetic mesh were performed and the results were compared with composites reinforced by typical mesh. The results showed that auxetic mesh more effectively restrained the deformation(shortening) of cementitious composites perpendicular to the load direction comparing with typical mesh.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.514-515
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• 2005

본 논문에서는 As-Ge-Se-S 박막에 (P:P) 편광빔을 이용하여 회절격자를 형성시키고 비편광 (Non-Polarization) 빔을 이용하여 생성된 격자를 소거시키고 그에 따른 회절효율을 조사 하였다. (P:P) 편광으로 기록된 회절 효율은 시간이 지나도 최대 회절효율의 변화가 없었으나 비편광 빔으로 기록된 회절효율은 시간이 지남에 따라 급격한 회절효율의 감소를 보인다. 따라서 (P:P) 편광으로 회절격자를 형성시키고 비편광빔으로 격자의 소거를 진행하여 약 83%의 회절격자의 소거가 이루어졌다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.8
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• pp.1-7
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• 2006

In the present study, A 3-D chimera technique for overlapped bodies in relative motion is studied using unstructured meshes. If all node points of a mesh element at solid boundary are in another body, this element is excluded from computational domain. For computation of unsteady flow, non-active cells have proper variables using interpolation and extrapolation. These variables are used in next time step. The motion of a launching trajectory ejected from a wing and the motion of deploying fins of a trajectory which have not been simulated are computed to conform practicality of this technique.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.157-164
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• 2016

The performance of convective heat transfer in rod bundle flow was experimentally evaluated using a twist-vane spacer grid. A $4{\times}4$ square-arrayed rod bundle was prepared as the test section, with a pitch-to-diameter ratio(P/D) of ~1.35. To check the convective heat transfer performance, the circumferential and longitudinal variations in rod-wall temperatures were measured downstream of the twist-vane spacer grid. In the circumferential measurements, the rod-wall temperature toward the twist-vane tip showed the lowest value, which might be due to the deflected water flow caused by the twist-vane. On the other hand, the wall temperature of the longitudinal measurements near the twist-vane spacer grid decreased dramatically, which implies that the convective heat transfer performance was enhanced. A heat transfer enhancement of ~35 % was achieved near downstream of the twist-vane spacer grid, as compared with the upstream value. Based on the present experimental data, a correlation for predicting the heat transfer performance of a twist-vane spacer grid was proposed.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.14-15
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• 2000

현재 많은 분야에서 광섬유를 이용한 센서 연구가 활발하게 진행되고 있다. 광섬유 코어 부분에 규칙적인 굴절률 변화를 준 광섬유 격자는 외부의 기계적, 열적 변화에 대한 높은 민감도를 가지며 따라서 이를 위한 광센서로 많이 이용되고 있다. 본 연구에서는 장주기를 갖는 격자가 한쌍으로 새겨진 광섬유 격자를 이용하여 비틀림에 의한 파장 스펙트럼의 변화를 측정하여 비틀림 센서로서의 응용 가능성을 모색하였다. (중략)

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.17-25
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• 2006

In the present study, a 2-D chimera technique for overlapped bodies in relative motion is developed using unstructured triangular meshes. The solid boundary nodes located next to the intersecting point between bodies are merged to the intersecting point to assure accurate representation of the intersecting region. In order to assign proper value of flow variables at the nodes located out of the computational field, interpolation is conducted for non-active nodes. For validation, the motions of a NACA64A006 airfoil and a NACA0012 airfoil with a plane flap are computed and the results are compared with other simulations. The motion of a launching missile ejected from a NACA0012 airfoil is also simulated.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.2
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• pp.94-104
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• 2002

As a part of scientific data visualization automatic generation algorithms for a contour map have been investigated mainly on data which are defined at every lattice point. But in actual situation like weather data measurement. it is impossible to get data defined at every lattice point This is because the exact value on every lattice point can not be obtained due to characteristics in sampling devices or sampling methods. In order to define data on every lattice point where data were not sampled an interpolation method. was applied to the sample data to assign approximate values for some lattice type data but by using the non-lattice type of sample data sets. A triangle data link was defined by using non lattice points directly based on actually sample data set, not by using the pre-processed rectangle lattice points. The suggested algorithm generates a contour map a contour map only by using sample data set which are much smaller than old one without data interpolation and there is no skew on data any more since it does not need any interpolation to get the values of the defined lattice points.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.116-123
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• 2017

This study has been investigated the applicability of auxetic mesh for the reinforcement of structural members. Typical materials including concrete behaves with positive poisson's ratio when external force is applied. In this study, it has been theoretically verified that metallic auxetic mesh restrains as such mechanical behaviors of concrete resulting in the stiffness increase. Also, regarding the applicability to construction field, a type of auxetic mesh has been suggested and the mechanical characteristics were numerically analyzed.

• Journal of Korea Water Resources Association
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• v.43 no.1
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• pp.105-117
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• 2010

This paper presents a new and simple technique to perform MUSCL reconstruction for solving 2D shallow water equations. The modified MUSCL scheme uses weighted area ratio to apply non-uniform grid in stead of the previous method that equally distributed the difference of conservation variables to each interface. The suggested method can physically reconstruct conservation variables in case of uniform grid as well as non-uniform grid. In this study, Unsplit scheme applicable to unstructured grid is used and efficient slope limiter of TVD scheme is used to control numerical oscillation which can be occurred in modified MUSCL scheme. For accurate and efficient treatment of bed slope term, the modified MUSCL scheme is coupled with the surface gradient method. The finite volume model applied to suggested scheme is verified through a comparison between numerical solution and laboratory measurements data such as the simulations of isolated building test case and Bellos's dam break test case.

• Journal of the Korean Society of Radiology
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• v.17 no.4
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• pp.573-579
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• 2023

This study compares dose difference between the presence or absence of grid in Chest PA radiography using auto exposure control and compares image quality among presence, absence or virtual grid, and proposes a new clinically useful grid combination for chest radiography. The human body phantom was placed Chest PA position and the dosimeter was placed at T6. The same irradiation conditions and field size were applied. 30 images were obtained in the state in which grid was applied and in the state in which grid was not applied, and an additional 30 images in which the virtual grid was applied to the image without the grid were obtained. Radiation dose was presented to entrance surface dose. The image quality was analyzed by comparing the signal-to-noise and contrast-to-noise ratio. ESD decreased by 48% when the grid was not used, compared to when the grid was used. SNR and CNR increased by 32% and 30% compared to grid use when grid was not used, respectively. In the case of using the virtual grid, it increased by 18% and 16% respectively, compared to the case of using the grid. As a result of this study, it is believed that when using a virtual grid instead of a grid, the quality of the image can be maintained while reducing the patient dose.