• Journal of Institute of Convergence Technology
• /
• v.4 no.1
• /
• pp.33-35
• /
• 2014

Investigation of flow characteristics behind a edged backward facing step is important for selecting appropriate positions of building constructions in the desert area. In the present study, the effect of edge angles on the flow characteristics is investigated using a commercial software CFD-ACE+. When the edge angle is less than 30 degree, reattachment length decreases, whereas when the edge angle is larger than 30 degrees, reattachment angle increases. It can be concluded that the flow patterns behind an edged backward facing step is classified as the two, streamlined and bluffed bodies. Appropriate edge angles have an effect of increasing the momentum toward the wall, which can reduce the reattachment length. It can be said that present results can be utilized for diverse industrial applications that includes the backward facing step.

• Proceedings of the KSME Conference
• /
• 2001.11b
• /
• pp.312-317
• /
• 2001

Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow with the edge are studied numerically. The vortical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential field. To investigate the effects of the edge shape the rectangular forward step is chamfered with various angles. Calculation show that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vortex height. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

• 한국초전도학회:학술대회논문집
• /
• v.10
• /
• pp.99-102
• /
• 2000

We have studied the effects of d-wave symmetry on the critical current of YBa$_2$Cu$_3$O$_7$ step-edge Josephson junctions. The critical current along various misorientation angle was measured and analyzed with the concept of grain-boundary junctions with d-wave symmetry. Experimental results of c-oriented YBCO step-edge junctions with various in-plane misorientation angles were qualitatively in good agreement with the theory. The out-of-plane misorientation angle is usually formed between two grains with the c axes perpendicular to each other and is normally not controllable.

• Journal of Broadcast Engineering
• /
• v.18 no.4
• /
• pp.619-630
• /
• 2013

In this paper, we propose an edge directed color demosaicing algorithm considering color channel correlation. The proposed method consists of local region classification step and edge directional interpolation step. In the first step, each region of a given Bayer image is classified as normal edge, pattern edge, and flat regions by using intra channel and inter channel gradients. Especially, two criteria and verification process for the normal edge and pattern edge classification are used to reduce edge direction estimation error, respectively. In the second step, edge directional interpolation process is performed according to characteristics of the classified regions. For horizontal and vertical directional interpolations, missing color components are obtained from interpolation equations based on intra channel and inter channel correlations in order to improve the performance of the directional interpolations. The simulation results show that the proposed algorithm outperforms conventional approaches in both objective and subjective terms.

• Journal of Sensor Science and Technology
• /
• v.28 no.4
• /
• pp.251-255
• /
• 2019

We propose a two-step lithography process to minimize edge-bead issues caused by thick photoresist (PR) coating. In the conventional PR process, the edge bead can be efficiently removed by applying an edge-bead removal (EBR) process while rotating the silicon wafer at a high speed. However, applying conventional EBR to the production of desired PR mold with unique negative patterns cannot be used because a lower rpm of spin coating and a lower temperature in the soft bake process are required. To overcome this problem, a two-step lithography process was developed in this study and applied to the fabrication of a polydimethylsiloxane (PDMS) film having super-hydrophobic characteristics. Following UV exposure with a first photomask, the exposed part of the silicon wafer was selectively removed by applying a PR developer while rotating at a low rpm. Then, unique PR mold structures were prepared by employing an additional under-exposure process with a second mask, and the mold patterns were transferred to the PDMS. Results showed that the fabricated PDMS film based on the two-step lithography process reduced the height difference from 23% to 5%. In addition, the water contact angle was greatly improved by spraying of hydrophobic nanosilica on the dual-scaled PDMS surface.

• Journal of the Korean Institute of Telematics and Electronics B
• /
• v.32B no.8
• /
• pp.1074-1084
• /
• 1995

In this paper, we investigate edge extraction and segmentation of range images. We first discuss problems that arise in the conventional region-based segmentation methods and edge-based ones using principal curvatures, then we propose an edge-based algorithm. In the proposed algorithm, we extract edge contours by using the Gaussian filter and directional derivatives, and segment a range image based on extracted edge contours, Also we present the problem that arises in the conventional thresholding, then we propose a new threshold selection method. To solve the problem that local maxima of the first- and second- order derivatives gather near step edges, we first find closed roof edge contours, fill the step edge region, and finally thin edge boundaries. Computer simulations with several range images show that the proposed method yields better performance than the conventional one.

• Journal of Advanced Marine Engineering and Technology
• /
• v.24 no.2
• /
• pp.82-89
• /
• 2000

Edge detection is the first step and very important step in image analysis. In this paper, proposed edge detection operators based on informations of edge types and it is different from other classical edge detection operators such as gradient and surface fitting operators. The first, we defined characteristics of edge types such as localization, thinness, length. The second, we defined valid edge types and ideal edge pixel positions in $3\times3$window based on edge characteristics of edge types. And we proposed edge detection algorithm and twelve windows based on valid edge types. In specially, proposed algorithm was shown better performence of edge detection than other operators such as gradient operator and the LoG(Laplacian of Gaussian) operator of zero crossings.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.12 no.3
• /
• pp.213-220
• /
• 2002

Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow and the edge are studied numerically. The vertical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential fields. To investigate the effects of the edge shape the rectangular forward step is chamfered wish various angles. Calculation shows that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vertex height and its strength. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.

• 한국초전도학회:학술대회논문집
• /
• v.9
• /
• pp.133-133
• /
• 1999

We have fabricated and tested a simple circuit of the rapid single-flux-quantum(RSFQ) four-stage shift register using a single layer high-T$_c$ superconducting (HTS) YBa$_2Cu_3O_{7-x}$ (YBCO) thin film structure with 9 step-edge Josephson junctions. The circuit includes two read superconducting quantum interference devices(SQUID) and four stages. To establish a robust HTS RSFQ device fabrication process, we have focussed the reproducible process of sharp and straight step-edge formation as well as the ratio of film thickness to step height t/h. The spread of step-edge junction parameters was measured from each13 junctions with t/h=l/3, l/2, and 2/3 at various temperatures. We have demonstrated the simplified operation of the shift register at 65 K..

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.38 no.6
• /
• pp.675-683
• /
• 2001

In this paper, we propose the edge compensation algorithm which connects the adjacent edges without losing the information of the skeletons on the edge image. The proposed edge compensation algorithm is composed of succeeding two steps. In the first step, the uplifted image is obtained by uplifting the edge image repeatedly. The next step is to extract the edge image from the uplifted image using the skeleton extraction algorithm. Experimental results show that the proposed method connects the adjacent edges without the distortion of the original edge information compared to the traditional method.