• Journal of Digital Contents Society
• /
• v.18 no.1
• /
• pp.175-182
• /
• 2017

Noises are usually generated by various external causes and low quality devices in image data acquisition and recording as well as by channel interference in image transmission. Since these noise signals result in the loss of information, subsequent image processing is subject to the corruption of the original image. In general, image processing is performed in the mixed noise environment where common types of noise, known to be Gaussian and impulse, are present. This study proposes an iterative weighted mean filter for reducing mixed type of noise. Impulse noise pixels are first turned off in the input image, then $3{\times}3$ sliding window regions are processed by replacing center pixel with the result of weighted mean mask operation. This filtering processes are iterated until all the impulse noise pixels are replaced. Applied to images corrupted by Gaussian noise with ${\sigma}=10$ and different levels of impulse noise, the proposed filtering method improved the PSNR by up to 12.98 dB, 1.97 dB, 1.97 dB respectively, compared to SAWF, AWMF, MMF when impulse noise desities are less than 60%.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.03a
• /
• pp.1-13
• /
• 2008

An efficient segregated algorithm for the coupling of velocity and pressure of incompressible fluid flow, called IDEAL Inner Doubly-Iterative Efficient Algorithm for Linked-Equations), has been proposed by the present authors. In the algorithm there exist double inner iterative processes for pressure equation at each iteration level, which almost completely overcome two approximations in SIMPLE algorithm. Thus the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate and stability of solution process. The performance of the IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems is analyzed and a systemic comparison is made between the algorithm and three other most widely-used algorithms (SIMPLER, SIMPLEC and PISO). It is found that the IDEAL algorithm is the most robust and the most efficient one among the four algorithms compared. This new algorithm is used for the velocity prediction of a new interface capturing method. VOSET, also proposed by the present author. It is found that the combination of VOSET and IDEAL can appreciably enhance both the interface capture accuracy and convergence rate of computations.

• 한국전산유체공학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1-13
• /
• 2008

An efficient segregated algorithm for the coupling of velocity and pressure of incompressible fluid flow, called IDEAL (Inner Doubly-Iterative Efficient Algorithm for Linked-Equations), has been proposed by the present authors. In the algorithm there exist double inner iterative processes for pressure equation at each iteration level, which almost completely overcome two approximations in SIMPLE algorithm. Thus the coupling between velocity and pressure is fully guaranteed, greatly enhancing the convergence rate and stability of solution process. The performance of the IDEAL algorithm for three-dimensional incompressible fluid flow and heat transfer problems is analyzed and a systemic comparison is made between the algorithm and three other most widely-used algorithms (SIMPLER, SIMPLEC and PISO). It is found that the IDEAL algorithm is the most robust and the most efficient one among the four algorithms compared. This new algorithm is used for the velocity prediction of a new interface capturing method -VOSET, also proposed by the present author. It is found that the combination of VOSET and IDEAL can appreciably enhance both the interface capture accuracy and convergence rate of computations.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.46 no.6
• /
• pp.26-35
• /
• 2009

In this paper, we present morphology-based step region extraction and regularized iterative point-spread-function (PSF) estimation methods. The proposed PSF estimation method uses canny edge detector to extract the edge of the input image. We extract feasible vertical and horizontal edges using morphology analysis, such as the hit-or-miss transform. Given extracted edges we estimate the optimal step-response using flattening and normalization processes. The PSF is finally characterized by solving the equation which relates the optimal step response and the 2D isotropic PSF. We shows the restored image by the estimated PSF. The proposed algorithm can be applied a fully digital auto-focusing system without using mechanical focusing parts.

• Korean Journal of Remote Sensing
• /
• v.24 no.4
• /
• pp.309-324
• /
• 2008

In this study the retrieval algorithms have been developed to retrieve total precipitable water (TPW) from Terra/Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) infrared measurements using a physical iterative retrieval method and a split-window technique over East Asia. Retrieved results from these algorithms were validated against Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSM/I) over ocean and radiosonde observation over land and were analyzed for investigating the key factors affecting the accuracy of results and physical processes of retrieval methods. Atmospheric profiles from Regional Data Assimilation and Prediction System (RDAPS), which produces analysis and prediction field of atmospheric variables over East Asia, were used as first-guess profiles for the physical retrieval algorithm. We used RTTOV-7 radiative transfer model to calculate the upwelling radiance at the top of the atmosphere. For the split-window technique, regression coefficients were obtained by relating the calculated brightness temperature to the paired radiosonde-estimated TPW. Physically retrieved TPWs were validated against SSM/I and radiosonde observations for 14 cases in August and December 2004 and results showed that the physical method improves the accuracy of TPW with smaller bias in comparison to TPWs of RDAPS data, MODIS products, and TPWs from split-window technique. Although physical iterative retrieval can reduce the bias of first-guess profiles and bring in more accurate TPWs, the retrieved results show the dependency upon initial guess fields. It is thought that the dependency is due to the fact that the water vapor absorption channels used in this study may not reflect moisture features in particular near surface.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.5
• /
• pp.2474-2480
• /
• 2013

A stress ribbon pedestrian bridge is the structure in which the axial force of prestressed deck, which is developed by introducing prestressed force into the thin deck with the very low value of span to deck-depth ratio which is installed on bearing cables with the specified sag, resists most of external loadings. Since the design of stress ribbon pedestrian bridges should be conducted by assuming the cross-section of deck, the area of bearing cables and post-tensioning cables, and the prestressed force of post-tensioning cables, it requires much more iterative processes than the design of general bridges. In this research, to minimize such iteration processes, regression equations which can reasonably assume the area of bearing cables and post-tensioning cables, and the prestressed force of post-tensioning cables, are suggested for the bridge length of 80m with the sag-span ratios of 1/30, 1/40, and 1/50.

• Journal of Engineering Education Research
• /
• v.9 no.2
• /
• pp.52-70
• /
• 2006

Systems Engineering(SE), as a special discipline evolved from multidisciplinary and interdisciplinary design knowledges and practical lessons learned from development practices, is required to develop today's ever-growing large complex systems. As computer speed and analytic sophistication accelerate their applications, modern society's needs have become increasingly varied and complex. Rapid advances in Systems Engineering and its education programs among the developed countries demonstrate their needs as an alternative to what is lacking from traditional disciplinary engineering to meet new challenges of our changing social environments. Systems Engineering is an interdisciplinary approach that includes both management and technical processes. Its processes, methods, and tools are used to evolve, define, and verify an integrated, life-cycle balanced set of system solution that satisfy customer needs and requirements. The process methodology offers a top-down comprehensive, iterative and recursive problem solving process which includes the stating the problems, investigating the alternatives, architecting and modeling the system, integrating and operating the system, assessing and re-evaluating the system performances. The purpose of this paper is to research the cases of SE educational programs for both domestic and other developed countries and to propose recommendations for the domestic SE educational programs in the future.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.5
• /
• pp.873-882
• /
• 1992

The study is concerned with the rigid-plastic element analysis for axisymmetric hydromechanical deep drawing in which the fluid flow influences the metal deformation. Due to the fluid pressure acting on the sheet material hydromechanical deep drawing is distinguished from the conventional deep drawing processes. In considering the pressure effect, the governing equation for fluid pressure is solved and the result is reflected on the global stiffness matrix. The solution procedure consists of two stages ; i.e., initial bulging of the sheet surface before the initiation of steady fluid flow in the flange and fluid-lubricated stage. The problem is decoupled between fluid analysis and analysis of solid deformation by deformation by iterative feedback of mutual computed results. The corresponding experiments are carried out for axisymmetric hydro-mechanical deep drawing of annealled aluminium sheet as well as for deep drawing. It has been shown from the experiments that the limit drawing ratio for hydro-mechanical deep drawing is improved as compared with deep drawing. The computed results are in good agreement with the experiment for variation of punch head and chamber pressure with respect to the punch travel and for distribution of thicknees strain. It is thus shown that the present method of analysis can be effectively applied to the analysis of axisymmetric hydro-mechanical deep drawing processes.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.6
• /
• pp.23-29
• /
• 2003

Transonic two-phase flow of Saturated humid air, in which relative humidity is 100%, with various condensation processes around thin airfoils is investigated. The study uses an extended transonic small-disturbance(TSD) model of Rusak and Lee [11, 12] which includes effects of heat addition to the flow due to condensation. Two possible limit types of condensation processes are considered. In the nonequilibrium and homogeneous process, the condensate mass fraction is calculated according to classical nucleation and droplet growth rate models. In the equilibrium process, the condensate mass fraction is calculated by assuming an isentropic process. The flow and condensation equations are solved numerical1y by iterative computations. Results under same upstream conditions describe the flow structure, field of condensate, and pressure distribution on airfoil's surfaces. It is found that flow characteristics, such as position and strength of shock waves and airfoil’s pressure distribution, are different for the two condensation processes. Yet, in each case, heat addition as a result of condensation causes significant changes in flow behavior and affects the aerodynamic performance of airfoils.

• Journal of information and communication convergence engineering
• /
• v.14 no.1
• /
• pp.26-34
• /
• 2016

The alignment of DNA sequences is one of the important processes in the field of bioinformatics. The Smith-Waterman algorithm (SWA) performs optimally for aligning sequences but is computationally expensive. Field programmable gate array (FPGA) performs the best on parameters such as cost, speed-up, and ease of re-configurability to implement SWA. The performance of FPGA-based SWA is dependent on efficient cell-basic implementation-unit design. In this paper, we present an optimized systolic cell design while avoiding oversimplification, very large-scale integration (VLSI)-level design, and direct mapping of iterative equations such as previous cell designs. The proposed design makes efficient use of hardware resources and provides portability as the proposed design is not based on gate-level details. Our cell design implementing a linear gap penalty resulted in a performance improvement of 32× over a GPP platform and surpassed the hardware utilization of another implementation by a factor of 4.23.