• Title/Summary/Keyword: optimization problem

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Performance Improvement of Independent Component Analysis by Fixed-point Algorithm of Adaptive Learning Parameters (적응적 학습 파라미터의 고정점 알고리즘에 의한 독립성분분석의 성능개선)

  • Cho, Yong-Hyun;Min, Seong-Jae
    • The KIPS Transactions:PartB
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    • v.10B no.4
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    • pp.397-402
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    • 2003
  • This paper proposes an efficient fixed-point (FP) algorithm for improving performances of the independent component analysis (ICA) based on neural networks. The proposed algorithm is the FP algorithm based on Newton method for ICA using the adaptive learning parameters. The purpose of this algorithm is to improve the separation speed and performance by using the learning parameters in Newton method, which is based on the first order differential computation of entropy optimization function. The learning rate and the moment are adaptively adjusted according to an updating state of inverse mixing matrix. The proposed algorithm has been applied to the fingerprints and the images generated by random mixing matrix in the 8 fingerprints of 256${\times}$256-pixel and the 10 images of 512$\times$512-pixel, respectively. The simulation results show that the proposed algorithm has the separation speed and performance better than those using the conventional FP algorithm based on Newton method. Especially, the proposed algorithm gives relatively larger improvement degree as the problem size increases.

Construction of an Educational Computer Model for FAB of Semiconductor Manufacturing (반도체 웨이퍼 가공(FAD) 공정에서의 교육용 컴퓨터 모델 구축)

  • Jeon, Dong-Hoon;Lee, Chil-Gee
    • Journal of KIISE:Computing Practices and Letters
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    • v.6 no.3
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    • pp.311-318
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    • 2000
  • The importance of the semiconductor industry in Korea has been growing, but the manufacturers are experiencing two major problems: poor optimization of production and low localization ratio of production equipments. Due to the complex manufacturing processes and special features such as OTD (On Time Delivery) and LIPAS (Line Item Performance Against Schedule) possibilities, several attempts to apply MRP or spreadsheet have been failed to meet the expectations. This paper describes the computer modeling technique as the solutions to analyze the problem, to formalize the semiconductor manufacturing process, and to build an advanced manufacturing environments. The computer simulation models are built referring the FAB facilities of the National Inter - University Semiconductor Research Center to show the FAB processes and the functions of each process.

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A Period Assignment Algorithm for Real-Time System Design (실시간 시스템 설계를 위한 주기 할당 알고리즘)

  • Ryu, Min-Soo;Hong, Seong-Soo
    • Journal of KIISE:Computer Systems and Theory
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    • v.27 no.1
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    • pp.61-67
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    • 2000
  • Digital controllers found in many industrial real-time systems consist of a number of interacting periodic tasks. To sustain the required control quality, these tasks possess the maximum activation periods as performance constraints. An essential step in developing a real-time system is thus to assign each of these tasks a constant period such that the maximum activation requirements are met while the system utilization is minimized [1]. Given a task graph design allowing producer/consumer relationships among tasks [2], resource demands of tasks, and range constraints on periods, the period assignment problem falls into a class of nonlinear optimization problems. This paper proposes a ploynomial time approximation algorithm which produces a solution whose utilization does not exceed twice the optimal utilization. Our experimental analysis shows that the proposed algorithm finds solutions which are very close to the optimal ones in most cases of practical interest.

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Perceptual Color Difference based Image Quality Assessment Method and Evaluation System according to the Types of Distortion (인지적 색 차이 기반의 이미지 품질 평가 기법 및 왜곡 종류에 따른 평가 시스템 제안)

  • Lee, Jee-Yong;Kim, Young-Jin
    • Journal of KIISE
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    • v.42 no.10
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    • pp.1294-1302
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    • 2015
  • A lot of image quality assessment metrics that can precisely reflect the human visual system (HVS) have previously been researched. The Structural SIMilarity (SSIM) index is a remarkable HVS-aware metric that utilizes structural information, since the HVS is sensitive to the overall structure of an image. However, SSIM fails to deal with color difference in terms of the HVS. In order to solve this problem, the Structural and Hue SIMilarity (SHSIM) index has been selected with the Hue, Saturation, Intensity (HSI) model as a color space, but it cannot reflect the HVS-aware color difference between two color images. In this paper, we propose a new image quality assessment method for a color image by using a CIE Lab color space. In addition, by using a support vector machine (SVM) classifier, we also propose an optimization system for applying optimal metric according to the types of distortion. To evaluate the proposed index, a LIVE database, which is the most well-known in the area of image quality assessment, is employed and four criteria are used. Experimental results show that the proposed index is more consistent with the other methods.

Selectivity Estimation for Multidimensional Sequence Data in Spatio-Temporal Databases (시공간 데이타베이스에서 다차원 시퀀스 데이타의 선택도추정)

  • Shin, Byoung-Cheol;Lee, Jong-Yun
    • Journal of KIISE:Databases
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    • v.34 no.1
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    • pp.84-97
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    • 2007
  • Selectivity estimation techniques in query optimization have been used in commercial databases and histograms are popularly used for the selectivity estimation. Recently, the techniques for spatio-temporal databases have been restricted to existing temporal and spatial databases. In addition, the selectivity estimation techniques focused on time-series data such as moving objects. It is also impossible to estimate selectivity for range queries with a time interval. Therefore, we construct two histograms, CMH (current multidimensional histogram) and PMH (past multidimensional histogram), to estimate the selectivity of multidimensional sequence data in spatio-temporal databases and propose effective selectivity estimation methods using the histograms. Furthermore, we solve a problem about the range query using our proposed histograms. We evaluated the effectiveness of histograms for range queries with a time interval through various experimental results.

Statistical Analysis on Process Variables in Linear Roll-CMP (선형 Roll-CMP에서 공정변수에 관한 통계적 분석)

  • Wang, Han;Lee, Hyunseop;Jeong, Haedo
    • Tribology and Lubricants
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    • v.30 no.3
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    • pp.139-145
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    • 2014
  • Nowadays, most micro-patterns are manufactured during flow line production. However, a conventional rotary chemical mechanical polishing (CMP) system has a limited throughput for the fabrication of large and flexible electronics. To overcome this problem, we propose a novel linear roll-CMP system for the planarization of large-area electronics. In this paper, we present a statistical analysis on the linear roll-CMP process of copper-clad laminate (CCL) to determine the impacts of process parameters on the material removal rate (MRR) and its non-uniformity (NU). In the linear roll-CMP process, process parameters such as the slurry flow rate, roll speed, table feed rate, and down force affect the MRR and NU. To determine the polishing characteristics of roll-CMP, we use Taguchi's orthogonal array L16 (44) for the experimental design and F-values obtained by the analysis of variance (ANOVA). We investigate the signal-to-noise (S/N) ratio to identify the prominent control parameters. The "higher is better" for the MRR and "lower is better" for the NU were selected for obtaining optimum CMP performance characteristics. The experimental and statistical results indicate that the down force and roll speed mainly affect the MRR and the down force and table feed rate determine the NU in the linear roll-CMP process. However, over 186.3 N of down force deteriorates the NU because of the bending of substrate. Roll speed has little relationship to the NU and the table feed rate does not impact on the MRR. This study provides information on the design parameter of roll-CMP machine and process optimization.

Assessing the Impact of Advanced Technologies on Utilization Improvement of Substations

  • Han, Dong;Yan, Zheng;Zhang, Dao-Tian;Song, Yi-Qun
    • Journal of Electrical Engineering and Technology
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    • v.10 no.5
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    • pp.1921-1929
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    • 2015
  • The smart substation is the heart of a transmission system, which is particularly emphasized as the most significant composition of smart grids in China. In order to assess the functionality performance of substation technologies, this paper presents methods used to identify the most promising solutions for smart substation design and to evaluate the technical levels of available technologies. The multi-index optimization model is presented to address the issue of smart substation planning. A mathematical model of the planning decision problem is established with multiple objectives consisting of economic, reliability, and green key indices, and many kinds of concerns including physical and environmentally friendly operations are formulated as a set of constraints. With respect to the assessment of the technical level regarding integration of advanced technologies into a substation, a modified grey whitenization weight function is adopted to structure a novel grey clustering method. The proposed grey clustering approach is used to overcome the difficulty of insufficient quantitative assessment capacity for traditional methods. The evaluation of technical effects provides the classification definition for the development phase and the maturity level of the smart substation. The effectiveness of the proposed approaches in planning decision-making and evaluation of construction efforts is demonstrated with case studies involving the actual smart substation projects of Wenchongkou substation in China Southern Power Grid (CSG) and Mengzi substation in State Grid Corporation of China (SGCC).

A Study on Selecting the Optimal Location of BTB HVDC for Reducing Fault Current in Metropolitan Regions Based on Genetic Algorithm Using Python (Python을 이용한 유전 알고리즘 기반의 수도권 고장전류 저감을 위한 BTB HVDC 최적 위치 선정 기법에 관한 연구)

  • Song, Min-Seok;Kim, Hak-Man;Lee, Byung Ha
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.8
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    • pp.1163-1171
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    • 2017
  • The problem of fault current to exceed the rated capacity of a power circuit breaker can cause a serious accident to hurt the reliability of the power system. In order to solve this issue, current limiting reactors and circuit breakers with increased capacity are utilized but these solutions have some technical limitations. Back-to-back high voltage direct current(BTB HVDC) may be applied for reducing the fault current. When BTB HVDCs are installed for reduction in fault current, selecting the optimal location of the BTB HVDC without causing overload of line power becomes a key point. In this paper, we use genetic algorithm to find optimal location effectively in a short time. We propose a new methodology for determining the BTB HVDC optimal location to reduce fault current without causing overload of line power in metropolitan areas. Also, the procedure of performing the calculation of fault current and line power flow by PSS/E is carried out automatically using Python. It is shown that this optimization methodology can be applied effectively for determining the BTB HVDC optimal location to reduce fault current without causing overload of line power by a case study.

Evaluation of Quality Improvement Achieved by Deterministic Image Restoration methods on the Pan-Sharpening of High Resolution Satellite Image (결정론적 영상복원과정을 이용한 고해상도 위성영상 융합 품질 개선정도 평가)

  • Byun, Young-Gi;Chae, Tae-Byeong
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.29 no.5
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    • pp.471-478
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    • 2011
  • High resolution Pan-sharpening technique is becoming increasingly important in the field of remote sensing image analysis as an essential image processing to improve the spatial resolution of original multispectral image. The general scheme of pan-sharpening technique consists of upsampling process of multispectral image and high-pass detail injection process using the panchromatic image. The upsampling process, however, brings about image blurring, and this lead to spectral distortion in the pan-sharpening process. In order to solve this problem, this paper presents a new method that adopts image restoration techniques based on optimization theory in the pan-sharpening process, and evaluates its efficiency and application possibility. In order to evaluate the effect of image restoration techniques on the pansharpening process, the result obtained using the existing method that used bicubic interpolation were compared visually and quantitatively with the results obtained using image restoration techniques. The quantitative comparison was done using some spectral distortion measures for use to evaluate the quality of pan-sharpened image.

A review on thermochemical pretreatment in Lignocellulosic bioethanol production (목질계 바이오에탄올 제조공정에서 열화학적 전처리에 관한 고찰)

  • Ko, Jae-Jung;Yun, Sang-Leen;Kang, Sung-Won;Kim, Seog-Ku
    • Journal of the Korea Organic Resources Recycling Association
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    • v.16 no.1
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    • pp.79-88
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    • 2008
  • The production of bioethanol, which is one of the alternative fuel, cause the various problem such as agflation in human society. As a substitute for the feedstock, lignocellulosic biomass have a big potential. However, bioethanol production with cellulosic material is not commercialized due to high cost. Thermochemical pretreatment to improve the rate of enzyme hydrolysis and increase the recovery of fermentable sugar, is required in order to achieve the cost down in bioethanol production. In this study, various problems and technologies for pretreatment is introduced. Acid hydrolysis, alkali hydrolysis, steam explosion, organosolv process, ammonia explosion, and wet oxidation pretreatment remove lignin and hemicellulose, and reduce cellulose crystallinity. Optimization of pretreatment process on various sources of lignocellulosic biomass such as softwood, hardwood, and straw should be performed.

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