• 대한산업공학회지
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• 제39권6호
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• pp.535-545
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• 2013

The goal of stock investment is earning high rate or return with stability. To accomplish this goal, using a portfolio that distributes stocks with high rate of return with less variability and a stock price prediction model with high accuracy is required. In this paper, three methods are suggested to require these conditions. First of all, in portfolio re-balance part, Max-Return and Min-Risk (MRMR) model is suggested to earn the largest rate of return with stability. Secondly, Entering/Leaving Rule (E/L) is suggested to upgrade portfolio when particular stock's rate of return is low. Finally, to use outstanding stock price prediction model, a model based on Semi-Supervised Learning (SSL) which was suggested in last research was applied. The suggested methods were validated and applied on stocks which are listed in KOSPI200 from January 2007 to August 2008.

• Structural Engineering and Mechanics
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• 제80권5호
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• pp.539-551
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• 2021

With the continuous increase of computational capacity, more and more complex nonlinear elastoplastic constitutive models were developed to study the mechanical behavior of elastoplastic materials. These constitutive models generally contain a large amount of physical and phenomenological parameters, which often require a large amount of computational costs to determine. In this paper, an inverse parameter determination method is proposed to identify the constitutive parameters of elastoplastic materials, with the consideration of both strain rate effect and temperature effect. To carry out an efficient design, a hybrid optimization algorithm that combines the genetic algorithm and the Nelder-Mead simplex algorithm is proposed and developed. The proposed inverse method was employed to determine the parameters for an elasto-viscoplastic constitutive model and Johnson-cook model, which demonstrates the capability of this method in considering strain rate and temperature effect, simultaneously. This hybrid optimization algorithm shows a better accuracy and efficiency than using a single algorithm. Finally, the predictability analysis using partial experimental data is completed to further demonstrate the feasibility of the proposed method.

• 한국측량학회지
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• 제33권5호
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• pp.343-351
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• 2015

차량 항법장치에서 활용하고 있는 GNSS는 차분기법을 이용하더라도 수 미터 수준의 측위 정밀도를 확보할 수 있으므로, 길안내 수준의 위치기반서비스만 가능하다. 반면 정밀 측지/측량분야에서는 민간용 코드 대신 반송파 위상정보를 이용하여 센티미터에서 밀리미터까지의 위치 정확도를 확보할 수 있다. 본 연구에서는 국토교통부 국토지리정보원의 NRTK(Network-RTK) 서비스를 차량항법에 적용하기 위한 기반연구를 수행하였다. 이를 위해, 차량에 GNSS 장비를 탑재하고 전국범위에서 NRTK를 수행하였으며, 그 결과를 바탕으로 NRTK의 차량항법 적용가능 여부를 판단하고자 하였다. 본 연구의 분석결과, NRTK는 대체적으로 높은 모호정수 결정율을 보이며, 지상 차량항법에 충분히 적용할 수 있을 것으로 판단된다. 다만, 도심지에서는 모호정수 결정율이 급격히 낮아지며, 실수해일 경우에는 측위 오차가 10m 이상의 수준에 달할 정도로 불안정할 수 있다. 따라서 안정적인 위치정확도를 확보하기 위해서는 실수해의 오차영향을 최소화할 수 있는 방안 등이 모색되어야 할 것으로 사료된다. 그러나 수신환경이 양호한 일부 도심지에서는 NRTK를 활용하여 센티미터 수준의 측위 정확도를 확보할 수 있을 것으로 판단된다. FKP는 고속 주행 시 모호정수 결정율이 약 55%까지 낮아지는 경우가 발생하였으므로 여러 수신환경을 고려하여 측위 정확도를 결정하여야 한다. 마지막으로 대기교란(2단계 이상)에 의해 NRTK(FKP) 접속오류로 의심되는 사례가 발생하였으며, 이에 대한 정확한 원인규명이 필요하다.

• 대한방사선기술학회지:방사선기술과학
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• 제29권1호
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• pp.29-37
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• 2006

유방암은 여성의 암발생에서 가장 많이 차지하고 있으며 생활양식의 변화에 따라 점점 증가하고 있다. 전 인구의 50%을 차지하고 있는 여성에서 유방 검사는 유방X-선촬영이 스크리닝 검사로 가장 많이 사용되고 있어 정도관리가 매우 중요하다. 따라서 본 조사는 경상북도를 4개 구역으로 나누어 유방촬영장비에 대한 조사야와 광조사야의 일치도, 광학농도, 압박율, 팬톰을 이용한 전체모조 병소 수 및 일반적인 정도관리의 실태를 조사 하였다. 조사야의 일치도에서는 조사대상 11개 병원비 장비 중 7곳이 기준치에 적합했으며, 광학농도는 6곳, 압박율은 7곳이 합격한 것으로 조사되었다. 전체모조병소 속의 섬유소, 석희화그룹, 종괴들의 수는 모두 10개 이상으로 나와 기준치 내에 포함 되었으나 전용현상기와 판독대를 보유하고 있는 의료기관은 3곳이였다. 이와 같은 결과는 유방영상의 화질관리가 제대로 되고 있지 않음을 반영한다. 또한 압박장치, 조사야 일치도, 팬텀 영상 평가의 3개 항목을 모두 충족시키는 경우는 27.2%로 나타나 정확한 유방암의 진단을 위해 정도관리에 대한 관심이 더욱 필요하다고 사료된다.

• 핵의학기술
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• 제28권1호
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• pp.57-69
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• 2024

Purpose: Quantitative analysis through count measurement in nuclear medicine planar images is limited by analysis techniques that are useful for obtaining various clinical information or by organ overlap or artifacts in actual clinical practice. On the other hand, the use of SPECT tomography images is quantitative analysis using volume rather than planar, which is not only free from problems such as projection overlap, but also has excellent quantitative accuracy. In the use of developing SPECT quantitative analysis technology, this study aims to compare the accuracy of quantitative analysis between ROI of the conventional planar images and VOI of the SPECT tomographic images in evaluating the count change happened by the volume change of the source. Materials and Methods: A ^99mTcO₄^- source(200.17 MBq) was filled with sterilized water in the syringe to create a phantom with an inner diameter volume of 60 cc, and a planar image and a SPECT image were obtained by reducing the volume by 15 cc (25%) respectively. ROI and VOI(threshold: 1~45%, 5% interval) were set for each image obtained to estimate true count and measure the total count, and compared with the preseted volumetric change rate(%). Results: When volume changes of 25%, 50%, and 75% occurred in the initial volume of 60 cc(100%) of the phantom, the average count changes of the measured planar image were 26.8%, 53.2%, 77.5%, and the average count changes of the SPECT image were 24.4%, 50.9%, and 76.8%. In this case, the VOI size(cm³) set showed an average change rate of 25.4%, 51.1%, and 76.6%. The highest threshold value for the accuracy of radioactive concentration by VOI size (average error -1.03%) was 35%, and the VOI size of the same threshold had an error of -17.1% on average compared to the actual volume. Conclusion: On average, the count-based volumetric change rate in nuclear medicine images was able to track changes more accurately using VOI than ROI, but there was no significant difference with relatively similar value. However, the accuracy of radioactive concentration according to individual VOI sizes did not match, but it is considered that a relatively accurate quantitative analysis can be expected when the size of VOI is set smaller than the actual volume.

• 동의생리병리학회지
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• 제21권1호
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• pp.338-346
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• 2007

For Objectivity development of the body shape that is an importance standard for the classification of sasang constitutional medicine diagnosis, We made a comparison between Automatic & Physical measuring. This study uses 2 attitude which lies down & standing. We measured the body of patients(Width 5 places and circumference 8 places) and analyzed the anthropometric data dividing into sex, age, BMI. 296 patients's data are used in the analysis.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.555-564
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• 2020

The purpose of this study is to analyze the efficiency of research institutes of futures companies, and to promote the development of futures market and real economy. This study employs DEA-solver software to conduct super-efficiency data envelopment analysis (SE-DEA), and also selects 40 representative futures research institutes in China as decision-making units (DMUs). For data of input and output indicators, we collect from the China Futures Association, Futures Daily, Hexun.com and Webstock.com respectively, and the time duration is the 103 trading days between from October 2019 to February 2020. Then the indicator for the strategy accuracy rate is calculated separately by analyzing the strategies published by each DMUs in public media. In conclusions, most institutes have excessive investment in human resources, and also have insufficient strategy accuracy rate and insufficient published research reports. The findings of this study suggest that Chinese futures companies need to improve the efficiency of research institutes, and better meet the demand of the financial market. In fact, the analysis of the efficiency of the futures company research institute has not been found in the literature worldwide, Application of DEA model in efficiency analysis of securities and futures research institutions and establishment of indicators are the innovations of this paper.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.132-132
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• 2015

Virtual metrology (VM) model based on plasma information (PI) parameter for C4F8 plasma-assisted oxide etching processes is developed to predict and monitor the process results such as an etching rate with improved performance. To apply fault detection and classification (FDC) or advanced process control (APC) models on to the real mass production lines efficiently, high performance VM model is certainly required and principal component regression (PCR) is preferred technique for VM modeling despite this method requires many number of data set to obtain statistically guaranteed accuracy. In this study, as an effective method to include the 'good information' representing parameter into the VM model, PI parameters are introduced and applied for the etch rate prediction. By the adoption of PI parameters of b-, q-factors and surface passivation parameters as PCs into the PCR based VM model, information about the reactions in the plasma volume, surface, and sheath regions can be efficiently included into the VM model; thus, the performance of VM is secured even for insufficient data set provided cases. For mass production data of 350 wafers, developed PI based VM (PI-VM) model was satisfied required prediction accuracy of industry in C4F8 plasma-assisted oxide etching process.

• 한국지능시스템학회논문지
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• 제23권3호
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• pp.262-267
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• 2013

The recognition of human emotional state is one of the most important components for efficient human-human and human- computer interaction. In this paper, four emotions such as fear, disgust, joy, and neutral was a main problem of classifying emotion recognition and an approach of visual-stimuli for eliciting emotion based on physiological signals of skin conductance (SC), skin temperature (SKT), and blood volume pulse (BVP) was used to design the experiment. In order to reach the goal of solving this problem, half-against-half (HAH) multi-class support vector machine (SVM) with Gaussian radial basis function (RBF) kernel was proposed showing the effective techniques to improve the accuracy rate of emotion classification. The experimental results proved that the proposed was an efficient method for solving the emotion recognition problems with the accuracy rate of 90% of neutral, 86.67% of joy, 85% of disgust, and 80% of fear.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1934-1935
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• 2011

In order for a service robot to perform several tasks, basically autonomous navigation technique such as localization, mapping, and path planning is required. The localization (estimation robot's pose) is fundamental ability for service robot to navigate autonomously. In this paper, we propose a new system for point pattern matching based visual global localization using spot lightings in ceiling. The proposed algorithm us suitable for system that demands high accuracy and fast update rate such a guide robot in the exhibition. A single camera looking upward direction (called ceiling vision system) is mounted on the head of the mobile robot and image features such as lightings are detected and tracked through the image sequence. For detecting more spot lightings, we choose wide FOV lens, and inevitably there is serious image distortion. But by applying correction calculation only for the position of spot lightings not whole image pixels, we can decrease the processing time. And then using point pattern matching and least square estimation, finally we can get the precise position and orientation of the mobile robot. Experimental results demonstrate the accuracy and update rate of the proposed algorithm in real environments.