• 응용통계연구
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• 제26권3호
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• pp.431-440
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• 2013

우리는 두꺼운 꼬리를 갖는 분포의 모수를 추정하는 방법론을 연구하였다. 일반적으로 MLE(최대우도 추정량)가 모수추정 방법론중에 가장 많이 사용되는데, 이는 MLE가 점근적 일치성과 정규성 그리고 효율성을 가지고 있기 때문이다. 하지만 MLE가 늘 가장 좋은 추정법은 아니다. 어떤 경우에는 MLE가 존재하지 않을 수도 있고 계산이 안정적이지 않을 수도 있다. 본 논문에서는 비선형 최소제곱추정법을 이용한 모수추정 방법론을 제시하고 그 성능을 MLE와 비교하였다. NLS 추정량은 empirical CDF와 이론적 CDF의 차이의 제곱을 최소화 하는 방법론이다. 본 논문에서는 두꺼운 꼬리를 가지는 다양한 분포하에서 우리가 제안하는 NLS방법론과 MLE와의 성능을 비교하였다. 그 결과, Burr 분포에서 표본의 수가 적을 때 우리의 방법론이 MLE보다 좋은 성능을 보여주었고, Frechet 분포에서도 좋은 결과를 얻을 수 있었다.

• 한국습지학회지
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• 제18권2호
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• pp.132-147
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• 2016

동아시아 지역의 위성 토양수분 데이터 활용을 위해 Soil Moisture Ocean Salinity (SMOS) 위성에 탑재된 Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) 센서와 Global Change Observation Mission-Water (GCOM-W1) 위성에 탑재된 Advanced Microwave Scanning Radiometer 2 (AMSR2) 센서 기반 토양수분 데이터를 자료동화 데이터인 Global Land Data Assimilation System (GLDAS)를 기준 값으로 Cumulative Distribution Function (CDF) 기법과 회귀식을 활용하여 보정하는 연구를 수행하였다. 동아시아 지역에서 발생하는 전파간섭의 영향을 고려하여 토양수분 산출에 적합하다고 판단되는 Radio Frequency Interference (RFI), Data Quality indeX (DQX) 한계값과, 합성일수를 제시하였다. 보완된 위성 토양수분 데이터를 지점 토양수분 데이터와 비교한 결과 상관계수가 평균 27%, 11% 증가하였고, Root Mean Square Deviation (RMSD, 평균제곱근 편차)는 평균 61%, 57% 감소하였다. 추가적으로, 보정된 위성데이터를 GLDAS 토양수분 데이터와 비교했을 때, 보정된 MIRAS 및 AMSR2 데이터는 한반도의 80% 및 90%의 지역에서 상관계수가 증가하였으며, 한반도 전역에서 RMSD가 감소하였다. 본 연구를 통해 향후 MIRAS 및 AMSR2 위성 데이터를 융합하여 각 위성의 토양수분 데이터를 보완 할 수 있는 가능성을 제시하였다.

• 전자공학회논문지
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• 제50권8호
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• pp.45-52
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• 2013

다중 포인트 협력 통신 기술(CoMP; Coordinated Multi-Point)은 3GPP(3rd Generation Partnership Project)의 LTE-A(Long Term Evolution-Advanced) 시스템 기술 중 하나로 고려된다. 본 논문에서는 CoMP 기술의 세부 기법 중 하나인 CB(Coordinated Beamforming) 기법에 대하여 설계하고, 이를 바탕으로 성능 분석이 이루어졌다. LTE-A 시스템의 이종 네트워크(HetNet; Heterogeneous Network) 환경에서 몬테카를로 모의실험이 이루어졌으며, CDF(Cumulative Distribution Function) 그래프를 통하여 그 성능을 확인한다. 모의실험 결과를 통해 CoMP 기술을 사용하였을 때 성능 이득을 얻을 수 있으며, CoMP 기술에 다양한 스케줄링 및 프리코딩 기법을 적용하였을 때 더 좋은 성능을 가져오는 것을 확인할 수 있다.

• 전자공학회논문지
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• 제53권9호
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• pp.3-11
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• 2016

향상된 무선 통신 시스템을 이용하여 교통안전을 개선하기 위해 V2X (Vehicle to Everything) 통신에 대한 연구가 활발히 진행되고 있다. V2X 통신은 미래 교통안전 및 이동성의 발전을 위한 하나의 주요 솔루션이다. 본 논문에서는 LTE (Long Term Evolution) 기반 V2X 시스템 레벨 시뮬레이터 (SLS : System Level Simulator)를 개발하고 차량통신을 위한 적응적 전송 기법을 제안한다. 제안 기법은 시간 및 주파수 영역에서 랜덤하게 자원을 할당하고 전송 확률에 따라 메시지 전송을 결정한다. 성능 분석은 주기적 메시지 전송에서 고속도로의 경우에 대하여 이루어 졌다. 모의실험 결과, 제안한 기법에서 자원 충돌 및 간섭이 감소함 따라 PRR (Packet Reception Ratio)의 CDF (Cumulative Distribution Function) 및 평균 PRR이 향상 되는 것을 볼 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권6호
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• pp.3188-3207
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• 2017

In this paper, we propose an image enhancement algorithm to improve license plate extraction rate in various environments (Day Street, Night Street, Underground parking lot, etc.). The proposed algorithm is composed of image enhancement algorithm and license plate extraction algorithm. The image enhancement method can improve an image quality of the degraded image, which utilizes a histogram information and overall gray level distribution of an image. The proposed algorithm employs an interpolated probability distribution value (PDV) in order to control a sudden change in image brightness. Probability distribution value can be calculated using cumulative distribution function (CDF) and probability density function (PDF) of the captured image, whose values are achieved by brightness distribution of the captured image. Also, by adjusting the image enhancement factor of each part region based on image pixel information, it provides a function that can adjust the gradation of the image in more details. This processed gray image is converted into a binary image, which fuses narrow breaks and long thin gulfs, eliminates small holes, and fills gaps in the contour by using morphology operations. Then license plate region is detected based on aspect ratio and license plate size of the bound box drawn on connected license plate areas. The images have been captured by using a video camera or a personal image recorder installed in front of the cars. The captured images have included several license plates on multilane roads. Simulation has been executed using OpenCV and MATLAB. The results show that the extraction success rate is more improved than the conventional algorithms.

• 대한금속재료학회지
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• 제46권9호
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• pp.554-562
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• 2008

The distribution and prediction interval for the misorientation angle of grain boundary at which $Cr_2N$ was precipitated during heating at $900^{\circ}C$ for $10^4$ sec were newly estimated, and followed by the estimation of mathematical and median rank methods. The probability density function of the misorientation angle can be estimated by a statistical analysis. And then the ($1-{\alpha}$)100% prediction interval of misorientation angle obtained by the estimated probability density function. If the estimated probability density function was symmetric then a prediction interval for the misorientation angle could be derived by the estimated probability density function. In the case of non-symmetric probability density function, the prediction interval could be obtained from the cumulative distribution function of the estimated probability density function. In this paper, 95, 99 and 99.73% prediction interval obtained by probability density function method and cumulative distribution function method and compared with the former results by median rank regression or mathematical method.

• 조명전기설비학회논문지
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• 제21권9호
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• pp.87-94
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• 2007

This paper presents new criteria for DGA(Dissolved Gases Analysis) using CDF(Cumulative Distribution Function) obtained from the data from the diagnosis of transformers operated in KEPCO over a period of 16 years. Because of differences in operating environments, construction type, oil volume, and other factors, the interpretative criteria of DGA at KEPCO differs from other standards such as IEC-60599, or Rogers and Doernenburg. To suggest the most appropriate criteria, the DGA data from transformers under normal conditions as well as from developing fault transformers were collected. Using these data, this study suggests the limitative gas level of transformers under normal operating conditions and verifies the suitability of the criteria. Because the application of this new criterion to transformers at KEPCO increases the detectable ratio of incipient faults and reduces unnecessary follow-up sampling and analysis, the new criteria yields a more reliable prediction of transformer condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권4호
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• pp.1866-1883
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• 2019

As the youngest branch of information hiding, network covert timing channels conceal the existence of secret messages by manipulating the timing information of the overt traffic. The popular model-based framework for constructing covert timing channels always utilizes cumulative distribution function (CDF) of the inter-packet delays (IPDs) to modulate secret messages, whereas discards high-order statistics of the IPDs completely. The consequence is the vulnerability to high-order statistical tests, e.g., entropy test. In this study, a rich security model of covert timing channels is established based on IPD chains, which can be used to measure the distortion of multi-order timing statistics of a covert timing channel. To achieve rich security, we propose two types of covert timing channels based on nested lattices. The CDF of the IPDs is used to construct dot-lattice and interval-lattice for quantization, which can ensure the cell density of the lattice consistent with the joint distribution of the IPDs. Furthermore, compensative quantization and guard band strategy are employed to eliminate the regularity and enhance the robustness, respectively. Experimental results on real traffic show that the proposed schemes are rich-secure, and robust to channel interference, whereas some state-of-the-art covert timing channels cannot evade detection under the rich security model.

• Journal of applied mathematics & informatics
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• 제42권3호
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• pp.647-661
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• 2024

This study aims to determine the optimal solution to transportation problems. We proposed a novel approach for tackling the initial basic feasible solution. This is a critical step toward achieving an optimal or near-optimal solution. The transportation issue is an issue of distributing goods from several sources to several destinations. The literature demonstrates many ways to improve IBFS. In this work, to solve the IBFS, we suggested a new method based on the statistical formula called cumulative distribution function (CDF) in exponential distribution, and inverse contra-harmonic mean (ICHM). The spreadsheet converts transportation cost values into exponential cost cell values. The stepping-stone method is used to identify an optimum solution. The results are compared with other existing methodologies, the suggested method incorporates balanced, and unbalanced, maximizing the profits, random values, and case studies which produce more effective outcomes.

• 대한음성학회지:말소리
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• 제55권
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• pp.131-142
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• 2005

A mismatch between the training and the test conditions often causes a drastic decrease in the performance of the speech recognition systems. In this paper, non-linear transformation techniques based on histogram equalization in the acoustic feature space are studied for reducing the mismatched condition. The purpose of histogram equalization(HEQ) is to convert the probability distribution of test speech into the probability distribution of training speech. While conventional histogram equalization methods consider only the probability distribution of a test speech, for noise-corrupted test speech, its probability distribution is also distorted. The transformation function obtained by this distorted probability distribution maybe bring about miss-transformation of feature vectors, and this causes the performance of histogram equalization to decrease. Therefore, this paper proposes a new method of calculating noise-removed probability distribution by using assumption that the CDF of noisy speech feature vectors consists of component of speech feature vectors and component of noise feature vectors, and this compensated probability distribution is used in HEQ process. In the AURORA-2 framework, the proposed method reduced the error rate by over $44\%$ in clean training condition compared to the baseline system. For multi training condition, the proposed methods are also better than the baseline system.