• Journal of Information Processing Systems
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• 제16권2호
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• pp.508-521
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• 2020

We compared a novel encoding Lempel-Ziv complexity (ELZC) with three common complexity algorithms i.e., approximate entropy (ApEn), sample entropy (SampEn), and classic Lempel-Ziv complexity (CLZC) so as to determine a satisfied complexity and its corresponding quality indices for assessing quality of multi-lead electrocardiogram (ECG). First, we calculated the aforementioned algorithms on six artificial time series in order to compare their performance in terms of discerning randomness and the inherent irregularity within time series. Then, for analyzing sensitivity of the algorithms to content level of different noises within the ECG, we investigated their change trend in five artificial synthetic noisy ECGs containing different noises at several signal noise ratios. Finally, three quality indices based on the ELZC of the multi-lead ECG were proposed to assess the quality of 862 real 12-lead ECGs from the MIT databases. The results showed the ELZC could discern randomness and the inherent irregularity within six artificial time series, and also reflect content level of different noises within five artificial synthetic ECGs. The results indicated the AUCs of three quality indices of the ELZC had statistical significance (>0.500). The ELZC and its corresponding three indices were more suitable for multi-lead ECG quality assessment than the other three algorithms.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1573-1582
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• 2015

In lifetime data analysis, it is generally known that the lifetimes of test items may not be recorded exactly. There are also situations wherein the withdrawal of items prior to failure is prearranged in order to decrease the time or cost associated with experience. Moreover, it is generally known that more than one cause or risk factor may be present at the same time. Therefore, analysis of censored competing risks data are needed. In this article, we derive the Bayes estimators for the entropy function under the exponential distribution with an unknown scale parameter based on multiply Type II censored competing risks data. The Bayes estimators of entropy function for the exponential distribution with multiply Type II censored competing risks data under the squared error loss function (SELF), precautionary loss function (PLF) and DeGroot loss function (DLF) are provided. Lindley's approximate method is used to compute these estimators.We compare the proposed Bayes estimators in the sense of the mean squared error (MSE) for various multiply Type II censored competing risks data. Finally, a real data set has been analyzed for illustrative purposes.

• Bioinformatics and Biosystems
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• 제1권2호
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• pp.134-138
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• 2006

우울증은 가장 유병율이 높은 '기분 장애'(mood disorder)의 일종으로, 약 20%의 인구가 일생동안 우울증 증상을 한번쯤 경험한다. 이러한 우울증은 크게 '우울 장애'(major depressive disorder)와 '양극성 장애'(bipolar disorder)로 구분된다. 환자의 질병 분류에 따라 사용되는 약과 의학적 처방이 다르기 때문에, 우울증 환자의 빠르고 정확한 진단 및 분류는 매우 중요하다. 기존의 다면성 인성검사(MMPI)와 같은 통계적인 방법이 우울증 환자의 진단을 위해 사용돼 왔으나, 장시간의 집중력을 요구하기 때문에 집중력 저하의 특징을 보이는 우울증 환자들에게 적용하는데 어려움이 있다. 이 논문에서는 이러한 문제를 해결하고자, 빠른 측정이 가능하고 측정동안 집중력을 요하지 않는 EEC 데이터의 분석을 통해 우울증 환자의 분류를 시도하였다. EEG 채널 간 정보 흐름에서의 비선형성과 근사 엔트로피(approximate entropy)의 크기를 속성(attribute)으로 사용하여 데이터 마이닝 기법 중 의사 결정 트리(decision tree)와 가능성 기반 서포트 벡터머신(possibilistic support vector machines) 통해 분석을 수행하였다. 30명의 주요 우울장애환자와 24명의 양극성 장애 환자를 통해 위의 분석을 수행한 결과 의사 결정 트리의 경우 85.19% 의 정확도를 가지며 분류해냈고, 가능성 기반 서포트 벡터머신의 경우 77.78%의 정확도를 보여줬다. 본 연구는 가능성 기반 서포트 벡터 머신 분석이 우울증 환자는 진단하고 분류하는데 유용하게 적용될 수 있는 가능성을 제시하고 있다.

• 한국운동역학회지
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• 제25권3호
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• pp.323-333
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• 2015

Objective : The purpose of this study was to investigate the changes of gait patterns and muscle activations with increased loads during stair walking. Also, it can be used as descriptive data about continuous stair walking in a real life setting. Method : Twelve sedentary young male adults(Age: $27.0{\pm}1.8yrs$, Weight: $65.8{\pm}9.9kg$) without any lower extremity injuries participated in this study. Participants performed stair walking up 7 floors and their ascending and descending motion on each floor was analyzed. A wireless electromyography(EMG) were attached on the Rectus Femoris(RF), Biceps Femoris(BF), Gastrocnemius(GN), Tibialis Anterior(TA) muscle to calculate integrated EMG(iEMG), median frequency(MDF) and co-contraction index(CI). Chest and left heel accelerometer signal were recorded by wireless accelerometer and those were used to calculate approximate entropy(ApEn) for analyzing gait pattern. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was LSD. Results : During ascending stairs, there were a statistically significant difference in Walking time between 1-2nd and other floors(p=.000), GN iEMG between 2-3th and 6-7th(p=.043) floor, TA MDF between 1-2nd and 5-6th(p=.030), 6-7th(p=.015) floor and TA/GN CI between 2-3th and 6-7th(p=.038) floor and ApEn between 1-2nd and 6-7th(x: p=.003, y: p=.005, z: p=.006) floor. During descending stairs, there were a statistically significant difference in TA iEMG between the 6-5th and 3-2nd(p=.026) floor, and for the ApEn between the 1-2nd and 6-7th(x: p=.037, y: p=.000, z: p=.000) floor. Conclusion : Subjects showed more regular pattern and muscle activation response caused by regularity during ascending stairs. Regularity during the first part of stair-descending could be a sign of adaptation; however, complexity during the second part could be a strategy to decrease the impact.

• 대한수학회보
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• 제52권4호
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• pp.1059-1068
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• 2015

The paper is devoted to studying a fourth-order degenerate parabolic equation, which arises in fluid, phase transformation and biology. Based on the existence and uniqueness of one semi-discrete problem, two types of approximate solutions are introduced. By establishing some necessary uniform estimates for those approximate solutions, the existence and uniqueness of the corresponding parabolic problem are obtained. Moreover, the long time asymptotic behavior is established by the entropy functional method.

• Journal of the Korean Statistical Society
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• 제24권1호
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• pp.225-231
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• 1995

An eventual uniform equicontinuity condition is investigated in the context of the uniform central limit theorem (UCLT) for continuous martingales. We assume the usual intergrability condition on metric entropy. We establish an exponential inequality for a martingales. Then we use the chaining lemma of Pollard (1984) to prove an eventual uniform equicontinuity which is a sufficient condition of UCLT. We apply the result to approximate a stochastic integral with respect to a martingale to that of a Brownian motion.

• 한국통계학회:학술대회논문집
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• 한국통계학회 2005년도 춘계 학술발표회 논문집
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• pp.221-226
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• 2005

우리나라의 애국가(愛國歌), 일본(Kimigayo) 그리고 미국국가(The star-spangled Banner) 등에 대해서 악보가 갖는 고유정보를 카오스적 접근 방법인 근사엔트로피(approximate entropy)와 허스트(Hurst) 지수를 이용하여 각각 음계(scale)의 복잡도(複雜度)와 장기기억속성(長期 記憶 屬性)을 계산하여 비교하였던 바, 애국가가 상대적으로 복잡도에서 가장 높았으며, 세 국가 모두 장기 기억효과가 있는 것으로 나타났는데, 지속적인(persistent) 성향은 일본국가가 가장 컸다.

• 대한토목학회논문집
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• 제32권1B호
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• pp.21-27
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• 2012

T. Linde가 제안한 HLLL 기법에서는 일반화된 엔트로피 함수의 도입으로 중앙파가 평가되므로 모든 파속이 초기 상태로부터 결정된다. HLLE 기법과 달리 Roe의 선형화 기법과 완전히 결별되고 HLLC 기법과 달리 정확해에 의존되지 않으므로 모태인 HLL 기법의 온전한 계승으로 볼 수 있다. 이 연구에서는 생성항이 없는 1차원 천수방정식에 농도와 관련된 보존변수를 추가한 지배방정식에 대해 총 에너지를 일반화된 엔트로피 함수로 두고 HLLL 기법을 적용하여 모형을 구성하였다. 정확해가 알려진 세 경우에 대해 모의한 결과, 1차 정확도 수치해의 한계에도 불구하고, 대체로 정확해와 잘 일치하였다. HLLL 기법은 그 외 HLL 형 기법에 비해 우수한 것으로 나타났다. 특히, 물이 빠져 바닥이 드러나는 경우에서 그 전선이 비교적 정확하게 포착되었다. 다만, 그 외 기법에 비해 계산 시간이 더 오래 걸리는 단점이 드러났다.

• 한국운동역학회지
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• 제27권1호
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• pp.45-52
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• 2017

Objective: The aim of this study was to investigate the periodicity of the lower extremity joint flexion/extension angle to compare the local stability between young and elderly women during walking on a treadmill. Method: Eighteen young women (mean $age=21.2{\pm}1.6y$; mean $mass=57.1{\pm}6.1kg$; mean $height=1.61{\pm}0.04m$) and 18 elderly women (mean $age=66.4{\pm}1.2y$; mean $mass=55.4{\pm}8.3kg$; mean $height=1.56{\pm}0.04m$) participated in this study. Approximate entropy (ApEn) was used to determine the periodicity in the lower limb joint angles. Results: The ApEn values of the two groups were statistically greater in the surrogate data test than in the original time series data (p<.05). The periodicity of the hip and ankle flexion/extension angles decreased in the elderly women group compared with the young women group (p<.05). The periodicity of the lower extremity joint flexion/extension angle showed that the ankle joint increased dominatingly in both groups (p<.05); the hip joint decreased compared with the knee joint in the young women group; and the knee joint decreased compared with the hip joint in the elderly women group (p<.05). Conclusion: These results suggest that the lower extremity joint flexion/extension angles of the young and elderly women during walking contained random noises as well as biological signals. In addition, the differences in the periodicity in the lower extremity joint between the young and elderly women may provide some insight in predicting potential falls and be used as a characteristic indicator for determining local stability in elderly women during walking.

• 한국운동역학회지
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• 제29권4호
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• pp.247-254
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• 2019

Objective: The goal of this study was to determine the center of pressure (CoP) complexity pattern in approximate entropy technique between genders at different conditions of running speed. Background: It is conducted to evaluate the complexity pattern of CoP in the increment of running speed to have insights to injury prediction, stability, and auxiliary aids for the foot. Method: Twenty men (age=22.3±1.5 yrs.; height=176.4±5.4 cm; body weight=73.9±8.2 kg) and Twenty women (age=20.8±1.2 yrs.; height=162.8±5.2 cm; body weight=55.0±6.3 kg) with heel strike pattern were recruited for the study. While they were running at 2.22, 3.33, 4.44 m/s speed on a treadmill (instrumented dual belt treadmills, USA) with a force plate, CoP data were collected for the 10 strides. The complexity pattern of the CoP was analyzed using the ApEn technique. Results: The ApEn of the medial-lateral and antero-posterior CoP in the increment of running speed showed significantly difference within genders (p<.05), but there were not statistically significant between genders at all conditions of running speed. Conclusion: Based on the results of this study, CoP complexity pattern in the increment of running speed was limited to be characterized between genders as an indicator to judge the potential injury and stability. Application: In future studies, it is needed to investigate the cause of change for complexity of CoP at various running speed related to this study.