• Communications for Statistical Applications and Methods
• /
• 제19권2호
• /
• pp.287-292
• /
• 2012

Sample periodogram is widely known as an inconsistent estimator for true spectral density. We show that it becomes consistent when the true spectrum at the zero frequency (often known as long-run variance) equals zero. Asymptotic results for consistency of the periodogram as well as the rate of convergence are formally derived.

• Journal of the Korean Statistical Society
• /
• 제34권1호
• /
• pp.49-60
• /
• 2005

In this paper we introduce a nonparametric method for estimating the probability density function of detection distances in line transect sampling. The estimator is obtained using a frequency histogram density estimation method. The asymptotic properties of the proposed estimator are derived and compared with those of the kernel estimator under the assumption that the data collected satisfy the shoulder condition. We found that the asymptotic mean square error (AMSE) of the two estimators have about the same convergence rate. The formula for the optimal histogram bin width is derived which minimizes AMSE. Moreover, the performances of the corresponding k-nearest-neighbor estimators are studied through simulation techniques. In the absence of our knowledge whether the shoulder condition is valid or not a new semi-parametric model is suggested to fit the line transect data. The performances of the proposed two estimators are studied and compared with some existing nonparametric and semiparametric estimators using simulation techniques. The results demonstrate the superiority of the new estimators in most cases considered.

• 한국콘텐츠학회논문지
• /
• 제12권5호
• /
• pp.515-524
• /
• 2012

본 연구는 초등학교 6학년 국어교과서 4종(6-1 읽기, 6-1 말하기 듣기 쓰기, 6-2 읽기, 6-2 말하기 듣기 쓰기)에 나타나는 어휘들에 대한 통계(전체 음절수, 음절종류, 음절 출현빈도, 어절 개수, 어절 종류, 어절 평균길이, 어절 출현빈도, 품사 등)를 조사하였다. 한글 음절수는 194,683개, 음절종류는 1,290개, 평균 음절 출현빈도는 150.9회이다. 어절 개수는 70,185개, 어절 종류는 22,647개, 어절 평균 출현빈도는 3.1회이다. 평균 음절 길이는 2.8음절이며, 가장 긴 어절은 10음절이다. 품사는 읽기 교과는 명사가 말하기 듣기 쓰기교과는 동사가 약간 많다.

• 한국대기환경학회지
• /
• 제5권1호
• /
• pp.88-95
• /
• 1989

The aspects of the occurence frequency of $SO_2$ concentration were studied with the observed data in Seoul and the scheme that is capable of estimating not only highest concentration for a variety of averaging times but also concentrations for arbitary occurrence frequency with long term arithmatic mean and geometric standard deviation data, was evaluated. The results of the statistical analysis show that the occurrence frequency is almost log normal except a few cases, and 3rd highest values of daily mean concentration were about 4.2 $\sim$ 5.2 times higher than annual arithmatic mean. The evaluation with the observed hourly concentration shows that the scheme fairly well estimate the short concentration of arbitary occurrence frequence and it can be used for air quality management and environmental impact assessment.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2000년도 춘계학술대회논문집
• /
• pp.1108-1113
• /
• 2000

A condition monitoring methodology for rotating machinery is proposed based on multivariate statistical analysis. The CMS usually are using the vibration signal amplitude such as acceleration RMS, peak and velocity RMS to detect machine faults but the information is not so enough that CMS cannot perform reliable monitoring. So new parameters are added such as shape factor, crest factor, kurtosis and skewness as time domain parameters and spectrum amplitude of rotating frequency, $2^{nd}$ harmonics and gear mesh frequency etc. as frequency domain parameters. Many parameters are combined to represent the machine state using the Hotelling's $T^2$ statistics. The proposed methodology is tested in laboratory and the on-line experiment has shown that the proposed methodology offers a reliable monitoring for rotating machinery.

• Advances in aircraft and spacecraft science
• /
• 제4권5호
• /
• pp.543-553
• /
• 2017

Vibration is a source of performance degradation in all optical imaging systems. Performance of high resolution remote sensing payloads is often limited due to satellite platform vibrations. Effects of Linear and high frequency sinusoidal vibrations on the system MTF are known exactly in closed form but the low frequency vibration effects is a random process and must be considered statistically. Usually the vibration MTF budget is defined based on the mission requirements and the overall MTF limitations. For analyzing low frequency effects, designer must know all the systems specifications and parameters. With a good understanding of harmful vibration frequencies and amplitudes in the system preliminary design phase, their effects could be removed totally or partially. This procedure is cost effective and let the designer to eliminate just harmful vibrations and avoids over-designing. In this paper we have analyzed the effects of low-frequency platform vibrations on the payload's modulation transfer function. We have used a statistical analysis to find the probability of imaging with a MTF equal or greater than a pre-defined budget for different missions. The worst and average cases have been discussed and finally we have proposed "look-up figures". Using these look-up figures, designer can choose the electro-optical parameters in such a way that vibration effects be less than its pre-defined budget. Furthermore, using the results, we can propose a damping profile based on which vibration frequencies and amplitudes must be eliminated to stabilize the payload system.

• 한국통신학회논문지
• /
• 제30권7A호
• /
• pp.578-586
• /
• 2005

본 논문에서는 하향링크에서 사용자 용량 증가를 위하여 통계적 다중화에 기반한 RFH-OFDMA(Random Frequency Hopping-Orthogonal Frequency Division Multiple Access) 방식을 제안한다. 사용자 용량은 한 셀에서 주어진 기본 데이터 전송률로 데이터 전송이 가능한 최대 사용자의 수를 의미한다. 본 논문에서는 제안된 통계적 다중화 기반의 RFH-OFDMA 방식의 하향링크 사용자 용량과 기존 FH-OFDMA 방식에서의 하향링크 사용자 용량을 비교한다. 사용자 용량은 부반송파 개수와 인접 셀 간섭에 의하여 제한되며 수신 SINR이 가장 열악한 환경에서의 시스템 용량을 상호 비교하기 위하여 사용자는 모두 셀 경계에 있다고 가정하고 인접 셀 간섭은 최대 값을 갖는다고 가정한다. 시뮬레이션 결과를 통하여, 사용자의 채널 활성도가 0.1, 수신단에서 요구되는 Eb/IO가 6dB, 3-sector 안테나가 사용된 경우에 제안된 RFH-OFDMA 방식이 262명을 수용한 반면에 기존의 FH-OfDMA방식의 경우 51명의 사용자를 수용할 수 있음을 보여준다.

• Communications for Statistical Applications and Methods
• /
• 제6권1호
• /
• pp.327-336
• /
• 1999

In a multinomial sampling scheme some categories may be observed as partially classified because of technical or economic reasons. In this paper the maximum likelihood estimators(M.L.E) of multinomial probabilities are obtained when some frequencies are merged. We obtained the M.L.E and a method to evaluate the information gained by including merged frequencies in M.L.E we obtained an estimator of the covariance matrix and it is used to examine the information gained by including the merged frequency counts in estimating the cell probabilities. When certain individual frequency counts are missing a method is proposed for estimating the cell probabilities using EM algorithms.

• Communications for Statistical Applications and Methods
• /
• 제24권1호
• /
• pp.1-13
• /
• 2017

This manuscript summarized advances in bootstrap methods for long-range dependent time series data. The stationary linear long-memory process is briefly described, which is a target process for bootstrap methodologies on time-domain and frequency-domain in this review. We illustrate time-domain bootstrap under long-range dependence, moving or non-overlapping block bootstraps, and the autoregressive-sieve bootstrap. In particular, block bootstrap methodologies need an adjustment factor for the distribution estimation of the sample mean in contrast to applications to weak dependent time processes. However, the autoregressive-sieve bootstrap does not need any other modification for application to long-memory. The frequency domain bootstrap for Whittle estimation is provided using parametric spectral density estimates because there is no current nonparametric spectral density estimation method using a kernel function for the linear long-range dependent time process.

• Journal of Nutrition and Health
• /
• 제35권3호
• /
• pp.332-351
• /
• 2002

The purpose of this study was to investigate effect of living condition and aging on food intake in Korea. 98 free-meal receivers and 81 members in well-being center for the aged were asked about their food frequency and food consumption and their socioeconomic status by a questionnaire. All data were analyzed by SPSS (Statistical Packages for the Social Sciences) 10.0 program. There were statistical differences of living condition, marital status, former job and teeth status between free-meal receivers and people with stable lives. Moreover, all age groups of free-meal receivers had lower income, living expenses, educational period and frequency of physical activity than those of people with stable lives. But smoking and drinking was much higher in free-meal receivers. Arthritis was the most prevalent disease in both groups. And free-meal receivers had higher blood pressure and lower Body Mass Index than people with stable lives. Food consumption of free-meal receivers was definitely lower than that of people with stable lives in terms of food frequency and standard amount of food eaten. But noodles, bean sprouts and eggs were very important foods for free-meal receives. Food consumption of the aged was affected by age, educational period, income, blood pressure, duration after retirement, frequency of physical activity and Body Mass Index. Therefore, as various socioeconomic status affects on food intakes of the aged, more effective and practical nutritional programs which consider the receivers'socioeconomic status are needed for the nutritionally at-risk groups like the aging free-meal receivers.