• Communications for Statistical Applications and Methods
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• 제21권2호
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• pp.147-160
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• 2014

In this paper, we introduce the exponentiated Weibull-geometric (EWG) distribution which generalizes two-parameter exponentiated Weibull (EW) distribution introduced by Mudholkar et al. (1995). This proposed distribution is obtained by compounding the exponentiated Weibull with geometric distribution. We derive its cumulative distribution function (CDF), hazard function and the density of the order statistics and calculate expressions for its moments and the moments of the order statistics. The hazard function of the EWG distribution can be decreasing, increasing or bathtub-shaped among others. Also, we give expressions for the Renyi and Shannon entropies. The maximum likelihood estimation is obtained by using EM-algorithm (Dempster et al., 1977; McLachlan and Krishnan, 1997). We can obtain the Bayesian estimation by using Gibbs sampler with Metropolis-Hastings algorithm. Also, we give application with real data set to show the flexibility of the EWG distribution. Finally, summary and discussion are mentioned.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.359-364
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• 2002

Statistical energy method is widely used for the prediction of vibrational and acoustical behavior of complex structures, such as ship building and automobile in mid-, high frequency ranges. However. in order to convince this SEA result, it is important to verify estimated SEA parameters, e. g. modal density, energy in each subsystem, damping loss factor, coupling loss factor. with possible other method. For modal density parameter, the experimental estimations via Experimental Modal Analysis are checked with those from finite element method for both beam- plate and plate-plate cans. Loss factors are calculated by Lyon's simple method for the two subsystem. finally. modal experiments are carried out by varying the mass added on the junction of two subsystem for the purpose of investigating the influence on the coupling loss factor's behavior.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.207-209
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• 2005

Recently, the use of IPMSM is coming to be active, in many industrial applications. In sensorless drive of IPMSM, it is important to know the exact information of the initial rotor position, because the wrong estimation of the initial rotor position brings about the decrease of the starting torque, or a temporary reverse revolution, In addition, PMSM is necessary to use the accurate information of the inductance for the precise torque control owing to the reluctance torque. In this paper presents initial rotor position estimation method and, measure method of the each-axis inductance. And to minimize the speed estimations error, the estimated speeds are compensated by using an instantaneous reactive power in synchronously rotating reference frame.

• ETRI Journal
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• 제43권2호
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• pp.324-331
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• 2021

Space-based automatic dependent surveillance-broadcast (ADS-B) is an important emerging augmentation of existing ground-based ADS-B systems. In this paper, the problem of space-based ultra-long-range reception processing of ADS-B signals is described. We first introduce a header detection method for accurately determining the pulse position of a weak ADS-B signal. We designed a signal encoding method, shaping method, and fitness function. We then employed a genetic algorithm to perform high-precision frequency and phase estimations of the detected weak signal. The advantage of this algorithm is that it can simultaneously estimate the frequency and phase, meaning a direct coherent demodulation can be implemented. To address the computational complexity of the genetic algorithm, we improved the ratio algorithm for frequency estimation and raised the accuracy beyond that of the original ratio algorithm with only a slight increase in the computational complexity using relatively few sampling points.

• Educational Technology International
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• 제10권2호
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• pp.63-83
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• 2009

The purpose of this study was to investigate the cognitive mechanism of e-Learning contents development projects on the basis of the Shared Mental Model theory perspective. To pursue the purpose, a theoretical model and several hypotheses were developed based on relevant literature. Thirty five (35) e-Learning contents development teams composed of 202 instructional designers from for-profit professional e-Learning companies in Korea were participated in this study. For the analyses of the fit of the Model and parameter estimations, Structural Equation Modeling (SEM) method was employed. As hypothesized, e-Learning contents development team members' interaction leads to higher SMMs which in turn facilitate member satisfaction within the team. Meanwhile, the frequency of interaction among team members decreases as projects progress.

• Asian-Australasian Journal of Animal Sciences
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• 제26권8호
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• pp.1119-1126
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• 2013

The objective of this study was to compare the goodness of fit of four lactation curve models: Wood's Gamma model (WD), Wilmink (WL), and Pollott's multiplicative two (POL2) and three parameters (POL3) and to determine the environmental factors affecting the complete lactation curve of F1 dairy sheep under organic management. A total of 5,382 weekly milk yields records from 150 ewes, under organic management were used. Residual mean square (RMS), determination coefficients ($R^2$), and correlation (r) analysis were used as an indicator of goodness of fit for each model. WL model best fitted the lactation curves as indicated by the lower RMS values (0.019), followed by WD (0.023), POL2 (0.025) and POL3 (0.029). The four models provided total milk yield (TMY) estimations that were highly correlated (0.93 to 0.97) with observed TMY (89.9 kg). The four models under estimated peak yield (PY), whereas POL2 and POL3 gave nearer peak time lactation estimations. Ewes lambing in autumn had higher TMY and showed a typical curve shape. Higher TMY were recorded in second and third lambing. Season of lambing, number of lambing and type of lambing had a great influenced over TMY shaping the complete lactation curve of F1 dairy sheep. In general terms WL model showed the best fit to the F1 dairy sheep lactation curve under organic management.

• 대한전자공학회논문지TC
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• 제38권11호
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• pp.30-40
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• 2001

본 논문은 무선 ATM 망에서 VBR 서비스의 가변적인 슬롯 요구량을 신속하고 정확하게 반영함으로써 무선 구간에서의 전송 효율을 최대화할 수 있는 Hybrid DP 제어기법 기반의 동적 슬롯 할당 알고리즘을 제안한다. 제안한 Hybrid DP 제어기법은 기존의 In-band 제어기법과 Out-of-band 제어기법의 장점을 보존하고 단점 및 제어의 한계성을 개선한 방법으로 이동 단말기의 버퍼 상태 변화에 따라 기지국으로 전송되는 ATM 셀에 동적 파라미터 값을 삽입하거나 별도의 제어 채널을 사용하여 단말기의 필요 슬롯 수를 기지국에 전송하는 방식이다. 따라서 VBR 서비스의 유동적인 데이터 발생률을 효율적으로 기지국에게 전송하여 슬롯 할당에 반영함으로써 제한된 무선 채널을 효율적으로 이용하면서 VBR 서비스의 QoS를 보장할 수 있다. 제안한 동적 슬롯 할당 알고리즘의 성능 평가를 위해 해석적 분석 및 시뮬레이션을 실시하였으며, 할당효율, 지연 및 셀 손실률 관점에서 기존의 제어기법보다 우수한 성능을 보였다.

• 대한토목학회논문집
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• 제13권1호
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• pp.131-140
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• 1993

본 연구의 주요 목적은 댐 설계를 위한 유역의 비유사량 추정방법을 개발하는 것으로 유역면적 $200km^2{\sim}2,000km^2$의 중규모 유역을 대상으로 한다. 이를 위하여, 먼저 연구(I)에서는 비유사량 추정방법의 개발방향을 결정하고, 기존 저수지 퇴사자료에서 5점과 하천 유사량 실측 자료에서 8 점 등 총 13 점의 비유사량 자료를 도출하였다. 본 연구(II)에서는 이러한 중규모 유역에서 수집된 유역 비유사량 자료와 유역특성 인자들을 이용하여 3 변수 경험공식과 6 변수 도표식 방법을 개발하였다. 제한된 범위와 비교 분석 결과, 본 연구에서 개발된 방법들은 기존의 방법들보다 모형 개발에 이용된 자료의 범위와 신뢰도 면에서 적용성이 높은 것으로 나타났다. 한편, 본 연구에서 수집된 비유사량 자료 및 개발된 모형에 의하면, 우리나라에서 중규모 유역의 경우 비유사량의 하한치는 $100tons/km^2/yr$정도이며 상한치는 $1,000tons/km^2/yr$ 정도로 추정된다.

• Advances in aircraft and spacecraft science
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• 제2권2호
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• pp.217-232
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• 2015

To prevent over-testing of the test-item during random vibration testing Scharton proposed and discussed the force limited random vibration testing (FLVT) in a number of publications. Besides the random vibration specification, the total mass and the turn-over frequency of the load (test item), $C^2$ is a very important parameter for FLVT. A number of computational methods to estimate $C^2$ are described in the literature, i.e., the simple and the complex two degrees of freedom system, STDFS and CTDFS, respectively. The motivation of this work is to evaluate the method for the computation of a realistic value of $C^2$ to perform a representative random vibration test based on force limitation, when the adjacent structure (source) description is more or less unknown. Marchand discussed the formal description of getting $C^2$, using the maximum PSD of the acceleration and maximum PSD of the force, both at the interface between load and source. Stevens presented the coupled systems modal approach (CSMA), where simplified asparagus patch models (parallel-oscillator representation) of load and source are connected, consisting of modal effective masses and the spring stiffness's associated with the natural frequencies. When the random acceleration vibration specification is given the CSMA method is suitable to compute the value of the parameter $C^2$. When no mathematical model of the source can be made available, estimations of the value $C^2$ can be find in literature. In this paper a probabilistic mathematical representation of the unknown source is proposed, such that the asparagus patch model of the source can be approximated. The chosen probabilistic design parameters have a uniform distribution. The computation of the value $C^2$ can be done in conjunction with the CSMA method, knowing the apparent mass of the load and the random acceleration specification at the interface between load and source, respectively. Data of two cases available from literature have been analyzed and discussed to get more knowledge about the applicability of the probabilistic method.

• 한국생활과학회지
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• 제15권3호
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• pp.491-499
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• 2006

The purpose of this study is to measure the pizza purchasing behavioral characteristics of respondents and importances of factors affecting pizza purchase, to estimate the effects of attributes on choice of pizza restaurant, and to predict probability of selecting a particular pizza restaurant. The questionnaire consisted of two parts: The paired experimental profiles, purchasing behavior and importances of factors affecting pizza purchase. This study generated profiles of 16 hypothetical pizza restaurants based on seven attributes. The profiles comprised 16 discrete sets of variables, each of which had two levels. For this study, researcher randomly selected 150 university students as respondents. Twenty one students did not complete the survey instrument, resulting in a final sample size of 129. All estimations were carried out using frequencies, $X^2$, independent samples t-test, phreg procedure of SAS package. The results were as followed: Some purchasing behavioral characteristics and importances of factors affecting pizza purchase were significantly different by purchase frequency. Based on the estimated models developed for the two purchase frequency groups, the Chi-square statistics were significant at p<0.001. The parameter estimate for late delivery time with frequently purchase frequency group was highest, and the parameter estimate for price with frequently purchase frequency group was highest. The pizza restaurants that charged 20,000 won, offered 100% discount on eleventh pizza, promised to deliver pizza in 20 min, usually delivered the pizza as promised, offered 2 or more types of pizza crust, delivered steaming hot pizza, and did not offer a money-back guarantee which was favored by each of the two purchase frequency groups. The results from this study suggested that there was an opportunity to increase market share and profit by improving operations so that customers can receive discount and money-back guarantee simultaneously, and by reducing price, delivery time.