• 자연과학논문집
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• 제17권1호
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• pp.51-54
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• 2006

확률변수의 랜덤 가중합에 대한 완전수렴 정리를 얻는다.

• Journal of the Korean Statistical Society
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• 제25권3호
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• pp.303-311
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• 1996

We consider the discrete time randomly perturbed systems on sep-arable Banach space given by $X_{n+1};=;{Gamma}_{n+1}(X_n);+;{epsilon}_{n+1}$ where {${Gamma}_n$} is a sequence of random functions and {${epsilon}_n$} is a sequence of disturbances Sufficient conditions for non-ergodicity of {$X_n$} are obtained.

• Communications for Statistical Applications and Methods
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• 제24권5호
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• pp.519-531
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• 2017

We consider goodness-of-fit test statistics for Weibull distributions when data are randomly censored and the parameters are unknown. Koziol and Green (Biometrika, 63, 465-474, 1976) proposed the $Cram\acute{e}r$-von Mises statistic's randomly censored version for a simple hypothesis based on the Kaplan-Meier product limit of the distribution function. We apply their idea to the other statistics based on the empirical distribution function such as the Kolmogorov-Smirnov and Liao and Shimokawa (Journal of Statistical Computation and Simulation, 64, 23-48, 1999) statistics. The latter is a hybrid of the Kolmogorov-Smirnov, $Cram\acute{e}r$-von Mises, and Anderson-Darling statistics. These statistics as well as the Koziol-Green statistic are considered as test statistics for randomly censored Weibull distributions with estimated parameters. The null distributions depend on the estimation method since the test statistics are not distribution free when the parameters are estimated. Maximum likelihood estimation and the graphical plotting method with the least squares are considered for parameter estimation. A simulation study enables the Liao-Shimokawa statistic to show a relatively high power in many alternatives; however, the null distribution heavily depends on the parameter estimation. Meanwhile, the Koziol-Green statistic provides moderate power and the null distribution does not significantly change upon the parameter estimation.

• 전기학회논문지
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• 제63권7호
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• pp.976-986
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• 2014

In this paper, the problem of reliable control of linear systems with time-varying delays, randomly occurring disturbances, and actuator failures is investigated. It is assumed that actuator failures occur when disturbances affect to the systems. Firstly, by using a suitable Lyapunov-Krasovskii functional and some recent techniques such as Wirtinger-based integral inequality and reciprocally convex approach, stabilization criterion for nominal systems with time-varying delays is derived. Secondly, the proposed method is extended to the reliable $H_{\infty}$ controller design for linear dynamic systems with time-varying delays, randomly occurring disturbances, and actuator failures. Since nonlinear matrix inequalities (NLMIs) are involved in proposed results, the cone complementarity algorithm will be introduced. Finally, two numerical examples are included to show the effectiveness of the proposed criteria.

• Steel and Composite Structures
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• 제14권6호
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• pp.523-545
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• 2013

In this study, the effect of presence and distribution of masonry infill walls on the mid-rise steel frame structures having soft ground storey was evaluated by implementing finite element (FE) methods. Masonry infill walls were distributed randomly in the upper storey keeping the ground storey open without any infill walls, thus generating the worst case scenario for seismic events. It was observed from the analysis that there was an increase in the seismic design forces, moments and base shear in presence of randomly distributed masonry infill walls which underlines that these design values need to be amplified when designing a mid-rise soft ground storey steel frame with randomly distributed masonry infill. In addition, it was found that the overstrength related force modification factor increased and the ductility related force modification factor decreased with the increase in the amount of masonry infilled bays and panels. These must be accounted for in the design of mid-rise steel frames. Based on the FE analysis results on two mid-rise steel frames, design equations were proposed for determining the over strength and the ductility related force modification factors. However, it was recommended that these equations to be generalized for other steel frame structure systems based on an extensive analysis.

• Communications for Statistical Applications and Methods
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• 제26권5호
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• pp.431-443
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• 2019

Goodness-of-fit techniques are an important topic in statistical analysis. Censored data occur frequently in survival experiments; therefore, many studies are conducted when data are censored. In this paper we mainly consider test statistics based on the empirical distribution function (EDF) to test normal distributions with unknown location and scale parameters when data are randomly censored. The most famous EDF test statistic is the Kolmogorov-Smirnov; in addition, the quadratic statistics such as the $Cram{\acute{e}}r-von$ Mises and the Anderson-Darling statistic are well known. The $Cram{\acute{e}}r-von$ Mises statistic is generalized to randomly censored cases by Koziol and Green (Biometrika, 63, 465-474, 1976). In this paper, we generalize the Anderson-Darling statistic to randomly censored data using the Kaplan-Meier estimator as it was done by Koziol and Green. A simulation study is conducted under a particular censorship model proposed by Koziol and Green. Through a simulation study, the generalized Anderson-Darling statistic shows the best power against almost all alternatives considered among the three EDF statistics we take into account.

• 한국정보통신학회논문지
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• 제17권9호
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• pp.2219-2226
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• 2013

광 위상 공액과 분산 제어 (DM; dispersion management)를 결합한 기술은 그룹 속도 분산과 비선형 Kerr 효과에 의한 광 신호 왜곡을 보상하는 대표적인 기술이다. 하지만 일반적으로 사용되는 고정된 중계 구간 당 잉여 분산(RDPS; residual dispersion per span)은 광전송 링크의 유연한 구성을 방해한다. 본 논문에서는 유연한 광 네트워크 구축을 위해 랜덤하게 분포하는 RDPS의 DM과 결합된 새로운 OPC 링크를 제안하였다. 본 논문을 통해 WDM 채널의 입사 전력을 비교적 적게 제한하면 랜덤한 분포의 RDPS크기에 관계없이 보상 특성을 우수하게 할 수 있으며, 평균값을 0 ps/nm가 아닌 50 ps/nm부터 100 ps/nm가 되도록 중계 구간의 RDPS를 랜덤하게 분포시키면 비교적 큰 입사 전력의 WDM 채널들도 우수한 성능으로 전송시킬 수 있는 것을 확인하였다.

• 한국측량학회지
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• 제15권2호
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• pp.207-213
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• 1997

본 연구는 저밀도 임의지점의 지형정보를 이용하여 수치지형도를 제작하는데 있어 시간적, 경제적 측면을 포함하는 효율성과 정밀도 측면에서 각각의 수치지형도 제작기법을 비교 분석하여 향후 지형정보시스템의 구축에 있어서 저밀도의 제한된 지형정보를 이용하여 지형분석과 같은 많은 응용분야에 유용하게 이용될 수 있는 3차원 지형모델링의 효율적 기법을 제시하는 연구로써 다음과 같은 결론을 얻었다. 수치지형도를 제작함에 있어 A, B지역 모두 저밀도 임의지점의 지형정보를 이용하여 TIN기반의 지형모델링 기법으로 수치지형도를 제작하는 기법이 가장 신속하면서도 양호한 결과를 가져왔으며 TIN과 GRID기반의 지형모델링 기법으로 제작한 수치지형도를 시각적으로 분석한 결과 A, B지역모두 거의 홉사한 결과를 가져왔으나 DXF 파일로 저장한 데이터의 크기는 TIN기반의 지형모델링 기법이 GRID기반보다 상대적으로 적은 저장용량을 차지하는 것으로 나타났다. 또한 Grid기반의 지형모델링 기법에 의해 제작한 수치지형도에 있어서 저밀도 임의지점의 원형 데이터와 Gridding방법에 의해 보간된 데이터의 표준편차는 A, B지역 모두 Radial basis function 보간기법이 가장 정밀한 보간 결과를 제시하였다.

• Archives of Plastic Surgery
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• 제46권5호
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• pp.399-404
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• 2019

Background The objectives of this study were to design polycaprolactone nanofibers with a radial pattern using a modified electrospinning method and to evaluate the effect of radial nanofiber deposition on mechanical and biological properties compared to non-patterned samples. Methods Radially patterned polycaprolactone nanofibers were prepared with a modified electrospinning method and compared with randomly deposited nanofibers. The surface morphology of samples was observed under scanning electron microscopy (SEM). The tensile properties of nanofibrous mats were measured using a tabletop uniaxial testing machine. Fluorescence-stained human bone marrow stem cells were placed along the perimeter of the radially patterned and randomly deposited. Their migration toward the center was observed on days 1, 4, and 7, and quantitatively measured using ImageJ software. Results Overall, there were no statistically significant differences in mechanical properties between the two types of polycaprolactone nanofibrous mats. SEM images of the obtained samples suggested that the directionality of the nanofibers was toward the central area, regardless of where the nanofibers were located throughout the entire sample. Florescence images showed stronger fluorescence inside the circle in radially aligned nanofibers, with significant differences on days 4 and 7, indicating that migration was quicker along radially aligned nanofibers than along randomly deposited nanofibers. Conclusions In this study, we successfully used modified electrospinning to fabricate radially aligned nanofibers with similar mechanical properties to those of conventional randomly aligned nanofibers. In addition, we observed faster migration along radially aligned nanofibers than along randomly deposited nanofibers. Collectively, the radially aligned nanofibers may have the potential for tissue regeneration in combination with stem cells.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1169-1171
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• 2002

In this paper, RFRPP(Random Frequency Randomized Pulse Position ) PWM for three-phase voltage-controlled inverters is proposed. The LLPWM(Lead-Lag PWM) techinquc is that three switching pulses are located randomly back and forth in each switching interval. But with the restriction of random distribution, the harmonic spectrum cannot be dispersedly and continuously distributed. This paper calculates the duty ratio of the switching pulse firstly. Second, the switching pulses are located randomly in the switching interval. Third, the fixed switching frequency of the space vector modulation is randomly varied. To verify the validity of the proposed technique, simulation study is tried using Matlab/Simulink. When a proposed techniquc is employed, the harmonic spectrum of the inverter output voltagc varies from one cycle to the next and the EMI(Electromagnetic Interference) and resonant vibration are greatly alleviated.