• Journal of KIISE:Computing Practices and Letters
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• v.16 no.6
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• pp.742-746
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• 2010

In this paper, we propose new randomness testing methods based on approximate periods in order to improve the previous randomness testing method using exact pattern matching. Finding approximate periods of random sequences enables us to search similarly repeated parts, but it has disadvantages since it takes long time. In this paper we propose randomness testing methods whose time complexity is O($n^2$) by reducing the time complexity of computing approximate periods from O($n^3$) to O($n^2$). Moreover, we perform some experiments to compare pseudo random number generated by AES cryptographic algorithms and true random number.

• The Korean Journal of Financial Management
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• v.16 no.2
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• pp.243-261
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• 1999

본 논문은 순이익의 시계열 속성을 조사하고, 순이익의 시계열이 랜덤워크 모형과 일치하는지를 단위근 검증방식을 사용하여 조사하며, 시계열 속성에 근거하여 도출된 예측모형과 흔히 사용되어 온 랜덤워크 모형의 예측능력을 비교하여 선행연구에서 사용되고 있는 랜덤워크 모형에 실증적 타당성을 제시하는 것을 주목적으로 하고 있다. 본 연구는 한국신용평가주식회사의 데이터 베이스에 1980년부터 1996년까지 17년간 자료가 연속적으로 포함되어 있는 금융기업을 제외한 모든 기업(272개)을 표본으로 사용하고 있다. 표본기업의 순이익 시계열에 가장 적합한 과정은 랜덤워크나 AR(1) 또는 AR(2) 모형이다. 또한 본 논문은 대부분의 기업에 때해 순이익이 랜덤워크 과정을 따른다는 가설을 기각할 수 없음을 보였다. 이들 상이한 모형의 표본외 예측력(out-of-sample predictive ability)을 비교한 결과 상수항을 포함한 랜덤워크 모형이 가장 작은 평균 절대 예측오차(mean absolute forecast error)를 갖는 것으로 나타나고 있다. 본 연구는 기존의 연구가 순이익 시계열의 불안정성(nonstationarity) 문제를 무시하거나 명시적으로 다루고 있지 않은 것과는 달리 단위근 검증(unit root test)을 통해 연간 순이익이 대체로 불안정하다는 것을 보였으며, 또한 상이한 모형의 표본외 예측능력을 비교한 결과 선행연구에서 사용하여 온 랜덤워크 모형의 우월성에 대한 실증적 증거를 제공하였다는 데 의의가 있다.

• Proceedings of the KIPE Conference
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• 2004.11a
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• pp.54-58
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• 2004

본 연구에서는 고정 주파수를 갖는 유사 랜덤 주파수 캐리어 PW(PRC-PWM)을 제안하고 단상 5-레벨 캐스케이드 인버터에 적용하였다. 제안된 PRC-PWM의 펄스는 고정 주파수를 갖는 삼각파 캐리어와 그 역상의 삼각파 캐리어를 랜덤 비트 발생기(PRBS)에 의하여 랜덤하게 선택함으로서 새롭게 합성된 랜덤 주파수의 캐리어에서 얻고 있다. 제안된 PRC-PWM은 고정 주파수의 캐리어 합성만으로 랜덤 주파수의 캐리어를 매우 간단하게 구현할 수 있으며, R-L부하와 연결된 단상 5-레벨 캐스케이드 인버터를 제작하여 타당성을 입증하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.323-324
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• 2020

논문에서는 3D 체적형 모델을 이용하여 홀로그램에 랜덤 위상 효과를 주는 방법을 제안한다. CGH(Computer Generated Hologram)에서 랜덤 위상의 추가는 실제 촬영하여 획득한 홀로그램에서 물체 표면의 난반사에 대한 영향을 고려한 것이다. 이 랜덤 위상은 생성한 홀로그램의 광 시야각 확장 효과가 있다. 하지만 이것은 랜덤으로 발생하기 때문에 홀로그램 시퀀스를 생성할 때 같은 객체 표면에 대해서 고정된 효과를 줄 수 없다. 본 논문에서는 CGH를 진행할 때 물체의 고유한 랜덤 위상 추가를 위해 3D 체적형 모델을 사용하는 방법을 제안한다.

• The Korean Journal of Applied Statistics
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• v.28 no.6
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• pp.1121-1131
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• 2015

Logistic models with a random intercept are useful to analyze longitudinal binary data. Traditionally, the random intercept of the logistic model is assumed to be parametric (such as normal distribution) and is also assumed to be independent to variables. Such assumptions are very strong and restricted for application to real data. Recently, Garcia and Ma (2015) derived semiparametric efficient estimators for logistic model with a random intercept without these assumptions. Their estimator shows the consistency where we do not assume any parametric form for the random intercept. In addition, the method is computationally simple. In this paper, we apply this method to analyze toenail infection data. We compare the semiparametric estimator with maximum likelihood estimator, penalized quasi-likelihood estimator and hierarchical generalized linear estimator.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.5
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• pp.501-507
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• 2005

This paper proposes a Hybrid Random PWM(HRPWM) technique using a LF2407 DSP board in order to spread the power spectra of an induction motor. The proposed method is composed to the PRBS (Pseudo-Random Binary Sequence) with the Lead-Lag random bit and the random triangular carrier for the logical comparison. Also, a DSP generates the random number, the PRBS and the three-phase reference signal, a MAX038 chip operating as frequency modulator generates the random triangular carrier. For verification of the proposed method, the experiments were conducted with a three-phase adjustable speed a.c drives, and the results of simulations and experiments are presented.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.7
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• pp.1-5
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• 2009

Random beanforming exploits multiuser diversity gain in static channels. Since the gain is restricted by the user population, some extended works have been proposed. Among them, a codebook-based opportunistic beamforming technique forms multiple random beams with small pilots. The technique however has difficulty in designing beams flexibly by the channel statistics. In this paper, we propose a technique forming the multiple random beams by rotating codebooks. The proposed technique enables the flexible design of beams so that multiuser diversity and beam selection diversity are exploited simultaneously with small pilots robust to the channel statistics.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.8
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• pp.48-56
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• 2000

Effects of the correlated random fluctuation in each grating half-period have been studied by an effective index transfer matrix method in quarter wavelength shifted DFB lasers. As the correlation coefficient changes from 0 to -1, single mode stability and wavelength accuracy are less degraded by the reduced error in the grating period. This fact shows that holographic grating fabrication is better than electron-beam lithography in discrete device fabrication provided that the magnitude of the random fluctuation is the same.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.540-546
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• 2013

Using the free volume of van der Waals equation, Carnahan-Starling equation for hard spheres, Wilson equation for nonrandom mixing of solution, NRTL equation and our equation, several new equations of states for pure gases are derived. Using these equations, compressibility factors for pure gases are calculated and compared with Nelson-Obert generalized compressibility factor charts. The equation of states using the concept of molecular nonrandom distribution gave better results than those of molecular random distribution. This shows that the molecular nonrandom distribution makes considerable effect on the equation of states.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.59-64
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• 2024

The small tracking radar randomly changes the transmission period to avoid deceptive signals such as RGPO (Range Gaet Pull Off) operated on the target. Since the code repeats after a specific section, it becomes difficult to avoid a deceptive signal when the repetition is exposed. In this paper, a more realistic transmission pulse code is generated by adding random code generation through FPGA and system white noise. We present the research results of code generation that generates PRF that can avoid repetition while using pseudo-random code in EPROM using FPGA. Also, the result of designing random PRF pulse was confirmed by applying it to tracking radar.