• Wind and Structures
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• 제16권5호
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• pp.433-455
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• 2013

A phase delay spectrum model towards the representation of spatial coherence of stochastic wind fields is proposed. Different from the classical coherence functions used in the spectral representation methods, the model is derived from the comprehensive description of coherence of fluctuating wind speeds and from the thorough analysis of physical accounts of random factors affecting phase delay, building up a consistent mapping between the simulated fluctuating wind speeds and the basic random variables. It thus includes complete probabilistic information of spatial stochastic wind fields. This treatment prompts a ready and succinct scheme for the simulation of fluctuating wind speeds, and provides a new perspective to the accurate assessment of dynamic reliability of wind-induced structures. Numerical investigations and comparative studies indicate that the developed model is of rationality and of applicability which matches well with the measured data at spatial points of wind fields, whereby the phase spectra at defined datum mark and objective point are feasibly obtained using the numerical scheme associated with the starting-time of phase evolution. In conjunction with the stochastic Fourier amplitude spectrum that we developed previously, the time history of fluctuating wind speeds at any spatial points of wind fields can be readily simulated.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.165-170
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• 1998

The paper describes developed method of feedforward digital modulation of line-to-line voltage of 3-phase inverter for drive application. It is based on representation of parameters of output voltage of inverter in function of operating frequency of drive system. Pure algebraic control laws and big computational simplicity characterize this scheme of modulation. It has been presented results of simulation of adjustable drive systems with the method of pulse-width modulation described.

• 한국CDE학회논문집
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• 제5권4호
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• pp.380-392
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• 2000

This paper proposes a qualitative reasoning approach for the spatial configuration of mechanisms that could be applied in the early phase of the conceptual design. The spatial configuration problem addressed in this paper involves the relative direction and position between the input and output motion, and the orientation of the constituent primitive mechanisms of a mechanism. The knowledge of spatial configuration of a primitive mechanism is represented in a matrix form called spatial configuration matrix. This matrix provides a compact and convenient representation scheme for the spatial knowledge, and facilitates the manipulation of the relevant spatial knowledge. Using this spatial knowledge of the constituent primitive mechanisms, the overall configuration of a mechanism is described and identified by a spatial configuration state matrix. This matrix is obtained by using a qualitative reasoning method based on sign algebra and is used to represent the qualitative behavior of the mechanism. The matrix-based representation scheme allows handling the involved spatial knowledge simultaneously and the proposed reasoning method enables the designer to predict the spatial behavior of a mechanism without knowing specific dimension of the components of the mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권11호
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• pp.4268-4289
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• 2020

Advanced traffic signal timing method plays very important role in reducing road congestion and air pollution. Reinforcement learning is considered as superior approach to build traffic light timing scheme by many recent studies. It fulfills real adaptive control by the means of taking real-time traffic information as state, and adjusting traffic light scheme as action. However, existing works behave inefficient in complex intersections and they are lack of feasibility because most of them adopt traffic light scheme whose phase sequence is flexible. To address these issues, a novel adaptive traffic signal timing scheme is proposed. It's based on actor-critic reinforcement learning algorithm, and advanced techniques proximal policy optimization and generalized advantage estimation are integrated. In particular, a new kind of reward function and a simplified form of state representation are carefully defined, and they facilitate to improve the learning efficiency and reduce the computational complexity, respectively. Meanwhile, a fixed phase sequence signal scheme is derived, and constraint on the variations of successive phase durations is introduced, which enhances its feasibility and robustness in field applications. The proposed scheme is verified through field-data-based experiments in both medium and high traffic density scenarios. Simulation results exhibit remarkable improvement in traffic performance as well as the learning efficiency comparing with the existing reinforcement learning-based methods such as 3DQN and DDQN.

• 한국통신학회논문지
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• 제27권8B호
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• pp.796-801
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• 2002

CL1(closed loop mode 1)은 3GPP WCDMA가 규정한 폐루프(closed loop) 송신 다이버시티 기술 중의 하나로서, 기지국에 설치된 2개의 송신 안테나를 통해 방사되는 신호들의 위상을 적절히 조절하여 가입자 단말기의 입력단에 나타나는 신호의 전력을 최대화하고자 하는 방식이다. 이 방식의 핵심 요소는 서로 다른 송신 안테나를 거쳐 가입자 수신기에 도달하는 수신 신호간의 위상 차이 정보를 가입자 단말기가 부호화하여 기지국에 전달하는 것이다. 본 논문에서는 적응 델타 변조(adaptive delta modulation) 방식으로 위상 차이 정보를 표현하여 전달하는 새로운 방안을 제안하고, 이를 기존의 CL1 방식에서 사용하는 위상 차이 표현 방안과 비교한다. 컴퓨터 실험 결과, 페이딩(fading) 특성이 비교적 천천히 변하는 환경에서, 제안한 방식이 CL1의 경우보다 위상 차이를 좀 더 정확하게 표현할 수 있으며, 이로 인해 궁극적으로 더 낮은 BER을 확보할 수 있음을 확인하였다.

• Management Science and Financial Engineering
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• 제7권2호
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• pp.73-90
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• 2001

This paper presents the reliability models for redundant systems composed of repairable components whose failure time and repair time distributions are phase-type. It is shown that the distribution of time to system failure is also phase-type. The dependency between components are considered and integrated into the model by the used of the rate adjustment factor. The phase-type representation is constructed for the system through algebraic operations on the parameters of components\` failure time and repair time distributions and the corresponding rate adjustment factors. Types of system structures considered are parallel, k-out-of-N system with load sharing scheme and standby system with operation priority.

• 한국철도학회논문집
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• 제18권1호
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• pp.25-32
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• 2015

일반도로와 노면전차가 교차하는 신호교차로에서 준비되어야 하는 교통신호제어 운영조건을 검토하고 이를 토대로 노면전차 교통신호와 일반차량 교통신호의 효율적 통합 운영을 지원하기 위해 현재의 교통신호제어기가 추가 확보하여야 하는 기능적 및 기술적 요구사항을 진단한다. 본 연구의 검토 내용은 도로 현장에서 발생 가능한 일반차량과 노면전차의 다양한 교차상황, 노면전차 전용신호등의 등기단자 최소 구성, 교통신호현시 순서 운영상황 조합 및 이를 기반으로 한 현시표출방안을 포함한다. 분석결과 우회전 중첩현시 표출을 위한 중첩현시 등기장치 및 노면전차와 일반차량 복합 현시운영을 위한 사중고리현시표출체계 기능을 포함하는 교통신호제어기 도입이 필요함을 제안한다.

• Wind and Structures
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• 제3권1호
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• pp.1-10
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• 2000

Recently, an efficient and practical method has been developed for the generation of univariate non-Gaussian wind pressure time histories on low building roofs; this methodology requires intermittent exponential random numbers for the simulation. On the other hand, the conventional spectral representation scheme with random phase is found suitable for the generation of univariate Gaussian wind pressure time histories on low building roofs; this simulation scheme requires uniform random numbers. The dependency of these simulation methodologies on the random number generator is one of the items affecting the accuracy of the simultion result; therefore, an attempt has been made to investigate the issue. This note presents the observed sensitivity of random number sets in repetitive simulations of Gaussian and non-Gaussian wind pressures.

• Journal of Information Processing Systems
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• 제13권1호
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• pp.57-67
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• 2017

In this paper, Atanassov's intuitionistic fuzzy set theory is used to handle the uncertainty of students' knowledgeon domain concepts in an E-learning system. Their knowledge on these domain concepts has been collected from tests that were conducted during their learning phase. Atanassov's intuitionistic fuzzy user model is proposed to deal with vagueness in the user's knowledge description in domain concepts. The user model uses Atanassov's intuitionistic fuzzy sets for knowledge representation and linguistic rules for updating the user model. The scores obtained by each student were collected in this model and the decision about the students' knowledge acquisition for each concept whether completely learned, completely known, partially known or completely unknown were placed into the information table. Finally, it has been found that the proposed scheme is more appropriate than the fuzzy scheme.

• 대한치과보철학회지
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• 제38권3호
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• pp.321-327
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• 2000

Statement of Problem. As a standard means of diagnostics, an orthopantomogram(OPT) permits to measure the vertical and mesiodistal dimension of available bone at the desired implant site with the help of suitable radioopaque references. Based on the clinical investigation of the dentition and the edentulous sites, information upon the width of the implant site can be obtained and documented in the dental scheme. Both findings permit together systematic primary planning for endosteal implants. Purpose of Study. Contents of the present article are the representation of a semiquantitative classification of available bone with the aim to simplify the primary phase of a systematic implant planning. Results. Thus the ASCIi- system permits a clear protocol of bone findings for the implant case with all information available during the primary appointment for treatment planning as a basis of further diagnostic and therapeutic measures. Conclusion. With the ASCIi system, important parameters such as alveolar height and sub-crestal alveolar width can be documented systematically, easily and time saving in the dental scheme as a basis for exact treatment planning.