• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 춘계학술대회 논문집 에너지변화시스템부문
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• pp.29-31
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• 2009

Optimal efficiency control of synchronous reluctance motor(SynRM) is very important in the sense of energy saving and conservation of natural environment because the efficiency of the SynRM is generally lower than that of other types of AC motors. This paper is proposed an efficiency optimization control for the SynRM which minimizes the copper and iron losses. The design of the speed controller based on fuzzy-neural networks (FN)-PI controller that is implemented using fuzzy control and neural networks. There exists a variety of combinations of d and q-axis current which provide a specific motor torque. The objective of the efficiency optimization control is to seek a combination of d and q-axis current components, which provides minimum losses at a certain operating point in steady state. It is shown that the current components which directly govern the torque production have been very well regulated by the efficiency optimization control scheme. The proposed algorithm allows the electromagnetic losses In variable speed and torque drives to be reduced while keeping good torque control dynamics. The control performance of the proposed controller is evaluated by analysis for various operating conditions. Analysis results are presented to show the validity of the proposed algorithm.

• 한국정보전자통신기술학회논문지
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• 제13권5호
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• pp.344-352
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• 2020

수중음향통신의 적용을 위해 고려되어야 할 두 가지 지표인 성능과 은밀성 관점에서 다중 밴드 통신 기법 및 직접 확산 변조 방식을 적용한 효율적인 통신 모델을 설정하고 성능 분석을 하였다. 최적의 모델에 대한 성능 분석을 위해 송수신기의 채널 부호화 알고리즘을 부호화 비트 수 336 bit를 가지는 부호화율 1/3인 turbo pi 부호화기를 적용하여 등화기와 채널 복호화기를 반복하여 성능을 향상시키는 터보 등화 구조를 제시하였다. 본 논문에서는 다중 밴드 기반 대역 확산 구조의 Rake 처리 과정에서 임계값을 설정하여, 대역 확산 신호의 chip 수를 8개, 16개, 32개로, 다중 밴드 수는 1개에서 4개로 변경하면서 성능을 분석하였다. 시뮬레이션 결과 밴드 수 및 chip 수가 증가함에 따른 성능 이득을 확인할 수 있었으며, 동일한 밴드 수에서 chip 수를 증가시켰을 때 2~3dB 정도 성능이 향상되었다.

• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2696-2707
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• 2021

The purpose of this study is to investigate the efficiency of various structural modeling schemes for evaluating seismic performances and fragility of the reactor containment building (RCB) structure in the advanced power reactor 1400 (APR1400) nuclear power plant (NPP). Four structural modeling schemes, i.e. lumped-mass stick model (LMSM), solid-based finite element model (Solid FEM), multi-layer shell model (MLSM), and beam-truss model (BTM), are developed to simulate the seismic behaviors of the containment structure. A full three-dimensional finite element model (full 3D FEM) is additionally constructed to verify the previous numerical models. A set of input ground motions with response spectra matching to the US NRC 1.60 design spectrum is generated to perform linear and nonlinear time-history analyses. Floor response spectra (FRS) and floor displacements are obtained at the different elevations of the structure since they are critical outputs for evaluating the seismic vulnerability of RCB and secondary components. The results show that the difference in seismic responses between linear and nonlinear analyses gets larger as an earthquake intensity increases. It is observed that the linear analysis underestimates floor displacements while it overestimates floor accelerations. Moreover, a systematic assessment of the capability and efficiency of each structural model is presented thoroughly. MLSM can be an alternative approach to a full 3D FEM, which is complicated in modeling and extremely time-consuming in dynamic analyses. Specifically, BTM is recommended as the optimal model for evaluating the nonlinear seismic performance of NPP structures. Thereafter, linear and nonlinear BTM are employed in a series of time-history analyses to develop fragility curves of RCB for different damage states. It is shown that the linear analysis underestimates the probability of damage of RCB at a given earthquake intensity when compared to the nonlinear analysis. The nonlinear analysis approach is highly suggested for assessing the vulnerability of NPP structures.

• Advances in Computational Design
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• 제4권2호
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• pp.119-139
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• 2019

Planning and management building projects should tackle the coordination of works and the management of limited spaces, traffic and supplies. Activities cannot be performed without the resources available and resources cannot be used beyond the capacity of workplaces. Otherwise, workspace congestion will negatively affect the flow of works. Better on-site management allows for substantial productivity improvements and cost savings. The procurement system should be able to manage a wider variety of materials and products of the required quality in order to have less stock, in less time, using less space, with less investment and avoiding multiple storage stations. The objective of this paper is to demonstrate the advantages of using the Chronographic modeling, by combining spatiotemporal technical scheduling with the 4D simulations, the Last Planner System and the Takt-time when modeling the construction of building projects. This paper work toward the aforementioned goal by examining the impact that material flow has on site occupancy. The proposed spatiotemporal model promotes efficient site use, defines optimal site-occupancy and workforce-rotation rates, minimizes intermediate stocks, and ensures a suitable procurement process. This paper study the material flow on the site and consider horizontal and vertical paths, traffic flows and appropriate means of transportation to ensure fluidity and safety. This paper contributes to the existing body of knowledge by linking execution and supply to the spatial and temporal aspects. The methodology compare the performance and procurement processes for the proposed Chronographic model with the Gantt-Precedence diagram. Two examples are presented to demonstrate the benefits of the proposed model and to validate the related concepts. This validation is designed to test the model's graphical ability to simulate construction and procurement.

• 디지털융복합연구
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• 제20권1호
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• pp.185-190
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• 2022

Bluetooth는 다양한 소비자 전자 장치 간의 연결 매체로 널리 사용되는 공통 무선 기술이다. Bluetooth 수신기는 주로 신호 대 잡음비 성능 개선을 위해 일반적으로 Viterbi 알고리즘을 채택하지만 전송단에서의 irrational modulation index(무리수 변조 지수)로 수신단의 지속적인 탐색 및 추정이 필요하며 이를 위한 복잡한 하드웨어와 계산을 요구한다. 본 논문에서는 이러한 복잡도 문제를 해결하기 위해 비동기 최대 우도 추정(MLE, Maximum-likelihood Estimation) 기반 8-state Viterbi FSM을 제안한다. 본 논문에서 제안한 최적의 Viterbi FSM은 전송단에서의 변조 지수에 대한 사전 정보 및 추정이 필요 없으며 GFSK(Gaussian Frequency Shift Keying) 심볼 검출이 가능하다. 제안한 알고리즘에 대한 성능은 HV1/HV2 패킷을 사용하여 평가하였으며, 시뮬레이션 결과는 DD(Decision Direct)와 같은 이상적인 접근 방식과 비교하여 10^-3 BER에서 약 2dB 성능 향상을 보여주었다.

• 웰빙융합연구
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• 제5권4호
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• pp.19-31
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• 2022

Purpose: This study was conducted to identify indoor air quality in various living spaces using sensors that can measure noise, vibration, fine dust, and odor in real time and to propose optimal indoor air quality maintenance management using Internet of Things(IoT). Research design, data and methodology: Using real-time sensors to monitor physical factors and environmental air pollutants that affect the comfort of the residential environment, Noise, Vibration, Atmospheric Pressure, Blue Light, Formaldehyde, Hydrogen Sulfide, Illumination, Temperature, Ozone, PM10, Aldehyde, Amine, LVOCs and TVOCs were measured. It were measured every 1 seconds from 4 offices and 4 stores on a small scale from November 2018 to January 2019. Results: The difference between illuminance and blue light for each measuring point was found to depend on lighting time, and the ratio of blue light in total illumination was 0.358 ~ 0.393. Formaldehyde and hydrogen sulphide were found to be higher than those that temporarily attract people in an indoor office space that is constantly active, requiring office air ventilation. The noise was found to be 50dB higher than the office WHO recommendation noise level of 35 ~ 40dB. The most important factors for indoor environmental quality were temperature> humidity> illumination> blue light in turn. Conclusions: Various factors that determine the comfort of indoor living space can be measured with real-time sensors. Further, it is judged that the use of IoT can help maintain indoor air quality comfortably.

• 대한토목학회논문집
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• 제28권2D호
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• pp.205-216
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• 2008

도시고속도로란 도시지역 내 고속의 자동차 전용도로로서 대량의 교통량을 신속하게 처리하기 위해 높은 설계기준이 요구되는 4차선 이상의 도로를 의미한다. 그러나 대부분의 도시고속도로는 오전 오후첨두시 또는 도심 부도심방향에 관계없이 도로의 용량을 초과하는 교통량의 증가로 인하여 심각한 교통혼잡을 겪고 있는 실정이다. 따라서 이 연구의 목적은 부산항과 연계된 도시고속도로의 연결로 접속영향권을 대상으로 실시간 교통특성을 수집하여 교통특성을 파악하고, 연결로 접속영향권내 각 차로에 대한 교통특성관계를 비교 분석하며, 마지막으로 연결로 접속영향권내 각 차로에 대한 최적의 용량을 평가하여 차로별 소통능력을 제시하고자 한다.

• 대한토목학회논문집
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• 제29권2D호
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• pp.295-303
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• 2009

본 연구에서는 가이드웨이의 특성이 중저속 자기부상열차의 주행성에 미치는 영향을 파악하는데 목적을 두고 있다. 이를 위하여 자기 공극의 피드백을 포함한 2자유도 차량에 대한 운동방정식을 구성하고, 최적능동제어기법을 적용하여 수치해석을 수행하였다. 매개변수 연구로 차량 속도, 레일조도, 교량 처짐, 경간의 연속성, 경간장 등이 UTM-01 자기부상열차의 응답에 미치는 영향을 파악하였다. 해석 결과를 보면, 차량 설계속도 내에서는 차량의 응답이 크게 증가하지 않고 일정한 수준을 유지하였으며, 차량의 응답은 주로 가이드웨이 처짐에 의하여 지배를 받은 것으로 나타났다. 결론적으로 차량 공극의 변화를 줄여서 주행성을 향상시키려면 가이드웨이의 최대 처짐을 작게 하고, 단순거더 보다는 연속거더 구조로 구성하는 것이 유리한 것으로 나타났다.

• 반도체디스플레이기술학회지
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• 제22권3호
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• pp.119-124
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• 2023

In this study, experimental approach of the measurement of condensation and evaporation heat transfer coefficients is discussed for mixed refrigerants using in the ultra low-temperature cooling system for semiconductor etching process. An experimental apparatus was described performing the condensation and evaporation heat transfer measurements for mixed refrigerants. The mixed refrigerant used in this study was composed of the optimal mixture determined in previous research, with a composition of Ar:R14:R23:R218 = 0.15:0.4:0.15:0.3. The experiments were conducted over a temperature range from -82℃ to 15℃ and at pressures ranging from 18.5 bar to 5 bar. The convection heat transfer coefficients of the mixed refrigerant were measured at flow rates corresponding to actual operating conditions. The condensation heat transfer coefficient ranged from approximately 0.7 to 0.9 kW/m2K, while the evaporation heat transfer coefficient ranged from 1.0 to 1.7 kW/m2K. The detailed discussion of the experimental methods, procedures, and results were described in this paper.

• 대한치과기공학회지
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• 제46권1호
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• pp.1-7
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• 2024

Purpose: The goal of this study was to determine the clinical acceptability of various cement space settings for the marginal and internal fit of a zirconia core manufactured using additive manufacturing. Methods: The maxillary right incisor served as the master model. After scanning the maxillary right incisor with a dental 3D (three-dimensional) scanner, the stereo lithography file was created using different cement space settings of 40, 120, and 200 ㎛ using computer-aided design software (Dental System 2018; 3Shape). The marginal and internal fit of the 3 groups were determined using the silicon replica technique. Measurement points were divided into the following three categories: margin, axial wall, and incisal. To ensure more accurate measurements, these three measurement points were divided into 8 points. The Shapiro-Wilk, one-way ANOVA, and Tukey's honestly significant difference test (for all tests α=0.05) were the statistical analyses that were included in the study. Results: The CS (cement space)-200 group had better marginal and internal fit than the CS-40 and CS-120 groups, and there were statistically significant differences at the marginal and incisal points, except for the axial wall points. CS-200 group, both marginal and internal fit were within 120 ㎛, which is the clinically acceptable value. Conclusion: This study suggests that a 200 ㎛ cement space setting is ideal for optimal marginal and internal fit of 3D-printed ceramic crowns.