• 제목/요약/키워드: mathematical change

검색결과 880건 처리시간 0.02초

분산전원형 PV 인버터 성능 개선을 위한 실시간 처리기반의 PV-Power-Hardware-In-Loop 시뮬레이터 개발 (Development of PV-Power-Hardware-In-Loop Simulator with Realtime to Improve the Performance of the Distributed PV Inverter)

  • 김대진;김병기;유경상;이광세;장문석;고희상
    • 한국태양에너지학회 논문집
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    • 제37권3호
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    • pp.47-59
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    • 2017
  • As the global warming threats to humanity, renewable energy is considered the key solution to overcome the climate change. In this circumstance, distributed PV systems are being expanded significantly its market share in the renewable energy industry. The performance of inverter is the most important component at PV system and numerous researches are focusing on it. In order to improve the inverter, PV simulator is an essential device to experiment under various load and conditions. This paper proposes the PV Power-Hardware-In-Loop simulator (PHILS) with real-time processing converted electrical and mathematical models to improve computation speed. Single-diode PV model is used in MATLAB/SIMULINK for the PV PHILS to boosting computation speed and dynamic model accuracy. In addition, control algorithms for sub-components such as DC amplifier, measurement device and several interface functions are implemented in the model. The proposed PV PHILS is validated by means of experiments with commercial PV module parameters.

FAST, GH Bladed 및 CFD기법을 이용한 5MW 해상풍력터빈 시스템 설계하중조건 해석 및 비교 (Design Load Case Analysis and Comparison for a 5MW Offwhore Wind Turbine Using FAST, GH Bladed and CFD Method)

  • 김기하;김동현;곽영섭;김수현
    • 한국유체기계학회 논문집
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    • 제18권2호
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    • pp.14-21
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    • 2015
  • Design lifetime of a wind turbine is required to be at least 20 years. The most important step to ensure the deign is to evaluate the loads on the wind turbine as accurately as possible. In this study, extreme design load of a offshore wind turbine using Garrad Hassan (GH) Bladed and National Renewable Energy Laboratory (NREL) FAST codes are calculated considering structural dynamic loads. These wind turbine aeroelastic analysis codes are high efficiency for the rapid numerical analysis scheme. But, these codes are mainly based on the mathematical and semi-empirical theories such as unsteady blade element momentum (UBEM) theory, generalized dynamic wake (GDW), dynamic inflow model, dynamic stall model, and tower influence model. Thus, advanced CFD-dynamic coupling method is also applied to conduct cross verification with FAST and GH Bladed codes. If the unsteady characteristics of wind condition are strong, such as extreme design wind condition, it is possible to occur the error in analysis results. The NREL 5 MW offshore wind turbine model as a benchmark case is practically considered for the comparison of calculated designed loads. Computational analyses for typical design load conditions such as normal turbulence model (NTM), normal wind profile (NWP), extreme operation gust (EOG), and extreme direction change (EDC) have been conducted and those results are quantitatively compared with each other. It is importantly shown that there are somewhat differences as maximum amount of 18% among numerical tools depending on the design load cases.

p38 MAPK을 이용한 항염증 효능 규명 프로토타입 개발 (Development of Prototype for Screening Anti-Inflammation Effects concerning p38 MAPK Signal Pathway)

  • 김철;예상준;남기엽;김상균;장현철;김진현;김영은;송미영
    • 한국한의학연구원논문집
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    • 제17권3호
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    • pp.77-85
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    • 2011
  • Objectives : The purpose of this study was to develop a simulator which can analyze the anti-inflammatory effects of medical herbs based on e-cell concerning p38 MAPK signal pathway. Methods : We collected data concerning medical herbs with anti-inflammatory effects and the active compounds to provide as a fundamental databse and to validate the newly developed algorithm. At this time, we used the target database as pubmed and gathered the data by data mining tool, pathway studio. Also we have developed the web-based search system for confirming database related to anti-inflammation. We researched the mechanism of actions of proteins in p38 MAPK signal pathway when active compound has been inserted into the network. We reduced total network into TAK-MKK3-p38 and made the two types of mathematical model about active compounds' interaction. Results & Conclusion : We constructed the database which have 69 cases of medical herbs, 71 cases of active compounds, about 8,000 cases of URL(Uniform Resource Locator) related to papers and reports. We designed the ordinary differential equations for response of TAK, MKK3, p38 in e-cell's cytosol and nucleus. We used this formular as measure whether an active compound of medicinal plants which is inputted by an user would have an anti-inflammation effects. We developed the visualization program which could show the change of concentration over time.

LTE 네트워크에서 인증 시그널링의 감소 기법 (Reducing of Authentication Signaling Traffic in LTE Networks)

  • 김선호;정종필
    • 정보처리학회논문지:컴퓨터 및 통신 시스템
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    • 제1권2호
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    • pp.109-118
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    • 2012
  • 현재 많은 스마트폰의 보급으로 LTE 네트워크를 통해 다양하고 빠른 모바일 서비스를 하게 되었다. 이에 수많은 모바일 기기들이 이전보다 더 많은 무선서비스를 이용하게 되고 그에 따른 수많은 인증 시그널링이 발생하게 된다. 이러한 무선네트워크에서 인증은 무선기기를 식별할 수 있는 중요한 역할을 하며 무선네트워크의 시작이기도 하다. 그래서 본 논문에서는 이전에 인증이 발생된 패턴을 분석하여 또 다른 외부 네트워크로 접근할 때 이전 보다 효과적인 인증을 수행한다. 그래서 LTE 네트워크에서 외부 네트워크와 인증서버 사이의 시그널링 비용을 최소화하여 빠른 무선 인증 서비스를 제안한다. LTE 네트워크에서 인증이 발생되는 비율을 수학적 모델링을 이용하여 계산하였고, 이를 다양한 환경에서 인증 시그널링 비용의 변화를 계산하였다. 본 논문에서 제안한 최적 인증 데이터의 수를 계산하여 이전 보다 효율적인 인증 시그널링 비용이 발생함을 보인다.

CSTR 하.폐수처리장의 국지 제어 및 원격 최적화 시스템 (Local Control and Remote Optimization for CSTR Wastewater Treatment Systems)

  • 배현;서현용;김성신
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2002년도 춘계합동학술대회 논문집
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    • pp.21-25
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    • 2002
  • Activated sludge processes are widely used in biological wastewater treatment processes. The main motivation of this research is to develop an intelligent control strategy for activated sludge process (ASP). ASP is a complex and nonlinear dynamic system because of the characteristic of wastewater, the change in influent rate, weather conditions, and so on. The mathematical model of ASP also includes uncertainties which are ignored or not considered by process engineer or controller designer. The ASP model based on Matlab/Simulink is designed in this paper. The performance of the model is tested by IWA (International Water Association) and COST (European Cooperation in the filed of Scientific and Technical Research) data that include steady-state results during 14 days. In this paper, fuzzy logic control approach is applied to control the DO (dissolved oxygen) concentration. The fuzzy logic controller that includes two inputs and one output can adjust air flowrate. Also, this paper introduces the remote monitoring and control system that is applied for the CSTR (Continuously Stirred Tank Reactor) wastewater treatment system. The CSTR plant has a local control and the remote monitoring system which is contained communication parts which consist of LAN (Local Area Network) network and CDMA (Code Division Multiple Access) wireless module. Remote control and monitoring systems are constructed in the laboratory.

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모델기반의 전기자동차용 전지 잔존용량계 개발 (Development of Model Based Battery SOC Indicator for Electric Vehicle)

  • 임영철;박종건;류영재;이흥수;변성천;김의선
    • 센서학회지
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    • 제5권6호
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    • pp.35-42
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    • 1996
  • 본 논문에서는 전기자동차에서 사용할 수 있는 모델 기반 잔존용량계(model based battery indicator)를 개발했다. 제안된 방법을 이용하면 잔존용량을 측정하는 데 전지의 전압과 전류만 측정하면 되고, 초기 잔존용량값의 영향을 받지 않으며, 전기자동차와 같이 부하가 급변하는 상태에서도 정확하게 계측할 수 있을 뿐 아니라, 그에 따라 주행 가능 거리를 계산하여 예측할 수 있다. 전지의 방전 특성 데이터를 이용해 수학적인 모델링을 한 후, 전압과 전류를 검출하여 이를 모델링한 식에 대입하면, 추정된 전지 전압을 얻을 수 있다. 이 추정 전압과 측정 전압의 차이가 최소가 되도록 하는 잔존용량의 반화량을 이용히여 잔존용량을 추정한다. 실험에서는 제작한 충방전장치와 PC를 이용하여 전지의 전압과 전류를 계측하여 수학적으로 모델링을 하고, 실제의 전기자동차에 탑재 가능한 스탠드 얼론(stand alone)타입의 마이크로 콘트롤러에 모델식 및 알고리즘을 장착하여 모델 기반 잔존용량계를 실제 검증하여 그 유용성을 입증하였다.

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교통상황과 확률적 수요를 고려한 차량경로문제의 Hybrid 유전자 알고리즘 (A Hybrid Genetic Algorithm for Vehicle Routing Problem which Considers Traffic Situations and Stochastic Demands)

  • 김기태;전건욱
    • 대한교통학회지
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    • 제28권5호
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    • pp.107-116
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    • 2010
  • 도심지에서 수요지간의 이동시간은 복잡한 도로사정과 외부환경으로 인하여 실시간 변화하는 교통상황에 큰 영향을 받고 있으며, 수요는 시기나 성향에 따라 확률적으로 변화하고 있다. 대부분의 차량경로문제 연구는 차량경로를 선정함에 있어 수요지간의 이동거리와 평균속력, 확정된 수요를 고려하여 경로를 구성하고 있으며, 교통상황과 확률적인 수요의 동적인 외부환경 반영이 미흡하였다. 본 연구에서는 원활 지체 정체의 교통상황과 확률적인 수요를 고려한 현실적인 차량경로문제를 제안하였다. 수리모형을 구축하고, CPLEX 11.1을 이용하여 검증하였으며, 총 소요시간을 최소화하는 Hybrid 유전자 알고리즘을 제안하였다. 교통상황과 확률적 수요를 고려한 차량경로문제의 결과를 기존의 휴리스틱 알고리즘과 비교하였으며, 본 연구에서 제안한 알고리즘이 가장 우수한 해를 제공하였다.

수학에서 과학으로의 전이학습프로그램의 효과 (Influence of transfer learning program from mathematics to science)

  • 성창근
    • 한국수학교육학회지시리즈C:초등수학교육
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    • 제18권1호
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    • pp.31-44
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    • 2015
  • 본 연구는 수학 교과에서 학습한 지식을 과학적 개념을 학습하는데 직접 적용해보는 전이학습프로그램의 효과를 확인하는데 있다. 구체적으로 수학 교과에서 학습한 비율 개념이 과학 교과의 속력 개념과 어떻게 관련이 있는지를 학생들 스스로 탐구해보는 전이학습프로그램을 개발 적용하고, 그것이 학생들의 비율 개념 이해와 수학적 태도에 어떤 영향을 미치는 지를 확인하는 것을 목적으로 한다. 연구 결과는 다음과 같다. 첫째, 전이 학습은 학생들의 비율 개념 이해를 향상시키는데 통계적으로 또한 실제적으로 효과가 있었다. 더욱이 '고정된 비' 수준에 머물러 있던 35명의 학생 중, 17명의 학생이 '내면화된 비' 수준으로 이동하였다. 둘째, 학생들의 수학학습 태도를 긍정적으로 변화시키는데 효과가 있었다. 따라서 전이 학습 프로그램은 학생들의 비율개념이해 수준을 높이고 긍정적인 수학학습 태도를 형성하는데 효과적인 학습 방법이다. 본 연구는 전이에 성공할 수 있는 인지적 조건을 찾는데 주안점을 두기보다는 전이를 직접 경험할 수 있는 학습 프로그램을 구안하고 그것의 효과를 검증했다는 점에서 그 의의를 찾을 수 있다.

Impact of Self-Citations on Impact Factor: A Study Across Disciplines, Countries and Continents

  • Pandita, Ramesh;Singh, Shivendra
    • Journal of Information Science Theory and Practice
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    • 제3권2호
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    • pp.42-57
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    • 2015
  • Purpose. : The present study is an attempt to find out the impact of self-citations on Impact Factor (IF) across disciplines. The study examines the number of research articles published across 27 major subject fields covered by SCImago, encompassing as many as 310 sub-disciplines. The study evaluates aspects like percentage of self-citations across each discipline, leading self-citing countries and continents, and the impact of self-citation on their IF. Scope. : The study is global in nature, as it evaluates the trend of self-citation and its impact on IF of all the major subject disciplines of the world, along with countries and continents. IF has been calculated for the year 2012 by analyzing the articles published during the years 2010 and 2011. Methodology/Approach. : The study is empirical in nature; as such, statistical and mathematical tools and techniques have been employed to work out the distribution across disciplines. The evaluation has been purely under-taken on the secondary data, retrieved from SCImago Journal and Country Ranking. Findings. : Self-citations play a very significant part in inflating IF. All the subject fields under study are influenced by the practice of self-citation, ranging from 33.14% to 52.38%. Compared to the social sciences and the humanities, subject fields falling under the purview of pure and applied sciences have a higher number of self-citations, but a far lesser percentage than the social sciences and humanities. Upon excluding self-citations, a substantial amount of change was observed in the IF of subject fields under study, as 18 (66.66%) out of 27 subjects fields faced shuffle in their rankings. Variation in rankings based on IF with and without self-citation was observed at subject level, country level, and continental level.

Isotopic Fissile Assay of Spent Fuel in a Lead Slowing-Down Spectrometer System

  • Lee, Yongdeok;Jeon, Juyoung;Park, Changje
    • Nuclear Engineering and Technology
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    • 제49권3호
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    • pp.549-555
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    • 2017
  • A lead slowing-down spectrometer (LSDS) system is under development to analyze isotopic fissile content that is applicable to spent fuel and recycled material. The source neutron mechanism for efficient and effective generation was also determined. The source neutron interacts with a lead medium and produces continuous neutron energy, and this energy generates dominant fission at each fissile, below the unresolved resonance region. From the relationship between the induced fissile fission and the fast fission neutron detection, a mathematical assay model for an isotopic fissile material was set up. The assay model can be expanded for all fissile materials. The correction factor for self-shielding was defined in the fuel assay area. The corrected fission signature provides well-defined fission properties with an increase in the fissile content. The assay procedure was also established. The assay energy range is very important to take into account the prominent fission structure of each fissile material. Fission detection occurred according to the change of the Pu239 weight percent (wt%), but the content of U235 and Pu241 was fixed at 1 wt%. The assay result was obtained with 2~3% uncertainty for Pu239, depending on the amount of Pu239 in the fuel. The results show that LSDS is a very powerful technique to assay the isotopic fissile content in spent fuel and recycled materials for the reuse of fissile materials. Additionally, a LSDS is applicable during the optimum design of spent fuel storage facilities and their management. The isotopic fissile content assay will increase the transparency and credibility of spent fuel storage.