원자력 계통 열수력 해석코드의 부수로 유동혼합 모델 개발

김동위(Dong Wi Kim),정재준(Jae Jun Jeong) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.10

부수로 유동혼합은 원자로 노심의 냉각수 온도 및 기포율 분포 예측 관점에서 매우 중요한 현상이다. 부수로 해석을 목적으로 만들어진 코드들은 이른바 EM 모델 혹은 EVVD 모델을 채택하여 부수로 유동혼합을 해석하고 있다. 전자는 단상 유동 조건에 적합하며 후자는 단상과 2상 유동 조건 모두에 적합하나 다소 복잡한 점이 있다. 원자력 계통 열수력 해석코드 SPACE 코드는 가압경수로의 설계 및 안전 해석을 위해 개발되었다. 본 연구에서는 SPACE 코드 적용 영역을 부수로 열수력 해석까지 확장시키기 위해, SPACE 코드에 EVVD 모델을 삽입하였다. EVVD 모델이 삽입된 SPACE 코드를 핵연료집합체 실험 자료(GE 9-핵연료 실험, ISPRA 16-핵연료 실험, PSBT 25-핵연료 실험)을 이용하여 평가하였다. 그 결과를 바탕으로 EVVD 모델의 중요 인자인 기포이동계수 KVD를 새로 제안하고 평가하였다. Subchannel flow mixing is mportant for the accurate prediction of temperature and void fraction distributions in a nuclear reactor core. Dedicated subchannel analysis codes have been used for subchannel flow analysis by adopting either the so-called equal mass exchange (EM) or the equal-volume exchange and void drift (EVVD) model. The former is known to be good for a single-phase flow and, meanwhile, the latter is appropriate for both single- and two-phase flows. The nuclear thermal-hydraulic system code, SPACE code, has been developed for the design and safety analysis of a pressurized water reactor. To extend its applicability to subchannel analysis, the state-of-the art EVVD model has been implemented into the SPACE code in this work. The modified SPACE code with the EVVD model was evaluated using the measured data from two-phase flow rod bundle tests (GE 9-rod test, ISPRA 16-rod test and PSBT 25-rod test). Based on the results, a new void drift coefficient KVD was suggested, which is an important parameter of the EVVD model.

Forecasting Algorithm Parameters Solving Method based on Phase-space Reconstruction and Its Application in Price Prediction

Hu Shuyu,Huang Ming 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.4

To improve the forecasting accuracy of oil prices, this paper has proposed oil price predicting model (PSR-LSSVM) based on unified solving by phase space reconstruction and predicting algorithm parameters using interrelation between phase-space reconstruction and predicting algorithm. The LSSVM is selected as the predicting algorithm of oil prices, and the parameters of phase space reconstruction and LSSVM are taken as individuals of the genetic algorithm, and the optimal delay time, embedding dimension and LSSVM parameters are obtained through selection, crossover and mutation evolutionary mechanism, and finally, the predicting model of oil prices is established and the performance of predicting model is tested by Daqing oil price time series. The results show that the proposed model PSR-LSSVM obtains higher predicting accuracy than the oil-price forecasting models of independently optimized phase-space reconstruction and LSSVM, which provides a new research idea for the predicting problem of chaotic time series.

A Small Signal Rotating Frame Model of a Self-synchronizing Single-phase Grid-tied Inverter

R. Agrawal,B. P. McGrath,C. A. Teixeira,R. H. Wilkinson 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-

A self-synchronizing grid-tied inverter uses the internal dynamic states of the current regulator to estimate the grid voltage for synchronization. The stability analysis of a single-phase grid-tied inverter is complex because of the lack of an orthogonal channel and non-linearities present due to the phase-locked loop (PLL). This paper introduces fictitious orthogonal quantities for a single-phase grid-tied inverter, creating a model in the synchronous reference frame. This approach enables Jacobian linearization to develop a small-signal inverter model. The stability analysis of the small-signal model using Floquet theory then allows for stability boundaries to be determined across a wide range of operating conditions. The model has been validated using detailed switched simulations of a single-phase grid-tied inverter with matching experimental results.

Background Considerations for the 2H(7Be,3H)6Be Experimental Data Using the Phase Space Model

K. Y. Chae,V. Guimaraes 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.9

The 2H(7Be,3H)6Be reaction was measured at the Holifield Radioactive Ion Beam Facility of theOak Ridge National Laboratory in 2004 to search for the resonances in the unbound 6Be nucleus. The results showed, however, no resonance was evident in the experimental data, which impliedthat the direct transfer to 6Be levels was not particularly strong compared to other reaction mechanismsthat produced tritons in their exit channels. In the present work, theoretical calculationswith background considerations are performed to better understand the cross-section data for the2H(7Be,3H)6Be reaction using the phase space model.

Model predictive current control with modified discrete space vector modulation for three‑leg two‑phase VSI

Gi-Heon Jeong,Hyung-Woo Lee,Tae-Yong Yoon,Hyeon-Jun Park,Kyo-Beum Lee 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.6

This paper proposes a model predictive current control (MPCC) method for a three-leg two-phase voltage source inverter to reduce the ripple of the output current. The proposed MPCC method is based on discrete space vector modulation, which is implemented by eliminating nonlinear modulation regions and generating virtual voltage vectors based on the stationary reference voltage vector axis. In addition, based on a voltage angle estimated using load parameters, the candidate voltage vectors in a specific region are generated, which reduces the calculation burden. Subsequently, the cost function is calculated using these candidate voltage vectors, and the optimal voltage vector selected using the proposed MPCC method is more accurate than the vector selected using the conventional MPCC method. Therefore, by applying the proposed method to increase the number of virtual voltage vectors, it is possible to obtain a delicate reference voltage. Consequently, the total harmonic distortion of the output current is reduced, resulting in an increase in power quality. The effectiveness and feasibility of the proposed method are verified through simulations and experiments.

Signal of Unusual Large Fluctuations in 32S-Em Interactions at SPS Energies

Mir Hashim Rasool,Shafiq Ahmad,M. Ayaz Ahmad 한국물리학회 2015 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.67 No.3

An investigation on the presence of large dynamical fluctuations was carried out in the pseudorapidity phase space (-space) of relativistic charged particles produced in 32S-Em interactions at 200 AGeV/c by the method of scaled factorial moments, Fq, in terms of the new scaled variable X() suggested by Bialas and Gazdzicki. The Nuclear emulsion technique was employed to collect the experimental data. We compared our experimental results with those obtained from simulated events by using Monte Carlo Code FRITIOF. The variation of lnFq with lnM in pseudorapidity () phase space revealed a power law behavior. The values of the slopes, q, determined from the analyses of the Fq moments are discussed. The generalized fractal dimensions, Dq, determined from the above method are calculated and found to decrease with the order of the moments, q, indicating multifractality in multiparticle production. Also, the anomalous fractal dimension dq obtained was found to increase linearly with the order of moments, q suggesting a self-similar cascade mechanism. In order to check for the presence of the statistical fluctuations, we generated uncorrelated Monte Carlo events (MC-RAND) randomly in -space based on the assumption of independent emission of particles and compared the results with the experimental and FRITIOF data. The experimental data on intermittency were found to exhibit a remarkable proximity to the analogous data obtained from the FRITIOF code. However, the uncorrelated Monte Carlo events exhibited no such dependence on M, which indicates the absence of a statistical contribution in the experimental data. The flat behavior in the Monte Carlo events is expected for an independent emission of particles.

Theoretical and Experimental Modeling of Phase Change Material–Based Space Heating Using Solar Energy

Vaidhyanathan Ashwath,Banker N. D. 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.2

Recently, renewable sources of energy, particularly, solar thermal energy, have gained significant attention for developing heating and cooling mechanisms for buildings. This work aims at developing a theoretical model for space heating based on phase change material (PCM) using solar energy in winter conditions for the Northern region of India. The system has two PCM containers placed inside the room on the two opposite walls, which receives heat from concentrating solar system during the daytime. After achieving the temperature of PCM above its melting point using the solar system, the stored heat of PCM is released to the room ambient during the nighttime when the room ambient is at lower temperature. OM-37, having melting temperature of [Formula: see text]C, has been used as a PCM for the current research work. The numerical investigation of the system shows that temperature of the room reaches to 26–[Formula: see text]C from [Formula: see text]C in 4–5[Formula: see text]h of operation and thus ensuring thermal comfort of occupants.