Numerical evaluation of hypothetical core disruptive accident in full-scale model of sodium-cooled fast reactor

Zhihong Guo,Xiaodong Chen,Guoqing Hu 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6

A hypothetical core destructive accident (HCDA) has received widespread attention as one of the mostserious accidents in sodium-cooled fast reactors. This study combined recent advantages in numericalmethods to realize realistic modeling of the complex fluidestructure interactions during HCDAs in a fullscale sodium-cooled fast reactor. The multi-material arbitrary LagrangianeEulerian method is used todescribe the fluidestructure interactions inside the container. Both the structural deformations and plugrises occurring during HCDAs are evaluated. Two levels of expansion energy are considered with twodifferent reactor models. The simulation results show that the container remains intact during an accident with small deformations. The plug on the top of the container rises to an acceptable level after thesealing between the it and its support is destroyed. The methodology established in this study provides areliable approach for evaluating the safety feature of a container design.

Secondary Voltage Control for Reactive Power Sharing in an Islanded Microgrid

Guo, Qian,Wu, Hongyan,Lin, Liaoyuan,Bai, Zhihong,Ma, Hao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

Genome Sequencing Highlights the Plant Cell Wall Degrading Capacity of Edible Mushroom Stropharia rugosoannulata

Guo Mengpei,Ma Xiaolong,Zhou Yan,Bian Yinbing,Liu Gaolei,Cai Yingli,Huang Tianji,Dong Hongxia,Cai Dingjun,Wan Xueji,Wang Zhihong,Xiao Yang,Kang Heng 한국미생물학회 2023 The journal of microbiology Vol.61 No.1

The basidiomycetous edible mushroom Stropharia rugosoannulata has excellent nutrition, medicine, bioremediation, and biocontrol properties. S. rugosoannulata has been widely and easily cultivated using agricultural by-products showing strong lignocellulose degradation capacity. However, the unavailable high-quality genome information has hindered the research on gene function and molecular breeding of S. rugosoannulata. This study provided a high-quality genome assembly and annotation from S. rugosoannulata monokaryotic strain QGU27 based on combined Illumina-Nanopore data. The genome size was about 47.97 Mb and consisted of 20 scaffolds, with an N50 of 3.73 Mb and a GC content of 47.9%. The repetitive sequences accounted for 17.41% of the genome, mostly long terminal repeats (LTRs). A total of 15,726 coding gene sequences were putatively identified with the BUSCO score of 98.7%. There are 142 genes encoding plant cell wall degrading enzymes (PCWDEs) in the genome, and 52, 39, 30, 11, 8, and 2 genes related to lignin, cellulose, hemicellulose, pectin, chitin, and cutin degradation, respectively. Comparative genomic analysis revealed that S. rugosoannulata is superior in utilizing aldehyde-containing lignins and is possible to utilize algae during the cultivation.

Interactive Feature Extraction on 3D Meshes

Zhihong, Mao,Lee, Kunwoo,Guo, Cao,Yanzhao, Ma CAD Solutions, LLC 2011 Computer-aided design and applications Vol.8 No.5

Secondary Voltage Control for Reactive Power Sharing in an Islanded Microgrid

Qian Guo,Hongyan Wu,Liaoyuan Lin,Zhihong Bai,Hao Ma 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.

Vibration-based structural health monitoring using CAE-aided unsupervised deep learning

Tong Guo,Minte Zhang,Ruizhao Zhu,Yueran Zong,Zhihong Pan 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.30 No.6

Vibration-based structural health monitoring (SHM) is crucial for the dynamic maintenance of civil building structures to protect property security and the lives of the public. Analyzing these vibrations with modern artificial intelligence and deep learning (DL) methods is a new trend. This paper proposed an unsupervised deep learning method based on a convolutional autoencoder (CAE), which can overcome the limitations of conventional supervised deep learning. With the convolutional core applied to the DL network, the method can extract features self-adaptively and efficiently. The effectiveness of the method in detecting damage is then tested using a benchmark model. Thereafter, this method is used to detect damage and instant disaster events in a rubber bearing-isolated gymnasium structure. The results indicate that the method enables the CAE network to learn the intact vibrations, so as to distinguish between different damage states of the benchmark model, and the outcome meets the high-dimensional data distribution characteristics visualized by the t-SNE method. Besides, the CAE-based network trained with daily vibrations of the isolating layer in the gymnasium can precisely recover newly collected vibration and detect the occurrence of the ground motion. The proposed method is effective at identifying nonlinear variations in the dynamic responses and has the potential to be used for structural condition assessment and safety warning.

An Enhanced Power Sharing Strategy for Islanded Microgrids Considering Impedance Matching for Both Real and Reactive Power

Lin, Liaoyuan,Guo, Qian,Bai, Zhihong,Ma, Hao The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

There exists a strong coupling between real and reactive power owing to the complex impedances in droop based islanded microgrids (MGs). The existing virtual impedance methods consider improvements of the impedance matching for sharing of the voltage controlled power (VCP) (reactive power for Q-V droop, and real power for P-V droop), which yields a 1-DOF (degree of freedom) tunable virtual impedance. However, a weak impedance matching for sharing of the frequency controlled power (FCP) (real power for $P-{\omega}$ droop, and reactive power for $Q-{\omega}$ droop) may result in FCP overshoots and even oscillations during load transients. This in turn results in VCP oscillations due to the strong coupling. In this paper, a 2-DOF tunable adaptive virtual impedance method considering impedance matching for both real and reactive power (IM-PQ) is proposed to improve the power sharing performance of MGs. The dynamic response is promoted by suppressing the coupled power oscillations and power overshoots while realizing accurate power sharing. In addition, the proposed power sharing controller has a better parametric adaptability. The stability and dynamic performances are analyzed with a small-signal state-space model. Simulation and experimental results are presented to investigate the validity of the proposed scheme.

An Enhanced Power Sharing Strategy for Islanded Microgrids Considering Impedance Matching for Both Real and Reactive Power

Liaoyuan Lin,Qian Guo,Zhihong Bai,Hao Ma 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.1

There exists a strong coupling between real and reactive power owing to the complex impedances in droop based islanded microgrids (MGs). The existing virtual impedance methods consider improvements of the impedance matching for sharing of the voltage controlled power (VCP) (reactive power for Q-V droop, and real power for P-V droop), which yields a 1-DOF (degree of freedom) tunable virtual impedance. However, a weak impedance matching for sharing of the frequency controlled power (FCP) (real power for P-ω droop, and reactive power for Q-ω droop) may result in FCP overshoots and even oscillations during load transients. This in turn results in VCP oscillations due to the strong coupling. In this paper, a 2-DOF tunable adaptive virtual impedance method considering impedance matching for both real and reactive power (IM-PQ) is proposed to improve the power sharing performance of MGs. The dynamic response is promoted by suppressing the coupled power oscillations and power overshoots while realizing accurate power sharing. In addition, the proposed power sharing controller has a better parametric adaptability. The stability and dynamic performances are analyzed with a small-signal state-space model. Simulation and experimental results are presented to investigate the validity of the proposed scheme.

Phase identification of $C_3N_4$ in CN films prepared by rf plasma chemical vapor deposition and dc magnetron sputtering

Fu, Dejun,Wu, Dawei,Zhang, Zhihong,Meng, Xianquan,He, Mengbing,Guo, Huaixi,Peng, Yougui,Fan, Xiangjun The Korean Vacuum Society 1998 Applied Science and Convergence Technology Vol.7 No.1

We prepared $C_3N_4$ films by rf plasma enhanced chemical vapor deposition(PCVD) and alternating $C_3N_4$/TiN composite films by dc magnetron sputtering. X-ray diffraction (XRD) and transmission electron diffraction (TED) revealed that the structure of the films is amorphous or polycrystalline, depending on deposition conditions and heat treatment. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy confirmed the presence of $sp_3\; and sp _2$ hybridized C atoms bonded with N atoms in the tetrahedral and hexagonal configurations, respectively. Graphite-free $C_3N_4$ films were obtained by PCVD under optimal conditions. To prepare well crystallized $C_3N_4$ films by magnetron sputtering, we introduced negatively biased gratings in the sputtering system. CN films deposited at grating voltages (Vg) lower than 400V are amorphous. Crystallites of cubic and $\beta$-$C_3N_4$ were formed at increased voltages.

Research on Covert Communication Technology Based on Matrix Decomposition of Digital Currency Transaction Amount

Lejun Zhang,Bo Zhang,Ran Guo,Zhujun Wang,Guopeng Wang,Jing Qiu,Shen Su,Yuan Liu,Guangxia Xu,Zhihong Tian,Sergey Gataullin 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.4

With the development of covert communication technologies, the number of covert communication technologies using blockchain as a carrier is increasing. However, using the transaction amount of digital currency as a carrier for covert communication has problems such as low embedding rate, large consumption of transaction amount, and easy detection. In this paper, firstly, by experimentally analyzing the distribution of bitcoin transaction amounts, we determine the most suitable range of amounts for matrix decomposition. Secondly, we design a novel matrix decomposition method that can successfully decompose a large amount matrix into two small amount matrices and utilize the elements in the small amount matrices for covert communication. Finally, we analyze the feasibility of the novel matrix decomposition method in this scheme in detail from four aspects, and verify it by experimental comparison, which proves that our scheme not only improves the embedding rate and reduces the consumption of transaction amount, but also has a certain degree of resistance to detection.