Bacterial Community Shift during the Startup of a Full-Scale Oxidation Ditch Treating Sewage

( Yajun Chen ),( Lin Ye ),( Fuzheng Zhao ),( Lin Xiao ),( Shupei Cheng ),( Xu-xiang Zhang ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.1

The oxidation ditch (OD) is one of the most widely used processes for treating municipal wastewater. However, the microbial communities in the OD systems have not been well characterized, and little information about the shift of bacterial community during the startup process of the OD systems is available. In this study, we investigated the bacterial community changes during the startup period (over 100 days) of a full-scale OD. The results showed that the bacterial community dramatically changed during the startup period. Similar to the activated sludge samples in other studies, Proteobacteria (accounting for 26.3%-48.4%) was the most dominant bacterial phylum in the OD system, but its relative abundance declined nearly 40% during the startup process. It was also found that Planctomycetes proliferated greatly (from 4.79% to 13.5%) and finally replaced Bacteroidetes as the second abundant phylum in the OD system. Specifically, some bacteria affiliated with genus Flavobacterium exhibited remarkable decreasing trends, whereas bacterial species belonging to the OD1 candidate division and Saprospiraceae family were found to increase during the startup process. Despite of the bacterial community shift, the organic matter, nitrogen, and phosphorus in the effluent were always in low concentrations, suggesting the functional redundancy of the bacterial community. Moreover, by comparing with the bacterial community in other municipal wastewater treatment bioreactors, some potentially novel bacterial species were found to be present in the OD system. Collectively, this study improved our understandings of the bacterial community structure and microbial ecology during the startup of a full-scale wastewater treatment bioreactor.

Cuprum Metal-Organic-Framework and Polyacrylonitrile-Derived Cu-N-C Electrocatalyst for Application in Zinc-Air Batteries

Yajun Zhao,Jintao Chen,Xiaorui Li,Jiaqing Zhang,Yanan Li,Yajun Zhao,Liye Cao,Xiaoshi Jin 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02

Cu-N-C electrocatalyst was successfully prepared with Cu-BTC and polyacrylonitrile as templates by electrospinning and in-situ growth method. The effect of various N-doped content on the electrochemical performance of the catalyst were investigated and the Cu-N-C-0.25 exhibited the best OER/ORRcatalytic activities. When it was applied to the cathode of the zinc-air batteries, the power density of Cu-N-C-0.25 was 209.1 mW cm -2, which exceeded that of the commercial Pt/C + IrO2 hybrid catalyst (157 mW cm -2). The excellent electrochemical performance may be attributed to large number of active sites and high specific surface area on Cu-N-C electrocatalyst. It will be a promising alternative to precious metal catalysts containing Pt, Ir or Ru and their oxides.

Secure Transmission Scheme Based on the Artificial Noise in D2D-Enabled Full-Duplex Cellular Networks

( Chen Yajun ),( Yi Ming ),( Zhong Zhou ),( Ma Keming ),( Huang Kaizhi ),( Ji Xinsheng ) 한국인터넷정보학회 2019 KSII Transactions on Internet and Information Syst Vol.13 No.10

In this paper, a secure transmission scheme based on the artificial noise is proposed for D2D communications underlaying the full-duplex cellular network, and a secure power allocation scheme to maximize the overall secrecy rate of both the cellular user and D2D transmitter node is presented. Firstly, the full-duplex base station transmits the artificial noise to guarantee the secure communications when it receives signals of cellular uplinks. Under this secure framework, it is found that improving the transmission power of the cellular user or the D2D transmitter node will degrade the secrecy rate of the other, although will improve itself secrecy rate obviously. Hence, a secure power allocation scheme to maximize the overall secrecy rate is presented subject to the security requirement of the cellular user. However, the original power optimization problem is non-convex. To efficiently solve it, we recast the original problem into a convex program problem by utilizing the proper relaxation and the successive convex approximation algorithm. Simulation results evaluate the effectiveness of the proposed scheme.

Design and torque calculation of permanent magnet eddy current coupling with sinusoidal torque output

Ke Chen,Hongyang Shi,Yajun Guo,Lei Yin,Ziwei Bao,Hongmei Zheng 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.4

Due to its unique characteristic of non-contact torque transmission between its permanent magnetic rotor and conductorrotor, permanent magnet eddy current coupling (PMECC) is preferable in transmitting torque from the outside to the insideof a sealed container, which can effectively avoid the tricky problem of dynamic seals. To mix non-uniform liquid solutionsor gas mixtures in sealed containers more effectively, a sinusoidal torque is also required. Thus, permanent magnet eddy current coupling with a slotted conductor is proposed in this paper, which can adaptively output sinusoidal torque under a real-time load when the input rotational speed is constant. Based on the equivalent magnetic circuit method, an analytical model for calculating torque is proposed. When establishing the equivalent magnetic circuit model of the PMECC, the radial magnetic flux leakage circuit is added to the equivalent magnetic circuit diagram, and the cross-sectional shape of the eddy current region is equivalent to an octagon, which simplifies the torque calculation process. The analytical model is verified by finite element method (FEM) simulation and experiments. According to a comparison, the peak and lowest values of output torque obtained by the experiments, the analytical model, and the FEM simulation are consistent. The output torque waveform obtained by the analytical model and FEM simulation are also consistent.

A Feasibility Study on the Application of Seawater-source Heat Pump in the Subway of Qingdao

Youyuan Chen,Yajun Han,Yonggang Jia,Ruixia Li,Wenwei Li,Yuanlin Zou 한국도시환경학회 2010 한국도시환경학회지 Vol.10 No.2

A Self-adaptive Workload Balancing Algorithm on GPU Clusters

Jianjiang Li,Yajun Liu,Peng Zhang,Qingsong Miao,Lei Zhang,Wei Chen 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.11

With the wide application of GPU in High Performance Computing, more and more heterogeneous CPU+GPU clusters have been establishedin many fields. But with the comprehensive using of heterogeneous CPU+GPU clusters, workload balancing has become an important problem when the process nodes coordinate with each other, and the execution time of a program on imbalanced clusters resides on the slowest node. Although there are many strategies and algorithms that can solve the problem of workload balancing to some extent, they generally face the problem of high consumption of communication caused by the task migration. In order to make up for the existing deficiencies, this paper proposes a virtual task migration algorithm adapted to GPU clusters on CUDA platform. This algorithm uses virtual task migration to avoid actual data transmission between nodes, so the communication overhead is obviously decreased. At last, this paper performs an actual test using matrix multiplication to verify this algorithm. The experiment results show that compared with static task partitioning, the algorithm proposed in this paper can effectively achieve dynamic workload balancing and reduce the execution time of programs on GPU clusters, thus the algorithm can significantly improve program execution performance of GPU clusters on CUDA platform.

Comparative Genomics Uncovers the Genetic Diversity and Synthetic Biology of Secondary Metabolite Production of Trametes

( Yan Zhang ),( Jingjing Wang ),( Chen Yajun ),( Minghui Zhou ),( Wei Wang ),( Ming Geng ),( Decong Xu ),( Zhongdong Xu ) 한국균학회 2020 Mycobiology Vol.48 No.2

The carbohydrate-active enzyme (CAZyme) genes of Trametes contribute to polysaccharide degradation. However, the comprehensive analysis of the composition of CAZymes and the biosynthetic gene clusters (BGCs) of Trametes remain unclear. Here, we conducted comparative analysis, detected the CAZyme genes, and predicted the BGCs for nine Trametes strains. Among the 82,053 homologous clusters obtained for Trametes, we identified 8518 core genes, 60,441 accessory genes, and 13,094 specific genes. A large proportion of CAZyme genes were cataloged into glycoside hydrolases, glycosyltransferases, and carbohydrate esterases. The predicted BGCs of Trametes were divided into six strategies, and the nine Trametes strains harbored 47.78 BGCs on average. Our study revealed that Trametes exhibits an open pan-genome structure. These findings provide insights into the genetic diversity and explored the synthetic biology of secondary metabolite production for Trametes.

A Joint Design for Multi-band Heterogeneous Networks when Deploying Reconfigurable Intelligent Surface

Wenyu Jiang,Kaizhi Huang,Yajun Chen,Xiaoli Sun,Jie Yang,Kai Zhao 한국통신학회 2022 Journal of communications and networks Vol.24 No.5

Reconfigurable Intelligent Surface (RIS) technique is effective to improve the capacity and coverage of various networks. However, the practical RIS has dissimilar responses to signals in different frequencies due to its structure. Therefore, directly applying existing schemes to multi-band heterogeneous networks leads to beam misalignment and performance degra- dation issues. This paper considers RIS-assisted multi-band heterogeneous networks where base stations (BSs) use different frequencies. We formulate the problem for maximizing the sum rate of all users (SR) in every frequency band, and aim to jointly design BSs precoding vectors and RIS parameters while taking user choices into account. Based on the closed-form relationship of phase shifts between frequencies, an iterative algo- rithm is proposed to solve the challenging non-convex problems. In particular, we use fractional programming to decouple the problem, and solve the subproblems with Quadratic Transform (QT) and Genetic Algorithm (GA). Simulation results show that the proposed scheme can significantly improve SR among all frequency bands, which could instruct the coexistence of mul- tiple communication systems in future heterogeneous networks. What’s more, results also prove that deploying RISs recklessly will result in a degradation of the network.

Data Partitioning Strategy of GPU Heterogeneous Clusters Based on Learning

Jianjiang Li,Wei Chen,Jin Tian,Hongyan Zheng,Peng Zhang,Yajun Liu 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.9

With the rapid progress of computational science and computer simulation ability, a lot of properties can be predicted by the powerful ability of parallel computation before the actual research and development. With the development of high performance computer architecture, GPU is more and more widely used in high performance computation field as an emerging architecture, and a growing number of computations use GPU heterogeneous cluster architecture. However, how to partition workload and map to computing resource has always been the focus and difficult point. In the current study of GPU, according to the problems of the computing power provided by each node and the cluster hardware architecture which the application programmers don't understand, some partitioning strategies will result in serious load imbalance problem. Aimed at the complexity brought by the different computing ability of the nodes of GPU clusters, this paper proposes a GPU data partitioning strategy of heterogeneous clusters based on learning. It collects the states of each node in the process of running a program, and then estimates the calculation ability of each node dynamically, so as to guide the data partitioning. Actual testing results show that, this strategy allocates different tasks to nodes based on computing ability to ensure load balancing among nodes, so as to improve the execution performance of CUDA programs on heterogeneous GPU clusters and it laid a solid foundation for efficient computing on heterogeneous GPU clusters.

Mitochondrial Location of Severe Acute Respiratory Syndrome Coronavirus 3b Protein

Yuwen Cong,Xiaoling Yuan,Yajun Shan,Zhenyu Yao,Jianyong Li,Zhenhu Zhao,Jiapei Chen 한국분자세포생물학회 2006 Molecules and cells Vol.21 No.2