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Traveling Wave Characteristics Based Pilot Protection Scheme for Hybrid Cascaded HVDC Transmission Line

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Journal of Modern Power Systems and Clean Energy 2024年第3期12卷 971-980页

作者： Dalin mu Sheng Lin Xiaopeng Li the School of Electrical Engineering Southwest Jiaotong UniversityChengdu 611756China the State Grid Sichuan Electric Power Research Institute Chengdu 610041China

The hybrid cascaded high-voltage direct current(HVDC)transmission system has various operation modes,and some operation modes have sharply increasing requirements for protection rapidity,while the traditional pilot differential protection(PDP)has poor rapidity,and even refuses to operate when faults occur on the DC ***,a novel pilot protection scheme based on traveling wave characteristics is ***,the adaptability of the traditional PDP applied in engineering is analyzed for different operation ***,the expressions of the forward traveling wave(FTW)and backward traveling wave(BTW)on the rectifier side and the inverter side are derived for different fault *** the theoretical derivation,the difference between the BTW and FTW on the rectifier side is less than zero,and the same is true on the inverter ***,in the event of an external fault of DC line,the difference between the BTW and FTW at nearfault terminal protection installation point is greater than ***,by summing over the product of the difference between BTW and FTW of the rectifier side and that of the inverter side,the fault identification criterion is *** simulation results show that the proposed pilot protection scheme can quickly and reliably identify the short-circuit faults of DC line in different operation modes.

关键词： Hybrid cascaded high-voltage direct current(HVDC)transmission system DC line operation mode pilot protection

An optimization-oriented modeling approach using input convex neural networks and its application on optimal chiller loading

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Building Simulation 2024年第4期17卷 639-655页

作者： Shanshuo Xing Jili Zhang Song mu Dalian University of Technology Dalian116024China Guangdong Airport Baiyun Information Technology Co. Ltd.Guangzhou510000China

Optimization for the multi-chiller system is an indispensable approach for the operation of highly efficient chiller *** optima obtained by model-based optimization algorithms are dependent on precise and solvable objective *** classical neural networks cannot provide convex input-output mappings despite capturing impressive nonlinear fitting capabilities,resulting in a reduction in the robustness of model-based *** this paper,we leverage the input convex neural networks(ICNN)to identify the chiller model to construct a convex mapping between control variables and the objective function,which enables the NN-based OCL as a convex optimization problem and apply it to multi-chiller optimization for optimal chiller loading(OCL).Approximation performances are evaluated through a four-model comparison based on an experimental data set,and the statistical results show that,on the premise of retaining prior convexities,the proposed model depicts excellent approximation power for the data set,especially the unseen ***,the ICNN model is applied to a typical OCL problem for a multi-chiller system and combined with three types of optimization *** with conventional and meta-heuristic methods,the numerical results suggest that the gradient-based BFGS algorithm provides better energy-saving ratios facing consecutive cooling load inputs and an impressive convergence speed.

关键词： chiller plant input convex neural network optimal load distribution convex optimization

Strong synergy between physical and chemical properties:Insight into optimization of atomically dispersed oxygen reduction catalysts

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Journal of Energy Chemistry 2024年第4期91卷 36-49页

作者： Yifan Zhang Linsheng Liu Yuxuan Li Xueqin mu Shichun mu Suli Liu Zhihui Dai School of Chemistry and Molecular Engineering Nanjing Tech UniversityNanjing 211816JiangsuChina State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of Technology InstitutionWuhan 430070HubeiChina School of Chemistry and Materials Science Nanjing Normal UniversityNanjing 210023JiangsuChina

Atomically dispersed catalysts exhibit significant influence on facilitating the sluggish oxygen reduction reaction(ORR)kinetics with high atom economy,owing to remarkable attributes including nearly 100%atomic utilization and exceptional catalytic ***,accurately controlling atomic physical properties including spin,charge,orbital,and lattice degrees of atomically dispersed catalysts can realize the optimized chemical properties including maximum atom utilization efficiency,homogenous active centers,and satisfactory catalytic performance,but remains ***,through physical and chemical insight,we review and systematically summarize the strategies to optimize atomically dispersed ORR catalysts including adjusting the atomic coordination environment,adjacent electronic orbital and site density,and the choice of dual-atom *** the emphasis is on the fundamental understanding of the correlation between the physical property and the catalytic behavior for atomically dispersed ***,an overview of the existing challenges and prospects to illustrate the current obstacles and potential opportunities for the advancement of atomically dispersed catalysts in the realm of electrocatalytic reactions is offered.

关键词： Atomically dispersed catalysts Coordination environment Electronic orbitals Inter-site distance effect Oxygen reduction reaction

Sea level rise along China coast from 1950 to 2020

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Science China Earth Sciences 2024年第3期67卷 802-810页

作者： Dapeng mu Tianhe XU Haoming YAN Institute of Space Sciences Shandong UniversityWeihai 264209China Innovation Academy for Precision Measurement Science and Technology Chinese Academy of SciencesWuhan 430071China Institute of Marine and Antarctic Science University of TasmaniaHobartTasmania 7004Australia

Global mean sea level rise has been reconstructed using tide gauges. However, long-term sea level rise along the China coast is unclear. To address this issue, a data assimilation approach is developed to reconstruct sea level rise along the China coast from 1950 to 2020 using a global distribution of tide gauges(TGs). This approach combines climate models and sea level fingerprints. The climate models provide stereodynamic sea level changes. The sea level fingerprints include increases in ocean mass due to global ice melting and changes in water storage on land. The reconstructed global mean sea level rise agrees well with previous studies. We quantify sea level rise at 20 TGs along the China coast. The results suggest that sea level rise along the China coast(1.95±0.33 mm yr^(-1)) is greater than the global mean(1.71±0.17 mm yr^(-1)). We also find that China's coastal sea level rise is more than three times faster after 1980, increasing from 0.84±0.28 mm yr^(-1)for 1950–1980 to3.12±0.21 mm yr^(-1)for 1980–2020. This finding implies a significant sea level acceleration along the China coast. Our results advance the understanding of long-term sea level changes along the China coast.

关键词： Sea level rise China coast Tide gauges Data assimilation

Rethinking the Encoder-decoder Structure in Medical Image Segmentation from Releasing Decoder Structure

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Journal of Bionic Engineering 2024年第3期21卷 1511-1521页

作者： Jiajia Ni Wei mu An Pan Zhengming Chen School of Artificial Intelligence Anhui Polytechnic UniversityWuhu241000China School of Information Science and Engineering HoHai UniversityChangzhou213000China

Medical image segmentation has witnessed rapid advancements with the emergence of encoder-decoder based *** the encoder-decoder structure,the primary goal of the decoding phase is not only to restore feature map resolution,but also to mitigate the loss of feature information incurred during the encoding ***,this approach gives rise to a challenge:multiple up-sampling operations in the decoder segment result in the loss of feature *** address this challenge,we propose a novel network that removes the decoding structure to reduce feature information loss(CBL-Net).In particular,we introduce a Parallel Pooling Module(PPM)to counteract the feature information loss stemming from conventional and pooling operations during the encoding ***,we incorporate a multiplexed Dilation Convolution(MDC)module to expand the network's receptive ***,although we have removed the decoding stage,we still need to recover the feature map ***,we introduced the Global Feature Recovery(GFR)*** uses attention mechanism for the image feature map resolution recovery,which can effectively reduce the loss of feature *** conduct extensive experimental evaluations on three publicly available medical image segmentation datasets:DRIVE,CHASEDB and MoNuSeg *** results show that our proposed network outperforms state-of-the-art methods in medical image *** addition,it achieves higher efficiency than the current network of coding and decoding structures by eliminating the decoding component.

关键词： Medical image segmentation Encoder-decoder architecture Attention mechanisms Releasing decoder architecture Neural network

High Order IMEX Stochastic Galerkin Schemes for Linear Transport Equation with Random Inputs and Diffusive Scalings

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Communications on Applied Mathematics and Computation 2024年第1期6卷 325-339页

作者： Zheng Chen Lin mu Department of Mathematics University of Massachusetts Dartmouth285 Old Westport RoadDartmouth02747MAUSA Department of Mathematics University of GeorgiaAthens30602GAUSA

In this paper,we consider the high order method for solving the linear transport equations under diffusive scaling and with random *** tackle the randomness in the problem,the stochastic Galerkin method of the generalized polynomial chaos approach has been ***,the high order implicit-explicit scheme under the micro-macro decomposition framework and the discontinuous Galerkin method have been *** provide several numerical experiments to validate the accuracy and the stochastic asymptotic-preserving property.

关键词： Stochastic Galerkin scheme linear transport equations generalized polynomial approach stochastic asymptotic-preserving property

Study of 26 Galactic Open Clusters with Extended Main-sequence Turnoffs

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Research in Astronomy and Astrophysics 2024年第6期24卷 28-37页

作者： Yang-Yang Deng Zhong-mu Li Yunnan Observatories Chinese Academy of SciencesKunming 650216China University of Chinese Academy of Sciences Beijing 100049China Institute of Astronomy and Information Dali UniversityDali 671003China

Recent studies indicate that some Galactic open clusters(OCs)exhibit extended main-sequence turnoff(eMSTO)in their color–magnitude diagrams(CMDs).However,the number of Galactic OCs with eMSTO structures detected so far is limited,and the reasons for their formation are still *** work identifies 26 Galactic OCs with undiscovered eMSTOs and investigates the causes of these *** population types and fundamental parameters of cluster samples are acquired using CMD fitting *** them,the results of 11 OCs are reliable as the observed CMDs are *** propose the crucial role of stellar binarity and confirm the importance of stellar rotation in reproducing eMSTO *** results also show that the impact of age spread is important,as it can adequately explain the structure of young OCs and fit the observed CMDs of intermediate-age OCs better.

关键词： (stars:)binaries:general Galaxy:fundamental parameters (Galaxy:)open clusters and associations:general (stars:)Hertzsprung Russell and C-M-diagrams

BSEC Method for Unveiling Open Clusters and its Application to Gaia DR3:83 New Clusters

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Research in Astronomy and Astrophysics 2024年第5期24卷 169-184页

作者： Zhong-mu Li Cai-Yan Mao Institute of Astronomy and Information Dali UniversityDali 671003China

Open clusters(OCs) are common in the Milky Way, but most of them remain undiscovered. There are numerous techniques, including some machine-learning algorithms, available for the exploration of OCs. However, each method has its limitations and therefore, different approaches to discovering OCs hold significant values. We develop a comprehensive approach method to automatically explore the data space and identify potential OC candidates with relatively reliable membership determination. This approach combines the techniques of Hierarchical Density-Based Spatial Clustering of Applications with Noise, Gaussian mixture model, and a novel cluster member identification technique, color excess constraint. The new method exhibits efficiency in detecting OCs while ensuring precise determination of cluster memberships. Because the main feature of this technique is to add an extra constraint(EC) for the members of cluster candidates using the homogeneity of color excess,compared to typical blind search codes, it is called Blind Search-Extra Constraint(BSEC) method. It is successfully applied to the Gaia Data Release 3, and 83 new OCs are found, whose color–magnitude diagrams(CMDs) are fitted well to the isochrones. In addition, this study reports 621 new OC candidates with discernible main sequence or red giant branch. It is shown that BSEC technique can discard some false negatives of previous works, which takes about three percentage of known clusters. It shows that as an EC, the color excess(or twocolor) constraint is useful for removing fake cluster member stars from the clusters that are identified from the positions and proper motions of stars, and getting more precise CMDs, when differential reddening of member stars of a cluster is not large(e.g., ΔE(G_(BP)-G_(RP)) < 0.5 mag). It makes the CMDs of 15% clusters clearer(in particular for the region near turnoff) and therefore is helpful for CMD and stellar population studies. Our result suggests that the color excess con

关键词： Galaxy stellar content-(Galaxy:)open clusters and associations general-stars fundamental parameters

On convergence of covariance matrix of empirical Bayes hyper-parameter estimator

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Control Theory and Technology 2024年第2期22卷 149-162页

作者： Yue Ju Biqiang mu Tianshi Chen School of Data Science and Shenzhen Research Institute of Big Data The Chinese University of Hong KongShenzhenShenzhen518172GuangdongChina Division of Decision and Control Systems School of Electrical Engineering and Computer ScienceKTH Royal Institute of Technology10044StockholmSweden Key Laboratory of Systems and Control Institute of Systems ScienceAcademy of Mathematics and System ScienceChinese Academy of SciencesBeijing100190China

Regularized system identification has become the research frontier of system identification in the past *** related core subject is to study the convergence properties of various hyper-parameter estimators as the sample size goes to *** this paper,we consider one commonly used hyper-parameter estimator,the empirical Bayes(EB).Its convergence in distribution has been studied,and the explicit expression of the covariance matrix of its limiting distribution has been ***,what we are truly interested in are factors contained in the covariance matrix of the EB hyper-parameter estimator,and then,the convergence of its covariance matrix to that of its limiting distribution is *** general,the convergence in distribution of a sequence of random variables does not necessarily guarantee the convergence of its covariance ***,the derivation of such convergence is a necessary complement to our theoretical analysis about factors that influence the convergence properties of the EB hyper-parameter *** this paper,we consider the regularized finite impulse response(FIR)model estimation with deterministic inputs,and show that the covariance matrix of the EB hyper-parameter estimator converges to that of its limiting ***,we run numerical simulations to demonstrate the efficacy of ourtheoretical results.

关键词： Regularized system identification Hyper-parameter estimator Empirical Bayes Convergence of covariance matrix