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Damping Characteristic Analysis and Optimization of Wind-thermal-bundled Power Transmission by LCC-HVDC systems

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Journal of Modern Power systems and Clean Energy 2024年第1期12卷 299-312页

作者： Liwen Zheng Shiying Ma the Power system department China Electric Power Research InstituteBeijing 100192China

With the rapid development of renewable energy,wind-thermal-bundled power transmission by line-commutated converter based high-voltage direct current(LCC-HVDC)systems has been widely *** dynamic interaction mechanisms among permanent magnet synchronous generators(PMSGs),synchronous generators(SGs),and LCC-HVDC system become *** deal with this issue,a path analysis method(PAM)is proposed to study the dynamic interaction mechanism,and the damping reconstruction is used to analyze the damping characteristic of the ***,based on the modular modeling,linearized models for the PMSG subsystem,the LCC-HVDC subsystem,and the SG subsystem are ***,based on the closed-loop transfer function diagram of the system,the disturbance transfer path and coupling relationship among subsystems are analyzed by the PAM,and the damping characteristic analysis of the SG-dominated oscillation mode is studied based on the damping *** with the PAM,the small-signal model of the system is obtained and eigenvalue analysis results are ***,the effect of the control parameters on the damping characteristic is analyzed and the conclusions are verified by time-domain ***,the penalty functions of the oscillation modes and decay modes are taken as the objective function,and an optimization strategy based on the Monte Carlo method is proposed to solve the parameter optimization *** simulation results are presented to validate the effectiveness of the proposed strategy.

关键词： Wind-thermal-bundled power transmission line-commutated converter based high-voltage direct current(LCC-HVDC) path analysis method(PAM) damping characteristic analysis Monte Carlo method

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Multiscale spatiotemporal meteorological drought prediction:A deep learning approach

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Advances in Climate Change Research 2024年第2期15卷 211-221页

作者： Jia-Li ZHANG Xiao-Meng HUANG Yu-Ze SUN department of Earth system Science Ministry of Education Key Laboratory for Earth System ModellingInstitute for Global Change StudiesTsinghua UniversityBeijing 100084China

Reliable monitoring and thorough spatiotemporal prediction of meteorological drought are crucial for early warning and decision-making regarding drought-related *** utilisation of multiscale methods is effective for a comprehensive evaluation of drought occurrence and progression,given the complex nature of meteorological ***,the nonlinear spatiotemporal features of meteorological droughts,influenced by various climatological,physical and environmental factors,pose significant challenges to integrated prediction that considers multiple indicators and time *** address these constraints,we introduce an innovative deep learning framework based on the shifted window transformer,designed for executing spatiotemporal prediction of meteorological drought across multiple *** formulate four prediction indicators using the standardized precipitation index and the standard precipitation evaporation index as core methods for drought definition using the ERA5 reanalysis *** indicators span time scales of approximately 30 d and one ***-term indicators capture more anomalous variations,whereas long-term indicators attain comparatively higher accuracy in predicting future *** focus on the East Asian region,notable for its diverse climate conditions and intricate terrains,to validate the model's efficacy in addressing the complexities of nonlinear spatiotemporal *** model's performance is evaluated from diverse spatiotemporal viewpoints,and practical application values are analysed by representative drought *** results substantiate the effectiveness of our proposed model in providing accurate multiscale predictions and capturing the spatiotemporal evolution characteristics of *** of the four drought indicators accurately delineates specific facets of the meteorological drought ***,three representative drought events,namely flash drought,sustained drought and severe drought,

关键词： Meteorological drought Spatiotemporal prediction Multiscale Swim transformer Deep learning

Novel Cs-Mg-Al mixed oxide with improved mobility of oxygen species for passive NOx adsorption

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Green Energy & Environment 2024年第10期9卷 1581-1591页

作者： Yimeng Yin Chizhong Wang Lei Qiu Xing Li Feilin Zhao Jie Yu Jinchi Han Huazhen Chang School of Environment and Natural Resources Renmin University of China department of Earth system Science Tsinghua University

The development of passive NOxadsorbers with cost-benefit and high NOxstorage capacity remains an on-going challenge to after-treatment technologies at lower temperatures associated with cold-start ***,Cs1Mg3Al catalyst prepared by sol±gel method was cyclic tested in NOxstorage under 5 vol%*** 100°C,the NOxstorage capacity (1219μmol g-1) was much higher than that of Pt/Ba O/Al2O3(610μmol g-1).This provided new insights for non-noble metal catalysts in low-temperature passive *** addition of Cs improved the mobility of oxygen species and thus improved the NOxstorage *** XRD,XPS,IR spectra and in situ DRIFTs with NH3probe showed an interaction between CsOxand AlOxsites via oxygen species formed on Cs1Mg3Al *** improved mobility of oxygen species inferred from O2-TPD was consistent with high NOxstorage capacity related to enhanced formation of nitrate and additional nitrite species by ***,the addition of Mg might improve the stability of Cs1Mg3Al by stabilizing surface active oxygen species in cyclic experiments.

关键词： Passive NO x adsorber Low-temperature NO x storage Cesium Oxygen mobility

Orthogonal waveform design with fractional programming on the ambiguity suppression of SAR systems

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Science China(Information Sciences) 2024年第9期67卷 263-279页

作者： Yunkai DENG Yongwei ZHANG Zhimin ZHANG Wei WANG Heng ZHANG department of Space Microwave Remote Sensing system Aerospace Information Research InstituteChinese Academy of Sciences

Waveform diversity(WD) represents a dynamic and transformative technology widely used in radar systems to enhance sensitivity and discrimination capabilities. Recently, WD techniques have been extensively explored for their potential ambiguity suppression within synthetic aperture radar(SAR) *** these, the alternate transmitting mode combined with orthogonal waveforms emerges as a particularly promising solution. This study focuses on optimizing the power spectrum density(PSD) of signals to design and generate an orthogonal waveform pair that achieves both a low cross-correlation-to-autocorrelation ratio(CAR) and satisfactory imaging performance. Initially, we construct a fractional programming model with convex constraints to minimize the CAR. To address this challenge, we introduce an iterative optimization procedure for the PSD variable, which sequentially reduces the CAR. Each optimization step can be efficiently solved using a quadratically constrained quadratic program, ensuring that the resulting computational complexity remains low. Building on the optimized PSD, we established a parametric piecewise linear model to generate an orthogonal waveform pair. This model not only maintains a low CAR but achieves satisfactory imaging performance in real-time applications. Consequently, this orthogonal waveform pair effectively suppresses range ambiguity in SAR systems. Finally, we demonstrated the practicability and effectiveness of the proposed orthogonal waveforms through detailed simulation experiments, specifically targeting ambiguity suppression in conventional quad-polarization SAR systems.

关键词： synthetic aperture radar (SAR) waveform diversity (WD) ambiguity suppression orthogonal waveform fractional programming power spectrum density (PSD)

Developing a Model for Parkinson’s Disease Detection Using Machine Learning Algorithms

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Computers, Materials & Continua 2024年第6期79卷 4945-4962页

作者： Naif Al Mudawi department of Computer Science College of Computer Science and Information SystemNajran UniversityNajran55461Saudi Arabia

Parkinson’s disease(PD)is a chronic neurological condition that progresses over *** start to have trouble speaking,writing,walking,or performing other basic skills as dopamine-generating neurons in some brain regions are injured or *** patient’s symptoms become more severe due to the worsening of their signs over *** this study,we applied state-of-the-art machine learning algorithms to diagnose Parkinson’s disease and identify related risk *** research worked on the publicly available dataset on PD,and the dataset consists of a set of significant characteristics of *** aim to apply soft computing techniques and provide an effective solution for medical professionals to diagnose PD *** research methodology involves developing a model using a machine learning *** the model selection,eight different machine learning techniques were adopted:Namely,Random Forest(RF),Decision Tree(DT),Support Vector Machine(SVM),Naïve Bayes(NB),Light Gradient Boosting Machine(LightGBM),K-Nearest Neighbours(KNN),Extreme Gradient Boosting(XGBoost),and Logistic Regression(LR).Subsequently,the concentrated models were validated through 10-fold Cross-Validation and Receiver Operating Characteristic(ROC)—Area Under the Curve(AUC).In addition,GridSearchCV was utilised to measure each algorithm’s best parameter;eventually,the models were trained through the hyperparameter tuning *** 98%accuracy,LightGBM had the highest accuracy in this ***,KNN,and SVM came in second with 96%***,the performance scores of NB and LR were recorded to be 76%and 83%,*** is to be mentioned that after applying 10-fold cross-validation,the average performance score of LightGBM accounted for 93%.At the same time,the percentage of ROC-AUC appeared at 0.92,which indicates that this LightGBM model reached a satisfactory ***,we extracted meaningful insights and figured out potential gaps on top of *** extracting meaningful in

关键词： Light GBM cross-validation ROC-AUC Parkinson’s disease(PD) SVM and XGBoost

Refractory autoimmune hemolytic anemia in a patient with systemic lupus erythematosus and ulcerative colitis:A case report

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World Journal of Clinical Cases 2024年第13期12卷 2286-2292页

作者： Dai-Xing Chen Yue Wu Sui-Feng Zhang Xiao-Jun Yang department of Digestive system Chongqing Traditional Chinese Medicine HospitalChongqing 400021China

BACKGROUND Ulcerative colitis(UC)and systemic lupus erythematosus(SLE)are both systemic immunoreactive diseases,and their pathogenesis depends on the interaction between genes and environmental *** are no reports of UC with SLE in China,but six cases of SLE with UC have been reported in *** combination of these two diseases has distinct effects on the pathogenesis of both *** SUMMARY A female patient(30 years old)came to our hospital due to dull umbilical pain,diarrhea and mucous bloody stool in August 2018 and was diagnosed with *** symptoms were relieved after oral administration of mesalazine(1 g po tid)or folic acid(5 mg po qd),and the patient were fed a control *** June 24,2019,the patient was admitted for treatment due to anemia and *** hospitalization,the patient had repeated low-grade fever and a progressively decreased Hb *** tests revealed positive antinuclear antibody test,positive anti-dsDNA antibody,0.24 g/L C3(0.9-1.8 g/L),0.04 g/L C4(0.1-0.4 g/L),32.37 g/L immunoglobulin(8-17 g/L),and 31568.1 mg/24 h total 24-h urine protein(0-150 mg/24 h).The patient was diagnosed with SLE involving the joints,kidneys and blood *** reported cases of SLE were retrieved from PubMed to characterize clinicopathological features and identify prognostic factors for *** The patient was discharged in remission after a series of treatments,such as intravenous methylprednisolone sodium succinate,intravenous human immunoglobulin,cyclophosphamide injection,and plasma *** discharge,the patient took oral prednisone acetate tablets,cyclosporine capsules,hydroxychloroquine sulfate tablets and other treatments for symptoms and was followed up regularly for 1 month,after which the patient's condition continued to improve and stabilize.

关键词： Plasma exchange Autoimmune hemolytic anemia systemic lupus erythematosus Ulcerative colitis Case report

Integrated optical frequency transfer and optical physical layer key distribution with enhanced link reciprocity detection

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Science China(Information Sciences) 2024年第7期67卷 335-336页

作者： Kunfeng XIE Liang HU Jianping CHEN Guiling WU State Key Laboratory of Advanced Optical Communication system and Networks Department of Electronic EngineeringShanghai Jiao Tong University

Optical fiber transmission has been widely used in communications and metrology, wherein optical frequency transfer (OFT) and optical physical layer secure key distribution (OKD) have become research hotspots [1, 2]. Moreover,OFT can perform a comparison between state-of-the-art optical atomic clocks and implement coherent optical phase transfer over long distances to support geodesy [1, 3].

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Is it necessary to stop glucagon-like peptide-1 receptor agonists prior to endoscopic procedure? A retrospective study

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World Journal of Gastroenterology 2024年第26期30卷 3221-3228页

作者： Haider Ghazanfar Nismat Javed Abeer Qasim Franklin Sosa Faryal Altaf Shazia Khan Jaydeep Mahasamudram Abhilasha Jyala Sameer Datta Kandhi Dongmin Shin Nikhitha Mantri Haozhe Sun Siddarth Hanumanthu Harish Patel Jasbir Makker Bhavna Balar Anil Dev Sridhar Chilimuri Division of Gastroenterology Department of Internal MedicineBronxCare Health SystemIcahn School of Medicine at Mount SinaiBronxNY 10457United States department of Internal Medicine BronxCare Health SystemIcahn School of Medicine at Mount SinaiBronxNY 10457United States

BACKGROUND Glucagon-like peptide-1 receptor agonists(GLP-1 RA)are effective in diabetes and obesity,reducing hyperglycemia by increasing insulin release and delaying gastric ***,they can cause gastroparesis,raising concerns about aspiration during *** guidelines advise discontinuing GLP-1 RA before surgery to reduce the risk of pulmonary *** To evaluate the effect of GLP-1 RAs on gastric residual contents during endosco-pic *** A retrospective chart review at BronxCare Health system,New York,from January 2019 to October 2023,assessed gastric residue and aspiration in GLP-1 RA patients undergoing endoscopic *** groups were compared based on dietary status before the *** included demographics,symptoms of gastroparesis,opiate use,hemoglobin A1c,GLP-1 agonist indication,endo-scopic details,and aspiration *** SPSS was used for analysis,cal-culating means,standard deviations,and applying Pearson’s chi-square and t-tests for associations,with P<0.05 as being *** During the study,306 patients were included,with 41.2%on a clear liquid/low residue diet and 58.8%on a regular diet before *** patients(63.1%)were male,with a mean age of 60±12 *** majority(85.6%)were on GLP-1 RAs for diabetes,and 10.1%reported digestive symptoms before *** those on a clear liquid diet,1.5%had residual food at endoscopy compared to 10%on a regular diet,which was statistically significant(P=0.03).Out of 31 patients with digestive symptoms,13%had residual food,all from the regular diet group(P=0.130).No complications were reported during or after the *** The study reflects a significant rise in GLP-1 RA use for diabetes and obesity.A 24-hour liquid diet seems safe for endoscopic procedures without *** with upper gastrointestinal symptoms might have a higher residual food risk,though not statistically *** research is needed

关键词： Glucagon-like peptide-1 agonists Gastroparesis Endoscopic procedures Residual food Complications

Tuning Second Chern Number in a Four-Dimensional Topological Insulator by High-Frequency Time-Periodic Driving

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Chinese Physics Letters 2024年第4期41卷 77-89页

作者：刘峥嵘陈锐周斌 department of Physics Hubei UniversityWuhan 430062China Key Laboratory of Intelligent Sensing system and Security of Ministry of Education Hubei UniversityWuhan 430062China

Floquet engineering has attracted considerable attention as a promising approach for tuning topological phase *** investigate the effects of high-frequency time-periodic driving in a four-dimensional(4D)topological insulator,focusing on topological phase transitions at the off-resonant quasienergy *** 4D topological insulator hosts gapless three-dimensional boundary states,characterized by the second Chern number C_(2).We demonstrate that the second Chern number of 4D topological insulators can be modulated by tuning the amplitude of time-periodic *** includes transitions from a topological phase with C_(2)=±3 to another topological phase with C_(2)=±1,or to a topological phase with an even second Chern number C_(2)=±2,which is absent in the 4D static ***,the approximation theory in the high-frequency limit further confirms the numerical conclusions.

关键词： topological transitions Periodic

维普期刊数据库