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Numerical Study on Reduction in Aerodynamic Drag and Noise of High-Speed Pantograph

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Computer Modeling in Engineering & Sciences 2024年第5期139卷 2155-2173页

作者： Deng Qin xing du Tian li Jiye Zhang State Key Laboratory of Rail Transit Vehicle System Southwest Jiaotong UniversityChengdu610031China School of Electrical Engineering Southwest Jiaotong UniversityChengdu610031China

Reducing the aerodynamic drag and noise levels of high-speed pantographs is important for promoting environmentally friendly,energy efficient and rapid advances in train technology.Using computational fluid dynamics theory and the K-FWH acoustic equation,a numerical simulation is conducted to investigate the aerodynamic characteristics of high-speed pantographs.A component optimization method is proposed as a possible solution to the problemof aerodynamic drag and noise in high-speed pantographs.The results of the study indicate that the panhead,base and insulator are the main contributors to aerodynamic drag and noise in high-speed pantographs.Therefore,a gradual optimization process is implemented to improve the most significant components that cause aerodynamic drag and noise.By optimizing the cross-sectional shape of the strips and insulators,the drag and noise caused by airflow separation and vortex shedding can be reduced.The aerodynamic drag of insulator with circular cross section and strips with rectangular cross section is the largest.Ellipsifying insulators and optimizing the chamfer angle and height of the windward surface of the strips can improve the aerodynamic performance of the pantograph.In addition,the streamlined fairing attached to the base can eliminate the complex flow and shield the radiated noise.In contrast to the original pantograph design,the improved pantograph shows a 21.1%reduction in aerodynamic drag and a 1.65 dBA reduction in aerodynamic noise.

关键词： High-speed pantograph aerodynamic drag aerodynamic noise reduction optimizing

Double-ring high-frequency common-mode switching oscillation current sensor for inverter-fed machine winding insulation monitoring

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Global Energy Interconnection 2024年第1期7卷 106-116页

作者： lingqing Pan Xizhou du xing Lei Ting Ye Dawei Xiang Hao li College of Electrical Power Engineering Shanghai University of Electric PowerShanghai 200090P.R.China State Grid Shanghai Municipal Electric Power Company Shanghai 200122P.R.China College of Electronics and Information Engineering Tongji UniversityShanghai 201804P.R.China

Insulation failure significantly contributes to the unpredictable shutdown of power equipment.Compared to the partial discharge and high-frequency(HF)injection methods,the HF common-mode(CM)leakage current method offers a non-intrusive and highly sensitive alternative.However,the detection of HF CM currents is susceptible to interference from differential-mode(DM)currents,which exhibit high-amplitude and multifrequency components during normal operation.To address this challenge,this paper proposes a double-ring current sensor based on the principle of magnetic shielding for inverter-fed machine winding insulation monitoring.The inner ring harnesses the magnetic aggregation effect to isolate the DM current magnetic field,whereas the outer ring serves as the magnetic core of the Rogowski current sensor,enabling HF CM current monitoring.First,the magnetic field distributions of the CM and DM currents were analyzed.Then,a correlation between the sensor parameters and signal-to-noise ratio of the target HF CM current was established.Finally,an experimental study was conducted on a 3-kW PMSM for verification.The results indicate that the proposed double-ring HF CM sensor can effectively mitigate DM current interference.Compared to a single-ring sensor,a reduction of approximately 40%in the DM component was achieved,which significantly enhanced the precision of online insulation monitoring.

关键词： Magnetic shielding Double-ring Common-mode current Maxwell simulation

Sparse Modal Decomposition Method Addressing Underdetermined Vortex-Induced Vibration Reconstruction Problem for Marine Risers

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China Ocean Engineering 2024年第2期38卷 285-296页

作者： du Zun-feng ZHU Hai-ming YU Jian-xing State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation School of Civil EngineeringTianjin UniversityTianjin 300350China

When investigating the vortex-induced vibration(VIV)of marine risers,extrapolating the dynamic response on the entire length based on limited sensor measurements is a crucial step in both laboratory experiments and fatigue monitoring of real risers.The problem is conventionally solved using the modal decomposition method,based on the principle that the response can be approximated by a weighted sum of limited vibration modes.However,the method is not valid when the problem is underdetermined,i.e.,the number of unknown mode weights is more than the number of known measurements.This study proposed a sparse modal decomposition method based on the compressed sensing theory and the Compressive Sampling Matching Pursuit(Co Sa MP)algorithm,exploiting the sparsity of VIV in the modal space.In the validation study based on high-order VIV experiment data,the proposed method successfully reconstructed the response using only seven acceleration measurements when the conventional methods failed.A primary advantage of the proposed method is that it offers a completely data-driven approach for the underdetermined VIV reconstruction problem,which is more favorable than existing model-dependent solutions for many practical applications such as riser structural health monitoring.

关键词： motion reconstruction vortex-induced vibration(VIV) marine riser modal decomposition method compressed sensing

Early diagnosis and management of neonatal sepsis:a perspective

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World Journal of Pediatrics 2024年第4期20卷 303-306页

作者： li‑Zhong du Neonatal Intensive Care Unit Children’s Hospital Zhejiang University School of MedicineNational Clinical Research Center for Child Health3333 Binsheng RoadHangzhou 310052China

Neonatal sepsis is an illness caused by bloodstream bacteria or fungal infections that affect newborn infants under 28 days of age.It stands as a significant contributor to morbidity and mortality in neonatal intensive care units(NICUs).With the improved survival rates of very low-birth-weight or extremely premature infants,a growing number of these vulnerable infants are receiving intensive care and undergoing invasive procedures,making nosocomial infections a persistent challenge in NICUs.The mortality rate associated with neonatal sepsis varies depending on factors such as birth weight,gestational age,and other co-morbidities.It can also lead to a range of long-term health consequences,including neurodevelopmental disabilities like cerebral palsy,visual or hearing impairments,and cognitive problems.Furthermore,neonatal sepsis is linked to various adverse outcomes,including respiratory complications,bronchopulmonary dysplasia,nutritional and growth issues,and immunological dysfunction[1].due to its atypical clinical presentation and the low rate of specific diagnostic indicators,such as a positive blood culture,accurately diagnosing neonatal sepsis is challenging.Consequently,the appropriateness of antibiotic treatment is often a matter of controversy.

关键词： neonatal mortality diagnosis

Review on regulation of MnS in non-qquenched and tempered steel

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Journal of Iron and Steel Research(International) 2024年第4期31卷 779-789页

作者： Guo-xing Qiu Qing du Feng Lu De-jun Miao Yong-kun Yang Xiao-ming li School of Metallurgical Engineering Xi'an University of Architecture and TechnologyXi'an 710055ShaanxiChina Laigang Technique Center Shandong Iron and Steel Group Co.Ltd.Jinan 271104ShandongChina

An overview of the current research status and control methods of MnS in non-quenched and tempered steel was provided.As a low-melting plastic inclusion,the morphology and distribution of MnS were influenced by various production processes.Therefore,control of MnS is a systematic problem that must be integrated into the entire production process.Based on the production process,the factors affecting the morphology and distribution of MnS in steel were introduced.The effects of oxygen activity,manganese,sulfur,and some alloys on MnS inclusion precipitation were summarized,mainly including MnS modification treatment and oxygen-sulfide composite precipitation control.It is believed that MnS precipitates during the solidification process of steel,and controlling the solidification cooling rate could effectively regulate the size and morphology of MnS,avoiding the precipitation of II-MnS.Additionally,by changing the deformation rate,deformation amount,deformation temperature during the hot deformation process,and heating time and temperature during heat treatment,the distribution and morphology of MnS could be improved.Through the fine control of the above process parameters,the number of II-MnS in steel could be effectively reduced,and their morphology could be improved,thereby enhancing the performance of non-quenched and tempered steel and promoting its wider application.Furthermore,applying laboratory research results to industrial production is an important direction for future research efforts in this field.

关键词： MnS Non-quenched and tempered steel Control technology Process parameter Morphology Distribution

Cambricon-QR:a sparse and bitwise reproducible quantized training accelerator

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High Technology Letters 2024年第1期30卷 52-60页

作者：李楠 ZHAO Yongwei ZHI Tian liU Chang du Zidong HU xing li Wei ZHANG Xishan li ling SUN Guangzhong School of Computer Science and Technology University of Science and Technology of ChinaHefei 230026P.R.China State Key Laboratory of Processors Institute of Computing TechnologyChinese Academy of SciencesBeijing 100086P.R.China Cambricon Tech.Ltd Beijing 100191P.R.China Institute of Software Chinese Academy of SciencesBeijing 100086P.R.China

Quantized training has been proven to be a prominent method to achieve deep neural network training under limited computational resources.It uses low bit-width arithmetics with a proper scaling factor to achieve negligible accuracy loss.Cambricon-Q is the ASIC design proposed to efficiently support quantized training,and achieves significant performance improvement.However,there are still two caveats in the design.First,Cambricon-Q with different hardware specifications may lead to different numerical errors,resulting in non-reproducible behaviors which may become a major concern in critical applications.Second,Cambricon-Q cannot leverage data sparsity,where considerable cycles could still be squeezed out.To address the caveats,the acceleration core of Cambricon-Q is redesigned to support fine-grained irregular data processing.The new design not only enables acceleration on sparse data,but also enables performing local dynamic quantization by contiguous value ranges(which is hardware independent),instead of contiguous addresses(which is dependent on hardware factors).Experimental results show that the accuracy loss of the method still keeps negligible,and the accelerator achieves 1.61×performance improvement over Cambricon-Q,with about 10%energy increase.

关键词： quantized training sparse accelerator Cambricon-QR

Style-conditioned music generation with Transformer-GANs

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Frontiers of Information Technology & Electronic Engineering 2024年第1期25卷 106-120页

作者： Weining WANG Jiahui li Yifan li Xiaofen xing School of Electronic and Information Engineering South China University of TechnologyGuangzhou 510600China

Recently,various algorithms have been developed for generating appealing music.However,the style control in the generation process has been somewhat overlooked.Music style refers to the representative and unique appearance presented by a musical work,and it is one of the most salient qualities of music.In this paper,we propose an innovative music generation algorithm capable of creating a complete musical composition from scratch based on a specified target style.A style-conditioned linear Transformer and a style-conditioned patch discriminator are introduced in the model.The style-conditioned linear Transformer models musical instrument digital interface(MIDI)event sequences and emphasizes the role of style information.Simultaneously,the style-conditioned patch discriminator applies an adversarial learning mechanism with two innovative loss functions to enhance the modeling of music sequences.Moreover,we establish a discriminative metric for the first time,enabling the evaluation of the generated music’s consistency concerning music styles.Both objective and subjective evaluations of our experimental results indicate that our method’s performance with regard to music production is better than the performances encountered in the case of music production with the use of state-of-the-art methods in available public datasets.

关键词： Music generation Style-conditioned Transformer Music emotion

Sequential Propagation of Chaos for Mean-Field BSDE Systems

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Chinese Annals of Mathematics,Series B 2024年第1期45卷 11-40页

作者： Xiaochen li Kai du Shanghai Center for Mathematical Sciences Fudan UniversityShanghai 200433China. Shanghai Artificial Intelligence Laboratory 701 Yunjin RoadShanghai 200433China

A new class of backward particle systems with sequential interaction is proposed to approximate the mean-field backward stochastic differential equations.It is proven that the weighted empirical measure of this particle system converges to the law of the McKean-Vlasov system as the number of particles grows.Based on the Wasserstein met-ric,quantitative propagation of chaos results are obtained for both linear and quadratic growth conditions.Finally,numerical experiments are conducted to validate our theoretical results.

关键词： Backward propagation of chaos Particle system Sequential interaction McKean-Vlasov BSDE Convergence rate

Theoretical and experimental cocrystal screening of temozolomide with a series of phenolic acids, promising cocrystal coformers

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Chinese Chemical Letters 2024年第5期35卷 407-417页

作者： Hongmei Yu Baoxi Zhang Meiju liu Cheng xing Guorong He li Zhang Ningbo Gong Yang Lu Guanhua du Beijing Key Laboratory of Polymorphic Drugs Institute of Materia MedicaChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100050China Beijing City Key Laboratory of Drug Target Identification and Drug Screening Institute of Materia MedicaChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100050China

The virtual cocrystal screening approach based on molecular electrostatic potential surface(MEPS)maps is a fast and feasible computational method to estimate the probability of cocrystal formation by calculating the difference in the interaction site pairing energies of monomers and that of their assemblies prior to experimental screening.In this paper,we report 12 cocrystal forms of temozolomide with mono-,di-,and trihydroxy benzoic acids,namely,3-hydroxy-,2,4-dihydroxy-,2,5-dihydroxy-,2,6-dihydroxy-,3,4-dihydroxy-,and 3,4,5-trihydroxy-benzoic acids,as well as benzoic acid,as pharmaceutical coformers for the first time.10 single crystals out of the 12 cocrystal forms were obtained and unequivocally determined by single-crystal X-ray diffraction,which clarified spatial arrangements,molecular conformations,and supramolecular synthons.MEPS further gains some insights into the sites of hydrogen bonding interactions for exploring combination patterns in these assemblies.Modulated stability of TMZ was successfully achieved by cocrystallization with these acids.

关键词： Virtual Cocrystal Temozolomide Supramolecular synthon Phenolic acid Stability