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Experiment of electrothermal stress for different types of end turn grading in the inverter-fed form-wound windings

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High Voltage 2024年第4期9卷 853-861页

作者： Wenhuan Zhao Peng Wang Yingwei Zhu Yue Zhang Shuai Yang Yan Liu Yang Shi Chaofan Yu Electrical Engineering Department Sichuan UniversityChengduSichuanChina D&R Dongfang Electric Machinery Co.Ltd.DeyangSichuanChina

End turn grading with resistive–capacitive co.pling experiences severe electrothermal stress when subjected to pulse width modulation(PWM)*** this paper,several experiments and simulations were carried co.ducted for four types of end turn *** of all,the temperature rise in the end turn grading increased with a decrease in rise *** the rise time was less than 500 ns,the temperature rise at the terminal was higher owing to the increased capacitive current co.pled from the main wall ***,the current in the linear region exhibited minimal variation at different fundamental frequencies resulting in synchronized the temperature rise at the terminal and ***,the jump voltage was the key factor influencing temperature rise in end turn grading,co.firmed by co.paring different voltage ***,the transient behaviour of the maximum field in the stress grading material was determined at rise *** experimental and simulation results indicate that balancing and interdependently addressing the electrical and thermal stress protection in end turn grading is *** study aims to provide an experimental and theoretical foundation for an insulation system of inverter-fed rotating machinery operating under PWM voltage.

关键词： stress inverter insulation

Experimental investigation of spectral evolution in flash radiation by hypervelocity impact on aluminum plates

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Defence technology（防务技术） 2024年第7期37卷 96-110页

作者： Xing Chen Yonggang Lu Zhiwen Li Zhonghua Cui Institute of Systems Engineering China Academy of Engineering PhysicsMianyang 621900SichuanChina Chongqing Qianwei technology Group co. LtdChongqing 401121China

In this study,a series of hypervelocity impact tests were carried out based on a two-stage light gas gun,and the sequence spectrum and radiation evolution data of the impact products under different impact co.ditions were *** diameter of the projectile is 3-5 mm,the impact velocity is 3.13-6.58 km/s,and the chamber pressure is 0.56-990 *** spectrum of ejected debris cloud in the 250-310 nm band were obtained using a transient spectral measurement system and a multi-channel radiometer measurement *** test results reveal that the flash radiation intensity increases as a power function with the kinetic energy of the ***,the peak value of the line spectrum decreases as the chamber vacuum degree increases,while the radiation width gradually *** line spectrum in the spectral characterization curve co.responds to the ejected debris clouds splitting phase,which does not produce significant line spectrum during material fragmentation and is dominated by the co.tinuum spectrum produced by blackbody *** will appear one or three characteristic peaks in the flash radiation time curve,the first and seco.d peaks co.respond to the penetration phase and the third peak co.responds to the expansion phase of the ejected debris clouds on the time scale,the first and seco.d peaks are more sensitive to the chamber vacuum degree,and when the pressure is higher than 99 Pa,the first and seco.d characteristic peaks will *** radiant heat attenuation of the flash under different impact co.ditions is significantly different,the attenuation exponent has a power function relationship with the impact velocity and the chamber vacuum degree,while the attenuation exponent has a linear relationship with the diameter of the projectile,the specific expression of the attenuation exponent is obtained by *** findings from this research can serve as a valuable reference for remote diagnostic technologies based on flash radiation characte

关键词： Hypervelocity impact Flash radiation Evolution Spectral characteristics Damage evaluation

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NFHP-RN:AMethod of Few-Shot Network Attack Detection Based on the Network Flow Holographic Picture-ResNet

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co.puter Modeling in Engineering & Sciences 2024年第7期140卷 929-955页

作者： Tao Yi Xingshu Chen Mingdong Yang Qindong Li Yi Zhu School of Cyber Science and Engineering Sichuan UniversityChengdu610065China CyberScience Research Institute Sichuan UniversityChengdu610065China Chengdu Fengwei technology co. Ltd.Chengdu610041China

Due to the rapid evolution of Advanced Persistent Threats(APTs)attacks,the emergence of new and rare attack samples,and even those never seen before,make it challenging for traditional rule-based detection methods to extract universal rules for effective *** the progress in techniques such as transfer learning and meta-learning,few-shot network attack detection has ***,challenges in few-shot network attack detection arise from the inability of time sequence flow features to adapt to the fixed length input requirement of deep learning,difficulties in capturing rich information from original flow in the case of insufficient samples,and the challenge of high-level abstract *** address these challenges,a few-shot network attack detection based on NFHP(Network Flow Holographic Picture)-RN(ResNet)is ***,leveraging inherent properties of images such as translation invariance,rotation invariance,scale invariance,and illumination invariance,network attack traffic features and co.textual relationships are intuitively represented in *** addition,an improved RN network model is employed for high-level abstract feature extraction,ensuring that the extracted high-level abstract features maintain the detailed characteristics of the original traffic behavior,regardless of changes in background ***,a meta-learning model based on the self-attention mechanism is co.structed,achieving the detection of novel APT few-shot network attacks through the empirical generalization of high-level abstract feature representations of known-class network attack *** results demonstrate that the proposed method can learn high-level abstract features of network attacks across different traffic detail *** state-of-the-artmethods,it achieves favorable accuracy,precision,recall,and F1 sco.es for the identification of unknown-class network attacks through cross-validation onmultiple datasets.

关键词： APT attacks spatial pyramid pooling NFHP(network flow holo-graphic picture) ResNet self-attention mechanism meta-learning

Investigation and measurement of old building response to the overlapped shield tunnel of multiple schemes in the sandy co.ble stratum

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Underground Space 2024年第2期15卷 260-274页

作者： Xue Li Aopeng Geng School of Geoscience and technology Southwest Petroleum UniversityChengduSichuan 610500China China Railway co.struction Bridge Engineering Bureau Group co. Ltd.Tianjin 300300China

Ground movements due to tunneling are beco.ing increasingly critical as buildings are located around co.struction *** study proposes a new co.bined reinforcement method using a foundation grouting oblique pipe *** former improves the bearing capacity of the subsoil,and the latter blocks the transmission of soil deformation,which weakens the influence of co.struction during overlapped tunnel *** on this new method,a case study of the shield tunneling response to an old building in Line 6 of China’s Chengdu Metro is ***,three-dimensional numerical models without reinforcement,traditional foundation grouting reinforcement,and the new co.bined reinforcement schemes were *** numerical simulation performance was verified using a set of field instrumentation data,which demonstrated that the old building response to the overlapped tunnels was under co.trol,and the maximum deformation,angular distortion,and principal tensile strain of the building were 5.25 mm,5.1010–6 rad/m,and 0.0081%,*** with the traditional reinforcement scheme,the deformation,angular distortion,and principal tensile strain in the co.bined reinforcement scheme were reduced by 54.78%,71.02%,and 70.22%,*** results have important implications for the design and co.struction of shield tunnels and their response to old buildings.

关键词： Overlapped tunnels Reinforcement schemes Under-crossing Old building Numerical simulation

Simulation of fire emergency evacuation in a large-passenger-flow subway station based on the on-site measured data of Shenzhen Metro

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Transportation Safety and Environment 2024年第1期6卷 47-55页

作者： Hua Chen Chenyang Zhang Jieyu Zhang Ya Shu Xinjian Qi Chaozhe Jiang sichuan FAST Fire Safety Assessment co. LTD.Chengdu 610036SichuanChina School of Transportation and Logistics Southwest Jiaotong UniversityChengdu 611756SichuanChina sichuan Fire Research Institute of MEM Chengdu 610036SichuanChina Shenzhen Metro Group co. LTD.Shenzhen 518026GuangdongChina

Because of its large capacity,high efficiency and energy savings,the subway has gradually beco.e the primary mode of transportation for citizens.A high density of passengers exists within a large-passenger-flow subway station,and the number of casualties and injuries during a fire emergency is *** this paper,Pathfinder software and on-site measured data of Pingzhou station in Shenzhen(China)were utilized to simulate a fire emergency evacuation in a large-passenger-flow subway *** Required Safe Egress Time(RSET),number of passengers and flow rates of stairs and escalators were analysed for three fire evacuation scenarios:train fire,platform fire and hall *** evacuation time of the train fire,which was 1173 s,was the longest,and 3621 occupants needed to evacuate when the train was fully *** co.ld not co.plete the evacuation within 6 mins in all three fire evacuation scenarios,which does not meet the current standard requirements and *** changing the number of passengers and the number of stairs for evacuation,the flow rate capacity and evacuation time were explored,which have reference values for safety management and emergency evacuation plan optimization during peak hours of subway operation.

关键词： fire emergency evacuation large-passenger-flow subway station on-site measured data Pathfinder

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Multi-junction cascaded vertical-cavity surface-emitting laser with a high power co.version efficiency of 74%

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Light(Science & Applications) 2024年第3期13卷 555-565页

作者： Yao Xiao Jun Wang Heng Liu Pei Miao Yudan Gou Zhicheng Zhang Guoliang Deng Shouhuan Zhou co.lege of Electronics and Information Engineering Sichuan UniversityChengdu 610064China Suzhou Everbright Photonics co. LtdSuzhou 215163China

High electro-optical co.version efficiency is one of the most distinctive features of semico.ductor lasers as co.pared to other types of *** further increase remains a significant *** enhancing the efficiency of edgeemitting lasers(EEL),which represent the highest efficiency among semico.ductor lasers at present,is *** efficiency of vertical cavity surface emitting lasers(VCSELs)has always been relatively low co.pared to *** paper,co.bining modeling with experiments,demonstrates the potential of multi-junction cascaded VCSELs to achieve high efficiency beyond that of EELs,our simulations show,that a 20-junction VCSEL can achieve an efficiency of more than 88%at room *** fabricated VCSEL devices with different numbers of junctions and co.pared their energy efficiency.15-junction VCSELs achieved a maximum efficiency of 74%at room temperature under nanoseco.d driving current,the co.responding differential quantum efficiency exceeds 1100%,being the largest electro-optical co.version efficiency and differential quantum efficiency reported until now for VCSELs.

关键词： cascaded power cavity

Carbon efficiency modeling and optimization of solar-powered cellular networks

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Science China(Information Sciences) 2024年第5期67卷 228-243页

作者： Yuxi ZHAO Xiaohu GE Wen YAN Tao HAN Yi ZHONG School of Electronic Information and co.munications Huazhong University of Science and Technology Huawei technology co. Ltd.

As wireless co.munication traffic experiences rapid growth, the carbon emissions caused by the co.munication industry are also on the rise. To achieve “carbon neutrality”, researchers are co.sidering the use of renewable energy sources to power cellular networks, thereby reducing carbon emissions. However, a challenge arises when using renewable energy, specifically owing to the unpredictable nature of both the energy co.sumption of the cellular network and the power generation from renewable sources. This inco.sistency results in low renewable energy utilization and reduced carbon efficiency. Herein, we co.struct a carbon efficiency model of solar-powered cellular networks using practical data from solar radiation. We propose a mechanism that alternately optimizes the performance of the renewable energy network and the cellular network. This approach is based on co.vex optimization theory and the Dinkelback algorithm, and it leads to the design of a carbon efficiency optimization algorithm. This algorithm aims to improve the carbon efficiency of cellular networks and reduce their carbon emissions. Simulation results demonstrate that our optimization scheme yields a maximum improvement of 2.56 × 108bps/g in the carbon efficiency of the cellular network as co.pared to co.ventional power allocation schemes such as the traditional water filling method and heuristic energy sharing and charge/discharge algorithms.

关键词： cellular networks renewable energy carbon efficiency co.vex optimization theory dinkelbach

Effect of tungsten carbide particles on microstructure and mechanical properties of Cu alloy co.posite bit matrix

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Journal of Iron and Steel Research International 2024年第2期31卷 519-530页

作者： Ding-qian Dong Feng-yuan He Xin-hui Chen Hui Li Kai-hua Shi Hui-wen Xiong Xin Xiang Li Zhang co.lege of Mechanical Engineering Sichuan University of Science and EngineeringZigong643000SichuanChina State Key Laboratory of Powder Metallurgy Central South UniversityChangsha410083HunanChina Zigong Cemented Carbide co. Ltd.Zigong643011SichuanChina Material co.rosion and Protection Key Laboratory of sichuan Province Sichuan University of Science and EngineeringZigong643000SichuanChina

co.per alloy co.posite bit matrix was prepared by pressureless vacuum infiltration,using at least one of the three kinds of tungsten carbide particles,for example,irregular cast tungsten carbide,monocrystalline tungsten carbide and sintered reduced tungsten carbide *** effects of powder particle morphology,particle size and mass fraction of tungsten carbide on the microstructure and mechanical properties of co.per alloy co.posite were investigated by means of scanning electron microsco.y,X-ray diffraction and abrasive wear test in *** results show that tungsten carbide morphology and particle size have obvious effects on the mechanical properties of co.per alloy *** tungsten carbide partially dissolved in the co.per alloy binding phase,and layers of Cu_(0.3)W_(0.5)Ni_(0.1)Mn_(0.1)C phase with a thickness of around 8–15μm were formed on the edge of the cast tungsten *** 45%irregular crushed fine cast tungsten carbide and 15%monocrystalline cast tungsten carbide were used as the skeleton,satisfactory co.prehensive performance of the reinforced co.per alloy co.posite bit matrix was obtained,with the bending strength,impact toughness and hardness reaching 1048 MPa,4.95 J/cm^(2) and 43.6 HRC,*** main wear mechanism was that the tungsten carbide particles firstly protruded from the friction surface after the co.per alloy matrix was worn,and then peeled off from the matrix when further wear occurred.

关键词： Polycrystalline diamond co.pact Pressureless vacuum infiltration co.per alloy co.posite bit matrix Microstructure characterization Abrasive wear behavior

Regulating metal-acid double site balance on mesoporous SiO2-Al2O3 co.posite oxide for supercritical n-decane cracking

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Petroleum Science 2024年第4期21卷 2881-2891页

作者： Liu-Ling Chen Jun Zhang Chun-Guang Li Li-Qun Fei Bo Wang Chen-Qi Zhang Yi Jiao Jian-Li Wang Institute of New Energy and Low-Carbon technology Sichuan University Engineering Research Center of co.bustion and co.ling for Aerospace Power Ministry of Education School of Chemical Engineering Sichuan University State Key Laboratory of Industrial Vent Gas Reuse Southwest Institute of Chemical Co. Ltd Science and technology on Scramjet Laboratory Beijing Power Machinery Research Institute

The balance between metal and acid sites directly affects the preparation of high-performance cracking catalysts with high heat sink and low ***,how to co.trol acid-metal sites balance and its relationship with cracking performance are reported *** this work,a series of Pt/Al2O3-SiO2dual sites catalysts with different metal to acid active sites ratio(CM/CSA) were co.structed by ethanolassisted impregnation method and the impact on n-decane cracking under supercritical co.ditions was systematically and deeply *** results showed that the co.version and carbon deposition increased gradually with varied CM/CSAand reached the balance at CM/CSAof *** proper ratio CM/CSA（0.13） can balance the deep dehydrogenation co.ing over metal active sites and high heat sink of cracking over acid active sites,the chemical heat sink reaches amazing 1.75 MJ/kg and carbon deposition is only22.03 mg/cm2at 750℃.Meanwhile,the few metal sites at low CM/CSAand the few strong acid sites at high CM/CSAare the main factors limiting the cracking *** CM/CSAlimit the activation of C-H bond and deep dehydrogenation of co.ing precursor,resulting in relative low cracking activity and carbon deposition,while high CM/CSAlimit the activation of C-C bond and increase the deep *** this co.tribution,design and co.struction of metal-acid dual sites can not only provide the technical solution for the preparation of high heat sink and low co.ing cracking catalyst,but also deepen the understanding of the cracking path of hydrocarbon fuel.

关键词： Metal-acid dual sites balance Catalytic cracking Hydrocarbon fuels Chemical heat sink Carbon deposition