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Influence of pantograph fixing position on aerodynamic characteristics of high-speed trains 被引量:8
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作者 Liang Zhang Jiye Zhang +1 位作者 Tian Li Weihua Zhang 《Journal of Modern Transportation》 2017年第1期34-39,共6页
To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of com- pu... To study the influence of the pantograph fixing position on aerodynamic characteristics of high-speed trains, the aerodynamic models of high-speed trains with eight cars were established based on the theory of com- putational fluid dynamics, and eight cases with pantographs fixed on different positions and in different operational orientations were considered. The pantographs were fixed on the front or the rear end of the first middle car or fixed on the front or the rear end of the last middle car. The external flow fields of the high-speed trains were numeri- cally simulated using the software STAR-CCM+. The results show that the pantograph fixing position has little effect on the aerodynamic drag force of the head car and has a large effect on the aerodynamic drag force of the tail car. The influences of the pantograph fixing position on the aerodynamic lift forces of the head car, tail car and pan- tographs are obvious. Among the eight cases, considering the total aerodynamic drag force of the train and the aerodynamic lift force of the lifted pantograph, when the pantographs are fixed on the rear end of the last middle car and the lifted pantograph is in the knuckle-upstream ori- entation, the aerodynamic performance of the high-speed train is the best. 展开更多
关键词 High-speed train PANTOGRAPH Fixing position Aerodynamic characteristics Computational fluid dynamics
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Detecting the Position of the Moving-iron Solenoid by Non-displacement Sensor Based on Parameter Identification of Flux Linkage Characteristics
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作者 WANG Xuping QUAN Long XIONG Guangyu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2013年第6期1204-1211,共8页
Currently, most researches use signals, such as the coil current or voltage of solenoid, to identify parameters; typically, parameter identification method based on variation rate of coil current is applied for positi... Currently, most researches use signals, such as the coil current or voltage of solenoid, to identify parameters; typically, parameter identification method based on variation rate of coil current is applied for position estimation. The problem exists in these researches that the detected signals are prone to interference and difficult to obtain. This paper proposes a new method for detecting the core position by using flux characteristic quantity, which adds a new group of secondary winding to the coil of the ordinary switching electromagnet. On the basis of electromagnetic coupling theory analysis and simulation research of the magnetic field regarding the primary and secondary winding coils, and in accordance with the fact that under PWM control mode varying core position and operating current of windings produce different characteristic of flux increment of the secondary winding. The flux increment of the electromagnet winding can be obtained by conducting time domain integration for the induced voltage signal of the extracted secondary winding, and the core position from the two-dimensional fitting curve of the operating winding current and flux-linkage characteristic quantity of solenoid are calculated. The detecting and testing system of solenoid core position is developed based on the theoretical research. The testing results show that the flux characteristic quantity of switching electromagnet magnetic circuit is able to effectively show the core position and thus to accomplish the non-displacement transducer detection of the said core position of the switching electromagnet. This paper proposes a new method for detecting the core position by using flux characteristic quantity, which provides a new theory and method for switch solenoid to control the proportional valve. 展开更多
关键词 switch solenoid flux characteristic quantity position detection non-displacement sensor
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An Analysis of Theme Positioning of Tourism-oriented Characteristic Towns——A Case Study of Jiangwan Town,Jiangxi Province
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作者 Xiaotian LIU Qunhong LIU 《Asian Agricultural Research》 2019年第1期29-32,共4页
The tourism-oriented characteristic town is a main part of China's tourism development.Tourism-oriented characteristic towns take up the largest proportion in the characteristic towns and have the largest developm... The tourism-oriented characteristic town is a main part of China's tourism development.Tourism-oriented characteristic towns take up the largest proportion in the characteristic towns and have the largest development potential and value.Taking Jiangwan Town of Jiangxi Province as an example,this paper analyzed the factors influencing the development of tourism-oriented characteristic towns,including natural resources,regional conditions,market demands and perceived value.It refined and built the theme of Jiangwan Town: ecological history and culture tourism,a scenic spot of Fujian,Zhejiang and Anhui provinces,and experience-type farm culture and traditional ancient culture tourism. 展开更多
关键词 characteristic TOWNS THEME positioning REFINING
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Experimental and numerical simulation study of the effect for the anode positions on the discharge characteristics of 300W class low power Hall thrusters
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作者 陈新伟 高俊 +5 位作者 杨三祥 耿海 郭宁 顾左 杨俊泰 张宏 《Plasma Science and Technology》 SCIE EI CAS CSCD 2023年第1期100-110,共11页
Low-power Hall thruster(LHT) generally has poor discharge efficiency characteristics due to the large surface-to-volume ratio.Aiming to further refine and improve the performance of 300 W class LHT in terms of thrust ... Low-power Hall thruster(LHT) generally has poor discharge efficiency characteristics due to the large surface-to-volume ratio.Aiming to further refine and improve the performance of 300 W class LHT in terms of thrust and efficiency,and to obtain the most optimal operating point,the experimental study of the discharge characteristics for three different anode positions was conducted under the operation of various discharge voltages(100-400 V) and anode mass flow rates(0.65 mg·s-1and 0.95 mg·s-1).The experimental results indicated that the thruster has the most excellent performance in terms of thrust and efficiency etc at a channel length of 27 mm for identical operating conditions.In addition,particle in cell simulations,employed to reveal the underlying physical mechanisms,show that the ionization and acceleration zone is pushed downwards towards the channel exit as the anode moves towards the exit.At the identical operating point,when the channel length is reduced from 32 to 27 mm,the ionization and acceleration zone moves towards the exit,and the parameters such as thrust and efficiency increase due to the high ionization rate,ion number density,and axial electric field.When the channel length is further moved to 24 mm,the parameters in terms of thrust(F) and efficiency(ηa) are reduced as a result of the decreasing ionization efficiency(ηm) and the larger plume divergence angle(α).In this paper,the results indicated that an optimum anode position(ΔL=27 mm) exists for the optimum performance. 展开更多
关键词 low-power Hall thruster discharge characteristics PIC-MCC simulation anode positions
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CHARACTERISTICS OF LIP-MOUTH REGION IN SMILING POSITION FROM 80 PERSONS WITH ACCEPTABLE FACES AND INDIVIDUAL NORMAL OCCLUSIONS
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作者 张江恒 陈扬熙 周秀坤 《Chinese Medical Sciences Journal》 CAS CSCD 2002年第3期189-192,共4页
OBJECTIVE: The characteristics of lip-mouth region including the soft and hard tissues in smiling position with frontal fixed position photographic computer-aided analysis were studied. METHODS: The subjects were 80 p... OBJECTIVE: The characteristics of lip-mouth region including the soft and hard tissues in smiling position with frontal fixed position photographic computer-aided analysis were studied. METHODS: The subjects were 80 persons (40 male and 40 females, age range: 17 to approximately 25 years) with acceptable faces and individual normal occlusions. The subjects were asked to take maximum smiling position to accept photographic measurement with computer-aided analysis. RESULTS: The maximum smile line could be divided into 3 categories: low smile line (16.25%), average smile line (68.75%), and high smile line (15%). CONCLUSION: The method adopting maximum smiling position to study the lip-month region is reproducible and comparable. This study would be helpful to provide a quantitative reference for clinical investigation, diagnosis, treatment and efficacy appraisal. 展开更多
关键词 PERSON LIP smilingObjective. The characteristics of lip mouth region including the soft and hard tissues in smiling position with frontal fixed position photographic computer aided analysis were studied. Methods. The subjects were 80 person
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Relations Between Characteristic Function,Positive P-Representation and Coherent Thermal State 被引量:1
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作者 FAN Hong-Yi XU Xing-Lei Department of Material Science and Engineering,University of Science and Technology of China,Hefei 230026,China2 Department of Physics,Shanghai Jiao Tong University,Shanghai 200030,China3 Department of Physics,Heze University,Heze 274015,China 《Communications in Theoretical Physics》 SCIE CAS CSCD 2007年第7期67-70,共4页
We employ the coherent thermal states(a kind of entangled states)in thermal field dynamics to establisha complete entangled state formalism expressing pseudo-classical representations of density operator for light fie... We employ the coherent thermal states(a kind of entangled states)in thermal field dynamics to establisha complete entangled state formalism expressing pseudo-classical representations of density operator for light field.Especially,the relationship between the coherent thermal state and the characteristic function and the positive Prepresentation in quantum optics theory are obtained. 展开更多
关键词 coherent thermal state characteristic function positive P-representation
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Characteristic Innovation of City Square at Guangxi Minority Nationality Regions 被引量:1
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作者 黄维拥 《Journal of Landscape Research》 2011年第2期49-51,55,共4页
After description of the concept of urban feature with Nanning and Liuzhou City as example,the paper illustrated regional characteristics of Guangxi City and highlighted its cultural atmosphere of minority nationaliti... After description of the concept of urban feature with Nanning and Liuzhou City as example,the paper illustrated regional characteristics of Guangxi City and highlighted its cultural atmosphere of minority nationalities.It emphasized that only when regional urban feature was further enhanced could city development be promoted,and that only when urban feature was clearly identified could city square was characteristic.As for site selection of city square,it should follow principles of people-orientation,integrity,landscape,economy,ecology and geomancy.As for construction of city square,it should pay attention to integrate urban cultural feature based on relevant principles,and both inherit local historical culture and highlight local natural characteristic.In addition,folk artistic elements could be applied in city square,and folk artistic elements of nonmaterial culture could be integrated into the theme of city square.Material artistic elements could be also extracted and concluded as a kind of aesthetic art,reflected in concrete architectural forms.Characteristic innovation of city square should respect planning,start from city actuality,be based on self characteristics,consider citizens' willingness,and draw on local resources,so as to manifest regional cultural characteristic and promote city influence and competitiveness. 展开更多
关键词 characteristic INNOVATION CITY positioning Site selection of CITY square Regional culture FOLK ARTISTIC element
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Experimental study on aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds 被引量:18
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作者 HE Xu-hui ZUO Tai-hui +2 位作者 ZOU Yun-feng YAN Lei TANG Lin-bo 《Journal of Central South University》 SCIE EI CAS CSCD 2020年第8期2465-2478,共14页
In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measur... In this study, experiments were carried out to investigate aerodynamic characteristics of a high-speed train on viaducts in turbulent crosswinds using a 1:25 scaled sectional model wind-tunnel testing. Pressure measurements of two typical sections, one train-head section and one train-body section, at the windward and leeward tracks were conducted under the smooth and turbulence flows with wind attack angles between-6° and 6°, and the corresponding aerodynamic force coefficients were also calculated using the integral method. The experimental results indicate that the track position affects the mean aerodynamic characteristics of the vehicle, especially for the train-body section. The fluctuating pressure coefficients at the leeward track are more significantly affected by the bridge interference compared to those at the windward track. The effect of turbulence on the train-head section is less than that on the train-body section. Additionally, the mean aerodynamic force coefficients are almost negatively correlated to wind attack angles, which is more prominent for vehicles at the leeward track. Moreover, the lateral force plays a critical role in determining the corresponding overturning moment, especially on the train-body section. 展开更多
关键词 high-speed train viaducts aerodynamic characteristics turbulent crosswinds wind attack angle train section shape track position pressure measurement
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Changes in neurotransmitter levels,brain structural characteristics,and their correlation with PANSS scores in patients with firstepisode schizophrenia 被引量:1
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作者 Xian-Jia Xu Tang-Long Liu +1 位作者 Liang He Ben Pu 《World Journal of Clinical Cases》 SCIE 2023年第22期5215-5223,共9页
BACKGROUND In patients with schizophrenia,the brain structure and neurotransmitter levels change,which may be related to the occurrence and progression of this disease.AIM To explore the relationships between changes ... BACKGROUND In patients with schizophrenia,the brain structure and neurotransmitter levels change,which may be related to the occurrence and progression of this disease.AIM To explore the relationships between changes in neurotransmitters,brain structural characteristics,and the scores of the Positive and Negative Symptom Scale(PANSS)in patients with first-episode schizophrenia.METHODS The case group comprised 97 patients with schizophrenia,who were evaluated using the Canadian Neurological Scale and confirmed by laboratory tests at Ningbo Mental Hospital from January 2020 to July 2022.The control group comprised 100 healthy participants.For all participants,brain structural characteristics were explored by measuring brain dopamine(DA),glutamic acid(Glu),and gamma-aminobutyric acid(GABA)levels,with magnetic resonance imaging.The case group was divided into negative and positive symptom subgroups using PANSS scores for hierarchical analysis.Linear correlation analysis was used to analyze the correlations between neurotransmitters,brain structural character istics,and PANSS scores.RESULTS Patients in the case group had higher levels of DA and lower levels of Glu and GABA,greater vertical and horizontal distances between the corpus callosum and the inferior part of the fornix and larger ventricle area than patients in the control group(P<0.05).Patients with positive schizophrenia symptoms had significantly higher levels of DA,Glu,and GABA than those with negative symptoms(P<0.05).In patients with positive schizophrenia symptoms,PANSS score was significantly positively correlated with DA,vertical and horizontal distances between the corpus callosum and the infrafornix,and ventricular area,and was significantly negatively correlated with Glu and GABA(P<0.05).In patients with negative schizophrenia symptoms,PANSS score was significantly positively correlated with DA,vertical distance between the corpus callosum and the infrafornix,horizontal distance between the corpus callosum and the infrafornix,and ventricular area,and was significantly negatively correlated with Glu and GABA(P<0.05).CONCLUSION In patients with first-episode schizophrenia,DA levels increased,Glu and GABA levels decreased,the thickness of the corpus callosum increased,and these variables were correlated with PANSS scores. 展开更多
关键词 Brain structural characteristics Negative symptoms Neurotransmitters positive symptoms SCHIZOPHRENIA
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The effect of anode axial position on the performance of a miniaturized cylindrical Hall thruster with a cusp-type magnetic field
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作者 Yuanyuan GAO Weizong WANG +2 位作者 Yifei LI Shuwen XUE Guobiao CAI 《Plasma Science and Technology》 SCIE EI CAS CSCD 2022年第7期15-22,共8页
A 200 W cylindrical Hall thruster with a cusp-type magnetic field was proposed, manifesting convergent plume and high specific impulse. In this paper, a series of ring-shaped anodes are designed and the influence of a... A 200 W cylindrical Hall thruster with a cusp-type magnetic field was proposed, manifesting convergent plume and high specific impulse. In this paper, a series of ring-shaped anodes are designed and the influence of anode axial position on the performance of CHT with a cusp-type magnetic field is studied. The experimental results indicate that the thruster keeps stable operation at the condition of 140–270 W discharge power. When the anode moves axially towards the upstream cusp field, the thrust enhances from 6.5 mN to 7.6 mN and specific impulse enhances from 1658 s to 1939 s significantly. These improvements of thruster performance should be attributed to the enhancement of current utilization, propellant utilization and acceleration efficiency. According to the analyses on the discharge characteristics, it is revealed that as the anode moves upstream, the electron transport path could be extended, the magnetic field in this extended path could impede electron cross-field transport and facilitate the ionization intensity, yielding to the enhancement of current utilization and propellant utilization efficiency.Moreover, along with this enhancement of upstream ionization at the given anode flow rate, the main ionization region is thought to move upstream and then separate more apparently from the acceleration region, which has been demonstrated by the narrowing of ion energy distribution function shape. This change in acceleration region could decrease the ion energy loss and enhance acceleration efficiency. This work is beneficial for optimizing the electrode structure of thruster and recognize the ionization and acceleration process under the cusp magnetic field. 展开更多
关键词 PERFORMANCE ionization characteristics acceleration characteristics cylindrical Hall thruster anode axial position
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Optimization Method of Bearing Support Positions in a High-Speed Flexible Rotor System
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作者 TANG Changke JIANG Yanhong LIU Jing 《Journal of Donghua University(English Edition)》 EI CAS 2020年第6期504-511,共8页
Bearing support position is one of main factors affecting vibration characteristics of rotor systems. To optimize the bearing support positions in a high-speed flexible rotor system (HSFRS) based on the vibration char... Bearing support position is one of main factors affecting vibration characteristics of rotor systems. To optimize the bearing support positions in a high-speed flexible rotor system (HSFRS) based on the vibration characteristics, an optimization method of bearing support positions in the HSFRS is proposed. In this method, a finite element (FE) model of a high-speed flexible rotor (HSFR) was established. The natural frequencies and mode shapes of the HSFRS were used to obtain the initial design scheme of the bearing support positions. A frequency characteristic equation of the HSFRS was established to obtain the critical speeds of the HSFRS. And a dynamic model of the HSFRS was established to analyze the vibration characteristics for different bearing support position cases. The problem of optimizing bearing support positions in the HSFRS was solved by the developed method. The results showed that vibration amplitudes of the HSFRS were more stable when the bearing support positions were optimized. This study can provide a new method for optimizing bearing support positions of rotor systems. 展开更多
关键词 flexible rotor system optimal design vibration characteristic bearing support position
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Predictive value of positive lymph node ratio in patients with locally advanced gastric remnant cancer
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作者 Meng Zhuo Lei Tian +3 位作者 Ting Han Teng-Fei Liu Xiao-Lin Lin Xiu-Ying Xiao 《World Journal of Gastrointestinal Oncology》 SCIE 2024年第3期833-843,共11页
BACKGROUND Traditional lymph node stage(N stage)has limitations in advanced gastric remnant cancer(GRC)patients;therefore,establishing a new predictive stage is necessary.AIM To explore the predictive value of positiv... BACKGROUND Traditional lymph node stage(N stage)has limitations in advanced gastric remnant cancer(GRC)patients;therefore,establishing a new predictive stage is necessary.AIM To explore the predictive value of positive lymph node ratio(LNR)according to clinicopathological characteristics and prognosis of locally advanced GRC.METHODS Seventy-four patients who underwent radical gastrectomy and lymphadenectomy for locally advanced GRC were retrospectively reviewed.The relationship between LNR and clinicopathological characteristics was analyzed.The survival analysis was performed using Kaplan-Meier survival curves and Cox regression model.RESULTS Number of metastatic LNs,tumor diameter,depth of tumor invasion,Borrmann type,serum tumor biomarkers,and tumor-node-metastasis(TNM)stage were correlated with LNR stage and N stage.Univariate analysis revealed that the factors affecting survival included tumor diameter,anemia,serum tumor biomarkers,vascular or neural invasion,combined resection,LNR stage,N stage,and TNM stage(all P<0.05).The median survival time for those with LNR0,LNR1,LNR2 and LNR3 stage were 61,31,23 and 17 mo,respectively,and the differences were significant(P=0.000).Anemia,tumor biomarkers and LNR stage were independent prognostic factors for survival in multivariable analysis(all P<0.05).CONCLUSION The new LNR stage is uniquely based on number of metastatic LNs,with significant prognostic value for locally advanced GRC,and could better differentiate overall survival,compared with N stage. 展开更多
关键词 Gastric remnant cancer positive lymph node ratio Clinicopathological characteristics PROGNOSIS
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不同坡位对荒漠草原植物群落特征的影响
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作者 宁璐 要振宇 +7 位作者 高天明 穆文奎 达古拉 张增宝 刘心宇 赵天启 刘静 杨振奇 《东北林业大学学报》 CAS 北大核心 2025年第1期15-22,共8页
荒漠草原是草原生态系统重要的组成部分,也是草原区向荒漠区过渡地带,物种多样性和生产力较低,并且随着生态环境的恶化,荒漠草原荒漠化程度不断加剧,对植物的生长及群落分布产生重要影响。为了解不同坡位对荒漠草原植被群落结构特征的影... 荒漠草原是草原生态系统重要的组成部分,也是草原区向荒漠区过渡地带,物种多样性和生产力较低,并且随着生态环境的恶化,荒漠草原荒漠化程度不断加剧,对植物的生长及群落分布产生重要影响。为了解不同坡位对荒漠草原植被群落结构特征的影响,以希拉穆仁荒漠草原作为研究区,在无人为干扰活动的荒漠草原围封区内,选择坡度25°的3块长方形样地(300 m×100 m),分别在3块长方形样地的坡上、坡中、坡下分别设置1 m×1 m的样方,调查记录每个样方内植被的种名(科、属、种)、植被的高度、密度等,通过野外调查数据,分析不同坡位对荒漠草原植物群落区系特征和结构特征的影响。结果表明:野外调查共统计植物39种,隶属22科33属;生活型以多年生草本为主,总计34种,占物种总数的87.18%;水分生态类型以旱生植物为主,总计27种,占物种总数的69.23%;地理成分以东古北极分布种为主,总计17种,占物种总数的43.58%。受坡位的影响,植被盖度、建群种高度、群落生产力、Shannon-Wienner指数和Simpson指数由大到小的顺序均为坡下、坡中、坡上,Pielou指数由大到小的顺序为坡上、坡中、坡下。 展开更多
关键词 荒漠草原 坡位 植物群落区系 植物群落特征
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Effect of bristle pack position on the rotordynamic characteristics of brush-labyrinth seals at various operating conditions 被引量:5
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作者 Yuanqiao ZHANG Jun LI +1 位作者 Zhigang LI Xin YAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2020年第4期1192-1205,共14页
Over the last few decades,the research on the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals is not sufficient.To this end,two kinds of brush-labyrinth seals for the b... Over the last few decades,the research on the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals is not sufficient.To this end,two kinds of brush-labyrinth seals for the bristle pack element installed upstream of the labyrinth teeth named BSU and installed downstream of the labyrinth teeth called BSD were used to investigate the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals.Using the numerical model combining the porous medium model and the whirling rotor method,the rotordynamic characteristics of the BSU and BSD at various operating conditions including four kinds of pressure ratios,five kinds of inlet preswirl speeds and four kinds of rotor spinning speeds were conducted.The obtained results show that the effects of operating conditions on rotordynamic coefficients for the different seal configurations are different.The direct stiffness,cross-coupled stiffness and direct damping of the BSU are lower than those of the BSD.The rotordynamic coefficients of the BSU are more insensitive to the operating conditions variation.From the perspective of the seal stability,the BSU is a better brush-labyrinth seal configuration at high pressure ratio,high positive preswirl or high rotor spinning speed conditions.While in the case of low pressure ratio,low positive preswirl or low rotor spinning speed conditions,the BSD is a better choice. 展开更多
关键词 Bristle pack position Brush-labyrinth seal Porous medium Rotordynamic characteristics Whirling rotor method
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Improvement of the electrical resistivity of epoxy resin at elevated temperature by adding a positive temperature coefficient BaTiO3-based compound 被引量:1
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作者 Chenyuan TENG Wenjun ZHOU +4 位作者 Yuanxiang ZHOU Ling ZHANG Yunxiao ZHANG Zhongliu ZHOU Wenpeng LI 《Plasma Science and Technology》 SCIE EI CAS CSCD 2020年第4期15-23,共9页
The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in... The DC electrical resistivity-temperature characteristic is an important property for insulating materials to operate at a high stress level.In order to improve the DC electrical resistivity at elevated temperature in a targeted way,a positive temperature coefficient(PTC)material(Ba Ti O3-based compound(BT60))was selected as the filler in this paper,whose electrical resistivity has a PTC effect when the temperature exceeds its Curie temperature.The BT60 was treated with hydrogen peroxide and(3-Aminopropyl)triethoxysilane.Epoxy composites with different loadings of BT60 fillers(0 wt%,0.5 wt%,and 2 wt%of epoxy)were prepared,denoted as EP-0,EP-0.5,and EP-2.It was shown that BT60 was able to maintain the DC breakdown strength when its loading was less than 2 wt%of epoxy.As the temperature exceeds 60°C,BT60 will compensate for the negative temperature coefficient effect of epoxy resin to some extent.The electrical resistivity of EP-2 was improved by 55%compared with that of neat epoxy at 90°C.It was found that the potential barrier at the grain boundary of BT60 and the deep traps in the interface between BT60 and the epoxy resin hinder the migration of carriers and thus increase the electrical resistivity of epoxy composite. 展开更多
关键词 epoxy resin positive TEMPERATURE coefficient BARIUM TITANATE based compounds resistivity-temperature characteristics TRAPS
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Influence of the cathode position on beam current characteristics in the thermionic electron gun 被引量:1
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作者 Jikang Fan Jian Zhang +4 位作者 Haiying Xu Yong Peng Xinghua Sang Qi Zhou Kehong Wang 《Radiation Detection Technology and Methods》 CSCD 2022年第3期401-408,共8页
Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.Methods The electricfield distribution,bias voltage range and electron beam... Purpose The research focuses on the simulation of influence of cathode positions on beam current characteristics in the thermionic electron gun.Methods The electricfield distribution,bias voltage range and electron beam quality under different cathode positions were simulated by CST software.Results Changes in the cathode position can cause changes in the electricfield distributions under the cathode emission surface change,thereby changing the size of the effective emitting area and affecting the relationship between the bias voltage and beam current.Conclusions Only when the cathode is installed in the proper positions,the beam current and the bias voltage have an approximately linear proportional relationship.When the cathode is installed improperly,the electron beam emission is disordered,resulting in decreased electron beam quality. 展开更多
关键词 SIMULATION Thermionic electron gun Cathode position Beam current characteristics
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Human epidermal growth factor receptor 2 positive rates in invasive lobular breast carcinoma: The Singapore experience
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作者 Ga-Jing Kee Ryan Ying-Cong Tan +11 位作者 Sultana Rehena Joycelyn Jie-Xin Lee Ma Wai-Wai Zaw Wei-Xiang Lian Joe Yeong Su-Ming Tan Swee-Ho Lim Benita Kiat-Tee Tan Yoon-Sim Yap Rebecca Alexandra Dent Fuh-Yong Wong Guek-Eng Lee 《World Journal of Clinical Oncology》 CAS 2020年第5期283-293,共11页
BACKGROUND Invasive lobular carcinomas(ILC)form 5%-10%of breast cancer and rarely show overexpression of human epidermal growth factor receptor 2(HER2).AIM To describe the prevalence and prognostic factors of HER2 pos... BACKGROUND Invasive lobular carcinomas(ILC)form 5%-10%of breast cancer and rarely show overexpression of human epidermal growth factor receptor 2(HER2).AIM To describe the prevalence and prognostic factors of HER2 positive(HER2+)ILC in an Asian population.METHODS A retrospective review of patients with ILC seen between January 1985 and March 2018 at various SingHealth medical institutions was conducted.Demographic and clinical data were collected from medical records.We examined clinicopathological characteristics and survival in relation to HER2 status.RESULTS A total of 864 patients were included.Prevalence of HER2 positivity was 10.1%(87 patients).Compared with HER2 negative(HER2-)ILC,HER2+ILC was associated with a higher proportion of estrogen receptor negative(24.4%vs 5.9%,P<0.001),progesterone receptor negative(PR-)(40.2%vs 24%,P=0.002)and grade 3 tumours(Grade 3,29.0%vs 10.2%,P<0.001).Overall survival rate was poorer in patients with HER2+compared to HER2-ILC(56.7%vs 72.9%alive at 10 years;hazard ratio 1.87,95%confidence interval:1.21-2.90,P=0.004).Based on multivariate analysis,negative prognostic factors for overall survival included HER2 positivity,PR negativity,older age,Indian ethnicity and higher tumour stage.CONCLUSION Prevalence of HER2+ILC was 10.1%.HER2+ILC was more likely to have poorer prognostic features such as estrogen receptor negative,PR-and higher tumour grade,and have a poorer survival. 展开更多
关键词 Lobular breast cancer Invasive breast cancer Human epidermal growth factor receptor 2 positive SINGAPORE Clinicopathological characteristics Prognostic value
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开放型区域产教融合实践中心的基本特征、功能定位与推进路径 被引量:4
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作者 雷世平 谢盈盈 乐乐 《职教通讯》 2024年第2期33-40,共8页
开放型区域产教融合实践中心(简称“产教融合实践中心”)是对标产业发展前沿,由政府搭台、市场驱动,汇集产教资源,政、校、行、企等多元主体参与,旨在推动区域职业教育实训实践资源均衡发展,提升职业学校关键办学能力,为企业培养急需人... 开放型区域产教融合实践中心(简称“产教融合实践中心”)是对标产业发展前沿,由政府搭台、市场驱动,汇集产教资源,政、校、行、企等多元主体参与,旨在推动区域职业教育实训实践资源均衡发展,提升职业学校关键办学能力,为企业培养急需人才和提供技术服务的生产性实践组织形态。产教融合实践中心分为学校实践中心、公共实践中心、企业实践中心,具有参与主体的多元性、服务面向的区域性以及运营模式的多样性等基本特征;具备实践教学、社会培训、真实生产和技术服务等功能。要扎实推进产教融合实践中心建设,必须坚持政府引导,统筹谋划产教融合实践中心建设;坚持市场驱动,以股份制混合所有制推进产教融合实践中心建设;坚持同步发力,分类推进产教融合实践中心建设。 展开更多
关键词 产教融合实践中心 基本特征 功能定位 推进路径
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基于形色筛选的苹果园羽化害虫粘连图像分割方法 被引量:1
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作者 刘双喜 王云飞 +5 位作者 张宏建 孙林林 马博 慕君林 任卓 王金星 《农业机械学报》 EI CAS CSCD 北大核心 2024年第3期263-274,共12页
针对苹果园害虫识别过程中的粘连问题,提出了一种基于形色筛选的害虫粘连图像分割方法。首先,采集苹果园害虫图像,聚焦于羽化害虫。害虫在羽化过程中已完成大部分生长发育,其外部形态、颜色、纹理更为稳定显著。因此,基于不同种类害虫... 针对苹果园害虫识别过程中的粘连问题,提出了一种基于形色筛选的害虫粘连图像分割方法。首先,采集苹果园害虫图像,聚焦于羽化害虫。害虫在羽化过程中已完成大部分生长发育,其外部形态、颜色、纹理更为稳定显著。因此,基于不同种类害虫的形色特征信息分析,来获取害虫HSV分割阈值和模板轮廓。其次,利用形状因子判定分割粘连区域,通过颜色分割法和轮廓定位分割法来实现非种间与种间粘连害虫的分割。最后,对采集的苹果园害虫图像进行了试验分析,采用基于形色筛选的分割法对单个害虫进行分割,结果表明,本文方法的平均分割率、平均分割错误率和平均分割有效率分别为101%、3.14%和96.86%,分割效果优于传统图像分割方法。此外,通过预定义的颜色阈值,本文方法实现了棉铃虫、桃蛀螟与玉米螟的精准分类,平均分类准确率分别为97.77%、96.75%与96.83%。同时,以Mask R-CNN模型作为识别模型,平均识别精度作为评价指标,分别对已用本文方法和未用本文方法分割的害虫图像进行识别试验。结果表明,已用本文方法分割的棉铃虫、桃蛀螟和玉米螟害虫图像平均识别精度分别为96.55%、94.80%与95.51%,平均识别精度分别提高16.42、16.59、16.46个百分点。这表明该方法可为果园害虫精准识别提供理论和方法基础。 展开更多
关键词 苹果园 羽化害虫 粘连图像 精准分割 形色特征 轮廓定位
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永磁同步发电机匝间短路故障对绕组绝缘温升特性的影响 被引量:1
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作者 何玉灵 李勇 +3 位作者 张文 白怡凡 徐明星 王晓龙 《电机与控制学报》 EI CSCD 北大核心 2024年第4期18-30,共13页
本文分析了永磁同步发电机匝间短路故障前后的绕组绝缘温升特性。首先推导了正常情况和匝间短路故障下的气隙磁通密度,相电流、铁心损耗和绕组铜耗解析表达式;然后建立了发电机三维有限元仿真模型,将电磁场中计算得到的各类损耗作为热... 本文分析了永磁同步发电机匝间短路故障前后的绕组绝缘温升特性。首先推导了正常情况和匝间短路故障下的气隙磁通密度,相电流、铁心损耗和绕组铜耗解析表达式;然后建立了发电机三维有限元仿真模型,将电磁场中计算得到的各类损耗作为热源导入温度场计算绕组绝缘温度分布;最后实测了LR-5型故障模拟永磁同步发电机组在不同短路程度下的绕组绝缘温度,理论分析、仿真计算与实验结果相互吻合。结果表明:匝间短路故障后在故障绕组电流的作用下,绕组绝缘温度明显上升,并且随着短路程度的增加而加剧,由绕组绝缘热载荷分布不均而引起的变形、应变和应力也将增加;绕组鼻端处绝缘易因高温而受损,可通过改进冷却散热结构,或在鼻端绝缘局部涂覆耐热涂层提高鼻端绝缘的可靠性。 展开更多
关键词 永磁同步发电机 绕组绝缘 匝间短路 温升特性 危险位置
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