检索结果-南通市图书馆

Investigation on Centrifugal Impeller in an Axial-radial Combined Compressor with Inlet Distortion

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2011年第6期20卷 486-494页

作者： Du Li Ce Yang Ben Zhao mi zhou mingxu Qi Jizhong Zhang School of Mechanical Engineering Beijing Institute of Technology Beijing China Basic Subject Department Bohai Shipbuilding Vocational College Huludao China National Key Laboratory of Diesel Engine Turbocharging Technology Datong China

Assembling an axial rotor and a stator at centrifugal compressor upstream to build an axial-radial combined compressor could achieve high pressure ratio and efficiency by appropriate size *** upstream potential flow and wake effect appear at centrifugal impeller *** this paper,the axial-radial compressor is unsteadily simulated by three-dimensional Reynolds averaged Navier-Stokes equations with uniform and circumferential distorted total pressure inlet condition to investigate upstream effect on radial *** results show that spanwise nonuniform total pressure distribution is generated and radial and circumferential combined distortion is formed at centrifugal rotor *** upstream stator wake deflects to rotor rotation direction and decreases with blade span *** distortion causes different separated flow formations at different pitch *** tip leakage vortex is suppressed in centrifugal blade *** distorted inlet condition,flow direction of centrifugal impeller leading edge upstream varies evidently near hub and shroud but varies slightly at *** addition,compressor stage inlet distortion produces remarkable effect on blade loading of centrifugal blade both along chordwise and pitchwise.

关键词： axial-radial combined compressor centrifugal impeller wake inlet distortion

Numerical and experimental research on different inlet configurations of high speed centrifugal compressor

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2012年第1期55卷 174-181页

作者： LI Du YANG Ce zhou mi ZHU ZhiFu WANG Hang School of Mechanical Engineering Beijing Institute of Technology Beijing 100081 China Basic Subject Department Bohai Shipbuilding Vocational College Huludao 125000 China Kangyue Technology Co. Ltd. Shouguang 262711 China

Three different inlet configurations,including a original straight pipe and two bend pipes with different axial length,for a high speed low mass flow centrifugal compressor were modeled with whole blade passages and simulated unsteadily by 3D viscous Navier-Stokes *** performance disparities of compressor stage were tested and verified by experiments in which dynamic pressure data acquisition of internal flow field was *** the result shows,the choke point decreases to lower mass flow rate due to the distortion caused by bend-pipe inlet and is aggravated as the rotation speed *** distortion effect spreads circumferentially in impeller and makes the flow structure *** longer axial distance bent inlet leads to larger radial distortion and heavy blockage at mid-span under large mass flow mainly causes compressor choke margin *** pipe distortion brings an impact up to diffuser on unsteady pressure pulsation caused by blades sweep and the impact appears more powerful when it is closer to volute tongue.

关键词： centrifugal compressor inlet distortion numerical simulation dynamic data acquisition

Effect of Molecular Weight on the Properties of Poly(butylene succinate)

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2014年第7期32卷 953-960页

作者： Tian-xiang Jin mi zhou Shao-dong Hu Feng Chen 傅强 Yi Fu College of Polymer Science and Engineering Sichuan UniversityState Key Laboratory of Polymer Materials Engineering Guangdong Silver Age Sci & Tech Co. Ltd.

Poly（butylene succinate）（PBS） with different molecular weight was synthesized from 1, 4-butanediol and succinic acid by direct melt condensation. The synthesized PBS was identified by IH-NMR and FTIR spectrometry. The molecular weight was calculated from the intrinsic viscosity, and its value was between 20000 and 70000. The crystallization behavior and crystal morphology as function of molecular weight were investigated by DSC and PLM, respectively. The mechanical properties and hydrolytic degradation behaviors related with change of molecular weight were also studied in this work. The results demonstrated that the properties of PBS were determined by both molecular weight and crystallization properties （crystallinity as well as crystal morphology）. Our work is important for the design and preparation of PBS with proper molecular weight for its practical application.

关键词： Poly(butylene succinate) Molecular weight Properties.

在线全文

学校读者我要写书评

暂无评论

激光光束整形技术研究进展

激光与光电子学进展 2024年第5期61卷 47-58页

作者：亓岩朱英杰张晶王延伟周密孙晨曦颜博霞韩巍王宇中国科学院大学集成电路学院北京100049 中国科学院微电子研究所光电技术研发中心北京100094 北京积水潭医院北京100035

激光器谐振腔输出的光束呈高斯分布,需要通过光束整形来提高均匀性,以满足应用的需求。从光学系统的特性出发,总结归纳了当前主要的三种激光光束整形技术,包括光阑法、场映射器法和多孔径光束聚焦法,分别介绍了三种激光光束整形技术的... 详细信息

激光器谐振腔输出的光束呈高斯分布,需要通过光束整形来提高均匀性,以满足应用的需求。从光学系统的特性出发,总结归纳了当前主要的三种激光光束整形技术,包括光阑法、场映射器法和多孔径光束聚焦法,分别介绍了三种激光光束整形技术的基本原理、应用范围和主要实现方法,阐述了不同激光光束整形方法的典型应用和研究进展,最后,综合讨论了激光光束整形技术目前所面临的问题及未来的发展方向。本综述对激光光束整形技术的研究具有一定的参考意义。

关键词：光束整形光阑场映射器多孔径光束聚焦

在线全文

学校读者我要写书评

暂无评论

中国性科学 2024年第9期33卷 14-18页

作者：朱培江周密黄华建易凌霄湖州市南浔区人民医院泌尿外科浙江湖州313009 浙江省人民医院泌尿外科杭州310014

目的探讨前列腺特异性抗原前体(p2PSA)及前列腺健康指数(PHI)相关参数诊断血清总前列腺特异性抗原(tPSA)灰区前列腺癌(PCa)患者的临床价值。方法选取2019年1月至2023年1月湖州市南浔区人民医院诊治的286例前列腺病变患者作为研究对象,... 详细信息

目的探讨前列腺特异性抗原前体(p2PSA)及前列腺健康指数(PHI)相关参数诊断血清总前列腺特异性抗原(tPSA)灰区前列腺癌(PCa)患者的临床价值。方法选取2019年1月至2023年1月湖州市南浔区人民医院诊治的286例前列腺病变患者作为研究对象,根据病理学结果将其分组为PCa组(n=78)和良性前列腺病变组(n=208)。所有患者入院后均接受前列腺增强磁共振成像(MRI)检查,并测定血清tPSA、游离前列腺特异性抗原(fPSA)和p2PSA水平,计算%fPSA、%p2PSA和PHI参数,绘制受试者工作特征(ROC)曲线分析MRI第2版前列腺影像报告和数据系统(PI-DADS)评分、血清p2PSA、%p2PSA、PHI单项及联合检测对PCa的诊断价值,分析血清p2PSA、%fPSA、%p2PSA、PHI、MRI PI-DADS评分单项及联合检测评估Gleason评分危险度的价值。结果PCa组MRI PI-DADS评分、血清p2PSA、%p2PSA、PHI水平高于良性前列腺病变组(P<0.05)。MRI PI-DADS评分、血清p2PSA、%p2PSA及PHI联合检测诊断PCa的曲线下面积(AUC)为0.961,灵敏度、特异度分别为83.62%、90.66%,诊断效能高于单项检测(P<0.05)。Gleason评分≥7分、Gleason评分≤6分分别有29例、49例。Gleason评分≥7分组MRI PI-DADS评分、血清p2PSA、%p2PSA和PHI高于Gleason评分≤6分组,%fPSA低于Gleason评分≤6分组(P<0.05)。MRI PI-DADS评分、p2PSA、%fPSA、%p2PSA及PHI联合检测评估Gleason评分危险度的AUC为0.928,灵敏度、特异度分别为89.53%、81.24%,评估效能高于单项检测(P<0.05)。结论p2PSA及PHI相关参数可早期诊断PCa的发生,也能进一步提高对侵袭性PCa的诊断效果。

关键词：前列腺癌前列腺健康指数前列腺特异性抗原前体 Gleason评分

在线全文

学校读者我要写书评

暂无评论

用户画像分析的诉求工单实时风险预警方法

长江信息通信 2024年第7期37卷 100-102页

作者：曾玲周颖廖婷宋薇方佳甄思佳周密海南电网有限责任公司客户服务中心海南海口571100

由于传统预警方法无法发现数据背后的深层次规律,导致诉求工单风险预警结果误差较大,提出基于用户画像分析的诉求工单实时风险预警方法。通过对诉求工单中的用户信息、投诉内容、问题反馈、服务评价等数据的挖掘,构建电力用户画像,利用X... 详细信息

由于传统预警方法无法发现数据背后的深层次规律,导致诉求工单风险预警结果误差较大,提出基于用户画像分析的诉求工单实时风险预警方法。通过对诉求工单中的用户信息、投诉内容、问题反馈、服务评价等数据的挖掘,构建电力用户画像,利用XGBoost模型对用户画像进行深度分析,预测出用户满意度下降的风险并发出警告,实现诉求工单实时风险预警。实验结果表明,设计方法下诉求工单实时风险预警结果的AUC值高达0.91,证实了该方法的准确性和泛化能力良好。

关键词：用户画像诉求工单实时风险风险预警

维普期刊数据库博看期刊

可切换智能负载的T型三电平电力弹簧负载电压谐波含量和超调量研究

在线全文

学校读者我要写书评

暂无评论

电机与控制应用 2024年第8期51卷 97-108页

作者：黄准王晓虎周密赵朝会上海电机学院电气学院上海201306

首次把单相T型三电平逆变器应用在可切换智能负载的电力弹簧中,降低了负载电压的谐波含量,建立了可切换智能负载的T型三电平电力弹簧的数学模型。并推导了传统载波调制对可切换智能负载的T型三电平电力弹簧直流侧中点电位的影响,引入了... 详细信息

首次把单相T型三电平逆变器应用在可切换智能负载的电力弹簧中,降低了负载电压的谐波含量,建立了可切换智能负载的T型三电平电力弹簧的数学模型。并推导了传统载波调制对可切换智能负载的T型三电平电力弹簧直流侧中点电位的影响,引入了中点电位控制方案,结合积分分离控制思想得到了可切换智能负载的T型三电平电力弹簧的控制策略。该控制策略能有效降低负载电压在网侧电压波动时的超调量。最后,通过Matlab/Simulink仿真验证,在稳关键和非关键负载电压时,改进后的谐波含量降低了3.47%和1.65%,超调量降低了0.34%和0.1%。

关键词：可切换智能负载电力弹簧 T型三电平超调量

Characteristics of acoustic response from simulated impulsive lightning current discharge

在线全文

学校读者我要写书评

暂无评论

High Voltage 2019年第3期4卷 221-227页

作者： Jianguo Wang Jinxin Cao Li Cai Yadong Fan mi zhou Quanxin Li School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072People's Republic of China

Acoustic observation of laboratory simulated lightning discharge can greatly avoid the observation difficulties under natural thunderstorm *** acoustic observation experiment based on the impulsive current generation system and a microphone array was carried out and illustrated in this study.A quantitative study on characteristics of response sound pressure initiated from simulated lightning current was *** first arrived acoustic N-waves measured at different distances initiated from different discharge amplitudes were compared and *** acoustic amplitude,rise time and duration time defined for N-waves and peak frequencies were found to have an obvious correlation with the discharging amplitudes of simulated lightning currents and the observing *** linear change of acoustic amplitude is more obvious than that of the other parameters with the changed discharging amplitude or observing distance.A certain degree of shape change of the simulated lightning current except for the amplitude may not significantly affect the response acoustic characteristics when comparing the first acoustic N-waves from 8/20μs lightning current and another kind of impulsive current which has a wider shape and two subsequent *** subsequent current peaks in short time delays were proved to successively generate acoustic N-waves independently without overlapping,which meanwhile,indicated a consistent linear relationship of amplitude and time delay between electrical and acoustic pulses.

关键词： impulsive subsequent initiated

Infrared Spectroscopic Investigations of J-aggregates of Protonated Tetraphenylporphine

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chemical Research in Chinese Universities 2009年第2期25卷 257-260页

作者： zhou mi LU Guo-hui GAO Shu-qin LI Zuo-wei State Key Laboratory of Superhard Materials College of Physics Jilin University Changchun 130023 China

Protonated tetraphenylporphine（H2TPP） J-aggregates were prepared by aggregation on the liquid-air interface. Using FTIR spectroscopy, the authors observed the infrared absorption spectra of H2TPP and its J-aggregates. The IR spectra of H2TPP J-aggregates show significant changes compared with that of HETPP monomer. Intensity changes（e.g., strong enhancement of the in-plane vibronic mode and weakening of the out-of-plane vibronic mode of phenyl and porphyrin skeletal） were interpreted on the basis of stacking effects. Observation of the same type of bands collapse into single band was explained by the increase in the symmetry of H2TPP molecules. And the new bands at 1635 and 3407 cm^-1 indicate the aggregates containing a large amount of bound water.

关键词： J-aggregate Meso-tetraphenylporphine Stacking effect