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Effects of rotational speed and fill level on particle mixing in a stirred tank with different impellers 被引量:8
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作者 Yuyun Bao Yu Lu +1 位作者 Ziqi Cai Zhengming Gao 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2018年第6期1383-1391,共9页
The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bott... The particle mixing was studied in a cylindrical stirred tank with elliptical dished bottom by experiments and simulations.The impeller types used were double helical ribbon(HR) + bottom HR,pitched blade ribbon + bottom HR,inner and outer HR + bottom HR,and pitched blade ribbon + Pfaudler + bottom HR labeled as impellers Ⅰ to Ⅳ,respectively.The quantitative correlations among the rotational speed,fill level and power consumption for impeller Ⅰ and impeller Ⅱ were obtained by experiments to validate the discrete element method(DEM) simulations.The particle mixing at different operating conditions was simulated via DEM simulations to calculate the mixing index using the Lacey method,which is a statistical method to provide a mathematical understanding of the mixing state in a binary mixture.The simulation results reveal that as the rotational speed increases,the final mixing index increases,and as the fill level increases,the final mixing index decreases.At the same operating conditions,impeller Ⅲ is the optimal combination,which provides the highest mixing index at the same revolutions. 展开更多
关键词 Particle Mixing Discrete element method(DEM) Rotational speed Fill level Lacey index
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A Methodology for Developing Speed and Endurance of Teenagers
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作者 Velizar T. Pavlov Veneta Simeonova 《Journal of Sports Science》 2015年第5期223-227,共5页
The problem is a sustained decline in the average level of overall physical abilities of young people in Bulgaria. The aim of this work is to prepare a methodology for developing physical qualities: speed and enduran... The problem is a sustained decline in the average level of overall physical abilities of young people in Bulgaria. The aim of this work is to prepare a methodology for developing physical qualities: speed and endurance of teenagers and to implement it in lessons in Physical Education and Sport. Research methods include sports pedagogical experiment, testing and data analysis. Two groups were observed: a control and an experimental one. Our methodology is based on specialized athletics exercises. Their effectiveness is proved by depth statistical data analysis. The main result of the application of the methodology is significant positive changes in the speed and endurance of boys in the experimental group. Some personal comments about the experiment and conclusions are given. 展开更多
关键词 Physical workability speed endurance ATHLETICS methods data analysis.
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Preliminary Study on the Differences between Automatic-observed and Manual-observed Wind Speed and Its Correction
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作者 张志富 任芝花 范邵华 《Meteorological and Environmental Research》 CAS 2010年第4期1-6,10,共7页
Comparing and analyzing the difference between automatic-observed and manual-observed wind speed based on the wind speed parallel observations in two methods, we find that many elements can influence the difference be... Comparing and analyzing the difference between automatic-observed and manual-observed wind speed based on the wind speed parallel observations in two methods, we find that many elements can influence the difference between automatic-observed and manual-observed wind speed, including the levels of speed wind, observation instruments and different regions. According to these elements, correction has been conducted, and find that the correction according to the level of wind speed has the best correction effect. 展开更多
关键词 Manual observation Automatic observation level of wind speed Observation instruments China
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Changes in Wind Speed and Extremes in Beijing during 1960–2008 Based on Homogenized Observations 被引量:36
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作者 李珍 严中伟 +2 位作者 涂锴 刘伟东 王迎春 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2011年第2期408-420,共13页
Daily observations of wind speed at 12 stations in the Greater Beijing Area during 1960–2008 were homogenized using the Multiple Analysis of Series for Homogenization method. The linear trends in the regional mean an... Daily observations of wind speed at 12 stations in the Greater Beijing Area during 1960–2008 were homogenized using the Multiple Analysis of Series for Homogenization method. The linear trends in the regional mean annual and seasonal (winter, spring, summer and autumn) wind speed series were-0.26,-0.39,-0.30,-0.12 and-0.22 m s-1 (10 yr)-1 , respectively. Winter showed the greatest magnitude in declining wind speed, followed by spring, autumn and summer. The annual and seasonal frequencies of wind speed extremes (days) also decreased, more prominently for winter than for the other seasons. The declining trends in wind speed and extremes were formed mainly by some rapid declines during the 1970s and 1980s. The maximum declining trend in wind speed occurred at Chaoyang (CY), a station within the central business district (CBD) of Beijing with the highest level of urbanization. The declining trends were in general smaller in magnitude away from the city center, except for the winter case in which the maximum declining trend shifted northeastward to rural Miyun (MY). The influence of urbanization on the annual wind speed was estimated to be about-0.05 m s-1 (10 yr)-1 during 1960–2008, accounting for around one fifth of the regional mean declining trend. The annual and seasonal geostrophic wind speeds around Beijing, based on daily mean sea level pressure (MSLP) from the ERA-40 reanalysis dataset, also exhibited decreasing trends, coincident with the results from site observations. A comparative analysis of the MSLP fields between 1966–1975 and 1992–2001 suggested that the influences of both the winter and summer monsoons on Beijing were weaker in the more recent of the two decades. It is suggested that the bulk of wind in Beijing is influenced considerably by urbanization, while changes in strong winds or wind speed extremes are prone to large-scale climate change in the region. 展开更多
关键词 HOMOGENIZATION daily mean wind speed URBANIZATION mean sea level pressure geostrophic wind East Asian monsoon
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The effects of mean sea level rise and strengthened winds on extreme sea levels in the Baltic Sea 被引量:1
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作者 Magnus Hieronymus Christian Dieterich +1 位作者 Helén Andersson Robinson Hordoir 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2018年第6期366-371,I0003,共7页
Mean sea level rise and climatological wind speed changes occur as part of the ongoing climate change and future projections of both variables are still highly uncertain. Here the Baltic Sea’s response in extreme sea... Mean sea level rise and climatological wind speed changes occur as part of the ongoing climate change and future projections of both variables are still highly uncertain. Here the Baltic Sea’s response in extreme sea levels to perturbations in mean sea level and wind speeds is investigated in a series of simulations with a newly developed storm surge model based on the nucleus for European modeling of the ocean(NEMO)-Nordic. A simple linear model with only two tunable parameters is found to capture the changes in the return levels extremely well. The response to mean sea level rise is linear and nearly spatially uniform, meaning that a mean sea level rise of 1 m increases the return levels by a equal amount everywhere. The response to wind speed perturbations is more complicated and return levels are found to increase more where they are already high. This behaviour is alarming as it suggests that already flooding prone regions like the Gulf of Finland will be disproportionally adversely affected in a future windier climate. 展开更多
关键词 Extreme sea levels Sea level rise Wind speeds Baltic Sea
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The effect of sex and performance level on pacing in cross-country skiers:Vasaloppet 2004-2017 被引量:1
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作者 Pantelis Theodoros Nikolaidis Elias Villiger Beat Knechtle 《Journal of Sport and Health Science》 SCIE 2018年第4期453-458,共6页
Background: Pacing, defined as percentage changes of speed between successive splits, has been extensively studied in running and cycling endurance sports; however, less information about the trends in change of spee... Background: Pacing, defined as percentage changes of speed between successive splits, has been extensively studied in running and cycling endurance sports; however, less information about the trends in change of speed during cross-country (XC) ski racing is available. Therefore, the aim of the present study was to examine the effect of performance (quartiles of race time (Q), with Q1 the fastest and Q4 the slowest) level on pacing in the Vasaloppet ski race, the largest XC skiing race in the world. Methods: For this purpose, we analyzed female (n = 19,465) and male (n = 164,454) finishers in the Vasaloppet ski race from 2004 to 2017 using a one-way (2 sexes) analysis of variance with repeated measures to examine percentage changes of speed between 2 successive splits. Overall, the race consisted of 8 splits. Results: The race speeds of Q1, Q2, Q3, and Q4 were 13.6 ± 1.8, 10.6 ± 0.5, 9.2 ± 0.3, and 8.1 ±- 0.4 km/h, respectively, among females and 16.7 ± 1.7, 13.1 ± 0.7, 10.9 ± 0.6, and 8.9 ± 0.7 km/h, respectively, among males. The overall pacing strategy of finishers was variable. A small sex × split interaction on speed was observed (η^2= 0.016, p 〈 0.001), with speed difference between sexes ranging from 14.9% (Split 7) to 27.0% (Split 1) and larger changes in speed between 2 successive splits being shown for females (p 〈 0.001, η^2=0.004). A large performance × split interaction on speed, with Q1 presenting the smallest changes of speed between splits, was shown for females (η^2= 0.149, p 〈 0.001) and males (η^2 = 0.169,p 〈 0.001). Conclusion: Male and fast XC skiers are more even pacers. Coaches and athletes should develop tailored sex- and performance-level pacing strategies; for instance, they should advise fast XC skiers to start fast and maintain their speed, rather than starting slowly and trying to make up time by going faster at times during the race.2018 Published by Elsevier B.V. on behalf of Shanghai University of Sport. This is an open access article under the CC BY-NC-ND license. (http://creativecommons.org/licenses/by-nc-nd/4.0/). 展开更多
关键词 endurance exercise Race speed SEX Sport performance Winter sport
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Non-Native English Speaker Readability Metric: Reading Speed and Comprehension
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作者 Aissa Boudjella Mukti Sharma Deepti Sharma 《Journal of Applied Mathematics and Physics》 2017年第6期1257-1268,共12页
This paper presents an investigation to evaluate the reading speed and reading comprehension of non-native English speaking students by presenting a simple analytical model. For this purpose, various readability softw... This paper presents an investigation to evaluate the reading speed and reading comprehension of non-native English speaking students by presenting a simple analytical model. For this purpose, various readability softwares were used to estimate the average grade level of the given texts. The relationship between the score obtained by the students and their reading speed under average grade level 9 and 14 using font size 12 and 14 is presented. The experimental results show that the reading speed and the score versus the students may be explained by a linear regression. Reading speed decreases as the score decreases. The students with a higher magnitude of reading speed scored better marks. More importantly, we find that the reading speed of our students is lower than the native English speakers. This approach of modeling the readability in linear form significantly simplifies the readability analysis. 展开更多
关键词 READABILITY Reading speed Software READABILITY Flesch-Kincaid Grade level Gunning-Fog Score Coleman-Liau INDEX SMOG INDEX Automatic READABILITY INDEX Linear Regression
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An Efficient Liver-Segmentation System Based on a Level-Set Method and Consequent Processes 被引量:1
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作者 Walita Narkbuakaew Hiroshi Nagahashi +1 位作者 Kota Aoki Yoshiki Kubota 《Journal of Biomedical Science and Engineering》 2014年第12期994-1004,共11页
This paper presents an efficient liver-segmentation system developed by combining three ideas under the operations of a level-set method and consequent processes. First, an effective initial process creates mask and s... This paper presents an efficient liver-segmentation system developed by combining three ideas under the operations of a level-set method and consequent processes. First, an effective initial process creates mask and seed regions. The mask regions assist in prevention of leakage regions due to an overlap of gray-intensities between liver and another soft-tissue around ribs and verte-brae. The seed regions are allocated inside the liver to measure statistical values of its gray-intensities. Second, we introduce liver-corrective images to represent statistical regions of the liver and preserve edge information. These images help a geodesic active contour (GAC) to move without obstruction from high level of image noises. Lastly, the computation time in a level-set based on reaction-diffusion evolution and the GAC method is reduced by using a concept of multi-resolution. We applied the proposed system to 40 sets of 3D CT-liver data, which were acquired from four patients (10 different sets per patient) by a 4D-CT imaging system. The segmentation results showed 86.38% ± 4.26% (DSC: 91.38% ± 2.99%) of similarities to outlines of manual delineation provided by a radiologist. Meanwhile, the results of liver segmentation only using edge images presented 79.17% ± 5.15% or statistical regions showed 74.04% ± 9.77% of similarities. 展开更多
关键词 LIVER SEGMENTATION level-SET GEODESIC Active CONTOUR speed Images STATISTICAL Thresholds
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Relativistic Reduction of the Electron-Nucleus Force in Bohr’s Hydrogen Atom and the Time of Electron Transition between the Neighbouring Quantum Energy Levels
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作者 Stanisław Olszewski 《Journal of Modern Physics》 2020年第6期944-951,共8页
The aim of the paper is to get an insight into the time interval of electron emission done between two neighbouring energy levels of the hydrogen atom. To this purpose, in the first step, the formulae of the special r... The aim of the paper is to get an insight into the time interval of electron emission done between two neighbouring energy levels of the hydrogen atom. To this purpose, in the first step, the formulae of the special relativity are applied to demonstrate the conditions which can annihilate the electrostatic force acting between the nucleus and electron in the atom. This result is obtained when a suitable electron speed entering the Lorentz transformation is combined with the strength of the magnetic field acting normally to the electron orbit in the atom. In the next step, the Maxwell equation characterizing the electromotive force is applied to calculate the time interval connected with the change of the magnetic field necessary to produce the force. It is shown that the time interval obtained from the Maxwell equation, multiplied by the energy change of two neighbouring energy levels considered in the atom, does satisfy the Joule-Lenz formula associated with the quantum electron energy emission rate between the levels. 展开更多
关键词 Hydrogen Atom The Bohr Model Lorentz Transformation Done with the Aid of the Electron Orbital speed Maxwell Equation Applied to Calculate the Time Interval of Electron Transitions between Two Quantum Energy levels Comparison with the Joule-Lenz Law for Energy Emission
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Sequential Filtering for Surface Wind Speed Estimation from Ambient Noise Measurement 被引量:1
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作者 XIAO Peng YANG Kun-de LEI Zhi-xiong 《China Ocean Engineering》 SCIE EI CSCD 2017年第1期74-78,共5页
Many research results show that ocean ambient noise and wind speed are highly relevant, and the surface wind speed can be effectively inverted using ocean noise data. In most deep-sea cases, the ambient noise of mediu... Many research results show that ocean ambient noise and wind speed are highly relevant, and the surface wind speed can be effectively inverted using ocean noise data. In most deep-sea cases, the ambient noise of medium frequency is mainly determined by the surface wind, and there is a conventional relationship between them. This paper gives an equation which shows this relationship firstly, and then a surface-wind inversion method is proposed. An efficient particle filter is used to estimate the speed distribution, and the results exhibit more focused close to the actual wind speed. The method is verified by the measured noise data, and analysis results showed that this approach can accurately give the trend of sea surface wind speed. 展开更多
关键词 particle filtering wind speed noise spectrum level INVERSION
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MEDICAL IMAGE SEGMENTATION BASED ON A MODIFIED LEVEL SET ALGORITHM
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作者 杨勇 林盘 +1 位作者 郑崇勋 顾建文 《Journal of Pharmaceutical Analysis》 SCIE CAS 2005年第1期29-32,56,共5页
Objective To present a novel modified level set algorithm for medical image segmentation. Methods The algorithm is developed by substituting the speed function of level set algorithm with the region and gradient infor... Objective To present a novel modified level set algorithm for medical image segmentation. Methods The algorithm is developed by substituting the speed function of level set algorithm with the region and gradient information of the image instead of the conventional gradient information. This new algorithm has been tested by a series of different modality medical images. Results We present various examples and also evaluate and compare the performance of our method with the classical level set method on weak boundaries and noisy images. Conclusion Experimental results show the proposed algorithm is effective and robust. 展开更多
关键词 medical image segmentation level set speed function region information
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Investigation of monitoring system for high-speed railway subgrade frost heave
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作者 GuoTao Yang ZaiTian Ke +3 位作者 DeGou Cai HongYe Yan JianPing Yao Feng Chen 《Research in Cold and Arid Regions》 CSCD 2015年第5期528-533,共6页
This paper presents methods for monitoring frost heave, device requirements, testing principals, and data analysis re- quirements, such as manual leveling observation, automatic monitoring (frost heave, frost depth, ... This paper presents methods for monitoring frost heave, device requirements, testing principals, and data analysis re- quirements, such as manual leveling observation, automatic monitoring (frost heave, frost depth, and moisture), track dynamic detection, and track status detection. We focused on the requirements of subgrade frost heave monitoring for high speed railways, and the relationship of different monitoring methods during different phases of the railway. The com- prehensive monitoring system of high speed railway subgrade frost heave provided the technical support for dynamic design during construction and safe operation of the rail system. 展开更多
关键词 high speed railway frost heave monitoring automatic monitoring manual leveling observation rail detection
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The Method of Flotation Froth Image Segmentation Based on Threshold Level Set
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作者 Ji Zhao Huibin Wang +1 位作者 Lina Zhang Conghui Wang 《Advances in Molecular Imaging》 2015年第2期38-48,共11页
A novel flotation froth image segmentation based on threshold level set method is put forward in view of the problem of over-segmentation and under-segmentation which occurs when the existing method segmented the flot... A novel flotation froth image segmentation based on threshold level set method is put forward in view of the problem of over-segmentation and under-segmentation which occurs when the existing method segmented the flotation froth images. Firstly, the proposed method adopts histogram equalization to improve the contrast of the image, and then chooses the upper threshold and lower threshold from grey value of histogram of the image equalization, and complete image segmentation using the level set method. In this paper, the model which integrates edge with region level set model is utilized, and the speed energy term is introduced to segment the target. Experimental results show that the proposed method has better segmentation results and higher segmentation efficiency on the images with under-segmentation and incorrect segmentation, and it is meaningful for ore dressing industrial. 展开更多
关键词 FLOTATION Froth Image Segmentation Active CONTOUR Model HISTOGRAM EQUALIZATION speed Function THRESHOLD level Set
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Canda/A软件在预测高铁噪声对住宅小区声环境影响的应用 被引量:1
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作者 肖青 朱杰 王萌 《江西建材》 2019年第12期23-24,26,共3页
利用Cadna/A软件建立了高速铁路沿线高层住宅交通噪声的预测模型,对拟建住宅小区受高铁噪声的影响进行评价,分析了高铁噪声在住宅小区内传播规律,预测了住宅小区内建筑立面噪声,找出了受高铁噪声影响的最不利房间,探讨了一些室内外噪声... 利用Cadna/A软件建立了高速铁路沿线高层住宅交通噪声的预测模型,对拟建住宅小区受高铁噪声的影响进行评价,分析了高铁噪声在住宅小区内传播规律,预测了住宅小区内建筑立面噪声,找出了受高铁噪声影响的最不利房间,探讨了一些室内外噪声防治措施,为高层建筑交通噪声污染防治提供依据。 展开更多
关键词 高速铁路 噪声预测 防治 同层排水
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A study on aerodynamic noise characteristics of a high-speed maglev train with a speed of 600 km/h
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作者 Jie Zhang Yuwei Wu +2 位作者 Jianyong Gao Guangjun Gao Zhigang Yang 《Railway Sciences》 2023年第3期310-326,共17页
Purpose–This study aims to explore the formation mechanism of aerodynamic noise of a high-speed maglev train and understand the characteristics of dipole and quadrupole sound sources of the maglev train at different ... Purpose–This study aims to explore the formation mechanism of aerodynamic noise of a high-speed maglev train and understand the characteristics of dipole and quadrupole sound sources of the maglev train at different speed levels.Design/methodology/approach–Based on large eddy simulation(LES)method and Kirchhoff–Ffowcs Williams and Hawkings(K-FWH)equations,the characteristics of dipole and quadrupole sound sources of maglev trains at different speed levels were simulated and analyzed by constructing reasonable penetrable integral surface.Findings–The spatial disturbance resulting from the separation of the boundary layer in the streamlined area of the tail car is the source of aerodynamic sound of the maglev train.The dipole sources of the train are mainly distributed around the radio terminals of the head and tail cars of the maglev train,the bottom of the arms of the streamlined parts of the head and tail cars and the nose tip area of the streamlined part of the tail car,and the quadrupole sources are mainly distributed in the wake area.When the train runs at three speed levels of 400,500 and 600 km$h1,respectively,the radiated energy of quadrupole source is 62.4%,63.3%and 71.7%,respectively,which exceeds that of dipole sources.Originality/value–This study can help understand the aerodynamic noise characteristics generated by the high-speed maglev train and provide a reference for the optimization design of its aerodynamic shape. 展开更多
关键词 High-speed maglev train Aerodynamic noise Penetrable integral surface Large eddy simulation speed level
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速度350km/h高速铁路长大下坡地段闭塞分区设置方法研究 被引量:1
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作者 张守帅 张雨洁 +2 位作者 闫海峰 田长海 骆泳吉 《铁道学报》 EI CAS CSCD 北大核心 2024年第1期72-80,共9页
通过分析长大下坡道闭塞分区长度对CTCS-3级和后备CTCS-2级列控系统的影响,指出二者对闭塞分区长度的需求完全相反,并针对CTCS-3级列控系统的行车许可回缩、速度突降等问题的产生原因进行分析。阐述坡度、闭塞分区长度与不同列控模式下... 通过分析长大下坡道闭塞分区长度对CTCS-3级和后备CTCS-2级列控系统的影响,指出二者对闭塞分区长度的需求完全相反,并针对CTCS-3级列控系统的行车许可回缩、速度突降等问题的产生原因进行分析。阐述坡度、闭塞分区长度与不同列控模式下列车运行速度、追踪间隔时间等要素之间的关系,制定闭塞分区设置的基本原则。检算典型坡度下闭塞分区长度设置的合理区间范围及相应追踪间隔时间,指出坡度超过-30‰后将无法兼顾不同列控等级下的运行速度。设计模拟退火算法,根据闭塞分区设置原则及闭塞分区取值规律,给出压缩求解空间、提高求解效率的方法。以郑万高速铁路长大下坡地段为例,对闭塞分区设置进行优化,在不考虑其他约束的前提下,与设计院优化方案相比,本求解优化方案在确保CTCS-3级控车模式下允许速度可达350 km/h的同时,将CTCS-2级控车模式下的允许速度提高30 km/h,追踪间隔时间压缩23 s。 展开更多
关键词 高速铁路 长大下坡道 CTCS-3级列控系统 闭塞分区 行车许可
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弹力带抗阻训练对脑卒中下肢运动功能障碍患者肌力水平和运动耐力的影响
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作者 李民 丰谢华 +4 位作者 李爱 杨剑峰 杜文文 史荣芬 张超 《中国实用神经疾病杂志》 2024年第5期611-615,共5页
目的 探讨弹力带抗阻训练对脑卒中下肢运动功能障碍患者肌力水平、运动耐力的影响。方法 选择2021-06—2022-12在南京市江宁医院接受治疗的80例脑卒中下肢运动功能障碍患者进行研究,采用随机数表法分为试验组(n=40)和对照组(n=40)。对... 目的 探讨弹力带抗阻训练对脑卒中下肢运动功能障碍患者肌力水平、运动耐力的影响。方法 选择2021-06—2022-12在南京市江宁医院接受治疗的80例脑卒中下肢运动功能障碍患者进行研究,采用随机数表法分为试验组(n=40)和对照组(n=40)。对照组给常规运动指导治疗,试验组加用弹力带抗阻训练治疗。比较2组临床疗效、肌力水平、峰值摄氧量(VO_(2)peak)、无氧阈值(AT)、6 min步行距离、步态参数及Barthel指数、平衡功能评分变化情况。结果 治疗后,试验组总有效率85%,高于对照组的65%,差异有统计学意义(P<0.05);试验组下肢肌力评分低于对照组[(1.40±0.23)分比(1.98±0.63)分],Fugl Meyer运动量表评分高于对照组[(29.87±3.58)分比(24.15±3.74)分],差异均有统计学意义(P<0.05);试验组VO_(2)peak、AT及6 min步行距离分别为(20.42±1.71)m L/(min·kg)、(13.89±1.01)mL/(min·kg)、(140.56±23.78)m,均高于对照组的(18.46±1.23)m L/(min·kg)、(13.02±1.21)mL/(min·kg)、(116.58±29.61)m,差异均有统计学意义(P<0.05);试验组步长、步速、步频及单支撑相水平分别为(36.87±4.71)cm、(57.78±7.23)cm/s、(69.31±5.41)step/s、(31.05±3.01)%,均高于对照组的(31.52±3.67)cm、(52.84±6.09)cm/s、(63.05±6.08)step/s、(27.21±3.08)%,差异均有统计学意义(P<0.05);试验组Barthel指数、平衡功能评分分别为(78.61±5.61)分、(41.15±2.31)分,均高于对照组的(67.59±6.13)分、(32.56±5.47)分,差异均有统计学意义(P<0.05)。结论 在脑卒中下肢运动功能障碍患者中弹力带抗阻训练治疗有较好的效果,可有效改善肌力水平、运动耐力水平。 展开更多
关键词 脑卒中 弹力带抗阻训练 下肢运动功能障碍 肌力水平 运动耐力
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400 km/h高速铁路直立式声屏障降噪效果及安全性研究 被引量:2
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作者 丁亚超 《中国铁路》 北大核心 2024年第2期31-37,共7页
开展400 km/h高速铁路噪声影响研究是践行“交通强国”战略的有力举措。为研究400 km/h高速铁路噪声特性及辐射源强,获取现有直立式声屏障在速度400 km/h条件下降噪效果及适应性,采用有限元模型进行仿真计算,模拟计算400 km/h高速铁路... 开展400 km/h高速铁路噪声影响研究是践行“交通强国”战略的有力举措。为研究400 km/h高速铁路噪声特性及辐射源强,获取现有直立式声屏障在速度400 km/h条件下降噪效果及适应性,采用有限元模型进行仿真计算,模拟计算400 km/h高速铁路噪声源强并进行组成分析,对高速铁路通用的直立式声屏障降噪效果、耐久性、安全性等进行分析研究,对目前直立式声屏障适应性提出实施建议。研究表明:高速列车以速度400 km/h运行时,距离铁路外轨中心线25 m、轨上3.5 m处,桥梁段总声级为97.8 dB(A),路基段总声级为96.7 dB(A),气动噪声大于轮轨噪声;提出现有直立式声屏障在速度400 km/h条件下插入损失为2.7~8.9 dB(A);在安全方面,提出立柱底部螺栓养护年限;针对目前铁路直立式声屏障通用图适用性进行分析,提出结构安全优化建议。研究结果可指导400 km/h高速铁路噪声影响分析及直立式声屏障设计工作。 展开更多
关键词 400 km/h高速铁路 噪声总声压级 直立式声屏障 声屏障降噪 气动噪声 轮轨噪声
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业绩期望落差对企业国际化速度的影响机理
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作者 衣长军 郭敏敏 +1 位作者 赵晓阳 颜春 《科技进步与对策》 CSSCI 北大核心 2024年第20期141-150,共10页
持续推进更高水平的对外开放是融入国际经济大循环的重要战略,把握好国际化速度对跨国企业海外投资布局具有重要现实价值。利用2010—2020年中国上市公司对外投资数据,探讨业绩期望落差对企业国际化速度的影响及作用机制。结果表明,业... 持续推进更高水平的对外开放是融入国际经济大循环的重要战略,把握好国际化速度对跨国企业海外投资布局具有重要现实价值。利用2010—2020年中国上市公司对外投资数据,探讨业绩期望落差对企业国际化速度的影响及作用机制。结果表明,业绩期望落差对企业国际化速度具有正向影响;企业风险承担水平是业绩期望落差影响国际化速度的重要机制。进一步研究发现,行业期望落差对企业国际化速度的促进作用更为显著;高管团队海外背景异质性情境下,业绩期望落差对企业国际化速度的影响更为显著。结论对提高跨国企业海外投资效率和海外经营稳定性具有一定的启示。 展开更多
关键词 期望落差 企业风险承担水平 国际化速度
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普速铁路控制网测量技术方法探讨
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作者 曹娟华 吴维军 +2 位作者 刘焕明 刘尚华 吴孝泉 《铁道勘察》 2024年第6期36-41,共6页
为改善普速铁路有砟轨道长期运营后容易变形、损坏,线位逐年变化导致维修难度和维修成本增高等难题,对引入坐标控制的相关可行性方案进行探讨,并对测量费用、测量精度、测量效率及技术前景等进行分析。研究表明:直接引入高速铁路CPⅢ控... 为改善普速铁路有砟轨道长期运营后容易变形、损坏,线位逐年变化导致维修难度和维修成本增高等难题,对引入坐标控制的相关可行性方案进行探讨,并对测量费用、测量精度、测量效率及技术前景等进行分析。研究表明:直接引入高速铁路CPⅢ控制网测量方法,必将导致精度有余而效率不足等适用性问题。基于全站仪免置平测量的三维平差技术对控制网进行整体施测和整体平差,为控制网测量与线路测量合二为一创造了条件,数据资源利用率大幅提高,有利于测量效率的提升;避开了高程异常的解算,为高程测量精度的提高另辟蹊径;为全站仪工程测量坐标系统、卫星测量地心坐标系统的统一提供一种新的思路和方法。因此,不宜直接引入高速铁路CPⅢ控制网测量方法,而基于全站仪免置平测量的三维平差技术与方法在诸多方面都具有良好特性和应用前景,值得研究和推广。 展开更多
关键词 普速铁路 坐标控制 全站仪免置平 三维平差
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