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Effect of continuous casting speed on mold surface flow and the related near-surface distribution of non-metallic inclusions 被引量:9
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作者 Peng Fei Yi Min +1 位作者 Cheng-jun Liu Mao-fa Jiang 《International Journal of Minerals,Metallurgy and Materials》 SCIE EI CAS CSCD 2019年第2期186-193,共8页
For the control of surface defects in interstitial-free(IF) steel, quantitative metallographic analyses of near-surface inclusions and surface liquid flow detection via the nail-board tipping method were conducted. Th... For the control of surface defects in interstitial-free(IF) steel, quantitative metallographic analyses of near-surface inclusions and surface liquid flow detection via the nail-board tipping method were conducted. The results show that, at casting speeds of 0.8 and 1.0 m/min, a thin liquid mold flux layer forms and non-uniform floating of argon bubbles occurs, inducing the entrainment and subsequent entrapment of the liquid flux; fine inclusion particles of Al_2O_3 can also aggregate at the solidification front. At higher casting speeds of 1.4 and 1.6 m/min, the liquid mold flux can be entrained and carried deeper into the liquid steel pool because of strong level fluctuations of the liquid steel and the flux. The optimal casting speed is approximately 1.2 m/min, with the most favorable surface flow status and, correspondingly, the lowest number of inclusions near the slab surface. 展开更多
关键词 non-metallic INCLUSIONS distribution CASTING speed surface flow
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Effect of tool rotational speed on the particle distribution in friction stir welding of AA6092/17.5 SiCp-T6 composite plates and its consequences on the mechanical property of the joint 被引量:2
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作者 Uttam Acharya Barnik Saha Roy Subhash Chandra Saha 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2020年第2期381-391,共11页
This study investigates the effect of tool rotational speed(TRS)on particle distribution in nugget zone(NZ)through quantitative approach and its consequences on the mechanical property of friction stir welded joints o... This study investigates the effect of tool rotational speed(TRS)on particle distribution in nugget zone(NZ)through quantitative approach and its consequences on the mechanical property of friction stir welded joints of AA6092/17.5 SiCp-T6 composite.6 mm thick plates are welded at a constant tool tilt angle of 2°and tool traverse speed of 1 mm/s by varying the TRS at 1000 rpm,1500 rpm and 2000 rpm with a taper pin profiled tool.Microstructure analysis shows large quantity of uniformly shaped smaller size SiC particle with lower average particle area which are homogeneously distributed in the NZ.The fragmentation of bigger size particles has been observed because of abrading action of the hard tool and resulting shearing effect and severe stress generation due to the rotation of tool.The particles occupy maximum area in the matrix compared to that of the base material(BM)due to the redistribution of broken particles as an effect of TRS.The migration of particles towards the TMAZ-NZ transition zone has been also encountered at higher TRS(2000 rpm).The microhardness analysis depicts variation in average hardness from top to bottom of the NZ,minimum for 1500 rpm and maximum for 2000 rpm.The impact strength at 1000 rpm and 1500 rpm remains close to that of BM(21.6 J)while 2000 rpm shows the accountable reduction.The maximum joint efficiency has been achieved at 1500 rpm(84%)and minimum at 1000 rpm(68%)under tensile loading.Fractographic analysis shows mixed mode of failure for BM,1000 rpm and 1500 rpm,whereas 2000 rpm shows the brittle mode of failure. 展开更多
关键词 Friction STIR welding Aluminium matrix composite TOOL ROTATIONAL speed Particle distribution Mechanical property
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Evaluating Traffic Congestion Using the Traffic Occupancy and Speed Distribution Relationship: An Application of Bayesian Dirichlet Process Mixtures of Generalized Linear Model 被引量:1
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作者 Emmanuel Kidando Ren Moses +1 位作者 Eren E. Ozguven Thobias Sando 《Journal of Transportation Technologies》 2017年第3期318-335,共18页
Accurate classification and prediction of future traffic conditions are essential for developing effective strategies for congestion mitigation on the highway systems. Speed distribution is one of the traffic stream p... Accurate classification and prediction of future traffic conditions are essential for developing effective strategies for congestion mitigation on the highway systems. Speed distribution is one of the traffic stream parameters, which has been used to quantify the traffic conditions. Previous studies have shown that multi-modal probability distribution of speeds gives excellent results when simultaneously evaluating congested and free-flow traffic conditions. However, most of these previous analytical studies do not incorporate the influencing factors in characterizing these conditions. This study evaluates the impact of traffic occupancy on the multi-state speed distribution using the Bayesian Dirichlet Process Mixtures of Generalized Linear Models (DPM-GLM). Further, the study estimates the speed cut-point values of traffic states, which separate them into homogeneous groups using Bayesian change-point detection (BCD) technique. The study used 2015 archived one-year traffic data collected on Florida’s Interstate 295 freeway corridor. Information criteria results revealed three traffic states, which were identified as free-flow, transitional flow condition (congestion onset/offset), and the congested condition. The findings of the DPM-GLM indicated that in all estimated states, the traffic speed decreases when traffic occupancy increases. Comparison of the influence of traffic occupancy between traffic states showed that traffic occupancy has more impact on the free-flow and the congested state than on the transitional flow condition. With respect to estimating the threshold speed value, the results of the BCD model revealed promising findings in characterizing levels of traffic congestion. 展开更多
关键词 TRAFFIC Congestion Multistate speed distribution TRAFFIC OCCUPANCY Dirichlet Process Mixtures of Generalized Linear Model BAYESIAN CHANGE-POINT Detection
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Speed Spatial Distribution Models for Traffic Accident Section of Freeway Based on Computer Simulation
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作者 Decai Li Jiangwei Chu +2 位作者 Wenhui Zhang Xiaojuan Wang Guosheng Zhang 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2015年第3期123-128,共6页
Simulation models for accident section on freeway are built in microscopic traffic flow simulation environment. In these models involving 2-lane,3-lane and 4-lane freeway,one detector is set every 10 m to measure sect... Simulation models for accident section on freeway are built in microscopic traffic flow simulation environment. In these models involving 2-lane,3-lane and 4-lane freeway,one detector is set every 10 m to measure section running speed. According to the simulation results,speed spatial distribution curves for traffic accident section on freeway are drawn which help to determine dangerous sections on upstream of accident section. Furthermore,the speed spatial distribution models are obtained for every speed distribution curve. The results provide theoretical basis for determination on temporal and spatial influence ranges of traffic accident and offer reference to formulation of speed limit scheme and other management measures. 展开更多
关键词 traffic safety FREEWAY accident section speed distribution simulation
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Steady state speed distribution analysis for a combined cellular automaton traffic model
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作者 王俊峰 陈桂生 刘进 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第8期2850-2858,共9页
Cellular Automaton (CA) based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain (DTMC) analytical framewo... Cellular Automaton (CA) based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain (DTMC) analytical framework for a Nagel-Schreckenberg and Fukui Ishibashi combined CA model (W^2H traffic flow model) from microscopic point of view to capture the macroscopic steady state speed distributions. The inter-vehicle spacing Maxkov chain and the steady state speed Markov chain are proved to be irreducible and ergodic. The theoretical speed probability distributions depending on the traffic density and stochastic delay probability are in good accordance with numerical simulations. The derived fundamental diagram of the average speed from theoretical speed distributions is equivalent to the results in the previous work. 展开更多
关键词 cellular automaton traffic flow model speed distribution discrete time Markov chain
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A New Method for Calculating the Wind Speed Distribution of a Moving Tropical Cyclone
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作者 胡邦辉 杨修群 +2 位作者 谭言科 王咏青 范勇 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2010年第1期69-79,共11页
Based on gradient wind equations, including frictional force, and considering the effect of the movement of a tropical cyclone on wind speed, the Fujita Formula is improved and further simplified, and the numerical sc... Based on gradient wind equations, including frictional force, and considering the effect of the movement of a tropical cyclone on wind speed, the Fujita Formula is improved and further simplified, and the numerical scheme for calculating the maximum wind speed radius and wind velocity distribution of a moving tropical cyclone is derived. In addition, the effect of frictional force on the internal structure of the tropical cyclone is discussed. By comparison with observational data, this numerical scheme demonstrates great advantages, i.e. it can not only describe the asymmetrical wind speed distribution of a tropical cyclone reasonably, but can also calculate the maximum wind speed in each direction within the typhoon domain much more accurately. Furthermore, the combination of calculated and analyzed wind speed distributions by the scheme is perfectly consistent with observations. 展开更多
关键词 tropical cyclone maximum wind speed radius wind velocity distribution
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Modeling flame propagation speed and quenching distance of aluminum dust flame with spatially random distribution of particles
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作者 Mehdi Bidabadi Alireza Khoeini Poorfar 《Journal of Central South University》 SCIE EI CAS CSCD 2017年第1期81-89,共9页
In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimat... In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimate flame propagation speed in a lean/rich reaction medium.Flame speed for different particle diameters and the effects of various oxidizers such as carbon dioxide and oxygen on flame speed were studied.Nitrogen was considered the inert gas.In addition,the quenching distance and the minimum ignition energy(MIE) were studied as a function of dust concentration.Different burning time models for aluminum were employed and their results were compared with each other.The model was based on conduction heat transfer mechanism using the heat point source method.The combustion of single-particle was first studied and the solution was presented.Then the dust combustion was investigated using the superposition principle to include the effects of surrounding particles.It is found that larger particles have higher values of quenching distance in comparison with smaller particles in an assumed dust concentration.With the increase of dust concentration the value of MIE would be decreased for an assumed particle diameter.Considering random discrete heat sources method,the obtained results of random distribution of fuel particles in space provide closer and realistic predictions of the combustion physics of aluminum dust flame as compared with the experimental findings. 展开更多
关键词 flame propagation speed random particle distribution quenching distance random discrete combustion aluminum
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Joint Return Value Estimation of Significant Wave Heights and Wind Speeds with Bivariate Copulas
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作者 TAO Shanshan DONG Sheng +1 位作者 LIN Yifan GUEDES SOARES Carlos 《Journal of Ocean University of China》 SCIE CAS CSCD 2023年第5期1181-1192,共12页
The joint design criteria of significant wave heights and wind speeds are quite important for the structural reliability of fixed offshore platforms.However,the design method that regards different ocean environmental... The joint design criteria of significant wave heights and wind speeds are quite important for the structural reliability of fixed offshore platforms.However,the design method that regards different ocean environmental variables as independent is conservative.In the present study,we introduce a bivariate sample consisting of the maximum wave heights and concomitant wind speeds of the threshold by using the peak-over-threshold and declustering methods.After selecting the appropriate bivariate copulas and univariate distributions and blocking the sample into years,the bivariate compound distribution of annual extreme wave heights and concomitant wind speeds is constructed.Two joint design criteria,namely,the joint probability density method and the conditional probability method,are applied to obtain the joint return values of significant wave heights and wind speeds.Results show that(28.5±0.5)m s^(-1)is the frequently obtained wind speed based on the Atlantic dataset,and these joint design values are more appropriate than those calculated by univariate analysis in the fatigue design. 展开更多
关键词 joint design wave height wind speed compound distribution COPULA
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Pressure Distribution Characters of Flow Field around High-Speed Train
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作者 李人宪 刘应清 《Journal of Modern Transportation》 2000年第2期114-122,共9页
Based on incompressible viscous fluid Navier-stokes equation and k-ε 2-equations turbulent model, an investigation on 3D turbulent flow field around four kinds of train models has been made by finite element method. ... Based on incompressible viscous fluid Navier-stokes equation and k-ε 2-equations turbulent model, an investigation on 3D turbulent flow field around four kinds of train models has been made by finite element method. From the calculation, the pressure distribution characters of now field around high-speed trains have been obtained. It is significant for strength design of the high-speed train body, for resisting wind design of the facilities beside the high-speed railways and for determining the aerodynamic force of induced air to the human body near the railways. 展开更多
关键词 high-speed train flow field pressure distribut|
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Thermodynamic properties at the kinetic freeze-out in the Au + Au and Cu + Cu collisions at the RHIC using the Tsallis distribution
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作者 Wei-Hao Wu Jun-Qi Tao +4 位作者 Hua Zheng Wen-Chao Zhang Xing-Quan Liu Li-Lin Zhu Aldo Bonasera 《Nuclear Science and Techniques》 SCIE EI CAS CSCD 2023年第10期73-82,共10页
The thermodynamic properties of charged particles,such as the energy density,pressure,entropy density,particle density,and squared speed of sound at the kinetic freeze-out in the Au+Au collisions from the relativistic... The thermodynamic properties of charged particles,such as the energy density,pressure,entropy density,particle density,and squared speed of sound at the kinetic freeze-out in the Au+Au collisions from the relativistic heavy ion collider (RHIC)beam energy scan program √S_(NN) and in the Cu+Cu collisions at √S_(NN),200 GeV are studied using the thermodynamically consistent Tsallis distribution.The energy density,pressure,and particle density decrease monotonically with the collision energy for the same collision centrality;These properties also decrease monotonically from the central to peripheral collisions at the same collision energy.While the scaled energy densityε∕T^(4) and scaled entropy density s∕T^(3) demonstrate the opposite trend with the collision energy for the same collision centrality.There is a correlation betweenε∕T^(4) and s∕T^(3) at the same centrality.In addition,the squared speed of sound was calculated to determine that all the collision energies share nearly the same value at different collision centralities. 展开更多
关键词 Heavy-ion collision Tsallis distribution Kinetic freeze-out Energy density Entropy density Particle density Squared speed of sound Pressure
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Statistical delay distribution analysis on high-speed railway trains
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作者 Yuxiang Yang Ping Huang +2 位作者 Qiyuan Peng Jie LI Chao Wen 《Journal of Modern Transportation》 2019年第3期188-197,共10页
The focus of this study is to explore the statis-tical distribution models of high-speed railway (HSR) train delays. Based on actual HSR operational data, the delay causes and their classification, delay frequency, nu... The focus of this study is to explore the statis-tical distribution models of high-speed railway (HSR) train delays. Based on actual HSR operational data, the delay causes and their classification, delay frequency, number of affected trains, and space–time delay distributions are discussed. Eleven types of delay events are classified, and a detailed analysis of delay distribution for each classifica-tion is presented. Models of delay probability delay prob-ability distribution for each cause are proposed. Different distribution functions, including the lognormal, exponen-tial, gamma, uniform, logistic, and normal distribution, were selected to estimate and model delay patterns. The most appropriate distribution, which can approximate the delay duration corresponding to each cause, is derived. Subsequently, the Kolmogorov–Smirnov (K–S) test was used to test the goodness of fit of different train delay distribution models and the associated parameter values. The test results show that the distribution of the test data is consistent with that of the selected models. The fitting distribution models show the execution effect of the timetable and help in finding out the potential conflicts in real-time train operations. 展开更多
关键词 High-speed railway TRAIN DELAY CAUSE Actual operation data distribution model
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Wind Speed and Power Density Analysis for Sustainable Energy in Batouri, East Region of Cameroon
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作者 Pierre Pokem Elie Bertrand Kengne Signe +1 位作者 Jean Nganhou Yaouba 《Journal of Power and Energy Engineering》 2023年第6期44-55,共12页
This paper develops the modeling of wind speed by Weibull distribution in the intention to evaluate wind energy potential and help for designing small wind energy plant in Batouri in Cameroon. The Weibull distribution... This paper develops the modeling of wind speed by Weibull distribution in the intention to evaluate wind energy potential and help for designing small wind energy plant in Batouri in Cameroon. The Weibull distribution model was developed using wind speed data collected from a metrological station at the small Airport of Batouri. Four numerical methods (Moment method, Graphical method, Empirical method and Energy pattern factor method) were used to estimate weibull parameters K and C. The application of these four methods is effective using a sample wind speed data set. With some statistical analysis, a comparison of the accuracy of each method is also performed. The study helps to determine that Energy pattern factor method is the most effective (K = 3.8262 and C = 2.4659). 展开更多
关键词 Weibull distribution Mean Wind speed Statistical Tests Wind Energy
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受电弓仿生导流罩对高速列车横风气动特性影响研究 被引量:2
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作者 张洁 丁艳思 +2 位作者 邓海 韩帅 高广军 《铁道科学与工程学报》 EI CAS CSCD 北大核心 2024年第3期936-948,共13页
横风作用下高速列车气动横向力和倾覆力矩显著增加,气动性能显著恶化,列车脱轨、倾覆可能性增大,严重影响列车运行安全。受电弓作为高速列车核心的外突部件,直接受到横风的影响,因此改善受电弓区域的横风气动性能显得尤为重要。以鞘翅... 横风作用下高速列车气动横向力和倾覆力矩显著增加,气动性能显著恶化,列车脱轨、倾覆可能性增大,严重影响列车运行安全。受电弓作为高速列车核心的外突部件,直接受到横风的影响,因此改善受电弓区域的横风气动性能显得尤为重要。以鞘翅目生物形态为原型,构建受电弓仿生导流罩几何外形,并以8车编组高速列车为基准,建立4种不同的计算模型:原始模型(模型Ⅰ)、仅受电弓Ⅰ加装导流罩(模型Ⅱ)、仅受电弓Ⅱ加装导流罩(模型Ⅲ)、受电弓Ⅰ和Ⅱ均加装导流罩(模型Ⅳ)。基于三维稳态SST k-ω双方程湍流模型,分析不同方案下高速列车整车以及受电弓区域的横风气动性能。研究结果表明:安装受电弓导流罩后,气流更为平顺地越过受电弓区域,阻滞效应减小,下游车体顶部和受电弓Ⅱ(升弓)区域的气流速度有所增加,同时造成列车背风侧的流场结构改变。相比原始模型(模型Ⅰ),导流罩模型(模型Ⅱ、Ⅲ和Ⅳ)均可减小列车气动横向力和倾覆力矩,其中模型Ⅱ和模型Ⅲ的横向力分别减少9.65%、4.18%,倾覆力矩分别减少11.47%、4.37%;受电弓Ⅰ与受电弓Ⅱ均被包裹的模型Ⅳ效果最为显著,8车编组列车横向力和倾覆力矩分别减少11.39、16.81%。研究成果可为横风环境下新一代高速列车受电弓区域优化设计提供参考。 展开更多
关键词 高速受电弓 仿生导流罩 横风适应性 速度分布
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无人机作业参数对苹果树雾滴沉积分布的影响 被引量:1
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作者 张亚莉 白禄超 +2 位作者 陈鹏超 兰玉彬 于保宏 《农机化研究》 北大核心 2024年第4期183-187,共5页
为了研究植保无人飞机在苹果果树雾滴分布的情况,选用韦加JF01-20电动八旋翼四轴植保无人机作为测试平台,探讨飞行速度和喷雾助剂对于苹果果树雾滴分布的影响。试验设定了6组试验处理,以水敏纸为雾滴分布测试工具,分别布置在果树的上中... 为了研究植保无人飞机在苹果果树雾滴分布的情况,选用韦加JF01-20电动八旋翼四轴植保无人机作为测试平台,探讨飞行速度和喷雾助剂对于苹果果树雾滴分布的影响。试验设定了6组试验处理,以水敏纸为雾滴分布测试工具,分别布置在果树的上中下冠层,统计果树立体冠层的雾滴分布数据。研究结果表明:果树相同冠层水平面的雾滴分布差异性较大,雾滴分布的变异系数值范围在49.1%~227.6%之间变化;雾滴的分布数值结果在果树冠层从上至下逐步降低,雾滴分布的数值结果随着飞行速度的增加而降低,各雾滴测试指标的变化趋势相同;添加助剂后,各个试验处理以及冠层间的雾滴分布结果具有显著的提升。研究结果可为植保无人飞机应用于苹果果树的喷洒提供数据支持。 展开更多
关键词 雾滴沉积分布 植保无人飞机 飞行速度 喷雾助剂
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1979-2020年西北地区地表风速的年代际变化特征
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作者 王勇 周子涵 +3 位作者 王澄海 肖栋 秦豪君 黄武斌 《高原气象》 CSCD 北大核心 2024年第6期1380-1396,共17页
基于1979-2020年西北地区173个气象站点10 m风速观测资料和ERA-5再分析资料,揭示了西北地区年、各季节风速的年代际变化特征及2003/2004年年代际变化可能的环流背景。结果表明:1979-2020年趋势分布存在显著的区域差异,风速增大区域主要... 基于1979-2020年西北地区173个气象站点10 m风速观测资料和ERA-5再分析资料,揭示了西北地区年、各季节风速的年代际变化特征及2003/2004年年代际变化可能的环流背景。结果表明:1979-2020年趋势分布存在显著的区域差异,风速增大区域主要位于甘肃中部和东部、陕西、新疆西南和东北部分地区,其余站点风速大体减小。呈现减小趋势的站点数明显多于增加趋势的站点数,呈现减小趋势站点平均地表风速大于整个西北平均的风速值,呈现增加趋势的站点的平均地表风速小于整个西北平均的风速值,并且在2004年后明显增大。年平均和各季节第一模态的空间分布与1979-2020年趋势分布相似,时间序列的年代际变化发生在2000年前后。年平均和各季节第二模态除宁夏和陕西南部地区为负异常,其余站点大体均为正异常,其时间序列均发生了两次突变,分别发生在1987/1988年和2003/2004年。1987/1988年的西北地区风速变化成因已有大量研究,本研究重点分析了2003/2004年西北风速年代际变化成因的环流因子。从500 hPa位势高度2004-2020年与1988-2003年的合成差图可知,春季环流场呈现中亚-北欧的经向偶极子模态,夏季和秋季呈现为“丝绸之路”模态,冬季呈现“斯堪的纳维亚”模态,年平均呈现为北极涛动负位相。可见,2003/2004年前后四季和年平均环流背景变化都各有特点,它们如何影响中国西北地表风速2003/2004年的年代际变化的物理过程待于进一步深入研究。 展开更多
关键词 地表风速 时空分布 年代际变化 西北地区 趋势
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基于Dinkelbach-Quadratic算法的高速铁路通信能效优化功率分配研究
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作者 高云波 李翠然 +1 位作者 王国荣 李茂青 《铁道学报》 EI CAS CSCD 北大核心 2024年第9期69-75,共7页
为了提高高速铁路通信能量效率,提出一种基于Dinkelbach-Quadratic变换的迭代算法来解决高速铁路通信下行链路的功率分配问题。通过在小区内部署远程天线单元构建高速铁路通信分布式天线系统模型,基于完美信道状态信息(CSI)和列车内接... 为了提高高速铁路通信能量效率,提出一种基于Dinkelbach-Quadratic变换的迭代算法来解决高速铁路通信下行链路的功率分配问题。通过在小区内部署远程天线单元构建高速铁路通信分布式天线系统模型,基于完美信道状态信息(CSI)和列车内接入点反馈的最小速率要求建立能效优化模型;基于所建立的非凸优化模型,采用Dinkelbach变换将分数形式的非线性规划问题转换为求差形式;利用Quadratic变换特性对目标函数进一步展开;采用交替迭代的方法完成能效最优的功率分配。仿真结果表明:所提算法在满足最小传输速率和最大发射功率的同时,可以兼顾系统能量效率和频谱效率;随着发射天线数量和接收中继数量的增加,系统性能也有明显提升,相比传统算法系统的能效和频谱效率至少提升5%。 展开更多
关键词 高速铁路 分布式天线系统 功率分配 能量效率 分式规划
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考虑车流速度分布扰动的干道绿波最大带宽协调控制
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作者 徐建闽 刘鹏 +2 位作者 首艳芳 林永杰 卢凯 《重庆交通大学学报(自然科学版)》 CAS CSCD 北大核心 2024年第3期64-72,共9页
城市车辆速度受多种因素影响呈现某种分布,鲁棒的干道协调控制模型应考虑不同速度下的车辆带宽需求。针对速度波动变化干道传统协调控制方法适用性差的问题,分析了带干扰的干道车辆速度时空分布特征,以推荐速度带宽最大与期望带宽最大... 城市车辆速度受多种因素影响呈现某种分布,鲁棒的干道协调控制模型应考虑不同速度下的车辆带宽需求。针对速度波动变化干道传统协调控制方法适用性差的问题,分析了带干扰的干道车辆速度时空分布特征,以推荐速度带宽最大与期望带宽最大为目标,提出了考虑车流速度分布扰动的干道绿波最大带宽协调控制方法。针对佛山市同济路4交叉口干道,速度分布扰动干道协调方法能够提供更符合车辆分布特性的协调方案,比Maxband模型和改进的Maxband模型提升约70%和14%的期望带宽。研究结果表明:笔者方法能够降低Maxband模型平均停车次数25%,平均延误45%和平均排队长度17%;针对不同速度期望和方差情况下的灵敏度分析实验表明,该方法能够为干道提供更具有鲁棒性的干道协调控制方案。 展开更多
关键词 交通运输工程 智能交通 速度分布区间 最大带宽协调模型 期望带宽
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煤巷掘进过程中煤岩破裂微震事件研究
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作者 雷东记 刘宁 +2 位作者 王登科 刘丽英 贾子强 《河南理工大学学报(自然科学版)》 CAS 北大核心 2024年第1期25-34,共10页
目的为了监测和预警煤矿掘进巷道前方可能发生的危险,方法利用微震监测技术实时监测,利用监测系统捕获到的数据信息研究掘进影响下微震事件的空间分布规律、发生时间、频次和能量关键点,然后利用短时傅里叶变换和S变换方法分析典型煤岩... 目的为了监测和预警煤矿掘进巷道前方可能发生的危险,方法利用微震监测技术实时监测,利用监测系统捕获到的数据信息研究掘进影响下微震事件的空间分布规律、发生时间、频次和能量关键点,然后利用短时傅里叶变换和S变换方法分析典型煤岩破裂微震信号的时频特征。结果结果表明:(1)微震事件主要分布在沿掘进巷道前方50~100 m区域,大多为中低能量微震事件,仅在掘进工作面前方出现少量强度较大的煤岩破裂事件,且震级多为-2~0;(2)掘进速度和发生微震事件的数量及能量大小成正相关,同时掘进速度也影响着煤岩动力灾害的发生;(3)巷道掘进会造成煤岩体失稳,其中岩体破裂信号频率高,为0~2000 Hz,比重值大,主频约700 Hz;煤岩破裂微震事件信号频率为90~1000 Hz,主频约250 Hz;岩体破裂后,支撑力下降,压力转移给煤体,导致煤体破裂,煤体破裂微震事件信号频率为90~1000 Hz,主频约350 Hz。结论微震事件能够综合反映煤岩体受力破坏程度,判别掘进过程中煤岩破裂类型,为矿井生产中煤岩动力灾害的预警提供理论基础。 展开更多
关键词 煤巷 微震监测 空间分布规律 关键点 时频特征 掘进速度 煤岩破裂
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一种声速识别空气成分波动的自监督学习方法
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作者 滕旭东 滕博欣 《应用声学》 CSCD 北大核心 2024年第6期1360-1365,共6页
实际空气成分比较复杂,其声速的大小与标准空气的计算值有较大差异。文中根据维里展开式推导的声速方程,分析实际空气成分的浓度微量波动与声速变化定量关系。基于理论计算值,对比声速实测值,提出一种基于声速差值的自监督学习方法分析... 实际空气成分比较复杂,其声速的大小与标准空气的计算值有较大差异。文中根据维里展开式推导的声速方程,分析实际空气成分的浓度微量波动与声速变化定量关系。基于理论计算值,对比声速实测值,提出一种基于声速差值的自监督学习方法分析空气成分波动。该方法首先计算各个时刻声速差值的分布距离,接着确定分布最聚集区域,进行统计声速差发生比例,最后利用概率分布变化来发现空气成分,尤其微量成分的波动。实测结果表明:声速差发生概率曲线较好地反映空气成分浓度变化的起始、扩散和累积等阶段,通过发生概率P值分布能够对空气成分波动状态进行识别和实时监控。 展开更多
关键词 声速 维里展开式 成分波动 概率分布
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基于短期观测记录的重现期风速预测
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作者 田玉基 刘文珽 +2 位作者 李波 周长东 陈伟湖 《建筑结构》 北大核心 2024年第2期106-109,151,共5页
在偏僻地区或山区建设重要建筑物、构筑物或桥梁时,通常在附近安装风速观测仪器,获得至少1年的短期风速记录。提出了根据短期风速记录预测指定重现期风速极值及风压方法,为结构抗风设计提供了科学依据。提出独立风暴法提取短期风速记录... 在偏僻地区或山区建设重要建筑物、构筑物或桥梁时,通常在附近安装风速观测仪器,获得至少1年的短期风速记录。提出了根据短期风速记录预测指定重现期风速极值及风压方法,为结构抗风设计提供了科学依据。提出独立风暴法提取短期风速记录的最大值,建立极值I型概率分布模型,采用最好线性无偏估计方法确定概率分布参数。依据短期风速最大值概率与年风速最大值概率的变换关系,建立年发生最大值的概率分布及重现期风速、风压的表达式。算例结果表明,重现期风速预测值的离散性与风速阈值有关,在预测值离散系数较小的情况下可确定重现期风速及其置信区间。 展开更多
关键词 短期风速记录 极值I型分布 最好线性无偏估计 风速极值
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