Evaluating Traffic Congestion Using the Traffic Occupancy and Speed Distribution Relationship: An Application of Bayesian Dirichlet Process Mixtures of Generalized Linear Model

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.

The December 26, 2004, off the west coast of northern Sumatra, Indonesia, M_W=9.0, earthquake and the critical-point-like model of earthquake preparation

Long-term seismic activity prior to the December 26, 2004, off the west coast of northern Sumatra, Indonesia, MW=9.0 earthquake was investigated using the Harvard CMT catalogue. It is observed that before this great earth-quake, there exists an accelerating moment release (AMR) process with the temporal scale of a quarter century and the spatial scale of 1 500 km. Within this spatial range, the MW=9.0 event falls into the piece-wise power-law-like frequency-magnitude distribution. Therefore, in the perspective of the critical-point-like model of earthquake preparation, the failure to forecast/predict the approaching and/or the size of this earthquake is not due to the physically intrinsic unpredictability of earthquakes.

A hydrocarbon enrichment model and prediction of favorable accumulation areas in complicated superimposed basins in China

The geologic conditions of superimposed basins in China are very complicated. This is mainly shown by multi-phase structural evolution, multiple sets of source-reservoir-cap rock combinations, multiple stages of hydrocarbon generation and expulsion from source rocks, multi-cycle hydrocarbon enrichment and accumulation, and multi-phase reservoir adjustment and reconstruction. The enrichment, accumulation and distribution of hydrocarbon is mainly controlled by the source rock kitchen, paleo- anticline, regional cap rock and intensity of tectonic movement. In this paper, the T-BCMS model has been developed to predict favorable areas of hydrocarbon accumulation in complicated superimposed basins according to time and spatial relationships among five key factors. The five factors include unconformity surface representing tectonic balancing （B）, regional cap rock representing hydrocarbon protection （C）, paleo-anticline representing hydrocarbon migration and accumulation （M）, source rock kitchen representing hydrocarbon generation and expulsion （S） and geological time （T）. There are three necessary conditions to form favorable areas of hydrocarbon accumulation. First, four key factors BCMS should be strictly in the order of BCMS from top to bottom. Second, superimposition of four key factors BCMS in the same area is the most favorable for hydrocarbon accumulation. Third, vertically ordered combination and superimposition in the same area of BCMS should occur at the same geological time. The model has been used to predict the most favorable exploration areas in Ordovician in the Tarim Basin in the main hydrocarbon accumulation periods. The result shows that 95% of the discovered Ordovician hydrocarbon reservoirs are located in the predicted areas, which indicates the feasibility and reliability of the key factor matching T-BCMS model for hydrocarbon accumulation and enrichment.

Spatial and Temporal Distribution Characteristics of Agricultural Non-point Source Pollution in Xixi Watershed of Jinjiang Basin

The SWAT model was applied to analyze the temporal-spatial distribution patterns of non-point source pollution loads and the difference of pollution loads of different land use types in Xixi Watershed of Jinjiang Basin. The results showed that both yearly nitrogen and phosphorus pollution loads were evenly distributed during 1973 to 1979,the annual TN pollution from non-point source was 1530 t,or 6. 3 kg / ha,and the annual TP pollution from non-point source was 270 t,or 1. 1 kg / ha during 1973 to 1979 in the watershed. Considerable differences were identified on both monthly nitrogen and phosphorus pollution loads. The TN and TP pollution loads during the flood season( from April to September) accounted for 76. 2% and 75. 8% of the annual load respectively. There were great differences in both TN and TP pollution loads of different land use types in the study area,and the pollution load of both farmland and orchard was higher than that of the other land use types. TN and TP pollution loads of farmland accounted for 66% and 83% of total watershed. There was a great spatial difference in the nonpoint source pollution load of the study area. The critical source areas of non-point source pollution are mainly located at Guanqiao Town,Longmen Town,Changkeng Town,Shangqing Town and Dapu Town,where the efforts of controlling pollution should be made.

Interplay Between Scission-Point Model and Experimental Data for Sub-Barrier Fusion-Fission

The fragment angular distributions of fusion-fission reactions for the systemsof 16O+232Th,19F+232Th and 16O+238U at near-and sub-barrier energies were measured.The measured fragment anisotropies obviously deviate from the predictions ofscission-point transition-state model.We also compared the excitation energy of tiltingmode with the statistical assumption.It was found that thermal equilibrium is not estab-lished at scission for the reactions studied.

Convex decomposition of concave clouds for the ultra-short-term power prediction of distributed photovoltaic system

Concave clouds will cause miscalculation by the power prediction model based on cloud ieatures for distributed photovoltaic （PV） plant. The algorithm for decomposing concave cloud into convex images is proposed. Adopting minimum polygonal approximation （MPP） to demonstrate the contour of concave cloud, cloud features are described and the subdivision lines of convex decomposition for the concave clouds are determined by the centroid point scattering model and centroid angle func- tion, which realizes the convex decomposition of concave cloud. The result of MATLAB simulation indicates that the proposed algorithm can accurately detect cloud contour comers and recognize the concave points. The proposed decomposition algorithm has advantages of less time complexity and decomposition part numbers compared to traditional algorithms. So the established model can make the convex decomposition of complex concave clouds completely and quickly, which is available for the existing prediction algorithm for the ultra-short-term power output of distributed PV system based on the cloud features.

基于等效分布质点的发动机悬置系统试验建模

为获得发动机悬置系统的相关参数,将非刚性、小柔性弹性体的发动机近似为含有n个质点的分布质点系。首先,根据拉格朗日方程建立了发动机悬置系统6自由度(6 degrees of freedom,简称6DOF)振动微分方程,包括质量阵、刚度阵和阻尼阵;其次,基于等效分布质点系统,构建发动机悬置3n DOF系统;然后,针对3点支撑的发动机台架系统,利用地磅测得每一个悬置处支撑的静态质量,通过发动机悬置测试试验系统测得发动机的激励输入信号及响应信号;最后,利用递推最小二乘法辨识得到分布质点系统的阻尼矩阵和刚度矩阵,在Matlab/Simulink中建立发动机悬置系统的仿真模型,并通过测试值与仿真值的对比,证明了辨识的准确性。给出的发动机悬置等效分布质点3n DOF系统在工程实际中,为悬置系统设计悬置支撑参数反解、悬置参数系统辨识提供了理论基础与实现途径。

配电网间歇性重燃电弧模型的建立与断续弧光接地故障特征分析研究

电弧间歇性重燃是配电网单相接地故障最显著的特征。现有的电弧模型甚少考虑电弧间歇性重燃特性,导致无法精确描述断续弧光接地特征,进而影响继电保护动作。为此,论文提出一种间歇性重燃电弧模型的建立方法,并在此基础上对断续弧光接地故障特征进行了分析。弧道阻抗的随机变化是电弧间歇性重燃的重要标志,故论文重点围绕弧道阻抗变化的随机性和重燃时间间隔的随机性开展间歇性重燃电弧模型的研究。黑盒电弧模型中,Cassie-Mayr联合模型能完整的描述电弧电流从大电流到小电流的变化过程,但存在从大电流变化为小电流的判据模糊,转换过程突变的问题。为此,论文通过引入连续过渡函数解决上述问题。同时,为描述弧道电阻的变化特性,利用Fermi函数对联合模型中Mayr模型和Cassie模型进行权重分配。以改进的Cassie-Mayr单次燃弧模型为基础,根据工频熄弧理论,通过设置燃弧时间长短表征间歇性重燃的随机性,从而建立了间歇性重燃电弧模型。利用该模型,对典型10kV配电网单辐射型网架结构的接地故障进行模拟仿真,采用快速傅里叶变换(fast Fourier transform,FFT)和小波包分析提取了不同条件下故障电压、电流、高次谐波、零序分量以及频率分布等故障特征。研究结果表明:改进后Cassie-Mayr联合模型不但解决了电弧电流从大电流到小电流的转换突变问题,且不同模型权重占比的分配更能准确地表征实际燃弧弧道阻抗变化的随机性;通过设置电弧燃弧时间长短,准确地描述间歇性重燃的随机性;电弧断续时刻为非整数周期下的过电压、过电流幅值高于整数周期;电缆线路增大了故障线路电流,过电流可达3.81~7.20pu,不利于熄弧;大电流系统故障相零序电流主频在0~400Hz,小电流系统故障相零序电流主频在1200~1600Hz。

动态牵伸过程中浮游纤维变速点分布模拟

为研究牵伸条件的变化对牵伸过程的影响,通过建立动态牵伸模型,仿真浮游纤维在动态牵伸过程中受到摩擦力作用的加速过程,得到动态牵伸过程中浮游纤维变速点分布。纤维的牵伸过程被细化为后纤维、慢浮游纤维、快浮游纤维和前纤维4种纤维运动状态变化的过程。通过记录纤维在牵伸过程中速度和位置的变化,计算得到纤维保持每种状态的时间。模拟过程中,通过获取纤维在牵伸过程中速度和位置的变化,得到每根纤维在牵伸区内分别维持4种运动状态的时间,从而建立动态的牵伸模型。此外,通过确定浮游纤维与快速纤维和慢速纤维相互接触的长度,计算浮游纤维在动态牵伸过程中受到的控制力与引导力,模拟浮游纤维在动态牵伸过程中的加速过程。同时计算简单罗拉牵伸的摩擦力界分布,通过改变牵伸模型的牵伸倍数和纤维长度,模拟不同牵伸条件下浮游纤维变速点分布。结果表明:仿真得到的变速点分布近似于正态分布,与实际牵伸过程中变速点分布形态接近;牵伸倍数越大,纤维的长度越长,变速点分布越接近前罗拉,并且变速点分布范围越小。

光纤光栅传感器在遥感相机强振动环境监测系统的应用

为验证光纤光栅传感器在强振动环境下对遥感相机进行多点分布式测量的可行性及精度,实现光纤布拉格光栅(FBG)在空间遥感器振动传感领域的应用。首先对光学遥感相机构建有限元仿真模型,进行模态分析、振动响应分析。设计实施了系统级装机环境下光纤光栅传感器与相机不同部位、形式、材料的连接工艺,提出一种使用光纤光栅传感器对遥感相机进行单光纤多点分布测量的试验方法,开展正弦振动和随机振动试验。经光纤光栅传感器测量结果与标准压电式振动传感器测量结果的对比,正弦振动加速度响应测量的最大误差为3.25%,随机振动均方根加速度响应测量的最大误差为3.14%,测量值吻合良好,拟合精度均达到0.99;仿真分析结果与测量结果的拟合精度达到0.97,具有较好的一致性。可见,光纤光栅传感器在强振动环境下对相机进行多点分布式加速度测量的精度高、可行,满足系统监测要求,为光纤光栅传感在空间遥感器强振动响应的高精度测量应用提供借鉴。

大型水轮发电机定子绕组分布电容对位移电压影响分析

景洪电站发电机三相电势对称,且静态实测三相对地电容近似相等,在此条件下发电机正常运行时中性点仍有明显的位移电压,集中参数电路模型无法解释该现象,因此提出基于准分布电容参数模型的中性点位移电压分析方法。通过电路分析,得到定子绕组对地准分布电容与中性点位移电压的关系式,理论解释了分布电容不均匀会导致位移电压出现。采用兰州电机厂制造的12kW实验样机进行了实验验证,并针对准分布电容中偏大或偏小电容所在位置以及电容不均匀度对位移电压影响的实验结果进行了定量分析。针对由分布电容不均匀所带来的位移电压偏大的问题,提出在机端外挂电容的解决方案,理论求解外挂电容值,并通过仿真实验验证了方案的有效性。

Design of a Level-3 electric vehicle charging station using a 1-MW solar system via the distributed maximum power point tracking technique

Solar power is mostly influenced by solar irradiation,weather conditions,solar array mismatches and partial shading conditions.Therefore,before installing solar arrays,it is necessary to simulate and determine the possible power generated.Maximum power point tracking is needed in order to make sure that,at any time,the maximum power will be extracted from the photovoltaic system.However,maximum power point tracking is not a suitable solution for mismatches and partial shading conditions.To overcome the drawbacks of maximum power point tracking due to mismatches and shadows,distributed maximum power point tracking is util-ized in this paper.The solar farm can be distributed in different ways,including one DC-DC converter per group of modules or per module.In this paper,distributed maximum power point tracking per module is implemented,which has the highest efficiency.This technology is applied to electric vehicles(EVs)that can be charged with a Level 3 charging station in<1 hour.However,the problem is that charging an EV in<1 hour puts a lot of stress on the power grid,and there is not always enough peak power reserve in the existing power grid to charge EVs at that rate.Therefore,a Level 3(fast DC)EV charging station using a solar farm by implementing distributed maximum power point tracking is utilized to address this issue.Finally,the simulation result is reported using MATLAB®,LTSPICE and the System Advisor Model.Simulation results show that the proposed 1-MW solar system will provide 5 MWh of power each day,which is enough to fully charge~120 EVs each day.Additionally,the use of the proposed photovoltaic system benefits the environment by removing a huge amount of greenhouse gases and hazardous pollutants.For example,instead of supplying EVs with power from coal-fired power plants,1989 pounds of CO_(2) will be eliminated from the air per hour.

Ruin Probability and Joint Distributions of Some Actuarial Random Vectors in the Compound Pascal Model

The compound negative binomial model, introduced in this paper, is a discrete time version. We discuss the Markov properties of the surplus process, and study the ruin probability and the joint distributions of actuarial random vectors in this model. By the strong Markov property and the mass function of a defective renewal sequence, we obtain the explicit expressions of the ruin probability, the finite-horizon ruin probability, the joint distributions of T, U（T - 1）, ｜U（T）｜ and inf U（n） （i.e., the time of ruin, the surplus immediately before ruin, the deficit at ruin and maximal deficit from ruin to recovery） and the distributions of some actuarial random vectors.

空间飞行器的指向误差混合分布模型

在空间探测任务中,飞行器会受到机械冲击、跟踪噪声等因素的影响发生角微振动,使天线指向误差恒不为0,从而影响通信链路.针对典型的指向误差单一分布模型如高斯分布、瑞利分布和莱斯分布忽略多种误差源共同影响的缺点,提出指向误差混合分布模型,将多种误差源同时考虑在内,极大地提高了模型的准确性.首先,根据多个空间飞行器奥林巴斯通信卫星OLYMPUS、工程测试卫星ETS-VI、光学轨道间通信工程试验卫星OICETS和量子科学实验卫星MICIUS角微振动信号的功率谱密度拟合指向误差信号.然后,对比单一分布模型和混合分布模型与指向误差拟合信号的确定系数R^(2),确定最优分布模型.结果表明:由高斯分布和莱斯分布组成的混合分布模型拟合度最高.以OLYMPUS飞行器为例,高斯-莱斯混合分布模型的拟合度比单一分布模型中的瑞利模型提高27.44%,误比特率偏差降低2.87 dB.

基于改进型混沌遗传算法的分布式光伏储能输出最大功率点追踪方法

针对当前分布式光伏储能输出最大功率点追踪过程受多峰特性影响而导致追踪效果不佳的情况,提出了基于改进型混沌遗传算法的分布式光伏储能输出最大功率点追踪方法。该方法首先通过构建光伏储能电池等效模型及分析光伏储能电池特性基础上,将时间、光照强度和环境温度作为输入,建立基于径向基函数(Radial Basis Function,RBF)神经网络的分布式光伏储能最大功率点追踪模型。其次,在遗传算法中引入混沌因子,形成改进型混沌遗传算法。经过参数设置、种群初始化、添加混沌因子以及交叉和变异等操作后,利用该算法求解基于RBF神经网络的分布式光伏储能最大功率点追踪模型。最后,利用该模型输出分布式光伏储能输出最大功率点追踪结果。实验结果表明:该方法追踪分布式光伏储能输出最大功率点时,具备较好的收敛性和逼近性;可在不同环境温度和光照强度情况下,有效追踪布式光伏储能输出最大功率点,应用效果较为显著。

基于图模型的配电系统抢修预案综合研判方法

针对故障定位基础数据存在异常值,导致故障研判定位时间较长、准确率较低的问题,提出基于图模型的配电系统抢修预案综合研判方法。利用统计量,检验抢修数据正常样本和实测样本的差异程度,聚类样本数据为多个簇,将与聚类中心差异最大的数据作为异常值,过滤后得到修正数据集,根据跳闸开关等数据,综合研判配电系统故障类别,计算不同类别开关量信息,将信息存在变化的区间视为故障区域,根据区域内设备电流信息熵值,定位故障点,标记在故障传播图模型上,直观展示抢修预案综合研判结果。以某地区实际配电系统抢修预案为例,进行实例测试,其预案包括主线停运、支线停运、台区停运、单户停运故障类别,测试结果表明,该方法缩短了故障研判定位时间,提高了故障研判定位准确率,配电系统抢修预案反馈更加及时可靠。

基于高斯分布和多元正态分布结合模型的点云异常点检测与去噪方法研究

针对异常点检测在点云采集中,由于复杂数据分布导致去噪准确率和效率下降的问题,文章提出了一种结合高斯分布模型和多元正态分布模型的异常点检测方法。实验结果表明,该方法能够快速有效地去除大量外部噪声,并且去噪后的点云数据较好地保留了原始点云特征。

重庆万盛雷电活动特征研究

利用重庆万盛国家气象观测站1978~2012年人工观测的雷暴资料和重庆市闪电监测网2008~2020年系统监测的万盛闪电定位资料,采用线性回归趋势方程、气候倾向率、Mann-Kendall突变检验、Morlet小波分析等方法对雷暴日和雷电日进行统计和差异性分析,得到万盛的雷电活动时间分布特征。

非点源模型中的水文模拟——以SWAT模型在芦溪小流域的应用为例

结合分散参数非点源模型SWAT在芦溪小流域的应用,讨论了连续模拟非点源模型水文模块的计算结果。由讨论结果来看,SWAT能够有效地模拟长时间序列的水文过程。一般来说,长期径流量模拟准确,短期径流量的结果较差,尤其是对日径流量的模拟存在着系统性的误差,这主要是由模型的内部结构和数据的时间精度决定的。

四川盆地中部下二叠统茅口组岩溶储集层地震预测

基于近年来新的测井和地震资料,综合利用地球物理技术对四川盆地中部(川中地区)下二叠统茅口组岩溶储集层开展研究。定量岩石物理建模和分析表明,随着孔隙度、泥质含量以及含气饱和度的增加,岩溶储集层的纵、横波速度和密度均呈减小的趋势。基于岩石物理模型的地震正演分析结果证实,川中地区岩溶储集层在茅口组顶面具有弱振幅、低频率的"暗点"地震反射特征。通过地震属性和波阻抗反演预测了4个规模有利岩溶储集层发育带。综合评价认为川中地区茅口组岩溶储集层具备形成上倾岩性尖灭型岩性气藏的成藏条件,预测射洪西部和盐亭地区为川中地区最为有利的勘探区带。