公交车停靠诱发交通瓶颈的元胞自动机模拟

利用双车道元胞自动机模型,研究公交车停靠对道路混合交通流的影响.针对港湾式和非港湾式两种不同公交车站设置,在开放边界下模拟了公交车停靠所产生的交通瓶颈问题,给出了车辆入流概率-公交车比例相平面上的相图,区分了自由流相和拥挤相,研究了相图各区中公交车站附近的平均密度和速度分布图,比较了两种公交车站情况下的道路交通流的动力学特征.研究发现,当公交车比例较小时,与非港湾式车站相比,港湾式车站可以显著改善车站处的交通状况. 关键词： 元胞自动机 混合交通流 交通瓶颈 公交车站     

公交车站对交通流影响模拟分析

采用元胞自动机模型对城市道路中公交车站影响下的交通流特性进行模拟分析.研究了非港湾式车站和港湾式车站两种设置方式下交通流特性,对公交车比例和公交车站长度的影响进行了分析.模拟结果显示非港湾式车站对交通流的影响较大,通过增加车站长度并不能有效地提高系统流量;港湾式车站对交通流的影响较小,通过增加车站长度可以较大程度地增加系统流量. 关键词： 公交车站 混合交通流 元胞自动机     

Phonological systems in bilinguals: age of learning effects on the stop consonant systems of Korean-English bilinguals

Interaction of Korean and English stop systems in Korean-English bilinguals as a function of age of acquisition (AOA) of English was investigated. It was hypothesized that early bilinguals (mean AOA=3.8 years) would more likely be native-like in production of English and Korean stops and maintain greater independence between Korean and English stop systems than late bilinguals (mean AOA=21.4 years). Production of Korean and English stops was analyzed in terms of three acoustic-phonetic properties: voice-onset time, amplitude difference between the first two harmonics, and fundamental frequency. Late bilinguals were different from English monolinguals for English voiceless and voiced stops in all three properties. As for Korean stops, late bilinguals were different from Korean monolinguals for fortis stops in voice-onset time. Early bilinguals were not different from the monolinguals of either language. Considering the independence of the two stop systems, late bilinguals seem to have merged English voiceless and Korean aspirated stops and produced English voiced stops with similarities to both Korean fortis and lenis stops, whereas early bilinguals produced five distinct stop types. Thus, the early bilinguals seem to have two independent stop systems, whereas the late bilinguals likely have a merged Korean-English system.     

A study on the effects of the transit parking time on traffic flow based on cellular automata theory

This paper mainly deals with the effects of transit stops on vehicle speeds and conversion lane numbers in a mixed traffic lane.Based on thorough research of traffic flow and cellular automata theory,it calibrates the cellular length and the running speed.Also,a cellular automata model for mixed traffic flow on a two-lane system under a periodic boundary condition is presented herewith,which also takes into consideration the harbour-shaped transit stop as well.By means of computer simulation,the article also studies the effects of bus parking time on the traffic volume,the transit speed and the fast lane speed at the same time.The results demonstrate that,with the increase of the bus parking time,the traffic volume of the transit stop and the transit speed decrease while the fast lane speed increases.This result could help calculate the transit delay correctly and make arrangements for transit routes reasonably and scientifically.     

基于复杂网络理论的北京公交网络拓扑性质分析

为分析公交复杂网络的拓扑性质, 本文以北京市为例, 选取截止到2010年7月的北京全市(14区、2县)的1165条公交线路和9618个公交站点为样本数据, 运用复杂网络理论构建起基于邻接站点的有向加权复杂网络模型. 该方法以公交站点作为节点, 相邻站点之间的公交线路作为边, 使得网络既具有复杂网络的拓扑性质同时节点(站点)又具有明确的地理坐标. 对网络中节点度、点强度、强度分布、平均最短路径、聚类系数等性质的分析显示, 公交复杂网络的度和点强度分布极为不均, 网络中前5%和前10%节点的累计强度分布分别达到22.43%和43.02%; 点强度与排列序数、累积强度分布都服从幂律分布, 具有无标度和小世界的网络特点, 少数关键节点在网络中发挥着重要的连接作用. 为分析复杂网络中的关键节点, 本文通过承载压力分析和基于"掠夺" 的区域中心节点提取两种方法, 得到了公交复杂网络中两类不同表现的关键节点. 这些规律也为优化城市公交网络及交通规划发展提供了新的参考建议.     

Analysis of the influence of occupation rate of public transit vehicles on mixing traffic flow in a two-lane system

Based on the existing classical cellular automaton model of traffic flow, a cellular automaton traffic model with different-maximum-speed vehicles mixed on a single lane is proposed, in which public transit and harbour-shaped bus stops are taken into consideration. Parameters such as length of cellular automaton, operation speed and random slow mechanism are re-demarcated. A harbour-shaped bus stop is set up and the vehicle changing lane regulation is changed. Through computer simulation, the influence of occupation rate of public transit vehicles on mixed traffic flow and traffic capacity is analysed. The results show that a public transport system can ease urban traffic congestion but creates new jams at the same time, and that the influence of occupation rate of public transit vehicles on traffic capacity is considerable. To develop urban traffic, attention should be paid to the occupation rate of public transit vehicles and traffic development in a haphazard way should be strictly avoided.     

The capacity drop caused by the combined effect of the intersection and the bus stop in a CA model

The aim of this work is to investigate the combined effect of the signalized intersection and its near-by bus stop, by using a two-lane CA model. Four cases that the stop locates upstream or downstream the intersection, and ones with the special stop lane or not are considered. The effect of the distance L_D between the stop and the intersection on the capacity is studied, with respect to the traffic light cycle T and the bus dwell time T_s. It is found that acting as a bottleneck, the bus stop near the intersection causes the drop of the capacity. The negative effect only appears below a critical point L_Dc, which is related to the T and the T_s in no stop lane cases. The larger T and T_s have the tendency to create the higher loss of the capacity. While for stop lane cases, the critical value L_Dc changes little. Comparisons among four cases suggest that the special stop lane can effectively enhance the capacity, and the downstream stops perform better than the upstream ones at small L_D or small T or large T_s. The results imply that the capacity can be maximized by adjusting both the position of the bus stop and the cycle time, or adding a special stop lane. These findings may be useful to offer scientific guidance for the management and the design of traffic networks.     

Analysis of robustness of urban bus network

In this paper,the invulnerability and cascade failures are discussed for the urban bus network.Firstly,three static models(bus stop network,bus transfer network,and bus line network) are used to analyse the structure and invulnerability of urban bus network in order to understand the features of bus network comprehensively.Secondly,a new way is proposed to study the invulnerability of urban bus network by modelling two layered networks,i.e.,the bus stop-line network and the bus line-transfer network and then the interactions between different models are analysed.Finally,by modelling a new layered network which can reflect the dynamic passenger flows,the cascade failures are discussed.Then a new load redistribution method is proposed to study the robustness of dynamic traffic.In this paper,the bus network of Shenyang City which is one of the biggest cities in China,is taken as a simulation example.In addition,some suggestions are given to improve the urban bus network and provide emergency strategies when traffic congestion occurs according to the numerical simulation results.     

考虑公交港湾式停靠的多速混合城市交通流元胞自动机模型研究

在Nagel-Schreckenberg提出的元胞自动机模型基础上,建立了考虑公交车辆和港湾式公交停靠站的多速混合车辆单车道城市交通流元胞自动机模型.通过计算机模拟,给出了随机减速概率、混合车流密度、公交车辆平均停靠时间、公交车辆占有率和港湾式公交车站间距对混合车流速度和流量的影响图.对混合车流的特性进行了分析和讨论. 关键词： 元胞自动机 港湾式公交停靠站 混合交通流模型 计算机模拟     

Combined bottleneck effect of on-ramp and bus stop in a cellular automaton model

The combined bottleneck effect is investigated by modeling traffic systems with an on-ramp and a nearby bus stop in a two-lane cellular automaton model. Two cases, i.e. the bus stop locates in the downstream section of the on-ramp and the bus stop locates in the upstream section of the on-ramp, are considered separately. The upstream flux and downstream flux of the main road, as well as the on-ramp flux are analysed in detail, with respect to the entering probabilities and the distance between the on-ramp and the bus stop. It is found that the combination of the two bottlenecks causes the capacity to drop off, because the vehicles entering the main road from the on-ramp would interweave with the stopping (pulling-out) buses in the downstream (upstream) case. The traffic conflict in the former case is much heavier than that in the latter, causing the downstream main road to be utilized inefficiently. This suggests that the bus stop should be set in the upstream section of the on-ramp to enhance the capacity. The fluxes both on the main road and on the on-ramp vary with the distance between the two bottlenecks in both cases. However, the effects of distance disappear gradually at large distances. These findings might give some guidance to traffic optimization and management.     

Traffic Congestion Mechanism in Two Ramp Systems

The aim of this paper is to study traffic properties in an on/off-ramp system with a bus stop close to the on/off ramp. The location of the bus stop in the on/off-ramp (thereafter downstream or upstream case) is discussed. The simulation results show that in the two ramp systems, the reasons for traffic congestions are different. In the on-ramp system, buses and cars coming from on-ramp interweave each other, while in the off-ramp system, busesinterweave with cars exiting to off-ramp. Thus, in the on-ramp (off-ramp) system, the upstream (downstream) bus stop is helpful to reduce the interweaving situation. Moreover, the negative effect will disappear when the distance between the bus stop and the on/off-ramp is more than 20 cells (i.e. 150 m). These qualitative findings may provide some suggestions on traffic management and optimization.     

电站机组动态过程在线预测的一种实现方法

本文针对当前电站动态过程在线预测难以实现的主要原因—计算精度和速度之间的矛盾,提出了一种新的工程解决方法。该方法将整个计算分为两部分:离线生成结果网部分和在线预测部分。离线部分求解微分方程生成结果供在线部分使用,从而使在线部分避开了耗时的微分方程求解。该方法可应用于同类的动态过程的在线预测问题。     

Phase space description of vignetting in optical systems

A general theory of vignetting in real optical systems has been developed. Considered a beam of light rays limited by a field stop, an aperture stop inside of the real optical system (aberration vignetting) and a stop outside of it (natural vignetting). It is shown that each of these 2D-stops can be replaced by a virtual 4D-phase stop, and the result stop for 4D-phase result stops is their intersection. In case of an axially-symmetrical optical system with circular stop openings all phase stops are solids of revolution and can be fully characterized by their meridional cross sections in a 3D-space, which can be easily drawn.     

腭裂语音中齿龈塞音的声门代偿现象声学分析与判定

对齿龈塞音在腭裂语音中的声门塞音代偿现象进行了声学分析,计算频谱分布的多阶统计量—谱矩,并将代偿塞音和正常塞音进行对比。结果显示声门塞音爆破段的第一阶谱矩即频谱质心的频率位置比正常塞音低,因为声门塞音的阻塞部位在声门,导致声道腔体偏长从而共振频率偏低。还观察到声门塞音的第二阶谱矩即标准偏差偏高,说明其谱能量分布比正常塞音更加分散。声门塞音的第三阶谱矩即偏度大多为正值,反映了声门塞音功率谱的非对称性且大头朝向低频区而长尾朝向高频区。采用逻辑回归模型进行样本分类,通过交叉验证选出最优的四阶谱矩作为模型自变量,分类正确率为89.7%。结合塞音爆破时刻自动检测,实现了音节/di/的声门塞音客观判定。      

Analysis of stop consonant production errors in developmentally dysphasic children

The speech production skills of 12 dysphasic children and of 12 normal children were compared. The dysphasic children were found to have significantly greater difficulty than the normal children in producing stop consonants. In addition, it was found that seven of the dysphasic children, who had difficulty in perceiving initial stop consonants, had greater difficulty in producing stop consonants than the remaining five dysphasic children who showed no such perceptual difficulty. A detailed phonetic analysis indicated that the dysphasic children seldom omitted stops or substituted nonstop for stop consonants. Instead, their errors were predominantly of voicing or place of articulation. Acoustic analyses suggested that the voicing errors were related to lack of precise control over the timing of speech events, specifically, voice onset time for initial stops and vowel duration preceding final stops. The number of voicing errors on final stops, however, was greater than expected on the basis of lack of differentiation of vowel duration alone. They appeared also to be related to a tendency in the dysphasic children to produce final stops with exaggerated aspiration. The possible relationship of poor timing control in speech production in these children and auditory temporal processing deficits in speech perception is discussed.     

Influence of bus stop with left-turn lines between two adjacent signalized intersections

Based on the symmetric two-lane Nagel–Schreckenberg(STNS) model, a three-lane cellular automaton model between two intersections containing a bus stop with left-turning buses is established in which model the occurrences of vehicle accidents are taken into account. The characteristics of traffic flows with different ratios of left-turn lines are discussed via the simulation experiments. The results indicate that the left-turn lines have more negative effects on capacity,accident rate as well as delay if the stop is located close to the intersections, where the negative effect in a near-side stop is more severe than that in a far-side one. The range of appropriate position for a bus stop without the bottleneck effect becomes more and more narrow with the increase of the ratio of left-turn bus lines. When the inflow is small, a short signal cycle and a reasonable offset are beneficial. When the inflow reaches or exceeds the capacity, a longer signal cycle is helpful. But if the stop position is inappropriate, the increase of cycle fails in reducing the negative effect of left-turning buses and the effectiveness of offset is weakened.     

Laryngeal Gestures During Stop Production Using High-Speed Digital Images

On acoustic and fiberscopic studies of stop consonants, voice onset time and glottal width have been shown to be greatest in heavily aspirated stops, next greater for slightly aspirated stops, and least for unaspirated stops. Integrated activity of the thyroarytenoid and posterior cricoarytenoid muscles has been reported to be involved in differentiating aspirate characteristics of the stops. However, the fine movement of mucosal edges of vocal folds during the production of stops has not been well documented. In recent years, a new method for high-speed digital recording of laryngeal dynamics has made this possible. In the current study, the movements of vocal fold edges were documented during the period of stop production using a fiberscopic system of high-speed digital images. By observing the glottal width and the visual vibratory movements of vocal folds before voice onset, the heavily aspirated stop was characterized as being more prominent and dynamic than the slightly aspirated and unaspirated stops.     

Fundamental frequency correlates of stop consonant voicing and vowel quality in the speech of preadolescent children

Fundamental frequency (F0) and voice onset time (VOT) were measured in utterances containing voiceless aspirated [ph, th, kh], voiceless unaspirated [sp, st, sk], and voiced [b, d, g] stop consonants produced in the context of [i, e, u, o, a] by 8- to 9-year-old subjects. The results revealed that VOT reliably differentiated voiceless aspirated from voiceless unaspirated and voiced stops, whereas F0 significantly contrasted voiced with voiceless aspirated and unaspirated stops, except for the first glottal period, where voiceless unaspirated stops contrasted with the other two categories. Fundamental frequency consistently differentiated vowel height in alveolar and velar stop consonant environments only. In comparing the results of these children and of adults, it was observed that the acoustic correlates of stop consonant voicing and vowel quality were different not only in absolute values, but also in terms of variability. Further analyses suggested that children were more variable in production due to inconsistency in achieving specific targets. The findings also suggest that, of the acoustic correlates of the voicing feature, the primary distinction of VOT is strongly developed by 8-9 years of age, whereas the secondary distinction of F0 is still in an emerging state.     

Deep-BiGRU based channel estimation scheme for MIMO–FBMC systems

Deep Learning (DL)–based wireless communication systems have the potential to improve the conventional functions and current architecture of communication systems. In this paper, we propose a novel DL-based channel estimation scheme for multiple-input multiple-output filter bank multicarrier with offset quadrature amplitude modulation (MIMO-FBMC/OQAM) systems called deep bidirectional gated-recurrent unit (BiGRU) scheme. This scheme can easily be applied to a single-input single-output (SISO) system. The proposed scheme is divided into two stages: offline and online. The network is first trained in the offline stage. The prediction of channel information and estimation of the channel matrix using the trained network is then performed in the online stage. The simulation results in terms of the normalized mean square error (NMSE) and bit error rate (BER) demonstrate that, under different time-varying channel models, the proposed DL scheme significantly improves the channel estimation performance of FBMC for single and multiple antennas compared to conventional interference approximation method (IAM) channel estimation methods.     

Modified locus equations categorize stop place in a perceptually realistic time frame

Slope and y-intercepts of locus equations have previously been shown to successfully classify place of articulation for English voiced stop consonants when derived from measurements at vowel onset and vowel midpoint. However, listeners are capable of identifying English voiced stops when less than 30 ms of vowel is presented. The present results show that modified locus equation measurements made within the first several pitch periods of a vowel following an English voiced stop were also successful at classifying place of articulation, consistent with the amount of vocalic information necessary for perceptual identification of English voiced stops /b d g/.