图的闭通路覆盖数

本文研究了图的闭通路覆盖数的一些性质,获得了一些有意义的结果。提出了树的4-闭通路覆盖数的多项式时间算法。

非石英光纤放大器为WDM开辟新的波长区域

为增加DWDM的通路数，需要更宽的带宽窗口。新的掺稀土元素的和非石英光纤在这方面有着令人鼓舞的特性。

衡量网络可靠性的新模型

本文分析了传统的网络可靠性优化设计方法所存在的问题 ,给出了网络的通信通路数的定义 ,并基于网络的通信通路数给出了更能反映网络运行的实际情况的网络可靠性的定量模型 ,从而解决了传统网络可靠性优化设计方法所存在的问题 .

A New Macro Model for Traffic Flow on a Highway with Ramps and Numerical Tests

In this paper, we present a new macro model for traffic flow on a highway with ramps based on the existing models. We use the new model to study the effects of on-off-ramp on the main road traffic during the morning rush period and the evening rush period. Numerical tests show that, during the two rush periods, these effects are often different and related to the status of the main road traffic. If the main road traffic flow is uniform, then ramps always produce stop-and-go traffic when the main road density is between two critical values, and ramps have little effect on the main road traffic when the main road density is less than the smaller critical value or greater than the larger critical value. If a small perturbation appears on the main road, ramp may lead to stop-and-go traffic, or relieve or even eliminate the stop-and-go traffic, under different circumstances. These results are consistent with real traffic, which shows that the new model is reasonable.

Travel time prediction model of freeway based on gradient boosting decision tree

To investigate the travel time prediction method of the freeway, a model based on the gradient boosting decision tree (GBDT) is proposed. Eleven variables (namely, travel time in current period T i , traffic flow in current period Q i , speed in current period V i , density in current period K i , the number of vehicles in current period N i , occupancy in current period R i , traffic state parameter in current period X i , travel time in previous time period T i -1 , etc.) are selected to predict the travel time for 10 min ahead in the proposed model. Data obtained from VISSIM simulation is used to train and test the model. The results demonstrate that the prediction error of the GBDT model is smaller than those of the back propagation (BP) neural network model and the support vector machine (SVM) model. Travel time in current period T i is the most important variable among all variables in the GBDT model. The GBDT model can produce more accurate prediction results and mine the hidden nonlinear relationships deeply between variables and the predicted travel time.

A GA approach to vehicle routing problem with time windows considering loading constraints

As a new variant of vehicle routing problem( VRP),a finished vehicle routing problem with time windows in finished vehicle logistics( FVRPTW) is modeled and solved. An optimization model for FVRPTW is presented with the objective of scheduling multiple transport routes considering loading constraints along with time penalty function to minimize the total cost. Then a genetic algorithm( GA) is developed. The specific encoding and genetic operators for FVRPTW are devised.Especially,in order to accelerate its convergence,an improved termination condition is given. Finally,a case study is used to evaluate the effectiveness of the proposed algorithm and a series of experiments are conducted over a set of finished vehicle routing problems. The results demonstrate that the proposed approach has superior performance and satisfies users in practice. Contributions of the study are the modeling and solving of a complex FVRPTW in logistics industry.

SDCMA BLIND DETECTION IN FREQUENCY DOMAIN FOR MC DS-CDMA SYSTEMS

This paper proposes Steepest Decreasing Constant Modulus Algorithm （SDCMA） detection in frequency dornain for MultiCarrier Direct Sequence-Code Division Multiple Access （MC DS-CDMA） systems. The proposed algorithm is used to equalize independent ladings of all subcarriers. At the same time we compare the SDCMA blind detection with subspace-based Minimum Mean-Squared Error （MMSE） detection. The simulation results show that the pertbrmance of SDCMA blind detection is superior to that of subspace-based MMSE detection and the complexity of the former is much lower than that of the latter.

Vehicle emissions calculation for urban roads based on the Macroscopic Fundamental Diagram method and real-time traffic information

Vehicle emissions calculation methods mostly use ownership information or annual road monitoring data as the activity level to calculate air pollutant emissions,but it is hard to reflect either the emissions intensity under different conditions or the spatiotemporal characteristics in various sections based on such approaches.This paper presents a method based on the Macroscopic Fundamental Diagram and real-time traffic data to calculate vehicle emissions,which could reflect the operation conditions and emission characteristics of vehicles.Following the‘Technical Guide for the Compiling of Road Vehicle Air Pollutant Emissions Inventories’,the emissions of three roads with different lane numbers and road grades in Beijing were estimated and verified using this method.Compared with monitoring data,the average deviations of the traffic flow on the Fifth Expressway,Jingfu National Highway,and Jingzhou Provincial Highway were?25.5%,?26.5%,and?13.4%,respectively,and the average deviations of nitrogen oxides emissions were?27.7%,?12.9%,and?12%,respectively.This method showed good application potentials to construct the emissions inventory applied to the block-scale model and analyze the spatiotemporal distribution characteristics of motor vehicle emissions in urban areas.

Energy-Aware Traffic Routing with Named Data Networking

Greening Internet is an important issue now, which studies the way to reduce the increas- ing energy expenditure. Our work focuses on the network infrastructure and considers its energy awareness in traffic routing. We formulate the model by traffic engineering to achieve link rate a- daption, and also predict traffic matrices to pre- serve network stability. However, we realize that there is a tradeoff between network performance and energy efficiency, which is an obvious issue as Internet grows larger and larger. An essential cause is the huge traffic, and thus we try to fred its so- lution from a novel architecture called Named Data Networking （NDN） which tent in edge routers and can flexibly cache con- decrease the backbone traffic. We combine our methods with NDN, and finally improve both the network performance and the energy efficiency. Our work shows that it is effective, necessary and feasible to consider green- ing idea in the design of future Internet.

OFDM-based Low-voltage Powerline High Rate Communication

Based on the experimental results, a simplified model for low-voltage powerline used as a high frequency communication channel is presented. With this model, the Orthogonal Frequency Division Multiplexing (OFDM) based high rate digital communication over low-voltage powerline is analyzed and simulated. The capability of the signal transmission system in overcoming multi-path interference and selection of the system parameters are discussed. And time-domain simulation is carried out to investigate the transmission capability of the OFDM communication system for different mapping schemes and transmission power levels. Simulation results show that it is possible to realize high rate digital communication over low-voltage powerline using OFDM when the transmitted power is large enough.

Radio Channel Measurements and Analysis at 2.4/5GHz in Subway Tunnels

There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment services(e.g.,Internet,etc.) to passengers as well.The wireless channel in tunnels is quite unique due to the confined space and the waveguide effects.Therefore,modeling the radio channel characteristics in tunnels is critically important for communication systems design or optimization.This paper investigates the key radio channel characteristics of a subway tunnel at 2.4 GHz and 5 GHz,such as the path loss,root mean square(RMS) delay spread,channel stationarity,Doppler shift,and channel capacity.The field measurements show that channel characteristics in tunnels are highly location-dependent and there exist abundant components in Doppler shift domain.In the straight section of the subway tunnel,the measured path loss exponents are close to1.6,lower than that in free space.

Macro modeling and analysis of traffic flow with road width

The macro modeling and the solution of traffic flow with road width were investigated.Firstly,a new macro model with the consideration of road width was proposed.Secondly,the effects of road width on uniform flow and small perturbation were studied.The analytical and numerical results show that widening (shrinking) road can enhance (reduce) the equilibrium speed and flow,and the increments (decrements) will increase with the absolute value of road width gradient.In addition,the numerical results illustrate that the new model can describe the effects of road width on the evolutions of uniform flow and small perturbation.

Investigating the factors affecting traffic violations based on electronic enforcement data:A case study in Shangyu,China

To study the influencing factors of traffic violations,this study investigated the effects of vehicle attribution,day of week,time of day,location of traffic violations,and weather on traffic violations based on the electronic enforcement data and historical weather data obtained in Shangyu,China.Ten categories of traffic violations were determined from the raw data.Then,chi-square tests were used to analyze the relationship between traffic violations and the potential risk factors.Multinomial logistic regression analyses were conducted to further estimate the effects of different risk factors on the likelihood of the occurrence of traffic violations.By analyzing the results of chi-square tests via SPSS,the five factors above were all determined as significant factors associated with traffic violations.The results of the multinomial logistic regression revealed the significant effects of the five factors on the likelihood of the occurrence of corresponding traffic violations.The conclusions are of great significance for the development of effective traffic intervention measures to reduce traffic violations and the improvement of road traffic safety.

Statistical Multiplexing of Video Traffic and Data Traffic

This paper studies statistical multiplexing performance by input of video traffic and data traffic. The inputs have different Qos requirements such as loss and delay jitter. By applying a modified FBM model, we present methods to estimate effective bandwidth of the aggregated traffic. Simulations were performed to evaluate effective bandwidth. The comparison between the estimation and the simulation shows that the estimations can give correct data for the effective bandwidths in terms of our interests. The analysis of gain by using priority multiplexing also addresses proper Qos configuration for the inputs in order to achieve positive gains.

A Sample of Semi-Actuated Traffic Control versus Fixed-Time Traffic Control

Fixed-time control of traffic signals pursues the regulation of phases based on historical data of traffic demand, in this way, neglecting of the random arrival rates of traffic flow on different intersection streams causes increasing of the stops and delays and fuel consumption at the same time. Coordinated semi-actuated control due to ability to respond traffic demands on both main and secondary directions, based on road detector registration saves the coordinated features, serving the unused time to the main road, while the secondary clears early. In this paper, the authors analyzed and explained comparatively the results of LOS （level of service） parameters of the current state of control （fixed-time） with the proposed control （semi-actuated coordinated） of the artery of length 2,348 km consisted of four signalized T intersections. Highway Capacity Manual and Synchro/Sim Traffic software are used for analysis and optimization of parameters in this paper.

Civic Engagement, Fake News and the Path Forward

Media literacy and understanding the digital information around us are an area of communication that affects all of us. How people are represented in the media, social media and our civic participation affect our representations and understanding of the truth. The author would argue through research and practical examples that civic engagement and associations with a peer group can counteract some of the issues facing digital media today. In an age of the so-called ＂fake news,＂ there are tools we can provide for our teams, our employees, and our collaborators to make sure we are all on the same page and dealing with the same set of verifiable facts

Ship Waste Management in the Port of Igoumenitsa, Greece

Port of Igoumenitsa in Greece is one of the most important Ports in European Union and enjoys a privileged position being located at the starting point of Egnatia Motorway The Port is one of the largest passenger ports in the East Mediterranean Sea basin, which, handles around 1,000,000 passengers per year for international destinations. The paper investigates current waste management and disposal options for ship generated waste and the associated impact of the waste for port. Data about the ship traffic were provided by the Port Authority and about the amount and characteristics of the wastes by the contractors for the disposal of the ship generated waste. It was concluded that all vessels should be encouraged to use the reception facilities and should pursue a waste reduction strategy and the port authority to provide adequate recycling facility. An electronic recording data system has to be adopted for better evaluation of the performance of the system. This system must record the deliveries for every ship in the port, the amount and the type of wastes are generated. Also must provide information about the maximum storage capacity of waste on board and about management of waste treatment options by the ships.

Numerical Investigation of Two-Phase Flow through a T-Junction Microchannel Reactor

Recently, microreactors have become available to be fabricated and used safely. The performance of these microreactors depends on the behavior of the multiphase flow hydrodynamics. Gas-liquid flow through T-junction microchannel reactor is simulated numerically using VOF （volume of fluid） method. 2-D （Two-dimensional） and 3-D （three-dimensional） models of the T-junction microchannel reactor were introduced to the simulations. Both 2-D and 3-D simulations for nitrogen-water flow were performed in the FLUENT （Fluent. Inc.） computational fluid dynamics package. The third direction effect has been studied by comparing the results of the 2-D and 3-D simulations with the published experimental data. Also, the bubble slug length was calculated for the 2-D and 3-D simulations. Furthermore, the hydrodynamics of the flow was studied for the 2-D and 3-D simulations, and compared with other experimental data. The pressure drop, mean bubble velocity, the velocity distribution and the void fraction were calculated and found to be in good agreement with published data.

Research on the adjustment model of ventilation characteristic parameters based on integrated method of circuit and path

Ventilation characteristic parameters are the base of ventilation network solution; however, they are apt to be affected by operating errors, reading errors, airflow stability, and other factors, and it is difficult to obtain accurate results. In order to check the ventilation characteristic parameters of mines more accurately, the integrated method of circuit and path is adopted to overcome the drawbacks caused by the traditional path method or circuit method in the digital debugging process of ventilation system, which can improve the large local error or the inconsistency between the airflow direction and the actual situation caused by inaccuracy of the ventilation characteristic parameters or checking in the ventilation network solution. The results show that this method can effectively reduce the local error and prevent the pseudo-airflow reversal phenomenon; in addition, the solution results are consistent with the actual situation of mines, and the effect is obvious.

Dynamic evaluation of traffic flows on city roads

This paper presents an analysis of the random fluctuations, deferred conduction effect and periodicity of road traffic based on the basic features of road networks. It also discusses the limitations of road network evaluation theories based on road "V/C". In addition, it proposes a set of theoretical and technical methods for the real-time evaluation of traffic flows for entire road networks, and for solving key technical issues, such as real-time data collection and processing in areas with no blind zones, the spatial-temporal dynamic analysis of road network traffic, and the calibration of key performance index thresholds. It also provides new technical tools for the strategic transportation planning and real-time diagnosis of road traffic. The new tools and methodology presented in this paper are validated using a case study in Beijing.