Abstract:The mismatching of supply and demand in bus systems in the space-time dimension leads to the waste of spatiotemporal resources as near-empty buses are still running according to schedules， especially during off-peak hours. In order to quantify the above problems， a bi-objective evaluation method was built upon the investigation of the interactions among passengers， buses， and road resources. The evaluation system consists of two indexes， the supply-demand matching index （SDMI） and the space-time occupancy index （STOI）. The SDMI quantifies the matching degree of travel demand and bus line capacity， while the STOI measures the per capita occupancy of spatiotemporal resources in bus operation. The calculation of the SDMI and STOI were based on the global positioning system （GPS） data and the integrated circuit （IC） card transaction data， etc. Finally， four bus lines with different characteristics in Shanghai were used for case study. Considering the actual distribution of the two indexes， the classification thresholds of the bi-objective evaluation system were identified according to the cumulative frequency curve of the SDMI and STOI. The proposed method can be further utilized in the evaluation of public transit infrastructures and the optimization of bus type selection and bus scheduling， etc.

Abstract:In order to accurately identify travel mode split rate of transfer passenger flow in high-speed rail hubs， a travel mode choice model is proposed based on a generalized trip chain model based on multimodal public transportation big data. Through the correlation and fusion of different public transportation modes in the transfer phase， the individual generalized trip chain with the high-speed rail hub as the origin is extracted. Then， the temporal-spatial distribution characteristics of the transfer flow in high-speed rail hubs are analyzed. Comprehensively considering the influence of individual economic and social attributes， and subjective psychological factors in combination with individual travel characteristics on transfer mode choice behavior， a transfer mode choice model for passengers in high-speed rail hubs is proposed based on multiple indicators and multiple causes （MIMIC） and multi-nominal logit（MNL） model. Taking the actual data of Beijing South Railway Station as the input， the estimated travel mode split rate of the commuting passenger flow is obtained. A comparison and analysis of ground true data indicates that the estimation error is within an acceptable range.

Abstract:This paper proposed a fusion analysis model for leaving station identification， based on the 5-day continuous （24 h） bus travel data， bus travel GPS data， and bus stop data of a certain city， in combination with the travel chain method and random forest network. In the model， the GPS data and bus stop data were first matched to determine the bus arrival information at different moments， then the passenger boarding location， travel frequency， activity scope， land use around the leaving station， and the probability of getting off the bus were applied as inputs to identify the passenger leaving station. The final calculation rate is improved to 100%， and the full sample efficiency rate reaches 76.2%. Compared with the existing methods based on the bus travel chain， the recognition efficiency is improved by 37%.

Abstract:In order to optimize the operation of the mixed bus fleet， a scheduling method that balances the environmental and economic costs of electric buses and fuel buses is proposed. Firstly， the constraints are given by combining the operation characteristics of buses with different power energy， and the carbon emissions and time-of-use electricity prices are integrated into the energy consumption and cost analysis of electric buses and fuel buses， then， considering the economic cost and environmental cost of the public transport system， a comprehensive operation cost minimization model is established， finally， an improved genetic algorithm with nested tabu search is used to solve the model. The algorithm not only compensates for the shortcomings of traditional genetic algorithms that converge prematurely and fall into local optimal solutions easily but also improves the quality and accuracy of the model solution. Bus No. 1 in Wenshan City， Yunnan Province， was taken as an example for verification. The results show that the improved genetic algorithm with nested tabu search improves the solution accuracy by about 12% compared with the traditional genetic algorithm， and the scheduling scheme generated achieves the best balance between reducing carbon emission costs and improving vehicle utilization and effectively reduces the overall operation cost. In addition， the scheduling scheme realizes the effect of electric bus task execution period and electricity price peak staggering and saves the charging cost， which provides a green， efficient， and reliable scheduling method for the smooth realization of the “electrification” of the bus fleet.

Abstract:To deal with problems of destroying the existing arterial signal coordination and travel efficiency reduction of private vehicles due to bus priority control， a real-time bus priority control method with arterial signal coordination is established under connected vehicle environment. The method includes three steps. A speed advisory algorithm is proposed for the connected buses that are out of the intersection control area in order to guide the buses to arrive when the traffic light is green. Further， the bus signal priority requests together with the collaborative speed advisory and bus holding time is calculated when the bus reaches the intersection control area. Finally， satisfying the bus signal priority requests， the signal timing scheme is optimized to minimize private vehicle delay. Therefore， a speed advisory， bus holding time， and signal priority control method is constructed. The experimental results demonstrate the proposed method can cooperate with existing signal coordination， cater to bus priority demands， and ensure the benefits of private vehicles at the same time. Further numerical studies on the speed advisory algorithm and the bus signal request generation algorithm indicate a significant enhancement on preventing buses from stopping for red lights. Sensitivity analysis shows that a longer control distance of the intersection is more beneficial to reduce bus delay.

Abstract:Aimed at the problem of main cable form-finding of suspension bridges in the finished dead load state and the unloaded state， a modified force density method is proposed. This method combines the concept of unstressed length， assuming the initial cable shape is straight line segment. A structural balance equation is established to find the target cable shape under limited conditions by iterations， which is based on the force density method. The proposed method was used to calculate the cable shape of the Beijing-Hangzhou Grand Canal Suspension Bridge by Matlab. The comparison of the numerical calculation results and measured values of the coordinates shows that the proposed method has a stable convergence， high computational efficiency and high accuracy. The proposed method was verified to be suitable for self-anchored suspension bridges with three-dimensionally cables through the calculation example.

Abstract:Low cycle tests on the main tee splices， main-cross tee joints and peripheral joints of suspended ceiling were conducted. The failure modes of grid joints and splices were summarized. The load-bearing ability and deformation capacity of grid joints and splices were analyzed. The Pinching4 model in OpenSEES software was used to establish the force-displacement hysteretic model for grid joints and splices. The force-displacement hysteresis curve based on the hysteretic model is consistent with that obtained from the experiments， and as the number of cyclic loading increases， the change rule of the accumulated energy dissipation based on the hysteretic model agrees well with the corresponding experimental results. On this basis， the generic hysteretic model for various grid joints and splices was further established， and the recommended values of generic hysteretic model parameters for grid joints and splices were given.

Abstract:Soil differential-settlement， which will change the stress state of buried pipelines， is one of the important causes for the damage of the buried pipelines. In this paper， pipeline-soil integrated models are established for four kinds of pipelines by utilizing the ABAQUS software. For continuous pipelines， such as steel pipelines and PE pipelines， the stress response of the pipelines are mainly analyzed. But for socket pipelines， represented by ductile iron pipelines and grey cast iron pipelines， the joint deformation is the mainly research object. Thus， the soil settlement displacement that causes the limit state of pipelines are obtained， which reflects the anti-settlement ability of different types of pipelines. Moreover， the effects of pipe diameter and length of the soil settlement area are discussed.

Abstract:Recycled aggregate concrete （RAC） is different from ordinary concrete in its internal microstructure， mechanical and thermodynamic properties due to the addition of recycled concrete aggregates （RCA）. At present， there have been many studies on the mechanical properties of RAC， but less attention has been paid to its thermodynamic properties. In this paper， effects of several important factors such as physical properties and replacement level of RCA， recycled concrete powders， and service temperature on the thermal conductivity of RAC are reviewed. Based on the experimental data in literature， an empirical equation for predicting the thermal conductivity of RAC is proposed. Existing studies show that the porosity of RCA affects the thermal conductivity of RAC. The incorporation of RCA and recycled concrete powder as well as the increase of ambient temperature can lead to a significant decrease in the thermal conductivity of concrete and with 100% recycled fine aggregate， the reduction of thermal conductivity can reach 48%. Functionalized RAC together with an enhanced mechanical performance would promote a wider industrial application and lead to less CO2 emission of the construction industry.

Abstract:In this paper， the printability of 13 kinds of engineering spoil with different mix proportion in extrusion process was studied. Meanwhile， unconfined compressive strength test and direct shear test were carried out for spoil samples mixed with river sand and recycled powder respectively， and the feasibility of river sand and recycled powder as engineering spoil admixture was discussed. The experimental results show that the mixing proportion of clayey spoil will affect the extrusion effect of composite spoil. When the mixing proportion of clay reaches 50%， the extrusion effect is good. The addition of recycled powder can improve the unconfined compressive strength and elastic modulus of spoil. Beyond this range， the super water absorption of recycled powder will seriously affect the cohesion of spoil， resulting in the decrease of strength and the maintenance time of elastic deformation stage. On the premise of ensuring the strength improvement and extrudability of engineering spoil， it is suggested that the content of recycled powder is 5%， and the unconfined compressive strength of spoil can be increased by 22.5%， while the incorporation of river sand will reduce the unconfined compressive strength and elastic modulus of spoil as a whole， showing an inverse skeleton effect. In terms of reducing environmental pollution and promoting intelligent earth building， 3D printing extrusion technology is used to produce engineering 3D printing bricks that meet different requirements， which has high application value and potential.

Abstract:Shoving and subsidence are common pavement distresses. However， the traditional judgment method based on two-dimensional image cannot obtain depth information. The linear laser scanning method is precise， yet the single scan range is limited. Thus， it is difficult to obtain the global situation in a short time when identifying deformation distresses. A method is proposed for detecting deformation distresses and extracting their 3D features by using a vehicle-mounted mobile lidar system. Point cloud data are segmented and abnormal deformation points are extracted. 3D features of deformation distress are obtained. The reliability and effectiveness of the method are verified by the measured data. The results show that the method can automatically detect the deformation such as shoving， subsidence， and potholes. It can effectively improve the detection efficiency. Compared with the total station measurement results， the 3D feature extraction results are complete with an accuracy of 84.662%.

Abstract:Considering the interaction between bus service mode and timetable， this paper proposed a bi-level model to design the schedule of multiple bus services， in which the upper-level jointly optimized the timetable and service modes while the lower-level assigned the passenger trip demand to bus services. Due to the complexity of the bi-level model， it proposed a heuristic algorithm to solve the model efficiently. It used a genetic algorithm （GA） to solve the upper-level model and applied the Dial algorithm to assign the passenger flow to bus trips. It used the real-world data of No. K1 bus in Jiangyin， Jiangsu and No. 737 bus in Shanghai to validate the effectiveness of the proposed model. The results show that the coordinated design model can decrease bus operational costs and efficiently improve service quality.

Abstract:To quantitatively identify the safety risk factors in rail transit signaling system accidents， an accident data mining method is presented. First， the original accidents were divided into different types of accident data in accordance with the law of Heinrich. Then， a 5M（management-machine-man-media-mission factor） based factor analysis identification method was adopted to identify respectively the 254 larger-casualty accidents and the 220 minor-casualty accidents considering the accident causation multi-factors after the general-statistic method and the statistic identification method analysis. The results indicate that the natural disaster， the signal equipment material fault， the poor construction management， and the inadequate staff protection are the most important major factors leading to the signaling system accident. The 5M based factor analysis method can be used to sort quantitatively the importance ranking of accident causation factors under multi-scale comprehensive measurement. A comparison of the general-statistic method and the statistic identification method suggests that the 5M based factor analysis method has the best identification effect， with a relatively higher influencing rate of 106% increase and moderate coverage rate.

Abstract:An optimal design method of rail grinding profile based on multi-dimensional index is proposed. The method comprehensively considers four indexes， including vehicle stability， curve guidance， smoothness of contact characteristic function and contact uniform distribution， and reversely solves the problem based on wheel rail contact characteristic function. It can realize the automatic optimization of wheel-rail contact characteristic function and the computer intelligent design of rail grinding target profile. Taking the application of the design results in the grinding of Datong-Fenglingdu railway line of Taiyuan Railway Bureau as an example， the implementation effect was tracked and observed. The results show that the rail light band position and the measured wheel rail contact position after grinding is more reasonable， the rail surface fatigue damage and corrugation are effectively controlled， and the rail wear rate is reduced by 20% to 45%， which proves that the design method is effective.

Abstract:Micro-nano bubbles （MNBs） are more energy-efficient than traditional macro bubbles in terms of environmental water remediation because of their perfect characteristics， such as small dimension， large specific surface area， long residence time in water， high Zeta potential， strong oxidization， high mass transfer efficiency， enhancement in biological activity， and no secondary pollution. Based on the analysis of existing researches， first， the bubble classification and generation method are introduced. Next， the excellent characteristics of MNBs and the corresponding influencing factors are discussed in detail. Subsequently， the migration regulation and controlled factors of MNBs in water and porous media are analyzed， focusing on the mechanism of MNBs in remediating environmental water. Finally， a systematic review of the current status of the research on MNBs and the application in environmental water remediation is evaluated， with the promising application prospects of ozone MNBs as the priority. The future research directions of MNBs in environmental water remediation are discussed as well.

Abstract:In order to reduce the workload of modeling and calculation of water distribution systems， the hydraulic equivalent method or flow equal division method is often used to simplify the flow along the link， which distributes the flow along the link to the upper and lower nodes of the link. In order to explain theoretically the influence of simplification of the flow along the link， the differences of water head and traveling time before and after simplification of the general flow along link were analyzed， and the differences of water head and traveling time before and after simplification of the uniform flow along the link were analyzed. These two aspects were calculated and discussed in combination with cases. It is concluded that the hydraulic equivalent simplification ensures that the water head at the upper and lower nodes of the link is the same as that before the simplification， while the water head at each point in the link before and after the simplification is usually different. After hydraulic equivalent simplification， the flow distribution ratio of the upper node is related to the number of demand points in the link and the flow proportion along the link， but has nothing to do with the diameter， the upper node head， the inlet flow， the length and the friction coefficient of the link， The simplification method is suitable for the extend period simulation model with variable water head at the upper node or link inlet flow. The uniform discharge along the link is treated according to the hydraulic equivalent method （or flow equal division method）， which is suitable for simplifying the flow along the link where the internal flow along the link accounts for a small proportion （the links close to the water treatment plant）.

Abstract:Accurate recognition of indoor occupant behavior， including the recognition of position and activity type， is an important input for multi-scene control mode of various electrical equipment at intelligent homes. In the study described in this paper， the passive infrared （PIR） sensor array is used to monitor indoor occupant behavior. After analyzing the data characteristics of different positions and different activity intensities， based on the machine learning algorithm， the indoor occupant position and activity recognition model is established and the recognition accuracy of different cumulative time and machine learning algorithms are compared. The cumulative count value of this minute and of the previous 30 minutes of the PIR sensors are selected as the model input and the random forest algorithm is used to construct the final position and activity recognition model. The accuracy of the model is 99.9% under the 10-fold cross-validation of the training data set， while 88.3% under the new test data set， which shows that the position and activity recognition model has a certain validity and generality.