Demand adaptive paired-line hybrid transit systems that integrate fixed- and flex-route transit have emerged in the last decade and attracted increasing attention because of their potential to improve accessibility for passengers. To facilitate the operation of such a hybrid transit system, this study develops a model to determine the optimal fare and headways associated with fixed- and flex-route transit along a rectangular corridor. Compared with existing literature, the novelty of this study lies in designing the fare structure while simultaneously considering demand elasticity and passenger behaviour. A continuous approximation modelling approach is employed to derive the agency's and travellers' cost components. Using these, a nonlinear programming optimisation model is formulated to minimise the total user cost subject to the agency's nonnegative revenue constraints and passengers' route choice behaviour, which is characterised as a path-size logit model. Numerical experiments are performed using a stylised network to examine the properties of the model, in which the solution is obtained by combining a brute force method that enumerates headway and fare combinations and an iterative method that determines equilibrated passenger choices. The results show that as potential demand density increases, fare and headway fluctuate and drop, while the percentage of passengers choosing to ride on flex-route transit increases. In addition, there may be an optimal maximum offset distance, which is defined as the width of the corridor to be covered by the transit system, when the potential demand density is low, leading to minimum user cost and maximum travel demand within the service area.
This paper explores the highly subjective issue of global equity and presents two models for defining and measuring it over time. The paper makes several basic assumptions to simplify the problem, including using various child indicators to evaluate quality of life, subjectively assessing their impact, and weighting them to obtain the quality-of-life value. The paper defines absolute and relative fairness and shows how the quality of life of newborns correlates with equity. The models use the Analytic Hierarchy Process and quality-of-life values to identify factors that affect equity and assess it between different countries. The paper validates the models using historical data and existing conclusions. Overall, the paper provides a framework for evaluating and improving global equity that can help address issues such as poverty, environmental pollution, and lack of resources.
Different curing compounds for cement concrete (CC) used in mechanical construction of CC pavement are introduced in this paper. Curing compounds normally used are paraffin emulsion, sodium silicate solution, solvent resin and SC-90 type curing dual composite. Comparative test results show that SC-90 type curing dual composite has best performance among the above compounds. Application of SC-90 type curing dual composite in China, on the Fokai and Shenshan expressways is introduced.
Abstract. In this paper, three regularization methods, such as the mollification method, the modified Tikhonov regularization method, the Fourier regularization method, for the identification of an unknown source for the modified Helmholtz equation are considered and compared. We have solved the model problem with these methods, investigated the differences between them, analyzed their convergence estimates under a priori choice of the regularization parameter and proved the effectiveness of these methods. Two numerical examples are provided to show the main results.
Synchronized transfers in schedule-based public transport (PT) networks are used to reduce interroute or intermodal passenger transfer waiting time and provide a well-connected service. However, in practice, synchronized transfers do not always materialize because of some stochastic and uncertain factors, such as traffic disturbances and disruptions, fluctuations in passenger demand, and erroneous behavior of PT drivers. As a result, missed direct transfers not only frustrate existing users but also discourage potential passengers from using PT service. This work presents an optimization procedure based on a model predictive control (MPC) to increase the actual occurrence of synchronized transfers in schedule-based PT networks. The procedure aims to reduce the uncertainty of meetings between PT vehicles. MPC uses selected online operational tactics based on real-time data, such as skip stop, speed change, and holding. First a library of operational tactics was built to serve as a basis for the sequential receding horizon control process in the MPC. Then, an event activity network with dynamic moving elements was constructed to represent the logical process of the PT transfer synchronization problem. The MPC procedure for a real-time deployment of operational tactics was explicated. A detailed example was used as an expository device to illustrate the procedure developed, along with a real-life example from Auckland, New Zealand.
Abstract Perforated wells in ultra‐deep sandstone reservoirs are characterized by high reservoir temperature, high formation pressure, and high production, and sand production will cause severe safety hazards to these wells. Based on Drucker‐Prager (DP) rock failure criterion, a practical analytical model for predicting critical drawdown pressure (CDP) of sanding onset for perforated wells is established by comprehensively considering the influence of drag stress, formation water production, reservoir pressure depletion, temperature difference in the perforated wellbore. The proposed model is verified by field sanding onset monitoring data. The calculation results show that CDP changes with well inclination, and it decreases with the increase in wellbore temperature difference, reservoir pressure depletion, and water saturation. However, the CDP increases with the number of perforations and the ratio of diameter to length. The optimization of perforation parameters has an important influence on sand control. This study can effectively guide the prediction of CDP and provides basis for efficient and safe development of similar ultra‐deep and high yield sandstone reservoirs.
With the development of charging technology, chargers with dropped price and increased charging power make fast charging more applicable and competitive to provide efficient and effective charging solution to electric vehicles. Compared to normal chargers, fast chargers can top up battery in a short time, which enables battery electric buses to get top-up charging at selected bus stops when the buses load and unload passengers. Such en-route charging solution can avoid deadhead trips during daily operation and further reduce energy consumption due to smaller size of battery required. In this paper, we develop a two-stage stochastic programming model to locate fast chargers at selected bus stops considering uncertainties of passenger demand and energy consumption during bus operation. A modified L-shaped method is proposed to solve the challenging problem since its size grows expo-nentially with the increasing number of scenarios. Numerical results show that the en-route top-up charging time keeps in line with passengers' boarding and alighting time at intermediate stops when the bus loads and unloads passengers, which causes negligible passengers' extra waiting time and corresponding penalty cost caused by charging activities. The modified L-shaped method is further compared to the commercial solver Gurobi with better performance and higher efficiency.
The process of full-thickness skin regeneration is complex and has many parameters involved, which makes it difficult to use a single dressing to meet the various requirements of the complete regeneration at the same time. Therefore, developing hydrogel dressings with multifunction, including tunable rheological properties and aperture, hemostatic, antibacterial and super cytocompatibility, is a desirable candidate in wound healing. In this study, a series of complex hydrogels were developed via the hydrogen bond and covalent bond between chitosan (CS) and alginate (SA). These hydrogels exhibited suitable pore size and tunable rheological properties for cell adhesion. Chitosan endowed hemostatic, antibacterial properties and great cytocompatibility and thus solved two primary problems in the early stage of the wound healing process. Moreover, the sustained cytocompatibility of the hydrogels was further investigated after adding FGF and VE-cadherin via the co-culture of L929 and EC for 12 days. The confocal 3D fluorescent images showed that the cells were spherical and tended to form multicellular spheroids, which distributed in about 40-60 μm thick hydrogels. Furthermore, the hydrogel dressings significantly accelerate defected skin turn to normal skin with proper epithelial thickness and new blood vessels and hair follicles through the histological analysis of in vivo wound healing. The findings mentioned above demonstrated that the CS/SA hydrogels with growth factors have great potential as multifunctional hydrogel dressings for full-thickness skin regeneration incorporated with hemostatic, antibacterial, sustained cytocompatibility for 3D cell culture and normal skin repairing.
The effects of different test parameters on the creep of axially compressed concrete members were investigated under standard test conditions, considering loading ages of 7, 14 and 28 days and mineral powder admixtures of 0, 15%, 25% and 35%, respectively. The test results show that the creep of concrete decreases with the increase of mineral powder content when the loading age was fixed. When the content of mineral powder was unchanged, the creep of concrete would decrease with the increase of loading age. Based on the CEB-FIP MC 1990 concrete creep calculation model, the creep correction coefficient of mineral powder concrete considering the strength of mineral powder concrete, mineral powder content and loading age was proposed. The formula for the concrete creep correction coefficient which considers the loading age and mineral powder content was established by combining the existing creep test data and the test results of mineral powder concrete strength with the different loading ages and mineral powder contents in this paper. The comparison of the CEB-FIP MC 1978 and experiment values shows that the proposed formula in this paper can predict the development of creep of mineral powder concrete better. Finally, using the creep coefficient formula of mineral powder concrete, the creep coefficient values of concrete under different loading ages and mineral powder contents in CEB-FIP MC 1990 code were modified.
Programs for simulating coastal flowing were developed by applying two-dimensional shallow water mathematical model and hybrid finite analytic method for feasibility analysis of using the pure implicit scheme in engineering.The method of freezing and standard of distinguishing dry-flood grids are used together to deal with beach existing in computational area.Flowing in Zhanjiang bay was simulated and numerical results were compared and analyzed with those measured.It shows the mathematical model and pure implicit scheme used can simulate real flowing exactly.Scale of efficiency and cost is acceptable and results are believable.It′s worth extending the pure implicit scheme to application in real engineering.
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