ecai Xu

Deterministic approach to the fairest revenue-sharing coefficient in logistics service supply chain under the stochastic demand condition

In the design of the revenue-sharing contract, it is critical to determine a rational revenue-sharing coefficient which affects the coordination and stability of supply chain. In order to improve the existing system, one should take into account that the current revenue-sharing coefficient study only figures out its range rather than the specific value. This paper investigates the fairest revenue-sharing coefficient when the logistics service integrator and the functional logistics service provider implement revenue-sharing contract under stochastic demand condition; by focusing on a two-echelon logistics service supply chain composed of a logistics service integrator and a functional logistics service provider. Taken into consideration the non-storage property of logistics service supply chain, this paper establishes a Stackelberg game model by giving priority to the logistics service integrator. The interval of the revenue-sharing coefficient is obtained by revenue-sharing contract mechanism. Based on the principle of profit distribution equity, a fair entropy function is introduced and a non-linear programming model for solving the fairest revenue-sharing coefficient is established. Furthermore, this method is extended to a three-echelon logistics service supply chain composed of a logistics service integrator, a functional logistics service provider, and a logistics subcontractor. It is assumed that the logistics subcontractor fully commits to the logistics capacity of the functional logistics service provider and consequently a non-linear programming model is constructed to solve the fairest revenue-sharing coefficient of a three-echelon logistics service supply chain under stochastic demand condition. The results exemplifies that the proposed method can find out the fairest revenue-sharing coefficient in a two-echelon and a three-echelon logistics service supply chain, which provides an approach to revenue-sharing contract study.

Modeling Signalized-Intersection Safety with Corner Clearance

Signalized intersections next to each other on the same arterial share some unobservable information, such as traffic flow and roadway characteristics. This study investigated the impact of access management techniques on crash counts at signalized intersections. The analysis was performed using crash data from 275 signalized intersections in southern Nevada. The panel data random-effect model was used to account for the unobserved factors for each unique arterial. It was found that the negative binomial (NB) regression models were the best in reflecting the dispersion in the crash data. Therefore, the random-effects negative binomial model (RENB) was applied to investigate the relationship between crash occurrence and access-management techniques. The results of the panel data RENB models were compared with those from the pooled NB models, which did not account for the panel data structure. Evaluation of the goodness-of-fit of the models developed indicated that the random-effect negative binomial model was the best-fit for the data at hand. The results from the panel data RENB showed that nine variables significantly affecting the safety at signalized intersections were the average length of corner clearance, traffic flow, land-use types, number of left-turn lanes for main streets, number of through lanes for main and minor streets, posted speed limit on main and minor streets, and grades of legs.

An order allocation model in multi-period logistics service supply chain based on cumulative prospect theory and capacity matching constraint

By considering a two-echelon supply chain that consists of a logistics service integrator (LSI) and several functional logistics service provider (FLSP), this study builds a comprehensive subjective utility (CSU) function of FLSP in multi-period based on cumulative prospect theory and establishes an order allocation model in multi-period logistics service supply chain. This model considers three goals: to minimise the cost of LSI, to maximise the satisfaction of the FLSP and to maximise the capacity matching degree among different logistics capacities. This study uses an improved technique for order performance by similarity to ideal solution to obtain the optimal solution. A numerical example is given by software MATLAB 7.8. The effects of the behavioural parameters of FLSPs on order allocation are also discussed. When the LSI allocates orders, the FLSP, who has larger ratio of loss to gain range by the sensitivity decreasing rate, should be selected to obtain a large value of CSU. No obvious rule is found for the influence of the loss aversion coefficient of FLSPs on the CSU of FLSPs in a multi-period.

Identifying Access Management Factors Associated With Safety of Urban Arterials Mid-Blocks: A Panel Data Simultaneous Equation Models Approach

Objective: The objective of this study was to evaluate the safety impact of selected access management techniques in urban areas because access management techniques play an important role in urban roadway safety on the roadway network. Methods: In order to correct the interdependency between safety and mobility for heterogeneous mid-block segments, simultaneous equation models were adopted. The panel data structure of the model was used to address the heterogeneity issue for mid-block segments along a corridor. The integrated random coefficient simultaneous equation models were proposed to interpret both issues. Results: The models developed were used to identify influential factors. The length of mid-block segments, driveway density, and median opening density were among the significant factors found to be associated with crash rate on mid-block segments. Conclusions: From the results it can be concluded that the access management techniques, mid-block segment length, driveway density, and median opening density are significant factors that influence safety on mid-block segments. The longer the distance between signals, driveways, and median openings, the fewer the potential crashes are. In addition to these access management techniques, land use, especially the commercial land type, influences the safety on mid-block segments.

Analysis on evolving model with modular growth of urban roadway network topology structure

Purpose – The purpose of this paper is to explore the evolving mechanism of urban roadway network. With the consideration of self-organization effect and planning effect during evolution, the authors try to demonstrate the impact of preferential attachment, module scale and module structure on the evolving network model. Design/methodology/approach – The roadway network is built in the form of abstract network by dual approach. By using the evolving model of modular growth, the authors analyze the effects and mechanism of the evolving process. Then through numerical analysis, the impact of evolving effects on urban roadway network topology structure is discussed from the aspects of preferential attachment, module scale and module structure. Findings – The module structure property, small-world property and scale-free property of roadway network can be affected with various degrees by the change of preferential attachment and module scale. However, the impact of module structure on network properties is sm...

Cascade defense in urban road network by inserting modular topologies

Purpose – By aiming at defending cascade failures effectively, the purpose of this paper is to present a strategy of inserting modular topologies into urban road network through reducing the burdens of critical components with too much traffic flow. Design/methodology/approach – Each module is considered as a small-world random network, which is inserted into the initial Barabasi-Albert scale-free network. Based on the user-equilibrium assignment, the strategy searches for remote nodes with low betweeness and flow in the network, and sets these nodes to be connected with the modular topologies. In this sense, the inserted modules are supposed to attach to the nodes with lower intensity of shorter path, and avoid bringing more impact to the nodes with higher betweeness and traffic flow. By using efficiency as the measurement of cascading failures, the performance of the networks generated through the strategy is tested. Findings – The results show that the performance of the strategy is sensitive to the av...

A Heckman selection model for the safety analysis of signalized intersections

Purpose The objective of this paper is to provide a new method for estimating crash rate and severity simultaneously. Methods This study explores a Heckman selection model of the crash rate and severity simultaneously at different levels and a two-step procedure is used to investigate the crash rate and severity levels. The first step uses a probit regression model to determine the sample selection process, and the second step develops a multiple regression model to simultaneously evaluate the crash rate and severity for slight injury/kill or serious injury (KSI), respectively. The model uses 555 observations from 262 signalized intersections in the Hong Kong metropolitan area, integrated with information on the traffic flow, geometric road design, road environment, traffic control and any crashes that occurred during two years. Results The results of the proposed two-step Heckman selection model illustrate the necessity of different crash rates for different crash severity levels. Conclusions A comparison with the existing approaches suggests that the Heckman selection model offers an efficient and convenient alternative method for evaluating the safety performance at signalized intersections.

Quasi-induced exposure method for pedestrian safety at signalized intersections

ABSTRACT To investigate pedestrian exposure when only pedestrian-crash data are available, the quasi-induced exposure method is used to identify the factors that contributed to pedestrian-vehicle crashes in Las Vegas from 2004 to 2008. The results show that overall crash severity, light conditions, and weather conditions are potentially risky factors in pedestrian crashes, and the time of day or day of the week are less risky. Multiple-correspondence analysis (MCA) is then used to investigate how pedestrian crash severity is influenced by the interactions among a range of variables. The results indicate that among instances of pedestrian-vehicle crashes cases of property damage only tend to occur during off-peak daytime hours and under dark or dawn light conditions in clear weather. Crashes resulting in injuries usually occur during weekday peak hours in daylight and under rainy conditions. Most fatal crashes occur during off-peak hours, at night on the weekends.

Research on the procedure joint process and synthesized performance evaluation of logistics service supply chain

The study of the procedure joint process of logistics service supply chain (LSSC) can help evaluate the synthesized performance scientifically as well as understand the coordination process systematically from microcosmic viewpoint. This paper systematically analyzes the three aspects of the joint procedure, namely: before, during, and after. Before the procedure joint, the paper investigates four essential mechanism environment required to achieve procedure joint, including trust mechanism environment, information sharing mechanism environment, incentive and constraint mechanism environment, and evaluation mechanism environment. During the procedure joint, the joint mode between functional logistics service provider (FLSP) and logistics service integrator (LSI) is proposed from the viewpoint of operation management and the organization structure. After the procedure joint, the synthesized evaluation index system is proposed, which consists of the result level, process level and environment level, corresponding to the posterior evaluation, the intermediate evaluation and the beforehand evaluation, respectively. Then an analytical network process (ANP) model for comprehensive performance evaluation index system of LSSC is established and evaluated with superdecision software. The example results indicate that this method could overcome the correlation among those evaluating factors, and improve the accuracy of performance evaluation. Consequently, it can provide a quantitative method for the synthesized performance evaluation of procedure joint process in LSSC.

Safety Impact of Access Management Techniques at Signalized Intersections

Signalized intersections next to each other spatially on the same arterial share some unobservable information such as traffic flow and roadway characteristics, thus this study is to investigate the impact of access management techniques on crash counts at signalized intersections where the unobservable information is considered by developing panel data crash count data models based on crash data from 300 signalized intersections in Southern Nevada. Panel data random-effect model was selected to take into account the unobserved factors for each unique arterial. It was showed that Negative Binomial regression models were better able to reflect the dispersion in the crash data. Therefore, the random-effect negative binomial model (RENB) was applied to investigate the relationship between crash occurrence and access management techniques. The results showed that five variables significantly affected the safety at signalized intersections. The average length of corner clearance had negative impact on intersection crash occurrence while the total traffic flow in all directions, land use types, the number of lanes for minor streets and posted speed limit on minor streets were positively related to crashes at signalized intersections.