Supply Network Model Research Articles

Development and Application of Water Supply Network Simulation Analysis Platform

Nowadays, the demand of people for urban water supply security is increasing. Meanwhile, the scale of water supply system is expanding and the topology is being more and more complicated. Aiming at these problems above, the technology of simulation modling and software development for urban water supply network is researched in this article. First of all, through studying the parameter testing technique, the load and change law of water consumption, the pressure distribution law, and the actual conveyance capacity of main pipes of the whole water supply network are accurately mastered. Correspondingly, the simulation database is built. On this basis, aiming at scientific operation and water quality protection, taking opening territorial water supply network of one city for example, the microscopic hydraulic model of water supply network of this area is built, meanwhile, the simulation analysis platform is developed, with the application of on-line monitoring technology. The platform which has well expansibility and utility has been applied to water supply network of an urban city.

Embedded devices for supply chain applications: Towards hardware integration of disparate technologies

The emergence of the RFID technology and its application to supply chain processes has in particular led to the creation of such standards as the EPCglobal’s model of supply networks as a tool for materializing intra- and inter-enterprise visibility of resources and products, collaboration and integration. Among other critical uses, RFID has been deployed by supply networks to improve asset utilization, effectively combat counterfeiting, and advance targeted product recalls. However, new affordable and deployable technologies and microsensors have recently appeared and keep maturing. This paper discusses the needs and the possibilities that exist for leveraging these technologies and sensors with RFID to guarantee continuous and seamless visibility of all assets (fixed and mobile resources and field personnel) of smart enterprises, thereby expanding and complementing the roles of RFID. It examines the design challenges for the integration of these technologies for advanced logistics operations at the level of product classes or their instances. It then outlines our development of an embedded microsystem that combines RFID, GPRS, GPS and environmental sensors for applications in logistics. The prototyped microsystem demonstrated the feasibility of the multi-sensor integration paradigm that the paper proposes.

Evolution of cooperation on heterogeneous supply networks

Strategies can significantly influence the performances of individual players and groups in supply networks. However, these strategies evolve over time. Thus, it is essential to probe the evolution of strategies in this context. This paper investigates the evolution of cooperation on supply networks focusing on the impacts of network topologies. Due to the difficulty in mapping the topological structures of large-scale supply networks, we introduce a topological model for supply networks. Then repeated prisoner’s dilemma game is played on the resulting networks. The simulation results show that topological structures have close relevance to the cooperation level in the networks. Compared with homogeneous structures, heterogeneous structures are helpful to promote cooperation. In addition, strategy payoff and competition pressure are also involved with the evolution of cooperation. This work may offer a useful insight into understanding complex strategy behaviours in supply networks.

Combining expert knowledge and local data for improved service life modeling of water supply networks

The presented approach aims to overcome the scarce data problem in service life modeling of water networks by combining subjective expert knowledge and local replacement data. A procedure to elicit imprecise quantile estimates of survival functions from experts, considering common cognitive biases, was developed and applied. The individual expert priors of the parameters of the service life distribution are obtained by regression over the stated distribution quantiles and aggregated into a single prior distribution. Furthermore, a likelihood function for the commonly encountered censored and truncated pipe replacement data is formulated. The suitability of the suggested Bayesian approach based on elicitation data from eight experts and real network data is demonstrated. Robust parameter estimates could be derived in data situations where frequentist maximum likelihood estimation is unsatisfactory, and to show how the consideration of imprecision and in-between-variance of experts improves posterior inference.

Hybrid Modelling of Distributed Water Supply Networks

In this paper, the modelling of a class of distributed water supply networks is considered, where the modelling of pipes, valves, pump stations and reservoirs are presented separately. Two laws, nodal mass balance and energy conservation, are introduced to derive a general model for the water supply networks. The pumps are assumed to be working in parallel and a hybrid model is provided to describe the dynamics of pump stations, the discrete/ continuous variables in which represent the status (on or off) and the speed of pumps, respectively. Finally, a case study is given to illustrate the effectiveness of our proposed methods.

Designing a Fresh Food Supply Chain Network: An Application of Nonlinear Programming

In today’s business environment, many fresh food companies have complex supply networks to distribute their products. For example, agricultural products are distributed through a multiechelon supply chain which includes agricultural association, agricultural produce marketing corporations (APMCs), markets, and so forth. In this paper a fresh produce supply network model is designed to determine the optimal service area for APMCs, the replenishment cycle time of APMCs, and the freshness-keeping effort, while maximizing the total profit. The objective is to address the integrated facility location, inventory allocation, and freshness-keeping effort problems. This paper develops an algorithm to solve the nonlinear problem, provides numerical analysis to illustrate the proposed solution procedure, and discusses the effects of various system parameters on the decisions and total profits. A real case of an agricultural product supply chain in Taiwan is used to verify the model. Results of this study can serve as a reference for business managers and administrators.

Research on Inverse Transient Leakage Location of Water Supply Network Based on Genetic Algorithm

In order to realize real-time leakage (online) diagnosis, through correlation analysis of the network leakage and pressure variation, using the established microscopic model as the basic hydraulic analysis model, using the position of the network leakage point and the water of leakage point as the variables, using minimizing difference of the network pressure points monitoring value and simulation value as the target when leakage occurs, establish inverse transient leakage location of water supply network model based on genetic algorithm. Finally through the two modes of leakage verification, the result shows that this model can effectively achieve the network leakage location and quantitative.

Joint allocation and transportation problem in supply network optimisation

Received: 1 July 2012 Abstract Accepted: 30 August 2012 The paper concerns joint allocation and transportation as an optimization problem in selected supply networks. The network consists of a set of suppliers of the raw material, a set of production units and a set of product receivers. The raw material is treated as fast perishing good like vegetables or fruits. The production units are described by time models. In the optimization process, the time of the production and cost of the transportation is taken into account. The objective function is in general non-convex function of raw material allocation and transportation plans of the raw material and the product. To solve the problem considered, exact and heuristic algorithms have been developed and presented. To solve convex problems, solver Lingo developed by Lindo systems is proposed. The idea of a computer decision supported system integrating all presented algorithms is presented as well as four numerical examples illustrating some properties of the assumed supply network model.

Markov Process for Service Facility systems with perishable inventory and analysis of a single server queue with reneging Stochastic Model

ABSTRACT In this paper, we develop a supply network model for a service facility system with perishable inventory (on hand) by considering a two dimensional stochastic process of the form (L, X) =   0 )); ( ), ( (  t t X t L , where L (t) is the level of the on hand inventory and X (t) is the number of customers at time t. The inter-arrival time to the service station is assumed to be exponentially distributed with mean 1/λ. The service time for each customer is exponentially distributed with mean 1/ μ. The maximum inventory level is S and the maximum capacity of the waiting space is N. The replenishment process is assumed to be (S-1, S) with a replenishment of only one unit at any level of the inventory. Lead time is exponentially distributed with parameter β. The items are replenished at a rate of β whose mean replenishment time is 1/β. Item in inventory is perishable when it’s utility drops to zero or the inventory item become worthless while in storage. Perishable of any item occurs at a rate of γ. Once entered a queue, the customer may choose to leave the queue at a rate of α if they have not been served after a certain time (reneging). The steady state probability distributions for the system states are obtained. A numerical example is provided to illustrate the method described in the model.

Robustness Optimization Based on PERT in the Civil Aircraft Supply Network

The civil aircraft’s manufacturing process is complicated because of its complex structure and various parts in need. The stability and high efficiency of the based supply network decides the coordination ability among departments and the development cycle completion date. Now it’s very urgent to study the robustness of the collaborative supply network. This paper optimized and designed the robustness of the civil aircraft supply network, first with the project evaluation and review technique (PERT) we set a supply network model; then optimized the critical path to make the system functions remain constant, and the civil aircraft supply network robustness got optimized

Robustness Optimization Based on PERT in the Civil Aircraft Supply Network

The civil aircraft’s manufacturing process is complicated because of its complex structure and various parts in need. The stability and high efficiency of the based supply network decides the coordination ability among departments and the development cycle completion date. Now it’s very urgent to study the robustness of the collaborative supply network. This paper optimized and designed the robustness of the civil aircraft supply network, first with the project evaluation and review technique (PERT) we set a supply network model; then optimized the critical path to make the system functions remain constant, and the civil aircraft supply network robustness got optimized

Critical Path Detection for Civil Aircraft Collaborative Supply Network

Civil aircraft is a complex product to manufacture, and the collaborative supply network consist of grades suppliers plays an important part in the progress of development. Due to the interferences from every kind of uncertainties to the network, it’s necessary to find out the critical supply path which decides the completion date for the network going well. This paper first sets the supply network model based on the hierarchical structure of civil aircraft, and then uses Dijkstra and ant colony optimization (ACO) searching for the critical path respectively, in the last the two methods are compared in order to prove performance and superiority.

Critical Path Detection for Civil Aircraft Collaborative Supply Network

Civil aircraft is a complex product to manufacture, and the collaborative supply network consist of grades suppliers plays an important part in the progress of development. Due to the interferences from every kind of uncertainties to the network, it’s necessary to find out the critical supply path which decides the completion date for the network going well. This paper first sets the supply network model based on the hierarchical structure of civil aircraft, and then uses Dijkstra and ant colony optimization (ACO) searching for the critical path respectively, in the last the two methods are compared in order to prove performance and superiority.

Reconfiguration framework of a supply network based on flexibility strategies

Because the supply network of an enterprise should be flexible enough to capture and overcome market dynamics, one of the major concerns of global enterprises is to make their supply network reconfigurable. Although many strategies for flexible management of a supply network have been proposed, especially for mitigating supply network risks, it still remains unclear how to apply the strategies to a supply network and how to reconfigure the supply network. This paper examines the influence of flexibility strategies in a dynamic global market environment on the structure of supply network, and proposes a method of reconfiguring the supply network of an enterprise to cope with its flexibility strategies. A reconfigurable supply network model is proposed, and flexibility strategies are classified, and critical indices of strategies are defined. In the proposed model, each business actor is defined as a network node and each node has its own goal. A node optimizes its goal to reduce and overcome the risk of market environments. The result of optimization indicates that the supply network structure is reconfigured dynamically.

How altruism works: An evolutionary model of supply networks

Recently, supply networks have attracted increasing attention from the scientific community. However, it lacks serious consideration of social preference in Supply Chain Management. In this paper, we develop an evolutionary decision-making model to characterize the effects of suppliers’ altruism in supply networks, and find that the performances of both suppliers and supply chains are improved by introducing the role of altruism. Furthermore, an interesting and reasonable phenomenon is discovered that the suppliers’ and whole network’s profits do not change monotonously with suppliers’ altruistic preference, η, but reach the best at η=0.6 and η=0.4, respectively. This work may shed some light on the in-depth understanding of the effects of altruism for both research and commercial applications.

Modeling the operation of hydrogen supply networks considering facility location

Hydrogen draws increasing attention as an alternative energy source. In order to provide hydrogen to various sectors such as industry, transportation on a global scale, how to produce and distribute it economically is an essential issue not to be missed. This study thereby addresses mathematical modeling of hydrogen supply networks. The proposed model is concerned with how much H2 can be produced, where can be stored with the aim of maximizing the total net profit. Particularly the physical form of the hydrogen in the network is explicitly taken into account in terms of whether it is stored as a gas or a liquid. The applicability of the proposed model will be demonstrated by a case study of the Korean H2 supply network with some remarks.

Metabolic scaling in insects supports the predictions of the WBE model

The functional association between body size and metabolic rate (BS–MR) is one of the most intriguing issues in ecological physiology. An average scaling exponent of 3/4 is broadly observed across animal and plant taxa. The numerical value of 3/4 is theoretically predicted under the optimized version of West, Brown, and Enquist's vascular resource supply network model. Insects, however, have recently been proposed to express a numerically different scaling exponent and thus application of the WBE network model to insects has been rejected. Here, we re-analyze whether such variation is indeed supported by a global deviation across all insect taxa at the order and family levels to assess if specific taxa influence insect metabolic scaling. We show that a previous reported deviation is largely due to the effect of a single insect family (Termitidae). We conclude that the BS–MR relationship in insects broadly supports the core predictions of the WBE model. We suggest that the deviation observed within the termites warrants further investigation and may be due to either difficulty in accurately measuring termite metabolism and/or particularities of their life history. Future work on allometric scaling should assess the nature of variation around the central tendencies in scaling exponents in order to test if this variation is consistent with core assumptions and predictions of the WBE model that stem by relaxing its secondary optimizing assumptions that lead to the 3/4 exponent.

Existence of solutions to Cauchy problems for a mixed continuum-discrete model for supply chains and networks

We consider a continuum-discrete model for supply chains based on partial differential equations. The state space is formed by a graph: The load dynamics obeys to a continuous evolution on each arc, while at nodes the good density is conserved, while the processing rate is adjusted. To uniquely determine the dynamics at nodes, the through flux is maximized, with the minimal possible processing rate change. Existence of solutions to Cauchy problems is proven. The latter is achieved deriving estimates on the total variation of the density flux, density and processing rate along a wave-front tracking approximate solution. Then the extension to supply networks is showed.

Rationalisation and reliability improvement of fire-fighting systems – the Novi Sad case study

Water supply systems are commonly used to supply fire-fighting water in most EU countries. To provide fast access to water, the standard practice is to install a huge number of hydrants along the entire water supply network. Pipe diameters and working pressures in the network are designed for a combination of the maximum hourly water demand and fire-fighting needs. However, in poorly managed water supply systems most of the hydrants are out of order. Although hundreds of hydrants exist in the network, the reality is that fire water tankers are usually refilled at just a few locations that are equipped with reliable hydrants maintained by the fire brigades. This paper presents a somewhat different approach for the provision of fire-fighting water. The approach discussed in the paper is based on the concept being introduced in the city of Novi Sad, Serbia, by cooperative efforts of the municipal Water Supply and Sewerage Company and the fire-fighting service. In addition to presenting the experience gained in the case study, some generic conclusions are drawn. As an alternative to having a number of unreliable and small hydrants distributed throughout the network, the new concept proposes the construction of several strategically positioned filling stations, with high-flow-rate pillar hydrants and good access roads for the manoeuvering of fire water tankers. If properly designed and distributed around the city, such filling stations would increase the reliability of fire-fighting operations. The filling stations' design methodology presented in this paper is composed of a fire-risk spatial assessment, a hydraulic check of water supply network operations and a worst-case traffic load analysis. By employing the proposed methodology, not only can the reliability of fire-fighting operations be increased, but if accepted and implemented the methodology can lead to leakage reduction and improvements in water quality and the system's energy efficiency. In the test case of Novi Sad, a large number of hydrants were replaced by 14 filling stations that have been designed and constructed. A hydraulic model of the water supply network was calibrated using pressure-drop tests and flow capacity measurements of the existing hydrants. The model was used to examine the performance of the designed filling stations during their parallel operation. The paper presents the results of the test application and recommendations for the possible implementation of the concept.

Modelling supply networks with partial differential equations

A continuum-discrete model for supply networks is introduced. The model consists of a system of conservation laws: a conservation law for the goods density and an evolution equation for the processing rate. The network is formed by subchains and nodes at which, motivated by real cases, two routing algorithms are considered: the first maximizes fluxes taking into account the goods’ final destinations, while the second maximizes fluxes without constraints. We analyze waves produced at nodes and equilibria for both algorithms, relating the latter to production rates in real supply networks. In particular, we show how the model can reproduce the well-known Bullwhip effect.