A network approach to modeling the multi-echelon spare-part inventory system with backorders and interval-valued demand

A multi-echelon inventory system implies the existence of a hierarchy of stocking locations, and the dependence and interaction between them. We consider a multi-echelon, spare-part inventory management problem with outsourcing and backordering. The problem is characterized by deterministic repair time/cost, and supply and demand that lie within prescribed intervals and that vary over time. The objective is to minimize the total inventory and transportation costs. We develop a network model for problem analysis and present a network flow algorithm for solving the problem. We prove that the Wagner-Whitin property, known for the lot-sizing problem, can be extended to the spare-part inventory management problem under study.     

Smart city networks' governance: The Spanish smart city network case study

The governance of smart city networks emerges as a new research area intersecting smart governance and public networks studies. This work aims to contribute to the literature on smart cities governance by studying councillor's governance in complex networks and on network performance. To carry out this analysis, the Spanish Network of Smart Cities (RECI), one of the first of its kind and an international reference for city networks, is reviewed as a case study, with the main objective of establishing a theory on its global innovation capacity and operations, together with the local level spurring influenced on its members. A PEST (Political, Economic, Social and Technological) analysis was carried out in order to assess the impact of the smart city network both at local, national and international level. This research was completed with a consultation carried out among some of RECI's municipalities. The analysis of the results shows how RECI can be considered an example of a well organised network with quantifiable savings for its members, capable of configuring future policies in local administration, necessarily related to efficiency, digitalization and citizen-centricity and with key topics to build the future. The study also suggests recommendations oriented to potential improvements that smart city networks could undertake.     

Identifying new dimensions of business incubation: A multi-level analysis of Karolinska Institute's incubation system

Relying on an in-depth case study of the incubator related to the Swedish medical university Karolinska Institute's (KI), this paper identifies new analytical and strategic dimensions of incubation. Departing from the current literature's prevalent focus on incubators as organizations performing a predefined set of activities for incubatees (facility renting, coaching, training and connecting), we perform a multilevel analysis embracing, next to the organizational and the project-specific levels, also the broader institutional and inter-organizational level. Our analysis relies on seven key components of incubation, namely its time, place, sources, resources, control/governance, activities/services and outcomes. Further, we view incubators as strategic actors engaged in value creation on a broader arena than the strict incubation context, even an international arena, where incubators' choices and interactions can be analyzed with the help of concepts from various streams in the business strategy literature. The specific strategic drivers of business incubation that we identify in the KI incubator's case are six: positioning in the value chain, risk taking/time perspective, revenue model, governance/control, internationalization, and cooperation/competition. The paper concludes with managerial implications urging incubators to take more of a strategic perspective rather than focussing only on the established components of their operations.     

Global engineering services: Shedding light on network capabilities

This paper addresses the operations challenges of effectively managing professional services on a global scale. The specific context for the study is professional engineering services and particularly those that are delivered globally – global engineering services (GES). Estimates suggest that the market for GES was around US$930 billion in 2012, rising to US$1.4 trillion by 2020 (ISG, 2013). Yet this influential sector receives scant attention in the operations management literature. The paper draws on six case studies to explore the operations management challenges of delivering GES. In doing so the paper introduces the concept of network capabilities for GES, highlighting the centrality that: (i) network resources – accessing and deploying dispersed resources, (ii) network coordination – coordinating and integrating network activities, and (iii) network learning – collective learning and knowledge management, all play in enabling the successful operational management of GES.     

Raising the Bar (3)

This editorial summarizes and comments on the papers published in issue 11(3) so as to raise the bar in applied spatial economic research and highlight new trends. The first paper proposes spatial and a-spatial indicators to describe the networks of airline companies around the world. The second paper sets forth a two-regime gravity-type model with an endogenous threshold parameter to assess the effect of labour market conditions on interregional migration flows. The third paper utilizes micro-data to explain student migration flows to higher education institutions. The fourth paper is among the first to make use of simulation-based location quotients in a multiregional input–output model. Finally, the last paper provides a purely economic–theoretical model on cooperative limit pricing in the context of spatial competition.     

Network concentration and airport congestion in a post de-regulation context: A case study of Brazil 2000–2010

This paper empirically investigates the main drivers of airline network concentration in an air transport market subject to rapid growth. We consider the Brazilian air transport industry of the 2000s, in which network concentration rapidly increased and was followed by a period of massive flight delays and cancelations, which resulted in the “big blackout” of 2006–2007. We develop an econometric model of network concentration, accounting for demand, cost and competition variables that may affect the propensity of carriers to concentrate flights and passenger connections on a few airports of a network. The main focus of the paper is on the relation between networks leading to the problems of the blackout episode. We investigate the dynamic pattern of the evolution of concentration before and after the abnormal period of operations and find that concentration began to rise at least six quarters before, and persisted at a high level until two quarters after the blackout – and then plunged steeply toward the end of the decade. We believe that our analysis contributes to an improved understanding of the behavior of air transport systems subject to network concentration and congestion. With respect to methodology, we suggest and employ the use of alternative measures of network concentration to check the robustness and validity of our results.     

Interregional trade network analysis for road freight transport in Greece

This paper suggests a flexible decision support framework for the strategic planning of a freight transport hub network in Greece. The proposed methodology treats practical aspects related to the optimal number, location and geographical covering of hubs, through the network analysis of interregional trade, based on original survey data for road freight flows during 2004–2012. The results offer insights into the hierarchical structure of the network and related investment priorities, as the hub role of a prefecture is found to be strongly influenced by high population densities and manufacturing specialization, and its location along highway corridors.     

Stochastic optimization for investment in facilities in emergency prevention

A coordinated approach is developed to integrate three preventive measures (i.e. building reinforcement, reinforcement of road networks, and facility location of relief supplies), with the objectives of minimizing budgets and risk-induced penalties. The Conditional Value-at-Risk is employed as a decision-making tool to evaluate diverse decisions of prevention based on the degree of risk aversion. Based on a real-world case of an earthquake, a series of scenarios were designed, and the applicability of the proposed model was studied. The coordinated approach for investing preventive measures is cost-efficient in helping reduce the impact of disaster on society.     

Analysis of the Chinese Airline Network as multi-layer networks

This paper encapsulates the Chinese Airline Network (CAN) into multi-layer infrastructures via the “k-core decomposition” method. The network is divided into three layers: Core layer, containing airports of provincial capital cities, is densely connected and sustains most flight flow; Bridge layer, consisting of airports in Tier 2 and Tier 3 cities, mainly connects two other layers; and Periphery layer, comprising airports of remote areas, sustains little flight flow. Moreover, it is unveiled that CAN stays the most robust when low-degree nodes or high flight flow links are removed, which is similar to the Worldwide Airline Network (WAN), albeit less redundant.     

On the multi-dimensionality and sampling of air transport networks

Complex network theory is a framework increasingly used in the study of air transport networks, thanks to its ability to describe the structures created by networks of flights, and their influence in dynamical processes such as delay propagation. While many works consider only a fraction of the network, created by major airports or airlines, for example, it is not clear if and how such sampling process bias the observed structures and processes. In this contribution, we tackle this problem by studying how some observed topological metrics depend on the way the network is reconstructed, i.e. on the rules used to sample nodes and connections. Both structural and simple dynamical properties are considered, for eight major air networks and different source datasets. Results indicate that using a subset of airports strongly distorts our perception of the network, even when just small ones are discarded; at the same time, considering a subset of airlines yields a better and more stable representation. This allows us to provide some general guidelines on the way airports and connections should be sampled.