Olivier Gallay

• PhD
• Professor at University of Lausanne

This study delves into the gender-specific challenges and opportunities in sweet potato farming in Goromonzi District, Zimbabwe, against the backdrop of escalating droughts. Through a blend of surveys, expert analysis, and high-resolution satellite imagery, the research uncovers critical factors shaping sweet potato production—ranging from land acc...

This study delves into the gender-specific challenges and opportunities in sweet potato farming in Goromonzi District, Zimbabwe, against the backdrop of escalating droughts. Through a blend of surveys, expert analysis, and high-resolution satellite imagery, the research uncovers critical factors shaping sweet potato production—ranging from land acc...

This study leverages a Discrete Event Simulation (DES) model to optimize the sweet potato supply chain in Zimbabwe, focusing on production, distribution, and market dynamics under varying climate conditions. The integration of climate data into the simulation model reveals significant insights into the resilience of different sweet potato varieties...

The renowned van der Waals (VDW) state equation quantifies the equilibrium relationship between the pressure P, volume V, and temperature kBT of a real gas. We assign new variable interpretations adapted to the economic context: P→Y, representing price; V→X, representing demand; and kBT→κ, representing income, to describe an economic state equilibr...

This research provides an in-depth analysis of drought impacts in West Pokot, Kenya, utilizing both remote sensing surveys and focus group discussions. The study commenced by assessing the impact of drought on vegetation health via spatial sensors. It then utilized surveys and focus group discussions (FGDs) to engage farmers from the most drought-a...

This Project funded by CROSS, focuses in assessing the impact of drought on vegetable health by employing a multidimensional approach, incorporating remote sensing, surveys, and focus group discussions (FGDs), to comprehensively assess the impacts of drought in West Pokot, Kenya. Local perceptions identified 2017 as an exceptionally challenging yea...

Beliefs inform the behavior of forward-thinking agents in complex environments. Recently, se- quential Bayesian inference has emerged as a mechanism to study belief formation among agents adapting to dynamical conditions. However, we lack critical theory to explain how preferences evolve in cases of simple agent interactions. In this paper, we deri...

We consider the management of cross-docking platforms (CPs). Every day, suppliers deliver products to the CP by trucks (inbound flow). The same day or during another day, the products are then loaded into containers (outbound flow). At the end of the planning horizon (one week in this work), boats ship the containers to offshore production plants....

In this paper, we consider a parcel-delivery situation encountered in practice by a logistics provider in France, involving a truck and a drone. Whereas the majority of the deliveries take place in the valley, some parcels have to be delivered to a remote place located in a mountainous area with poor accessibility. These remote deliveries can be pe...

We propose a model for solving a parcel delivery problem with a fleet of trucks embedded with drones. When appropriate, drones are loaded with a parcel, launched directly from the truck, and sent to a client. Afterward, the drones autonomously return to the truck to be replenished and recharged. Inspired by the case of a large European logistics pr...

We propose a microscopic model to describe how individual opinions shared between interacting agents initiate excessive collective expectations about a new idea or an innovation, followed by a swift collapse towards a dramatic collective disillusionment. The basic assumption which underlies the dynamics is that the information gathering process is...

We consider the optimization of the cross-docking operations at three INtermodal LOgistics Platforms (INLOPs) of a large European car manufacturer (ECM). The planning horizon is a week and the time bucket is a day. An inbound flow of products is gradually received over the week by truck from inland suppliers, and has to be loaded into containers wh...

Measuring the average time that a process takes from start to finish, using observation time windows (OTWs) of different length, is required for numerous operational monitoring and control processes. We refer to this measure as the Mean Lead‐Time (MLT). This study is based on the fact that computing the MLT in an operational context is often mislea...

This chapter discusses Vehicle Routing Problem by finding optimal vehicle routes that visit a set of jobs in a given region. Depending on the situation, a job can be a service provided on‐site, a delivery of goods, or a collection of components. Strongly relying on Coindreau et al. and Gallay and Zuffrey, it describes how car sharing and independen...

With the ever increasing prominence of data in retail operations, sales forecasting has become an essential pillar in the efficient management of inventories. When facing high demand, the use of backroom storage and intraday shelf replenishment is necessary to avoid stock-out. In that context, the mandatory input for any successful replenishment po...

This paper is based on the premise that economic growth is driven by an interplay between innovation and imitation in an economy composed of interacting firms operating in a stochastic environment. A novel approach to modeling imitation is presented based on range-dependent processes that describe how firms consider proximity when imitating peers w...

We consider the optimization of container loading at three intermodal logistics platforms (ILP) of a large European car manufacturer (ECM). The decisions focus both on the loading day of each container and on its filling with the products in inventory, which are gradually received over the week from inland suppliers. The objective is either to redu...

We propose a microscopic model to describe how individual opinions shared between interacting agents initiate excessive collective expectations about a new idea or an innovation, followed by a swift collapse towards a dramatic collective disillusionment. The basic assumption which underlies the dynamics is that the information gathering process is...

In the classical Vehicle Routing Problem (VRP), it is assumed that each worker moves using an individually assigned vehicle. Removing this core hypothesis opens the door for a brand new set of solutions, where workers are seen as transportable resources that can also move without the help of a vehicle. In this context, motivated by a major European...

Variable neighborhood search (VNS) is a well-known metaheuristic. Two main ingredients are needed for its design: a collection \(M=(N_1, \ldots , N_r)\) of neighborhood structures and a local search LS (often using its own single neighborhood L). M has a diversification purpose (search for unexplored zones of the solution space S), whereas LS plays...

We introduce a new view of parked cars as a massive, flexible resource that is currently wasted. Given the power supply in batteries as well as computing, communication, and sensing facilities in cars in conjunction with the precise localization they can provide, parked cars have the potential to serve as a service delivery platform with a wide ran...

The mean-field dynamics of a collection of stochastic agents evolving under local and nonlocal interactions in one dimension is studied via analytically solvable models. The nonlocal interactions between agents result from (a) a finite extension of the agents interaction range and (b) a barycentric modulation of the interaction strength. Our modeli...

Inspired by the spectacular observation that non-territorial songbirds (titmouses) propagate innovation (i.e. how to drill a hole in the cover of a milk bottle) more efficiently than territorial fellows (robins), we propose a stylized mathematical model of knowledge propagation founded on an analytically solvable multi-agent system. Individual agen...

The mean-field dynamics of a collection of stochastic agents with local versus nonlocal interactions is studied via analytically soluble models. The nonlocal interactions result from a barycentric modulation of the observation range of the agents. Our modeling framework is based on a discrete two-velocity Boltzmann dynamics which can be analyticall...

We construct a model of innovation diffusion that incorporates a spatial component into a classical imitation-innovation dynamics first introduced by F. Bass. Relevant for situations where the imitation process explicitly depends on the spatial proximity between agents, the resulting nonlinear field dynamics is exactly solvable. As expected for non...

We propose a new real-time load sharing policy (LSP), which optimally dispatches the incoming workload according to the current availability of the operators. Optimality means here that the global service permanently requires the engagement of a minimum number of operators while still respecting due dates. To cope with inherent randomness due to op...

Today’s supply networks consist of a certain amount of logistics objects that are enabled to interact with each other and to decide autonomously upon their next steps; in other words, they exhibit a certain degree of autonomous cooperation. Therefore, modern logistics research regards them as complex adaptive logistics systems. In order to analyze...

Waiting time in any network is often a costly and hence a bad experience. Therefore, to avoid jamming regions becomes essential in the optimization of traffic flows. In this regard, the conception and the control of complex networks supporting flows of units are key issues in various strategic engineering and service areas ranging from manufacturin...

This paper studies the crew planning problem as observed in the transportation industry. We first survey the existing literature on crew scheduling applications in railways and airlines. Next, we identify the synergies in the two domains and propose new directions for railway crew scheduling inspired from the applications in airlines.

The inherent complexity characterizing production and/or service networks strongly favors decentralized and self-organizing mechanisms to regulate the flows of matter and information in circulation. This basic observation motivates us to study the flow dynamics in queueing networks roamed by autonomous agents which, at a given time and at a given v...

We study the market partition between two distinct firms that deliver services to waiting time sensitive customers. In our model, the incoming customers select a firm on the basis of its posted price, the expected waiting time and its brand. More specifically, we quantify by a cost any departure from the ideal brand expected by each incoming custom...

For recurrent service providers (fast-food, entertainment, medical care,...), retaining loyal customers is obviously a key issue. The customers' loyalty essentially depends on their service satisfaction defined via an ad-hoc utility function. Among several criteria, the utility function strongly depends on the past perceived waiting time. Moreover,...

We consider queueing networks (QN’s) with feedback loops roamed by “intelligent” agents, able to select their routing on the basis of their measured waiting times at the QN nodes. This is an idealized model to discuss the dynamics of customers who stay loyal to a service supplier, provided their service time remains below a critical threshold. For...

We study the market partition between two competing firms that de-liver services to waiting-time sensitive customers. In our model, the incoming customers select a firm on the basis of its posted price, the expected waiting time and its brand. More specifically, we quan-tify by a cost any departure from the ideal brand expected by each incoming cus...