G Rossitto
email: giacomo.rossitto@ensma.fr

C Sicot

V Ferrand

J Bor Ée

F Harambat

Influence of afterbody rounding on the near wake of fastback vehicle Influence of afterbody rounding on the near wake of fastback vehicle

Keywords: PIV, Drag Reduction, Wake analysis, Vorticity, Rounded edges

Experimental and numerical analyzes were performed to investigate the aerodynamic performances of a realistic vehicle with different afterbody rounding. Rounding the side pillars generated moderate changes in drag and important lift reductions. The minor effect on the drag force was found to result from opposite drag effects on the slanted and vertical surfaces. The vorticity distribution in the near wake was also analyzed to understand the flow field modifications due to afterbody rounding.

Introduction

For the last decades car manufacturers have been facing the challenging task of reducing fuel consumption and CO 2 emissions. In response to that, optimization algorithms have been applied to generate new vehicle shapes minimizing the aerodynamic drag. Since the obtained optimum shapes has no brand differentiating details, stylists are nowadays trying to give back a brand signature by proposing "non-conventional" shapes. In that framework, important rear pillars rounding becomes a differentiation strategy. The current study suggests to qualify the influence of such afterbody rounding on the flow field and on drag development over a fastback vehicle.

Very few papers have addressed the question of rear edges curvature in aerodynamic vehicle performances. One of the first works was presented by Gilhaus et al. [START_REF] Alfons | Drag and driving-stability-related aerodynamic forces and their interdependence-results of measurements on 3/8-scale basic car shapes[END_REF] and Howell [START_REF] Howell | C466/036 shape features which influence crosswind sensitivity[END_REF]. Thanks to balance measurements, it was found that rounded pillars reduced drag and rear lift but yawing moment had a pronounced increase. Only recently, advanced techniques were used to achieve better understanding of the afterbody rounding. Thacker et al. [START_REF] Thacker | Effects of suppressing the 3d separation on the rear slant on the flow structures around an ahmed body[END_REF] showed that rounding the edge between the roof and the rear slant of the Ahmed body results in a 10% drag reduction. Authors attributed this reduction to the fully attached flow over the backlight and the downstream shift of the rotating structures developing in the near wake. Fuller et al. [START_REF] Fuller | The importance of rear pillar geometry on fastback wake structures[END_REF] analyzed the benefits of rounding the rear side pillars on the Davis model. They observed that rounded edges generate a different wake structure dominated by the interaction between the longitudinal vortices and the separated region. The rounded edges model resulted in drag and lift reduction of 11% and 25% respectively. The impact of afterbody rounding was mentioned also during the development of the Tesla Model S by Palin et al. [START_REF] Palin | The aerodynamic development of the tesla model s-part 1: Overview[END_REF]. Important curved side pillars were avoided to reduce highly dynamic wake, which caused large variation in base pressure.

From the literature review, it appears that rounding afterbodies affects considerably aerodynamic loads and flow development, but systematic investigation into the effects of changing radii of side backlight edges was not reported. In complement to the recent study proposed by the same authors in [START_REF] Rossitto | Influence of afterbody rounding on the pressure distribution over a fastback vehicle[END_REF] over a simplified car model (Ahmed body), the present study addresses this question on a realistic car model equipped with various rear pillars curvatures. Special care is taken to understand how the modified flow on the backlight interacts with the near wake and promotes drag and lift changes.

Four rear ends were analyzed combining PIV to balance and wall pressure measurements to fully characterize the flow structures and the associated aerodynamic forces. Complementary numerical simulations were systematically applied to complete the experimental data and help physical analysis.

Experimental and numerical set-up

The model and its relevant dimensions are reported in figure 1. Four rear ends are tested, they differ by their side pillars curvature. The curvature radius is given as a percentage of the model span, i.e. 300mm. The model equipped with sharp pillars having 0% radius is referred as S 0 and it is considered as the reference case. The others models are S 8 , S 20 and S 40 . All the rear ends have the same curvature at the end of the roof to avoid flow separation. The corresponding radius is chosen to maximize the room for the rear passengers for a fixed backlight angle of 23 degrees. The horizontal projection of the slanted surface, ξ = 440mm, will be used as reference length. Starred spatial coordinates are normalized by the reference length.

The experimental results reported in this work were obtained from tests conducted in the PSA Groupe wind tunnel of La Ferté Vidame. The Eiffel wind tunnel is 52 meters long and has a test section 2 meters high, 5.2 meters large and 6 meters long. It has a maximum free stream velocity of 53 m/s. The wind tunnel blockage ratio was 1.4%. All the data were obtained at 40m/s which gives a Reynolds number based on the length of the model of 2.6e6. Starred velocities are normalized by the free stream velocity. A six components balance was used to measure the aerodynamic forces acting on the model. The drag and lift coefficients were calculated as follows:

C d,l = F d,l 1 2 ρU 2 0 S
where F is the force measured by the balance, ρ the density of the air, and S the frontal surface area Static wall pressure was recorded by 35 pressure probes over the vertical surface of the rear end.

Those probes were connected to a SCANdaq 8000 acquisition system. The acquisition rate was 40

Hz for 3000 samples giving 75s of time recording. The static wall pressure coefficient at one point i was computed from the expression:

C P (i) = P(i) -P 0 1 2 ρU 2 0
where P(i) is the static pressure of point (i), P 0 the static pressure measured upstream of the model.

The static accuracy of the system is ±13Pa, i.e. 0.015 Cp.

Furthermore, PIV measurements were performed in the wake of the model. by the low value of pressure over the curved roof edge and from the low pressure foot-print of the longitudinal vortices, the so-called C-pillar vortices [START_REF] Rossitto | Influence of afterbody rounding on the pressure distribution over a fastback vehicle[END_REF]. These vortices are generated by the interaction of the flow coming from the side of the model and the flow over the rear window. Since the roof radius is constant among the four models, lift reductions are caused by the C-pillar vortices intensity modifications due to side rounding. For a moderate value of C-pillars rounding, the origin of the longitudinal vortices is displaced towards the base of the body along the C-pillars [START_REF] Rossitto | Influence of afterbody rounding on the pressure distribution over a fastback vehicle[END_REF].

For larger rounding, three-dimensional flow separation does not occur anymore on the side of the model and thus the side vortices disappear [START_REF] Rossitto | Wake structure and drag of vehicles with rounded rear edges[END_REF]. The weakening of the C-pillar vortices allows a pressure recovery over the rear window reducing its contribution to drag and lift. However, the variation of the average base pressure over the vertical surface, reported in figure 4 and in table 2,

gives evidence that the base pressure is reduced when the curvature side radius is increased. For S 40 , the base pressure is 17% lower than for S 0 , resulting in an important local drag increase. This effect counter-balances the local drag reduction of the rear window and can explain the weak effect of pillars rounding on the global drag (table 2).

∆Cd ∆Cl ∆Cp Base S 0 - - - S 8 0% -13% -12% S 20 -1.5% -18% -15% S 40 -2% -27% -17%
Table 2: Variation of aerodynamic coefficients and averaged base pressure compared to S 0 .

The mean velocity fields in the symmetry plane are reported in figure 5. noticed between the two models. The flow is attached to the slanted surface due to the important roof radius for both models. For S 0 , the average separated zone in the close wake is characterized by two counter-rotating structures. The mean recirculating length, identified by the saddle point of the 2D mean streamlines, is at X * = 0.33 and X * = 0.23 respectively for S 0 and S 40 . Adding pillar curvature reduces then the length of the near wake and modifies the topology of the enclosed structures. For S 40 , the mean curvature of the near wake is increased due to important negative normal velocity. Regarding the flow organization inside the near wake, the upper structure is not evidenced anymore and the lower structure seems to be reduced. Such a strong modification of the near wake properties in the symmetry plane, may result from a 3D modification of the flow field due to side rounding.

To understand this complex mechanism, cross-flow planes are displayed in figures 6 and 7. The data are issued from the numerical simulations to overcome the size limitation of the experimental data. Each picture is divided in two: the left side represents S 0 and the right side S 40 . At X * = 0.02, right after the rear slant, the longitudinal vorticity (Ω x * = Ω x * ξ U 0 ) is concentrated in the Cpillar vortex for S 0 (figure 6). At the same X plane, a diffuse horizontal small area of longitudinal vorticity is present for S 40 located in the shear layer (figure 6). Two-dimensional lines tangent at each point to the vector (V,W) are also drawn in figure 6 After X * = 0.4, Γ * is higher for the sharp model than for the rounded one, in accord with the lift value reported in Table 2. Figure 10 reports the time averaged streamlines issued from the numerical simulations. A comparison between the two models permits to reveal the mean differences generated by side pillars rounding. The sharp side pillars force the lateral flow to separate, generating longitudinal vortices. As analyzed by the same authors in [START_REF] Rossitto | Influence of afterbody rounding on the pressure distribution over a fastback vehicle[END_REF], it is suggested that, for S 0 , the sharp lateral edges "shield" the wake separation region at the base and enable a "two-dimensional" separation,"2D" meaning that the mean streamlines at separation are more parallel to the orientation of the flow over the window, while longitudinal vorticity is concentrated in the C-pillar vortices.

On the contrary, for rounded edges, the flow is drawn in from the sides, toward the center over the slanted surface. The separation at the base is then notably 3D for S 40 , associated with high spanwise and vertical velocity components [START_REF] Rossitto | Influence of afterbody rounding on the pressure distribution over a fastback vehicle[END_REF]. This work has been performed in the framework of the "OpenLab Fluidics" @Poitiers.

18thFigure 1 :

 1 Figure 1: Fastback vehicle model and location of the rounded edges

Figure 2 :Figure 3 :Figure 4 :

 234 Figure 2: Comparison of mean streamwise velocity profiles. • Numerical, -Experimental

Figure 5 :

 5 Figure 5: Time averaged streamlines and mean streamwise velocity U * at Y * =0.

Figure 6 :Figure 7 :Figure 8 :CpFigure 9 :

 6789 Figure 6: Mean Streamwise Vorticity Ω * x at X * = 0.02. Left S 0 , Right S 40 .

Figure 10 :

 10 Figure 10: Time averaged streamlines from numerical simulations. The streamlines and the surface of the body are colored by the pressure coefficient C p

Table 1 :

 1 International Symposium on the Application of Laser and Imaging Techniques to Fluid Mechanics • LISBON | PORTUGAL • JULY4 7, 2016 in table 1. The model size for the numerical simulations corresponds to a real vehicle scale. At Reynolds 1.04e7, 324000 time-steps were computed (3 seconds of real time). Local variable refinement regions VRs were defined to locally allow coarsening the grid by a factor of 2 starting from the Minimum Level of VR[START_REF] Fares | Unsteady flow simulation of the ahmed reference body using a lattice boltzmann approach[END_REF]. The computational grid consisted of 1.2 million volume elements and 0.6 million surface elements. In the following, temporally averaged velocity and pressure fields will be shown. These averages are computed over approximately 25 convective time scales L/U 0 where L is the length of the body and U 0 the external velocity.This setting allowed good agreements between numerical and experimental results, as it is possible to examine in figure1.1 that reports a comparison of mean streamwise velocity profiles. Numerical PowerFLOW c setting

	post-processing was performed with a final interrogation window of 16*16 pixels, after an initial
	window of 32*32 pixels, with an overlap of 50% in horizontal and vertical directions. The grid
	spacing was 1.82mm. A SNR filter was applied to remove vectors with SNR< 1.2. 900 images
	were recorded with a 7Hz trigger rate. With this setting, the 95% confidence limit represents ap-
	proximately ±3% of the mean velocity [7].

The laser sheet was set by a 2*120mJ Nd:Yag Quantum Big Sky Laser. The Dantec Flowsense 4M mkII camera (2024pixel*2024 pixels) equipped with 105 mm lenses generated 462mm*462mm fields of view. 2D PIV was performed on the symmetry (x,z) plane Y * =0. Cross-flow planes (y,z), were recorded using the Stereo-PIV technique to obtain the 3 velocity components of the flow field. For all the PIV measurements, The numerical simulations presented in this work were computed with the commercial code PowerFLOW c (version 5.0c) based on lattice Boltzmann model. The simulation setting is reported 18th Physical Time Scaling 1 timestep = 9.308e -06sec Minimum Level of VR VR 9 (2.50e-03 m/voxel)


domain: phys sdv

text:
Adrien Casanova

Marie-Charline Blatché

Fabrice Mathieu

Aurélie Lecestre

Cécile Ferré

Daniel Gonzales-Dunia

Liviu Nicu

Guilhem Larrieu

Probing electrical activity of single neurons based on 1D nanostructures: from

Abstract -The struggle against neurodegenerative diseases is one of the major challenges in the near future and the global understanding of these diseases goes through a better expertise at the single cell level of basic mechanisms involved in neuronal networks. We need to investigate closer to the cellular material and in this way, miniaturization of electronic components and emergence of nano-biotechnology open new perspectives. Indeed, we are now able to fabricate high sensitive nano-devices to follow neuronal activities. Here, we will present two different approaches to interface neurons, a first one based on a nano-FET for extracellular recordings and a second one using vertical nanowire arrays (nano-electrodes) for intracellular measurements.

I. INTRODUCTION

Due to constant aging of the world population, neurodegenerative diseases will constitute a major issue in the near future. Neurons are basic building blocks of brain architecture and location of numerous of these diseases and to struggle against them, we need to increase our comprehension of basic mechanisms involved in a neuronal network. To have a more detailed understanding of neurons behavior, we need to reduce the scale of our study and investigate closer to the cellular material down to the cell level over the long term with in-vitro cultures. Indeed, a roadblock in the development of new therapies is related to the poor understanding of agerelated diseases at the single cell level due to limits of space / time resolution of current characterization tools. In that scope, we need to develop high sensibility recording devices able to interface single cells, to increase both the recording resolution and the spatial resolution of the measures. In this context, miniaturization of electronic components and emergence of nano-biotechnology open new perspectives for addressing this kind of neurobiological issues and holds great promise to improve the resolution levels. First demonstrations have been published in this direction based on nanowireFET [1] or vertical nanowire probes [2]. In this work, we propose to co-integrate extra and intracellular approaches in a same platform, (vertical nanowire arrays and nano-FETs), to accurately compare the advantages and drawbacks of each device to interface neuron electrical activity.

II. EXTRA/INTRACELULLAR APPROACHES

The interaction between a cell and a recording electrode (active or passive), can be schematized by two junctions composed by a resistance in parallel with a capacitance (Figure 1). The first one characterizes the membrane impedance and the second one defines the electrode impedance caused by the interface between the ionic current from the cell and the electronic current in the electrode. These parameters play an important role in the recording resolution and depend on the mechanical interaction between the cell and the electrode but also the electrode characteristics. A 3D passive nanostructure, such as vertical nanowire, allows a high affinity with cell (potentially intraneuronal interfacing) but is governed by its electrode impedance, which fixes the coupling between the value of the cell potential (Vintra) and the measured potential (Vmes). On the other hand, a nano-FET enables an active transduction of the signal that is not limited by the electrode impedance but the multi-terminal configuration of the device limits the possibility of a close affinity with the cell.

III. DEVICE FABRICATION

The nanowire recording devices are created with a large scale and cost effective top-down approach combining conventional lithography tools and reactive ion etching. Firstly, a silicon on insulator 4" wafer (Si 4µm/Buried oxide 1µm/Si wafer 400µm) has been structured by photolithography (i-line stepper), to obtain resist nanodots with diameter around 350 nm (Figure 2). The diameter has been tuned by an oxygen plasma step before the plasma etching of the silicon layer by deep reactive ionic etching. Figure 2 presents the vertical Si NW array obtained with 200 nm diameter and 3.5 µm long.

Probing electrical activity of single neurons based on 1D nanostructures: from extra to intracellular interfacing.

Adrien CASANOVA1 , Marie-Charline BLATCHE 1 , Fabrice MATHIEU 1 , Aurélie LECESTRE 1 , Cécile FERRE2 , Daniel GONZALEZ-DUNIA 2 , Liviu NICU 1 , Guilhem LARRIEU 1 . To ensure a signal recording in liquid environment, we developed a core-shell-type device (Figure 3A) with a conductive part at the center, encapsulated by a conformal silicon oxide to isolate the probing nanostructures from the culture media. The bottom part of the NWs is connected to encapsulated metallic lines to drive the potential registered at the NW level to external interface.

In parallel, silicon nano-FETs (active devices) have been developed (Figure 3B) by top down approach. The active channel is a planar NW (50 nm) connected by two source/drain extensions composed by silicided contacts on highly doped regions (boron p-type doped at 1.E19 at.cm -3 ).

IV. RESULTS AND DISCUSSIONS

The devices have been electrically characterized in order to extract their main characteristics in liquid media. For instance, Figure 4 shows the impedance of a 9 NW array structures as function of the frequency. Considering a frequency of an action potential of neurons (1kHz), the impedance value is below 10 7 Ω, which should lead to the high neuron/probe coupling coefficient [3]. Nanowire-FETs have been characterized using the back-gate contact as gate electrode to get the intrinsic characteristic of the devices (Ion/Ioff ratio ~ 6 decades) and then in liquid media to study their sensing behavior. In particular, Figure 5 shows a pH sensibility of the NW-FETs close to the Nernst limit (58mV/pH). Finally, rat hippocampal and cortical neurons have been cultured on the devices and after 10 days in-vitro (10DIV), the electrical activity has been successfully recorded with both approaches. Fig. 6 shows several examples of local field potentials from few somas and action potentials from a single soma (1ms duration). We will discuss and compare these results from electrical and technical point of view. V. CONCLUSION

In summary, we realized a platform based on nanowire devices combining vertical nanowires and nano-FETs to interface neurons and compare both approaches in the same culture conditions. Neuronal culture on this platform had been performed and we succeeded to accurately record neuronal activity with both devices.

Figure 1 :

 1 Figure 1: Electrical model of the interaction between a cell and a passive or active electrode.

Figure 2 :

 2 Figure 2: Resist nanodots after the photolithography step and transferred into silicon by DRIE to get 200nm diameter nanowires (H=3.5µm).

Figure 3 :

 3 Figure 3: A) core-shell-type nanowire device for passive nanoprobes structures B) Nano-FET composed by a planar nanowire channel.

Figure 4 :

 4 Figure 4: Impedance characterization of a 9-nanowire-array.

Figure 5 :

 5 Figure 5: Current-voltage characteristics in liquid media with several pH values.

Figure 6 :

 6 Figure 6: a) Local field potentials train by extra-cellular recording. b) A local field potential (10ms) and a action potential (1ms) with vertical nanowire approach.

LAAS-CNRS, Université de Toulouse, CNRS, Toulouse, France.

CPTP INSERM UMR 1043, CNRS UMR 5282, Université Toulouse.


Sarah Zribi
email: szribi@mines-albi.f

Frédérick Bénaben
email: frederick.benaben@mines-albi.f

Jean-Pierre Lorré
email: jplorre@linagora.com

Hervé Pingaud
email: pingaud@univ-jfc.fr

Enhancing Services Selection by Using Non-Functional Properties within BPMN in SOA Context

Keywords: Collaborative Process, Interoperability, Non Functional Properties, Service Selection, SOA Governance, BPMN, SLA

In the Future Internet vision, multiple services coming from heterogeneous organizations have to collaborate together in order to achieve the customers' demands from both functional and non-functional point of view. Hence, it is necessary, within an organization, to put in place an interoperable approach that ensures the best functioning control and selection of services. This paper presents a comprehensive framework for representing the customer Non-Functional Properties (NFP) within a collaborative Business Process Management (BPM) and the contribution of the Service Oriented Architecture Governance (SOA Governance) to give customers a better selection of services that best suits their business NFPs requirements among all Web Services candidates provided by functional matching.

Introduction

In an era marked by a deep and growing technological progress, the environment in which firms are located has become more complex and characterized by increasing competition. Companies have realized that they can ensure their future development using new technologies such as Service-Oriented Architecture (SOA) and by migrating their Information System to this paradigm. SOA is a computer system architectural style based on distributed and loosely coupled applications in which functions are separated into distinct web services. A Web Service (WS) can be defined as an autonomous and distributed entity, independent of any platform and that responds to a particular need. However, to achieve the user's requirements, several heterogeneous WS can be assembled to interact and collaborate within a business process [START_REF] Earl | Service-oriented Architecture: Concepts, Technology, and Design[END_REF]. Selecting the right WS in each task of this business process has become a major challenge in a collaborative context. On one hand, this is due, to the inexorable rise of services existing in the web. On the other hand, it is also due to the fact that the number of services offering the similar functional properties is relatively huge. That is why the NFPs play a crucial role to sort them.

Our Contribution. To address the aforementioned challenge, this paper takes into account these properties with a particular focus on Non-Functional ones. It presents a complete framework for modeling NFPs annotations within a Business Process Management Notation (BPMN) 2.0, discovering WS, selecting and ranking them. The contribution of this paper is threefold. First, we propose a solid way to annotate NFPs in BPMN. Since interoperability is an important factor in SOA, it is essential to ease it by adopting standards. Thus, we are principally interested in the use of common agreed standards for the NFPs annotations in BPMN. We also incorporate a graphical representation of these NFPs annotations to enable the user to annotate his NFPs requirements in each task of the BPMN2.0 process. Second, an essential component in our approach is the SOA Governance Registry. It provides an uniform way of governing WS. We use the SOA Governance Framework to facilitate and standardize the discovery of WS and their NFPs. Our third contribution binds the two previously ones. We propose algorithms that match BPMN business tasks with the set of WS candidates published in SOA Governance registry and provided by semantic matching according to the NFPs requirements of the user. Related Work. BPMN, non-functional properties and WS selection are very active research topics. Guangjun and al., in [START_REF] Earl | Service-oriented Architecture: Concepts, Technology, and Design[END_REF], present a method for WS selection based on ontology to select the best WS from a functional and QoS (Quality of Services) points of view. However, their NFPs selection approach never takes into account the user's NFPs preferences values. Their QoS filter consists on ranking services candidates between them according only to the user's NFPs weights. Youakim and al. propose, in [2] a framework for selecting WS based on the user's NFPs. Even if they take into account the user's preferences, they do not use a common well-known model for representing NFPs. Besides, they don't detail the registry where WS are published. In [START_REF] Mylopoulos | Representing and Using Non-Functional Requirements: A Process-Oriented Approach[END_REF], John and al. also present a framework that details how to represent and use NFPs within a process. In contrast, their work enumerates only some NFPs and they mostly focus on representing them in the development phase and not in the entire life-cycle. The key difference between previous approaches and our solution is that we take into account all the user's preferences in the selection and ranking of the set of WS provided by the semantic functional matching. Thus, the result is very close and fits the user's expectations. What's more, none of those previous approaches does address the issue of a robust registry where the discovery of WS is done. The rest of the paper is structured as follows. First, in Section 2 we present an overview of the important techniques related to our approach. Then, the architecture of our approach is detailed in the Section 3. Finally, a conclusion and future works are presented in Section 4.

Preliminaries

This section briefly outlines the major concepts and techniques used in our approach.

BPMN is a standard supported by the Object Management Group (OMG). It allows the design of a wide variety of business processes, the design of diagrams, which are easily understandable and potentially executable. The graphical modeling using BPMN is done using a quite intuitive set of elements allowing a quick understanding for any user if the diagram is not too big or too complicated.

Web Service-Policy (WS-Policy) was developed by the W3C in 2006. The basic construct around WS-Policy is the assertion, which is a bit of metadata. Assertions are not defined, but rather left to developers of individual standards. That's why to define NFPs assertions, we propose to combine WS-Policy with the use of the Web Service Quality Factors (WSQF) model that clearly depicts a model for NFPs.

WSQF was published in 2011 by the WS Quality Model TC as an OASIS Committee specification. According to the specification [START_REF]Web Qervice Quality Factors (WSQF) Specification[END_REF], WSQF refer to a set of several properties which are classified into six groups: 1-Business Value Quality (refers to the business perspective to evaluate the business value of WS), 2-Service Level Measurement (characterize the quality that a user perceives when actually using WS), 3-Interoperability (represents the ability to evaluate whether a WS system conforms to standards), 4-Business Processing (indicates the capability of a WS platform for assuring correctness in business processing), 5-Manageability (delineates the capability of a WS platform for assuring correctness in business processing), and 6-Security (identifies the degree of ability that can protect WS from various threats).

Based on this, WSQF model comprises the majority of NFPs that can concern a WS during its entire life-cycle. Which resonates perfectly with our needs.

SOA Governance, according to definitions presented in [START_REF] Lesbegueries | Multilevel Event-Based Monitoring Framework for the Petals Enterprise Bus[END_REF], can be defined as a set of processes, rules, mechanisms of control, enforcement policies and best practices put in place to ensure the successful achievement of the SOA. Its central component is the registry that promotes the discovery and reusability of WS. As detailed in [START_REF] Lesbegueries | Multilevel Event-Based Monitoring Framework for the Petals Enterprise Bus[END_REF] and [START_REF] Lesbegueries | Multilevel Event-Based Monitoring Framework for the Petals Enterprise Bus[END_REF], SOA Governance registries serve not only to catalog and inventory data, but also as places to store metadata about services as the descriptions of their functionalities, service contracts, capabilities and NFPs.

Service Level Agreement (SLA) is a commonly used way to indicate nonfunctional objectives to be reached by the business service once deployed. They are also needed to define the responsible entities to be alerted if a constraint is violated. SLA template is a model used for the representation of its various clauses and the main NFPs that can be measured at the runtime phase.

General Architecture

In the remainder of this section, we focus on the description of our approach. Formally, the proposed framework, as defined in Figure 2, consists of two major parts. The first one concerns the graphic representation of BPMN with NFPs Annotations. The second one defines an algorithm witch matches the user's NFPs requirements with WS that are provided from the functional matching. ) and NFPs (how does the WS do its functionalities?). The final selection of WS depends on matching according to both of them. The functional matching, as detailed in [START_REF] Benaben | Semantic issues in model-driver management of information system interoperability[END_REF], provides a set of WS that match functionally (syntactic and semantic) with the target business task request. Then, using this provided set of WS, we match them, this time, according to their NFPs which is our main interests in this section. As explained previously, we use the WSQF model that extends WS-Policy as support to such annotations. The Figure 3 shows a screenshot of our graphical framework that supports NFPs annotations at the design phase of the business process. SOA Governance Registry. According to the BPMN annotated file and the algorithm of functional matching, as explained in [START_REF] Lesbegueries | Multilevel Event-Based Monitoring Framework for the Petals Enterprise Bus[END_REF], a first set of services candidates is given. For each service of this set and among to our SOA Governance Registry framework, we can extract all NFPs that correspond to it. For example the response time property can be found it in the SLA template published by the service provider.

Finally, among all this information, we can apply the non-functional algorithm presented in the following.

NFP Services Selection and Ranking Algorithm. Since the non-functional features play different roles, we can identify two sorts of NFPs: those where it is better to maximize the value, such as the availability, the service recognition, the service provider reputation, etc.; and those where it is better to minimize their values like the price, the response time. We call the first set of properties "NFPs to maximize" and the second set "NFPs to minimize". Besides, NFPs are also subdivided into further levels according to the type of the property. We identify three levels of types: Numerical values, Boolean values, and Ranges. Our NFPs matching algorithm take into account this levels and is presented below.

Step1: Elimination of Services Candidates outliers: our approach aims to be very close to the user's preference, so all services provided by the functional matching do not necessarily have to be kept in the case where they unduly deviate from the user's NFPs requirements. Hence, we set a threshold tolerance parameter (we consider the default 30%) and we eliminate any service, from the services candidates, that at least has one NFP value that exceeds this threshold.

Step2: Normalization and Centering of Services Candidates: Since the values and dimensions of NFPs properties are different, they cannot be compared directly between them. It is necessary to normalize the NFPs values to bring all the features into proportion with one another. Once the normalization of the set of Services candidates is done, the centering part aims to represent them around the target business task. In the following, we explain clearly this steps using the adequate formula in each case.

For the business task: As our main interest is to be close to the user's requirements, we normalize the values NFPs values of services candidates according to the user's preferences. Each value of the business task will be equal to 1 in the normalization part and 0 after the centering step.

Normalized and Centered Business Task [m] = 0 .

(

) (1) (1) 1
For Services Candidates: the coefficients of NFPs for each service candidate reflect meaning between the NFPs of the service and the NFP of the user requirement. We distinguish three different ways to normalize according to each type of NFPs.

A) Case of Boolean values: there is not any change because the NFPs can have only two values: 1 or 0. Then there is not any obligation to normalize them.

B) Case of Numerical values: the normalization and centering of the value of each NFP of Service Candidates is depending on the NFPs Properties when it is a property to maximize, we use the formula (2) and the formula (2') when it is a to minimize.

Normalized and Centered Service Candidate

[nm] = ୗୣ୰୴୧ୡୣ େୟ୬ୢ୧ୢୟ୲ୣ[୬୫] ୳ୱ୧୬ୣୱୱ ୟୱ୩ [୫] -1 .
(2) who rolls the highest value. Once we classify the entire services candidates of the first sub-matrix, we address the second one. In the first step, for each positive NFP value, we replace it by zero, we calculate the weighted distance for each WS, and the rank them starting with the lowest value. In case of ex-aequo, we addition to the founded distance the weighted distance of NFPs positives values and finally we rank them starting with the higher global distance.

Illustrative example: In the following example, we try to match a Business Task (BT) from our BPMN process once the user annotated it with his NFPs constraints. As shown in the vector « Business Task », we consider that the user annotated this BT with four NFPs: response time (in milliseconds), availability (a float value expressed by a percentage), price (in milliseconds) and encryption (is a boolean value). Response Time and Price are properties to minimize. Availability and Encryption are properties to maximize. WS Candidates corresponds to the six services provided by the functional matching. The NFPs values of these WS are expressed in the matrice « Services Candidates ».

According to the step 1 of the algorithm, we deduce that the service candidate "S3" is an outlier because its availability value is out the threshold tolerance. Thus, it is necessary to eliminate it. The second step of the algorithm is normalization and centering. Thus, for the target business task, we apply the formula (1) and we obtain the vector "Normalized and Centered Business Task" below. Then, for Services Candidates, we apply the formula (2') for Response time and Price, the formula (2) for Availability and finally for Encryption we keep the same values as it is a Boolean NFP as shown below.

Once the business task and the services candidates are normalized and centered, the third step of our algorithm is to select and rank these services according to their degree of NFPs matching with the target business task. As we detailed previously, we divide services candidates into two sub-matrixes: the first one includes services candidates that have all NFPs values equal to or greater than zero, so in our example S2 and S5 and S1, S4 and S6 belong to the second one. Then, for the first sub-matrix (S2 and S5), to rank services we need to take into account the weights defined by the user to calculate the weighted distance as depicted in the sub-matrix below:

Likewise, for those that belong to the second sub-matrix (S1, S4 and S6), we obtain the following matrix:

Finally, the final selecting and ranking of services candidates that best match with NFPs user requirements defined in the business task is: S2, S5, S1, S6, S4.

Conclusion

In this paper, we present a complete solution for enhancing WS selection with a particular focus on NFPs according to the NFPs BPMN business tasks requirements. Indeed, we try to match each business task annotated NFPs by the user with NFPs of the set of WS provided by the semantic matching. Thus, we consider that for one business task, there is a set of services that each meets fully the functional requirement of the user (1-1 approach). However, in many cases services need to collaborate together to achieve the requirements of the Business Task. Thus, for one business task, a collaboration of several services is required (1-n approach). We have started working on the extension of our solution by adding the 1-n matching.

Fig. 2 .

 2 Fig. 2. General architecture of enhancing WS selection according to NFPs BPMN annotations Modeling NFPs annotations in BPMN. WS is characterized by two sorts of properties: functional properties (what does the WS do?) and NFPs (how does the WS do its functionalities?). The final selection of WS depends on matching according to both of them. The functional matching, as detailed in[START_REF] Benaben | Semantic issues in model-driver management of information system interoperability[END_REF], provides a set of WS that match functionally (syntactic and semantic) with the target business task request. Then, using this provided set of WS, we match them, this time, according to their NFPs which is our main interests in this section. As explained previously, we use the WSQF model that extends WS-Policy as support to such annotations. The Figure3shows a screenshot of our graphical framework that supports NFPs annotations at the design phase of the business process.

Fig. 3 .

 3 Fig. 3. Screenshot from our BPMN design framework supporting NFPs annotations

Acknowledgement. This paper is based on an ongoing work supported by the Agence Nationale pour la Recherche (ANR) through the Project SocEDA: SOCial Event Driven Architecture.

Normalized and Centered Service Candidate [nm] = 1 -Service Candidate [nm] Business Task [m] .

(2') However, there is a particular case when the value of NFP in Business Task is equal to zero. So in this case, for each non-zero NFP of services candidates, we apply the formula (3) if it NFP to maximize and (3') in the other way.

Normalized and Centered Service Candidate [nm] =

Service Candidate [nm] Max (Service Candidate [m]) .

(3)

Normalized and Centered Service Candidate

')

C) Case of Ranges in the Business Task: for each NFP value in the services candidates that is includes in the range of corresponding NFP in business task, satisfy the requirement of the user on this NFP. The value of NFP for each service candidate after the normalization and centering is calculated according to (4) if it is NFP to maximize and (4') else.

Else, when the NFP value is out of the range, it is normalize with the upper bound when it is superior -formula (5)-and, else, with the lower one-formula (5').

.

(

.

(

')

As previously the centering of NFPs values depends on where it is a property to maximize, then we use the formula [START_REF] Lesbegueries | Multilevel Event-Based Monitoring Framework for the Petals Enterprise Bus[END_REF] or to minimize, then we use the formula (6').

Normalized and Centered Service Candidate [nm] = Normalized Service Candidate [nm]-1 .

Normalized and Centered Service Candidate [nm] = 1 -Normalized Service Candidate [nm] .

(6')

Step3: Selection and Ranking Services Candidates basing on to the NFPs values At this step, we have a matrix of services candidates with normalized and centered NFPs values. We distinguish three types of NFPs values: positive ones (that means that the NFP value acts positively towards the corresponding user's NFP requirement), null ones (that means that the NFP value is exactly the same as the user one), and finally negative ones (in this case, NFP value acts negatively towards the corresponding user's NFP requirement). Indeed, each NFP value of this matrix reflects the degree to which it influences the user's requirements.

To tackle with that, we propose to divide the matrix into two sub-matrixes. The first one includes services candidates that have all NFPs values equal to or greater than zero. The second sub-matrix contains the rest of services candidates. For those services in the first sub-matrix 1, we are sure that all of them match the user's NFPs requirements. Thus, for sorting them we need to calculate the weighted distance (according to the weights of NFPs defined by the user and that express his preferences) of each service candidate and then to rank them starting with the one


Abdelhamid Moutaoukil

Ridha Derrouiche

Gilles Neubert

Modeling a Logistics Pooling Strategy for Agri-Food SMEs

Keywords: Logistics Pooling, Sustainable development, Agri-food SMEs, Discrete event modeling, Reception

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

To be competitive, manufacturers must optimize their supply chain. This optimization, long based on an economic approach; happen today through the integration of environmental and social concerns, in line with the objectives of sustainable development [START_REF] Rosen | Sustainable Manufacturing and Design:Concepts, Practices and Needs[END_REF]. In addition, a constant pressure of European regulations pushes industry to integrate sustainability concerns in their supply chains. The regulatory developments translates into economic terms, with the Modernization Law Economy-LME whose objective is lower selling price to consumers [2], or notably with Grenelle law (-20% emission of greenhouse gas emissions by 2020), or with the new Ecotax law.

In this context, new requirements have been added to the requirements of economic efficiency. Logistics systems must now meet the requirements of sustainable development, namely:

• At the economic level: reducing logistics costs.

• At the ecological level: reduce both CO2 emissions and energy consumption, with an incentive to make more recycling and waste treatment [START_REF] Ülkü | Dare to care: Shipment consolidation reduces not only costs, but also environmental damage[END_REF] and [START_REF] Wang | A multi-objective optimization for green supply chain network design[END_REF].

• At the societal level, take into consideration the expectations of different stakeholders in the process of making business decisions [START_REF] Mccarter | Northcraft Happy together? Insights and implications of viewing managed supply chains as a social dilemma[END_REF] and [START_REF] Piotrowicz | A structured approach for assessing Suistainable best practices in supply chains[END_REF].

These requirements are more difficult to reach for SMEs, because their logistics performance does not allow them to engage in a sustainable approach [START_REF]Enquête Nationale : La logistique dans les PME-PMI de l'agroalimentaire, synthese des resultats[END_REF] and [START_REF]Organisation logistique du secteur agroalimentaire dans la Loire[END_REF]. In addition, Just in Time-JIT policy has been implemented in most sectors: to deliver faster, more frequently and in small quantities. These changes in flow management explode SMEs logistics costs, which endangers the entire implementation of a sustainable development approach. In this context of accelerating flow and inventory reduction, logistics sharing between SMEs is more than ever at the heart of priorities. These are strategic decisions for these companies: what is the structure of a pooled logistics network to ensure a better economic, environmental and social performance?

Research Context and Approach

In the continuation of literature review presented in [START_REF] Moutaoukil | Pooling Supply Chain: literature review of collaborative strategies[END_REF], logistics pooling was treated in three ways: i) The pooling of transport and platforms from a single source in order to serve a set of customers [START_REF] Chen | Mathematical model and solution approach for collaborative logistics in less than truckload (LTL) transportation[END_REF], [START_REF] Xuefeng | An Integrated Multi-depot Location-inventory-routing Problem for Logistics Distribution System Planning of a Chain Enterprise[END_REF] and [START_REF] Ülkü | Dare to care: Shipment consolidation reduces not only costs, but also environmental damage[END_REF]. ii) The pooling of transport and platforms of a set of suppliers to serve one or more clients [START_REF] Leitner | Structural concepts for horizontal cooperation to increase efficiency in logistics[END_REF], [START_REF] Cruijssen | Horizontal cooperation in transport and logistics[END_REF], [START_REF] Ballot | Reducing transportation CO2 emissions through pooling of supply networks: perspectives from a case study in French retail chains[END_REF] and [START_REF] Howard | Evaluation of stock allocation policies in a divergent inventory system with shipment consolidation[END_REF].

iii) The pooling of transport with vehicle routing and exchange delivery orders between carriers to reduce empty returns and increase the use of means of transport [START_REF] Howard | Evaluation of stock allocation policies in a divergent inventory system with shipment consolidation[END_REF] and [START_REF] Martel | La collaboration dans le transport en Chargements Complets[END_REF].

In this literature, taking into account the objectives of sustainable development is recent. The research work of [START_REF] Cruijssen | Horizontal cooperation in transport and logistics[END_REF] focused on the economic dimension, while the work of [START_REF] Pan | The reduction of greenhouse gas emissions from freight transport by merging supply chains[END_REF] and [START_REF] Ballot | Reducing transportation CO2 emissions through pooling of supply networks: perspectives from a case study in French retail chains[END_REF] introduced the environmental dimension by calculating the CO2 emissions of their scenarios. Sustainable development is mostly treated as an environmental perspective while the societal dimension is generally not considered.

Finally, previous studies consider important flow treaties in number of pallets, mostly in retail distribution. These studies generally consider a stationary demand and call upon distribution systems of batch of products which occur according to long delays in the distribution network, particularly through storage platforms. The importance of massified flow in these contexts provides the ability to transit to other means of transportation that are more economical and ecological (e.g. rail), as studied in [START_REF] Pan | The reduction of greenhouse gas emissions from freight transport by merging supply chains[END_REF] and [START_REF] Leitner | Structural concepts for horizontal cooperation to increase efficiency in logistics[END_REF].

The specificity that we have identified in the context of agri-food sector, resides on a modality of logistic flow of small quantities, expressed in number of parcels (a few pounds) to be distributed in J+1, J+2 or in J+3 to different destinations through different operations: loading, consolidation, unbundling and distribution. This service falls within the "express mail" and based on small transport systems. Economic criteria sometimes push these agri-food SMEs to delay deliveries, even losing orders to avoid logistical costs associated with too small shipments.

Finally, research on logistics pooling as in [START_REF] Cruijssen | Horizontal cooperation in transport and logistics[END_REF], [START_REF] Ballot | Reducing transportation CO2 emissions through pooling of supply networks: perspectives from a case study in French retail chains[END_REF] and [START_REF] Pan | The reduction of greenhouse gas emissions from freight transport by merging supply chains[END_REF] are based on analytical methods and call upon strong constraints to simplify their models: e.g. fixing the carrying capacity, or the failure to take into account the factor "loaded weight" for the calculation of CO2 emissions in vehicle routing.

For our research, it is essential to consider the constraints of transportation as a variable in the performance evaluation of pooled networks, which bring us to test various hypotheses, more appropriate to express small package. For this, we chose use methods based on simulation. Among its advantages, simulation offers the possibility to take into account realistic assumptions (compared to analytical models). However, the results are only valid for studied scenarios, and to be generalizable, it must conduct a sensitivity analysis of the model relative to different parameters. Our goal is to compare the performance of a traditional logistics network with different models of pooled logistics networks. Given the complexity of logistics systems and the difficulty to take into account different constraints in analytical model, the simulation appeared to us as the most appropriate tool for this research.

Modeling a Logistics Pooling Strategy

Logistics pooling is a partnership agreement that involves voluntary pooling of physical and information and skills in order to achieve economic and environmental and social gains, or to counter in the short term a constraint or to access a service unavailable individually [START_REF] Moutaoukil | Pooling Supply Chain: literature review of collaborative strategies[END_REF]. The framework of this partnership can assume various organizational forms depending on the nature of the partners and resources and products [START_REF] Derrouiche | B2B Relationship Management: A Framework to Explore Impact of Collaboration[END_REF].

Modeling approach. To model a logistics pooling strategy, we first define different pooled schemas (sharing scenarios). To model these different scenarios, we construct a model which consists of a simulation model coupled with an optimization model. The simulation model is used to simulate different scenarios and the optimization model is used to optimize vehicles routing in certain scenarios. To choose the most relevant scenarios, we develop a system of performance indicators to evaluate and compare different scenarios.

Scenarios

Relevant scenarios Based on these two types of pooling, we identified different scenarios (Table 1). We consider two configurations: C1 (Many to one) where a set of manufacturers distribute their products to a single common client and C2 configuration (Many to Many), in which several clients deliver a set of manufacturers that are not necessarily common using or not a cross docking platform. Scenarios with a storage platform are normally possible in a logistics pooling strategy. In our particular case, given the above requirements on the agri-food SMEs, including short delivery time of small parcels, we will not take into account these scenarios. S0 scenario for both configurations refers to the initial situation, without pooling. For C2 configuration, transportation between partners can be directly to the cross docking platform or in multipick mode (vehicles routing for collecting products). Delivery transport to different customers can be also either directly from the cross docking platform or in multidrop mode (vehicles routing for the distribution of products).

Model

Proposed Model: Assumptions & Parameters. The proposed model in C2 configuration is a logistics network with I manufacturers and J clients. All companies are at the same level of decision and there is information sharing. Since we are interested only in patterns of distribution, we ignore the production processes of manufacturers, and it is assumed that they have an infinite stock of finished products.

For each customer i, the demand for a product of reference j follows a normal distribution with mean X ୨

୧ and standard deviation Y ୨ ୧ with an arrival rate F , over a period T ୨ of the year. To take into account the seasonality of products in the agri-food sector, we consider that a further period T ୨ ᇱ of the year, demand for the same product i to the same customer j follows a normal distribution with mean X′ ୨ ୧ and standard deviation Y′ ୨ ୧ with arrival frequency F ᇱ . Demand is directly transformed in order of delivery of finished products. Daily delivery orders to the same destination are consolidated.

To give an overview of the modeling we have done, this paper is focused on the example scenario C2S2. This strategy aims to establish cross dock platforms that collect parcels from several manufacturers, consolidates these expeditions, and directs them to the appropriate client in grouped form.

The objective of this scenario is to assign platforms consolidation to suppliers and to customers to improve network performance. We select an appropriate number of platforms from potential hubs, and assign suppliers to different platforms. Platforms receive products from manufacturers and consolidate all products that have the same destination before sending products to the customer in question.

Each company has a physical system composed of an infinite stock module of finished product, a "Preparing order" process and a transport module for the products delivery to the platform. Production processes are ignored. Transport module simulates the transport and delivery times. This module is composed of a transport resource that includes a human resource (driver) and a truck from a heterogeneous fleet of trucks. The capacity of the truck is chosen according to quantity to be carried. A CO2 emissions calculator is connected to transport module.

At the platform, is made cross-docking operations of different manufacturers' references that are consolidate according to different destinations. In this perspective, we can consider that the cross-dock operations are summarized in their time, with generation of costs.

We make the following general assumptions:

• Each supplier produces a single product [if a supplier produces different products, we can create an additional fictitious provider for each additional type of product] • All products are compatible and stackable.

• Deliveries are made into A to C (Command sent the day J and received the days J+2)

• The capacity of transport is limited by weight and volume.

• Transportation in the logistics network is operated by a carrier.

• Each platform can serve more than one customer and each customer can be served from multiple platforms. There are no links between platforms.

Vehicle routing optimization. Among the scenarios that we consider, we find several scenarios that are based on vehicle routing. The optimization of vehicle routing problem is in tactical-operational level of decision-making. While the issue of our research concerns the design of logistics distribution network that reports to the strategic level of decision-making. However, optimization of vehicle routing is important, because it contributes to the evaluation of different scenarios.

For this purpose, we build an optimization system of vehicle routing which is based on three-step, as shown in the following figure. The proposed optimization system begins by determining the optimal tour passes through all manufacturers and minimizes the traveled distance. In a second step, the constraint of back time to the platform is introduced. This time constraint is the maximum duration not to exceed by a tour vehicle. With this constraint, we determine the exact number of tours to do. Knowing the manufacturers included in each tour and the amount to be charged at each, we can specify the capacity truck to send on each tour.

The optimization of vehicle routing model is coupled to the simulation model of different scenarios.

Fig.2. optimization model of vehicles routing 4 Parameters & Performance Indicators

We have summarized in Table 2, all data and parameters necessary for the simulation of C2S2 scenario. These parameters are used to evaluate the various performance indicators for this scenario, which then allow us to make a comparison with the other scenarios.

Economic Indicator. Throughout logistics network, three cost factors are considered: transportation cost, cross-docking cost and handling costs. Handling cost includes cost of loading and unloading. The total logistics costs of each scenario are calculated using the following formula: Environmental indicator. We summarize the environmental indicator in CO2 emissions. To model CO2 emissions, we rely on references [START_REF] Pan | The reduction of greenhouse gas emissions from freight transport by merging supply chains[END_REF], [START_REF] Hickman | Methodology for calculating transport emissions and energy consumption (Report for the Projet MEET)[END_REF] and [START_REF] Ademe | Calcul des facteurs d'émissions et sources bibliographiques utilisées, Méthode bilan carbone[END_REF].

To calculate CO2 emissions, we must model the distance between manufacturers, between clients, and the distance between platforms and manufacturers and customers. We must also consider the weight carried. In fact, CO2 emissions depend on the weight carried, on the capacity of the truck used, the distance traveled and the average speed of the travel. The average speed of course depends on the type of path in regional or national routes.

We have adapted the formula given by [START_REF] Howard | Evaluation of stock allocation policies in a divergent inventory system with shipment consolidation[END_REF] and [START_REF] Derrouiche | B2B Relationship Management: A Framework to Explore Impact of Collaboration[END_REF], to calculate the CO2 emissions based on truck type k, by setting the value of the average speed for each location:

ሺ݀ according different transport capacity are based on the data provided in [START_REF] Hickman | Methodology for calculating transport emissions and energy consumption (Report for the Projet MEET)[END_REF] [START_REF] Ademe | Calcul des facteurs d'émissions et sources bibliographiques utilisées, Méthode bilan carbone[END_REF].

Societal indicator.

In France, more than 80% of freight transport is done by road transport [START_REF] Cgdd | rapport du Commissariat général au développement durable[END_REF], this leads to strongly solicit transport system and infrastructure. Trade in goods actually creates congestion on some roads, insecurity and various nuisances to the public.

Therefore, other criteria must be taken into account when evaluating logistics pooling projects, which are societal incidents on the various parties involved in such projects. Two parties are mostly affected: carriers and residents. Carriers are the main actors of transport pooling, and their needs and expectations should be taken into account. Any reduction in the number of kilometers traveled, helps reduce the risk of accidents. Decreasing congestion, reducing the number of trucks involved in logistics pooling projects, also plays a role in reducing accident risk. For our purposes, we chose to use the shipping rate and traveling distance for the accident risk assessment.

The second stakeholder is the rest of the population, who are not directly involved in the transport of goods, but who share the same transport network. Network congestion by trucks, which increases especially near to logistics areas (platforms), the noise and blocking streets causes of trucks, and other situations are considered negative by residents. Thus, a logistics pooling system that reduce congestion, or reduce the perception of large vehicles in transportation networks can be considered as a good solution. Note that all of these indicators are difficult to quantify empirically, because they are linked to more sociological aspects. For this reason, we consider the indicator of the number of trucks used, which can tell us about other less quantifiable indicators.

Conclusion

The particular case of agri-food SMEs logistics pooling is an original issue not addressed in the literature. In this context, our work proposes a new model that integrates characteristics of agri-food SMEs logistics flow in the Loire region, and that takes into account sustainable development objectives with its three dimensions: economic, environmental and social. The elements necessary for modeling the research question have now been identified and allowed a first proposal of the conceptual model. As future research lines, we are currently working on its validation in a real agri-food SMEs pooled network.

Fig. 1 .

 1 Fig.1. Modeling approach

Fig. 3 .

 3 Fig.3. Simulation Model of C2S2 scenario

  No passage through Platform Mode = 1 : passage through Platform We have proposed a method of calculating the total cost of transportation (provided by the carrier) summarized in this formula: Transport cost = Variable cost + hourly cost + Fixed cost Variable cost = Traveled distance* cost per kilometer Hourly cost = (Load time + Transport time + Unload time)* cost per hour Fixed cost = [(Load time + Transport time + Unload time)/Working time]*Fixed cost Transport time = Traveled distance / average speed The transportation cost for each manufacturer is a function of the quantity transported, the distance, travel time and the type of truck used.

:୩:

  , ,ݔ ݇ሻ = ݀ * ቈሺ -Emission of truck type k in full load E ୣ୫୮୲୷ Emission of empty truck type k. X : Total weight of transported parcel C ୩ : Weight capacity of k type truck. The calculation of emission E ୳୪୪ ୩ and E ୣ୫୮୲୷ ୩

Table .

 .

			1. Various scenarios of logistics pooling
	Configuration	Scenarios	Transport upstream Direct Multi-pick Yes No cross dock plateform	Transport downstream Direct Multi-drop
	C1	S0
	Many to One	S1
		S2
		S0
	C2	S1
	Many to	S2
	Many	S3
		S4
		S5

Table . 2

 . . Parameters and constraints and performance indicators of C2S2 scenario simulation.

	Provider 1				Demand + Commands
	Production	Storage	Order Preparation	Transport
	Provider 2				PF
	Production	Storage	Order Preparation	Transport	Reception	Cross-dock	Order Preparation	Transport
	Provider n
	Production	Storage	Order Preparation	Transport

Acknowledgments

Authors would like to thank Region Rhône-Alpes for its financial support (Research Cluster GOSPI).


Stephane Pagano
email: stephane_pagano@esc-saint-etienne.fr

Ridha Derrouiche

Gilles Neubert

Collaborative Inter-firm Relationships Based on Sustainability: Towards a New Framework

Keywords: Value creation, Inter-firm collaboration, responsible supply chain, business models, industry ecosystems

After decades of industrial decline, the models of firm competitiveness, green economy, green growth, are making the news. Indeed, there is a growing trend in the reversal of outsourcing or offshoring production of goods and services while inter-firm relationships are under scrutiny. A trend being reinforced by the global awareness on resources scarcity, to integrate in the processes the impacts of climate change and eventually reduce them, to prepare for growing energy costs. The linear economy and it's models of value creation based on trading margins of imported, outsourced, goods and services, global competition between companies, resources spillage, has shown it's limits.

Introduction

The twenty-first century started on a profound global crisis affecting the fundamental living supports of human kind: it's social and environmental conditions. Now in the era of anthropocene, human kind has become a geological agent itself that is able to change the very structure of the biosphere, causing the sixth mass extinction of species and posing a global threat to all our global systems with an "economy that extracts resources at increasing rates without consideration for the environment in which it operates, without consideration for our natural planetary boundaries." [START_REF] The | Towards the circular economy[END_REF] Since the Brundtland Commission has given the first definition of sustainable development as a development that "meets the needs of the present without compromising the ability of future generations to meet their own needs" [START_REF]Our common future[END_REF], we keep going towards financial crises and natural catastrophes: as the latest report from the World Economic Forum put's it: "Future simultaneous shocks to systems could trigger the 'perfect global storm', with potentially insurmountable consequences" that can doom chances of developing an effective, long-term solution [START_REF] Howell | Risk Response Network[END_REF]. How did we get there and what can we do to shift the model?

The State of Our Industries

An outdated model based on unsustainability. In a paper published in 2011 in Harvard Business Review, Michael E. Porter and Mark R. Kramer declared: "Capitalism is under siege, business being increasingly viewed as a major cause of social, environmental and economic problems". Indeed, global growing concern for Corporate Social Responsibility speaks for itself.

According to Porter and Kramer, the problem lies in the fact that most companies are trapped in an "outdated model of value creation" which can be summarized in this description: "Facing growing competition and short term performance pressures from shareholders, managers resorted to waves of restructuring, personnel reductions, and relocation to lower-cost regions, while leveraging balance sheets to return capital to investors" [START_REF] Porter | Creating Shared Value[END_REF].

Industrial decline and value creation. Michael Porter and Jan Rivkin asked HBS alumni [START_REF] Porter | Prosperity at risk[END_REF] about where they intended to locate their future business and found that many of them thought wages abroad were lower, and that they needed to reach customers in big new markets, a case to leave or offshore. Though Porter and Rivkin state that firms are now ready to reconsider offshoring, realizing "they overdid it" discovering hidden costs, they argue that "America's government is not making the country's business environment attractive enough for companies to want to come back." One can ask what the government as to do with the responsibility of firms and investors.

A brief look at OECD value added by industry and services, unemployment and commercial balance of goods (figure 1), seems to show some correlation. In 1980, Porter described "Techniques for Analyzing Industries and Competitors" based on "five forces that shape competitive intensity". This model is focused on the environment of the company and comprises three horizontal threats and two vertical powers [START_REF] Porter | Competitive strategy: techniques for analyzing industries and competitors[END_REF]. Horizontal threats are new competitors addressing the market (new entrants), new products that could replace the company's products (substitute products) and the existing rivalry between established companies in the same industry. Vertical powers are on the opposite sides of the value chain of the company: the bargaining power of the suppliers on one side, the bargaining power of the customers on the other side. A model exclusively orientated on confrontation (figure 2). Of course this five forces model is just a part of Porter's strategic model. It has been widely used over the last decades by companies to design their strategies with heavy consequences: in this model, suppliers are exercising a pressure on the company. This vision pushes procurement or buyers to weaken the position of the suppliers [START_REF] Poissonnier | Les achats collaboratifs : pourquoi et comment collaborer avec vos fournisseurs[END_REF] by improving the bargaining power of the buyer, for example by using strategies such as "Spread Purchases" (divide to rule) or even manipulate the perception of suppliers to "Create a Threat of Backward Integration: Whether or not the purchaser actually desires to backward integrate into" voluntarily leaking word of internal studies of the feasibility of integration [START_REF] Porter | Competitive advantage: creating and sustaining superior performance: with a new introduction[END_REF]. Is this a justifiable mean for the purpose of gaining power against suppliers? For Porter, "The objective of all these approaches is obviously to lower the total long-run costs of purchasing".

Other strategic models have been studied and advocated in the management of the Supply Chain. In a worldwide opened market, suppliers being available to competitors of the firm, purchasing started to become a strategic function, but most common reference models in dealing with suppliers' portfolio are based on power relations between suppliers and buyers. [START_REF] Kraljic | Purchasing must become supply management[END_REF]. Moreover, Porter in 1985, described "Creating and sustaining superior performance" [START_REF] Porter | Competitive advantage: creating and sustaining superior performance: with a new introduction[END_REF] based on two main approaches that can be complementary: competitive strategies based on costs or based on differentiation. In this complimentary book, Porter describes Generic strategies, and the Value chain of the firm, and goes into a finely grained approach of building strategic advantages through extensive cost analysis in the value chain, but also provides a customer approach to "Buyer purchase criteria" that describes the approaches that can be used to create value on differentiation: Use purchase criteria that lower buyer cost or enhance buyer performance, which can comprise product quality, features, delivery time etc. Signaling purchase criteria that are based on signals that infer on the perception of the value by the customer, and can include advertising, attractiveness or reputation.

Though since the 70s research literature reflected growing concerns to integrate stakeholders and environmental issues in the business models of firms [10][11][12][13] [START_REF] Wartick | The Evolution of the Corporate Social Performance Model[END_REF], Porters' strategic models kept five types of stakeholders for which the firm creates value based on their power of influence: customers, employees, financial partners, community and shareholders. While shareholders value creation model was gaining momentum, reducing costs and not to mention, neglecting worldwide locations became mainstream. Over the last decades, the evolution of strategic and business models have mainly focused on shareholders value creation and global offshoring and outsourcing [START_REF] Oshri | The Handbook of Global Outsourcing and Offshoring[END_REF]. "Overdoing offshoring" is not what we can describe as a discovery.

Regarding industrial decline specifically, the loss of industrial employment was analyzed as not posing a threat for the economies [START_REF] Jacquemin | Le phénomène de désindustrialisation et la Communauté Européenne[END_REF] provided it was due to both an increase in productivity in the industries (and a shift to high value industries), improving the population wealth, and, as consequence, a rise of the service economy to absorb the workers, all with the strict provision that the demand for manufactured products wouldn't be satisfied by other industrialized countries. Otherwise, it would lead to a systemic deficit of the balance of payments for countries. We can see that, not only services haven't been able to compensate for industrial jobs losses, but also that the dynamics of the service industry is directly connected to the dynamics of the manufacturing industry, with a ratio connecting both industries [START_REF] Jacquemin | Le phénomène de désindustrialisation et la Communauté Européenne[END_REF]. Roughly, there cannot be a service industry without consistent manufacturing industry.

"Improper" outsourcing contributes to the industrial decline of western firms [START_REF] Bettis | Outsourcing and industrial decline[END_REF]: outsourcing decision can individually make sense and create value, but multiple outsourcing decisions analyzed in the industrial ecosystem reduces the capabilities of a whole industry to remain competitive. Companies get trapped in a "spiral of decline" resulting from defensive incremental outsourcing decisions under the pressure of "underperforming business units to improve cost or profit performance", while corporate executives try to maintain continuous growth in earnings to support stock values, as shown in figure 3: After decades of this industrial decline, the models of firm competitiveness, green economy, green growth and reindustrialization, are making the news. Indeed, there is a growing trend in the reversal of outsourcing or offshoring production of goods and services while inter-firm relationships are under scrutiny.

This trend is being reinforced by the global awareness on resources scarcity, the necessity to protect high value research and development, to integrate in the processes the impacts of climate change and eventually reduce them, to prepare for ever growing energy costs. The business models based on high margin trading on imported, outsourced, goods and services, and global competition between companies and even territories, without sound rules, seem to have shown their limits.

Measuring the Losses to Rethink the Models

A case for reindustrialization? In the United Kingdom, while the number of companies manufacturing outside the UK increased from 32% to 42% between 2009 and 2012, a survey by the EEF [START_REF] Hopley | EEF Economics Blog | Reshoring -is it real? eef, The manufacterers' organisation[END_REF] showed that 40% of manufacturers have brought a part of their manufacturing capacities back from overseas. For these companies who still need to be competitive on price, the cost conceptual model has changed: "UK manufacturers are increasingly securing orders based on quality, service and providing complete solutions". More than half of UK manufacturers expect to increase domestic sourcing over the next few years [START_REF]Global Manufacturing Outlook: Fostering Growth through Innovation[END_REF]. The balance between trying to enhance the part of the value chain offshored, integrating the costs of managing uncertainty, quality, logistics, production and suppliers, spread all over the world, plus the wage inflation in some emerging markets are adding up to the Total Costs. Strategic thinking can then add more value by having both suppliers and customers nearby: this gives an advantage in term of reactivity, building supplier relationships beyond transactional, to a collaborative relationships on new products and processes, and a visibility on their financial health. This is not just about UK. Many OECD countries are thinking alike. The United States for example are on the same reevaluation process: the reshoring idea is at the heart of a program from the Obama Administration initiated in June 2011 called Advanced Manufacturing Program [20] to recreate hi-tech manufacturing base to create jobs for American workers and reduce trade deficit, and the trend is on with the president's FY 2013 budget with a strong focus on strengthening advanced manufacturing capabilities. Harry Moser who created a non-profit program called the Reshoring Initiative, declares [START_REF]The Next Wave of Manufacturing[END_REF]: "The goal is to balance the U.S. trade deficit, which is $600 billion a year. That is largely due to offshoring of manufacturing jobs. Since the 1950s, about three million manufacturing jobs have been lost to imported goods. So to balance the deficit we'll need to bring back three million jobs." Harry Moser states that in the U.S. 61 percent of larger companies surveyed "are considering bringing manufacturing back to the U.S.".

Industrial decline and linear model. Since the first and the second industrial revolutions, the industrial model and the business models associated with it has been based on a linear flow: raw materials extraction and transformation, use and waste. Though older economies were taking into account reuse or regeneration models, "consumer goods society" has been largely adopted worldwide and a form of prosperity seems to have been achieved for developed nations. But the "nature and causes of the wealth of nations" [START_REF] Smith | An inquiry into the nature and causes of the wealth of nations: a selected edition[END_REF] seems to become the nature and cause of doom time for human kind.

First, we are already experiencing the "limits to growth" [START_REF] Meadows | The Limits to growth: a report for the Club of Rome's project on the predicament of mankind[END_REF] predicted back in 1972. Developed and emerging markets for consumer goods is estimated [START_REF] The | Towards the circular economy[END_REF] around USD 12 trillion in 2012 while tapping into non renewable and finite resources for about USD 3 trillions [START_REF] The | Towards the circular economy[END_REF] and producing about 75% of municipal solid waste [START_REF] The | Towards the circular economy[END_REF][24]. Second, while the physical and environmental limits and issues are already here, the demand is growing with an estimated middle class to boom from 1.9 billion in 2009 to 4.9 in 2030 according to OECD [START_REF]Perspectives on global development 2012: social cohesion in a shifting world[END_REF].

Pushed by the competitive cost models we've examined previously, the paradigm of linear economy is based on globally spread actors along value chains, going from raw sourcing and chemicals inputs, globally spread manufacturing processes, global distribution and retail channels to reach consumers that trash products that are, for the best, ending in landfills or being incinerated. This globalized flow relies on intensive energy consumption of fossil fuels. The underlying economic model for each economic actor is competition based on costs and differentiation [6][9], each of them needing to maintain the growth of large volume of the flow, short products lifespan and complex heavy packaging to either meet global transportations requirements for conservation or for simple marketing differentiation.

Consumers are globally spread just like are different economic agents, located according the markets to be addressed and the cost model of agents building models to reduce labor cost by compensating with resource and energy intensity. Cheap non renewable fossil fuels have been the engine of the economic growth [START_REF] Dobbs | Resource revolution: Meeting the world's energy, materials, food, and water needs[END_REF] with growing transport flows of materials and goods, allowing offshoring of production for consumption to lower costs regions where fiscal and legal regimes left negative externalities easily uncounted, while cheap energy and resources allowed agents to focus on margin and shareholder return on investments.

This actual mismanagement of resources in the linear economy carry vast amounts of value destruction: spillage and degradations all along the value chain of agroindustries, value lost in design and processing, value lost in distribution, use and end of life [START_REF] The | Towards the circular economy[END_REF]. All the value lost in spillage adds up to the rising health, environmental and economic costs of disposals. When unmanaged, spillage and waste ends-up in nature, destroying environmental ecosystems, reducing furthermore the "ecosystem services" [START_REF] Costanza | The value of the world's ecosystem services and natural capital[END_REF] and ultimately, just like plastic in the Pacific Garbage Patch, affects our own food chain. Environmental risks and their costs can be evaluated, but the intrinsic uncertainties of the consequences in the long run they could cost are not [START_REF] Éloi | Economie de l'environnement et économie écologique[END_REF] so perhaps it's about time to redesign the models.

Beyond the environmental impacts [START_REF]Ecosystems and human well-being: current state and trends: findings of the Condition and Trends Working Group of the Millennium Ecosystem Assessment[END_REF] this vast amounts of resources spillage started to become really visible and in fact turned into a heavy burden when rising prices and volatility on commodity (150% from 2002 to 2010), fossil fuels and agricultural prices revealed the weaknesses of the model. These new risks are putting a high pressure on companies that were not prepared to confront the meeting of limited resource and growing consumption, and in an interconnected world, all issues are related [START_REF] Howell | Risk Response Network[END_REF].

Closing the loop.

A rapid review on circular economy shows there is limited research literature on this topic for global systems, but rather in the evaluation of eco-industrial parks [START_REF] Wenbo | Comprehensive evaluation research on circular economic performance of ecoindustrial parks[END_REF] [START_REF] Ying | Study on Green Supply Chain Management Based on Circular Economy[END_REF]. The models have to be studied on a more global scale and cases studies need to be compiled. New business models are emerging from real life economy and adaptive capacities of a limited part of the players. There is paradigm shift that needs to be taken and both academic institutions, and economic schools need to experiment new models that are currently out of their scope, even when multinational companies are leading the experiments.

Towards circular economy

As we've seen, the actual linear economy cannot be sustainable and is widely based on reducing responsibility of agents to the minimal requirements imposed by the market and the legal environment. Given the figures of consumption growth, it's self evident that making processes more efficient, even recycling up to 50% of the metals we use for example, by the actual growth, will not change the scarcity of these resources on the market [START_REF] Raisson | atlas des futurs du monde[END_REF], we would just delay the problems. Moreover, very efficient systems are fragile in essence [START_REF] Taleb | Anti-fragile: how to live in a world we don't understand[END_REF] as they are built with fewer nodes and connections. To build an industrial circular economy, there is a necessary paradigm shift: "Circular economy changes the traditional one-way linear economic model of "resource -product -waste" with value destruction at each step (noted VD in figure 3), into feedback circular economy mode of "resource -productwaste -renewable resource", which conforms to the concept of sustainable development, utilizes resource and protects environment more effectively so as to gain maximal economic and social benefits with minimal resource consumption and environment cost." [START_REF] Ying | Study on Green Supply Chain Management Based on Circular Economy[END_REF] Collaboration at the heart of the model. Circular economy requires also to change the approach to a view by flows that are of two types [START_REF] Mcdonough | Cradle to cradle: remaking the way we make things[END_REF]: The flow of materials that can re-enter into the biosphere without harming it and even rebuilding it, and the flow of technical materials that cannot re-enter the biosphere and need to be "designed to be recovered, refreshed and upgraded, minimizing the energy input required and maximizing the retention of value" [START_REF] The | Towards the circular economy[END_REF].

Circular economy also builds on "functional service" models where the value is not created by the consumption or the possession of products, but by their use and the services they provide [START_REF] Kazazian | Il y aura l'âge des choses légères: design et développement durable[END_REF]. Most of all, it requires to think industry development reusing principles found in nature: systems where agents are connected, pursuing individual or collective objectives but in systemic collaborative business models pursuing zero waste. This requires interdependency and constant feedback, that is actual collaborative models, extracting value in a cascade of transformation through other applications (noted VA in figure 3), for example by converting waste into byproducts, design multicriteria models and with a definitive shift to renewable energy.

Conclusion

Energy prices, commodity prices volatility, agriculture and food prices, natural catastrophes are exposing every region and every economic agent worldwide by ripple effects. Our specialization models and dependence on globalized infrastructure and markets are threatening all systems [START_REF] Howell | Risk Response Network[END_REF]. For companies this implies redesign of business models, integrating end of life products by design collection and reverse logistics. Increasing circularity of flows from cradle to cradle, reducing energy intensity and create most value of by-products requires rebuilding local networks of partners and industries: ecosystems. As stated in the Ellen MacArthur report "Towards Circular Economy" [START_REF] The | Towards the circular economy[END_REF]: "Closing the loop' in the circular economy essentially requires much closer and more extended collaboration between participants. (…) A circular economy could cut net materials costs and reduce price volatility and supply risks. Local job creation will be another important benefit, alongside greater innovation and greater resilience". What else do we need?

Fig. 1 .

 1 Fig. 1. Evolution of value added by industry and services (source OECD Stats) The models behind the decline. Michael E. Porter came up with a model that have been at the base of the value creation model he criticizes in 2011:In 1980, Porter described "Techniques for Analyzing Industries and Competitors" based on "five forces that shape competitive intensity". This model is focused on the environment of the company and comprises three horizontal threats and two vertical powers[START_REF] Porter | Competitive strategy: techniques for analyzing industries and competitors[END_REF]. Horizontal threats are new competitors addressing the market (new entrants), new products that could replace the company's products (substitute

Fig. 2 .

 2 Fig. 2. Porters' five forces that shape competitive intensity.

Fig. 3 .

 3 Fig. 3. Spiral of decline of the U.S. and western industries described by Bettis and al.

Fig. 3 .

 3 Fig. 3. Value in linear economy and circular economy, adapted from EllenMac Arthur TCE.

Acknowledgements. This paper is part of the PEAK research program (Purchasing European Alliance For Knowledge).