Following the collapse of Arthur Andersen in the Enron debacle, whistle-blowing within audit firms has taken on greater importance. Given the profession's requirements to be confidential, independent and to act in the public's interest, there is a need for a model that addresses auditors' whistle-blowing intentions. This thesis presents a conceptual model on whistle-blowing intentions among external auditors, where individual-led antecedents influence whistle-blowing intentions, but are moderated by isomorphic and issue-specific factors. Survey questionnaires were administered to 226 external auditors, and 18 individual interviews as well as 2 focus groups were conducted in Barbados. Results indicated that individual antecedents (attitudes, perceived behavioural control, independence commitment, personal responsibility for reporting, and personal cost of reporting) were significantly related to internal whistle-blowing, but only perceived behavioural control was significantly related to external whistle-blowing. Partial support was found for the moderating effects of perceived organizational support, moral intensity, team norms and group cohesion on the relationships between the majority of the independent variables (attitudes, perceived behavioural control, independence commitment, personal responsibility for reporting and personal cost of reporting) and internal whistle-blowing. However, partial support was found for the moderating effects of perceived organizational support, moral intensity, team norms iii and group cohesion on the relationships between fewer independent variables and external whistle-blowing. Overall, respondents preferred anonymous internal channels of reporting, and showed a general reluctance to report externally. The presence of an open-door policy, ethics partners, hotline, on-going training and clearly defined policies could encourage whistle-blowing. Further implications for research and practice are discussed. / University of the West Indies

The work presented in this dissertation is the first numerical investigation conducted to study leading edge film cooling with Large Eddy Simulation (LES). A cylindrical leading edge with a flat after-body represents the leading edge, where coolant is injected with a 30Ë compound angle. Three blowing ratios of 0.4, 0.8, and 1.2 are studied. Free-stream Reynolds number is 100,000 and coolant-to-mainstream density ratio is unity. At blowing ratio of 0.4, the effect of coolant inlet condition is investigated. Results show that the fully-turbulent coolant jet increases mixing with the mainstream in the outer shear layer but does not influence the flow dynamics in the turbulent boundary layer at the surface. As a result, the turbulent jet decreases adiabatic effectiveness but does not have a substantial effect on the heat transfer coefficient. At B.R.=0.4, three types of coherent structures are identified which consist of a primary entrainment vortex at the leeward aft-side of the coolant hole, vortex tubes at the windward side of the coolant hole, and hairpin vortices typical of turbulent boundary layers produced by the turbulent interaction of the coolant and mainstream downstream of injection. At B.R. = 0.8 and 1.2, coherent vortex tubes are no longer discernable, whereas the primary vortex structure gains in strength. In all cases, the bulk of the mixing occurs by entrainment which takes place at the leeward aft-side of the coolant jet. This region is characterized by a low pressure core and the primary entrainment vortex. Turbulent shear interaction between coolant jet and mainstream increases substantially with blowing ratio and contributes to the dilution of the coolant jet. As a result of the increased mixing in the shear layer and primary structure, adiabatic effectiveness decreases and heat transfer coefficient increases with increase in blowing ratio. The dissertation also investigates the deposition and erosion of Syngas ash particles in the film cooled leading edge region. Three ash particle sizes of 1, 5, and 10 microns are investigated at all blowing ratios using Lagrangian dynamics. The 1 micron particles with momentum Stokes number St = 0.03 (based on approach velocity and cylinder diameter), show negligible deposition/erosion. The 10 micron particles, on the other hand with a high momentum Stokes number, St = 3, directly impinge and deposit on the surface, with blowing ratio having a minimal effect. The 5 micron particles with St=0.8, show the largest receptivity to coolant flow and blowing ratio. On a mass basis, 90% of deposited mass is from 10 micron particles, with 5 micron particles contributing the other 10%. Overall there is a slight decrease in deposited mass with increase in blowing ratio. About 0.03% of the total incoming particle energy can potentially be transferred as erosive energy to the surface and coolant hole, with contribution coming from only 5 micron particles at B.R.=0.4 and 0.8, and both 5 and 10 micron particles at B.R.=1.2. / Ph. D.

Syftet med denna studie är att undersöka bankernas syn på internkontroll och vidare undersöka vilka mekanismer som används föratt effektivisera den interna kontrollen. Studien riktar sig på attundersöka huruvida visselblåsning används som en av demmekanismerna för att stärka förmågan med att upptäcka ochförhindra oegentligheter av ekonomisk art. Studien använder en induktiv metod för att leda insamlingen avdatamaterial. Vidare använder studien en kvalitativ metod baseradpå intervjuer med fyra olika banker där datamaterialet analyserasmed datamaterialet i kapitel två. Studien visar att det finns en positiv syn på den interna kontrollenoch visselblåsning som mekanism för att skapa en framgångsrikverksamhet. Fastän visselblåsning anses ha en kompliceradfunktion, används den fortfarande för att upptäcka och förhindraoegentligheter, såsom ekonomiska brott. Förutom visselblåsning,använder bankerna mer mekanismer för att stärka och effektiviseraden interna kontrollen. Att uppmana medarbetarna att följa lagaroch principer, utbilda medarbetarna inom olika områden samt attskapa olika arbetarsätt inom verksamheten, att genomföra interntillsyn och ständiga granskningar är en del av de mekanismer somanvänds. / The purpose of the study is to examine the banks view of internalcontrol and further investigate what mechanisms are used tostreamline the internal controls. The study is directed into whetherthe whistle-blowing is used as one of the tools in the internalcontrol to enhance the ability to detect and prevent irregularities ofa financial character. The study use a inductive method to lead the collection of datamaterial. The study further use a qualitative method based on fourinterviews with different banks were this data material is comparedwith existing theories in the second chapter. The study shows that the view of internal control and whistleblowingis positive in the process to create a successful company inthe banks. Despite that the whistle- blowing is known as acomplicated function, it’s still used to detect and preventirregularities of crimes, such of financial character. Except whistleblowing,the banks are using more tools to streamline the internalcontrol. To urge employees to comply laws and other principles,education in different areas for employers but also to createdifferent work approaches in the company, to make internal checkupsand constant supervision of the organization work is some ofthe tools that are used.

Thesis (MComm)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Corruption in South Africa has become a topical issue, especially in the public sector. Public officials are expected to uphold the public interest, but corrupt officials abuse public office for personal gain. Corruption has many forms and facets and it occurs on both large and petty scales. Despite the scale, corruption has negative consequences, such as the loss of public confidence, the undermining of efficiency in service delivery and the diversion of resources. The reporting of corruption through whistle blowing is important because it alerts the organisation of corrupt activities that have been witnessed. However, even though whistle blowers disclose corrupt activities which are detrimental to the public interest, they often experience retaliation, for example harassment, victimization and threats. Whistle blowers are thus often reluctant to blow the whistle. The South African government has enacted legislation, in particular the Protected Disclosures Act (2000), which protects whistle blowers from retaliation; however, in itself this may not be sufficient to encourage employees to blow the whistle. Organisations therefore need to devise effective whistle blowing mechanisms and create a culture of transparency that encourages employees to blow the whistle In light of the above, this study focuses on employee perceptions of whistle blowing mechanisms within Stellenbosch Municipality as a case study, with the primary objective of ascertaining the importance of whistle blowing in curbing corruption in the public sector. The study also investigates the extent to which employees are well informed on whistle blowing legislation and other mechanisms. Additionally the study focuses on the challenges and the consequences that whistle blowers face when they expose corruption. A literature review was also conducted to explore the conceptualisation of whistle blowing, corruption and anti-corruption strategies. From the literature review, it became evident that there is a need for the effective management and application of whistle blowing mechanisms to effectively curb corruption. The research design used was methodological triangulation; this consisted of a quantitative research method, namely a structured questionnaire, as well as a qualitative research method, namely semi-structured interviews. The different methods were used because they allowed for a more comprehensive approach to the study. Ninety-eight respondents, who are employees of Stellenbosch Municipality, participated in the study by completing the questionnaire. The results of the study indicate that the majority of respondents view the term whistle blowing negatively which might contribute to why individuals are reluctant to blow the whistle. Furthermore, employees agreed unanimously that they lacked confidence in their manager/supervisors to deal with disclosures of corruption. Based on the findings of this study, Stellenbosch Municipality is commended for its efforts in developing a Fraud and Corruption Policy and establishing a Fraud Hotline. However, there should be enhanced protection of whistle blowers at the Municipality in order to encourage employees to blow the whistle on any corruption that they witness in the organisation. The study contributes to anti-corruption research, and in particular whistle blowing mechanisms within the public sector in South Africa. / AFRIKAANSE OPSOMMING: Korrupsie in Suid-Afrika is 'n aktuele kwessie, veral in die openbare sektor. Van staatsamptenare word verwag om openbare belang te prioritiseer, maar korrupte amptenare misbruik hul staatsamp vir persoonlike gewin. Korrupsie het baie vorme en fasette en kom voor op groot en klein skaal. Ongeag die skaal het korrupsie negatiewe gevolge, soos die verlies van vertroue deur die publiek, die ondermyning van doeltreffendheid in dienslewering en die misbruik van hulpbronne. Die aanmelding van korrupsie deur die fluitjie te blaas is van groot belang omdat dit organisasies inlig oor korrupte aktiwiteite wat opgemerk word. Selfs al word korrupte aktiwiteite, wat nadelig is vir die openbare belang, aangemeld deur fluitjieblasers, ervaar hulle dikwels vergelding deur die beweerde partye, byvoorbeeld teistering, viktimisering en dreigemente. Fluitjieblasers is dus dikwels huiwerig om die fluitjie te blaas. Die Suid-Afrikaanse regering het wetgewing uitgevaardig, veral die Wet op Openbare Bekendmakings (2000), wat fluitjieblasers teen weerwraak beskerm; hierdie wetgewing alleen mag egter nie voldoende wees om werknemers aan te moedig om die fluitjie te blaas nie. Organisasies moet dus effektiewe fluitjieblaas meganismes ontwikkel en 'n kultuur van deursigtigheid skep wat werknemers sou aanmoedig om die fluitjie te blaas. In die lig van bogenoemde, fokus hierdie studie op werknemer persepsies van fluitjie-blaas binne die Stellenbosch Munisipaliteit as 'n gevallestudie, met die oorhoofse doel om die belangrikheid van fluitjie-blaas as meganisme om korrupsie in die openbare sektor te bekamp, vas te stel. Die studie ondersoek ook tot watter mate werknemers ingelig is oor fluitjieblaas wetgewing en ander meganismes. Daarbenewens fokus die studie op die uitdagings en die gevolge wat fluitjieblasers in die gesig staar wanneer hulle korrupsie ontbloot. 'n Literatuurstudie is ook gedoen ten einde die konseptualisering van fluitjie blaas, korrupsie en anti-korrupsie strategieë te verken. Uit die literatuuroorsig, het dit duidelik geword dat daar 'n behoefte is aan doeltreffende bestuur en toepassing van fluitjie blaas meganismes om korrupsie teen te werk. Metodologiese triangulasie is as navorsingontwerp gebruik; dit bestaan uit 'n kwantitatiewe navorsingsmetode, naamlik 'n gestruktureerde vraelys, sowel as 'n kwalitatiewe navorsingsmetode, naamlik semi-gestruktureerde onderhoude. Die verskillende metodes is toegepas aangesien dit lei tot 'n meer omvattende benadering tot die studie. Agt en negentig persone, in diens van Stellenbosch Munisipaliteit, het aan die studie deelgeneem deur die vraelys te voltooi. Die resultate van die studie dui daarop dat die meerderheid van die respondente die term “fluitjie blaas” as negatief beskou, wat kan bydra tot ‘n huiwering deur indiwidue om wel die fluitjie te blaas. Verder dui die resultate eenvormig daarop dat werknemers nie vertroue het in hul bestuurder / toesighouers om die openbaarmaking van korrupsie te hanteer nie. Gebaseer op die bevindinge van hierdie studie, word die Stellenbosch Munisipaliteit geprys vir sy pogings met die ontwikkeling van 'n bedrog en korrupsie beleid en die vestiging van 'n bedrogblitslyn. Beskerming van fluitjieblasers by die Munisipaliteit moet egter verbeter word om sodoende werknemers aan te moedig om die fluitjie te blaas oor enige korrupsie wat opgemerk word in die organisasie. Die studie dra by tot anti-korrupsie navorsing, en in besonders, fluitjie-blaas meganismes binne die openbare sektor in Suid-Afrika.

Dans cette thèse, nous nous intéressons aux équations aux dérivées fractionnaires et leurs applications au traitement d'images. Une attention particulière a été apportée à un système non linéaire d'équations différentielles fractionnaires. En particulier, nous avons étudié les propriétés qualitatives des solutions d'un système non linéaire d'équations différentielles fractionnaires qui explosent en temps fini. L'existence des solutions locales pour le système, le profil des solutions qui explosent en temps fini sont présentés. Nous étudierons le problème inverse pour l'équation de diffusion linéaire en une dimension et en deux dimensions. Nous sommes intéressés par trouver un terme source inconnu d'une équation de diffusion non locale. Les conditions aux limites considérées sont non locales et le problème spectral est non auto-adjoint. L'existence et l'unicité de la solution du problème inverse sont présentées.D'autre part, nous proposons un modèle basé sur l'équation de la chaleur linéaire avec une dérivée fractionnaire en temps pour le débruitage d'images numériques. L'approche utilise une technique de pixel par pixel, ce qui détermine la nature du filtre. En contraste avec certain modèles basés sur les équations aux dérivées partielles pour le débruitage de l'image, le modèle proposé est bien posé et le schéma numérique est convergent. Une amélioration de notre modèle proposé est suggéré. / In this thesis we study a nonlinear system of fractional differential equations with power nonlinearities; the solution of the system blows up in a finite time. We provide the profile of the blowing-up solutions of the system by finding upper and lower estimates of the solution. Moreover, bilateral bounds on the blow-up time are given.We consider the inverse problem concerning a linear time fractional diffusion equation for the determination of the source term (supposed to be independent of the time variable) and temperature distribution from initial and final temperature data. The uniqueness and existence of the continuous solution of the inverse problem is proved. We also consider the inverse source problem for a two dimensional fractional diffusion equation. The results about the existence, uniqueness and continuous dependence of the solution of the inverse problem on the data are presented.We apply the linear heat equation involving a fractional derivative in time for denoising (simplification, smoothing, restoration or enhancement) of digital images. The order of the fractional derivative has been used for controling the diffusion process, which in result preserves the fine structures in the image during denoising process. Furthermore, an improvement in the proposed model is suggested by using the structure tensor of the images.

Enemies of the People is a book that examines whistle-blowing—i.e., the unauthorized conveyance of sensitive information to mass media and authorities—and the social responses this performance provokes. The book develops a fresh view of this phenomenon by framing the trend of events according to a couple of fundamental elements found in tragedy. The book also includes a critical appraisal of the perspectives that set the tone in the existent whistle-blowing research. The prevalent one-sidedness found in this field of research is reviewed and contrasted with the contributions delivered in the present study. The analysis is based on three famous whistle-blowing cases that received a lot of attention in mass media: Ingvar Bratt and the Bofors affair; Odd F. Lindberg and the Norwegian seal hunting affair; and finally, Paul van Buitenen and the Leonardo-affair in the European Commission. The author claims that by studying the sociology of tragedy, it is possible to develop a new way of examining social processes where the final outcome is the excommunication of the appointed culprits through, for example, expulsion or avoidance. This purgatorial process is treated as a social status degradation, where the offender experiences a thorough social identity transformation that turns his or her social position to a lower social rank than initially held. The title of this book alludes to a stage play written by the Norwegian playwright Henrik Ibsen. His dramatic piece An Enemy of the People, written in 1882, plays a prominent part in this study.

With the advantage of modern high speed computers, there has been an increased interest in the use of first-principles based computational approaches for the aerodynamic modeling of horizontal axis wind turbine (HAWT). Since these approaches are based on the laws of conservation (mass, momentum, and energy), they can capture much of the physics in great detail. The ability to accurately predict the airloads and power output can greatly aid the designers in tailoring the aerodynamic and aeroelastic features of the configuration. First-principles based analyses are also valuable for developing active means (e.g., circulation control), and passive means (e.g., Gurney flaps) of reducing unsteady blade loads, mitigating stall, and for efficient capture of wind energy leading to more electrical power generation. In this present study, the aerodynamic performance of a wind turbine rotor equipped with circulation enhancement technology (trailing edge blowing or Gurney flaps) is investigated using a three-dimensional unsteady viscous flow analysis. The National Renewable Energy Laboratory (NREL) Phase VI horizontal axis wind turbine is chosen as the baseline configuration. Prior to its use in exploring these concepts, the flow solver is validated with the experimental data for the baseline case under yawed flow conditions. Results presented include radial distribution of normal and tangential forces, shaft torque, root flap moment, surface pressure distributions at selected radial locations, and power output. Results show that good agreement has been for a range of wind speeds and yaw angles, where the flow is attached. At high wind speeds, however, where the flow is fully separated, it was found that the fundamental assumptions behind this present methodology breaks down for the baseline turbulence model (Spalart-Allmaras model), giving less accurate results. With the implementation of advanced turbulence model, Spalart-Allmaras Detached Eddy Simulation (SA-DES), the accuracy of the results at high wind speeds are improved. Results of circulation enhancement concepts show that, at low wind speed (attached flow) conditions, a Coanda jet at the trailing edge of the rotor blade is effective at increasing circulation resulting in an increase of lift and the chordwise thrust force. This leads to an increased amount of net power generation compared to the baseline configuration for moderate blowing coefficients. The effects of jet slot height and pulsed jet are also investigated in this study. A passive Gurney flap was found to increase the bound circulation and produce increased power in a manner similar to the Coanda jet. At high wind speed where the flow is separated, both the Coanda jet and Gurney flap become ineffective. Results of leading edge blowing indicate that a leading edge blowing jet is found to be beneficial in increasing power generation at high wind speeds. The effect of Gurney flap angle is also studied. Gurney flap angle has significant influence in power generation. Higher power output is obtained at higher flap angles.

This dissertation employs both design science and behavioral science research paradigms to investigate an emerging form of technology-enabled human collective intelligence known as information markets. This work establishes a conceptual foundation for the study of organizational information markets and the design and use processes of information markets inside organizations. This research conceptualizes markets from an information systems perspective and presents an information systems research framework for organizational information markets. This work develops a systems theory of information markets to facilitate investigation of the relationships and interactions between markets as systems and their context of use. It proposes a structuration model for design and use of IT artifacts in organizations and applies it to the study of information markets. A framework of market users is developed to guide market design to satisfy the different motivational and informational needs of market users. A design based solution is proposed to an important open question in the information markets literature; how to generate sufficient uninformed trades. This research extends structuration theory by developing the structuration model of technology-induced organization development. A well-designed information market can generate several benefits to organizations that contribute to their growth and development. Due to the importance of software in everyday life, and the high costs and percentages of failure in software projects, this dissertation proposes an information market solution to help organizations better manage the risks facing software projects. It also develops a theoretical framework for the determinants of software project risk assessment accuracy and evaluates the market‘s efficacy in improving assessment accuracy via the use of controlled laboratory experiments. The results of the experiments demonstrate the market‘s efficacy in improving assessment accuracy by increasing the currency, accuracy and completeness of reported status information about project main objectives such as cost, schedule, performance and functionality. The results also demonstrate the market‘s efficacy in increasing individual willingness to report negative status information by decreasing their perception of information asymmetry between them and management/clients, and by increasing their perception of both the anonymity of the reporting mechanism and their perceived self-interest in reporting negative status information.

Το αντικείμενο της παρούσας εργασίας είναι η μαθηματική μοντελοποίηση της εφαπτομενικής ροής του ψυχρού αέρα, ο οποίος παρέχεται εξωτερικά της διεργασίας εκβολής πολυμερούς με εμφύσηση (film blowing) και η αριθμητική επίλυση των εξισώσεων που προκύπτουν. Η διεργασία εκβολής πολυμερών με εμφύσηση είναι η βασική μέθοδος παραγωγής φύλλων πλαστικού μεγάλης επιφάνειας τα οποία χρησιμοποιούνται κυρίως ως υλικά συσκευασίας και σε θερμοκήπια. Στην παρούσα εργασία αναπτύχθηκε μεθοδολογία η οποία επιτρέπει την μοντελοποίηση της ροής και της μεταφοράς θερμότητας του αέρα καθώς και του πολυμερούς και μας δίνει τη δυνατότητα να μελετήσουμε την επίδραση που έχει τόσο η ροή όσο και η ψύξη που προκαλεί ο αέρας στο φιλμ που σχηματίζει το πολυμερές. Αρχικά οι διέπουσες εξισώσεις του αέρα και του πολυμερούς απλοποιήθηκαν με την βοήθεια της θεωρίας των διαταραχών. Η μαθηματική ανάλυση και οι παραδοχές που έγιναν είχαν ως αποτέλεσμα i) η ροή και η παραμόρφωση του πολυμερούς να περιγράφεται από τις εξισώσεις του “λεπτού φιλμ” και ii) η ροή του αέρα να προσομοιάζεται με συνοριακό στρώμα, του οποίου η λύση προκύπτει με την μέθοδο ομοιότητας. Η επίδραση της θερμοκρασίας του αέρα στο πολυμερές μελετήθηκε θεωρώντας την αρχικά σταθερή, ενώ στην περίπτωση που και ο αέρας θεωρείται ότι θερμαίνεται από το πολυμερές, η κατανομή της θερμοκρασίας του προσεγγίζεται με ένα πολυώνυμο 4ου βαθμού στην ακτινική διεύθυνση. Τα αποτελέσματα που προκύπτουν εξαιτίας της ψύξης του φιλμ δείχνουν ότι οι παραμορφώσεις και οι μεταβολές του πάχους μειώνονται επιτρέποντας στο φιλμ που σχηματίζει το πολυμερές να αποκτά σωληνοειδή μορφή. Η λύση της εφαπτομενικής ροής του αέρα κατά μήκος του φιλμ έδειξε ότι στο φιλμ ασκούνται τάσεις οι οποίες μετατοπίζουν το φιλμ προς τον άξονα συμμετρίας και έτσι λαμβάνονται πιο ομοιόμορφα σχήματα σε σχέση με τα σχήματα που λαμβάνονται χωρίς την επίδραση του αέρα. Η επίδραση της ροής του αέρα φαίνεται να συμβαίνει στο χαμηλότερο τμήμα του φιλμ και κυρίως μέχρι ύψους . Τέλος, η σύγκριση μεταξύ του θεωρητικού μοντέλου που αναπτύχθηκε με πειραματικά αποτελέσματα δείχνει ότι υπάρχει, τουλάχιστον ποιοτικά, συμφωνία. / The object of present work is the mathematical modelling of tangential flow of cold air, which is provided externally to the polymer film produced in the well-known industrial process for manufacturing biaxial stretched films, Film Blowing Process, and the numerical solution of equations as well. In the present work was developed methodology which describes the flow and heat transfer of air as well as polymer. This analysis gives us the possibility of studying the effect of the flow as well as refrigeration that causes the air in the film of the polymer. Initially the governing equations of air and polymer were simplified with the help of theory of perturbations. The mathematic analysis and the assumptions that became had as result i) the flow and deformation of polymer described with the equations of "thin film" and ii) the flow of air simulated as a boundary layer, which its solution obtained by method of similarity. The effect of temperature of air in polymer was studied considering initially constant, while in the case where also the air is considered that is heated from polymer, the temperature distribution is approached with a polynomial of 4th degree in the radial direction. The results that arise because of refrigeration of film show that the deformations and the changes of thickness are decreased allowing in the film makes solenoids shape. The solution of tangential flow of air along the film showed that stresses in the film shift the film to the axis of symmetry and thus are received more uniform shapes in regard the shapes which are received without the air effect. The air flow effect appears to happen in the lower part of film and mainly until height . Finally, the comparison between the theoretical model that was developed with experimental results shows that exists qualitatively agreement.

Ce travail de thèse porte sur le développement d’une nouvelle génération de mousses polymères biosourcées capables de satisfaire la fonction d’âme alvéolaire et structurale de pièces automobiles. Les formulations époxy choisies comme base polymère reposent sur deux différents prépolymères époxy, l’huile de lin époxydée (ELO) et le glycérol époxydé (GE). Ces derniers, associés en proportions variables, sont réticulés avec deux différents durcisseurs : l’isophorone diamine (IPDA) ou l’anhydride méthyl tétrahydrophtalique (MTHPA). Les formulations ternaires « ELO – GE – durcisseur » ont été caractérisées selon une approche multi-techniques (DSC, TGA, rhéométrie dynamique et en mode permanent) permettant d’établir des relations structure-propriétés fiables. Puis, la production d’une mousse a été possible grâce à la maîtrise d’une réaction chimique qui se déroule parallèlement à la réticulation de la résine époxy. Le bicarbonate de sodium et de potassium ont été retenus comme agents moussants. Afin d’améliorer les performances finales des mousses, la proportion de GE au sein des formulations polymère à base IPDA a été augmentée. Mais, une telle modification induit la dégradation thermique du système à cause de l’exothermicité élevée de la réaction de réticulation. L’introduction d’un absorbeur d’exothermicité, permet grâce à sa décomposition endothermique de contrôler l’excès de chaleur dégagée et par la même d’empêcher la dégradation. Une dernière classe de durcisseurs a également été étudiée et donne après optimisation des mousses dotés d’excellentes propriétés ultimes. Ainsi, une large gamme de mousses biosourcées rigides et légères pouvant être mises en œuvre dans un temps très court a été développée. / This thesis focuses on the development of a new generation of bio-based polymer foams able to produce low density core in sandwich structure for automotive applications. The polymer formulations used in this research contain two different epoxy compounds, epoxidized linseed oil (ELO) and the epoxidized glycerol (GE). Combined in varying proportions, they were cured with two different hardeners, isophorone diamine (IPDA) or methyl tetrahydrophthalic anhydride (MTHPA). Ternary formulations “ELO – GE – hardener” were characterized by a multi-techniques approach (DSC, TGA, rheometry in steady or dynamic mode) in order to establish structure-property relationships. The production of polymeric-foam materials was carried out by tuning a chemical reaction which takes place during curing. Sodium bicarbonate and potassium bicarbonate were used as harmless foaming agents. In order to improve the final performances of the foams, the ratio GE/ELO was increased in the reactive formulations based on IPDA hardener. But, such modification provokes also the thermal degradation of the system because of the high exothermicity of the curing reaction. The introduction of “exothermicity regulators” that undergo endothermic transformations allowed to control the excess of released heat and consequently, to prevent the material degradation. A last class of hardener was also studied and made it possible after optimization the production of foams with good ultimate properties. To conclude, a large range of biobased and lightweight rigid foams able to be produced in a few minutes was developed.