Der steigende Bedarf an Internettraffic, Speicher und Verarbeitung benötigt immer mehr Hardwareressourcen. Zusätzlich überdimensionieren Datenzentrumbetreiber ihre Infrastruktur, um auch bei Bedarfsspitzen hinreichend Leistung zur Verfügung stellen zu können. Das führt zu einer geringen Ressourcenauslastung und damit zu einem erhöhten Energieverbrauch. Durch Konsolidierung der aktiven Dienste auf einer Teilmenge der physischen Server zu Zeiten geringer Auslastung können zum einen nicht benötigte Server ausgeschaltet werden und zum anderen sind die verbleibenden Server besser ausgelastet. Jedoch müssen sich Dienste nach der Konsolidierung die physischen Ressourcen mit anderen Diensten teilen. Durch Wechselwirkungen auf gemeinsam genutzten Ressourcen, sogenannten Interferenzen, verschlechtert sich die Performanz der Dienste. In dieser Arbeit wird auf Interferenzen eingegangen, die aufgrund des zeitlich variierenden Ressourcenverbrauchs von Diensten entstehen. Am Beispiel von der Rechenzeit einzelner Prozessorkerne wird mit Hilfe des Cutting Stock Problems mit nichtdeterministischen Längen (ND-CSP) der Energieverbrauch durch die Zahl der benötigten Ressourcen um bis zu 64,1% gesenkt. Durch Berücksichtigung der zeitlichen Variation des Ressourcenverbrauchs verbessert sich die Performanz um bis zu 59,6% gegenüber anderen Konsolidierungsstrategien. Außerdem wird das Konzept des Überlappungskoeffizienten eingeführt. Dieser beschreibt die probabilistische Beziehung zweier parallel laufender Dienste, inwiefern sie gleichzeitig aktiv sind. Sind Dienste nicht gleichzeitig aktiv, können sie ohne zu erwartende Interferenzen konsolidiert werden. Umgekehrt sollte die Konsolidierung gleichzeitig aktiver Dienste vermieden werden. Die Analyse eines Datenzentrums von Google zeigt, dass beide Szenarien einen signifikanten Anteil darstellen. Zur Berücksichtigung des Überlappungskoeffizienten wird das ND-CSP erweitert und näherungsweise gelöst. Hier zeigt sich jedoch weder eine Verbesserung noch eine Verschlechterung der Performanz der Dienste bei gleichem Energieverbrauch. Perspektivisch, bei der exakten Lösung und weiterer Optimierung, können aber damit Dienste eventuell so allokiert werden, dass ihre Interferenzen reduziert oder im Idealfall sogar weitgehend ausgeschlossen werden können. / An increasing portion of IP traffic is processed and stored in data centers. However, data center providers tend to over-provision their resources. Therefore, underutilized resources unnecessarily waste energy. Consolidating services allows them to be executed within a subset of the entire data center and to turn off the unnecessary, idling machines. Additionally, the remaining machines are properly utilized and, hence, more energy-efficient. Nevertheless, this has to be balanced against degrading the quality of service due to the shared resources of the physical machines after the consolidation. This thesis focuses on the above mentioned interferences due to fluctuating workloads. These are treated in the framework of the Cutting Stock Problem, where items with non-deterministic length are introduced. This reduces the power consumption by minimizing the necessary, active resources by up to 64.1% for the exemplary CPU time of individual cores. Thanks to the awareness of workload fluctuations, it improves the performance of services by up to 59.6% compared to other allocation schemes. Additionally, the concept of 'overlap coefficients' is introduced, which describes the probabilistic relation between two services which run in parallel. The more often these services are active at the same time the higher the overlap coefficient and vice versa. Services which are not active at the same time can be consolidated without any expected interference effects, while these with common activity periods should not be consolidated. The analysis of one of Google's data centers unveils that most of the services can be mapped onto one of the two patterns, while few with undetermined relation remain. The ND-CSP is extended by the 'overlap coefficient' and approximatively solved. In contrast to the former ND-CSP, neither an improvement nor a deterioration of the consolidation results is obtained. In the future, the services can be allocated with reduced or even without interference effects if an exact solution or a multi-objective optimization is applied.

Le sujet de thèse porte sur la planification tactique et opérationnelle d’une chaîne logistique dans un contexte dynamique. Nous proposons un modèle de planification basé sur une structure décisionnelle à deux niveaux. Adoptant un processus dynamique permettant d’actualiser les données à chaque étape de planification, le premier niveau planifie la production en recherchant le meilleur compromis entre les leviers décisionnels disponibles liés aux aspects capacité et coût de production. Le deuxième niveau établit un ordonnancement agrégé des opérations de fabrication en minimisant les en-cours. Le recours à une structure décisionnelle intégrée nous a conduit à établir une interaction entre les niveaux supérieur et inférieur de décision, mise en oeuvre par des contraintes dites de conservation d’énergie. Notre approche est modélisée sous la forme d’un problème de satisfaction de contraintes (CSP, Constraint Satisfaction Problem) et évaluée par simulation dans un contexte de données incertaines. Nous avons mené différentes expérimentations portant sur la variation de la demande, la variation de la capacité et la re-planification de la demande. Toutes les expérimentations sont réalisées par deux méthodes de résolution différentes : une méthode basée sur un CSP statique et une méthode basée sur un CSP dynamique. La performance d’une solution de planification/ordonnancement est renseignée par l’ensemble des mesures de la stabilité et de la robustesse. Les expérimentations réalisées offrent une démonstration de la performance de la méthode de résolution basée sur un CSP dynamique par rapport à la méthode statique / This work focuses on the supply chain operational and tactical planning problem in an uncertain environment. We propose a tactical planning model, based on a two-level decisional structure. Adopting a dynamic process, which enables data updating at each planning step, the first level performs a plan by searching for the best compromise between available decision-making levers for production costs and capacity. The second level establishes an aggregate scheduling of production tasks by minimizing the total weighted completion time. The use of an integrated decision structure involves interaction between the upper and lower decision levels constraints, implemented by constraints known as energy conservation constraints. Our approach is formulated according to a constraint satisfaction problem (CSP) and evaluated by simulation under uncertain data. For this, we have developed various experiments related to the variation of customer demand, resource capacity, and the re-planning of demand. All the experiments are carried out by two different methods : a method based on a static CSP and a method based on a dynamic CSP. The performance of a scheduling/planning solution is reported through a set of robustness and stability measurements. Results of experiments confirm the performance of the method based on a dynamic CSP

The constraint satisfaction problem (CSP) over a structure A with a finite relational signature, denoted by CSP(A), is the problem of deciding whether a given finite structure B with the same signature as A has a homomorphism to A. Using concepts and techniques from universal algebra, Bulatov and Zhuk proved independently that if A is finite, then the CSP over A is always in P or NP-complete. Following this result, it is a natural question to ask when and how this dichotomy can be generalized for infinite structures. The infinite-domain CSP dichotomy conjecture (originally formulated by Bodirsky and Pinsker [BPP14]) states that the same complexity dichotomy holds for first-order reducts of finitely bounded homogeneous structures. This conjecture has been solved for many special classes of structures. In this thesis we are developing new techniques involving canonical polymorphisms to attack this conjecture. Using these techniques we prove a new CSP dichotomy result, namely we show that the CSP over every finitely related ω-categorical monadically stable structure is in P or NP-complete.

Malaria ist eine Krankheit, die durch den Protozoen Plasmodium verursacht und von Anopheles Moskitos durch infektiöse Stiche übertragen wird. Diese ̈Übertragung kann durch verschiedene Interventionsstrategien blockiert werden. Eine relativ neue Strategie, die bisher nur im Labor getestet wurde, ist der Einsatz genetisch veränderter Moskitos, die den Parasiten nicht auf einen neuen menschlichen Wirt übertragen können. Ein Ansatz ist die Entwicklung von Moskitos, die mit murinen Antikoepern ausgestattet sind, die gegen relevante Oberflächenproteine des Parasiten, dem Circumsporozoite Protein (CSP) gerichtet sind. Es ist jedoch nach wie vor unklar, welches Entwicklungsstadium angegriffen werden soll und welche Antikörper für diesen Ansatz effizient sind. Hier zeige ich, dass in Stechmücken, die mit einem humanen Anti-CSP-Antikörper ausgestattet sind, die Sporogonie der Oozysten in Abhängigkeit von der Parasiten-dichte blockiert wird und somit die Sporozoitenlast in den Mücken signifikant verringern. Insbesondere Antikörper, die sich an die ’Repeat Region’ des CSP binden, können die Sporozoitenlast in der Stechmücke verringern. Des Weitern, zeigen diese Stechmücken kaum Defekte in der Entwicklung und im Überleben. Diese Ergebnisse bestätigen die zuvor beschriebene Bedeutung von CSP während der Sporogonie und unterstreichen die Effizienz von humanen, ’Repeat Region’ bindenden Anti-CSP-Antikörpern bei der Beeinträchtigung der Parasitenentwicklung in dem Vektor. Darüber hinaus ist in Stechmücken, die mit humanen Anti-CSP Antikörpern ausgestattet sind, die Entwicklung von Sporozoiten teils limitiert und teils komplett verhindert. Dies macht sie zu einem vielversprechenden Instrument für Maßnahmen zum Malaria Kontrolle. In dieser Arbeit habe ich weitere Einblicke in den Mechanismus , durch den Anti-CSP-Antikörper die Parasitenentwicklung in der Mücke stören, und gezeigt, dass Oozysten ein effizientes Ziel für diesen Ansatz sind. / Malaria is a disease caused by the protozoan parasite Plasmodium and transmitted by Anopheles mosquitoes trough infectious bites, these transmission events can potentially be blocked by different intervention strategies. A relatively new strategy which has been only tested in the laboratory is the use of genetically modified mosquitoes unable to transmit the parasite to a new human host. In the past, murine derived antibodies directed against relevant parasite surface proteins were used with limited success. It remains unclear which developmental stage is targeted, and which antibodies are useful. Here, I show that in mosquitoes equipped with a human derived anti-CSP repeat binding antibody, oocyst sporogony is blocked in a parasite density dependent manner. Only repeat binding antibodies could decrease sporozoite loads in the mosquito. These results confirm the previously described importance of CSP during sporogony and highlight the efficiency of human derived repeat binding anti-CSP antibodies in interfering with parasite development even in a different host. Additionally, mosquitoes equipped with human derived anti-CSP antibodies show little (in high density infections) to no (in low density infections) sporogonic development, making them a promising tool for malaria transmission blocking interventions. I provided additional insights into the mechanism by which anti-CSP antibodies interfere with parasite development in the mosquito showing that oocysts are an efficient target for this approach. Therefore, the mosquitoes used here are potentially resistant in a more natural setting. Additionally, I provided a new tool allowing a faster screening of antibodies in a mosquito context by injection of single chain Fabs into the mosquito hemolymph. Taken together, this approach could one day give rise to alternative strategies in tackling malaria transmissions.

Concentrated solar power (CSP) is an efficient means of renewable energy that makes use of solar radiation to produce electricity instead of making use of conventional fossil fuel techniques such as burning coal. The aim of this study is the simulation and characterisation of a CSP plant in order to gain a better understanding of the dominant plant dynamics. Due to the nature of the study, the dissertation is divided into two main parts namely the simulation of a CSP plant model and the characterisation of the plant model. Modelling the CSP plant takes the form of developing an accurate Flownex® model of a 40 MW combined cycle CSP plant. The model includes thermal energy storage as well as making use of a duct burner. The Flownex® model is based on an existing TRNSYS model of the same plant. The Flownex® model is verified and validated, by making use of a bottom-up approach, to ensure that the developed model is in fact correct. The characterisation part of this dissertation involves evaluating the dynamic responses unique to that of a CSP plant as stated in the literature. This involves evaluating the dominant dynamic behaviour, the presence of resonant and anti-resonant modes found within the control bandwidth, and the change in the dynamics of the plant as the plants’ operating points change throughout the day. Once the developed model is validated, characterisation in the form of evaluating the open loop local linear models of the plant is implemented. In order to do so, these models are developed based on model identification processes, which include the use of system identification software such as Matlab® SID Toolbox®. The dominant dynamic behaviour of the plant model, obtained from the developed local linear models, represents that of an over damped second order system that changes as the operating points of the plant change; with the models’ time responses and the bandwidth decreasing and increasing respectively as the thermal energy inputs to the plant increases. The frequency response of the developed local linear models also illustrates the presence of resonant and antiresonant modes found within the control bandwidth of the solar collector field’s temperature response. These modes however are not found to be present in the mechanical power output response of the plant. The use of adaptive control, such as feedforward and gain-scheduled controllers, for the plant should be developed to compensate for the dynamic behaviours associated with that of a CSP plant. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

Concentrated solar power (CSP) is an efficient means of renewable energy that makes use of solar radiation to produce electricity instead of making use of conventional fossil fuel techniques such as burning coal. The aim of this study is the simulation and characterisation of a CSP plant in order to gain a better understanding of the dominant plant dynamics. Due to the nature of the study, the dissertation is divided into two main parts namely the simulation of a CSP plant model and the characterisation of the plant model. Modelling the CSP plant takes the form of developing an accurate Flownex® model of a 40 MW combined cycle CSP plant. The model includes thermal energy storage as well as making use of a duct burner. The Flownex® model is based on an existing TRNSYS model of the same plant. The Flownex® model is verified and validated, by making use of a bottom-up approach, to ensure that the developed model is in fact correct. The characterisation part of this dissertation involves evaluating the dynamic responses unique to that of a CSP plant as stated in the literature. This involves evaluating the dominant dynamic behaviour, the presence of resonant and anti-resonant modes found within the control bandwidth, and the change in the dynamics of the plant as the plants’ operating points change throughout the day. Once the developed model is validated, characterisation in the form of evaluating the open loop local linear models of the plant is implemented. In order to do so, these models are developed based on model identification processes, which include the use of system identification software such as Matlab® SID Toolbox®. The dominant dynamic behaviour of the plant model, obtained from the developed local linear models, represents that of an over damped second order system that changes as the operating points of the plant change; with the models’ time responses and the bandwidth decreasing and increasing respectively as the thermal energy inputs to the plant increases. The frequency response of the developed local linear models also illustrates the presence of resonant and antiresonant modes found within the control bandwidth of the solar collector field’s temperature response. These modes however are not found to be present in the mechanical power output response of the plant. The use of adaptive control, such as feedforward and gain-scheduled controllers, for the plant should be developed to compensate for the dynamic behaviours associated with that of a CSP plant. / MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

Poster exhibited at GPSC Student Showcase, February 24th, 2016, University of Arizona. / To make photovoltaics (PV) and concentrated solar thermal power (CSP) more practical forms of alternative energy, creative innovations to current solar energy methods must be employed. The PVMirror – a new technology – is our solution to that problem. The PVMirror combines PV and CSP technologies by splitting the spectrum of sunlight using a dichroic mirror film. Light that is not transmitted to the solar cell is to instead be reflected to a focus, by way of a curved mirror. This hybrid of technologies is competitive, as it is both efficient and affordable compared to many other innovations in renewable energy. The PVMirror is designed to be an easy and cost-effective replacement to the reflectors used in existing CSP plants. Ultimately, we hope to demonstrate this PVMirror technology on a large scale and market it. As validated from interviewing with industry professionals, this technology has the potential to impact the world of solar energy because many industrial companies and utility-scale CSP project developers are interested in pairing CSP and PV to increase efficiency. Currently, using an outdoor sun tracker, we are testing an 18 inch by 18 inch prototype with four solar cells.

Cette recherche vise à analyser les liens entre la performance financière (PF) et le niveau de développement durable (NDD) dans le contexte canadien et adapté à la conjoncture actuelle. Le premier objectif est de déterminer si les mesures de PF peuvent être expliquées par les mesures du NDD, tout en contrôlant pour la taille, le risque et l’industrie des entreprises. Le deuxième objectif est de vérifier s’il existe un lien entre les mesures de risque d’une entreprise et les mesures du NDD, tout en contrôlant pour la taille et l’industrie des entreprises. Le troisième objectif est de déterminer si les mesures du NDD peuvent être expliquées par les mesures de PF, tout en contrôlant pour la taille et le risque.

Current concentrated solar power plants (CSP) use molten salt at 565°C as a heat transfer and energy storage fluid. Due to thermal energy storage (TES), these solar plants can deliver dispatachable electricity to the grid; however, the levelized cost of electricity (LCOE) for these plants is 12-15 c/kWh, about 2.5 times as high as fossil fuel electricity generation. Molten salt technology limits peak operating temperatures to 565°C and a heat engine efficiency of 40%. Liquid metal (LM), however, can reach >1350°C, and potentially utilize a more efficient (60%) heat engine and realize cost reductions. A 1350 °C LM-CSP plant would require ceramic containment, inert atmosphere containment, additional solar flux concentration, and redesigned internal receiver. It was initially unclear if these changes and additions for LM-CSP were technically feasible and could lower the LCOE compared to LS-CSP. To answer this question, a LM-CSP plant was designed with the same thermal input as a published LS-CSP plant. A graphite internal cavity receiver with secondary concentration heated liquid Sn to 1400°C and transferred heat to a 2-phase Al-Si fluid for 9 hours of thermal energy storage. Input heat to the combined power cycle was 1350°C and had 60% thermal efficiency for a gross output of 168 MW. The cost of this LM-CSP was estimated by applying material cost factors to the designed geometry and scaling construction costs from published LS-CSP estimates. Furthermore, graphite was experimentally tested for reactivity with liquid Sn, successful reaction bonds, and successful mechanical seals. The result is switching to molten metal can reduce CSP costs by 30% and graphite pipes, valves, and seals are possible at least at 400°C.

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Concentrating solar power promises to be a potential solution for meeting the worlds energy needs in the future. One of the key features of this type of renewable energy technology is its ability to store energy effectively and relatively cheaply. An air-rock bed thermal energy storage system promises to be an effective and reasonably inexpensive storage system for concentrating solar power plants. Currently there is no such storage system commercially in operation in any concentrating solar power plant, and further research is required before such a system can be implemented. The main research areas to address are the thermal-mechanical behaviour of rocks, rock bed pressure drop correlations and effective and practical system designs. Recent studies have shown that the pressure drop over a packed bed of rocks is dependant on various aspects such as particle orientation relative to the flow direction, particle shape and surface roughness. The irregularity and unpredictability of the particle shapes make it difficult to formulate a general pressure drop correlation. Typical air-rock bed thermal design concepts consist of a large vertical square or cylindrical vessel in which the bed is contained. Such system designs are simple but susceptible to the ratcheting effect and large pressure drops. Several authors have proposed concepts to over-come these issues, but there remains a need for tools to prove the feasibility of the designs. The purpose of this paper is to investigate aDEM-CFD coupled approach that can aid the development of an air-rock bed thermal energy storage system. This study specifically focuses on the use of CFD. A complementary study focusses on DEM. The two areas of focus in this study are the pressure drop and system design. A discrete CFD simulation model is used to predict pressure drop over packed beds containing spherical and irregular particles. DEM is used to create randomly packed beds containing either spherical or irregularly shaped particles. This model is also used to determine the heat transfer between the fluid and particle surface. A porous CFD model is used to model system design concepts. Pressure drop and heat transfer data predicted by the discrete model, is used in the porous model to describe the pressure drop and thermal behaviour of a TES system. Results from the discrete CFD model shows that it can accurately predict the pressure drop over a packed bed of spheres with an average deviation of roughly 10%fromresults found in literature. The heat transfer between the fluid and particle surface also is accurately predicted, with an average deviation of between 13.36 % and 21.83 % from results found in literature. The discrete CFD model for packed beds containing irregular particles presented problems when generating a mesh for the CFD computational domain. The clump logic method was used to represent rock particles in this study. This method was proven by other studies to accurately model the rock particle and the rock packed bed structure using DEM. However, this technique presented problems when generating the surface mesh. As a result a simplified clump model was used to represent the rock particles. This simplified clump model showed characteristics of a packed bed of rocks in terms of pressure drop and heat transfer. However, the results suggest that the particles failed to represent formdrag. This was attributed to absence of blunt surfaces and sharp edges of the simplified clumpmodel normally found on rock particles. The irregular particles presented in this study proved to be inadequate for modelling universal characteristics of a packed bed of rocks in terms of pressure drop. The porous CFD model was validated against experimental measurement to predict the thermal behaviour of rock beds. The application of the porous model demonstrated that it is a useful design tool for system design concepts. / AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag beloof om ’n potensiële toekomstige oplossing te wees vir die wêreld se groeiende energie behoeftes. Een van die belangrikste eienskappe van hierdie tipe hernubare energie tegnologie is die vermoë om energie doeltreffend en relatief goedkoop te stoor. ’n Lug-klipbed termiese energie stoorstelsel beloof om ’n doeltreffende en redelik goedkoop stoorstelsel vir gekonsentreerde sonkragstasies te wees . Tans is daar geen sodanige stoorstelsel kommersieël in werking in enige gekonsentreerde sonkragstasie nie. Verdere navorsing is nodig voordat so ’n stelsel in werking gestel kan word. Die belangrikste navorsingsgebiede om aan te spreek is die termies-meganiese gedrag van klippe, klipbed drukverlies korrelasies en effektiewe en praktiese stelsel ontwerpe. Onlangse studies het getoon dat die drukverlies oor ’n gepakte bed van klippe afhanklik is van verskeie aspekte soos partikel oriëntasie tot die vloeirigting, partikel vormen oppervlak grofheid. Die onreëlmatigheid en onvoorspelbaarheid van die klip vorms maak dit moeilik om ’n algemene drukverlies korrelasie te formuleer. Tipiese lug-klipbed termiese ontwerp konsepte bestaan uit ’n groot vertikale vierkantige of silindriese houer waarin die gepakte bed is. Sodanige sisteem ontwerpe is eenvoudig, maar vatbaar vir die palrat effek en groot drukverliese. Verskeie studies het voorgestelde konsepte om hierdie kwessies te oorkom, maar daar is steeds ’n behoefte aanmetodes om die haalbaarheid van die ontwerpe te bewys. Die doel van hierdie studie is om ’n Diskreet Element Modelle (DEM) en numeriese vloeidinamika gekoppelde benadering te ontwikkel wat ’n lug-klipbed termiese energie stoorstelsel kan ondersoek. Hierdie studie fokus spesifiek op die gebruik van numeriese vloeidinamika. ’n Aanvullende studie fokus op DEM. Die twee areas van fokus in hierdie studie is die drukverlies en stelsel ontwerp. ’n Diskrete numeriese vloeidinamika simulasie model word gebruik om drukverlies te voorspel oor gepakte beddens met sferiese en onreëlmatige partikels. DEM word gebruik om lukraak gepakte beddens van óf sferiese óf onreëlmatige partikels te skep. Hierdie model is ook gebruik om die hitte-oordrag tussen die vloeistof en partikel oppervlak te bepaal. ’n Poreuse numeriese vloeidinamika model word gebruik omdie stelsel ontwerp konsepte voor te stel. Drukverlies en hitte-oordrag data, voorspel deur die diskrete model, word gebruik in die poreuse model om die drukverlies- en hittegedrag van ’n TES-stelsel te beskryf. Resultate van die diskrete numeriese vloeidinamikamodel toon dat dit akkuraat die drukverlies oor ’n gepakte bed van sfere kan voorspel met ’n gemiddelde afwyking van ongeveer 10%van die resultatewat in die literatuur aangetref word. Die hitte-oordrag tussen die vloeistof en partikel oppervlak is ook akkuraat voorspel, met ’n gemiddelde afwyking van tussen 13.36%en 21.83%van die resultate wat in die literatuur aangetref word. Die diskrete numeriese vloeidinamika model vir gepakte beddens met onreëlmatige partikels bied probleme wanneer ’n maas vir die numeriese vloeidinamika, numeriese domein gegenereer word. Die "clump"logika metode is gebruik om klip partikels te verteenwoordig in hierdie studie. Hierdiemetode is deur ander studies bewys om akkuraat die klip partikel en die klip gepakte bed-struktuur te modelleer deur die gebruik van DEM. Hierdie tegniek het egter probleme gebied toe die oppervlak maas gegenereer is. As gevolg hiervan is ’n vereenvoudigde "clump"model gebruik om die klip partikels te verteenwoordig. Die vereenvoudigde "clump"model vertoon karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies en hitte oordrag. Die resultate het egter getoon dat die partikels nie vorm weerstand verteenwoordig nie. Hierdie resultate kan toegeskryf word aan die afwesigheid van gladde oppervlaktes en skerp kante, wat normaalweg op klip partikels gevind word, in die vereenvoudigde "clump"model. Die oneweredige partikels wat in hierdie studie voorgestel word, blykomnie geskik tewees vir die modellering van die universele karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies nie. Die poreuse numeriese vloeidinamika model is met eksperimentele metings bevestig omdie termiese gedrag van klipbeddens te voorspel. Die toepassing van die poreuse model demonstreer dat dit ’n nuttige ontwerp metode is vir stelsel ontwerp konsepte.