The history of Easter Island, with its cultural and ecological mysteries, has attracted the interests of archaeologists, anthropologists, ecologists, and economists alike. Despite the great scientific efforts, uncertainties in the available archaeological and palynological data leave a number of critical issues unsolved and open to debate. The maximum size reached by the human population before the arrival of Europeans and the temporal dynamics of deforestation are some of the aspects still fraught with controversies. By providing a quantitative workbench for testing hypotheses and scenarios, mathematical models are a valuable complement to the observational-based approaches generally used to reconstruct the history of the island. Previous modelling studies, however, have shown a number of shortcomings in the case of Easter Island, especially when they take no account of the stochastic nature of population growth in a temporally and spatially varying environment. Here, I present a new stochastic, Agent-Based Model characterised by (1) realistic physical geography of the island and other environmental constraints (2) individual agent decision-making processes, (3) non-ergodicity of agent behaviour and environment, and (4) randomised agent-environment interactions. I use the model and the best available data to determine plausible spatial and temporal patterns of deforestation and other socioecological features of Easter Island prior to the European contact. I further identify some non-trivial connections between microscopic decisions or constraints (like local confinement of agents' actions or their adaptation strategy to environmental degradation) and macroscopic behaviour of the system that can not easily be neglected in a discussion about the history of Easter Island before European contact. / Påsköns historia har, med dess kulturella och ekologiska mysterier, väckt intressen hos arkeologer, antropologer, ekologer och ekonomer. Trots de stora vetenskapliga ansträngningarna lämnar osäkerheten i de tillgängliga arkeologiska och palynologiska data ett antal kritiska frågor olösta och öppna för debatt. Den maximala storleken som den mänskliga befolkningen nådde före européernas ankomst, och avskogningens tidsmässiga dynamik, är några av de aspekter som fortfarande är fyllda med kontroverser. Genom att tillhandahålla en kvantitativ arbetsbänk för att testa hypoteser och scenarier är matematiska modeller ett värdefullt komplement till de observationsbaserade metoder som vanligtvis används för att rekonstruera öns historia. Tidigare modelleringsstudier har emellertid visat ett antal brister i fallet med Påskön, särskilt när de inte tar hänsyn till den stokastiska karaktären av befolkningsökningen i en tillfällig och rumsligt varierande miljö. Här presenters en ny stokastisk, agentbaserad modell som kännetecknas av (1) realistisk fysisk geografi av ön och andra miljömässiga begränsningar, (2) individuella beslutsprocesser av agenter, (3) icke-ergodicitet av agentens beteende och miljö och (4) randomiserade agent-miljöinteraktioner. Modellen används tillsammans med de bästa tillgängliga data för att bestämma rimliga rumsliga och temporära mönster av avskogning och andra socioekologiska egenskaper på Påskön före européers ankoms. Vidare identifieras några icke-triviala förbindelser mellan mikroskopiska beslut eller begränsningar (till exempel lokal inneslutning av agentens handlingar eller deras anpassningsstrategi till miljöförstöring) och makroskopiskt beteende hos systemet som inte lätt kan försummas i en diskussion om påsköns historia före europeisk kontakt.

The analogue models and the kinematic models based on the seismic data results were used to simulate the fault pattern which develops above a basement horst. The two major normal faults intersect with each other along the strike in the sedimentary covers. The fault pattern developed in the sedimentary cover is controlled by the dip of the basement fault and the width of the basement horst. The single horst structure was only developed in the sedimentary covers above the wider end of the basement horst. The hourglass structure was developed in the sedimentary covers above the narrower end of the basement horst. The precursor faults developed ahead of the major second-order normal faults when the dip angle of the basement fault is larger than 60°. The antithetic faults developed ahead of the major second-order normal faults when the dip angle of the basement fault is less than 50°. The analogue models were designed in a way that the two hanging wall blocks glide down along the basement horst simultaneously to simulate the activity of the basement faults. The kinematic models were designed based on the alternative sequential slip method to study the kinematic behaviors of the conjugate normal faults. The Lufeng Sag was characterized by the basement horst in the center and the deep half-grabens developed beside the horst. The width of the basement horst decreases along its strike. The models indicates that the second-order normal faults developed above the basement horst, observed in the Lufeng Sag seismic profiles, were reproducible and much more detailed structures were revealed / Detta projekt har analog modellering och kinematiska modeller baserade på seismiska data använts för att simulera förkastningsmönster ovanför en berggrundshorst. Två stora normal förkastningar möts i strykningsriktningen hos de ovanliggande sedimentlagren. Förkastningsmönstret som utvecklats i ovanliggande sedimentlager styrs av stupningen hos underliggande urberg samt bredden hos den underliggande horsten. Den enda horststrukturen som utvecklades i sedimentlagren skedde i fallet med en bredare underliggande horststruktur. En timglasstruktur bildades i den sedimentära successionen vid den smalare ändan av berggrundshorsten. De initiala förkastningarna bildades tidigt för att sedan övergå i andra ordningens normalförkastningar i de fall då stupningen hos underliggande berggrund överstiger 60°. Mindre antitetiska förkastningar bildades före andra ordningens förkastningar där berggrunds-stupningen understiger 50°. Den analoga modell som nyttjades experimentellt var konstruerad så att de två hängväggskomponenterna kunde röra sig fritt samtidigt längs med berggrundshorsten för att simulera aktivering av befintliga förkastningar i berggrunden. De kinematiska modeller som nyttjades var konstruerade enligt metoden för sekventiella rörelser (eng - sequential slip method) för att studera kinematiska beteenden hos konjugerande förkastningspar. Lufeng-sänkans utseende har kontrollerats av berggrundshorsten i mitten samt av de djupa halv-grabens på båda sidorna av horsten. Bredden på berggrundshorsten minskar längs dess stupning. Modellerna påvisar att andra ordningens normal-förkastningar bildades ovanför berggrundshorsten, likt i de seismiska profilerna över området, samt att strukturerna var reproducerbara och väldigt detaljrika.

Inom 3D-grafik, visualiseringar, spel och VR finns ett behov av måttriktig modellering. Traditionellt så används CAD-program för att uppnå ett exakt eller precist resultat. Men då CAD-program inte utmatar polygonal geometri så fungerar det inte att använda resultatet direkt i tidigare nämnda kategorier. Denna studie ämnar att underlätta måttriktig polygonal modellering i Autodesk Maya genom ett tillägg i form av ett grafiskt användargränssnitt. Effektiviteten av detta mäts genom tidtagning på modellering av CAD-ritningar i polygoner hos en testgrupp både med och utan tillägget samt en kvalitetskontroll där resultatet jämförs med specifikationen. Medelresultatet av testgruppens användning av tillägget var en förbättring i tidsåtgång gentemot endast Maya. Geometrin hade även bättre måttriktighet.

The design and analysis of large casted parts present significant challenges due to their complex geometry. Finite Element (FE) modeling is a vital tool for understanding the performance of casted components. However, the computational requirements associated with these parts often lead to excessive processing times and resource utilization. This thesis aims to enhance the efficiency of the mid-surface model creation by developing an FE modeling approach suited explicitly for large casted components. The study begins by exploring the background of casted parts and their applications. A comprehensive analysis of modeling and meshing techniques is conducted, emphasizing their application to large casted components. Building upon this knowledge, different ideas are examined, leading to the proposal of a methodology combining CAD strategies for design features, hybrid meshing techniques, and approaches aimed at reducing FE modeling time to streamline the overall process.To validate the proposed approach, a series of case studies involving casted parts with varying levels of complexity are undertaken. Real-world casting process parameters are considered, highlighting the advantages and limitations in each ideation phase. The proposed methodology is tested and show cased to expert engineers to evaluate its efficiency and feasibility. Furthermore, the efficiency of the new approach is quantitatively evaluated in terms of processing time. The developed methodology offers engineers and researchers a powerful tool to accelerate the design process and optimize FE modeling time while managing computational costs. As industries continue to push the boundaries of size and complexity in casted part design, the insights and techniques presented in this thesis offer a valuable resource for addressing the various engineering challenges inherent in future endeavors. / Utformningen och analysen av stora gjutna delar innebär betydande utmaningar på grund av deras komplexa geometri. Finita Element (FE)-modellering är ett viktigt verktyg för att förstå prestandan hos gjutna komponenter. De beräkningskrav som är förknippade med dessa delar leder dock ofta till alltför långa handläggningstider och resursutnyttjande. Detta examensarbete syftar till att förbättra effektiviteten av skapandet av mittyteta modeller genom att utveckla en FE-modelleringsmetod som är specifikt lämpad för stora gjutna komponenter. Studien börjar med att utforska bakgrunden till gjutna delar och deras tillämpningar. En omfattande analys av modellerings-och diskret iseringstekniker genomförs, med tonvikt på deras tillämpning på stora gjutna komponenter. Med utgångspunkt i denna kunskap undersöks olika idéer, vilket leder till förslaget om en metod som kombinerar CAD-strategier för designfunktioner, hybridmodelleringstekniker och tillvägagångssätt som syftar till att minska FE-modelleringstiden för att effektivisera den övergripande processen. För att validera det föreslagna tillvägagångssättet genomförs en serie fallstudier som involverar gjutna delar med varierande nivåer av komplexitet. Verkliga gjutprocessparametrar beaktas, vilket belyser fördelarna och begränsningarna i varje idéfas. Den föreslagna metoden testas och visas upp för expertingenjörer för att utvärdera dess effektivitet och genomförbarhet. Dessutom utvärderas effektiviteten av det nya tillvägagångssättet kvantitativt i termer av handläggningstid. Den utvecklade metoden erbjuder ingenjörer och forskare ett kraftfullt verktyg för att påskynda designprocessen och optimera FE-modelleringstiden samtidigt som de hanterar beräkningskostnader. När industrier fortsätter att tänja på gränserna för storlek och komplexitet idesign av gjutna delar, erbjuder de insikter och tekniker som presenteras i denna avhandling en värdefull resurs för att ta itu med de olika tekniska utmaningarna som är inneboende i framtida strävanden.

This master thesis report is focused on the development and study of a tendon driven soft actuator for use on the Honda Haru robot. The single degree of freedom actuator will be used to actuate the eyes of the robot. Motivating development of this new actuator is the operational safety of the robot. A soft continuum actuator can provide a higher level of inherent safety as compared with the currently used rigid actuator. After development, a factorial study of the developed actuator was performed in order to understand the effect of velocity, load and material hardness on the actuator motion. The results of this study show that the linearity, hysteresis and current draw of the actuator are all affected by varying material and velocity. No significant effect of actuator load was measured. Data-driven system identification of the actuator was later performed using polynomial models. A relative comparison of standard-, nonlinear- and adaptive ARX models showed that adaptive ARX is most suitable to capture the dynamics of the developed actuator under dynamic conditions. / Denna examesarbetesrapport täcker utveckling samt studie av ett 3d-utskrivet mjukt ställdon. Det vajerdrivna ställdonet är designat för att driva ögonrörelser på den sociala roboten HARU och utvecklingen motiverades av den ökade säkerhet som en mjuk och eftergivlig komponent kan ge robotens användare jämfört med den nuvarande stela mekanismen. Den utvecklade komponenten undersöktes sedan i två faser. Först utfördes en faktorstudie där rörelsehastighets, lastvikts samt materialhårdhets påverkan på ställdonets kinematik undersöktes. Resultaten från denna studie visar att linjäritet, hysteres samt strömförbrukning av det utvecklade ställdonet påverkas av rörelsehastighet samt materialets hårdhet. Ingen signifikant påverkan av lastvikt uppmättes. Utöver faktorstudien undersöktes även förmågan av olika polynomialmodeller att modellera ställdonet med god nogrannhet. Linjära, ickelinjära samt rekursiva linjära modeller utvecklades via systemidentifiering och deras prestanda jämfördes. Resultaten från detta visar att rekursiva linjära modeller är bäst lämpade för att modellera det utvecklade ställdonet under dynamiska förhållanden.

In this study, an attempt was made to identify the electronic and steric properties of the precatalyst ligands that determine the characteristics of phosphine ligated Grubbs-type precatalysts for alkene metathesis by means of molecular modelling. It was found from studying the literature that the possibilities for synthesising a wide range of phosphine ligands are almost unlimited. Additionally, it was found that there is no easy method to determine the electronic and steric properties of the precatalyst ligands in existence. Molecular modelling might provide a method to study potential ligands and precatalysts before tedious synthesis methods are attempted. It was found that the theoretically calculated structures of the commercially available precatalysts compared well with the experimental data reported in literature. It is also shown that the energy profiles for alkene metathesis of simplified model systems do not compare well with non-simplified systems. Correlations between these simplified model systems and experimental work have to be regarded as serendipitous at best. When the energy profiles of the various new and commercially available precatalysts are compared, similarities in the energy trends for 1-octene metathesis are observed. These similarities raise questions about the significance of the differences in the energy barriers. In an effort to better understand this, two low activity precatalysts were also investigated in an attempt to identify the area or trend of poor catalysis. Instead of providing the desired different result, trends very similar to that of the highly active precatalysts were observed. This led to the observation that, without a sufficiently large dataset, great care should be taken before conclusions are drawn from theoretical work. Since the electronic investigation did not provide the desired result of finding a fast and effective method of determining which ligand merits further investigation, some steric aspects were studied. Once again, the precatalysts proved to be remarkably similar and no definitive answer for the observed differences in the various precatalysts could be determined. A preliminary experimental study into the feasibility of the synthesis of the new potential ligands was done. The multi-step synthesis route resulted in low yields in some cases, with the need for large volumes of solvents to purify the products. The toxicity of phenylphosphine also has to be taken into account when considering these types of ligands. A new precatalyst obtained by using a new ligand should show a remarkable improvement over the current commercially available precatalysts to justify the additional cost to synthesise a new ligand. It would seem that for future projects more consideration should be given to the deactivation mechanism of the Grubbs-type precatalysts, since this seems to be the logical starting point to look for the answers to the experimentally observed differences. A deeper understanding of the mechanism of alkene metathesis can only be obtained if all aspects are investigated in as much detail as possible. While the results did not provide the initially expected outcome, some valuable insights were gained that challenge the current way of thinking about the alkene metathesis mechanism. It is also clear that to oversimplify a very complex reaction and using limited data will lead to false assumptions being made. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

In this study, an attempt was made to identify the electronic and steric properties of the precatalyst ligands that determine the characteristics of phosphine ligated Grubbs-type precatalysts for alkene metathesis by means of molecular modelling. It was found from studying the literature that the possibilities for synthesising a wide range of phosphine ligands are almost unlimited. Additionally, it was found that there is no easy method to determine the electronic and steric properties of the precatalyst ligands in existence. Molecular modelling might provide a method to study potential ligands and precatalysts before tedious synthesis methods are attempted. It was found that the theoretically calculated structures of the commercially available precatalysts compared well with the experimental data reported in literature. It is also shown that the energy profiles for alkene metathesis of simplified model systems do not compare well with non-simplified systems. Correlations between these simplified model systems and experimental work have to be regarded as serendipitous at best. When the energy profiles of the various new and commercially available precatalysts are compared, similarities in the energy trends for 1-octene metathesis are observed. These similarities raise questions about the significance of the differences in the energy barriers. In an effort to better understand this, two low activity precatalysts were also investigated in an attempt to identify the area or trend of poor catalysis. Instead of providing the desired different result, trends very similar to that of the highly active precatalysts were observed. This led to the observation that, without a sufficiently large dataset, great care should be taken before conclusions are drawn from theoretical work. Since the electronic investigation did not provide the desired result of finding a fast and effective method of determining which ligand merits further investigation, some steric aspects were studied. Once again, the precatalysts proved to be remarkably similar and no definitive answer for the observed differences in the various precatalysts could be determined. A preliminary experimental study into the feasibility of the synthesis of the new potential ligands was done. The multi-step synthesis route resulted in low yields in some cases, with the need for large volumes of solvents to purify the products. The toxicity of phenylphosphine also has to be taken into account when considering these types of ligands. A new precatalyst obtained by using a new ligand should show a remarkable improvement over the current commercially available precatalysts to justify the additional cost to synthesise a new ligand. It would seem that for future projects more consideration should be given to the deactivation mechanism of the Grubbs-type precatalysts, since this seems to be the logical starting point to look for the answers to the experimentally observed differences. A deeper understanding of the mechanism of alkene metathesis can only be obtained if all aspects are investigated in as much detail as possible. While the results did not provide the initially expected outcome, some valuable insights were gained that challenge the current way of thinking about the alkene metathesis mechanism. It is also clear that to oversimplify a very complex reaction and using limited data will lead to false assumptions being made. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

Den ökade användningen av BIM har ändrat villkoren inom byggsektorn. Arbetet syftar till att identifiera och definiera de krav och kvalitetssäkringar av BIM-objekt som finns inom projektering, produktion samt förvaltning. Avsaknad av en gemensam standard försvårar kravställning och kvalitetssäkring av BIM-objekt vilket har lett till vissa komplikationer, främst vid konvertering mellan olika programvaror. BIM är med sin potential med största sannolikhet en stor del av byggsektorns framtid. För att kunna ta nästa steg i utvecklingen måste en gemensam standard gällande krav och kvalitetssäkring utarbetas.

The aim was to identify geographical areas of concern in the process of catchment delineation in urban areas in geographic information systems, GIS. The aim was also to develop a new method for the delineation in order to address identified problems. The calculations of the catchment areas are important for subsequent hydraulic modeling, which is performed in order to properly design storm water systems capable of handling the storm water. An object oriented method was developed that took into account the identified, problematic factors in the infrastructure and buildings of the urban area. An alternative algorithm for the preprocessing of the digital elevation model, DEM, was tested to see how the results would differ from a current method for catchment delineation with another algorithm for the preprocessing of the DEM. The two different algorithms for DEM preprocessing were used before the same procedure of catchment delineation was performed on the DEMs in ArcGIS. The delineated catchments from the two different preprocessing algorithms along with the object oriented method, were evaluated against reference catchment areas manually plotted by hydraulic modeling specialists. The object oriented method showed a higher correlation to the reference than the topographic methods for the most important target parameters when performing well. However the object oriented method has to improve in precision and efficiency if it is to be used for the calculations. The catchment delineation methods with different DEM preprocessing algorithms yields different results. For the DEM preprocessing, an algorithm from Whitebox GAT seemed to performed better in flat areas and in areas where the storm water lines have been lowered into the DEM, than the ArcGIS method did. However the combination of Whitebox GAT and ArcGIS resulted in some problems with the catchment delineation and hence the combined method has to be refined in order to be used.

No description available.