Dissertations / Theses on the topic 'Modelli moto'

This thesis deals with the modeling and control of electohydraulic systems. On basis on an accurate nonlinear model, an innovative position control scheme is proposed. Such a control scheme is mady by some decoupled actions, each one aimed at achieving a specific target in the dynamic response of the system. Besides that, an original and innovative scheme for the coordinated motion control of multi-dof hydraulic systems is proposed. Such a control scheme, referred to as Delayed Reference Synchronization Control, aims at reducing the synchronization error by delaying the references of the inner position loop of the axis, on basis on an equivalent elastic error. The effectiveness of both control schemes is assessed by numerical simulations by means of an accurate simulator employed in Simulink.

In questo elaborato è stato realizzato uno studio delle dinamiche del rischio di credito in una rete economica. Il rischio di credito rappresenta uno dei rischi di più difficile definizione e quantificazione; tuttavia negli ultimi decenni tali argomenti sono stati affrontati in letteratura e sono stati proposti diversi modelli per la stima del rischio di insolvenza. Questo lavoro di tesi focalizza l'attenzione sull'approccio strutturale. In particolare vengono analizzati due studi: un modello di first passage time con frontiera di default costante e un modello con frontiera di default definita da una funzione deterministica del tempo. L'analisi del rischio di credito viene effettuata in vista di una gestione dello stesso attraverso derivati creditizi, come i credit default swaps. Dall'applicazione dei modelli per la valutazione di questi derivati si possono effettuare stime e osservazioni con lo scopo di prevedere e controllare il rischio di insolvenza.

Un modello cinetico per il moto di interfaccia Guido Manzi Sommario Dopo una breve introduzione sui limiti di scala e i processi di segregazione di fase, presentiamo un modello per il moto di interfaccia tra due fluidi differenti, descritti da una coppia di equazioni cinetiche. Le loro soluzioni forniscono la dinamica degli stati finali attesa in base all’equazione di Cahn-Hilliard. La segregazione di fase è una transizione di fase del primo ordine che avviene nelle miscele quando la temperatura è abbassata al di sotto della curva di coesistenza. Domini ricchi in componenti diverse cominciano ad emergere tramite vari meccanismi. I domini sono separati da strati che divengono sempre più sottili nelle fasi finali del processo; a tal punto si dicono interfacce. Lo strumento principale usato è l’espansione di Hilbert, in cui il parametro piccolo è il rapporto tra le unità di misura cinetica e macroscopica. Il problema può essere affrontato in vari modi. Noi mostriamo come calcolare la dinamica limite e le correzioni del primo ordine ad essa. Si trova che gli stadi finali della segregazione di fase sono caratterizzati da un riarrangiamento geometrico delle interfacce che tende a minimizzare la superficie mentre il volume dei domini resta costante. In ogni punto dell’interfaccia la velocità nella direzione ortogonale è data da gradienti di funzioni armoniche, il cui valore sul bordo dipende dalla curvatura e dalla tensione superficiale. Il moto limite è quindi dato in termini di un problema di frontiera libera. D’altra parte le correzioni a tale moto sono ancora soluzioni di un problema non lineare, ma con bordi fissati. Il nostro modello ha soltanto un tipo di quantità conservata: la massa totale di ciascuna componente. Così può essere pensato descrivere il comportamento di fluidi altamente viscosi, dove l’energia e l’impulso che produrrebbero effetti fluidodinamici sono dissipati su scale di tempo molto più brevi di quelle cui siamo interessati. Un esempio di tali sistemi è dato dalle miscele di polimeri.
A Kinetic Model Of Interface Motion Guido Manzi Abstract After a brief introduction on scale limits and processes of phase segregation, we present a model of interface motion between two different fluids, described by a pair of kinetic equations. They provide the late stages dynamics expected by the Cahn-Hilliard equation. Phase segregation is a first order phase transition which happens in mixtures when the temperature is lowered below the coexistence curve. Domains rich in different components begin to arise with several mechanisms. Domains are separated by layers, which become sharp in the last stages of the process and then they are called interfaces. The main tool used is Hilbert expansion, the small parameter being the ratio between kinetic and macroscopic unit of length. The problem can be faced to in several ways. We show how to compute the limiting dynamics and the first order corrections to it. It turns out that the late stages of phase segregation are characterized by a geometrical rearrangement of the interfaces which tends to minimize the surface, while keeping fixed the volume of the domains. The normal velocity in each point of the interface is given by gradients of harmonic functions, whose value on the boundary depends on the curvature and on the surface tension. The limiting motion is thus given in terms of a free boundary problem. On the other hand the corrections to that motion are solution of a yet non linear problem, but with boundaries fixed. Our model has only a kind of conserved quantity: the total mass of each component. So it can be interpreted to describe the behaviour of highly viscous fluids, where energy and momentum yielding fluidodynamic effects are dissipated on much smaller time scales than those we are interested in. An example of such mixtures is given by polymer blends.

In questo lavoro si presenta il fenomeno fisico nominato moto browniano, s’illustra il modello matematico atto a descriverlo e si analizza come questo abbia avuto notevole importanza in ambito finanziario, in particolare nell’elaborazione del modello di Black, Scholes e Merton per la valutazione dei derivati.

This project involves modelling and simulating a real three-phase induction motor to determine its transient and steady-state characteristics, such as its torque-speed characteristics, torque-time characteristics, speed-time characteristics and its rotor and stator currents. For the simulation the computer program MATLAB/Simulink was used. The motors equivalent circuit parameters were determined by performing the standard equivalent circuit parameter tests; the DC test, no-load test and the blocked-rotor test. The moment of inertia of the motor was attempted to be determined through power and deceleration tests, although the method proposed in this paper proved to be unsuccessful. The resulting equivalent circuit parameters determined from the suggested tests were highly unlikely for the 0.37 kW motor used, however the MATLAB/Simulink computer program proved to be a suitable program to simulate three-phase induction motors.

Brushless dc motor drives have become increasingly popular, following recent developments in rare-earth permanent-magnet materials and the semiconductor devices used to control the stator input power and to sense the rotor position. They are now frequently used in applications such as flight control systems and robot actuators, and for drives which require high reliability, long life, little maintenance and a high torque-to-weight ratio. In many motor drives the presence of torque and speed ripples, especially at low speed, is extremely undesirable. The mathematical model developed in this thesis was used to investigate their occurrence in a typical brushless dc drive system, with the objective of establishing factors which effect their magnitude and ways by which they may be reduced. The model is based on the numerical solution of the differential equations for the system, with those for the motor being formulated in the phase reference frame. Tensor methods are used to account for both the varying topology and the discontinuous operation of the motor arising from changes in the conduction pattern of the inverter supply switches. The thesis describes the design, construction and testing of an experimental voltage source PWM inverter, using MOSFET switching devices, to drive a 1.3 kW 3-phase brushless dc motor. A practical circuit is described which implements current profiling to minimize torque ripple, and the optimum phase current waveforms are established. The effect of changes in the firing angle of the inverter switches on the torque ripple are also examined. Throughout the thesis, theoretical predictions are verified by comparison with experimental results.

Amyotrophic Lateral Sclerosis (ALS) is the most common adult motor neuron disease. The majority of ALS cases are sporadic (SALS), but 10% of patients have a familial form of ALS (FALS). Mutations in Fused in Sarcoma (FUS) occur in approximately 4% of FALS and less than 1% of SALS. A hallmark feature of ALS is the degeneration of upper and lower motor neurons in the brain and spinal cord; however, the mechanism underlying this loss is not known. Studies of degenerative mechanisms have been impeded by the inaccessibility of human neural tissue. A possible solution is to use induced pluripotent stem cells (iPSCs) derived from patients, which may be differentiated into the cell types affected by disease. To test whether patient-specific stem cells can be used to model aspects of ALS pathogenesis, iPSC lines were generated from a patient carrying the pathogenic FUS R521C mutation. FUS iPSCs derived from patient fibroblasts and WT iPSCs derived from fibroblasts from two healthy controls were differentiated into neural progenitors and motor neurons. FUS iPSC-derived neuronal cells recapitulate key aspects of FUSassociated ALS, including mislocalisation of FUS protein, the redistribution of FUS protein into cytoplasmic stress granules, and increased apoptotic cell death. The second study uses this iPSC model to investigate the effects of mutant FUS on dendritic morphology and synaptic regulation. FUS iPSC-derived neurons display abnormal dendritic morphology, such as reduced neurite outgrowth and reduced density of dendritic protrusions. FUS iPSC-derived neurons also show differences in the localisation of synaptic proteins. This study suggests that physiological levels of mutant FUS protein affect the morphology and synaptic structure of human neurons. These studies validate the stem cell approach to disease modelling and provide support for the use of patient-specific stem cells for the study of disease mechanisms.

Humans can interact with their environment by tuning the properties of the musculoskeletal system to control force and impedance at the contact points with the environment. Many activities that require the use of tools, such as handling a screwdriver or chisel, involve an unstable interaction with the environment. This instability will amplify any disturbance or noise and cause unpredictable motion. For example, when chiselling a piece of rough wood, motor noise or involuntary movements can make the hand slip out of the desired track. When a single reaching movement is repeated in unstable dynamics, the central nervous system (CNS) learns to compensate for the instability by coordinating muscle in an appropriate way. However, it is still unclear how humans can learn to perform unstable tasks in various directions. Do they co-contract in an isotropic way to ensure good performance in all directions, or do they learn direction specific impedance? And what are the underlying processes of this adaptation?This thesis addresses those questions through psychophysical experiments in which arm movements were investigated as subjects interacted with computer controlled dynamics produced by a robotic interface, as well as by developing computational models of human motor learning. Observations of learning unstable dynamics simultaneously in two different directions show that the CNS is able to compensate for the instability specifically for each direction, by adapting impedance optimally to the environment. A computational model was developed to simulate human reaching movements in stable and unstable dynamics in various directions of the workspace. The model learns feedforward muscle tension by minimising movement error in muscle space and energy. The computer model is a useful tool to predict and investigate (generalisation in) motor learning. It can predict the results of our experiment as well as many motor learning observations in past experiments.

La crisi economica che nel 2008 investì i mercati americani e che, a distanza di poco tempo, colpì anche quelli europei, ha portato con sé conseguenze profonde che hanno modificato in via definitiva gli equilibri interni di alcuni Stati. A distanza di otto anni, alcuni di essi hanno superato tale momento di crisi. Altri ne pagano ancora le conseguenze. Uno degli indici rivelatori del superamento di tale stato di crisi è quello relativo alla disoccupazione giovanile. In Europa, le discrepanze tra gli Stati in merito a questo parametro sono notevoli e profonde. Se infatti Paesi come la Germania possono vantare uno degli indici di disoccupazione giovanili più bassi del continente, altri Stati come l'Italia presentano dati allarmanti. I giovani italiani dopo aver conseguito un titolo un studio faticano a trovare un'occupazione. Se la crisi economica ha peggiorato una situazione già debole del mercato del lavoro italiano, l'elevato tasso di disoccupazione giovanile è da ricercarsi anche in un mancato raccordo tra mondo della Scuola e mondo delle Aziende. La Germania, già negli anni '70 del secolo scorso, aveva intuito come tale mismatch tra i due mondi avrebbe potuto creare serie difficoltà e per tale motivo aveva approntato un modello d'istruzione che, in tempi recenti, ha riscosso grande attenzione in quegli Stati che, come l'Italia, faticano a dare una risposta ai problemi della disoccupazione giovanile: il modello duale tedesco. Il presente studio ha quindi l'obiettivo di indagare se è possibile introdurre un modello duale, ispirato a quello tedesco, all'interno del modello di istruzione italiano. A tal fine, nella prima parte, viene presentata la letteratura inerente il modello duale tedesco nonché quella relativa agli strumenti messi a disposizione del Legislatore italiano, ovvero l'Alternanza Scuola Lavoro e l'apprendistato, per poter applicare un simile modello anche in Italia. Nella seconda parte viene analizzata l'Alternanza Scuola Lavoro, nella sua evoluzione sia normativa che pedagogica, evidenziando i passaggi che hanno portato alla sua attuale definizione all'interno della L. 107/2015. Nella terza parte viene analizzato lo strumento normativo dell'apprendistato, mettendo a confronto le sue peculiarità ed il suo utilizzo il Germania ed in Italia. La quarta parte è dedicata all'analisi di caso del Progetto DESI, acronimo che sta per Dual Education System Italy, primo esperimento in Italia di applicazione del modello duale tedesco, all'interno di Ducati Motor Holding.
The economic crisis that hit in 2008 the American Market and, shortly afterwards, also the European ones, has brought profound consequences, definitively changing the internal stability of some Countries. Eight years later, some of them have overcome the economic crisis. Others, nevertheless, are still paying its consequences. One of the most valuable indicators that reveals the overcoming this critical state is related to Youth Unemployment. In Europe, the discrepancies among the Member States about this parameter are significant and deep. In fact, if countries like Germany can boast one of the lowest youth unemployment rates in the continent, other states such as Italy provides alarming figures. Young Italians, after earning a title of study, still struggle to find a job. If the economic crisis has worsened the already fragile situation of the Italian labor market, the high rate of youth unemployment is also to be found in a lack of coordination between the world of Education and the world of Companies. Germany, in the 70s of the last century, realized that the above mentioned mismatch between the two worlds could create serious problems to the economy and, for this reason, prepared an education model that, in recent times, has received much attention in those State which, like Italy, are struggling to respond to the problems of youth unemployment: the German dual model. Therefore, the present study aims to investigate whether it is possible to introduce a dual model, inspired by the German one, in the Italian system of education. To this end, in the first part it presents the literature on the German dual model and the definition relating to the tools made available to the Italian Legislator, or the school-work alternating training and apprenticeship, in order to apply a similar model in Italy. In the second part is analyzed the school-work alternating training, in its evolution both legislation pedagogical, highlighting the steps that led to its current definition within the Law n. 107/2015. The third part analyzed the legal instrument of apprenticeship, comparing its characteristics and its use in Germany and in Italy. The fourth part is devoted to the analysis of the case of DESI Project, which stands for Dual Education System Italy, the first experiment in Italy for the implementation of German dual model in Ducati Motor Holding.

The study presents a one-dimensional, transient and compressible flow models of a commercial Common Rail Injector (CRI) and a prototype of a single-fuel Hydraulically actuated Electrically controlled Unit Injector (HEUI) developed at the University of New South Wales (UNSW) in conjunction with local industry. The unique feature of the UNSW HEUI is the fact that it uses diesel fuel as the driver for pressure amplification within the unit injector. The work undertaken is part of a wider study aimed at optimization of the design of diesel injectors for dual-fuel systems to reduce green house gas emissions. The contribution of this thesis is the development of the model of the UNSW HEUI injector, which can be used to investigate possible modifications of the injector for its use in dual-fuel injection systems. The developed models include electrical, mechanical and hydraulic subsystems present in the injectors. They are based on Kirchhoff??s laws, on the mass and momentum conservation equations and on the equilibrium of forces. The models were implemented in MATLAB/SIMULINK graphical software environment, which provides a high degree of flexibility and allows simulation of both linear and nonlinear elements. The models were used to perform sensitivity analysis of both injectors. The sensitivity analysis has revealed that the temperature of the solenoid coil is one of the critical parameters affecting the timing and the quantity of the fuel injection of both injectors. Additional critical parameters were found to be the dimensions of the piston of the CRI, the stiffness of the needle spring of the HEUI and the dimensions of the intensifier of the HEUI. The models also revealed that in the case of pilot injections the speed of the solenoid is the major limiting factor of the performance. The developed models provide better understanding of the issues and limitations of the injectors. They give detailed insight into their working principles. The investigations of the models permit making quantitative analysis of the timing of the HEUI solenoid and to evaluate the proposed change of the direction of the pressure acting on the HEUI solenoid plunger.

L’obiettivo di questo lavoro di tesi è l'implementazione di un modello dinamico rappresentativo dei carrelli di atterraggio di un elicottero, adatto alla simulazione del volo. Inizialmente sono state cercate informazioni teoriche su varie risorse disponibili in letteratura riguardanti gli elicotteri e, in particolare, i diversi tipi di carrelli; inoltre ho cercato di reperire informazioni sui modelli dinamici che permettono di calcolare le forze ed i momenti che agiscono sui carrelli degli elicotteri, specialmente in fase di atterraggio. L’elicottero è stato approssimato come un corpo rigido e si sono cercate le equazioni differenziali che descrivono la dinamica del moto, sia in un sistema di riferimento solidale all’elicottero (assi body), che in un sistema di riferimento inerziale (assi NED). Sono state quindi individuate le formule utili a modellare il contatto carrello-suolo e a stimare, durante l’atterraggio ed il decollo, le forze ed i momenti scambiati con il terreno. Sono quindi state individuate le matrici che permettono di passare da un sistema di riferimento all’altro attraverso gli angoli di Eulero. Successivamente si è studiato come modellare a livello dinamico il carrello di atterraggio di un elicottero, specialmente per quanto riguarda il contatto ruota-pneumatico con il terreno. Si è scelto di modellare il contatto approssimando la fisica del problema mediante un sistema molla-smorzatore. Una volta sviluppato un modello teorico del problema, esso è stato implementato in ambiente Simulink, un modulo del codice di calcolo ingegneristico Matlab che consente di creare modelli dinamici attraverso blocchi predefiniti ed effettuare simulazioni in diverse condizioni. I risultati ottenuti dalle simulazioni forniscono il valore numerico delle variabili interessate nella simulazione istante per istante e si riesce a salvare l’andamento nel tempo delle forze e dei momenti che agiscono sulle gambe del carrello dell’elicottero durante l’atterraggio.

The anterior cruciate ligament (ACL) is one of four major intra-articular knee ligaments and plays a key role in knee stability. Rupture of the ACL is one of the most common and debilitating sport-related knee injuries. Most ACL ruptures do not involve direct collisions, but occur during landing, cutting, and pivoting tasks common to sports such as soccer, basketball, and netball. Rates of ACL rupture in young people have increased enormously in Australia over the past two decades. Generally, ACL ruptures are 3.5-4 times more frequent in female compared to male athletes. Among females, those aged 15-19 years are at highest risk of ACL rupture being ~4 times more likely to sustain injury than their pre-pubertal counterparts. Analysis of video footage of ACL injury events, cadaveric experiments, and biomechanical studies has yielded a consensus that external knee loads applied in three planes of motion (i.e., sagittal, frontal, and transverse) contribute to ACL rupture. Laboratory-based biomechanical studies that directly instrumented the ligament have been performed, albeit sparingly for obvious reasons of invasiveness, and show the ACL sustains substantial loading during non-injurious motor tasks. Moreover, studies using external biomechanical measures to examine ACL loading employing computational models have been limited, and have not included, and thus are insensitive to, an individual’s knee muscle activation patterns in muscle force estimates Valid models of the ACL and its loading profile have been challenging to create, and instrumented measures of ACL loading without concurrent modelling of the neuromusculoskeletal dynamics will fail to provide insight into the role of specific muscle and external loads in loading the ACL. Therefore, the mechanisms underlying ACL loading during dynamic motor tasks, through the interaction of muscles, contacting articular bodies, and other soft tissues, remain unclear. This deprives injury prevention and rehabilitation programs of personalized targets that are mechanistically linked to in vivo ACL loading. The purposes of this thesis were to develop and validate a computational model that can accurately estimate ACL force based on outputs of neuromusculoskeletal models in individuals with an intact ACL; determine ACL loading in drop-land-lateral jump task in mature females, therein examining the mechanisms that contribute to ACL loading, and; and determine effects of pubertal maturation on females’ ACL loading during a dynamic motor task considered provocative for the ACL. This thesis involved the development, validation, and application of a computational model to quantify ACL force during dynamic motor tasks. First, an ACL force model was developed using the most relevant, complete, and accessible cadaveric data from the literature. These data comprised measurements of ACL force or strain across various knee flexion angles in response to uni- and multiplanar external knee loads. Using a portion of these data, algebraic equations were fitted to well describe ACL loading in response to both uni- and multiplanar knee loading. The model was then validated using the remaining experimental data not used in model development. The validated ACL force model was then combined with an electromyography (EMG) -informed neuromusculoskeletal model to estimate ACL force developed during a standardised drop-land-lateral jump task performed by healthy females in laboratory conditions. Ninety-three females, aged 8 to 20 years, volunteered to participate in this study. All participants were recreationally active and had no history of lower limb injury or knee pain. Participants were divided into 3 groups: pre-, early/mid-, or late/post-pubertal based on Tanner’s pubertal classification system. Each participant attended a laboratory-based testing session, wherein three repeated trials of a standardized drop-land-lateral jump from a box with box height set to 30% of their lower limb length, while 3D motion capture, ground reaction forces, and surface EMG were acquired. For purposes of calibrating the EMG-informed neuromusculoskeletal model, three trials of running at a natural self-selected style (speed range from 2.8 to 3.2 m.s-1) were performed. These laboratory data were then used in a neuromusculoskeletal model to estimate ACL loading. The OpenSim modelling software was used to scale a generic anatomical model to match each participant’s gross dimensions, mass, and inertia, followed by morphometric scaling to preserve fibre and tendon operating ranges, and last adjust each muscle’s maximum isometric strength based on empirical relationships between mass and height with lower limb muscle volume. Using this scaled model, the external biomechanics (i.e., model motions and joint loading) and muscle tendon unit actuator kinematics (i.e., moment arms, lengths, and lines of action) were determined. The EMG signals were conditioned into normalized linear envelopes, which were combined with the OpenSim external biomechanics and muscle tendon unit actuator kinematics to drive a model in the Calibrated EMG-informed Neuromusculoskeletal Modelling (CEINMS) toolbox. The CEINMS was first calibrated and then run with an EMG-informed neural solution to estimate lower limb muscle and tibiofemoral contact forces. The muscle tendon unit kinematics and forces, along with the joint loads were then incorporated into the validated ACL force model to quantify ACL force. For each participant, the contribution of muscle and intersegmental loads to ACL forces were calculated across the stance phase of the drop-land-lateral jump task. Specific statistical analyses were run to address each of the research questions and encapsulated as a series of research manuscripts in the format of journal articles. The first study developed and validated a computational model that predicted the force applied to ACL in response to multiplanar knee loading that was estimated by a subject-specific neuromusculoskeletal knee model, as described above. The study demonstrated these models’ utility by applying it to a sample of motion capture data. First, a three-dimensional (3D) computational model was developed and validated using available cadaveric experimental data to estimate ACL force. The ACL force model was valid as it well predicted the cadaveric data, showing strong statistical correlation (r2=0.96 and P<0.001), minimal bias, and narrow limits of agreement. Second, by combining a neuromusculoskeletal model with the ACL force model, it was revealed that during a drop-land-lateral jump task the ACL is primarily loaded through the sagittal plane, mainly due to muscular loading. The computational model developed in study one was the first validated accessible tool that could be used to develop and test knee ACL injury prevention programs for people with normal ACL. The method used to develop this model can be extended to study the abnormal ACL upon the availability of relevant experimental data. The paper describing these results was published as Nasseri A., Khataee H., Bryant A.L., Lloyd D.G., Saxby D.J. Modelling the loading mechanics of anterior cruciate ligament, Computer Methods & Programs in Biomedicine, 184 (2020) 105098. doi: 10.1016/j.cmpb.2019.105098. Study two determined ACL force and the key muscular and biomechanical contribution to this ACL loading in a standardized drop-land-lateral jump task performed by sexually mature young females. Three-dimensional whole-body kinematics, ground reaction forces, and muscle activation patterns from eight lower limb muscles were collected during dynamic tasks performed by healthy females (n=24), all who were recreationally active. Collected data were used to model the external biomechanics, muscle-tendon unit kinematics, and muscle activation patterns using established biomechanical modelling software packages (i.e., OpenSim and MotoNMS). These biomechanical and electromyographic data were then used to calculate the lower limb muscle, joint contact and the ACL forces through an EMG-informed neural solution combined with a validated ACL force model. Peak ACL force (2.3 ± 0.5 BW) was observed to occur at 14% of the stance phase during the drop-land-lateral jump task. The ACL force was primarily developed through the sagittal plane, and muscles were the dominant source of ACL loading. The main ACL muscular antagonists were the gastrocnemii and quadriceps, while the hamstrings were the main ACL agonists. Our results highlighted the important role of gastrocnemius in ACL loading, which could be considered more prominently in ACL injury prevention and rehabilitation programmes. The paper describing these results is accepted for publication as Nasseri A., Lloyd D.G., Bryant A.L., Headrick J., Sayer T.A., Saxby D.J. Mechanism of anterior cruciate ligament loading during dynamic motor tasks. Medicine and Science in Sports and Exercise. Study three determined and compared ACL loading during a drop-land-lateral jump task in females across three pubertal stages of maturation. Further, the relative contributions to ACL force from three planes of motion (sagittal, frontal, and transverse) were compared. In this, sixty-two participants were divided into pre-pubertal (n=19), early/mid-pubertal (n=19) or late/post-pubertal (n=24) groups based on Tanner’s pubertal classification system. Each participant completed a biomechanical testing session wherein we collected three-dimensional body motion, ground reaction forces, and EMG during drop-land-lateral jump task. Using these data, the aforementioned ACL force and neuromusculoskeletal knee model was used to assess ACL loading and the key contributions to this loading. To analyse the ACL force in a continuous manner, statistical parametric mapping (SPM) analysis was used. SPM ANOVA and post-hoc t-tests were used to compare total ACL force and contributors to this force over the stance phase of the drop-land-lateral jump task between three groups of females across maturation. Compared to pre- and early/mid-pubertal, females in late/post pubertal group showed significantly higher ACL force during a large percentage of the stance phase, which encompassed the peak ACL forces. The forces developed through sagittal and transverse planes were significantly higher in late/post-pubertal group compared to the two other groups over large percentages of the stance phase. The contribution of the frontal plane mechanisms to ACL force was not significantly different across sexual maturation, while the pre- and early/mid-pubertal groups were not significantly different for any of the outcome measures. The larger ACL forces observed in late/post-puberty group (14-20 years) may partially explain the higher rate of ACL injury in females aged 15-19 years in the last decades. In addition, it has been shown that ACL growth plateaus at the age of 10, prior to full sexual maturation and cessation of growth in stature. Thus, females in late/post pubertal group are potentially heavier, have similar sized ACL, but with greater ACL forces compared to their less sexually mature counterparts. These reasons together could be the foundation, at least in part, for the higher ACL forces observed in this group. The manuscript describing these results is under review as Nasseri A., Lloyd D.G., Minahan C., Sayer T.A., Paterson K., Vertullo C.J., Bryant A.L, Saxby D.J. Effects of pubertal maturation on anterior cruciate ligament forces during a landing task in females. American Journal of Sports Medicine. In conclusion, a computational ACL force model was developed and validated that provided a platform for integration of external biomechanics, muscle and joint contact forces to calculate in vivo ACL force. This ACL force model enabled examination of the ACL loading mechanism by exploring the main muscular and biomechanical contributions to ACL loading; and the effects of pubertal maturation on ACL loading in females. The variability in the magnitude and contributions to ACL force across a wide age range of participants suggest estimation of ACL force is necessary to understand the potential ACL injury mechanisms and design ACL injury prevention programs, rather than relying on external biomechanics that are proposed as surrogates of ACL injury.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School Allied Health Sciences
Griffith Health
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L’aumento del consumo di energia globale e le problematiche legate all’inquinamento stanno rendendo indispensabile lo spostamento verso fonti di energia rinnovabile. La digestione anaerobica rappresenta una possibile soluzione in quanto permette di produrre biogas da biomassa organica di scarto ma, l’ottimizzazione del processo risulta difficoltosa a causa delle numerose variabili chimiche, biologiche, fisiche e geometriche correlate. Nel presente elaborato, concentrandosi sulle problematiche relative alla miscelazione interna, è stata investigata la fluidodinamica interna di un reattore modello ottenuto tramite scale-down di un digestore anaerobico industriale che presentava problemi di sedimentazione di sostanza solida sul fondo del reattore. Tramite tecniche di diagnostica ottiche, è stato studiato il movimento del fluido, prima utilizzando acqua demineralizzata e poi una soluzione di gomma di xantano come fluido di processo, al fine di studiare il campo di moto medio interno al reattore. Le tecniche utilizzate sono la Particle Image Velocimetry (PIV) e la Planar Laser Induced Fluorescence (PLIF). Al fine di rendere il sistema investigato il più rappresentativo possibile del digestore industriale, è stato utilizzato come fluido di processo per alcune delle prove raccolte, una soluzione acquosa 1,0g/kg di gomma di xantano, le cui proprietà reologiche sono state investigate grazie ad un Reometro Anton Paar MCR 301.

The work presented here provides a comprehensive dynamic and aerodynamic helicopter model. The possible applications of this work are wide including, control systems applications, reference and trajectory tracking methods implementation amongst others. The model configuration corresponds to a Sikorsky helicopter; a main rotor in perpendicular combination with a tail rotor. Also, a particular model of unmanned aerial vehicle has been modelled as part of collaboration with the La Laguna University (Spain). The modelling tool is VehicleSim, a program that builds rigid body systems, solves the nonlinear equations of motion and generates the time histories of the corresponding state variables of the vehicle under study. VehicleSim is able to provide the linearised equations of motion in a Matlab file and the symbolic state-space model. This is useful when control systems are to be designed. The main rotor model accounts for flap, lag and feather motions for each blade as well as for their nonlinear dynamic coupling. The tail rotor is modelled including the flap-feather coupling via delta three angle. The main and tail rotors' angular velocities are implemented by PID controllers. Main rotor linear and nonlinear equations are derived and validated by comparison with the theory. Main rotor flap and lag degrees of freedom are validated using frequency domain approaches in the absence of external forces. Also, fuselage-main rotor interaction is studied and validated by using modal analysis and root locus methodology. Vibrations originated at the main rotor are simulated and their effects on the fuselage are examined by a Short Time Fourier transformation. The aerodynamic model uses blade element theory on the main-tail rotors. Hover, climb, descent and forward flight conditions are simulated and they allow the helicopter to follow certain trajectories. Finally, the ensuing vibrations when an external perturbation is applied to the main rotor are investigated.

The more-electric aircraft concept is a major trend in aircraft electrical power system engineering and results in an increase in electrical loads based on power electronic converters and motor drive systems. Unfortunately, power electronic driven loads often behave as constant power loads having the small-signal negative impedance that can significantly degrade the power system stability margin. Therefore, the stability issue of aircraft power systems is of great importance. The research of the thesis deals with the modelling and stability analysis of an aircraft power system. The aircraft power system architecture considered in the thesis is based on the More Open Electrical Technologies (MOET) aircraft power system with one generator as only a single generator can be connected to a system at any one time. The small-signal stability analysis is used with the system dynamic model derived from the dq modelling method under the assumption that the aircraft power system operating point does not change rapidly during normal operation mode. The linearization technique using the first order terms of a Taylor expansion is used so as to achieve a set of linear models around an equilibrium point for a small-signal stability study. The thesis presents the development of effective models capable of representing the electrical power system dynamic behaviour for stability studies. The proposed model can be used to predict the instability point for variations in operating points and/or system parameters. Agreement between the theoretical estimation, simulation, and experimental results for a simple system are achieved that ranges from acceptable to very good. Finally, the subsystem models described in the thesis can be interconnected in an algorithmic way that is representative of a more generalized aircraft power system model. The generalized model is also applied to a more complex and realistic aircraft power system with simulation validations for thorough investigations of aircraft power system stability. This model may be considered as a powerful and flexible stability analysis tool to analyse the complex multi-converter electrical power systems.

Computer simulation models are increasingly necessary as a design tool for modern vehicles, for which a subcategory relates to motorcycles. Simulation models can be employed for a variety of applications, an important area of which relates to the motorcycle's dynamic responses. The response of a motorcycle is heavily dependent on the rider's control actions, and consequently a means of replicating the rider's actions provides an important extension to this area. The application of mathematical control techniques for replicating the motorcycle rider's control actions is presented in this thesis, detailing specifically the techniques of optimal control and model predictive control. The work begins with modelling the dynamics of the motorcycle using standard procedures. The application of optimal control to a motorcycle rider is not new, but the available results have been extended significantly over those previously available, allowing further insights into the behaviour and therefore applicability of this strategy to modelling a motorcycle rider. Use of the model predictive control approach is new in the field of motorcycle rider modelling, and a similarly extensive parametric study is conducted to evaluate the suitability of this approach, and to highlight the similarities and differences between this and the optimal control approach. Both controller models were simulated over a standard single lane-change manoeuvre. Comparison of the relative performances of the two control approaches confirmed strong similarities between the techniques, particularly when the modelled rider is permitted an extensive knowledge of the approaching road path to follow. When this knowledge is restricted, differences were apparent between the two, suggesting the predictive control approach is capable of better performance here, and therefore represents a more robust control strategy. An option of the predictive control approach allows more elaborate target paths for the rider to follow to be set. However, defining the target path for the rider model to follow as the road centreline, and then permitting the controller itself to select the most appropriate course to take, has also been shown to be the more suitable option. The predictive control technique for motorcycle rider modelling is shown to be a theoretically suitable application. Further work is suggested to validate the results presented here. If it can be confirmed that the model accurately captures a motorcycle rider's actions, this will prove a very useful tool for the understanding of a motorcycle rider's control actions, with potential benefits towards rider safety and furthermore as a design tool for the motorcycle industry.

The anticipated growth of air traffic worldwide requires enhanced Air Traffic Management (ATM) technologies and procedures to increase the system capacity, efficiency, and resilience, while reducing environmental impact and maintaining operational safety. To deal with these challenges, new automation and information exchange capabilities are being developed through different modernisation initiatives toward a new global operational concept called Trajectory Based Operations (TBO), in which aircraft trajectory information becomes the cornerstone of advanced ATM applications. This transformation will lead to higher levels of system complexity requiring enhanced Decision Support Tools (DST) to aid humans in the decision making processes. These will rely on accurate predicted aircraft trajectories, provided by advanced Trajectory Predictors (TP). The trajectory prediction process is subject to stochastic effects that introduce uncertainty into the predictions. Regardless of the assumptions that define the aircraft motion model underpinning the TP, deviations between predicted and actual trajectories are unavoidable. This thesis proposes an innovative method to characterise the uncertainty associated with a trajectory prediction based on the mathematical theory of Polynomial Chaos Expansions (PCE). Assuming univariate PCEs of the trajectory prediction inputs, the method describes how to generate multivariate PCEs of the prediction outputs that quantify their associated uncertainty. Arbitrary PCE (aPCE) was chosen because it allows a higher degree of flexibility to model input uncertainty. The obtained polynomial description can be used in subsequent prediction sensitivity analyses thanks to the relationship between polynomial coefficients and Sobol indices. The Sobol indices enable ranking the input parameters according to their influence on trajectory prediction uncertainty. The applicability of the aPCE-based uncertainty quantification detailed herein is analysed through a study case. This study case represents a typical aircraft trajectory prediction problem in ATM, in which uncertain parameters regarding aircraft performance, aircraft intent description, weather forecast, and initial conditions are considered simultaneously. Numerical results are compared to those obtained from a Monte Carlo simulation, demonstrating the advantages of the proposed method. The thesis includes two examples of DSTs (Demand and Capacity Balancing tool, and Arrival Manager) to illustrate the potential benefits of exploiting the proposed uncertainty quantification method.

The theme of this thesis is concerned with the modelling of the multi-physics interactions that occur in lightning and arc discharge. The main contributions of this research are presented as combining different physical studies namely, electromagnetic (EM) propagation, thermal diffusion and non-linear materials using a numerical algorithm. The algorithm was developed based on the two dimensional (2D) numerical transmission line method (TLM). The algorithm was applied to several practical examples namely, to model the electro-thermal analysis and the temperature development in a plasmonic nano-heat sources for terahertz applications; to predict the shape and the location of an arc discharge channel caused by a lightning strike using electro-thermal analysis, and to model diverter strips for lightning protection on aeroplanes. Different electro-thermal coupling approaches, such as fully and partially coupled methods were used to investigate the efficiency and accuracy of the model. In the fully coupled method the thermal model was allowed to change the electrical properties of materials in the electromagnetic model. On the other hand partial coupling did not consider the temperature dependency of the electrical properties in the electromagnetics model. Both of the models used the dissipated power from the electromagnetic model as a source signal to evaluate the temperature profile in the thermal model. Also different coupling interval timesteps were investigated to minimize the computational power needed without affecting the model accuracy.

I detta arbete behandlas transient simulering i ett 1D-simuleringsprogram, i detta fall Gamma technologies GT-Power. Vad som behöver ändras i en modell för att den skall kunna simulera en motor under transienta driftsfall med god noggrannhet har undersökts. När detta är gjort, skall det undersökas hur väl den transient kalibrerade modellen kan simulera en motor med förändrad rörgeometri på insugs- eller avgassidan, och vad som måste omkalibreras om detta inte är fallet. Den viktigaste slutsatsen av detta arbete är vikten av att ha en korrekt framtagen kompressormapp i modellen. Den som fanns tillgänglig under arbetet hade bara mätdata ned till 70000 rpm. Detta resulterade i en överskattning av massflödet i den lägre regionen i den av GT-Power framställda kompressormappen. Detta pga. att GT-power verkar överskatta massflödet under extrapolationen av mappen. För att få ett korrekt simulerat turbovarvtal under transienten var turbineffektivitetsmultiplikatorer introducerade. Med det var inte tillräckligt med tvåpunkts kalibrering av dessa och låta GT-Power interpolera emellan utan flera varvtal behövde kalibreras in för att få ett korrekt simulerat turbovarvtal. Andra viktiga områden att modifiera för att kunna simulera transienter var förbränningen, luft/bränsleförhållandet och grenrörets termiska egenskaper. När sedan geometrin i modellen förändrades krävdes en omkalibrering av turbineffektivitetsmultiplikatorerna. Studien var uppdelad i en kalibreringsdel och en valideringsdel. I kalibreringsdelen kalibrerades GM-motorn med modellbeteckningen L850 mot transienta mätdata. När modellen var kalibrerad studerades hur väl den kunde simulera samma motor men med olika rörgeometrier på insug och avgassidan. Detta för att ta reda på hur mycket kalibreringen behöver ändras när geometrin ändras.
The subject of this thesis work is to investigate transient simulations in a 1Dsimulation program, in this case Gamma Technologie’s GT-Power. The investigation consists of a study what needs to be changed on a model in order to make it perform transient simulations of an engine with accurate results. And when the simulation is calibrated the model is validated to see if it can predict transients accurately when the piping system is changed to different geometries, and if not what is needed to be recalibrated in the model to do so. The most important conclusion of this work is the importance to have a correctly generated compressor map in the model. The one present in the investigation had only measured data beginning from a turbo speed of 70000 rpm an up. This resulted in an over-predicted massflow in the lower region of the GT-power generated compressor map. This is because GT-Power seems to overestimate the massflow when extrapolating the map. To get an accurately modeled turbo, turbine efficiency multipliers (TEM) had to be introduced. It was not sufficient to do a two point calibration and let GT-Power interpolate in between. More calibrated points had to be introduced to model the turbo speed accurately. Other important areas to alter to make them able to perform transient simulations are the combustion, AFR and thermal properties of the exhaust. When changing the geometry of the piping system the calibrated TEM’s had to be recalibrated. The study was made up of a calibration part and a validation part. In the calibration part a model of the GM engine L850 was calibrated against transient measurements. When the model was calibrated the validation part of the work commenced by changing the geometry of the piping system around the engine to se what parts had to be recalibrated.

Molecular and functional analysis of small molecule binding to protein can provoke insights into cellular signaling and regulatory systems as well as facilitate pharmaceutical drug discovery. In label free small molecule detection the displacement assay format can be applied. This assay format comprises the displacement of receptor molecules bond to immobilized ligand by a competition reaction with ligand in solution. This is beneficial because displacement of high molecular receptors is detected compared to low molecular ligand as in classical binding analysis therefore potentially lowering the method detection limit. It was hypothesized that with choosing appropriate measuring methods and theoretical modeling reaction rate constants can be determined separately in every kinetic stage of the assay format. Herein elucidating the dominant valence of antibody antigen binding in the established assay was of great importance. Using the Influenza Hemagglutinin (HA) peptid binding to mono or bivalent Anti-Hemagglutinin peptide antibody displacement assay formats could be established. The exact time resolved analysis of binding and dissolution of ligand HA and Anti-Hemagglutinin peptide antibody was achieved with surface plasmon resonance (SPR) spectroscopy. Mathematical models could be developed from kinetic equations of ligand binding to mono or bivalent antibody. With this, an accurate simulation of the SPR results was reached. The simulation plot had to be exactly adjusted to the SPR results to determine all kinetic rate constants defining ligand and receptor binding kinetics. Large variations in receptor concentration gave almost identical rate constants in binding; this proves the quality of SPR measurements and demonstrates consistence between measurement, simulation, and binding model. Maximum decline of SPR response could be used to determine ligand concentrations in analyte. Displacement dependence from antigen concentration was found to be exponential and was explained by rebinding. Kinetic data and models could be transferred for the simulation of almost stationary displacement assay formats realized with impedance and fluorescence spectroscopy. With the obtained results it was possible to detect the displacement of the bacterial signaling autoinducer AI-2 by a displacement assay format using periplasmic binding protein LuxP as receptor. Concluding it can be said that the hypothesis could be proved and the obtained results can facilitate the use of displacement assay formats in biosensing. Displacement assay formats should be especially interesting in small molecule detection and in compact integrated mass sensitive sensor designs suitable as mobile sensors in outdoor screening
Die Analyse des Bindungsverhaltens niedermolekularer Liganden an Proteine ist für die Aufklärung von biologischen Regulationssystemen oder bei der Suche neuer medizinischer Wirkstoffe von Wichtigkeit. Ein markierungsfreies Detektions¬prinzip zur Erfassung niedermolekularer Liganden ist die Displacement- oder Replacement-Methode. Bei dieser tritt die Bindung des Rezeptors an den immobilisierten Liganden mit der Bindung an freien Liganden in Konkurrenz, sodass anstelle der niedermolekularen Liganden die hochmolekularen Rezeptoren detektiert werden können. In dieser Arbeit wurde von der Hypothese ausgegangen, dass durch die Auswahl geeigneter Messverfahren und der zugeordneten Modellierung die einzelnen kinetischen Stadien des Displacements separat zur Bestimmung der kinetischen Konstanten der Displacementprozesse genutzt werden können. Dabei sollte unter anderem auch eine Aussage über die dominierende Valenz der Antigen-Antikörper-Bindung erreicht werden. Hierzu wurden auf der Basis des Modellsystems Hämagglutinin-Peptid/ Hämagglutinin-Antikörper Displacement-Assays mit mono- und bivalenten Anti-körpern entwickelt, anhand derer eine genaue zeitaufgelöste Analyse des Bindungs- und Ablösungsverhaltens vom Liganden HA an den Anti-HA-Antikörper (Rezeptor) mittels Oberflächenplasmonenresonanz(SPR)-Spektroskopie erzielt wurde. Ausgehend von den Reaktionsgleichungen zwischen Liganden und mono- und bivalenten Rezeptoren wurden mathematische Modelle entwickelt, die eine exakte Simulation der SPR-Ergebnisse ermöglichten. Durch genaues Anpassen der Simulationsplots an die Messplots konnten alle Ratenkonstanten, die die Kinetik der Reaktionen zwischen Liganden, Rezeptoren und ihren Komplexen bestimmen, ermittelt werden. Da auch für eine große Variation der Rezeptorkonzentrationen in der Analytlösung nahezu identische Werte für die Ratenkonstanten erhalten wurden, ergeben Messungen und Simulationen ein konsistentes Bild der Anbindungskinetik und bestätigen die Qualität der Messungen. Aus Messungen des maximalen Responsabfalles kann die Konzentration der freien Antigene beim Displacement ermittelt werden. Man findet eine exponentielle Abhängigkeit des Displacements von der Konzentration der freien Antigene, die sich durch den sogenannten „Rebindingeffekt“ erklären lässt. Die gewonnenen kinetischen Daten und entwickelten Modellierungsverfahren konnten zur Simulation quasistationärer Detektionsverfahren, die mit Fluoreszenz- und Impedanzspektroskopie durchgeführt wurden, erfolgreich angewandt werden. Die erzielten Erkenntnisse konnten auf ein wissenschaftlich herausforderndes biologisches System (LuxP/AI2) angewandt werden, bei dem das niedermolekulare Signalmolekül AI2 über ein Displacementassay detektiert wurde. Dieses System ermöglicht einen Einblick in die Intra- und Interspezieskommunikation bei Bakterien. Insgesamt zeigt sich, dass die hier formulierte Hypothese als bewiesen angesehen werden kann. Die in dieser Arbeit gewonnenen Erkenntnisse eröffnen verschiedene Einsätze der Displacementmethode in der Biosensorik. Insbesondere lassen sich damit kleine Moleküle markierungsfrei quantitativ bestimmen, ohne hoch präzise Analysengeräte einsetzen zu müssen. Damit ergibt sich die Möglichkeit, sehr kompakte integrierte massensensitive Sensoren, die nicht die Empfindlichkeit hochempfindlicher SPR-Spektrometer erreichen, zur Detektion kleiner Moleküle einzusetzen. Dies ist besonders für mobile Anwendungen von Interesse

Denna uppsats behandlar ett vanligt problem i dagens skola, mobbning. Syftet är att belysa vad mobbning är samt att få en förståelse för vilka teorier och modeller som kan användas i arbetet med mobbning. Syftet är även att belysa hur mobbning tar sig i uttryck i en mångkulturell och en monokulturell skola samt hur man förebygger mobbning i dessa skolor.

Vi har använt oss av följande frågeställningar:

· Finns det likheter respektive skillnader avseende form och orsak till mobbning i en mångkulturell samt en monokulturell skola?

· Vilka vägar finns för att förebygga och åtgärda mobbning i en mångkulturell och en monokulturell skola?

· Vilka teorier och modeller används i arbetet med mobbning i en mångkulturell samt monokulturell skola?

För att besvara våra frågeställningar, har vi studerat vetenskaplig litteratur med syfte att skapa en bakgrundsbild av ämnet mobbning. Vi har även utfört en empirisk undersökning på en monokulturell skola samt en mångkulturell skola, där vi jämfört deras arbetssätt gällande mobbning. Vi har använt oss av intervju som metod.

Resultatet i vår undersökning visar att beträffande likheter respektive skillnader avseende form och orsak till mobbning i skolorna har uttryckssätten för att mobba inte skiljt sig åt. Däremot kan orsaken till varför mobbning uppstår skilja sig åt, det vill säga att i en mångkulturell skola har språket stor betydelse medan i en monokulturell skola kan fördomar vara en bidragande orsak till mobbning. Resultatet i vår intervjustudie visar även att tillvägagångssätten för att förebygga mobbning i en mångkulturell samt en monokulturell skola generellt sett stämmer överens. Gällande teorier och modeller samt åtgärdsprogram utgår skolorna från samma principer och har mycket gemensamt.

Although human sustained control movements are continuous in nature there is still controversy on the mechanisms underlying such physiological systems. A popular topic of debate is whether human motor control mechanisms could be modelled as engineering control systems, and if so, what control algorithm is most appropriate. Since the early years of modelling sustained control tasks in human motor control the servomechanism has been an adequate model to describe human tracking tasks. Another continuous-time system model that is often used to model sustained control tasks is the predictive controller which is based on internal models and includes prediction and optimisation. On the other hand, studies have suggested intermittent behaviour of the ``human controller'' in sustained motor control tasks. This thesis investigated whether intermittent control is a suitable approach to describe sustained human motor control. It was investigated how well an intermittent control system model could approximate both the deterministic and non-deterministic parts of experimental data, from a visual-manual compensatory tracking task. Finally, a preliminary study was conducted to explore issues associated with the practical implementation of the intermittent control model. To fit the deterministic part of experimental data, a frequency domain identification method was used. Identification results obtained with an intermittent controller were compared against the results using continuous-time non-predictive and predictive controllers. The results show that the identified frequency response functions of the intermittent control model not only fit the frequency response functions derived from the experimental data well, but most importantly resulted in identified controller parameters which are similar to those identified using a predictive controller, and whose parameter values appear to be physiologically meaningful. A novel way to explain human variability, as represented by the non-deterministic part of the experimental data (the \emph{remnant}), was developed, based on an intermittent control model with variable intermittent interval. This model was compared against the established paradigm, in which variability is explained by a predictive controller with added noise, either signal dependent control signal noise, or observation noise. The study has shown that the intermittent controller with a variable intermittent interval could model the non-deterministic experimental data as well as the predictive controller model with added noise. This provides a new explanation for the source of remnant in human control as inherent to the controller structure, rather than as a noise signal, and enables a new interpretation for the physiological basis for human variability. Finally, the theoretical intermittent control model was implemented in real-time in the context of the physiological control mechanism of human standing balance. An experimental method was developed to apply automatic artificial balance of an inverted pendulum in the context of human standing, via functions electrical stimulation control of the lower leg muscles of a healthy subject. The significance of this study is, firstly, that frequency domain identification was applied for the first time with intermittent control, and it could be shown that both intermittent and predictive control models can model deterministic experimental data from manual tracking tasks equally well. Secondly, for the first time the inherent variability, which is represented by the remnant signal, in human motor control tasks could be modelled as part of the structure of the intermittent controller rather than as an added noise model. Although, the experimental method to apply automatic artificial balance of an inverted pendulum in the context of human standing was not successful, the intermittent controller was implemented for the first time in real-time and combined with electrical muscle stimulation to control a physiological mechanism.

Deleterious effects such as surface heating and turning moments can arise as a consequence of the impingement of thruster plumes with spacecraft surfaces. Such thrusters are normally fired for attitude control. The prediction of such effects must be undertaken at the design stage of the vehicle. In this study, the modelling of such plumes was undertaken. The following prediction techniques were implemented into computer programmes: (a) the Simons model, (b) the Method of Characteristics (MOC), and (c) the Direct Simulation Monte Carlo method (DSMC). The first two methods are derived from continuum equations whilst the third adopts a discrete particle approach. Several DSMC schemes exist for treating the collisional behaviour of the gas, and it was unclear which would be best suited for the intended application. A thorough assessment of the implementation and performance of several such schemes was therefore completed. Having determined the most suitable DSMC scheme, the three modelling techniques were then applied to the isentropic core expansion of a small hydrazine thruster plume. It was found that significant errors occur in the determination of impingement quantities through application of the continuum methods in the flow regime lying between the continuum and free molecular limits. The DSMC technique was also used to calculate the nozzle lip and backflow expansion regions of the same hydrazine thruster. A significant degree of backflow was found with flow angles of up to 140º. The sensitivity of the calculations to the conditions initially assumed were assessed and found to be important.

Today, tightening tools are widely used in the industry and on the market you will find several products that have been assembled with the help of tightening tools. For example, tightening tools are used in the automotive industry and when assembling computer hardware. It is important that the tightening tools are robust and of high quality in order to fulfil the demanded requirements. High assembly speed has entailed an extensive use of tightening tools. To ensure that the tightening tools have the desired properties, tightening tools are tested continuously using so-called test systems. This puts high demands on the test systems since it is of importance that the tightening tools can be tested in a simple, fast and reliable way as well as repeatedly. Therefore, Atlas Copco would like to investigate whether a test system constructed with an electrical motor is a good choice. The idea of this thesis is to investigate possibilities and limitations in a test system consisting of an electrical motor that emulates the behaviour of a screw joint. To be able to investigate hardware limitations a test rig is constructed and then modelled in MATLAB. Further, simulations have been carried out in order to analyse the possibilities and limitations of such a test rig. The conclusion is that the implemented LQ controller seems to be able to control the braking motor sufficiently like a screw joint.

A dynamic inflow model is a powerful tool for predicting the induced velocity distribution over a rotor disc. On account of its closed form and simplicity, the model is highly practical especially for studying flight mechanics and designing control systems for helicopters. However, scant attention has been so far paid to applying this model to analyse autorotative rotors (i.e. rotors in the windmill-brake state), which differ from powered helicopter rotors (i.e. rotors in the normal working state) in that the geometric relation between the inflow and the rotor disc. The principal aim of this research is to theoretically investigate the applicability of existing dynamic inflow models for autorotative rotors, and if necessary, to provide a new dynamic inflow model for autorotative rotors. The contemporary dynamic inflow modelling is reviewed in detail from first principles in this thesis, and this identifies a modification to the mass-flow parameter for autorotative rotors. A qualitative assessment of this change indicates that it is likely to have a negligible impact on the trim state of rotorcraft in autorotation, but a significant effect on the dynamic inflow models in certain flight conditions. In addition, this thesis includes a discussion about the small wake skew angle assumption, which is invariably used in the derivation of Peters and He model. The mathematical validity of the assumption is cast doubt, despite the resultant model has experimentally been fully validated. The author discusses on a theoretical ground the possible reason why the Peters and He model works well in spite of its inconsistent derivation

This thesis presents an initial Finite Element (FE) based modelling investigation aimed at supporting the development of 'smart' tyre or intelligent tyre technologies. Physical tests carried out with a stationary (non-rolling) and rolling experimental tyre are used to enhance understanding of tyre behaviour in the contact patch and validate the modelling methodology. Simulation results with the explicit FE package LS-DYNA are then used to characterise the internal stresses and strains at several positions in the tyre tread. Two separate FE models are developed to simulate the stationary and rolling tyre behaviour at the macroscopic level. The models differ only with respect to the mesh density in the circumferential direction, the mesh through the cross section is identical. The complex tyre structure is represented as a rubber and reinforced rubber composite, and the mesh specification and the material descriptions used in the models are discussed. The structural behaviour of the stationary experimental tyre under normal load is simulated. The inflation of the tyre, the wheel fit and the normal loading against the horizontal surface are represented. Simulation results are also presented when a subsequent longitudinal or lateral load is applied to the stationary tyre. These analyses were conducted to determine the longitudinal and lateral tyre stifffiesses, respectively. The predicted normal load-deflection characteristics and contact patch dimensions (length and width) are compared with a reasonable degree of success to those obtained in the full-scale physical tests. The longitudinal and lateral simulations also appear to give realistic tyre stiffnesses. The contact patch dimensions give a good trend-wise agreement, but the length and width are greater than the experimental measurements. A parametric study is carried out and this disparity is related to a deficiency in the performance of the contact algorithms. It is concluded that it not straightforward to accurately predict contact patch behaviour, and therefore the internal transient stresses and strains in a rolling tyre in absolute terms. However, the good trend-wise agreement suggests that the modelling methodology should be capable of predicting internal transient responses which are related to the 'actual' deformations in the contact region. To simulate the rolling tyre behaviour on flat bed and drum surfaces, consideration is given to the inflation of the tyre, the wheel fit, the normal loading and the rotation of the tyre. Numerical instabilities are found to occur and these are related to imperfections inherent in version 950d of the code. This version was, at the time, the most up to date release. The current release is version 960 and it does not contain many of the imperfections in the earlier version. Thus, the flat bed simulation is repeated using the current version. The predicted contact patch stresses are presented and a reasonable correlation is achieved with the experimental data. The internal stresses and strains are then characterised at a number of selected positions in the tread region. These stresses and strains are discussed in context with the development of smart tyre technologies and are useful as a guide to the most appropriate location for an in-tyre sensor (or sensors).

This thesis introduces a novel framework for life cycle mission modelling during conceptual aeronautical design. The framework supports object-oriented mission definition using Geographical Information System technology. Design concepts are defined generically, enabling simulation of most aeronautical vessels and many non-aeronautical vehicles. Moreover, the framework enables modelling of entire vessel fleets, business competitors and dynamic opera-tional changes throughout a vessel life cycle. Vessels consist of components deteriorating over time. Vessels carry payload that operates within the vessel environment. An agent-based simulation model implements most framework features. It is the first use of an agent-based simulation utilising a Geographical Information System during conceptual aero-nautical design. Two case studies for unmanned aircraft design apply the simulation. The first case study explores how the simulation supports conceptual design phase decisions. It simulates four different unmanned aircraft concepts in a search-and-rescue scenario including lifeboats. The goal is to learn which design best improves life cycle search performance. It is shown how operational and geographical impacts influence design decision making by generating novel performance information. The second case study studies the simulation optimisation capability: an existing aircraft design is modified manually based on simulation outputs. First, increasing the fuel tank capacity has a negative effect on life cycle performance due to mission constraints. Therefore, mission definition becomes an optimisation parameter. Changing mission flight speeds during specific segments leads to an overall improved design.

This thesis begins with a brief overview of vehicle control. The thesis places powertrain control, which is discussed in more detail, within the wider context of vehicle control. Traction control is one aspect of powertrain control. The available methods of traction control are reviewed together with a discussion on the systems in current production. The traditional method adopted by the automotive industry for traction control is analysed. The powertrain system is analysed from a control stand-point and a control oriented approach to traction control design identified. The emphasis in this thesis is on the analysis of traction control systems. The analysis is performed on simulation models and is supported by implementations on the real vehicle. The level of modelling appropriate for the analysis is justified and models developed in a modular manner. The individual modules are developed on the basis of published material and previous work within Ford Motor Company. Based on the analysis, two traction control strategies are developed which are subsequently developed and implemented on real vehicles. The results of this vehicle work is discussed.

The aim of this PhD thesis is to develop a one-dimensional (1D) mathematical model to study in designing and improving emission control systems such as those in Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). This was achieved by capturing the fundamental reaction kinetics from the microreactor data within the careful choice of concentrations/ temperatures domain; together with good understanding of the physical phenomena’s occurring in these systems. When considering a DOC, it is important to have a good description of the catalyst activity as a function of Platinum Group Metal (PGM) loading, which in this case is Pt, this enables mathematical models to be used in the optimization of the PGM loading. The work presented here looks at the design of a DOC based aftertreatment system through development of kinetics from data obtained from the microreactor for a wide range of PGM loadings (2.5-75g ft-3). The variation in catalyst activity with different PGM loadings for the key reactions was determined. The model developed in this study predicts well all the experimental data for the various loadings. DPF is another important aftertreatment technology that is used for the control of Particulate Matter (PM) emission from diesel engines. Under favourable conditions, the soot collected on the filter can be removed by oxidation with NO2 from temperatures as low as 200°C. The work presented in this thesis shows the fundamental modelling approach to develop kinetics for soot oxidation by NO2. The selectivity to CO was found to differ only marginally with temperature, and is independent of NO2 concentrations. By modelling these data using a 1D model, the rate equations for the soot-NO2 reaction were determined, and experimental data were predicted.

In this work physics-based modelling of bluff-body noise was performed with application to landing gear noise production. The landing gear is a primary contributor to airframe noise during approach. Noise is primarily generated from the unsteady pressures resulting from the turbulent flow around various components. The research was initiated in response to the need for an improved understanding of landing gear noise prediction tools. A computational approach was adopted so that the noise generating physics of the problem could be captured. Governing laws were solved numerically to predict the noise source characteristics and the resulting acoustic far-field. Three-dimensional compressible Navier-Stokes simulations were performed to solve the unsteady turbulent near-field flow and the acoustic analogy was used to predict the resulting far-field acoustic pressure. The flow solver included a high-order computational aeroacoustics code adopting large-eddy simulation, whilst a Ffowcs Williams and Hawkings solver was used for the acoustic prediction. Circular cylinders in various configurations were selected to represent basic landing gear struts and results were used to form a modelling database. Initially, cylinders at various Reynolds numbers were investigated in cross-flow to determine the noise characteristics of a simple model strut. The work was extended to investigate the effect of strut alignment to the flow by simulating cylinders in yaw. The effect of yaw was shown to modify the peak level and frequency of far-field noise spectra. Component interaction effects were then investigated by simulating cylinders in tandem arrangements. The resulting aerodynamic and far-field noise characteristics were shown to be complex and extremely sensitive to the separation distance between the cylinders. Finally, a prediction model was developed and validated by comparing predictions against theory and measurements of the noise radiated by a simple two-wheel landing gear model. The results demonstrated the capability of the model to accurately predict correct spectral and directivity characteristics.