Pulse detonation engines show potential to increase the efficiency of conventional gas turbine engines if used in place of the steady combustor. However, since the interaction of pressure pulses with the turbine is not yet well understood, a rig was built to compare steady flow with pulsing flow. Compressed air is used in place of combustion gases and pressure pulses are created by rotating a ball valve with a motor. This work accomplishes two main objectives that are different from previous research in this area. First, steady flow through an axial turbine is compared with full annular pulsed flow closely coupled with the turbine. Second, the error in turbine efficiency is approximately half the error of previous research comparing steady and pulsed flow through an axial turbine. The data shows that a turbine driven by full annular pressure pulses has operation curves that are similar in shape to steady state operation curves, but with a decrease in turbine performance that is dependent on pulsing frequency. It is demonstrated that the turbine pressure ratio increases with pulsed flow through the turbine and that this increase is less for higher pulsing frequencies. For 10 Hz operation the turbine pressure ratio increases by 0.14, for 20 Hz it increases by 0.12, and for 40 Hz it increases by 0.06. It is demonstrated that the peak turbine efficiency is lower for pulsed flow when compared with steady flow. The difference between steady and pulsed flow peak efficiency is less severe at higher pulsing frequencies. For 40 Hz operation the turbine efficiency decreases by 5 efficiency points, for 20 Hz it decreases by 9 points, and for 10 Hz it decreases by 11 points. It is demonstrated that the specific power at a given pressure ratio for pulsed flow is lower than that of steady flow and that the decrease in specific power is lower for higher pulsing frequencies. On average, the difference in specific power between steady and pulsed flow is 0.43 kJ/kg for 40 Hz, 1.40 kJ/kg for 20 Hz, and 1.91 kJ/kg for 10 Hz.

Regulation of the bacterial second messenger cyclic-di-GMP in Salmonella Typhimurium allows it to delicately alter phenotypes to optimize invasion and survive intracellularly in epithelial cells and macrophages to become virulent and cause infection. Cyclic-di-GMP concentration is regulated by the presence of external stimuli, sensory diguanylate cyclases (DGCs) and phosphodiesterases (PDEs), and cyclic-di-GMP binding effectors. Previous studies established that maintenance of low cyclic-di-GMP concentrations is required for survival in macrophages, and that deletion of 3 active PDEs reduces this survival. Here I showed that these 3 PDEs also influenced the infection of epithelial cells. Further studies re-established the decreased survival in an immortalized macrophage cell line and determined that cyclic-di-GMP-binding cellulose synthase BcsA was responsible for the decreased survival in macrophages. Finally, I also identified an active DGC whose deletion within the 3xKO restores survival levels, suggesting that this enzyme is responsible for the synthesis of cyclic-di-GMP during macrophage infection.

Yes / In this work we propose a talking head system for animating facial expressions using a template face generated from Partial Differen- tial Equations (PDEs). It uses a set of preconfigured curves to calculate an internal template surface face. This surface is then used to associate various facial features with a given 3D face object. Motion retargeting is then used to transfer the deformations in these areas from the template to the target object. The procedure is continued until all the expressions in the database are calculated and transferred to the target 3D human face object. Additionally the system interacts with the user using an artificial intelligence (AI) chatterbot to generate response from a given text. Speech and facial animation are synchronized using the Microsoft Speech API, where the response from the AI bot is converted to speech.

Bakgrund och problemformulering: Plattformsstrategier har blivit ett allt vanligare fenomen och i dagsläget är flera av världens största företag plattformsföretag. Digitala plattformar för beställning och leverans av mat är en typ av plattformar som ökat markant de senaste åren, speciellt i och med covid-19 pandemin då restaurangbranschen fick helt nya förutsättningar. Vi har funnit en kunskapslucka gällande restaurangers perspektiv och vilka risker som följer med att verka på digitala matleveransplattformar, samt en avsaknad av forskning kring hur dessa risker hanteras.  Syfte och forskningsfrågor: Syftet med denna studie är att bidra med kunskap och förståelse kring fenomenet plattformstrategi och hur det är att som säljare befinna sig på en plattform, genom att mer specifikt undersöka de risker restauranger som verkar på digitala matleveransplattformar upplever, samt vilka metoder de använder sig utav för att minimera eller eliminera dessa.  • Vilka risker medför det för restauranger att verka på digitala plattformar gällande matleverans?  • Vilka metoder använder sig restauranger av för att minimera eller eliminera de risker de upplever på digitala matleveransplattformar?  Resultat: Resultatet visar att de risker restauranger utsätts för då de verkar på digitala matleveransplattformar är försämrad kundkontakt, förlorad kundbas, begränsad differentiering vid exponering på plattform, påverkan på produktkvalitet samt att en felaktig bild förmedlas till kund. De metoder som restaurangerna nyttjar för att motverka dessa risker är att hota med att lämna eller ej ansluta verksamhetsenheter, skapa större marknadsandel på plattform, verka via fler säljkanaler, verka på fler plattformar, nyttja information från andra parter vid förhandling med plattform, kollektiv handling vid skapande av egen säljkanal, kollektiv avtalsförhandling med plattform och marknadsföring av egen säljkanal via plattform.  Kunskapsbidrag: Denna studie har genom att studera företag som verkar på digitala matleveransplattformar lyft deras perspektiv kring risker som uppstår då de verkar på dessa samt metoder för att motverka riskerna, vilket bidrar till att fylla den identifierade kunskapsluckan. Genom att studera en specifik bransch, bidrar denna studie ytterligare till den kunskapslucka som identifierats. Resultatet visar nya risker och strategier men bekräftar även vissa som förekommer i tidigare litteratur. / Background and formulation of problem: Platform strategy has become a more common phenomenon and many of today’s biggest companies are platforms. Digital platforms that are used for order and delivery of food are one platform type that have increased significantly during these last years, especially due to covid-19 which created challenging conditions for the restaurant industry. We have found a lack of knowledge when it comes to the perspective of restaurants and risks that arise from operating on a digital food delivery platform and how these are handled.  Purpose: The purpose of this study is to contribute with knowledge and understanding of the phenomenon platform strategy and the experience of companies operating on platform by more specifically explore perceived risks, by the restaurants, that arise when operating on a digital food delivery platform and how these can be minimized or eliminated.  What risks arise for restaurants when operating on digital food delivery platforms?  What methods are used by restaurants to minimize or eliminate risks while operating on a digital food delivery platform?  Result: Risks that have been identified in this study are worsened customer contact, lost customer base, limited possibilities to differentiate when presented on platforms, impact on the quality of products and the wrong picture gets painted to the customer. The methods that the restaurants use to counteract these risks are threaten to leave or not let business units join, create a bigger market share on the platform, participate on more sales channels, participate on more platforms, use information from other parties when negotiating with platform, collective actions to create their own sales channel, collective actions when negotiating with platform and marketing of their own sales channels via the platform.  The study's contribution of knowledge: By studying companies operating on digital food delivery platform, this study has shed light on their perspective on risks that arise from operating on a digital platform and methods used to minimize these risks, which contribute to fill the gap of knowledge that has previously been identified. Also, by studying a specific industry, which has not been done before, this study has contributed further to the knowledge within this field. The result of this study shows both strategies and methods that have and have not previously been identified in the literature.

This thesis discusses a novel method for modelling facial action units. It presents facial action units model based on boundary value problems for accurate representation of human facial expression in three-dimensions. In particular, a solution to a fourth order elliptic Partial Differential Equation (PDE) subject to suitable boundary conditions is utilized, where the chosen boundary curves are based on muscles movement defined by Facial Action Coding System (FACS). This study involved three stages: modelling faces, manipulating faces and application to simple facial animation. In the first stage, PDE method is used in modelling and generating a smooth 3D face. The PDE formulation using small sets of parameters contributes to the efficiency of human face representation. In the manipulation stage, a generic PDE face of neutral expression is manipulated to a face with expression using PDE descriptors that uniquely represents an action unit. A combination of the PDE descriptor results in a generic PDE face having an expression, which successfully modelled four basic expressions: happy, sad, fear and disgust. An example of application is given using simple animation technique called blendshapes. This technique uses generic PDE face in animating basic expressions. / Ministry of Higher Education, Malaysia and Universiti Malaysia Terengganu

<p dir="ltr">This dissertation encompasses my research work during my Ph.D. career, focusing on the controllability properties of liquid crystal flow. I have achieved two main results, which are as follows: Firstly, I have established the local exact controllability to the trajectory of the simplified Ericksen-Leslie model and its Ginzburg-Landau approximation. Secondly, I have successfully proven the global null controllability of the simplified Ericksen-Leslie model with Lions boundary condition for u and Neumann boundary condition for d, with the aid of a globally defined magnetic field which is independent of the spatial variable x. </p>

No / In this paper we discuss a novel method of mathematically modelling facial action units for accurate representation of human facial expressions in 3- dimensions. Our method utilizes the approach of Facial Action Coding System (FACS). It is based on a boundary-value approach, which utilizes a solution to a fourth order elliptic Partial Differential Equation (PDE) subject to a suitable set of boundary conditions. Here the PDE surface generation method for human facial expressions is utilized in order to generate a wide variety of facial expressions in an efficient and realistic way. For this purpose, we identify a set of boundary curves corresponding to the key features of the face which in turn define a given facial expression in 3-dimensions. The action units (AUs) relating to the FACS are then efficiently represented in terms of Fourier coefficients relating to the boundary curves which enables us to store both the face and the facial expressions in an efficient way.

A plethora of physical phenomena are modelled by hyperbolic partial differential equations, for which the exact solution is usually not known. Numerical methods are employed to approximate the solution to hyperbolic problems; however, in many cases it is difficult to satisfy certain physical properties while maintaining high order of accuracy. In this thesis, we develop high-order time-stepping methods that are capable of maintaining stability constraints of the solution, when coupled with suitable spatial discretizations. Such methods are called strong stability preserving (SSP) time integrators, and we mainly focus on perturbed methods that use both upwind- and downwind-biased spatial discretizations. Firstly, we introduce a new family of third-order implicit Runge–Kuttas methods with arbitrarily large SSP coefficient. We investigate the stability and accuracy of these methods and we show that they perform well on hyperbolic problems with large CFL numbers. Moreover, we extend the analysis of SSP linear multistep methods to semi-discretized problems for which different terms on the right-hand side of the initial value problem satisfy different forward Euler (or circle) conditions. Optimal perturbed and additive monotonicity-preserving linear multistep methods are studied in the context of such problems. Optimal perturbed methods attain augmented monotonicity-preserving step sizes when the different forward Euler conditions are taken into account. On the other hand, we show that optimal SSP additive methods achieve a monotonicity-preserving step-size restriction no better than that of the corresponding non-additive SSP linear multistep methods. Furthermore, we develop the first SSP linear multistep methods of order two and three with variable step size, and study their optimality. We describe an optimal step-size strategy and demonstrate the effectiveness of these methods on various one- and multi-dimensional problems. Finally, we establish necessary conditions to preserve the total variation of the solution obtained when perturbed methods are applied to boundary value problems. We implement a stable treatment of nonreflecting boundary conditions for hyperbolic problems that allows high order of accuracy and controls spurious wave reflections. Numerical examples with high-order perturbed Runge–Kutta methods reveal that this technique provides a significant improvement in accuracy compared with zero-order extrapolation.

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