The desire for smaller, faster, and more efficient products places a strain on thermal management in components ranging from gas turbine blades to computers. Heat exchangers that utilize internal cooling flows have shown promise in both of these industries. Although pin fins are often placed in the cooling channels to augment heat transfer, their addition comes at the expense of increased pressure drop. Consequently, the pin fin geometry must be judiciously chosen to achieve the desired heat transfer rate while minimizing the pressure drop and accompanying pumping requirements. This project culminates in the construction of a new test facility and the development of a unique force measurement methodology. Direct force measurement is achieved with a cantilever beam force sensor that uses sensitive piezoresistive strain gauges to simultaneously measure aerodynamic lift and drag forces on a pin fin. After eliminating the detrimental environmental influences, forces as small as one-tenth the weight of a paper clip are successfully measured. Although the drag of an infinitely long cylinder in uniform cross flow is well documented, the literature does not discuss the aerodynamic forces on a cylinder with an aspect ratio of unity in channel flow. Measured results indicate that the drag coefficient of a cylindrical pin in a single row array is greater than the drag coefficient of an infinite cylinder in cross flow. This phenomenon is believed to be caused by an augmentation of viscous drag on the pin fin induced by the increased viscous effects inherent in channel flow. / Master of Science

The present study was undertaken to determine the effects of the aerodynamics on a close earth orbit and reentry trajectory. The aerodynamic influence is compared to the effects of the earth’s oblateness, the sun, and the moon. In order to obtain maximum accuracy and computational speed Encke’s perturbative procedures were used during orbital periods and Cowell’s integration procedures during thrust and reentry periods. / M.S.

This essay explores drag as an artform, guided by the lens of queer theory, offering insights into the nuanced expressions of drag. Exploring three theatrical productions across genres like modern dance, opera and musical theatre, the study focuses on character portrayal and design, seeking to understand the essence of drag and why certain cross- dressings are more closely associated with drag than others. By combining performance analyses with existing research on drag, this paper reveals the complex and dynamic nature of drag culture. With a particular emphasis on the exploration and subversion of gender norms, the study sheds light on how drag is portrayed and understood within the Swedish theatrical context through Matilda the Musical, Askungen and Everlasting Event. Through this investigation, the essay offers valuable insights into the evolving role of drag as a form of artistic expression and social commentary.

Syftet med föreliggande studie är att bidra med kunskap om hur matematiklärare i årskurs 4–6 uppfattar och tänker om dialogiska drag. Dialogiska drag innebär att läraren skapar tillfällen där eleverna tillåts diskutera innehållet i matematiken. Studien bygger på semistrukturerade intervjuer som erhåller insikter i lärarnas perspektiv rörande deras tankar och uppfattningar kring dialogisk undervisning. Resultatet analyseras med hjälp av ett teoretiskt ramverk bestående av fyra grundläggande mål som bör uppfyllas för att genomföra givande dialogisk undervisning. Det kartlägger vilka mål lärarna strävar mot och i vilken utsträckning, samt vilka dialogiska drag de tillämpar för att uppnå dessa mål. Resultatet belyser att vissa mål uppnås i större utsträckning än andra, samt de fördelar, utmaningar och förutsättningar som identifieras med dialogbaserad undervisning.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25236号 / 工博第5195号 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 八木 知己, 教授 KIM Chul-Woo, 教授 高橋 良和 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Yes / Aquatic vegetation can significantly affect flow structure, sediment transport, bed scour and water quality in rivers, lakes, reservoirs and open channels. In this study, the lattice Boltzmann method is applied for performing the two dimensional numerical simulation of the flow structure in a flume with rigid vegetation. A multi-relaxation time model is applied to improve the stability of the numerical scheme for flow with high Reynolds number. The vegetation induced drag force is added in lattice Boltzmann equation model with the algorithm of multi-relaxation time in order to improve the simulation accuracy,. Numerical simulations are performed for a wide range of flow and vegetation conditions and are validated by comparing with the laboratory experiments. Analysis of the simulated and experimentally measured flow field shows that the numerical simulation can satisfactorily reproduce the laboratory experiments, indicating that the proposed lattice Boltzmann model has high accuracy for simulating flow-vegetation interaction in open channel. / National Natural Science Foundation of China (grant number: 11861003 and 11761005)

Under de senaste åren har den mobila tekniken i stort sett helt gått över till smartphones. Smartphones är i princip mer datorer än telefoner, som vi alltid bär med oss och som innehåller allt mer känslig information. Detta medför att kraven på säkerheten kring enheten ökar. Detta arbete undersöker om det är möjligt att finna en ny metod att låta användaren autentisera sig på, som är säkrare än de som är vedertagna idag, men samtidigt har liknande nivå av användbarhet. Vår idé, som vi arbetar med under namnet Colour a Symbol, baseras på att kombinera symboler och färger i par. För att utveckla idén skapade vi en funktionell prototyp, som sedan utvärderadesmed hjälp av en mindre testgrupp. Empirin visar på att Colour a Symbol har en god användbarhet, om än något för lång inloggningstid. Idéer för att förbättra inloggningstiden presenteras. Teoretiskt sett så är Colour a Symbol säkrare än exempelvis pinkod, men testgruppen var inte tillräckligt stor för att kunna bedöma den praktiska lösenordsrymden. Utformning av symboltema påverkar även förmodligen i hög grad den praktiska lösenordsrymden. Vår slutsats är att idén har en klar potential, men att det behövs ytterligare studier för att finslipa den. / During the past years mobile technology has moved almost entirely to smartphones. Smartphones are in essence more computers than phones, which we always carry with us and that contain ever more sensitive information. This requires that the level of security around the device increases. This study strives to find a new method of authenticating users, that is more secure than those that are established today, but at the same time has a similar level of usability. Our idea, which we work with under the name Colour a Symbol, is based upon making combinations of symbols and colours in pairs. In order to develop the idea we created a functional prototype, that was evaluated by a smaller test group. The empirical data implies that Colour a Symbol has good usability, if only a little too long login time. Ideas as to shorten the login time are suggested. Theoretically, Colour a Symbol is more secure than for an example pincode, but the test group was not large enough to estimate the practical password space. Design of the symbol theme probably also affects the practical password space to a high degree. Our conclusion is that the idea has clear potential, but that further studies are needed to fine-tune it.

No description available.

The flow of polymer solutions in the high Elasticity number, El, regime in complex geometries may lead to strong viscoelastic behaviour and eventually become unstable as the Weissenberg number, Wi, is increased beyond a critical level. So far, the success of numerical simulations in predicting the highly non-linear behaviour of polymer solutions in complex flows has been limited. In this thesis, selected constitutive models are evaluated under the high El flow regime in the cross-slot and contraction benchmark flows using a numerical technique based on the finite volume method. The numerical technique is implemented within the OpenFOAM framework and thoroughly validated in the benchmark flow. A modification to the FENE dumbbell model based on the non-affine deformation of polymer solutions is proposed, which enabled the prediction of some non-linear material functions and also enhanced numerical stability, allowing a higher Wi to be attained. Asymmetric flow instability in the cross-slot flow has been studied. Time-dependent stability diagrams were constructed based on Wi and the strain, ε, both of which govern the stretching of a polymer chain. In the contraction flow, elastic instability is simulated for the first time in this geometry. Substantial time-dependent asymmetric flow patterns were predicted as seen in experiments. The effect of the contraction ratio is investigated through a stability diagram. Three-dimensional finite element simulations were also carried out to study the effect of the aspect ratio in the contraction flow of a Phan-Thien-Tanner fluid. The simulations suggest that a lip vortex mechanism is a signature for the onset of strong viscoelastic behaviour.

This master thesis deals with the construction design of two different pipeline drag chain conveyors for transport of wheat and sewage sludge. The first part describes the operation principle and the main parts of this conveyor. The examples of designs from several manufacturers follow. Next part is devoted to determining the resistance to movement in individual sections of the transport route. Thesis continues with design proposals of both variants of conveyors, including suitable technological and strength calculations. The outputs of this work are also assembly drawings of these two conveyors.