Unmanned helicopters in recent years have gained much attention due to their potential in both civil as well as military applications. Helicopter is an inherently unstable system. As a result there is a growing need of developing a control structure that allows the helicopter to perform various applications while remaining stable throughout the flight. This thesis presents developments of a robust controller for the vertical channel of an unmanned helicopter while carrying and dropping a payload. In addition, a simulation platform is developed in Simulink that uses a nonlinear six degree of freedom helicopter model. Quantitative Feedback Theory, a frequency domain technique, is used to design a controller that meets specific performance criteria when uncertainties associated with different payload weights exist in the system. The controller performance is examined in simulation for an Xcell 60 helicopter for effective lifting and dropping of up to 10 lb payload. The performance is then compared with a traditional Proportional-Integral-Derivative controller. Further, the effect of actuator dynamics on the controller performance is also evaluated. Finally, a controller that is robust in minimizing the effect of actuator dynamics and the payload drop while keeping the helicopter stable in flight is designed.

Bakgrund: Hopphöjden är en viktig faktor inom volleyboll och kan vara direkt avgörande i spelsituationer. Drop jump (DJ) är en vanligt förekommande plyometrisk övning som används för att förbättra hopphöjden. Ett fåtal studier har påvisat den omedelbara effekten utav att implementera DJ i ett träningsupplägg. Syfte: Syftet med studien var att undersöka om ett set med fem repetitioner av DJ kan förbättra hopphöjden efter tre minuters aktiv vila. Avsikten med studiens upplägg var att det med enkelhet ska kunna implementeras i en matchsituation. Metod: Nio kvinnliga volleybollspelare på elitnivå deltog i studien i åldern 25±7 år, med vikt 73±6 kg och längd 172±8 cm. Deltagarnas hopphöjd testades med tre countermovement jump (CMJ) och 72 timmar senare utfördes fem DJ innan liknande CMJ utfördes. Hopphöjden uppmättes med Ivar jump system.   Resultat: Resultatet påvisade ingen signifikant förbättring i hopphöjd (p = 0,6) efter utförandet av fem DJ. Dock noterades en positiv trend då åtta av nio deltagare förbättrade sin hopphöjd med ±1,6 cm. Slutsats: Utförandet av fem DJ före en hopprestation kan ge positiv effekt. Ytterligare forskning krävs dock för att kunna fastställa slutsatsen och hur länge effekten håller i sig.

Zugl.: Ilmenau, Techn. Univ., Diplomarbeit, 2005

Ce travail expérimental concerne l'analyse du transfert de chaleur au sem d'un écoulementturbulent d'air humide en présence ou non d'un phénomène de condensation. Pour cela, une souffleriespécifique a été conçue au sein du laboratoire afi n de générer un écoulement d'air contrôlé en vitesse,en température et en teneur en humidité. Cet écoulement traverse un canal d'étude rectangulairehorizontal dont les parois inférieures sont maintenues à température constante. Une première partie destravaux permet de décrire l'écoulement au se in du canal par l'analyse des champs de vitesse PlVmoyenne et fluctuante pour différents nombres de Reynolds (Re = 10056 à Re = 55333) et dedétailler les régimes dynamiques obtenus. Dans la zone pleinement turbulente, une attentionparticulière a été portée sur la caractérisation de la sous-couche visqueuse par PlV à haute résolutionspatiale. L'analyse fine du profil de température d'air en proche paroi permet d'estimer avec précisionle transfert convectif local. Les résultats obtenus sans changement de phase ne montrent pasd'influence de la teneur en humidité sur le flux convectif. Au-delà des résu ltats en milieu non-saturé,le phénomène de condensation est abordé. La visualisation du dépôt de vapeur d'eau condenséepermet d' identifier macroscopiquement les différents régimes de condensation (film, gouttes oumixte). L' analyse fine à échelle locale permet de définir différentes étapes de la condensation:développement par grossissement et par fusion entre plusieurs gouttes, mouvements de frontièresaprès fusion. Cette étude a été menée pour des substrats de nature et de conditions de mouillabilitédifférentes, ainsi que pour des taux d'humidité absolue variables. Enfin, l' identification de ces étapesest complétée par la quantification de la condensation à partir des mesures de masse condensée.Celles-ci sont exploitées pour estimer les flux de chaleur latente et pour comparer le comportement surdifférents substrats. / Heat transfer in a turbulent moist airflow field is under investigation with or without condensation phenomena. A dedicated experimental set-up was developed and with special attention was given to the control of mass flow rate, temperature and moisture content at inlet. Flow field then develops within a rectangular channel with thermal regulation at walls. Characteristic Reynolds number range studied is between 10 056 and 53 333 and average and fluctuating dynamic and thermal fields were depicted by PIV and thermocouple investigation respectively. In the turbulent region, a refined analysis was carried to characterize the sub-layer viscous region (from high-resolution PIV measurements) and temperature profiles at the very close vicinity of the wall allows one to locally estimate convective heat flux. Results underline that the degree of moisture of unsaturated humid air does not play any major role on the thermal flux exchanged. Beyond the saturation regime, condensation occurs and water vapor deposited along the flat horizontal wall is analyzed. Condensation is driven by several regimes (film-wise, dropwise and mixed) and within drop-wise condensation, size distribution as well as drop coalescence is detailed. Our analyses was carried on three substrates presenting different wettability conditions while moisture degree was considered as an additional parameter. Finally, the mass of condensed water was measured in time and latent heattransfer was estimated and compared between the different substrates.

An inkjet printer can deposit a very small volume of liquid with high positional accuracy, high speed and low cost. As a maskless, non-contact additive patterning method, inkjet printing technology is increasingly being explored as an alternative to lithography, etching and vapour deposition processes to pattern electrical conductors and thin films with applications in printed electronic devices. The functional inks used in many of the applications involve non-linear viscoelasticity and their behaviours in the context of inkjet printing have not been fully understood. This thesis aims to characterise Newtonian and non-Newtonian properties of inkjet fluids and identify the key parameters affecting drop impact and spreading processes. Various fluid characterisation techniques such as the filament stretching rheometer and piezoelectric axial vibrator are explored. We propose an experimental method to assess the jettability of non-Newtonian inkjet fluids, without using an inkjet print head. The oblique collision of two continuous liquid jets leads to the formation of a thin oval liquid sheet bounded by a thicker rim which disintegrates into ligaments and droplets. Under certain conditions the flow structure exhibits a remarkably symmetrical 'fishbone' pattern composed of a regular succession of longitudinal ligaments and droplets. Good correlation was found between the maximum included angle of the fishbone pattern and the maximum ligament length in the jetting experiments, which suggests that a test based on oblique impinging jets may be useful in the development of fluids for ink jet printing. High-speed imaging is used to analyse the impact and spreading of sub-30 μm drops of diethyl phthalate or polystyrene solutions in diethyl phthalate on to smooth glass surfaces with controlled wettability at speeds from 3 to 8 m s-1, under conditions representative of drop-on-demand inkjet printing. Data on drop height and spreading diameter are generated with high time and spatial resolution, over eight orders of magnitude in timescale. The effects of fluid viscosity and elasticity, which significantly affect jetting performance, are negligible throughout the whole deposition process, with no significant difference between spreading curves. The values of the fluid surface tension and the substrate wettability also have no effect on the kinematic, spreading or relaxation phases, but a marked influence on the wetting phase, in terms of the speed of expansion of the contact diameter and the final spreading factor.

The recent development in society, such as the increased digitalisation, has brought new terms for both production and consumption within the cultural field. One of the main goals within Swedish Cultural Policies today is that everyone should have the same opportunities to practice and participate in cultural activities, with the right to develop their creative abilities. The cultural policies also contain the possibility to encourage spontaneous culture practice. The question is how to reach this goal. During the spring of 2012 I have been examining the term ’spontankultur’ (spontaneous culture practice) as it appears in the discussion around participation in cultural activities and its connection to creativity. A bid for the development of Drop in-culture is currently in progress in the municipality of Karlstad. The target group is children and young adults and the aim is to make the cultural field available for more people and in that way encourage participation. The implementation of the new ideas will be done by creating free activities that does not require a continued partipication, in contrast to more traditional club activities. This study also contains a comparison with previous research on spontaneous culture and a insight to how the cultural policies are used in the region Värmland at the moment. The main finding of this study shows that the current bid for developing Drop in-culture in Karlstad could be a good way to start working for increased participation. However, although children and young adults are prioritised in Karlstad, the target group limits the outcome in relation to the goals in national cultural policies that aims for equal possibilities for people of all ages.

The impact of fuel drops on the walls of combustion chambers is unavoidable in direct-injection automotive engines. These drop-solid interactions can lead to splashing of the lubrication oil, its dilution or removal, which can damage the piston or the liner from dewetting. This can also cause irregular and inferior combustion or soot formation. Understanding the drop-splashing dynamics is therefore important, especially as modern IC engines are being down-sized to achieve higher thermal efficiency. Typical cylinders of IC engines contain metal liners on their walls, which have fine azimuthal grooves to support the lubricating oil as the piston moves inside the cylinder. In this thesis we study how these grooves affect the deposition or splashing of impacting diesel drops, while the solid surface is kept dry without the lubricating oil. For these experiments we use sections of actual cylinder liners and apply high-speed video imaging to capture the details of the drop impacts. The first set of experiments used normal impacts on horizontal substrates. These experiments include a range of drop sizes and impact velocities, to identify impact conditions in Reynolds and Weber number space where the transition from deposition to splashing occurs. We also study the maximum radial spreading factor of the impact lamella, finding about 8% larger spreading along the grooves than perpendicular to them. In the second set of experiments we look at the impact on inclined substrates, where the inclination angle is between 30o–60o. This produces strong asymmetry in the maximum spreading, with the tangential velocity governing the maximum radial motion. The inclined impacts change the splashing threshold, requiring larger impact velocities for splashing. The splashing threshold deviates quantitatively from earlier theories, but shows the same qualitative trends. Furthermore, a new splashing mechanism is observed, where the impact forms a prominent ejecta crown from the downstream edge. This crown ruptures first from the grooves at the sides and subsequently the capillarity detaches the downstream levitated liquid sheet from the substrate generating a myriad of splashed droplets. Preliminary observations with impacts on wet substrates show much stronger crown-formation from the lubricating oil film, with potential for dewetting.

Objectives: To understand how and to what extent drop-in centres are associated with the physical and mental health and substance use status of street children in New Delhi. Methods: In a qualitative study, I interviewed 23 street children and two drop-in centre staff members in New Delhi. Subsequently, I conducted a cross-sectional study with 69 street children who attended centres and 65 street children who did not visit centres. I used questionnaires to assess their physical and mental health and substance use. Findings: Participants believed that because street children regularly visited drop-in centres, their health outcomes improved. Street children participated in drop-in services because staff members were nonjudgmental, they were free to be a child, their daily struggles were lessened, they received protection, they were given moral direction and they had an opportunity for a better life. However, children continued to live on the streets because street life had become normal. Quantitative findings showed that street children who visited centres had better physical and mental health outcomes and engaged in less substance use than street children who did not visit centres (p<0.01). For every month of attendance, street children experienced 2.1% (95% CI 0% to 4.1%, p=0.05) fewer ill health outcomes per month and used 4.6% (95% CI 1.3% to 8%, p=0.01) fewer substances. Street children were also less likely to have been a current substance user than a never substance user for every additional month at a center (OR: 0.79, 95% CI: 0.66 to 0.96, p=0.02). Duration of attendance was not significant in predicting mental health. Conclusion: According to participants, drop-in centres positively influence the physical and mental health and substance use status of street children by providing services in an environment tailored for them. Quantitatively, centres may improve the physical health of street children and reduce their substance use. / Thesis / Doctor of Philosophy (PhD) / Street children in low- and middle-income countries (LMICs) experience poor health. Drop-in centres are one of most common interventions for street children; however, they have not been evaluated in LMICs. I aimed to understand how and how much drop-in centres influence the physical and mental health and substance use status of street children in New Delhi, India. Street children and drop-in centre staff members were interviewed about how they believed centres influenced the health and substance use habits of street children. Participants felt that drop-in centres improve children’s health and substance use habits because the centres provided services in an environment tailored for street children. I also used questionnaires to evaluate the impact of drop-in centre attendance on 69 street children who regularly came to centres and 65 street children who did not come to centres. Quantitatively, centres may improve the physical health and substance use status of street children.

Violent crimes involving bloodshed may result in the formation of a number of blood drops that move through air and impact onto a surface producing a bloodstain pattern. Bloodstain Pattern Analysis (BPA), the analysis of the position, distribution, size and morphology of the stains within the pattern present at a crime scene, may provide information about the events that gave rise to the bloodshed. The location of blood origin, i.e. victim’s position at the moment of wounding and (or) wound location, determination is of major interest to BPA. This study investigated the dynamics of formation and flight of blood drops commonly found at a crime scene (so-called passive, cast-off, impact and gunshot drops) with the aim to facilitate blood origin determination. Features of blood drop formation at passive dripping with correlation to dripping surface characteristics were studied experimentally. A numerical scheme for accurate blood drop flight characteristics modelling, including oscillations, deformation and disintegration, was developed and validated against a number of analytical and experimental cases with special attention to the passive blood drop oscillations and ultimate deformation at terminal velocity, cast-off and impact blood drop deformation and breakup features. This provided an efficient and accurate method for typical blood drop flight reconstruction from the blood origin to impact as well as from the bloodstain location to the possible blood origin. Factors affecting blood drop trajectory and blood origin estimation were studied using the developed scheme.

The current study is part of a long term experimental project devoted to investigating single-phase flow pressure drop and heat transfer, flow boiling pressure drop and heat transfer, flow boiling instability and flow visualization of de-ionized water flow in microchannels. The experimental facility was first designed and constructed by S. Gedupudi (2009) and in the present study; the experimental facility was upgraded by changing the piping and pre-heaters so as to accommodate the objectives of the research. These objectives include (i) modifying the test rig, to be used for conducting experiments in microchannels in single and two-phase flow boiling heat transfer, pressure drop and visualization, (ii) redesign metallic single microchannels using copper as the material. The purpose of the redesign is to provide microchannels with strong heaters, high insulation performance and with test sections easy to dismantle and reassemble, (iii) obtaining the effect of hydraulic diameter on single-phase flow, flow pattern, heat transfer and pressure drop, (iv) studying the effects of heat flux, mass flux,and vapour quality on flow pattern, flow boiling heat transfer and pressure drop, (v)comparing experimental results with existing correlations. However, the main focus in this present study is to investigate the effects of hydraulic diameter, heat flux, mass flux and vapour quality on flow pattern, flow boiling heat transfer coefficient and pressure drop. In addressing (iii) many possible reasons exist for the discrepancies between published results and conventional theory and for the scatter of data in published flow boiling heat transfer results: 1. Accuracy in measuring the dimensions of the test section, namely the width, depth and length and in the tested variables of temperature, pressure, heat flux and mass flux. 2. Variations in hydraulic diameter and geometry between different studies. 3. Differences in working fluids. 4. Effects of hydrodynamic and thermal flow development 5. Inner surface characteristics of the channels. Three different hydraulic diameters of copper microchannels were investigated: 0.438mm, 0.561 mm and 0.635 mm. For single-phase flow the experimental conditions included mass fluxes ranging from 278 – 5163 kg/m2 s, heat fluxes from 0 - 537 kW/m², and inlet temperatures of 30, 60 and 90°C. In the flow boiling experiments the conditions comprised of an inlet pressure of 125 kPa (abs), inlet temperature of 98°C (inlet sub-cooling of 7 K), mass fluxes ranging from 200 to 1100 kg/m²s, heat fluxes ranging from 0 to 793 kW/m² and qualities up to 0.41. All measurements were recorded after the system attained steady states. The single-phase fluid flow results showed that no deviation of friction factors was found from the three different hydraulic diameters. The effect of fluid temperature on friction factor was insignificant and the friction factors themselves were in reasonable agreement with developing flow theory. The typical flow patterns observed in all three test sections were bubbly, slug/confined churn and annular, however, based on the observation performed near the outlet, the bubbly flow was not detected. The effects of mass flow and hydraulic diameter on flow pattern for the three test sections investigated in the range of experimental conditions were not clear. The single-phase heat transfer results demonstrated that smaller test sections result in higher heat transfer coefficients. However, for heat transfer trends presented in the form of Nusselt number versus Reynolds number, the effect of hydraulic diameter was insignificant.The flow boiling experiments gave similar heat transfer results; they exhibited that the smaller hydraulic diameter channels resulted in higher heat transfer coefficients. The nucleate boiling mechanism was found for all three test sections, evidenced by the significant effect of heat flux on the local heat transfer coefficient. Moreover, the heat flux had a clear effect on average heat transfer coefficient for the 0.561 mm and 0.635mm test sections, whilst for the 0.438 mm test section, there was no discernible effect. At the same heat flux, increases in mass flux caused heat transfer coefficients to decrease. This could be due to the decrease of pressure inside the test section. When a higher mass flux was tested, the inlet pressure increased, and in reducing the inlet pressure to the original value, a decrease in system pressure resulted. Consequently, the outlet pressure and local pressure became lower. Existing flow pattern maps, flow boiling heat transfer and pressure drop correlations were compared with the experimental results obtained for all three test sections. The comparison showed that the flow pattern map proposed by Sobierska et al. (2006) was the most successful in predicting the experimental data. The local heat transfer coefficient data were compared with existing published correlations. The correlations of Yu et al. (2002), Qu and Mudawar (2003) and Li and Wu (2010) are found to predict the current local heat transfer coefficient better than other correlations tested. Pressure drop results showed that as the heat flux and mass flux were increased, the two-phase pressure drop increased too. These were due to the increase in bubble generations and the inertia momentum effect. As the channel was reduced, the twophase pressure drop increased because the pressure drop related inversely with the channel hydraulic diameter. The pressure and pressure drop fluctuations were indentified in this project, however, the maximum pressure fluctuation was found in the 0.438 mm channel whilst the minimum fluctuation was attained in the 0.561 mm channel. This indicated that the effect of decreasing in hydraulic diameter on pressure and pressure drop fluctuations is not clear and needs to be investigated further. The two-phase pressure drop data were compared with selected correlations. The Mishima and Hibiki (1996)’s correlation was found to predict the current two-phase pressure drop better than the other correlations examined in this study.