1,627 research outputs found
The intersection of technology and aesthetics in contemporary cinema
The continuity of change in the film industry is evident, with cinematographers seeking new forms of lighting expression and production efficiency while manufacturers aim to sell. However, the rapid pace of technological development means that professionals often rely on personal preferences and recommendations from colleagues to create appropriate lighting setups that serve the needs of the story. Since content and form of expression are interlinked, technology enables new practices of emulating lighting for cinematographers. Although, there is a misconnect between the needs of cinematographers and manufacturers, which can result in the oversaturation of just one type of lighting that the industry focuses on, such as the soft light of LED lighting. It is important to remember that there are multiple ways of emulating lighting, even if newer practices have surpassed older ones. New technology should not necessarily replace old ways of working but should instead be an addition to the already plentiful ways of expressing through light.
One aspect of this research is examining the impact that technological advancements in camera equipment have had on the art of lighting. The historical origins of the symbiotic relationship between camera and lighting technology are traced back to the late 19th century with the invention of the first moving image camera, the Kinetographe. Moreover, this thesis highlights significant lighting inventions which remain ubiquitous on contemporary sets. These fixtures have been adapted and developed over the years, offering more possibilities for contemporary filmmaking than they did in early cinema.
It is essential to recognise that new technologies continually drastically influence how we perceive, and just as we make the technology, technology guides our decisions. By observing the details and paying attention to the connections between lighting technology and productions in contemporary cinema, we can create a working method that aligns with the vision of storytellers and avoids the negative impacts of technological advancements on film as an art form. This is not a study that can be completed and forgotten; rather, it requires continuous exploration throughout a cinematographer's life to facilitate contemporary and authentic expression through lighting in cinematography.Media files notes:
A Day Without Prohibition, 2023. An MA thesis film for Aalto University.
Description:
Two young women decide to defy the dancing prohibition set by the Finnish government by organizing a secret graduation dance in war-torn Helsinki in 1944.
Media creators:
An MA thesis film for Aalto University
Optical Measurement of Airborne Particles on Unmanned Aircraft
Aerosols and clouds are persistent causes of uncertainty in climate and weather models,
which is due to their heterogeneous suspension and occurrence within the atmosphere, and
complex interactions which are chaotic and exist on small scales. Unmanned aerial vehicles
(UAVs) have grown in popularity, and are becoming more commonly used for general atmospheric
measurement, particularly measurement of aerosols and clouds. This thesis presents
and evaluates a synergy between two UAVs, a multi-rotor: the UH-AeroSAM octocopter and
a fixed-wing: the FMI-Talon, and an optical particle instrument: the Universal Cloud and
Aerosol Sounding System. Computational fluid dynamics with Lagrangian particle tracking
(CFD-LPT) was used as a tool for the characterisation of the velocity fields and particle
trajectories around both UAVs. In both instances CFD-LPT was used to develop an operational
envelope, with particular attention to angle of attack constraints and size distribution
perturbation, for the UAV â instrument synergy. UCASS was the first open path instrument
to be used on a UAV, and a good case has been made for its continued use, particularly
on fixed-wing UAVs, which exhibit less complex aerodynamics and superior stability in the
induced sampling airflow through the instrument
An Intelligent Time and Performance Efficient Algorithm for Aircraft Design Optimization
Die Optimierung des Flugzeugentwurfs erfordert die Beherrschung der komplexen ZusammenhĂ€nge mehrerer Disziplinen. Trotz seiner AbhĂ€ngigkeit von einer Vielzahl unabhĂ€ngiger Variablen zeichnet sich dieses komplexe Entwurfsproblem durch starke indirekte Verbindungen und eine daraus resultierende geringe Anzahl lokaler Minima aus. KĂŒrzlich entwickelte intelligente Methoden, die auf selbstlernenden Algorithmen basieren, ermutigten die Suche nach einer diesem Bereich zugeordneten neuen Methode. TatsĂ€chlich wird der in dieser Arbeit entwickelte Hybrid-Algorithmus (Cavus) auf zwei HauptdesignfĂ€lle im Luft- und Raumfahrtbereich angewendet: Flugzeugentwurf- und Flugbahnoptimierung. Der implementierte neue Ansatz ist in der Lage, die Anzahl der Versuchspunkte ohne groĂe Kompromisse zu reduzieren. Die Trendanalyse zeigt, dass der Cavus-Algorithmus fĂŒr die komplexen Designprobleme, mit einer proportionalen Anzahl von PrĂŒfpunkten konservativer ist, um die erfolgreichen Muster zu finden.
Aircraft Design Optimization requires mastering of the complex interrelationships of multiple disciplines. Despite its dependency on a diverse number of independent variables, this complex design problem has favourable nature as having strong indirect links and as a result a low number of local minimums. Recently developed intelligent methods that are based on self-learning algorithms encouraged finding a new method dedicated to this area. Indeed, the hybrid (Cavus) algorithm developed in this thesis is applied two main design cases in aerospace area: aircraft design optimization and trajectory optimization. The implemented new approach is capable of reducing the number of trial points without much compromise. The trend analysis shows that, for the complex design problems the Cavus algorithm is more conservative with a proportional number of trial points in finding the successful patterns
Sampling-Based Motion Planning: A Comparative Review
Sampling-based motion planning is one of the fundamental paradigms to
generate robot motions, and a cornerstone of robotics research. This
comparative review provides an up-to-date guideline and reference manual for
the use of sampling-based motion planning algorithms. This includes a history
of motion planning, an overview about the most successful planners, and a
discussion on their properties. It is also shown how planners can handle
special cases and how extensions of motion planning can be accommodated. To put
sampling-based motion planning into a larger context, a discussion of
alternative motion generation frameworks is presented which highlights their
respective differences to sampling-based motion planning. Finally, a set of
sampling-based motion planners are compared on 24 challenging planning
problems. This evaluation gives insights into which planners perform well in
which situations and where future research would be required. This comparative
review thereby provides not only a useful reference manual for researchers in
the field, but also a guideline for practitioners to make informed algorithmic
decisions.Comment: 25 pages, 7 figures, Accepted for Volume 7 (2024) of the Annual
Review of Control, Robotics, and Autonomous System
Finite difference method in prolate spheroidal coordinates for freely suspended spheroidal particles in linear flows of viscous and viscoelastic fluids
A finite difference scheme is used to develop a numerical method to solve the
flow of an unbounded viscoelastic fluid with zero to moderate inertia around a
prolate spheroidal particle. The equations are written in prolate spheroidal
coordinates, and the shape of the particle is exactly resolved as one of the
coordinate surfaces representing the inner boundary of the computational
domain. As the prolate spheroidal grid is naturally clustered near the particle
surface, good resolution is obtained in the regions where the gradients of
relevant flow variables are most significant. This coordinate system also
allows large domain sizes with a reasonable number of mesh points to simulate
unbounded fluid around a particle. Changing the aspect ratio of the inner
computational boundary enables simulations of different particle shapes ranging
from a sphere to a slender fiber. Numerical studies of the latter particle
shape allow testing of slender body theories. The mass and momentum equations
are solved with a Schur complement approach allowing us to solve the zero
inertia case necessary to isolate the viscoelastic effects. The singularities
associated with the coordinate system are overcome using L'Hopital's rule. A
straightforward imposition of conditions representing a time-varying
combination of linear flows on the outer boundary allows us to study various
flows with the same computational domain geometry. {For the special but
important case of zero fluid and particle inertia we obtain a novel formulation
that satisfies the force- and torque-free constraint in an iteration-free
manner.} The numerical method is demonstrated for various flows of Newtonian
and viscoelastic fluids around spheres and spheroids (including those with
large aspect ratio). Good agreement is demonstrated with existing theoretical
and numerical results.Comment: 32 pages, 12 figures. Accepted at Journal of Computational Physic
Exploring space situational awareness using neuromorphic event-based cameras
The orbits around earth are a limited natural resource and one that hosts a vast range of vital space-based systems that support international systems use by both commercial industries, civil organisations, and national defence. The availability of this space resource is rapidly depleting due to the ever-growing presence of space debris and rampant overcrowding, especially in the limited and highly desirable slots in geosynchronous orbit. The field of Space Situational Awareness encompasses tasks aimed at mitigating these hazards to on-orbit systems through the monitoring of satellite traffic. Essential to this task is the collection of accurate and timely observation data. This thesis explores the use of a novel sensor paradigm to optically collect and process sensor data to enhance and improve space situational awareness tasks. Solving this issue is critical to ensure that we can continue to utilise the space environment in a sustainable way. However, these tasks pose significant engineering challenges that involve the detection and characterisation of faint, highly distant, and high-speed targets. Recent advances in neuromorphic engineering have led to the availability of high-quality neuromorphic event-based cameras that provide a promising alternative to the conventional cameras used in space imaging. These cameras offer the potential to improve the capabilities of existing space tracking systems and have been shown to detect and track satellites or âResident Space Objectsâ at low data rates, high temporal resolutions, and in conditions typically unsuitable for conventional optical cameras. This thesis presents a thorough exploration of neuromorphic event-based cameras for space situational awareness tasks and establishes a rigorous foundation for event-based space imaging. The work conducted in this project demonstrates how to enable event-based space imaging systems that serve the goals of space situational awareness by providing accurate and timely information on the space domain. By developing and implementing event-based processing techniques, the asynchronous operation, high temporal resolution, and dynamic range of these novel sensors are leveraged to provide low latency target acquisition and rapid reaction to challenging satellite tracking scenarios. The algorithms and experiments developed in this thesis successfully study the properties and trade-offs of event-based space imaging and provide comparisons with traditional observing methods and conventional frame-based sensors. The outcomes of this thesis demonstrate the viability of event-based cameras for use in tracking and space imaging tasks and therefore contribute to the growing efforts of the international space situational awareness community and the development of the event-based technology in astronomy and space science applications
Investigating the potential for detecting Oak Decline using Unmanned Aerial Vehicle (UAV) Remote Sensing
This PhD project develops methods for the assessment of forest condition utilising modern remote sensing technologies, in particular optical imagery from unmanned aerial systems and with Structure from Motion photogrammetry. The research focuses on health threats to the UKâs native oak trees, specifically, Chronic Oak Decline (COD) and Acute Oak Decline (AOD). The data requirements and methods to identify these complex diseases are investigatedusing RGB and multispectral imagery with very high spatial resolution, as well as crown textural information. These image data are produced photogrammetrically from multitemporal unmanned aerial vehicle (UAV) flights, collected during different seasons to assess the influence of phenology on the ability to detect oak decline. Particular attention is given to the identification of declined oak health within the context of semi-natural forests and heterogenous stands. Semi-natural forest environments pose challenges regarding naturally occurring variability. The studies investigate the potential and practical implications of UAV remote sensing approaches for detection of oak decline under these conditions. COD is studied at Speculation Cannop, a section in the Forest of Dean, dominated by 200-year-old oaks, where decline symptoms have been present for the last decade. Monks Wood, a semi-natural woodland in Cambridgeshire, is the study site for AOD, where trees exhibit active decline symptoms. Field surveys at these sites are designed and carried out to produce highly-accurate differential GNSS positional information of symptomatic and control oak trees. This allows the UAV data to be related to COD or AOD symptoms and the validation of model predictions. Random Forest modelling is used to determine the explanatory value of remote sensing-derived metrics to distinguish trees affected by COD or AOD from control trees. Spectral and textural variables are extracted from the remote sensing data using an object-based approach, adopting circular plots around crown centres at individual tree level. Furthermore, acquired UAV imagery is applied to generate a species distribution map, improving on the number of detectable species and spatial resolution from a previous classification using multispectral data from a piloted aircraft. In the production of the map, parameters relevant for classification accuracy, and identification of oak in particular, are assessed. The effect of plot size, sample size and data combinations are studied. With optimised parameters for species classification, the updated species map is subsequently employed to perform a wall-to-wall prediction of individual oak tree condition, evaluating the potential of a full inventory detection of declined health. UAV-acquired data showed potential for discrimination of control trees and declined trees, in the case of COD and AOD. The greatest potential for detecting declined oak condition was demonstrated with narrowband multispectral imagery. Broadband RGB imagery was determined to be unsuitable for a robust distinction between declined and control trees. The greatest explanatory power was found in remotely-sensed spectra related to photosynthetic activity, indicated by the high feature importance of nearinfrared spectra and the vegetation indices NDRE and NDVI. High feature importance was also produced by texture metrics, that describe structural variations within the crown. The findings indicate that the remotely sensed explanatory variables hold significant information regarding changes in leaf chemistry and crown morphology that relate to chlorosis, defoliation and dieback occurring in the course of the decline. In the case of COD, a distinction of symptomatic from control trees was achieved with 75 % accuracy. Models developed for AOD detection yielded AUC scores up to 0.98,when validated on independent sample data. Classification of oak presence was achieved with a Userâs accuracy of 97 % and the produced species map generated 95 % overall accuracy across the eight species within the study area in the north-east of Monks Wood. Despite these encouraging results, it was shown that the generalisation of models is unfeasible at this stage and many challenges remain. A wall-to-wall prediction of decline status confirmed the inability to generalise, yielding unrealistic results, with a high number of declined trees predicted. Identified weaknesses of the developed models indicate complexity related to the natural variability of heterogenous forests combined with the diverse symptoms of oak decline. Specific to the presented studies, additional limitations were attributed to limited ground truth, consequent overfitting,the binary classification of oak health status and uncertainty in UAV-acquired reflectance values. Suggestions for future work are given and involve the extension of field sampling with a non-binary dependent variable to reflect the severity of oak decline induced stress. Further technical research on the quality and reliability of UAV remote sensing data is also required
Design and optimisation of solar sail orbits in proximity of asteroids
A solar sail is a large reflective membrane which is capable of producing thrust for a spacecraft by the reflection of sunlight. Such a propellant-less propulsion system can offer solutions to high-energy missions which would be impossible for conventional propulsion systems. As a result, this technology has been proposed by many authors as the ideal candidate for a multiple asteroid rendezvous mission.
At the time of writing, there are more than 30,000 known near-Earth asteroids (NEAs) alone.
Adding to this those contained in the main belt and elsewhere in the solar system, the abundance of these small rocky worlds becomes apparent. Focusing only on the NEAs, there are many reasons for interest in missions to these bodies. In the first instance, they represent the earliest building blocks of the rocky worlds of the solar system, and are often still in pristine condition, similar to how they would have been since these earliest moments. As such, there is massive scientific interest in visiting and extracting samples of their constituent materials. There is another community which is also interested in the extraction of these materials: the future asteroid miners. This mining could provide propellant for deep space missions, materials for in-space infrastructure and potentially also in the return of minerals which are rare on Earth, and so of great value. However, although these bodies provide many opportunities, they are not without threat. Although the frequency of impacts of large bodies capable of causing considerable damage to Earth-based infrastructure is relatively low, there are still recent examples of just such events. With the potential for large scale loss of life due to an asteroid impacting populated areas, the science of planetary defence requires greater knowledge of the make-up of these bodies. Yet another reason for mission designers to examine further options in achieving efficient missions to these bodies.
It would be beneficial, in terms of cost, for a single spacecraft to be able to carry out a mission to multiple asteroids. Such a high-energy mission is ideally suited to the solar sail. Although the literature has provided many works on orbital transfers to multiple bodies, the operation of the sail when in proximity of the asteroid has not received quite as much attention. It is in this phase of the mission, where the science objectives would be carried out, that this thesis focuses. There are numerous challenges which the sail faces in the near-asteroid environment. These include the irregular gravity field, the strength of the acceleration provided by the sail in a relatively weak gravitational field, the often fast rotational velocities of the asteroid and higher demands on slew rates for the sail due to the shorter period of low-altitude orbits.
The work will consider three main proximity phases. The first operation is in the control of an orbit using the solar sail in an irregular gravity field. In this operation, the sail must counter the perturbative effects of a non-spherical body. This manifests in the rotation of the orbit node line, referred to as nodal regression. A new tool, referred to as the Control Transition Matrix (CTM), which aids in forcing a periodic orbit solution over multiple orbits is then presented. The second operation deals with the control of a sail at the point of and subsequent to the deployment of a lander and during the deployment of a series of small ChipSat probes. The landing conditions for deployments from various locations around the asteroid are analysed before the deployment is presented from a low-asteroid orbit. The control of the sail along a nominal orbit while the lander is still on-board is presented before the sail control subsequent to the lander deployment is considered. Given the high velocity impacts for a ballistic lander deployed at large distances from the surface, an alternative mission scenario of the deployment of small ChipSat probes is presented. These probes are envisaged to carry out their science goals during the descent and so the landing conditions are less important. The final operation is in the gravitational capture of the sail around the asteroid. This work provides a preliminary analysis of the capability of the sail in achieving this by using a simple on/off control law. Following this, a more detailed two-phase approach is presented. In the first âinitial captureâ phase, the sail uses the value of Jacobi constant in the 3 body system as a guide to reduce the orbit radius to within a defined region. After this, the âorbit shapingâ phase aims to circularise the orbit at this radius. Subsequently, preliminary investigations into an optimal approach are presented.
In controlling the effects due to the non-spherical asteroid shape, an optimally controlled solution, where a minimum effort control law is sought, is presented. Following this, a novel method of updating a control law was successfully applied to force a periodic orbit. In the work carried out on lander deployment, it was found that the sail was capable of maintaining a periodic orbit after the point of lander separation by application of time-delay feedback control. For the deployment of a series of small probes, it was found that maintaining a fixed attitude for the sail during the deployment was not considerably different in station-keeping performance compared with LQR control, and performed this with no effort required of the sail. Finally, in the work on capture, the two-phase approach provided successful capture trajectories down to the desired orbit radius. The work showed that, for reducing size of asteroid, there was a reduction in the time to capture. This is due to the fact that the same size of sail is used in the weakening gravity field of each asteroid. This makes the sail relatively more powerful and so able to affect quicker capture. It was also seen that long period capture trajectories are compounded by the need for the sail to spend periods of time waiting for the position of the Sun relative to the orbit to be in such a way as to permit the capture operations to proceed. There was also the successful demonstration of an optimally controlled capture which minimised the orbit semi-parameter over one orbit revolution.
The work contained in this thesis provides preliminary analysis for the consideration of future solar sail mission designers in the proximity operations of a sail near an asteroid. The findings presented here have shown that the sail can be of considerable utility in these proximity operations. They also present challenges to the mission designer given the continuous thrust that they may provide. Where a powerful sail may benefit the interplanetary phase of a mission in reaching many more asteroids further from the Earth, this can also present a challenge in the relatively weak asteroid gravitational field. However, these challenges are not insurmountable and so the sail remains a promising option for these high-energy missions
Deformations of an active liquid droplet
A fluid droplet in general deforms, if subject to active driving, such as a
finite slip velocity or active tractions on its interface. We show that these
deformations and their dynamics can be computed analytically in a perturbation
theory in the inverse surface tension using an approach based on vector
spherical harmonics. In lowest order, the deformation is of first order, yet it
affects the flow fields inside and outside of the droplet in zeroth order.
Hence a correct description of the flow has to allow for shape fluctuations,
even in the limit of large surface tension
Electron Thermal Runaway in Atmospheric Electrified Gases: a microscopic approach
Thesis elaborated from 2018 to 2023 at the Instituto de AstrofĂsica de AndalucĂa under the supervision of Alejandro Luque (Granada, Spain) and Nikolai Lehtinen (Bergen, Norway). This thesis presents a new database of atmospheric electron-molecule collision cross sections which was published separately under the DOI :
With this new database and a new super-electron management algorithm which significantly enhances high-energy electron statistics at previously unresolved ratios, the thesis explores general facets of the electron thermal runaway process relevant to atmospheric discharges under various conditions of the temperature and gas composition as can be encountered in the wake and formation of discharge channels
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