Thèses sur le sujet « Redundancy of Degrees of Freedom »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Redundancy of Degrees of Freedom.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleures thèses pour votre recherche sur le sujet « Redundancy of Degrees of Freedom ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les thèses sur diverses disciplines et organisez correctement votre bibliographie.
1
Wang, Yu-Cheng. « Dual 7-Degree-of-Freedom Robotic Arm Remote Teleoperation Using Haptic Devices ». Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5793.
Texte intégralRésumé :
A teleoperated system of dual redundant manipulator will be controlled in this thesis. The robot used with the dual redundant manipulator in this thesis is Baxter. Baxter’s redundant robot arms are 7-degree-of-freedom arms. The problem that will be solved in this thesis is optimization of the 7-degree-of-freedom robot arms. The control algorithm of the 7-degree-of-freedom robot arms will be discussed and built. A simulation program will be built to test the control algorithm. Based on the control algorithm, a teleoperation system will be created for Baxter. The controller used is Omni, which is a six-joint haptic device. Omni will also be used to give force feedback upon collision while the user is controlling the robot. Hence, a collision force feedback system is going to be created and combined with the teleoperation system. The teleoperation system will be tested in common daily applications.
2
Alqasemi, Redwan M. « Maximizing manipulation capabilities of persons with disabilities using a smart 9-degree-of-freedom wheelchair-mounted robotic arm system ». [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002004.
Texte intégral
3
Eklund, Elin. « Cykeltidsoptimering av sjuaxligt robotsystem ». Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2756.
Texte intégralRésumé :
This master thesis studies how much the cycle time, i.e. the time it takes for an industrial robot to perform a given task, can be reduced if an extra degree of freedom (DOF) is added to the robot system. The extra DOF consists of a linear track, which is supposed to be used in an optimal way. The problem has been studied using simulations in the robot simulation tool RobotStudio.
To be able to run an optimization in Matlab, with the RobotStudio simulation cycle time as the object function, communication between Matlab and RobotStudio has been set up with an interface written in Visual Basic. An algorithm has been developed to solve the problem. Two different optimization methods have been examined and compared.
The resulting algorithm has been applied to test cases. The results show that the cycle time in several cases can be reduced by 20-30 percent, if the movements along the track are optimized with the suggested method.
4
Patterson, Timothy Fredrick. « Reduction of compliance in space-based redundant degree-of-freedom manipulators ». Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/18396.
Texte intégral
5
Keselman, Leo. « Motion planning for redundant manipulators and other high degree-of-freedom systems ». Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51895.
Texte intégralRésumé :
Motion planning for redundant manipulators poses special challenges because the required inverse kinematics are difficult and not complete. This thesis investigates and proposes methods for motion planning for these systems that do not require inverse kinematics and are potentially complete. These methods are also compared in performance to standard inverse kinematics based methods.
6
Ahmed, Abu Hanieh. « Multi degrees of freedom vibration isolation ». Doctoral thesis, Universite Libre de Bruxelles, 2001. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211553.
Texte intégral
7
Pollmann, Frank. « Charge degrees of freedom on frustrated lattices ». [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=982205066.
Texte intégral
8
Jong, Boudewijn Ruben de. « A six degrees of freedom MEMS manipulator ». Enschede : University of Twente [Host], 2006. http://doc.utwente.nl/57599.
Texte intégral
9
Borade, Shashibhushan Prataprao 1981. « Maximizing degrees of freedom in wireless networks ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16692.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 61-63).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
We consider communication from a single source to a single destination in a wireless network with fading. Both source and destination have multiple antennas. The information reaches the destination through a sequence of layers of single-antenna relays. A non-separation-based strategy is proposed and shown to achieve a rate equal to the capacity of a point-to-point multiantenna system in the high SNR regime. This implies that lack of coordination between relay nodes does not reduce the achievable rate at high SNR. We then derive the tradeoffs between network size and rate. We also derive the rate-diversity tradeoff for this network and study how it is affected by the network size. This shows that increasing network size is much more difficult when the codelength does not span a large number of fading realizations. Finally some implications to ad-hoc networks are discussed.
by Shashibhushan Prataprao Borade.
S.M.
10
Hagio, Shota. « Muscle synergy for coordinating redundant motor system ». Kyoto University, 2016. http://hdl.handle.net/2433/215620.
Texte intégralRésumé :
Kyoto University (京都大学)0048
新制・課程博士
博士(人間・環境学)
甲第19794号
人博第765号
新制||人||184(附属図書館)
27||人博||765(吉田南総合図書館)
32830
京都大学大学院人間・環境学研究科共生人間学専攻
(主査)教授 神﨑 素樹, 教授 森谷 敏夫, 教授 石原 昭彦
学位規則第4条第1項該当
11
O'Brien, Aroon. « Charge degrees of freedom on the kagome lattice ». Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-71860.
Texte intégralRésumé :
Within condensed matter physics, systems with strong electronic correlations give rise to fascinating phenomena which characteristically require a physical description beyond a one-electron theory, such as high temperature superconductivity, or Mott metal-insulator transitions. In this thesis, a class of strongly correlated electron systems is considered. These systems exhibit fractionally charged excitations with charge +e/2 or -e/2 in two dimensions (2D) and three dimensions (3D), a consequence of both strong correlations and the geometrical frustration of the interactions on the underlying lattices.
Such geometrically frustrated systems are typically characterized by a high density of low-lying excitations, leading to various interesting physical effects. This thesis constitutes a study of a model of spinless fermions on the geometrically frustrated kagome lattice. Focus is given in particular to the regime in which nearest-neighbour repulsions V are large in comparison with hopping t between neighbouring sites, the regime in which excitations with fractional charge occur.
In the classical limit t = 0, the geometric frustration results in a macroscopically large ground-state degeneracy. This degeneracy is lifted by quantum fluctuations. A low-energy effective Hamiltonian is derived for the spinless fermion model for the case of 1/3 filling in the regime where |t| << V . In this limit, the effective Hamiltonian is given by ring-exchange of order ~ t^3/V^2, lifting the degeneracy. The effective model is shown to be equivalent to a corresponding hard-core bosonic model due to a gauge invariance which removes the fermionic sign problem. The model is furthermore mapped directly to a Quantum Dimer model on the hexagonal lattice. Through the mapping it is determined that the kagome lattice model exhibits plaquette order in the ground state and also that fractional charges within the model are linearly confined.
Subsequently a doped version of the effective model is studied, for the case where exactly one spinless fermion is added or subtracted from the system at 1/3 filling. The sign of the newly introduced hopping term is shown to be removable due to a gauge invariance for the case of hole doping. This gauge invariance is a direct result of the bipartite nature of the hole hopping and is confirmed numerically in spectral density calculations. For further understanding of the low-energy physics, a derivation of the model gauge field theory is presented and discussed in relation to the confining quantum electrodynamic in two dimensions.
Exact diagonalization calculations illustrate the nature of the fractional charge confinement in terms of the string tension between a bound pair of defects. The calculations employ topological symmetries that exist for the manifold of ground-state configurations.
Dynamical calculations of the spectral densities are considered for the full spinless fermion Hamiltonian and compared in the strongly correlated regime with the doped effective Hamiltonian. Calculations for the effective Hamiltonian are then presented for the strongly correlated regime where |t| << V .
In the limit g << |t|, the fractional charges are shown to be effectively free in the context of the finite clusters studied. Prominent features of the spectral densities at the Gamma point for the hole and particle contributions are attributed to approximate eigenfunctions of the spinless fermion Hamiltonian in this limit. This is confirmed through an analytical derivation. The case of g ~ t is then considered, as in this case the confinement of the fractional charges is observable in the spectral densities calculated for finite clusters. The bound states for the effectively confined defect pair are qualitatively estimated through the solution of the time-independent Schroedinger equation for a potential which scales linearly with g. The double-peaked feature of spectral density calculations over a range of g values can thus be interpreted as a signature of the confinement of the fractionally charged defect pair.
Furthermore, the metal-insulator transition for the effective Hamiltonian is studied for both t > 0 and t < 0. Exact diagonalization calculations are found to be consistent with the predictions of the effective model. Further calculations confirm that the sign of t is rendered inconsequential due to the gauge invariance for g in the regime |t| << V . The charge-order melting metal-insulator transition is studied through density-matrix renormalization group calculations. The opening of the energy gap is found to differ for the two signs of t, reflecting the difference in the band structure at the Fermi level in each case. The qualitative nature of transition in each case is discussed.
As a step towards a realization of the model in experiment, density-density correlation functions are introduced and such a calculation is shown for the plaquette phase for the effective model Hamiltonian at 1/3 filling in the absence of defects. Finally, the open problem of statistics of the fractional charges is discussed.
12
Mattingly, Sean Walter. « Velocity Space Degrees of Freedom of Plasma Fluctuations ». Thesis, The University of Iowa, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10263114.
Texte intégralRésumé :
This thesis demonstrates a measurement of a plasma fluctuation velocity-space cross-correlation matrix using laser induced fluorescence. The plasma fluctuation eigenmode structure on the ion velocity distribution function can be empirically determined through singular value decomposition from this measurement. This decomposition also gives the relative strengths of the modes as a function of frequency. Symmetry properties of the matrix quantify systematic error. The relation between the eigenmodes and plasma kinetic fluctuation modes is explored. A generalized wave admittance is calculated for these eigenmodes. Since the measurement is a localized technique, it may be applied to plasmas in which a single point measurement is possible, multipoint measurements may be difficult, and a velocity sensitive measurement technique is available.
13
Cable, Hugo Vaughan. « Localising relational degrees of freedom in quantum mechanics ». Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424451.
Texte intégral
14
Massimino, Michael James. « Teleoperator tracking performance in six degrees of freedom ». Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14063.
Texte intégralRésumé :
Thesis (Mech. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1990.Title as it appears in the M.I.T. Graduate List, June 1990: Teleoperator tracking in six degrees of freedeom.
Includes bibliographical references (leaf 40).
by Michael James Massimino.
Mech.E.
15
Feagin, Aprell McQueeney. « “The Angular Degrees of Freedom” and Other Stories ». Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700030/.
Texte intégralRésumé :
The preface, " Performing Brain Surgery: The Problematic Nature of Endings in Short Fiction," deals with the many and varied difficulties short story writers encounter when attempting to craft endings. Beginning with Raymond Carver and Flannery O’Connor and moving to my own work, I discuss some of the obscure criteria used to designate a successful ending, as well as the more concrete idea of the ending as a unifying element. Five short stories make up the remainder of this thesis: "In-between Girls," "Crocodile Man," "Surprising Things, Sometimes Amusing," "Good Jewelry," and "The Angular Degrees of Freedom."
16
Mattingly, Sean Walter. « Velocity space degrees of freedom of plasma fluctuations ». Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5967.
Texte intégralRésumé :
This thesis demonstrates a measurement of a plasma fluctuation velocity-space cross-correlation matrix using laser induced fluorescence. The plasma fluctuation eigenmode structure on the ion velocity distribution function can be empirically determined through singular value decomposition from this measurement. This decomposition also gives the relative strengths of the modes as a function of frequency. Symmetry properties of the matrix quantify systematic error. The relation between the eigenmodes and plasma kinetic fluctuation modes is explored. A generalized wave admittance is calculated for these eigenmodes. Since the measurement is a localized technique, it may be applied to plasmas in which a single point measurement is possible, multipoint measurements may be difficult, and a velocity sensitive measurement technique is available.
17
Smith, Jason T. (Jason Thomas) 1978. « A pseudo-optimal control approach for a redundant degree-of-freedom in a gimbaled mechanical system ». Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28887.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.Includes bibliographical references (p. 185-186).
Unaided inertial navigation systems of sufficient quality allow a missile or other body to navigate freely for potentially long periods of time. The use of four gimbals in such systems allows for elimination of large platform excursions while avoiding the uncontrollable condition of gimbal lock. The thesis investigates the benefits of applying a Linear Quadratic Regulator (LQR) to the control of the redundant degree-of-freedom present in a four gimbal inertial navigation system. Equations of motion for a four gimbal system are defined and linearized. A benchmark controller is developed, using classical time and frequency domain techniques, for comparison with the LQR controller. The quadratic weightings for the LQR controller are investigated using principles of loop shaping. Due to the time-varying nature of the linearized gimbal system, optimal gains are calculated for a variety of nominal conditions and stored in a look-up table. The classical and LQR controllers, as well as models of the four gimbal system components and sensors, are evaluated strictly via simulation. Metrics for determining controller performance are defined and a search is made for worst-case initial conditions and disturbances. A comparison with the benchmark controller at these worst-case conditions is made. It is found that the LQR control technique is of significant benefit when applied to the redundant degree-of-freedom. In particular, several of the metrics show significant improvement and others show marginal improvement. Also, the LQR controller makes more complete use of the available torque capacity, improving the performance of the four gimbal system. Ideas for future areas of investigation are presented.
by Jason T. Smith.
S.M.
18
Rajagopal, Gunaretnam. « Systems of coupled quantum and classical degrees of freedom ». Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/30689.
Texte intégral
19
Ng'andu, Alvert Namasamu. « Estimation of rotational degrees of freedom using spline functions ». Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282786.
Texte intégral
20
Chinneck, Robert. « An automated welding system with 6 degrees of freedom ». Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397385.
Texte intégral
21
Norell, Emil. « Gamma Knife treatment planning with new degrees of freedom ». Thesis, KTH, Optimeringslära och systemteori, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-246149.
Texte intégralRésumé :
The Leksell Gamma Knife® is an instrument designed for high precision treatment of tumours and lesions located in the brain and upper spine. Today, the radioactive cobalt-60 sources can only move linearly along the radiation unit, but the machine could be modified to include rotational motion as well. We extend an existing linear programming approach to inverse planning for the Gamma Knife by examining the benefits from rotational degrees of freedom. The improvements offered from rotations are limited, but easy to make use of. We investigate the model in four patient cases, and find that an upper bound on the improvement of the optimization cost function is between 4.5% and 7.0% depending on case. With a total of four angles distributed uniformly over a 45 degree interval, one can in each case achieve a solution that performs up to within 1% of this bound. The average maximal improvements in terms of clinical metrics are 0.5% selectivity and 1.9% gradient index, at the cost of 5.9% worse beam-on time. No statistically significant change in coverage is found. A dynamic model based on column generation is proposed, which allows treatment during constant velocity angular motion and can achieve practically the same plan quality as the model with uniformly distributed angles at a significantly lower problem size. A similar algorithm can be designed to locate the most effective angles in a non-uniform manner that achieves better plans with fewer added rotational degrees of freedom. Trade-offs between memory and solution times are used to successively reduce the RAM occupation by around 90% and make significantly larger models computationally feasible to solve. A voxel clustering approach with emphasis on surface voxels, adapted to the radiosurgical framework, can significantly reduce the problem size while still producing competitive plans.Strålkniven Leksell Gamma Knife® är ett instrument designat för högprecisionsbestrålning av tumörer och lesioner i hjärnan och övre delen av ryggraden. Idag kan de radioaktiva källorna endast förflyttas linjärt under behandlingen, men maskinen skulle kunna modifieras för att även tillåta rotationsrörelser. Vi utvidgar ett ramverk för inversplanering, formulerat som ett linjär-programmeringsproblem, genom att undersöka fördelarna med nya rotationsfrihetsgrader. Förbättringarna som rotationer möjliggör är begränsade, men kan relativt enkelt tas till vara. Vi undersöker de potentiella förändringarna i fyra patientfall och finner att den övre gränsen av förbättringarna för målfunktionsvärdet i optimeringsproblemet är mellan 4.5% och 7.0% beroende på fall. Genom att tillåta rotation av källorna till fyra jämnt fördelade vinklar över 45 grader kan man i samtliga fall hitta en lösning som är inom 1% från det bästa målfunktionsvärdet. De genomsnittliga förbättringarna i form av kliniska metriker är 0.5% selektivitet och 1.9% gradient-index, dock på bekostnad av en försämring av bestrålningstiden med 5.9%. Ingen tydlig förändring av täckningen kunde påvisas. En modell baserad på kolumngenerering, som tillåter behandling under rotation av kollimator-kroppen med konstant hastighet, föreslås. I denna modell kan praktiskt taget lika bra lösningar uppnås som för likformigt fördelade vinklar, men med betydligt mindre problemstorlek. En liknande algoritm kan lokalisera de mest effektiva vinklarna och åstadkomma samma plankvalitet med färre, men olikformt fördelade, rotationsfrihetsgrader. RAM-användningen kan reduceras med cirka 90% genom avvägningar mellan minne och beräknings-tider, vilket möjliggör lösning av probleminstanser som tidigare var beräkningsmässigt omöjliga. Klustringsmetoder av voxlar anpassade till strålkniven kan minska problemstorleken betydelsefullt medan de resulterande behandlingsplanerna är fortsatt konkurrenskraftiga.
22
Moreu, Gamazo Jaime. « A kinematic coupling based 6 degrees of freedom dynamometer ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55278.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 130-131).
A new 6-degree of freedom dynamometer is presented. Six load cells measure the normal forces at the contact points of a three groove kinematic coupling. Three toggle clamps are used to preload the machine, so that it does not come apart. The device was designed, analyzed, built and tested. The error will mainly depend on frictional forces, load cells error and the toggle clamps. Frictional forces affect hysteresis, absorption and settlement of the coupling. Different solutions have been designed and tested to reduce friction. First, we tried direct contact between three stainless-steel rods and the stainless-steel load cells. The results were fully distorted due to the high friction of hard steel. We also tried three stainless-steels rods with flexures to contact the steel button cells. The results were much better and more repeatable, but absorption was not good enough. Finally, we tried using Teflon. Teflon is stuck to a steel plate that touches the contact points, leaving Teflon free of high stresses and allowing it to reduce friction between the contacts. The outcome was acceptable. In this case, hysteresis will be reasonably low, absorption is moderate and settlement-based problems are small for small preloads. Fortunately, settlement ability will be improved thanks to vibrations. Future investigations shall look towards low friction solutions, since the sturdiest and most user-friendly design will be the one that minimizes friction during the settlement process.
by Jaime Moreu Gamazo.
S.M.
23
Williams, Mark E. (Mark Edd). « Precision six degrees of freedom magnetically-levitated photolithography stage ». Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/9850.
Texte intégral
24
Olsson, Henrik. « Utilizing the Degrees of Freedom in Radiation Therapy Optimization ». Thesis, KTH, Optimeringslära och systemteori, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214566.
Texte intégralRésumé :
The development of advanced software for radiation therapy treatment has had a significant role in the last decades’ improvements in cancer treatment. By optimizing the radiation dose given to each patient, the probability of a successful treatment increases. The development of mathematical optimization methods, required to produce as good radiation therapy treatment plans as possible, is therefore of high importance. When producing treatment plans for Volumetric Modulated Arc Therapy (VMAT) today, there are degrees of freedom that are not fully utilized. The possibility of rotating the patient couch and collimator during radiation delivery, to achieve a better dose distribution over the patient, is not taken advantage of. In order to take full advantage of these extra degrees of freedom, methods for predicting how good different arcs will perform during VMAT-delivery need to be developed. Since the number of possible VMAT-arcs is very large, such a method needs to be very time efficient in order to be of conventional use. In this thesis, a heuristic method for finding good VMAT-arcs for patients with multiple brain metastasis is proposed. In the method, the sphere around the patient’s head is discretized into a number of beam directions. From each of these beam directions a projection of the patient’s anatomy is produced, and based on the relative location of the cancer metastasis and the organs desired to protect, a cost is assigned. By linking together adjacent beam direction, VMAT-arcs can be created, and each possible VMATarc is assigned an arc cost depending on the cost of the beam directions it traverses. Such arc cost is used as an indication of how good a VMAT-arc will perform during VMAT-delivery. The heuristic method is tested and evaluated on four different patient cases. In three of the patient cases, the proposed method gives good results. Overall the results indicate that it is possible to predict how good a VMAT-arc will perform during VMAT-delivery, by looking at the relative locations of the target and organ projections in a discrete number of points along the arc. However, since the number of test cases are few, no statistically significant conclusions can be drawn.Utvecklingen av avancerad mjukvara för strålningsterapi är en del av de senaste decenniernas framsteg inom cancerbehandling. Genom att optimera stråldosen som ges till varje patient ökar sannolikheten att behandlingen lyckas. Utvecklingen av matematiska optimeringsmetoder, som används för att producera så bra strålningsplaner som möjligt, är därför av högsta vikt. När man producerar strålningsplaner för VMAT (Volumetric Modulated Arc Therapy) idag, utnyttjas inte alla frihetsgrader. Möjligheten att rotera patientbritsen och kollimatorn för att leverera en bättre strålningsdos till patienten lämnas ute. För att kunna utnyttja dessa frigetsgrader fullt ut krävs utveckling av metoder som kan förutspå hur bra olika strålningstrajektorier är. Då det finns ett väldigt stort antal möjliga strålningstrajektorier måste dessa metoder vara tidseffektiva. Under detta exjobb har en heuristisk metod för att hitta bra VMAT-trajektorier för patienter med flera hjärnmetastaser utvecklats. I metoden discretiseras sfären runt patientens huvud i ett antal strålningsriktningar. Från varje strålningsriktning produceras en projektion av patientens anatomi. Baserat på de relativa positionerna av hjärnmetastaserna och de organ man vill skydda tilldelas varje strålningsriktning ett straff. Genom att binda samman intilliggande strålningsriktningar kan sedan VMAT-trajektorier produceras, och varje VMAT-trajektorie tilldelas ett straff baserat på straffen hos de strålningsriktningar som bundits samman för att bilda trajektorien. Straffet som tilldelats en trajektorie används sedan som en indikator för hur bra trajektorien är för VMAT-behandling. Den heuristiska metoden är testad i fyra olika patientfall. I tre av patientfallen ger metoden bra resultat. I sin helhet tyder resultaten på att det är möjligt att förutsäga hur bra en VMAT-trajektorie är för VMAT-behandling, genom att från ett par punkter längst trajektorien titta på de relativa positionerna av metastaserna och de organ som man vill skydda. Dock gör det låga antalet av testfall att inga statisktiskt säkerställda slutsatser kan dras.
25
Tomasin, Marco. « Quantum information with polarization and temporal degrees of freedom ». Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3423242.
Texte intégralRésumé :
This work deals with creation, manipulation and detection of quantum photon states, in one and two degrees of freedom, encoded in polarization and time-bin basis. A particular quantum state, an entangled state, carries a wide range of implementations, that are impossible via classical tasks, such as teleportation, dense coding, and quantum communication protocols. One of these tasks, quantum cryptography, allows intrinsically secure transmission of information. Nowadays, quantum key distribution is implemented in intercity quantum networks, by using telecommunication fibers to connect nodes within the network. In future scenarios, photons could travel through greater distances, but, due to losses, fiber links need for quantum repeater, a very demanding engineering solution. An alternative way, is the use of free-space satellite quantum networks.
Here we focus on polarization and time bin degrees of freedom (DOFs) of the photons as a resource for quantum information. In particular we study the possibility to share an hyper-entangled state in polarization and time-bin DOFs between two spatially separated users. In addition we study a new tomographic method, based on compressed sensing, to recover the density matrix of a quantum state when prior information are available.
Typical implementation of time-bin photon source, based on Franson’s scheme, suffers on intrinsic loophole. To overcome that we experimentally demonstrated that with a time-bin source it is possible to obtain a very high visibility in order to violate a chained Bell inequality.
Interference at single photon level through satellite-ground channels is presented here, showing that, temporal encoding is preserved along turbulent channels. With this experiment we show that temporal encoding can be use for a future implementation of satellite quantum communication. Finally, to complete this work, we demonstrate a new method to certified the randomness of a source, useful in many task, such as quantum cryptography by using a polarization entangled photons source.Questo lavoro è incentrato sulla creazione, manipolazione e rivelazione di fotoni, in uno o due gradi di libertà, codificati nel dominio del tempo o della polarizzazione. L’entanglement quantistico può essere usato per una vasta gamma di applicazioni che non sono possibili classicamente, come il teletrasporto quantistico, il denscoding e la crittografia quantistica. Quest’ultima, fornisce un grado di sicurezza incondizionato, poichè basata su leggi fisiche. Attualmente, le reti di comunicazione quantistica sono state implementate a livello cittadino utilizzando fibre ottiche per le telecomunicazioni. In uno scenario futuro, sarà necessario raggiungere distanze maggiori, ma a causa delle alte perdite, soluzioni basate su link in fibra saranno difficili da implementare. Un’alternativa è quella di utilizzare reti satellitari per le comunicazioni quantistiche. In questo lavoro ci focalizziamo sulla realizzazione di una sorgente di fotoni hyper-entangled in tempo e polarizzazione. La particolarità di questa sorgente è la possibilità di condividere lo stato tra due utenti spazialmente separati. Inoltre, abbiamo sviluppato un algoritmo di tomografia quantistica basato sul compressed sensing, per la ricostruzione di uno stato con un numero molto limitato di misure. Per poter funzionare, questo algoritmo ha bisogno di informazioni sullo stato di partenza. Successivamente, vedremo come il loophole dovuto alla postselezione in una sorgente di fotoni entangled in time-bin, può essere superato con una buona implementazione del setup ottico. Infatti nel nostro esperimento è stato possibile raggiungere una visibilità molto elevata, che ha permesso di violare le disuguaglianze di Bell concatenate. Vedremo inoltre, la possibilità di utilizzare fotoni codificati nel dominio temporale in un canale satellite-terra. Infatti, abbiamo dimostrato che la turbolenza non rovina lo stato inviato, aprendo la strada a futuri sviluppi basati sulla codifica temporale. Infine, per completare questo lavoro, una sorgente di fotoni entangled in polarizzazione è stata utilizzata per dimostrare un nuovo metodo per la certificazione della randomicità di una sorgente.
26
Planes, Conangla Gerard. « Levitation and control of particles with internal degrees of freedom ». Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669610.
Texte intégralRésumé :
Levitodynamics is a fast growing field that studies the levitation and manipulation of micro- and nanoobjects, fuelled by both fundamental physics questions and technological applications. Due to the isolated nature of trapped particles, levitated systems are highly decoupled from the environment, and offer experimental possibilities that are absent in clamped nanomechanical oscillators. In particular, a central question in quantum physics is how the transition between the classical and quantum world materializes, and levitated objects represent a promising avenue to study this intermediate regime.
In the last years, most levitation experiments have been restricted to optically trapped silica nanoparticles in vacuum, controlling the particle's position with intensity modulated laser beams. However, the use of optical traps severely constrains the experiments that can be performed, because few particle materials can withstand the optical absorption and resulting heating in vacuum. This completely prevents the use of objects with internal degrees of freedom, which---coupled to mechanical variables---offer a clear path towards the study of quantum phenomena at the macroscale.
In this thesis, we address these issues by considering other types of trap and feedback schemes, achieving excellent control on the dynamics of optically active nanoparticles. With stochastic calculus, simulations and experiments, we study the dynamics of trapped particles in different regimes, considering also a hybrid quadrupole-optical trapping scheme. Then, using a Paul trap of our own design, we demonstrate the trapping, interrogation and feedback cooling of a nanodiamond hosting a single NV center in vacuum, a clear candidate to perform quantum physics experiments at the single spin level. Finally, we discuss and implement an optimal controller to cool the center of mass motion of an optically levitated nanoparticle. The feedback is realized by exerting a Coulomb force on a charged particle with a pair of electrodes, and thus requires no optics.La levitodinàmica és un camp de la física en ràpida expansió que estudia la levitació i manipulació de micro- i nano-objectes, empesa per la possibilitat de solucionar trencaclosques de física fonamental i de desenvolupar noves aplicacions tecnològiques. Gràcies al gran aïllament de les partícules en levitació, l’evolució dels sistemes levitodinàmics està molt desacoplada del seu entorn. Per consegüent, permeten fer experiments que no serien possibles en nanooscil·ladors mecànics sobre substrat. En particular, una qüestió central en física consisteix en entendre com es produeix la transició entre els mons clàssic i quàntic; els objectes en levitació permeten estudiar aquest règim intermedi de manera innovadora. En els últims anys, la majoria d’experiments de levitodinàmica s’han limitat a atrapar òpticament partícules de sílice en el buit, tot controlant la posició de la partícula amb feixos làser modulats. Tot i així, l’ús de trampes òptiques suposa un obstacle a l’hora d’exportar aquests experiments a règims més diversos perquè, a baixes pressions, pocs materials són capaços de suportar les altes temperatures resultants de l’absorció de llum làser. Això impedeix l’ús d’objectes amb graus de llibertat interns, que –acoplats a variables mecàniques– suposen un full de ruta clar per estudiar fenòmens quàntics a escala macroscòpica En aquesta tesi, adrecem aquestes qüestions tot considerant altres tipus de trampa i tècniques de feedback, i assolim un control excel·lent de la dinàmica de nanopartícules òpticament actives en levitació. Mitjançant càlcul estocàstic, simulacions i experiments, estudiem la dinàmica de les partícules en règims diversos, àdhuc considerant un esquema híbrid de trampa de Paul-òptica. A continuació, utilitzant una trampa de Paul, demostrem experimentalment l’atrapament, interrogació i feedback-cooling en el buit d’un nanodiamant que conté un únic NV− center, un clar candidat per a la realització d’experiments de física quàntica amb un únic spin. Finalment, estudiem i implementem un controlador òptim per a refredar el centre de massa d’una partícula òpticament levitada. El feedback es realitza exercint una força de Coulomb sobre una partícula carregada positivament mitjançant un parell d’elèctrodes, i per tant no requereix elements òptics
27
Huthmann, Martin. « Free cooling of granular particles with rotational degrees of freedom ». Doctoral thesis, [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=963700979.
Texte intégral
28
Canbaloglu, Guvenc. « Structural Modification With Additional Degrees Of Freedom In Large Systems ». Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610664/index.pdf.
Texte intégralRésumé :
In the design and development stages of mechanical structures, it is important to predict the dynamic characteristics of modified structures. Since time and cost are critical in design and development stage, structural modification methods predicting the dynamic responses of modified structures from those of the original structure and modification properties are very important, especially for large systems.
In this thesis structural modification methods are investigated and an effective structural modification method for modifications with additional degrees of freedom is adapted to structures with distributed modifications and the performance of the method is investigated. A software program is developed in order to apply the structural modification method with additional degrees of freedom. In the software, the dynamic response of the modified structure is predicted by using the modal analysis results of ANSYS for the original structure and dynamic stiffness matrix of the modifying structure. In order to validate the approach used and the program developed, the dynamic analysis results obtained for modified structures by ANSYS are compared with those obtained by using the software. In order to investigate the performance of the structural modification method in real applications, the method is applied to a scaled aircraft model, and the results are compared with experimental results.
In order to demonstrate the importance of using the structural modification method with additional degrees of freedom for distributed modification, lumped and distributed models are used for a distributed modification and results are compared.
It is concluded in this study that using structural modification methods with additional degrees of freedom for a distributed modification increases the accuracy of the results, and it is observed that the method adapted is efficient for local modifications.
29
Huang, Ming-Sheng. « Coupled elastic rotor/body vibrations with inplane degrees of freedom ». Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/12495.
Texte intégral
30
Chang, Woo Sok 1964. « A high precision three degrees of freedom friction drive stage ». Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80626.
Texte intégral
31
Spurr, James Christopher. « Statistically modelling tennis racket impacts with six degrees of freedom ». Thesis, Sheffield Hallam University, 2017. http://shura.shu.ac.uk/18749/.
Texte intégralRésumé :
The International Tennis Federation (ITF) is responsible for protecting the nature of tennis. The ITF uses computational models to predict how trends in equipment parameters could affect the games future. The current ball-racket impact model is limited to non-spinning, on-axis, normal ball impact simulations. The aim of this project was to develop a model of oblique, spinning, on- and off-axis ball-racket impacts. Large scale test data (n > 1000) was collected using an impact rig and calibrated high-speed cameras. Impacts for a range of realistic velocities, spin rates and impact locations were collected, measured using automated image processing algorithms to digitise ball centroids. An established spin measurement method was improved to correct for perspective errors associated with the proximity of the cameras to the test volume. The automated algorithms were validated with experimental data and manual methods. Multi-variate polynomial models to predict the lateral and vertical components of rebound velocities and rebound spin rate were trained and validated using a curve fitting toolbox and ‘n-fold and leave one out cross-validation’ method. Second order models best fit the training data, with the low predictive errors. Root-mean-squared errors were calculated using a test dataset, independent of the training data. These were 0.57 m·s-1 for the lateral rebound velocity model, 0.48 m·s-1 for the vertical rebound velocity model and 30.5 rad·s-1 for the rebound spin rate model. Variance was partially explained by experimentally established inherent variability of the ball and stringbed. Model output confidence was established by simulating small changes in model inputs. The simulated lateral and vertical components of rebound velocity, but not the simulated spin rate, were an order of magnitude greater than the measurement precision. The new models were combined with ball aerodynamics and ball-to-surface impact models to simulate tennis court trajectories for oblique, spinning, on- and off-axis ball-racket impacts. Increasing stringbed stiffness or the lateral offset of impact location were found to decrease rebound velocity and increase rebound angle – markedly so for a 60 mm lateral offset. Increasing lateral offset also increased the rebound spin rate.
32
Biverot, Hans. « Multi-user retinal displays with two components. New degrees of freedom ». Doctoral thesis, KTH, Physics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3281.
Texte intégral
33
Skrøvseth, Stein Olav. « Entanglement and its applications in systems with many degrees of freedom ». Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-927.
Texte intégralRésumé :
Entanglement are the non-local correlations permitted by quantum theory, believed to play a fundamental role in a quantum computer. We have investigated these correlations in a number of theoretical models for condensed matter systems. Such systems are likely candidates for quantum computing, and experimentally feasible for instance as superconducting qubits. At quantum critical points the ground state of these systems is very complicated, and the entanglement is usually larger than at non-critical points. This entanglement can be used to identify the critical points through what we denote the entanglement signature, even for very small systems. From another perspective, it seems that the entanglement is an essential tool to find an unknown ground state, since this gives rise to a simple decomposition of the state.
34
Brouwer, Dannis Michel. « Design principles for six degrees-of-freedom MEMS-based precision manipulators ». Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57871.
Texte intégral
35
Glaser, Rainer [Verfasser]. « Semiclassics for quantum systems with internal degrees of freedom / Rainer Glaser ». Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2004. http://d-nb.info/1015471161/34.
Texte intégral
36
Grotz, Bernhard [Verfasser]. « Coupling Single NV Centers to External Degrees of Freedom / Bernhard Grotz ». München : Verlag Dr. Hut, 2014. http://d-nb.info/1047037203/34.
Texte intégral
37
Yoo, Euisoo. « Investigating CMOS amplifier design using the Degrees of Design Freedom method ». Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66813.
Texte intégralRésumé :
A design methodology based on generating the performance space of amplifiers by sweeping independent control variables has been investigated. The method is used to optimize the performance of CMOS amplifiers with respect to gain, bandwidth, noise, distortion and power directly in SPICE without the aid of mathematical models or external software routines. The method works in all SPICE programs from Cadence to the student version of PSPICE. The technique is based on tuning the voltage of specific nodes of the amplifier using a self-biasing current source technique in conjunction with a replica amplifier circuit to span the entire performance space with a resolution of choice. The method has been tested with discrete implementation of the design. Both single-stage and multi-stage amplifiers are considered in this work. The method is generic, and it can be easily extended onto any amplifier topology for any performance measure.Une méthodologie de conception originale basée sur la production de l'espace desperformances des amplificateurs en balayant les variables de contrôle indépendantesest examinée. Cette méthodologie peut optimiser des amplificateurs de CMOS parrapport au gain, à la bande passante, au bruit, à la déformation et à la puissance.L'espace des performances est recherché directement dans les logiciels SPICE sansl'aide d'aucun modèle mathématique ou des logiciels externes. Cette méthode fonctionnedans tous les logiciels SPICE, allant de Cadence à la version d'étudiantde PSPICE. La technique est basée sur la variation de tension dans des noeudsspécifiques de l'amplificateur en utilisant une source de courante dépendente et, enparrallèle, un circuit d'amplificateur copie pour créer l'espace des performances completavec une résolution de choix. Cette méthodologie a été testé avec les composantesséparées. Des amplificateurs à étage unique et à étages multiples sont considérés dansce travail. Cette méthode est générique, et elle peut être facilement appliquée surn'importe quelle topologie d'amplificateur pour n'importe quelle mesure de performance.
38
Taub, Daniel Matthew. « The BoPen : a tangible pointer tracked in six degrees of freedom ». Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/61297.
Texte intégralRésumé :
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 77-86).
In this thesis, I designed and implemented an optical system for freehand interactions in six degrees of freedom. A single camera captures a pen's location and orientation, including roll, tilt, x, y, and z by reading information encoded in a pattern at the infinite focal plane. The pattern design, server-side processing, and application demo software is written in Microsoft C#.NET, while the client-side pattern recognition is integrated into a camera with an on-board DSP and programmed in C. We evaluate a number of prototypes and consider the pen's potential as an input device.
by Daniel Matthew Taub.
M.Eng.
39
Mezei, Márk (Márk Koppany). « Counting degrees of freedom in quantum field theory using entanglement entropy ». Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91389.
Texte intégralRésumé :
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2014.141
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 199-208).
We devote this thesis to the exploration of how to define the number of degrees of freedom in quantum field theory. Intuitively, the number of degrees of freedom should decrease along the renormalization group (RG) flow, and should be independent of the RG scale at a conformal fixed point. We argue that a refinement of entanglement entropy is a promising candidate for such measure. Indeed, in two and three spacetime dimensions the number of degrees of freedom defined this way can be proven to monotonically decrease under RG flows. Firstly, we define renormalized entanglement entropy (REE) and show that it is finite in the continuum limit in a renormalizable field theory. We argue that it is most sensitive to degrees of freedom at a scale determined by the size of the entangling region, and interpolates between the ultraviolet and infrared RG fixed point vales. We discuss how it can be used to count the degrees of freedom at a given scale. Secondly, we test whether REE is monotonic along the RG flow. In two dimensions it was known to be monotonic before our study. In higher dimensions, we study REE in free theory examples and in the framework of holography. Holography is tailormade for the study of RG flows, and allows an efficient determination of entanglement entropy. We make use of its power and flexibility to conjecture that in three spacetime dimensions REE is monotonic, while in four dimensions it is neither monotonic nor positive. Subsequent work has proven the conjecture. Thirdly, we count the degrees of freedom in three-dimensional superconformal field theories that are the infrared limit of supersymrnetric gauge theories with matter. Supersymmetric localization reduces the computation of entanglement entropy to a matrix integral. We solve this matrix model in the large N number of colors limit using two different methods; in a saddle point approximation we obtain the next-to-leading order expression in 1/N, while mapping the matrix model to a non-interacting Fermi gas enables us to determine the result to all orders in 1/N. We match the leading piece with N3/ 2 scaling - a strong coupling phenomenon in the field theory - with the holographic duals of these theories. Establishing a measure for the number of degrees of freedom provides nonperturbative understanding of RG fixed points and flows. Our hope is that the constraints coming from RG monotonicity can be efficiently used to constrain the long-distance physics of certain systems of interest. The first applications are only starting to emerge.
by Márk Mezei.
Ph. D.
40
Tournier, Glenn P. (Glenn Paul). « Six degrees of freedom estimation using monocular vision and moiré patterns ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37951.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (p. 105-107).
We present the vision-based estimation of the position and orientation of an object using a single camera relative to a novel target that incorporates the use of moire patterns. The objective is to acquire the six degree of freedom estimation that is essential for the operation of vehicles in close proximity to other craft and landing platforms. A target contains markers to determine relative orientation and locate two sets of orthogonal moire patterns at two different frequencies. A camera is mounted on a small vehicle with the target in the field of view. An algorithm processes the images extracting the attitude and position information of the camera relative to the target utilizing geometry and 4 single-point discrete Fourier transforms (DFTs) on the moire patterns. Manual and autonomous movement tests are conducted to determine the accuracy of the system relative to ground truth locations obtained through an external indoor positioning system. Position estimations with accompanying control techniques have been implemented including hovering, static platform landings, and dynamic platform landings to display the algorithm's ability to provide accurate information to precisely control the vehicle. The results confirm the moire target system's feasibility as a viable option for low-cost relative navigation for indoor and outdoor operations including landing on static and dynamic surfaces.
by Glenn P. Tournier.
S.M.
41
Todd, Frankie. « Degrees of freedom : a study of collaborative learning in higher education ». Thesis, University of York, 1989. http://etheses.whiterose.ac.uk/14032/.
Texte intégral
42
Staupendahl, Daniel [Verfasser]. « 3D Profile Bending with Five Controlled Degrees of Freedom / Daniel Staupendahl ». Düren : Shaker, 2021. http://d-nb.info/1235301095/34.
Texte intégral
43
Ortega, Francisco Raul. « 3D Navigation with Six Degrees-of-Freedom using a Multi-Touch Display ». FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1594.
Texte intégralRésumé :
With the introduction of new input devices, such as multi-touch surface displays, the Nintendo WiiMote, the Microsoft Kinect, and the Leap Motion sensor, among others, the field of Human-Computer Interaction (HCI) finds itself at an important crossroads that requires solving new challenges. Given the amount of three-dimensional (3D) data available today, 3D navigation plays an important role in 3D User Interfaces (3DUI). This dissertation deals with multi-touch, 3D navigation, and how users can explore 3D virtual worlds using a multi-touch, non-stereo, desktop display.
The contributions of this dissertation include a feature-extraction algorithm for multi-touch displays (FETOUCH), a multi-touch and gyroscope interaction technique (GyroTouch), a theoretical model for multi-touch interaction using high-level Petri Nets (PeNTa), an algorithm to resolve ambiguities in the multi-touch gesture classification process (Yield), a proposed technique for navigational experiments (FaNS), a proposed gesture (Hold-and-Roll), and an experiment prototype for 3D navigation (3DNav). The verification experiment for 3DNav was conducted with 30 human-subjects of both genders. The experiment used the 3DNav prototype to present a pseudo-universe, where each user was required to find five objects using the multi-touch display and five objects using a game controller (GamePad). For the multi-touch display, 3DNav used a commercial library called GestureWorks in conjunction with Yield to resolve the ambiguity posed by the multiplicity of gestures reported by the initial classification. The experiment compared both devices. The task completion time with multi-touch was slightly shorter, but the difference was not statistically significant. The design of experiment also included an equation that determined the level of video game console expertise of the subjects, which was used to break down users into two groups: casual users and experienced users. The study found that experienced gamers performed significantly faster with the GamePad than casual users. When looking at the groups separately, casual gamers performed significantly better using the multi-touch display, compared to the GamePad. Additional results are found in this dissertation.
44
Ho, Zuleita K. M., et Eduard Jorswieck. « Secure degrees of freedom on widely linear instantaneous relay-assisted interference channel ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-128420.
Texte intégralRésumé :
The number of secure data streams a relay-assisted interference channel can support has been an intriguing problem. The problem is not solved even for a fundamental scenario with a single antenna at each transmitter, receiver and relay. In this paper, we study the achievable secure degrees of freedom of instantaneous relay-assisted interference channels with real and complex coefficients. The study of secure degrees of freedom with complex coefficients is not a trivial multiuser extension of the scenarios with real channel coefficients as in the case for the degrees of freedom, due to secrecy constraints. We tackle this challenge by jointly designing the improper transmit signals and widely-linear relay processing strategies.
45
Lange, Karsten [Verfasser]. « Two-mode entanglement in spin and spatial degrees of freedom / Karsten Lange ». Hannover : Gottfried Wilhelm Leibniz Universität Hannover, 2018. http://d-nb.info/1166313921/34.
Texte intégral
46
BERGMAN, CHRISTOPH. « THREE-DIMENSION REPRESENTATION OF THIN-WALL SHELLS USING TRANSLATION DEGREES-OF-FREEDOM ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1993. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24964@1.
Texte intégralRésumé :
Neste trabalho apresenta-se a formulação e implementação de um modelo bidimensional de elementos finitos para análise estática, isotérmica, linear elástica de cascas finas tridimensionais isotrópicas submetidas à carregamentos gerais.
A Geometria e o campo associado de deslocamentos do elemento quadrilateral proposto são representados por número variável de 4 a 16 pontos nodais definidos na superfície mediana de casca. O modelo emprega a formulação isoparamétrica, e a cinemática de deformação da casca é representada por três graus-de-liberdade à translação, definidos na superfície mediana do elemento.
A partir da condição de que segmentos inicialmente retos e perpendiculares à superfície mediana da casca, permanecem retos, normais e inextensíveis durante e após o processo de deformação – teoria de LOVE para cascas finas – as rotações são definidas nas direções de curvatura principais da casca com os graus-de-liberdade à translação.
As condições de contorno de continuidade da rotação da normal à casca entre elementos ou de nulidade da rotação no contorno de um elemento, devido à fixação, são garantidos utilizando-se o Método de Penalidades.
No estado plano de deformação considerado os mecanismos de flexão e distensão da casca são associadas às direções das curvaturas principais em cada ponto da superfície mediana, devido à simplicidade da expressão analítica das equações de compatibilidade geométrica.
Soluções numéricas para algumas estruturas, utilizando o modelo proposto, são comparadas com outros resultados analíticos e/ou numéricos disponíveis na literatura, demonstrando a aplicabilidade do elemento na representação de cascas finas tridimensionais utilizando apenas graus-de-liberdade à translação.The formulation of a simple but effective bi dimensional isoparametric displacemnet –based element for 3/D thin shell analysis is presented. The geometry and displacement fields are approximated using cubic interpolation functions defined on the shell mid –surface and represented by three spatial coordinates and three displacements only. The element Kinematics incorporates membrane and bending strain components with the assumption of zero transverse shear deformations being imposed in both shell curvature principal directions. This condition allows formulation of the element without using rotation as an independent degree-of-freedom, but the continuity conditions between two adjoining elements or the fixity condition between an element and a rigid wall are modeled by using a penalty procedure to enforce the boundary conditions on the local coordinate derivatives in the element mid-surface radial displacements. The element formulation has been implemented and the results of various sample analyses are given in order to illustrate the effectiveness of the proposed model in handling typical engineering shell analysis.
47
CARDOZO, WILLIAM SCHROEDER. « NUMERICAL AND EXPERIMENTAL STUDY OF A TWO DEGREES OF FREEDOM ELECTROHYDRAULIC MANIPULATOR ». PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=31839@1.
Texte intégralRésumé :
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE EXCELENCIA ACADEMICA
O controle de empuxo vetorial (TVC) é usado para o controle de atitude de foguetes aeroespaciais. No caso de propulsão usando combustível líquido, tradicionalmente o bocal é conectado ao corpo do foguete através de uma junta cardânica. Dois atuadores hidráulicos são colocados ao redor do bocal para controlar sua orientação. Nesta tese, o TVC é tratado como uma plataforma robótica de base fixa. Ao invés de usar servo-válvulas comerciais para controlar os atuadores, uma nova válvula de controle é proposta. Primeiro uma plataforma cardânica é considerada com transdutores de posição angular medindo o deslocamento da cruzeta da junta. Em seguida, uma nova configuração da plataforma é proposta substituindo o cardan por uma junta homocinética. Neste caso, a realimentação da posição da plataforma é feito usando um estimador de atitude em tempo real. Este estimador é um filtro complementar baseado em matrizes de orientação que coleta dados de uma central inercial (IMU). A modelagem do sistema começa com a cinemática. Na sequência, a modelagem dinâmica utiliza a formulação de Newton-Euler para obter a equação de movimento. A modelagem do sistema hidráulico é apresentada com o modelo da nova válvula de controle e do atuador. Inicialmente, um controlador puramente proporcional é proposto. Durante a validação experimental é mostrado que devido as características do sistema de atuação, mesmo este simples controlador é preciso e confiável. Em seguida é demonstrado um método para avaliar outras estratégias de controle. A comparação entre a plataforma cardânica e homocinética mostra que, nas condições analisadas, ambas têm um comportamento dinâmico similar. Nas duas configurações da plataforma o sistema se mostrou preciso e confiável.
Thrust Vector Control (TVC) is used for the attitude control of spacecrafts. In the case of liquid-propellant fuel, the nozzle is traditionally connected to the rocket frame through a gimbal. Two hydraulic actuators are placed around the nozzle to control its orientation. In this Thesis, TVC is treated as a fixed base robotic platform. Instead of using commercial servo-valves to control the actuators, a novel control valve is proposed. First a gimbaled platform is considered with two angular position transducers to measure the angular displacement of the joint crosshead. Then, a homokinetic platform configuration is proposed replacing the gimbal by a constant velocity joint. In this case, the platform position feedback is done using a real-time attitude estimator. The estimator is a complementary filter based on orientation matrices that collects data from an inertial measurement unit (IMU). The modeling of the system begins with kinematics. Then, the dynamic modeling uses the Newton-Euler formulation to obtain the equation of motion. The modeling of the electro-hydraulic system is presented with the model of the novel control valve and the linear actuator. Initially, a full proportional controller is proposed. During the experimental validation it is shown that due to the characteristics of the actuation system, even this simple controller is accurate and reliable. Thereafter, method is demonstrated to evaluate novel control strategies. The comparison between the gimbaled and homokinetic platform shows that, under the analyzed conditions, they have a similar dynamic behavior. In both platform configurations the system is accurate and reliable.
48
Shahar, Eyal. « SoundStrand : a tangible interface for composing music with limited degrees of freedom ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76531.
Texte intégralRésumé :
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 83-88).
This thesis presents SoundStrand, a novel tangible interface for composing music. A new paradigm is also presented - one that allows for music composition with limited degrees of freedom, and therefore is well suited for music creation through the use of tangible interfaces. SoundStrand is comprised of a set of building blocks that represent pre-composed musical segments. By sequentially connecting building blocks to one another, the user arranges these segments into a musical theme; and by individually twisting, stretching and bending the blocks, variations of the melodic, harmonic and rhythmic content are introduced. Software tools are made available to program the musical segments and govern SoundStrand's behavior. Additional work, namely the Coda system, is presented in order to put SoundStrand and the described paradigm in a wider context as tools for music sharing and learning.
by Eyal Shahar.
S.M.
49
Yao, Miao. « Exploiting Spatial Degrees-of-Freedom for Energy-Efficient Next Generation Cellular Systems ». Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77402.
Texte intégralRésumé :
This research addresses green communication issues, including energy efficiency, peak-to-average power ratio (PAPR) reduction and power amplifier (PA) linearization. Green communication is expected to be a primary goal in next generation cellular systems because it promises to reduce operating costs.
The first key issue is energy efficiency of distributed antenna systems (DASs). The power consumption of high power amplifiers (HPAs) used in wireless communication systems is determined by the transmit power and drain efficiency. For unequal power allocation of orthogonal frequency division multiplexing (OFDM), the drain efficiency of the PA is determined by the PAPR and hence by the power distribution. This research proposes a PAPR-aware energy-efficient resource allocation scheme for joint orthogonal frequency division multiple access (OFDMA)/space division multiple access (SDMA) downlink transmission from DASs. Grouping-based SDMA is applied to exploit the spatial diversity while avoiding performance degradation from correlated channels. The developed scheme considers the impact of both system data rate and effective power consumption on the PAPR during resource allocation. We also present a suboptimal joint subcarrier and power allocation algorithm to facilitate implementation of power-efficient multi-channel wireless communications. By solving Karush-Kuhn-Tucker conditions, a closed-form solution for the power allocation of each remote radio head is obtained.
The second key issue is related with PAPR reduction in the massive multiple-input multiple-output (MIMO) systems. The large number of PAs in next generation massive MIMO cellular communication system requires using inexpensive PAs at the base station to keep array cost reasonable. Large-scale multiuser (MU) MIMO systems can provide extra spatial degrees-of-freedom (DoFs) for PAPR reduction. This work applies both recurrent neural network (RNN)- and semidefinite relaxation (SDR)-based schemes for different purposes to reduce PAPR. The highly parallel structure of RNN is proposed in this work to address the issues of scalability and stringent requirements on computational times in PAPR-aware precoding problem. An SDR-based framework is proposed to reduce PAPR that accommodates channel uncertainties and intercell coordination. Both of the proposed structures reduce linearity requirements and enable the use of lower cost RF components for large-scale MU-MIMO-OFDM downlink.
The third key issue is digital predistortion (DPD) in the massive MIMO systems. The primary source of nonlinear distortion in wireless transmitters is the PA, which is commonly modeled using polynomials. Conventional DPD schemes use high-order polynomials to accurately approximate and compensate for the nonlinearity of the PA. This is impractical for scaling to tens or hundreds of PAs in massive MIMO systems. This work therefore proposes a scalable DPD method, achieved by exploiting massive DoFs of next generation front ends. We propose a novel indirect learning structure which adapts the channel and PA distortion iteratively by cascading adaptive zero-forcing precoding and DPD. Experimental results show that over 70% of computational complexity is saved for the proposed solution, it is shown that a 3rd order polynomial with the new solution achieves the same performance as the conventional DPD using 11th order polynomial for a 100x10 massive MIMO configuration.Ph. D.
50
Trout, Joseph Ewell. « Trajectory Tracking of a Statically-stable Biped with Two Degrees of Freedom ». Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/9647.
Texte intégralRésumé :
This research investigates the possibility of controlling a simple biped having two degrees of freedom only. The biped robot walked on large feet. Having large feet enabled the robot to stand on one leg stably. At any time, the robotà Âs center of gravity remained above the area covered by one of the feet. Two servos actuated the two degrees of freedom tilting the robot to the side or moving the legs forward and backward. The biped moved by alternately tilting and striding. Turns were produced by dragging the feet along the ground. As the feet dragged, the friction generated under the feet created a turning moment that rotated the robot. Thus, the robot was able to step and turn on a flat surface. A control algorithm was developed to attempt trajectory tracking with the biped. Trajectories along a surface can be defined in terms of linear and angular velocities. In this research, it was assumed that a high level controller had transformed a desired trajectory into discrete steps of linear and angular velocities. Motion tests showed how various settings of the servos affected the step length and turning angle of the robot. To produce the desired velocities, a program was created to select the servo commands and set the speed parameters. This program applied knowledge of the expected step length and turning angle and performed feedforward control of the velocities. This investigation identified a trajectory tracking scheme that could be used in an observer feedback scenario to achieve accurate control.Master of Science