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1
Adhynugraha, Muhammad Ilham. "Longitudinal dynamics of wing in ground effect craft in waves." Thesis, Cranfield University, 2017. http://dspace.lib.cranfield.ac.uk/handle/1826/13095.
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An assessment of the longitudinal motion of a hybrid configuration called the aerodynamically alleviated marine vehicle (AAMV) with the presence of waves, is demonstrated in the thesis. The development of this type of vehicle requires a mathematical framework to characterise its dynamics with the influence of external forces due to the waves’ motion. An overview of the effect of waves towards the models of dynamics developed for wing in ground effect (WIGE) craft and high-speed marine vehicles (planing craft) is carried out. However, the overview only leads to a finding that the longitudinal stability of a lifting surface over wavy ground effect is not entirely established. Taking this fact into account, the analysis of the model is proposed for a WIGE craft configuration. A simplification is adopted considering heave motion only in the modelling of oscillation. The simplification is made to thoroughly capture the effect of oscillation toward dynamic stability of the vehicle. To support the model verification, a numerical simulation followed by a semi-empirical design method was adopted to produce aerodynamic data, both in two-dimensional and three-dimensional domains, respectively. The results show that the combination of underpinning parameters, i.e. ride height, frequency and amplitude of oscillation, remarkably influence the aerodynamics. The characteristics in aerodynamics affect the production of stability derivatives and eventually stability behaviour of the chosen configuration. Some patterns in the results are identified but there also some data that show the peculiarity. Thus further investigation is needed.
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Stephens, Joshua. "Longitudinal stability of effect sizes in educational research." Cleveland State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=csu1367322715.
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Fino, Peter C. "Longitudinal Locomotor and Postural Control Following Mild Traumatic Brain Injury." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/73775.
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Millions of people sustain a mild traumatic brain injury (concussion) each year. While most clinical signs and symptoms resolve within 7-10 days for the majority of typical concussions, some gait and balance tasks have shown abnormalities lasting beyond the resolution of clinical symptoms. These abnormalities can persist after athletes have been medically cleared for competition, yet the implications of such changes are unclear. Most prior research has examined straight gait and standard measures of balance, yet there is a lack of knowledge regarding potential persistent effects on non-straight maneuvers or on indicators of motor control variability or complexity. To expand the knowledge of post-concussion locomotor and postural changes, this investigation examined the recovery of recently concussed athletes longitudinally, over the course of one year, in three domains: 1) path selection and body kinematics during turning gait, 2) non-linear local dynamic stability during straight gait, and 3) postural control complexity during quiet standing. Compared to matched health controls, concussed athletes exhibited significant and persistent differences in turning kinematics, local dynamic stability, and postural complexity over the initial six weeks following injury. These motor differences may increase the risk of injury to concussed athletes who are cleared to return to play. Given the persistent nature of these effects, future clinical tests may benefit from incorporating gait assessments before returning athletes to competition. Future research should prospectively and longitudinally monitor locomotor and postural control in conjunction with structural and functional changes within the brain to better understand the pathophysiology of concussions and potential rehabilitation strategies.Ph. D.
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Camillo, Giannino Ponchio. "Longitudinal stability analysis and control of an airbreathing hypersonic vehicle." Instituto Tecnológico de Aeronáutica, 2014. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=3154.
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This work presents the open-loop stability analysis and an active control strategy for an airbreathing hypersonic vehicle. The 14-XB, a bidimensional flow airframe derived from the Brazilian 14-X Aerospace Hypersonic Vehicle, is adopted as study platform. In order to perform such analyses, a simulation mathematical model of the airframe longitudinal forces and moments is obtained using perfect gas equations, after considering the relevance of the real gas hypotheses for the expected Mach number range and verifying that the simpler formulation is sufficient. An all-moving horizontal tail is designed in order to enable the aircraft trimming. The horizontal tail design considered simple constraints based on static analysis, and the same gas equations as those used for the airframe study. In order to analyze the aircraft';s dynamic behavior, a Six-Degree-of-Freedom set of equations of motion considering a spherical, rotating Earth is presented in detail, and the necessary conditions to have adequate longitudinal trimming in this scenario are discussed. The open-loop stability of the 14-XB with the designed horizontal tail is assessed through eigenvalue analysis and numerical flight simulations with the horizontal tail fixed at a trim position. Having observed that the aircraft presents unstable long-term natural modes, an active control strategy is suggested in order to stabilize the vehicle and track a desired flight path angle, assuming that thrust is constant and the control surface is an all-moving horizontal tail. The suggested control structure presents pitch stability augmentation system and flight path angle compensator. Optimal gains are calculated using linear quadratic design, along with a gain-scheduling strategy based on simultaneous control design, and the resulting controller presents proper results.
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Lazarus, Sophie A. "Social network stability in borderline personality disorder: A longitudinal analysis." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1433783752.
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Dassanayake, Achala Viomy. "Machining dynamics and stability analysis in longitudinal turning involving workpiece whirling." Thesis, [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1817.
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Fortman, Tyler L. "A Longitudinal Study of the Stability of Hope in Late Adolescence." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1295288937.
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Cramond, Alexander J. "The Longitudinal Stability of Memory in Males with Autism Spectrum Disorder." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3284.
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Previous research has demonstrated mixed evidence on impaired memory functioning in autism spectrum disorder (ASD), with the only consensus that there appears to be much heterogeneity. In addition, no research to date has examined the stability of memory in ASD. This study examined the stability of memory function in ASD compared to typically developing age-matched controls. Participants were administered the Test of Memory and Learning (TOMAL) twice, three years apart, in an established longitudinal NIH-supported investigation of ASD. Based on available research contrasting memory development in healthy individuals versus those with ASD, it was hypothesized that memory performance in the control group would be stable across time and that, compared to the control group, the autism group would demonstrate less stable memory function as measured by the TOMAL. Repeated Measures ANOVA and Reliable Change Index calculations of TOMAL Index and Subtest scores largely supported these hypotheses. The control group remained stable across time on all TOMAL indices and the ASD group showed improvement on the Composite Memory Index, Verbal Memory Index, and Delayed Memory Index but not the Non Verbal Memory Index. Clinical and research implications are discussed.
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Leite, Nelson Paiva Oliveira, Leonardo Mauricio de Faria Lopes, and Fernando Walter. "The Design of an Application Used for Aircraft Stability Evaluation." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/605926.
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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, CaliforniaOne of the most important characteristics of an aircraft is its capability to return to its stable trimmed flight state after the occurrence of a disturbance or gust without the pilot intervention. The evaluation of such behavior, known as the aircraft stability, is divided into three sections: Lateral; Directional; and Longitudinal stabilities. The determination of the stability of an experimental aircraft requires the execution of a Flight Test Campaign (FTC). For the stability FTC the test bed should be equipped with a complete Flight Test Instrumentation (FTI) System which is typically composed by: a Pulse Code Modulation (PCM) Data Acquisition System (DAS); A sensor set; An airborne transmitter; and A data recorder. In the real-time operations, live data received over the Telemetry Link, that are processed, distributed and displayed at the Ground Telemetry System (GTS) enhances the FTC safety level and efficiency. The due to the lack of reliability, recorded data is retrieved in the post mission operations to allow the execution of data reduction analysis. This process is time consuming because recorded data has to be downloaded, converted to Engineering Units (EU), sliced, filtered and processed. The reason for the usage of this less efficient process relies in the fact that the real-time Telemetry data is less reliable as compared to recorded data (i.e. noisier). The upcoming iNET technology could provide a very reliable Telemetry Link. Therefore the data reduction analysis can be executed with live telemetry data in quasi-real time after the receipt of all valid tests points. In this sense the Brazilian Flight Test Group (GEEV) along with EMBRAER and with the support of Financiadora de Estudos e Projetos (FINEP) started the development of several applications. This paper presents the design of a tool used in the Longitudinal Static Stability Flight Tests Campaign. The application receives the Telemetry data over either a TCP/IP or a SCRAMnet Network, performs data analysis and test point validation in real time and when all points are gathered it performs the data reduction analysis and automatically creates Hyper Terminal Markup Language (HTML) formatted tests reports. The tool evaluation was executed with the instruction flights for the 2009 Brazilian Flight Test School (CEV). The result shows an efficiency gain for the overall FTC.
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Agenbag, Daniël Sarel. "Longitudinal handling characteristics of a tailless gull-wing aircraft." Pretoria : [s.n.], 2008. http://upetd.up.ac.za/thesis/available/etd-09182008-132941.
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Rossouw, Paul Emile. "A longitudinal study of the stability of the dentition following orthodontic treatment." Thesis, Stellenbosch : Stellenbosch University, 1992. http://hdl.handle.net/10019.1/70107.
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Thesis (PhD) -- Stellenbosch University , 1992.ENGLISH ABSTRACT: The maintenance of dental alignment following orthodontic treatment has been, and continues to be, a challenge for the orthodontist (McReynolds and Little, 1991). Orthodontists should endeavour to establish normal occlusions and function to the end that physiologic balance and retentive stability may be achieved (Goldstein, 1953). Many philosophies and theories have been formulated in response to this challenge, but few have successfully withstood the test of rigorous post-orthodontic evaluation. The present study comprises longitudinal assessments of dentofacial changes which occurred in South African Caucasian subjects during their orthodontic treatment as well as a mean of 7 years following active treatnent. The sample consists of 88 Caucasian subjects; 33 males and 55 female sUbjects who have undergone conventional edgewise orthodontic treatment (Lindquist; 1985). The treatment includes extraction (56%) and nonextraction (44%) therapy. Due to the intricate structure of the craniofacial complex, it is deemed important to discuss the major components of this complex separately and then to compare the variables describing the area with post-orthodontic lower incisor crowding. Lower incisor crowding or irregularity, most often referred to as relapse when occurring in the post-orthodontic dentition, is a phenom~non that is clinically visible and easily assessed using the Little Irregularity Index (Little, 1975). A variety of orthodontic study cast and cephalometric variables represent the changes which occur at the three time intervals selected for this study, namely pre-treatment (T1), post-treatment (T2) and following active treatment (T3). statistical analysis of th~ data was undertaken by the Institute for Biostatistics of the Medical Research Council, Tygerberg, RSA utilising the SAS (1985). The significance level of the results of this study is set at p = 0.05. x No previous study has documented the evaluated and described the various craniofacial skeleton in this format. literature parts or has of the The thesis is divided into thirteen chapters.
AFRIKAANSE OPSOMMING: Die instandhouding van tandbelyning na voltooiing van ortodontiese behandeling was en sal nag steeds in die toekoms 'n uitdaging bied vir ortodontiste (McReynolds en Little, 1991). Die ortodontis se strewe moet wees am 'n normale okkli'lsie in die ortodontiese pasient te veE)tig, waartydens die funksie van die kake herstel word, asook fisiologiese harmonie en stabiliteit van die okklusie gevestig ~lOrd (Goldstein, 1953) • Menige filosofiee en teoriee is al voorgestel om hierdie doelwitte te kan bereik, maar baie min het nag daarin geslaag. Tydens die huidige longitudinale studie is gepoog om In ondersoek te doen van die veranderinge wat plaasvind in die dentofasiale omgewing van agt-en-tagtig Suid-Afrikaanse Kaukasiese pasiente tydens hulle ortodontiese behandeling, asook na die verloop van 'n gemiddeld van sewe jaar sedert die behandeling voltooi was. Die monster het uit 33 manlike en 55 vroulike pasiente bestaan wat met 'n konvensionele vierkantsdraad ("edg~wise") ortodontiese tegniek behandel was (Lindquist, 1985). Die behandeling het 56% ekstraksie en 44% ni~-ekstraksie behandelingsbeplannings ingesluit. Weens die baie komplekse kraniofasiale omgewing is dit besluit am elke deel waaruit hierdie omgewing bestaan, afsonderlik te beskryf en te bespreek. Die veranderlikes wat elke deel beskryf is vervolgens gekorreleer met die na-behandelings ondersnytand-bondeling. Ondersnytandbondeling is 'n verskynsel wat klinies sigbaar is en meestal na verwys word as terugval indien dit voorkom in die na-behandelings resultaat. Dit kan maklik gemeet word met behulp van die "Little Irregularity Index" (Little, 1975). 'n Verskeidenheid van ortodontiese studiemodelle en kefalometrie~Je verander.likes is tydens die voor-behandelings (T1), na-behandelings (T2) asook na verloop van 'n gemidd.eld van sewe jaar na afhandeling van die behandeling (T3) gemeet. Die statistiese verwerkinge is deuI' die Institu,ut vir Biostatistiek van die Mediese Navorsingsraad, Tygerberg, R.S.A. gedoen deur middel van die SAS (1985). Die betekenisvolheidsperk van die studie is op P = 0.05 gestel. Geen studie het al voorheen die literatuur gedefineerde areas van die kranio-fasiale skelet formaat ondersoek of be~kryf nie. Die proefskrif bestaan uit dertien hoofstukke.
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Iyer, Priyanka. "Stability of the Oral Microbiome in Children - A Six Month Longitudinal Study." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469201519.
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Jermann, Cyril. "Eclatement tourbillonnaire dans le sillage turbulent d'un véhicule générique." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4340/document.
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La thèse est une contribution à l’étude des tourbillons longitudinaux qui se développent sur la lunette arrière des véhicules automobiles, dans l’idée de provoquer leur éclatement afin de réduire la traînée aérodynamique. On conçoit tout d’abord un système d’acquisition dénommé A-SPIV, permettant de reconstruire le champ moyen de vitesse 3D d’un sillage turbulent à partir de plans stéréo-PIV acquis par translation du système caméras-laser, sans qu’il soit nécessaire de le recalibrer. En complément, on propose une méthode de reconstruction de la pression moyenne reposant sur les données A-SPIV et sur une mesure de la pression pariétale. L’ensemble forme un nouveau protocole expérimental, validé dans le sillage d’un corps d’Ahmed 25° et dont les résultats à haut Reynolds sont comparés à la littérature existante. L'analyse topologique des tourbillons longitudinaux suggère l’existence d’un éclatement tourbillonnaire spontané dans le sillage proche, malgré l’absence de point de stagnation. On démontre formellement l’existence de cet éclatement par deux critères théoriques qui considèrent ce phénomène, soit comme la conséquence d’une réorganisation de la vorticité, soit comme la résultante d’une accumulation, en un point critique, d’ondes inertielles se propageant le long du tourbillon. Les analyses sous-jacentes sont menées dans un repère cylindrique attaché à l’axe tourbillonnaire et prédisent une même position d’éclatement, en bon accord avec la position singulière issue des mesures A-SPIV. La thèse se conclut par une analyse de stabilité globale de l'écoulement moyen qui suggère un lien possible entre l’éclatement et une instabilité globale de l’écoulement tourbillonnaireThis thesis is a contribution to the study of the longitudinal vortices developing in the near wake of ground vehicles, with the general purpose of reducing the aerodynamic drag by triggering the vortex breakdown phenomenon. We present a new data acquisition system called A-SPIV, allowing to reconstruct a 3D turbulent time-averaged velocity field from stereo-PIV planes measured by translation of the whole cameras-laser system, with no need to recalibrate. We also propose a method to reconstruct the mean pressure in the bulk from the A-SPIV data and from a dedicated wall static pressure measurement. This new overall experimental protocol is applied to a standard aerodynamic test-case, the 25° Ahmed body, all results being compared and validated at high turbulent Reynolds number against existing data from the literature. A thorough analysis of the longitudinal vortices suggests the occurrence of a spontaneous vortex breakdown in the near-wake, although there exist no stagnation point in the experimental data. Such vortex breakdown is therefore evidenced using two different theoretical criteria considering the phenomenon as the consequence of either a reorganization of the vorticity, or an accumulation of inertial waves propagating along the vortex core. The underlying analyses are carried out in a cylindrical system attached to the vortex axis and predict a single breakdown position, in good agreement with the singular position initially inferred from the A-SPIV data. The thesis ends with a global stability analysis of the turbulent mean flow suggesting a possible connection between the occurrence of vortex breakdown and a global instability of the longitudinal vortex
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Vu, Alexander. "Sluggish Cognitve Tempo: Stability, Validity, and Heritability." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1446570242.
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Page, Kyle S. "Fear of Alzheimer's Disease in Middle to Late Adulthood: a Two Year Investigation of Change Versus Stability." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc283854/.
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The term dementia refers to a progressive decline in cognitive functioning resulting in a significant impairment in daily living. Given the devastating impacts of the disease and lack of a cure, it is reasonable to expect people fear developing a dementia. Alzheimer's disease ranks high among the most feared diseases in national samples of the American population. As a topic of study, little is known about the determinants of fear of Alzheimer's disease and how this fear may change as a function of aging, time, or experience. The current study sought to fill this gap by investigating the nature of changes in fear of Alzheimer's disease by following participants (N = 227) over the course of two years. Volunteers completed measures on fear of dementia, knowledge about Alzheimer's disease, knowledge about the aging process, personality traits, memory self-efficacy, anxiety about aging, and Alzheimer's-related experiences (i.e., family history, caregiving experience, number of people known with the disease, personal diagnosis, etc.). Results supported the notion that fear for becoming a burden to others, a component of fear of dementia, decreased over the two years. In addition, personality traits and memory self-efficacy mediated the two-year change in concerns about perceived symptoms of cognitive decline. In predicting fear for various aspects of Alzheimer's disease, anxiety about aging and experience/exposure to the disease emerged as prominent predictors. These results highlight dementia concerns and offer guidance for early interventions, such as an open communication with family and health care providers about fear of dementia.
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Pudas, Sara. "Brain characteristics of memory decline and stability in aging : Contributions from longitudinal observations." Doctoral thesis, Stockholms universitet, Psykologiska institutionen, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-93026.
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Aging is typically associated with declining mental abilities, most prominent for some forms of memory. There are, however, large inter-individual differences within the older population. Some people experience rapid decline whereas others seem almost spared from any adverse effects of aging. This thesis examined the neural underpinnings of such individual differences by using longitudinal observations of episodic memory change across 15-20 years, combined with structural and functional magnetic resonance imaging of the brain. Study I found significant correlations between volume and activity of the hippocampus (HC), and memory change over a 6-year period. That is, individuals with decline in HC function also had declining memory. In contrast, Study II showed that successfully aged individuals, who maintained high memory scores over 15-20 years, had preserved HC function compared to age-matched elderly with average memory change. The successful agers had HC activity levels comparable to those of young individuals, as well as higher frontal activity. Study III revealed that individual differences in memory ability and brain activity of elderly reflect both differential age-related changes, and individual differences in memory ability that are present already in midlife, when age effects are minimal. Specifically, memory scores obtained 15-20 years earlier reliably predicted brain activity in memory-relevant regions such as the frontal cortex and HC. This observation challenges results from previous cross-sectional aging studies that did not consider individual differences in cognitive ability from youth. Collectively the three studies implicate HC and frontal cortex function behind heterogeneity in cognitive aging, both substantiating and qualifying previous results from cross-sectional studies. More generally, the findings highlight the importance of longitudinal estimates of cognitive change for fully understanding the mechanisms of neurocognitive aging.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
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Dulisse, Brandon C. "Does Stickiness Matter?A Longitudinal Examination of the Stability of Adolescent Peer Groups." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439282030.
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Kilkenny, E. A. "An experimental study of the longitudinal aerodynamic and static stability characteristics of hang gliders." Thesis, Cranfield University, 1986. http://dspace.lib.cranfield.ac.uk/handle/1826/11096.
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A mobile experimental test facility has been developed to carry
out the aerodynamic evaluation of hang glider wings normally performed
in a wind tunnel.
Longitudinal aerodynamic data obtained using this facility is
presented for three modern hang glider wings, a Silhouette, Demon 175
and Magic 166, together with surface flow patterns for the latter two
wings.
The longitudinal stability criterion are studied and alternatives
established, equivalent to the stick fixed and stick free criterion for
conventional aircraft, relevant to weight shift controlled wings. These
are based on the pilot's position and control force to trim.
The aerodynamic data obtained from the mobile facility is used to
calculate these parameters and the longitudinal static stability of each
wing is examined.
The influence of several rigging parameters, variable by the pilot
before flight, on the longitudinal static stability and control of the
hang glider are also investigated.
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Mazon, Didier. "Etude de la stabilité linéaire du mode acoustique longitudinal d'un propulseur à propergol solide." Aix-Marseille 1, 1996. http://www.theses.fr/1996AIX11076.
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Cette these est consacree a l'etude de la stabilite lineaire du mode acoustique longitudinal d'un propulseur a propergol solide. L'objectif est d'obtenir l'expression analytique du taux d'amortissement lineaire par les mecanismes stabilisants et d'identifier en particulier l'effet de l'ecoulement stationnaire. L'etude considere la dissipation moleculaire ainsi que la reponse instationnaire de la combustion et de la tuyere aux fluctuations de pression. L'analyse physique du probleme revele differents regimes classes suivant la valeur de la frequence acoustique. Pour les hautes et moyennes frequences, les modes acoustiques presentent un cisaillement de courte longueur d'onde, localise dans une couche limite pres de la paroi debitante. Pour les basses frequences, l'oscillation envahit toute la chambre. L'etude du regime intermediaire montre que la viscosite disparait de l'expression finale du taux d'amortissement par dissipation visqueuse. De plus, le bilan d'energie, effectue hors de la couche limite, met en evidence un mecanisme non dissipatif, represente par le tenseur du taux de deformation de l'ecoulement de base. Sa contribution au taux d'amortissement est du meme ordre de grandeur que celle apportee par la dissipation visqueuse ou par la tuyere (proportionnelle a la vitesse de combustion divisee par le rayon de la chambre). Le chapitre 2 traite de la resolution analytique du cas monophasique par des methodes de perturbations systematiques (echelles multiples et/ou developpements asymptotiques raccordes). Les resultats obtenus pour le domaine des frequences intermediaires montrent le role respectif des mecanismes d'amortissements, dissipatifs ou non. Pour les basses frequences, l'expression du taux d'amortissement reste le meme et les mecanismes sont identiques. Le chapitre 3 prend en compte l'amortissement supplementaire produit par des particules d'alumine en suspension dans les gaz brules. L'effet du cisaillement n'influence pas le resultat du taux d'amortissement par les particules qui reste egal a celui obtenu pour un mode acoustique longitudinal dans un milieu au repos
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Allievi, Alejandro. "Experimental and numerical analysis of a fishing vessel motions and stability in a longitudinal seaway." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26680.
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Motions and stability of a typical B.C. fishing vessel were experimentally and numerically investigated in a longitudinal seaway condition. The experimental model was self-propelled, radio-controlled and equipped with an on-board data acquisition system. Pitch, roll, yaw, surge, and heave responses to regular waves of predetermined frequencies and amplitudes generated along a 220-ft model basin were obtained. Different displacement conditions and GM configurations were tested.
The numerical model for the dynamic analysis of the fishing vessel motions has been implemented using strip theory. A computer program was developed to study the nonlinear motions of the vessel. The velocity dependent coupling terms, responsible for a major part of the nonlinear behavior, were included. A time dependent component analysis of the roll damping has been performed. Regular linear and nonlinear waves were used.
A parametric study of the fishing vessel stability has been carried out by considering its dynamic response in waves of varying characteristics. Unstable behaviour was found to be closely related to waves of length of similar magnitude to the ship length. The effects of wave amplitude and rudder usage were found to be of capital importance in the capsizing process. Experimental and numerical results showed good agreement.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Parker, Richard J. "Closeness and Conflict in Children’s Friendships: Relations with Friendship Stability, Adjustment and Sociometric Status." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19847.
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Not many children report relationships with friends that are both close and conflictual. There is a paucity of research examining the trajectory of children's relationship closeness and conflict together over time. This is unfortunate because contentious relationships are related to cardiovascular problems, at least in young adults and because the trajectories of these two aspects of children's relationship quality over time is not understood. Therefore, two longitudinal data sets with younger (mean age 7.5 years at Time 1; four data points over 2 years) and older (mean age 9.9 years at Time 1; two data points over 1 year) children were studied. In both cohorts, measures of friendship quality and peer nominations of liking/disliking as well as overt and relational (older cohort) aggression were completed. Children who reported relationships high in both closeness and conflict were generally satisfied with their friendships; they were not more likely to end their friendships than were children who reported different levels of closeness and conflict (younger cohort). Both boys' and girls' relationship closeness increased over time according to growth curve analyses. The relationships of girls who remained in the same friendship, and who therefore provided ratings on the same friend at each time point, tended to increase in closeness at a different rate over time than the relationships of girls who provided ratings on different friends (younger cohort). Children who reported relationships high in closeness and in conflict were not more aggressive over time than were children who reported different levels of relationship closeness and conflict. However, girls' closeness and overt aggression tracked each other (increased) over time (younger cohort). Girls who reported low social support and negative interactions in their friendships increased the most in overt aggression over time (older cohort). Aggressive and nonaggressive children generally reported similar friendship quality (both cohorts), but the friendship closeness of chronically aggressive boys decreased over time (younger cohort). There were negligible friendship quality differences amongst the sociometric groups. The discussion centers on friendship quality changes in children's continuing friendships, the potential dire effects of turbulent friendships and the friendships of aggressive as well as controversial children.
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Arnold, J. M. "Change and stability in occupational self-concepts amongst students and recent graduates : A longitudinal study." Thesis, University of Sheffield, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383511.
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Herritsch, Alfred. "Investigations on Wood Stability and Related Properties of Radiata Pine." Thesis, University of Canterbury. Chemical and Process Engineering, 2007. http://hdl.handle.net/10092/1203.
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Previous studies on wood instability have identified some wood basic properties which influence the timber distortion and shape changes while the wood is losing or gaining moisture. These properties include wood anisotropic shrinkage, equilibrium moisture content (EMC) in both desorption and adsorption, fibre saturation point (FSP) and water diffusion coefficient. This study investigated the stability related wood properties and their variations within the stems of the New Zealand grown radiata pine trees. The basic density, EMC and shrinkage for the earlywood and the latewood were also experimentally determined. In taking into account these properties and their variations, an analytical model was developed to simulate the wood distortion. The equilibrium moisture content was determined at 30°C and humidity range from 27% to 90%. It was found that the EMC difference between the earlywood and the latewood was negligible. The experimental results also show that the EMC decreases from pith towards the bark over the disc cross section and the trend is most obvious at high humidities (70-90%). Along the tree height, the EMC decreases from ground towards the top of the stem. The tangential shrinkage results were highly variable but, in general, the latewood has higher values than the earlywood. The opposite trend was found for the longitudinal shrinkage, higher values for the earlywood than the latewood. In the tree height direction, the tangential shrinkage was found to decrease with the tree height. This follows the same trend as the microfibril angle which in general also decreases with the tree height. The fibre saturation point (FSP) was determined from the tangential shrinkage values at different equilibrium moisture contents. These were taken as the intersection point of the tangential shrinkage line with the moisture content axis. The experimental results have revealed a trend that the FSP decreases from the pith towards the bark and also decreases with the tree height. Similar behaviour was found for the tangential and longitudinal swelling during the adsorption. The moisture transport within radiata pine was investigated based on the diffusion theory under transient and isothermal condition of 30°C. The moisture dependant diffusion coefficient was derived from the experimental data using the inverse analysis method. The surface emission coefficient was determined by taking into account the variable surface moisture content, wood density and the ambient conditions. In the experiments, 138 samples in total (46 samples for each XIV of the longitudinal, tangential and radial directions) were used and their diffusion coefficients were determined for both the adsorption and the desorption with moisture content ranging from 6% to 22%. The derived diffusion coefficients are comparable with the reported data in the literature. Further investigation of the wood type influence on the diffusion coefficient revealed that compression wood has the lowest diffusion coefficients in the three directions (longitudinal, tangential and radial) both in the desorption and in the adsorption. In addition, the moisture content has the least influence on the diffusion coefficient in the compression wood. Investigation on the effects of the wood density has shown that in general, the diffusion coefficient decreases with increasing wood density although the correlations are only significant for the longitudinal direction in desorption. An analytical model for the simulation of the wood twist was developed which is based on the geometry and geometrical changes of the grains aligning non parallel to the pith. A board consists of numerous such grains which change the length and shape with moisture content change. The model predictions confirm that the grain angle, the tangential and longitudinal shrinkage and the conical angle all affect the development of the board twist. However, the discrepancies between the model prediction and the experimental data are significant, partly due to the experimental uncertainties and partly due to the model errors. In this study, sound velocity in the longitudinal direction was measured for the test samples used in the shrinkage experiments. The results revealed that the correlations between the sound velocity and the volumetric shrinkage at oven dry are significant. Based on this finding, the relationship between the tangential shrinkage and the radial shrinkage, the tangential shrinkage can be predicted from the sound velocity measurements. As the tangential shrinkage has significant influence on the wood distortion, this method can be used to segregate logs which may be prone to wood distortion.
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Eriksson, Monica. "Recovery from an Acute Myocardial Infarction : A Longitudinal Study of Couples." Doctoral thesis, Mittuniversitetet, Institutionen för hälsovetenskap, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-12120.
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The overall aim of this thesis was to investigate recovery in the relationshipbetween couples following an acute myocardial infarction [AMI]. An additionalaim was to compare differences over time regarding hope and health‐relatedquality of life [HRQoL] for both patient and partner. The thesis is based on fourempirical studies (I‐IV), and has a longitudinal design employing both qualitativeand quantitative methods. A purposive sample was recruited comprising 15couples in which one partner had been diagnosed with an AMI. Study I wascarried out as individual tape‐recorded interviews aimed at describing thepatient´s and their partner´s experiences after hospital discharge. Study II alsoused individual tape‐recorded interviews, this time with the aim of describing andinterpreting the couple´s thoughts and expectations about their future life after thepatients’ discharge. Study III used the HHI‐S and SF‐36 measures to comparechanges over time in self‐rated hope and health‐related quality of life, anddifferences between patients’ ratings and their partner´s. Study IV used repeatedindividual tape‐recorded interviews with the aim of interpreting the couples´narratives about their relationship and daily life. The data were analysed andinterpreted using a number of qualitative content analysis methods (I, II, IV) anddescriptive and comparative statistics (III).Overall, the couples´ recovery from an AMI in the two years after an AMI consisted of a striving to reach some kind of balance and stability in their currentlife situation. The period after discharge from the hospital involved understandingthe importance of the home as a place in which one feels at home and which bringsa feeling of safety, experiencing the phenomenon of security and being at homewithin oneself, and seeking normalisation in returning to an ordinary life (I). Thecouples´ thoughts about their future lives were either optimistic, taking an activeapproach, or pessimistic, taking a wait‐and‐see approach. The couples could bedivided into four positions in terms of their visions of the future: life companions,who were in concordance regarding their future; tightrope walkers, who had incommon a need to reprioritise what they considered important in their future;pathfinders, who had in common an undefined vision of their future and observers, who saw their future including both physical as well as sociallimitations (II). Self‐rated hope and HRQoL both improved over time, but few ofthese improvements were statistically significant, and I found no statistically groupeffects. Estimation of the MDC index revealed that neither HHI‐S nor SF‐36measures stable traits (III). Finally, the repeated interviews revealed how thecouples viewed their daily life, mutual relationships and roles in their relationshipVIIover time. There was an abundant variation in a number of the couples´ storiesabout their relationship and daily life during the recovery period (IV).In conclusion, it is clear that what happen to one party in a relationship influencesthe other party. The couples in the studies showed improvements in both hope andhealth‐related quality of life over time. The HHI‐S and SF‐36 measures seemed tobe sensitive to and affected by the current situation. Going through an AMI is alife‐changing event that makes it necessary for the couple to make adjustments andadapt to their new situation. Different couples have different approaches tohandling this situation; no two couples are the same, and every couple willperceive and deal with the AMI differently. An AMI starts a process of transition,and over time a couple affected by AMI will undergo external as well as internal changes.Avhandlingens övergripande syfte var att undersöka återhämtning i parrelation efter hjärtinfarkt. Ett ytterligare syfte var att jämföra skillnader avseende hopp och hälsorelaterad livskvalitet över tid men också emellan patienter och deras partners.Avhandlingen baseras på fyra delstudier (I‐IV), och har en longitudinal designmed både kvalitativa och kvantitativa metoder. Ett ändamålsenligt urval av 15 par rekryterades där en i parrelationen diagnostiserats med akut hjärtinfarkt. DelstudieI genomfördes med individuella bandinspelade intervjuer med syfte att beskrivapatienter och deras partners erfarenheter efter utskrivning från sjukhus eftergenomgången hjärtinfarkt. Delstudie II använde också individuella bandinspelade intervjuer, den här gången med syfte att beskriva och tolka parens tankar ochförväntningar kring deras framtid efter att patienten skrivits ut från sjukhus.Delstudie III använde instrumenten HHI‐S och SF‐36 för att jämföra skillnader av självskattat hopp och hälsorelaterad livskvalitet över tid och emellan patienter och deras partners. Delstudie IV använde upprepade bandinspelade intervjuer medsyfte att tolka parens berättelser kring deras relation och det dagliga livet. Data haranalyserats och tolkats med kvalitativ innehållsanalys på olika sätt (I,II,IV) ochmed såväl deskriptiv som jämförande statistik (III).Avhandlingen visar att parens återhämtning efter hjärtinfarkt under en period avtvå år omfattar en strävan efter att uppnå någon form av balans och stabilitet i denrådande livssituationen. Perioden efter utskrivning från sjukhus innebar enförståelse för hur viktigt hemmet är som plats för att känna sig hemma eller för att skapa en känsla av trygghet samt erfarenheter av fenomenet trygghet och attkänna sig hemma i sig själv. Slutligen sökte paren efter normalisering för att återkomma till det vanliga livet (I). Parens tankar kring deras framtid var antingenoptimistisk, en aktiv inställning, eller pessimistisk, en vänta ‐ och ‐ se inställning.Paren kunde också grupperas i fyra positioner som beskrev deras visioner omframtiden. De som kallades livskamrater syntes vara i samklang vad gällde återhämtning, balanskonstnärerna hade gemensamt ett behov av att omprioriter a vad som var viktigt för framtiden, de som var gemensamt för de som kallades stigfinnare var deras odefinierade/oklara bild av framtiden och slutligenobservatörerna såg sin framtid omfatta såväl fysiska som sociala begränsningar(II). Både självrapporterat hopp och hälsorelaterad livskvalitet förbättrades övertid, men få av dem var statistiskt signifikanta och inga statistiska gruppeffekterhittades. Beräkning av MDC index visade att varken HHI‐S eller SF‐36 mäterstabila dimensioner (III). Slutligen visade de upprepade intervjuerna hur paren sågpå dagligt liv, den inbördes relationen och roller i relationen över tid. Det fanns enIXrikedom av variationer i parens berättelser om deras relation och det dagliga livetunder återhämtningsprocessen (IV).Till sist framträder det klart att det som händer den ene i relationen fårkonsekvenser för den andre. Paren i studierna visade på att det skeddeförbättringar vad gäller både hopp och hälsorelaterad livskvalitet över tid. BådeHHI‐S och SF‐36 är instrument som synes vara känsliga för och påverkade av denrådande situationen. Att gå igenom en hjärtinfarkt är en livsavgörande händelsesom fodrar att paren ställer in sig på och gör anpassningar till en ny situation.Paren har dock olika sätt att handskas med den nya situationen och det finns intetvå par som är lika, och inte heller uppfattar och hanterar de hjärtinfarkten i vardagen och i relationen på samma sätt. En hjärtinfarkt startar en transitionsprocess och över tid genomgår paren såväl yttre som inre förändringar.
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Dibble, Ashley. "Antisocial Behavior from Adolescence to Early Adulthood: Heritability, Stability, and Correlates using a Longitudinal Twin Sample." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3025.
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The purpose of this study was to examine the heritability, stability, and outcomes of antisocial behavior from adolescence into adulthood in a longitudinal twin sample. Specifically, the genetic and environmental influences on conduct disorder, adult antisocial behavior, and alcohol dependence were examined. The influence of genes and environment on the relationship between these disorders was also examined. The study utilized a subset of FinnTwin12, a population-based twin study that consists of five consecutive birth cohorts. The subsample consisted of 1035 twin pairs (N = 2070) and of that 2070, 1854 completed the intensive interview at age 14. At age 22, 1345 twins completed the interview. Participants in the study completed age-appropriate variations of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA). Analyses were run separately by gender. Results provide support for the significant influence of genetic factors on the development and persistence of antisocial behavior. For both males and females, model fitting indicated that genetic influences are the most influential contributor to the association between conduct disorder and adult antisocial behavior and its stability across time. Additionally, there were no age specific genetic effects suggesting that the genes influencing conduct disorder are the same as those influencing adult antisocial behavior. Results for the relationship between conduct disorder and alcohol dependence differed by gender. For females, insufficient power made it difficult for the model to discriminate between the effects of genetics and shared environment, but the full model suggested that shared environmental influences explained the greatest proportion of variance in the relationship. For males, genetic influences were primarily responsible for the relationship between conduct disorder and alcohol dependence. Similar results were found for males when the relationship between alcohol dependence and adult antisocial behavior was explored. For females, genetic and nonshared environmental influences were the primary source of covariation between these two disorders. The data suggest that the etiology of conduct disorder, adult antisocial behavior, and alcohol dependence vary by gender.
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Long, Jacob Andrew. "Time Dynamics and Stability of Political Identity and Political Communication." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595519865595447.
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Melis, Gabriella. "Attitudes to authority : life-course stability, intergenerational transmission, and socio-psychological mechanisms in the British Cohort Study 1970." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/attitudes-to-authority-lifecourse-stability-intergenerational-transmission-and-sociopsychological-mechanisms-in-the-british-cohort-study-1970(f91f6734-e247-4fd1-926f-37b52f3ffa3e).html.
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My PhD work aimed to assess intergenerational transmission and life-course change of attitudes towards authority. Intergenerational transmission is hypothesised as the mechanism through which parents' authoritarian attitudes affect their children's attitudes towards authority in adulthood. In the assessment of this transmission mechanism, this analysis accounts for individual-level theoretically relevant factors such as gender, education, social class, offspring's cognitive ability in childhood, as well as family background, in a longitudinal, single-cohort perspective. The research used the British Cohort Study 1970 (BCS70), which allows for the analysis of change at both the intra- and inter-individual levels. The sweeps analysed are those in years 1975 for the parents, and 1980, 1996, 2000 and 2012 for the cohort members. The analytical chapters of the thesis are made of three papers: The first assessed change (or stability) in attitudes to authority in the BCS70 from 1996 to 2012; the second looked at how parental authoritarian worldviews affect their children's attitudes towards authority when the children are adults; finally, the third paper aimed to evaluate the effect of parental attitudes on cohort members' attitudes towards authority in adulthood, after controlling for the latter's cognitive ability in childhood. I found that attitudes had a reasonably high level of stability across the life course. Despite moderately strong correlations across attitudes within waves, the different attitudes showed different patterns of longitudinal evolution, suggesting different causal influences. The evidence for direct transmission of attitudes from parents to children was surprisingly weak; the social statuses of the parents and cohort members, and especially the members' childhood cognitive ability, were the strongest predictors of authoritarian attitudes in adulthood.
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Fogelqvist, Maria, and Michaela Andersson. "Vilka faktorer predicerar stabilitet och förändring av snedvriden kroppsuppfattning över tid bland gymnasieungdomar? : -en longitudinell studie." Thesis, Örebro universitet, Akademin för juridik, psykologi och socialt arbete, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-11075.
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Hur en individ uppfattar sin kropp har relaterats till självkänsla, fysisk aktivitet, matvanor, social ångest och mobbning. Studier som undersöker utvecklandet av kroppsuppfattning och riskfaktorer för snedvriden kroppsuppfattning efterfrågas. Denna longitudinella studies huvudsyfte var att undersöka om kroppsuppfattningen hos gymnasieungdomar (n=349) förändras över tid och hur det såg ut för tjejer respektive killar. Vidare undersöktes riskfaktorer för utveckling av snedvriden kroppsuppfattning. Resultatet visade stabilitet i utvecklingsmönster av snedvriden kroppsuppfattning över tid. Snedvriden kroppsuppfattning verkar redan ha befästs innan gymnasietiden. För killarna fanns ett statistiskt samband mellan social ångest och mobbning i utvecklingen av snedvriden kroppsuppfattning. Slutsatsen är därmed att killars förmåga att hävda sig i interpersonella sammanhang kan påverka kroppsuppfattningen. Skolan bör eftersträva ett tillåtande klimat och aktivt arbeta mot mobbning.
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Caliskan, Sevinc. "Development Of Forward Flight Trim And Longitudinal Dynamic Stability Codes And Their Application To A Uh-60 Helicopter." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610391/index.pdf.
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This thesis describes the development of a series of codes for trim and longitudinal stability analysis of a helicopter in forward flight. In general, particular use of these codes can be made for parametric investigation of the effects of the external and internal systems integrated to UH-60 helicopters. However, in this thesis the trim analysis results are obtained for a clean UH-60 configuration and the results are compared with the flight test data that were acquired by ASELSAN, Inc.
The first of the developed trim codes, called TRIM-CF, is based on closedform equations which give the opportunity of having quick results. The second code stems from the trim code of Prouty. That code is modified and improved during the course of this study based on the theories outlined in [3], and the resultant code is named TRIM-BE. These two trim codes are verified by solving the trim conditions of the example helicopter of [3]. Since it is simpler and requires fewer input parameters, it is more often more convenient to use the TRIM-CF code. This code is also verified by analyzing the Bo105 helicopter with the specifications given in [2]. The results are
compared with the Helisim results and flight test data given in this reference. The trim analysis results of UH-60 helicopter are obtained by the TRIM-CF code and compared with flight test data.
A forward flight longitudinal dynamic stability code, called DYNA-STAB, is also developed in the thesis. This code also uses the methods presented in [3]. It solves the longitudinal part of the whole coupled matrix of equations of motion of a helicopter in forward flight. The coupling is eliminated by
linearization. The trim analysis results are used as inputs to the dynamic stability code and the dynamic stability characteristics of a forward flight trim case of the example helicopter [3] are analyzed. The forward flight stability
code is applied to UH-60 helicopter.
The codes are easily applicable to a helicopter equipped with external stores. The application procedures are also explained in this thesis.
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Richier, Mathieu. "Conception de dispositifs actifs de maintien de stabilité pour les véhicules évoluant en milieux naturels." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2013. http://tel.archives-ouvertes.fr/tel-01066614.
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La problématique de cette thèse réside dans la caractérisation et le maintien de la stabilité des Véhicules Légers Tout Terrain (VLTT). Elle se concentre plus particulièrement sur le développement de systèmes de sécurité actifs capables à la fois de prévenir le conducteur des risques encourus mais aussi de les limiter afin d'assurer l'évolution du véhicule dans une zone de stabilité prédéfinie. Comme le cadre expérimental privilégié est l'application à la stabilité des quadricycles légers à moteurs, plus connus sous le terme anglophone "quad", une des contraintes du projet a été de se limiter à un système sensoriel bas-coût afin d'être en mesure d'industrialiser un tel système. En premier lieu, les métriques de stabilité (Transfert de Charge Latéral et Longitudinal : TCLa et TCLo) ont été choisies grâce à une étude préliminaire sur la stabilité des VLTT. Par la suite, une modélisation 2D en roulis et en tangage avec la prise en compte des déplacements du pilote sur le véhicule sont présentées, ce qui permet d'estimer respectivement le TCLa et le TCLo uniquement à partir de la mesure de l'accélération latérale et longitudinale. Étant donné que pour la suite des travaux, l'anticipation du risque de renversement latéral est nécessaire, un modèle 2D en lacet du véhicule est proposé afin d'obtenir un modèle analytique décrivant la dynamique latérale du véhicule. La suite du mémoire présente les différentes techniques d'observation proposées pour l'estimation des variables et paramètres non-directement mesurables du modèle en lacet du véhicule et qui influencent sa stabilité latérale : les glissements, les conditions d'adhérence et les inclinaisons du véhicule. Plusieurs observateurs ont été proposés, dont le dernier permet de considérer des conditions d'adhérence différentes entre les essieux avant et arrière en utilisant plus largement les accélérations mesurées. Cela permet d'intégrer les passages de sous- à sur-vireur qu'il est essentiel de considérer quand on étudie la stabilité de ce type de véhicule. Ainsi, l'estimation des glissements est toujours pertinente, ce qui permet d'obtenir par la suite une meilleure prédiction de la métrique de stabilité latérale (TCLa) quel que soit le comportement du véhicule. Puis en s'appuyant sur les estimations des observateurs couplées aux modèles dynamiques du véhicule et sur l'extrapolation des commandes du conducteur sur un horizon de prédiction, il est possible de prédire les évolutions du TCLa. Cette valeur prédite ainsi que les estimations en ligne des métriques de stabilité constituent alors le point d'entrée pour la synthétisation d'un système de sécurité actif dédié aux VLTT. Celui-ci est basé sur la génération d'un retour d'effort au niveau de la gâchette des gaz permettant soit d'informer le pilote du risque encouru par la création d'une sensation de dureté, soit d'imposer le retour complet de la gâchette des gaz, ce qui implique une diminution de la vitesse et donc la réduction du risque. Finalement, dans le cas où il est possible de maîtriser la vitesse du véhicule par l'installation d'un système de rétroaction sur les freins (Quad haut de gamme ou robot mobile), les derniers travaux présentés s'intéressent aux techniques de commande prédictive à modèle afin de calculer en temps-réel la vitesse maximale admissible, qui assure l'évolution du critère de stabilité choisi dans un domaine de stabilité. Les modèles, les observateurs, la prédiction du TCLa et les 2 systèmes de prévention présentés dans ce mémoire ont été validés et testés au travers de simulations avancées et d'essais expérimentaux réalisés sur un quad agricole et un robot autonome. Il apparaît alors qu'en plus d'être efficace pour la prévention des risques de renversement à hautes dynamiques, le système de sécurité est industriellement viable. Cela a été rendu possible grâce à une conception reposant uniquement sur des actionneurs et un système sensoriel, dont les coûts sont en adéquation avec le prix d'un VLTT.
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Polack, Philip. "Cohérence et stabilité des systèmes hiérarchiques de planification et de contrôle pour la conduite automatisée." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM025/document.
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La voiture autonome pourrait réduire le nombre de morts et de blessés sur les routes tout en améliorant l'efficacité du trafic. Cependant, afin d'assurer leur déploiement en masse sur les routes ouvertes au public, leur sécurité doit être garantie en toutes circonstances. Cette thèse traite de l'architecture de planification et de contrôle pour la conduite automatisée et défend l'idée que l'intention du véhicule doit correspondre aux actions réalisées afin de garantir la sécurité à tout moment. Pour cela, la faisabilité cinématique et dynamique de la trajectoire de référence doit être assurée. Sinon, le contrôleur, aveugle aux obstacles, n'est pas capable de la suivre, entraînant un danger pour la voiture elle-même et les autres usagers de la route. L'architecture proposée repose sur la commande à modèle prédictif fondée sur un modèle bicyclette cinématique afin de planifier des trajectoires de référence sûres. La faisabilité de la trajectoire de référence est assurée en ajoutant une contrainte dynamique sur l'angle au volant, contrainte issue de ces travaux, afin d'assurer que le modèle bicyclette cinématique reste valide. Plusieurs contrôleurs à haute-fréquence sont ensuite comparés afin de souligner leurs avantages et inconvénients. Enfin, quelques résultats préliminaires sur les contrôleurs à base de commande sans modèle et leur application au contrôle automobile sont présentés. En particulier, une méthode efficace pour ajuster les paramètres est proposée et implémentée avec succès sur la voiture expérimentale de l'ENSIAME en partenariat avec le laboratoire LAMIH de ValenciennesAutonomous vehicles are believed to reduce the number of deaths and casualties on the roads while improving the traffic efficiency. However, before their mass deployment on open public roads, their safety must be guaranteed at all time.Therefore, this thesis deals with the motion planning and control architecture for autonomous vehicles and claims that the intention of the vehicle must match with its actual actions. For that purpose, the kinematic and dynamic feasibility of the reference trajectory should be ensured. Otherwise, the controller which is blind to obstacles is unable to track it, setting the ego-vehicle and other traffic participants in jeopardy. The proposed architecture uses Model Predictive Control based on a kinematic bicycle model for planning safe reference trajectories. Its feasibility is ensured by adding a dynamic constraint on the steering angle which has been derived in this work in order to ensure the validity of the kinematic bicycle model. Several high-frequency controllers are then compared and their assets and drawbacks are highlighted. Finally, some preliminary work on model-free controllers and their application to automotive control are presented. In particular, an efficient tuning method is proposed and implemented successfully on the experimental vehicle of ENSIAME in collaboration with the laboratory LAMIH of Valenciennes
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Crombie, T. "Stability over time and the role of attachment in emerging personality disorder in adolescence : a two year longitudinal study." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1406084/.
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The overall focus of the thesis is on Personality Disorders (PD) and the factors that influence the development and maintenance of these. This thesis consists of three parts. Part one presents a systematic literature review on the relationship between childhood emotional abuse and emotional neglect and Borderline Personality Disorder (BPD). Although existing research evidences the link between childhood trauma and BPD, no systematic review has considered the specific impact of emotional abuse and emotional neglect as opposed to sexual or physical abuse. Evidence of variables that may account for or contribute to the relationship is considered. Part two is an empirical paper on the stability of PDs in adolescence over a two year period and the role that attachment plays in the maintenance of PD traits during this time. The results showed that PD traits in adolescence decline over time to an extent. Higher levels of overall quality of attachment and lower levels of alienation from peers, as measured at baseline, were predictive of improvement in the number of PD traits over time. The validity of the results is discussed in relation to problems of sample size and statistical power. The data collection for this study was conducted jointly with another trainee and in conjunction with a trial into Mentalization-Based Therapy (MBT) for adolescents with emerging PD. Part three is a critical appraisal discussing reflections on issues that arose during the process of the research and commenting more generally on current debates within the field of PD research.
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Hamel, Alain. "Propriétés d'un résonateur atomique à jet de césium pompé optiquement et à structure de champ longitudinale." Paris 11, 1989. http://www.theses.fr/1989PA112204.
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Caractérisation du résonateur, génération du champ magnétique statique et performance du système optique de détection. Mesure de la distribution des vitesses des atomes dans le jet. Rapport signal sur bruit lors de la détection de la frange de Ramsey. Mesures de stabilité pour confirmer les prédictions théoriques. On montre que l'emploi du pompage optique dans la configuration la plus simple (une seule diode laser) permet d'accroitre considérablement les performances des horloges à jet de césiumLn this thesis, we study from the experimental and theoretical point of view, the clock signal characteristics delivered by a single-laser optically pumped cesium beam resonator. Our new resonator CSIII has been designed in order to avoid drawbacks due to Hanle effect which had arisen with our previous resonator CSII. Several parts have been significantly improved in order to get full benefit from optical pumping advantages. Ln the first part we examine some interesting aspects of the operation of cesium beam resonator i-e : - Determination of Hanle effect free experimental conditions; - Very low C-field resonance; - Experimental study of velocity distribution in the atomic beam; - Observance of extra resonances on the Rabi pedestal. Ln the second part, we determine owing to rate equation the theoretical signal to noise ratio assuming that no extra noise is brought by the laser. We take into account the effect of optical collecting efficiency. These theoretical predictions are compared with experiments on our resonator CSIll. Ln the last part we have measured the short term stability. Ln conclusion, this study clearly shows that optical pumping allows an improvement of cesium atomic clock performances using a single conventional laser diode configuration. Optical pumping is performed this way in our resonator and reaches its theoretical limitations for usual atomic fluxes
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Biau, Damien. "Étude des structures longitudinales dans la couche limite laminaire et de leur lien avec la transition." Toulouse, ENSAE, 2006. https://tel.archives-ouvertes.fr/tel-00160727.
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Ce travail est, consacré à la modélisation des stries dans une couche limite laminaire et à l’étude de leur influence sur la transition. Dans une première partie, on présente une modélisation de ces structures longitudinales en utilisant les équations de Navier-Stokes paraboliques. La résolution numérique est basée sur des schémas de projection, de type Chorin-Temam, associés à des méthodes de discétisation spectrales. Ce modèle parabolique est appliqué au problème de réceptivité de la couché limite laminaire vis-a-vis de différentes perturbations extérieures. La dernière étape du processus de transition vers la turbulence est abordée par une étude de stabilité linéaire ainsi qu’une simulation numérique directe. Enfin on propose un modèle pragmatique pour reproduire la dynamique des stries et estimer le seuil de transition ’bypass’. Sur l'ensemble, on a cherché à comparer les résultats à différents travaux expérimentaux existants.
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Pienaar, D. van V. "Longitudinal stability and control analysis and parameter sensitivity investigation of fixed wing aircraft in ground proximity using various aerodynamic approaches." Doctoral thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/5486.
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Summary in English.The investigation of the stability of longitudinal motion of fixed wing aircraft in ground proximity presented here focuses on rectangular wing and tail configurations similar to that of the Piper Cherokee PA-28-180. The majority of our results pertain to the height range down to one quarter of the wing span, and th main objectives of the investigation were the following: to reveal the physical nature and causes of the instability encountered in the close ground proximity; to assess the influence the design parameters such as the centre of the mass placement, tail length, tail height and wing aspect ration have on the stability of longitudinal motion; and to suggest a feedback control strategy that would alleviate the instability.
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Kóňa, Marián. "Aerodynamický návrh transsonického bezpilotního kluzáku." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232008.
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This master thesis is focused on aerodynamic design of transonic glider, which is assigned for following an airliner at cruising regime of flight. Main goal of the thesis is to determine basic geometrical design of airplane with respect to Whitcomb aera rule, mass analysis and drag polar. Weight analysis includes determining center of gravity according to longitudinal static stability margin. The drag polar of the airplane is determine for cruising regime of flight, that means the regime of following an airliner.
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Blimbaum, Jordan Matthew. "Finite element analysis of acoustic wave transverse to longitudinal coupling during transverse combustion instability." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44757.
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Velocity-coupled combustion instability is a major issue facing lean combustor design in modern gas turbine applications. In this study, we analyze the complex acoustic field excited by a transverse acoustic mode in an annular combustor. This work is motivated by the need to understand the various velocity disturbance mechanisms present in the flame region during a transverse instability event. Recent simulation and experimental studies have shown that much of the flame response during these transverse instabilities may be due to the longitudinal motion induced by the fluctuating pressure field above the nozzles. This transverse to longitudinal coupling has been discussed in previous work, but in this work it is given a robust acoustic treatment via computational methods in order to verify the mechanisms by which these two motions couple.
We will provide an in-depth discussion of this coupling mechanism and propose a parameter, Rz, also referred to as the Impedance Ratio, in order to compare the pressure/velocity relationship at the nozzle outlet to quasi one-dimensional theoretical acoustic approximations. A three-dimensional inviscid simulation was developed to simulate transversely propagating acoustic pressure waves, based on an earlier experiment designed to measure these effects. Modifications to this geometry have been made to account for lack of viscosity in the pure acoustic simulation and are discussed.
Results from this study show that transverse acoustic pressure excites significant axial motion in and around the nozzle over a large range of frequencies. Furthermore, the development of Rz offers a defined physical parameter through which to reference this important velocity-coupled instability mechanism. Therefore, this study offers an in-depth and quantifiable understanding of the instability mechanism caused by transversely propagating acoustic waves across a combustor inlet, which can be applied to greatly improve annular combustor design in future low-emissions gas turbine engines.
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Mundim, Fabrício Mariano. "Estudo longitudinal da influência da ação de soluções fluoretadas sobre alteração de cor e rugosidade de superfície de compósitos odontológicos." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/58/58131/tde-09062011-101400/.
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A doença cárie pode ser tratada com tratamento preventivo e ou tratamento restaurador. Para o tratamento preventivo, pode-se lançar mão da utilização do flúor, sendo sua utilização bastante difundida na Odontologia como eficaz método de promoção de saúde bucal. Já para o tratamento restaurador, utilizam-se materiais restauradores, sendo os compósitos odontológicos umas das principais escolhas entre os materiais restauradores estéticos usados na Odontologia. O objetivo deste estudo foi avaliar a ação de soluções fluoretadas na estabilidade de cor, rugosidade de superfície e análise qualitativa por microscopia eletrônica por varredura de compósitos odontológicos. Após confecção e polimento, os corpos de prova foram imersos em água destilada (controle), flúor fosfato acidulado (1,23%), gel fluoretado neutro (2%) e solução de flúor para bochechos diário (0,05%) por períodos de simulação correspondentes a 1 a 5 anos de uso clínico da solução fluoretada. Foram realizadas leituras de cor (ΔE), rugosidade de superfície (Ra) e microscopia eletrônica de varredura previamente e posteriormente a cada ano de ciclagem com as soluções fluoretadas estudadas. Após análise estatística (3-way ANOVA com medidas repetidas Bonferroni nível de significância em p<0.05), observou-se que todos os compósitos estudados apresentaram discreta alteração de cor, dentro do limite clinicamente aceitável (ΔE<3,3), sendo crescente de acordo com os anos de simulação clínica de 1 até 5 anos. Quanto à rugosidade, observou-se um padrão de comportamento não homogêneo, sendo, após 5 anos de simulação de uso clínico das soluções fluoretadas, menor que a rugosidade de superfície necessária para causar um aumento da retenção de biofilme dentário (Ra>0,2 μm) para todos os compósitos analisados. A análise das fotomicrografias demonstrou o aparecimento de pequenas depressões na superfície das amostras e penetração de água (solvente) no interior dos compósitos diretos. Conclui-se que a alteração de cor dos compósitos foi clinicamente aceitável e a alteração de rugosidade de superfície não é clinicamente significante após imersão em todas as soluções fluoretadas e tempos estudados.Dental caries can be treated with preventive treatment or restorative treatment. For preventive treatment, we can resort to the use of fluoride, and its widespread use in Dentistry as an effective method of promoting oral health. As for the restorative treatment, are used restorative materials, dental composites are one of the first choices among the materials used in aesthetic restorative dentistry. The aim of this study was to evaluate the effect of fluoride solution in color stability, surface roughness and qualitative analysis by scanning electron microscopy of dental composites. After preparation and polishing, the specimens were immersed in distilled water (control), acidulated phosphate fluoride (1.23%), neutral sodium fluoride gel (2%) and fluoride mouthwashes for daily (0.05%) for periods simulation corresponding to 1 to 5 years of clinical use of fluoride solution. Readings were taken in color (ΔE), surface roughness (Ra) and scanning electron microscopy before and after each year of cycling with the fluoride solution studied. After statistical analysis (3-way repeated measures ANOVA - Bonferroni - a significance level of p<0.05), was observed that all the composites studied showed a slight color change, within clinically acceptable (ΔE<3.3), being increased according to the years of clinical simulation from 1 to 5 years. As for the roughness, there was a pattern of behavior is not homogeneous, and, after five years of simulated clinical use of fluoride solution, smaller than the surface roughness required to cause an increased retention of dental plaque (Ra>0.2 μm) for all composites analyzed. The analysis of the photomicrographs showed the appearance of small depressions on the surface and penetration of water (solvent) within the direct composites. We conclude that the color change of the composites was clinically acceptable and the surface roughness change is not clinically significant after immersion in all fluoride solution and times studied.
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Weaver, Gillian Margaret. "Stability, ability, work and learning : a longitudinal and comparative study of the effects of adult education programmes upon problem drug users." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425778.
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Biau, Damien. "Etude des structures longitudinales dans la couche limite laminaire et de leur lien avec la transition." Phd thesis, Ecole nationale superieure de l'aeronautique et de l'espace, 2006. http://tel.archives-ouvertes.fr/tel-00160727.
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Ce travail est consacré à la modélisation des stries dans une couche limite laminaire et à l'étude de leur influence sur la transition. Dans une première partie, on présente une modélisation de ces structures longitudinales en utilisant les équations de Navier-Stokes paraboliques. La résolution numérique est basée sur des schémas de projection, de type Chorin-Temam, associés à des méthodes de discétisation spectrales. Ce modèle parabolique est appliqué au problème de réceptivité de la couche limite laminaire vis-à-vis de différentes perturbations extérieures. La dernière étape du processus de transition vers la turbulence est abordée par une étude de stabilité linéaire ainsi qu'une simulation numérique directe. Enfin on propose un modèle pragmatique pour reproduire la dynamique des stries et estimer le seuil de transition 'bypass'. Sur l'ensemble, on a cherché à comparer les résultats à différents travaux expérimentaux existants.
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Mcmahan, Melanie M. "A Longitudinal Examination of High School Students' Group Membership in a Dual-Factor Model of Mental Health: Stability of Mental Health Status and Predictors of Change." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4369.
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A dual-factor model of mental health includes indicators of wellness (i.e., subjective well-being; SWB) and psychopathology (i.e., internalizing and externalizing behavior problems) in defining youth mental health. In this model, four categories of psychological functioning with distinct levels of SWB and psychopathology emerge, including two that are overlooked (i.e., Vulnerable and Symptomatic but Content) in traditional assessments that assume SWB and psychopathology are opposite ends of the same continuum. The present study investigated the 1-year stability of adolescent mental health as classified by a dual-factor model, and identified predictors of stability and change, in a sample of 425 high school students. Results included that 60% of the high school students remained in the same mental health group over both time points. The Complete Mental Health Group (i.e., high SWB and low psychopathology) showed the most stability over time as nearly 80% of students initially in this group retained that mental health profile one year later. The initially Symptomatic but Content group (i.e., high SWB and high psychopathology) showed the least stability, with only 17% of students remaining in this mental health group the following year. Higher socioeconomic status and lower neuroticism reliably and uniquely predicted which students who initially experienced Complete Mental Health remained that way. Low neuroticism also predicted which students with partial mental health initially (i.e., Vulnerable or Symptomatic but Content) improved to Complete Mental Health. Once the shared variance amongst factors had been accounted for, no factors reliably and uniquely predicted which students initially Troubled stayed that way, nor which students moved from partial mental health (i.e., Vulnerable, Symptomatic but Content) to Troubled. This study contributes to the literature by providing the first examination of the stability of high school students' mental health as defined by a dual-factor model. Additionally, this study provides insight into the factors which predict students' stability and movement across mental health groups over time. Both sets of findings can be useful for school-based mental health professionals' prevention and intervention work with regard to how to operationalize student mental health, and intrapersonal risk factors important to detect.
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Prenoveau, Jason Matthew. "Stability of and structural relations among anxiety, depression, neuroticism, and extraversion during adolescence results from a 3-year longitudinal latent variable study /." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1970597961&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Guillet, Audrey. "Commande locale décentralisée de robots mobiles en formation en milieu naturel." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22609/document.
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La problématique étudiée dans cette thèse concerne le guidage en formation d’une flotte de robots mobiles en environnement naturel. L’objectif poursuivi par les robots est de suivre une trajectoire connue (totalement ou partiellement) en se coordonnant avec les autres robots pour maintenir une formation décrite comme un ensemble de distances désirées entre les véhicules. Le contexte d’évolution en environnement naturel doit être pris en compte par les effets qu’il induit sur le déplacement des robots. En effet, les conditions d’adhérence sont variables et créent des glissements significatifs des roues sur le sol. Ces glissements n’étant pas directement mesurables, un observateur est mis en place, permettant d’obtenir une estimation de leur valeur. Les glissements sont alors intégrés au modèle d’évolution, décrivant ainsi un modèle cinématique étendu. En s’appuyant sur ce modèle, des lois de commande adaptatives sur l’angle de braquage et la vitesse d’avance d’un robot sont alors conçues indépendamment, asservissant respectivement son écart latéral à la trajectoire et l’interdistance curviligne de ce robot à une cible. Dans un second temps, ces lois de commande sont enrichies par un algorithme prédictif, permettant de prendre en compte le comportement de réponse des actionneurs et ainsi d’éviter les erreurs conséquentes aux retards de la réponse du système aux commandes. À partir de la loi de commande élémentaire en vitesse permettant d’assurer un asservissement précis d’un robot par rapport à une cible, une stratégie de commande globale au niveau de la flotte est établie. Celle-ci décline l’objectif de maintien de la formation en consigne d’asservissement désiré pour chaque robot. La stratégie de commande bidirectionnelle conçue stipule que chaque robot définit deux cibles que sont le robot immédiatement précédent et le robot immédiatement suivant dans la formation. La commande de vitesse de chaque robot de la formation est obtenue par une combinaison linéaire des vitesses calculées par la commande élémentaire par rapport à chacune des cibles. L’utilisation de coefficients de combinaison constants au sein de la flotte permet de prouver la stabilité de la commande en formation, puis la définition de coefficients variables est envisagée pour adapter en temps réel le comportement de la flotte. La formation peut en effet être amenée à évoluer, notamment en fonction des impératifs de sécurisation des véhicules. Pour répondre à ce besoin, chaque robot estime en temps réel une distance d’arrêt minimale en cas d’urgence et des trajectoires d’urgence pour l’évitement du robot précédent. D’après la configuration de la formation et les comportements d’urgence calculés, les distances désirées au sein de la flotte peuvent alors être modifiées en ligne afin de décrire une configuration sûre de la formationThis thesis focuses on the issue of the control of a formation of wheeled mobile robots travelling in off-road conditions. The goal of the application is to follow a reference trajectory (entirely or partially) known beforehand. Each robot of the fleet has to track this trajectory while coordinating its motion with the other robots in order to maintain a formation described as a set of desired distances between vehicles. The off-road context has to be considered thoroughly as it creates perturbations in the motion of the robots. The contact of the tire on an irregular and slippery ground induces significant slipping and skidding. These phenomena are hardly measurable with direct sensors, therefore an observer is set up in order to get an estimation of their value. The skidding effect is included in the evolution of each robot as a side-slip angle, thus creating an extended kinematic model of evolution. From this model, adaptive control laws on steering angle and velocity for each robot are designed independently. These permit to control respectively the lateral distance to the trajectory and the curvilinear interdistance of the robot to a target. Predictive control techniques lead then to extend these control laws in order to account for the actuators behavior so that positioning errors due to the delay of the robot response to the commands are cancelled. The elementary control law on the velocity control ensures an accurate longitudinal positioning of a robot with respect to a target. It serves as a base for a global fleet control strategy which declines the overall formation maintaining goal in local positioning objective for each robot. A bidirectionnal control strategy is designed, in which each robot defines 2 targets, the immediate preceding and following robot in the fleet. The velocity control of a robot is finally defined as a linear combination of the two velocity commands obtained by the elementary control law for each target. The linear combination parameters are investigated, first defining constant parameters for which the stability of the formation is proved through Lyapunov techniques, then considering the effect of variable coefficients in order to adapt in real time the overall behavior of the formation. The formation configuration can indeed be prone to evolve, for application purposes and to guarantee the security of the robots. To fulfill this latter requirement, each robot of the fleet estimates in real time a minimal stopping distance in case of emergency and two avoidance trajectories to get around the preceding vehicle if this one suddenly stops. Given the initial configuration of the formation and the emergency behaviors calculated, the desired distances between the robots can be adapted so that the new configuration thus described ensures the security of each and every robot of the formation against potential collisions
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Nyström, Sara. "Kön och den svårförklarade ohälsan : Betydelsen av kön, emotionell stabilitet och kondition försvenska polisstudenters stressrelaterade hälsobesvär - en longitudinell studie om möjliga interaktionseffekter av kön." Thesis, Södertörns högskola, Institutionen för samhällsvetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-46016.
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Stressrelaterad ohälsa är ett stort problem som bland annat bidrar till många sjukskrivningar. Det är därför angeläget att bättre förstå vilka faktorer som motverkar skadlig stress. Två viktiga skyddsfaktorer är emotionell stabilitet och kondition. Kön är också en betydelsefull faktor men det är oklart om det finns mer komplexa samband relaterade till kön. Syftet med denna studie är därför att undersöka om kön kan moderera betydelsen av emotionell stabilitet respektive kondition som skydd mot stressrelaterad ohälsa. Två grupper som är relevanta att studera i det här sammanhanget. är studenter och poliser. Undersökningsgruppen i studien utgörs av studenter vid polisutbildningen (N=446). Studien omfattar data från två insamlingstillfällen; vid polisutbildningens antagningsprocess våren 2008 och i slutet av utbildning, våren 2010. För att besvara studiens frågeställningar genomfördes två typer av statistiska analyser; först en hierarkisk multipel regressionsanalys och sedan två moderationsanalyser. Resultaten visar att emotionell stabilitet, kondition och kön tillsammans förklarade 18% av polisstudenternas totala ohälsa. Samtliga tre variabler bidrog till att predicera ohälsa både enskilt och tillsammans. Kvinnor uppgav högre grad av ohälsa än män. Moderationsanalyserna påvisade ingen moderationseffekt av kön. Generaliserbarheten är osäker då den aktuella undersökningsgruppen är unik. Det är därför angeläget att undersöka om det kan finnas mer komplexa samband i andra grupper, exempelvis bland äldre poliser.
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Zettergren, Peter. "Children’s Peer Status and Their Adjustment in Adolescence and Adulthood : Developmental issues in sociometric research." Doctoral thesis, Stockholm University, Department of Psychology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-6646.
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The present research intended to examine the relationship between childhood stable peer status and adjustment in midadolescence for both genders, and adjustment in early and middle adulthood for women. One-year stably peer rejected, popular, and average boys and girls were identified by an age 10 and age 11 sociometric classification procedure using positive nominations and rank-ordering. These groups were examined in midadolescence. Findings indicated that stable peer rejection in childhood was associated with negative school adjustment and problems in peer relations in adolescence for both genders, and that many rejected boys were school dropouts. However, rejected children did not associate with deviant peers or show more antisocial behavior than their counterparts. For the adulthood follow-up, cluster analysis using LICUR was applied on rank-ordering data from age 10 and age 13 in order to identify 3-year stably rejected, popular, and average groups of girls. A methodological comparison with a standard sociometric method showed that the applied cluster analysis seems to be a useful additional tool in the arsenal of sociometric classification methods. Furthermore, one seems to arrive at larger stable peer status groups with this method than with other sociometric classification methods. The longitudinal follow-up into adulthood showed that rejected girls were at increased risk for criminal offending and alcohol abuse in young adulthood. Childhood aggressive behavior explained the significant association between peer rejection and criminality. There were no significant differences between the stable peer status clusters in the midadulthood adjustment areas of social relations, health, occupation, and subjective well-being, except that popular girls had achieved more successful vocational careers (which in its turn was explained by their higher academic achievement in childhood). Constraints and implications for future research were discussed.
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Пестунов, В. М., В. В. Свяцкий, Л. П. Свяцкая, V. Pestunov, V. Sviatskyi та L. Sviatska. "Увеличение производительности процесса глубокого сверления повышением жесткости установки сверла". Thesis, Nauka i studia, 2008. http://dspace.kntu.kr.ua/jspui/handle/123456789/6497.
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Рассмотрены схемы повышения продольной устойчивости сверл при глубоком сверлении. Предложен механизм подачи с изменяемой величиной вылета инструмента, позволяющий повысить ефективность обработки глубоких отверстий. The schemes for increasing the longitudinal stability of drills during deep drilling are considered. A feed mechanism with variable tool discharge size is proposed, which makes it possible to improve the efficiency of processing deep holes.
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Junior, Luiz Eduardo Alessio. "Avaliação longitudinal da estabilidade do tratamento da má oclusão de Classe II com o aparelho Pendulum seguido do aparelho fixo." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/25/25134/tde-01042009-131113/.
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Compulsando a literatura nota-se uma diversidade de formas de tratamento, apoiadas em diferentes mecanismos terapêuticos, para a correção da má oclusão de Classe II. No entanto, poucos trabalhos estudam a estabilidade da correção com o aparelho Pendulum. Sendo assim, o objetivo deste estudo foi verificar a estabilidade do tratamento da Classe II em longo prazo (5 anos) com o aparelho Pendulum, seguido pelo aparelho fixo. A amostra consistiu de 20 pacientes (14 do gênero feminino e 6 do masculino). A média da idade, ao inicio do tratamento (T1), foi de 14,02 ± 1,62 anos, ao final do tratamento (T2), 18,38 ± 1,84 anos, e no pós-tratamento (T3), 22,94 ± 1,34 anos. Para a análise, foram utilizados traçados cefalométricos e modelos de estudo nas 3 fases. As variáveis nos 3 grupos, foram comparadas pela análise de variância a um critério ANOVA, considerando significativo o valor de P < 0,05. Os resultados mostraram uma grande estabilidade das variáveis cefalométricas, sendo estatisticamente diferentes somente a inclinação do primeiro molar e a posição ântero-posterior do lábio superior. A avaliação do índice PAR demonstrou que o tratamento com o aparelho Pendulum seguido pelo aparelho fixo, foi estável 5 anos pós-tratamento. Conclui-se que o tratamento da Classe II com o aparelho Pendulum e o aparelho fixo, foi estável em longo prazo.There are, in the literature, several forms of treatment, supported by different therapeutic mechanisms for the correction of Class II malocclusion. However, a few works have studied the stability of Class II correction with the Pendulum appliance. Therefore, this study aimed at verifying the long-term stability (5 years) of a treatment with the Pendulum appliance followed by a fixed one. The sample consisted of 20 patients (14 females and 6 males). The average age at the beginning of the treatment (T1) was 14,02 ± 1,62 yrs, and at the end of the treatment (T2), 18,38 ± 1,84 yrs, and at the post-treatment (T3), 22,94 ± 1,34 yrs. Cephalometric measurements and cast models were used in the 3 phases and the variables for the 3 groups were compared by ANOVA variance analysis, by considering P<0,05, a significant value. The results show a great stability of the cephalometric variables, being statistically different, only the tipping of the 1st molar and the upper lip thickness. The PAR index assessment demonstrated that the treatment with the pendulum appliance, followed by a fixed one, was stable, 5 yrs post-treatment. It was concluded that the Class II treatment with the Pendulum appliance, followed by a fixed one, was more stable in the long term.
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Denis, Dieumet. "Contribution à la modélisation et à la commande de robots mobiles reconfigurables en milieu tout-terrain : application à la stabilité dynamique d'engins agricoles." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22565/document.
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La thématique étudiée dans ce mémoire est axée sur la préservation de la stabilité dynamique de véhicules évoluant en environnement naturel. En effet, la mobilité en milieu tout-terrain est une activité particulièrement pénible et dangereuse en raison de la nature difficile de l'environnement de conduite et de la reconfigurabilité des machines. Le caractère changeant et incertain des interactions rencontrées entre des véhicules à dynamique complexe et variable et leur environnement entraîne régulièrement des risques accrus de renversement et/ou de perte de contrôle (dévalement, dérapage déclenché par une perte soudaine d'adhérence) pour le conducteur. Une forte accidentalité mortelle est, en effet, recensée dans ce secteur, en particulier, dans le milieu agricole ou le renversement de véhicule est classé comme étant la première cause de mortalité au travail. A l'heure actuelle, les approches existantes sur la stabilité d'engins agricoles sont qualifiées à juste titre de passives car elles ne permettent pas d'éviter que les accidents ne se produisent. Par ailleurs, la transposition directe des solutions de sécurité active du secteur de l'automobile (ABS, ESP) s'est révélée inadaptée aux véhicules tout-terrain a cause des hypothèses simplificatrices (routes plates et homogènes, conditions d'adhérence constantes, etc.) dont souffre la conception de ces dispositifs. Ainsi, le développement de systèmes actifs de sécurité prenant en compte les spécificités de la conduite en milieu tout-terrain se révèle être la meilleure voie d'amélioration à suivre. Eu égard à ces circonstances, ce projet se propose d'adresser cette problématique en étudiant des métriques de stabilité pertinentes permettant d'estimer et d'anticiper en temps réel les risques afin de permettre des actions correctives pour la préservation de l'intégrité des machines tout-terrain. Afin de faciliter l'industrialisation du dispositif actif de sécurité conçu, l'une des contraintes sociétales et commerciales de ce projet a été l'utilisation de capteurs compatibles avec le coût des machines visées. L'objectif ambitieux de cette étude a été atteint par différentes voies. En premier lieu, une approche de modélisation multi-échelle a permis de caractériser l'évolution dynamique de véhicules en milieu tout-terrain. Cette approche à dynamique partielle a offert l'avantage de développer des modèles suffisamment précis pour être représentatifs du comportement réel de l'engin mais tout en présentant une structure relativement simple permettant la synthèse d'asservissements performants. Puis, une étude comparative des avantages et des inconvénients des trois grandes familles de métriques répertoriées dans la littérature a permis de mettre en exergue l'intérêt des métriques analytiques à modèle dynamique par rapport aux catégories de critères de stabilité dits statiques et empiriques. Enfin, l'analyse approfondie des métriques dynamiques a facilité le choix de trois indicateurs (Lateral and Longitudinal Load Transfer (LLT), Force Angle Stability Measurement (FASM) et Dynamic Energy Stability Measurement (DESM)) qui sont représentatifs d'un risque imminent de renversement du véhicule. La suite du mémoire s'appuie sur la théorie d'observation pour l'estimation en ligne des variables non directement mesurables en milieu tout-terrain telles que les rigidités de glissement et dérive du pneumatique. Jumelée aux différents modèles dynamiques du véhicule, la synthèse d'observateurs a permis donc d'estimer en temps réel les efforts d'interaction pneumatiques-sol nécessaires à l'évaluation des indicateurs d'instabilité. Le couplage de ces modèles multi-échelles à la théorie d'observation a ainsi constitué un positionnement original à même de briser la complexité de la caractérisation de la stabilité de véhicules à dynamiques complexes et incertaines. (...)This work is focused on the thematic of the maintenance of the dynamic stability of off-road vehicles. Indeed, driving vehicles in off-road environment remains a dangerous and harsh activity because of the variable and bad grip conditions associated to a large diversity of terrains. Driving difficulties may be also encountered when considering huge machines with possible reconfiguration of their mechanical properties (changes in mass and centre of gravity height for instance). As a consequence, for the sole agriculture sector, several fatal injuries are reported per year in particular due to rollover situations. Passive protections (ROllover Protective Structure - ROPS) are installed on tractors to reduce accident consequences. However, protection capabilities of these structures are very limited and the latter cannot be embedded on bigger machines due to mechanical design limitations. Furthermore, driving assistance systems (such as ESP or ABS) have been deeply studied for on-road vehicles and successfully improve safety. These systems usually assume that the vehicle Center of Gravity (CG) height is low and that the vehicles are operating on smooth and level terrain. Since these assumptions are not satisfied when considering off-road vehicles with a high CG, such devices cannot be applied directly. Consequently, this work proposes to address this research problem by studying relevant stability metrics able to evaluate in real time the rollover risk in order to develop active safety devices dedicated to off-road vehicles. In order to keep a feasible industrialization of the conceived active safety device, the use of compatible sensors with the cost of the machines was one of the major commercial and societal requirements of the project. The ambitious goal of this study was achieved by different routes. First, a multi-scale modeling approach allowed to characterize the dynamic evolution of off-road vehicles. This partial dynamic approach has offered the advantage of developing sufficiently accurate models to be representative of the actual behavior of the machine but having a relatively simple structure for high-performance control systems. Then, a comparative study of the advantages and drawbacks of the three main families of metrics found in the literature has helped to highlight the interest of dynamic stability metrics at the expense to categories of so-called static and empirical stability criteria. Finally, a thorough analysis of dynamic metrics has facilitated the choice of three indicators (Longitudinal and Lateral Load Transfer (LLT), Force Angle Stability Measurement (FASM) and Dynamic Energy Stability Measurement (DESM)) that are representative of an imminent rollover risk. The following of the document is based on the observation theory for estimating online of variables which are not directly measurable in off-road environment such as slip and cornering stiffnesses. Coupled to the dynamic models of the vehicle, the theory of observers has helped therefore to estimate in real time the tire-soil interaction forces which are necessaries for evaluating indicators of instability. The coupling of these multiscale models to the observation theory has formed an original positioning capable to break the complexity of the characterization of the stability of vehicles having complex and uncertain dynamics. (...)
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Ben, Ahmed Haykel. "Étude de la convection mixte d'origine thermosolutale sous l'influence de l'effet SORET dans un milieu poreux : analyse de stabilité linéaire et simulations 3D." Phd thesis, Université de Cergy Pontoise, 2008. http://tel.archives-ouvertes.fr/tel-00337572.
Full textAbstract:
Lorsqu'un fluide en écoulement ou au repos est chauffé par le bas, l'instabilité thermique apparaît permettant une dissipation du gradient de température au-delà de ce qui est possible par simple conduction ou diffusion. Le fluide est soumis à des forces qui permettent un écoulement convectif lié à la différence de température entre les faces inférieure et supérieure de la couche. Le problème est rendu encore plus complexe par le fait que la distribution de température est elle-même déterminée par l'écoulement convectif. En d'autres termes, la force qui engendre l'écoulement est elle-même modifiée par l'écoulement. Pour un fluide multi composants, et avec prise en compte de l'effet SORET le phénomène devient d'une complexité particulièrement ardue, car la séparation des constituants engendre une compétition entre les forces volumiques d'origine thermique et compositionnelle. Le phénomène admet des développements extrêmement larges et de multiples applications en science et en ingénierie. En effet, l'instabilité thermique peut être étudiée avec tension superficielle variable, sans approximation de BOUSSINESQ, avec génération de chaleur au sein du fluide, avec ou sans confinement, etc. Ici, par souci de simplicité, nous étudierons le cas particulier d'une couche de mélange de fluides binaires entre deux plaques horizontales à températures fixées influencée par un écoulement forcé à faible nombres de PECLET. Nous commencerons par une étude qualitative du phénomène via une analyse de stabilité linéaire marginale et transitoire par éléments finis, laquelle démarche nous a conduit à réduire sous forme diagonale un opérateur linéaire rigoureusement déterminé. Les éléments spectraux de cet opérateur contiennent les informations utiles à déterminer les plus déstabilisants parmi une infinité de modes propres. Ces résultats nous serviront comme guide afin de déterminer une démarche d'expérimentation numérique par usage d'un code 3D en volumes finis hautement précis en espace, et utilisant le schéma d'EULER en temps, ouvrant la porte à des études qualitative spatiale et quantitative ultérieures. L'ensemble de ces opérations nous ont conduit à déterminer le comportement d'un fluide binaire en convection mixte. Des relations littérales déterminant les seuils de transitions entre les différents états du système ont été démontrées. Des diagrammes de stabilité généraux ont été établis ; la mécanique de la convection est mieux éclaircie, l'influence de l'allongement du canal a été étudiée, la propagation dans les deux sens des ondes progressives des rouleaux transversaux ont été mises en évidence, un recueil de paramètres caractéristiques de ces écoulements est donné en termes de nombre d'ondes, pulsations, vitesses de phase et de transferts de chaleur et de masse. Pour finir, nous nous sommes intéressés au cas particulier de la séparation en essayant de mettre au point des idées permettant de séparer des constituants par appui sur les résultats trouvés.
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Pereira, Natanael de Carvalho. "Desenvolvimento de um sistema de aumento de estabilidade longitudinal de uma aeronave com enflechamento negativo e canard, com ensaios em túnel de vento." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/18/18135/tde-18022016-094528/.
Full textAbstract:
As pesquisas modernas em aeronáutica envolvem a expansão dos envelopes de vôo, como resultado do desejo de melhorar a manobrabilidade e controlabilidade em operações táticas, e melhorar a segurança do vôo. Esses objetivos podem ser alcançados através do desenvolvimento de sistemas automáticos de controle de vôo. Os sistemas de controle aplicados a aeronaves podem ser desenvolvidos e simulados através de métodos computacionais. No entanto, existem imperfeições na simulação computacional por não se conseguir reproduzir algumas características do vôo real ou devido a simplificações no modelo matemático da aeronave. Desta forma, a construção de um modelo físico de uma aeronave em escala reduzida e a implementação de um controlador a este modelo, torna-se uma ferramenta bastante importante para validar resultados teóricos e métodos computacionais. Os custos associados a estes testes são geralmente muito menores que aqueles dos ensaios em vôo e com maior flexibilidade de instrumentação. Este trabalho descreve a construção de um modelo de aeronave, baseado no X-29, o desenvolvimento de um mecanismo de fixação do modelo ao túnel de vento, tipo rótula, e a implementação de um sistema de aumento de estabilidade longitudinal, através de um sistema de controle automático. O modelo físico possui uma configuração de asa com enflechamento negativo e canard, e que tende a ser inerentemente instável, sendo necessário o auxílio de um sistema de aumento de estabilidade. Testes de estabilidade dinâmica em arfagem foram realizados no túnel de vento em diferentes posições do centro de gravidade. Os parâmetros de estabilidade foram registrados e analisados através de uma curva de ajuste exponencial.Modern aeronautical research involves flight envelope expansion as the result of a desire for improvement in tactical operation handling qualities and improvement in flight safety. These objectives can be achieved through the development of automatic flight control systems. Aircraft flight control systems can be developed and simulated through computational methods. However, there are imperfections in the computational simulation of flight dynamics due to the difficulty in reproducing real flight conditions or due simplifications in the aircraft mathematical model. The construction of a reduced scale physical aircraft model and the implementation of a controller is a very valuable tool to validate theoretical results and computational methods. The costs associated with these tests are usually much smaller than those associated with full scale flight testing and may offer greater flexibility for instrumentation. The present work describes the construction of an airplane model, based on the X-29, the development of a wind tunnel gimbal type support and the implementation of a longitudinal stability augmentation system using automatic flight control. The model configuration has forward swept wings and canard with a tendency to be inherently unstable and, thus, requiring a stability augmentation system. Pitching dynamic stability tests where conducted in a wind tunnel in different center of gravity positions. Stability parameters were acquired and analyzed by exponential fit curve.