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1
Lezra, Esther Margaret. "Looking for monsters : mechanism of history, mechanisms of power /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2005. http://wwwlib.umi.com/cr/ucsd/fullcit?p3170235.
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Hyatt, Lance Parker. "Designing Developable Mechanisms on Conical and Cylindrical Developable Surfaces." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8467.
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The research results presented in this thesis provide tools and methods to aid in the design of developable mechanisms. This work will help engineers design compact mechanisms onto developable surfaces, making it possible for them to be used in future applications. The thesis introduces terminology and definitions to describe conical developable mechanisms. Models are developed to describe mechanism motion with respect to the apex of the conical surface, and connections are made to cylindrical developable mechanisms using projected angles. The Loop Sum Method is presented as an approach to determine the geometry of the cone to which a given spherical mechanism can be mapped. A method for position analysis is presented to determine the location of any point along the link of a mechanism with respect to the conical geometry. These methods are also applied to multiloop spherical mechanisms. This work created tools and methods to design cylindrical and conical developable mechanisms from flat, planar patterns. Equations are presented that relate the link lengths and link angles of planar and spherical mechanisms to the dimensions in a flat configuration. These flat patterns can then be formed into curved, developable mechanisms. Guidelines are established to determine if a mechanism described by a flat pattern can exhibit intramobile or extramobile behavior. A developable mechanism can only potentially exhibit intramobile or extramobile behavior if none of the links extend beyond half of the flat pattern. The behavior of a mechanism can change depending on the location of the cut of the flat pattern. Different joint designs are discussed including lamina emergent torsional (LET) joints. It is shown that developable mechanisms on regular cylindrical surfaces can be described using cyclic quadrilaterals. Mechanisms can exist in either an open or crossed configuration, and these configurations correspond to convex and crossed cyclic quadrilaterals. Using equations developed for both convex and crossed cyclic quadrilaterals, the geometry of the reference surface to which a four-bar mechanism can be mapped is found. Grashof mechanisms can be mapped to two surfaces in open or crossed configurations. The way to map a non-Grashof mechanism to a cylindrical surface is in its open configuration. Extramobile and intramobile behavior can be achieved depending on selected pairs within a cyclic quadrilateral and its position within the circumcircle. Selecting different sets of links as the ground link changes the potential behavior of the mechanism. Different cases are tabulated to represent all possibilities.
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Ciniero, Alessandra. "Triboemission mechanisms." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/62826.
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Reducing mechanical friction by improving lubrication in tribological contacts is still an important goal for researches around the word. The extensive use of lubricants in applications, ranging from heavy industry to micro-biology, makes the understanding of the mechanisms by which these lubricants behave an important challenge. The fact that certain boundary lubricating films form only on contacting surfaces implies that phenomena linked to wear may play a key role in this process. One of these phenomena is known as triboemission which refers to the emission of electrons, photons and other charged particles that occur when surfaces undergo wear. Despite the possibility that triboemission events may lead to the formation of protective boundary films and also may also be responsible for lubricant degradation, the mechanism behind this phenomenon is still not well understood. In this study, spatially resolved triboemission events were analysed in a sliding contact under vacuum condition. This was achieved using an in-house developed tribometer consisting of a system of electron multipliers coupled with a phosphor screen, which allowed the in situ visualization of emission events for the first time. A range of materials were assessed in order to understand the effects of mechanical and electrical properties on the triboemission behaviour. This showed unequivocally that conductive materials show negligible emission, while those with high electrical resistivity not only produce high levels of emission but also sustained after-emission, which has not been seen before. Moreover, following the application of certain image processing techniques, a strong correlation between the spatial distribution of emission events and the topography of surface wear features was revealed. This supports the theory that triboemission is a subset of fractoemission and arises due to the uneven distribution of charge on the opposing faces of wear cracks. It also raises the possibility of using triboemission to monitor wear in real time under high magnification. In addition to this, methods were developed to differentiate between negative, positive and neutral particles, showing that each of these is emitted simultaneously but with a different spatial distribution. Surface charge was also monitored simultaneously to emission detection, showing for the first time the interactions between triboemission and tribocharging – in particular, the generation of fractures causes emission events, which reverse the expected charging trend. This may explain tribocharging mechanisms. Finally, the use of this technique to monitor coating failure was investigated. Specifically, Diamond-Like-Carbon coating specimens were assessed in vacuum and atmosphere condition revealing that coating failure can be detected in real time by observing both emission and surface charge measurements. The results presented here shed light on poorly understood triboemission mechanisms, and helps to understand how the emission interacts with the surrounding environment.
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Traylor, Pamina. "Defense mechanisms /." Online version of thesis, 1995. http://hdl.handle.net/1850/12151.
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Gajdošech, Martin. "Purchase Price Mechanisms." Master's thesis, Vysoká škola ekonomická v Praze, 2012. http://www.nusl.cz/ntk/nusl-162617.
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My diploma thesis focuses on the M&A transaction closing mechanisms. Their function is to reflect the value changes of the target company into the purchase price. Value change occurs during the time lag between the date of the financial statements and the date of the transaction closing. Throughout history, there have been two major approaches developed. The "Completion Accounts Mechanism" uses post-completion price adjustments to reflect the change of the net working capital and net debt during the interim period. The "Locked Box Mechanism", using fixed price, assures non-fluctuation of target value in the interim period by imposing strict restrictions on the seller's activities. In this research, I have analyzed 44 transactions closed in the Czech Republic. I have challenged the theoretical foundations and described the application of the mechanisms in practice. At the end, I have compared the Czech and European practices. Thesis findings: 1. All the theoretical features of the mechanisms were proven by an analyzed sample of closed transactions. The completion accounts mechanism is buyer-friendly, while the locked box is a seller-friendly mechanism. 2. The main driver in mechanism selection is bargaining power. Buyers were in a better negotiating position in 69% of the completion account transactions. On the contrary, the sellers had bargaining power in 100% of the locked box transactions. 3. The Czech Republic is an environment where buyers (big multinational companies) dominate. They have preferred the completion account mechanism that provides them with higher protection from value leakage or other risks associated with small CEE economies. A total of 91% of analyzed transactions were executed by the completion account mechanism in the Czech Republic between 2011 and 2012.
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Jensen, Brian D. "Identification of Macro- and Micro-Compliant Mechanism Configurations Resulting in Bistable Behavior." BYU ScholarsArchive, 2003. https://scholarsarchive.byu.edu/etd/83.
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The purpose of this research is to identify the configurations of several mechanism classes which result in bistable behavior. Bistable mechanisms have use in many applications, such as switches, clasps, closures, hinges, and so on. A powerful method for the design of such mechanisms would allow the realization of working designs much more easily than has been possible in the past. A method for the design of bistable mechanisms is especially needed for micro-electro-mechanical systems (MEMS) because fabrication and material constraints often prevent the use of simple, well-known bistable mechanism configurations. In addition, this knowledge allows designers to take advantage of the many benefits of compliant echanisms, especially their ability to store and release energy in their moving segments. Therefore, an analysis of a variety of mechanism classes has been performed to determine the configurations of compliant segments or rigid-body springs in a mechanism which result in bistable behavior. The analysis revealed a relationship between the placement of compliant segments and the stability characteristics of the mechanism which allows either analysis or synthesis of bistable mechanisms to be performed very easily. Using this knowledge, a method of type synthesis for bistable mechanisms has been developed which allows bistable mechanisms to be easily synthesized. Several design examples have been presented which demonstrate the method. The theory has also been applied to the design of several bistable micromechanisms. In the process of searching for usable designs for micro-bistable mechanisms, a mechanism class was defined, known as "Young" mechanisms, which represent a feasible and useful way of achieving micro-mechanism motion similar to that of any four-bar mechanism. Based on this class, several bistable micro-mechanisms were designed and fabricated. Testing demonstrated the ability of the mechanisms to snap between the two stable states. In addition, the mechanisms showed a high degree of repeatability in their stable positions.
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Merriam, Ezekiel G. "Fully Compliant Mechanisms for Bearing Subtraction in Robotics and Space Applications." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3564.
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Robotics and space applications represent areas where compliant mechanisms can continue to make a significant impact by reducing costs and weight while improving performance. Because of the nature of these applications, a common need is for bearing replacement mechanisms, or mechanisms that perform the function of a bearing without the complexity and failure modes associated with bearings. Static balancing is a design strategy that attempts to reduce the actuation effort of a mechanism, and has been applied to compliant mechanisms in some applications. Monolithic construction, especially by means of 3D printing technology, is a strategy whereby the mechanism links and joints are built as a single "chunk" of material. This eliminates assembly and failure modes associated with wear and friction in traditional joints. In this work we examine these design strategies in the context of robotics and space applications. Matlab and Ansys batch files can be found in Appendix A. A fully compliant zero-torque, statically balanced mechanism is described that can undergo greater than 100 of motion. Because compliant mechanisms achieve their motion from the deflection of their constituent members, there is some strain energy associated with actuated positions. By introducing an appropriate pre-load, strain energy can be held constant. This can reduce or nearly eliminate the input force required from the actuating device. This paper describes the statically balanced rotary joint concept, and demonstrates its optimization, testing, and implementation for a haptic pantograph mechanism. The statically balanced properties of the constituent joints result in a mechanism with two balanced degrees of freedom. Matlab and Ansys batch files can be found in Appendix B. The conception, modeling, and development of a fully compliant two-degree-of-freedom pointing mechanism for application in spacecraft thruster, antenna, or solar array systems is described. The design objectives and the advantages of a compliant solution are briefly discussed. A single design concept is selected for final development from a field of generated concepts. Analytical and numerical models are accompanied by prototype testing and measurements in several iterations. A final design is described in detail, a fully compliant prototype is fabricated in titanium, and its performance is measured.
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Mann, Catherine. "Mechanisms of action of antidepressant drugs: Presynaptic and postreceptor mechanisms." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/10600.
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The etiology of clinical depression is unknown, but thought to be related to an impairment in brain transmission of monoamines. Depression is treated with antidepressant drugs which, regardless of classification, ultimately result in increased efficacy of aminergic transmission. Tricyclic antidepressants are known to inhibit the presynaptic uptake of amines. [3H]Imipramine, the prototype tricyclic antidepressant and a potential biological marker in depression, binds to both high- and a low-affinity sites in the brain. The high-affinity binding of [3H]imipramine to its binding site on the serotonin (5-HT) neuronal transporter has been shown to be a sodium-dependent process. However, that of [3H]paroxetine, a novel and selective 5-HT uptake inhibitor, has not yet been investigated. Because of a discrepancy between the onset of uptake-blocking effect and alleviation of depressive symptoms, the blockage of uptake is probably not the only pharmacological action of antidepressants underlying their clinical effect. Recent studies have reported decreases in beta-adrenoceptor and 5-HT2 receptor numbers following long-term treatment with antidepressants, and suggested that an adaptive change in amine receptors may be more relevent for the clinical effect. However, not all 5-HT uptake inhibitors elicit this downregulation. Recent research has thus centred on elucidating changes in the signal transduction apparatus of aminergic neurons. The 5-HT2 receptor in the brain is coupled to the phosphoinositide turnover cascade and protein kinase C (PKC) activity. The subcellular distribution of PKC following chronic antidepressant treatment has not yet been investigated. This study was undertaken (1) To compare the sodium dependence of [3H]paroxetine binding and [3H]5-HT uptake in rat diencephalon in order to confirm whether paroxetine binds to the 5-HT recognition site on the transporter, and (2) to investigate the effects of both acute and chronic antidepressant treatment on PKC location and activity (both basal and 5-HT2 receptor agonist (DOI)-challenged) in rat cortex and hippocampus. Results indicate that, antidepressant drugs induce differing but significant effects on PKC activity in the subcellular fractions of neurons both after acute and chronic treatment. These changes in PKC activity may alter transduction of cellular signals evoked by the binding of 5-HT to receptors. (Abstract shortened by UMI.)
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Statham, A. J. "Reward mechanisms, depression and drug dependence : psychobiological and developmental mechanisms." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639101.
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Exposing rodents to a chronic regime of mild stressors (CMS) has been shown to produce enduring decreases in the consumption of palatable weak (1%) sucrose solution. This effect is thought to be analogous to the decreases in reward sensitivity observed in patients suffering from depression. It has been argued that this CMS model represents the most realistic model of depression. Chronic mild stress failed to produce any enduring reductions in sucrose intake, in either inbred or outbred Lister hooded male rats, in three studies. It was hypothesised that early abberant mother-infant interactions would facilitate the appearance of CMS-induced deficits. However, CMS failed to reduce sucrose consumption in either male (inbred Lister hooded) or female (inbred and outbred Lister hooded) rats which had undergone a regime of repeated maternal separation (RMS), or in the respective control rates. These findings add to the growing number of studies challenging the central status of CMS as a valid and reliable animal model of depression. Furthermore, these findings provide compelling evidence in favour of re-evaluating our approach to the study of chronic stress in this country and, furthermore, its contribution to the aetiology of depression. The RMS regime enhanced the locomotor activating effects of a low dose of d-amphetamine. Subsequent studies revealed that 24-hr maternal separation (at postnatal day 3) enhanced and reduced the locomotor activating effects of cocaine in females and males, respectively. These findings are potentially interesting with regard to the study of individual differences in the propensity to drug abuse. However, methodological difficulties impeded the full replication of these findings. The corticosterone synthesis inhibitor metyrapone produced a massive potentiation of the behavioural activating effects of d-amphetamine. This effect was probably the result of metyrapone-induced inhibition of cytochrome P450 2D1, an enzyme involved in the metabolism of d-amphetamine. This finding has potential serious implications for the current clinical use of metyrapone.
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Bergström, Roger. "Fibre flow mechanisms." Doctoral thesis, KTH, Fiber- och polymerteknik, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240.
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The flow behaviour, and primarily the floc-floc interaction, of pulp paper suspensions have been studied visually. Analogy models based on these observations have been developed as well as the identification of important parameters of floc break-up in low shear rate flow fields. Floc compressions and the locations of voids (areas of lower fibre concentration) where found to influence the floc splitting mechanism. Based on this investigation an equipment for measuring the load carrying ability of fibre flocs and networks was designed, and the effect of measurement geometry, network structure and fibre suspension concentration was investigated. The load carrying ability with concentration increases rapidly when going from 1% to 2% in initial suspension concentration. A model handling the fibre floc behaviour during extension and compression has been developed, and some basic flocculated flow mechanisms are discussed on an analogy basis. A modified Voigt element is use, describing mainly the compressional behaviour and plastic behaviour of loose fibre network structures. Further the pos- sibility of stress chain formation is discussed on a fibre level as well as on a floc level. The effect of fibre flow (shear field) occurring in the forming zone of a roll former has been studied in detail. Basic forming mechanisms on floc scale has been investi- gated, and the effect of running parameters like dewatering pressure and jet-to-wire speed difference as well as the fibre type and concentration of the pulp suspension has been evaluated. It is evident that floc elongation increases with shear rate (jet-to-wire speed difference) and lower dewatering rate. The latter is because the fibre floc is subjected to the shear field longer due to slower immobilisation. Shorter fibre tends to create weaker networks, which promotes a higher elongation of the flocs.QC 20100901
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Smyth, Kenneth Jeffrey. "Debris torrent mechanisms." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26739.
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The phenomenon of the debris torrent is explored by examining the mechanisms of initiation, particularly those of rainfall and deforestation.
The types of precipitation likely to contribute to instability are identified and data collection is reviewed.
Debris torrents have characteristics unlike that of ordinary stream flow, and are capable of transporting massive quantities and sizes of material. Models to explain this transport capability are compared and contrasted. A theoretical analysis of the flow regime is carried out which is argued to be consistent with the observed turbulent nature of a debris torrent. This analysis is extended to the calculation of superelevation
in bends and shows that current attempts to estimate velocities from super-elevation data may be very conservative.
Further application of the turbulent stress analysis is used to estimate the angle of spread of the debris torrent in the deposition zone, and this analysis may be useful in zoning the downstream area to safeguard construction.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Bergström, Roger. "Fibre flow mechanisms /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-240.
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Kruchinin, Dennis. "Lithium amide mechanisms." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437356.
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El-Kaddar, Yousef Younis. "Organosilicon reaction mechanisms." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375169.
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This thesis is concerned with the preparation and reactions of some highly sterically hindered organosilicon compounds, mainly of the type TeiSiMe2X where Tsi denotes the (Me3Si)3C group. The first detailed study of the reactions of TsiS1Me20CN has shown that reactions with NaN3 in MeOH or KSCN or KOCN in MeCN give exclusively the corresponding TsiSiMe2X compounds (X = N3, NCS, or NCO), whereas those with other salts, viz. LiCl, CsF, KSCN, and KOCN, give the TsiSiMe2X species along· with other products, including in many cases TsiSiMe2NCO and TsiSiMe20H (from traces of water), and (in MeOH) TsiSiMe20Me. The reaction with MeOH alone was never found to give less than 10% ot TslSiMe20H, along with the expected TsiSiMe20Me, however carefully the MeOH was dried. The extreme sensitivity of the cyanate towards water was illustrated by the fact that the rate ot solvolysis in 'dry' MeOH was increased by~. 90% by addition of 0.05 vol-% of H2o, and the hydroxide was the sole product, whereas the rate for the triflate TsiSiMe2- OS02CF3 was increased by only 13% and the product was a 60:40 mixture of TsiSiMe20Me and TsiSiMe20H. The rate constant for the triflate increased linearly with the water concentration but that of the cyanate did not. The presence of NaOMe in MeOH led to rapid isomerization of the cyanate to the isocyanate, TsiSiMe2NCO, with the rate of isomerization being proportional to the base concentration: a possible explanation of this effect of base is suggested. Isomerization catalysed by ICI in CC14 was found to be of ca. second order with respect to both the cyanate and the IcI: A detailed kinetic study has been carried out of the the reactions of TsiSiMe2X compounds, with X c I, Br, Cl, or ON02' with various alkali metal salts, MY, viz. NaN3' CsF, KSCN, and KOCN in MeOH and with KSCN in MeCN. For X • I, Br, or Cl, the reactions have been shown to be much more complex than was previously thought, the compounds TsiSiMe20Me, TsiSiMe20H, and (Me3Si}2CHSiMe2oMe commonly being formed along with TsiSiMe2Y. The order of effectiveness of the salts in the formation of TsiSiMe2Y is CsF > NaN3 > KSCN > KOCN, except that for X - I the order for CsF and NaN3 is reversed. Approximate values of the activation parameters have been obtained: the activation entropies have very high negative values, consistent with formation of a very crowded transition state. The nitrate is markedly more reactive even than the iodide, and gives cleaner conversions into TsSiMe2Y compounds: the activation energies are much lower and the activation entropies much more negative than those tor the halides. Reactions of the compounds (Me3Si)2C(SiMe2H)(SiMe2Cl) with alkali metal salts have been shown to be much faster than those of TsiSiMe2Cl, casting doubt on an earlier suggestion that the ease of solvolysis of the former chloride might be due to anchimeric assistance by y-H.
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Jenkinson, Peter Colin. "Mechanisms of teratogenesis." Thesis, University of Surrey, 1987. http://epubs.surrey.ac.uk/628/.
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Seereeram, Videsh Ramjas. "Compliant shell mechanisms." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610867.
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Bird, Geoffrey Peter. "Mechanisms of imitation." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446562/.
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This thesis aims to discover the mechanisms of imitation by testing the predictions of three theories. These are Associative Sequence Learning Theory (Heyes and Ray, 2000), Ideomotor Theory (e.g. Prinz, 1997), and Active Intermodal Mapping (e.g. Meltzoff Moore, 1997). Chapter 1 identifies three issues upon which the theories of imitation can be differentiated. The first is concerned with the development of effector-dependent representations through observation. The second and third relate to the role of awareness and experience in imitation. These differences form the basis of the experiments reported in Chapters 2, 3 and 4. Experiments 1 - 3 (Chapter 2) investigated whether effector-dependent representations could be formed through action observation. A series of tests based on the serial reaction task (SRT) were utilised. It was found that with relatively short, simple movement sequences, participants learned the structure of the sequence as effector-dependent motor representations. Sequence knowledge could not be expressed using effectors other than those used by the observed model. Experiments 4 - 6 (Chapter 3) used similar tests to those in Chapter 2 but investigated whether a longer, more complex, movement sequence could be learned implicitly i.e. without concurrent awareness. Two experiments suggested that observation of a movement sequence, but not inanimate stimuli, could support implicit learning. Experiments 7 and 8 (Chapter 4) investigated the role of experience in imitation. It was shown that while responses made to movement stimuli were faster when stimulus and response movements matched, compared to when they were different, the advantage for matching movements disappeared after incompatible training. This result supports an experience-based, rather than innate, view of imitation. The results of the experiments reported in this thesis suggest imitation is experience- based, supports effector-dependent learning by observation, and can operate without awareness. This combination is best described by Associative Sequence Learning Theory.
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Tidwell, Paul H. "Wrapping CAM mechanisms." Diss., Virginia Tech, 1995. http://hdl.handle.net/10919/39149.
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Vaughan, Christopher W. "Mechanisms of continence." Thesis, The University of Sydney, 1991. https://hdl.handle.net/2123/26421.
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While disorders of urine storage are of considerable clinical significance, little is known about autonomic nervous system dysfunction and the neural control of continence. The paucity of studies on the sympathetic reflex to the bladder may be partly related to doubts about the involvement of the nervous system in the continence process, particularly at filling rates within the naturally occurring range.
In the present study, the characteristics of the postganglionic sympathetic outflow to the feline bladder were examined at filling rates within the naturally occurring range. The sympathetic outflow was observed to have a net inhibitory effect on bladder wall tension for a significant portion of the continence process, although both tonic sympathoinhibitory and phasic sympatho-excitatory influences were detected. The sympathetic reflex to the bladder was characterised as a simple rate independent reflex, the tonic increases in activity being augmented by prolonged after-discharges, possibly arising at the ganglion level. Both the level of sympathetic reflex activation and the degree of sympatho-inhibitory control over the bladder appeared to be dependent on the level of bladder wall tension, as transduced by the pelvic and possibly hypogastric afferent mechanoreceptors.
Bladder distension dependent activity from the whole hypogastric nerve was similar to activity in hypogastric filaments near the bladder wall. However, a large vasomotor component in the hypogastric nerves of female animals was probably destined for the female genital organs. The present observations were made while deliberately using pentobarbitone anaesthesia. The continence control system appeared functionally similar under other anaesthetics.
The sympatho-inhibitory reflex reduced bladder wall tension, promoting urine storage by reducing the level of afferent discharge impinging upon the nervous system. The sympatho-excitatory reflex appears to be involved in the production of non-micturating contractions in the anaesthetised cat, by providing a synchronous excitation of the bladder detrusor.
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Fagelson, Marc A. "Tinnitus Mechanisms: Auditory." Digital Commons @ East Tennessee State University, 2015. https://dc.etsu.edu/etsu-works/1953.
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Teuten, Emma L. "Radical mechanisms in the nitrosation of N, N-dialkylanilines." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074447.
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Terakawa, Tatsuro. "Omnidirectional Mobile Mechanisms and Integrated Motor Mechanisms for Wheeled Locomotion Devices." Kyoto University, 2019. http://hdl.handle.net/2433/242493.
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付記する学位プログラム名: デザイン学大学院連携プログラムKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第21755号
工博第4572号
新制||工||1713(附属図書館)
京都大学大学院工学研究科機械理工学専攻
(主査)教授 小森 雅晴, 教授 松野 文俊, 教授 松原 厚
学位規則第4条第1項該当
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Ustun, Deniz. "Kinematic And Force Analyses Of Overconstrained Mechanisms." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613880/index.pdf.
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This thesis comprises a study on the kinematic and force analyses of the
overconstrained mechanisms. The scope of the overconstrained mechanisms is too
wide and difficult to handle. Therefore, the study is restricted to the planar
overconstrained mechanisms. Although the study involves only the planar
overconstrained mechanisms, the investigated methods and approaches could be
extended to the spatial overconstrained mechanisms as well.
In this thesis, kinematic analysis is performed in order to investigate how an
overconstrained mechanism can be constructed. Four methods are used. These are
the analytical method, the method of cognates, the method of combining identical
modules and the method of extending an overconstrained mechanism with extra links.
This thesis also involves the force analysis of the overconstrained mechanisms. A
method is introduced in order to eliminate the force indeterminacy encountered in the
overconstrained mechanisms. The results are design based and directly associated
with the assembly phase of the mechanism.
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Jaffit, Danielle. "Mechanisms for embedding sustainability into organisational strategic decision-making: technology as an enabling mechanism." Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/23751.
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There is a growing need for businesses to shift toward a more sustainable strategic focus if they are to positively impact the societies within which they operate and remain viable businesses in the future. This is becoming increasingly acknowledged amongst South African organisations, however the challenge they face is in refocusing their strategic goals to be sustainably oriented. In order to tackle this challenge many organisations internationally and locally are starting to utilise information technology based tools and technological platforms as a mechanism for embedding sustainability into their business – tracking their impact and linking sustainability goals to their performance management structures using dashboards to visually represent this data. The intention of this research has been to explore the drivers of this organisational shift towards sustainability, internally and externally, the changes that are being implemented (the content of these strategic changes) and the processes organisations are implementing to become more sustainable. The specific focus is on the tools and technology they are utilising to enable this shift towards sustainability. This research takes the form of a qualitative cross case analysis of six organisations and utilises Pettigrew's framework for strategic change that looks at three parts of a change process: the context, content and process, to attempt to answer the question: How do technology platforms, and the ability for organisations to gather, monitor and manage organisational data relating to sustainability indicators result in more sustainable strategic decision-making within South African organisations? The results of this research demonstrate the link between quantifying activities and deeper integration of sustainable activities within the organisation. The role technology plays, based on the analysis of six South African companies, is frequently dependent on the driver of the quantifying activity and the degree to which the data has an effect on the broader business targets.
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Ferenc, Veszteg Róbert. "Auctions, Mechanisms and Uncertainty." Doctoral thesis, Universitat Autònoma de Barcelona, 2004. http://hdl.handle.net/10803/4057.
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Los mecanismos que permiten la interacción de los individuos tienen un gran impacto sobre los resultados de esta interacción. La teoría económica de diseño de mecanismos estudia el diseño de procedimientos de decisión social en situaciones en la cuales los agentes económicos guardan información privada y se comportan, la utilizan, de forma estratégica.Como ejemplo, considérese el caso en el cual la autoridad central de un país está considerando la posibilidad de declarar como "reserva nacional" una determinada área geográfica. Para poder tomar la decisión óptima, por ejemplo la que maximiza el bienestar social, ésta se tiene que basar en la información individual de las ciudades, estados, o agentes, cuya opinión sobre el problema que se considera se puede preguntar directamente, pero la verdad no se expresará sin los incentivos adecuados. Estos pueden aparecen como transferencias monetarias u otros instrumentos controlados por la autoridad. Con otras palabras, la teoría de diseño de mecanismos estudia la harmonización de los incentivos que se tienen que aplicar cuando un conjunto de agentes interactúa para que estos muestren un comportamiento deseado, es decir para que el resultado sea el intencionado.
La primera formalización de este problema se encuentra en el trabajo de Hurwitz (1972). No obstante, una de las primeras aplicaciones que se puede considerar como parte de la literatura de diseño de mecanismos lleva el nombre de Hayek, quien empezó a estudiar las limitaciones, en cuanto a la cantidad de información, de los planificadores centrales en los años 20. Él consideró un problema de gran escala al centrar su atención en el mecanismo del mercado libre. Se opuso firmemente al sistema socialista y describió su fallo principal como un problema de información.
Una aplicación similar es el diseño de una constitución que determina las acciones que los agentes pueden realizar (espacio de estrategias) y las reglas de votación que transforman votos en decisiones (funciones de pago). Al lado de la literatura sobre cómo reducir los fallos del mercado, sobre impuestos óptimos y teoría de bienes públicos, el diseño de subastas también aparece entre los sujetos del diseño de mecanismos.
Esta tesis está dividida en tres capítulos que presentan estudios completos y separados de situaciones económicas en las cuales la información, la incertidumbre, juega un papel importante. Los resultados se han obtenido con la ayuda de la teoría de juegos y el enfoque estándar de la literatura del diseño de mecanismos. El primer capítulo propone el uso del mecanismo "multipujas" ("multibidding game"; veáse Pérez-Castrillo y Wettstein (2002)) en situaciones con información imperfecta y desarrolla sus propiedades teóricas. El segundo capítulo es un trabajo empírico, utiliza datos experimentales y contrasta las predicciones teóricas del primero. La tesis se finaliza con el estudio de los conceptos de justicia en un marco donde los agentes toman sus decisiones bajo incertidumbre.
Mechanisms through which individuals interact may have important impact on the outcomes of this interaction. The economic theory of mechanism design is concerned with the design of social decision procedures for situations in which economic agents own relevant private information and behave, i.e. use it, strategically.
As an example, consider the case in which the central authority of a country is studying the possibility of declaring national reserve a given geographic area. In order to come up with the optimal decision, that for instance maximizes social welfare, it should be conditioned on the related information owned by cities, states, or individuals. They might be asked directly for their opinion on the underlying problem, but will not report their information truthfully unless proper incentives are given to them through monetary transfers or some other instruments controlled by the authority. In other words, mechanism design theory is concerned with the harmonization of incentives that must be applied to a set of agents that interact in order to get those agents to exhibit some desired behavior, i.e. in order the schemes to work as intended. The central authority, or social planner, of this example who acts on behalf of the whole society can also be replaced by an imaginary social goal or by a principal who is pursuing his own interest.
The formalization of this problem can be find in the seminal work by Hurwicz (1972). Nevertheless, one of the first applications that can be considered as from the theory of mechanism design is due to Hayek who started to study the limitations on the amount of information that central planners can acquire in the early 1920s. He considered a large scale problem focusing his attention on the free market mechanism. He fiercely opposed to the socialist system from every angle and described the main problem as a problem of information.
A similar application is the design of a constitution that determines the actions that agents may take (strategy space) and the electoral rules that transform votes into decisions (outcome function). Along with the literature on the ways of reducing market failures, on optimal taxation and public good theory, the design of auctions is also subject of the field of mechanism design.
This thesis dissertation is divided into three chapters that present self-contained studies of economic situations in which private information, i.e. uncertainty, plays an important role. In deriving the results game theoretic tools and the approach taken by the mechanism design literature are used. The first chapter proposes the use of the multibidding mechanism (check Pérez-Castrillo y Wettstein (2002)) in situations with imperfect information and explores its theoretical properties. The second chapter is an empirical work, it uses experimental data and tests the theoretical predictions of the first. The thesis ends with the study of fairness concepts in an environment in which agents take their decisions under uncertainty.
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Haraldsson, Emil. "Strong user authentication mechanisms." Thesis, Linköping University, Department of Electrical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2688.
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For Siemens Industrial Turbomachinery to meet its business objectives a modular authentication concept has to be implemented. Such a mechanism must be cost- effective while providing a well-balanced level of security, easy maintenance and be as user-friendly as possible.
Authenticating users securely involves the combination of two fields, theory of authentication mechanisms in information systems and human computer interaction. To construct a strong user authentication system the correlations of these fields has to be understood and provide guidance in the design.
Strong user authentication mechanisms enforce the use of two-factor authentication or more. The combinations implemented rely on knowledge, possession and sometimes logical-location.
A user authentication system has been implemented using leading industrial products as building blocks glued together with security analysis, programming and usability research.
The thesis is divided into two parts, the first part giving the theoretical background of cryptography, authentication theory and protocols needed for the understanding of the second part, providing security analysis, blueprints, and detailed discussions on the implemented system.
Conclusions have been drawn regarding the implemented system and its context as well as from strict theoretical reasoning regarding the authentication field in general. Conclusions include:
· The unsuitability of remote authentication using biometrics
· The critical importance of client security in remote authentication
· The importance of a modular structure for the security of complex network-based systems
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Schaller, Heike. "Changes in Solvolysis Mechanisms." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-91684.
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Schmerwitz, Ulrike. "Novel mechanisms of flavopiridol." Diss., lmu, 2010. http://nbn-resolving.de/urn:nbn:de:bvb:19-116983.
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Szakálos, Peter. "Mechanisms of Metal Dusting." Doctoral thesis, KTH, Materialvetenskap, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3722.
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The primary intention with this Doctoral thesis is to fillin the knowledge gaps and raise the level of understandingregarding the different metal dusting mechanisms in general andexplain the process in detail for high alloyed materials.Considerable effort is put into identifying the driving forcesand elucidating the diffusional processes in metal dusting. The results are based on a series of long-term laboratory exposures of stainless steels and high-performance commercial alumina-forming Fe- and Ni-base alloys in synthesis gasmixtures, plus a separate shorter study on ultra pure iron. ANi-base alloy was also investigated after a two years field exposure in a methanol plant. Post exposure metallographic examinations and analysis aswell as thermodynamic calculations were made in order toidentify and describe the operating metal dusting mechanisms.Two main mechanisms were previously used to explain metaldusting, one on the basis of decomposition of metastable carbides (Type I) the other on graphite formation (TypeII). A new metal dusting mechanism has been identified in this Thesis which appears on high alloyed steels and Ni-base alloys,an active corrosion induced by carbon and oxygen, denoted TypeIII. Both the mechanisms and the type of corrosion products were consistent with the thermodynamic conditions of the material under the influence of a carbon and oxygen gradient.It was shown that this mechanism not only accelerates the metaldusting process, in fact, it determines the overall metaldusting kinetics on stainless steels and Ni-base alloys. Another feature, which may occur at temperatures where metalbulk and even static grain boundary diffusion is too slow forexplaining the metal dusting corrosion process, was identifiedon a Ni-base alloy. It involves a fast growing cellular structure with discontinuous precipitated carbides whichprovides fast metal dusting kinetics by the Type IIImechanism. A Type IV metal dusting mechanism, continued fragmentationby graphitization until nano-sized particles are formed andcatalyse carbon nanotube formation is also described. Thesteady state process and the driving force for metal dusting onpure iron was identified and described. With these additional processes it is now possible to extendour understanding of the metal dusting processes to a widerange of engineering alloys.QC 20100825
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Yu, Ru Qi. "Mechanisms of randomness cognition." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62682.
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The environment is inherently noisy, with regularities and randomness. Therefore, the challenge for the cognitive system is to detect signals from noise. This extraction of regularities forms the basis of many learning processes, such as conditioning and language acquisition. However, people often have erroneous beliefs about randomness. One pervasive bias in people’s conception of randomness is that they expect random sequences to exhibit greater alternations than typically produced by random devices (i.e., the over-alternation bias). To explain the causes of this bias, in the thesis, I examined the cognitive and neural mechanisms of randomness perception. In six experiments, I found that the over-alternation bias was present regardless of the feature dimensions, sensory modalities, and probing methods (Experiment 1); alternations in a binary sequence were harder to encode and are under-represented compared with repetitions (Experiments 2-5); and hippocampal neurogenesis was a critical neural mechanism for the detection of alternating patterns but not for repeating patterns (Experiment 6). These findings provide new insights on the mechanisms of randomness cognition; specifically, we revealed different mechanisms involved in representing alternating patterns versus repeating patterns.Arts, Faculty of
Psychology, Department of
Graduate
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Walsh, Bruce William. "Onshore/offshore transport mechanisms." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/28087.
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The onshore/offshore transport mechanisms are investigated. Careful and detailed observations of the surf zone are made to find any differences or similarities between the resulting flows caused by different breaking types. Emphasis is placed on the spilling and plunging breakers. Even though the physical breaking properties are significantly different, the time-averaged properties of the surf zone for each type of breaking wave are similar. Using this as a basis, a model of the beach is developed using a control volume that is bounded by the beach face, the time-averaged water level, and a vertical plane at the breaking point. The momentum acting on the control volume in the onshore and offshore horizontal directions is balanced.
The model shows that the onshore/offshore sediment transport is primarily dependent upon the magnitude of the wave setup shoreward of the breaking point, and the permeability of the beach. Increasing the permeability causes a reduction in the offshore net shear stress acting along the beach face which results in an increasing slope. Using this simple model, the difference between a gravel and sand beach can be explained, the gravel beach being steeper.
The model is used to calculated the offshore net shear stress for a plane impermeable beach in the laboratory. The calculation gives the right order of magnitude (<10 N/m2), but proves to be sensitive to small inaccuracies in the measurement of the setup.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Johansson, Alina. "Molecular mechanisms behind TRIM28expression." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-252834.
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Dickinson, Keith. "Receptor mechanisms in olfaction." Thesis, University of Warwick, 1987. http://wrap.warwick.ac.uk/98464/.
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This thesis is a study of receptor-mediated events occurring in olfaction. Potential enzymes involved in olfactory transduction were investigated using standard biochemical techniques, and an investigation of the fatty acid receptor/s was attempted using psychophysical methods. 1. Other investigators in olfaction have recently demonstrated an odorant modulated adenylate cyclase in the frog. We have shown that tissue preparations from the rat have high levels of the enzyme adenylate cyclase. This activity was stimulated in the presence of odorants by up to two times the basal value. The concentrations of odorants used were in the range expected to be physiologically relevant. Both basal and stimulated adenylate cyclase were inhibited by μM calcium ion. Tissue preparations from brain showed no odorant activation. Guanylate cyclase was present at a tenth the concentration of adenylate cyclase and showed no odorant simulation. 2. There are no studies in the literature characterising the cyclic nucleotide phosphodiesterases in olfactory tissue. The Sutherland criteria require the presence of a cyclic nucleotide phosphodiesterase (PDE) in olfactory tissue, if cyclic AMP is to be a second messenger in olfaction. It is possible that olfactory PDE is directly regulated by a receptor, as is found in vision. It is important, therefore, that the PDE’s in olfactory tissue are characterised. Tissue preparations of the rat and sheep were shown to have high levels of cyclic nucleotide phosphodiesterase. The activities were not stimulated in the presence of physiologically relevant concentrations of odorants; inhibition of these activities by odorants was not significantly different from that of brain homogenates. Characterisation of the phosphodiesterase isoenzymes separated by DEAE chromatography established that they resembled the isoenzymes characterised from other tissues. The evidence presented indicates that olfactory tissue does not resemble visual tissue, which has a receptor-linked phosphodiesterase. All evidence suggests that PDE’s in olfactory tissue serve to return cyclic nucleotide concentrations to resting levels after stimulation. The observation that the Type 1 (calcium/calmodulin stimulated) phosphodiesterase is present in high concentrations in olfactory tissue suggests that calcium ion concentration in vivo may be an important regulator of phosphodiesterase activity. 3. The threshold values of various short chain fatty acids, of high purity, were determined using human subjects. The results were one order of magnitude greater than found by Amoore (1970) but showed a similar group trend. Descriptive analysis was also performed on these acids by generating a series of descriptors sufficient to discriminate between the acids. Analysis of the results by principal component analysis yielded a three dimensional map that showed the acids clustering into four groups. These four groups could indicate the presence of four receptors. Attempts to demonstrate structure-activity relationships between the thresholds, and descriptive analysis results with various physical and chemical parameters, failed. This was probably due to the interaction of the acids with more than one receptor. So far, the lack of success in identifying olfactory receptors by researchers has meant that investigations of olfactory receptors have had to be done using psychophysical techniques such as those used in this report. It will probably not be known if these methods are useful for identifying receptors, until the receptors can be purified and characterised biochemically.
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Parboosingh, Jillian S. "Genetic mechanisms of neurodegeneration." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0018/NQ44548.pdf.
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Ahmed, Ejaz. "Immune mechanisms in atherosclerosis /." Stockholm, 2001. http://diss.kib.ki.se/2001/91-628-4612-4/.
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Kilarski, Witold. "Mechanisms of Tissue Vascularization." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4819.
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Herd, Seth Andrew. "Mechanisms of visual search." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/cr/colorado/fullcit?p3190399.
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Sullivan, Benjamin David. "Nanoscale optoentropic transduction mechanisms." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3294740.
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Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 30, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 208-230).
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Patra, Harisadhan. "Mechanisms of remote masking." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1199309775.
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Witkowski, Jens [Verfasser], and Bernhard [Akademischer Betreuer] Nebel. "Robust peer prediction mechanisms." Freiburg : Universität, 2015. http://d-nb.info/1119805538/34.
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Miller, Irene Ann. "Virulence mechanisms of Salmonella." Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385711.
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Honey, Karen J. "Mechanisms of transplantation tolerance." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301519.
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Wise, Matt. "Mechanisms of transplantation tolerance." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242039.
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Daniels, M. J. "Mechanisms regulating eukaryotic mitosis." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598272.
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The fertilised egg gives rise to the entire organism through the coordination of high fidelity chromosome replication and then segregation. When this mechanism is corrupted cells acquire stable genetic mutations that absolve them from the normal proliferative impediments at work to keep the organism healthy. This is the basis of cancer. In order to understand and then rationally treat cancer we must understand the process of cell division. In this thesis I elucidate novel information pertaining to three mechanisms that guide a cell through the process of mitosis. Firstly as cells enter mitosis I have identified the requirement of the Promyelocytic Leukaemia (PML) tumour suppressor for the integrity of the antephase checkpoint. PML limits the intracellular distribution and mobility of the CHFR checkpoint protein previously known to be required for the antephase checkpoint. During mitotic progression the RanGTPase orchestrates several distinct events. By showing that the principle GTPase activating protein (RanGAP1) is the subject of multiple mitotic phosphorylations that regulate its activity I have identified part of the mechanism that allows the cell cycle to control the actions of the RanGTPase in mitosis. Finally I have provided evidence that the tumour suppressor BRCA2 is required during the process of cytokinesis, and that in its absence cells frequently become aneuploid. Thus I have identified a new route of genetic instability in a hereditary form of cancer.
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Butterfield, Katherine J. "Seismic Liquefaction Trigger Mechanisms." Thesis, University of Canterbury. Civil Engineering, 2004. http://hdl.handle.net/10092/1179.
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Three possible mechanisms for the onset of excess pore water pressure generation due to seismic excitation of saturated soil are investigated using downhole array data from sixteen real earthquakes. The downhole data are used to synthesize both stress and strain at various depths within the ground. Stresses, strains and dissipated energy are then investigated as potential liquefaction trigger mechanisms. The hypothesis that the shear strain threshold is a liquefaction trigger mechanism is strongly supported by the results presented here. In all but one case the shear strain threshold accurately predicts the time of pore pressure rise for real earthquakes in the field. Additionally, the onset of energy dissipation is found to signal the initial rise in measured excess pore pressure remarkably accurately. The results suggest a fundamental link between Nemat-Nasser and Shokooh's pore pressure - dissipated energy.density relationship (1979) and Mindlin and Deresiewicz's (1953) theoretical strain threshold. Mindlin and Deresiewicz's work (1953) defined a theoretical strain threshold as the mechanism for the onset of gross sliding, and 'its associated energy dissipation'. Therefore the onset of energy dissipation constitutes a second, independent verification of the strain threshold hypothesis. The relationship between stress invariants and pore pressure increase is less clear. To date there does not appear to be an acceptable theory that describes a trigger mechanism in terms of stress alone.
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Masters, Iain George. "Deformation mechanisms in honeycombs." Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284155.
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Schwechheimer, Claus. "Transcriptional mechanisms in plants." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267258.
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Allen, Harriet Ann. "Mechanisms of motion processing." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325719.
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Chrystiuk, E. "Acyl group transfer mechanisms." Thesis, University of Kent, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374300.
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Hawker, Victoria. "Mechanisms underlying ozone tolerance." Thesis, University of Newcastle Upon Tyne, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413001.
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