Data shows that elderly people are more likely to live alone than younger people, meanwhile the percentage of elderly people with disabilities increases significantly with age. These trends and facts bring a number of issues. One of these we would like to solve is that it is difficult and dangerous for them to lift the heavy loads through ladder. Sometimes it is also very dangerous for normal people, not to mention to people with reduced mobility. In order to solve these issues and reduce the possibility of accident, we have come up with a new ladder used for attics that can transport the heavy loads automatically. As transmission part we use a rack and pinion mechanism to achieve a   smooth transport and a ratchet mechanism for stopper to avoid sudden accident drops.  The ladder also can be hidden when not using it.

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This thesis proposes that compliant mechanism theory can be used to design over-running ratchet and pawl clutches with reduced part count, lower assembly and manufacturing time while maintaining functionality. An extension of the theory to the micro regime is also briefly addressed. The results of the research show that the ratchet and pawl type of over-running clutch is a good choice for the use of compliance, and the clutch pawls should be loaded in compression to get the largest amount of output torque. It was found that com-pliant mechanism theory can be used to design ratchet and pawl clutches with fewer parts and lower manufacturing and assembly costs, and that these clutches perform comparable to traditional rigid-body ratchet and pawl clutches. Compliant ratchet and pawl clutches can replace traditional rigid-body clutches in some applications and now make it possible to be used in applications where it was once not economically feasible to use a over-running clutch. It was also found that these clutches function at the micro level.

This work describes the design, synthesis and operation of a (R,R)-(+)-hydrobenzoin-diacetic acid molecular walker attached to polyether tracks containing 2, 3 or 4 secondary alcohol footholds. A macrocycle-the walker attached to a 2-foothold track by two ester linkages-was regioselectively hydrolysed by lipase AS. The resultant seco¬-acid was recyclised using Yamaguchi chemistry, demonstrating a bipedal walker stepping off, and on to, a track. These conditions were extended to tracks containing 3 and 4 alcohol footholds and the design of a 3-foothold track that incorporated a pentaethylene glycol chain. Using an information type Brownian ratchet mechanism, ~90% of walkers stepped away from the starting position, and ~68% of walkers took 2 steps to a foothold 16 atoms away. Importantly only smaller or equal to4% of walkers were found to completely detach from the track per operation cycle.

The concept of tiny machines capable of selectively transporting particles between two compartments by Brownian motion dates back to the 19th century when James Clerk Maxwell pondered the significance of a hypothetical ‘sorting demon’ being able to perform such a task adiabatically. This thesis report the design, synthesis and operation of a compartmentalized molecular machine in which the distribution of a Brownian particle, the macrocycle in a rotaxane, is controlled by using the lightinduced transmission of information to lower a kinetic barrier according to the location of the particle. For an ensemble of such machines the particle distribution is driven further and further away from equilibrium, providing a non-adiabatic realization of Maxwell’s pressure demon in molecular form. The nanomachine does not break the Second Law of Thermodynamics because the energy cost of the information transfer is met by externally supplied photons. As the molecular structure can be understood in chemical terms, it is possible in this experimental system to pin-point precisely how information is traded for energy. Intriguingly, the chemical mechanism can also be understood in terms of game theory. This is the first example of a synthetic molecular machine designed to operate via an information ratchet mechanism, where knowledge of the object’s position is used to control its transport away from equilibrium.

This thesis analyses the ratchet effect in the context of the performance scheme implemented by Brazilian tax collection in 1988 to reward tax officials for their effort in collecting taxes and uncovering tax violations, using panel data for 110 tax agencies from August 1989 to April 1993 and employing the GMM-system estimator. The estimates suggest the presence of ratchet effect, i.e., the more the tax officials do today, the more the tax officials are asked to do in the future. This result endangers the credibility of the Brazilian tax authority's incentive program as an incentive system.

xvi, 127 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Brownian ratchets generate transport at the micron scale with the help of thermal motion. The Brownian ratchet studied here is the flashing ratchet which transports particles by switching on and off a spatially asymmetric, periodic potential. Experimental work in the literature indicates that interdigitated electrode arrays can been used to create such potentials in solution, but no detailed study of particle trajectories has accompanied such experiments. Here, interdigitated electrode array devices were fabricated. Analysis of the trajectories of individual particles moving in response to a switching voltage revealed that the transport is likely due to electroosmotically driven fluid flow, not the Brownian ratchet effect. Simulation work in the literature predicts that polymers in a ratchet potential will exhibit qualitatively different transport from the particle case. Here, polymer transport was tested experimentally using interdigitated electrode array devices, collecting images of individual à à à à à à » DNA molecules and applying a flashing voltage. The DNA was observed to move in response to the applied potential and the resulting images contain DNA trajectories and also information about its conformations and dynamics. Conformations were analyzed using principal components analysis, extracting the normal modes of the variations amongst large sets of polymer images. These results iv show no conformational changes indicative of the polymer ratchet mechanism, despite the polymer motion. This result and detailed analysis of the DNA trajectories, suggest that the observed motion was driven by bulk flow generated through electroosmosis, in agreement with results from experiments using particles in similar devices. Deterministic Lateral Displacement (DLD) uses an array of obstacles in a microfluidic channel to sort micron-scale objects with à à à à à ¢ à à à à à ¼10nm precision. However, very little work has been done to quantitatively address the role of diffusion in DLD sorting. Here, modeling of transport in DLD arrays has shown that using arrays of obstacles that are small compared to their separation can create sorting that is robust against changes in flow velocity. Also, novel sorting modes were revealed when the model was applied to unconventional array geometries that have not been discussed in the literature. / Adviser: Heiner Linke

What do Black Lives Matter and Freaknik have in common? In this paper, I will argue that moments of Black Lives Matter in Atlanta exhibited refusals and undoings of respectability politics through the method of the ratchet. I define the ratchet as moments of non-normative embodiment and political possibility that refuse statist and Eurocentric norms through slippage of the self and the engagement of Black queer sexual politics. Freaknik is foregrounded as a ripe space for excavating such a display of the politically ratchet in Atlanta. I will look at a few different moments in the Black Lives Matter movement in the city of Atlanta and read each for currents of ratchetness and respectability, highlighting the importance of the ratchet in political imagination and possibility.

La nanotechnologie est un domaine en voie d'expansion qui a attiré l'attention de la recherche en raison de ses applications potentielles illimitées. La technologie des ondes millimétriques est un autre domaine intéressant qui joue un rôle de premier plan dans le développement des systèmes de communications sans fil. La combinaison de ces deux champs de recherche avancée, donne naissance à l'innovation du Dispositif Ratchet qui est une nouvelle application qui représente un vrai défi. Ce dispositif est de taille nanométrique et son concept d'opération consiste à générer une tension DC lorsque le dispositif, basé sur le gaz d'électron bidimensionnel, est rayonné par l'énergie des micro-ondes. L'objectif de cette thèse est d'essayer d'améliorer la réponse du dispositif, ce qui ouvre de nouvelles perspectives dans la fabrication des détecteurs de champ à haute fréquence et à l'échelle nanométrique. Malheureusement, les Dispositifs Ratchet actuels, basés sur des hétérostructures de semiconducteurs, réalisés jusqu'à présent fonctionnent à basse température pour assurer une grande mobilité électronique. Cette condition nécessite l'utilisation d'un setup expérimental complexe qui a un grand impact sur la tension induite et sur la reproductibilité du phénomène Ratchet observé. Dans ce contexte, le travail effectué dans le cadre de cette thèse a abordé ce problème en deux parties. La première partie concerne l'analyse électromagnétique du setup expérimental. Ceci a été réalisé par la mise en oeuvre des simulations électromagnétiques intenses. D'autre part, différentes solutions ont été proposées afin d'optimiser le setup et ainsi améliorer la tension Ratchet produite. Outre l'étude électromagnétique, certaines mesures de modulation ont été réalisées pour tester la faisabilité du Dispositif Ratchet comme un démodulateur d'amplitude. La deuxième partie de cette thèse traite l'étude de la matière qui compose le Dispositif Ratchet. Récemment, le graphène commence à envahir le monde scientifique et technologique avec ses fascinantes propriétés électroniques, tels que sa mobilité d'électrons élevée à température ambiante, où les matériaux conventionnels sont en train de confronter des obstacles. En conséquence, l'idée de fabriquer un Dispositif Ratchet à base de graphène au lieu des hétérojonctions de semiconducteurs, a été introduite. Plusieurs modèles de conception, caractérisation et mesures RF ont été accomplis en vue d'obtenir un Dispositif Ratchet fiable approprié pour de nombreuses applications pratiques à la température ambiante, dans la gamme de fréquences micro-ondes et pourraient s'étendre à la bande térahertz. / Nanotechnology is a growing field that has attracted significant research attention due to its unlimited potential applications. Millimeter wave technology is another interesting field that plays a leading role in the development of wireless communications systems. Combining these two advanced research fields together, has given rise to the innovation of the Ratchet Device which is now a new challenging application. This device has a nanoscale size and its concept of operation consists of generating a DC voltage when radiating a two-dimensional electron gas based device with microwave energy. The aim of this thesis is in trying to improve the device response and hence opening new perspectives in the fabrication of high frequency field detectors on the nanoscale level. Unfortunately, the current Ratchet Devices, based on semiconductor heterostructures, realized till now, operate at low temperatures to ensure high electron mobility. This condition necessitates the use of a complex experimental setup that has a great impact on the induced voltage and on the reproducibility of the observed Ratchet phenomenon. In this context, the work performed within the framework of this thesis has addressed this problem in two parts. The first part concerns the electromagnetic analysis of the experimental setup behavior. This has been achieved by implementing intensive full wave electromagnetic simulations. Different solutions have been proposed to optimize the setup and thus enhance the Ratchet voltage produced. In addition to the electromagnetic study, some modulation measurements have been performed to test the feasibility of the Ratchet Device as an amplitude demodulator. The second part of this thesis deals with the study of the material composing the Ratchet Device. Recently, graphene has started to invade the scientific and the technological world with its fascinating electronic properties, such as its high electron mobility at room temperature, which distinguishes it from conventional materials that typically collide with obstacles. As a result, the idea of fabricating a Ratchet Device based on graphene instead of semiconductor heterojunctions has been introduced. Several design models, characterizations and RF measurements have been performed in order to obtain a reliable Ratchet Device suitable for many practical applications at room temperature. This has been done in the microwave frequency range and can also extend to the terahertz band.

Esta tese aborda diversos temas em evolução molecular, usando extensivamente o formalismo de funções geratrizes para obter resultados analíticos sempre que possível. Em primeiro lugar, apresenta-se a solução exata para o comportamento dinâmico de uma população infinita de seqüências infinitamente longas (não há mutações reversas) evoluindo sob a ação de mutações deletérias em um relevo adaptativo multiplicativo ou truncado. Além disso, foi estudado o comportamento de uma população submetida a sucessivas diluições de intensidades arbitrárias, como ocorre em alguns protocolos de evolução experimental. Foram obtidas expressões matemáticas que, em princípio, podem ser úteis na caracterização de populações reais de microorganismos. Demonstrou-se também que um processo estocástico de ramificação multidimensional generalizado é uma excelente ferramenta para analisar numericamente os efeitos da degeneração mutacional (especificamente, de um fenômeno denominado catraca de Muller) em populações sob variadas condições de crescimento exponencial. Finalmente, simulações foram extensivamente utilizadas para analisar a história evolutiva de populações finitas e averiguar a possibilidade de certas grandezas, como certas medidas da topologia de árvores genealógicas, serem empregadas na elaboração de testes estatísticos capazes de detectar as marcas deixadas pela seleção natural. / This thesis discusses some topics of molecular evolution, extensively using generating function methods to find analytical results whenever possible. In first place, it gives the exact solution for the dynamics of an infinite population of infinitely long sequences (no back mutations) evolving under the action of deleterious mutations on either multiplicative or truncated fitness landscapes. In addition, the behavior of a population subject to successive dilutions of arbitrary intensity, just like some experimental evolution protocols, is found. The mathematical expressions, in principle, may prove useful in characterizing real populations of microor¬ganisms. It was also demonstrated that a generalized multidimensional branching process is a nice tool in numerically studying mutational degeneration effects (specifically a pheno¬menon called Muller\'s ratchet) in populations under a wide variety of exponential growth settings. Finally, the evolutionary history of finite populations was studied by simulations to probe the viability of certain statistic, like some topological measures in genealogical trees, being incorporated in statistical tests to detect the fingerprints of natural selection.