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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
621

Dimensioning and designing a testing rig for impact loading on beams : .

Candemir, Erkan January 2010 (has links)
<p>This report is product of a degree project accomplishment at Linnaeus University in Växjö, Sweden. It is about designing a testing rig for impact loading of beams for laboratory use.</p><p>The specimens to be used were 1 meter long 8 standard profiles given in the project assignment. The first step in this project was to design and dimension a testing rig which is suitable for laboratory use. The height and the maximum mass were chosen according to laboratory use conditions and safety issues. The second step was designing the fixation for the test sample to the testing rig without any dislocation by the impact load. The third step was to measure the falling height of the mass onto the test sample and measure the deflection of the beam. In this case, the precision of falling height was not very important but measuring the deflection of the beam with the highest possible precision was most important. A measurement system is used considering this factor.</p><p>The project started with the idea of affecting the impact loads on the standard steel construction beams. The aim of this project is to design an impact loading testing rig which can be used for the purpose of laboratory experiments and compare the real results from the experiments with the theoretical results from the calculations.</p><p>In the project, Solid Works and AutoCAD software are often used both in the drawings and strength and stress analyses.</p>
622

Polymeric submicron optical ion-selective sensors

Bychkova, Valeriya 21 November 2011 (has links)
Ion-selective polymeric optical sensors – ion optodes – are a promising alternative to ion-selective electrodes and fluorescent dyes for analytical and biological applications, e.g. extra- and intracellular measurements. They are non-toxic, highly selective robust probes for ionic fluxes monitoring. A large-scale fabrication of ion optodes using a solvent displacement method is introduced. This method is a single-batch process that does not require any additional steps. The influence of numerous parameters, e.g. surfactant concentration, solvent nature and membrane concentration, on the average size of the synthesized optodes was studied. The solvent displacement method allows control of the particle size in 200 nm to 30 μm range. Ion optodes selective for sodium, potassium, and calcium cations were prepared and calibrated for hydrogen (pH), sodium, potassium, and calcium. Fabricated sensors demonstrated excellent selectivity, low drift, high stability and reproducibility. Further studies of ion-optodes of different sizes but the same chemical composition revealed a significant shift in their response function. This bias is clearly seen for all fabricated optodes. A strong correlation between a calculated specific surface area and the apparent ion-exchange constant was observed. Considering this, it may be hypothesized that the surface phenomena are contributing to the overall optode response resulting in the observed effect. As a consequence, the response models, developed for the macroscopic ion optodes, cannot be easily applied to the probes at micron- and nano-scale. A primary concern for continuous sensing application of optical sensors is photobleaching of lipophilic fluorescent dye which prevents quantitative fluorescence measurements. Quantum dots, known for their high photostability, brightness and broad excitation spectra with narrow emission bands, were incorporated into polymeric matrix. They excited a fluorophore indirectly, thus, reducing its photobleaching and increasing sensors life-time. We created a composite, quantum dots doped, polymeric sensor that can be integrated into high-throughput detection platforms, such as flow cytometry, chip-based micro-total analysis system technologies, or bundled optical fiber arrays. Ultimately, a fabricated ion-optode was introduced into a Boolean logic gate serving as a reporting microparticle. It responded to the pH changes generated in situ by the enzyme logic system. The present work aimed scaling down the size of biocomputing functional units which might reach the information processing by single molecules associated with signal-transducing single nanoparticles. / Graduation date: 2012
623

Selective Weakening and Post-Tensioning for the Seismic Retrofit of Non-Ductile RC Frames

Kam, Weng Yuen January 2010 (has links)
This research introduces and develops a counter-intuitive seismic retrofit strategy, referred to as “Selective Weakening” (SW), for pre-1970s reinforced concrete (RC) frames with a particular emphasis on the upgrading of exterior beam-column joints. By focusing on increasing the displacement and ductility capacities of the beam-column joints, simple retrofit interventions such as selective weakening of the beam and external post-tensioning of the joint can change the local inelastic mechanism and result in improved global lateral and energy dissipation capacities. The thesis first presents an extensive review of the seismic vulnerability and assessment of pre-1970s RC frames. Following a review of the concepts of performance-based seismic retrofit and existing seismic retrofit solutions, a thorough conceptual development of the SW retrofit strategy and techniques is presented. A “local-to-global” design procedure for the design of SW retrofit is proposed. Based on the evaluation of the hierarchy of strength at a subassembly level, a capacity-design retrofit outcome can be achieved using various combinations of levels of beam-weakening and joint post-tensioning. Analytical tools for the assessment and design of the SW-retrofitted beam-column joints are developed and compared with the test results. Nine 2/3-scaled exterior joint subassemblies were tested under quasi-static cyclic loading to demonstrate the feasibility and effectiveness of SW retrofit for non-ductile unreinforced beam-column connections. Parameters considered in the tests included the presence of column lap-splice, slab and transverse beams, levels of post-tensioning forces and location of beam weakening. Extensive instrumentation and a rigorous testing regime allowed for a detailed experimental insight into the seismic behaviour of these as-built and retrofitted joints. Experimental-analytical comparisons highlighted some limitations of existing seismic assessment procedures and helped in developing and validating the SW retrofit design expressions. Interesting insights into the bond behaviour of the plain-round bars, joint shear cracking and post-tensioned joints were made based on the experimental results. To complement the experimental investigation, refined fracture-mechanic finite-element (FE) modelling of the beam-column joint subassemblies and non-linear dynamic time-history analyses of RC frames were carried out. Both the experimental and numerical results have shown the potential of SW retrofit to be a simple and structurally efficient structural rehabilitation strategy for non-ductile RC frames.
624

Historical aerial photographs and digital photogrammetry for landslide assessment

Walstra, Jan January 2006 (has links)
This study demonstrates the value of historical aerial photographs as a source for monitoring long-term landslide evolution, which can be unlocked by using appropriate photogrammetric methods. The understanding of landslide mechanisms requires extensive data records; a literature review identified quantitative data on surface movements as a key element for their analysis. It is generally acknowledged that, owing to the flexibility and high degree of automation of modern digital photogrammetric techniques, it is possible to derive detailed quantitative data from aerial photographs. In spite of the relative ease of such techniques, there is only scarce research available on data quality that can be achieved using commonly available material, hence the motivation of this study. In two landslide case-studies (the Mam Tor and East Pentwyn landslides) the different types of products were explored, that can be derived from historical aerial photographs. These products comprised geomorphological maps, automatically derived elevation models (DEMs) and displacement vectors. They proved to be useful and sufficiently accurate for monitoring landslide evolution. Comparison with independent survey data showed good consistency, hence validating the techniques used. A wide range of imagery was used in terms of quality, media and format. Analysis of the combined datasets resulted in improvements to the stochastic model and establishment of a relationship between image ground resolution and data accuracy. Undetected systematic effects provided a limiting constraint to the accuracy of the derived data, but the datasets proved insufficient to quantify each factor individually. An important advancement in digital photogrammetry is image matching, which allows automation of various stages of the working chain. However, it appeared that the radiometric quality of historical images may not always assure good results, both for extracting DEMs and vectors using automatic methods. It can be concluded that the photographic archive can provide invaluable data for landslide studies, when modern photogrammetric techniques are being used. As ever, independent and appropriate checks should always be included in any photogrammetric design.
625

Automatic pilot : cognitive, attentional and neurological aspects of the online correction of manual aiming movements

Mulroue, Amy January 2011 (has links)
When the target of a reaching movement is displaced suddenly, people update their movement to take account of the jump, correcting their trajectory online to end the movement at the new target location. These corrections are initiated too rapidly to be conscious, and occur when they are uninstructed (Pisella et al., 2000) or the participant is unaware of the change in location (Goodale et al., 1986). These findings have been taken as evidence that fast corrections occur automatically, and the spatial updating of reach trajectories has become known as the ‘automatic pilot’ (Pisella et al., 2000). This thesis set out to investigate the cognitive, attentional and neurological aspects of the automatic pilot, in three series of related experiments, all employing a double-step reaching task. Experiments 1 - 4 investigated how strongly automatic reach corrections are, by manipulating the influence of conscious intention and cognitive load. These experiments confirmed that the automatic pilot is at most weakly automatic, as correction efficiency is enhanced by an explicit instruction to follow target jumps and, conversely, corrections can be overridden by an intention to resist them. However, voluntary inhibition of the automatic pilot can be disrupted by placing participants under heavy cognitive load, whilst voluntary enhancement is unaffected by this manipulation. Thus, voluntary suppression of the automatic pilot is effortful, but enhancement towards greater responsiveness is seemingly effortless. Experiments 5 - 8 explored the properties of the visual target displacement that drive the automatic pilot response in a double-step reaching task. These experiments demonstrate that correction efficiency is lawfully related to jump salience, but that the onset of the new target location drives correction responses more powerfully than the offset of the original target. However, the maximal correction rates obtained from a simultaneous onset and offset, were too great to be attributed simply to the additive influences of onsets and offsets. The onset and offset components of the target jump are thus synergistic. It is suggested that this reflects the contribution of an apparent motion signal induced by simultaneous onset and offsets, which strongly drives the automatic pilot system. Experiment 9 examined an asymmetry in correction efficiency, favouring rightward over leftward target jumps, evident throughout the earlier experiments. Correction efficiency was assessed for right- and left-handed participants responding to rightward and leftward target jumps. The pattern of results indicated that each hand is advantaged for responding to ipsilaterallydirected jumps, which may reflect biomechanical or hemispheric compatibility effects. However, there was also an overall differential advantage for rightward jumps, which was independent of handedness, or hand used. This suggests a left-hemispheric advantage for automatic correction behaviour, independent of handedness. Finally, Experiments 10 - 14 considered whether the automatic pilot deficit in optic ataxia is simply a manifestation of the more general misreaching deficit. Across several different target conditions, the pattern of online correction in optic ataxia refuted a simple misreaching explanation, suggesting that it is a specific functional consequence of dorsal stream damage.
626

Analyse de la corrélation conditionnelle dérivée de la coévolution d’un système de trois gènes par un modèle du maximum de vraisemblance

Benoit Bouvrette, Louis Philip 08 1900 (has links)
Les gènes codant pour des protéines peuvent souvent être regroupés et intégrés en modules fonctionnels par rapport à un organelle. Ces modules peuvent avoir des composantes qui suivent une évolution corrélée pouvant être conditionnelle à un phénotype donné. Les gènes liés à la motilité possèdent cette caractéristique, car ils se suivent en cascade en réponse à des stimuli extérieurs. L’hyperthermophilie, d’autre part, est interreliée à la reverse gyrase, cependant aucun autre élément qui pourrait y être associé avec certitude n’est connu. Ceci peut être dû à un déplacement de gènes non orthologues encore non résolu. En utilisant une approche bio-informatique, une modélisation mathématique d’évolution conditionnelle corrélée pour trois gènes a été développée et appliquée sur des profils phylétiques d’archaea. Ceci a permis d’établir des théories quant à la fonction potentielle du gène du flagelle FlaD/E ainsi que l’histoire évolutive des gènes lui étant liés et ayant contribué à sa formation. De plus, une histoire évolutive théorique a été établie pour une ligase liée à l’hyperthermophilie. / Protein coding gene may often be grouped and integrated in functional modules with respect to an organelle. These modules may have constituents that follow a conditional correlated evolution to a given phenotype. Genes linked to motility posses this characteristic as they follow a cascade in response to external stimuli. Similarly, hyperthermophily is related to reverse gyrase, however no other element that could be associated with certainty is known. This may be caused by an unresolved case of non-orthologous gene displacement. Using a bioinformatic approach, a mathematical model for conditional correlated evolution for three genes has been developed and applied to the phyletic profiles of archaea. This has helped to develop theories about the potential functions of the flagellar gene FlaD/E and the evolutionary history of the genes that are linked to it and that may have contributed to its formation. In addition, a theoretical evolutionary history has been established for a ligase associated with hyperthermophily.
627

Control and observation of DNA nanodevices

Machinek, Robert R. F. January 2014 (has links)
The uniquely predictable and controllable binding mechanism of DNA strands has been exploited to construct a vast range of synthetic nanodevices, capable of autonomous motion and computation. This thesis proposes novel ideas for the control and observation of such devices. The first of these proposals hinges on introducing mismatched base pairs into toehold-mediated strand displacement – a fundamental primitive in most dynamic DNA devices and reaction networks. Previous findings that such mismatches can impede strand displacement are extended insofar as it is shown that this impediment is highly dependent on mismatch position. This discovery is examined in detail, both experimentally and through simulations created with a coarse-grained model of DNA. It is shown that this effect allows for kinetic control of strand displacement decoupled from reaction thermodynamics. The second proposal improves upon a previously presented strand displacement scheme, in which two strands perform displacement cooperatively. This scheme is extended to be cascadable, so that the output of one such reaction serves as input to the next. This scheme is implemented in reaction networks capable of performing fundamental calculations on directed graphs. The third proposal is exclusively concerned with a novel observation methodology. This method is based on single-molecule fluorescence microscopy, and uses quantum dots, a fluorescent type of semiconductor nanocrystal, as a label. These quantum dots display a set of characteristics particularly promising for single-molecule studies on the time- and length scales most commonly encountered in DNA nanotechnology. This method is shown to allow for highly precise measurements on static DNA devices. Preliminary data for the observation of a complex dynamic device is also presented.
628

Estimation of Machining System Dynamic Properties - Measurement and Modelling

Österlind, Tomas January 2017 (has links)
Dynamic characteristics of machining systems are analysed for improved understanding of both structural and process properties. The thesis stresses the use of testing methods under operational like conditions as these are more representative of closed loop systems, such as machining systems, as compared to conventional testing methods. The test instrument proposed is a contactless excitation and response system, developed for testing of machine tool spindles under load and with rotating spindle. The instrument uses electromagnetic excitation and displacement sensors for analysis of rotating milling tools subject to load. A graphical tool for displaying and analysing rotor displacement was developed in conjunction with this. A modelling procedure for both off-line and on-line estimation of dynamic properties of mechanical structure and process information is presented. The proposed auto-regressive moving average models enable calculation of operational dynamic parameters and they can be estimated in a recursive manner, thus enabling real-time monitoring. The discrimination between stable and unstable processes, both in turning and milling, was performed by analysing the damping obtained from the operational dynamic parameters. / <p>QC 20170330</p>
629

Voluntary Associations: Membership Attrition and Structural Characteristics

Huffman, Ellen Jane 05 1900 (has links)
The problem of this research was to investigate David Sills' explanation of membership attrition in voluntary associations. Using the membership population of the Dallas Association for Retarded Citizens from 1969 through 1974, a survey was conducted to determine whether the organizational characteristics of bureaucracy, minority rule, and goal displacement are associated with membership attrition in a selected voluntary association. The findings of this study support Sills' ideas about the association of goal displacement and minority rule with membership attrition in voluntary associations. Bureaucratization, however, was not found to be related to membership attrition.
630

Microfluidic cells as a model 2D granular material

Fantinel, Paolo 25 January 2017 (has links)
No description available.

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