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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.
51

Lateral resolution in laser induced forward transfer

Wang, Qing 11 1900 (has links)
In this thesis the lateral resolution limits of the Laser Induced Forward Transfer (LIFT) technique are being investigated. LIFT is a laser direct write process with micron and below resolution and is suitable for modifying, repairing and prototyping micro-devices. Single laser pulses with wavelength of 800 nm and duration of 130 fs from a Ti:Sapphire laser system were focused onto a transparent donor substrate coated with thin film to transfer the thin film material in the form of micro-disks through a small air gap onto an acceptor substrate. In this thesis, donor glass substrate coated with 80nm continuous Cr film and also Cr disks array patterned by photolithography or e-beam lithography were used as targets. The ablation threshold and transfer threshold were determined experimentally and compared to results from two-temperature model (TTM) simulations and reasonably agreement was obtained. For the continuous film target, the size of the LIFT disks depend on the laser fluences and the smallest sizes of around 700 nm were obtained near the transfer threshold. For the pre-patterned disks array targets, initially 1.3m Cr disks were fabricated on the donor substrates by photolithography. Small focused, larger defocused and large top-hat laser beams were used to transfer the pre-patterned Cr disks. The morphology of the transferred material and reliability of transfer were studied. It was found that the large top-hat beam gave the most reliable and high quality transfer results, resulting in mostly intact LIFT disks on the acceptor substrate. To push the resolution limit further, 500nm Cr disks fabricated on the donor substrate by e-beam lithography were used. The successful transfer of these 500 nm Cr disks gives a positive indication that LIFT can potentially be extended further to the nano-scale regime (usually defined as having sub-100 nm resolution).
52

Modelling data storage in nano-island magnetic materials

Kalezhi, Josephat January 2011 (has links)
Data storage in current hard disk drives is limited by three factors. These are thermal stability of recorded data, the ability to store data, and the ability to read back the stored data. An attempt to alleviate one factor can affect others. This ultimately limits magnetic recording densities that can be achieved using traditional forms of data storage. In order to advance magnetic recording and postpone these inhibiting factors, new approaches are required. One approach is recording on Bit Patterned Media (BPM) where the medium is patterned into nanometer-sized magnetic islands where each stores a binary digit.This thesis presents a statistical model of write errors in BPM composed of single domain islands. The model includes thermal activation in a calculation of write errors without resorting to time consuming micromagnetic simulations of huge populations of islands. The model incorporates distributions of position, magnetic and geometric properties of islands. In order to study the impact of island geometry variations on the recording performance of BPM systems, the magnetometric demagnetising factors for a truncated elliptic cone, a generalised geometry that reasonably describe most proposed island shapes, were derived analytically.The inclusion of thermal activation was enabled by an analytic derivation of the energy barrier for a single domain island. The energy barrier is used in a calculation of transition rates that enable the calculation of error rates. The model has been used to study write-error performance of BPM systems having distributions of position, geometric and magnetic property variations. Results showed that island intrinsic anisotropy and position variations have a larger impact on write-error performance than geometric variations.The model was also used to study thermally activated Adjacent Track Erasure (ATE) for a specific write head. The write head had a rectangular main pole of 13 by 40 nm (cross-track x down-track) with pole trailing shield gap of 5 nm and pole side shield gap of 10 nm. The distance from the pole to the top surface of the medium was 5 nm, the medium was 10 nm thick and there was a 2 nm interlayer between the soft underlayer (SUL) and the medium, making a total SUL to pole spacing of 17 nm. The results showed that ATE would be a major problem and that cross-track head field gradients need to be more tightly controlled than down-track. With the write head used, recording at 1 Tb/in² would be possible on single domain islands.
53

Minulé a současné charakteristiky a formy vázané na permafrost a činnou vrstvu jako indikátory pozdně kvartérních změn přírodního prostředí / Past and Present Permafrost and Active-Layer Phenomena as Indicators of Late Quaternary Environmental Changes

Uxa, Tomáš January 2020 (has links)
Late Quaternary has seen numerous major permafrost expansions and retreats associated with alternating glacial and interglacial periods as well as stadials and interstadials, the research of which is necessary to understand the past environmental evolution, but also provides useful analogues for its present-day and future behaviour. How- ever, observations of permafrost and active-layer phenomena are still limited, and sometimes misleading, even in many present-day permafrost regions, and naturally less comprehensive evidence is available from areas where permafrost existed in the past. The thesis provides comprehensive information on the distribution and morphology of mostly relict patterned ground and rock glaciers in the High Sudetes Mts. and in the Western and High Tatra Mts., respectively, which are the most widespread permafrost features that occur in these Central European mountain ranges situated north of the Alps. It shows that the landforms are closely related to increased severity of climates and/or sparser vegetation at higher elevations and as such they attest to the environmental conditions, which prevailed there towards the end of the Last Glacial Period to the early Holocene, but also to their current states. Similar elevation trends in the pattern morphology are also documented for...
54

Polohové a morfometrické charakteristiky polygonů mrazových klínů na Marsu / Spatial and morphometric features of thermal contraction crack polygons on Mars

Žížalová, Ivana January 2019 (has links)
The aim of this thesis is to analyze zonality of the thermal contraction crack polygons on the surface of Mars. Their morphology and its variation are analyzed in relation to the latitude of Mars. For spatial and morphological analysis were selected 64 images from the HiRISE (Mars Reconnaissance Orbiter) polychromatic camera dataset, images are covering the bandwidths proportionally. Images were first visually analyzed using HiView. 258 areas containing the thermal contraction crack polygons (with total area of 1184 km2 ) and 1036 well developed thermal contraction crack polygons were further vectorized using ArcMap. The thermal contraction crack polygons were found in every searched latitude which proves the ubiquity of permafrost. The largest amount of the thermal contraction crack polygons have been found in latitudes ±60ř and 45ř. In these latitudes were also found the largest and probably the deepest thermal contraction crack polygons (average length ranges from 42,1 - 73,6 m). The smallest polygons (average length 7,7 m) were found around the equator. "Altitude" has no effect on the spread of the thermal contraction crack polygons on Mars; however it has the effect on its morphology. The most widespread are pentagonal polygons, which occur mainly in the southern hemisphere. The next most...
55

The Acute Effects of Patterned Electrical Neuromuscular Stimulation on Quadriceps Torque Production and Motor Unit Recruitment

Derington, John A. 06 June 2014 (has links) (PDF)
Electric muscle stimulation (EMS) has been widely used in the rehabilitation of musculoskeletal injuries. Patterned electrical neuromuscular stimulation (PENS), a specific form of EMS, has been developed to better educate muscles to contract properly. The physiological efficacy of PENS has not been quantifiably identified. OBJECTIVES: The aim of this study is to determine the acute effect of one PENS training session (3 sets of 10 1-sec repetitions) on maximal isometric knee extensor (MVIC) torque production and surface EMG (sEMG) in healthy nonathlete college students. DESIGN: A randomized repeated-measures design was used in this study. METHODS: Twenty-two male college students participated in the study. All participants completed two training sessions, one with PENS and one without, in a randomized crossover design. RESULTS: One bout of PENS training significantly increased MVIC (3.1% ± 1.7%, p = 0.03) which was greater than the change in MVIC of the control group (p = 0.03). Control training did not alter MVIC but resulted in significant decrease in average sEMG amplitude (-7.8% ± 1.6%, p ≤ 0.01) and peak sEMG amplitude (-10.4% ± 2.7%, p ≤ 0.01). These reductions in sEMG following control training were significantly different from the PENS group (p = 0.03 and p ≤ 0.01). CONCLUSIONS: The findings suggest that strength training in conjunction with PENS can enhance torque production after just one bout of training. The increase in torque with no change in sEMG amplitude can be explained by increased motor unit synchronization or decreased cocontraction of antagonist muscles.
56

Fabrication of Responsive Polymer Brushes for Patterned Cell Growth and Detachment

Sutherland, Ashley B. 21 August 2013 (has links)
No description available.
57

Rozšíření a morfologie polygonálních sítí pseudomorfóz mrazových a ledových klínů na území ČR / Spatial distribution and morphology of polygonal nets of frost and ice wedges pseudomorphs in the Czech Republic

Vohradský, Lukáš January 2013 (has links)
Ice and frost wedges are a geomorphological phenomenon which is directly related to periglacial environment and permafrost (Murton, 2007). The presence of permafrost in the territory of the Czech Republic in the Pleistocene period is directly proven by polygonal nets of ice and frost wedge pseudomorphs, which are clearly visible in some remote sensing images. Among others, they can also be used as indicators of paleoenvironmental conditions for the period in which their recent forms originated and developed and for the period of their secondary infilling (Sekyra, 1958). The present thesis focuses on the spatial distribution and morphology of polygonal nets of ice and frost wedge pseudomorphs which were created in the territory of the Czech Republic at the end of Pleistocene and the beginning of Holocene. The analysis of the spatial distribution of polygonal nets was carried out with freely available remote sensing images provided by the GoogleEarth Pro application (Google Inc., 2011). The number of locations with a potential presence of pseudomorphs was 629. Out of these, 49 were subjected to a morphometric analysis of polygonal nets and their corresponding landscape. Statistical data analysis showed that the described polygonal nets of ice and frost wedge pseudomorphs in the territory of the Czech Republic...
58

Informative ornament: ‘The machine’ : enhancing the communicative potential of colour : a thesis presented in partial fulfilment of the requirements for the degree of Master of Design in Illustration at Massey University, Wellington, New Zealand

Malcolm, Sabrina Barkley January 2009 (has links)
Accompanying workbook not available in digital format / Both empirical and anecdotal evidence indicates that visual communication1 design practices implemented by designers with full colour vision often disadvantage, and sometimes endanger, colour-blind people. The thesis The Machine postulates that colour-blind people – comprising approximately 8% of males and 0.5% of females (Lewis et al., 1990) – are marginalized by such practices. It argues that this group could benefit from a design strategy that enhances the communicative potential and visibility of colour. The proposed strategy involves embedding pattern into potentially confusing colours such as red and green. The embedded pattern would function for colour-blind people as an additional clue to the identity of these colours. The thesis contends that while colour alone can be confusing for colour-blind people, patterned colour could offer a solution with a wide range of possible applications. The research aims of The Machine include: developing a system of patterned colour; creating a wordless picture book that demonstrates the effectiveness of the system; constructing a narrative around the condition of red-green colourblindness; and employing visual rhetoric2 to increase awareness of and sensitivity to colour-blindness among those with full colour vision. The design of the thesis is supported by research in a number of interrelated areas. These include the history of pattern post-1850, particularly in Western culture; precedents for patterned colour; and visual rhetoric in story-telling. The research also incorporates an analysis of the defining characteristics of ten late twentieth-century and early twenty-first-century wordless picture books. The thesis is further supported by applied research into patterned colour and visual rhetoric. The Machine aims to benefit colour-blind people, a significant minority group whose visual needs are currently inadequately met. In addition, it proposes broadening the cultural role and significance of pattern. Moreover, by incorporating informative elements usually associated with pedagogic material, it aspires to extend the boundaries of the fantasy picture book genre. 1 Visual communication (n): communication that relies on vision (Wordnet, 2006). 2 Visual rhetoric: the use of visual techniques, such as the creation of visually ‘engaging’ characters, as a means of persuading a target audience
59

Informative ornament: ‘The machine’ : enhancing the communicative potential of colour : a thesis presented in partial fulfilment of the requirements for the degree of Master of Design in Illustration at Massey University, Wellington, New Zealand

Malcolm, Sabrina Barkley January 2009 (has links)
Accompanying workbook not available in digital format / Both empirical and anecdotal evidence indicates that visual communication1 design practices implemented by designers with full colour vision often disadvantage, and sometimes endanger, colour-blind people. The thesis The Machine postulates that colour-blind people – comprising approximately 8% of males and 0.5% of females (Lewis et al., 1990) – are marginalized by such practices. It argues that this group could benefit from a design strategy that enhances the communicative potential and visibility of colour. The proposed strategy involves embedding pattern into potentially confusing colours such as red and green. The embedded pattern would function for colour-blind people as an additional clue to the identity of these colours. The thesis contends that while colour alone can be confusing for colour-blind people, patterned colour could offer a solution with a wide range of possible applications. The research aims of The Machine include: developing a system of patterned colour; creating a wordless picture book that demonstrates the effectiveness of the system; constructing a narrative around the condition of red-green colourblindness; and employing visual rhetoric2 to increase awareness of and sensitivity to colour-blindness among those with full colour vision. The design of the thesis is supported by research in a number of interrelated areas. These include the history of pattern post-1850, particularly in Western culture; precedents for patterned colour; and visual rhetoric in story-telling. The research also incorporates an analysis of the defining characteristics of ten late twentieth-century and early twenty-first-century wordless picture books. The thesis is further supported by applied research into patterned colour and visual rhetoric. The Machine aims to benefit colour-blind people, a significant minority group whose visual needs are currently inadequately met. In addition, it proposes broadening the cultural role and significance of pattern. Moreover, by incorporating informative elements usually associated with pedagogic material, it aspires to extend the boundaries of the fantasy picture book genre. 1 Visual communication (n): communication that relies on vision (Wordnet, 2006). 2 Visual rhetoric: the use of visual techniques, such as the creation of visually ‘engaging’ characters, as a means of persuading a target audience
60

Hyaluronic acid hydrogel materials

Zawko, Scott Andrew 02 February 2011 (has links)
Hyaluronic acid (HA) is one of the primary chemical building blocks of the extracellular matrix and thus is an attractive material for biomedical applications. FDA approved HA-based materials are available as dermal fillers, joint viscosupplements, vitreous substitutes, and abdominal adhesion barriers. The engineering of new HA-based materials and applications is an active area of research. Here we develop several new types of HA-based hydrogels with unique and useful properties. To address the challenge of delivering hydrophobic drugs from hydrophilic hydrogel matrices we have grafted HA hydrogels with [Beta]-cyclodextrin to create hydrogels capable of binding poorly water soluble drugs. To create HA hydrogels with unique anisotropic swelling behavior we have developed a dual-crosslinking technique in which a super-swelling chemically crosslinked hydrogel is patterned with low-swelling photocrosslinked domains. When this dual-crosslinked hydrogel is swelled it contorts into a new shape because of differential swelling among photopatterned regions. To address the challenge of creating hydrogel scaffolds with biomimetic branched porosity we have invented a "crystal templating" technique. This technique grows dendritic crystals throughout a biopolymer solution, crosslinks the biopolymer around the crystals, and washes the crystals away to yield a hydrogel with a dendritic macroporous network. Lastly, we invented a method for patterning a substrate with a microarray of hydrogel compartments. A microarray of living cells is obtained when cells are seeded on the hydrogel patterned substrate. This method addresses the need for an inexpensive, simple method for obtaining living cell microarrays that does not require clean room labs and lithographic expertise. Each of these new materials were based on hyaluronic acid hydrogels but the methods are generalizable to hydrogels of other polymers too. In conclusion, the novel methods in this dissertation are a significant contribution to the engineering of HA-based materials. / text

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