• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 912
  • 174
  • 171
  • 113
  • 36
  • 32
  • 28
  • 25
  • 22
  • 14
  • 10
  • 10
  • 10
  • 6
  • 6
  • Tagged with
  • 2037
  • 629
  • 480
  • 384
  • 262
  • 252
  • 191
  • 173
  • 164
  • 157
  • 142
  • 134
  • 131
  • 111
  • 103
  • 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.
311

Detection of insect and fungal damage and incidence of sprouting in stored wheat using near-infrared hyperspectral and digital color imaging

Singh, Chandra B. 14 September 2009 (has links)
Wheat grain quality is defined by several parameters, of which insect and fungal damage and sprouting are considered important degrading factors. At present, Canadian wheat is inspected and graded manually by Canadian Grain Commission (CGC) inspectors at grain handling facilities or in the CGC laboratories. Visual inspection methods are time consuming, less efficient, subjective, and require experienced personnel. Therefore, an alternative, rapid, objective, accurate, and cost effective technique is needed for grain quality monitoring in real-time which can potentially assist or replace the manual inspection process. Insect-damaged wheat samples by the species of rice weevil (Sitophilus oryzae), lesser grain borer (Rhyzopertha dominica), rusty grain beetle (Cryptolestes ferrugineus), and red flour beetle (Tribolium castaneum); fungal-damaged wheat samples by the species of storage fungi namely Penicillium spp., Aspergillus glaucus, and Aspergillus niger; and artificially sprouted wheat kernels were obtained from the Cereal Research Centre (CRC), Agriculture and Agri-Food Canada, Winnipeg, Canada. Field damaged sprouted (midge-damaged) wheat kernels were procured from five growing locations across western Canada. Healthy and damaged wheat kernels were imaged using a long-wave near-infrared (LWNIR) and a short-wave near-infrared (SWNIR) hypersprctral imaging systems and an area scan color camera. The acquired images were stored for processing, feature extraction, and algorithm development. The LWNIR classified 85-100% healthy and insect-damaged, 95-100% healthy and fungal-infected, and 85-100% healthy and sprouted/midge-damaged kernels. The SWNIR classified 92.7-100%, 96-100% and 93.3-98.7% insect, fungal, and midge-damaged kernels, respectively (up to 28% false positive error). Color imaging correctly classified 93.7-99.3%, 98-100% and 94-99.7% insect, fungal, and midge-damaged kernels, respectively (up to 26% false positive error). Combined the SWNIR features with top color image features correctly classified 91-100%, 99-100% and 95-99.3% insect, fungal, and midge- damaged kernels, respectively with only less than 4% false positive error.
312

Near Images: A Tolerance Based Approach to Image Similarity and its Robustness to Noise and Lightening

Shahfar, Shabnam 27 September 2011 (has links)
This thesis represents a tolerance near set approach to detect similarity between digital images. Two images are considered as sets of perceptual objects and a tolerance relation defines the nearness between objects. Two perceptual objects resemble each other if the difference between their descriptions is smaller than a tolerable level of error. Existing tolerance near set approaches to image similarity consider both images in a single tolerance space and compare the size of tolerance classes. This approach is shown to be sensitive to noise and distortions. In this thesis, a new tolerance-based method is proposed that considers each image in a separate tolerance space and defines the similarity based on differences between histograms of the size of tolerance classes. The main advantage of the proposed method is its lower sensitivity to distortions such as adding noise, darkening or brightening. This advantage has been shown here through a set of experiments.
313

Tracking Language Tuning across the First Year of Life using Near-infrared Spectroscopy

Fava, Eswen Elizabeth 2011 December 1900 (has links)
Both behavioral and neurophysiological data indicate that many factors contribute to how infants tune to their native language(s) in early infancy. However, substantial debate remains regarding the neural mechanisms that underlie this tuning process. This study was designed to determine whether the behavioral changes in infants' processing of native and non-native speech during the second half of the first year correspond to qualitative neural processing changes that can be measured using near-infrared spectroscopy (NIRS). Specifically, we used NIRS to examine changes in hemodynamic activity in monolingually-exposed infants between the ages of 3 and 14 months while they were exposed to native (English) and non-native (Spanish) speech. In all infants, measurements were taken from the bilateral temporal regions of the cerebral cortex. Three age groups were tested: pre-tuned infants, who should show no sensitivity to phonological differences between the native and non-native speech samples (3-to-6-month-olds), actively tuning infants, who should be beginning to differentiate between the phonology of the native and non-native speech samples (7-to-10-month-olds), and tuned infants, who should readily distinguish between the phonologies of the native and non-native speech samples (11-to-14-month-olds). Results demonstrated significant differences in hemodynamic activity during the processing of native speech compared to non-native speech in each of the three age groups, with qualitatively different patterns of hemispheric lateralization emerging in response to the two types of speech in each of the three groups. These findings point to a potential neural marker of infants' sensitivity to the phonology of their native language as it emerges with increasing age that will be useful in future research.
314

Gamification and its effect on employee engagement and performance in a perceptual diagnosis task

Ong, Michael January 2013 (has links)
Gamification is an emerging phenomenon that has been advocated for its potential to improve organisational outcomes. The present study aimed to examine the effect of gamification in a perceptual diagnosis task. Forty participants completed a 22-minute visual search task. To investigate the role of game mechanics participants were divided into four conditions resulting from the factorial combination of the narrative mechanic (narrative and control condition) and the points mechanic (Points and no-points control condition). Attention effort, motivation, and work engagement were measured through performance metrics, functional near-infrared spectroscopy (fNIRS), and self-report questionnaires. The results revealed points significantly increased task performance while narrative significantly increased intrinsic motivation and prefrontal oxygenation. These findings may provide much needed contributions to the literature surrounding gamification. It was also revealed that fNIRS measures of frontal activation may be a reasonable objective indicator of initial cognitive effort. This presents significant real world applications for objectively measuring motivation.
315

Distortion in conformable masks for evanescent near field optical lithography

Wright, Alan James January 2007 (has links)
In this thesis the in-plane pattern distortion resulting from the use of Evanescent Near Field Optical Lithography (ENFOL) masks was investigated. ENFOL is a high resolution low-cost technique of lithography that is able to pattern features beyond the diffraction limit of light. Due to its use of the evanescent near field, ENFOL requires the use of conformable masks for intimate contact. Such masks can stretch and skew as they come into contact with silicon substrates and therefore distort the high resolution features patterned on them. It was desired to measure this distortion to ascertain the patterning performance of ENFOL masks and possibly correct for any uniform distortion found. To this end a sophisticated measuring process was successfully demonstrated. This involved the use of a Raith 150 Electron Beam Lithography (EBL) system with precision laser interferometer stage and metrology software module for automated measurements. Custom software was written for the Raith to enable it to take additional measurements to compensate for electron beam drift. Processing algorithms were then employed to using the measurements to compensate for beam drift and correcting for shift and rotation systematic errors. The performance of the in-plane distortion measuring process was found to have a precision of 60nm. With the ability to measure distortion, ENFOL masks were used to pattern substrates and distortion was found to be large, on the order of 1µm. This is much larger than desired for sub 100nm patterning as is expected of ENFOL. The distortions were non-uniform patterns of localised displacements. This, the observation of Newton's rings beneath a test mask and the observation of a single particle distortion across measurements of the same mask across different loadings in the EBL pointed to particulate contamination causing the distortion. In order to prove beyond doubt that particulate contamination was the cause of the spurious distortions, mechanical modelling using the Finite Element Method (FEM) of analysis was employed. The results from this matched the distortions observed experimentally, particles 20-40µm modelling the observed distortion.
316

Exploiting Near Field and Surface Wave Propagation for Implanted Devices

Besnoff, Jordan January 2014 (has links)
<p>This thesis examines the bandwidth shortcomings of conventional inductive coupling biotelemetry systems for implantable devices, and presents two approaches toward an end-to-end biotelemetry system for reducing the power consumption of implanted devices at increased levels of bandwidth. By leveraging the transition zone between the near and far field, scattering in the near field at UHF frequencies for increased bandwidth at low power budgets can be employed. Additionally, taking advantage of surface wave propagation permits the use of single-wire RF transmission lines in biological tissue, offering more efficient signal routing over near field coupling resulting in controlled implant depth at low power budgets.</p><p>Due to the dielectric properties of biological tissue, and the necessity to operate in the radiating near field to communicate via scattered fields, the implant depth drives the carrier frequency. The information bandwidth supplied by each sensing electrode in conventional implants also drives the operating frequency and regime. At typical implant depths, frequencies in the UHF range permit operation in the radiating near field as well as sufficient bandwidth.</p><p>Backscatter modulation provides a low-power, high-bandwidth alternative to conventional low frequency inductive coupling. A prototype active implantable device presented in this thesis is capable of transmitting data at 30 Mbps over a 915 MHz link while immersed in saline, at a communication efficiency of 16.4 pJ/bit. A prototype passive device presented in this thesis is capable of operating battery-free, fully immersed in saline, while transmitting data at 5 Mbps and consuming 1.23 mW. This prototype accurately demodulates neural data while immersed in saline at a distance of 2 cm. This communication distance is extended at similar power budgets by exploiting surface wave propagation along a single-wire transmission line. Theoretical models of single-wire RF transmission lines embedded in high permittivity and conductivity dielectrics are validated by measurements. A single-wire transmission line of radius 152.4 um exhibits a loss of 1 dB/cm at 915 MHz in saline, and extends the implant depth to 6 cm while staying within SAR limits.</p><p>This work opens the door for implantable biotelemetry systems to handle the vast amount of data generated by modern sensing devices, potentially offering new insight into neurological diseases, and may aid in the development of BMI's.</p> / Dissertation
317

Potential of development of mycotoxins in stored durum wheat under near-ambient drying conditions in Western Canada

Parker, Vincent Russell 04 October 2010 (has links)
The use of near ambient air drying for the preservation of wheat stored in granaries is common in Western Canada. Guidelines have been developed to assist farmers in selecting appropriate drying methods. During this process the top layer of wheat can remain at moisture contents (m.c.) greater than the safe storage limit, 14.5% wet bulb (wb), for up to 12 weeks. This study tested the effects of this drying procedure on the development of ochratoxin A (OTA) using 1 m3 bulks of durum wheat at 18% m.c. (wb) contained within steel bins inside a Weather Simulation Lab. In a second study using 20 L volumes of wheat at a m.c. of 20% (wb) within an environmental growth chamber potential development of OTA was also evaluated. The wheat was exposed to two treatments, airflow and no airflow, for a period of 12 weeks under conditions of high relative humidity (greater than 80%) and typical Manitoba fall temperatures. The storage quality parameters of germination, fat acidity value, and presence of OTA were measured weekly. It was found that high moisture wheat stored under all treatment conditions showed a rapid decrease in germination and increase in fat acidity value over time, with no significant difference between the treatments. Under the tested conditions the development of ochratoxin A was not detected in significant quantities in the 1 m3 bulks of grain but was detected in the smaller 20 L bulks.
318

Optimization of Thiolate Stabilized Gold Nanoclusters For Near Infrared Emission in Subcellular Imaging

Conroy, Cecil Vincent 12 August 2014 (has links)
Monothiolate protected gold nanoclusters with near IR luminescence underwent a five-to-ten fold enhancement of quantum efficiency by heating in the presence of excess thiols. Two monothiolate nanoclusters, mercaptosuccinic acid and tiopronin, were shown to benefit from this procedure. Emission maximum around 700-900 nm is favorable for bioimaging applications due to reduction of background signal from autofluorescence. Dithiolate lipoic acid protected gold nanoclusters with higher near IR quantum efficiency present an interesting candidate for biological imaging due to the difference in hydrophobicity, resistance to quenching by divalent cations and cell growth media, and retained quantum efficiency when coupled to agents such as polyethylene glycol. Intracellular and nuclear internalization of mercaptosuccinic gold nanoclusters demonstrate a potential vector for delivery of nuclear targeting agents. The small size, chemical stability, high luminescence, and potential for targeting various intracellular domains make gold nanoclusters worthwhile for further studies as potential bioimaging probes.
319

Subwavelength Imaging using Scanning Near-field Antenna Arrays

Markley, Loic 20 June 2014 (has links)
This thesis examines a series of near-field antenna arrays used to perform subwavelength focusing and subwavelength imaging outside the extreme near field. For this purpose, slot and dipole arrays have been designed to produce a subwavelength focal spot at a distance of a quarter wavelength from the array. The dipole arrays are then used as scanning probes to produce images with subwavelength resolution based on perturbations in the scattered field. Unlike negative-refractive-index metamaterial superlenses, the imaging resolution is not affected by losses in the array. Furthermore, the arrays are simple to fabricate and are frequency scalable up to Terahertz frequencies and beyond. A near-field analogue to classic antenna-array theory called ``shifted beam theory'' is presented as a design tool. Based on the linear independence of element field patterns in the near field, this theory is very intuitive and provides a simplified way to calculate the element current weights necessary to generate a given target near-field pattern. Two-dimensional near-field subwavelength focusing is demonstrated using a slotted transmission-screen, or ``meta-screen'', under plane-wave incidence. At a distance of a quarter wavelength, the transverse electric field was measured in experiment to have a full-width half-maximum beamwidth of 0.40 by 0.27 wavelengths. This is compared to a single slot transmission-screen which had a beamwidth of 0.60 by 0.58 wavelengths. Broadside and end-fire dipole arrays are used to perform subwavelength imaging in one and two dimensions, respectively. The experimental minimum resolvable separation between two objects at a quarter-wavelength distance was 0.26 wavelengths using the end-fire array probe, as compared to 0.43 wavelengths for a single monopole probe. For an experiment using eight objects scattered over a one-square-wavelength area, however, the array probe imaging resolution remained around 0.25 wavelengths while the baseline monopole probe was no longer able to resolve any of the objects. Experiments were also conducted using objects buried behind a dielectric barrier as well as objects immersed within a dielectric. These results were consistent with the resolution improvements observed in the free-space resolution experiments.
320

Subwavelength Imaging using Scanning Near-field Antenna Arrays

Markley, Loic 20 June 2014 (has links)
This thesis examines a series of near-field antenna arrays used to perform subwavelength focusing and subwavelength imaging outside the extreme near field. For this purpose, slot and dipole arrays have been designed to produce a subwavelength focal spot at a distance of a quarter wavelength from the array. The dipole arrays are then used as scanning probes to produce images with subwavelength resolution based on perturbations in the scattered field. Unlike negative-refractive-index metamaterial superlenses, the imaging resolution is not affected by losses in the array. Furthermore, the arrays are simple to fabricate and are frequency scalable up to Terahertz frequencies and beyond. A near-field analogue to classic antenna-array theory called ``shifted beam theory'' is presented as a design tool. Based on the linear independence of element field patterns in the near field, this theory is very intuitive and provides a simplified way to calculate the element current weights necessary to generate a given target near-field pattern. Two-dimensional near-field subwavelength focusing is demonstrated using a slotted transmission-screen, or ``meta-screen'', under plane-wave incidence. At a distance of a quarter wavelength, the transverse electric field was measured in experiment to have a full-width half-maximum beamwidth of 0.40 by 0.27 wavelengths. This is compared to a single slot transmission-screen which had a beamwidth of 0.60 by 0.58 wavelengths. Broadside and end-fire dipole arrays are used to perform subwavelength imaging in one and two dimensions, respectively. The experimental minimum resolvable separation between two objects at a quarter-wavelength distance was 0.26 wavelengths using the end-fire array probe, as compared to 0.43 wavelengths for a single monopole probe. For an experiment using eight objects scattered over a one-square-wavelength area, however, the array probe imaging resolution remained around 0.25 wavelengths while the baseline monopole probe was no longer able to resolve any of the objects. Experiments were also conducted using objects buried behind a dielectric barrier as well as objects immersed within a dielectric. These results were consistent with the resolution improvements observed in the free-space resolution experiments.

Page generated in 0.0322 seconds