1,530 research outputs found
Laser beam characterisation for industrial applications
This thesis describes the theory, development and applications of laser beam
characterisation for industrial laser materials processing systems. Descriptions are given
of novel forms of beam diagnostic systems and their integration into highly automated
industrial tools. Work is also presented that has contributed to the new ISO standard on
beam characterisation. Particular emphasis is given to excimer laser applications and UV
micromachining. [Continues.
Development of a high-resolution target movement monitoring system for convergence monitoring in mines
The research performed for this dissertation has been conducted with the goal of developing a ground convergence monitor that may better meet the needs of some mines, leading to increased use of ground monitoring programs and reduced fatality rates from falling and sliding rock. The developed monitor is a convergence monitor capable of achieving sensitivities similar to those of currently available convergence meters such as tape extensometers. The monitor is inexpensive and is capable of totally remote operation in some circumstances...A physical model of the meter was developed based on experimental results and compared to a derived theoretical model to show that the monitor was capable of accurately reproducing the predicted sensitivity values --Abstract, page iii
A high resolution digital system for automated aerial surveying.
Thesis (MSc.)- University of Natal,Pietermaritzburg, 2000.Resource managers frequently require moderate to high resolution imagery within short turnaround
periods for use in a GIS-based management system. These spatial data can greatly enhance
their ability to make timely, cost-saving decisions and recommendations.
MBB Consulting Engineers, Inc., of Pietermaritzburg, South Africa had for many years made use
of airborne videography to provide the imagery for several resource-based applications.
Applications included detailed land use mapping in various South African river catchments and
identification, density classification and mapping of alien vegetation. While the system was low
cost and easy to operate, MBB had found that their system was inherently limited, particularly by
its lack of automation and poor spatial resolution. This project was started because of a need to
address these limitations and provide an airborne remote sensing system that was more automated
and could produce higher resolution imagery than the existing system. In addition, the overall cost
and time required to produce a map of the resource of interest needed to be reduced.
The system developed in this project aimed to improve upon the pre-flight planning and in-flight
image acquisition aspects of the existing system. No new post-flight image processing procedures
were developed, but possible future refinement of the post-flight image processing routine was
considered throughout the development of the system. A pre-flight planning software package was
developed that could quickly and efficiently calculate the positions offlight lines and photographs
or images with a minimum of user input. The in-flight image acquisition setup developed involved
the integration of a high resolution digital still camera, a Global Positioning System (GPS), and
camera control software. The use of the rapidly developing and improving technology of a digital
still camera was considered to be a better alternative than a video graphic or traditional film camera
system for a number of reasons. In particular, digital still cameras produce digital imagery without
the need for development and scanning of aerial photographs or frame grabbing of video images.
Furthermore, the resolution of current digital still cameras is already significantly better than that
of video cameras and is rivalling the resolution of 35rnm film.
The system developed was tested by capturing imagery of an urban test area. The images obtained
were then rectified using photogrammetric techniques. Results obtained were promising with
planimetric accuracies of 5 to 1 Om being obtained. From this test it was concluded that for high accuracy applications involving numerous images, use would be made of softcopy
photogrammetric software to semi-automatically position and rectify images, while for
applications requiring fewer images and lower accuracy, images could be rectified using the
simpler technique of assigning GCPs for each image from scanned orthophotos
Digital Image Processing
This book presents several recent advances that are related or fall under the umbrella of 'digital image processing', with the purpose of providing an insight into the possibilities offered by digital image processing algorithms in various fields. The presented mathematical algorithms are accompanied by graphical representations and illustrative examples for an enhanced readability. The chapters are written in a manner that allows even a reader with basic experience and knowledge in the digital image processing field to properly understand the presented algorithms. Concurrently, the structure of the information in this book is such that fellow scientists will be able to use it to push the development of the presented subjects even further
Meteoroids: The Smallest Solar System Bodies
This volume is a compilation of articles reflecting the current state of knowledge on the physics, chemistry, astronomy, and aeronomy of small bodies in the solar system. The articles included here represent the most recent results in meteor, meteoroid, and related research fields and were presented May 24-28, 2010, in Breckenridge, Colorado, USA at Meteoroids 2010: An International Conference on Minor Bodies in the Solar System
Near Infrared Thermal Imaging for Process Monitoring in Additive Manufacturing
This work presents the design and development of a near infrared thermal imaging system
specifically designed for process monitoring of additive manufacturing. The overall aims of
the work were to use in situ thermal imaging to develop methods for monitoring process
parameters of additive manufacturing processes. The main motivations are the recent
growth in use of additive manufacturing and the underutilisation of near infrared camera
technology in thermal imaging. The combination of these two technologies presents
opportunities for unique process monitoring methods which are demonstrated here.
A thermal imaging system was designed for monitoring the electron beam melting process
of an Arcam S12. With this system a new method of dynamic emissivity correction based
on tracking the melted material is shown. This allows for the automatic application of
emissivity values to previously melted areas of a layer image. This reduces the potential
temperature error in the thermal image caused by incorrect emissivity values or the
assumption of a single value for a whole image. Methods for determining materials
properties such as porosity and tensile strength from the in situ thermal imaging are also
shown. This kind of analysis from in situ images is the groundwork for allowing part
properties to be tuned at build time and could remove the need for post build testing that
would determine if it is suitable for use.
The system was also used to image electron beam welding and gas tungsten arc welding.
With the electron beam welding of dissimilar metals, the thermal images were able to
show the preheating effect that the melt pool had on the materials, the suspected reason
for the process’s success. For the gas tungsten arc welding process analysis methods that
would predict weld quality were developed, with the aim of later integrating these into the
robotic welding process. Methods for detecting the freezing point of the weld bead and
tracking slag spots were developed, both of which could be used as indicators of weld
quality or defects. A machine learning algorithm was also applied to images of pipe
welding on this process. The aim of this was to develop an image segmentation algorithm
that could be used to measure parts of the weld in process and inform other analysis, like
those above
Optical Camera Communications: Principles, Modulations, Potential and Challenges
Optical wireless communications (OWC) are emerging as cost-effective and practical solutions to the congested radio frequency-based wireless technologies. As part of OWC, optical camera communications (OCC) have become very attractive, considering recent developments in cameras and the use of fitted cameras in smart devices. OCC together with visible light communications (VLC) is considered within the framework of the IEEE 802.15.7m standardization. OCCs based on both organic and inorganic light sources as well as cameras are being considered for low-rate transmissions and localization in indoor as well as outdoor short-range applications and within the framework of the IEEE 802.15.7m standardization together with VLC. This paper introduces the underlying principles of OCC and gives a comprehensive overview of this emerging technology with recent standardization activities in OCC. It also outlines the key technical issues such as mobility, coverage, interference, performance enhancement, etc. Future research directions and open issues are also presented
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