Optimisation of Bacillus thuringiensis var. israelensis (Vectobac®) applications for the blackfly control programme on the Orange River, South Africa
- Authors: Rivers-Moore, Nick A , Bangay, Shaun D , Palmer, R W
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:7090 , http://hdl.handle.net/10962/d1012421
- Description: The Orange River, South Africa's largest river, is a critical water resource for the country. In spite of the clear economic benefits of regulating river flows through a series of impoundments, one of the significant undesirable ecological consequences of this regulation has been the regular outbreaks of the pest blackfly species Simulium chutteri and S. damnosum s.l. (Diptera: Simuliidae). The current control programme, carried out by the South African National Department of Agriculture, uses regular applications, by helicopter, of the target-specific bacterial larvicide Bacillus thuringiensis var. israelensis. While cost-benefit analyses show significant benefits to the control programme, benefits could potentially be further increased through applying smaller volumes of larvicide in an optimised manner, which incorporates upstream residual amounts of pesticide through downstream carry. Using an optimisation technique applied in the West African Onchocerciasis Control Programme, to a 136 km stretch of the Orange River which includes 31 blackfly breeding sites, we demonstrate that 28.5% less larvicide could be used to potentially achieve the same control of blackfly. This translates into potential annual savings of between R540 000 and R1 800 000. A comparison of larvicide volumes estimated using traditional vs. optimised approaches at different discharges, illustrates that the savings on optimisation decline linearly with increasing flow volumes. Larvicide applications at the lowest discharge considered (40 m3·s-1) showed the greatest benefits from optimisations, with benefits remaining but decreasing to a theoretical 30% up to median flows of 100 m3·s-1. Given that almost 70% of flows in July are less than 100 m3·s-1, we suggest that an optimised approach is appropriate for the Orange River Blackfly Control Programme, particularly for flow volumes of less than 100 m3·s-1. We recommend that trials be undertaken over two reaches of the Orange River, one using the traditional approach, and another using the optimised approach, to test the efficacy of using optimised volumes of B.t.i.
- Full Text:
- Date Issued: 2008
Evaluating parts-of-speech taggers for use in a text-to-scene conversion system
- Authors: Glass, Kevin R , Bangay, Shaun D
- Date: 2005
- Language: English
- Type: Conference paper
- Identifier: vital:6603 , http://hdl.handle.net/10962/d1009323
- Description: This paper presents parts-of-speech tagging as a first step towards an autonomous text-to-scene conversion system. It categorizes some freely available taggers, according to the techniques used by each in order to automatically identify word-classes. In addition, the performance of each identified tagger is verified experimentally. The SUSANNE corpus is used for testing and reveals the complexity of working with different tagsets, resulting in substantially lower accuracies in our tests than in those reported by the developers of each tagger. The taggers are then grouped to form a voting system to attempt to raise accuracies, but in no cases do the combined results improve upon the individual accuracies. Additionally a new metric, agreement, is tentatively proposed as an indication of confidence in the output of a group of taggers where such output cannot be validated.
- Full Text:
- Date Issued: 2005
A generic virtual reality interaction system and its extensions using the common object request broker architecture (CORBA)
- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432684 , vital:72892 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper03.pdf
- Description: The paper describes the design and implementation of an immersive Virtual Reality (VR) interaction system. The system aims to provide a flexible mechanism for programmers to implement interaction in their VR applications, making good use of all accepted practices in the field. The paper further describes how the system was extended to a multi-user system using the CORBA middleware layer.
- Full Text:
- Date Issued: 1999
From virtual to physical reality with paper folding
- Authors: Bangay, Shaun D
- Date: 2000
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432669 , vital:72891 , https://doi.org/10.1016/S0925-7721(99)00048-6
- Description: Objects in a virtual world can be converted into hardcopy by per-pendicular projection of each face onto a sheet of paper, cutting and gluing. Previously, use of this technique was restricted to a limited class of polyhedral objects. This paper extends this process to realis-tic virtual objects, with the traditional origami restriction of using only a single sheet of paper. A number of algorithms are explored to achieve this goal. The use of heuristics allows solutions to be found without exhaustive search of all possible layouts. Approaches to deal with pathological cases are described. The techniques have al-ready been successfully applied to a number of complex models, selected from a number of model archives on the Internet.
- Full Text:
- Date Issued: 2000
Rendering Primitives for a Virtual Holodeck
- Authors: Morkel, Chantelle , Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432795 , vital:72901 , https://www.cs.ru.ac.za/research/groups/vrsig/pastprojects/039virtualholodeck/paper02.pdf
- Description: The main objective of this research is to implement a “Star Trek”-like holodeck in a computer environment. An experiment to create graphical primitives and images solely out of spheres is being conducted. We investigate several approaches of creating primitives using spheres, and then using these primitives to create images. Initial results of this experiment are presented and we conclude that using spheres to create primitives and images is a viable approach to creating realistic-looking three-dimensional (3D) images.
- Full Text:
- Date Issued: 2001
A digital watermarking scheme for Bezier surfaces
- Authors: Chadwick, J , Bangay, Shaun D , Wentworth, Peter E
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432769 , vital:72898 , https://www.cs.ru.ac.za/research/groups/vrsig/pastprojects/046watermarking/paper01.pdf
- Description: Owners and vendors are increasingly publishing their materials in digital form. Because such materials can be exactly copied, a mechanism is required that will protect the legitimate owners of these works, by providing proof of original ownership. Digital watermarking has now become one accepted method of establishing ownership of digital materials. The owner of a work embeds a pattern, called a digital watermark, in the content. This embedded watermark is normally undetectable, but its presence can be demonstrated by the owner of the work or his agent, thereby proving ownership. Digital watermarking has been used for many types of multimedia content, primarily audio, video and flat images. Recently, interest has been shown in applying digital watermarking schemes to 3D surfaces, in various formats. In this paper, we examine a method whereby a digital watermark can be embedded in a Bezier surface. A prototype watermarking method for such surfaces is presented, with some experimental results, and a discussion of directions for future research.
- Full Text:
- Date Issued: 2003
A Prototyping Environment for Investigating Context Aware Wearable Applications.
- Authors: Tsegaye, Melekam , Bangay, Shaun D , Terzoli, Alfredo
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432783 , vital:72900 , https://www.cs.ru.ac.za/research/g98t4414/static/papers/wearprototsegaye05.pdf
- Description: In this paper we introduce the concept of a contextaware, wearable application prototyping environment, which can be used to support research into new wearable applications. We also present an initial specification for such an environment and show how different types of sensors can be modelled to produce data that describes a given context scenario using our prototyping approach.
- Full Text:
- Date Issued: 1999
The Virtual Remote Control-An Extensible, Virtual Reality, User Interface Device
- Authors: Rorke, Michael , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432743 , vital:72896 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/013interaction/paper02.pdf
- Description: Immersive virtual reality (VR) places the user inside of the computing envi-ronment, blurring the distinction between the environment itself and the user interface to access that environment non-obvious. This lack of distinction between environment and interface makes it difficult to place menus and other interface elements where the user is both able to access them easily and where they do not obscure large parts of the users field of view. We propose a system called the 'Virtual Remote Control' (VRC). The VRC con-sists of a physical device (a small touchpad tracked using a Polhemus In-sideTrak magnetic tracker) which the user is able to hold and for which there is a representation in the virtual environment. The VRC is represented in the environment by a virtual menu. The user is able to make selections from the virtual menu by moving their finger around the touch pad part of the VRC and 'tapping' on the required action. Additionally, the user is able to select an object for the action to be applied on, by 'pointing' the representa-tion of the VRC at the object-as one would point a remote control at a Hi-fi of TV set.
- Full Text:
- Date Issued: 1999
An Investigation into the feasibility of Human Facial Modeling
- Authors: Panagou, Sotcri , Bangay, Shaun D
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432711 , vital:72894 , https://citeseerx.ist.psu.edu/document?repid=rep1ype=pdfoi=c305c27d16322208e0e6815ca261d61019a4cbd0
- Description: In this paper, virtual videoconferencing is investigated. The goal of the project is to develop a cheap, realistic yet real-time 3D face-modeling tool using a number of camera feeds. Bandwidth utilisation can then be minimised by transferring only the actual model (and subsequently, changes to the model) of the actor's face. Using a virtual reality system, reconstruction of a human face is performed and transmitted, thereby reducing bandwidth requirements. The modeling process is discussed, with results.
- Full Text:
- Date Issued: 1998
Virtual reality interaction techniques
- Authors: Rorke, Michael , Bangay, Shaun D , Wentworth, Peter E
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432756 , vital:72897 , https://citeseerx.ist.psu.edu/document?repid=rep1type=pdfdoi=d0b11136ef6d2701e15cdda896bc5bfd0786752e
- Description: This paper addresses the problems associated with interaction in immersive virtual reality and makes recommendations as to how best to deal with these problems, thereby producing a usable virtual reality interactive environment. Immersive virtual reality means that the users are immersed or contained inside the environment in which they are working. For example, they are able to turn their heads and look around, as well as use their bodies to control the system. The work in progress involves a study of various virtual reality input devices, some designed and implemented as part of the project. Additionally, the paper describes a simple framework for separation of the interaction and application parts of a virtual reality system in order to facilitate an object ori-ented approach to the implementation of the recommendations, and to the building of future virtual reality applications which incorporate these ideas.
- Full Text:
- Date Issued: 1998
The Development of a Generic Framework for the Implementation of Cheap, Component-Based Virtual Video-Conferencing System
- Authors: Panagou, Soteri , Bangay, Shaun D
- Date: 1999
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432824 , vital:72903 , https://www.cs.ru.ac.za/research/Groups/vrsig/pastprojects/014humanmodelling/paper03.pdf
- Description: We address the problem of virtual-videoconferencing. The proposed solution is effected in terms of a generic framework based on an in-house Virtual Reality system. The framework is composed of a number of distinct components: model acquisition, head tracking, expression analysis, network transmission and avatar reconstruction. The framework promises to provide a unique, cheap, and fast system for avatar construction, transmission and animation. This approach affords a conversion from the traditional video stream approach to the management of an avatar remotely and consequently makes minimal demands on network resources.
- Full Text:
- Date Issued: 1999
Wearing your PIM: experiments with an audio enhanced PIM
- Authors: Tsegaye, Melekam , Bangay, Shaun D , Terzoli, Alfredo
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432854 , vital:72904 , https://www.cs.ru.ac.za/research/g98t4414/static/papers/wpimfinal.pdf
- Description: PIM systems help organise people’s lives by providing address book, schedule and task management facilities. Current PIM’s manage this information by collecting and storing it as textual data. With the advent of the wearable computer, using text only is no longer an efficient and convenient mechanism for managing personal information. A wearable computer should use data from various sensors (video, audio, location, environmental, user state) to organise personal information. In this paper we examine how audio can be used to enhance the facilities provided by text-only PIM’s and present an example implementation of an audio based wearable PIM (wPIM) that has the capability of storing and retrieving PIM information as audio recordings. The results of the user evaluation we conducted, which was carried out outside of the laboratory, suggests that users strongly accept audio as a way to manage their personal information and to augment their memory, supporting our hypothesis that audio enhances wearable personal information management.
- Full Text:
- Date Issued: 2004
Super-realistic rendering using real-time tweening
- Authors: Winnemöller, Holger , Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432810 , vital:72902 , https://citeseerx.ist.psu.edu/document?repid=rep1type=pdfoi=eec3809e91a26dbf991a37a3a6a4f1291ae4ec4d
- Description: The realism of contemporary computer graphics (and especially Virtual Reality {VR}) is limited by the great computational cost of rendering objects of appropriate complexity with convincing lighting and surface effects. We introduce a framework that allows rendering of objects in true photographic quality using tweening. The simple but effective design of our system allows us not only to perform the necessary operations in real-time on standard hardware, but also achieve other effects like morphing. Furthermore, it is shown how our system can be gainfully employed in non-VR contexts like extreme low-bandwidth video-conferencing and others.
- Full Text:
- Date Issued: 2001
A lightwave 3d plug-in for modeling long hair on virtual humans
- Authors: Patrick, Deborah , Bangay, Shaun D
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432953 , vital:72916 , https://doi.org/10.1145/602330.602360
- Description: Multimedia applications today make use of virtual humans. Generating realistic virtual humans is a challenging problem owing to a number of factors, one being the simulation of realistic hair. The difficulty in simulating hair is due to the physical properties of hair. The average human head holds thousands of hairs, with the width of each hair often smaller than the size of a pixel. There are also complex lighting effects that occur within hair. This paper presents a LightWave 3D plug-in for modeling thousands of individual hairs on virtual humans. The plug-in allows the user to specify the length, thickness and distribution of the hair, as well as the number of segments a hair is made up of. The plug-in is able to add hairs to a head model, which the user then modifies to define a hairstyle. The hairs are then multiplied by the plug-in to produce many hairs. By providing a plug-in that does most of the work and produces realistic results, the user is able to produce a hairstyle without modeling each individual strand of hair. This greatly reduces the time spent on hair modeling, and makes the possibility of adding realistic long hair to virtual humans reasonable.
- Full Text:
- Date Issued: 2003
Rendering optimisations for stylised sketching
- Authors: Winnemöller, Holger , Bangay, Shaun D
- Date: 2003
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432922 , vital:72913 , https://doi.org/10.1145/602330.602353
- Description: We present work that specifically pertains to the rendering stage of stylised, non-photorealistic sketching. While a substantial body of work has been published on geometric optimisations, surface topologies, space-algorithms and natural media simulation, rendering-specific issues are rarely discussed in-depth even though they are often acknowledged. We investigate the most common stylised sketching approaches and identify possible rendering optimisations. In particular, we define uncertainty-functions, which are used to describe a human-error component, discuss how these pertain to geometric perturbation and textured silhouette sketching and explain how they can be cached to improve performance. Temporal coherence, which poses a problem for textured silhouette sketching, is addressed by means of an easily computed visibility-function. Lastly, we produce an effective yet surprisingly simple solution to seamless hatching, which commonly presents a large computational overhead, by using 3-D textures in a novel fashion. All our optimisations are cost-effective, easy to implement and work in conjunction with most existing algorithms.
- Full Text:
- Date Issued: 2003
Duplicating road patterns in south african informal settlements using procedural techniques
- Authors: Glass, Kevin R , Morkel, Chantelle , Bangay, Shaun D
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432875 , vital:72909 , https://doi.org/10.1145/1108590.1108616
- Description: The formation of informal settlements in and around urban complexes has largely been ignored in the context of procedural city modeling. However, many cities in South Africa and globally can attest to the presence of such settlements. This paper analyses the phenomenon of informal settlements from a procedural modeling perspective. Aerial photography from two South African urban complexes, namely Johannesburg and Cape Town is used as a basis for the extraction of various features that distinguish different types of settlements. In particular, the road patterns which have formed within such settlements are analysed, and various procedural techniques proposed (including Voronoi diagrams, subdivision and L-systems) to replicate the identified features. A qualitative assessment of the procedural techniques is provided, and the most suitable combination of techniques identified for unstructured and structured settlements. In particular it is found that a combination of Voronoi diagrams and subdivision provides the closest match to unstructured informal settlements. A combination of L-systems, Voronoi diagrams and subdivision is found to produce the closest pattern to a structured informal settlement.
- Full Text:
- Date Issued: 2006
An investigation into factors influencing immersion in interactive virtual reality environments
- Authors: Bangay, Shaun D , Preston, Louise
- Date: 1998
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432864 , vital:72908 , https://pubmed.ncbi.nlm.nih.gov/10350927/
- Description: Two interactive virtual reality environments were used to identify factors that may affect, or be affected by, the degree of immersion in a virtual world. In particular, the level of stress in a "swimming with dolphins" simulation is measured, as is the degree of simulator sickness resulting form a virtual roller coaster. Analysis of the results indicates that a relationship between the degree of immersion and the following factors: excitement, comfort, quality and age. The following factors are found to depend on the degree of immersion: simulator sickness, control, excitement and desire to repeat the experience.
- Full Text:
- Date Issued: 1998
Kaleidoscope configurations for reflectance measurement
- Authors: Bangay, Shaun D , Radloff, Judith D
- Date: 2004
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/432891 , vital:72910 , https://doi.org/10.1145/1029949.1029979
- Description: Simulations of different configurations of the symmetrical tapered kaleidoscope are performed to assess their merits for measurement of BRDFs and BTFs. The relationship between optimal kaleidoscope layout, and factors such as hardware restrictions and the resolution of the required reflectance function, is derived. The effect on the measurement of the reflectance function of changing these independent variables is examined through the simulation. These experiments highlight issues affecting the measurement of BTFs using kaleidoscopes, and suggest configurations that allow sampling at regular parameter intervals. A number of other kaleidoscope architectures are explored, which offer the benefits of potentially doubling the range of directions that can be sampled, and allowing adaptive control of sample intervals.
- Full Text:
- Date Issued: 2004
A probabilistic movement model for shortest path formation in virtual ant-like agents
- Authors: Chibaya, Colin , Bangay, Shaun D
- Date: 2007
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433125 , vital:72945 , https://doi.org/10.1145/1292491.1292493
- Description: We propose a probabilistic movement model for controlling ant-like agents foraging between two points. Such agents are all identical, simple, autonomous and can only communicate indirectly through the environment. These agents secrete two types of pheromone, one to mark trails towards the goal and another to mark trails back to the starting point. Three pheromone perception strategies are proposed (Strategy A, B and C). Agents that use strategy A perceive the desirability of a neighbouring location as the difference between levels of attractive and repulsive pheromone in that location. With strategy B, agents perceive the desirability of a location as the quotient of levels of attractive and repulsive pheromone. Agents using strategy C determine the product of the levels of attractive pheromone with the complement of levels of repulsive pheromone. We conduct experiments to confirm directionality as emergent property of trails formed by agents that use each strategy. In addition, we compare path formation speed and the quality of the formed path under changes in the environment. We also investigate each strategy's robustness in environments that contain obstacles. Finally, we investigate how adaptive each strategy is when obstacles are eventually removed from the scene and find that the best strategy of these three is strategy A. Such a strategy provides useful guidelines to researchers in further applications of swarm intelligence metaphors for complex problem solving.
- Full Text:
- Date Issued: 2007
Hierarchical rule generalisation for speaker identification in fiction books
- Authors: Glass, Kevin R , Bangay, Shaun D
- Date: 2006
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433174 , vital:72949 , https://doi.org/10.1145/1216262.1216266
- Description: This paper presents a hierarchical pattern matching and generalisation technique which is applied to the problem of locating the correct speaker of quoted speech found in fiction books. Patterns from a training set are generalised to create a small number of rules, which can be used to identify items of interest within the text. The pattern matching technique is applied to finding the Speech-Verb, Actor and Speaker of quotes found in fiction books. The technique performs well over the training data, resulting in rule-sets many times smaller than the training set, but providing very high accuracy. While the rule-set generalised from one book is less effective when applied to different books than an approach based on hand coded heuristics, performance is comparable when testing on data closely related to the training set.
- Full Text:
- Date Issued: 2006