No description available.

本論文的主要目的是建立一套人臉辨識系統，即使在光源不足或甚至是完全黑暗的環境下也能夠正確地進行身分辨識。在完全黑暗的情形下，我們可以利用具有夜視功能(近紅外線)的攝影機來擷取影像，然而，近紅外線影像通常呈現亮度非常不均勻的情形，導致我們無法直接利用現有的人臉辨識系統來作辨識。因此，我們首先觀察近紅外線影像的特性，然後依據此特性提出一個影像成像的模型；接著，利用同構增晰的原理來減低因成像過程所造成的不均勻現象；經由實驗的結果，我們得知現有的全域式人臉辨識系統無法有效地處理近紅外線影像，因此，我們提出了一個新的區域式的人臉辨識演算法，針對光線不足的情況作特殊考量，以得到較佳的辨識結果。本論文實作的系統是以最近點分類法來作身份辨識，在現有的32個人臉影像資料集中，正確的辨識率達75%。 / The main objective of this thesis is to develop a face recognition system that could recognize human faces even when the surrounding environment is totally dark. The images of objects in total darkness can be captured using a relatively low-cost camcorder with the NightShot® function. By overcoming the illumination factor, a face recognition system would continue to function independent of the surrounding lighting condition. However, images acquired exhibit non-uniformity due to irregular illumination and current face recognition systems may not be put in use directly. In this thesis, we first investigate the characteristics of NIR images and propose an image formation model. A homomorphic processing technique built upon the image model is then developed to reduce the artifact of the captured images. After that, we conduct experiments to show that existing holistic face recognition systems perform poorly with NIR images. Finally, a more robust feature-based method is proposed to achieve better recognition rate under low illumination. A nearest neighbor classifier using Euclidean distance function is employed to recognize familiar faces from a database. The feature-based recognition method we developed achieves a recognition rate of 75% on a database of 32 people, with one sample image for each subject.

We live in a visually rich environment yet our brains are only equipped to process a small fraction of all available information at any point in time. For successful and efficient perception, the brain relies on attention to differentiate and select specific stimuli for further analysis. Attention can be directed to features – feature based attention – which enhances the processing of other similar features independent of spatial location. I have recently shown that the benefits of feature-based attention not only apply to lower-level features, but also to processes of object perception. The aim of the thesis was to examine the behavioural and electrophysiological correlates underlying the influence of feature-based attention on object perception. Chapter 1 measured the electric field activity associated with attending to higher-level features (object contours) and comparing it with the neural activity while attending to motion stimuli. We found temporally later effects for contours relative to motion, suggesting that feature-based attention to objects might be mediated by higher-tier visual areas, such as the lateral occipital cortex. In Chapter 2, I describe a study designed to investigate the time course of neural activity while cueing attention within the feature dimension of shape that more directly targets higher-tier visual areas. Consistent with Chapter 1, I iii found temporally late modulation, but behavioural effects that were weaker than expected. To account for these findings, I proposed a “wrong-turn” model which explains the perceptual benefits and costs coupled to expecting the correct or incorrect feature by taking into consideration the hierarchical structure of the visual system. Moreover, the model also makes specific predictions about the pattern of behavioural and electrophysiological activity while attending to features of varying complexity during object perception. The aim of Chapter 3 was to test the predictions of the model; I cued attention to colour, a lower-level feature essential to perceiving the object. I found much stronger behavioural cueing effects, and a biphasic pattern (early and late) electric brain activity that confirmed the predictions of the model. Together the results indicate that feature-based attention plays an important role in object perception that is mediated by a flexible perceptual system.

We live in a visually rich environment yet our brains are only equipped to process a small fraction of all available information at any point in time. For successful and efficient perception, the brain relies on attention to differentiate and select specific stimuli for further analysis. Attention can be directed to features – feature based attention – which enhances the processing of other similar features independent of spatial location. I have recently shown that the benefits of feature-based attention not only apply to lower-level features, but also to processes of object perception. The aim of the thesis was to examine the behavioural and electrophysiological correlates underlying the influence of feature-based attention on object perception. Chapter 1 measured the electric field activity associated with attending to higher-level features (object contours) and comparing it with the neural activity while attending to motion stimuli. We found temporally later effects for contours relative to motion, suggesting that feature-based attention to objects might be mediated by higher-tier visual areas, such as the lateral occipital cortex. In Chapter 2, I describe a study designed to investigate the time course of neural activity while cueing attention within the feature dimension of shape that more directly targets higher-tier visual areas. Consistent with Chapter 1, I iii found temporally late modulation, but behavioural effects that were weaker than expected. To account for these findings, I proposed a “wrong-turn” model which explains the perceptual benefits and costs coupled to expecting the correct or incorrect feature by taking into consideration the hierarchical structure of the visual system. Moreover, the model also makes specific predictions about the pattern of behavioural and electrophysiological activity while attending to features of varying complexity during object perception. The aim of Chapter 3 was to test the predictions of the model; I cued attention to colour, a lower-level feature essential to perceiving the object. I found much stronger behavioural cueing effects, and a biphasic pattern (early and late) electric brain activity that confirmed the predictions of the model. Together the results indicate that feature-based attention plays an important role in object perception that is mediated by a flexible perceptual system.

Computer assisted surgery uses a collection of different techniques including but not limited to: CT-guided, fluoroscopy-guided, and ultrasound-guided imaging which allows medical staff to view bony anatomy of a patient in relation to surgical tools on a computer screen. By providing this visual data to surgeons less invasive surgeries can be performed on a patient's fractured scaphoid. The data required for a surgeon to perform a minimally invasive surgery while looking only at a computer screen, and not directly at a patient's anatomy, will be provided by CT and ultrasound data. We will discuss how ultrasound and CT data can be used together to allow a minimally invasive surgery of the scaphoid to be performed. In this thesis we will explore two techniques of registering segmented ultrasound images to CT data; an Iterative Closest Point (ICP) approach, and an Unscented Kalman Filter-based Registration (UKF). We use two different ultrasound segmentation methods; a semi-automatic segmentation, and a Bayesian segmentation technique. The segmented ultrasound data is then registered to a CT volume. The success or failure of the registrations is measured by the error calculated in mapping the corresponding land- marks to one another and calculating the target registration error. The results show that the Unscented Kalman Filter-based registration using the Bayesian segmentation of ultrasound images has the least registration error, and has the most robustness to error in initial alignment of the two data sets. / Thesis (Master, Computing) -- Queen's University, 2010-05-28 11:17:31.934

Feature-based attention refers to the phenomenon that attending to a feature value (e.g., a specific shade of red) enhances the detection of similar feature values (e.g., the same shade of red or other shades of red similar to the attended shade) relative to different feature values (e.g., green) that belong to a different object, and that this facilitation effect can be found across the visual field. In previous studies, the participants’ task was primarily the detection or discrimination of simple features such as orientation, colour or motion. The experiments reported in this thesis investigated whether feature-based attention could also influence the speed and/or accuracy of discriminating alphanumeric stimuli such as letters and numbers. In three experiments, participants saw displays that consisted of a series of stimulus patterns at a central location followed by the appearance of an alphanumeric stimulus at one of two peripheral locations. Experiment 1 tested whether paying attention to a specific orientation in a central stimulus would affect the speed and/or accuracy of identifying a peripheral letter whose principal axis was either the same as or different from the attended orientation of the central stimulus. Experiment 2 changed the peripheral stimulus from a letter to a number. In Experiment 3, a peripheral stimulus occurred randomly on 50% of the trials instead of on 100% of the trials. The results showed that attending to a specific orientation of a central stimulus could affect the processing efficiency of both letters and numbers at a peripheral location when the alphanumeric stimulus occurred on every trial (Experiments 1 and 2), but not when it appeared on 50% of the trials. These results suggest that feature-based attention could influence the identification of alphanumeric stimuli. However, the effect may be quite short-lived.

The gap between business goals (problem domain), such as cost reduction, new business processes, increasing competitive advantage, etc., and the supporting Information Technology infrastructure (solution domain), such as the ability to implement software solutions to achieve these goals, is complex and challenging to bridge. This gap emerges for many reasons; for instance, inefficient communication, domain terminology misunderstanding or external factors, e.g. business change. As most business and software products can be described by a set of features, a promising solution would be to link both the problem and solution domains based on these features. Thus, the proposed approach aims to bridge the gap between the problem and the solution domains by using a feature-based technique in order to provide a quick and efficient means for understanding the relationships between IT solutions and business goals. The novelty of the proposed framework emanates from the three characteristics of the business-IT gap: the problem domain, the solution domain and the matching process. Besides the proposed feature-based IT-business framework, other contributions are proposed: a feature extracting method and feature matching algorithms. The proposed approach is achieved in three phases. The first phase is to decompose business needs and transform them into a feature model (presented in UML diagrams); this is represented as a top-to-middle process. The second phase is a reverse engineering process. A system program code is sliced into modules and transformed into feature-based models (again, in UML diagrams); these are represented as a bottom-to-middle process. The third phase is a model-driven engineering process. It uses model comparison techniques to match the UML feature models of the top-to-middle and bottom-to-middle phases. The presented approach in this research shows that features elicited from the business goals can be matched to features extracted from in the IT side. This proposed approach is feasible and able to provide a quick and efficient means for improving feature-based business IT matching. Two case studies are presented to demonstrate that the feature-oriented view of features from the users' perspective can be matched to the feature-oriented view of features in the IT side. This matching can serve to remove any ambiguities that may cause difficulties in the cases of system maintenance or system evolution, in particular when there are changes in requirements, which is to be expected when there is any business change.

Comment les différents aspects d'une scène visuelle sont-ils encodés en mémoire visuelle à court-terme (MVCT) ? S'il est communément admis que la MVCT ne peut stocker simultanément qu'un nombre extrêmement limité d'informations, la question du format des représentations est actuellement loin d'être résolue. Cette thèse avait pour objectif d'étudier les influences de l'organisation perceptive des différents éléments d'une scène visuelle sur la capacité de stockage de la MVCT. Pour ce faire, dix expériences, utilisant le paradigme de détection de changement (c'est-à-dire en présentant deux séries de stimuli séparées par un court laps de temps et en demandant aux participants de détecter un éventuel changement entre ces deux séries) ont été réalisées. La principale manipulation expérimentale était la comparaison entre différentes organisations perceptives des stimuli dans le champ visuel. Les résultats de nos recherches ont contribué de façon significative à une meilleure compréhension de la façon dont les différents aspects d'une scène visuelle sont traités et encodés en MVCT et suggèrent l'existence de différents types de représentations organisées hiérarchiquement. Tout d'abord, les relations spatiales entre tous les éléments d'une scène visuelle seraient encodées sous la forme d'une configuration spatiale. Cette représentation configurale permettrait, dans un deuxième temps, l'analyse et l'encodage de l'identité individuelle des différents éléments. A ce niveau, nous avons montré que le nombre d'éléments pouvant être simultanément encodés et maintenus en MVCT pourrait dépendre considérablement de la manière dont ils sont présentés dans le champ visuel des participants. Ainsi, lorsque différents traits (couleur, forme, texture, orientation, etc.) occupent la même localisation spatiale, formant ainsi une même partie d'un objet, ils seraient traités et encodés aussi efficacement qu'un simple trait. Dans ce cas, la capacité de stockage de la MVCT doit être comprise en terme d'objets intégrés. Par contre, lorsque les traits d'un objet sont spatialement séparés les uns des autres, constituant différentes parties d'objets, le nombre d'éléments pouvant être simultanément encodés en MVCT est fonction du nombre de traits présents dans le champ visuel, et non du nombre d'objets. L'organisation perceptive des informations visuelles a donc une influence directe sur le nombre d'éléments pouvant être simultanément encodés en MVCT en modifiant la nature des représentations./ How are the different aspects of a visual scene encoded in visual short-term memory (VSTM)? Although it is acknowledged that only a small number of information can be simultaneously stored in VSTM, the format of representation is far to be understood. The goal of the present thesis was to study the perceptual influences of the items in a visual scene on the VSTM storage capacity. Ten experiments, using the change detection paradigm (i.e., two stimuli arrays were presented and separated by a short period of time, and the task was to detect a possible change between the two arrays) were conducted. The major experimental manipulation was to contrast different perceptual organisations of the stimuli in an array. The results of those experiments have significantly contributed to a better understanding about how the different aspects of a visual scene are processed and encoded in VSTM and suggest the existence of different types of representation, hierarchically organised. Firstly, the spatial relations between items in a visual scene would be encoded though spatial configuration. Then, this configural representation would allow the processing and the encoding of the identities of each individual item. Here, the number of items that can be simultaneously encoded in VSTM might greatly depend on the way they are presented in the visual field. Indeed, we provided evidence that visual features (colour, shape, texture, orientation), that share the same spatial location, are encoded in VSTM as accurately as single features. In that case, the VSTM storage capacity must be understood in terms of integrated objects rather than in terms of single features. In contrast, when visual features are spatially distributed over different spatial locations, the limitation in the storage capacity is function of the number of features. The perceptual organisation of the visual information has thus a direct influence on the number of items that can be simultaneously encoded in VSTM by modulating the nature of representations.

Recent improvements in structural genomics efforts have greatly increased the number of hypothetical proteins in the Protein Data Bank. Several computational methodologies have been developed to determine the function of these proteins but none of these methods have been able to account successfully for the diversity in the sequence and structural conformations observed in proteins that have the same function. An additional complication is the flexibility in both the protein active site and the ligand. In this dissertation, novel approaches to deal with both the ligand flexibility and the diversity in stereochemistry have been proposed. The active site analysis problem is formalized as a classification problem in which, for a given test protein, the goal is to predict the class of ligand most likely to bind the active site based on its stereochemical nature and thereby define its function. Traditional methods that have adapted a similar methodology have struggled to account for the flexibility observed in large ligands. Therefore, I propose a novel fragment-based approach to dealing with larger ligands. The advantage of the fragment-based methodology is that considering the protein-ligand interactions in a piecewise manner does not affect the active site patterns, and it also provides for a way to account for the problems associated with flexible ligands. I also propose two feature-based methodologies to account for the diversity observed in sequences and structural conformations among proteins with the same function. The feature-based methodologies provide detailed descriptions of the active site stereochemistry and are capable of identifying stereochemical patterns within the active site despite the diversity. Finally, I propose a Markov Random Field approach to combine the individual ligand fragment classifications (based on the stereochemical descriptors) into a single multi-fragment ligand class. This probabilistic framework combines the information provided by stereochemical features with the information regarding geometric constraints between ligand fragments to make a final ligand class prediction. The feature-based fragment identification methodology had an accuracy of 84% across a diverse set of ligand fragments and the mrf analysis was able to succesfully combine the various ligand fragments (identified by feature-based analysis) into one final ligand based on statistical models of ligand fragment distances. This novel approach to protein active site analysis was additionally tested on 3 proteins with very low sequence and structural similarity to other proteins in the PDB (a challenge for traditional methods) and in each of these cases, this approach successfully identified the cognate ligand. This approach addresses the two main issues that affect the accuracy of current automated methodologies in protein function assignment.

This thesis describes the application of a novel decision support process for machined part estimating in small and medium-sized engineering companies. Many SMEs tend to adopt manual estimating techniques, however this dependence on human expertise represents a risk to such organizations. Better information management in estimating can improve process performance and contribute to increased competitiveness. The research which is the subject of this thesis investigated whether a systems approach to machined part estimating would extend the capacity of an SME to manage knowledge more effectively. The research explored the workplace learning context, the provision of learning opportunities and the management of organizational knowledge; before determining that an intelligent information system offered the most beneficial solution to the situation-of-interest. The case study company produce low-volume, make-to-order, medium and large sized machined steel forgings; utilising conventional machine tool equipment. The application of the decision support system enabled novice estimators to produce viable cost estimates; reducing the risk from reliance on human expertise inherent in manual estimating. The hybrid feature-based costing / case-based reasoning estimating technique, which is the core of the novel METALmpe cost model, proved exceptionally well suited to the SME environment. Estimates produced using METALmpe were consistently more accurate than those of the human expert; with a level of accuracy that exceeds the initial research aim, i.e. a tolerance of -5% / +10%. Significantly, implementation of METALmpe (hardware, software and support for 5 users), can be provided at a cost which is within the typical information technology budget of many SMEs. With demands on organizations to process and disseminate ever increasing volumes of information, METALmpe can improve an SME’s information management capabilities and contribute to competitive advantage through strengthening strategic assets and core competencies.