Rozprawy doktorskie na temat „Redundancy”

Dos de las limitaciones de rendimiento más importantes en los procesadores de hoy en día provienen de las operaciones de memoria y de las dependencias de control. Para resolver estos problemas, las memorias cache y los predictores de salto son dos alternativas hardware bien conocidas que explotan, entre otros factores, el reuso temporal de memoria y la correlación de saltos. En otras palabras, estas estructuras tratan de explotar la redundancia dinámica existente en los programas. Esta redundancia proviene parcialmente de la forma en que los programadores escriben código, pero también de limitaciones existentes en el modelo de compilación tradicional, lo cual introduce instrucciones de memoria y de salto innecesarias. Pensamos que los compiladores deberían ser muy agresivos optimizando programas, y por tanto ser capaces de eliminar una parte importante de esta redundancia.
Por otro lado, las optimizaciones aplicadas en tiempo de enlace o directamente al programa ejecutable final han recibido una atención creciente en los últimos años, debido a limitaciones existentes en el modelo de compilación tradicional. Incluso aplicando sofisticados análisis y transformaciones interprocedurales, un compilador tradicional no es capaz de optimizar un programa como una entidad completa. Un problema similar aparece aplicando técnicas de compilación dirigidas por profiling: grandes proyectos se ven forzados a recompilar todos y cada uno de sus módulos para aprovechar dicha información. Por el contrario, seria más conveniente construir la aplicación completa, instrumentarla para obtener información de profiling y optimizar entonces el binario final sin recompilar ni un solo fichero fuente.
En esta tesis presentamos nuevas técnicas de compilación dirigidas por profiling para eliminar la redundancia encontrada en programas ejecutables a nivel binario (esto es, redundancia binaria), incluso aunque estos programas hayan sido compilados agresivamente con un novísimo compilador comercial. Nuestras técnicas de eliminación de redundancia están diseñadas para eliminar operaciones de memoria y de salto redundantes, que son las más importantes para mitigar los problemas de rendimiento que hemos mencionado. Estas propuestas están basadas en técnicas de eliminación de redundancia parcial sensibles al camino de ejecución. Los resultados muestran que aplicando nuestras optimizaciones, somos capaces de alcanzar una reducción del 14% en el tiempo de ejecución de nuestro conjunto de programas.
En este trabajo también revisamos el problemas del análisis de alias en programas ejecutables, identificando el por qué la desambiguación de memoria es uno de los puntos débiles en la modificación de código objeto. Proponemos varios análisis para ser aplicados en el contexto de optimizadores binarios. Primero un análisis de alias estricto para descubrir dependencias de memoria sensibles al camino de ejecución, el cual es usado en nuestras optimizaciones para la eliminación de redundancias de memoria.
Seguidamente, dos análisis especulativos de posibles alias para detección de independencias de memoria. Estos análisis están basados en introducir información especulativa en tiempo de análisis, lo que incrementa la precisión en partes importantes de código manteniendo el análisis eficiente. Los resultados muestran que nuestras propuestas son altamente útiles para incrementar la desambiguación de memoria de código binario, lo que se traduce en oportunidades para aplicar optimizaciones.
Todos nuestros algoritmos, tanto de análisis como de optimización, han sido implementados en un optimizador binario, enfatizando los problemas más relevantes en la aplicaciones de nuestros algoritmos en código ejecutable, sin la ayuda de gran parte de la información de alto nivel presente en compiladores tradicionales.
Two of the most important performance limiters in today's processor families comes from solving the memory wall and handling control dependencies. In order to address these issues, cache memories and branch predictors are well-known hardware proposals that take advantage of, among other things, exploiting both temporal memory reuse and branch correlation. In other words, they try to exploit the dynamic redundancy existing in programs. This redundancy comes partly from the way that programmers write source code, but also from limitations in the compilation model of traditional compilers, which introduces unnecessary memory and conditional branch instructions. We believe that today's optimizing compilers should be very aggressive in optimizing programs, and then they should be expected to optimize a significant part of this redundancy away.
On the other hand, optimizations performed at link-time or directly applied to final program executables have received increased attention in recent years, due to limitations in the traditional compilation model. First, even though performing sophisticated interprocedural analyses and transformations, traditional compilers do not have the opportunity to optimize the program as a whole. A similar problem arises when applying profile-directe compilation techniques: large projects will be forced to re-build every source file to take advantage of profile information. By contrast, it would be more convenient to build the full application, instrument it to obtain profile data and then re-optimize the final binary without recompiling a single source file.
In this thesis we present new profile-guided compiler optimizations for eliminating the redundancy encountered on executable programs at binary level (i.e.: binary redundancy), even though these programs have been compiled with full optimizations using a state-ofthe- art commercial compiler. In particular, our Binary Redundancy Elimination (BRE) techniques are targeted at eliminating both redundant memory operations and redundant conditional branches, which are the most important ones for addressing the performance issues that we mentioned above in today's microprocessors. These new proposals are mainly based on Partial Redundancy Elimination (PRE) techniques for eliminating partial redundancies in a path-sensitive fashion. Our results show that, by applying our optimizations, we are able to achieve a 14% execution time reduction in our benchmark suite.
In this work we also review the problem of alias analysis at the executable program level, identifying why memory disambiguation is one of the weak points of object code modification. We then propose several alias analyses to be applied in the context of linktime or executable code optimizers. First, we present a must-alias analysis to recognize memory dependencies in a path- sensitive fashion, which is used in our optimization for eliminating redundant memory operations. Next, we propose two speculative may-alias data-flow algorithms to recognize memory independencies. These may-alias analyses are based on introducing unsafe speculation at analysis time, which increases alias precision on important portions of code while keeping the analysis reasonably cost-efficient. Our results show that our analyses prove to be very useful for increasing memory disambiguation accuracy of binary code, which turns out into opportunities for applying optimizations.
All our algorithms, both for the analyses and the optimizations, have been implemented within a binary optimizer, which overcomes most of the existing limitations of traditional source-code compilers. Therefore, our work also points out the most relevant issues of applying our algorithms at the executable code level, since most of the high-level information available in traditional compilers is lost.

High Redundancy Actuation (HRA) is a novel type of fault tolerant actuator. By comprising a relatively large number of actuation elements, faults in the elements can be inherently accommodated without resulting in a failure of the complete actuation system. By removing the possibility of faults detection and reconfiguration, HRA can provide high reliability and availability. The idea is motivated by the composition of human musculature. Our musculature can sustain damage and still function, sometimes with reduced performance, and even complete loss of a muscle group can be accommodated through kinematics redundancy, e.g. the use of just one leg. Electro-mechanical actuation is used as single element inside HRA. This thesis is started with modelling and simulation of individual actuation element and two basic structures to connect elements, in series and in parallel. A relatively simple HRA is then modelled which engages a two-by-two series-in-parallel configuration. Based on this HRA, position feedback controllers are designed using both classical and optimal algorithms under two control structures. All controllers are tested under both healthy and faults injected situations. Finally, a hardware demonstrator is set up based simulation studies. The demonstrator is controlled in real time using an xPC Target system. Experimental results show that the HRA can continuously work when one element fails, although performance degradation can be expected.

Program optimizations analyze and transform the programs such that better performance results can be achieved. Classical optimizations mainly use the static properties of the programs to analyze program code and make sure that the optimizations work for every possible combination of the program and the input data. This approach is conservative in those cases when the programs show the same runtime behaviors for most of their execution time. On the other hand, profile-guided optimizations use runtime profiling information to discover the aforementioned common behaviors of the programs and explore more optimization opportunities, which are missed in the classical, non-profile-guided optimizations. Redundancy elimination is one of the most powerful optimizations in compilers. In this thesis, a new partial redundancy elimination (PRE) algorithm and a partial dead code elimination algorithm (PDE) are proposed for a profile-guided redundancy elimination framework. During the design and implementation of the algorithms, we address three critical issues: optimality, feasibility and profitability. First, we prove that both our speculative PRE algorithm and our region-based PDE algorithm are optimal for given edge profiling information. The total number of dynamic occurrences of redundant expressions or dead codes cannot be further eliminated by any other code motion. Moreover, our speculative PRE algorithm is lifetime optimal, which means that the lifetimes of new introduced temporary variables are minimized. Second, we show that both algorithms are practical and can be efficiently implemented in production compilers. For SPEC CPU2000 benchmarks, the average compilation overhead for our PRE algorithm is 3%, and the average overhead for our PDE algorithm is less than 2%. Moreover, edge profiling rather than expensive path profiling is sufficient to guarantee the optimality of the algorithms. Finally, we demonstrate that the proposed profile-guided redundancy elimination techniques can provide speedups on real machines by conducting a thorough performance evaluation. To the best of our knowledge, this is the first performance evaluation of the profile-guided redundancy elimination techniques on real machines.

Although redundancy became widespread in the late 2Wh century, research was lacking on the perceived impact of redundancy and redundancy management policies on the individual. During the 1980s redundancy became more prevalent for managerial populations and outplacement was used increasingly for redundant executives. Survey data gathered in 1990 indicated that, the practical nature of outplacement, and the help in overcoming personal and career transitions, were valued by redundant executives. Redundant executives were dissatisfied with the fact that outplacement did not always secure them a job. Another survey in 1992 identified the corporate rationale for outplacement policies. Perceived benefits included professional, objective help to facilitate the transition for redundant individuals and a potentially ameliorating effect on the survivors of redundancy. However, a survey in 1994 indicated that companies were more focussed on managing organisational needs than the personal or career transition issues of survivors. The research suggested that outplacement had become a normative HR policy response which may have been instrumental in setting new parameters for the psychological contracts of redundant executives, such as re-balancing work and non-work life, and reviewing commitment and attachment to a corporate entity. For the survivors of redundancy, a psychological contract based on a looser association appeared to be the corporate offer. As highlighted by the study of the employment deal for graduates in the mid 1990s, against the backdrop of large scale redundancy, companies were quite ekplicitly offering developmental opportunities rather than a career, even to those destined for senior management levels. These combined data signalled shifts in the employment relationship. This thesis describes and analyses some of the apparent ambiguities between theory and practice relating to redundancy management, and outcomes at the individual level. It seeks clarification through the development of a model of redundancy management.

The problem of this study is whether between-channel redundancy in an instructional audio-visual message enhances immediate recall of information more than within—channel redundancy. A secondary purpose was to compare three forms of between—channel redundancy! audio—video, audio—video—caption, and audio-caption with one form of within-channel redundancy: video-caption. These comparisons were designed to demonstrate which form of redundancy had a higher association with recall of information. The subjects were administered the Kentucky Comprehensive Listening Inventory to measure listening skills, and the Receiver Apprehension Inventory to identify subjects who experienced significantly high apprehension as receivers of information. Then the subjects were randomly divided into four treatment groups and shown an eight minute newscast. All four groups were presented the same instructional message, but the mode of presentation differed depending upon the treatment group. After viewing the instructional program each member of each group was given a forty item multiple-choice retention inventory based on the information presented in the newscast. The data were presented in terms of correct responses on the Kentucky Comprehensive Listening Inventory and the forty item retention inventory. Discriminate analysis was used to determine which items from the multiple-choice retention inventory accounted for the most variance. Thirteen items were found to account for the greatest amount of variance. Reliability estimates were calculated for all four story categories and for the forty items collectively. All reliability estimates were acceptable.

Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 117-120).
With ever-increasing pollution and scarcity of resources, structural optimization, the science of finding the optimal structural arrangements under equilibrium constraints, is becoming an increasing necessity in engineering practice. However, designers are hesitant to adopt a method that is by nature a limit state and thus potentially unreliable. This thesis embeds a level of safety, namely redundancy, within the structural optimization process. Redundancy is the ability to remove a certain number of elements from the structure without losing stability. The thesis translates this constraint into a linear mathematical optimization problem. Then, a topology optimization algorithm is developed that identifies the least volume structure with the ability to remove any element(s) while maintaining stability under the initial loading. Besides the developed algorithm, this thesis shows the relation between the internal forces of redundant structures and their substructures, and in fact shows that it can be expressed linearly when only 1 level of redundancy is provided, and polynomial for higher levels. The algorithm is eventually implemented and extensively analyzed for a series of configurations, showing that redundant optimal shapes have considerably less volume than twice that of the pure volumetric optimal, and hence effectively combine safety with material efficiency. Overall, this thesis constitutes the early stage of a novel structural optimization algorithm that is unique to its volumetric optimization objectives.
by Dimitrios Pagonakis.
M. Eng.

Cases of brittle fractures in major bridges prompted AASHTO to publish its first fracture control plan in 1978. It focused on material and fabrication standards, and required periodic 24-month hands-on inspection of bridges with fracture critical members. The practical result of this plan was to significantly increase the life cycle cost of these bridges, rendering them uneconomical. Apart from the Point Pleasant Bridge that failed in 1967, no other bridge has collapsed in the USA following a fracture, even though large fractures have been observed in many other bridges. All these bridges showed some degree of redundancy and therefore could be reclassified as non-fracture critical if detailed analyses are carried out. The goal of this study is to provide guidance on redundancy evaluation of fracture critical bridges, specifically three girder bridges and twin box-girder bridges. The effect of various loading, analysis and geometric parameters on the post fracture response and the remaining load carrying capacity of the damaged bridge is evaluated through nonlinear finite element analysis of two well-documented structures: the Hoan Bridge and the twin box-girder bridge. Parameters such as damping definition, modelling of composite action, modelling of secondary elements, boundary conditions, and rate dependent material properties are found to be crucial in capturing the bridge response. A two-step methodology for system redundancy analysis of fracture critical bridges is proposed, leading to a reclassification of these elements as non-fracture critical for in-service inspection. The first step evaluates bridge capacity to withstand collapse following fracture based on whether the residual deformation is perceivable to people on or off the bridge. If the bridge satisfies the first step requirements, then the reserve load carrying capacity of the damaged bridge is evaluated in the second step. The Hoan Bridge failed to satisfy the proposed requirements in the first step and therefore its girders could not be reclassified as non-fracture critical. The twin box-girder bridge successfully resisted the collapse in two out three loading scenarios and displayed reserve load carrying capacity following full depth fracture in the exterior girder, and therefore can be reclassified as non-fracture critical for in-service inspection.
Ph. D.

Historical collapse events are testament to the inherent dangers of non-robust structures. Designing robust structures is vital to ensure that localised damage events, such as the failure of a single structural element, do not lead to catastrophic disproportionate collapse. While the advent of robustness research can be dated to the collapse of the Ronan Point building in 1968, the quantification of robustness remains an active and important research field. The importance of developing effective robustness assessment methods is emphasized by a number of factors. One issue is the growing problem of inspecting, maintaining and ensuring the safety of ageing infrastructure. Older structures are more likely to be non-redundant and are more susceptible to structural defects. Another factor is the pursuit of greater efficiency and design optimisation, which has eliminated traditional design conservatism and many undocumented factors of safety. As a result, modern buildings may be more vulnerable to unforeseen conditions during their service life. The objective of quantifying robustness highlights the need for a new system-oriented perspective on structural performance to complement traditional component-based design. There is, as of yet, no single framework that incorporates all the essential aspects in an explicit, transparent and quantitative manner leading to a comprehensive outcome in terms of quantification of the structural robustness. This thesis focuses primarily on the quantification of redundancy and robustness, with the view that the capacity of a structure to withstand a damage event is an inherent property of the structure, which can be considered complementary to other commonly discussed structural properties, such as strength and ductility. Hence, a comprehensive unified framework for redundancy quantification is proposed, which builds upon existing strength-based measures. The role of structural uncertainties in the quantification of robustness is investigated, with a focus on the importance of the sequence of events which precede the collapse of a structure. Directly incorporating structural uncertainties into robustness quantification typically requires computationally expensive methods such as Monte Carlo simulations. Moreover, such collapse analyses are susceptible to numerical instabilities, further complicating the simulation of multiple collapse scenarios. To address these issues, a novel incremental elastic analysis method is proposed in this thesis, which analyses the full load-displacement relationship of a structure and additionally, has an inbuilt capacity to incorporate structural variability and thus output a spectrum of possible response outcomes.

In multimedia learning environments, research suggests that simultaneous presentation of redundant text (i.e. identical narration and on-screen text) may inhibit learning when presented with animation at the same time. However, related studies are limited to testing with cause-and-effects content information (e.g., Moreno & Mayer, 1999, 2002). This study examined the effects of redundant text on learners' memory achievement and problem solving ability. The study replicated and extended prior research by using descriptive, rather than cause-and-effect content information. The primary research questions were (a) does redundant text improve learning performance if learners are presented with instructional material that addresses subject matter other than cause-and-effect relationship? and (b) does sequential presentation of animation followed by redundant text help learning? To answer the research questions, five hypotheses were tested with a sample of 224 Taiwanese students enrolled in a college level Management Information System (MIS) courses at a management college in southern Taiwan. Statistically significant differences were found in memory achievement and problem solving test scores between simultaneous and sequential groups; while no statistically significant differences were found in memory achievement and problem solving test scores between verbal redundant and non-redundant groups. These results were supported by interviewees expressing difficulty in connecting animation and verbal explanation in the two sequential presentation groups. The interview responses also helped to explain why insignificant results were obtained when redundant and non-redundant verbal explanations with animation were presented simultaneously. In general, the results support previous research on the contiguity principle, suggesting that sequential presentations may lead to lower learning performance when animation and verbal explanation are closely related. The separation of the two types of information may increase cognitive load. In addition, the study found that impairment of redundant text was also affected by various learning characteristics, such as the structure of the instructional content and learners previous learning experiences. Recommendations for future study include: (a) research on various situations such as characteristics of the content, characteristics of learners, and difficulty of the instructional material that influences the effects of redundant text, and (b) research on prior learning experience that influences the effects of simultaneous redundant text presentations.
Ph.D.
Department of Educational Research, Technology and Leadership
Education
Education: Ph.D.

A new approach to structural equation modeling based on so-called extended redundancy analysis (ERA) is proposed. In ERA, latent variables are obtained as exact linear combinations of observed variables, and model parameters are estimated by consistently minimizing a single criterion. As a result, the method can avoid limitations of covariance structure analysis (e.g., stringent distributional assumptions, improper solutions, and factor score indeterminacy) in addition to those of partial least squares (e.g., the lack of a global optimization procedure). The method is simple yet versatile enough to fit more complex models; e.g., those with higher-order latent variables and direct effects of observed variables. It can also fit a model to more than one sample simultaneously. Other relevant topics are also discussed, including data transformations, missing data, metric matrices, robust estimation, and efficient estimation. Examples are given to illustrate the proposed method.

This thesis focuses on the collective responses of union members and unions to redundancy. It adopts a theory of trade union action based on the idea that workers react to violations of what they perceive to be "rights" in the employment context. "Rights" are to a degree inculcated into the minds of workers by "union cultures", which condition moral and ethical judgements of behaviour. Connections are drawn between "cultures", "ideologies" and "world views". Workers' responses to redundancy it is suggested should show evidence of the influence of union cultures in a sequence of events over long periods of time. This is borne out in the empirical chapters; Chapter 4 (which describes the historical background to the 1965 Redundancy Payments Act) quotes developments in union responses to redundancy since the 1930s. In a further section, Chapter 5, a case study of a series of redundancy events in the computer company, ICL, is provided, covering union responses to redundancy in the period 1969 to 1979. The evidence also calls into question the view expressed in some academic and policy work on redundancy, that the 1965 Redundancy Payments Act has defused union opposition to redundancy. The period before 1965, the evidence suggests, could not be characterised as a period of strong union opposition, and the years since the passing of the Act have not seen a predominance of union acquiescence. On this basis, too, Hardy's argument that managements have managed redundancy and closure by a process of legitimisation, is called in to question. Also, the work of neo-classical labour economists, who see workers and union attitudes towards redundancy in terms of the decisions of "economic man", is refuted by the evidence and the argument in the thesis, which emphasises the moral influence of unions and the practice of unionism.

In current bridge practice, all tension members in a truss bridge are identified as fracture critical members which implies that a collapse is expected to occur once a member of this type fails. However, there are several examples which show that bridges have remained standing and shown little distress even after a fracture critical member was completely damaged. Due to the high inspection cost for fracture critical members, it would be beneficial to remove fracture critical designation from some tension members. This could be achieved via considering system redundancy. Since there is no clear guidance in existing codified provisions for assessing system redundancy, this research is undertaken to develop simplified analysis techniques to evaluate system redundancy in truss bridges. The proposed system redundancy analysis in this research starts with the identification of the most critical main truss members whose failure may significantly affect the system redundancy. The system redundancy is then measured by the remaining load capacity of a damaged bridge after losing one of the critical members. The bridge load capacity is checked using 3D models with nonlinear features that can capture the progression of yielding and buckling in a bridge system. The modeling techniques are validated through the case studies of the I-35W Bridge and one test span of the Milton-Madison Bridge. Reasonable correlations are demonstrated between the models and the measured data for these two bridges both in an undamaged and in a damaged state. The feasibility of the proposed methodology for system redundancy evaluation is examined by applying the methodology blindly to two other simple truss bridges. The application shows that the proposed methodology can efficiently measure the system redundancy. To improve the system redundancy, this research also proposes sample retrofit strategies for the four example bridges.
Ph. D.

La robotique de service est un domaine émergent où il est nécessaire de commander des robots en interaction forte avec leur environnement. Ce travail présente une méthode adaptative de commande combinant de l'apprentissage de modèles physiques et de la commande dans l'espace opérationnel de robots redondants. L'apprentissage des modèles cinématiques est obtenu soit par dérivation de modèles géométriques appris, soit par apprentissage direct. Ces modèles cinématiques, également appelés matrices Jacobiennes, peuvent être utilisés dans le calcul de pseudo-inverse ou de projecteurs pour la commande du robot. Cette combinaison de méthodes permet d'obtenir un contrôleur qui s'adapte à la géométrie du robot commandé. D'une façon similaire, il est également possible d'apprendre un modèle dynamique inverse du robot de manière à commander le robot en couple plutôt qu'en vitesse. Cela a pour avantage de pouvoir s'adapter aux modifications dynamiques qui s'appliquent sur le robot comme par exemple l'application d'une force extérieure ou l'ajout d'un poids. Les expériences menées dans le cadre de cette thèse montrent comment réaliser plusieurs tâches hiérarchiques ou comment s'adapter à des perturbations avec des modèles appris. Des application sur un robots réel ont également été menées afin de rendre compte de la plausibilité de l'approche proposée.

This thesis is concerned with parameter redundancy in statistical ecology models. If it is not possible to estimate all the parameters, a model is termed parameter redundant. Parameter redundancy commonly occurs when parameters are confounded in the model so that the model could be reparameterised in terms of a smaller number of parameters. In principle, it is possible to use symbolic algebra to determine whether or not all the parameters of a certain ecological model can be estimated using classical methods of statistical inference. We examine a variety of different ecological models: We begin by exploring models based on marking a number of animals and observing the same animals at future time points. These observations can either be when the animal is marked and then recovered dead in mark-recovery modelling, or when the animal is marked and then recaptured alive in capture-recapture modelling. We also explore capture-recapture-recovery models where both dead recoveries and alive recaptures can be observed in the same study. We go on to explore occupancy models which are used to obtain estimates of the probability of presence, or absence, for living species by the use of repeated detection surveys, where these models have the advantage that individuals are not required to be marked. A variety of different occupancy models are examined included the addition of season-dependent parameters, group-dependent parameters and species-dependent, along with other models. We investigate parameter redundancy by deriving general results for a variety of different models where the model's parameter dependencies can be relaxed suited to different studies. We also analyse how the results change for specific data sets and how sparse data influence whether or not a model is parameter redundant using procedures written in Maple. This theory on parameter redundancy is vital for the correct use of these ecological models so that valid statistical inference can be made.

This thesis has a goal of analysing different methods used for identifying redundant faults in synchronous sequential circuits as a part of reducing the complexity of ATPG algorithms and minimizing the test sets. It starts with an overview of various faults which occur in digital circuits of different types and moves on to the common testing methods used for fault detection. As it is not possible to perform an exhaustive search in order to detect every possible fault in any given circuit due to time and power consumption issues, there are certain needs for minimizing the set of tests which detects the existing faults. Therefore discovering the untestable and redundant faults is so important when testing. The overview of both classical and novel methods for detecting untestable and redundant faults is presented followed by the analysis of the results and the benefits each of these methods promises.

Many mycolic acid-containing actinobacteria are oleaginous, accumulating high amounts of triacylglycerols (TAGs) under conditions of nutrient stress. These bacteria contain multiple copies of the genes involved in TAG biosynthesis: glycerol-phosphate acyltransferase (GPAT), acylglycerol-phosphate acyltransferase (AGPAT), phosphatidic acid phosphatase (PAP) and diglyceride acyltransferases (WS/DGAT), encoded by plsB, plsC, pap, and atf, respectively. Analysis of Rhodococcus jostii RHA1’s genome revealed that it carries 1 plsB, 8 plsC, 7 pap, and 16 atf. Quantitative, time-dependent data of six of these atf genes, selected based on previous transcriptomics data, revealed distinct expression patterns under nitrogen-limiting (N-) and carbon-limiting (C-) conditions. For example, the levels of atf10, atf3 and atf8 transcripts dropped ~10-fold upon growth substrate depletion, while the levels of atf4, atf6 and atf9 transcripts rose. Under N- conditions, RHA1 cells continued to accumulate TAGs for five days after ammonia depletion, during which time atf10 and atf8 transcripts remained abundant. Targeted deletion of any one of atf3, atf4, atf6, atf9 and atf10 did not significantly affect TAG accumulation under N- conditions, consistent with the redundancy of putative acyltransferases in the RHA1 genome. However, deletion of both atf8 and atf10 resulted in a 50% decrease in TAG accumulation. Furthermore, the fatty acid profile of the ∆atf8∆atf10 mutant was significantly perturbed, and was restored by complementation with either atf8 or atf10. RT-qPCR data analysis also revealed that the expression patterns of plsC (RS27555) and plsB were the same as that of atf9, consistent with their occurrence in an operon. Unexpectedly, deletion of plsB did not affect TAG accumulation, suggesting an alternative pathway for TAG and phospholipids biosynthesis. Finally, I identified three genes encoding HAD-type hydrolases as being putatively involved in TAG biosynthesis, including one that occurs as a fusion with plsC. The available data suggest that they act as PAPs. Overall, the results establish that there is a certain degree of functional redundancy in TAG biosynthesis, and that Atf8 and Atf10 play a major role in TAG accumulation. At the same time, the results also highlight important gaps in our knowledge of TAG biosynthesis in mycolic acid-containing oleaginous actinobacteria.
Science, Faculty of
Graduate

The growth of the web, authoring software, and electronic publishing has led to the emergence of a new type of document collection that is decentralised, amorphous, dynamic, and anarchic. In such collections, redundancy is a significant issue. Documents can spread and propagate across such collections without any control or moderation. Redundancy can interfere with the information retrieval process, leading to decreased user amenity in accessing information from these collections, and thus must be effectively managed. The precise definition of redundancy varies with the application. We restrict ourselves to documents that are co-derivative: those that share a common heritage, and hence contain passages of common text. We explore document fingerprinting, a well-known technique for the detection of co-derivative document pairs. Our new lossless fingerprinting algorithm improves the effectiveness of a range of document fingerprinting approaches. We empirically show that our algorithm can be highly effective at discovering co-derivative document pairs in large collections. We study the occurrence and management of redundancy in a range of application domains. On the web, we find that document fingerprinting is able to identify widespread redundancy, and that this redundancy has a significant detrimental effect on the quality of search results. Based on user studies, we suggest that redundancy is most appropriately managed as a postprocessing step on the ranked list and explain how and why this should be done. In the genomic area of sequence homology search, we explain why the existing techniques for redundancy discovery are increasingly inefficient, and present a critique of the current approaches to redundancy management. We show how document fingerprinting with a modified version of our algorithm provides significant efficiency improvements, and propose a new approach to redundancy management based on wildcards. We demonstrate that our scheme provides the benefits of existing techniques but does not have their deficiencies. Redundancy in distributed information retrieval systems - where different parts of the collection are searched by autonomous servers - cannot be effectively managed using traditional fingerprinting techniques. We thus propose a new data structure, the grainy hash vector, for redundancy detection and management in this environment. We show in preliminary tests that the grainy hash vector is able to accurately detect a good proportion of redundant document pairs while maintaining low resource usage.

This thesis reports work not only on the numerics behind, but also the implementation of real-time redundancy-resolution schemes on a real robot. Furthermore, the robot that was chosen as the experimental platform is, isotropic. Redundant robots have more degrees of freedom than needed to perform a class of tasks. A new performance index is proposed in the thesis, that is quadratic in the joint variables and its weighting function has units of frequency. It is shown how this performance index can produce cyclic trajectories in a simple manner, thereby eliminating the undesired drift of the joint angles upon tracking a closed Cartesian trajectory.
Isotropic robots can be postured in such a way that the condition number of their Jacobian matrices can attain a minimum value of unity. It is shown in the thesis that this feature is closely related to the performance of the robot. It appears that trajectories that are close to the set of isotropic postures are performed with smaller errors than trajectories lying far from that set.
The experiments reported here were conducted on the McGill-IRIS C3 Arm, an isotropic, four-revolute redundant manipulator, used to position the operation point of its end link. (Abstract shortened by UMI.)

The High Redundancy Actuator (HRA) project investigates a novel approach to fault tolerant actuation, which uses a high number of small actuation elements, assembled in series and parallel in order to form a single intrinsically fault tolerant actuator. Element faults affect the maximum capability of the overall actuator, but through control techniques, the required performance can be maintained. This allows higher levels of reliability to be attained in exchange for less over-dimensioning in comparison to conventional redundancy techniques. In addition, the combination of both serial and parallel elements provides intrinsic accommodation of both lock-up and loose faults. Research to date has concentrated on HRAs based on electromechanical technology, of relatively low order, controlled through passive Fault Tolerant Control (FTC) methods. The objective of this thesis is to expand upon this work. HRA configurations of higher order, formed from electromagnetic actuators are considered. An element model for a moving coil actuator is derived from first principles and verified experimentally. This element model is then used to form high-order, non-linear HRA models for simulation, and reduced-order representations for control design. A simple, passive FTC law is designed for the HRA configurations, the results of which are compared to a decentralised, active FTC approach applied through a framework based upon multi-agent concepts. The results indicate that limited fault tolerance can be achieved through simple passive control, however, performance degradation occurs, and requirements are not met under theoretically tolerable fault levels. Active FTC offers substantial performance improvements, meeting the requirements of the system under the vast majority of theoretically tolerable fault scenarios. However, these improvements are made at the cost of increased system complexity and a reliance on fault detection. Fault Detection (FD) and health monitoring of the HRA is explored. A simple rule-based FD method, for use within the active FTC, is described and simulated. An interacting multiple model FD method is also examined, which is more suitable for health monitoring in a centralised control scheme. Both of these methods provide the required level of fault information for their respective purposes. However, they achieve this through the introduction of complexity. The rule-based method increases system complexity, requiring high levels of instrumentation, and conversely the interacting multiple model approach involves complexity of design and computation. Finally, the development of a software demonstrator is described. Experimental rigs at the current project phase are restricted to relatively low numbers of elements for practical reasons such as cost, space and technological limitations. Hence, a software demonstrator has been developed in Matlab/Simulink which provides a visual representation of HRAs with larger numbers of elements, and varied configuration for further demonstration of this concept.

Recently, the environmental impact of aircraft and rising fuel prices have become an increasing concern in the aviation industry. To address these problems, organizations such as NASA have set demanding goals for reducing aircraft emissions, fuel burn, and noise. In an effort to reach the goals, a movement toward more-electric aircraft and electric propulsion has emerged. With this movement, the number of critical electrical loads on an aircraft is increasing causing power system reliability to be a point of concern. Currently, power system reliability is maintained through the use of back-up power supplies such as batteries and ram-air-turbines (RATs). However, the increasing power requirements for critical loads will quickly outgrow the capacity of the emergency devices. Therefore, reliability needs to be addressed when designing the primary power distribution system. Power system reliability is a function of component reliability and redundancy. Component reliability is often not determined until detailed component design has occurred; however, the amount of redundancy in the system is often set during the system architecting phase. In order to meet the capacity and reliability requirements of future power distribution systems, a method for redundancy allocation during the system architecting phase is needed. This thesis presents an aircraft power system design methodology that is based upon the engineering decision process. The methodology provides a redundancy allocation strategy and quantitative trade-off environment to compare architecture and technology combinations based upon system capacity, weight, and reliability criteria. The methodology is demonstrated by architecting the power distribution system of an aircraft using turboelectric propulsion. The first step in the process is determining the design criteria which includes a 40 MW capacity requirement, a 20 MW capacity requirement for the an engine-out scenario, and a maximum catastrophic failure rate of one failure per billion flight hours. The next step is determining gaps between the performance of current power distribution systems and the requirements of the turboelectric system. A baseline architecture is analyzed by sizing the system using the turboelectric system power requirements and by calculating reliability using a stochastic flow network. To overcome the deficiencies discovered, new technologies and architectures are considered. Global optimization methods are used to find technology and architecture combinations that meet the system objectives and requirements. Lastly, a dynamic modeling environment is constructed to study the performance and stability of the candidate architectures. The combination of the optimization process and dynamic modeling facilitates the selection of a power system architecture that meets the system requirements and objectives.

Thesis (Ph.D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2001.
Includes bibliographical references (p. 113-120).
Computational audition has always been a subject of multiple theories. Unfortunately very few place audition in the grander scheme of perception, and even fewer facilitate formal and robust definitions as well as efficient implementations. In our work we set forth to address these issues. We present mathematical principles that unify the objectives of lower level listening functions, in an attempt to formulate a global and plausible theory of computational audition. Using tools to perform redundancy reduction, and adhering to theories of its incorporation in a perceptual framework, we pursue results that support our approach. Our experiments focus on three major auditory functions, preprocessing, grouping and scene analysis. For auditory preprocessing, we prove that it is possible to evolve cochlear-like filters by adaptation to natural sounds. Following that and using the same principles as in preprocessing, we present a treatment that collapses the heuristic set of the gestalt auditory grouping rules, down to one efficient and formal rule. We successfully apply the same elements once again to form an auditory scene analysis foundation, capable of detection, autonomous feature extraction, and separation of sources in real-world complex scenes. Our treatment was designed in such a manner so as to be independent of parameter estimations and data representations specific to the auditory domain. Some of our experiments have been replicated in other domains of perception, providing equally satisfying results, and a potential for defining global ground rules for computational perception, even outside the realm of our five senses.
Paris Smaragdis.
Ph.D.

Doutoramento em Engenharia Electrotécnica
Os sistemas distribuídos embarcados (Distributed Embedded Systems – DES) têm sido usados ao longo dos últimos anos em muitos domínios de aplicação, da robótica, ao controlo de processos industriais passando pela aviónica e pelas aplicações veiculares, esperando-se que esta tendência continue nos próximos anos. A confiança no funcionamento é uma propriedade importante nestes domínios de aplicação, visto que os serviços têm de ser executados em tempo útil e de forma previsível, caso contrário, podem ocorrer danos económicos ou a vida de seres humanos poderá ser posta em causa. Na fase de projecto destes sistemas é impossível prever todos os cenários de falhas devido ao não determinismo do ambiente envolvente, sendo necessária a inclusão de mecanismos de tolerância a falhas. Adicionalmente, algumas destas aplicações requerem muita largura de banda, que também poderá ser usada para a evolução dos sistemas, adicionandolhes novas funcionalidades. A flexibilidade de um sistema é uma propriedade importante, pois permite a sua adaptação às condições e requisitos envolventes, contribuindo também para a simplicidade de manutenção e reparação. Adicionalmente, nos sistemas embarcados, a flexibilidade também é importante por potenciar uma melhor utilização dos, muitas vezes escassos, recursos existentes. Uma forma evidente de aumentar a largura de banda e a tolerância a falhas dos sistemas embarcados distribuídos é a replicação dos barramentos do sistema. Algumas soluções existentes, quer comerciais quer académicas, propõem a replicação dos barramentos para aumento da largura de banda ou para aumento da tolerância a falhas. No entanto e quase invariavelmente, o propósito é apenas um, sendo raras as soluções que disponibilizam uma maior largura de banda e um aumento da tolerância a falhas. Um destes raros exemplos é o FlexRay, com a limitação de apenas ser permitido o uso de dois barramentos. Esta tese apresentada e discute uma proposta para usar a replicação de barramentos de uma forma flexível com o objectivo duplo de aumentar a largura de banda e a tolerância a falhas. A flexibilidade dos protocolos propostos também permite a gestão dinâmica da topologia da rede, sendo o número de barramentos apenas limitado pelo hardware/software. As propostas desta tese foram validadas recorrendo ao barramento de campo CAN – Controller Area Network, escolhido devido à sua grande implantação no mercado. Mais especificamente, as soluções propostas foram implementadas e validadas usando um paradigma que combina flexibilidade com comunicações event-triggered e time-triggered: o FTT – Flexible Time- Triggered. No entanto, uma generalização para CAN nativo é também apresentada e discutida. A inclusão de mecanismos de replicação do barramento impõe a alteração dos antigos protocolos de replicação e substituição do nó mestre, bem como a definição de novos protocolos para esta finalidade. Este trabalho tira partido da arquitectura centralizada e da replicação do nó mestre para suportar de forma eficiente e flexível a replicação de barramentos. Em caso de ocorrência de uma falta num barramento (ou barramentos) que poderia provocar uma falha no sistema, os protocolos e componentes propostos nesta tese fazem com que o sistema reaja, mudando para um modo de funcionamento degradado. As mensagens que estavam a ser transmitidas nos barramentos onde ocorreu a falta são reencaminhadas para os outros barramentos. A replicação do nó mestre baseia-se numa estratégia líder-seguidores (leaderfollowers), onde o líder (leader) controla todo o sistema enquanto os seguidores (followers) servem como nós de reserva. Se um erro ocorrer no nó líder, um dos nós seguidores passará a controlar o sistema de uma forma transparente e mantendo as mesmas funcionalidades. As propostas desta tese foram também generalizadas para CAN nativo, tendo sido para tal propostos dois componentes adicionais. É, desta forma possível ter as mesmas capacidades de tolerância a falhas ao nível dos barramentos juntamente com a gestão dinâmica da topologia de rede. Todas as propostas desta tese foram implementadas e avaliadas. Uma implementação inicial, apenas com um barramento foi avaliada recorrendo a uma aplicação real, uma equipa de futebol robótico onde o protocolo FTT-CAN foi usado no controlo de movimento e da odometria. A avaliação do sistema com múltiplos barramentos foi feita numa plataforma de teste em laboratório. Para tal foi desenvolvido um sistema de injecção de faltas que permite impor faltas nos barramentos e nos nós mestre, e um sistema de medida de atrasos destinado a medir o tempo de resposta após a ocorrência de uma falta.
Distributed embedded systems (DES) have been widely used in the last few decades in several application domains, from robotics, industrial process control, avionics and automotive. In fact, it is expectable that this trend will continue in the next years. In some of these application fields the dependability requirements are very important since the fail to provide services in a timely and predictable manner may cause important economic losses or even put humans in risk. In the design phase it is impossible to predict all the possible scenarios of faults, due to the non deterministic behaviour of the surrounding environment. In that way, the fault tolerance mechanisms must be included in the distributed embedded system to prevent failures occurrence. Also, many application domains require a high available bandwidth to perform the desired functions, or to turn possible the scaling with the addition of new features. The flexibility of a system also plays an important role, since it improves the capability to adapt to the surrounding world, and to the simplicity of the repair and maintenance. The flexibility improves the efficiency of all the system by providing a way to efficiently manage the available resources. This is very important in embedded systems due to the limited resources often available. A natural way to improve the bandwidth and the fault tolerance in distributed systems is to use replicated buses. Commercial and academic solutions propose the use of replicated fieldbuses for a single purpose only, either to improve the fault tolerance or to improve the available bandwidth, being the first the most common. One illustrative exception is FlexRay where the bus replica can be used to improve the bandwidth of the overall system, besides enabling redundant communications. However, only one bus replica can be used. In this thesis, a flexible bus replication scheme to improve both the dependability and the throughput of fieldbuses is presented and studied. It can be applied to any number of replicated buses, provided the required hardware support is available. The flexible use of the replicated buses can achieve an also flexible management of the network topology. This claim has been validated using the Controller Area Network (CAN) fieldbus, which has been chosen because it is widely spread in millions of systems. In fact, the proposed solution uses a paradigm that combines flexibility, time and event triggered communication, that is the Flexible Time- Triggered over CAN network (FTT-CAN). However, a generalization to native CAN is also presented and studied. The inclusion of bus replication in FTT-CAN imposes not only new mechanisms but also changes of the mechanisms associated with the master replication, which has been already studied in previous research work. In this work, these mechanisms were combined and take advantage of the centralized architecture and of the redundant masters to support an efficient and flexible bus replication. When considering the system operation, if a fault in the bus (or buses) occurs, and the consequent error leads to a system failure, the system reacts, switching to a degraded mode, where the message flows that were transmitted in the faulty bus (or buses) change to the non-faulty ones. The central node replication uses a leader-follower strategy, where the leader controls the system while the followers serve as backups. If an error occurs in the leader, a backup will take the system control maintaining the system with the same functionalities. The system has been generalized for native CAN, using two additional components that provide the same fault tolerance capabilities at the bus level, and also enable the dynamic management of the network topology. All the referred proposals were implemented and assessed in the scope of this work. The single bus version of FTT-CAN was assessed using a real application, a robotic soccer team, which has obtained excellent results in international competitions. There, the FTT-CAN based embedded system has been applied in the low level control, where, mainly it is responsible for the motion control and odometry. For the case of the multiple buses system, the assessment was performed in a laboratory test bed. For this, a fault injector was developed in order to impose faults in the buses and in the central nodes. To measure the time reaction of the system, a special hardware has been developed: a delay measurement system. It is able to measure delays between two important time marks for posterior offline analysis of the obtained values.

In the last decade the dominance of the general computing systems market has being replaced by embedded systems with billions of units manufactured every year. Embedded systems appear in contexts where continuous operation is of utmost importance and failure can be profound. Nowadays, radiation poses a serious threat to the reliable operation of safety-critical systems. Fault avoidance techniques, such as radiation hardening, have been commonly used in space applications. However, these components are expensive, lag behind commercial components with regards to performance and do not provide 100% fault elimination. Without fault tolerant mechanisms, many of these faults can become errors at the application or system level, which in turn, can result in catastrophic failures. In this work we study the concepts of fault tolerance and dependability and extend these concepts providing our own definition of resilience. We analyse the physics of radiation-induced faults, the damage mechanisms of particles and the process that leads to computing failures. We provide extensive taxonomies of 1) existing fault tolerant techniques and of 2) the effects of radiation in state-of-the-art electronics, analysing and comparing their characteristics. We propose a detailed model of faults and provide a classification of the different types of faults at various levels. We introduce an algorithm of fault tolerance and define the system states and actions necessary to implement it. We introduce novel hardware and system software techniques that provide a more efficient combination of reliability, performance and power consumption than existing techniques. We propose a new element of the system called syndrome that is the core of a resilient architecture whose software and hardware can adapt to reliable and unreliable environments. We implement a software simulator and disassembler and introduce a testing framework in combination with ERA’s assembler and commercial hardware simulators.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Florianópolis, 1986.
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La compréhension du trafic sans fil est fondamentale pour améliorer les réseaux et concevoir des algorithmes et des protocoles avancés. Dans ce contexte, les mesures passives ont l'avantage sur les mesures actives, car elles ne dépendent d'aucune modification des équipements réseau existants. Elles sont souvent moins coûteuses et plus faciles à déployer que d'autres méthodes. Cette approche consiste à surveiller le support sans fil et à collecter des données sur divers paramètres de réseau, tels que la force du signal, l'occupation des canaux et la perte de paquets. Elle consiste à déployer plusieurs sniffeurs dans la zone cible (les sniffeurs sont des dispositifs fonctionnant en « monitor mode » qui collectent les paquets sans fil indépendamment de leur nature). Cependant, l'un des principaux défis des mesures passives est d'assurer la complétude de la trace, c'est-à-dire la capacité à collecter un ensemble de données complet et précis. Nous montrons qu'un seul sniffeur ne peut pas capturer tout le trafic en raison des caractéristiques inhérentes du support sans fil, où l'environnement peut être hautement dynamique et imprévisible. Il existe plusieurs facteurs qui peuvent affecter la complétude de la trace dans les mesures passives sans fil. Celles-ci incluent des facteurs environnementaux, tels que les interférences provenant d'autres dispositifs sans fil, les changements dans l'environnement physique (comme les objets en mouvement) et les variations de propagation du signal sans fil dues aux changements des conditions atmosphériques. De plus, des problèmes avec l'équipement de mesure lui-même, tels que des erreurs de calibration ou des problèmes de traitement des données, peuvent également affecter la complétude de la trace. L'importance de la complétude de la trace dans les mesures passives sans fil ne peut être surestimée. Des données inexactes ou incomplètes peuvent conduire à des conclusions incorrectes sur les performances du réseau, ce qui peut avoir des implications significatives pour la planification, l'optimisation et le dépannage du réseau. Par exemple, des données incomplètes peuvent entraîner des opportunités manquées pour identifier et résoudre des problèmes de réseau, ainsi qu'une reconstruction de trajectoire incorrecte ou incomplète. Dans cette thèse, nous étudions la qualité des traces capturées par des sniffeurs et examinons les améliorations résultantes en introduisant de la redondance dans le nombre de sniffeurs. Nous étudions l'impact des deux aspects suivants sur la qualité des traces sans fil : le nombre de sniffeurs et le type de matériel utilisé. Nous étudions la variation de l'indicateur de force du signal reçu (RSSI) et son impact sur l'estimation de la distance. L'analyse est facilitée par le développement d'un outil facilement utilisable et disponible appelé PyPal pour la synchronisation et la fusion de traces Wi-Fi collectées simultanément
Understanding wireless traffic is fundamental for improving networks and designing advanced algorithms and protocols. In this context, passive measurements have the edge over active measurements, as there is no requirement for any modification in existing network devices. Passive measurements are often less expensive and easier to deploy than other methods. This approach involves monitoring the wireless medium and collecting data on various network parameters, such as signal strength, channel occupancy, and packet loss. It consists of deploying multiple sniffers throughout the target area (sniffers are devices operating in monitor mode that collect the wireless packets regardless of their nature). However, one of the main challenges with passive measurements is ensuring trace completeness, or the ability to collect a complete and accurate dataset. We know that a single sniffer cannot capture all the traffic due to the inherent characteristics of the wireless medium where the environment can be highly dynamic and unpredictable. Several factors can impact trace completeness in wireless passive measurements. These include environmental factors, such as interference from other wireless devices, changes in the physical environment (such as moving objects), and variations in wireless signal propagation due to changes in atmospheric conditions. Additionally, issues with the measurement equipment itself, such as calibration errors or data processing issues, can also impact trace completeness. The importance of trace completeness in wireless passive measurements cannot be overstated. Inaccurate or incomplete data can lead to incorrect conclusions about network performance, which can have significant implications for network planning, optimization, and troubleshooting. For example, incomplete data can result in missed opportunities to identify and address network issues, and incorrect or incomplete trajectory reconstruction. In this thesis, we study the quality of traces captured by a sniffer and investigate the resulting improvements by introducing redundancy in the number of sniffers. We explore the impact of the following two aspects on the quality of wireless traces: the number of sniffing devices and the type of hardware used. We study the variation in the Received Signal Strength Indicator (RSSI) and its impact on distance estimation. The analysis is helped by the development of a readily-usable and easily-available tool, called PyPal, for the synchronization and merging of Wi-Fi traces collected simultaneously

This thesis deals with theoretical analysis of First Hop Redundancy Protocols. It describes Hot Standby Router Protocol, Virtual Router Redundancy Protocol and Gateway Load Balancing Protocol. It also shows examples of configuration of each protocol on Cisco devices with supported version of the Cisco IOS. Furthermore, this thesis includes design of two of these protocols, Hot Standby Router Protocol and Gateway Load Balancing Protocol, and their implementation in discrete event simulator OMNeT++ and Automated Network Simulation and Analysis library. Finally, the thesis presents results of testing of the implementations in comparison with actual Cisco devices.

Thesis (M.S. in Electrical Engineering and M.S. in Systems Engineering) Naval Postgraduate School, December 1994.
"December 1994." Thesis advisor(s): David C. Jenn. Includes bibliographical references. Also available online.

Based on the definition given in the AASHTO LRFD Bridge Design Specifications, twin steel box-girder bridges are classified as bridges with fracture critical members (FCMs), in which a failure of a tension member is expected to lead to a collapse of the bridge. However, a number of such bridges with either a partial or full-depth crack in one girder have been reported and are still providing service without collapsing. The main objective of this research project is to understand the behavior of twin steel box-girder bridges and to develop methods for evaluating their redundancy level in the event of the fracture of one tension member. The research project included an experimental investigation on a small-scale steel twin box-girder bridge, field testing of a full-scale twin box-girder, analysis of existing research and design data, and an extensive amount of numerical analyses carried out on calibrated 3-D nonlinear finite element models. The results from this study provide in-depth understanding of twin steel box-girder bridge behavior before and after a fracture in the tension member occurs. In addition to the experimentally verified finite element method, the report also proposes simplified methods for evaluating the load-carrying capacity of twin steel box-girder bridges under vii concentrated loads and provides a list of important factors that could control the reserve capacity of the damaged bridge. The main conclusion of this research is that the redundancy exists in twin steel boxgirder bridges in an event that a fracture of a tension member(s) takes place. This research project also provides a comprehensive roadmap for assessing the redundancy of twin steel box-girder bridges in which the elements of the roadmap are identified, and solutions for several of the steps are provided. The development of solutions for remaining steps of the roadmap is proposed for a future research.

Improving communication between people and computer applications is a major concern of Human–Computer Interaction. One possible way of improving such communication is to capitalise on the way human beings use speech and gesture in a complementary manner, exploiting the redundancy of information between the input modes of a system. Redundant data input entered into a computer system through multiple modes, provides considerable scope for the resolution of error and ambiguity in the input message.

碩士
國立成功大學
製造工程研究所
87
A novel measure, called Redundancy Indices, is proposed to quantify the amount of redundancy for kinematically redundant manipulators. With the Redundancy Indices, we can not only compute the total redundancy of a redundant manipulator but also monitor the rate range of each joint. Many kinematic constraints, such as joint-angle limits, joint-rate limits, and joint-acceleration bounds, are involved in the proposed measure. Furthermore, the dynamic effects, such as joint-torque bounds, can be included as well. Multiple-goal optimization for window-shaped obstacle avoidance, joint-limit avoidance, singularity avoidance, and drift free are also described and resolved. The Redundancy Indices is easy to compute and can be applied to all types of redundant manipulators. Straight-line motion planning to reduce the execution time for a 3-DOF planar manipulator, a 4-DOF planar manipulator, and a 7-DOF CESAR manipulator are used as examples to exemplify the applications of the Redundancy Indices. Simulation results show that utilization of the Redundancy Indices in the motion planning can reduce the execution time significantly. Specifically, the execution time of the motion planning with/without Redundancy Indices are 6.96/11.2 seconds, 7.56/10.6 seconds, and 12.26/20.0 seconds for the 3-DOF planar manipulator, the 4-DOF planar manipulator, and the 7-DOF spatial manipulator, respectively.