The stability and attractivity of neural associative memories.

Han-bing Ji.Thesis (Ph.D.)--Chinese University of Hong Kong, 1996.Includes bibliographical references (p. 160-163).Microfiche. Ann Arbor, Mich.: UMI, 1998. 2 microfiches ; 11 x 15 cm

Formal concept matching and reinforcement learning in adaptive information retrieval

The superiority of the human brain in information retrieval (IR) tasks seems to come firstly from its ability to read and understand the concepts, ideas or meanings central to documents, in order to reason out the usefulness of documents to information needs, and secondly from its ability to learn from experience and be adaptive to the environment. In this work we attempt to incorporate these properties into the development of an IR model to improve document retrieval. We investigate the applicability of concept lattices, which are based on the theory of Formal Concept Analysis (FCA), to the representation of documents. This allows the use of more elegant representation units, as opposed to keywords, in order to better capture concepts/ideas expressed in natural language text. We also investigate the use of a reinforcement leaming strategy to learn and improve document representations, based on the information present in query statements and user relevance feedback. Features or concepts of each document/query, formulated using FCA, are weighted separately with respect to the documents they are in, and organised into separate concept lattices according to a subsumption relation. Furthen-nore, each concept lattice is encoded in a two-layer neural network structure known as a Bidirectional Associative Memory (BAM), for efficient manipulation of the concepts in the lattice representation. This avoids implementation drawbacks faced by other FCA-based approaches. Retrieval of a document for an information need is based on concept matching between concept lattice representations of a document and a query. The learning strategy works by making the similarity of relevant documents stronger and non-relevant documents weaker for each query, depending on the relevance judgements of the users on retrieved documents. Our approach is radically different to existing FCA-based approaches in the following respects: concept formulation; weight assignment to object-attribute pairs; the representation of each document in a separate concept lattice; and encoding concept lattices in BAM structures. Furthermore, in contrast to the traditional relevance feedback mechanism, our learning strategy makes use of relevance feedback information to enhance document representations, thus making the document representations dynamic and adaptive to the user interactions. The results obtained on the CISI, CACM and ASLIB Cranfield collections are presented and compared with published results. In particular, the performance of the system is shown to improve significantly as the system learns from experience.The School of Computing, University of Plymouth, UK

Multiuser detection employing recurrent neural networks for DS-CDMA systems.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.Over the last decade, access to personal wireless communication networks has evolved to a point of necessity. Attached to the phenomenal growth of the telecommunications industry in recent times is an escalating demand for higher data rates and efficient spectrum utilization. This demand is fuelling the advancement of third generation (3G), as well as future, wireless networks. Current 3G technologies are adding a dimension of mobility to services that have become an integral part of modem everyday life. Wideband code division multiple access (WCDMA) is the standardized multiple access scheme for 3G Universal Mobile Telecommunication System (UMTS). As an air interface solution, CDMA has received considerable interest over the past two decades and a great deal of current research is concerned with improving the application of CDMA in 3G systems. A factoring component of CDMA is multiuser detection (MUD), which is aimed at enhancing system capacity and performance, by optimally demodulating multiple interfering signals that overlap in time and frequency. This is a major research problem in multipoint-to-point communications. Due to the complexity associated with optimal maximum likelihood detection, many different sub-optimal solutions have been proposed. This focus of this dissertation is the application of neural networks for MUD, in a direct sequence CDMA (DS-CDMA) system. Specifically, it explores how the Hopfield recurrent neural network (RNN) can be employed to give yet another suboptimal solution to the optimization problem of MUD. There is great scope for neural networks in fields encompassing communications. This is primarily attributed to their non-linearity, adaptivity and key function as data classifiers. In the context of optimum multiuser detection, neural networks have been successfully employed to solve similar combinatorial optimization problems. The concepts of CDMA and MUD are discussed. The use of a vector-valued transmission model for DS-CDMA is illustrated, and common linear sub-optimal MUD schemes, as well as the maximum likelihood criterion, are reviewed. The performance of these sub-optimal MUD schemes is demonstrated. The Hopfield neural network (HNN) for combinatorial optimization is discussed. Basic concepts and techniques related to the field of statistical mechanics are introduced and it is shown how they may be employed to analyze neural classification. Stochastic techniques are considered in the context of improving the performance of the HNN. A neural-based receiver, which employs a stochastic HNN and a simulated annealing technique, is proposed. Its performance is analyzed in a communication channel that is affected by additive white Gaussian noise (AWGN) by way of simulation. The performance of the proposed scheme is compared to that of the single-user matched filter, linear decorrelating and minimum mean-square error detectors, as well as the classical HNN and the stochastic Hopfield network (SHN) detectors. Concluding, the feasibility of neural networks (in this case the HNN) for MUD in a DS-CDMA system is explored by quantifying the relative performance of the proposed model using simulation results and in view of implementation issues

Dynamics of Macrosystems; Proceedings of a Workshop, September 3-7, 1984

There is an increasing awareness of the important and persuasive role that instability and random, chaotic motion play in the dynamics of macrosystems. Further research in the field should aim at providing useful tools, and therefore the motivation should come from important questions arising in specific macrosystems. Such systems include biochemical networks, genetic mechanisms, biological communities, neutral networks, cognitive processes and economic structures. This list may seem heterogeneous, but there are similarities between evolution in the different fields. It is not surprising that mathematical methods devised in one field can also be used to describe the dynamics of another. IIASA is attempting to make progress in this direction. With this aim in view this workshop was held at Laxenburg over the period 3-7 September 1984. These Proceedings cover a broad canvas, ranging from specific biological and economic problems to general aspects of dynamical systems and evolutionary theory

Development of biotraps based on Cladophora SP Alga for the biosorption of mercury from environmental waters

A Thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy, 2018Trace metal pollution of environmental waters is a serious ecological concern that causes degradation of water quality in rivers and lakes. Mercury is considered as one of the most toxic trace metals due to its propensity to bioaccumulate in food webs thus causing severe detriment to human health. Biosorption using algae as biosorbents is emerging as a technology for the remediation of trace metal-polluted waters because algae are widely abundant and have high adsorption capacities. Algae can also be immobilized on polymeric supports to enhance their performance, selectivity, and industrial applicability. This work presents the development of novel algal-based biosorbents via the immobilization of Cladophora sp alga in silica gel and alginate beads for the removal of mercury from synthetic aqueous solutions under batch equilibrium and continuous flow modes. Both the modified and unaltered algae were also characterized for biosorption of mercury using several techniques including Fourier Transform Infrared Spectroscopy (FTIR), Braunner-Emmet-Taylor (BET), Scanning Electron Microscopy (SEM) and Electron Dispersive Spectroscopy (EDX). The research also describes a first attempt to elucidate the mechanism for mercury biosorption using pristine and modified forms of Cladophora sp alga. The best performing modified biosorbent (alga immobilized in alginate beads) was also utilized to construct biotraps where were then utilized for mercury removal from acid mine water formed by dissolving salt crusts in deionized water. Batch equilibrium studies revealed that the optimum conditions for metal biosorption were pH 5, 10 g L-1 biosorbent dosage and 25˚C for the modified forms of Cladophora sp alga. However, the equilibrium agitation time and initial metal concentration using the biosorbents were 30 minutes and 100 mg L-1, respectively. The maximum biosorption capacities were 121.3 and 183.4 mg g-1 for the alga immobilized in silica gel and alga immobilized in alginate beads. These biosorption capacities represented removal efficiencies of 82.75 and 86.6%, respectively. Biosorption experimental data also fitted the pseudo-second kinetic model, the Langmuir, and Dubinin-Radushkevich isotherms thus suggesting that biosorption iv occurs on a homogeneous layer and was limited by chemisorptive ion exchange mechanism. Kinetic modeling using the Webber-Morris model showed that intraparticle diffusion was rate limiting only at the start of the biosorption process. Mercury adsorption using the biosorbents involved several functional groups. Chemical modification, FTIR analysis and EDX analysis showed that the amine, sulfonate and carboxyl groups were key players in the mechanism for the biosorption of mercury by the biosorbents. The biosorption process occurred via complex processes wherein ion exchange was the most dominant mechanism. This was confirmed using FTIR analysis, EDX analysis and chemical modification of functional groups on the algal surface. The biosorbents were also effective in retrieving mercury from multi-elemental synthetic aqueous solutions. However, the alga immobilized in alginate beads was more selective for mercury removal than that immobilized in silica gel. Optimal removal under continuous flow operation occurred at 7 cm bed height, 2 mL min-1 flow rate and 2 mg L-1 inlet metal concentration. The column data was also best described by the Bed depth service time, Thomas and Yoon Nelson models. This implied that the service time of the column was proportional to the bed height and external mass transfer and internal diffusion were not the rate limiting mechanisms. Application of the biotraps to acid-impacted environmental waters also significantly reduced the total mercury concentration. The adsorption capacity and removal efficiency obtained were 6.081 mg g-1 and 67.81% respectively. These results demonstrated that Cladophora sp algal-based biotraps have potential for use in remediation technologies for mercury in environmental samples. They can be used to augment wetlands by offering protective screens that will reduce the direct impact of wastewaters flowing through them thus enhancing their longevity.XL201

Georisks in the Mediterranean and their mitigation

An international scientific conference organised by the Seismic Monitoring and Research Unit, Department of Geoscience, Faculty of Science, Department of Civil and Structural Engineering and Department of Construction and Property Management, Faculty of the Built Environment, University of Malta.Part of the SIMIT project: Integrated civil protection system for the Italo-Maltese cross-border area. Italia-Malta Programme – Cohesion Policy 2007-2013This conference is one of the activities organised within the SIMIT strategic project (Integrated Cross-Border Italo-Maltese System of Civil Protection), Italia-Malta Operational Programme 2007 – 2013. SIMIT aims to establish a system of collaboration in Civil Protection procedures and data management between Sicilian and Maltese partners, so as to guarantee the safety and protection of the citizens and infrastructure of the cross-border area. It is led by the Department of Civil Protection of the Sicilian region, and has as other partners the Department of Civil Protection of Malta and the Universities of Palermo, Catania and Malta. SIMIT was launched in March 2013, and will come to a close in October 2015. Ever since the initial formulation of the project, it has been recognised that a state of national preparedness and correct strategies in the face of natural hazards cannot be truly effective without a sound scientific knowledge of the hazards and related risks. The University of Malta, together with colleagues from other Universities in the project, has been contributing mostly to the gathering and application of scientific knowledge, both in earthquake hazard as well as in building vulnerability. The issue of seismic hazard in the cross-border region has been identified as deserving foremost importance. South-East Sicily in particular has suffered on more than one occasion the effects of large devastating earthquakes. Malta, although fortunately more removed from the sources of such large earthquakes, has not been completely spared of their damaging effects. The drastic increase in the building density over recent decades has raised the level of awareness and concern of citizens and authorities about our vulnerability. These considerations have spurred scientists from the cross-border region to work together towards a deeper understanding of the underlying causes and nature of seismic and associated hazards, such as landslide and tsunami. The SIMIT project has provided us with the means of improving earthquake surveillance and analysis in the Sicily Channel and further afield in the Mediterranean, as well as with facilities to study the behaviour of our rocks and buildings during earthquake shaking. The role of the civil engineering community in this endeavour cannot be overstated, and this is reflected in the incorporation, from the beginning, of the civil engineering component in the SIMIT project. Constructing safer buildings is now accepted to be the major option towards human loss mitigation during strong earthquakes, and this project has provided us with a welcome opportunity for interaction between the two disciplines. Finally the role of the Civil Protection authorities must occupy a central position, as we recognize the importance of their prevention, coordination and intervention efforts, aided by the input of the scientific community. This conference brings together a diversity of geoscientists and engineers whose collaboration is the only way forward to tackling issues and strategies for risk mitigation. Moreover we welcome the contribution of participants from farther afield than the Central Mediterranean, so that their varied experience may enhance our efforts. We are proud to host the conference in the historic city of Valletta, in the heart of the Mediterranean, which also serves as a constant reminder of the responsibility of all regions to protect and conserve our collective heritage.peer-reviewe

VERSUS: Heritage for Tomorrow

Vernacular architecture represents a great resource that has considerable potential to define principles for sustainable design and contemporary architecture. This publication is the result of an overall aim to produce a valuable tool for analysis regarding vernacular heritage through different assessments, in order to define principles to consider for sustainable development. This was possible through a comprehensive reflection on the principles established and the strategies to recognise in different world contexts. The present publication was the result of an in-depth approach by 46 authors from 12 countries, concerned with the analysis and critical assessment of vernacular heritage and its sustainable perspective. The book presents 8 chapters addressing operational definitions and synopses advances, regarding the main areas of vernacular heritage contribution to sustainable architecture. It also presents 15 chapters and 53 case studies of vernacular and contemporary approaches in all the 5 continents, regarding urban, architectural, technical and constructive strategies and solutions. VERSUS, HERITAGE FOR TOMORROW: Vernacular Knowledge for Sustainable Architecture is the result of a common effort undertaken by the partners ESG | Escola Superior Gallaecia, Portugal, as Project leader; CRAterre | École Nationale Supérieure d’Architecture de Grenoble, France; DIDA | Università degli Studi di Firenze, Italy; DICAAR | Università degli Studi di Cagliari, Italy; and UPV | Universitat Politècnica de València, Spain. This is the final outcome of VerSus, an European project developed from 2012 to 2014, in the framework of the Culture 2007-2013 programme

Analyses expérimentales de la réponse sismique non-linéaire du système sol-structure

The concentration of population in urban areas in seismic-prone regions can generate more and more damages and losses. Seismic response in urban areas depends on site effects (direct amplification and nonlinearity of the soil) and the coupling between the soil and structures (soil-structure and site-city interaction). Therefore, the understanding of urban seismology, that is the ground motion incorporating the urban environment, is critical to reduce the damage. This requires the prediction of ground motion in urban areas, a fundamental element in the evaluation of the seismic hazard. Taking into account the amplification caused by the presence of sediment has been widely studied. However, the non-linearity of the soil and the coupling between the ground and the structure is seldom integrated to the prediction of the ground motion. Because of their complexity, these problems have been addressed separately. In this context, this dissertation analyzes the non-linear response of the soil-structure by integrating the non-linearity of the soil and the soil-structure interaction. Two experimental studies were performed, with the aim of providing a proxy that reflects the non-linearity of the soil. The first is the centrifuge test that reproduces the response of soil and structures at reduced scale. The state of stress and strain is conserved by applying an artificial acceleration model. This test was performed at IFSTTAR Nantes in the framework of the ANR ARVISE. Different configurations were tested with and without buildings, under different stress levels, to analyze the response of the soil and structures. The second uses the vertical accelerometric networks of two sites in California: Garner Valley Downhole (GVDA) and the Wildlife Liquefaction Array (WLA), both managed by the University of California, Santa Barbara (UCSB), USA. In-situ response is important since it describes the actual behavior of the site. Information describing the conditions of sites is widely available and the earthquakes recorded were used to test several levels of shaking to reconstruct the overall response of each site. In addition, the GVDA site is equipped with a Soil-Foundation-Structure-Interaction structure (SFSI) which aims to study the problems of soil-structure interaction. In both experiments, thanks to the vertical accelerometer network in the ground and the structure we are able to apply the 1D wave propagation method to extract the response of these systems. The waves are considered as an SH wave which propagates in a 1D horizontal layer. Seismic interferometry by deconvolution method is applied to extract the Impulse Response Function (IRF) of the 1D system. Thus the analysis of the variation in function of elastic properties of the soil and the structure is done under several magnitude of shaking, including variation in depth and the elements of the total response of the structure including the soil-structure interaction. At the end, a deformation proxy to evaluate and also to predict the nonlinear response of the soil, the structure and the soil-structure interaction is proposed.La concentration de plus en plus importante de la population dans les milieux urbains exposés à une forte sismicité peut générer de plus en plus de dommages et de pertes. La réponse sismique en milieu urbain dépend des effets du site (direct amplification et non-linéarité du sol) et du couplage entre le sol et les structures (interaction sol-structure et site-ville). Par conséquent, la compréhension de la sismologie urbaine, c'est-à-dire le mouvement du sol intégrant l'environnement urbain, est critique pour réduire les dommages. Cela passe par la prédiction du mouvement du sol dans le milieu urbain, ingrédient fondamental à l'évaluation de l'aléa sismique. La prise en compte de l'amplification provoquée par la présence de sédiments est largement étudiée. Au contraire, la réponse non-linéarité du sol et du couplage entre le sol et la structure est rarement intégrée à la prédiction du mouvement du sol. A cause de leur complexité, ces problèmes ont toujours été abordés séparément. Dans ce contexte, cette thèse analyse la réponse non-linéaire du système sol-structure en intégrant la non-linéarité du sol et de l'interaction sol-structure. Deux travaux expérimentaux ont été conduits, avec comme but de proposer un proxy, rendant compte de la non-linéarité du sol. Le premier est l'essai en centrifugeuse qui reproduit à échelle réduite la réponse du sol et des structures. L'état de contrainte et de déformation est conservé en appliquant une accélération artificielle au modèle. Cet essai a été effectué à IFSTTAR Nantes dans le cadre de l'ANR ARVISE. Différentes configurations ont été testées, avec et sans bâtiments, sous différents niveaux de sollicitation, pour analyser la réponse du sol et des structures. Le deuxième utilise les enregistrements des réseaux accélérométriques verticaux de deux sites tests californiens : Garner Valley Downhole Arrat (GVDA) et Wildlife Liquefaction Array (WLA), gérés tout deux par l'Université de Californie, Santa Barbara (UCSB), Etats-Unis. La réponse in-situ est importante car elle décrit le comportement réel du site. Plusieurs informations décrivant les conditions de sites sont disponibles et les séismes enregistrés ont permis de tester plusieurs niveaux de déformations pour reconstruire la réponse globale de chaque site. De plus, le site GVDA est équipé d'une structure Soil-Foundation-Structure-Interaction (SFSI) qui a comme objectif d'étudier les problèmes d'interaction sol-structure. Dans les deux expériences, grace au réseau accélérométrique vertical dans le sol et la structure, on peut appliquer la méthode de propagation d'ondes 1D pour extraire la réponse de ces systèmes. Les ondes sont considérées comme des ondes SH qui se propage horizontalement dans une couche 1D. La méthode interférométrie sismique par déconvolution est appliquée pour extraire l'Impulse Response Function (IRF) du système 1D. On analyse ainsi la variation de Vs en fonction de la solliictation et à différente position dans le sol ainsi que la variation des éléments expliquant la réponse dynamique du système sol-structure. On propose au final un proxy de déformation permettant de rendre compte mais aussi de prédire la nonlinéarité des sols en fonction des niveaux sismiques subits