| 111. |
- Mathiason, Gunnar, 1966-
(författare)
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Virtual Full Replication for Scalable Distributed Real-Time Databases
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A fully replicated distributed real-time database provides high availability and predictable access times, independent of user location, since all the data is available at each node. However, full replication requires that all updates are replicated to every node, resulting in exponential growth of bandwidth and processing demands with the number of nodes and objects added. To eliminate this scalability problem, while retaining the advantages of full replication, this thesis explores Virtual Full Replication (ViFuR); a technique that gives database users a perception of using a fully replicated database while only replicating a subset of the data.We use ViFuR in a distributed main memory real-time database where timely transaction execution is required. ViFuR enables scalability by replicating only data used at the local nodes. Also, ViFuR enables flexibility by adaptively replicating the currently used data, effectively providing logical availability of all data objects. Hence, ViFuR substantially reduces the problem of non-scalable resource usage of full replication, while allowing timely execution and access to arbitrary data objects.In the thesis we pursue ViFuR by exploring the use of database segmentation. We give a scheme (ViFuR-S) for static segmentation of the database prior to execution, where access patterns are known a priori. We also give an adaptive scheme (ViFuR-A) that changes segmentation during execution to meet the evolving needs of database users. Further, we apply an extended approach of adaptive segmentation (ViFuR-ASN) in a wireless sensor network - a typical dynamic large-scale and resource-constrained environment. We use up to several hundreds of nodes and thousands of objects per node, and apply a typical periodic transaction workload with operation modes where the used data set changes dynamically. We show that when replacing full replication with ViFuR, resource usage scales linearly with the required number of concurrent replicas, rather than exponentially with the system size.
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| 112. |
- Mathiason, Gunnar
(författare)
-
Virtual Full Replication for Scalable Distributed Real-Time Databases (Thesis Proposal)
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Distributed real-time systems increase in size an complexity, and the nodes in such systems become difficult to implement and test. In particular, communication for synchronization of shared information in groups of nodes becomes complex to manage. Several authors have proposed to using a distributed database as a communication subsystem to offload database applications from explicit communication. This lets the task for information dissemination be done by the replication mechanisms of the database. With increasingly larger systems, however, there is a need for managing the scalability for such database approach. Furthermore, timeliness for database clients requires predictable resource usage, and scalability requires bounded resource usage in the database system. Thus, predictable resource management is an essential function for realizing timeliness in a large scale setting. We discuss scalability problems and methods for distributed real-time databases in the context of the DeeDS database prototype. Here, all transactions can be executed timely at the local node due to main memory residence, full replication and detached replication of updates. Full replication contributes to timeliness and availability, but has a high cost in excessive usage of bandwidth, storage, and processing, in sending all updates to all nodes regardless of updates will be used there or not. In particular, unbounded resource usage is an obstacle for building large scale distributed databases. For many application scenarios it can be assumed that most of the database is shared by only a limited number of nodes. Under this assumption it is reasonable to believe that the degree of replication can be bounded, so that a bound also can be set on resource usage. The thesis proposal identifies and elaborates research problems for bounding resource usage in large scale distributed real-time databases. One objective is to bound resource usage by taking advantages of pre-specified data needs, but also by detecting unspecified data needs and adapting resource management accordingly. We elaborate and evaluate the concept of virtual full replication, which provides an image of a fully replicated database to database clients. It makes data objects available where needed, while fulfilling timeliness and consistency requirements on the data. In the first part of our work, virtual full replication makes data available where needed by taking advantages of pre-specified data accesses to the distributed database. For hard real-time systems, the required data accesses are usually known since such systems need to be well specified to guarantee timeliness. However, there are many applications where a specification of data accesses can not be done before execution. The second part of our work extends virtual full replication to be used with such applications. By detecting new and changed data accesses during execution and adapt database replication, virtual full replication can continuously provide the image of full replication while preserving scalability. One of the objective of the thesis work is to quantify scalability in the database context, so that actual benefits and achievements can be evaluated. Further, we find out the conditions for setting bounds on resource usage for scalability, under both static and dynamic data requirements.
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| 113. |
- Mathiason, Gunnar, et al.
(författare)
-
Virtual Full Replication for Wireless Sensor Networks
- 2007
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Ingår i: Proceedings work-in-progress session of the 19th Euromicro conference on Real-Time Systems (ECRTS 2007), 4-6 July, 2007, Pisa, Italy. - Skövde : Högskolan i Skövde. ; , s. 4-, s. 45-48
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We propose to use a distributed real-time database with Virtual Full Replication by Adaptive Segmentation, for whiteboard communication in a sensor network with mobile sink nodes. Sensor networks are large scale applications with limited resources, so they need scalable propagation of sensor data, both to the users inside the network and to the network edges. Virtual full replication enables scalable and adaptive propagation of sensor data, by bounding resource usage to the current data needs. We use a two-tiered wireless sensor network, where each sensor value is published in the distributed database at gateways of the upper tier. Mobile users search for sensor data only at the gateways, which limits the search space.
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| 114. |
- Mauritsson, Karl, et al.
(författare)
-
A new flexible model for maintenance and feeding expenses that improves description of individual growth in insects
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic theories in ecology interpret ecological patterns at different levels through the lens of metabolism, typically applying allometric scaling to describe energy use. This requires a sound theory for individual metabolism. Common mechanistic growth models, such as ‘von Bertalanffy’, ‘dynamic energy budgets’ and the ‘ontogenetic growth model’ lack some potentially important aspects, especially regarding regulation of somatic maintenance. We develop a model for ontogenetic growth of animals, applicable to ad libitum and food limited conditions, based on an energy balance that expresses growth as the net result of assimilation and metabolic costs for maintenance, feeding and food processing. The most important contribution is the division of maintenance into a ‘non-negotiable’ and a ‘negotiable’ part, potentially resulting in hyperallometric scaling of maintenance and downregulated maintenance under food restriction. The model can also account for effects of body composition and type of growth at the cellular level. Common mechanistic growth models often fail to fully capture growth of insects. However, our model was able to capture empirical growth patterns observed in house crickets.
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| 115. |
- Mauritsson, Karl, et al.
(författare)
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A new mechanistic model for individual growth suggests upregulated maintenance costs when food is scarce in an insect
- 2024
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Ingår i: Ecological Modelling. - : Elsevier. - 0304-3800 .- 1872-7026. ; 491
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Tidskriftsartikel (refereegranskat)abstract
- A growing animal ingests food from the environment and distributes the assimilated energy between chemical energy stored in synthesized biomass and energy spent on metabolic processes, including food processing, maintenance, activity and overhead costs for growth. Under food restriction, the growth rate is usually decreased. However, the extent of this reduction may be influenced by a potential trade-off with maintenance metabolism. The latter seems to be down-regulated under food restriction in some animals and up-regulated in others. Recently, the Maintenance-Growth Model (MGM) was developed for ontogenetic and post-mature growth, including several aspects not considered by common mechanistic growth models, most importantly the division of maintenance costs into non-negotiable and negotiable parts, where the latter can be up- or downregulated under food restriction. Using empirical data, MGM has been calibrated and successfully applied to an insect growing under ad libitum conditions. Here, the model is further calibrated to newly collected individual data for the same species growing under two different regimes of food restriction, complemented with previously collected data for food-limited cohorts. We find that two alternative model scenarios of MGM are able to generate rather good predictions of observed growth under food restriction, assuming either upregulated maintenance or decreased effective assimilation (assimilation minus energy spent on processing and searching food). We find the latter scenario least plausible, implying that the current study provides the first indication for the occurrence of upregulated maintenance in an insect species when food is scarce, an unexpected result that requires further investigation. The inclusion of maintenance regulation in MGM enables the new growth model to be used in the modelling of life-history dependent trade-offs between maintenance, growth and maturation for various other species.
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| 116. |
- Meng, N, et al.
(författare)
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RECK, a novel matrix metalloproteinase regulator
- 2008
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Ingår i: Histology and Histopathology. - : Hernandéz. - 0213-3911 .- 1699-5848. ; 23:8, s. 1003-1010
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Forskningsöversikt (refereegranskat)abstract
- Extracellular matrix (ECM) macromolecules are important for creating the cellular environments required during development and morphogenesis of tissues. Matrix metalloproteinases (MMPs) are a family of Zn-dependent endopeptidases that collectively are capable of cleaving virtually all ECM substrates, and play an important role in some physiological and pathological processes. MMP activity can be inhibited by some natural and artificial inhibitors. A newly found membrane-anchored regulator of MMPs, the reversion-inducing-cysteine-rich protein with kazal motifs (RECK), is downregulated when the cells undergo a process of malignant transformation, and is currently the subject of considerable research activity because of its specific structure and function. In this review, we have chosen to concentrate our efforts on the structure, function, regulation, and future prospect of RECK in order to provide a new target for prevention and treatment of tumours
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| 117. |
- Montebelli, Alberto, et al.
(författare)
-
Microbial fuel cell driven behavioural dynamics in robot simulations
- 2010
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Ingår i: Artificial Life XII. - Cambridge, Massachusetts : MIT Press. - 9780262290753 - 0262290758 ; , s. 749-756
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Konferensbidrag (refereegranskat)abstract
- With the present study we report the first application of a recently proposed model for realistic microbial fuel cells (MFCs) energy generation dynamics, suitable for robotic simulations with minimal and extremely limited computational overhead. A simulated agent was adapted in order to engage in a viable interaction with its environment. It achieved energy autonomy by maintaining viable levels of the critical variables of MFCs, namely cathodic hydration and anodic substrate biochemical energy. After unsupervised adaptation by genetic algorithm, these crucial variables modulate the behavioral dynamics expressed by viable robots in their interaction with the environment. The analysis of this physically rooted and self-organized dynamic action selection mechanism constitutes a novel practical contribution of this work. We also compare two different viable strategies, a self-organized continuous and a pulsed behavior, in order to foresee the possible cognitive implications of such biologicalmechatronics hybrid symbionts in a novel scenario of ecologically grounded energy and motivational autonomy.
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| 118. |
- Montebelli, Alberto
(författare)
-
Modeling the Role of Energy Management in Embodied Cognition
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The quest for adaptive and autonomous robots, flexible enough to smoothly comply with unstructured environments and operate in close interaction with humans, seems to require a deep rethinking of classical engineering methods. The adaptivity of natural organisms, whose cognitive capacities are rooted in their biological organization, is an obvious source of inspiration. While approaches that highlight the role of embodiment in both cognitive science and cognitive robotics are gathering momentum, the crucial role of internal bodily processes as foundational components of the biological mind is still largely neglected.This thesis advocates a perspective on embodiment that emphasizes the role of non-neural bodily dynamics in the constitution of cognitive processes in both natural and artificial systems. In the first part, it critically examines the theoretical positions that have influenced current theories and the author's own position. The second part presents the author's experimental work, based on the computer simulation of simple robotic agents engaged in energy-related tasks. Proto-metabolic dynamics, modeled on the basis of actual microbial fuel cells for energy generation, constitute the foundations of a powerful motivational engine. Following a history of adaptation, proto-metabolic states bias the robot towards specific subsets of behaviors, viably attuned to the current context, and facilitate a swift re-adaptation to novel tasks. Proto-metabolic dynamics put the situated nature of the agent-environment sensorimotor interaction within a perspective that is functional to the maintenance of the robot's overall `survival'. Adaptive processes tend to convert metabolic constraints into opportunities, branching into a rich and energetically viable behavioral diversity.
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| 119. |
- Montebelli, Alberto, et al.
(författare)
-
More from the Body : Embodied anticipation for swift re-adaptation in neurocomputational cognitive architectures for robotic agents
- 2010
-
Ingår i: Advances in Cognitive Systems. - Stevenage : Institution of Engineering and Technology. - 1849190755 - 1849190763 - 9781849190756 - 9781849190763 ; , s. 249-270
-
Bokkapitel (refereegranskat)abstract
- The coupling between a body (in an extended sense that encompasses both neural and non-neural dynamics) and its environment is here conceived as a critical substrate for cognition. We propose and discuss the plan for a neurocomputational cognitive architecture for robotic agents, so far implemented in its minimal form for supporting the behavior of a simple simulated robotic agent. A non-neural internal bodily mechanism (crucially characterized by a time scale much slower than the normal sensory-motor interactions of the robot with its environment) extends the cognitive potential of a system composed of purely reactive parts with a dynamic action selection mechanism and the capacity to integrate information over time. The same non-neural mechanism is the foundation for a novel, minimalist anticipatory architecture, implementing our bodily-anticipation hypothesis and capable of swift re-adaptation to related yet novel tasks.
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| 120. |
- Montebelli, Alberto, et al.
(författare)
-
On Cognition as Dynamical Coupling : An Analysis of Behavioral Attractor Dynamics
- 2008
-
Ingår i: Adaptive Behavior. - : Sage Publications. - 1059-7123 .- 1741-2633. ; 16:2-3, s. 182-195
-
Tidskriftsartikel (refereegranskat)abstract
- The interaction of brain, body, and environment can result incomplex behavior with rich dynamics, even for relatively simpleagents. Such dynamics are, however, often difficult to analyze.In this article, we explore the case of a simple simulated roboticagent, equipped with a reactive neurocontroller and an energylevel, which the agent has been evolved to recharge. A dynamicalsystems analysis shows that a non-neural internal state (energylevel), despite its simplicity, dynamically modulates the behavioralattractors of the agent—environment system, such thatthe robot's behavioral repertoire is continually adapted toits current situation and energy level. What emerges is a dynamic,non-deterministic, and highly self-organized action selectionmechanism, originating from the dynamical coupling of four systems(non-neural internal states, neurocontroller, body, and environment)operating at very different timescales.
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