996 resultados para same basic integrator


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Abstract Sitting between your past and your future doesn't mean you are in the present. Dakota Skye Complex systems science is an interdisciplinary field grouping under the same umbrella dynamical phenomena from social, natural or mathematical sciences. The emergence of a higher order organization or behavior, transcending that expected of the linear addition of the parts, is a key factor shared by all these systems. Most complex systems can be modeled as networks that represent the interactions amongst the system's components. In addition to the actual nature of the part's interactions, the intrinsic topological structure of underlying network is believed to play a crucial role in the remarkable emergent behaviors exhibited by the systems. Moreover, the topology is also a key a factor to explain the extraordinary flexibility and resilience to perturbations when applied to transmission and diffusion phenomena. In this work, we study the effect of different network structures on the performance and on the fault tolerance of systems in two different contexts. In the first part, we study cellular automata, which are a simple paradigm for distributed computation. Cellular automata are made of basic Boolean computational units, the cells; relying on simple rules and information from- the surrounding cells to perform a global task. The limited visibility of the cells can be modeled as a network, where interactions amongst cells are governed by an underlying structure, usually a regular one. In order to increase the performance of cellular automata, we chose to change its topology. We applied computational principles inspired by Darwinian evolution, called evolutionary algorithms, to alter the system's topological structure starting from either a regular or a random one. The outcome is remarkable, as the resulting topologies find themselves sharing properties of both regular and random network, and display similitudes Watts-Strogtz's small-world network found in social systems. Moreover, the performance and tolerance to probabilistic faults of our small-world like cellular automata surpasses that of regular ones. In the second part, we use the context of biological genetic regulatory networks and, in particular, Kauffman's random Boolean networks model. In some ways, this model is close to cellular automata, although is not expected to perform any task. Instead, it simulates the time-evolution of genetic regulation within living organisms under strict conditions. The original model, though very attractive by it's simplicity, suffered from important shortcomings unveiled by the recent advances in genetics and biology. We propose to use these new discoveries to improve the original model. Firstly, we have used artificial topologies believed to be closer to that of gene regulatory networks. We have also studied actual biological organisms, and used parts of their genetic regulatory networks in our models. Secondly, we have addressed the improbable full synchronicity of the event taking place on. Boolean networks and proposed a more biologically plausible cascading scheme. Finally, we tackled the actual Boolean functions of the model, i.e. the specifics of how genes activate according to the activity of upstream genes, and presented a new update function that takes into account the actual promoting and repressing effects of one gene on another. Our improved models demonstrate the expected, biologically sound, behavior of previous GRN model, yet with superior resistance to perturbations. We believe they are one step closer to the biological reality.

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This project focuses on studying and testing the benefits of the NX Remote Desktop technology in administrative use for Finnish Meteorological Institutes existing Linux Terminal Service Project environment. This was done due to the criticality of the system caused by growing number of users as the Linux Terminal Service Project system expands. Although many of the supporting tasks can be done via Secure Shell connection, testing graphical programs or desktop behaviour in such a way is impossible. At first basic technologies behind the NX Remote Desktop were studied, and after that started the testing of two possible programs, FreeNX and NoMachine NX server. Testing the functionality and bandwidth demands were first done in a closed local area network, and results were studied. The better candidate was then installed in a virtual server simulating actual Linux Terminal Service Project server at Finnish Meteorological Institute and connection from Internet was tested to see was there any problems with firewalls and security policies. The results are reported in this study. Studying and testing the two different candidates of NX Remote Desktop showed, that NoMachine NX Server provides better customer support and documentation. Security aspects of the Finnish Meteorological Institute had also to be considered, and since updates along with the new developing tools are announced in next version of the program, this version was the choice. Studies also show that even NoMachine promises a swift connection over an average of 20Kbit/s bandwidth, at least double of that is needed. This project gives an overview of available remote desktop products along their benefits. NX Remote Desktop technology is studied, and installation instructions are included. Testing is done in both, closed and the actual environment and problems and suggestions are studied and analyzed. The installation to the actual LTSP server is not yet made, but a virtual server is put up in the same place in the view of network topology. This ensures, that if the administrators are satisfied with the system, installation and setting up the system will go as described in this report.

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Epidemiological processes leave a fingerprint in the pattern of genetic structure of virus populations. Here, we provide a new method to infer epidemiological parameters directly from viral sequence data. The method is based on phylogenetic analysis using a birth-death model (BDM) rather than the commonly used coalescent as the model for the epidemiological transmission of the pathogen. Using the BDM has the advantage that transmission and death rates are estimated independently and therefore enables for the first time the estimation of the basic reproductive number of the pathogen using only sequence data, without further assumptions like the average duration of infection. We apply the method to genetic data of the HIV-1 epidemic in Switzerland.

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The aim of this research was to structure a conceptual model of hope and hopelessness based on dictionary definitions, and to verify this model on the basis of the experiences of the severely depressive and non-depressive elderly. This research has produced a substantive theory of hope and hopelessness which is based on the experiences of the depressive and non-depressive elderly, and on the concept analysis of hope and hopelessness based on English dictionary definitions. The patients who participated in the research were 65 years old and older men and women (n=22) who had been admitted to a psychiatric hospital because of major depression, and another group: the non-depressive elderly (n=21), who were recruited from the pensioners’ clubs. The data were collected in interviews using the Clinical Assessment Tool, developed by Farran, Salloway and Clark (1990) and Farran, Wilken and Popovich (1992), and it produced 553 pages of written text, which were analysed using the ATLAS/ti programme. ATLAS/ti is a tool for analysing qualitative data and is based on Grounded Theory. The medical and nursing records of the depressive elderly completed source triangulation. The concept analysis of hope and hopelessness was made on the basis of the definitions of English dictionaries (n=103), using semantic analysis and the ATLAS/ti programme. The most important hope-promoting factors were human relations, health and managing in everyday living. Autonomy, self-determination and feeling of security were highly appreciated among the elderly. Hopelessness, on the other hand, was most often associated with the same factors: human relations, health and everyday living. Especially, losses of significant others were experienced as strongly hope-diminishing. Old age had brought freedom from duties concerning others, but now, when you finally had an opportunity to enjoy yourself, you could not accomplish anything; you were clasped in the arms of total inability, depression had come. The most obvious difference in the life course of the depressive and nondepressive elderly was the abundance of traumatic experiences in the childhood and youth of the depressive elderly. The continuous circulation of fearful thoughts was almost touchable, and suicidality was described in connection with these thoughts. You were afraid to be awake and also to go to sleep. Managing day by day was the goal. The research produced the Basic Social Process (BSP) of hope: achieving - maintaining - losing, which expresses a continuous balancing between Being without and Being with. The importance of the object of hope was combined with the amount of hope and disappointment. The process of approaching defined the realisation of hope and the process of withdrawal that of losing. Joy and security versus grief and insecurity defined the Being with and Being without. Two core categories were found. The first one “If only I could�? reflects lack of energy, lack of knowledge, lack of courage and lack of ability. The other one “There is always a loophole�? reflects deliberate tracing of possibilities and the belief in finding solutions, and managing.