263 research outputs found
A Comparative Study of Thermo-Mechanical Fatigue Performance of Different Grades of SiMo Nodular Cast Iron
No full textThis thesis is a comparative study of the Thermo-Mechanical Fatigue (TMF) performance of different grades of SiMo nodular cast iron for heavy-duty diesel engine exhaust gas manifold applications. The TMF performance of the current SiMo variant used to manufacture exhaust manifolds - SiMo 5.10 (C-3.25Si-4.45Mo-0.76), is compared with that of the variants SiMo 4.05 (C-3.22Si-4.66Mo-0.56) and SiMoNi (C-3.3Si-4.5Mo-1Ni-1.3) by performing three out-of-phase (OP) TMF test series under partial constraint conditions. A benchmark TMF test series in the temperature range: 50 ˚C to 550 ˚C with a hold time of 30 s at 550 ˚C showed that SiMo 5.10 had relatively better performance due to development of lower mechanical crack driving forces compared to other variants. However, a long holding time of 600 s at 550 ˚C saw a larger decrease of average TMF lifetimes for SiMo 5.10 than that of SiMo 4.05 despite similar crack driving forces. An investigation of the stress relaxation during TMF of the two variants showed that the SiMo 4.05 performs better during long hold time due to better stress relaxation properties. The SiMoNi variant which is very brittle at low temperatures was found to fail by a fracture by overloading mechanism taking over quite early in the fatigue cycle; which is confirmed by examination of the fracture surfaces and numerical estimations. This also explained the low lifetimes and scatter in previously performed TMF tests under total constraint conditions. The TMF test series performed in the temperature range: 150 ˚C to 550 ˚C with a hold time of 30 s at 550 ˚C found that a heat-treatment seemed to reduce the TMF performance of the SiMo 5.10 variant. Metallographic investigations and hardness measurements of as-cast and heat-treated materials revealed that the distribution of the Mo-rich phase from the grain boundary regions into the matrix due to an annealing heat-treatment seemed to affect the TMF performance.Materials Science and Engineerin
Parasta Foucault'ia, sattumanvaraisesti
No full textParhaat / Michael Foucault ; suomentaneet Tapani Kilpeläinen, Simo Määttä ja Johan L. Pii. Tampere : Niin & näin, 2014
Book Reviews: Cochlear Implants in Children: Ethics and Choices; Title: Ethics in Mental Health and Deafness
No full textTitle: Cochlear Implants in Children: Ethics and Choices
Authors: John B. Christiansen & Irene W. Leigh
Publisher: Gallaudet University Press, 2002
Cost: 65.00, hardcover
ISBN: 1-56368-120-X
Reviewer: Simo Vehma
Luovat järjestelmät, toimijat sekä yhteisöt : Teoreettisia analyysimenetelmiä ja empiirisiä yhteistyötutkimuksia
No full textCreativity is a multi-faceted phenomenon that can be observed in diverse individuals and contexts, both natural and artificial. This thesis studies computational creativity, i.e. creativity in machines, which can be broadly categorised as a subfield of artificial intelligence. In particular, the thesis deals with three important perspectives on computational creativity: (1) identifying properties of creative individuals, (2) studying processes that lead to creative outcomes, and (3) observing and analysing social aspects of creativity, e.g. collaboration which may allow the individuals to create something together which they could not do alone.
One of the key interests in computational creativity is how computational entities may exhibit creativity in their own right, implying that the creative entities and their compositions, roles, processes and interactions are potentially different from those encountered in nature. This calls for theoretical analysis methods specifically tailored for artificial creative entities, and carefully controlled empirical experiments and simulations with them. We study both of these aspects. The analysis methods allow us to scrutinise exactly how creativity occurs in artificial entities by providing appropriate conceptual elements and vocabulary, while experiments enable us to test and confirm the effectiveness of different design decisions considering individual artificial creative entities and their interaction with each other.
We propose three novel, domain-general analysis tools for artificial creative entities, i.e. creative systems and creative agents, and collections of them, called creative societies. First, we distinguish several conceptual components relevant for metacreative systems, i.e. systems that can reflect and control their creative behaviour, and discuss how these components are interlinked and affect the system's creativity. Second, we merge elements from sequential decision making in intelligent agents, i.e. Markov Decision Processes, into formal creativity as search model called the Creative Systems Framework, providing a detailed account of various elements which compose the decision-making process of a creative agent. Third, we map elements from an eminent social creativity theory, the Systems View of Creativity, a.k.a. Domain-Individual-Field-Interaction model, into the elements of the Creative Systems Framework and show how creative societies may be analysed formally with it.
Each of the proposed analysis tools provides new ways to analyse creativity in artificial entities. The analysis of metacreative systems assumes an architectural point of view to creativity, which has not been previously addressed in detail. Deconstructing the decision-making process of a creative agent gives us additional means to discuss and understand why or how a creative agent selects certain actions. Lastly, the contributions to the creative societies are the first formal framework for their analysis.
We also investigate in two consecutive case studies collaborator selection in creative societies. In the first study, we focus on what kind of cues, e.g. selfish or altruistic, assist in choosing beneficial collaboration partners when all the agents can observe from their peers are the individually created end products. The second study allows the agents to adjust their aesthetic preferences during the simulations and inspects what emerges from society as a whole. We conclude that selfish cues seem to be more effective in choosing the collaboration partners in our settings and that the society exhibits distinct emergence depending on how much the agents are willing to change their aesthetic preferences.Luovuus on monitahoinen ilmiö, jonka osatekijöitä voidaan tunnistaa monissa eri asiayhteyksissä. Tässä väitöskirjassa käsitellään laskennallista luovuutta, eli luovuutta koneissa, mikä voidaan karkeasti luokitella tekoälyn yhdeksi osa-alueeksi.
Yksi laskennallisen luovuuden tärkeimmistä kiinnostuksen kohteista tutkii miten koneet voivat olla luovia omasta ansiostaan. Tämä tarkoittaa että luovat järjestelmät ja toimijat, menetelmät, yhteisöt sekä niiden vuorovaikutus voivat erota ihmisten vastaavista. On siis tärkeää kyetä keskustelemaan luovien järjestelmien, toimijoiden ja yhteisöjen ominaisuuksista riippumatta niiden toteutuksien yksityiskohdista sekä suunnittelemaan simulaatioita ja kokeita joissa voidaan todentaa suunnitteluratkaisujen vaikutukset järjestelmän luovuudelle.
Väitöskirja esittelee kolme uutta luovuuden analyysimenetelmää, jotka on kehitetty analysoimaan (1) luovia järjestelmiä, (2) luovia toimijoita sekä (3) luovia agenttiyhteisöjä. Lisäksi kahdessa osajulkaisussa tutkitaan yhteistyöprosesseja simuloiduissa yhteisöissä, joissa itsenäiset luovat toimijat tuottavat abstraktia taidetta evolutiivisia menetelmiä käyttäen.
Ehdotetut analyysimenetelmät mahdollistavat luovuuden monialaisen tarkastelun sekä tarjoavat yhden mahdollisen suunnan kohti laskennallisen luovuuden yhtenäistä analyysimenetelmää. Havainnot empiirisistä simulaatioista antavat uutta tietoa laskennallisista yhteistyöprosesseista ja ovat askel kohti monimutkaisempia kokeita luovan yhteistyön saralla.ei saavutettav
A Feature-Based Call Graph Distance Measure for Program Similarity Analysis
No full textA measurement for how similar (or distant) two computer programs are has a wide range of possible applications. For example, they can be applied to malware analysis or analysis of university students' programming exercises. However, as programs may be arbitrarily structured, capturing the similarity of two non-trivial programs is a complex task. By extracting call graphs (graphs of caller-callee relationships of the program's functions, where nodes denote functions and directed edges denote function calls) from the programs, the similarity measurement can be changed into a graph problem.
Previously, static call graph distance measures have been largely based on graph matching techniques, e.g. graph edit distance or maximum common subgraph, which are known to be costly. We propose a call graph distance measure based on features that preserve some structural information from the call graph without explicitly matching user defined functions together. We define basic properties of the features, several ways to compute the feature values, and give a basic algorithm for generating the features.
We evaluate our features using two small datasets: a dataset of malware variants, and a dataset of university students' programming exercises, focusing especially on the former. For our evaluation we use experiments in information retrieval and clustering. We compare our results for both datasets to a baseline, and additionally for the malware dataset to the results obtained with a graph edit distance approximation.
In our preliminary results we show that even though the feature generation approach is simpler than the graph edit distance approximation, the generated features can perform on a similar level as the graph edit distance approximation. However, experiments on larger datasets are still required to verify the results
Symbol Error Rate for Nonblind Adaptive Equalizers Applicable for the SIMO and FGn Case
No full textA nonzero residual intersymbol interference (ISI) causes the symbol error rate (SER) to increase where the achievable SER may not answer any more on the system's requirements. Recently, a closed-form approximated expression was derived by the same author for the residual ISI obtained by nonblind adaptive equalizers for the single-input single-output (SISO) case. Up to now, there does not exist a closed-form expression for the residual ISI obtained by nonblind adaptive equalizers for the single-input multiple-output (SIMO) case. Furthermore, there does not exist a closed-form expression for the SER valid for the SISO or SIMO case that takes into account the residual ISI obtained by nonblind adaptive equalizers and is valid for fractional Gaussian noise (fGn) input where the Hurst exponent is in the region of 0.5 ≤ < 1. In this paper, we derive a closed-form approximated expression for the residual ISI obtained by nonblind adaptive equalizers for the SIMO case (where SISO is a special case of SIMO), valid for fGn input where the Hurst exponent is in the region of 0.5 ≤ < 1. Based on this new expression for the residual ISI, a closed-form approximated expression is obtained for the SER valid for the SIMO and fGn case
On Collaborator Selection in Creative Agent Societies : An Evolutionary Art Case Study
No full textWe study how artistically creative agents may learn to select favorable collaboration partners. We consider a society of creative agents with varying skills and aesthetic preferences able to interact with each other by exchanging artifacts or through collaboration. The agents exhibit interaction awareness by modeling their peers and make decisions about collaboration based on the learned peer models. To test the peer models, we devise an experimental collaboration process for evolutionary art, where two agents create an artifact by evolving the same artifact set in turns. In an empirical evaluation, we focus on how effective peer models are in selecting collaboration partners and compare the results to a baseline where agents select collaboration partners randomly. We observe that peer models guide the agents to more beneficial collaborations.Peer reviewe
Action Selection in the Creative Systems Framework
No full textThe Creative Systems Framework (CSF) formalises creativity as search through a space of concepts. As a formal account of Margaret Boden’s descriptive hierarchy of creativity, it is at the basis of multiple studies dealing with diverse aspects of Computational Creativity (CC) systems. However, the CSF at present neither formalises action nor action selection during search, limiting its use in analysing creative processes. We extend the CSF by explicitly modelling these missing components in the search space traversal function. We furthermore integrate the distinction between a concept and an artefact, and provide stopping criteria for creative search. Our extension, the Creative Action Selection Framework (CASF), is informed by previous studies in CC and draws on concepts from Markov Decision Processes (MDPs). It allows us to describe a creative system as an agent selecting actions based on the value, validity and novelty of concepts and artefacts. The CASF brings more analytical depth for creative systems that can be modelled as utilising an action selection procedure.Peer reviewe
Extending the Creative Systems Framework for the Analysis of Creative Agent Societies
No full textDesign and analysis of creative agent societies is often done in the context of computational sociology, which has evolved into its own field called computational social creativity. In this paper, we propose a formal framework for describing and analysing creative agent societies based on the Creative Systems Framework (CSF). We extend the CSF for single agents to include creative agent societies. The extended CSF allows us to describe society wide phenomena relevant for creativity, identify how individual agents relate to the whole society and characterise societal consequences caused by adopting certain policies. All these formal tools may be used when analysing designated creative agent societies. We demonstrate this by devising a straightforward practical procedure which may be used to gain insight into the influence individual agents have on the society over time.Peer reviewe
Towards Goal-aware Collaboration in Artistic Agent Societies
No full textWe study the effects of goal-awareness in artistic agent societies creating evolutionary art. Particularly, we examine how goal-awareness may be utilized in modeling agent's peers when the aesthetic goals of the agent and its peers are subject to change. The agents use the learned peer models to choose their collaboration partners, and may alter their own aesthetic goal for the duration of the collaboration in order to enhance the potential of the collaboration outcomes. In addition, we demonstrate how goal-awareness can be used to guide the aesthetic goal change. The empirical evaluation indicates that agents which can adapt to their collaboration partners are more likely to reach favorable collaboration outcomes, even when their partners perceive fundamentally different properties from the artifacts.Peer reviewe
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