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Lehdonvirta V.,Helsinki Institute for Information Technology
Journal of Technology, Learning, and Assessment | Year: 2010

I argue that much influential scholarship on massively-multiplayer online games and virtual environments (MMO) is based on a dichotomous a ̂creal world vs. virtual worldac model. The roots of this dichotomy can be traced to the magic circle concept in game studies and the cyberspace separatism of early Internet thought. The model manifests on a number of dimensions, including space, identity, social relationships, economy and law. I show a number of problems in the use of this model in research, and propose an alternative perspective based on Anselm Straussa's concept of overlapping social worlds. The world of players does not respect the boundaries of an MMO server, as it frequently flows over to other sites and forums. At the same time, other social worlds, such as families and workplaces, penetrate the site of the MMO and are permanently tangled with the players' world. Research programs that approach MMOs as independent mini-societies are therefore flawed, but there are many other kinds of research that are quite feasible. © 2001-2010 Game Studies. Source

Heiskanen E.,National Consumer Research Center | Johnson M.,Helsinki Institute for Information Technology | Vadovics E.,Green Dependent Sustainable Solutions Association
Journal of Cleaner Production | Year: 2013

European energy policy aims to shift the energy market towards an increased focus on energy services based on end-user needs. This requires a close understanding of the role of end-users and their needs and practices. Based on a European project called CHANGING BEHAVIOUR, we examine the interaction between energy users and energy efficiency practitioners. Using previous cases and our own pilots as data, we uncover the main difficulties in understanding and working with energy users. We argue that formal user research and interaction methods are helpful, yet insufficient for project success or even genuine user responsiveness. Additionally, methods and skills are needed for interacting with broader networks of stakeholders in the user context. Moreover, user responsiveness requires informal interaction with energy users, interpersonal skills and human judgement, which are difficult to develop merely by using better methods. © 2012 Elsevier Ltd. All rights reserved. Source

Heinonen M.,University of Helsinki | Heinonen M.,Helsinki Institute for Information Technology | Shen H.,University of Helsinki | Zamboni N.,ETH Zurich | And 2 more authors.
Bioinformatics | Year: 2012

Motivation: Metabolite identification from tandem mass spectra is an important problem in metabolomics, underpinning subsequent metabolic modelling and network analysis. Yet, currently this task requires matching the observed spectrum against a database of reference spectra originating from similar equipment and closely matching operating parameters, a condition that is rarely satisfied in public repositories. Furthermore, the computational support for identification of molecules not present in reference databases is lacking. Recent efforts in assembling large public mass spectral databases such as MassBank have opened the door for the development of a new genre of metabolite identification methods. Results: We introduce a novel framework for prediction of molecular characteristics and identification of metabolites from tandem mass spectra using machine learning with the support vector machine. Our approach is to first predict a large set of molecular properties of the unknown metabolite from salient tandem mass spectral signals, and in the second step to use the predicted properties for matching against large molecule databases, such as PubChem. We demonstrate that several molecular properties can be predicted to high accuracy and that they are useful in de novo metabolite identification, where the reference database does not contain any spectra of the same molecule. © The Author 2012. Published by Oxford University Press. All rights reserved. Source

Cao H.,National University of Defense Technology | Zhu P.,National University of Defense Technology | Lu X.,National University of Defense Technology | Gurtov A.,Helsinki Institute for Information Technology
IEEE Network | Year: 2013

Networked critical infrastructures improve our lives, but they are attractive targets for adversaries. In such infrastructures, to secure sensitive data is vital, as the information system is a foundation of today¿s critical infrastructures, and data security is a main concern in such systems. Cryptography is an approach for data security, but this method should be altered according to various features of infrastructure networks. Since complex and distributed critical infrastructures usually spread over large geographic areas, different parts of those infrastructures have different levels of perimeter defense. Devices in weakly protected zones are more likely to be captured than those in well protected zones. If an adversary captures devices, s/he can bypass cyber security measures and obtain secret information directly. Such a threat requires a layered security mechanism that can prevent adversaries from invading the whole infrastructure network from these weak zones. In this article, we propose a layered encryption mechanism based on hash chain technology for protecting sensitive data. Besides showing the layered defense, the mechanism is also lightweight and has convenient key management. It can be used independently or as a supplement to existing security measures. We evaluate performance of the proposed mechanism over different kinds of devices. © 2013 IEEE. Source

Pajarinen J.,Aalto University | Hottinen A.,Asparrow Ltd. | Peltonen J.,Aalto University | Peltonen J.,Helsinki Institute for Information Technology
IEEE Transactions on Mobile Computing | Year: 2014

The performance of medium access control (MAC) depends on both spatial locations and traffic patterns of wireless agents. In contrast to conventional MAC policies, we propose a MAC solution that adapts to the prevailing spatial and temporal opportunities. The proposed solution is based on a decentralized partially observable Markov decision process (DEC-POMDP), which is able to handle wireless network dynamics described by a Markov model. A DEC-POMDP takes both sensor noise and partial observations into account, and yields MAC policies that are optimal for the network dynamics model. The DEC-POMDP MAC policies can be optimized for a freely chosen goal, such as maximal throughput or minimal latency, with the same algorithm. We make approximate optimization efficient by exploiting problem structure: the policies are optimized by a factored DEC-POMDP method, yielding highly compact state machine representations for MAC policies. Experiments show that our approach yields higher throughput and lower latency than CSMA/CA based comparison methods adapted to the current wireless network configuration. © 2002-2012 IEEE. Source

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