Showing papers by "Aalto University published in 2009"
Journal Article•
TL;DR: A survey of the concepts, methods, and applications of community detection can be found in this article, where the authors provide a guide to available methodology and open problems, and discuss why scientists from diverse backgrounds are interested in these problems.
Abstract: We survey some of the concepts, methods, and applications of community detection, which has become an increasingly important area of network science. To help ease newcomers into the field, we provide a guide to available methodology and open problems, and discuss why scientists from diverse backgrounds are interested in these problems. As a running theme, we emphasize the connections of community detection to problems in statistical physics and computational optimization.
807 citations
TL;DR: In this article, the authors show that there is a trade-off between exploration and exploitation and that the optimal balance between exploring and exploitation depends upon environmental conditions. And they find an inverted U-shaped relationship between the relative share of explorative orientation and financial performance, positively moderated by the R&D intensity of the industry in which the firm operates.
Abstract: The literature suggests that established firms need to balance their exploration and exploitation activities in order to achieve superior performance. Yet, previous empirical research has modeled this balance as the interaction of orthogonal activities. In this study, we show that there is a trade-off between exploration and exploitation and that the optimal balance between exploration and exploitation depends upon environmental conditions. Using a novel methodology to measure the relative exploration versus exploitation orientation, we find an inverted U-shaped relationship between the relative share of explorative orientation and financial performance. This relationship is positively moderated by the R&D intensity of the industry in which the firm operates.
757 citations
TL;DR: The case study debate in the general methodological literature to how this method is practiced within this particular scientific community is explored in this article, where case study practices within a specific management discipline, that of international business, are explored.
Abstract: This article explores case study practices within a specific management discipline, that of international business. The authors contrast the case study debate in the general methodological literature to how this method is practiced within this particular scientific community. They review 135 case study—based articles published in four international business journals from 1995 to 2005 and 22 from 1975 to 1994, finding the disciplinary convention in these journals to be exploratory, interview-based multiple case studies, drawing on positivistic assumptions and cross-sectional designs. Alternative perspectives on the case study that the authors identify in the methodological literature have had little impact on this field. Even the most commonly cited methodological literature is not consistently followed. Given these limitations of the disciplinary convention, the authors argue for greater methodological pluralism in conducting case studies and provide suggestions for researchers seeking to adopt alternativ...
484 citations
TL;DR: These findings advance knowledge of IT adoption and suggest that it should start to identify the contexts of both the benefits of use and in learning to use the system.
466 citations
TL;DR: The results demonstrate that the D2D radio, sharing the same resources as the cellular network, can provide higher capacity compared to pure cellular communication where all the data is transmitted through the base station.
Abstract: In this article we propose to facilitate local peer-to-peer communication by a Device-to-Device (D2D) radio that operates as an underlay network to an IMT-Advanced cellular network It is expected that local services may utilize mobile peer-to-peer communication instead of central server based communication for rich multimedia services The main challenge of the underlay radio in a multi-cell environment is to limit the interference to the cellular network while achieving a reasonable link budget for the D2D radio We propose a novel power control mechanism for D2D connections that share cellular uplink resources The mechanism limits the maximum D2D transmit power utilizing cellular power control information of the devices in D2D communication Thereby it enables underlaying D2D communication even in interference-limited networks with full load and without degrading the performance of the cellular network Secondly, we study a single cell scenario consisting of a device communicating with the base station and two devices that communicate with each other The results demonstrate that the D2D radio, sharing the same resources as the cellular network, can provide higher capacity (sum rate) compared to pure cellular communication where all the data is transmitted through the base station
405 citations
TL;DR: In this paper, the authors draw attention to several corporate social responsibility (CSR) questions in developing countries and draw illustrations from South America and Africa, includ- ing African voi...
Abstract: This paper draws attention to several corporate social responsibility (CSR) questions in developing countries. (1) Illustrations from, for example, South America and Africa, includ- ing African voi ...
354 citations
TL;DR: A preference-based evolutionary approach that can be used as an integral part of an interactive algorithm that does not have to be generated with equal accuracy is proposed.
Abstract: In this paper, we discuss the idea of incorporating preference information into evolutionary multi-objective optimization and propose a preference-based evolutionary approach that can be used as an integral part of an interactive algorithm One algorithm is proposed in the paper At each iteration, the decision maker is asked to give preference information in terms of his or her reference point consisting of desirable aspiration levels for objective functions The information is used in an evolutionary algorithm to generate a new population by combining the fitness function and an achievement scalarizing function In multi-objective optimization, achievement scalarizing functions are widely used to project a given reference point into the Pareto optimal set In our approach, the next population is thus more concentrated in the area where more preferred alternatives are assumed to lie and the whole Pareto optimal set does not have to be generated with equal accuracy The approach is demonstrated by numerical examples
341 citations
TL;DR: In this paper, case studies of successful adaptation and mitigation strategies are presented, suggesting that these successes be translated into local contexts and communalized with the involvement of local authorities using participatory approaches.
327 citations
TL;DR: In this paper, the authors extended the different conceptualizations of corporate responsibility and elaborated both the financial and the societal outcomes of different types of CR, and pointed out that while the majority of CR research conducted within business studies concentrates on the financial outcomes for the firm, the societal outcome of CR are left largely unexplored.
Abstract: This article argues that previous research on the outcomes of corporate responsibility should be refined in two ways. First, although there is abundant research that addresses the link between corporate responsibility (CR) and financial performance, hardly any studies scrutinize whether the type of corporate responsibility makes a difference to this link. Second, while the majority of CR research conducted within business studies concentrates on the financial outcomes for the firm, the societal outcomes of CR are left largely unexplored. To tackle these two deficiencies, this article extends the different conceptualizations of corporate responsibility and elaborates both the financial and the societal outcomes of different types of CR.
305 citations
TL;DR: In this paper, the authors analyzed the relationship between unemployment and self-assessed health using the European Community Household Panel (ECHP) for Finland over the period 1996-2001.
Abstract: We analyse the relationship between unemployment and self-assessed health using the European Community Household Panel (ECHP) for Finland over the period 1996-2001. Our results reveal that the event of becoming unemployed does not matter as such for self-assessed health. The health status of those that end up being unemployed is lower than that of the continually employed. Hence, persons who have poor health are being selected for the pool of the unemployed. This explains why, in a cross-section, unemployment is associated with poor self-assessed health. However, we are somewhat more likely to obtain the negative effects of unemployment on health when long-term unemployment is used as the measure of unemployment experience.
291 citations
TL;DR: In this article, the authors estimate the effect of a major education reform on intergenerational income mobility using a representative sample of males born between 1960 and 1966, using a differences-in-differences approach and exploits the fact that the reform was implemented gradually across the country during a six-year period.
TL;DR: In this paper, the authors discuss the motivation for and role of theory in management accounting and argue that theories in an applied field such as management accounting research should provide explanations that are useful for those we study.
Abstract: In this article we discuss the motivation for and role of theory in management accounting. We argue that theories in an applied field such as management accounting research should provide explanations that are useful for those we study – managers, organizations and society. We evaluate the nature of theories currently used and developed. Those theories that are considered theories by the research community are largely imported from other disciplines, but have hardly anything that makes them unique to management accounting. Those theories that are not currently regarded as theories by many of our colleagues attempt to explain how to apply management accounting to achieve superior performance. We argue that both forms of theories, at present, largely fail to provide valid support for practitioners. We contend that management accounting theory should help us to answer questions of what kind of management accounting systems we should apply, how, in what circumstances, and how to change them. We provide sugges...
TL;DR: In this paper, double perovskites were investigated as anode materials for a solid oxide fuel cell, and the results showed that they are tetragonal (I4/m) at room temperature.
Abstract: Double-perovskites Sr2MMoO6 (M = Co, Ni) have been investigated as anode materials for a solid oxide fuel cell. At room temperature, both Sr2CoMoO6 and Sr2NiMoO6 are tetragonal (I4/m). X-ray absorption spectroscopy confirmed the presence of Co2+/Mo6+ and Ni2+/Mo6+ pairs in the oxygen-stoichiometric compounds. The samples contain a limited concentration of oxygen vacancies in the reducing atmospheres at an anode. Reoxidation is facile below 600 °C; they become antiferromagnetic at low temperatures TN = 37 and 80 K for M = Co and Ni, respectively. As an anode with a 300 μm thick La0.8Sr0.2Ga0.83Mg0.17O2.815 electrolyte and SrFe0.2Co0.8O3−δ as a cathode, Sr2CoMoO6 exhibited maximum power densities of 735 mW/cm2 in H2 and 527 mW/cm2 in wet CH4 at 800 °C; Sr2NiMoO6 shows a notable power output only in dry CH4. The high performance of Sr2CoMoO6 in wet CH4 may be due to its catalytic effect on steam reforming of methane, but some degradation of the structure that occurred in CH4 obscures identification of the ca...
TL;DR: In this paper, a logically consistent evolutionary model was proposed to link a level of strategic consistency to long-term organizational survival, showing that strategic consistency seems to be related to both organizational survival and the most efficient change over time concerning the key elements of a firm's strategy.
Abstract: This study investigates strategic consistency in competitive behavior. We construct a logically consistent evolutionary model, providing a causal argument to link a level of strategic consistency to long-term organizational survival. According to our results, strategic consistency seems to be related to both organizational survival and the most efficient change over time concerning the key elements of a firm's strategy. One of the benefits of the model is that some of the components and processes may be manipulated through experimental or simulation interventions. This means that the model can be formally tested in future studies and managers can use it to fine-tune patterns of competitive behavior. Copyright © 2008 John Wiley & Sons, Ltd.
Yale University1, Boston University2, Saint Petersburg State University3, University of Southampton4, University of Michigan5, Aalto University6, Georgia State University7, Bucknell University8, University of California, Irvine9, University of Nebraska–Lincoln10, Southwestern University11, University of Texas at Austin12, Academy of Sciences of Uzbekistan13, Pennsylvania State University14, New Mexico State University15, Chinese Academy of Sciences16, Iowa State University17, National University of Uzbekistan18
TL;DR: In this paper, the authors present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray (2-10 keV), optical (R and V bands), and radio (14.5 and 37 GHz) wave bands, as well as imaging with the Very Long Baseline Array (VLBA) at 43 GHz.
Abstract: We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray (2-10 keV), optical (R and V bands), and radio (14.5 and 37 GHz) wave bands, as well as imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. Furthermore, the total radiative output of a radio flare is related to the equivalent width of the corresponding X-ray dip. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole (BH) based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). These findings provide support for the paradigm that BHXRBs and both radio-loud and radio-quiet active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central BH. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the emitting regions from the central BH. In addition, we discuss physical scenarios for the disk-jet connection that are consistent with our observations.
TL;DR: In this article, the authors take a post-structuralist perspective on consumer research and discuss the role of personal interviews in cultural analysis, arguing that the underlying research paradigm, existential phenomenology, is not necessarily adequate for cultural analysis because it focuses attention primarily on the individual and the first-person experience.
Abstract: This paper takes a post‐structuralist perspective on consumer research and discusses the role of personal interviews in cultural analysis. It problematizes the use of the phenomenological interview in cultural consumer research, arguing that the underlying research paradigm, existential‐phenomenology, is not necessarily adequate for cultural analysis because it focuses attention primarily on the individual and the first‐person experience. Such a paradigmatic perspective is problematic because it tends to sustain a view of human agency that is highly individualistic and thus fails to account for the cultural complexity of social action. Overall, the paper contributes to the further development of the post‐structuralist approaches to postmodern marketing thought. Post‐structuralist ideas and assumptions challenge the central principles of modern marketing and consumer research in many ways and it is the aim of the paper to contribute to a better understanding of the methodological implications that they entail.
21 Apr 2009
TL;DR: This paper addresses bilevel multi-objective optimization issues and proposes a viable algorithm based on evolutionary multi-Objective optimization (EMO) principles and proof-of-principle simulation results demonstrate the viability of the proposed EMO technique for solving such problems.
Abstract: Bilevel optimization problems require every feasible upper-level solution to satisfy optimality of a lower-level optimization problem. These problems commonly appear in many practical problem solving tasks including optimal control, process optimization, game-playing strategy development, transportation problems, and others. In the context of a bilevel single objective problem, there exists a number of theoretical, numerical, and evolutionary optimization results. However, there does not exist too many studies in the context of having multiple objectives in each level of a bilevel optimization problem. In this paper, we address bilevel multi-objective optimization issues and propose a viable algorithm based on evolutionary multi-objective optimization (EMO) principles. Proof-of-principle simulation results bring out the challenges in solving such problems and demonstrate the viability of the proposed EMO technique for solving such problems. This paper scratches the surface of EMO-based solution methodologies for bilevel multi-objective optimization problems and should motivate other EMO researchers to engage more into this important optimization task of practical importance.
TL;DR: In this paper, the authors find that goodwill write-offs under Statement of Financial Accounting Standards No 142 (SFAS 142) are associated with future expected cash flows as mandated by the standard.
Abstract: I find that goodwill write-offs under Statement of Financial Accounting Standards No 142 (SFAS 142) are associated with future expected cash flows as mandated by the standard However, there are indications that goodwill write-offs lag behind the economic impairment of goodwill Additional analysis reveals that the association between goodwill write-offs and future cash flows is insignificant for firms with contemporaneous restructuring I hypothesize that this finding is due to agency-based motives Finally, I examine a sample of non-impairment firms in which there are indications that goodwill is impaired I fail to find convincing evidence that these firms are opportunistically avoiding impairments
TL;DR: A metatheoretical, contingency-based framework of inter-organizational network management is introduced and it is argued that management tasks, derived from more general management functions and contingent upon network characteristics, differ according to network type.
TL;DR: In this article, the authors study the determinants and dominant strategies of foreign direct investment (FDI) inflows into Russia before and after the 1998 financial crisis and reveal a shift from horizontal FDI to vertical FDI strategy in the post-crisis period.
Abstract: Using a spatial autoregressive model of cross-sectional and panel data, we study the determinants and dominant strategies of foreign direct investment (FDI) inflows into Russia before and after the 1998 financial crisis. The important determinants of FDI inflows into Russian regions since the start of transition appear to be market size, the presence of large cities and sea ports, oil and gas availability, proximity to European market, and political and legislative risks. Since 1998, it appears the importance of big cities, the Sakhalin region, oil and gas resources, proximity to European markets, and legislation and political risks has increased. Our results also reveal a shift from horizontal FDI strategy to vertical FDI strategy in the post-crisis period. Using a multiple spatial lags approach, we show that neighbouring port-endowed regions tend to have emerged in the post-crisis era as competitors for FDI.
TL;DR: In this paper, the authors explore the management challenges of emerging new business fields by using a network perspective and identify and examine the company-level capabilities involved in the management of these core activities.
TL;DR: In this article, the authors focus on the issues of context and consequences of corporate responsibility (CR), to which CR research has not given the attention these issues would be worth paying.
TL;DR: In this paper, the authors describe the Expectational Stability (E-stability) principle and the stochastic approximation tools used to assess equilibria under learning, and apply it to the design of monetary and fiscal policy, business cycles, self-fulfilling prophecies, hyperinflation, liquidity traps, and asset prices.
Abstract: Expectations play a central role in modern macroeconomic theories. The econometric learning approach models economic agents as forming expectations by estimating and updating forecasting models in real time. The learning approach provides a stability test for rational expectations and a selection criterion in models with multiple equilibria. In addition, learning provides new dynamics if older data are discounted, if models are misspecified, or if agents choose between competing models. This paper describes the expectational stability (E-stability) principle and the stochastic approximation tools used to assess equilibria under learning. Applications of learning to a number of areas are reviewed, including the design of monetary and fiscal policy, business cycles, self-fulfilling prophecies, hyperinflation, liquidity traps, and asset prices.
TL;DR: In this paper, a multi-wavelength campaign from radio to gamma rays was carried out between the end of March and the beginning of July 2009, which confirmed the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.
Abstract: Following the recent discovery of gamma rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z=0.5846), we started a multiwavelength campaign from radio to gamma rays, which was carried out between the end of March and the beginning of July 2009. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to gamma-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the gamma-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day-scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.
TL;DR: In this paper, an exploratory study based on qualitative and ethnographic online research methods was conducted to initiate the academic discourse about marketing in virtual worlds, and it can act as a reasonable starting point for future discussion.
Abstract: Purpose – Drawing from recent work on online social networking and communities of consumption, the purpose of this paper is to explore, identify, and postulate key factors facilitating the growth and success of marketing in virtual worlds.Design/methodology/approach – An empirical study was conducted employing netnographic evidence from three different virtual worlds and related user‐generated blog discussions.Findings – The findings suggest mechanisms which enable virtual worlds to gain and maintain the interest of their users and therefore underlie successful marketer practices.Research limitations/implications – This is an exploratory study based on qualitative and ethnographic online research methods, and therefore the results are of a descriptive nature. The study was conducted to initiate the academic discourse about marketing in virtual worlds. As such, the paper believes that it can act as a reasonable starting‐point for future discussion.Practical implications – The study suggests that traditiona...
TL;DR: New ways of utilizing preference information specified by the decision maker in interactive reference point based methods are introduced to take the desires of the decision makers into account more closely when projecting the reference point onto the set of nondominated solutions.
Abstract: In this paper, we introduce new ways of utilizing preference information specified by the decision maker in interactive reference point based methods. A reference point consists of desirable values for each objective function. The idea is to take the desires of the decision maker into account more closely when projecting the reference point onto the set of nondominated solutions. In this way we can support the decision maker in finding the most satisfactory solutions faster. In practice, we adjust the weights in the achievement scalarizing function that projects the reference point. We identify different cases depending on the amount of additional information available and demonstrate the cases with examples. Finally, we summarize results of extensive computational tests that give evidence of the efficiency of the ideas proposed.
TL;DR: In this paper, the authors examine Figge and Hahn's estimator for opportunity cost, and show that the proposed estimator rests on a number of strong, unrealistic assumptions.
TL;DR: In this article, a detailed mass balance comprising the chemical composition of all three phases: the autohydrolysate, the released gas, and the solid residue was established for the pre-hydrolysis kraft pulping of Eucalyptus globulus.
Abstract: Autohydrolysis of Eucalyptus globulus was conducted at three different intensity levels typical for prehydrolysis kraft pulping as utilized for manufacturing dissolving pulp grades. The objective was to establish for the autohydrolysis process a detailed mass balance comprising the chemical composition of all three phases: the autohydrolysate, the released gas, and the solid residue. Carbohydrate determination involved both acid methanolysis combined with gas chromatography (GC) and sulfuric acid total hydrolysis with high performance anion exchange chromatography (HPAEC) coupled with pulsed amperometric detection (PAD); this allowed reliable quantification of neutral as well as acidic sugar units in cellulosic and non-cellulosic polysaccharides. Uronic acids present in the Eucalyptus globulus wood were progressively degraded through decarboxylation, leading to substantial carbon dioxide formation. The degree of acetylation of xylan remaining in the wood residue was clearly reduced, while the amount of bound acetyl groups in dissolved xylo-oligosaccharides (XOS) stayed relatively constant as a function of autohydrolysis intensity. The bulk of the lignin that was dissolved during autohydrolysis could be attributed to the acid-soluble lignin content of the wood. Only small amounts of Klason lignin were dissolved.
TL;DR: In this paper, an intensive multi-wavelength campaign was conducted on the intermediate-frequency-peaked BL Lacertae object W Com (z = 0.102) during a strong outburst of very high energy gamma-ray emission in 2008 June.
Abstract: We report results from an intensive multiwavelength campaign on the intermediate-frequency-peaked BL Lacertae object W Com (z = 0.102) during a strong outburst of very high energy gamma-ray emission in 2008 June. The very high energy gamma-ray signal was detected by VERITAS on 2008 June 7-8 with a flux F(>200 GeV) =(5.7 ± 0.6) × 10–11 cm–2 s–1, about three times brighter than during the discovery of gamma-ray emission from W Com by VERITAS in 2008 March. The initial detection of this flare by VERITAS at energies above 200 GeV was followed by observations in high-energy gamma rays (AGILE; E γ≥ 100 MeV), X-rays (Swift and XMM-Newton), and at UV, and ground-based optical and radio monitoring through the GASP-WEBT consortium and other observatories. Here we describe the multiwavelength data and derive the spectral energy distribution of the source from contemporaneous data taken throughout the flare.
Proceedings Article•
01 Jan 2009TL;DR: This paper focuses on randomization techniques for unweighted undirected graphs for graph mining within the framework of statistical hypothesis testing, and describes three alternative algorithms based on local edge swapping and Metropolis sampling.
Abstract: Mining graph data is an active research area Several data mining methods and algorithms have been proposed to identify structures from graphs; still, the evaluation of those results is lacking Within the framework of statistical hypothesis testing, we focus in this paper on randomization techniques for unweighted undirected graphs Randomization is an important approach to assess the statistical significance of data mining results Given an input graph, our randomization method will sample data from the class of graphs that share certain structural properties with the input graph Here we describe three alternative algorithms based on local edge swapping and Metropolis sampling We test our framework with various graph data sets and mining algorithms for two applications, namely graph clustering and frequent subgraph mining