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Showing papers by "Helsinki University of Technology published in 2003"


Journal ArticleDOI
TL;DR: This study clarifies the nature of user involvement and its expected benefits, and reviews three streams of research, to evaluate the benefits and problems of varied user involvement approaches in practice.
Abstract: User involvement is a widely accepted principle in development of usable systems. However, it is a vague concept covering many approaches. This study first clarifies the nature of user involvement and its expected benefits, and secondly reviews three streams of research, to evaluate the benefits and problems of varied user involvement approaches in practice. The particular focus of this study is on the early activities in the development process. An analysis of the literature suggests that user involvement has generally positive effects, especially on user satisfaction, and some evidence exists to suggest that taking users as a primary information source is an effective means of requirements capture. However, the role of users must be carefully considered and more cost-efficient practices are needed for gathering users' implicit needs and requirements in real product development contexts.

826 citations


Journal ArticleDOI
TL;DR: The time dependence of the recently introduced minimum spanning tree description of correlations between stocks, called the "asset tree", has been studied in order to reflect the financial market taxonomy and the basic structure of the tree topology is very robust with respect to time.
Abstract: The time dependence of the recently introduced minimum spanning tree description of correlations between stocks, called the ‘‘asset tree’’ has been studied in order to reflect the financial market taxonomy. The nodes of the tree are identified with stocks and the distance between them is a unique function of the corresponding element of the correlation matrix. By using the concept of a central vertex, chosen as the most strongly connected node of the tree, an important characteristic is defined by the mean occupation layer. During crashes, due to the strong global correlation in the market, the tree shrinks topologically, and this is shown by a low value of the mean occupation layer . The tree seems to have a scale-free structure where the scaling exponent of the degree distribution is different for ‘‘business as usual’’ and ‘‘crash’’ periods. The basic structure of the tree topology is very robust with respect to time. We also point out that the diversification aspect of portfolio optimization results in the fact that the assets of the classic Markowitz portfolio are always located on the outer leaves of the tree. Technical aspects such as the window size dependence of the investigated quantities are also discussed.

695 citations


Journal ArticleDOI
TL;DR: In this paper, it was shown that there exist composite media that exhibit strong spatial dispersion even in the very large wavelength limit, where the description of this medium by means of a local dispersive uniaxial dielectric tensor is not complete.
Abstract: It is found that there exist composite media that exhibit strong spatial dispersion even in the very large wavelength limit. This follows from the study of lattices of ideally conducting parallel thin wires (wire media). In fact, our analysis reveals that the description of this medium by means of a local dispersive uniaxial dielectric tensor is not complete, leading to unphysical results for the propagation of electromagnetic waves at any frequencies. Since nonlocal constitutive relations have been usually considered in the past as a second-order approximation, meaningful in the short-wavelength limit, the aforementioned result presents a relevant theoretical interest. In addition, since such wire media have been recently used as a constituent of some discrete artificial media (or metamaterials), the reported results open the question of the relevance of the spatial dispersion in the characterization of these artificial media.

583 citations


Journal ArticleDOI
TL;DR: In this paper, the authors discuss the potential of utilizing RFID technology for increasing efficiency in the supply chain of short shelf life products, and analyze the potential benefits of RFID for short shelf-life products retailers and conclude that when applied with recyclable transport containers, RFID investments can provide quick amortisation of capital whilst offering a range of operational benefits.
Abstract: Short shelf‐life grocery goods present some of the biggest challenges for supply chain management due to a high number of product variants, strict traceability requirements, short shelf‐life of the products, the need for temperature control in the supply chain, and the large volume of goods handled. A Radio Frequency Identification (RFID) based data capture system can help solve the problems associated with the logistics of short shelf life products. This article discusses the potential of utilising RFID technology for increasing efficiency in the supply chain of short shelf life products. The focus of this article is a RFID trial conducted at Sainsbury’s, which is discussed to study the potential benefits of RFID for short shelf‐life products retailers. Further this article analyses the potential impact of RFID for other supply chain participants. We conclude that when applied with recyclable transport containers, RFID investments can provide quick amortisation of capital whilst offering a range of operational benefits.

538 citations


Journal ArticleDOI
TL;DR: In this paper, the role of metal nanoparticles in the formation of single-walled carbon nanotubes (SWCNTs) is reviewed with an emphasis on their role in the processes.
Abstract: Recent progress in chemical vapour deposition and aerosol synthesis of single-walled carbon nanotubes (SWCNTs) is reviewed with an emphasis on the role of metal nanoparticles in the processes. The effect of the various parameters on SWCNT formation is reported on the basis of published experiments. Evolution of the catalyst particle size distribution due to collision, sintering and evaporation of metal during SWCNT synthesis is discussed. The active catalyst has been demonstrated to be in a reduced metal form by comparison of the experimental data and calculations regarding the equilibrium concentration of carbon and oxygen in iron. Also the effect of the catalyst particle size on melting temperature and carbon solubility in metal is discussed. The stability of different carbon precursors (hydrocarbons and carbon monoxide) is considered thermodynamically. Furthermore, estimation of the maximum length of 1 and 2.5 nm diameter SWCNTs as a function of carbon solubility is conducted to determine whether carbon dissolution and precipitation are simultaneous or subsequent process steps.

523 citations


Journal ArticleDOI
TL;DR: In this article, the authors discuss and compare the present status of computational modeling of two of the most popular SPM methods (scanning tunneling microscopy and scanning force microscopy) in conjunction with their applications to studies of surface structure and properties with atomic resolution.
Abstract: Significant progress has been made both in experimentation and in theoretical modeling of scanning probe microscopy. The theoretical models used to analyze and interpret experimental scanning probe microscope (SPM) images and spectroscopic data now provide information not only about the surface, but also the probe tip and physical changes occurring during the scanning process. The aim of this review is to discuss and compare the present status of computational modeling of two of the most popular SPM methods---scanning tunneling microscopy and scanning force microscopy---in conjunction with their applications to studies of surface structure and properties with atomic resolution. In the context of these atomic-scale applications, for the scanning force microscope (SFM), this review focuses primarily on recent noncontact SFM (NC-SFM) results. After a brief introduction to the experimental techniques and the main factors determining image formation, the authors consider the theoretical models developed for the scanning tunneling microscope (STM) and the SFM. Both techniques are treated from the same general perspective of a sharp tip interacting with the surface---the only difference being that the control parameter in the STM is the tunneling current and in the SFM it is the force. The existing methods for calculating STM and SFM images are described and illustrated using numerous examples, primarily from the authors' own simulations, but also from the literature. Theoretical and practical aspects of the techniques applied in STM and SFM modeling are compared. Finally, the authors discuss modeling as it relates to SPM applications in studying surface properties, such as adsorption, point defects, spin manipulation, and phonon excitation.

423 citations


Journal ArticleDOI
TL;DR: The Zn vacancies are dominant acceptors in both as-grown and irradiated ZnO, in agreement with the total acceptor density determined by temperature dependent Hall experiments.
Abstract: We have used positron annihilation spectroscopy to determine the nature and the concentrations of the open volume defects in as-grown and electron irradiated (${E}_{\mathrm{e}\mathrm{l}}=2\text{ }\mathrm{M}\mathrm{e}\mathrm{V}$, fluence $6\ifmmode\times\else\texttimes\fi{}{10}^{17}\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}2}$) ZnO samples. The Zn vacancies are identified at concentrations of $[{V}_{\mathrm{Z}\mathrm{n}}]\ensuremath{\simeq}2\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}3}$ in the as-grown material and $[{V}_{\mathrm{Z}\mathrm{n}}]\ensuremath{\simeq}2\ifmmode\times\else\texttimes\fi{}{10}^{16}\text{ }{\mathrm{c}\mathrm{m}}^{\ensuremath{-}3}$ in the irradiated ZnO. These concentrations are in very good agreement with the total acceptor density determined by temperature dependent Hall experiments. Thus, the Zn vacancies are dominant acceptors in both as-grown and irradiated ZnO.

420 citations


Journal ArticleDOI
TL;DR: Pronounced maxima or minima in g(r) appear exactly at the cutoff distance indicating that the truncation gives rise to artificial ordering between the polar phosphatidyl and choline groups of the DPPC molecules, whereas in systems described using PME, such artificial ordering is not present.

407 citations


Journal ArticleDOI
TL;DR: By applying a full spin-polarized description to the system, it is demonstrated that adatom defects have a magnetic moment of about 0.5micro(B) and its role in diffusion over the surface is calculated.
Abstract: We use ab initio methods to calculate the properties of adatom defects on a graphite surface. By applying a full spin-polarized description to the system we demonstrate that these defects have a magnetic moment of about $0.5{\ensuremath{\mu}}_{B}$ and also calculate its role in diffusion over the surface. The magnetic nature of these intrinsic carbon defects suggests that it is important to understand their role in the recently observed magnetism in pure carbon systems.

405 citations


Journal ArticleDOI
TL;DR: The ability of spatial-domain ICA to separate spontaneous physiological signal sources was evaluated in 15 anesthetized children known to present prominent vasomotor fluctuations in the functional cortices and was able to separate major artery and sagittal sinus related signal sources in each subject.

389 citations


Journal ArticleDOI
TL;DR: In this article, a model for a chiral material in which both the permittivity and permeability are equal to zero is discussed, referred by us as a "chiral nihility".
Abstract: A model for a chiral material in which both the permittivity and permeability are equal to zero is discussed. Such a material is referred by us as a "chiral nihility". It is shown that this exotic material can be realized as a mixture of small helical inclusions. Wave solutions and energy in such a medium are analyzed. It is shown that an extraordinary wave in chiral nihility is a backward wave. Wave reflection and refraction on a chiral nihility interface are also considered. It is shown that a linearly polarized wave normally incident onto this interface produces a wave of "standing phase" and the same wave in the case of oblique incidence causes two refracted waves, one of them with an anomalous refraction.

Journal ArticleDOI
TL;DR: In this article, the authors identify problems in managing multiple internal development projects, including lacking resources, competencies and methods, lacking commitment, unclear roles and responsibilities, inadequate portfolio level activities, inadequate information management, and inadequate management of project-oriented organizations.

Journal ArticleDOI
TL;DR: In this article, knowledge management and knowledge competences in project organizations, particularly framework programs, have been studied and two programs and a review project have been discussed. And a Learning Programme Model is presented.

Journal ArticleDOI
TL;DR: In this article, the authors quantified the significant environmental aspects of a new high-end office building over 50 years of service life and found that most of the impacts are associated with electricity use and building materials manufacturing.
Abstract: This paper quantifies the significant environmental aspects of a new high-end office building over 50 years of service life A comprehensive environmental life-cycle assessment—including data quality assessment—was conducted to provide detailed information for establishing the causal connection between the different life-cycle elements and potential environmental impacts The results show that most of the impacts are associated with electricity use and building materials manufacturing—in particular, electricity used in lighting, HVAC systems, and outlets; heat conduction through the structures; manufacturing and maintenance of steel; manufacturing of concrete and paint; water use and wastewater generation; and office waste management Construction and demolition were found to have relatively insignificant impacts The identified most significant aspects are quite predominant; 7% of all counted aspects cover over 50% of the life-cycle impacts Practical applications of the study’s results could be in the e

Journal ArticleDOI
TL;DR: The first observation of 15 voltammetric quantized charging peaks for a solution of hexanethiol-capped gold nanoparticles (so-called monolayer protected clusters MPCs) at room temperature is reported where the variation in peak spacing with increasing charge stored in the metal core is discussed in terms of MPC capacitance.
Abstract: The first observation of 15 voltammetric quantized charging peaks for a solution of hexanethiol-capped gold nanoparticles (so-called monolayer protected clusters MPCs) at room temperature is reported where the variation in peak spacing with increasing charge stored in the metal core is discussed in terms of MPC capacitance.

Journal ArticleDOI
TL;DR: It is shown how the tree length shrinks during a stock market crisis, Black Monday in this case, and how a strong reconfiguration takes place, resulting in topological shrinking of the tree.
Abstract: The minimum spanning tree, based on the concept of ultrametricity, is constructed from the correlation matrix of stock returns. The dynamics of this asset tree can be characterised by its normalised length and the mean occupation layer, as measured from an appropriately chosen centre called the ‘central node’. We show how the tree length shrinks during a stock market crisis, Black Monday in this case, and how a strong reconfiguration takes place, resulting in topological shrinking of the tree.

Journal ArticleDOI
TL;DR: In this paper, a method for handling interfaces between non-matching grids based on an approach suggested by Nitsche (1971) for the approximation of Dirichlet boundary conditions is presented.
Abstract: In this note, we propose and analyse a method for handling interfaces between non-matching grids based on an approach suggested by Nitsche (1971) for the approximation of Dirichlet boundary conditions. The exposition is limited to self-adjoint elliptic problems, using Poisson's equation as a model. A priori and a posteriori error estimates are given. Some numerical results are included.

Proceedings ArticleDOI
17 Sep 2003
TL;DR: An explorative visualization method is presented for investigating the relations between estimates from FastICA by running the algorithm many times with different initial values or with differently bootstrapped data sets, respectively.
Abstract: A major problem in application of independent component analysis (ICA) is that the reliability of the estimated independent components is not known Firstly, the finite sample size induces statistical errors in the estimation Secondly, as real data never exactly follows the ICA model, the contrast function used in the estimation may have many local minima which are all equally good, or the practical algorithm may not always perform properly, for example getting stuck in local minima with strongly suboptimal values of the contrast function We present an explorative visualization method for investigating the relations between estimates from FastICA The algorithmic and statistical reliability is investigated by running the algorithm many times with different initial values or with differently bootstrapped data sets, respectively Resulting estimates are compared by visualizing their clustering according to a suitable similarity measure Reliable estimates correspond to tight clusters, and unreliable ones to points which do not belong to any such cluster We have developed a software package called Icasso to implement these operations We also present results of this method when applying Icasso on biomedical data

Journal ArticleDOI
TL;DR: The paper presents a control system being built at Helsinki University of Technology, which is based on distributed programming, and wireless identification technologies, which enables the material flows in the project delivery chains to be controlled from the inside of the material flow itself.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated regionalization approaches to daily streamflow prediction for 13 catchments in the Coweeta Hydrologic Laboratory using a conceptual rainfall-runoff model of low complexity (six parameters).
Abstract: Regionalization approaches to daily streamflow prediction are investigated for 13 catchments in the Coweeta Hydrologic Laboratory using a conceptual rainfall-runoff model of low complexity (six parameters). Model parameters are considered to represent the dynamic response characteristics (DRCs) of a catchment. It is demonstrated that all catchments within the region cannot be assumed to have a similar hydrological behaviour, and thence a regionalization approach considering differences in physical catchment descriptors (PCDs) is required. Such a regionalization approach can be regarded as a top-down method, in the sense that factors controlling parameter variability are identified first within the entire region under study, and then such information is exploited to predict runoff in a smaller sub-region. Regionalization results reveal that consideration of interrelation s between dependent variables, which here are the parameters of the rainfall-runoff model, can improve performance of regression as a regionalization method. Breaking the parameter correlation structure inherent in the model, and exploiting merely relationships between model parameters and PCDs (no matter how weakly related they are), can result in a significant decrease in regionalization performance. Also, high significance of regression between values of PCDs and DRCs does not guarantee a set of parameters with a good predictive power. When there is a reason to believe that, in the sense of hydrological behaviour, a gauged catchment resembles the ungauged catchment, then it may be worthwhile to adopt the entire set of calibrated parameters from the gauged catchment instead of deriving quantitative relationships between catchment descriptors and model parameters. Copyright © 2003 John Wiley & Sons, Ltd.

Journal ArticleDOI
TL;DR: In this article, the authors present a roadmap of Finnish companies adopting and managing corporate social responsibility (CSR), highlighting the companies' views on CSR and highlights the practices that Finnish companies have adopted or are currently adopting.
Abstract: This paper presents a roadmap of Finnish companies adopting and managing corporate social responsibility (CSR). It discusses the companies' views on CSR and highlights the practices that Finnish companies have adopted or are currently adopting. It also presents a framework that outlines the CSR processes and management prospects. Results showed that Finnish companies are progressively managing CSR. This newly revived thinking about social responsibility is viewed as an issue traced back from Finland's history of industrial development. There is no general definition of CSR; however, various concepts are connoted into it. Driven by several factors, CSR is developing gradually as indicated by the positive responses and initiatives of the companies. CSR management and practices towards employees, suppliers, community and customers are well defined locally based generally on established socially responsible behavior which could be articulated by laws and regulations, corporate values and business ethics. However, managing CSR with a global scope, problems such as; lack of information and structured management system, different views and interpretations, supply chain complexities, overlap with environmental issues, etc. often lead some companies to manage CSR haphazardly. Views and management of CSR are also influenced by some distinct Finnish cultural attributes. An initial conceptual framework for CSR is drawn reflecting the current practices and prospects for management strategies. Such framework can be used in organizing and streamlining CSR elements for effective management approaches and measuring of performance. It could be expected that in due time, the efforts of the companies will become more evident, organized and systematically managed.

Book ChapterDOI
08 Sep 2003
TL;DR: This work presents how situational and planned acts intermesh in navigation, how people create personal spaces while waiting, and how temporal tensions develop and dissolve in Helsinki, and examines aspects of multitasking.
Abstract: Mobile urban environments present a challenge for context-aware computers, because they differ from static indoor contexts such as offices, meeting rooms, and lecture halls in many important ways. Internal factors such as task goals are different-external factors such as social resources are dynamic and unpredictable. An empirical, user-centered approach is needed to understand mobile contexts. For these ends, we present insights from an ethnomethodologically inspired study. The data consist of travel episodes of 25 adult urbanites (incl. elderly, single mothers, adolescents) in Helsinki. We present how situational and planned acts intermesh in navigation, how people create personal spaces while waiting, and how temporal tensions develop and dissolve. Furthermore, we provide examples of social solutions to navigation problems, examine aspects of multitasking, and consider design implications for context-aware mobile computing.

Journal ArticleDOI
TL;DR: In this article, a discrete event simulation is used to examine how a manufacturer can combine traditional order data available from non-VMI customers with sales data from VMI customers in its production and inventory control and what impact this has on the manufacturer's operational efficiency.
Abstract: Information sharing practices such as vendor‐managed inventory (VMI) give manufacturers access to more accurate demand information, e.g. customer sales data, than before. The value of this type of information sharing has been established in many studies. However, most of the research has focused on the ideal situation of the manufacturer having access to information from all downstream parties. In practice, this is rarely the case. In this paper, discrete‐event simulation is used to examine how a manufacturer can combine traditional order data available from non‐VMI customers with sales data available from VMI customers in its production and inventory control and what impact this has on the manufacturer's operational efficiency. The simulation model is based on a real‐life VMI implementation and uses actual demand and product data. The key finding is that even for products with stable demand a partial improvement of demand visibility can improve production and inventory control efficiency, but that the value of visibility greatly depends on the target products’ replenishment frequencies and the production planning cycle employed by the manufacturer.

Journal ArticleDOI
TL;DR: In this paper, the magnetic ordering of Mn-rich Ni-Mn-Ga alloys based on both experiments and theory is investigated. But the results of the experiments are limited to a vibrating sample magnetometer in magnetic fields of up to several tesla.
Abstract: Ni-Mn-Ga is interesting as a prototype of a magnetic shape-memory alloy showing large magnetic-field-induced strains We present here results for the magnetic ordering of Mn-rich Ni-Mn-Ga alloys based on both experiments and theory Experimental trends for the composition dependence of the magnetization are measured by a vibrating sample magnetometer in magnetic fields of up to several tesla and at low temperatures The saturation magnetization has a maximum near the stoichiometric composition and it decreases with increasing Mn content This unexpected behavior is interpreted via first-principles calculations within the density-functional theory We show that extra Mn atoms are antiferromagnetically aligned to the other moments, which explains the dependence of the magnetization on composition In addition, the effect of Mn doping on the stabilization of the structural phases and on the magnetic anisotropy energy is demonstrated

Journal ArticleDOI
TL;DR: The rhythmic interaction of the motor cortex with similar activity of the spinal motoneuron pool may reveal interesting information in several motor disorders, including essential tremor, Parkinson's disease, myoclonus epilepsy, and mirror movements.

Journal ArticleDOI
TL;DR: Several minor modifications appeared to be responsible for the increased thermal stability of family 11 xylanases: (a) higher Thr : Ser ratio, (b) increased number of charged residues, especially Arg, resulting in enhanced polar interactions, and (c) improved stabilization of secondary structures involved the higher number of residues in the beta-strands and stabilization of the alpha-helix region.
Abstract: The crystal structures of thermophilic xylanases from Chaetomium thermophilum and Nonomuraea flexuosa were determined at 1.75 and 2.1 A resolution, respectively. Both enzymes have the overall fold typical to family 11 xylanases with two highly twisted β-sheets forming a large cleft. The comparison of 12 crystal structures of family 11 xylanases from both mesophilic and thermophilic organisms showed that the structures of different xylanases are very similar. The sequence identity differences correlated well with the structural differences. Several minor modifications appeared to be responsible for the increased thermal stability of family 11 xylanases: (a) higher Thr : Ser ratio (b) increased number of charged residues, especially Arg, resulting in enhanced polar interactions, and (c) improved stabilization of secondary structures involved the higher number of residues in the β-strands and stabilization of the α-helix region. Some members of family 11 xylanases have a unique strategy to improve their stability, such as a higher number of ion pairs or aromatic residues on protein surface, a more compact structure, a tighter packing, and insertions at some regions resulting in enhanced interactions.

Proceedings ArticleDOI
22 Sep 2003
TL;DR: The findings indicate that the taxonomy for the smells could help explain the identified correlations between the subjective evaluations of the existence of the smells.
Abstract: This paper presents research in progress, as well as tentative findings related to the empirical study of so called bad code smells. We present a taxonomy that categorizes similar bad smells. We believe that taxonomy makes the smells more understandable and recognizes the relationships between smells. Additionally, we present our initial findings from an empirical study of the use of the smells for evaluating code quality in a small Finnish software product company. Our findings indicate that the taxonomy for the smells could help explain the identified correlations between the subjective evaluations of the existence of the smells.

Journal ArticleDOI
TL;DR: In this article, the authors introduced a new methodology for constructing a network of companies called a dynamic asset graph, which is similar to the dynamic asset tree studied recently, as both are based on correlations between asset returns.
Abstract: This paper introduces a new methodology for constructing a network of companies called a dynamic asset graph. This is similar to the dynamic asset tree studied recently, as both are based on correlations between asset returns. However, the new modified methodology does not, in general, lead to a tree but a disconnected graph. The asset tree, due to the minimum spanning tree criterion, is forced to "accept" edge lengths that are far less optimal (longer) than the asset graph, thus resulting in higher overall length for the tree. The same criterion also causes asset trees to be more fragile in structure when measured by the single-step survival ratio. Over longer time periods, in the beginning the asset graph decays more slowly than the asset tree, but in the long run the situation is reversed. The vertex degree distributions indicate that the possible scale free behavior of the asset graph is not as evident as it is in the case of the asset tree.

Journal ArticleDOI
TL;DR: In this paper, the authors assess the quality and performance of several novel dissipative particle dynamics integration schemes that have not previously been tested independently and identify the respective methods of Lowe and Shardlow as particularly promising candidates for future studies of large-scale properties of soft matter systems.

Journal ArticleDOI
TL;DR: This work model the hourly CHP operation as an LP problem with a special structure and presents the specialised Power Simplex algorithm that utilises this structure efficiently and performs from 21 to 190 times faster than the tabular Simplex.