Analytical solution for heat conduction due to a moving Gaussian heat flux with piecewise constant parameters

We provide an analytical solution of the heat equation in the half-space subject to a moving Gaussian heat flux with piecewise constant parameters. The solution is of interest in powder bed fusion applications where these parameters can be used to control the conduction of heat due to a scanning beam of concentrated energy. The analytical solution is written in a dimensionless form as a sum of integrals over (dimensionless) time. For the numerical computation of these integrals we suggest a quadrature scheme that utilizes pre-calculated look-up tables for the required quadrature orders. Such a scheme is efficient because the required quadrature orders are strongly dependent on the parameters in the heat flux. The possibilities of using the obtained computational technique for the control and optimization of powder bed fusion processes are discussed

“Here is the knowledge-where should I put it?” Findings from a study of how knowledge spaces are used within a support group

In order to design useful knowledge media spaces to knowledge workers it is essential that we understand the nature of the work conducted and the knowledge applied in real settings. This paper reports from a study of how a group of quality assurance specialists gather, structure and distribute information and knowledge. Based on the findings a number of overall requirements for knowledge mediaspaces are identified and discussed. The essential findingswere that information and knowledge are created and  handled in many different ways and have many differentforms. The core issues of our lessons learned so far are that we carefully need to consider knowledge media spaces both in terms of communication channels and knowledge archives. Knowledge media spaces should be seen as spaces in which knowledge and information is exchanged, filed,retrieved, presented and refined by actors having different vocabulary and perspectives on the knowledge. These characteristics must be taken into account when designing IT and multimedia based knowledge media spaces.</p

Structure and electronic properties of new model dinitride systems: A density-functional study of CN2, SiN2, and GeN2

The dinitrides CN2, SiN2, and GeN2 in assumed pyrite-type structures are studied by means of density functional theory using both ultrasoft pseudopotentials and the augmented spherical wave (ASW) method. The former two materials constitute the large-x limit of the broader class of CNx and SiNx compounds, which are well known for their interesting mechanical and electronic properties. For CN2 a large bulk modulus B_0 of 405 GPa was determined . While SiN2 is found to be a wide band gap compound, the calculated gaps of CN2 and GeN2 are considerably smaller. The trends in structural and electronic properties as e.g. bond lengths, band gaps and covalency are well understood in terms of the interplay of different types of bonding.Comment: 9 pages, 5 figure

Challenges for Knowledge Communities in Technical Work Domains

By drawing on the specific lessons learned from one case study, this paper will discuss collaboration, and issues upon knowledge communities in technical work domains. The results are based on a case study in a manufacturing process, thermal spraying, which can be characterised as very complex and technical. In order to understand the concept of knowledge communities in technical work domains I argue for an elaborated approach by going across different collaboration levels and organisational cultures, into issues of communities of practice. The discussion ends up with three main challenges for forming and supporting knowledge communities. These challenges might inspire an adequate work milieu, cultivated by both shared meanings and technology support

Innovation through Knowledge Codification

Academics and business professionals are currently showing a significant interest in understanding the management of knowledge and the roles to be played therein by information and communication technology (ICT). This paper takes a closer look at one of the primary issues raised when supporting the management of knowledge: how to understand the role of knowledge classification and codification as means for further organizational learning and innovation. Two manufacturing cases are analysed using particular perspectives from current theories on classification, namely the management of knowledge and organizational innovation. It is concluded that a more complex understanding of the interplay between cognitive and community models for knowledge management as informed by research on the social processes of classification can inform our understanding of both the role of classification of knowledge for organizational innovation and the viability of providing ICT support based on codified knowledge

Boundary dialogues in user-centric innovation

This paper is based on a user-centric innovation project, Free2Ride, which is seen as an example of community interaction that overcomes boundaries. Free2Ride aimed at developing a piece of ICT safety equipment consisting of a sender (on the horse) and a receiver (application in a smartphone) to be used by equestrian club members during their everyday riding activities. We will answer the research question of what the characteristics of a boundary dialogue in user-centric innovation activities are. The aim of the paper is to propose a model describing the characteristics of boundary dialogue in user-centric innovation that involve different communities of practices such as ICT developers, users and researchers. We applied a combination of research approaches consisting of action research and engaged scholarship approach. The theoretical framework for analyzing our findings is communities of practices with a specific interest in boundary spanning and learning dialogues. Our contribution is a model describing the characteristics of boundary dialogues in user-centric innovation. An important element of that model is the mental wandering, inwards and outwards, by core members in a community. We discuss the temporal as well as the symbolic nature of the mental wandering during the boundary dialogue in user-centric innovation activities

The Dynamics Of Interaction: Exploring A Living Lab Innovation Process From A Community Of Practice Perspective

This paper is based on a living lab project, which is an open, user-centric, innovation approach, where several actors from industry, user groups and academia are involved. The research question is: How can interaction dynamics be understood in a living lab innovation process? We applied an action-oriented research approach, where the empirical results are from The Find Project (TFP), which aim is to customize an ICT product based on the needs of a user group. The findings are analyzed from a community of practice perspective where three different communities, i) researchers from Halmstad Living Lab (HLL), ii) ICT developers (ICTD) and iii) next of kin of demented elderly persons (NOKD), represented the unit of analysis. We identified situations and activities that played a vital role for the innovation process in terms of boundary interaction dynamics. The contribution of our research to innovation theory is a combination and further exploration of the boundary spanning and communities of practice theories. We have developed a conceptual model describing the dynamics in boundary interactions of an ICT innovation process with regard to boundary objects-inuse and brokering. The conceptual model highlights two different levels of brokering: i) inner-level brokering and ii) outer-level brokering

A greedy algorithm for optimal heating in powder-bed-based additive manufacturing

Powder-bed-based additive manufacturing involves melting of a powder bed using a moving laser or electron beam as a heat source. In this paper, we formulate an optimization scheme that aims to control this type of melting. The goal consists of tracking maximum temperatures on lines that run along the beam path. Time-dependent beam parameters (more specifically, beam power, spot size, and speed) act as control functions. The scheme is greedy in the sense that it exploits local properties of the melt pool in order to divide a large optimization problem into several small ones. As illustrated by numerical examples, the scheme can resolve heat conduction issues such as concentrated heat accumulation at turning points and non-uniform melt depths

A greedy algorithm for optimal heating in powder-bed-based additive manufacturing

Powder-bed-based additive manufacturing involves melting of a powder bed using a moving laser or electron beam as a heat source. In this paper, we formulate an optimization scheme that aims to control this type of melting. The goal consists of tracking maximum temperatures on lines that run along the beam path. Time-dependent beam parameters (more specifically, beam power, spot size, and speed) act as control functions. The scheme is greedy in the sense that it exploits local properties of the melt pool in order to divide a large optimization problem into several small ones. As illustrated by numerical examples, the scheme can resolve heat conduction issues such as concentrated heat accumulation at turning points and non-uniform melt depths