Search results

For geometries exhibiting overhanging surfaces, support structures are needed to dissipate process heat and to minimize geometrical distortions attributed to internal stresses. The use of support structures is often time- and cost-consuming. For this reason, this study aims to propose an approach which minimizes the use of such structures.

For minimizing the use of support structures, process parameters in combination with a contour-like exposure strategy are developed to realize support-less overhanging structures of less than 35°. These parameters are implemented in a shell-core strategy, which follows the idea of applying different processing strategies to the critical (overhanging) shell and the uncritical core of the part. Thereby, the core is processed with standard parameters, aiming a dense material. On the critical shell, optimized processing parameters are applied, reaching good results in terms of surface quality, especially at extreme overhang situations.

The results show that the selective laser melting (SLM) technology is able to realize support-less overhanging surfaces by choosing suitable scan strategies and process parameters. Particularly good results are always obtained when the exposure direction of the shell is parallel to the contour of the sample.

The validity of the results is demonstrated through the successful reproduction of the build strategy on two commercial SLM machines, reaching support-free builds of surfaces with an angle to the horizontal of less than or equal to 30°.

This paper aims to describe an integration of the media naturalness theory, the continuum model of impression formation and the social identity model of deindividuation effects. The goal is to determine the compatibility of the central tenets and propositions of the two theories and reconcile their effects under a unified model that can be used to explain and predict changes in perceptions, attitudes and behaviors arising in computer-mediated interaction.

A review of the literature was used to determine whether the two theories were compatible. The reconciliation comes by way of a third theory, the motivated tactician theory, which focuses on the effects of cognitive effort on schema use, particularly on those schemas used in social categorization processes.

It was determined that the two models of focus could be combined via the tenets of the third. The combined model is expected to provide explanatory and predictive capabilities that exceed those of the individual theories and should prove to be relevant in the study of computed-supported collaboration, in the design of collaborative environments and in the analysis of individual and group behaviors in computer-mediated communication.

The current effort describes the main effects derived from the integration and offers four propositions that describe moderating factors that are derived from each of the three theories. The main effects must be tested and validated and, given support, must be extended to determine the validity of the moderating effects predicted by the propositions. Additionally, media naturalness theory is a relatively recent addition to theories of technology and so needs further empirical support for its propositions. As to the behavioral implications, the social identity model of deindividuation effects has yet to be tested with the specific intention of discovering how media characteristics affect self-concept.

The model can be used to inform information system designs that favor desirable behavioral outcomes or to prevent undesirable effects from occurring. For example, emphasis can place on media attributes and system features that individuate decision-makers within group decision support environments when consensus is a primary goal as a means to avoid group thinks and polarization. Conversely, attributes and features that are supportive of social categorization processes and deindividuation effects might be used to emphasize group membership, shared effort and to minimize social loafing or the frequency and intensity of inappropriate disparagement of ideas and contributions.

The combined model is principally useful in explaining and predicting human behavior in relation to computer-supported collaborative work such as distributed workgroups and online learning environments. For example, the explanatory elements of the combined theory can be used by managers as a diagnostic tool in problem situations within virtual teams. A specific instance would be to determine why a change to existing systems created a change in work habits. In a more proactive move, managers might use the predicted social categorization effects and subsequent depersonalization, to instill a group identity in an otherwise diverse workgroup.

The combined model is expected to provide explanatory and predictive capabilities that exceed those of the individual theories and should prove to be relevant in the study of computed-supported collaboration, in the design of collaborative environments and in the analysis of individual and group behaviors in computer-mediated communication.

Michael Holquist (1990), one of the commentators on Mikhail Bakhtin’s monumental work, stated flatly that “human existence is dialogue,” and Ivana Markova (2003) declared that “dialogism is the ontology of humanity.” Bakhtin (1985;1986) himself said that such dialogues are conducted by using “speech genres.” From another angle Kenneth Burke asked, “What is involved when we say what people are doing and why they are doing it?” and claimed – and showed – that this question can be best answered by using what he called the “grammar of motives,” which consisted of a hexad of terms: act, attitude, scene, agent, agency, and purpose. In this chapter, I examine, by using various examples, how the Burkean grammar is used in the construction of one speech genre or the other to achieve rhetorically effective dialogic communication.