Screw and Lie group theory in multibody dynamics

Screw and Lie group theory allows for user-friendly modeling of multibody systems (MBS), and at the same they give rise to computationally efficient recursive algorithms. The inherent frame invariance of such formulations allows to use arbitrary reference frames within the kinematics modeling (rather than obeying modeling conventions such as the Denavit–Hartenberg convention) and to avoid introduction of joint frames. The computational efficiency is owed to a representation of twists, accelerations, and wrenches that minimizes the computational effort. This can be directly carried over to dynamics formulations. In this paper, recursive \(O ( n ) \) Newton–Euler algorithms are derived for the four most frequently used representations of twists, and their specific features are discussed. These formulations are related to the corresponding algorithms that were presented in the literature. Two forms of MBS motion equations are derived in closed form using the Lie group formulation: the so-called Euler–Jourdain or “projection” equations, of which Kane’s equations are a special case, and the Lagrange equations. The recursive kinematics formulations are readily extended to higher orders in order to compute derivatives of the motions equations. To this end, recursive formulations for the acceleration and jerk are derived. It is briefly discussed how this can be employed for derivation of the linearized motion equations and their time derivatives. The geometric modeling allows for direct application of Lie group integration methods, which is briefly discussed.     

The Impact of Geographic Distance on Online Social Interactions

Online social networking services entice millions of users to spend hours every day interacting with each other. The focus of this work is to explain the effect that geographic distance has on online social interactions and, simultaneously, to understand the interplay between the social characteristics of friendship ties and their spatial properties. We analyze data from a large-scale online social network, Tuenti, with about 10 million active users: our sample includes user profiles, user home locations and online social interactions among Tuenti members. Our findings support the idea that spatial distance constraints whom users interact with, but not the intensity of their social interactions. Furthermore, friendship ties belonging to denser connected groups tend to arise at shorter spatial distances than social ties established between members belonging to different groups. Finally, we show that our findings mostly do not depend on the age of the users, although younger users seem to be slightly more constrained to shorter geographic distances. Augmenting social structure with geographic information adds a new dimension to social network analysis and a large number of theoretical investigations and practical applications can be pursued for online social systems, with many promising outcomes. As the amount of available location-based data is increasing, our findings and results open the door to future possibilities: researchers would benefit from these insights when studying online social services, while developers should be aware of these additional possibilities when building systems and applications related to online social platforms.     

How do investors decide? An interdisciplinary review of decision-making in crowdfunding

Crowdfunding is on the rise: its volume grew 1000% in only three years and is about to outpace worldwide venture capital spending. A quickly growing body of research is exploring the emerging crowdfunding phenomenon. While the literature offers a detailed and comprehensive picture of decision-making for traditional startup financing or bank loans, it does not provide a holistic understanding of decisions to invest in crowdfunded ventures. Many individual studies investigate isolated factors that influence investor decision-making in crowdfunding campaigns without integrating the findings regarding those influences. A comprehensive view of the relevant decision-making factors is necessary to build future research on and for practitioners to gain a better understanding of how investors choose. We conduct an interdisciplinary literature review to examine which factors influence the investment decisions in crowdfunding. From an analysis of 68 articles, we construct a comprehensive framework of relevant influence factors. Even though prior research covers many factors, others have received scant attention. Especially investors’ cognitive features and the context in which the investment decision is made seem to strongly influence decisions but are scarcely researched. In addition, most reviewed studies focus more on individual factors and campaign success than underlying decision processes. To highlight novel factors of crowdfunding investment decisions, we compare decision-making in traditional investments, such as venture capital and bank loans, to crowdfunding. Our findings offer new avenues for research toward understanding how the shift induced by crowdfunding changes our choices and actions. The analysis should support the endeavor to build better theories and provide a basis for further social and technological development.     

Dry Processing and Recycling of Thick Nacre–Mimetic Nanocomposites

Bioinspired nanocomposites with high levels of reinforcement hold great promise for future, green lightweight, and functional engineering materials, but they suffer from slow, tedious, and nonscalable preparation routes, that typically only lead to very thin films. A rapid and facile dry powder processing technique is introduced to generate bioinspired nanocomposite materials at high fractions of reinforcements (50 wt%) and with millimeter scale thickness. The process uses powder drying of vitrimer-coated nanoplatelets (nanoclay and MXene) from aqueous solution and subsequent hot-pressing. As a method of choice in industrial lightweight composite materials engineering, hot-pressing underscores a high potential to translate this approach to actual products. The use of the vitrimer chemistry with temperature-activated bond shuffling is important to facilitate smooth integration into the nanocomposite design, leading to layered nacre-inspired nanocomposites with nanoscale hard/soft order traced by X-ray diffraction and excellent mechanical properties investigated using flexural tests. Recycling by grinding and hot-pressing is possible without property loss. The compatibility with existing composite processing techniques, scalable thickness and dimensions, and recyclability open considerable opportunities for translating bioinspired nanocomposites to real-life applications.     

Sloshing dynamics estimation for liquid-filled containers performing 3-dimensional motions: modeling and experimental validation

Multibody System Dynamics - Many industrial applications require the displacement of liquid-filled containers on planar paths (namely, paths on a horizontal plane), by means of linear transport...     

The Fractional CIO in SMEs: conceptualization and research agenda

We conceptualize the new phenomenon of the Fractional Chief Information Officer (CIO) as a part-time executive who usually works for more than one primarily small- to medium-sized enterprise (SME) and develop promising avenues for future research on Fractional CIOs. We conduct an empirical study by drawing on semi-structured interviews with 40 individuals from 10 different countries who occupy a Fractional CIO role. We derive a definition for the Fractional CIO, distinguish it from other forms of employment, and compare it with existing research on CIO roles. Further, we find four salient engagement types of Fractional CIOs offering value for SMEs in various situations: Strategic IT management, Restructuring, Rapid scaling, and Hands-on support. The results reveal similarities with existing CIO roles as well as novel insights concerning the different engagement types. Lastly, we propose a research agenda for the Fractional CIO field, based on four research themes derived from existing CIO research and insights from the interviews.

     

Visual Analysis of Confocal Raman Spectroscopy Data using Cascaded Transfer Function Design

2D Confocal Raman Microscopy (CRM) data consist of high dimensional per‐pixel spectral data of 1000 bands and allows for complex spectral and spatial‐spectral analysis tasks, i.e., in material discrimination, material thickness, and spatial material distributions. Currently, simple integral methods are commonly applied as visual analysis solutions to CRM data which exhibit restricted discrimination power in various regards. In this paper we present a novel approach for the visual analysis of 2D multispectral CRM data using multi‐variate visualization techniques. Due to the large amount of data and the demand of an explorative approach without a‐priori restriction, our system allows for arbitrary interactive (de)selection of varaibles w/o limitation and an unrestricted online definition/construction of new, combined properties. Our approach integrates CRM specific quantitative measures and handles material‐related features for mixed materials in a quantitative manner. Technically, we realize the online definition/construction of new, combined properties as semi‐automatic, cascaded, 1D and 2D multidimensional transfer functions (MD‐TFs). By interactively incorporating new (raw or derived) properties, the dimensionality of the MD‐TF space grows during the exploration procedure and is virtually unlimited. The final visualization is achieved by an enhanced color mixing step which improves saturation and contrast.     

The impact of individual motivations on idea submission and future motivation to participate in an organization's virtual idea campaign

We used time‐lagged survey data to investigate the effects of various types of motivation on idea submission and future motivation to participate in a virtual idea campaign (VIC). We also used qualitative data to illuminate context and enrich explanations. Applying forms of motivation from self‐determination theory—intrinsic motivation and external motivation—and the additional composite form of identified‐prosocial motivation, our study offers insight into their effects on idea submission and future motivation to participate in idea campaigns. We found that intrinsic motivation led to idea submission and future motivation to participate, while external motivation negatively related to idea submission. Identified‐prosocial motivation positively related to participants' motivation to participate in future idea campaigns, but surprisingly, its interaction with intrinsic motivation did not lead to idea submission. We provide managers and innovation researchers with useful lessons for the effective management of idea campaigns in organizations, and our results highlight the value of autonomous forms of motivation, especially intrinsic motivation.