20005 research outputs found
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Impact of habitual flexion on bone formation after spinal fusion surgery: an In silico study
No full textBackground: Lumbar spinal fusion is currently regarded as one of the most effective surgical treatments for patients with spinal deformities, degenerative disc disease, and degenerative spondylolisthesis. However, the procedure still faces a high incidence of non-unions. A key factor contributing to non-union is stress shielding effects related to unfavorable mechanical signals at the fusion site. Mechanical conditions at the fusion site are determined by the loading conditions that result from daily activities. Recent studies have reported that humans spend most of the day with their spine in a flexed position. The role of flexion loading in the progression of bone fusion remains poorly understood. This study explores the influence of habitual flexion loading on the spinal fusion process using a computational modeling framework that integrates finite element analysis with bone healing algorithms to simulate bone regeneration following fusion surgery. Methods: A finite element model of the lumbar spine based on a healthy subject was developed and validated with in vitro experimental data. Thereafter, a virtual posterior lumbar interbody fusion was performed where 2 intervertebral cages were inserted at the L4-L5 level together with posterior fixation. The influence of two loading conditions on the predicted fusion process were investigated: (1) A compression load (2) A hybrid (compression + flexion) loading protocol simulating habitual flexion encountered during daily living. Results: Bone bridging was predicted to occur 14 weeks after surgery. At week 14, for the hybrid loading, the model predicted a bone volume of 70%, whereas for compression load, the bone volume prediction was 59%. Computer model predictions showed that habitual flexion loading can promote bone formation in the anterior and peripheral regions by inducing a mechanical environment favorable for bone formation. Conclusion: Flexion loading may enhance bone healing by promoting mechanically advantageous conditions. The computational framework could guide the development of optimized rehabilitation protocols to improve fusion outcomes
Navigating viewpoints in MBSE: challenges, potential and pathways for stakeholder participation in industry
No full textModel-based Systems Engineering (MBSE) supports managing complex engineering projects. A pivotal element of MBSE is the concept of views which provide tailored representations of a system model to address stakeholder concerns. Despite standards describing the use and generation of views, the adoption and practical implementation of MBSE views and viewpoints in industrial practice remain insufficiently explored. Interviews with German practitioners reveal a disconnect between theory and practice: views and viewpoints and the involvement in MBSE are often limited to technical experts, excluding non-technical stakeholders. High complexity, abstract representations, and tool-related barriers impede broader engagement. The findings suggest stakeholder-specific, accessible visualizations integrated into easy-to-use tools to improve understanding, collaboration, and decision-making.</jats:p
Das (ungenutzte) Potenzial von Lernaufgaben für die Hochschullehre
No full textMit dem Aufstieg der Kompetenzorientierung hat die Frage an Relevanz gewonnen, wie Lehr-Lern-Szenarien zu gestalten sind, die Kompetenzerwerb begünstigen. In diesem Zuge wird sich im Schulkontext schon länger intensiv mit der Konstruktion und Typologien von Lernaufgaben beschäftigt (vgl. Thonhauser, 2008; Reinfried, 2016; Kleinknecht, 2019). In der Hochschuldidaktik dagegen richtet sich der Fokus bisher seltener explizit auf Lernaufgaben; verbreiteter ist die Auseinandersetzung zum Beispiel mit Methoden, didaktischen Prinzipien wie problemorientierten Lernen oder Prüfungsaufgaben.
Ein naheliegender Grund für diese unterschiedliche Fokussierung ist, dass Lernen in Hochschulen weniger eng angeleitet wird als in Schulen. Im Kontext von Online-Selbstlernangeboten, die in der Hochschule an Relevanz gewinnen, nehmen Aufgaben jedoch einen zentralen Stellenwert ein, da sie maßgebliches Werkzeug zur Anleitung und Begleitung des Lernwegs sind und ihnen die Funktion zukommt, die fehlende Ad-hoc-Instruktion einer Lehrperson zu kompensieren. Das Potenzial guter Lernaufgaben wird in diesem Kontext allerdings noch nicht ausgeschöpft. Beispielsweise offenbart ein Blick in MOOCs, dass dort häufig multiple-choice-artige, wissensfokussierte Aufgaben dominieren, die nicht über der zweite (Verstehen) der sechs Kompetenzstufen der Bloom‘schen Taxonomie hinausreichen.
Vor diesem Hintergrund plädiert der Impulsbeitrag dafür, dass Potenzial der Konstruktion guter Lernaufgaben für die Hochschullehre systematischer auszuschöpfen. Es werden Möglichkeiten der Typologisierung von Aufgaben vorgestellt und auf ihr Potenzial als didaktische Planungshilfe, insbesondere für kompetenzorientierte Selbstlernszenarien, befragt. Angereichert wird der Beitrag durch Aufgabenbeispiele aus dem Lernangebot „SDG Campus“, das auf den Erwerb von Nachhaltigkeitskompetenzen gerichtet ist
Compensation of self-RCS and IQ-demodulation imperfections of continuous-wave radar systems
No full textThis contribution discusses the calibration of continuous-wave radar sys-tems used for relative displacement measurements. To address systematic measurement errors arising from receiver inphase-quadrature (IQ) imperfections as well as the own radar cross section of the radar device (self-RCS), a model of the radar response that accounts for both effects is presented. Given the model parameters, which are retrieved based on calibration measurements, the effects of both IQ-imbalance and self-RCS can be removed. Measurements with a custom 24-GHz six-port-based radar system validate the proposed concept enabling highly accurate relative displacement measurements
Soziale Normen und Controlling - Informelle Kontrolle zur Förderung ethischen Verhaltens in Unternehmen
No full textSocial norms and individual values are key drivers of ethical behavior. Norms such as honesty can serve as informal control mechanisms in companies and, e.g., promote honest budget reporting and contribute effectively to fraud prevention. Management control can support the development of desirable norms by creating the right conditions
Uncertainty-aware efficient estimation of the probability density function for excessive rolling of a ship
No full textThis paper proposes a methodology to efficiently quantify an uncertainty in the probability density function (PDF) of excessive rolling of a ship. To this end, the Bayesian inference scheme is introduced to estimate the posterior distribution of roll damping terms, having measured instantaneous roll angles and incoming waves. This study employs two sampling techniques to estimate the posterior distribution: the transitional Markov chain Monte Carlo (TMCMC) and sequential and adaptive probabilistic integration (SAPI). Resulting posterior distributions of damping terms are compared and their computational tractability are discussed. Furthermore, analytical formulae are devised to predict an uncertainty zone in the PDF of roll angle embedding the damping terms up to the second order. By this means, the uncertainty in the PDF of excessive rolling can be quantitatively and efficiently evaluated, avoiding the so-called double loop problem. Numerical demonstrations are presented referring to synthetic roll motion measurements based on low- and high-fidelity 1 degree-of-freedom roll models; the latter incorporates higher-order damping terms
A digital twin for robotic post mortem tissue sampling using virtual reality
No full textStudying tissue samples obtained during autopsies is the gold standard when diagnosing the cause of death and for understanding disease pathophysiology. Recently, the interest in post mortem minimally invasive biopsies has grown which is a less destructive approach in comparison to an open autopsy and reduces the risk of infection. While manual biopsies under ultrasound guidance are more widely performed, robotic post mortem biopsies have been recently proposed. This approach can further reduce the risk of infection for physicians. However, planning of the procedure and control of the robot need to be efficient and usable. We explore a virtual reality setup with a digital twin to realize fully remote planning and control of robotic post mortem biopsies. The setup is evaluated with forensic pathologists in a usability study for three interaction methods. Furthermore, we evaluate clinical feasibility and evaluate the system with three human cadavers. Overall, 132 needle insertions were performed with an off-axis needle placement error of 5.30±3.25 mm. Tissue samples were successfully biopsied and histopathologically verified. Users reported a very intuitive needle placement approach, indicating that the system is a promising, precise, and low-risk alternative to conventional approaches
Determination of the right level of detail: A methodical approach for life cycle costing integration in product development
No full textIn Life cycle costing the processing of the high amount of cost data is challenging for industrial companies. Depending on the existing product and business model the cost structure and the relevance of different cost types differs. To minimize the effort for data processing in product development, this paper presents a methodical approach to determine the needed level of detail concerning the consideration of life cycle cost. The necessary level of detail for business models can be defined by converting the existing cost data into a holistic cost model. The methodical approach presented is applied to an exemplary business model
Final report of the project Learning Conversational Action Repair for Intelligent Robots (LeCAREbot)
No full textWhat are the principal mechanisms required to capture the robustness and interactivity of hu-man communication, given the situational, noisy and often ambiguous nature of natural lan-guage? And how, and to what extent, can we integrate these mechanisms within an embodied functional model that is computationally and empirically verifiable? We addressed these re-search questions by investigating the linguistic phenomenon of conversational repair (CR) -- a method to edit and re-interpret previously uttered sentences that were not correctly understood by the hearer....Was sind die wichtigsten Mechanismen, um die Robustheit und Interaktivität der menschlichen Kommunikation zu erfassen, angesichts der situativen, verrauschten und oft mehrdeutigen Natur der natürlichen Sprache? Und wie können wir diese Mechanismen in ein funktionales Modell integrieren, das rechnerisch und empirisch überprüfbar ist? Wir untersuchten diese Fragen, indem wir das sprachliche Phänomen der konversationalen Reparatur (KR) betrachteten – eine Methode, um zuvor geäußerte Sätze zu bearbeiten und neu zu interpre-tieren, die nicht richtig verstanden wurden..
Molecular fluctuations in mixed-metal MOF-74: influence of the metal composition
No full textA selected series of metal–organic frameworks M-MOF-74 (M = Mg, Co, Ni) and mixed metal MM-MOF-74 (Mg/Co or Mg/Ni) with different compositions of metal atoms have been prepared and further investigated by broadband dielectric spectroscopy (BDS) in a wide temperature range. The dielectric spectra show at least two relaxation processes. Process-A is observed only for the Ni-containing MOFs and is attributed to localized fluctuations of the metal oxide corners. Relaxation processes-B and -C are observed for all prepared MOFs, except that process-B is not observed for Ni-MOF-74. Large-angle fluctuations such as free rotations of the linkers can be excluded due to the structure of MOF-74, but small-angle fluctuations such as torsions are possible. According to numerical simulations carried out for MOF-74, process-B can be attributed to inward and outward fluctuations of the linkers relative to the pore center. Process-C is related to small-angle rotational fluctuations of the linker together with co-rotations of the metal nodes. The latter interpretation is supported by the dependence of the activation energy of the relaxation rate of process-C on the metal composition of the MOFs, which is discussed in terms of the bond lengths between the metal atoms and the linker which decrease in the sequence Mg, Co and Ni