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Enhancing microcomb efficiency via pump recycling in a chip-integrated gain medium
No full textContinuous-wave (CW) laser-driven integrated Kerr microresonators enable broadband optical frequency combs with high repetition rates and low threshold power, in a compact footprint. A drawback of such microcombs is the low conversion efficiency from the pump laser to the comb lines, which is often in the few percent range or below. In recent works, improved conversion efficiency has been demonstrated by leveraging soliton crystal states [1], interferometric back-coupling to suppress the residual pump light [2], or tuning the resonance frequency of the pumped mode [3]. While these approaches achieve improved conversion efficiency, they add complexity to the design and operation of the system, relying on non-deterministic states, dynamic control, and/or a potentially reduced number of comb lines.</p
"I Can’t See You, But I Trust You!": Exploring the Impact of Reduced Vision On Object Handover Times in Human-Robot Collaboration
No full textDespite the potential benefits of assistive robots for aging populations or individuals with special interactive requirements, such as reduced vision or hearing, there is limited research in this area. We present a repeated-measures study that included twenty-nine participants who interacted in two phases, either blindfolded first and then not blindfolded or vice versa. The study measured trust and negative attitudes towards robots (NARS) before and after handover interactions, as well as social robot attributes (RoSAS) and handover times. Results revealed no significant differences in trust levels or social attributes. However, negative attitudes and handover times were significantly lower when participants interacted first blindfolded. These findings highlight the importance of considering reduced vision capabilities in Human-Robot Collaboration and suggest potential strategies for enhancing interaction experiences in this context. Further research could explore additional factors influencing collaborative interactions and inform the development of more inclusive and effective assistive robot technologies
Students’ conceptions of double integral bounds: an APOS theory perspective
No full textIn this article we use the Action, Process, Object, Schema framework as a theoretical lens to analyse students’ responses to an examination question in a multivariable calculus course for engineering majors. The exercise required students to translate between a geometric representation of a lamina into two different symbolic representations of the area of the lamina as double integrals in the Cartesian coordinate system. We designed and empirically refined a genetic decomposition of double integral for area and used this as an analysis tool to capture and characterise students’ conceptual understanding. A notable finding is that when the region needs to be partitioned to correctly describe it using double integrals, the success rate is significantly lower than when the region does not need to be partitioned. We present five different forms of incorrect double integral constructions and identify two primary elements of conceptual understanding which are necessary for successful construction of an iterated double integral for the area of a lamina
Anti-Backlash Mechanisms for Cycloidal Drive Robotic Actuators:Design and Evaluation
No full textWe design and experimentally evaluate two anti-backlash mechanisms for cycloidal reducers. The two mechanisms are integrated into variations of a proposed design of quasi-direct drive actuator. Three prototypes are realised to compare the two mechanisms against the baseline design. We evaluate the effectiveness of the anti-backlash mechanisms under varying preload with measurements of friction, backlash, and stiffness. The results demonstrate that the anti-backlash mechanisms are effective at reducing backlash by approx. 2-3x, at the expected expense of increased friction (< 2x).</p
On the thermal degradation of lubricant grease: Degradation analysis
No full textAn exact thermal degradation model for lubricant grease emerges as the sum of the contributions from the active thermal mechanisms of heat transfer, heat storage and evaporation. The second law's non-negative entropy generation is used as the basis for degradation characterization. The fundamental thermal entropy generation relation for the oven aging of grease is correlated with a degradation measure, as prescribed by the Degradation-Entropy Generation theorem. Five grease properties are selected as degradation measures. The model is evaluated by substituting temperature profiles and grease properties measured during oven aging of three different greases. A fit of R2 ≈ 1 was obtained for all the data, notwithstanding the non-monotonic aging evolution of the measured grease properties. Degradation coefficients, which indicate the influence of each active thermal mechanism on grease degradation, are quantified and compared for the three greases. The model is used to rank the greases according to their resistances to thermal degradation. Results show that the lithium-thickened grease with mineral base oil is the most susceptible to thermal degradation, followed by the lithium-thickened grease having a semi-synthetic base oil (a highly synthesized mineral oil with properties similar to synthetic polyalphaolefin oil). The polyurea-thickened grease with fully synthetic oil exhibits the highest thermal degradation resistance. These model predictions corroborate known empirical behaviors of these grease types. The proposed thermal degradation model applies to all greases and any material that undergoes thermal degradation
From Bouncing Break-ins to Frictional Firewalls:Ideas About Interacting Requirements for Vehicle Safety and Security
No full textWe explore requirement interactions related to safety and security properties with an example based on automotive braking systems, to show ideas about co-engineering trustworthy systems. We start from risk assessments TARA (Threat and Risk Assessment, ISO 21434) and HARA (Hazard Analysis and Risk Assessment, ISO 26262). These are often undertaken separately, resulting in requirements that may interact badly, for example, security features that compromise safety requirements, or sets of requirements that are impossible to satisfy together. Based on a minimal logical foundation for designing cyber-physical systems and considering requirement satisfaction across system changes, we classify several kinds of requirement interaction. These generalise the well-known case of (adverse) feature interactions; our suggestion is that understanding interactions can help during design or implementation revision cycles—even if requirements are considered without using formal methods.</p
Strong Group Delay Dispersion in 3D Photonic Band Gap Crystals and Planar Microcavities
No full textIt is well-known that nanophotonic structures give rise to intricate dispersion relations that strongly differ from those in homogeneous media, for instance, the appearance of band structures [1]. Such band structures reveal forbidden gaps where wave vectors become complex and the slope - the group velocity - is strongly modified to reveal slow light [3], [4], and a strong alteration of the group velocity dispersion, also known as chirp in optics and effective mass in solid state physics. Control thereof is crucial for applications (in comms and telecom) and for fundamental reasons namely as an alternative probe to local density of states and localization
Innovation and Value-Based Procurement in EU Healthcare
No full textBy driving adoption of novel technologies and care models, innovation and value-based procurement can help healthcare systems respond to demographic pressures, rising costs, and the need for more personalised, integrated services. Innovation Procurement (IP) enables healthcare organisations to procure novel solutions that satisfy unmet needs while delivering better outcomes for patients, service users, and society. Value-Based Procurement (VBP) focuses on buying outcomes rather than products. It is a powerful instrument for "reshaping commercial relationships and models to move beyond price and allow holistic appraisal of medical products through real-world evidence" . VBP aims to maximize overall value for patients, health systems, and society. These complementary approaches drive product and process innovation, yet both remain underutilised in healthcare across the European Union. There are multiple root causes which limit uptake of IP and VBP, including risk aversion among public buyers, skill gaps in innovation management, regulatory and administrative complexities, insufficient funding, and significant fragmentation across the healthcare ecosystem. Overcoming these barriers requires fostering entrepreneurial behaviours: embracing calculated risk-taking, encouraging iterative experimentation, and promoting genuine collaboration through public-private partnerships. Equally important is multi-stakeholder engagement and education. Such programmes must target procurement professionals, healthcare providers, policymakers, and innovative enterprises, equipping them with the knowledge and skills to navigate IP and VBP complexities and cultivate a culture of innovation
Upstream motion of oil droplets in co-axial Ouzo flow due to Marangoni forces
No full textTo explore the physicochemical hydrodynamics of phase-separating ternary liquids (“Ouzo-type”), a binary oil–ethanol mixture is introduced into a co-flowing stream of water. Oil droplets nucleate at the interface between the two liquids, leading to a larger oil droplet interacting with the ethanol-rich jet. Although buoyancy forces and hydrodynamic drag forces push the droplet in downstream direction, we observe an upstream motion. Using computational fluid dynamics simulations of a simplified model system, we identify the nucleation zone for oil droplets and uncover Marangoni forces to be responsible for the upstream motion of the droplet. A semi-analytical model allows us to identify the key parameters governing this effect. A general conclusion is that Marangoni stresses can reverse the motion of droplets through channels, where the surrounding liquid is a multi-component mixture. The insights from this work are not only relevant for channel flow, but more generally, for the physicochemical hydrodynamics of multiphase, multi-component systems.</p
Climate adaptation is also a social challenge:Implications for government
No full textPeople, society and nature are facing a changing climate. Climate events such as heatwaves, drought, heavy rainfall and rising sea levels can lead to social disruption. In that case, the impact of climate events extends beyond damage and casualties. The worst-case scenario is that people lose trust in the government and each other, communities fall apart and poverty increases. These examples show that climate events can have both physical and societal consequences. Conversely, the social context partly determines how well people are able to cope with climate events. Those with a strong network or sufficient resources are generally less likely to encounter severe problems and more likely to recover more quickly.Dutch climate adaptation policy pays too little attention to these social factors. The focus is on physical protection measures. Although these are essential, they are not sufficient. We argue that climate resilience in the Netherlands improves if the government also invests in the country’s social infrastructure, which enables people to look out for each other, increases mutual trust and offers perspectives for action.