132571 research outputs found
Sort by
Tunable Quantum Criticality in Multicomponent Rydberg Arrays
No full textArrays of Rydberg atoms have appeared as a remarkably rich playground to study quantum phase transitions in one dimension. One of the biggest puzzles that was brought forward in this context are chiral phase transitions out of density waves. Theoretically predicted chiral transition out of period-four phase is still pending experimental verification mainly due to extremely short interval over which this transition is realized in a single-component Rydberg array. In this Letter, we show that multicomponent Rydberg arrays with extra experimentally tunable parameters provide a mechanism to manipulate quantum critical properties without breaking translation symmetry explicitly. We consider an effective blockade model of two component Rydberg atoms. Weak and strong components obey nearest- and next-nearest-neighbor blockades correspondingly. When laser detuning is applied to either of the two components the system is in the period-3 and period-2 phases. But laser detuning applied to both components simultaneously stabilizes the period-4 phase partly bounded by the chiral transition. We show that relative ratio of the Rabi frequencies of the two components tunes the properties of the conformal Ashkin-Teller point and allows us to manipulate an extent of the chiral transition. The prospects of multicomponent Rydberg arrays in the context of critical fusion is briefly discussed.QN/Chepiga La
A quantitative comparison between the mHand Adapt passive adjustable hand prosthesis and its predecessor, the Delft Self-Grasping Hand
No full textIntroductionThe Delft Self-Grasping Hand (SGH) is an adjustable passive hand prosthesis that relies on wrist flexion to adjust the aperture of its grasp. The mechanism requires engagement of the contralateral hand meaning that hand is not available for other tasks. A commercialised version of this prosthesis, known as the mHand Adapt, includes a new release mechanism, which avoids the need to press a release button, and changes to the hand shape. This study is the first of its kind to compare two passive adjustable hand prostheses on the basis of quantitative scoring and contralateral hand involvement.Methods10 anatomically intact participants were asked to perform the Southampton Hand Assessment Procedure (SHAP) with the mHand. Functionality and contralateral hand involvement were recorded and compared against SGH data originating from a previous trial involving a nearly identical testing regime.ResultsmHand exhibited higher functionality scores and less contralateral hand interaction time, especially during release-aiding interactions. Additionally, a wider range of tasks could be completed using the mHand than the SGH.DiscussionGeometric changes make the mHand more capable of manipulating smaller objects. The altered locking mechanism means some tasks can be performed without any contralateral hand involvement and a higher number of tasks do not require contralateral involvement when releasing. Some participants struggled with achieving a good initial grip due to the inability to tighten the grasp once already formed.ConclusionThe mHand offers the user higher functionality scores with less contralateral hand interaction time and the ability to perform a wider range of tasks. However, there are some design trade-offs which may make it slightly harder to learn to use.Medical Instruments & Bio-Inspired Technolog
Irradiation resistance of thermo-optical properties of zirconium diboride by 3 MeV electrons
No full textDue to good thermal conductivity and thermal shock resistance, ultra-high temperature ceramics such as zirconium diboride (ZrB2) have been investigated as promising materials to be used in reusable thermal protection systems TPSs are vital to the heat balance of a spacecraft during atmospheric reentry and subsequent operation in space. Hence, the thermal and optical properties are especially critical for such applications. Meanwhile, radiation exposure in space can pose risks of degrading such material properties, especially over a prolonged mission duration. The interaction of electron radiation-which can be found in the outer Van Allen belt, with ZrB2 has not been studied previously and was chosen as the main scope of this study. An electron source of 3 MeV with different radiation exposure time was used. The response of thermo-optical properties of ZrB2 to increasing electron radiation fluences was investigated. ZrB2 samples were made through spark plasma sintering into sintered pellets and then exposed to 3 MeV electron irradiation. These ZrB2 samples were characterized by their microstructure, thermal conductivity, coefficient of thermal expansion (CTE), emittance, absorptivity, and surface roughness before and after irradiation. It was found that ZrB2’s thermo-optical properties showed high radiation resistance at these fluences, and no apparent microstructural change was observed after irradiation. However, the irradiated samples had, on average, a 29% lower surface roughness than the unirradiated samples, possibly originating from electron sputtering.Group Tan
A highly stable, pressure-driven, flow control system based on Coriolis mass flow sensors for organs-on-chips
No full textStable delivery of liquids to microfluidic systems is essential for their reproducible functioning, especially when supplying flows to organs-on-chips – delicate living models that recreate human physiology on the microscale and thus can be used to reduce the need for animal testing. Most flow control systems are unable to sustain a robust and stable flow in longer experiments (>1 week), particularly those based on the ubiquitous syringe pump. Though easy to use, syringe pumps have no mechanism for actually measuring flow, let alone flow regulation with sensor feedback. We have developed a liquid delivery system based on the generation of flow by applying a constant air pressure to liquids in sealed containers. A flow of liquid is monitored by accurate measurement of mass flows (mg/min) using downstream Coriolis-based mass flow sensors. Measured mass flows provide fast feedback to integrated valves, with valves opening or closing slightly to increase or decrease solution flows to the organs-on-chips as required. This mass flow sensing principle is not affected by changes in the density, temperature, and viscosity of the liquids being displaced. This is in contrast to systems that use volumetric flow sensors, which require recalibration when these parameters change. The rationale behind using this principle for organs-on-chips, is that the stability provided by this flow control system allows for more control over growth of these mini-organs. We demonstrate the functionality of this system with three examples: 1) Fast stabilization (within seconds) under changing physical conditions; 2) Short-term stability (minutes to hours) of delivered flows in a microreactor with interconnected inlets; and 3) Long-term stability (>1 week) of cell medium flows to a living organ-on-a-chip. Two categories of organs-on-chips (OOCs) can be distinguished: 1) solid OOC are designed for three-dimensional cell or tissue constructs that interact with each other and their surroundings, and 2) barrier-type OOC contain a selective cellular barrier between two compartments as do many barriers in the body. The latter of these two types is the most challenging to culture and maintain as they are very sensitive to variations in flow and pressure surges. The flow control system presented in this work provides a great improvement compared to the use of syringe pumps and volumetric flow sensors in OOC studies. The novelty of this work lies in the long-term stability use of this system for organs-on-chips, maintaining stability for short to very long periods of time without compromising the barrier function of the organ-on-chip by pressure surges, bacterial contamination, or other undesired effects from the flow delivery system.Precision and Microsystems Engineerin
Simulating decadal cross-shore dynamics at nourished coasts with Crocodile
No full textProjections of high rates of sea level rise have stimulated proposals for adaptation strategies with increasingly high nourishment volumes along sandy beaches. An underlying assumption is that coastal profiles respond rapidly to nourishments by redistributing sediments towards a (new) equilibrium shape. However, this perception may not be valid when high volumes of nourishment are applied, as the profile shape may then undergo significant deformation. Current state-of-the-art modelling techniques often concentrate on a single spatio-temporal scale, either lacking the necessary temporal horizon or failing to provide the required level of cross-shore detail. This article introduces Crocodile, a diffusion based cross-shore model designed to bridge the gap between short- and long-term nourishment modelling. The model simulates the effects of nourishment strategies on coastal volume, coastline position and beach width over a decadal timeframe. It incorporates different elements which compute cross-shore diffusion, sediment exchange with the dune and longshore sediment losses. To test the model performance, a series of idealized nourishment scenarios are examined, along with three case studies along the Dutch coast with different nourishment strategies over the past few decades. The modelled coastal volume, shoreline position and beach width strongly resemble the observations with only a 12% overestimation in profile volume and 13% underestimation in beach width. Averaged over selected periods of nourishment, trends and trend reversals between different strategies are well replicated with slight overestimation for coastal volume trends by 1.5m3/m/yr(10%), while beach width trends are underestimated by 0.2m/yr (15%). Given that the added nourishment volumes are typically in the order of 100m3/m, these model errors are considered sufficiently low to conclude that Crocodile effectively simulates variations in coastal volume, coastline position and beach width over a decadal timeframe in response to different nourishment strategies. Therefore, Crocodile can facilitate the evaluation of future nourishment strategies.Coastal Engineerin
Spatial Robotic Experiences as a Ground for Future HRI Speculations
No full textThis work illustrates how artistic robotic systems can provide a reservoir of unfamiliarity and a basis for speculation, to open the field toward new ways of thinking about HRI. We reflect on a collaborative project between design students, a media art studio, and design researchers working with the baggage handling department of the Schiphol airport. Engaging with the industrial context, we developed 'metabehaviours' - abstracted ideas of processes carried out on the worksite-and passed these over to the students who translated them into robotic enactions using a predefined hardware developed by the media art studio. The resulting visit experience challenges the audience to decode the installation in terms of metabehaviours and their possible relations to industrial HRI. We used this to reflect on the value of conducting artistic and speculative work in HRI and to distil actionable recommendations for future research.Human Information Communication DesignDesign AestheticsDesign Conceptualization and CommunicationHuman-Centred Artificial IntelligenceHuman-Robot Interactio
Advancements and insights in thermal and water management of proton exchange membrane fuel cells: Challenges and prospects
No full textIn response to the growing global demand for clean and sustainable energy solutions, proton exchange membrane fuel cells (PEMFCs) have emerged as vital components in diverse decarbonization strategies. Despite their increasing importance, a comprehensive synthesis of recent advancements, challenges, and future prospects in thermal and water management within this domain remains notably scarce. This paper aims to bridge this gap by conducting a meticulous literature review focused on thermal and water management in PEMFCs. Primarily, this study encapsulates the underlying mechanisms governing thermal and water generation in PEMFCs, intricately analyzing thermal and water generation analyses. Secondly, a multifaceted exploration of thermal and water transfer mechanisms, alongside their pivotal influencing factors, is presented. Furthermore, the discourse delves into sophisticated strategies for refining water and thermal management in PEMFCs. As well as delving into the complexities of high-power heat dissipation and water balance, especially water management for cold start and high temperature operating conditions. The culmination of this investigation yields valuable insights into the intricate dynamics of thermal and water management within PEMFCs, thereby culminating in forward-looking recommendations for future research trajectories. These findings not only offer scholars a vantage point to discern emerging research frontiers and trends but also extend theoretical precepts and reference points for technology innovators and product developers.Design & Construction Managemen
Thermal Stability of F-Rich Phlogopite and K-Richterite During Partial Melting of Metasomatized Mantle Peridotite With Implications for Deep Earth Volatile Cycles
No full textPhlogopite and K-richterite constitute important carrier phases for H and F in Earth's lithosphere and mantle. The relative importance depends on their stabilities at high pressure and temperature, which in turn depends on bulk composition. Most previous experimental studies focused on the thermal stability of phlogopite and K-richterite were conducted using simplified chemical compositions. Here, partial melting experiments on metasomatized and carbonated, OH ± F-bearing near-natural peridotite were performed at high pressures (2 and 5 GPa) and temperatures (1,100–1,350°C) to assess the thermal stability of F-free versus F-bearing phlogopite and K-richterite. Experimental results demonstrate that the thermal stability of F-bearing phlogopite is increased by >55°C/wt.% F, relative to F-free phlogopite, whereas K-richterite is absent in all experiments with significant degrees of melting (>2%). The thermal stability of phlogopite containing several wt.% F exceeds continental and oceanic geotherms within the upper 150 km. Fluorine-rich phlogopite would therefore be stable in virtually all of the continental lithosphere, only to be decomposed during large, regional melting events such as continental break-up, thereby acting as a major long-term sink for F and/or H. This could even be the case for the oceanic asthenosphere, depending on the oceanic geotherm of the area of interest.Planetary Exploratio
Non-unit protection method for MMC-HVDC grids based on selective drop rate of voltage traveling waves
No full textFast, sensitive, and selective protection principles are one of the major challenges in the feasibility of modular multi-terminal (MMC) high voltage direct current (HVDC) grids. Rate of change of voltage (ROCOV) and transient-based solutions are the traditional and widely accepted protection principles. Despite the speed and practicality of these solutions, they generally suffer from sensitivity and selectivity issues, particularly when dealing with high-resistance faults and low-size current limiting inductors (CLIs). To improve upon these methods, this paper proposes a new primary protection method that utilizes a selective drop rate of fault-generated voltage traveling waves (TW) to detect internal DC line faults. This is achieved by a comprehensive analysis of the line-mode fault-generated voltage (LFGV) under various internal and external fault scenarios. As the key fault characteristics, the proposed method exploits the minimum points of initial LFGV and the corresponding time to form the basis of the proposed protection method. The effectiveness of this approach is evaluated using a four-terminal MMC-HVDC grid in PSCAD/EMTDC. Compared to ROCOV and transient-based solutions, the proposed method identifies internal faults up to 1250 Ω with fast response, while maintaining its practicality and independence to CLI size.Intelligent Electrical Power Grid
Design of a normally closed MEMS- microvalve for micropropulsion systems in PocketQube satellites
No full textThere is a growing demand for nano-satellite missions that require advancements in micro-propulsion capabilities to facilitate a wider range of orbital maneuvers. Among these capabilities, the ability to accurately control thrust would unlock new possibilities for nano-satellite applications, including missions such as space debris removal and orbit transfer.Delft University of Technology is currently pioneering the development of an innovative green propellant-driven micro-propulsion system based on micro-electro-mechanical (MEMS) technologies for its PocketQube, known as Delfi-PQ, which features a compact form factor of 5x5x5 cm. While the thruster itself is in development, the interfacing and integration with other components are still ongoing.Given the stringent mass, volume, and power limitations imposed by PocketQube satellite requirements, there is a pressing need for micro-scale components to realize a highly integrated propulsion system.This thesis focuses on the design of a MEMS-based microvalve for proportional flow control in micro-resistojets. The design is conceptualized as comprising three components working in harmony: a valve seat with inlet and outlet, a flexible membrane, and a piezoelectric actuator. The valve seat with inlet and outlet, as well as the flexible membrane, utilize MEMS manufacturing techniques and are based on a silicon chip. And, a new design for piezoelectric actuators employing the d31 mode for contraction strokes is proposed.The proposed preliminary design is a normally closed microvalve designed for a flow rate of 5g/hr, with the flexibility to accommodate higher flow rates if needed. It offers proportional flow control, ensuring precise regulation of fluid flow. Additionally, it promises a low power consumption of less than 1W and a low response time. Furthermore, this thesis provides a detailed outline of the MEMS fabrication process flow available at TU Delft’s Else Kooi Laboratory for the device. It also features a comprehensive test plan aimedat assessing the feasibility of this design in future studies. Additionally, the thesis includes an elaborate risk analysis to help identify and mitigate potential risks during the manufacturing and testing phases.The design shows promise and could pave the way for future developments of the microvalve within the department.Aerospace Engineerin