39,683 research outputs found
Vibration suppression of suspended cables with three-to-one internal resonances via time-delay feedback
No full textBased on the time-delay feedback control, the vibration suppression of suspended cables with three-to-one internal resonances are investigated. Initially, the nonlinear differential equation of motion for a suspended cable under time-delay feedback control is considered, and a discrete model is derived using the Galerkin method. Subsequently, the method of multiple scales is employed to perturbatively solve the discrete time-delay differential equation, determining the modulation equations around the first primary resonance. Steady-state and periodic solutions of the modulation equations are detected numerically. Numerical results indicate that the internal resonance enhances the nonlinear dynamical complexity of the controlled suspended cable. It is observed that the time delay and control gain affect the controlled system: in particular, an increase in control gain leads to a reduction in response amplitude. By adjusting the time delay and control gain, the critical excitation can be altered, an aspect that could be very useful from a practical point of view. This research sheds light on the intricate dynamics of suspended cable and provides a theoretical foundation for designing more effective control strategies in engineering applications
Adaptive and Efficient Qubit Allocation Using Reinforcement Learning in Quantum Networks
No full textHow to classify microclimates more validly and finely? A novel method for mapping local climate zone (LCZ) on micro-scales
No full textGlobal climate change and rapid urbanization are driving microclimate variations in urban areas, intensifying the formation of urban heat islands (UHIs) vulnerable to extreme weather. The local climate zone (LCZ) framework, using remote sensing (RS) and geographic information system (GIS), has advanced with the World Urban Database and Access Portal Tool (WUDAPT), enabling microclimate understanding for improved urban planning and climate adaptation. However, mapping LCZs at the micro-scale relies on locally available GIS data or RS imagery, data gaps, authenticity issues, and low-resolution imagery often lead to inaccurate microclimate classifications. To enhance the validity and sophistication of microclimate classification, this study introduces a novel method for mapping LCZ using unmanned aerial vehicle (UAV) photogrammetry at the micro-scale (LCZ-UAV-MS), which constructs detailed land use and land cover (LULC) and 3D real scene (3DRS) models, calculates urban surface parameters (USPs) for each basic spatial unit (BSU) through spatial statistical analysis, and employs a decision-making classifier to categorize each BSU. This study validates the proposed method using Gulangyu as the study area, employing image overlay, temperature observation, and expert knowledge, with the following results: 1) Spatial percentage showing 51 % natural environments (LCZ A, B, C, and D), 27 % neutral environments (LCZ 7, 8, 9, 10, and Y), and 22 % built environments (LCZ 1, 2, 3, 4, 5, and 6) in Gulangyu. 2) The variance in mean LST across different LCZs was 1.02 in January and 5.18 in August 2024, with temperature differences more pronounced in summer, where the built environment had a higher mean LST of 41.3 °C compared to 35.2 °C in the natural environment and 38.3 °C in the neutral environment. 3) Field research at 22 random sample sites showed that 95 % of LCZ-UAV-MS classifications matched the field, outperforming WUDAPT LCZ, which matched only 10 %. These demonstrate that the LCZ-UAV-MS accurately captures microclimate temperature variations and provides a more precise micro-scale description than the WUDAPT LCZ. This study bridges the gap of LCZ studies in specific regions and scales, enhances the applicability of the LCZ framework at the micro-scale, and provides technical support for urban blue-green infrastructure management and resilient climate design strategies
Video Content Placement at the Network Edge: Centralized and Distributed Algorithms
No full textIn the traditional video streaming service paradigm, content providers typically provision the requested video content to viewers through a central content delivery network (CDN). However, remote viewers usually experience long video streaming delay due to uncertain wide area network delay, which severely affects the quality of experience. Multi-Access Edge Computing (MEC) offers a way to shorten the video streaming delay by building small-scale cloud infrastructures at the network edge, which are in close proximity to the viewers. In this paper, we present novel centralized and distributed algorithms for the video content placement problem in MEC. In the proposed centralized video content placement algorithm, we leverage the Lyapunov optimization technique to formulate the video content placement problem as a series of one-time-slot optimization problems and apply an Alternating Direction Method of Multipliers (ADMM)-based method to solve each of them. We further devise a distributed Multi-Agent Reinforcement Learning (MARL)-based method with value decomposition mechanism and parallelization policy update method to solve the video content placement problem. The value Decomposition mechanism deals with the credit assignment among multiple agents, which promotes the cooperative optimization of the global target and reduces the frequency of information exchange. The parallelization of policy network can speed up the convergence process. Simulation results verify the effectiveness and superiority of our proposed centralized and distributed algorithms in terms of performance.</p
Special issue: Process safety in times of a pandemic
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Safety and Security Scienc
Molecular dynamics simulation of the interfacial thermal resistance between phosphorene and silicon substrate
No full textPhosphorene is a recently discovered member of the two-dimensional (2D) monolayer materials, which has been reported to exhibit unique characteristics on mechanical and thermal properties. This study is the first time to show the exceptional thermal conductance between phosphorene and crystalline silicon substrate through classical molecular dynamics (MD) simulations. MD simulations revealed that under conventional conditions, the interfacial thermal resistance (R) between phosphorene and silicon is very low and independent on the thickness (h) of silicon substrate when h is larger than 3.12 nm. It was also found that R decreases remarkably with the increases in system temperature (Tie) and contact strength (χ). To further explicitly display the superiority of phosphorene on interfacial heat transfer, R of other two popular 2D monolayer materials, i.e., graphene and silicene, were calculated for comparison. The comparisons revealed that R of phosphorene shows two distinct advantages over graphene and silicene. On one hand, within the studied ranges of Tie and χ, R between phosphorene and silicon substrate is about quarter of that between graphene and silicon substrate, which proves that phosphorene is really a high-performance 2D monolayer material for interfacial heat transfer. On the other hand, with the increases in Tie and χ, R between phosphorene and silicon substrate decreases more sharply than that between silicene and silicon substrate, indicating that phosphorene is more sensitive to environmental variations
Distributed human computation framework for linked data co-reference resolution
No full textDistributed Human Computation (DHC) is a technique used to solve computational problems by incorporating the collaborative effort of a large number of humans. It is also a solution to AI-complete problems such as natural language processing. The Semantic Web with its root in AI is envisioned to be a decentralised world-wide information space for sharing machine-readable data with minimal integration costs. There are many research problems in the Semantic Web that are considered as AI-complete problems. An example is co-reference resolution, which involves determining whether different URIs refer to the same entity. This is considered to be a significant hurdle to overcome in the realisation of large-scale Semantic Web applications. In this paper, we propose a framework for building a DHC system on top of the Linked Data Cloud to solve various computational problems. To demonstrate the concept, we are focusing on handling the co-reference resolution in the Semantic Web when integrating distributed datasets. The traditional way to solve this problem is to design machine-learning algorithms. However, they are often computationally expensive, error-prone and do not scale. We designed a DHC system named iamResearcher, which solves the scientific publication author identity co-reference problem when integrating distributed bibliographic datasets. In our system, we aggregated 6 million bibliographic data from various publication repositories. Users can sign up to the system to audit and align their own publications, thus solving the co-reference problem in a distributed manner. The aggregated results are published to the Linked Data Cloud
Intersystem soft handover for converged DVB-H and UMTS networks
No full textDigital video broadcasting for handhelds (DVB-H) is the standard for broadcasting Internet Protocol (IP) data services to mobile portable devices. To provide interactive services for DVB-H, the Universal Mobile Telecommunications System (UMTS) can be used as a terrestrial interaction channel for the unidirectional DVB-H network. The converged DVB-H and UMTS network can be used to address the congestion problems due to the limited multimedia channel accesses of the UMTS network. In the converged network, intersystem soft handover between DVB-H and UMTS is needed for an optimum radio resource allocation, which reduces network operation cost while providing the required quality of service. This paper deals with the intersystem soft handover between DVB-H and UMTS in such a converged network. The converged network structure is presented. A novel soft handover scheme is proposed and evaluated. After considering the network operation cost, the performance tradeoff between the network quality of service and the network operation cost for the intersystem soft handover in the converged network is modeled using a stochastic tree and analyzed using a numerical simulation. The results show that the proposed algorithm is feasible and has the potential to be used for implementation in the real environment
Beyond interfaces: A usability study of Chinese journal databases
No full textA presentation at the Council on East Asian Libraries (CEAL) annual meeting in Boston, MA on March 21, 2007
- …
