60 research outputs found
Publication of the NCF
No full textIn this report we give anoverview of parallel and vector computers which are currently available or will become available within a short time frame from vendors; no attempt is made to list all machines that are still in the research phase. The machines are described according to their architectural class. Shared and distributed memory SIMD and MIMD machines are discerned. The information about each machine is kept as compact as possible. Moreover, no attempt is made to quote prices as these are often even more elusive than the performance of a system. This document re ects the technical state of the supercomputer arena as accurately as possible. However, the author nor NCF take any responsibility for errors or mistakes in this document. We encourage anyone who has comments or remarks on the contents to inform us, so we can improve this work. NCF, the National Computing Facilities Foundation, supports and furthers the advancement of technical and scienti c research with and into advanced computing facilities and prepares for the Netherlands national supercomputing policy. Advanced computing facilities are multi-processor vectorcomputers, massively parallel computing systems of various architectures and concepts and advanced networking facilities
Structural modelling of ASR-affected concrete: The approach developed in the PAT-ASR project
No full textThe Alkali-Silica Reaction is a harmful reaction which can compromise the integrity and capacity of concrete structures. Due to its nature, a multiscale material model has been chosen to perform structural analyses. The model aims to couple the chemical and mechanical effects in order to characterize the affected concrete into the structures, which is considered as an evolving material. The model has been developed in the project Performance Assessment Tool for Alkali-Silica Reaction (PAT-ASR), which started in 2010 at Delft University of Technology and involves collaboration with the Norwegian Public Roads Administration.Structural EngineeringCivil Engineering and Geoscience
Compression After Multiple Low Velocity Impacts of NCF, 2D and 3D Woven Composites
No full textThis paper investigates the effect of the fabric architecture and the z-binding yarns on the compression after multiple impacts behavior of composites. Four fiber architectures are investigated: non-crimp fabric (NCF), 2D plain weave (2D-PW), 3D orthogonal plain (ORT-PW) and twill (ORT-TW) weave. The specimens were subjected to single and multiple low-velocity impacts at different locations with the same energy level (15 J). Non-destructive techniques including ultrasonic C-scanning, X-ray CT and Digital Image Correlation (DIC) are employed to quantitatively analyze and capture the Barely Visible Impact Damage (BVID) induced in the specimens. Although the absorbed energy was approximately the same, damage was the least in 3D woven architectures. In the case of compression after impact, 3D woven composites demonstrated a progressive damage behavior with the highest residual strength (∼92%) while 2D plain weave and NCF specimens showed suddenly catastrophic damage and the residual strength of ∼65% and ∼55% respectively
Investigation on lithium migration for treating alkali-silica reaction affected concrete
No full textAlkali-silica reaction (ASR) is one of the major deterioration mechanisms that affect numerous concrete structures worldwide. During the reaction, hydroxyl and alkali (sodium and potassium ) ions react with certain siliceous compounds in the aggregate, forming a hygroscopic gel. The gel absorbs water from the cement paste and swells, possibly leading to deleterious expansion and cracking of the structure. Once ASR is detected in existing structures, there are no treatments to stop it and prolong their service life. Lithium is known to alter the reaction, as it binds to the alkali-silica gel and the latter is no longer expansive. Indeed, the use of lithium-based admixtures has been acknowledged as a preventive measure for over 50 years. In existing structures, nevertheless, the use of admixtures is no longer possible and lithium ions need to be transported into the cementitious matrix. Amongst other transport mechanisms, such as capillary absorption and diffusion, ionic migration is the most effective. In order for ionic migration to occur, power should be supplied between two electrodes, immersed in electrolytes. The reinforcement bar is often used as cathode and, therefore, attracts cations, such as lithium ions. Pore solution works as catholyte. The anolyte, on the other hand, should be a lithium compound solution. Although several studies have been conducted on the use of electric field to drive lithium ions into concrete, so far, there is no agreement on the conclusions. It is necessary to fully understand lithium migration into concrete before developing a possible treatment against ASR. This paper presents preliminary results on the investigation of the influence of different lithium compounds used as anolyte during migration through experimental testing.Structural EngineeringCivil Engineering and Geoscience
Damage assessment of NCF, 2D and 3D woven composites under compression after multiple-impact using acoustic emission
No full textThis study is devoted to the damage characterization of Non-Crimp Fabric (NCF), 2D plain-woven (2D-PW) and 3D orthogonal plain-woven (ORT-PW) carbon/epoxy laminates, subjected to compression after multiple-impact loading, using Acoustic Emission (AE). The ultrasonic C-scan images showed that the interlaminar damage area induced by the single and 3-impact in ORT-PW architecture is 3 and 2 times smaller than NCF and 2D-PW architectures respectively. The impacted specimens were then subjected to the in-plane compression load. Two indices, one based on the mechanical response and another one based on the AE behavior of the laminates, were proposed to compare the performance of different architectures. These indices showed that the ORT-PW had the best performance among all the architectures. Finally, AE was used to distinguish the different damage mechanisms including: matrix cracking, intra and inter-yarn debonding, defected-fiber breakage, intact-fiber breakage and z-binder fiber breakage in the CAI tests of the architectures
Fatigue delamination behaviour of carbon fibre/epoxy composites interleaved with thermoplastic veils
No full textInterleaving thermoplastic veils has proved to enhance the interlaminar fracture toughness of carbon fibre/epoxy composites under static loading conditions. However, the fatigue delamination behaviour has yet to be investigated. Herein, meltable Polyamide-12 (PA) veils and non-meltable Polyphenylene-sulphide (PPS) veils were used for interlay toughening of unidirectional (UD) and non-crimp fabric (NCF) laminates that were manufactured using a prepreg process and resin transfer moulding process, respectively. The results of Mode-I fatigue delamination tests demonstrated a significant improvement in the fatigue life of the laminates due to interleaving. Additionally, the fatigue resistance energy has been maximumly increased by 143% and 190% for the UD and NCF laminates, respectively. The microscopy analysis revealed that the toughening mechanisms of thermoplastic veils were affected by the form of the thermoplastic veils in the laminates (melted or non-melted), the fracture mechanisms of the reference laminates and the adhesion/miscibility between the thermoplastic veils and the epoxy.Green 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.Structural Integrity & Composite
Mode-II fracture behaviour of aerospace-grade carbon fibre/epoxy composites interleaved with thermoplastic veils
No full textThermoplastic veils based on Polyethylene-terephthalate (PET), Polyphenylene-sulfide (PPS) and Polyamide-12 (PA) fibres (∼10μm in diameter) were used to interlay unidirectional (UD), non-crimp fabric (NCF) and 5-Harness satin weave (5H) carbon fibre laminates. The PET and PPS veils remained in a fibrous form and the PA veils melted during the laminate curing process. The results of an end-loaded split test demonstrated significant improvements in the mode-II fracture performance in all cases. In general, interlaying thermoplastic veils was most efficient for toughening the UD laminates, with reduced improvements observed for the 5H and NCF laminates, respectively. The main toughening mechanism of the intact PET and PPS veils was thermoplastic fibre bridging. The melted PA veils mainly improved the fracture toughness of the epoxy at the mid-plane. The different toughening mechanisms of the veils, combined with different fracture mechanisms between the UD, NCF and 5H laminates, resulted in significantly different toughening levels
Network Coded Flooding
No full textPrior work of network coding is mainly focusing on multicast traffic. In this thesis, we propose a new network coding based communication algorithm called Network Coded Flooding (NCF) which is related to network wide broadcast. This designed algorithm is an integration of network coding and one of the commonly used broadcasting techniques in wireless networks. In this thesis, we choose Probabilistic Flooding Algorithm (PFA) to integrate with network coding since it is a simple and robust flooding algorithm; it can be used in random wireless networks; it can work without any network topology information. As with PFA, NCF has a parameter of rebroadcast probability that controls packets’ rebroadcasts when receiving innovative packets. During the process of designing NCF, we also consider the issues how efficient network coding can achieve in a random wireless network even if the system process ability is low and available memory space is also limited. Therefore, the idea of generation is used and we also propose a specific generation management method in this thesis that is able to let system occupy little system memory space while good network performance (such as successful packet delivery, low packet delay and great energy savings) and relatively low system process complexity are guaranteed. NCF is a practical network coding based flooding algorithm that can be used in random wireless networks; that does not need any network topology information; that huge amount of data is allowed to be transmitted during the communication process; that the requirements of buffering and network process ability are at a relatively low level. We simulate such algorithm in Network Simulator 2 (NS2), and the simulation results show that NCF can realize the benefits in terms of reliability, working efficiency and energy saving if related parameters (such as generation size or maximum number of generations per node has ) of NCF are set accurately. In addition, reasonable trade-off schemes are also given through analyzing the obtained simulation results, which give general ideas about how to accurately use and change the related parameters of NCF in order to efficiently balance the relationship between network requirements and network performance.TelecommunicationsMechanical, Maritime and Materials Engineerin
Stitch modeling of non crimp fabric in forming simulations
No full text21st International ESAFORM Conference on Material Forming (ESAFORM), Univ Palermo, Palermo, ITALY, APR 23-25, 2018International audienceThe use of Non Crimp Fabric composite has increased during the last years due to cheaper cost of manufacturing and high mechanicals properties suitable for applications such as aeronautic, automotive and wind turbines. The main difference between Non Crimp Fabric (NCF) and textile reinforcement is the mean of manufacturing: where in textile fibers are woven, in NCF layers of unidirectional oriented fibers are assembled with a stitch. As a consequence, the stitch especially its geometry (stitch pattern) will have a major influence on the deformation of this type of reinforcement during forming process. Experimental campaigns on NCF samples compared to textile with the same fibers orientation have showed that the stitch affects the shear behavior of the reinforcement which is the main mode of deformation in the forming process. A description of the stitch has been implemented in a shell element for macro scale forming simulation as a first approach based on simple hypothesis. Further works are focus on the specific behavior of the stitch along the fabric and interaction with the fibers layers during shear deformation of the reinforcement and a method to implement the stitch in a more refined model of the fabric
Dynamic Estimation of Vital Signs with mm-wave FMCW Radar
No full textIn this paper, we propose a method for continuous monitoring of vital signs-in particular, respiration frequency-with a commercial mm-wave radar. The nearly constant frequency (NCF) model is adopted to represent chest displacement due to respiration and simulate radar response. Based on this model, an extended Kalman filter (EKF) based estimator is developed to track the breathing frequency of a person. The impact of dynamic model parameters is investigated in numerical simulation. The possibility to track breathing frequency with the proposed method is demonstrated by experimental data processing. Green 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.Microwave Sensing, Signals & System
- …
