101 research outputs found
Kademuur m.b.v. diepwanden: Kostenvergelijking met conventionele methoden
No full textBij de kademuren die de laatste jaren in de diepere havens van Nederland gemaakt zijn, wordt de grand gekeerd door combiwanden. Dit is voor de hier gerdende grondopbouw en belastingen de meest geschikte constructievorm, deze wordt hier als 'conventionele methode' gezien. Een alternatieve manier om de grand te keren is de diepwand. Deze techniek wordt in Nederland relatief weinig gebruikt, voor kademuren is deze in diepe havens zelfs nog nooit toegepast. In de havens van de landen om ons heen, zoals Le Havre, Antwerpen en Hamburg wordt echter wel regelmatig voor de diepwand gekozen. Bij een toenemende havendiepte moeten de kerende wanden zwaarder en langer worden, wat bij de combiwanden tot problemen bij het heien leidt. Voor diepwanden geldt dat een gratere doorsnede of diepte nauwelijks extra moeilijkheden met zich meebrengt, zodat verwacht kan worden dat bij extreme omstandigheden de diepwand goedkoper is. In dit afstudeerpraject is voor de Amazonehaven op de Maasvrakte onderzocht in hoeverre dit, voor de havendiepten die in de nabije toekomst nodig zijn, kan leiden tot constructies waarbij de diepwand het goedkopere alternatief oplevert. Verder zijn redenen aangedragen waarom in de ons omringende landen de kademuren met diepwanden wel goedkoper kunnen zijn dan met combiwanden. Om de eerste doelstelling (Kan de diepwand voor de Amazonehaven in de nabije toekomst goedkoper zijn?) te bewerkstelligen zijn allereerst de conventionele typen en grondopbouw gemodelleerd en berekend (bodemniveau NAP. -18.50 m). De gegevens die hieruit volgen (veiligheden, deformaties) dienen als leidraad voor de ontwerpen waarbij de grond door diepwanden gekeerd wordt. Voor de diepwand-varianten zijn alternatieven opgesteld, waarvan de 6 meest reele vormen zijn gedimensioneerd. Bij de berekeningen van de eerste varianten zijn analyses gemaakt van het gedrag van de wanden bij verschillende inklemmingen, wandstijfheden en ankerstijfheden. De uitkomsten hiervan zijn op de overige alternatieven toegepast zodat het ontwerpen sneller kon geschieden. Uit de analyses blijkt dat de stijfheid van de verankering weinig invloed heeft op de optredende ankerkrachten en momenten in de wand, maar dat de verhouding van de stijfheid van de wand en de ankers wel de vorm van deformeren be;·nvloedt. Aangezien de deformaties geen maatgevend criterium vormen is deze invloed van klein belang. Verder bleek dat de mate van inklemming in de grond weliswaar een grate invloed heeft op het momentverloop in de wand maar dat per situatie (optredende maximale momenten en gekozen wanddikte) de optimale verhouding tussen de te produceren hoeveelheid diepwand en benodigde wapening moet worden gezocht. Uit de begrotingen van de gedimensioneerde alternatieven blijkt dat MV-palen aanzienlijk efficienter dat ankerstaven met -schermen zijn. Tevens is dUidelijk geworden dat varianten met een ontlastkoker boven de diepwanden verreweg de goedkoopste alternatieven zijn. Na de keuze van het ontwerp is gepoogd de kosten van dit alternatief te verlagen door de wand stijf te verbinden met de koker. Door deze 'verende inklemming' wordt het moment in het veld van de wand gereduceerd, voor het beschouwde bodemniveau (NAP. -18.50 m) is dit echter niet effectief. De extra wapening door het inklemmingsmoment is meer dan de vermindering van de wapening door de reductie van het veldmoment. Het gekozen diepwand-concept wordt vervolgens ook voor diepere havens gedimensioneerd, namelijk met een bodem op NAP. -21.50 m en NAP. -24.50 m. Voor de combiwand-varianten is dit eveneens gedaan om een vergelijking mogelijk te maken. De berekeningen van de diepere havens zijn voor beide wand-typen ook uitgevoerd met een hogere ontlastkoker. De duurdere koker maakt een kortere en minder zwaar belaste wand mogelijk, waardoor in sommige gevallen de totale kosten dalen.Hydraulic EngineeringCivil Engineering and Geoscience
Design of an adjustable gravity equilibrator using torsion bars
No full textStatic balancing is a useful concept to reduce operating effort in mechanisms. A statically balanced system which is designed to counterbalance a mass, is referred to as a gravity equilibrator. The potential energy in a gravity equilibrator is constant, which in most of the times is achieved by mechanical springs. Often helical springs are used, although these springs take a lot of space within the workspace of the mechanism. This paper presents the design of an adjustable gravity equilibrator using torsion bars, which saves space in the working area. Static balancing is achieved with a non-constant transmission (NCT). A new NCT design, and a general method to calculate the design parameters are presented. The stiffness of the torsion bars can be adapted by changing the active length. In this way it is possible to balance different masses with the same system.BMDBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Ambient care- interaction index: Designing caring relationships through ambient interfaces
No full textDesign for product care focusses on stimulating users to prevent early obsolescence of products, which is particularly valuable for electronic household products. One product care strategy is to create attachment and therefore care motivation by strengthening the product-user relationship.Currently, these strategies lack practicable design directions that designers can use easily, which is why little innovations occur. I propose to stimulate product care behaviour by improving the rela/onship between products and users through ambient interface implementa/on in design.Ambient interfaces embrace communication with a playful, unobtrusive, intuitive character and gradual presenta/on. The goal of this project was to create a tool that summarises the characteristics of ambient interfaces. This became the ‘Ambient Care-Interaction Index’, an online tool that contains informative text and inspiring examples. It can be used to learn about ambient interfaces and inspire designers to use the qualities to (in)directly stimulate care.Design for Interactio
Experimental study of fluid flow in the bifurcation of a patient specific carotid artery, with severe stenosis: Comparing PIV, PC-MRI and CFD
No full textMagnetic Drug Targeting is a relatively new technique whereby chemotherapeutic agents are attached to magnetic particles that will be injected in an artery upstream of an affected area. By exerting an external magnetic field an internal magnetic field gradient will be induced that will entrap the particles that contain the drugs in the affected region. By doing so only the affected region will be treated, leaving the rest of the body free from drugs and therefore the side effects are reduced as the total dose of the drugs is much lower than when more conventional procedures are used. Clinical trials have been performed using this technique on various types of cancer with promising results.Transport PhenomenaChemical EngineeringApplied Science
Levels of joint attention in an interaction between humans and an animal-like social robot
No full textJoint attention is the shared focus multiple people can have on the same object and it is subconsciously used by humans every day. The simple act of verbally or non-verbally pointing out an object to one another, is a form of joint attention. Its use facilitates human cooperation, such as when someone needs to hand over an object to another person. When robots display those same joint attention behaviours, it could be useful in improving human-robot interactions and perhaps variably so in various levels of jointness.This research investigates the effects of these levels of jointness on the interactions between a human and a robot. This is done by investigating the effect on the person's task performance, the effect on their mental model of the robot, and the effect on their perception of the robot as its own entity with its own mind. To this end, this research defines four levels of joint attention and designs an experiment that makes use of these four levels of joint attention. To perform this experiment, a system capable of establishing joint attention has been developed. The system is divided into two parts; hardware and software tools & applications which have not been developed in this project but are used as is, and software which has been actively developed in this research.In this experiment, participants played three guessing games with a robot. Task performance was measured by the amount of time and hints needed, as well as the accuracy of a participant. The participant's mental model and perception of the robot as its own entity with its own mind were measured using a questionnaire.This research found no significant effect on the mental model towards the robot and the perception of whether the robot is its own entity with its own mind, although it is not concluded that such an effect cannot be found.This research did find a significant effect on task performance; higher levels of joint attention lead to faster task completion with less hints needed. But interestingly, this did not necessarily lead to a higher accuracy.The system introduced by this research was originally intended to help children with autism spectrum disorder learn joint attention skills, but due to ethical and time constraints, the system was tested with and the experiment was performed with adults instead. Due to ethical constraints, the participants in this research were not asked to disclose whether they had an autism spectrum disorder diagnosis or not. However, future research could replicate this study with the intended target group.Electrical Engineerin
Estimation of multiple components and parameters for quantitative MRI
No full textMagnetic Resonance Imaging (MRI) is a flexible medical imaging technique that facilitates measurement of a wide range of contrasts particularly in soft tissue (e.g. brain and heart). Conventionally, qualitative images are acquired in which certain physical tissue properties are emphasized such as the transverse and longitudinal relaxation times. Such images are frequently referred to as "weighted", i.e. T1-weighted. Quantitative MRI (qMRI) aims at measuring the underlying tissue parameters governing the contrast instead of yielding mere weighted images. These quantitative parameter estimations were proven to be more reproducible than conventional MR images and more sensitive to certain disease processes, enabling enhanced longitudinal comparisons within subjects as well as comparisons between subjects.MR Fingerprinting (MRF) is an example of such a quantitative technique. MRF uses a combination of transient state acquisitions with varying flip angle patterns, severe undersampling and advanced signal models to allow for fast qMRI acquisitions and accurate estimation of a wide range of parameters.While most qMRI methods assume a single tissue type per voxel, this is almost never a valid assumption. This assumption especially breaks down at tissue boundaries or when tissues consist of multiple, mixed compartments, such as water contained between myelin sheets in the brain, often called myelin water surrounded by extra-cellular water. The goal of this thesis is to develop enhanced methodology for quantitative MRI by extending traditional signal and image post-processing methods. Specifically, the focus is on MR Fingerprinting in combination with multi-component estimations, in which different compartments are included in a mixed estimation model. This is done to obtain more information from the acquired data and to improve quantification, therefore possibly obtain new clinical insights. Important steps towards clinical use are to enhance estimation accuracy and precision compared to previous methods and reduce the scan time. In this thesis the Sparsity Promoting Iterative Joint NNLS (SPIJN) algorithm is proposed for obtaining multi-component estimations from MRF data. This enabled sub-voxel, fractional estimation of signal components in a region of interest, without making a priori assumptions about tissues expected to be present. The main novelty of this method is to combine a non-negativity with a joint-sparsity constraint that limits the total number of tissues identified in a region of interest. As a result it became possible to obtain magnetization fraction maps of the white matter, gray matter, CSF and a component with shorter relaxation times related to myelin water.The repeatability of the proposed method is studied in 5 subjects that were scanned 8 times with one week in between the scans each time. Comparison of the obtained white matter, gray matter and CSF maps with segmentations from conventional methods shows high repeatability of the estimated relaxation times and more fine structures in the CSF magnetization fraction maps. Additionally, the proposed SPIJN algorithm was applied to data from a more conventional qMRI sequence, i.e. a multi-echo spin-echo sequence, to obtain estimations of the so-called myelin water fraction in the brain. The resulting images show significantly improved noise robustness compared to the standard multi-component analysis method, improving the usability.MRF scans can be acquired in a relatively short acquisition time of less than 30 seconds per slice, but this will still result in 15 minutes of total scan-time when full brain coverage is needed. A further reduction in acquisition time is desirable for clinical usage, in which every minute counts. Therefore, improved reconstruction methods for MRF data are proposed, especially tailored to multi-component estimations. In in vivo scans we showed the improved image quality enabled by the proposed methods.In another study, We applied the SPIJN algorithm to MRF brain scans from MS patients. In the results that we obtained we observe that white matter changes are reflected in a component with prolonged transverse relaxation times which is less pronounced in data of healthy controls. We hypothesize that the observed component reflects an increase in extra-cellular water and allows for early characterization of white matter damage. In a related project, an adaptation on the SPIJN algorithm was introduced that is more sensitive to small local changes. The adjusted algorithm is applied to imaging data of MS patients and it is shown that it can help to identify small cerebral lesions. MRF sequences can be chosen rather freely, to further reduce the scan time and reduce the estimation error these sequences can be optimized. A method is proposed in which parameter maps of the brain are used as reference upon which the MRF flip-angle series is optimized, taking into account the used undersampling trajectories. As a result undersampling errors, a major source of estimation errors, are effectively minimized. Finally, we investigated an adjusted simulation method of MRF sequences that is able to accurately model the effects of through-plane motion, which is a major source of errors in MRF scans. Such a model may support the development of new retrospective correction methods for this type of motion as it enables proper simulation of its effects. In summary, this thesis proposes new methods for multi-component reconstruction and analysis, sequence optimization and studying the effects of motion in MRF and further investigates the possibilities of multi-component MRF.ImPhys/Computational ImagingImPhys/Vos grou
Multimodal sensory pipeline for Interactive Robots
No full textInteractive Robotics aims to familiarize children with robotics, which they try to do with their RoboTutor. Towards this goal they developed a platform for controlling the robots but this platform only worked for the Nao robot and not for the Pepper robot.So for our bachelor end project we have been asked to build a connection tunnel between the server and the Nao and Pepper robots so that it is possible to also use the Pepper robot.As our research progressed however, it became more clear to us that in order to make a generic solution for both the robots the existing platform would not suffice. So instead of only creating the tunnel we also worked on a new server side solution.the solution we came up with, virtualization, was sure to solve the problems that caused the Pepper robot to be incompatible with the current platform. By running the server side processes for each robot inside their own environment using Docker containers we where able to create a generic solution for both robots. And with some custom code on the robots themselves, we could ensure that the robots would always connect to the server if they where connected to the Internet.TI380
Modeling, Computing and Classifying Topographic Area Features based on topologically non-structured Line Input Data
No full textSenescence during early differentiation reduced the chondrogenic differentiation capacity of mesenchymal progenitor cells
No full textIntroduction: Mesenchymal stromal/progenitor cells (MSCs) are promising for cartilage cell-based therapies due to their chondrogenic differentiation capacity. However, MSCs can become senescent during in vitro expansion, a state characterized by stable cell cycle arrest, metabolic alterations, and substantial changes in the gene expression and secretory profile of the cell. In this study, we aimed to investigate how senescence and the senescence-associated secretory phenotype (SASP) affect chondrogenic differentiation of MSCs.Methods: To study the effect of senescence, we exposed MSCs to gamma irradiation during expansion or during chondrogenic differentiation (the pellet culture). Western blot analysis was used to evaluate MSCs response to the chondrogenic inductor TGF-β.Results: When senescence was induced during expansion or at day 7 of chondrogenic differentiation, we observed a significant reduction in the cartilage matrix. Interestingly, when senescence was induced at day 14 of differentiation, chondrogenesis was not significantly altered. Moreover, exposing chondrogenic pellets to the medium conditioned by senescent pellets had no significant effect on the expression of anabolic or catabolic cartilage markers, suggesting a neglectable paracrine effect of senescence on cartilage generation in our model. Finally, we show that senescent MSCs showed lower phosphorylated SMAD2 levels after TGFβ1 stimulation than control MSCs.Conclusion: Overall, these results suggest that the occurrence of senescence in MSCs during expansion or early differentiation could be detrimental for cartilage tissue engineering.Biomaterials & Tissue Biomechanic
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