50 research outputs found
Van Warder naar Zwitserland: Op het spoor van de fluit
No full textEen dwarsfluit uit het begin van de zestiende eeuw. Die doken archeologen op uit een scheepswrak in het Markermeer. Alleen dat al is een extreem zeldzame gebeurtenis. Maar van wie kan die fluit geweest zijn? Een stuk papier bij het mondgat zet een gevarieerd team van deskundigen op een spoor dat warmer en warmer wordtLab Geoscience and EngineeringGeo-engineerin
Internet telephony: technology, costs and strategy for cable operators
No full textInternet telephony is real-time voice communication over a packet-switched network using Internet protocols. This is in contrast to traditional telephony that occurs solely over a circuit-switched network, such as Public Switched Telephone Network (PSTN). Each call of traditional telephony on a circuit-switched network has a fixed amount of bandwidth with a guaranteed Quality of Service (QoS). Regardless of whether the parties are speaking or not, they are using the allocated bandwidth until the call ends. Any unused bandwidth due to a pause in conversation can not be allocated to another call. On the other hand, packet-switched network has been developed for applications where a variable QoS is tolerable. Internet being a packet-switched network does not guarantee QoS, but this has not prevented Internet telephony in becoming popular. Internet telephony as compared to traditional telephony requires all information to be broken into packets that are individually routed over the network. Hence, if there is a pause in the conversation of an Internet telephony call, no packets are generated and packets of other users can be transmitted. This report addresses the issue of providing Internet telephony over the cable network to cable subscribers. The technology, costs and strategy required for cable operators to offer this service are discussed. By upgrading the cable network from one-way transmission of video and radio signals to two-way transmission of video, data and radio signals, the cable network is made suitable for this service. By combining two technologies: Internet telephony technology and modern cable technology, a Technology Reference Model is developed for this service on the cable television (CATV) networks. A cost model is developed based on the Technology Reference Model. From the cost model, the cost of providing this service on the cable television networks is roughly determined. Cost analysis performed proves that the subscriber cost is the dominant cost among all the components in the cost model. Current policy and regulating issues surrounding Internet telephony are also presented. Interconnection, Pricing and Marketing Strategies, which will help cable operators to survive on the Internet telephony market, if they decide to enter into this market, are also addressed.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Social Marginalization: A Scoping Review Protocol
No full textThis is the preregistration of the protocol for a scoping review on social marginalization
Adaptive intent recognition for control of an active robotic lower limb prosthesis
No full textPassive and semi-active knee prostheses demand up to 60% more metabolic energy from transfemoral amputees compared to able-bodied subjects during walking. In addition to this, amputees have trouble with ambulation on stairs, slopes as well as transitioning from stand to sit and vice versa. This limitation is attributed to the nature of current solutions to either store or dissipate energy whereas an able-bodied subject generates energy in the knee during these locomotion modes. Active knee prostheses are able to generate net power. This has resulted in newly developed controllers for various locomotion modes such as ambulation on stairs/slopes and sitting but the question remains how to seamlessly transition between all of them. Intent recognition techniques are described in literature to classify real-time data to switch between these modespecific controllers. In intent recognition, machine learning methods are commonly proposed to differentiate between different locomotionmodes using on-board sensor data. An effective method for real-time classification of standing, walking and sitting are Linear discriminant analysis combined with Gaussian mixture models as these methods are computationally efficient. In the first part of this thesis, a combined model using the Linear discriminant analysis and Gaussian mixture model, is reproduced using an active knee prosthesis from Reboocon Bionics. Current intent recognition systems, however, still require user-specific training data, limiting commercialisation. Extending current research, updating a pre-trained Gaussian mixture model in real-time is researched in a simulated real-time environment. This "adaptive" approach is researched in the second part of this thesis together with adaptivity parameters such as the amount of training data, the type of training data and the learning rate. The adaptive classifier is compared to the initial classifier and the current rule-based system available in the prosthesis to see if it is able to improve its classification accuracy over time. With an optimal set of parameters, the adaptive system was able to increase its classification accuracy over time with a bad initial classifier (trained on a different subject) gaining an increase of approx. 5%. Moreover, the system was able to transcend the current commercial rule-based system by detecting mode-changes that the rule-based systemoverlooked.RebooconBiomedical Engineerin
Locomotion Intent Recognition Using a Multimodal Sensor Fusion Approach
No full textAn estimated 40,000 people have trauma related above knee amputations in the United States alone. A transfemoral prosthesis is an artificial limb that replaces the amputated limb. Although trauma related amputations are going down annually, there is still the need for prostheses that are capable of restoring normal biological knee function. Active micro-processor knees are a type of transfemoral prosthesis that can supply energy for activities therefore making many activities of daily living like chair and stair negotiation possible, how-ever these devices are not yet commercially available as it does not yet meet the requirement of robust and unambiguous mode switching. One aspect of active microprocessor knees that needs improvement is the intent recognition system that perceives the intent of the user. A novel hybrid intent recognition algorithm based on machine learning using solely mechanical signals was developed and tested in this thesis. The algorithm is capable of distinguishing be-tween the modes Standing, Sitting, Walking, Ramp Ascent, Ramp Descent, Stair Ascent and Stair Descent. The analysis of the algorithm was done on an open source healthy subject gait data set containing a total of 476 trials. The analysis involved determining recognition error rates and decision times for a novel subject’s data. The proposed algorithm fuses data from Inertial Measurement Units(IMUs) worn on the shank and knee joint encoders to make the decisions. The algorithm can achieve an overall error rate of 14.28%, the error rate reduces to 2.62% when grouping the Ramp Ascent and Ramp Descent together with the Walking mode.Decision times are, on average 9.59ms after a transition for critical transitions between stair modes and walking. For transitions between less critical modes like sitting and standing, decisions are taken with a maximum delay of 610ms. All transitions were successfully detected in 229 out of the 476 trials. The remaining trials had misclassifications due to improper labeling and variations in gait speed among the users. A preliminary analysis into adding ground reaction forces and moments indicates that the error rates can be decreased with it’s use. The research concludes that a hybrid classifier in which ramp walking is treated as level ground walking is a good starting point for implementing on the transfemoral prosthesis.Mechanical Engineering | Biomechanical Design - BioRobotic
Indispensability and Opposition to Separatist Movements
No full textThis preregistration gives information about our study on the role of indispensability in opposition to Frexit among Dutch people. We want to examine whether perceived functional indispensability and perceived identity indispensability of a group that wants to separate from the larger whole is associated with a stronger opposition to separation (attitudes) and indirectly to stronger willingness to engage in collective action against separation (protest behavior). We will test this in the context of a possible Frexit - the departure of France from the European Union, and from the perspective of the Dutch people
With or without you? Perceived indispensability and opposition to separatist movements
No full textPositive intergroup relations are shown to be related to the perception that, despite mutual differences, all subgroups are indispensable for the identity or functioning of the overall society. Yet, so far, the research on identity and functional indispensability is concerned with minorities that strive for inclusion in the larger nation-state (e.g., immigrants). In contrast, we examined the roles of identity and functional indispensability in the context of separatist movements. In Study 1 (N = 397), we found that Han Chinese' perceptions of identity and functional indispensability of Tibetans and Uyghurs were associated with higher willingness to engage in collective action against these groups' separatist movements. We replicated these findings in Study 2a and 2b among a diverse sample of the Dutch concerning the Brexit (N = 378) and Frexit (N = 279). In experimental Study 3, again among the Dutch (N = 405), we found that indispensability increased anti-Frexit action intentions. We conclude that, in the context of separatist movements, perceived indispensability can make attitudes towards separatist movements more antagonistic. The findings contribute to a better understanding of intergroup relations when subgroups' interests clash
Indispensability and Opposition to Separatist Movements
No full textIn this project you will find data and code of all studies in the paper and the preregistration of the experiment
Biofunctionalization of selective laser melted porous titanium using silver and zinc nanoparticles to prevent infections by antibiotic-resistant bacteria
No full textAntibiotic-resistant bacteria are frequently involved in implant-associated infections (IAIs), making the treatment of these infections even more challenging. Therefore, multifunctional implant surfaces that simultaneously possess antibacterial activity and induce osseointegration are highly desired in order to prevent IAIs. The incorporation of multiple inorganic antibacterial agents onto the implant surface may aid in generating synergistic antibacterial behavior against a wide microbial spectrum while reducing the occurrence of bacterial resistance. In this study, porous titanium implants synthesized by selective laser melting (SLM) were biofunctionalized with plasma electrolytic oxidation (PEO) using electrolytes based on Ca/P species as well as silver and zinc nanoparticles in ratios from 0 to 100% that were tightly embedded into the growing titanium oxide layer. After the surface bio-functionalization process, silver and zinc ions were released from the implant surfaces for at least 28 days resulting in antibacterial leaching activity against methicillin-resistant Staphylococcus aureus (MRSA). Furthermore, the biofunctionalized implants generated reactive oxygen species, thereby contributing to antibacterial contact-killing. While implant surfaces containing up to 75% silver and 25% zinc nanoparticles fully eradicated both adherent and planktonic bacteria in vitro as well as in an ex vivo experiment performed using murine femora, solely zinc-bearing surfaces did not. The minimum inhibitory and bactericidal concentrations determined for different combinations of both types of ions confirmed the presence of a strong synergistic antibacterial behavior, which could be exploited to reduce the amount of required silver ions by two orders of magnitude (i.e., 120 folds). At the same time, the zinc bearing surfaces enhanced the metabolic activity of pre-osteoblasts after 3, 7, and 11 days. Altogether, implant biofunctionalization by PEO with silver and zinc nanoparticles is a fruitful strategy for the synthesis of multifunctional surfaces on orthopedic implants and the prevention of IAIs caused by antibiotic-resistant bacteria. Statement of Significance: Implant-associated infections are becoming increasingly challenging to treat due to growing antibiotic resistance against antibiotics. Here, we propose an alternative approach where silver and zinc nanoparticles are simultaneously used for the biofunctionalization of rationally designed additively manufactured porous titanium. This combination of porous design and tailored surface treatment allows us to reduce the amount of required silver nanoparticles by two orders of magnitude, fully eradicate antibiotic-resistant bacteria, and enhance the osteogenic behavior of pre-osteoblasts. We demonstrate that the resulting implants display antibacterial activity in vitro and ex vivo against methicillin-resistant Staphylococcus aureus.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.Biomaterials & Tissue Biomechanic
