TU Delft Repository

    Three Phase Piezoelectric Composites for Energy harvesting applications

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    Piezoelectric materials have found application in wide range of devices from accelerometers to energy harvesters. They have proven their potential and versatility in aerospace, automotive, electronics and biomedical industry. Piezoelectric ceramics are not suitable for energy harvesting applications due to its brittleness and low strain levels, although having a high piezoelectric charge constant (d33). The polymer based piezoelectric composites offers high flexibility with low dielectric constant, hence having potential application in energy harvesting systems. Currently quasi-structured and fiber based piezoelectric composites offer the highest piezoelectric properties having the required flexibility for energy harvesting application. The polling processes of these composites though, are not so efficient due to the dielectric mismatch between the ceramic filer and surrounding polymer matrix. This leads to low piezoelectric charge constant than theoretically possible. To avoid this dielectric mismatch, dielectric constant cermic filler is added to get the required chain like particle structuring. The decrease in dielectric mismatch would lead to better poling due to increase in the active electric field experienced by the ceramic filler. The work here majorly focuses on development of a 3 phase piezoelectric composites having two different types of ceramic filers. Barium Titanate (BT) nanoparticles were added into a two phase Lead Zirconate Titanate (PZT)/Epoxy composite and were characterized to evaluate piezoelectric properties and particle structuring. The particle size effects of BT nanoparticles were also investigated

    AIS data analysis for the impacts of wind and current on ship behavior in straight waterways

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    Due to the increasing ship traffic flow in ports, maritime traffic safety has attracted much atten-tion. In addition to traffic flow, the ship safety in restricted waters is influenced by external navigational fac-tors (visibility, wind and current), encounter situations and human factors on board. In this paper, we investi-gate the effect of navigational factors on ship behavior. The raw AIS data and locally measured visibility, wind, and current data in the port of Rotterdam are collected to investigate the impacts of wind and current on ship speed and path (distance to the starboard bank). The results reveal that the wind mainly affects the paths of ships by the force of cross-wind, while the current impacts the speed over ground of ships when the current is with or against the heading of ship. The impacts on different sizes of ships are different as well. The port side wind has a larger impact on small ships than on large ships, while the impact of starboard side wind is larger for large ships than for small ships. The impact of current on the speed over ground is larger on small ships than large ships, and least on medium ships. The analysis results could assist the port authority in pre-dicting ship traffic in different situations, and be used in the development of a new maritime traffic model to simulate ship behavior while considering the external navigational factors.Rivers, Ports, Waterways and Dredging EngineeringTransport and PlanningTransport and Plannin

    Application of Bayesian Networks to Estimate River Discharges in Ecuador

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    Ecuadorian cities that are located near banks of rivers or near the sea and that have low elevation respect to sea level are more exposed to floods (MIDUVI, 2015). This research will focus on the study of the Guayas river basin, which encloses the city of Guayaquil, the most populated city of the country with 2’578.201 inhabitants where 993.123 inhabitants live in flood-prone areas (INEC, 2010) that can be translated as the 46.2% of the population of the city. This research aims to apply the Bayesian Network model proposed by Paprotny & Morales-Nápoles (2017) in the Guayas river basin, and to observe how this model performs in catchments like the ones in Ecuador by comparing it to the previous application in Europe. Other applications of the model (with their corresponding adjustments) were performed in the US and in Colombia, therefore this study can be used as a first step in order to develop a model for Ecuador

    Expeditie Rotterdam: of de ontdekkingstocht naar de verborgen Wederopbouwstad

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    The aim of this exploration is to reinterpretate and revitalise underused areas in the modernist urban fabric of Rotterdam. Since Rotterdam was bombed during the Second World War, a whole new modernist city could arise. The Reconstruction plan can still be seen as a manifesto of modern architecture and urbanism. Main focal points were the separation of functions, space for traffic and the suppression of residential functions. The organization of traffic and the aim of separation of functions are in shaping the plan, with main traffic routes, pedestrian shopping streets, mixed traffic/shopping streets and expedition courtyards and streets. The main traffic routes were executed as boulevards, with separate traffic lanes and wide sidewalks.In the Reconstruction plan of 1946 by Witteveen’s successor Van Traa, the concept of expedition courtyards have been translated in a purely functional manner. The plan is clearly hierarchically set up with main streets, an alley and an expedition street accessible through an entrance gate. Expedition streets and courtyards form an important part of Rotterdam’s reconstruction city. In the centre of Rotterdam they are found in all sorts of sizes. The expedition streets were once the system for supply of shops and companies, whereas they went through change in use over time and this development of the expedition courtyards has resulted in numerous unused spaces.The inner city of Rotterdam is on a turning point of becoming a more residential place. Converting underused spaces into defined places. Shaping the public space can be conceived as an important contrast be¬tween the traditional European city and the modern city. In the traditional city, the facades of the buildings define the boundaries of the public space and thus become a series of cavities in the urban fabric. While the public space in the modern city becomes an open space with detached objects, modernist buildings. This design proposes a structure in which the public, semi-public, collective and private spaces are shaped. This structure is related to the surrounding modernist building and creates various places with different degrees of publicness. The following research questions are formulated: How could the identity of the Rotterdam perimeter expedition block Sint-Janshof be updated in a sustainable way, fulfilling the current demands of densification and qualitative public space? What are the spatial and functional characteristic qualities of the Reconstruction period? What is the identity of the expedition building block and what are the potential values of the identity of the Sint-Janshof? The hypothesis is formulated that a sustainable reinvention is a critical revision of the architectural typology confronted with contemporary programmes and conditions. This approach guarantees the architectural and urban identity will live through. This design speculates on the future of the Rotterdam expedition building block. The design proposal engages in a retroactive densification of the inner city. A typological study of the expedition streets as urban artefacts has been made. <br/

    Spatial Development in a Post-Capitalistic Economy: A Contingency Plan for Leipzig and its Region

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    This research and design thesis addresses the transition towards a post-capitalistic economy and explores a corresponding spatial development perspective for Leipzig (Germany) and its hinterland. The starting point of this project is the theoretical assumption that there is a mutual relation between spatial and economic development. From there, it builds up the hypothesis that current neoliberal capitalism will fail and explores a spatial strategy, which prepares Leipzig and its hinterland for this event. At its base is the establishment of a self-sufficient regional agriculture and the spatial decentralization of the region. Sketching post-capitalistic socio-economic relations, in which the common good and not individual profits are the goal, the project explores the transformation of various example places in Leipzig and the region. In the end, this thesis promotes a new form of spatial organization, in which the city and its hinterland form one socio-economic and political unit.Architecture, Urbanism and Building Science

    Entrepreneurial orientation and firm performance: the mediating role of functional performances

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    Purpose: Earlier studies have generally shown a positive relationship between entrepreneurial orientation (EO) and the overall performance of the firm. The purpose of this paper is to understand in more detail how EO influences firm performance. It adds to the literature by distinguishing performances of different functions in a firm and by exploring how the dimensions of EO influence these functional performances and, in turn, overall firm performance. Design/methodology/approach: This study examined the relationship between three dimensions of EO (innovativeness, proactiveness, risk-taking), three types of functional performances of firms (R&amp;D performance, production performance, marketing and sales performance) and the overall performance of firms. The data are collected from 279 high-tech small-to-medium-sized enterprises (SMEs) using a postal survey. The proposed hypotheses are tested using structural equation modeling (SEM). Findings: The results indicate that the dimensions of (EO) are related in different ways to the performance of functions in a firm. A positive relationship is observed between innovativeness and R&amp;D performance and between proactiveness and marketing and sales performance. A negative relationship exists between risk-taking and production performance. The results also show a sequential positive relationship from R&amp;D via production and marketing and sales to overall performance of firms. Therefore, it is concluded that the R&amp;D, production and marketing and sales functions reinforce each other in a logic order and are complementary in their effect on overall firm performance. Practical implications: The results imply that the three functions, R&amp;D, production and marketing and sales, in a firm play different roles, both in the firm’s EO and in their contribution to overall performance. Managers can use the findings to monitor and influence the performance of different functions in a firm to increase overall firm performance. Originality/value: The first contribution of this study is that it unravels (i) which dimensions of EO have an effect on the performance of separate functions in a firm, indicating that functions contribute in different ways to entrepreneurial orientation of the firm. A second contribution is assessing how the performance of these functions influence the firm’s overall performance. This paper fills a gap in the literature by exploring internal firm variables mediating the relationship between EO and overall firm performance and contributes to the discussion on the contradictory results regarding the relationship between risk-taking and firm performance.Transport and LogisticsEconomics of Technology and Innovatio

    Noise correlations and template matching on neural recordings

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    Spike sorting is the gold standard algorithm to detect and classify neural spikes in extracellular electrophysiological data. The classical spike sorting algorithm is, however, not scalable to process thousands of neurons, and not fast enough to be applied on real time. Alternatively other algorithms have been implemented that are not only scalable to thousands of neurons but also faster in the classification task. In this work we focus on one of these algorithms: the Bayes Optimal Template Matching (BOTM). The BOTM presents the advantage of using a template matching procedure to solve, at the same time, the spike detection and classification. Within the BOTM algorithm we need to compute the noise covariance matrix. This matrix contains spatial, temporal, and spatio-temporal noise correlations among the electrodes used for recording the data, and it is important since its inverse works as a spatio-temporal whitening transformation. However, the matrix becomes too large to be computed or handled when large number of electrodes are used. In this work we focused on how to compute the noise covariance matrix when large number of electrodes are used for recording. First we separated its structure in two simpler matrices: one containing the spatial noise correlations, and one containing the temporal noise correlations among electrodes. We computed their inverses and applied three different whitening: spatial whitening, temporal whitening, and spatial and temporal whitening, one after each other. We evaluated the BOTM's performance under the different whitening approaches. Additionally, we took into account a new covariance matrix containing signal correlations, i.e. considering the whole signal, and not only the noise when computing correlations among the electrodes. We also evaluated the BOTM's performance for the signal covariance matrix. We were able to demonstrate that the spatio-temporal noise covariance matrix can be split in two simpler matrices: a spatial noise covariance matrix and a temporal noise covariance matrix. And that their inverses work as a spatial and as a temporal whitening transformations respectively. We also discuss about a problem we found within the toy data created for our measures: high-frequency components on inserted footprints. This problem can affect not only the BOTM algorithm, but also any other template matching based algorithm used. Finally, we concluded that the BOTM could not need any whitening transformation thanks to the redundancy on the recorded data when a large number of electrodes is used

    High-order-helix point spread functions for monocular three-dimensional imaging with superior aberration robustness

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    An approach for designing purely refractive optical elements that generate engineered, multi-order-helix point spread functions (PSFs) with large peak separation for passive, optical depth measurement is presented. The influence of aberrations on the PSF’s rotation angle, which limits the depth retrieval accuracy, is studied numerically and analytically. It appears that only Zernike modes with an azimuthal index that is an integer multiple of the number of PSF peaks introduce PSF rotation, and hence a depth estimation errors. This implies that high-order-helix designs have superior robustness with respect to aberrations. This is experimentally demonstrated by imaging an extended scene in the presence of severe system aberrations using novel, cost-e cient phase elements based on UV-replication on the wafer-scale.ImPhys/Imaging Physic

    Developing an explanatory model for the firm investments in submarine optic telecommunication cables: A case study of the investment behavior to the Netherlands and Spain

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    Interconnection with the internet is important for the business climate in a country. Therefore it is relevant for governments to understand the factors that influence the investments in submarine communication cables. However there is no singly comprehensive theory that explains the investments in this industry. Therefore the research question in this paper is: What factors explain the investment decisions in submarine communication cables? A pluralistic research framework is create based on three theories; resource-based view, transaction cost economics and transaction cost regulation. Analysis with help of this framework results in a list of factors that can explain the investments in submarine cables. These factors are used in a comparative qualitative case study between the Netherlands and Spain. In this way a first step is made to develop and validate an explanatory model for firm investment behaviour in submarine communication cables. Outcome of the analysis show that content and application providers and telecom operators have different investment strategies. Content and application providers invest in diverse connections between their datacentres as part of a vertical integration. Telecom providers connect regions which have high data transit demands

    Lost in a Nursing Home

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    Many people with senile dementia living in a home for the elderly or a nursing home have problems with finding their way. To a large extent these problems are caused by cognitive and perceptual impairments. Another important factor is the influence of the built environ-ment. The design of many buildings and outdoor spaces provides insufficient environmental support for route learning, wayfinding and topographical memory. A review of the literature on spatial orientation shows that many guidelines can be provided to reduce disorientation. However, little empirical research has been done into the effects of these guidelines.Accepted manuscriptReal Estate Managemen
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