231 research outputs found
Cement treated recycled crushed concrete and masonry aggregates for pavements
No full textThis research is focusing on the characterization of the mechanical and deformation properties of cement treated mixtures made of recycled concrete and masonry aggregates (CTMiGr) in relation to their mixture variables. An extensive laboratory investigation was carried out, in which the mechanical properties of CTMiGr and the deformation characteristics relevant to shrinkage crack susceptibility were evaluated. The main aim of this research is to develop models which allow the structural properties of CTMiGr to be estimated from its mixture composition. These models are then used to develop a mixture optimization tool for CTMiGr taking into account the requirements that have to be set to the material in structural pavement designs. To realize the research objective, firstly a series of tests were conducted on CTMiGr mixtures which varied in composition. The test program comprised of measuring compression, indirect tension and deformation properties of CTMiGr mixtures. The recycled construction and demolition materials used in this study were recycled masonry aggregate (RMA) and recycled concrete aggregate (RCA) which are used for unbound granular bases/sub-bases in the Netherlands. For a good understanding of the influence of the mixture variables on the properties of CTMiGr, four important mixture variables (ratio of amount of RMA to RCA by mass, cement content, degree of compaction and curing time) were selected to be taken into account in an elaborate experimental program. The experimental results gave insight into the influences of the different mixture variables on the structural properties of CTMiGr. They showed that the mechanical properties and deformation behavior of CTMiGr depend on the mixture proportioning of CTMiGr. It was possible to develop accurate models to estimate the structural properties of CTMiGr from the mixture variables. It is noteworthy that the RMA content in CTMiGr strongly determines its mechanical and deformation properties. Due to the presence of the low-strength RMA, failure of CTMiGr originates either through the RMA particles or in cracks and discontinuities in the internal structure (the matrix) or in the bonding layer between aggregates and matrix. This will depend on the mixture variables. Numerical work using a lattice model further demonstrated that if the tensile strength of RMA is higher than 1.0 MPa, its contribution to the strength of CTMiGr becomes less important. Finally, by implementing a comprehensive analysis of the structural properties of CTMiGr, some guidelines have been given for its mixture optimization. In this way the mixture design of CTMiGr can be optimally related to the characteristics of the designed pavement structure. If in a pavement the vertical compressive stresses at the top of the CTMiGr layer are low, crushing that might occur at the top of the CTMiGr layer is not an issue. In that case it is preferred to design the CTMiGr mixture by lowering the cement content, enhancing the degree of compaction and increasing the RMA content. On the other hand, when the vertical compressive stresses at the top of the CTMiGr layer are high, it is recommended to decrease the RMA content as well as to adjust the cement content and the degree of compaction. In all cases increasing the degree of compaction is beneficial.Structural EngineeringCivil Engineering and Geoscience
O(p6) extension of the large-NC partial wave dispersion relations
No full textAbstractContinuing our previous work [Z.H. Guo, J.J. Sanz-Cillero, H.Q. Zheng, JHEP 0706 (2007) 030], large-NC techniques and partial wave dispersion relations are used to discuss ππ scattering amplitudes. We get a set of predictions for O(p6) low-energy chiral perturbation theory couplings. They are provided in terms of the masses and decay widths of scalar and vector mesons
Some Aspects of Low Content Mono- and Hybrid-Fibre Reinforced Cementitious Composites
No full textCivil Engineering and Geoscience
Seeding Moral Responsibility in Ownership: How to Deal with Uncertain Risks of GMOs
No full textEthics & Philosophy of Technolog
Generation of design knowledge from the development of a theoretically idealized wind turbine
No full textWind turbines have significantly evolved in the last three decades, though they still need significant improvements to become more competitive in the energy market. These improvements depend to a great extent on the development of wind turbine technology. In this respect, the design of an idealized wind turbine may provide a potential quantitative insight into further improvement in the design of these systems. Therefore, the objective of this work is to generate design knowledge for wind turbine technology through the development of a theoretically idealized wind turbine. To do so, the concept and the design process of this idealized wind turbine are defined based on the general design theory. Moreover, a design case study is implemented as a demonstration of how the proposed design process is applied. The blade was selected for the case study because it is the most representative component of wind turbines and represents several challenges for the development of the future wind turbine industry. The results of this case study give insight into potential design knowledge generated from the proposed design process. Finally, some recommendations about how the designer can use this knowledge for the improvement of wind turbine design are given.Aerospace EngineeringSustainable Energy Technolog
Gone with the Wind: Conceiving of Moral Responsibility in the Case of GMO Contamination
Full text linkGenetically modified organisms are a technology now used with increasing frequency in agriculture. Genetically modified seeds have the special characteristic of being living artefacts that can reproduce and spread; thus it is difficult to control where they end up. In addition, genetically modified seeds may also bring about uncertainties for environmental and human health. Where they will go and what effect they will have is therefore very hard to predict: this creates a puzzle for regulators. In this paper, I use the problem of contamination to complicate my ascription of forward-looking moral responsibility to owners of genetically modified organisms. Indeed, how can owners act responsibly if they cannot know that contamination has occurred? Also, because contamination creates new and unintended ownership, it challenges the ascription of forward-looking moral responsibility based on ownership. From a broader perspective, the question this paper aims to answer is as follows: how can we ascribe forward-looking moral responsibility when the effects of the technologies in question are difficult to know or unknown? To solve this problem, I look at the epistemic conditions for moral responsibility and connect them to the normative notion of the social experiment. Indeed, examining conditions for morally responsible experimentation helps to define a range of actions and to establish the related epistemic virtues that owners should develop in order to act responsibly where genetically modified organisms are concerned.Values Technology and InnovationTechnology, Policy and Managemen
Transferring Moral Responsibility for Technological Hazards: The Case of GMOs in Agriculture
No full textThe use of genetically modified organisms in agriculture makes great promises of better seeds, but also raises many controversies about ownership of seeds and about potential hazards. I suggest that owners of these seeds bear the responsibility to do no harm in using these seeds. After defining the nature of this responsibility, this paper asks, if ownership entails moral responsibility, and ownership can be transferred, then how is moral responsibility transferred? Building on the literature on use plans, I suggest five conditions for a good transfer of moral responsibility for genetically modified seeds. I also look at the Monsanto Technology Use Guide and Technology/Stewardship Agreement, as an examplar of a use plan, to explore the extent to which these conditions are present. I conclude that use plans can play a role in the distribution and transfer of moral responsibility for technologies with high benefits and potential harmful uncertainties.</p
Onderzoek naar een bodemtransportmeter voor gebruik in het veld onder sheet flow conditie
No full textIn het kader van de afstudeerstudie aan de vakgroep Waterbouwkunde (studierichting Kustwaterbouwkunde) wordt er onderzoek gedaan naar een bodemtransportmeter onder sheet flow conditie voor gebruik in het veld. In Hoofdstuk 2 zal de rol van veldmetingen van zandtransport bij de behandeling van kustproblematiek aangestipt worden. Een kort overzicht van het literatuuronderzoek voor operationele meetmethoden en instrumenten is in Hoofdstuk 3 weergegeven. Een voor de hand liggend meetinstrument voor het meten van sheet flow in het veld is tot nu toe uit de literatuur nog niet te vinden. De eisen van het nieuwe te ontwikkelen meetinstrument, verder in dit rapport als sampler aangeduid, worden in Hoofdstuk 4 opgesteld. De beschrijving, aan de hand van een bestaand prototype van een dergelijke sampler is in Hoofdstuk 5 te vinden. Via twee wegen, theoretisch resp. experimenteel, is het geprobeerd om een dimensionering voor de sampler vast te leggen. Deze worden in Hoofdstuk 6 resp. Hoofdstuk 7 behandeld. In Hoofdstuk 8 komt een nieuw ontwerp voor de sampler aan de orde en het ijkingsproces voor deze nieuwe uitvoering wordt daarin aangegeven. De conclusies van het onderzoek worden in Hoofdstuk 9 samengevat.kustwaterbouwkundeHydraulic EngineeringCivil Engineering and Geoscience
A context-specific Conceptual Process Design for the Jamaican Sugar Industry
No full textVibrotactile wearable devices are a non-intrusive and inexpensive means to provide haptic feedback directly on the user’s skin. These devices utilize one or multiple vibrotactile actuators to generate vibrations across the skin and into the tissue. Combining these vibrations in amplitude can create the illusion of a funneled sensation on the skin at another location than at the actual sites of stimulation. This allows for the placement of virtual actuators on the skin, such that fewer actuators need to be deployed. However, the illusion does not take into account that the waves originating from the actuator attenuate and disperse due to the viscoelastic properties of the skin. We hypothesize that this diffusion of the elastic energy in the skin is affecting the perception of this illusion. Therefore, if we correct for the wave propagation speed, and temporally focus the stimulation, we hypothesized that the specificity of the stimulation on the skin could be drastically improved. In this paper, a novel technique, which is named the inverse filter technique, was introduced that enables to focus the amplitude, frequency and phase of vibrations to one location while cancelling them at the remaining nearby positions. We developed a wearable device for the volar surface of the forearm on which we could independently control arbitrary waveforms at any position between a set of four physical actuators. A human-subject study found that the performance in terms of localization confidence was improved significantly, whereas the precision and accuracy of the task did not improve compared to when we did not correct for the wave attenuation and dispersion. These results show that focusing waves towards a target location has a direct influence on our confidence of localizing vibrotactile stimuli on the arm. Therefore, we anticipate that our findings can benefit industries int Biorefineries are considered an integral part in the transition to sustainable bio-based economies as they can convert renewable biological resources into various bio-based products, while co-products are recycled and energy is produced out of the residuals. In this thesis, it is suggested to apply this biorefinery concept to revive the sugar industry of Jamaica, where currently only raw sugar is produced. For this, the development of a conceptual process design itself and the feasibility of the implementation is studied as the entire chain of utilizing biomass is influenced by both technical, environmental, social and economic aspects. With the Technological Innovation System (TIS) framework, the information obtained during the fieldwork about how (new) technologies function in the Jamaican agricultural industry are translated into context-specific design constraints. Those design constraints are used in the development of the context-specific conceptual process design for the Jamaican sugar industry. Three scenarios of the proposed design including the material balances and financial viability are discussed. The "status-quo" scenario predicts the bankruptcy of some of the sugar factories due to the reduced possibility to sell raw sugar, which will also leave the farmers without income. The "engineering-view" scenario was found to fail due to the unrealistic assumptions that all the products can be sold, that the farming yields can be improved, and that the Jamaican sugar sector can be seen as one. In the "most-realistic" scenario, it is considered that the energy generation from bagasse covers the energy demand for the processes and that the amount of plantation white sugar, anhydrous bio-ethanol and bio-pellets annually produced from 30,000 hectares of sugarcane land are considered to be 100,000 tonnes, 51 million liters, and 80,600 tonnes, respectively. It is suggested that this "most-realistic" scenario is able to revive the Jamaican sugar industry and to support the establishment of the sustainable bio-based economy, however the financial viability of the project and the inclusiveness of the various actors have to be taken into account.erested in including localized vibrotactile feedback on the human body surface.Chemical Engineerin
- …
