225 research outputs found
Are EU spatial ex ante coexistence regulations proportional?
No full textThe EU is currently struggling to implement coherent coexistence regulations on genetically modified (GM) and non-GM crops in all member states. While it stresses that any approach needs to be “proportionate to the aim of achieving coexistence”, very few studies have actually attempted to assess whether the proposed spatial ex ante coexistence regulations (SEACERs) satisfy this proportionality condition. In this article, we define proportionality as a functional relationship which is weakly increasing in the incentives for coexistence. We propose a spatial framework based on an existing landscape and introduce the new concept of shadow factor as a measure for the opportunity costs induced by SEACERs. This enables comparing the proportionality of (i) rigid SEACERs which are based on large isolation distances imposed on GM farmers versus (ii) flexible SEACERs based on pollen barrier agreements between neighboring farmers. Our theoretical and empirical findings argue for flexibility as rigid SEACERs violate the proportionality condition and, hence, are not consistent with the objectives of the EU.policy analysis, GIS, shadow factor, Agricultural and Food Policy, Crop Production/Industries,
Risk and De-Collectivisation: Evidence from the Czech Republic
No full textThe replacement of wage-labour farms by family farms in Central and Eastern Europe during the transformation has been more limited than was initially expected. In this paper a formal framework is developed in order to analyse the behaviour of family farms and socialist-style farms in the presence of risk, given the typical post-socialist environment. Management incentives, ownership structure, lump-sum transfers and consumption choices are shown to have the potential to limit the size of family farms relative to socialist-style farms. The hypotheses are tested with survey data collected by the author in the Czech Republic.transition, agriculture, structural change, risk, survey data, Risk and Uncertainty, D21, D81, O18, Q12,
To be awarded, or Not to Be Awarded. Is that the Question?:Theoretical and Methodological Aspects of the Study of Literary and Translation Prizes in the Context of Cultural Transfer
No full textTo be awarded the Nobel Prize in Literature or not to be awarded. Is that the question? Is not every author overwhelmed by the mere thought of being awarded the Noble Prize in Literature? After all, it means more translations, a broader audience, honour, money and fame. One good example of a writer who benefitted from the prize is the Icelandic author Halldór Laxness (1902-1998). A hitherto unknown poet and novelist, he became world famous after receiving the award in 1955, after which his works were translated into more than 25 languages.1 There have also been authors, however, who were anything but honoured to be nominated. Undoubtedly, the most famous example is Jean-Paul Sartre (1905-1980), who refused the Nobel Prize in 1964 to maintain his intellectual credibility as an anti-bourgeois philosopher and activist
Economics of spatial coexistence of genetically modified and conventional crops: Oilseed rape in Central France
No full textEurope is currently struggling to implement coherent coexistence regulations on genetically modified (GM) and non-GM crops in all EU Member States. We conduct simulations with the software ArcView® on a GIS dataset of a hypothetical case of GM herbicide tolerant oilseed rape cultivation in Central France. Our findings show that rigid coexistence rules, such as large distance requirements, may impose a severe burden on GM crop production in Europe. These rules are not proportional to the farmers’ basic incentives for coexistence and hence not consistent with the objectives of the European Commission. More alarming, we show that in densely planted areas a domino-effect may occur. This effect raises coexistence costs and even adds to the non-proportionality of rigid coexistence regulations. Instead, we show that flexible measures would be preferable since they are proportional to the incentives for coexistence and, hence, less counterproductive for European agriculture.regulation, GIS modelling, domino-effect, Crop Production/Industries,
Intention-Aware Routing to Minimise Delays at Electric Vehicle Charging Stations
No full textEn-route charging stations allow electric vehicles to greatly extend their range. However, as a full charge takes a considerable amount of time, there may be significant waiting times at peak hours. To address this problem, we propose a novel navigation system, which communicates its intentions (i.e., routing policies) to other drivers. Using these intentions, our system accurately predicts congestion at charging stations and suggests the most efficient route to its user. We achieve this by extending existing time-dependent stochastic routing algorithms to include the battery's state of charge and charging stations. Furthermore, we describe a novel technique for combining historical information with agent intentions to predict the queues at charging stations. Through simulations we show that our system leads to a significant increase in utility compared to existing approaches that do not explicitly model waiting times or use intentions, in some cases reducing waiting times by over 80% and achieving near-optimal overall journey times.Software and Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc
Wat moet eruit komen? Reactie op de kritische bijdrage van Kalmijn en De Graaf
No full textThe article focuses on the views of the author regarding the evaluation of his test book by Mathijs Kalmijn and Paul M. De Graaf meant for measuring professional status. Both Kalmijn and Graff have compared the scales proposed by the author and other scales for measuring professional status. They have claimed that GK-schaal is more effective than that of the author. According to the author, they have based their theoretical foundation of objective scales on training and profession
Route Planning with Breaks and Truck Driving Bans Using Time-Dependent Contraction Hierarchies
No full textMandatory breaks for truck drivers are nowadays scheduled after the route has been decided. However, in some cases it is beneficial to plan these breaks during waiting time caused by truck driving bans. Optimally planning a single break considering driving bans can be done using Dijkstra’s algorithm with multiple labels. This has large effects on predicted travel times: 17% of the analysed routes having a night rest obtain an earlier arrival time by 5 hours on average. However, the computation times of this algorithm are long. A novel heuristic version of time-dependent contraction hierarchies leads to significant reductions in computation times from several seconds to several milliseconds per route. Experiments show that the solutions are still optimal for a representative test set consisting of 10,000 route queries.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.AlgorithmicsTransport and Plannin
Advanced techniques for numerical contact analysis in spiral bevel gears
No full textDottorato di Rocerca in Ingegneria Civile ed Industriale. Ciclo XXXThe research presented in this dissertation treats the subject of efficient gear
contact simulation and is applied to the contact analysis of spiral bevel gears.
In today’s competitive environment getting better products to market faster
is essential to win a customer’s interest and loyalty. Therefore, engineers are
evermore in need of the correct solutions to rapidly predict, analyze and improve
their designs if they want to meet the tight development schedules and budgets.
Within the current development cycle of mechanical transmissions, computerized
tooth contact analysis (TCA) has proven to be an invaluable tool to predict a
gear pair’s key contact performance characteristics, while reducing the need
for expensive physical prototyping and labor-intensive experimental testing.
However, the geometrical complexity of the gear teeth still pose significant
computational challenges to the tooth contact simulation for spiral bevel gears.
Correctly capturing the spatial nature of the motion transfer and the resulting
contact load distribution requires a three-dimensional gear contact model.
Finite element method (FEM) based contact simulations are usually conducted,
especially in an industrial context, while various tailor-made solutions also
exist. When performing the contact detection, many of these solutions tend
to apply a general contact detection method (e.g. node-to-surface) that treats
the contacting gear teeth flanks as arbitrary surfaces. Not realizing that the
gear flanks are designed to transmit motion in a near-conjugate way, leads to
inefficient contact searches for which the associated computational cost not only
limits TCA’s application to static component-level analysis but also hinders
extension towards full-system level analysis or dynamic gear contact simulation.
Building upon the existing concept of the surface of roll angles to efficiently
detect contact, this dissertation develops a new penetration-based contact model
to compute the three-dimensional contact loads from the actual position and
orientation of the real tooth surfaces, whether misaligned or not. The proposed
methods show to correctly predict component behavior at a computational cost
that enables further application in system-level or dynamic analyses.
An accurate description of the spiral bevel gear tooth surfaces is deep-rooted
in the presented methodologies, since this proves vital to precisely describe
the gear pair kinematics but also to correctly include all the relevant complex
contact phenomena. However, a reference tooth profile, similar to the involute for
cylindrical gears, does not exist for spiral bevel gears. Therefore, a mathematical
model that simulates the cutting kinematics of the manufacturing process,
proves to be indispensable to correctly capture both the gear teeth’s macro- and
microgeometry. In this work the five-cut face-milling cutting process is adopted
to create a representative geometry of a face-milled spiral bevel gear set.
Contact detection based on the tooth flank’s surface of roll angles, combined
with the ease-off topography, has been proposed in the gear literature to reduce
the computational load, associated with the contact search. Yet, the ease-off
topography, which quantifies the geometrical mismatch of a pair of contacting
gear tooth surfaces, shows to hold limitations when moving beyond componentlevel
contact analysis, as it is sensitive to the instantaneous gear pair installment.
With the underlying idea of potential application of the presented methodologies
within multibody system simulation, the usage of ease-off topography concept
for contact detection is abandoned and replaced by a penetration-based contact
model. An analytical compliance model is formulated to translate the detected
penetrations into appropriate contact loads. The compliance model separates
the linear gear tooth deflection components from a tooth pair’s local nonlinear
deformation, which arises around the contact zone.
The developed gear contact model with surfaces of roll angles, computed for the
gear pair’s actual tooth flanks in the absence of misalignments, is then shown
to be well capable of predicting a misaligned gear pair’s contact performance.
In contrast, ease-off based contact models would require an update of the
(misaligned) ease-off topography, each time the gear pair’s configuration changes
(e.g. due to system-induced deflections), reducing their otherwise excellent
computational efficiency. The proposed penetration-based gear contact model
identifies the contact locations based on the surface of roll angles but computes
the flank mismatch based on the instantaneous position and orientation of the
real gear tooth surfaces, showing to be more robust to configurational changes.
Finally, a strategy to parametrically redefine the gear contact model’s surfaces
of roll angles in function of the instantaneous misaligned state of the gear pair,
is proposed to further increase the accuracy of the contact detection.
A prototype toolchain is created around the presented techniques for contact
modeling, covering the various analyses for unloaded and loaded tooth contact
analysis that are an essential part of today’s spiral bevel gear design process.
Automated finite element model creation routines are developed to support the
validation of the methods against nonlinear FEM-based contact simulations.
These tools will greatly support future research into methodological advancesUniversità della Calabria
Deproximating Tredgold's Approximation
No full textPresented is Tredgold’s Approximation for using an equivalent cylindrical gear with spur teeth to “approximate” a bevel gear with straight teeth. This relation is extended to spiral bevel and hypoid gears by utilizing pitch surface curvature in the direction perpendicular to the gear tooth spiral to establish an equivalent gear. Subsequently, the envelope of a planar gear
tooth profile in this perpendicular direction is presented. The envelope of the gear tooth profile is used to determine fully conjugate gear teeth profiles for spatial gear elements. This procedure is valid for any tooth profile along with circular and non-circular gears. To validate
the methodology, a virtual model of a bevel gear pair (“presented model”) is created and an unloaded tooth contact analysis is performed. The procedure used to perform the unloaded tooth contact analysis and determine the corresponding unloaded transmission error is based
on the concept of ease-off topography. An example of a face-milled bevel gear pair (“literature model”) serves as a reference of correctness in determining the ease-off for unloaded contact. To conclude the paper, the obtained ease-off topography and unloaded transmission error of
the presented model are calculated and displayed, demonstrating the specification of fully conjugate teeth.sponsorship: Department of Mechanical Engineering, University of Puerto Rico at Mayagüez, Mayagüez 00681, Puerto Rico
Department of Mechanical, Energy, and Management Engineering, University of Calabria, Ponte P. Bucci, 87036 Rende, Italy
Siemens Industry Software, Interleuvenlaan 68, B-3000 Leuven, Belgium
Department of Mechanical Engineering, Katholieke Universiteit Leuven, Celestijnenlaan 300B, B-3001 Heverlee, Leuven, Belgiumstatus: Publishe
Investigation of vertical cutter mining for increased primary resource recovery and decreased environmental impact
No full textThe purpose of this thesis is to aid in the development of vertical cutting mining as a mining method. In order to do so, the technical feasibility and viability, and environmental benefit of vertical cutting as a complementary mining method were investigated. The investigation was performed for the case of the Victor Diamond mine in northern Ontario, Canada, where open pit mining ends by the end of 2018 or beginning of 2019.Vertical cutting has been used for several decades for the construction of water retention walls in the civil engineering industry. By placing the vertical cutter system directly on top of an ore target and cutting straight, vertical trenches up to a maximum depth of 150 m, it is intended to cross over to the mining industry. Extraction with vertical cutting can occur according four extraction scenarios. Three of the scenarios are land-based, the fourth assumes flooding of the mine, and has not been considered for the Victor project. Checkerboard mining is the base case extraction scenario with an extraction rate of approximately 30%. The long trenching scenario would increase the recovery with an additional 15% but induces a high risk of instability in the existing pit walls and the kimberlite in between the trenches. Application of backfill is the third scenario and achieves a recovery of 98%. Backfilling of the trenches requires the movement of significant volumes of additional rock as well as induces time delays due to the curing time of the backfill. Financial evaluation of the vertical cutting scenarios shows a high dependency of the project value on a decreasing cutting performance. Cumulative cash flow analysis and NPV suggest that extending the mine life at the Victor Diamond mine with vertical cutting is favourable. Even in the case of increased rock strengths, as expected in the deeper parts of the Victor pipes, vertical cutting has a positive net present project value. Long trenching, which is considered to be of high risk for pit stability has only marginally greater project value than the base case. The development of alternative mining solutions also aims to reduce the impact of the mining operations on the surrounding environment. Vertical cutting combines multiple mining processes into one operating piece of equipment. It reduces the GHG emissions, improves the safety of extraction process and is expected to increase the support from stakeholders. Extending operational life using conventional methods would require large expansion of the mine involving the increase of the operational fleet, pumping capacity and land usage. The application of vertical cutting has the ability to prevent the negative impact of enlarged open pit mining while maintaining the benefit of continued production
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