408 research outputs found
Brown bullhead catfish (ameiurus nebulosus) in Lake Taupo
No full textBrown bullhead catfish (Ameiurus nebulosus) were first discovered in Lake Taupo during the early 1980s and are believed to have originated from an illegal liberation into the southern end of the lake. A native of the southern and eastern states of America, these catfish have been in New Zealand since 1878 and are now widespread throughout the Waikato region. In 1995 the population structure, abundance, age, growth rate and diet of catfish in the littoral zone (150 mm FL) and small fish. Low numbers of catfish across all size classes were caught from exposed sandy sites. The diet of catfish was size and habitat dependent. Small catfish (<150 mm FL) fed predominantly on chironomids, Cladocera, gastropods, caddisfly larvae, plant material and detritus. Larger catfish were found to prey to a greater extent on koura (Paranephrops planifrons), fish and terrestrial invertebrates
Sub-10 nm focused electron beam induced deposition
No full textWork started with a critical review of literature from the past 70-odd years. The review shows that the physical processes occurring in EBID are generally well understood. By combining models for electron scattering in a solid and electron beam induced heating and knowledge of growth regimes, the majority of the experimental results was explained qualitatively. The review makes clear that several major issues remain. The fact that cross sections for electron scattering in a solid and electron-induced precursor dissociation are not well known, makes it difficult to interpret experiments where the acceleration voltage is varied. Related to this is the limited understanding of electron-induced precursor dissociation. The dissociation mechanism is one of the key factors determining the purity of the deposits and a better understanding of this process will help to develop EBID to its full potential. The growth behavior at the sub-10 nm regime was explored by writing lines and arrays of dots from W(CO)6. The smallest average values that have been found for the full width at half maximum, are 1.9 nm for lines and 0.72 nm for dots. These are world records for EBID and for the first time, it is shown that growth on this scale is determined by random processes. The deposits consist of so few molecules, that the counting statistics become visible. The result is that, despite identical conditions, deposits are not identical. The final deposited mass varies from dot to dot and dots do not nucleate exactly on the irradiated position, but randomly around it. This results in nonsymmetrical dots in the early stage of growth. More insight into the deposition process is obtained by monitoring the annular dark field signal during the growth. This revealed that the growth rate during the deposition is not constant. The method also allowed control over the growth, for instance to prevent the occurrence of a proximity effect. Atomic force microscopy measurements allowed quantification of the deposited volume. The distributions of the deposited volume as a function of dwell time bear a close similarity to Poisson distributions, which suggests that the deposited dots consist of a number of discrete units. From a fit of Poisson distributions to the volume distributions, it was concluded that the volume per unit is as small as 0.4 nm3. This volume is almost just as small as a single W(CO)6 molecule in the solid phase. The work described in this thesis opens up a whole new decade of feature sizes from 20 to sub-1 nm and brings the ultimate resolution of single molecules within reach.Applied Science
Floating breakwaters; a theoretical study and preliminary design of a dynamic wave attenuating system
No full textHumans have been using ships to transport goods and people around the globe for hundreds and thousands of years. In all cases harbours have been critical for the exchange of goods and have played a significant role in the development of countries. Initially, harbours were located in sheltered natural bays; later breakwaters were used to provide shelter. An interesting next step would be the development of floating harbours at strategic locations. This would eliminate the need for capital dredging and can reduce the number of required harbour calls. A floating breakwater is an essential element in the design of a floating harbour to provide safe shelter for large scale floating structures. The missing link in designing an effective floating breakwater is a design-tool to make quick preliminary designs which can be developed further. A 2-dimensional linear spring model, the ReFBreak2D-model, has been developed to assess the performance of various floating breakwater designs. The hydrodynamic behaviour, as calculated by the model, has been validated with DELFRAC, a three dimensional potential model to determine reliability of the calculations. The results of the ReFBreak2D-model correspond well to the output of the DELFRAC simulation. The most important outcomes from the ReFBReak2D-model are: - The performance of the floating breakwater is primarily determined by the beam/draught ratio (Yw/T1-ratio) and the location of the centre of gravity (COG). - A rectangular floating breakwater with an Yw/T1-ratio of 5.0 and a high COG is the most optimal design. - A system of two floating breakwaters fulfils the requirements. These outcomes have been used to develop a preliminary design of the largest element. The length of the element is 500 metres, the beam is 100 metres and draught is 20 metres. This leads to a displacement of 1,000,000 tonnes, of which 270,000 tonnes are ballast. The element is moored using a turret mooring system; this makes it possible to weathervane during storm conditions.Hydraulic EngineeringCivil Engineering and Geoscience
Synthesis, Mesophase Behaviour and Charge Mobility of Phenyl-Thiophene Pentamers
No full textThe performance of opto-electronic devices based on semi-conducting organic molecules, dependence on the molecular order of the semi-conducting molecules. To get high charge transportation through the material a high order of the material is needed. In our research we used liquid crystalline phases to get relative high order over large distances. A series of all-aromatic phenyl-thiophene pentamers and a series of alkoxy terminated phenyl-thiophene pentamers have been synthesized. The mesophase behaviour and the UV-vis absorption have been determined. In the nematic phase the molecules possess only orientational order. It was found that the orientational order, in the nematic phase of p-quinquephenyl, determined by wide angle x-ray diffraction is less, due to temperature dependent fluctuations of the director at a macroscopic scale. The exact temperature dependence of the orientational order was determined by birefringence measurements and could be fitted with the predicted temperature dependence of the orientational order by the Maier-Saupe model. In the smectic phases the molecules possess orientational order as well as positional order. The charge mobility was determined by time resolved microwave conductivity. In the nematic phase the charge mobility is dependent on the orientational order. Hardly any charge mobility could be observed in the higher ordered smectic phases, because the concentration of charges is reduced.Chemical EngineeringApplied Science
Morfo-dynamiek strandsuppleties Egmond aan Zee
No full textOm inzicht te krijgen in de morfologie van het kustgebied ter hoogte van Egmond aan Zee en Bergen aan Zee is het kustgebied geanalyseerd tussen raai 30.00 en 43.00. Daarbij is een strook geanalyseerd tot 1600m zeewaarts en ongeveer 300m landwaarts van de RSP-lijn (Rijks StrandPalen-lijn). Om inzicht te krijgen in de gemiddelde morfologische ontwikkeling van het omschreven studiegebied is voor beide perioden en de drie afzonderlijke bereiken gekeken naar de gemiddelde ontwikkeling van de kuberingswaarden. Deze gemiddelde ontwikkeling (gemiddeld aanzanding of erosie of stabiel) is per raai bepaald door een lineaire trendlijn te berekenen door de reeks kuberingswaarden. De berekening van de trendlijn voor de periode 1964-1989 is niet gecompliceerd omdat alleen natuurlijke processen een rol spelen bij de ontwikkeling van de morfologie. Dat is anders in de periode 1990-1997 waar ook rekening moet worden gehouden met de uitgevoerde suppleties. De trendlijn is daarom zodanig berekend dat op het moment dat er een suppletie is uitgevoerd de trendlijn een sprong ter grootte van die suppletie maakt. Ter hoogte van Egmond aan Zee en Bergen aan Zee is al in 1990 een suppletie uitgevoerd. In de rest van het studiegebied is er pas vanaf 1992, of helemaal niet gesuppleerd. Het tijdstip van het begin van de suppletie-invloed (het trendbreukmoment) is dus niet voor alle raaien gelijk en is daarom voor elke raai apart vastgesteld. Dit trendbreukmoment vormt de overgang van de trendlijn berekend op basis van de kuberingen zonder invloed van suppleties (1964-trendbreukmoment) en de trendlijn met invloed (trendbreukmoment-1997). Op basis van de trendanalyse is duidelijk geworden dat ter hoogte van de kustgebieden Egmond aan Zee en Bergen aan Zee waar na 1990 intensief is gesuppleerd, inderdaad ook veel zandverlies plaatsvindt. Bij Bergen aan Zee is dit zandverlies gemiddeld per jaar ongeveer gelijk aan de hoeveelheid gesuppleerd zand en bij Egmond aan Zee is het zandverlies zelfs groter dan dat er is aangebracht door suppleties. Het langstransport in de belendende kustvakken lijkt te zijn toegenomen maar met veel minder dan de verliezen die worden geleden bij de intensief gesuppleerde gebieden. Ook is duidelijk geworden uit de trendanalyse dat het bereik tussen RSP+660m en RSP+1OOOm significant zandrijker is geworden. Verder valt op dat het zandverlies bij Egmond aan Zee veel groter is dan bij Bergen aan Zee. Als het studiegebied als geheel wordt bekeken is te zien dat er zowel voor 1990 als erna netto zand verdwijnt. Het verschil tussen beide perioden is niet groot waardoor gezegd kan worden dat het gesuppleerde zand voor het overgrote deel in het studiegebied terecht is gekomen. Tot slot is het probleem van de versnelde regressie nog van een financieel-economische kant bekeken. Er is in 1990 voor gekozen de kustlijn circa 34m zeewaarts te verschuiven. De kans op ernstige overlast en schade bij hoge stormvloeden ter hoogte van Egmond aan Zee is daarmee gebracht op gemiddeld 1/500 per jaar. Door de investeringen in extra suppleties is het wellicht economisch meer rendabel om de kustlijn minder ver zeewaarts te handhaven zodat minder suppletie investeringen nodig zijn maar waardoor ook de kans op ernstige schade toeneemt. Er is een financieel-economische analyse uitgevoerd voor stormen met een overschrijdingskans tussen gemiddeld 1/50 en 1/5000 per jaar. Uit de analyse is gebleken dat als globaal wordt gekeken naar de derving van inkomsten uit de toeristensector, de investeringen ten behoeve van de suppleties en de schade aan bebouwing bij grote stormen, een beperkte kustlijn verlegging het meest gunstig is.Hydraulic EngineeringCivil Engineering and Geoscience
Hydrodynamic pressures on large lock structures
No full textWhen a navigation lock, dam, or any other structure with water is subjected to an earthquake, one of the dynamic loads will be hydrodynamic pressure. This is the pressure exerted by the fluid on the structure as a result of the different behavior in motion of solid and fluid. To determine this pressure there are several available methods which focus mainly on large dams or fluid storage containers. However, the hydrodynamic behavior of these types of structures is different and these methods may or may not be applicable for navigation locks. Therefore an analysis is made to determine the factors that contribute to the hydrodynamic pressure distribution on large lock structures. As a case study the Third Set of Locks Project of the Panama Canal is used. This expansion project ensures that the Panama Canal can process larger ships than the current Panamax class of ships, which dimensions are limited by the existing locks. Therefore larger locks are required which will operate next to the existing locks. The new locks are planned to be operational in 2014-2015. The Panama region is prone to earthquakes which could result in large hydrodynamic pressures on the locks. For the evaluation of hydrodynamic pressure on large lock structures, two analytical (1D and 2D) and one 2D finite-element model using DIANA are made. Three main aspects that contribute to hydrodynamic pressure are treated in detail: - Lock dimensions and water levels; - The effect of surface waves on the hydrodynamic pressure distribution; - The flexibility of the structure.Hydraulic EngineeringCivil Engineering and Geoscience
Structural design of a sandwich wall as the quay wall for the future: And an investigation to apply parametric design to quay wall structures
No full textCivil Engineering and Geoscience
An adaptive pumping station at the Afsluitdijk
No full textThe degradation of infrastructure and sea level rise cause the existing discharge capacity of the Stevin and Lorentz sluices at the Afsluitdijk to be insufficient. This thesis focuses on the design of a new discharge facility at the Afsluitdijk with the possibility to anticipate on the changing conditions at both the IJsselmeer and Wadden Sea. The system is schematised as a closed-off estuary system within a water storage model, based on the water balance equation and a wind model from SOBEK. In contrast to previous studies, this study takes extreme conditions into account instead of only the daily conditions. The water storage system depends on the following governing parameters: the wind setup, tidal movement, target water level, sea level rise, in- and outflow conditions, in which the sea level rise is used as the function parameter. Within this schematisation three normative design conditions are considered for the acceptable water level prolongation at the inner basin: (I) the maximum acceptable height, (II) an acceptable duration of the high water level event and (III) the target water level boundaries. By means of a general sea level rise computation, the analyses showed that during daily conditions the need for pumps is inevitable from a sea level rise of +0.25m or more, because the daily discharge driven by gravity becomes limited. However, during extreme conditions discharge driven by gravity remains beneficial up to a sea level rise of +1.00m. Pumping is the only option beyond this point. Two design options are considered to be feasible for the combination of discharge driven by pumps and gravity: the open discharge sluice and the venturi culvert. The open discharge sluice is capable of discharging large volumes via gravity. In combination with the four pumps within a vertical door, the complete tidal cycle is utilised to discharge water, resulting in the most economical design option. On the other hand, there is the discharge facility made up of venturi culverts equipped with large pumps, capable of pumping large volumes during negative head differences. In addition, this option is capable of pumping water during small positive head difference, resulting in a very efficient option to pump large volumes. However, this concept is more expensive compared to the open discharge sluice. Within this thesis the discharge facility is designed for the +0.85m sea level rise scenario, based on the financial optimum composition. This optimal composition consists of twenty seven venturi culverts and twelve open discharge sluices. The total available pump capacity of the discharge facility is 1,250m3/s, with a maximum discharge capacity by gravity of 4,000 m3/s. Consequently, the maximum energy consumption is 32MW, equivalent to 32,000 households and requires an investment of \u801.4 billion. As a consequence of combining both design options, the discharge facility is capable of anticipating on small sea level rise variations without exceeding the tolerable limits. An insurmountable consequence of the design methodology is the overcapacity during daily circumstances. Only twelve of the twenty-seven pumps are required during daily conditions, the residual pumps are only required for the more extreme condition. The sensitivity analysis showed a possible reduction in pump capacity, due to small changes in the design conditions. These changes consist of: (I) an increase in acceptable water level duration, (II) an increase in summer target water level and (III) the possibility to allow temporary reduction of the target water level prior to the start of high inflow. The required discharge capacity by pumps decreases to 950 m3/s, a 25\% reduction compared to the initial design. Feasibility of a discharge facility, designed on the extreme conditions, is confirmed by means of the sensitivity analysis and endorses the strong relation between the required discharge capacity and the governing parameters of the water storage system.Hydraulic EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Adaptation of the Hollandsche IJssel storm surge barrier
No full textThe storm surge barrier and levees located in the Hollandsche IJssel do not fulfill the current safety standards according to the third nationwide safety assessment. The non-closure probability of the storm surge barrier is too high and the inner slope stability of the levees is too low. Besides the problems regarding the flooding safety also problems concerning salt intrusion into the Hollandsche IJssel, sea level rise that might occur, tidal ecology in the river and local developments in the surrounding play an important role. The objective of this thesis is the development and conceptual design of a solution for the important problems in the Hollandsche IJssel. The solution needs to be cost-effective and consists of a technically and societal feasible design. After analysis of different solutions, adaptation of the Hollandsche IJssel storm surge barrier is preferred because the investments needed to adapt the storm surge barrier are much lower than the construction of a dam or new storm surge barrier. The total solution adapts the Hollandsche IJssel storm surge barrier, changes the current closure scheme of the barrier and postpones the construction of a new structure that eventually will be needed. The adapted storm surge barrier has a lower closure level to decrease the governing water levels on the Hollandsche IJssel and therefore decreases the risk of flooding and the investments needed for the reinforcement of the levees. The non-closure probability of the storm surge barrier should decrease to limit the effect of the non-closure probability on the governing water levels. When the storm surge barrier does not close high water levels will be introduced on the Hollandsche IJssel, the effect of the non-closure probability should account for this high water levels. The storm surge barrier will also close during low discharges to prevent salt intrusion and consequently the stop of the fresh water inlet near Gouda. The inlet near Gouda uses fresh water to flush the canal system of Central Holland and prevents damage to agriculture. Due to the lower closure level and use of the storm surge barrier during salt intrusion governing loads on the storm surge barrier increase. The existing steel gate that closes the Hollandsche IJssel storm surge barrier needs to be adapted to withstand the increases loads. Steel plates need to be welded to increase the capacity of critical steel elements within the storm surge barrier. The effect of the adaptations is that a small part of the investments needed for the levee reinforcement is prevented and that the risks of flooding in dike ring 14 and 15 decrease. It is assumed that it is possible to decrease the non-closure probability and therefore reduce the effect of the governing water levels. The recommendations at the end of this study focus on the research that is needed into the exact effect and design of the adaptations.Hydraulic EngineeringHydraulic EngineeringCivil Engineering and Geoscience
Flying-V interior: Floorplan design for improved passenger comfort
No full textThis graduation project investigates the opportunities for the design of a new floorplan concept for the Flying-V aircraft. The aircraft’s unique V-shaped layout brings about limitations for how seating and other interior elements such as lavatories and galleys can be placed in the floorplan. Meaning that a different approach needs to be taken regarding the placement of these elements. Regulations for example dictate that aircraft seating cannot be placed at an angle greater than 18° from the direction of flight (DOF), without the need for additional safety precautions such as airbags. Because the passenger cabin of the aircraft is angled at approximately 26°, seats cannot be placed in rows perpendicular to the cabin wall such as in conventional aircrafts. Additionally, with the design of a new floorplan, opportunities arise for the design of a differentiating passenger experience through improvements in passenger comfort. As described in this report, literature research and an online questionnaire resulted in the definition of five main passenger comfort aspects that are of interest to tackle with the design of a new floorplan: legroom, personal space, boredom, sleeping, and walking or being physically active. Research has shown that these five aspects are considered highly important for passenger comfort, but that they score low with regard to this. Indicating that, if these aspects are improved, overall passenger experience can be improved as well. Using these outcomes, along with research into the Flying-V’s cabin design and geometry, aircraft interior trends and developments, and approaches to aircraft floorplan design, four different design directions were developed. The floorplan concept that is further elaborated on in this report focusses on three of these passenger discomforts: legroom, personal space and the possibility for passengers to walk around the aircraft. Further development of this floorplan aimed to find an appropriate balance between improvements in these aspects and required passenger capacity. The resulting floorplan proposal contains three different seating configurations, with each seating section dedicated to different types of travel groups: individual travellers, couple travellers, and group travellers. Firstly, staggered seats facing the DOF are placed at the front of the aircraft and along the outer cabin wall. These seats are dedicated to individual travellers, as they have proven to increase a passengers’ sense of individual personal space and legroom. Secondly, seats dedicated to couple and group travellers are minimally staggered (similar to conventional seating), as this still allows the passenger to easily communicate with their travel partners, one of the drawbacks of seats that are staggered at larger distances. Keeping passenger capacity in mind, the extent to which seats are staggered affects the width of a seating row. So by using a combination of differently staggered seating configurations the width of the aircraft’s cabin can be used most optimally. In this floorplan, making the difference between a 9 or 10-abreast configuration. Additionally, a walking route around the front of the aircraft is created, allowing passengers to be more physically active on long-haul flights, while highlighting of one of the aircrafts unique design features.Integrated Product Desig
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