166 research outputs found
The influence of sand mining on the coastal erosion of Ngapali, Myanmar
No full textThe beach at Ngapali, Myanmar is eroding, resulting in a shoreline which moves landward. The coastline gets closer to the vegetation each year and during the monsoon season, at high tide, it reaches the palm trees completely. The assumption is that this is due to people shovelling truckloads of sand from the beach to use for construction, this is otherwise known as sand mining. All around the world there are recorded cases of it, often with disastrous outcome. However, sand mining is done sensible, the consequences can be very limited. This research will make a quantification of the influence of sand mining on the beach, will help to understand at what rate the erosion of the beach over the past 30 and 15 years has been and will make a prediction with what rate this will continue. This is done by analysing 30 years of satellite data, gathering data about the movement of the ocean at the shore, looking at characteristics of the beach and talking to the locals. The conclusion is reached by looking at two different methods. Firstly the quantification of the amount of sand that is taken from the beach yearly with respect to the amount of sand that moves along the shore yearly. Secondly by looking at the satellite data to show if the erosion of the beach was already a trend before the sand mining started. The first method established that the sand mining is but a fraction (<1%) of the sand that moves along the shore each year. From the satellite data we can determine that the erosion of the beach already started when the satellites first started measuring. Therefore we can conclude that the erosion of the beach is not the result of sand mining activities
'One tree is better than three cows.' Motivations to invest in fruit orchards, North Cameroon
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Acidic flow experiments to seal highly permeable thief zones in chalk formations
No full textThis work is based on the idea that an acid mixture of hydrochloride and sulpheric acid react with the calcite in a chalk oilfield to create anhydrite which has a larger molecular size. This will clog the present fractures to prohibit that these fractures sometimes shortcut the injected water from the injector well to the producing oil well which otherwise would result in artificial thieve zones. In this work mass balance calculations and experimental lab work has been done to see how the acidic reaction works. It is concluded that during the conversion of calcite to anhydrite 60% of the resulting CO2 is dissolved in the present liquid; the rest is in the gaseous phase. The samples of fractured chalk are approximately 30 cm long and have a diameter of 10 cm. The fracture is situated in the flow direction. The samples are tested under reservoir conditions, and the flow rate of the acids is 2 ml/min. The resulting permeability change indicates that the fracture is sealed after half an hour of acid injection, but this seal in the fracture is only a pasty substance clogging the flow. After approximately six hours of injection the first wormholes appear and the fracture is totally sealed. Mass change is calculated based on the amount of anhydrite created during acid injection. The mass changes are equivalent to the mass change measured during the experiment. CT-scans are made before, during and after many experiments and each scan series of approximately 300 images. These images are used in a specially written program to divide all present volume components in the chalk: fracture, calcite, anhydrite, wormholes and fossils. They are also used to calculate volume percentages, and coincide with the calculated weight percentages. Fracture experiments under reservoir temperature and pressure conditions and Brazilian tests under atmospheric are done on the sealed samples to see if the fractures can be reopened. The samples were tested with an annular pressure of 310 bar, 80oC and injection pressure of 270 bar. The production pressure was released, even with a pressure difference over the core of 160 bar and did not fracture. The tensile strength of the sealed samples proved to be as strong as original chalk samples without fractures.Petroleum EngineeringGeotechnologyCivil Engineering and Geoscience
Identification and control of light propagation in optical waveguides
No full textOptical fibres are ideal for local light delivery in hard to access places due to their flexible nature and small size. In most applications, such as microscopy, micromanipulation and endoscopy, it is desired to obtain and maintain a specified intensity pattern at the fibre output. Multimode fibres (MMFs) are capable of carrying a large amount information encoded in the complex coefficients of the superimposed propagating transverse modes. The main obstacle of using MMFs for these purposes is the fact that the small imperfections and impurities in the fibre along with bending causes dispersion and coupling between the modes. As a result the intensity distribution at the fibre output becomes randomised, known as a speckle pattern. The speckle pattern of a stationary fibre is time-invariant and the transmission characteristic of the MMF can be fully described by typically a very large nonsparse complex transmission matrix (TM). However, when the fibre is moved or disturbed the transmission matrix changes making dynamic operation in real time difficult to achieve. A desired output intensity pattern can be obtained by controlling the phase of the light field at the MMF input with a spatial light modulator (SLM). The SLM settings can be computed directly by optimising a specified objective intensity at the MMF output, or by retrieving the TM first and subsequently deduce the associated SLM phases. In this thesis alternative ways are explored to identify a light transmission model that is able to exploit the high resolution of state of the art spatial light modulators by using intensity measurements only. The proposed methods in this report rely on basis expansions into the fundamental transverse fibre modes, as well as into the Fourier basis, resulting in a significant reduction of the problem’s dimensionality. Also an iterative learning control strategy is proposed to compensate for small fibre movements during and after the identification process.Mechanical, Maritime and Materials EngineeringDelft Center for Systems and Control (DCSC
The impact of high sea-level rise (1-5 m) on mainport hinterland transport networks: A method for assessing adaptive sea-level rise scenarios on container port competition; a case study for the port of Rotterdam
No full textClimate change & sea-level riseIt is well-known that the Netherlands is susceptible for sea-level rise. Half of the country is situated below sea level and in an estuary. Previous measures of the Dutch against the threat of inundation have resulted in the closure of estuary branches, decrease in the length of primal flood defences and the world-renowned Delta Works. The Nieuwe Waterweg is kept open for economic reasons, in order to provide unhindered access to the port of Rotterdam, the largest deep sea port in Europe. However, the rise in sea level poses a threat to the accessibility of the port. Sea-level rise adaptation scenarios for the NetherlandsThere are various scenarios conceivable for the Netherlands to adapt to sea-level rise. The main scenarios are 'Open protection', 'Closed protection', 'Seaward' and a 'Retreat' scenario. Each scenario brings its own set of challenges and benefits. There are many strategies to implement these scenarios for future landscape and sea-level rise adaptations.Currently, there are around ~180 sea-level rise adaptation strategies for the Netherlands, as collected by Deltares. Only a handful actually include the effects on modality networks, port activities and shipping. Furthermore, all strategies use the same method which uses multiple models and has a lead time which stretches over multiple weeks to determine the effects on waterborne supply chains. Moreover, this method is not compatible for the retreat scenario. This forms the knowledge gap of the thesis. Proposed method & modelThis thesis therefore sets out to mitigate that gap by developing a first-order method to quantify the consequences of large sea-level rise projections, landscape changes and hinterland modality network changes of a deep sea port and to provide the results in a comprehensive manner.Therefore, we propose and create a method and a model to quantify the consequences on spatial sea-level rise adaptation strategies on hinterland container port competition, by enforcing modality network changes and being able to easily adjust boundary conditions of the model. This thesis brings forth the method and model and subsequently applies it to the Netherlands and the port of Rotterdam as a case study. The ports of Antwerp and Hamburg are additionally taken into account to model the port competition. The method and model can account for any number of deep sea ports and countries. Conclusions & recommendations- This thesis shows that currently, the majority of the sea-level rise adaptation strategies do not take their effects on waterborne transport and port activities into account. Furthermore, the strategies that do currently all use the same method, which cannot account for a retreat scenario. Furthermore, this existing method uses four models which results in a total cycle time in the order of weeks. These existing models cannot account for landscape or network changes.- The proposed method shows that current port operations for Rotterdam are no longer viable at +3 m sea-level rise and a retreat scenario. Two options for are suggested for the port of Rotterdam: relocate the port to the new coastline or transform the current port in a deep sea terminal in combination with inland terminals at the new coastline. \item The proposed method further shows that Belgium and Germany experience less inundation at +3 sea-level rise and a retreat scenario. Moreover, the ports of Hamburg and Antwerp are less susceptible to the inundation and do not have to resort to the extreme measures as the port of Rotterdam. \item The model shows that by locating the port more inland and in close proximity to (current) modality networks, the competitive position of the port of Rotterdam increases, whilst losing the advantages the port presently enjoys over Antwerp and Hamburg, as the modalities are now closer to the hinterland destinations. This is most notable for the road modality. \item Following the model, it can be concluded that new port locations have to be chosen with care as the results suggest a large decrease of hinterland areas for two locations (-51% and -88%), whilst the (other) two locations only show a slight increase in hinterland port areas (+3% and +16%). The model suggests that the most promising new port location is Tiel. - The proposed model only accounts for the container commodity, other commodities, such as dry bulk and liquid bulk, could give different results and it is therefore recommended that further research is done based on the other commodities. - It is further recommended to improve the model by adding a common starting point, China for example. Currently, the model starts at the quay, when the containers are unloaded from the deep sea vessels. This would give the option to add (dis)advantages of ports, such as increased relative distances, a tidal window, or container dwell times. Civil Engineering | Hydraulic Engineerin
Impacts of agricultural land use histories on the properties of the main soils of the Diamare plain in Nort Cameroon
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Fig. 2 in Food preference of the Bornean elephant (Elephas maximus borneensis) in North Kalimantan Province, Indonesia, and its conservation implications
No full textFig. 2. The orthogonal projections to latent structures (OPLS) score plot (a) showing separation of nutritional values among the samples [C = Calamus sp., Dc = Donax canniformis, Eg = Elaeis guineensis, E = Etlingera sp., Mb = Musa borneensis, Ss = Saccharum spontaneum, Bo = Bambusa oldhamii, So = Saccharum officinarum, Cn = Cocos nucifera, Ah = Artocarpus heterophyllus, L = Licuala sp., Cm = Caryota mitis, Ap = Arenga pinanga] The response-related profile (b) showing signals that are positively and negatively correlated to the preference prediction [NDF = Neutral detergent fibre, ADF = Acid detergent fibre, HC = Hemicellulose, ADL = Acid detergent lignin, CP = Crude protein, P = Phosphorus, K = Potassium, Ca = Calcium, Mg = Magnesium, Na = Sodium].Published as part of Suba, Rachmat B., Beveridge, Nils G. P., Kustiawan, Wawan, de Snoo, Geert R., de Iongh, Hans H., van Wieren, Sip E., Choi, Young Hae & Kim, Hye Kyong, 2020, Food preference of the Bornean elephant (Elephas maximus borneensis) in North Kalimantan Province, Indonesia, and its conservation implications, pp. 791-802 in Raffles Bulletin of Zoology 68 on page 798, DOI: 10.26107/RBZ-2020-0090, http://zenodo.org/record/535042
Microbial diversity underground: do we need to protect the Earth's greatest source of biodiversity?
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