35 research outputs found
Analyse van de ontwikkeling van het aandeel woningen in meergezinshuizen
No full textOnderzoek uitgevoerd in opdracht van het Ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer.OTB Research Institute for the Built Environmen
Coagulation and ultrafiltration in seawater reverse osmosis pretreatment
No full textSeawater desalination is a globally expanding coastal industry with an installed capacity of over 80 million m3/day. Algal blooms pose a challenge to the operation of seawater reverse osmosis (SWRO) membranes and pre-treatment systems due to high concentrations of algal cells and algal organic matter (AOM) present in the seawater. During such periods, operators must ensure continuous production of high quality feed water for SWRO membranes while maintaining stable hydraulic operation of the pre-treatment system. Coagulation is commonly applied to stabilize hydraulic performance and enhance permeate quality of ultrafiltration (UF) systems in SWRO pre-treatment. From an operational point of view it is desirable to completely eliminate coagulation from the process in order to reduce associated costs and complexities including treatment, handling and discharge of coagulant-rich sludge. This study investigates the role of coagulation in enhancing hydraulic performance and permeate quality of UF membranes and provides insight into options for minimizing or ideally eliminating coagulation from UF pre-treatment to SWRO. Results show that coagulation improves UF hydraulic performance mainly by reducing non-backwashable fouling of the membranes. This can be achieved at very low coagulant dose (~ 0.5 mg Fe/L) by coating the membranes with sub-micron particles. Further reducing particle size of the coating suspensions to the lower nanometre range is expected to be more effective in reducing the required equivalent dose and is recommended for future research. The work highlights the applicability of UF membranes with low molecular weight cut-off as the coagulant free future of SWRO pre-treatment. Major benefits in terms of reduced environmental impact is expected when applying membranes with low molecular weight cut-off, as the need for coagulation (for AOM removal) is eliminated while ensuring longevity of downstream SWRO membranes. Further improvements in material properties of these membranes should be directed at increasing the surface porosity of the membranes to enhance permeability recovery and ensure stable hydraulic operation. In general terms, the research indicates that coagulant consumption can be significantly reduced in UF pre-treatment of SWRO by optimizing operational parameters and applying alternative solutions.Water ManagementCivil Engineering and Geoscience
Onderhouds- en verbeteringswerkzaamheden: Een overzicht van aantallen, uitgaven en verklarende factoren
No full textOnderzoek in opdracht van het Ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer.OTB Research Institute for the Built Environmen
Het onttrekken van woningen aan de voorraad
No full textOnderzoek in opdracht van het ministerie van Volkshuisvesting, Ruimtelijke Ordening en Milieubeheer.OTB Research Institute for the Built Environmen
Dielectric Loss Estimation using Damped AC Voltages
No full textInsulation failures in HV components may be caused by lower dielectric strength due to aging processes and by internal defects in the insulation system. It is known, that unlike voltage testing, measurements of the dielectric loss may give an absolute indicator for the quality level of the cable insulation. For several years the application of damped ac voltages for testing and diagnosis of HV components like power cables and stator insulation is being applied. This thesis is focused on the application of dielectric loss measurements to the insulation of service components. In particular, to discuss the principles of dielectric loss estimation using damped AC voltages theoretical investigation, calculation procedures will be presented and verified on laboratory experiments and field measurements.Electrical Power EngineeringHigh Voltage Components and Power SystemsElectrical Engineering, Mathematics and Computer Scienc
Social desirability and mobility impacts of early forms of automated vehicles
No full textDouble degree thesis: Part A: Civil Engineering Part B: Science Communication The first forms of automated vehicles (level 1 and 2) are already available at dealers, and next levels are being developed at this moment (level 3 and up). Literature indicates two development paths for automated vehicles: an autonomous and a cooperative path. Autonomous vehicles only monitor the driving environment, whereas cooperative vehicles also communicate with other vehicles or roadside systems. This thesis consists of two parts: one (part A) researching the mobility impact of these two development paths, the second (part B) develops a method to include the public in decision making around automated vehicles. Part A: Modelling the mobility impacts of automated vehicles Governments are eager to know the impacts that automated vehicles have on mobility. Investment plans and policies can be made with this information. Current macroscopic models that assess the large-scale impacts of automated vehicles are complex, unsuitable for explorations with many uncertainties and are not able to simulate multiple vehicle types. This thesis aims to explore the impacts of early forms of automated vehicles (level 1, 2 and 3) on mobility. To cope with this problem a System Dynamics model (SD-model) is built. This model is based on the structure of the ScenarioExplorer, a model developed by TNO in the 1990s. The SD-model is strongly explorative and does not make use of an explicit road network. The goal of this model is to capture the most important effects of automated vehicles, but not to go into all the details. As the structure is simple and the run time is short, the model can be used to assess different scenarios. In this model the road capacity, value of time and fuel economy effects of automated vehicles are researched. The different levels of automated vehicles are modelled as different user classes in the mode choice, time of day choice and the assignment. This is novel for modelling automated vehicles on a large scale. In the assignment PCU factors depended on the penetration rate are used per vehicle automation class. This PCU makes it possible to translate results of microsimulations easily to large scale models and to simulate mixed traffic. The SD-model is compared to three macroscopic models and historic data and shows similar results. In addition, other tests point out that the model is suitable for explorative studies. Simulations with the SD-model show that due to the benefits automated vehicles bring, they will lead to extra car traffic in all researched scenarios. In the cooperative development path, the travel times on characteristic relations will roughly stay the same due to capacity benefits. In the autonomous development path, the average speeds drop due to less capacity benefits. The model shows that early forms of automated vehicles will not reduce congestion and in most scenarios have a negative effect on mobility. The only benefits early forms of automated vehicles entail are for the drivers, but not for mobility as a whole. Governments should therefore invest in other measures to stimulate the mobility. Due to the increase in car traffic, more emissions are expected. Part B: A more responsible innovation through the use of a constructive dialogue Societal impacts of automated vehicles can be large, not only on mobility, but also on safety, privacy or security. Complicating aspect is that automated vehicles both influence the living environment of the consumers and other road users. Literature indicates that at this moment the public (both user and other road users) are important stakeholders, but are not enough involved in the automated vehicle innovation. Due to this, and other flaws, the automated vehicle innovation cannot be called a responsible innovation. not involving the public constitutes the risk of neglecting their fundamental ethical principles, as their opinions remain unheard. This research aims to develop a method to involve important actors and to translate their ethical principles into starting points for a design of future automated vehicles. The values of four important actor groups (the government, manufacturers, consumers and non-consumers) are investigated. The method aims to be a constructive dialogue method. The value profiles created from the questionnaire show that opinions of the various actors differ. All actors agree that safety is the most important value. Differences are that the government and non-consumer value traffic flow, whereas the car manufacturers value spending time differently and self-determination for the driver. The cooperative path therefore seems attractive for the government and the non-users, whereas the car manufacturers are most likely to be in favour of the autonomous path. The survey shows no preference for one of the two paths from the consumer. The value profiles created from the questionnaire show that opinions of the actors differ. All actors agree that safety is the most important value. Differences are that the government and non-consumer value traffic flow, whereas the car manufacturers value spending time differently and self-determination for the driver. The cooperative path therefore seems attractive for the government and the non-users, whereas the car manufacturers are in favour of the autonomous path. The survey shows no preference for one of the two paths for the consumer. To create a common value profile a dialogue is needed, this is done in workshops. Tests with the constructive dialogue workshops show promising results: tensions in values become clear and the students reach consensus in the workshop. This is empirical evidence for what Van de Poel (2013) describes in his paper on specifying values to design requirements. The set-up seems to be a way to involve the different actors. This method is therefore a step towards a more responsible innovation for automated vehicles. Another promising aspect of the method is that the new ideas which are not mentioned in literature on self-driving cars arise in the sessions. This research contributes to a more responsible innovation as stakeholders are involved. Still, other important steps have to be taken. The method which is developed in this thesis should be used by manufacturers to give input to future designs or by governments for policies. Future research should focus on the validation of the workshops and the embedding of the method.Science Communication TrackApplied Science
The influence of the wave height distribution on the stability of single layer concrete armour units
No full textThe dimensions of single layer concrete armour units (interlocking armour units) are calculated with a similar stability relation as the stability relation for quarry stone. In these design formulas an 'average/significant' wave load is used (Hs). Since quarry stone gains its stability only from gravity, this type of armour unit is constructed in a double layer and therefore some damage development is allowed. Interlocking armour units are constructed in a single layer and the design should be based on zero damage. This research investigates whether this different approach to damage leads to a different characteristic design wave load which will increase the accuracy of the design method for interlocking armour units. It is focussed on the influence of the wave height distribution on the stability of single layer concrete armour units in general and Xbloc in particular. For Xbloc, zero damage is defined as a criterion for rocking of the armour units: during design conditions "not more than 2% of the units are allowed to move during more than 2% of the waves". To find a stability relation based on this criterion, the stability of Xbloc is investigated according to rocking of armour units contrary to the conventionally approach to stability based on the number of displaced units from the armour layer. To find the relation between waves and rocking, physical model tests are performed. In these tests a model breakwater is loaded by wave series with different wave height distributions, wave steepness and groupiness. It resulted that every wave has a certain probability of causing rocking of an armour unit. This probability of rocking is mainly dependent on the height of individual waves and to a lesser extent on the groupiness of the wave series. The steepness of the waves appeared to have a negligible small influence. When the found rocking probability relation is combined with the criterion for rocking, it appears that H2% is mathematically a better fitting parameter for a stability relation according to rocking. A new stability relation for Xbloc is derived based on H2%. Additionally, it is found that very extreme wave heights can dislodge an armour unit in such a way that this armour unit does not interlock anymore. Because it is undesirable that armour units do not interlock anymore, dislodgement of armour units should be accounted for in the stability calculations. Therefore, also a stability relation based on dislodgement of units is provided.Hydraulic EngineeringCivil Engineering and Geoscience
Assessment on AnMBR for Removing Lipid and Carbohydrate from POME
No full textPalm oil is a popular ingredient in domestic products. The palm oil industry has been growing rapidly over the past decades, so that the amount of palm oil mill effluent (POME) generated from the palm oil production has been increasing as well. The anaerobic membrane bioreactor (AnMBR) is a treatment solution that can remove organic pollutants from POME while generating methane as an energy source. In comparison to conventional anaerobic digestors, the AnMBR technology has an additional membrane unit that can produce effluent with higher water quality. More specifically, if ultrafiltration is applied, the AnMBR will be able to effectively remove bacteria from the effluent, making it suitable for direct fertigation (Uman et al., 2021; Bray et al., 2021). However, in cases where infectious viruses are also present, further disinfection method might be required. In this experiment, a lab-scale AnMBR system was used for POME treatment. In order to evaluate how well the system can perform in terms of pollutant removal and methane production, under the controlled experimental conditions, several criteria were monitored: (1) chemical oxygen demand (COD) removal, (2) biomass growth, (3) biogas production, (4) digestion efficiency, and (5) volatile fatty acids (VFA) accumulation. A Long chain fatty acids (LCFA) analysis method was developed using the liquid chromatography/mass spectrometry (LC/MS), to elaborate on underlying conversion mechanisms. A COD balance analysis was also conducted. Factors that would potentially contribute to the COD gaps in the COD balance analysis were quantified and discussed in this paper as well to validate the experimental results. The solid retention time (SRT) was controlled at 140 days, and the organic loading rate (OLR) at 3 gCOD·L-1·d-1 during the first phase of the experiment, when synthetic POME and VFAs were added to the bioreactor. During the second phase, the SRT and the OLR of POME remained the same, whereas the VFAs were replaced by starch and the OLR of starch was increased, in order to simulate the real POME composition, because in addition to lipid, carbohydrate and protein are also found in POME. During Phase I, the AnMBR system could remove 98%-99% of the incoming COD, and produce about 5 L of methane each day. During Phase II, the microbes did not have enough time to adapt to the new experimental condition, but the stability of the AnMBR system could be achieved overtime, when the mixing is improved and the buffer solution is adjusted properly according to the pH variation. Although, based on the positive biomass net growth and the increased methane production, it could be predicted that adding carbohydrates to the feed for a more representative POME composition would promote biomass growth and methane production, suggesting that the AnMBR system would have higher potential when the real POME is used for energy recovery.Civil Engineerin
Biological Performance of Palm Oil Mill Effluent (POME) Treatment using AnMBR
No full textPalm Oil Mill Effluent (POME) is an attractive medium for biogas production in an anaerobic membrane bioreactor (AnMBR) because of its high lipid content. Long-chain fatty acid (LCFA) accumulation is toxic and considered harmful for the biological performance within the reactor as they can be absorbed by biomass particles causing sludge flotation and biomass washout from the reactor. Membrane fouling can be caused by LCFA inhibition through adsorption on membrane walls. The biodegradation efficiency and filterability are affected by several factors such as solids retention time (SRT), and an organic loading rate (OLR). The objective of this research was to determine biological performance and LCFA inhibition while operating the AnMBR system at SRT of 90 days and an OLR of 3 g COD/ L/d under thermophilic condition (55 degrees Celcius). It was observed that successful operation was achieved with high COD removal efficiencies over 98% and average biogas production of 5 NL/d. Acidification occur in the sludge causing signification drop in pH, biomass concentration and methane production. The reactor slowly recovered back normal after adding sodium bicarbonate in the VFA feed. In addition, acetic and propionic acid were the major VFA constituent presented in the sludge.Civil Engineering | Environmental Engineerin
An integrated model to email spam classification using an enhanced grasshopper optimization algorithm to train a multilayer perceptron neural network
No full textEmail is an important communication that the Internet has made available. One of the significance is seen in the great
ease in which immediate transmission of internet data is done during email transmission. This great ease emerges
with a major issue which is the continuous increase in spam emails. Thus, the need for a spam email detector. The
versatility and adaptability of the nature of spam influenced past innovations. However, previous techniques have been
weakened. This study introduces an email detection model that is designed based on use of an improved version of
the grasshopper optimization algorithm to train a Multilayer Perceptron in classifying emails as ham and spam. To
validate the performance of EGOA, executed on the spam email dataset are utilized, then the performance was
relatively compared with popular search algorithms. The implementation demonstrates that EGOA introduces the best
results with high accuracy of up to 96.09%
