Extracts from recent PhD theses

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Below are extract from a selection of recent PhD theses:

March 2018

"Buildings bound together stronger"

Photo: Jesper Harrild SørensenIn Denmark, new buildings are often composed of precast concrete elements. The immediate advantage is that the building can be erected faster. The precast concrete elements are bound together by cast-in-situ joints, ensuring structural context and overall stability. However, large loads in multi-storey or unconventionally designed buildings, for example, pose a challenge to the traditional joint system—both in terms of strength and deformation capacity.

In his thesis, Jesper Harrild Sørensen from DTU Civil Engineering www.byg.dtu.dk/english has examined a new design of shear connectors between the wall elements which have been developed and tested. His findings revealed huge potential, as the new connectors offer greater strength per assembly and, in particular, greater overall stability. An improvement of current best practice can lead to better and more economic design.

Photo: Jesper Harrild Sørensen

"Less noise for the hearing impaired"

Photo: ColourboxFor many people—especially those with hearing aids or cochlear implants—understanding speech in noisy surroundings can be a real challenge. Researchers are therefore working to develop noise-reduction strategies that can improve speech understanding in these devices. The effectiveness of these strategies is dependent on how well the speech and noise characteristics are known.

To achieve this, automatic methods for separating speech from ambient noise as precisely as possible are therefore required. These methods often use sophisticated software to calculate a time-frequency mask containing speech information.

In his thesis, Thomas Bentsen from DTU Electrical Engineering www.elektro.dtu.dk/english has investigated three of these methods and evaluated them with a view to improving, in particular, speech intelligibility for hearing aid and cochlear implant users in noisy environments.

Photo: Colourbox

"Alternative energy via cells"

Photo: ColourboxSociety’s strong dependency on fossil fuels and their impact on the environment is driving researchers to find sustainable alternatives. One of the alternatives may very well be microorganisms when they are converted into so-called microbial cell factories. Instead of crude oil, for example, cell factories use renewable resources or waste to generate energy.

The challenge, however, is that the formation of new cell factories causes congestion in protein production.
With her thesis, Maja Simone Rennig from DTU Biosustain www.biosustain.dtu.dk/english is contributing towards a basic knowledge of protein biosynthesis.

Photo: Colourbox

January 2018

"Brain essential for obesity treatment"

Photo: Colourbox The mean body mass index (BMI) is steadily increasing all over the world—in the USA, obesity affected more than 35 per cent of the population in 2009 to 2010. Obesity is a major health problem, as it often involves consequential illnesses. The brain, which is crucial for appetite regulation and body weight, is therefore an important organ when it comes to developing treatment options. But brain access for medicine is limited by the blood-brain barrier—just as a better understanding of how drugs enter the brain is needed.
Casper Jensen from DTU Compute has developed algorithms that can automatically quantify microscope images of the brain and provide valuable data on brain access, mapping of receptors, and brain activity. The analysis tools were used to study the peptides that affect appetite regulation, and it was found that peptides injected under the skin were able to gain access to the brain and be active in brain groups related to decreased food consumption. Together with future experiments, these findings may provide new knowledge about how to improve the treatment of people suffering from obesity.

Illustration: Colourbox

"Live 3D degradation of fuel cells"

Illustration: Salvatore Angelis Solid Oxide Fuel Cells (SOC) can play a key role in an energy system based on renewable energy, as they can effectively convert chemical energy into electrical energy. However, they have a limited lifetime, as they are degraded by changes in the microstructures. In order to understand the complex phenomena in the cell, it is crucial to be able to track this development during operation.
With the help of X-rays, Salvatore Angelis from DTU Energy has investigated these changes in 3D high resolution, enabling him to see phenomena approximately 800 times smaller than a human hair. By means of ptychographic tomography, he has observed the effect of—among other things—oxidation and how nickel particles in the cell become coarser over time. The time-consuming technique, however, cannot follow the entire oxidation process, for example. He has therefore turned to X-ray holotomography, which in exchange for a few minutes’ lower resolution can create 3D images of the missing steps. Among other things, the experiments enabled him for the first time to follow the oxidation of nickel particles live in 3D—something which increases our understanding of the degrading of SOCs.

Illustration: Salvatore Angelis

"Antimicrobial agents alone cannot explain resistance in Danish pigs"

Photo: Colourbox As part of a larger project aimed at providing new knowledge about antimicrobial resistance in Danish pig herds, Anna Camilla Birkegård from DTU Vet has used a cross-sectional study of collected samples from 681 Danish pig herds. Five pigs were tested from each herd and examined for seven genes for antimicrobial resistance. Among other things, she investigated whether the herd’s geographical location and the pigs’ lifetime exposure to antimicrobial agents affected antimicrobial resistance levels in the herds.
The geographical location had a limited impact on the levels of antimicrobial resistance, while lifetime exposure to antimicrobial agents had a clear effect on these levels. However, antibiotic consumption can only explain up to approximately 40 per cent of the variation in the resistance level—so it is clear that other—as yet unknown—factors are involved.

Photo: Colourbox


December 2017

"Turbine data can make energy cheaper"

Photo: Østerild, DTUVast amounts of data are collected minute by minute from wind turbines around the world. In connection with his business PhD at Siemens Gamesa Renewable Energy, Martin Bach-Andersen from DTU Compute has found new ways to treat these data flows—providing insights which can be used to lower wind turbines maintenance costs and increase wind turbine uptimes.

Martin Bach-Andersen demonstrates how simple data streams from sensors using more advanced data modelling techniques can be used to issue warnings about critical faults in the turbine over a month earlier than existing alarm systems. In addition, he shows that artificial intelligence (machine learning) can solve one of the most complex tasks associated with remote wind turbine diagnostics—namely early fault identification—using complex vibration patterns. In some cases, this system can detect faults months before human experts.

Wind turbine owners and operators can utilise data from these systems directly to optimize maintenance and keep the turbines operational—possibly reducing the cost of wind energy over the long term.

"Electrochemical processes measured in real time"

Photo: Jeppe CarlsenThe transition to sustainable energy sources such as solar and wind power is revolutionizing the global energy landscape. This, in turn, means that electrochemical and biochemical processes will play an increasingly major role in chemical industries. In order to obtain a more fundamental understanding of these processes there is a need for rapid and sensitive measurements in real time.

Daniel Bøndergaard Trimarco fra DTU Physics has developed a new analysis instrument which can do just this. The instrument, which uses a mass spectrometer to analyse volatile reaction products in liquids, has been used to detect two new phenomena—which would otherwise not have been visible—in electrochemical processes.

Both discoveries reveal important information on fundamental mechanisms in electrochemical reactions and illustrate the huge potential for similar discoveries in the future.

"Extra-strength salmon feed"

Photo: ColourboxSalmon producers in the aquaculture industry require fish feed with high energy densities and premium physical quality. The feed must contain 40 per cent fat while being able to withstand heavy exposure to external influences en route to the fish cages. At the same time, the feed pellets must not disintegrate or leak oil. A better understanding of the structural impact of the fish feed pellet on the physical quality of the feed is needed in order to address these challenges.

After having examined the microstructure of several feed pellets, Markus Wied Dethlefsen from DTU Food has concluded that the optimum pore structure is defined by a large pore surface in relation to the volume of the pellet’s pores. In order to achieve this structure, he has developed new nozzles for the production of fish feed.

Fish feed pellets from these nozzles are far stronger and leak far less oil than pellets from traditional nozzles. His dissertation—and the development of the new nozzle technology—has so far resulted in two patent applications.

November 2017


"Better design of offshore wind turbines"

Illustration: Kasper SandalStructural optimization is now an integral part of how cars, planes, and rockets are designed, but as yet the technology does not yet enjoy widespread application on the lattice structures (so-called ‘jackets’) that support offshore wind turbines. Offshore support structures are thus very heavy and costly to build, move, and install. Better design will be able to significantly reduce offshore wind expenditure and thus contribute to making wind energy even more profitable.
Kasper Sandal from DTU Wind Energy has therefore used advanced mathematics to design structures for offshore wind farms and has developed a method that can create a ‘jacket’ in just a few minutes. This has never been done before and the method can become a valuable tool for engineers. The method is valuable in the early design phase, while more time-consuming and advanced methods can be used when the design is almost complete.

"Less ammonium in drinking water"

Photo: ColourboxMore than one in ten of the larger waterworks has problems removing ammonium below the limit value for drinking water. This is problematic, as it can lead to the growth of micro-organisms in the water supply on its way to consumers.

During the production of drinking water from groundwater, ammonium is commonly removed through a process of nitrification using quick sand filters at the waterworks. Nitrification is a biological process, whereby microorganisms oxidize ammonium into nitrite—and subsequently into nitrate. Among other things, the process requires small amounts of copper.

This gave Florian Wagner from DTU Environment the idea of experimenting with copper dosing. He developed a new method and a new apparatus for dosing copper in very low—and non-polluting—concentrations. Studies were conducted at ten waterworks, and in all of them, the ammonium disappeared, on average, after 19 days. The effect lasted for over 238 days. Among others, Florian has been supervised by Rasmus Boe-Hansen, Kruger Veolia.

"Why carbon forms on nickel catalysts"

Photo: Sine Ellemann OlesenMethanation is the conversion of synthesis gas (CO and H2), typically from coal—or biomass into methane. Methane is the main component of natural gas, and as the natural gas infrastructure is well established in Denmark, it is an attractive alternative to the soon exhausted oil reserves.

Methanation catalysts are most often based on nickel due to the relatively low price of nickel and an acceptable activity level. Unfortunately, they tend to deactivate due to sintering (particles clumping together) and the formation of carbon.

Carbon formation is not a well-described process, and Sine Olesen from DTU Physics has therefore contributed to a greater understanding of carbon formation on nickel catalysts. Four types of carbon were identified, and one type in particular was shown to deactivate the catalyst. The results showed that temperature in particular has a big influence on which types of carbon are deposited. In the long term, this knowledge may help to extend the life of nickel catalysts.

October 2017


"Better windows for near-zero energy houses"

 According to EU legislation, all new buildings must be as close as possible to zero energy before the end of 2020. Windows are key to whether these requirements can be balanced with a well-lit, pleasant indoor environment that promotes human well-being—and roof windows are a particularly effective source of natural daylight.

Gunnlaug Cecilie Jensen Skarning from DTU Civil Engineering identified and compared the various combinations of window sizes and qualities that would make it possible to meet energy, daylight, and thermal comfort requirements. She found that the best standard roof windows can be improved in a way that makes the construction of almost zero-energy houses easier and more cost-effective. 

Improvements in the roof windows—which reduced heat losses in windows and frame structures—showed savings in the order of EUR 50-320 per m2 improved window. If similar improvements can be made available within the financial framework, almost zero-energy houses can be built in a more cost-efficient way than at present.

Photo: Colourbox

"Better understanding of nature’s CO2 contribution"

 Flux of CO2 from natural ecosystems into the atmosphere plays a crucial role in determining the amount of CO2 in the atmosphere—and its effect on the climate. Flux can be divided into several components—among them CO2 from plants and soil—each of which may react differently to ongoing climate change.

Accurate measuring methods are essential in predicting whether the world’s ecosystems will absorb or release more CO2 in the future. Around the world, CO2-flux is often measured using the so-called closed chamber method—but the method has certain drawbacks. For example, the contribution is overestimated during periods with calm wind conditions. Andreas Braendholt from DTU Environment has quantified the effect of this methodological bias and developed a method that permits precise measurements—even in calm weather.

Overall, the dissertation can lead to better predictions as to whether the natural ecosystems will contribute to reducing or worsening the effects of climate change, thus providing a better understanding of the social changes needed in order for us to adapt to the negative consequences of climate change.

Photo: Colourbox

"Better check on the critically ill"

 In hospitals, the vital parameters of critically ill patients—e.g. heart rate, blood pressure, blood oxygen saturation, breathing, and temperature—are constantly monitored. These parameters provide information about basic body functions and are measured using a medical device which alerts medical staff if the patient’s health deteriorates.

Most medical alarms do not require action, but are due to the fact that the parameters are taken in isolation and out of context. This forces staff to prioritize critical situations—and in the worst-case scenario—results in critical conditions being overlooked and a patient dying.

Adnan Vilic from DTU Electrical Engineering has investigated the combinations of vital parameters in connection with critically ill patients and developed a prototype that combines patients’ electronic medical records with vital signs to estimate health over time. This makes it easier to navigate through extensive patient records and allows for new methods for forming an overview of the condition of the patient during hospitalization.

Photo: Colourbox


September 2017

"IT tool creates the perfect vase"

Vase, Photo: Colourbox When companies develop a new product, design and functionality are equally important if the product is to be competitive.

Marta Perez Mata from DTU Management Engineering focuses on a particular aspect of the user experience—namely the perception of a product’s aesthetics. By examining the perception of different vases, she has succeeded in identifying the aesthetic features that have the biggest impact on the perception of a product. She has also discovered that the emotional reactions produced by different designs works independently of the viewer’s cultural background.

Her research, which has resulted in a new method and two IT tools, can be used by designers to find new aesthetic product solutions targeted at specific perceptions in consumers.

Photo: Colourbox

"Detect cancer earlier with MRI images"

MRI, Photo: Colourbox Medical science often faces major challenges in detecting cancer in time for the patient to be treated effectively.

In his dissertation, Abubakr Eldirdiri from the basic research centre HYPERMAG at DTU Electrical Engineering has contributed knowledge about how to detect cancer before it spreads. He has demonstrated how magnetic waves (hyperpolarized magnetic resonance spectroscopy) can be used to detect earlier stages of cancer than has previously been possible.

MRI can also help to monitor how the patient’s body reacts to individual treatment—subsequently tailoring it to the patient. The technology can also spare cancer patients a great deal of suffering and discomfort, as it speeds up the process of determining whether a given treatment will work before adverse reactions occur.

Photo: Colourbox

"Bacterial resistance explained"

Bacteria, Photo: Colourbox Gene evolution is an extremely complex area of study, as we are unable to see it taking place with our own eyes. However, if we examine the evolution at macro level, we can see how bacterial genes change when they clone themselves.

Sandra Wingaard Thrane from DTU Bioengineering has studied the development of the genes of the bacterium Pseudomonas aeruginosa. This bacteria, which lives in nature as a harmless soil bacterium, can develop into a hazardous infection in humans.

By studying changes in the bacterial DNA structure over time, Sandra Wingaard Thrane has shown how the bacterium can become immune to external influences—e.g. antimicrobial agents—and how a change in these genes can result in dangerous, resistant clones.

The thesis can be a step on the way to designing better treatment for patients and preventing more dangerous bacteria developing resistance through contact with medicinal products.


June 2017


"Chemo- and immunotherapy show positive results"

Photo: ColourboxChemotherapy is one of the most important forms of cancer treatment. Unfortunately, it is often hampered by low efficacy and serious side affects. By encapsulating the chemotherapeutic drug in liposomal nanoparticles (fat membrane with liquid core), the drug can be released directly at the tumour site, thus reducing contact with healthy tissue. However, many liposomes are too stable and will not release the drug into the tumour. This problem can be overcome by manipulating the liposomes with a sustained release mechanism.

Ragnhild Garborg Østrem from DTU Nanotech has developed two liposome systems for delivery of the chemotherapeutic drug Oxaliplatin. The systems are sensitive to particular enzymes in the tumour so that the meeting with the enzyme leads to an increased uptake of the liposome in cancer cells—or degradation of the liposome and release of the drug outside the cell. However, cancer is a very complex disease and very often chemotherapy cannot stand alone. Therefore, experiments on mice with the liposomal oxaliplatin were combined with an immunostimulating agent. This treatment cured 80 per cent of the treated mice.

"Electric cars can strengthen electricity grid"

Photo: Mikkel AdsboelElectrification of the transport sector is a crucial element in global climate change adaptation. Thus, electric cars can support the reduction of CO2 emissions. It may prove challenging to integrate them into the distribution network, as charging many electric cars can overload the electricity grid. With smart management of charging and discharging, electric vehicles will not constitute a burden. On the contrary, they can be used as a flexible resource to support the grid.

Katarina Knezovic from DTU Electrical Engineering has demonstrated how electric cars can actively support grid operation, and how network operators can benefit from electric vehicle properties without significantly increasing costs. She has also demonstrated how mass produced electric cars even now can support different grid services with short response times. However, there is still a gap between political green visions, current standards, and regulatory frameworks. Thus, her dissertation provides a number of recommendations for future adjustments to standards and regulatory frameworks.

"New knowledge about natural additives"

Photo: ColourboxThe walls in the plant cells account for almost 50 per cent of the biomass available in terrestrial plants and algae—and many of their components already have important industrial uses—among other things—in food and biomedical industries. For example, glucoses from red algae (carrageenan oligosaccharides) as a stabilizer in chocolate milk and ice cream. In order to optimize the production and utilization of glucose, there is a need for a better understanding of the cell walls at the molecular level—and here—most studies have focused on terrestrial plants. However, terrestrial plants originate from algae, so greater knowledge of algae cell walls can help to provide a more basic understanding of all plant cell walls. At the same time, this knowledge can be used to design more complex sugars which can be produced by chemical synthesis. Christine Kinnaert from DTU Chemistry has developed a strategy that allows for the synthetic production of ten types of carrageenan oligosaccharides from a single, sophisticated synthetic product.

May 2017


"Grid stability algorithm"

Photo: Louise Amalie Juel SøndergaardIn 2003, Eastern Denmark experienced an eight-hour power outage and technicians discovered that the electricity grid was moving in a problematic direction. Renewable energy sources and the introduction of market mechanisms in the power grid are making operation ever more complex, and it is uncertain whether the current level of stability can be maintained.

Intelligent (or flexible) electricity consumption—where certain units such as refrigerators or electric cars postpone their consumption—might be the answer. Flexible electricity consumption is already foreseen as a means of remedying the balance between production and consumption, but to date no one has examined whether it can also be used to improve the system’s dynamic stability quickly and cheaply.

Martin Lindholm Wittrock from DTU Electrical Engineering has devised an algorithm that makes it possible to determine the loads with the greatest impact on stability—and how much these loads need to utilize their flexible reserve to ensure stability.


"Model for assessing biogas raw materials"

Photo: ColourboxThere is growing interest in introducing separate collection of bio-waste from households, restaurants, and commercial and industrial sources with a view to producing biogas. However, there are technical challenges and barriers that must be overcome in order to render biogas production more attractive—among other things—the need to quantify the potential for different types of urban organic waste.

This is typically done by analysing the biochemical methane potential (BMP) and by the anaerobic gasification of biogas reactors. However, determining the BMP is extremely time-consuming and can take anywhere from 30 to 90 days—or more.

By combining analytical methods and modelling, Temesgen Fitamo from DTU Environment developed a fast, reliable, and robust method for predicting BMP from biowaste of urban origin. The model provides an initial estimate of BMP and biochemical transformation in less than 72 hours and has the potential to replace conventional techniques. It may allow for effective decision-making with regard to the materials to be used for gasification.


"More ‘natural’ sound in hearing aids"

Photo: ColourboxMan has two ears at his disposal. Hearing allows us to perceptually locate sounds at the site where they are generated—a phenomenon known as externalization. This ability enables us to identify and pinpoint audio sources in our surroundings. However, making hearing aids that allow the hearing-impaired to localize audio sources in the same way poses a significant challenge. Directionality is particularly challenging in noisy environments with significant reverberation.

In experiments involving both people with normal hearing and the hearing-impaired, Henrik Gert Hassager from DTU Electrical Engineering has analysed the ability to externalize audio sources. The experiments indicate that the ability is maintained if the relationship between the direct and reflected sound remains unchanged when the signal is amplified. Against this background, Henrik devised a method to amplify sound while retaining the spatial properties.

The results may lead to the development of hearing aids which enable the hearing-impaired to pinpoint audio sources—even in rooms with strong reverberation.

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