At DTU you can get a research education equal to the world’s very best in fields such as mathematics, physics, informatics, chemistry, biotechnology, chemical and biochemical engineering, electrical engineering, communications technology, space science, mechanical engineering, nanotechnology, energy, civil engineering, transport, environmental engineering, food science, veterinary science, and life science.
Below are extract from a selection of recent PhD theses:
"Grid stability algorithm"
In 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"
There 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"
Man 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.
"Longer, lighter blades"
A key aspect of wind energy research is reducing costs. This can be achieved by reducing the total weight of the rotor blades, while at the same increasing their size and performance. However, this requires finding a way to limit the aerodynamic loads on the blades. One possibility is passive control, where the blade is constructed so that the structure load is relieved when deformed. A wind turbine rotor that can be passively relieved is a cost-effective solution, as it allows a lighter design and longer blades without the need for actuators and other mechanical solutions. Christian Pavese from DTU Wind Energy has discovered a method to exploit the full potential of passive control, and demonstrated how integration of passive control as a design variable can pave the way for wind turbine blades where passive load reduction can result in significantly lower blade weight or enhance wind energy production.
"New tool for planning S-train operation"
With annual operating costs amounting to several hundred million kroner, planning is paramount at DSB (the Danish National Railways). A key planning parameter is ensuring adequate seating for passengers. Another is avoiding empty train compartments. Then, of course, there is the railway’s physical infrastructure, the timetable, rolling stock, maintenance, etc. Planning for all these parameters is a time-consuming and complex process—and the planning process is still predominantly manual. Per Thorlacius from DTU Management Engineering has designed automatic planning models which—in contrast to today—integrate all of DSB’s technical requirements for the S-train network. He has shown that the integrated planning models can be used to automate processes, which are currently manual—and not least, secure DSB substantial economic efficiency improvements in S-train operation.
"RNA-vaccine against widespread PRRS"
One of the biggest problems in global pig production is Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), which reduces the immune defence system, causes pneumonia, and in gestating sows can lead to miscarriages, premature birth, or stillborn piglets. Simon Welner from DTU Vet has developed a new vaccine based on RNA sequences that encode for virus peptides which activate a killer T cell response against PRRSV. The sequences are spliced into a living, weakened RNA virus (RNA vector replicon). In an experimental testing of the new RNA vector replicon vaccine, all the vaccinated pigs developed antibodies against the viral vector, but only a few specific killer T cells against PRRSV—and very weak protection against infection. The conclusion is that the design worked, but that there is still a long way to go before developing a functional vaccine against PRRSV.
"Molecules from intestinal bacteria protect health"
Billions of bacteria and microorganisms in our intestines—our intestinal microbiome—play an important role in relation to human health. Janne Marie Laursen from DTU Bioengineering has investigated how specific molecules produced by intestinal bacteria (endotoxins) affect the immune system in the intestines and help develop resistance to insulin—an important factor in type 2 diabetes.
A newly developed method was used to see which bacteria produce different variants of endotoxin. It showed that contrary to expectations, there are far more bacteria in the intestines producing a non-harmful variant of endotoxin than bacteria producing a harmful variant. The method also showed a correlation between insulin resistance and the quantity of endotoxin-producing bacteria in the intestines. Further analyses showed that a particular fatty acid can shut down production of pro-inflammatory proteins and instead produce other proteins that maintain healthy intestinal tissue.
This knowledge will eventually allow people to be treated by changing the composition of intestinal bacteria that cause lifestyle diseases.
Illustration: Tarmmikrobiom_Credit_Janne Marie Laursen / Omslag-hvid-kun-forside_Credit_Janne Marie Laursen
"Better industrial production of graphene"
There are great expectations of graphene—an extremely stable material consisting of a single layer of carbon atoms. It is currently used in a number of products, but applications where it can have a major impact—such as transparent electrodes in solar cells and flat screens—are still some way off. Graphene is currently produced via a chemical process whereby it is deposited onto copper. It is then necessary to move the thin graphene layer to another surface before it can be used. This often leads to defects.
Patrick Rebsdorf Whelan from DTU Nanotech is addressing this challenge and has developed new ways to transfer the graphene. In contrast to the existing method, where the copper substrate is etched away, they leave it intact, so it can be used to grow a new layer of graphene. Using these methods, the electronic properties of graphene are also better transferred than using the standard method.
The thesis also shows that the electronic properties of the transferred graphene can be mapped using a method that can be used in industrial production, thus ensuring that the transferred graphene is free of defects.
Illustration: Grafen_ Credit_Patrick Rebsdorf Whelan / PatricksHand_ Credit_Patrick Rebsdorf Whelan
"Natural process solves widely different challenges"
Clean water, clean energy and the transition to a bio-based economy are some of the major challenges facing our society. An advanced new filtering process called biomimetic direct osmosis can help to address them. The process builds on a biological cell’s need to transport water in and out of the cell, without allowing anything else to pass.
Protein channels called aquaporins allow water to pass by means of osmosis, whereby the water attempts to dilute a concentrated solution (typically salt). The process can be mimicked by inserting aquaporin proteins into a synthetic membrane. By placing a saline liquid on one side of the membrane, and the fluid you want to filter (e.g. waste water) on the other side, water will be transported from the wastewater over into the saltwater, leaving the contamination behind.
Niada Bajraktari from DTU Environment has looked at five applications for biomimetic osmosis and found that they offer promising results in relation to treating municipal wastewater, concentrating bio-products, and energy production based on strong saline solutions.
Illustration: FOGEO_Credit_Niada Bajraktari / FOROHybrid_Credit_Niada Bajraktari / Osmosis_Credit_Niada Bajraktari
"Chip can detect pneumonia"
Normally, when people suffering from the lung disease cystic fibrosis are tested for pneumonia, they undergo a coughing test. However, in children under eight years, such testing is not possible, and consequently, Rikke Kragh Lauridsen from DTU Nanotech modified a chip—originally designed to detect explosives in the air—to measure whether the patient’s expiratory gases contains the biomarker for hydrogen cyanide. This biomarker indicates that the bacterium Pseudomonas aeruginosa is present in the patient’s respiratory tract.
Patients with cystic fibrosis often develop pneumonia, as their airways are covered in a thick layer of mucus which stop the cilia from cleaning the respiratory tract. Patients are therefore more susceptible to attack from this bacterium, which is otherwise harmless to healthy people.
"Nanomaterials cannot be risk assessed"
Nanomaterials are now used in a wide range of products—from suntan lotions to mobile phones—but determining whether nanomaterials constitute a risk to the environment continues to pose a challenge for authorities and researchers.
Rune Hjorth from DTU Environment has therefore analysed the applicability of the risk assessment tools and ecotoxicological tests currently available—and the results are not promising.
"Acetone produced at high temperatures"
Thermophilic (heat-loving) bacteria possess several properties that make them interesting as host organisms in biotechnology. Among other things, they exhibit increased reaction rates at higher temperatures and a reduced risk of becoming contaminated with bacteria that thrive at moderate temperatures.
Ivan Pogrebnyakov from DTU Biosustain has described the development of a number of genetic and molecular tools that can be used to genetically engineer the thermophilic bacteria Geobacillus thermoglucosidasius—and in the course of this project—he has succeeded for the first time ever in genetically engineering the bacteria to produce acetone.
This research paves the way to expand and improve the biotechnological processes for the production of acetone and potentially create the basis for industrial applications.
"‘Small’ energy sources may lead to savings"
There is an appreciable political desire to save energy in the construction sector. This demands effective solutions. One option features what are known as Thermically Activated Building Systems (TABS), which heat up in cold conditions and cool down when the temperature rises. TABS make it possible to use ‘small’ energy sources such as surplus heat or earthed heat exchangers, which are insufficient sources of energy in and of themselves.
Benjamin Behrendt from DTU Civil Engineering has developed a simulation tool which can, for example, calculate the risk of overheating and the maximum cooling effect so as to avoid under-cooling. The tool is simpler than existing options, and also features a climate classification scale which makes it possible to predict how TABS should be used in buildings throughout Europe.
This classification is needed to calculate whether heating, cooling or both are required to achieve an acceptable indoor climate. The combination of the two tools makes it possible to prepare holistic assessments of construction projects at an early stage
"Chemistry in the embryonic period affects fertility"
Women can experience reduced fertility on account of disruptions to the development of the ovaries. It is suspected that this, in turn, may be attributable to exposure to endocrine-disrupting substances during the embryonic period. However, this is difficult to prove conclusively given that the effects do not become apparent until adulthood, and because people are typically exposed to extremely small doses. On the other hand, exposure to a wide range of chemicals takes place over a protracted period, which may lead to combination effects.
Hanna Katarina Lilith Johansson from DTU Food has identified several stages in the early development which are sensitive to exposure to chemicals. Her findings demonstrate that female rats exposed to endocrine-disrupting substances had fewer eggs in their ovaries before puberty, and that at the age of one year they showed signs of early reproductive ageing.
She has identified three biomarkers for influence on the development of the ovaries. However, more studies are required to determine whether they can be used in young individuals to predict disruptions to reproductive ability later in life, and whether the biomarkers can be used for diagnostic purposes in humans.
Illustration Hanna Katarina Lilith Johansson
"DNA analyses help trace source of cancer cells "
One key characteristic of cancer cells is that they form a variety of mutations that accumulate over time, imbuing the cell with new properties that allow the cancer to gain a foothold and then spread. However, some of these mutations simultaneously make cancer cells vulnerable to treatment.
Andrea Marion Marquard from DTU Bioinformatics has been working to find new points of attack to treat cancer on the basis of these mutations. For example, she has measured patterns of mutations which may reveal whether a cancer tumour is vulnerable to specific types of chemotherapy—a familiar method for some types of cancer (breast/ovarian). Similar patterns can also be identified in other forms of cancer, which means that other patients stand to benefit from this type of treatment.
Andrea Marion Marquard has also demonstrated that DNA analysis can be used to diagnose cancer in cases where the cancer spreads to other organs, but where clinical tests have proved unable to identify the original source organ. In analyses from thousands of cancer patients, the new analysis method succeeded in identifying the source of the cancer in 85 per cent of cases.