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  • richardmitnick 10:30 am on May 22, 2020 Permalink | Reply
    Tags: "New and improved drone mapping software", A miniaturized hybrid device, Emmanuel Cledat, EPFL-École Polytechnique Fédérale de Lausanne   

    From École Polytechnique Fédérale de Lausanne: “New and improved drone mapping software” 


    From École Polytechnique Fédérale de Lausanne

    5.22.20
    Sandrine Perroud

    1
    For his thesis, an EPFL PhD student Emmanuel Cledat has enhanced the accuracy and reliability of drone mapping – a technique that is gaining traction across many sectors of society.

    Making drone mapping more accurate is one of the goals of the Geodetic Engineering Laboratory (Topo), which is run by Bertrand Merminod within EPFL’s School of Architecture, Civil and Environmental Engineering (ENAC). Drones are not only toys for big and little kids – they also serve many practical purposes. They can be used to monitor dams and railroads in order to prevent accidents, or to create 3D digital copies of historical monuments in case they are accidentally or deliberately destroyed. They can also capture images from one season to the next in order to measure soil erosion.

    “It’s very important to be as accurate as possible,” says Emmanuel Cledat, who has just completed his PhD thesis at the Topo lab. “When it looks like a cliff has moved slightly over the winter, you have to be able to tell whether it’s a real topographical change or just a georeferencing error.” Cledat has spent the last four years developing software capable of accurately processing data acquired by sensors embedded on drones. He received the Best Young Author Award 2020 from the International Society for Photogrammetry and Remote Sensing (ISPRS) for an article about his thesis project.

    Planes and helicopters used for mapping are generally equipped with four types of sensor: a GPS (or GNSS) and an inertial measurement unit (IMU), which determine the vehicle’s position and orientation; a camera; and a LIDAR laser scanner, which measures distances by recording the time it takes for the laser beam to travel from the scanner to the object and back again.

    A miniaturized, hybrid device

    Until recently, LIDAR laser scanners could weigh up to 10 kilos. The Topo lab, together with EPFL spin-off Helimap System SA, were pioneers in developing aerial mapping systems involving helicopters, which can carry heavy equipment like a LIDAR scanner and a navigation-grade IMU. But in recent years, both industry professionals and researchers have been focused on making these measuring devices much smaller. Cledat was able to hybridize the data acquired by miniaturized sensors embedded on a drone (a GNSS, LIDAR, IMU and camera) such that the resulting map is almost as accurate as those obtained with a helicopter. A drone-based mapping technique is a greener alternative and one more suited to hard-to-reach terrain.

    As part of his thesis, Cledat carefully calibrated each sensor to make them as effective and reliable as possible. To do this, he used the lab’s calibration fields near Vufflens-la-Ville in Vaud Canton. He earned the ISPRS award for his work on camera calibration. The bundle adjustment software he developed is used to cross-check the measurements in order to correct them all simultaneously. This results in an accurate image of the area and of the drone’s position and orientation. Cledat’s software will be further developed within the lab as part of another thesis project.

    Cledat plans to return to earth for the next step in his career. His upcoming project will help people who are wary of cycling around town. He wants to equip bikes with mini sensors made for drones, together with noise and air-quality sensors. He will use the data collected to map out city traffic and quantify potential risks for cyclists so that road infrastructure and local road safety campaigns can be adjusted accordingly. Watch this space.

    References

    Emmanuel Cledat, “On the adjustment, calibration and orientation of drone photogrammetry and laser-scanning,” thesis under the supervision of Jan Skaloud and Davide Antonio Cucci, EPFL, May 2020.

    Emmanuel Cledat, Davide Antonio Cucci, Jan Skaloud, “Camera calibration models and methods in corridor mapping with UAVs,” ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLIII, 2020.

    E. Cledat, J. Skaloud, “Fusion of Photo with Airborne Laser Scanning,” ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences, XLIII, 2020.

    E. Cledat, D. A. Cucci, “Mapping GNSS restricted environments with a drone tandem and indirect position control,” ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences, vol. IV-2/W3, pp. 1–7, 2017.

    See the full article here .

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 10:35 am on March 22, 2020 Permalink | Reply
    Tags: "A new tool for identifying climate-adaptive coral reefs", , , EPFL-École Polytechnique Fédérale de Lausanne   

    From École Polytechnique Fédérale de Lausanne: “A new tool for identifying climate-adaptive coral reefs” 


    From École Polytechnique Fédérale de Lausanne

    3.22.20
    Marie Chatel

    1

    New tools to determine climate-adaptive coral reefs

    Climate change is threatening the world’s coral reefs, and saving them all will prove impossible. A team from EPFL has developed a method for identifying corals with the greatest adaptive potential to heat stress. The research, published in the journal Evolutionary Applications, should support improved and better-targeted marine biodiversity conservation strategies.

    Coral reefs are home to up to one-third of global marine biodiversity and, as such, are a high conservation priority. Yet these precious ecosystems have declined rapidly in the past 20 years, resulting in significant species loss and bringing socioeconomic hardship to tropical regions of the world that rely heavily on fishing and tourism. This decline is driven by bleaching, the process by which coral dies.

    Bleaching occurs when coral suffers from heat stress, which weakens the organism and can ultimately lead to its demise. “The future of coral reefs will depend on coral’s ability to adapt to warming oceans,” says Oliver Selmoni, a doctoral assistant at EPFL’s Laboratory of Geographic Information Systems (LASIG). “Temperature is the leading cause of coral death. We’ve found a way to predict which corals are best equipped to cope with heat stress – data that’s currently absent from global conservation strategies.”

    It is already known that certain corals are more accustomed to surviving in warmer waters and, therefore, better able to cope with abnormal temperature spikes. But extrapolating this knowledge to the scale of an entire reef has so far proved difficult. This new piece of research is a joint effort between EPFL and the French National Research Institute for Sustainable Development (IRD) based in Nouméa, New Caledonia, with the support of the United Nations Environment Programme (UNEP) and the International Coral Reef Initiative (ICRI). In addition to developing a method for locating so-called “adaptive” corals, the team also sought to determine how this information could be used to better protect corals by reinforcing their adaptive potential.

    A two-pronged study

    The study marks the first time that the principles of environmental genomics have been applied to the marine environment to support coral reef conservation. The researchers focused on a flagship coral species in Japan’s Ryukyu Archipelago, cross-referencing the results of a genetic analysis with satellite data showing changes in environmental conditions – specifically, ocean temperature – over the past 30 years.

    The team developed a model that uses objective, quantifiable and mappable variables to predict which genotypes are associated with adaptability and, therefore, make it more likely that a particular coral will be better suited to surviving in a given environment. They discovered six genomic regions involved in promoting resistance to heat stress. “We were able to identify individuals carrying potential heat-stress-adapted genotypes and to understand how they disperse to neighboring reefs,” says Selmoni.

    Scaling up

    At present, governments establish marine protected areas (MPAs) according to the level of threat posed by human activity. The EPFL team is calling for a different approach, with conservation efforts focusing on reefs with the greatest chance of survival because they carry the adapted genotypes. Another option would be to encourage genetic mutations by transplanting adaptive corals into reefs that are less able to withstand rising temperatures.

    Following a successful proof of concept, the model was incorporated into a web application that ranks corals by adaptability. The tool, developed for MPAs managers, will be scaled up in the future as the EPFL team studies other coral species and adds more genotypes to the database. The model is also set to be deployed in two other parts of the world. The Transnational Red Sea Research Center, founded by Professor Anders Meibom at EPFL and supported by the Swiss Federal Department of Foreign Affairs (FDFA), will use it to support coral reef conservation work in the Red Sea, and ManaCo, a network operating in the Pacific region, will likewise add the model to its suite of marine conservation tools.

    See the full article here .

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    Please help promote STEM in your local schools.

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 10:51 am on March 10, 2020 Permalink | Reply
    Tags: "Introducing the light-operated hard drives of tomorrow", , , , EPFL-École Polytechnique Fédérale de Lausanne   

    From École Polytechnique Fédérale de Lausanne: “Introducing the light-operated hard drives of tomorrow” 


    From École Polytechnique Fédérale de Lausanne

    03.10.20
    Tooba Neda Safi

    1
    What do you get when you place a thin film of perovkite material used in solar cells on top of a magnetic substrate? More efficient hard drive technology. EPFL physicist László Forró and his team pave the way for the future of data storage.

    “The key was to get the technology to work at room temperature,” explains László Forró, EPFL physicist. “We had already known that it was possible to rewrite magnetic spin using light, but you’d have to cool the apparatus to – 180 degrees Celsius.”

    Forró, along with his colleagues Bálint Náfrádi and Endre Horváth, succeeded at tuning one ferromagnet at room temperature with visible light, a proof of concept that establishes the foundations of a new generation of hard drives that will be physically smaller, faster, and cheaper, requiring less energy compared to today’s commercial hard drives. The results are published in PNAS.

    A hard drive functions as a data storage device in a computer, where a large amount of data can be stored with an electromagnetically charged surface.

    Nowadays, the demand for high capacity hard drives has increased more than ever. Computer users handle large files, databases, image or video files, using software, all of which require a large amount of memory in order to save and process the data as quickly as possible.

    The EPFL scientists used a halide perovskite/oxide perovskite heterostructure in their new method for reversible, light-induced tuning of ferromagnetism at room temperature. Having a perovskite structure represents a novel class of light-absorbing materials.

    As reported in the publication,

    “The rise of digitalization led to an exponential increase in demand for data storage. Mass-storage is resolved by hard-disk drives, HDDs, due to their relatively long lifespan and low price. HDDs use magnetic domains, which are rotated to store and retrieve information. However, an increase in capacity and speed is continuously demanded. We report a method to facilitate the writing of magnetic bits optically. We use a sandwich of a highly light sensitive (MAPbI3) and a ferromagnetic material (LSMO), where illumination of MAPbI3 drives charge carriers into LSMO and decreases its magnetism. This is a viable alternative of the long-sought-after heat-assisted magnetic recording (HAMR) technology, which would heat up the disk material during the writing process.”

    The method is still experimental, but it may be used to build the next generation of memory-storage systems, with higher capacities and with low energy demands. The method provides a stand for the development of a new generation of magneto-optical hard drives. Forró concludes: “ We are now looking for investors who would be interested in carrying on the patent application, and for industrial partners to implement this original idea and proof of principle into a product.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

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    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 5:03 pm on February 21, 2020 Permalink | Reply
    Tags: "Scientists finally confirm a 50-year-old theory in mechanics", , EPFL-École Polytechnique Fédérale de Lausanne, Mechanics, NGT-narrow groove theory which explains how air-lubricated bearings work in mechanical systems.   

    From École Polytechnique Fédérale de Lausanne: “Scientists finally confirm a 50-year-old theory in mechanics” 


    From École Polytechnique Fédérale de Lausanne

    21.02.20
    Nathalie Jollien

    An experiment by EPFL researchers has confirmed a theory that has been used in mechanics for over half a century – despite never having been fully validated. The team could now use the theory in bolder and more innovative ways in their quest to develop ever better energy systems.

    1
    Jürg Schiffmann and Eliott Guenat © EPFL 2020

    Some theories are widely used even though they have never been experimentally validated. One example is the so-called narrow groove theory, or NGT, which explains how air-lubricated bearings work in mechanical systems.

    The theory was proposed in 1965 but, until recently, it had only been tested partially or indirectly. Researchers at EPFL’s Laboratory for Applied Mechanical Design (LAMD), based at Microcity in Neuchâtel, have now closed a gap that has persisted in the scientific literature for over 50 years. The team has published its findings in the journal Mechanical Systems and Signal Processing.

    Why did it take so long to validate the theory? “At the time, engineers were content to observe that the theory worked,” says Eliott Guenat, a doctoral assistant at EPFL and the paper’s lead author. “But that’s all changed, because the mechanical parts we’re developing today are much more advanced and intricate.”

    The narrow groove theory was proposed in 1965 by J. H. Vohr and C. Y. Chow, two engineers at New York-based Mechanical Technology, Inc. The theory explains the working of herringbone grooved journal bearings, or HGJBs – a type of air-lubricated bearing that supports rotating parts in mechanical systems. Many different types of bearings exist, but HGJBs hold the most promise for developing ultrahigh-speed rotating machines because the rotor is supported on a cushion of air generated by the rotating shaft. “What makes HGJBs special is that they don’t cause wear and tear because there’s no contact,” explains Jürg Schiffmann, who heads the LAMD. “In my lab, we’re using this design to develop the energy systems of the future.”

    Validating the theory

    To validate the narrow groove theory, the researchers mounted a rotor supported by several HGJBs on a test rig, setting it spinning at 100,000 rotations per minute. Next, they used a shaker system to vibrate the rotor and watched how it reacted. The observations allowed them to calculate the bearings’ stiffness and damping coefficients, which they compared against the theory’s predictions. They found that NGT tended to marginally overestimate both values.

    “We were able to quantify the extent to which the theory holds,” says Guenat. “Now that we’ve shored up our understanding, we can take the theory and apply it in industry and research in new ways.”

    Guenat plans to conduct more experiments to take further measurements. “Instead of using air-lubricated bearings, we’ll run the experiment again with refrigerant, a gas used in heat pumps,” he explains. “The idea is to confirm that the theory holds not just in air, but also in a medium with markedly different chemical and physical properties.”

    Elegant in its simplicity

    NGT is a mathematically elegant theory that would likely never have seen the light of day had engineers only now taken an interest in air-lubricated bearings. “These days, we feed our data into a computer and let the processor do the heavy lifting,” explains Guenat. “But even with modern processing power, arriving at the result would take several minutes. With NGT, we can do the same in just a few seconds.” The fully validated theory could have innovative applications in energy system design.

    See the full article here .

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    Please help promote STEM in your local schools.

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    EPFL bloc

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 1:05 pm on February 12, 2020 Permalink | Reply
    Tags: EPFL-École Polytechnique Fédérale de Lausanne, Excitons-bound pairs of negative electrons and positive holes., , Mahan exciton, Mott density, , This quasiparticle has now been observed in a room temperature lead-halide perovskite.   

    From École Polytechnique Fédérale de Lausanne: “New quasiparticle unveiled in room temperature semiconductors” 


    From École Polytechnique Fédérale de Lausanne

    12.02.20
    Author: Mediacom

    1
    Physicists from Switzerland and Germany have unveiled fingerprints of the long-sought particle known as Mahan exciton in the room temperature optical response of the popular methylammonium lead halide perovskites.

    The optical properties of semiconductors are governed by the so-called “excitons”, which are bound pairs of negative electrons and positive holes. Excitons are important because they transport energy (with no net charge) across materials and thus they play a crucial role in a number of optoelectronic devices. The ability to control the excitonic properties of semiconductors (by tuning parameters such as temperature, pressure, charge density, electric and magnetic fields) is key to broadening the range and diversity of applications. In particular, when the density of charge carriers (electrons and holes) increases, excitons tend to melt and a semiconductor eventually turns into a metal at the so-called Mott density.

    However, back in 1967, Gerald Mahan predicted that a different type of exciton can still persist above the Mott density. Despite years of research, this so-called Mahan exciton has not been observed, let alone under the normal operating conditions of devices.

    This has now just been achieved by the group of Majed Chergui at EPFL, in collaboration with Alexander Steinhoff (University of Bremen), Ana Akrap (University of Fribourg), and the group of László Forró (EPFL). Publishing in Nature Communications, the teams uncovered signatures of Mahan excitons in the very popular lead-bromide organic-inorganic perovskite. The researchers mapped how the material’s optical properties modify at increasing densities of charge carriers with a temporal resolution of tens of femtoseconds (one femtosecond is one millionth of a billionth of a second). Mahan excitons emerged in the optical properties with the distinctive features predicted by theory.

    What is remarkable is that this quasiparticle has now been observed in a room temperature lead-halide perovskite, a cheap and abundant semiconductor that is intensely investigated for applications such as photovoltaics, luminescent materials, or lasers. The latter two applications strongly rely on high densities of charge carriers. Furthermore, on the fundamental side, these findings deepen our knowledge of many-body phenomena in condensed matter systems, paving the route toward the use of perovskites for the Bose-Einstein condensation of hybrid states of light and excitons.

    “We were studying how the excitons in the perovskite react to the presence of a high charge carrier density” says Edoardo Baldini (previous PhD student at the EPFL and now postdoctoral researcher at MIT). “Suddenly we observed a spectroscopic feature that could not be explained in the framework of other phenomena known in semiconductors.” “Digging into the theory we realized it could have been due to the excitons predicted by Mahan long ago” adds Tania Palmieri, the PhD student that led the project. “This discovery further demonstrates that hybrid perovskites are special materials not only for optoelectronic applications but also for unveiling new fundamental processes.”

    See the full article here .

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    Please help promote STEM in your local schools.

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 11:19 am on December 7, 2019 Permalink | Reply
    Tags: "Liquid flow is influenced by a quantum effect in water", , , , EPFL-École Polytechnique Fédérale de Lausanne, Quantum effect   

    From École Polytechnique Fédérale de Lausanne: “Liquid flow is influenced by a quantum effect in water” 


    From École Polytechnique Fédérale de Lausanne

    07.12.19
    STI

    1
    Researchers at EPFL have discovered that the viscosity of solutions of electrically charged polymers dissolved in water is influenced by a quantum effect. This tiny quantum effect influences the way water molecules interact with one another. Yet, it can lead to drastic changes in large-scale observations. This effect could change the way scientists understand the properties and behavior of solutions of biomolecules in water, and lead to a better understanding of biological systems.

    Water is the basis of all life on earth. Its structure is simple – two hydrogen atoms bound to one oxygen atom – yet its behavior is unique among liquids, and scientists still do not fully understand the origins of its distinctive properties.

    When charged polymers are dissolved in water the aqueous solution becomes more viscous than expected. This high viscosity is used by nature in the human body. The lubricating and shock-absorbing properties of the synovial fluid – a solution of water and charged biopolymers – is what allows us to bend, stretch and compress our joints over our entire lives without damage.

    In a study published in Science Advances, researchers from the Laboratory for Fundamental BioPhotonics (LBP) at EPFL’s School of Engineering have shed new light on the viscosity of aqueous solutions. They showed that, contrary to the traditional view that repulsive interactions between polymers are solely responsible for the increase in viscosity, a nuclear quantum effect between water molecules also has a part to play.

    “So far, our understanding of charged polymer-water solutions was based on theories that treated the water itself as a background,” says Sylvie Roke, head of the LBP. “Our study shows that water-water interactions actually play an important role. The same could also be true of other physical and chemical processes that influence biology.”

    Why water is unique

    Water derives its unique properties from hydrogen bonds – short lived bonds between an oxygen atom of one water molecule and a hydrogen atom of another – that break and re-form hundred-thousands of billions of times per second. These bonds give liquid water a short-lived three-dimensional structure.

    It has long been known that water becomes more viscous when charged polymers are dissolved in it. The viscosity is influenced by the size of the molecule and additionally by the charge. The reason why charged polymers increase viscosity more than neutral ones has been attributed to like charges on the polymers repelling one another. In this study, however, the EPFL researchers found that the electrical charges also interact with the water molecules and alter the water-water interactions, further hindering the flow of the solution.

    The researchers measured viscosity by recording how long it took different solutions to flow down through a narrow tube. They also used special laser technology, developed at the lab, to probe water-water interactions in the same solutions on a molecular level. They found that the polymers made the hydrogen bond network more ordered which, in turn, correlated with an increase in viscosity.

    The researchers then repeated the experiments with heavy water (D2O), a molecule that is almost identical to light water (H2O) but has a slightly different hydrogen bonding network. They found surprisingly large differences in both water-water interactions and viscosity. Since polymers repel one another in the same way in both light and heavy water, they concluded that these differences must arise from small differences in the way the two molecules interact, meaning that a nuclear quantum effect is at play.

    Their discovery – that the stickiness of charged polymer solutions partially stems from nuclear quantum effects in water – has fundamental implications. “Water is everywhere,” explains Roke. “It makes up around 60% of the human body. These insights into the properties of water and how it interacts with other molecules, including biomolecules, will prove useful for developing new technologies – not just in health and biosciences, but also in materials and environmental science.”

    See the full article here .

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    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 2:05 pm on December 6, 2019 Permalink | Reply
    Tags: , Computational Solid Mechanics, , EPFL-École Polytechnique Fédérale de Lausanne,   

    From École Polytechnique Fédérale de Lausanne: “Gaining insight into the energy balance of earthquakes” 


    From École Polytechnique Fédérale de Lausanne

    06.12.19
    Sarah Aubort

    1
    Researchers at EPFL’s Computational Solid Mechanics Laboratory and the Weizmann Institute of Science have modeled the onset of slip between two bodies in frictional contact. Their work, a major step forward in the study of frictional rupture, could give us a better understanding of earthquakes – including how far and fast they travel.

    It’s still impossible to determine where and when an earthquake will occur. For example, California has for years been under the threat of the “Big One,” and closer to home, a recent series of small shocks in Valais Canton in early November has raised fears of a major earthquake in the region. Although we can’t predict earthquakes, researchers from EPFL and the Weizmann Institute of Science in Israel have made a step forward in assessing earthquake dynamics through a better understanding of how frictional slip – the relative motion of two bodies in contact under shear stress, such as tectonic plates – begins. Their work has been published in two complementary parts, in Physical Review X and Earth and Planetary Science Letters.

    “We wanted to understand what happens when two bodies in frictional contact suddenly start moving following a gradual increase of the shear stress: the way they start sliding will determine the speed and extent of the movement and, potentially, the severity of an earthquake,” explains Fabian Barras, a doctoral assistant at EPFL’s Computational Solid Mechanics Laboratory (LSMS) during this research, and first author of both articles.

    Parallels between slip front and fracture

    The way in which frictional sliding begins between two bodies is not as uniform as it appears. Ultrafast cameras show that slip starts at a specific point and then spreads to the rest of the surface. “This slip front dynamics is very similar to the way a crack propagates within a brittle material,” says Barras. The researchers’ first publication looks at the similarities between frictional rupture and dynamic fracture. “Although the physics of a crack and a slip front is not exactly the same, they both propagate because of a drop in the material’s load-bearing capacity behind the rupture. Using the analogy with dynamic fracture, we studied the origin of the drop of frictional stress observed in the wake of a slip front when the interface starts to move.”

    The researchers then looked at the concentration of stress at the slip front and used theoretical tools from the field of rupture dynamics to study the energy balance. Unlike the situation with a crack, friction continues to dissipate energy after slip has started. During an earthquake, only part of the available energy is used to propagate the rupture front, and the remainder is dissipated by friction, mainly in the form of heat. It is here that the researchers were able to revise previously used models and achieve a better understanding of how much frictional energy is involved in the propagation of the rupture front.

    They used high-performance computers to simulate seismic ruptures based on generic laws of friction, which reproduce the change in frictional force depending on the slip velocity measured between different types of materials. Using dynamic rupture theory and applying it to friction, the researchers were able to assess laboratory experiments and ensure that their predictions were correct. “We were able to validate our predictions across a wide range of experimentally observed rupture velocities. The theoretical models we developed could in the future help us better understand why certain earthquakes in nature are fast and violent, while others propagate slowly and occur over longer periods of time,” adds Barras.

    Deep geothermal energy and induced seismicity

    These advances in fundamental research could one day be applied to more complex models, such as those representing conditions along tectonic faults, especially where fluids are naturally present or injected into the ground. “Today, several promising technologies in the context of the energy transition – like deep geothermal energy – relies on underground fluid injection. It is important to have a better understanding of how those injections affect seismic activity. I hope to use the tools developed during my PhD to study that impact,” says Barras.

    “This work shows how research developed in a civil engineering laboratory can have very interesting implications for earthquake science and lead to cutting-edge publications in areas such as physics,” says Professor Jean-François Molinari, the head of EPFL’s Computational Solid Mechanics Laboratory. Fabian Barras has also received a grant from the Swiss National Science Foundation to continue his research in a laboratory specializing in fault geology at the University of Oslo.

    2
    Between two solids in frictional contact, slip nucleates at a point on the surface (corresponding to the hypocenter of an earthquake) before spreading to the rest of the interface – just like a crack growing through a brittle material. Using numerical simulation, researchers computed the shear stress profile after the onset of slip and studied the drop of frictional stress observed behind the rupture fronts (blue area in the inset).

    Funding

    This research was made possible through funding from the Swiss National Science Foundation (Grant No. 162569, Fabian Barras PhD), as well as from the Rothschild Caesarea Foundation in order to kick off a collaboration between Jean-François Molinari’s lab at EPFL and Eran Bouchbinder’s theoretical physics group at Weizmann. Eran Bouchbinder would also like to thank the Israel Science Foundation for its support (Grant No. 295/16).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 5:35 pm on November 30, 2019 Permalink | Reply
    Tags: , EPFL-École Polytechnique Fédérale de Lausanne, , , ,   

    From École Polytechnique Fédérale de Lausanne: “Controlling the optical properties of solids with acoustic waves” 


    From École Polytechnique Fédérale de Lausanne

    29.11.19
    Majed Chergui
    Nik Papageorgiou

    1
    Physicists from Switzerland, Germany, and France have found that large-amplitude acoustic waves, launched by ultrashort laser pulses, can dynamically manipulate the optical response of semiconductors.

    One of the main challenges in materials science research is to achieve high tunability of the optical properties of semiconductors at room temperature. These properties are governed by “excitons”, which are bound pairs of negative electrons and positive holes in a semiconductor.

    Excitons have become increasingly important in optoelectronics and the last years have witnessed a surge in the search for control parameters – temperature, pressure, electric and magnetic fields – that can tune excitonic properties. However, moderately large changes have only been achieved under equilibrium conditions and at low temperatures. Significant changes at ambient temperatures, which are important for applications, have so far been lacking.

    This has now just been achieved in the lab of Majed Chergui at EPFL within the Lausanne Centre for Ultrafast Science, in collaboration with the theory groups of Angel Rubio (Max-Planck Institute, Hamburg) and Pascal Ruello (Université de Le Mans). Publishing in Science Advances, the international team shows, for the first time, control of excitonic properties using acoustic waves. To do this, the researchers launched a high-frequency (hundreds of gigahertz), large-amplitude acoustic wave in a material using ultrashort laser pulses. This strategy further allows for the dynamical manipulation of the exciton properties at high speed.

    This remarkable result was reached on titanium dioxide at room temperature, a cheap and abundant semiconductor that is used in a wide variety of light-energy conversion technologies such as photovoltaics, photocatalysis, and transparent conductive substrates.

    “Our findings and the complete description we offer open very exciting perspectives for applications such as cheap acousto-optic devices or in sensor technology for external mechanical strain,” says Majed Chergui. “The use of high-frequency acoustic waves, as those generated by ultrashort laser pulses, as control schemes of excitons pave a new era for acousto-excitonics and active-excitonics, analogous to active plasmonics, which exploits the plasmon excitations of metals.”

    “These results are just the beginning of what can be explored by launching high-frequency acoustic waves in materials,” adds Edoardo Baldini, the lead author of the article who is currently at MIT. “We expect to use them in the future to control the fundamental interactions governing magnetism or trigger novel phase transitions in complex solids”.

    Other contributors

    University of the Basque Country
    Max Planck Institute for the Structure and Dynamics of Matter
    Simons Foundation (Flatiron Institute)
    CNRS Joint Research Units

    Funding

    Swiss National Science Foundation (NCCR:MUST and R’EQUIP), European Research Council (Advanced Grant DYNAMOX), Horizon 2020

    See the full article here .

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    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 10:13 am on October 29, 2019 Permalink | Reply
    Tags: , EPFL-École Polytechnique Fédérale de Lausanne, , Ophthalmology, SPOT-RVC which is short for Safe Puncture Optimized Tool for Retinal Vein Cannulation., We wanted to develop a surgical method for treating retinal vein occlusion which occurs when the main vein carrying blood away from the eye is blocked., When the retinal vein is blocked by a blood clot this reduces the amount of oxygen carried to the retina and can trigger sudden vision loss.   

    From École Polytechnique Fédérale de Lausanne: “A high-precision instrument for ophthalmologists” 

    From École Polytechnique Fédérale de Lausanne

    29.10.19
    Nathalie Jollien

    1
    The high-precision miniaturized medical device, SPOT-RVC © Instant-Lab

    EPFL scientists have helped develop a microscopic glass device that doctors could use to inject medicine into retinal veins with unprecedented accuracy. Their instrument meets an important need in eye surgery, delivering exceptional stability and precision.

    A team of researchers presented a breakthrough device for eye surgery at EPFL Neuchâtel’s Research Day on 11 September. The device – called SPOT-RVC, which is short for Safe Puncture Optimized Tool for Retinal Vein Cannulation – was developed through an Innosuisse sponsored R&D project involving two EPFL Neuchâtel labs (Instant-Lab and Galatea), the Jules-Gonin Hospital of Ophthalmology in Lausanne and Ticino-based FEMTOprint as implementation partner. The team’s findings has been the subject of several publications, including one recently in the Journal of Medical Devices.

    SPOT-RVC is a high-precision, miniaturized medical device made entirely of glass. It’s just 6 cm long and 1 mm thick, and it contains a tiny fluidic channel no wider than a strand of hair as well as a sophisticated mechanism of flexible blades. Doctors can use the device to inject medicine directly into a patient’s retinal veins – something that has never before been possible.

    2
    The high-precision miniaturized medical device, SPOT-RVC © Instant-Lab

    “We wanted to develop a surgical method for treating retinal vein occlusion, which occurs when the main vein carrying blood away from the eye is blocked. There is currently no way to treat this condition – we can only treat the resulting complications,” says Professor Thomas J. Wolfensberger, the chief physician at Jules-Gonin Hospital. And those complications can be severe. When the retinal vein is blocked by a blood clot, this reduces the amount of oxygen carried to the retina and can trigger sudden vision loss. Over 16 million people around the world suffer from this condition, which mostly afflicts the elderly.

    Combining microengineering and microfluid mechanics

    Thanks to SPOT-RVC, doctors will be able to inject blood-clot-dissolving compounds directly into patients’ retinal veins safely, without damaging the surrounding tissue. “One of the biggest problems we faced is that because veins are so small and their walls so thin, it’s hard to get the needle into the vein without overpuncturing. It’s like if you want to drill a hole into a plank of wood but don’t want the hole to go all the way through,” says Dr. Charles Baur, a senior scientist at Instant-Lab who imagined this novel concept of surgical instruments.

    The researchers therefore drew on Instant-Lab’s expertise in flexible microstructures and multistable systems to engineer a microscopic device (< 1 mm in diameter) that can transition from one stable state to another very quickly – in around a millisecond – and in a controlled manner. “With this dynamic perforation mechanism that controls both the penetration force and direction of the needle, retinal veins don’t have time to deform. In addition, the penetration force is independent of the force exerted by the surgeon’s hand, which limits the risk of overpuncturing,” says Dr. Baur.

    Another innovative feature of SPOT-RVC is its microscopic, flexible channel that extends all the way down to the needle tip, enabling doctors to inject the medicine. The channel was developed using an innovative process developed by scientists at Galatea, that allows for fabricating, arbitrarily long and shaped, sealed cavities.

    And finally, the device is made of a single piece of fused silica (SiO2), thanks to the unique expertise of FEMTOprint for integrating multiple functions in a same substrate. “Since it’s monolithic, there’s no assembly required – a step that would be nearly impossible and would make it very difficult to sterilize the instrument,” says Dr. Baur. To achieve this complex monolithic integration with the required levels of precision, FEMTOprint uses ultrafast lasers 3D printing and proprietary post-processing techniques. In this context, the Galatea lab provides expertise in the understanding of ultrafast laser-matter interactions and its use for making complex micro-devices, such as optofluidics and optomechanical devices.

    Winner of the Swiss high-precision industry award

    FEMTOprint presented SPOT-RVC at the Swiss high-precision industry convention (EPHJ), which was held this past June in Geneva. The device won the 2019 Exhibitors’ Grand Prix – an encouraging start.

    For now the device is still in the prototyping stage. “We got good results from our in vitro and in vivo tests,” says Dr. Baur. “Now it is necessary to conduct preclinical trials and obtain the necessary certifications. Then we’ll move on to the production stage, which will require a fairly large investment from the industrial partner. We genuinely hope that one day the device will become a useful tool for eye surgeons.”

    Discover the mechanism in video on https://youtu.be/1ZNGuvkzNsE.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 8:43 am on October 21, 2019 Permalink | Reply
    Tags: , EPFL-École Polytechnique Fédérale de Lausanne, The Giotto project   

    From École Polytechnique Fédérale de Lausanne: “With Giotto, artificial intelligence gets a third dimension” 

    EPFL bloc

    From École Polytechnique Fédérale de Lausanne

    21.10.19
    Sarah Aubort

    1
    The Giotto project, launched by EPFL startup Learn to Forecast, intends to revolutionize the way we use artificial intelligence. Drawing on the science of shapes, Giotto pushes AI forward by making it more reliable and intuitive in areas such as materials science, neuroscience and biology. Giotto is open-source and available free of charge on GitHub, and it’s already being used by some EPFL scientists.

    Researchers use artificial intelligence to solve complex problems, but it’s not a transparent science: AI’s computational capabilities often exceed our understanding and raise issues of reliability and trust among users. “Algorithms are becoming increasingly complex,” says Matteo Caorsi, the lead scientist at Learn to Forecast (L2F). “It’s very hard to understand how they work and thus to trust the solutions they provide or predict when they might get things wrong.”

    Shapes hidden within data

    To address this problem, L2F followed an intuitive approach based on the science of shapes. The result is Giotto, a free and open-source library that aims to revolutionize the way we use machine learning. “Humans understand shapes and colors better than numbers and equations,” says Aldo Podestà, the CEO of L2F, “which is why we think that we can use topology – the science of shapes – to build a new language between AI and users.”

    Giotto offers a toolkit that uses algorithms inspired by topology to address some of the shortcomings of machine learning. Users don’t need to be fluent in advanced mathematics, since Giotto is a turnkey method of revealing structures previously hidden within a dataset. “This new form of AI is based on graphs and their multidimensional versions, in other words, geometrical objects that can reveal essential structures within the data,” says Thomas Boys, a co-founder at L2F.

    Until now, machine learning algorithms sought performance, even if that meant depriving users of a fuller understanding of the nature of the results. “Giotto helps identify the framework underlying all relationships among the data, and this allows users to understand the data better and extract meaning from them with greater accuracy,” adds Boys. The project is named for Giotto di Bondone, the 13th-century artist who first introduced perspective into painting. L2F hopes to usher in a similar paradigm change in data science by combining machine learning with topology.

    New horizons

    To develop Giotto, its creators worked with EPFL researchers who use topology every day. This includes Professor Kathryn Hess Bellwald, the head of the Laboratory for Topology and Neuroscience. “One of Giotto’s main advantages is that, because of its user friendliness, it will be possible for scientists from all kinds of fields to use these tools as a regular part of their data science toolkit,” says Prof. Hess Bellwald. “This should lead to new insights in many different areas that one could not attain without Giotto.”

    Learn to Forecast (L2F) was founded at EPFL in 2017. Its aim is to use artificial intelligence to address a wide variety of issues. The company raised three million francs via 4FO Ventures to develop the Giotto library, and it now has 25 employees.

    For more information : https://www.giotto.ai
    Git Hub : https://github.com/giotto-learn/giotto-learn

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
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