Recent additions

  • Deep Reinforcement Learning for Query-Conditioned Video Summarization 

    Zhang, Yujia; Kampffmeyer, Michael C.; Zhao, Xiaoguang; Tan, Min (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-21)
    Query-conditioned video summarization requires to (1) find a diverse set of video shots/frames that are representative for the whole video, and that (2) the selected shots/frames are related to a given query. Thus it can be tailored to different user interests leading to a better personalized summary and differs from the generic video summarization which only focuses on video content. Our work targets ...
  • Sparse signal recovery in MIMO specular meteor radars with waveform diversity 

    Urco, Miguel; Chau, Jorge Luis; Weber, Tobias; Vierinen, Juha; Volz, Ryan (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-15)
    Since the 1950s, specular meteor radars (SMRs) have been used to study the mesosphere and lower thermosphere (MLT) dynamics. Atmospheric parameters derived from SMRs are highly dependent on the number of detected meteors and the accuracy of the meteors' locations. Recently, incoherent and coherent multiple-input-multiple-output (MIMO) radar approaches combined with waveform diversity have been ...
  • Investigation of exceptionally radar-dark regions on the lunar nearside 

    Tveito, Torbjørn; Vierinen, Juha; Serrano, Alessandra (Conference object; Konferansebidrag, 2019-08)
    Remote sensing of planetary surfaces is an effective method for gaining knowledge of the processes that shape the planetary bodies in our solar system. This is useful for uncovering the environment of the primordial solar system and to study the current state of the upper crusts of the other planets in our neighborhood. A recent 6-meter wavelength polarimetric radar map of the Moon [?] showed ...
  • The Thorpex polar low analysed with AROME-Arctic 

    Stoll, Patrick J.; Valkonen, Teresa M.; Graversen, Rune G.; Noer, Gunnar (Conference object; Konferansebidrag, 2019-04)
  • Observing Mesospheric Turbulence With Specular Meteor Radars: A Novel Method for Estimating Second-Order Statistics of Wind Velocity 

    Vierinen, Juha; Chau, Jorge L.; Charuvil, Harikrishnan; Urco, Miguel; Clahsen, Matthias; Avsarkisov, Victor; Marino, Raffaele; Volz, Ryan (Journal article; Peer reviewed, 2019-07)
    There are few observational techniques for measuring the distribution of kinetic energy within the mesosphere with a wide range of spatial and temporal scales. <br>This study describes a method for estimating the three‐dimensional mesospheric wind field correlation function from specular meteor trail echoes. Each radar echo provides a measurement of a one‐dimensional projection of the wind velocity ...
  • Novel specular meteor radar systems using coherent MIMO techniques to study the mesosphere and lower thermosphere 

    Chau, J. L.; Urco, Miguel; Vierinen, Juha; Volz, Ryan; Clahsen, Matthias; Pfeffer, Nico; Trautner, Jörg (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-05)
    Typical specular meteor radars (SMRs) use one transmitting antenna and at least a five-antenna interferometric configuration on reception to study the mesosphere and lower thermosphere (MLT) region. The interferometric configuration allows the measurement of the angle-of-arrival (AOA) of the detected meteor echoes, which in turn is needed to derive atmospheric parameters (e.g., mean winds, momentum ...
  • MOSIDEO/CIRFA Tank Experiments on Behavior and Detection of Oil in Ice 

    Petrich, Christian; O'Sadnick, Megan Eileen; Brekke, Camilla; Myrnes, Marianne; Maus, Sønke; Salomon, Martina Lan; Woelk, Sofie; Grydeland, Tom; Jenssen, Rolf-Ole Rydeng; Eicken, Hajo; Oggier, Marc; Ferro-Famil, Laurent; Harkati, Lekhmissi; Rebane, Ott; Reimer, Nils (Journal article; Tidsskriftartikkel; Peer reviewed; Conference object; Konferansebidrag, 2019-06)
    In the Arctic, presence of sea ice presents a challenge to safe and sustainable operations. To optimize planning and minimize impact of inadvertent oil spills, oil-in-ice experiments were performed at the HSVA Arctic Environmental Test Basin (AETB) from 14 March to 4 April 2017. Following an under-ice spill and simulated springtime warming, the microscopic movement and distribution of oil in the sea ...
  • A low-cost coastal buoy for ice and metocean measurements 

    Petrich, Christian; O'Sadnick, Megan Eileen; Kleven, Øystein; Sæther, Irina Vasiljeva (Journal article; Tidsskriftartikkel; Peer reviewed; Conference object; Konferansebidrag, 2019-06)
    Regionally, an ice cover in fjords of mainland Norway may form and break up repeatedly during winter. Due to relatively high water temperatures, the freeze-up process is expected to be related to freshwater-induced stratification in the fjords in conjunction with low air temperatues. In an attempt to identify the variability of water conditions in the fjords leading up to and during ice cover ...
  • Radar studies of ionospheric dusty plasma phenomena 

    Mann, Ingrid; Gunnarsdottir, Tinna; Häggström, Ingemar; Eren, Saliha; Tjulin, Anders; Myrvang, Margaretha; Rietveld, Mike T; Dalin, Peter; Jozwicki, Dorota; Trollvik, Henriette Marie Tveitnes (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-17)
    We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of ...
  • Solar Flare Effects on 150-km Echoes Observed Over Jicamarca: WACCM-X Simulations 

    Pedatella, Nick; Chau, Jorge Luis; Vierinen, Juha; Qian, L; Reyes, Pablo; Kudeki, Erhan; Lehmacher, G; Oppenheim, Meers (Journal article; Tidsskriftartikkel; Preprint; Manuskript, 2019-09-11)
    Jicamarca Radio Observatory observations and Whole Atmosphere Community Climate Model with thermosphere‐ionosphere eXtension (WACCM‐X) simulations are used to investigate the effects of the September 7, 2005 X‐17 solar flare on 150‐km echoes, electron densities, and vertical plasma drifts. The solar flare produces a remarkably similar response in the observed 150‐km echoes and simulated electron ...
  • Characterization of color cross-talk of CCD detectors and its influence in multispectral quantitative phase imaging 

    Ahmad, Azeem; Kumar, Anand; Dubey, Vishesh Kumar; Butola, Ankit; Ahluwalia, Balpreet Singh; Mehta, Dalip Singh (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)
    Multi-spectral quantitative phase imaging (QPI) is an emerging imaging modality for wavelength dependent studies of several biological and industrial specimens. Simultaneous multi-spectral QPI is generally performed with color CCD cameras. Here, we present a new approach for accurately measuring the color crosstalk of 2D area detectors, without needing prior information about camera specifications. ...
  • Super-condenser enables labelfree nanoscopy 

    Ströhl, Florian; Opstad, Ida Sundvor; Tinguely, Jean-Claude; Dullo, Firehun Tsige; Mela, Ioanna; Osterrieth, Johannes W.M; Ahluwalia, Balpreet Singh; Kaminski, Clemens F. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-22)
    Labelfree nanoscopy encompasses optical imaging with resolution in the 100 nm range using visible wavelengths. Here, we present a labelfree nanoscopy method that combines coherent imaging techniques with waveguide microscopy to realize a <i>super-condenser</i> featuring maximally inclined coherent darkfield illumination with artificially stretched wave vectors due to large refractive indices of the ...
  • Maximizing Interpretability and Cost-Effectiveness of Surgical Site Infection (SSI) Predictive Models Using Feature-Specific Regularized Logistic Regression on Preoperative Temporal Data 

    Kocbek, Primoz; Fijacko, Nino; Soguero-Ruiz, Cristina; Mikalsen, Karl Øyvind; Maver, Uros; Brzan, Petra Povalej; Stozer, Andraz; Jenssen, Robert; Skrøvseth, Stein Olav; Stiglic, Gregor (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-19)
    This study describes a novel approach to solve the surgical site infection (SSI) classification problem. Feature engineering has traditionally been one of the most important steps in solving complex classification problems, especially in cases with temporal data. The described novel approach is based on abstraction of temporal data recorded in three temporal windows. Maximum likelihood L1-norm ...
  • A red tide in the pack ice of the Arctic Ocean 

    Olsen, Lasse Mork; Duarte, Pedro; Peralta-Ferriz, Cecilia; Kauko, Hanna Maria; Johansson, Malin; Peeken, Ilka; Różańska-Pluta, Magdalena; Tatarek, Agnieszka; Wiktor, Jozef; Fernández-Méndez, Mar; Wagner, Penelope Mae; Pavlov, Alexey K.; Hop, Haakon; Assmy, Phillipp (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-02)
    In the Arctic Ocean ice algae constitute a key ecosystem component and the ice algal spring bloom a critical event in the annual production cycle. The bulk of ice algal biomass is usually found in the bottom few cm of the sea ice and dominated by pennate diatoms attached to the ice matrix. Here we report a red tide of the phototrophic ciliate <i>Mesodinium rubrum</i> located at the ice-water interface ...
  • Dust trajectory simulations around Sun, Vega, and Fomalhaut 

    Stamm, Johann Immanuel; Czechowski, Andrzej; Mann, Ingrid; Baumann, Carsten; Myrvang, Margaretha (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
    <p><i>Context - </i>Vega and Fomalhaut display a thermal emission brightness that can possibly arise from hot dust near the stars, an inner extension of their planetary debris disks. There was brought up an idea that nm-sized dust particles are kept in the vicinity of the stars by electromagnetic forces. This resembles the trapping that model calculations show in the corotating magnetic field in the ...
  • Detection of meteoroid hypervelocity impacts on the Cluster spacecraft: First results 

    Vaverka, Jakub; Pellinen-Wannberg, Asta; Kero, Johan; Mann, Ingrid; De Spiegeleer, Alexandre; Hamrin, Maria; Norberg, Carol; Pitkaenen, Timo (Journal article; Peer reviewed, 2017-06-29)
    We present the first study of dust impact events on one of the Earth‐orbiting Cluster satellites. The events were identified in the measurements of the wide band data (WBD) instrument on board the satellite operating in monopole configuration. Since 2009 the instrument is operating in this configuration due to the loss of three electric probes and is therefore measuring the potential between the ...
  • Single-input and multiple-output surface acoustic wave sensing for damage quantification in piezoelectric sensors 

    Pamwani, Lavish; Habib, Anowarul; Melandsø, Frank; Ahluwalia, Balpreet Singh; Shelke, Amit (Journal article; Peer reviewed, 2018-06-22)
    The main aim of the paper is damage detection at the microscale in the anisotropic piezoelectric sensors using surface acoustic waves (SAWs). A novel technique based on the single input and multiple output of Rayleigh waves is proposed to detect the microscale cracks/flaws in the sensor. A convex-shaped interdigital transducer is fabricated for excitation of divergent SAWs in the sensor. An angularly ...
  • ICEBEAR: An All‐Digital Bistatic Coded Continuous Wave Radar for Studies of the E Region of the Ionosphere 

    Huyghebaert, Devin; Hussey, Glenn; Vierinen, Juha; McWilliams, Kathryn; St‐Maurice, Jean-Pierre (Journal article; Peer reviewed, 2019-04-15)
    The Ionospheric Continuous-wave E region Bistatic Experimental Auroral Radar (ICEBEAR) is a coherent scatter ionospheric radar. It operates at a frequency of 49.5 MHz, which is ideal for observing E region coherent echoes. The radar is located in Saskatchewan, Canada, and is operated by the University of Saskatchewan. The ICEBEAR system uses a continuous-wave (CW) signal and requires isolation between ...
  • Improved LLM Methods Using Linear Regression 

    Zhao, Zihang; Lang, Wenhui; Doulgeris, Anthony Paul; Chen, Lu (Journal article; Peer reviewed, 2017-12-04)
    This paper is focused on investigations of the improved correction of the effect of variation in incidence angle on ScanSAR data. Conventional correction methods (such as LLM, locally linear mapping) typically assume that each target class has a similarity distribution in the middle of the image. The objectives of this study are to extend the correction algorithm to full swath width without any ...
  • Speeding Up Non-Gaussian POLSAR Image Analysis 

    Doulgeris, Anthony Paul; Hu, Dingsheng (Journal article; Peer reviewed, 2017-12-04)
    Non-Gaussian statistical models fit SAR data better than Gaussian-based statistics, in most cases, but are complicated and time-consuming to use for unsupervised image segmentation via probabilistic clustering. The more advanced the model, the more complicated and slow the clustering. The U-distribution has been demonstrated to be one of the most flexible models, capturing the Gaussian/Wishart, the ...

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