Underwater SLAM in a marina environment

This paper describes a navigation system for autonomous underwater vehicles (AUVs) in partially structured environments, such as dams, harbors, marinas or marine platforms. A mechanical scanning imaging sonar is used to obtain information about the location of planar structures present in such environments. A modified version of the Hough transform has been developed to extract line features, together with their uncertainty, from the continuous sonar dataflow. The information obtained is incorporated into a feature-based SLAM algorithm running an Extended Kalman Filter (EKF). Simultaneously, the AUV's position estimate is provided to the feature extraction algorithm to correct the distortions that the vehicle motion produces in the acoustic images. Experiments carried out in a marina located in the Costa Brava (Spain) with the Ictineu AUV show the viability of the proposed approach

Positioning an underwater vehicle through image mosaicking

Mosaics have been commonly used as visual maps for undersea exploration and navigation. The position and orientation of an underwater vehicle can be calculated by integrating the apparent motion of the images which form the mosaic. A feature-based mosaicking method is proposed in this paper. The creation of the mosaic is accomplished in four stages: feature selection and matching, detection of points describing the dominant motion, homography computation and mosaic construction. In this work we demonstrate that the use of color and textures as discriminative properties of the image can improve, to a large extent, the accuracy of the constructed mosaic. The system is able to provide 3D metric information concerning the vehicle motion using the knowledge of the intrinsic parameters of the camera while integrating the measurements of an ultrasonic sensor. The experimental results of real images have been tested on the GARBI underwater vehicle

C3-symmetric peptide scaffolds are functional mimetics of trimeric CD40L.

Interaction between CD40, a member of the tumor necrosis factor receptor (TNFR) superfamily, and its ligand CD40L, a 39-kDa glycoprotein, is essential for the development of humoral and cellular immune responses. Selective blockade or activation of this pathway provides the ground for the development of new treatments against immunologically based diseases and malignancies. Like other members of the TNF superfamily, CD40L monomers self-assemble around a threefold symmetry axis to form noncovalent homotrimers that can each bind three receptor molecules. Here, we report on the structure-based design of small synthetic molecules with C3 symmetry that can mimic CD40L homotrimers. These molecules interact with CD40, compete with the binding of CD40L to CD40, and reproduce, to a certain extent, the functional properties of the much larger homotrimeric soluble CD40L. Architectures based on rigid C3-symmetric cores may thus represent a general approach to mimicking homotrimers of the TNF superfamily.

Iowa’s Bridge and Highway Climate Change and Extreme Weather Vulnerability Assessment Pilot, HEPN-707, 2015

The Iowa Department of Transportation (DOT) is responsible for approximately 4,100 bridges and structures that are a part of the state’s primary highway system, which includes the Interstate, US, and Iowa highway routes. A pilot study was conducted for six bridges in two Iowa river basins—the Cedar River Basin and the South Skunk River Basin—to develop a methodology to evaluate their vulnerability to climate change and extreme weather. The six bridges had been either closed or severely stressed by record streamflow within the past seven years. An innovative methodology was developed to generate streamflow scenarios given climate change projections. The methodology selected appropriate rainfall projection data to feed into a streamflow model that generated continuous peak annual streamflow series for 1960 through 2100, which were used as input to PeakFQ to estimate return intervals for floods. The methodology evaluated the plausibility of rainfall projections and credibility of streamflow simulation while remaining consistent with U.S. Geological Survey (USGS) protocol for estimating the return interval for floods. The results were conveyed in an innovative graph that combined historical and scenario-based design metrics for use in bridge vulnerability analysis and engineering design. The pilot results determined the annual peak streamflow response to climate change likely will be basin-size dependent, four of the six pilot study bridges would be exposed to increased frequency of extreme streamflow and would have higher frequency of overtopping, the proposed design for replacing the Interstate 35 bridges over the South Skunk River south of Ames, Iowa is resilient to climate change, and some Iowa DOT bridge design policies could be reviewed to consider incorporating climate change information.

Tuotealustapohjaisen suunnittelun vaikutukset risteilijän suunnitteluaikatauluihin

Tuotealustapohjaisella suunnittelulla pyritään hyödyntämään jo kertaalleen hyväksi todettuja kokonaisuuksia ja moduuleja, joiden avulla voidaan nopeasti suunnitella uusia tuotteita. Tarkoituksena on suunnitella asiakkaan näkökulmasta monia erilaisia tuotteita jopa sarjatuotannon kustannustehokkuudella. Tutkimuksessa esitetään risteilijän tuotealustapohjainen suunnitteluprosessi. Lisäksi työn tavoitteena on tutkia uuden suunnitteluprosessin vaikutukset risteilijän suunnitteluaikatauluihin. Tutkimuksessa haastateltiin Turun telakan suunnitteluosaston ja kehitysosaston johtajia. Haastatteluilla selvitettiin nykyisen suunnitteluprosessin haasteita, joiden nähtiin erityisesti viivästyttävät suunnitteluaikatauluja. Keskeisiä haasteita ovat suunnitteluresurssien ylikuormitus ja suunnittelulaadun huonontuminen. Lisäksi kartoitettiin tavoitteet risteilijän tuotealustaratkaisulle ja suunnitteluaikataululle. Haastattelukierroksen pohjalta ja teoriaa soveltaen analysoitiin risteilijän modulaariseen tuotealustaan perustuva suunnitteluprosessi. Tätä suunnitteluprosessia tutkittiin edelleen case-tutkimuksessa jääasemien osalta, jossa haastateltiin kyseisten alueiden suunnittelijoita. Lisäksi case-tutkimuksessa verrattiin jääaseman ja baaripentterin perussuunnittelun vaiheita toisiinsa. Näistä saatuja tutkimustuloksia verrattiin hyttialueen vakioidun perussuunnitteluohjeen vaikutuksiin suunnitteluprosessissa. Onnistunut tuotealustapohjainen suunnittelu vaatii sitoutumista jokaisella organisaation tasolla, jotta tuotealustassa olevien vakioituja moduuleja myös käytettäisiin. Modulaarisesta toiminnasta siirtyminen tuotealustapohjaiseen suunnitteluun vaatii vakioituja moduuleja ja vakioituja rajapintoja risteilijässä. Case-tutkimuksessa ja johtopäätöksissä on todettu uuden suunnitteluprosessin lyhentävän ja tuovan kustannussäästöjä tuotteen valmistusprosessissa.

Field-Programmable Gate Array Card for Readout and Control of Cryoelectronics

The main goal of the present Master’s Thesis project was to create a field-programmable gate array (FPGA) based system for the control of single-electron transistors or other cryoelectronic devices. The FPGA and similar technologies are studied in the present work. The fixed and programmable logic are compared with each other. The main features and limitations of the hardware used in the project are investigated. The hardware and software connections of the device to the computer are shown in detail. The software development techniques for FPGA-based design are described. The steps of design for programmable logic are considered. Furthermore, the results of filters implemented in the software are illustrated.

Mallipohjainen suunnittelu osana aurinkosähkövaihtosuuntaajan tuotekehitystä

Työssä selvitetään mallipohjaisen suunnittelun ja simulointimallista tuotetun ohjelmakoodin kelpoisuutta tuotekehityskäytössä. Työtapoja tutkitaan, koska halutaan selvittää parantavatko esitetyt toimintatavat aurinkosähkövaihtosuuntaajien ohjelmistokehitystä. Työssä käydään läpi mallipohjaisen suunnittelun työvaiheet, niiden sisältö ja tarkoitus. Aurinkosähköjärjestelmästä muodostetaan simulointimalli, josta tuotetaan maksimitehopisteseuraajan ohjelmakoodi, jonka toiminta testataan aurinkosähkövaihtosuuntaajan ohjausalustan simulaattorissa. Mallipohjainen suunnittelu mahdollistaa ohjelmistotuotekehityksen nopeuttamisen käyttämällä samaa järjestelmää useassa työvaiheessa. Ohjelmakoodin tuottaminen simulointimallista on mahdollista ja hyödyllistä, jos yrityksessä käytetään simulointitestausta säätö- ja ohjausjärjestelmän toiminnan suunnitteluun ja varmentamiseen.

Local Features in Image and Video Processing - Object Class Matching and Video Shot Detection

The usage of digital content, such as video clips and images, has increased dramatically during the last decade. Local image features have been applied increasingly in various image and video retrieval applications. This thesis evaluates local features and applies them to image and video processing tasks. The results of the study show that 1) the performance of different local feature detector and descriptor methods vary significantly in object class matching, 2) local features can be applied in image alignment with superior results against the state-of-the-art, 3) the local feature based shot boundary detection method produces promising results, and 4) the local feature based hierarchical video summarization method shows promising new new research direction. In conclusion, this thesis presents the local features as a powerful tool in many applications and the imminent future work should concentrate on improving the quality of the local features.

Découverte d'inhibiteurs de la dihydrofolate réductase R67 impliquée dans la résistance au triméthoprime.

Le triméthoprime (TMP) est un antibiotique communément utilisé depuis les années 60. Le TMP est un inhibiteur de la dihydrofolate réductase (DHFR) bactérienne chromosomale. Cette enzyme est responsable de la réduction du dihydrofolate (DHF) en tétrahydrofolate (THF) chez les bactéries, qui lui, est essentiel à la synthèse des purines et ainsi, à la prolifération cellulaire. La résistance bactérienne au TMP est documentée depuis plus de 30 ans. Une des causes de cette résistance provient du fait que certaines souches bactériennes expriment une DHFR plasmidique, la DHFR R67. La DHFR R67 n'est pas affectée par le TMP, et peut ainsi remplacer la DHFR chromosomale lorsque celle-ci est inhibée par le TMP. À ce jour, aucun inhibiteur spécifique de la DHFR R67 est connu. En découvrant des inhibiteurs contre la DHFR R67, il serait possible de lever la résistance au TMP que la DHFR R67 confère aux bactéries. Afin de découvrir des inhibiteurs de DHFR R67, les approches de design à base de fragments et de criblage virtuel ont été choisies. L'approche de design à base de fragments a permis d'identifier sept composés simples et de faible poids moléculaire (fragments) inhibant faiblement la DHFR R67. À partir de ces fragments, des composés plus complexes et symétriques, inhibant la DHFR R67 dans l'ordre du micromolaire, ont été élaborés. Des études cinétiques ont montré que ces inhibiteurs sont compétitifs et qu'au moins deux molécules se lient simultanément dans le site actif de la DHFR R67. L'étude d'analogues des inhibiteurs micromolaires de la DHFR R67 a permis de déterminer que la présence de groupements carboxylate, benzimidazole et que la longueur des molécules influencent la puissance des inhibiteurs. Une étude par arrimage moléculaire, appuyée par les résultats in vitro, a permis d'élaborer un modèle qui suggère que les résidus Lys32, Gln67 et Ile68 seraient impliqués dans la liaison avec les inhibiteurs. Le criblage virtuel de la librairie de 80 000 composés de Maybridge avec le logiciel Moldock, et les essais d'inhibition in vitro des meilleurs candidats, a permis d'identifier quatre inhibiteurs micromolaires appartenant à des familles distinctes des composés précédemment identifiés. Un second criblage virtuel, d'une banque de 6 millions de composés, a permis d'identifier trois inhibiteurs micromolaires toujours distincts. Ces résultats offrent la base à partir de laquelle il sera possible de développer iv des composés plus efficaces et possédant des propriétés phamacologiquement acceptables dans le but de développer un antibiotique pouvant lever la résistance au TMP conféré par la DHFR R67.

Alignment by Maximization of Mutual Information

A new information-theoretic approach is presented for finding the pose of an object in an image. The technique does not require information about the surface properties of the object, besides its shape, and is robust with respect to variations of illumination. In our derivation, few assumptions are made about the nature of the imaging process. As a result the algorithms are quite general and can foreseeably be used in a wide variety of imaging situations. Experiments are presented that demonstrate the approach registering magnetic resonance (MR) images with computed tomography (CT) images, aligning a complex 3D object model to real scenes including clutter and occlusion, tracking a human head in a video sequence and aligning a view-based 2D object model to real images. The method is based on a formulation of the mutual information between the model and the image called EMMA. As applied here the technique is intensity-based, rather than feature-based. It works well in domains where edge or gradient-magnitude based methods have difficulty, yet it is more robust than traditional correlation. Additionally, it has an efficient implementation that is based on stochastic approximation. Finally, we will describe a number of additional real-world applications that can be solved efficiently and reliably using EMMA. EMMA can be used in machine learning to find maximally informative projections of high-dimensional data. EMMA can also be used to detect and correct corruption in magnetic resonance images (MRI).

Positioning an underwater vehicle through image mosaicking

Mosaics have been commonly used as visual maps for undersea exploration and navigation. The position and orientation of an underwater vehicle can be calculated by integrating the apparent motion of the images which form the mosaic. A feature-based mosaicking method is proposed in this paper. The creation of the mosaic is accomplished in four stages: feature selection and matching, detection of points describing the dominant motion, homography computation and mosaic construction. In this work we demonstrate that the use of color and textures as discriminative properties of the image can improve, to a large extent, the accuracy of the constructed mosaic. The system is able to provide 3D metric information concerning the vehicle motion using the knowledge of the intrinsic parameters of the camera while integrating the measurements of an ultrasonic sensor. The experimental results of real images have been tested on the GARBI underwater vehicle

SLAM using an Imaging Sonar for Partially Structured Underwater Environments

In this paper we describe a system for underwater navigation with AUVs in partially structured environments, such as dams, ports or marine platforms. An imaging sonar is used to obtain information about the location of planar structures present in such environments. This information is incorporated into a feature-based SLAM algorithm in a two step process: (I) the full 360deg sonar scan is undistorted (to compensate for vehicle motion), thresholded and segmented to determine which measurements correspond to planar environment features and which should be ignored; and (2) SLAM proceeds once the data association is obtained: both the vehicle motion and the measurements whose correct association has been previously determined are incorporated in the SLAM algorithm. This two step delayed SLAM process allows to robustly determine the feature and vehicle locations in the presence of large amounts of spurious or unrelated measurements that might correspond to boats, rocks, etc. Preliminary experiments show the viability of the proposed approach

Underwater SLAM in a marina environment

This paper describes a navigation system for autonomous underwater vehicles (AUVs) in partially structured environments, such as dams, harbors, marinas or marine platforms. A mechanical scanning imaging sonar is used to obtain information about the location of planar structures present in such environments. A modified version of the Hough transform has been developed to extract line features, together with their uncertainty, from the continuous sonar dataflow. The information obtained is incorporated into a feature-based SLAM algorithm running an Extended Kalman Filter (EKF). Simultaneously, the AUV's position estimate is provided to the feature extraction algorithm to correct the distortions that the vehicle motion produces in the acoustic images. Experiments carried out in a marina located in the Costa Brava (Spain) with the Ictineu AUV show the viability of the proposed approach

Efficient topology estimation for large scale optical mapping

Large scale image mosaicing methods are in great demand among scientists who study different aspects of the seabed, and have been fostered by impressive advances in the capabilities of underwater robots in gathering optical data from the seafloor. Cost and weight constraints mean that lowcost Remotely operated vehicles (ROVs) usually have a very limited number of sensors. When a low-cost robot carries out a seafloor survey using a down-looking camera, it usually follows a predetermined trajectory that provides several non time-consecutive overlapping image pairs. Finding these pairs (a process known as topology estimation) is indispensable to obtaining globally consistent mosaics and accurate trajectory estimates, which are necessary for a global view of the surveyed area, especially when optical sensors are the only data source. This thesis presents a set of consistent methods aimed at creating large area image mosaics from optical data obtained during surveys with low-cost underwater vehicles. First, a global alignment method developed within a Feature-based image mosaicing (FIM) framework, where nonlinear minimisation is substituted by two linear steps, is discussed. Then, a simple four-point mosaic rectifying method is proposed to reduce distortions that might occur due to lens distortions, error accumulation and the difficulties of optical imaging in an underwater medium. The topology estimation problem is addressed by means of an augmented state and extended Kalman filter combined framework, aimed at minimising the total number of matching attempts and simultaneously obtaining the best possible trajectory. Potential image pairs are predicted by taking into account the uncertainty in the trajectory. The contribution of matching an image pair is investigated using information theory principles. Lastly, a different solution to the topology estimation problem is proposed in a bundle adjustment framework. Innovative aspects include the use of fast image similarity criterion combined with a Minimum spanning tree (MST) solution, to obtain a tentative topology. This topology is improved by attempting image matching with the pairs for which there is the most overlap evidence. Unlike previous approaches for large-area mosaicing, our framework is able to deal naturally with cases where time-consecutive images cannot be matched successfully, such as completely unordered sets. Finally, the efficiency of the proposed methods is discussed and a comparison made with other state-of-the-art approaches, using a series of challenging datasets in underwater scenarios

A proposal to estimate the motion of an underwater vehicle through visual mosaicking

This thesis proposes a solution to the problem of estimating the motion of an Unmanned Underwater Vehicle (UUV). Our approach is based on the integration of the incremental measurements which are provided by a vision system. When the vehicle is close to the underwater terrain, it constructs a visual map (so called "mosaic") of the area where the mission takes place while, at the same time, it localizes itself on this map, following the Concurrent Mapping and Localization strategy. The proposed methodology to achieve this goal is based on a feature-based mosaicking algorithm. A down-looking camera is attached to the underwater vehicle. As the vehicle moves, a sequence of images of the sea-floor is acquired by the camera. For every image of the sequence, a set of characteristic features is detected by means of a corner detector. Then, their correspondences are found in the next image of the sequence. Solving the correspondence problem in an accurate and reliable way is a difficult task in computer vision. We consider different alternatives to solve this problem by introducing a detailed analysis of the textural characteristics of the image. This is done in two phases: first comparing different texture operators individually, and next selecting those that best characterize the point/matching pair and using them together to obtain a more robust characterization. Various alternatives are also studied to merge the information provided by the individual texture operators. Finally, the best approach in terms of robustness and efficiency is proposed. After the correspondences have been solved, for every pair of consecutive images we obtain a list of image features in the first image and their matchings in the next frame. Our aim is now to recover the apparent motion of the camera from these features. Although an accurate texture analysis is devoted to the matching pro-cedure, some false matches (known as outliers) could still appear among the right correspon-dences. For this reason, a robust estimation technique is used to estimate the planar transformation (homography) which explains the dominant motion of the image. Next, this homography is used to warp the processed image to the common mosaic frame, constructing a composite image formed by every frame of the sequence. With the aim of estimating the position of the vehicle as the mosaic is being constructed, the 3D motion of the vehicle can be computed from the measurements obtained by a sonar altimeter and the incremental motion computed from the homography. Unfortunately, as the mosaic increases in size, image local alignment errors increase the inaccuracies associated to the position of the vehicle. Occasionally, the trajectory described by the vehicle may cross over itself. In this situation new information is available, and the system can readjust the position estimates. Our proposal consists not only in localizing the vehicle, but also in readjusting the trajectory described by the vehicle when crossover information is obtained. This is achieved by implementing an Augmented State Kalman Filter (ASKF). Kalman filtering appears as an adequate framework to deal with position estimates and their associated covariances. Finally, some experimental results are shown. A laboratory setup has been used to analyze and evaluate the accuracy of the mosaicking system. This setup enables a quantitative measurement of the accumulated errors of the mosaics created in the lab. Then, the results obtained from real sea trials using the URIS underwater vehicle are shown.