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  1. Article ; Online: Shape sensing of optical fiber Bragg gratings based on deep learning

    Samaneh Manavi Roodsari / Antal Huck-Horvath / Sara Freund / Azhar Zam / Georg Rauter / Wolfgang Schade / Philippe C Cattin

    Machine Learning: Science and Technology, Vol 4, Iss 2, p

    2023  Volume 025037

    Abstract: Continuum robots in robot-assisted minimally invasive surgeries provide adequate access to target anatomies that are not directly reachable through small incisions. Achieving precise and reliable shape estimation of such snake-like manipulators ... ...

    Abstract Continuum robots in robot-assisted minimally invasive surgeries provide adequate access to target anatomies that are not directly reachable through small incisions. Achieving precise and reliable shape estimation of such snake-like manipulators necessitates an accurate navigation system, that requires no line-of-sight and is immune to electromagnetic noise. Fiber Bragg grating (FBG) shape sensing, particularly eccentric FBG (eFBG), is a promising and cost-effective solution for this task. However, in eFBG sensors, the spectral intensity of the Bragg wavelengths that carries the strain information can be affected by undesired bending-induced phenomena, making standard characterization techniques less suitable for these sensors. We showed in our previous work that a deep learning model has the potential to extract the strain information from the eFBG sensor’s spectrum and accurately predict its shape. In this paper, we conducted a more thorough investigation to find a suitable architectural design of the deep learning model to further increase shape prediction accuracy. We used the Hyperband algorithm to search for optimal hyperparameters in two steps. First, we limited the search space to layer settings of the network, from which, the best-performing configuration was selected. Then, we modified the search space for tuning the training and loss calculation hyperparameters. We also analyzed various data transformations on the network’s input and output variables, as data rescaling can directly influence the model’s performance. Additionally, we performed discriminative training using the Siamese network architecture that employs two convolutional neural networks (CNN) with identical parameters to learn similarity metrics between the spectra of similar target values. The best-performing network architecture among all evaluated configurations can predict the shape of a 30 cm long sensor with a median tip error of 3.11 mm in a curvature range of 1.4 m ^−1 to 35.3 m ^−1 .
    Keywords supervised deep learning ; shape sensing ; bending birefringence ; bending loss ; eccentric FBG ; fiber sensor ; Computer engineering. Computer hardware ; TK7885-7895 ; Electronic computers. Computer science ; QA75.5-76.95
    Subject code 006
    Language English
    Publishing date 2023-01-01T00:00:00Z
    Publisher IOP Publishing
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Influence of electrospray deposition on C60 molecular assemblies

    Antoine Hinaut / Sebastian Scherb / Sara Freund / Zhao Liu / Thilo Glatzel / Ernst Meyer

    Beilstein Journal of Nanotechnology, Vol 12, Iss 1, Pp 552-

    2021  Volume 558

    Abstract: Maintaining clean conditions for samples during all steps of preparation and investigation is important for scanning probe studies at the atomic or molecular level. For large or fragile organic molecules, where sublimation cannot be used, high-vacuum ... ...

    Abstract Maintaining clean conditions for samples during all steps of preparation and investigation is important for scanning probe studies at the atomic or molecular level. For large or fragile organic molecules, where sublimation cannot be used, high-vacuum electrospray deposition is a good alternative. However, because this method requires the introduction into vacuum of the molecules from solution, clean conditions are more difficult to be maintained. Additionally, because the presence of solvent on the surface cannot be fully eliminated, one has to take care of its possible influence. Here, we compare the high-vacuum electrospray deposition method to thermal evaporation for the preparation of C60 on different surfaces and compare, for sub-monolayer coverages, the influence of the deposition method on the formation of molecular assemblies. Whereas the island location is the main difference for metal surfaces, we observe for alkali halide and metal oxide substrates that the high-vacuum electrospray method can yield single isolated molecules accompanied by surface modifications.
    Keywords alkali halide ; au(111) ; bulk insulator ; c60 ; electrospray ; electrospray deposition ; fullerene ; high-vacuum electrospray deposition (hv-esd) ; molecular assembly ; nc-afm ; nio ; single molecule ; thermal evaporation ; Technology ; T ; Chemical technology ; TP1-1185 ; Science ; Q ; Physics ; QC1-999
    Subject code 540
    Language English
    Publishing date 2021-06-01T00:00:00Z
    Publisher Beilstein-Institut
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  3. Article ; Online: Comparing a porphyrin- and a coumarin-based dye adsorbed on NiO(001)

    Sara Freund / Antoine Hinaut / Nathalie Marinakis / Edwin C. Constable / Ernst Meyer / Catherine E. Housecroft / Thilo Glatzel

    Beilstein Journal of Nanotechnology, Vol 10, Iss 1, Pp 874-

    2019  Volume 881

    Abstract: Properties of metal oxides, such as optical absorption, can be influenced through the sensitization with molecular species that absorb visible light. Molecular/solid interfaces of this kind are particularly suited for the development and design of ... ...

    Abstract Properties of metal oxides, such as optical absorption, can be influenced through the sensitization with molecular species that absorb visible light. Molecular/solid interfaces of this kind are particularly suited for the development and design of emerging hybrid technologies such as dye-sensitized solar cells. A key optimization parameter for such devices is the choice of the compounds in order to control the direction and the intensity of charge transfer across the interface. Here, the deposition of two different molecular dyes, porphyrin and coumarin, as single-layered islands on a NiO(001) single crystal surface have been studied by means of non-contact atomic force microscopy at room temperature. Comparison of both island types reveals different adsorption and packing of each dye, as well as an opposite charge-transfer direction, which has been quantified by Kelvin probe force microscopy measurements.
    Keywords coumarin ; Kelvin probe force microscopy ; metal oxide ; molecular resolution ; nickel oxide (NiO) ; non-contact atomic force microscopy ; porphyrin ; Technology ; T ; Chemical technology ; TP1-1185 ; Science ; Q ; Physics ; QC1-999
    Language English
    Publishing date 2019-04-01T00:00:00Z
    Publisher Beilstein-Institut
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Anchoring of a dye precursor on NiO(001) studied by non-contact atomic force microscopy

    Sara Freund / Antoine Hinaut / Nathalie Marinakis / Edwin C. Constable / Ernst Meyer / Catherine E. Housecroft / Thilo Glatzel

    Beilstein Journal of Nanotechnology, Vol 9, Iss 1, Pp 242-

    2018  Volume 249

    Abstract: The properties of metal oxides, such as charge-transport mechanisms or optoelectronic characteristics, can be modified by functionalization with organic molecules. This kind of organic/inorganic surface is nowadays highly regarded, in particular, for the ...

    Abstract The properties of metal oxides, such as charge-transport mechanisms or optoelectronic characteristics, can be modified by functionalization with organic molecules. This kind of organic/inorganic surface is nowadays highly regarded, in particular, for the design of hybrid devices such as dye-sensitized solar cells. However, a key parameter for optimized interfaces is not only the choice of the compounds but also the properties of adsorption. Here, we investigated the deposition of an organic dye precursor molecule on a NiO(001) single crystal surface by means of non-contact atomic force microscopy at room temperature. Depending on the coverage, single molecules, groups of adsorbates with random or recognizable shapes, or islands of closely packed molecules were identified. Single molecules and self assemblies are resolved with submolecular resolution showing that they are lying flat on the surface in a trans-conformation. Within the limits of our Kelvin probe microscopy setup a charge transfer from NiO to the molecular layer of 0.3 electrons per molecules was observed only in the areas where the molecules are closed packed.
    Keywords metal oxide ; nickel(II) oxide (NiO) ; non-contact atomic force microscopy ; p-type semiconductor ; sub-molecular resolution ; Technology ; T ; Chemical technology ; TP1-1185 ; Science ; Q ; Physics ; QC1-999
    Subject code 540
    Language English
    Publishing date 2018-01-01T00:00:00Z
    Publisher Beilstein-Institut
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: Transoid-to-Cisoid Conformation Changes of Single Molecules on Surfaces Triggered by Metal Coordination

    Sara Freund / Rémy Pawlak / Lucas Moser / Antoine Hinaut / Roland Steiner / Nathalie Marinakis / Edwin C. Constable / Ernst Meyer / Catherine E. Housecroft / Thilo Glatzel

    ACS Omega, Vol 3, Iss 10, Pp 12851-

    2018  Volume 12856

    Keywords Chemistry ; QD1-999
    Language English
    Publishing date 2018-10-01T00:00:00Z
    Publisher American Chemical Society
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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