621 research outputs found

    Touching points of s star-shaped set with an affine subspace

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    AbstractThe paper studies the following problem. Given a linear subspace L ⊂ Rn of dimension k, 1 ⩽ k ⩽ n – 1, the point x ∃ Rn, x ∉ L, and a star-shaped set A ⊂ Rn, characterize those τ> 0 for which L + x touches τA, and, if this is the case, describe the set τ cl(A)∩(L + x). Here A is star-shaped if λA ⊆ A for all 0 ⩽ λ ⩽ 1, L + x touches τA if L + x meets τA only on the boundary, and cl(A) means the closure of A. The problem is solved for two kinds of sets: convex A such that the origin θ is contained in the relative interior of A, and A equals to the closed unit ɭp-ball Gp for some 0 < p < 1. For convex A the set L⊥ ∩ A∗ plays a crucial role, where A∗ ≔ {z ∃ Rn:⇄z,y↩ ⩽ 1 for all y ∈ A} is the polar of A, and L⊊ is the orthogonal complement subspace to L. For Gp the problem is solved by a special geometrical construction based on “coordinate” subspaces RT such that L ∩ RT = {θ}

    Indium phosphide based membrane photodetector for optical interconnects on silicon

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    We have designed, fabricated and characterized an InP-based membrane photodetector on an SOI wafer containing a Si-wiring photonic circuit. New results on RF characterization up to 20 GHz are presented. The detector fabrication is compatible with wafer scale processing steps, guaranteeing compatibility towards future generation electronic IC processing

    Scalable quantum dot based optical interconnects

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    Scalable quantum dot based optical switches offer energy-efficient low-latency data routing. Low power penalty routing over multiple stages are feasible with with the prospect of larger scale photonic integration

    Earth Through the Eyes of NAPA-1: Commissioning Results and the Next Steps in CubeSat Earth Observation

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    Disruptive CubeSat technology has brought scientific missions within reach that were previously only achievable through larger spacecraft. Satellite Earth Observation is now the new frontier for governments, private industry, and academia. With the recent launch of the Napa-1 satellite the Royal Thai Airforce (RTAF) has joined the ranks by having its first ever Earth Observation CubeSat in space. Its design, launch, early operations (LEOPS), and commissioning have been carried out by ISISpace, supporting the market’s need for imagery from space. Napa-1, meaning firmament in Thai, is a 6U CubeSat with the Gecko Imager from SCS Space as its primary payload, capable of taking RGB snapshot images with a 39-meter ground sampling distance (GSD) from 500 km altitude. In addition, the TriScape camera from Simera Sense flies onboard as an in-orbit technology demonstrator and is capable of delivering high-quality images with a GSD of 5 meter in the RGB bands. With well over 200 images taken by the primary payload this paper will look back on this exciting first period of Napa-1’s operational life and proudly present the very first images taken by the satellite and the lessons learnt throughout this turnkey mission. With that many images taken and that much data generated, the implemented onboard- and on ground data handling systems have been put to the test. ISISpace has made use of KUBOS’ Major Tom for command and control and having integrated a low-level processing tool, also for image data preview and delivery. Insight is provided into the systems and tools in place for image target planning, image acquisition, satellite command and control, and data delivery to the customer. How is it ensured targets are successfully captured? How is the usefulness of the image data efficiently validated? Subsequently, how is knowledge transfer to the customer accomplished to ensure successful routine operations? ISISpace will share the valuable lessons learnt from the mission planning, data handling, operations, and training points of view and show relevant in-orbit data on, for example, attitude behavior and temperature. In parallel, ISISpace has taken the next step in CubeSat Earth observation by using Napa-1 as a baseline while accommodating larger data streams and leveraging a higher level of automation. Together with the companies Simera Sense and Pinkmatter Solutions, multispectral images with automated on ground data processing (L0 up to L3) are to be delivered by the follow-up mission, Napa-2, to be launched in the summer of 2021. Details on this mission, including a further outlook at how CubeSat imagery and on ground processing will be shaped in the next few years will be provided

    High-performance InP-based photodetector in an amplifier layer stack on semi-insulating substrate

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    A waveguide photodetector (PD) based on semi-insulating (SI) indium phosphide (InP) was simulated, designed, and fabricated. The layer stack for this PD was optimized for use as an optical amplifier or laser and it can be combined with the passive components. By using an SI substrate and deep etching, a small, efficient, and high-speed PD was made, which allows for easy integration of source, detector, and passive optical components on a single chip. A 3-dB bandwidth of 35 GHz and 0.25 A/W external radio-frequency reponsivity is measured at 1.55-mum wavelength for a 1.5-mum-wide and 30-mum-long waveguide PD at -4-V bias voltage. The polarization dependence in the responsivity is less than 0.27 d

    Genicular artery embolization as a novel treatment for mild to moderate knee osteoarthritis:protocol design of a randomized sham-controlled clinical trial

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    INTRODUCTION: Knee osteoarthritis is a common disease with pain as the most prevalent symptom. Previous cohort studies have shown genicular artery embolization to reduce pain symptoms in patients with mild to moderate knee osteoarthritis. Patients resistant to conservative therapy but not eligible yet for surgical treatment due to young age or comorbidities may profit from an effective and sustained pain reduction treatment. This study is a randomized sham-controlled trial to evaluate the efficacy of genicular artery embolization in patients with knee osteoarthritis. METHODS AND ANALYSIS: Fifty-eight patients with mild-to-moderate knee osteoarthritis will be recruited and randomly allocated to the treatment or control group in a 1:1 ratio. Participants in the treatment group will undergo genicular artery embolization. Patients in the control group will undergo sham treatment. Outcome measurements will be assessed at baseline and after 1, 4, 8, and 12 months with questionnaires, pressure pain threshold testing, and MR imaging. The MR imaging protocol is designed to (semi)quantitatively assess osteoarthritis in the knee joint. The primary outcome is the change from baseline of the Knee injury and Osteoarthritis Outcome Score (KOOS) pain subscale after 4 months. Secondary outcomes include change in osteoarthritis-related questionnaires, pressure pain threshold, and OA-related MRI features, particularly synovitis and bone marrow lesions. ETHICS AND DISSEMINATION: This trial will determine the efficacy of genicular artery embolization compared to a sham treatment. This is of importance to assess before proceeding to larger-scale efficiency studies and, ultimately, implementing this treatment into day to day clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov NCT03884049. Registered on 21 March 201