Korkean tason synteesin soveltaminen matka-aikatomografiaan

Tomography is used to acquire an image of inner contents of an object or material. Typically measurements are based on penetrating waves. Measurements require signal generating and recording hardware, data preprocessing and finally computationally heavy mathematical inversion to recover the unknown parameters. The goal is to decrease the data transfer requirement on, for example, tomography mission to a Near-Earth Asteroid. This could enable small, inexpensive spacecraft to collect tomography data. Travel-time tomography, which uses signal travel times, is one of the methods that can be used to achieve this goal. Tomography algorithms are still under heavy development, for which reason hardware prototyping cycle should be very short. High-level synthesis is used to generate hardware by using high level programming language. It helps the designer to implement hardware design changes quickly, especially when the requirements change. In this work, a setup to collect acoustic tomography data was developed. Data preprocessing hardware for travel-time tomography was implemented with Mentor Graphics Catapult high-level synthesis tool. The calculation of travel-time values was implemented first in Matlab and the scripts were then transformed to C code. Catapult was used to implement hardware on the FPGA from these C codes. Evaluation of the workflow was performed and interfacing options for the module to a PC running Matlab were studied. Travel-time tomography was shown to be a feasible method to recover target objects. Determinining the time period to use in measuring a travel-time is an issue. Simulation of signal noise sensitivity on an asteroid mission was accomplished by reducing the accuracy of preprocessor calculations. A method where signal power is integrated over a time period was evaluated and it proved to be surprisingly stable in recovering targets from the test area even with noisy signals. Tomography algorithms changed over the course of the project, and high-level synthesis enabled to implement the designs

DISCUS - The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid

We have performed an initial stage conceptual design study for the Deep Interior Scanning CubeSat (DISCUS), a tandem 6U CubeSat carrying a bistatic radar as main payload. DISCUS will be operated either as an independent mission or accompanying a larger one. It is designed to determine the internal macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few kilometers distance. The main goal will be to achieve a global penetration with a low-frequency signal as well as to analyze the scattering strength for various different penetration depths and measurement positions. Moreover, the measurements will be inverted through a computed radar tomography (CRT) approach. The scientific data provided by DISCUS would bring more knowledge of the internal configuration of rubble pile asteroids and their collisional evolution in the Solar System. It would also advance the design of future asteroid deflection concepts. We aim at a single-unit (1U) radar design equipped with a half-wavelength dipole antenna. The radar will utilize a stepped-frequency modulation technique the baseline of which was developed for ESA's technology projects GINGER and PIRA. The radar measurements will be used for CRT and shape reconstruction. The CubeSat will also be equipped with an optical camera system and laser altimeter to sup- port navigation and shape reconstruction. We provide the details of the measurement methods to be applied along with the requirements derived of the known characteristics of rubble pile asteroids.Comment: Submitted to Advances in Space Researc

Bistatic full-wave radar tomography detects deep interior voids, cracks and boulders in a rubble-pile asteroid model

In this paper, we investigate full-wave computed radar tomography (CRT) using a rubble-pile asteroid model in which a realistic shape (Itokawa) is coupled with a synthetic material composition and structure model. The aim is to show that sparse bistatic radar measurements can distinguish details inside a complex-structured rubble-pile asteroid. The results obtained suggest that distinct local permittivity distribution changes such as surface layers, voids, low-permittivity anomalies, high-permittivity boulders, and cracks can be detected with bistatic CRT, when the total noise level in the data is around -10 dB with respect to the signal amplitude. Moreover, the bistatic measurement set-up improves the robustness of the inversion compared to the monostatic case. Reconstructing the smooth Gaussian background distribution was found to be difficult with the present approach, suggesting that complementary techniques, such as gravimetry, might be needed to improve the reliability of the inference in practice.Comment: 15 pages, 7 figures, 3 tables, Published in the Astrophysical Journa

Suomen osa-aikaeläke ja osittaiset eläkkeet Euroopassa

Raportissa tarkastellaan Suomen osa-aikaeläkkeen kehitystä vuodesta 1987 vuoteen 2017. Siinä kuvataan osa-aikaeläkkeen historiaa ja käyttöä. Osa-aikaeläkeläisiä kuvataan tilasto- ja rekisteritietojen valossa. Raportissa myös kootaan yhteen aikaisemman, osa-aikaeläkeläisiä koskevan tutkimuksen tuloksia. Lisäksi siinä on tietoa muiden maiden, erityisesti Ruotsin ja Norjan, osittaisista eläkkeistä

The prevalence of cardiac complications and their impact on outcomes in patients with non-traumatic subarachnoid hemorrhage.

Subarachnoid hemorrhage (SAH) is a serious condition, and a myocardial injury or dysfunction could contribute to the outcome. We assessed the prevalence and prognostic impact of cardiac involvement in a cohort with SAH. This is a prospective observational multicenter study. We included 192 patients treated for non-traumatic subarachnoid hemorrhage. We performed ECG recordings, echocardiographic examinations, and blood sampling within 24 h of admission and on days 3 and 7 and at 90 days. The primary endpoint was the evidence of cardiac involvement at 90 days, and the secondary endpoint was to examine the prevalence of a myocardial injury or dysfunction. The median age was 54.5 (interquartile range [IQR] 48.0-64.0) years, 44.3% were male and the median World Federation of Neurological Surgeons (WFNS) score was 2 (IQR 1-4). At day 90, 22/125 patients (17.6%) had left ventricular ejection fractions ≤ 50%, and 2/121 patients (1.7%) had evidence of a diastolic dysfunction as defined by mitral peak E-wave velocity by peak e' velocity (E/e') > 14. There was no prognostic impact from echocardiographic evidence of cardiac complications on neurological outcomes. The overall prevalence of cardiac dysfunction was modest. We found no demographic or SAH-related factors associated with 90 days cardiac dysfunction