3,643 research outputs found
A simple disc wind model for broad absorption line quasars
No full textApproximately 20 per cent of quasi-stellar objects (QSOs) exhibit broad, blue-shifted absorption lines in their ultraviolet spectra. Such features provide clear evidence for significant outflows from these systems, most likely in the form of accretion disc winds. These winds may represent the ‘quasar’ mode of feedback that is often invoked in galaxy formation/evolution models, and they are also key to unification scenarios for active galactic nuclei (AGN) and QSOs. To test these ideas, we construct a simple benchmark model of an equatorial, biconical accretion disc wind in a QSO and use a Monte Carlo ionization/radiative transfer code to calculate the ultraviolet spectra as a function of viewing angle. We find that for plausible outflow parameters, sightlines looking directly into the wind cone do produce broad, blue-shifted absorption features in the transitions typically seen in broad absorption line (BAL) QSOs. However, our benchmark model is intrinsically X-ray weak in order to prevent overionization of the outflow, and the wind does not yet produce collisionally excited line emission at the level observed in non-BAL QSOs. As a first step towards addressing these shortcomings, we discuss the sensitivity of our results to changes in the assumed X-ray luminosity and mass-loss rate, Ṁwind. In the context of our adopted geometry, Ṁwind ∼ Ṁacc is required in order to produce significant BAL features. The kinetic luminosity and momentum carried by such outflows would be sufficient to provide significant feedback
Alpha particle spectroscopy using FNTD and SIM super-resolution microscopy
No full textStructured illumination microscopy (SIM) for the imaging of alpha particle tracks in fluorescent nuclear track detectors (FNTD) was evaluated and compared to confocal laser scanning microscopy (CLSM). FNTDs were irradiated with an external alpha source and imaged using both methodologies. SIM imaging resulted in improved resolution, without increase in scan time. Alpha particle energy estimation based on the track length, direction and intensity produced results in good agreement with the expected alpha particle energy distribution. A pronounced difference was seen in the spatial scattering of alpha particles in the detectors, where SIM showed an almost 50% reduction compared to CLSM. The improved resolution of SIM allows for more detailed studies of the tracks induced by ionising particles. The combination of SIM and FNTDs for alpha radiation paves the way for affordable and fast alpha spectroscopy and dosimetry. Journal compilatio
Efficient Jacobian-Based Inverse Kinematics With Sim-to-Real Transfer of Soft Robots by Learning
No full textThis article presents an efficient learning-based method to solve the <italic>inverse kinematic</italic> (IK) problem on soft robots with highly nonlinear deformation. The major challenge of efficiently computing IK for such robots is due to the lack of analytical formulation for either forward or inverse kinematics. To address this challenge, we employ neural networks to learn both the mapping function of forward kinematics and also the Jacobian of this function. As a result, Jacobian-based iteration can be applied to solve the IK problem. A sim-to-real training transfer strategy is conducted to make this approach more practical. We first generate a large number of samples in a simulation environment for learning both the kinematic and the Jacobian networks of a soft robot design. Thereafter, a sim-to-real layer of differentiable neurons is employed to map the results of simulation to the physical hardware, where this sim-to-real layer can be learned from a very limited number of training samples generated on the hardware.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Materials and ManufacturingMechatronic Desig
Similarities between 2D and 3D convection for large Prandtl number
No full textUsing direct numerical simulations of Rayleigh-B\'enard convection (RBC), we perform a comparative study of the spectra and fluxes of energy and entropy for large and infinite Prandtl numbers in two (2D) and three (3D) dimensions. We observe close similarities between the 2D and 3D RBC, in particular the kinetic energy spectrum , and the entropy spectrum exhibits a dual branch with a dominant spectrum. We showed that the dominant Fourier modes in the 2D and 3D flows are very close
sj-pdf-1-chc-10.1177_13674935211052148 – Supplemental Material for Clinician and healthcare managers’ perspectives on the delivery of secondary and tertiary pediatric weight management services
No full textSupplemental Material, sj-pdf-1-chc-10.1177_13674935211052148 for Clinician and healthcare managers’ perspectives on the delivery of secondary and tertiary pediatric weight management services by Jennifer Cohen, Shirley Alexander, Christina Signorelli, Kathryn Williams, Kyra A Sim, Lenina Chennariyil and Louise A Baur in Journal of Child Health Care</p
Post-disaster school relocation : a case study of Chinese students’ adjustment after the Wenchuan earthquake
No full textAuthor name used in this publication: Ng, Guat Tin.Author name used in this publication: Sim, Timothy.Accepted ManuscriptPublishedGreen (AAM
CAB-SIM: A cause based operator model for use in dynamic Probabilistic Safety Assessments for nuclear power plants
No full textToday's technology enables people to build complex systems, such as nuclear power plants, that carry big hazards in them. Consequences of accidents that involve such plants can be severe. Hence, safety is an important issue in design and operation. The attention that has been given to system safety has resulted in an increase of component reliability. An accompanying effect is that in relatively more cases, the human operators contribute to accidental situations. Because of that, the study of the impact of operator behavior on system safety has received more attention during the last decade. One of the achievements that was made, is the development of the CAUse based Behavioral model (CAB model), as a part of the Human Interaction TimeLINE (HITLINE) methodology, which studies the impact of intentional operator behavior on system safety. The CAB model was designed to be used in Probabilistic Safety Assessments (PSAs). It uses knowledge about operating procedures, plant configuration and process behavior to perform a simplified simulation of cognitive processes, and to generate a set of possible operator actions with associated probabilities. To make the CAB model available for use in dynartiic PSA techniques, which include the systematic simulation of a large number of accident sequences, a computerized version of the CAB model, called CAuse based Behavioral SIMulator (CAB-SIM) was developed. The CAB model's mechanisms were translated into computer algorithms. Additionally, some improvements to the model were made. As a case study, the HITLINE methodology was applied to a hypothetical two tank system, using CAB-SIM. CAB-SIM was linked with HITline-SIMulator (HIT-SIM), a model for dynamic PSA, that was developed for this case study. The results of the simulations were incorporated in a simple PSA model of the system, that was developed for the purpose of demonstration. Additionally, CAB-SIM was incorporated in Accident Dynamic Simulator (ADS), an existing simulation model for dynamic PSA. The incorporation process included the coding of proper communication channels between CAB-SIM and ADS, modifying ADS simulation driving mechanism and its existing operator model, and the development of application-specific data, i.e. a system representation for use CAB-SIM. Some elementary results were generated. It is concluded that CAB-SIM is a model that seems to be able to improve the modeling of plant-operator interaction in dynamic PSA techniques, by analyzing the impact of intentional operator behavior on system safety. However, parts of the cognitive process simulation need further investigation; further, to make CAB-SIM applicable for real nuclear power plant PSAs, the quantification of operator errors, which currently contains many subjective elements, needs to be improved.Biomechanical EngineeringMechanical, Maritime and Materials Engineerin
Connecticut State Innovation Model (SIM); Proposed framework--revised 4/30/19
No full text1 online resource (32 pages) : color illustrationsFinal version; "This report was prepared by Health Management Associates (HMA), a leading independent national research and consulting firm"--Page 3; "The project described was supported by Funding Opportunity Number CMS-1G1CMS331630-02-00 from the U.S. Department of Health & Human Services, Centers for Medicare & Medicaid Services."; "Approved June 2019."; Includes bibliographical reference
A first look at SIM-enabled wearables in the wild
No full text© 2018 Copyright held by the owner/author(s). Publication rights licensed to ACM. Recent advances are driving wearables towards stand-alone devices with cellular network support (e.g. SIM-enabled Apple Watch series-3). Nonetheless, a little has been studied on SIM-enabled wearable traffic in ISP networks to gain customer insights and to understand traffic characteristics. In this paper, we characterize the network traffic of several thousand SIM-enabled wearable users in a large European mobile ISP. We present insights on user behavior, application characteristics such as popularity and usage, and wearable traffic patterns. We observed a 9% increase in SIM-enabled wearable users over a five month observation period. However, only 34% of such users actually generate any network transaction. Our analysis also indicates that SIM-enabled wearable users are significantly more active in terms of mobility, data consumption and frequency of app usage compared to the remaining customers of the ISP who are mostly equipped with a smartphone. Finally, wearable apps directly communicate with third parties such as advertisement and analytics networks similarly to smartphone apps
The SIM card as control point for Mobile Network Operators: A secure means for authentication and identification services
No full textThe SIM card is as a secure authentication and identification means and that can be used for services that reach beyond the mobile world. Therefore this research tries identify markets where the SIM could possibly be exploited by applying the concept of control points.SEPAMICTTechnology, Policy and Managemen
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