459 research outputs found

    Super-resolution provided by the arbitrarily strong superlinearity of the blackbody radiation

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    Blackbody radiation is a fundamental phenomenon in nature, and its explanation by Planck marks a cornerstone in the history of Physics. In this theoretical work, we show that the spectral radiance given by Planck's law is strongly superlinear with temperature, with an arbitrarily large local exponent for decreasing wavelengths. From that scaling analysis, we propose a new concept of super-resolved detection and imaging: if a focused beam of energy is scanned over an object that absorbs and linearly converts that energy into heat, a highly nonlinear thermal radiation response is generated, and its point spread function can be made arbitrarily smaller than the excitation beam focus. Based on a few practical scenarios, we propose to extend the notion of super-resolution beyond its current niche in microscopy to various kinds of excitation beams, a wide range of spatial scales, and a broader diversity of target objects

    Channel and terminal description of the ACTS mobile terminal

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    The Advanced Communications Technology Satellite (ACTS) Mobile Terminal (AMT) is a proof-of-concept K/Ka-band mobile satellite communications terminal under development by NASA at JPL. Currently the AMT is undergoing system integration and test in preparation for a July 1993 ACTS launch and the subsequent commencement of mobile experiments in the fall of 1993. The AMT objectives are presented followed by a discussion of the AMT communications channel and mobile terminal design and performance

    Making sense of violence risk predictions using clinical notes

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    Violence risk assessment in psychiatric institutions enables interventions to avoid violence incidents. Clinical notes written by practitioners and available in electronic health records (EHR) are valuable resources that are seldom used to their full potential. Previous studies have attempted to assess violence risk in psychiatric patients using such notes, with acceptable performance. However, they do not explain why classification works and how it can be improved. We explore two methods to better understand the quality of a classifier in the context of clinical note analysis: random forests using topic models, and choice of evaluation metric. These methods allow us to understand both our data and our methodology more profoundly, setting up the groundwork for improved models that build upon this understanding. This is particularly important when it comes to the generalizability of evaluated classifiers to new data, a trustworthiness problem that is of great interest due to the increased availability of new data in electronic format

    Investigating how the attributes of live theatre productions influence consumption choices using conjoint analysis : the example of the National Arts Festival, South Africa

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    While there is a fair amount of work on determinants of demand for the live performing arts, results have often been contradictory with little explanatory power. This may be because of the difficulty in describing the attributes of a performance, particularly in terms of its quality, and the heterogeneity of consumer preferences. This article uses conjoint analysis, also called choice experiments, to investigate the impact of the attributes of live theatre performances on demand, using data collected from 483 randomly chosen attenders at live theatre performances at the 2008 South African National Arts Festival. Attributes include the type of cast (professional, semi-professional or amateur), reputation of the producer/director, the context or setting, production type and ticket price of the show. Results largely support the a priori expectations based on the results of other demand studies. For example, it is found that the age of consumers affects the type of show chosen, that utility and willingness to pay increase for shows with professional and semi-professional casts and that 93% of the potential audience prefer shows with a South African context. It is concluded that the method could prove useful to both event organisers and policy makers, especially where the goal is to broaden access to the arts

    Penalty Corner Routines in Elite Women’s Indoor Field Hockey: Prediction of Outcomes based on Tactical Decisions

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    Indoor hockey is a highly competitive international sport, yet no research to date has investigated the key actions within this sport. As with outdoor field hockey, penalty corners represent one of the most likely situations in which goals can be scored. All 36 matches of the round-robin phase of the 2010-2011 England Hockey League Women’s Premier Division ‘Super Sixes’ competition were analysed with the purpose of establishing which factors can predict the scoring of a goal using Binary Logistic Regression analysis. Seventy two (22.6%) of the 319 observed penalty corners resulted in a goal. The strongest predictor of scoring a goal was taking the penalty corner from the goalkeeper’s right. Based on the odds ratio (OR), the odds of the attacking team scoring were 2.27 (CI = 1.41 - 3.65) times higher with penalty corners taken from the goalkeeper’s right as opposed to the left. Additionally, if the goalkeeper decided to rush to the edge of the circle, the odds of the attacking team failing to score were 2.19 (CI = 1.18 - 4.08) times higher compared to when the goalkeeper remained near the goal line. These results suggest that strategic decisions from the players and coaches have an important part to play in the success of penalty corners. Future research should investigate the impact of goalkeepers’ movement and further examine the technical and tactical intricacies of penalty corners

    Metamaterial superlenses operating at visible wavelength for imaging applications

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    © 2018 The Authors. Published by Nature. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1038/s41598-018-33572-yIn this paper, a novel design for a metamaterial lens (superlens) based on a Photonic Crystal (PC) operating at visible wavelengths is reported. The proposed superlens consist of a gallium phosphide (GaP) dielectric slab waveguide with a hexagonal array of silver rods embedded within the GaP dielectric. In-house 2DFDTD numerical method is used to design and optimize the proposed superlens. Several superlenses are designed and integrated within a same dielectric platform, promoting the proof-of-concept (POC) of possible construction of an array of superlenses (or sub-lenses to create an M-Lens) for light field imaging applications. It is shown that the concavity of the superlens and positioning of each sub-lens within the array strongly affects the performances of the image in terms of resolution. Defects and various geometrical shapes are introduced to construct and optimize the proposed superlenses and increase the quality of the image resolution. It is shown that the orientation of the active region (ellipse) along x and y axis has tremendous influence on the quality of image resolution. In order to investigate the performance characteristics of the superlenses, transmitted power is calculated using 2D FDTD for image projections at various distances (in x and y plane). It is also shown, how the proposed superlens structures could be fabricated using standard micro fabrication techniques such as electron beam lithography, inductively coupled Reactive ion etching, and glancing angle evaporation methods. To the best of our knowledge, these are the first reported POC of superlenses, integrated in a monolithic platform suitable for high imaging resolution that can be used for light field imaging applications at visible wavelength. The proposed superlenses (integrated in a single platform M-Lens) will have tremendous impact on imaging applications

    Subdiffraction, Luminescence-Depletion Imaging of Isolated, Giant, CdSe/CdS Nanocrystal Quantum Dots

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    Subdiffraction spatial resolution luminescence depletion imaging was performed with giant CdSe/14CdS nanocrystal quantum dots (g-NQDs) dispersed on a glass slide. Luminescence depletion imaging used a Gaussian shaped excitation laser pulse overlapped with a depletion pulse, shaped into a doughnut profile, with zero intensity in the center. Luminescence from a subdiffraction volume is collected from the central portion of the excitation spot, where no depletion takes place. Up to 92% depletion of the luminescence signal was achieved. An average full width at half-maximum of 40 ± 10 nm was measured in the lateral direction for isolated g-NQDs at an air interface using luminescence depletion imaging, whereas the average full width at half-maximum was 450 ± 90 nm using diffraction-limited, confocal luminescence imaging. Time-gating of the luminescence depletion data was required to achieve the stated spatial resolution. No observable photobleaching of the g-NQDs was present in the measurements, which allowed imaging with a dwell time of 250 ms per pixel to obtain images with a high signal-to-noise ratio. The mechanism for luminescence depletion is likely stimulated emission, stimulated absorption, or a combination of the two. The g-NQDs fulfill a need for versatile, photostable tags for subdiffraction imaging schemes where high laser powers or long exposure times are used

    Investigation of waste heat recovery system at supercritical conditions with vehicle drive cycles

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    Waste heat recovery (WHR) for internal combustion engines in vehicles using Organic Rankine cycle (ORC) has been a promising technology. The operation of the ORC WHR system in supercritical conditions has a potential to generate more power output and thermal efficiency compared with the conventional subcritical conditions. However, in supercritical conditions, the heat transfer process in the evaporator, the key component of the ORC WHR system, becomes unpredictable as the thermo-physical properties of the working fluid change with the temperature. Furthermore, the transient heat source from the vehicle’s exhaust makes the operation of the WHR system difficult. We investigated the performance of the ORC WHR system at supercritical conditions with engine’s exhaust data from real city and highway drive cycles. The effects of operating variables, such as refrigerant flow rates, evaporator and condenser pressure, and evaporator outlet temperature, on the performance indicators of the WHR system in supercritical conditions were examined. Simulation of operating parameters and the boundary of the WHR system are also included in this paper
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