517 research outputs found

    Tuning and Switching a Plasmonic Quantum Dot Sandwich in a Nematic Line Defect

    Full text link
    We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot controllably sandwiched between two plasmonic nanorods. Control over the position and the sandwich confinement structure is achieved by the use of a linear-trap, liquid-crystal line defect and laser tweezers that push the sandwich together. This arrangement allows for the study of exciton plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photon-antibunching behavior of the quantum dot and its luminescence lifetime. The quantum dot behaves as a single emitter when nanorods are far away from the quantum dot but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic sandwich. These findings demonstrate that liquid crystal defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will.Comment: Supporting information at the en

    Non-rigid registration of breast surfaces using the laplace and diffusion equations

    Get PDF
    A semi-automated, non-rigid breast surface registration method is presented that involves solving the Laplace or diffusion equations over undeformed and deformed breast surfaces. The resulting potential energy fields and isocontours are used to establish surface correspondence. This novel surface-based method, which does not require intensity images, anatomical landmarks, or fiducials, is compared to a gold standard of thin-plate spline (TPS) interpolation. Realistic finite element simulations of breast compression and further testing against a tissue-mimicking phantom demonstrate that this method is capable of registering surfaces experiencing 6 - 36 mm compression to within a mean error of 0.5 - 5.7 mm

    MV3: A new word based stream cipher using rapid mixing and revolving buffers

    Full text link
    MV3 is a new word based stream cipher for encrypting long streams of data. A direct adaptation of a byte based cipher such as RC4 into a 32- or 64-bit word version will obviously need vast amounts of memory. This scaling issue necessitates a look for new components and principles, as well as mathematical analysis to justify their use. Our approach, like RC4's, is based on rapidly mixing random walks on directed graphs (that is, walks which reach a random state quickly, from any starting point). We begin with some well understood walks, and then introduce nonlinearity in their steps in order to improve security and show long term statistical correlations are negligible. To minimize the short term correlations, as well as to deter attacks using equations involving successive outputs, we provide a method for sequencing the outputs derived from the walk using three revolving buffers. The cipher is fast -- it runs at a speed of less than 5 cycles per byte on a Pentium IV processor. A word based cipher needs to output more bits per step, which exposes more correlations for attacks. Moreover we seek simplicity of construction and transparent analysis. To meet these requirements, we use a larger state and claim security corresponding to only a fraction of it. Our design is for an adequately secure word-based cipher; our very preliminary estimate puts the security close to exhaustive search for keys of size < 256 bits.Comment: 27 pages, shortened version will appear in "Topics in Cryptology - CT-RSA 2007

    Another Look at Some Isogeny Hardness Assumptions

    Get PDF
    The security proofs for isogeny-based undeniable signature schemes have been based primarily on the assumptions that the One-Sided Modified SSCDH problem and the One-More SSCDH problem are intractable. We challenge the validity of these assumptions, showing that both the decisional and computational variants of these problems can be solved in polynomial time. We further demonstrate an attack, applicable to two undeniable signature schemes, one of which was proposed at PQCrypto 2014. The attack allows to forge signatures in 24λ/5 steps on a classical computer. This is an improvement over the expected classical security of 2λ, where λ denotes the chosen security parameter.SCOPUS: cp.kinfo:eu-repo/semantics/publishedCryptographers Track at the RSA Conference, CT-RSA 2020; San Francisco; United States; 24 February 2020 through 28 February 2020ISBN: 978-303040185-

    Extracting Expert Knowledge and Building Strategic Decision in International Logistics and Kaohsiung Area

    Get PDF
    Evaluating the development and investment direction of complex transportation system for Kaohsiung international logistics is very important to Taiwan. According to the effect of internal and external variables factors, it is necessary to inspect the Kaohsiung metropolitan area epistemic development plan and trend of domestic industry develop international logistics. In order to achieve the benefits of developing logistics integration; we set the Kaohsiung harbour and airport as the core of this study. Exploring that how to strengthen the international logistics function and develop the strategy to improve the economic environment of Kaohsiung area. Consequently, this study is to extract critical expert knowledge and to build strategic decision to improve the economic environment of Kaohsiung area and international logistics

    The Solar Neighborhood X: New Nearby Stars in the Southern Sky and Accurate Photometric Distance Estimates for Red Dwarfs

    Full text link
    Photometric VRI and spectroscopic (6000-9500 A) observations of high proper motion stars discovered during the first phase of the SuperCOSMOS RECONS (SCR) search are used to estimate accurate distances to eight new nearby red dwarfs, including probable 10 pc sample members SCR 1845-6357 (M8.5V at 4.6 pc), the binary SCR 0630-7643AB (M6.0VJ at 7.0 pc), and SCR 1138-7721 (M5.0V at 9.4 pc). Distance estimates are determined using a suite of new photometric color-Mk relations defined using a robust set of nearby stars with accurate VRIJHK photometry and trigonometric parallaxes. These relations are utilized, with optical and infrared photometry, to estimate distances on a uniform system (generally good to 15%) for two additional samples of red nearby star candidates: several recently discovered members of the solar neighborhood, and known faint stars with proper motions in excess of 1.0"/yr south of DEC = -57.5. Of those without accurate trigonometric parallax measurements, there are five stars in the first sample and three in the second that are likely to be within 10 pc. The two nearest are SO 0253+1652 (M7.0V at 3.7 pc) and DEN 1048-3956 (M8.5V at 4.5 pc). When combined with SCR 1845-6357, these three stars together represent the largest increase in the 5 pc sample in several decades. Red spectra are presented for the red dwarfs and types are given on the RECONS standard spectral system. Red spectra are also given for two new nearby white dwarfs for which we estimate distances from the photometry of less than 20 pc -- WD 0141-675 (LHS 145, 9.3 pc) and SCR 2012-5956 (17.4 pc). WD 0141-675 brings the total number of systems nearer than 10 pc discussed in this paper to 12.Comment: accepted to The Astronomical Journal (scheduled for November 2004 issue
    corecore